0000950170-24-044237 | 10-K | XBRL Viewer

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

A summary of the Company’s stock option activity under the 2013 Plan, 2018 Plan and 2020 Plan for the year ended December 31, 2023 is as follows:


	Shares Available for Grant			Outstanding Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contract Term		Aggregate Intrinsic Value
									(in Years)		(in thousands)
Balance at December 31, 2022		68,838			1,609,938		$	27.51		8.3	$	251
Shares added		1,010,831			—			—
Granted		(446,200	)		446,200			2.79
Exercised		—			—			—
Canceled		153,367			(142,793	)		7.96
Balance at December 31, 2023		786,836			1,913,345		$	14.23		7.1	$	5
Vested and exercisable at December 31, 2023					1,179,366		$	20.51		6.0	$	—
Vested and expected to vest at December 31, 2023					1,913,345		$	14.23		7.1	$	5

Summary of Restricted Stock Units Activity

The following table summarizes the Company’s RSU activity for the year ended December 31, 2023:


	Shares			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2022		146,333		$	27.66
Granted		—		$	—
Released		(94,534	)	$	28.39
Canceled		(10,574	)	$	11.27
Unvested at December 31, 2023		41,225		$	30.18

Summary of Valuation Assumption to Estimate Fair Value of Stock Options

The Company uses the Black-Scholes option-pricing model for determining the estimated fair value and stock-based compensation related to stock options and ESPP awards. The fair value of stock options granted to employees was estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions:


	Year ended December 31,
	2023		2022		2021
Expected term of options (in years)	5.79		5.55		6.0
Expected stock price volatility	94.11%-98.92%		86.22%-93.17%		85.7%-88.5%
Risk-free interest rate	3.36%-4.13%		2.41%-4.01%		1.08%-1.35%
Expected dividend yield		—		—		—

Summary of Stock-based Compensation Expense

The following table sets forth the total stock-based compensation expense for all options granted to employees and nonemployees and costs associated with the 2018 ESPP included in the Company’s statement of operations (in thousands):


	Year Ended December 31,
	2023		2022		2021
Research and development	$	1,947	$	3,526	$	4,809
General and administrative		5,472		5,853		6,744
Total	$	7,419	$	9,379	$	11,553

Defined Contribution Plan	12 Months Ended
Dec. 31, 2023
Retirement Benefits [Abstract]
Defined Contribution Plan	16. Defined Contribution Plan The Company sponsors a 401(k) Plan that stipulates that eligible employees can elect to contribute to the 401(k) Plan, subject to certain limitations, on a pretax basis. In January 2019, the Company began to match 4% of employees’ salary. During the years ended December 31, 2023, 2022 and 2021, the Company recorded matching contributions of $0.3 million, $0.4 million and $0.5 million, respectively.

Defined Contribution Plan

12 Months Ended

Dec. 31, 2023

Retirement Benefits [Abstract]

Defined Contribution Plan

16. Defined Contribution Plan

The Company sponsors a 401(k) Plan that stipulates that eligible employees can elect to contribute to the 401(k) Plan, subject to certain limitations, on a pretax basis. In January 2019, the Company began to match 4% of employees’ salary. During the years ended December 31, 2023, 2022 and 2021, the Company recorded matching contributions of $0.3 million, $0.4 million and $0.5 million, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 70
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480794/715-70-50-1

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-17

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (q)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (l)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//715/tableOfContent

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (o)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (p)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (r)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (r)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480126/715-20-S99-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 60
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

+ Details

Restatement of Previously Issued Financial Statements - Schedule of Restated Statement of Changes in Stockholders' Equity (Parenthetical) (Details)	Oct. 19, 2022
Statement of Stockholders' Equity [Abstract]
Reverse stock split ratio	0.1

Restatement of Previously Issued Financial Statements (Tables)

12 Months Ended

Dec. 31, 2023

Prior Period Adjustment [Abstract]

Schedule Of Restated And Reconciliation From The Prior Period As Previously Reported To The Restated Amounts In Financial Statments

The following tables represent the restated amounts in the Balance Sheet, Statement of Operations and Comprehensive Loss, Statement of Changes in Stockholders’ Equity and Statement of Cash Flows for the year ended December 31, 2022.

The amounts as previously reported for fiscal year 2022 was derived from the Annual Report on Form 10-K for the fiscal year ended December 31, 2022, filed on March 15, 2023 (Original Report). These amounts are labeled as “As Previously Reported” in the tables below. The amounts labeled “Adjustment” represent the effects of this restatement described above.

Balance Sheet


	December 31, 2022
	As Previously Reported			Adjustment			As Restated
Assets
Current assets:
Cash and cash equivalents	$	12,736		$	—		$	12,736
Short-term marketable securities		82,059			—			82,059
Prepaid expenses and other current assets		1,740			—			1,740
Total current assets		96,535			—			96,535
Property and equipment, net		7,825			—			7,825
Operating lease right-of-use asset		19,042			—			19,042
Long-term restricted cash		896			—			896
Other long-term assets		52			—			52
Total assets	$	124,350		$	—		$	124,350
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	1,790		$	—		$	1,790
Accrued compensation		3,020			—			3,020
Accrued and other current liabilities		5,334			—			5,334
Current portion of long-term debt		9,476			—			9,476
Total current liabilities		19,620			—			19,620
Operating lease liability, net of current portion		26,991			—			26,991
Long-term debt, net		10,891			—			10,891
Warrant liability		—			10,764			10,764
Total liabilities		57,502			10,764			68,266
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—			—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2022; 14,215,302 shares issued and outstanding as of December 31, 2022		1			—			1
Additional paid-in capital		527,049			(26,222	)		500,827
Accumulated other comprehensive loss		(251	)		—			(251	)
Accumulated deficit		(459,951	)		15,458			(444,493	)
Total stockholders’ equity		66,848			(10,764	)		56,084
Total liabilities and stockholders’ equity	$	124,350		$	—		$	124,350

Statement of Operations and Comprehensive Loss


	Year Ended December 31, 2022
	As Previously Reported			Adjustment			As Restated
Licensing revenue - Related Party	$	236		$	—		$	236
Operating expenses:
Research and development		36,859			—			36,859
General and administrative		20,949			—			20,949
Total operating expenses		57,808			—			57,808
Loss from operations		(57,572	)		—			(57,572	)
Interest income		1,220			—			1,220
Interest expense		(3,558	)		—			(3,558	)
Gain (loss) on warrant liability		—			16,843			16,843
Other expense, net		(17	)		(1,385	)		(1,402	)
Net loss		(59,927	)		15,458			(44,469	)
Other comprehensive loss
Unrealized loss on marketable debt securities		(207	)		—			(207	)
Comprehensive loss	$	(60,134	)	$	15,458		$	(44,676	)
Net loss per share, basic and diluted	$	(6.31	)	$	—		$	(4.68	)
Weighted average number of shares used in computing net loss per share, basic and diluted		9,494,421			—			9,494,421

Statement of Changes in Stockholders' Equity


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at December 31, 2021		6,299,158	$	1	$	459,636		$	(44	)	$	(400,024	)	$	59,569
Issuance of common stock, net of issuance costs, under ATM equity offering program		1,019,046		—		12,155			—			—			12,155
Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs		6,428,571		—		41,648			—			—			41,648
Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		90,000		—		910			—			—			910
Issuance of common stock Hercules Capital, net of issuance costs		262,761		—		3,179			—			—			3,179
Issuance of common stock under 2018 ESPP		25,482		—		142			—			—			142
Vesting of restricted stock units		90,284		—		—			—			—			—
Stock-based compensation		—		—		9,379			—			—			9,379
Unrealized loss on available-for-sale marketable securities		—		—		—			(207	)		—			(207	)
Net loss		—		—		—			—			(59,927	)		(59,927	)
Balances at December 31, 2022		14,215,302	$	1	$	527,049		$	(251	)	$	(459,951	)	$	66,848

Adjustment
Balances at December 31, 2021		—	$	—	$	—		$	—		$	—		$	—
Issuance of common stock, net of issuance costs, under ATM equity offering program		—		—		—			—			—			—
Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs		—		—		(26,222	)		—			—			(26,222	)
Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		—		—		—			—			—			—
Issuance of common stock Hercules Capital, net of issuance costs		—		—		—			—			—			—
Issuance of common stock under 2018 ESPP		—		—		—			—			—			—
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		—			—			—			—
Unrealized loss on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			15,458			15,458
Balances at December 31, 2022		—	$	—	$	(26,222	)	$	—		$	15,458		$	(10,764	)

As Restated
Balances at December 31, 2021		6,299,158	$	1	$	459,636		$	(44	)	$	(400,024	)	$	59,569
Issuance of common stock, net of issuance costs, under ATM equity offering program		1,019,046		—		12,155			—			—			12,155
Sale of common stock under Follow-On Offering, net of issuance costs		6,428,571		—		15,426			—			—			15,426
Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		90,000		—		910			—			—			910
Issuance of common stock Hercules Capital, net of issuance costs		262,761		—		3,179			—			—			3,179
Issuance of common stock under 2018 ESPP		25,482		—		142			—			—			142
Vesting of restricted stock units		90,284		—		—			—			—			—
Stock-based compensation		—		—		9,379			—			—			9,379
Unrealized loss on available-for-sale marketable securities		—		—		—			(207	)		—			(207	)
Net loss		—		—		—			—			(44,469	)		(44,469	)
Balances at December 31, 2022		14,215,302	$	1	$	500,827		$	(251	)	$	(444,493	)	$	56,084

Statement of Cash Flow


	Year Ended December 31, 2022
	As Previously Reported			Adjustment			As Restated
Operating activities
Net loss	$	(59,927	)	$	15,458		$	(44,469	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		2,180			—			2,180
Amortization of debt issuance costs		1,318			—			1,318
Debt extinguishment gain upon conversion to equity		(199	)		—			(199	)
Net accretion and amortization of premium and discounts on marketable securities		(276	)		—			(276	)
Gain on disposal of property and equipment		(346	)		—			(346	)
Stock-based compensation		9,379			—			9,379
Non-cash rent expense		(2,136	)		—			(2,136	)
(Gain) loss on warrant liability		—			(16,843	)		(16,843	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		138			—			138
Other long-term assets		39			—			39
Accounts payable		(194	)		—			(194	)
Accrued compensation		(1,008	)		—			(1,008	)
Accrued liabilities and other current liabilities		26			—			26
Other long-term liabilities		(23	)		—			(23	)
Net cash used in operating activities		(51,029	)		(1,385	)		(52,414	)
Investing activities
Purchase of marketable securities		(98,827	)		—			(98,827	)
Maturities of marketable securities		74,000			—			74,000
Purchase of property and equipment		(96	)		—			(96	)
Sale of property and equipment		378			—			378
Net cash provided by (used in) investing activities		(24,545	)		—			(24,545	)
Financing activities
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		12,155			—			12,155
Proceeds from sale of common stock and warrants under Follow-On Offering		41,648			3,352			45,000
Issuance costs for sale of common stock		—			(1,967	)		(1,967	)
Proceeds from issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		910			—			910
Proceeds from issuance of common stock under 2018 ESPP		142			—			142
Net cash provided by financing activities		54,855			1,385			56,240
Net increase (decrease) in cash, cash equivalents and restricted cash		(20,719	)		—			(20,719	)
Cash, cash equivalents and restricted cash at beginning of the period		34,351			—			34,351
Cash, cash equivalents and restricted cash at end of the period	$	13,632		$	—		$	13,632
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	2,204		$	—		$	2,204
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt	$	3,179		$	—		$	3,179

The remainder of the notes to the Company's financial statements have been restated, as applicable, to reflect the impacts from the restatement discussed above.

Corporate Restructuring - Additional Information (Details) $ in Millions			1 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2023 Employee	May 31, 2023 Employee	May 31, 2023 Employee	Feb. 28, 2022 Position	Jun. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2023 USD ($) Employee	Dec. 31, 2022 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring implementation date		2023-05		2022-02
Number of positions eliminated				29			9
Percentage of positions eliminated		29.00%		50.00%
Severance charge in operating expenses						$ 1.9
Non-cash share-based payment compensation credits to forfeiture of stock options								$ 1.7
Expected number of employees departing \| Employee	3	9	6
Operating Expenses
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses					$ 0.6
Employee Termination Benefits
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses							$ 0.5	1.6
Employee Termination Benefits \| Research and Development Expense
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses							0.4	1.4
Employee Termination Benefits \| Employee-Related Benefits
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses							0.1	0.2
Employee Termination Benefits \| General and Administrative Expense
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses							$ 0.2	0.5
Employee Termination Benefits \| Payroll Taxes
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses								$ 0.1

Statements of Stockholders' Equity - USD ($)
$ in Thousands

Total

At The Market Equity Offering Program

Equity Purchase Agreement

Lincoln Park Capital Fund LLC

Follow-On Offering

Warrant Inducement Agreement

Loan Agreement

Hercules Capital

Common Stock

At The Market Equity Offering Program

Common Stock

Equity Purchase Agreement

Lincoln Park Capital Fund LLC

Common Stock

Follow-On Offering

Common Stock

Warrant Inducement Agreement

^[1]

Common Stock

Loan Agreement

Hercules Capital

Additional Paid-In Capital

At The Market Equity Offering Program

Additional Paid-In Capital

Equity Purchase Agreement

Lincoln Park Capital Fund LLC

Additional Paid-In Capital

Follow-On Offering

Additional Paid-In Capital

Warrant Inducement Agreement

Additional Paid-In Capital

Loan Agreement

Hercules Capital

Related Party Promissory Notes for Purchase of Common Stock

Accumulated Other Comprehensive Gain (Loss)

Accumulated Deficit

Beginning balance at Dec. 31, 2020

$ 82,881

$ 1

^[1]

$ 422,384

$ (210)

$ 5

$ (339,299)

Beginning balance, (in shares) at Dec. 31, 2020

^[1]

5,325,288

Issuance of common stock, net of issuance costs

$ 10,357

$ 9,039

$ 2,704

$ 10,357

$ 9,039

$ 2,704

Issuance of common stock (in shares)

^[1]

189,453

417,286

172,736

Issuance of common stock upon exercise of stock options

1,795

Issuance of common stock upon exercise of stock options (in shares)

^[1]

49,754

Repurchase of early exercised shares, (in shares)

^[1]

(3,337)

Vesting of restricted stock units, (in shares)

^[1]

96,269

Stock-based compensation

11,553

Common stock granted to third party

1,457

Common stock issued to third parties, (in shares)

^[1]

40,005

Repayment of promissory note from employee from purchase of common stock

210

$ 210

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

347

Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)

^[1]

11,704

Unrealized gain (loss) on available-for-sale marketable securities

(49)

Net gain (loss)

(60,725)

Ending balance at Dec. 31, 2021

59,569

$ 1

^[1]

459,636

(44)

(400,024)

Ending balance, (in shares) at Dec. 31, 2021

^[1]

6,299,158

Net gain (loss)

(37,047)

Ending balance at Sep. 30, 2022

$ 61,054

$ 1

498,401

(275)

(437,073)

Ending balance, (in shares) at Sep. 30, 2022

14,036,249

Beginning balance at Dec. 31, 2021

$ 59,569

$ 1

^[1]

459,636

(44)

(400,024)

Beginning balance, (in shares) at Dec. 31, 2021

^[1]

6,299,158

Issuance of common stock, net of issuance costs

12,155

$ 910

$ 15,426

$ 3,179

12,155

$ 910

$ 15,426

$ 3,179

Issuance of common stock (in shares)

^[1]

1,019,046

90,000

6,428,571

262,761

Vesting of restricted stock units, (in shares)

^[1]

90,284

Stock-based compensation

9,379

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

142

Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)

^[1]

25,482

Unrealized gain (loss) on available-for-sale marketable securities

(207)

Net gain (loss)

(44,469)

Ending balance at Dec. 31, 2022

$ 56,084

$ 1

^[1]

500,827

(251)

(444,493)

Ending balance, (in shares) at Dec. 31, 2022

14,215,302

^[1]

Beginning balance at Jun. 30, 2022

$ 39,931

$ 1

472,193

(187)

(432,076)

Beginning balance, (in shares) at Jun. 30, 2022

6,958,494

Issuance of common stock, net of issuance costs

8,570

$ 15,428

8,570

$ 15,428

Issuance of common stock (in shares)

633,464

6,428,571

Vesting of restricted stock units, (in shares)

15,720

Stock-based compensation

2,210

Unrealized gain (loss) on available-for-sale marketable securities

(88)

Net gain (loss)

(4,997)

Ending balance at Sep. 30, 2022

$ 61,054

$ 1

498,401

(275)

(437,073)

Ending balance, (in shares) at Sep. 30, 2022

14,036,249

Beginning balance at Dec. 31, 2022

$ 56,084

$ 1

^[1]

500,827

(251)

(444,493)

Beginning balance, (in shares) at Dec. 31, 2022

14,215,302

^[1]

Issuance of common stock, net of issuance costs

274

Issuance of common stock (in shares)

106,781

Vesting of restricted stock units, (in shares)

37,131

Stock-based compensation

$ 2,175

2,175

Unrealized gain (loss) on available-for-sale marketable securities

101

Net gain (loss)

(5,279)

Ending balance at Mar. 31, 2023

$ 53,355

$ 1

503,276

(150)

(449,772)

Ending balance, (in shares) at Mar. 31, 2023

14,359,214

Beginning balance at Dec. 31, 2022

$ 56,084

$ 1

^[1]

500,827

(251)

(444,493)

Beginning balance, (in shares) at Dec. 31, 2022

14,215,302

^[1]

Net gain (loss)

$ (20,735)

Ending balance at Jun. 30, 2023

$ 40,769

$ 1

506,132

(136)

(465,228)

Ending balance, (in shares) at Jun. 30, 2023

14,595,477

Beginning balance at Dec. 31, 2022

$ 56,084

$ 1

^[1]

500,827

(251)

(444,493)

Beginning balance, (in shares) at Dec. 31, 2022

14,215,302

^[1]

Net gain (loss)

$ (35,520)

Ending balance at Sep. 30, 2023

$ 27,725

$ 1

507,789

(55)

(480,010)

Ending balance, (in shares) at Sep. 30, 2023

14,614,890

Beginning balance at Dec. 31, 2022

$ 56,084

$ 1

^[1]

500,827

(251)

(444,493)

Beginning balance, (in shares) at Dec. 31, 2022

14,215,302

^[1]

Issuance of common stock, net of issuance costs

725

$ 3,687

$ 1

725

$ 3,686

Issuance of common stock (in shares)

274,781

^[1]

2,143,000

Vesting of restricted stock units, (in shares)

^[1]

94,467

Stock-based compensation

$ 7,419

7,419

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

116

Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)

^[1]

57,419

Unrealized gain (loss) on available-for-sale marketable securities

227

Net gain (loss)

(39,860)

Ending balance at Dec. 31, 2023

$ 28,398

$ 2

^[1]

512,773

(24)

(484,353)

Ending balance, (in shares) at Dec. 31, 2023

16,784,969

^[1]

Beginning balance at Mar. 31, 2023

$ 53,355

$ 1

503,276

(150)

(449,772)

Beginning balance, (in shares) at Mar. 31, 2023

14,359,214

Issuance of common stock, net of issuance costs

$ 518

Issuance of common stock (in shares)

168,000

Vesting of restricted stock units, (in shares)

26,766

Stock-based compensation

$ 2,247

2,247

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)

41,497

Unrealized gain (loss) on available-for-sale marketable securities

Net gain (loss)

(15,456)

Ending balance at Jun. 30, 2023

$ 40,769

$ 1

506,132

(136)

(465,228)

Ending balance, (in shares) at Jun. 30, 2023

14,595,477

Vesting of restricted stock units, (in shares)

19,413

Stock-based compensation

$ 1,705

1,705

Unrealized gain (loss) on available-for-sale marketable securities

Net gain (loss)

(14,782)

Ending balance at Sep. 30, 2023

$ 27,725

$ 1

$ 507,789

$ (55)

$ (480,010)

Ending balance, (in shares) at Sep. 30, 2023

14,614,890

[1]

The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net gain (loss)	$ (39,860)	$ (44,469)	$ (60,725)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,182	2,180	2,880
Amortization of debt issuance costs	705	1,318	813
Debt extinguishment loss upon paydown of principal	491	0	0
Debt extinguishment gain upon conversion to equity	0	(199)	(123)
Net accretion and amortization of premium and discounts on marketable securities	(1,503)	(276)	1,043
Other expense related to the commitment shares issued to Lincoln Park Capital Fund	0	0	825
Gain on disposal of property and equipment	(114)	(346)	0
Stock-based compensation	7,419	9,379	11,553
Common stock issued to third parties	0	0	1,457
Non-cash rent expense	(1,072)	(2,136)	(2,152)
Impairment of long-lived assets	5,602	0	0
(Gain) loss on warrant liability	(6,215)	(16,843)	0
Extinguishment loss and Issuance costs on warrant	668	0	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,664)	138	1,288
Other long-term assets	(74)	39	(91)
Accounts payable	(410)	(194)	(573)
Accrued compensation	(1,180)	(1,008)	(1,327)
Accrued liabilities and other current liabilities	(1,063)	26	(1,131)
Other long-term liabilities	0	(23)	24
Derivative liability related to debt	0	0	963
Deferred revenue	0	0	216
Net cash used in operating activities	(37,088)	(52,414)	(45,060)
Investing activities
Purchase of marketable securities	(28,609)	(98,827)	(81,492)
Maturities of marketable securities	89,000	74,000	121,000
Sale of property and equipment	115	378	0
Purchase of property and equipment	(11)	(96)	(195)
Net cash used in investing activities	60,495	(24,545)	39,313
Financing activities
Payment of debt principal	(20,000)	0	0
Payment of debt issuance costs	(1,563)	0	0
Issuance costs for sale of common stock	0	(1,967)	0
Proceeds from repayment of employee promissory notes	0	0	210
Proceeds from issuance of common stock upon exercise of stock options, net of repurchases	0	0	1,784
Proceeds from issuance of common stock under the 2018 ESPP	116	142	347
Current portion of long-term debt arrangement	0	0	(68)
Net cash provided by financing activities	(16,340)	56,240	20,845
Net decrease in cash, cash equivalents and restricted cash	7,067	(20,719)	15,098
Cash, cash equivalents and restricted cash at beginning of year	13,632	34,351	19,253
Cash, cash equivalents and restricted cash at end of year	20,699	13,632	34,351
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	1,969	2,204	2,370
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common shares in payment of debt	0	3,179	2,704
ATM Offering Program
Financing activities
Proceeds from issuance of common stock, net of issuance costs	725	12,155	10,357
Follow-on Offering
Financing activities
Proceeds from issuance of common stock, net of issuance costs	0	45,000	0
Warrant Inducement Agreement
Financing activities
Proceeds from issuance of common stock, net of issuance costs	4,382	0	0
Lincoln Park Capital Fund Equity Purchase Agreement
Financing activities
Proceeds from issuance of common stock, net of issuance costs	$ 0	$ 910	$ 8,215

Equity Financing - Additional Information (Details)

1 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

16 Months Ended

Nov. 09, 2023

USD ($)

$ / shares

Oct. 19, 2022

Aug. 31, 2022

USD ($)

$ / shares

Aug. 17, 2022

USD ($)

Oct. 31, 2022

USD ($)

Mar. 31, 2022

USD ($)

Sep. 30, 2021

USD ($)

$ / shares

Jul. 31, 2020

USD ($)

Jun. 30, 2019

USD ($)

Sep. 30, 2023

USD ($)

$ / shares

Jun. 30, 2023

USD ($)

$ / shares

Mar. 31, 2023

USD ($)

$ / shares

Sep. 30, 2022

USD ($)

$ / shares

Mar. 31, 2022

USD ($)

Jun. 30, 2023

USD ($)

$ / shares

Sep. 30, 2023

USD ($)

$ / shares

Sep. 30, 2022

USD ($)

$ / shares

Dec. 31, 2023

USD ($)

$ / shares

Dec. 31, 2022

USD ($)

$ / shares

Dec. 31, 2021

USD ($)

Dec. 31, 2020

USD ($)

Dec. 31, 2022

USD ($)

$ / shares

Jun. 30, 2022

Subsidiary Sale Of Stock [Line Items]

Reverse stock split ratio

0.1

Number of stock, authorized for issuance | shares

10,000,000

Number of stock, par value per share | $ / shares

$ 0.0001

Number of stock, shares issued | shares

Number of stock, shares outstanding | shares

Common stock, shares authorized | shares

300,000,000

Common stock, par value per share | $ / shares

$ 0.0001

Common stock, shares issued | shares

14,614,890

14,595,477

14,359,214

14,036,249

14,595,477

14,614,890

14,036,249

16,784,969

14,215,302

Common stock, shares outstanding | shares

14,614,890

14,595,477

14,359,214

14,036,249

14,595,477

14,614,890

14,036,249

16,784,969

14,215,302

Equity financing, authorized amount

$ 250,000,000

$ 125,000,000

$ 250,000,000

Common stock value

$ 1,000

$ 2,000

^[1]

$ 1,000

^[1]

$ 1,000

^[1]

Issuance cost

1,965,000

1,967,000

$ 0

Other expense related to the commitment shares issued to Lincoln Park Capital Fund

825,000

Gain (loss) on warrant liability

$ 253,000

$ (3,461,000)

$ 5,491,000

$ 10,974,000

$ 2,030,000

$ 2,283,000

$ 10,974,000

$ 6,215,000

$ 16,843,000

$ 0

Common Stock

Subsidiary Sale Of Stock [Line Items]

Common stock, shares outstanding | shares

14,614,890

14,595,477

14,359,214

14,036,249

14,595,477

14,614,890

14,036,249

16,784,969

^[2]

14,215,302

^[2]

6,299,158

^[2]

5,325,288

^[2]

14,215,302

^[2]

6,958,494

New Warrants | Holders | Inducement Offer

Subsidiary Sale Of Stock [Line Items]

Exercise price for warrant | $ / shares

$ 1.92

Warrants issued to purchase ordinary shares | shares

2,143,000

New Warrants | Holders | Inducement Offer | Maximum

Subsidiary Sale Of Stock [Line Items]

Warrants exercisable term

5 years

Existing Warrants | Inducement Offer

Subsidiary Sale Of Stock [Line Items]

Fair value of common stock

$ 3,700,000

Fair value of common warrants issued

2,700,000

Issuance costs and loss on extinguishment of warrants

1,000,000

Warrant liability

1,400,000

Existing Warrants | Holders | Inducement Offer

Subsidiary Sale Of Stock [Line Items]

Warrants issued to purchase ordinary shares | shares

2,143,000

Reduced exercise price of warrant | $ / shares

$ 2.045

Expected aggregate gross proceeds from exercise of warrants

$ 4,400,000

Placement Agent Warrants | H.C. Wainwright & Co.

Subsidiary Sale Of Stock [Line Items]

Exercise price for warrant | $ / shares

$ 2.5563

Warrants issued to purchase ordinary shares | shares

128,580

At The Market Equity Offering Program

Subsidiary Sale Of Stock [Line Items]

Proceeds from sale of common stock

$ 274,000

$ 792,000

$ 744,000

$ 12,003,000

725,000

$ 12,155,000

$ 10,357,000

Issuance of common stock, value

$ 518,000

$ 274,000

$ 8,570,000

$ 725,000

$ 12,155,000

$ 10,357,000

Remaining issuance cost of additional paid-in capital

$ 48,000

At The Market Equity Offering Program | Cowen | Sales Agreement

Subsidiary Sale Of Stock [Line Items]

Issuance of common stock (in shares) | shares

500,226

Proceeds from sale of common stock

$ 37,300,000

Payments for other offering expenses

$ 1,300,000

At The Market Equity Offering Program | Cowen | Sales Agreement | Maximum

Subsidiary Sale Of Stock [Line Items]

Equity financing, authorized amount

$ 75,000,000

Percentage of gross sales proceeds of common stock payable as compensation

3.00%

At The Market Equity Offering Program | Cowen | June 2019 Sales Agreement

Subsidiary Sale Of Stock [Line Items]

Issuance of common stock (in shares) | shares

118,707

At The Market Equity Offering Program | Common Stock

Subsidiary Sale Of Stock [Line Items]

Equity financing, authorized amount

$ 75,000,000

Issuance of common stock (in shares) | shares

168,000

106,781

633,464

274,781

^[2]

1,019,046

^[2]

189,453

^[2]

Additional At The Market Equity Offering Program | Cowen

Subsidiary Sale Of Stock [Line Items]

Proceeds from sale of common stock

$ 10,400,000

Payments for other offering expenses

$ 300,000

Additional At The Market Equity Offering Program | Cowen | July 2020 Sales Agreement

Subsidiary Sale Of Stock [Line Items]

Issuance of common stock (in shares) | shares

70,746

Additional At The Market Equity Offering Program | Cowen | July 2020 Sales Agreement | Maximum

Subsidiary Sale Of Stock [Line Items]

Equity financing, authorized amount

$ 50,000,000

Percentage of gross sales proceeds of common stock payable as compensation

3.00%

Additional At The Market Equity Offering Program | Common Stock

Subsidiary Sale Of Stock [Line Items]

Equity financing, authorized amount

$ 50,000,000

March 2022 ATM Offering Program | Common Stock | Cowen | March 2022 Sales Agreement

Subsidiary Sale Of Stock [Line Items]

Percentage of gross sales proceeds of common stock payable as compensation

3.00%

Issuance of common stock (in shares) | shares

274,781

Proceeds from sale of common stock

$ 1,000,000

Maximum Public Float

$ 75,000,000

March 2022 ATM Offering Program | Common Stock | Cowen | March 2022 Sales Agreement | Maximum

Subsidiary Sale Of Stock [Line Items]

Equity financing, authorized amount

$ 50,000,000

March 2022 ATM Offering Program Amendment | March 2022 Sales Agreement

Subsidiary Sale Of Stock [Line Items]

Common stock, capital shares reserved for future issuance | shares

14,600,000

March 2022 ATM Offering Program Amendment | Common Stock | Cowen | March 2022 Sales Agreement | Maximum

Subsidiary Sale Of Stock [Line Items]

Equity financing, authorized amount

$ 25,000,000

October 2022 At The Market Equity Offering Program | Cowen | October 2022 Sales Agreement

Subsidiary Sale Of Stock [Line Items]

Issuance of common stock (in shares) | shares

October 2022 At The Market Equity Offering Program | Cowen | October 2022 Sales Agreement | Maximum

Subsidiary Sale Of Stock [Line Items]

Equity financing, authorized amount

$ 50,000,000

Percentage of gross sales proceeds of common stock payable as compensation

3.00%

Equity Purchase Agreement | Lincoln Park Capital Fund LLC

Subsidiary Sale Of Stock [Line Items]

Issuance of common stock (in shares) | shares

102,040

380,000

Issuance of common stock, value

$ 910,000

$ 9,039,000

Purchase agreement term

36 months

Share purchase price | $ / shares

$ 2.94

Total gross purchase price of share

$ 3,000,000

Regular purchase capped amount

$ 2,000,000

Percentage of trading volume

30.00%

Percentage of purchase price

97.00%

Percentage of shares issued to common shares outstanding immediately prior to the execution of the purchase agreement

19.99%

Purchase agreement price per share | $ / shares

$ 29.4

Maximum percentage ownership of issued and outstanding shares

9.99%

Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Purchase Agreement 35.00 Closing Price

Subsidiary Sale Of Stock [Line Items]

Regular purchase amount closing price per share | $ / shares

$ 35

Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Purchase Agreement 50.00 Closing Price

Subsidiary Sale Of Stock [Line Items]

Regular purchase amount closing price per share | $ / shares

Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Purchase Agreement 70.00 Closing Price

Subsidiary Sale Of Stock [Line Items]

Regular purchase amount closing price per share | $ / shares

$ 70

Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Maximum

Subsidiary Sale Of Stock [Line Items]

Issuance of common stock (in shares) | shares

1,106,580

Issuance of common stock, value

$ 30,000,000

Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Maximum | Purchase Agreement 35.00 Closing Price

Subsidiary Sale Of Stock [Line Items]

Regular purchase amount shares | shares

15,000

Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Maximum | Purchase Agreement 50.00 Closing Price

Subsidiary Sale Of Stock [Line Items]

Regular purchase amount shares | shares

20,000

Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Maximum | Purchase Agreement 70.00 Closing Price

Subsidiary Sale Of Stock [Line Items]

Regular purchase amount shares | shares

25,000

Equity Purchase Agreement | Common Stock | Lincoln Park Capital Fund LLC

Subsidiary Sale Of Stock [Line Items]

Issuance of common stock (in shares) | shares

^[2]

90,000

417,286

Proceeds from sale of common stock

$ 6,200,000

Issuance of common stock as commitment fee | shares

25,244

Other expense related to the commitment shares issued to Lincoln Park Capital Fund

$ 800,000

Equity Purchase Agreement | Common Stock | Lincoln Park Capital Fund LLC | Regular Purchase Amount | Maximum

Subsidiary Sale Of Stock [Line Items]

Issuance of common stock (in shares) | shares

10,000

Follow-On Offering

Subsidiary Sale Of Stock [Line Items]

Gross proceeds

$ 45,000,000

Proceeds from sale of common stock

$ 41,700,000

Number of warrants exercised | shares

2,143,000

Issuance of common stock, value

$ 15,428,000

$ 15,426,000

Estimated fair value of common warrants exercised

$ 2,800,000

10,700,000

Gain (loss) on warrant liability

6,600,000

$ 16,800,000

Follow-On Offering | Maximum

Subsidiary Sale Of Stock [Line Items]

Warrants exercisable term

5 years

Warrant exercise percentage of ordinary shares outstanding beneficially owned

4.99%

Follow-On Offering | Common Stock

Subsidiary Sale Of Stock [Line Items]

Issuance of common stock (in shares) | shares

6,428,571

^[2]

Share purchase price | $ / shares

$ 7

Follow-On Offering | Existing Warrants

Subsidiary Sale Of Stock [Line Items]

Exercise price for warrant | $ / shares

$ 8.5

Warrants issued to purchase ordinary shares | shares

6,428,572

Gross proceeds

45,000,000

Fair value of common warrants issued

27,600,000

Issuance cost

3,300,000

Remaining issuance cost of additional paid-in capital

1,900,000

Follow-On Offering | Existing Warrants | Other Income (Expense)

Subsidiary Sale Of Stock [Line Items]

Issuance cost

$ 1,400,000

[1]

[2]

Fair Value Measurements - Summary of Financial Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis and Level of Inputs Used in Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022
Assets:
Short-term marketable securities	$ 23,398	$ 38,063	$ 49,974	$ 60,420	$ 82,059	$ 76,364
Restrcited Cash equivalents	896	$ 896	896	$ 896	896	896
Long-term marketable securities			$ 1,899			$ 4,980
Fair Value, Recurring
Assets:
Cash equivalents	15,853				5,083
Short-term marketable securities	23,398				82,059
Restrcited Cash equivalents	896
Total assets subject to fair value measurements on a recurring basis	40,147				87,142
Liabilities:
Total liabilities subject to fair value measurements on a recurring basis	5,913				10,764
Fair Value, Recurring \| Level 1
Assets:
Cash equivalents	12,864				5,083
Total assets subject to fair value measurements on a recurring basis	13,760				5,083
Fair Value, Recurring \| Level 2
Assets:
Cash equivalents	2,989
Short-term marketable securities	23,398				82,059
Total assets subject to fair value measurements on a recurring basis	26,387				82,059
Fair Value, Recurring \| Level 3 (Restated)
Liabilities:
Total liabilities subject to fair value measurements on a recurring basis	5,913				10,764
Money market funds \| Fair Value, Recurring
Assets:
Cash equivalents	12,864				5,083
Restrcited Cash equivalents	896
Money market funds \| Fair Value, Recurring \| Level 1
Assets:
Cash equivalents	12,864				5,083
Restrcited Cash equivalents	896
U.S. Treasuries
Assets:
Cash equivalents	2,989
U.S. Treasuries \| Fair Value, Recurring
Assets:
Short-term marketable securities	7,849				30,758
U.S. Treasuries \| Fair Value, Recurring \| Level 2
Assets:
Cash equivalents	2,989
Short-term marketable securities	7,849				30,758
U.S. government debt securities \| Fair Value, Recurring
Assets:
Short-term marketable securities	15,549				51,301
U.S. government debt securities \| Fair Value, Recurring \| Level 2
Assets:
Short-term marketable securities	15,549				51,301
Warrant Liability \| Fair Value, Recurring
Liabilities:
Total liabilities subject to fair value measurements on a recurring basis	5,913				10,764
Warrant Liability \| Fair Value, Recurring \| Level 3 (Restated)
Liabilities:
Total liabilities subject to fair value measurements on a recurring basis	$ 5,913				$ 10,764

Quarterly Financial Information (Unaudited) - Statements of Changes in Stockholders' Equity (Details) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

Aug. 31, 2022

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Sep. 30, 2022

Jun. 30, 2023

Sep. 30, 2023

Sep. 30, 2022

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Beginning balance

$ 40,769

$ 53,355

$ 56,084

$ 39,931

$ 56,084

$ 59,569

$ 56,084

$ 59,569

$ 82,881

Beginning balance, (in shares)

14,595,477

14,359,214

14,215,302

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

$ 91

$ 116

142

347

Stock-based compensation

$ 1,705

2,247

$ 2,175

2,210

7,419

9,379

11,553

Unrealized gain (loss) on available-for-sale marketable securities

101

(88)

227

(207)

(49)

Net gain (loss)

(14,782)

(15,456)

(5,279)

(4,997)

$ (20,735)

$ (35,520)

(37,047)

(39,860)

(44,469)

(60,725)

Ending balance

$ 27,725

$ 40,769

$ 53,355

$ 61,054

$ 40,769

$ 27,725

$ 61,054

$ 28,398

$ 56,084

59,569

Ending balance, (in shares)

14,614,890

14,595,477

14,359,214

14,036,249

14,595,477

14,614,890

14,036,249

16,784,969

14,215,302

ATM Equity Offering Program

Issuance of common stock, net of issuance costs

$ 518

$ 274

$ 8,570

$ 725

$ 12,155

10,357

$ (48)

Follow-On Offering

Issuance of common stock, net of issuance costs

15,428

15,426

Common Stock

Beginning balance

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

Beginning balance, (in shares)

14,595,477

14,359,214

14,215,302

^[1]

6,958,494

14,215,302

^[1]

14,215,302

^[1]

6,299,158

^[1]

14,215,302

^[1]

6,299,158

^[1]

5,325,288

^[1]

Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)

41,497

57,419

^[1]

25,482

^[1]

11,704

^[1]

Vesting of restricted stock units, (in shares)

19,413

26,766

37,131

15,720

94,467

^[1]

90,284

^[1]

96,269

^[1]

Ending balance

$ 1

$ 2

^[1]

$ 1

^[1]

$ 1

^[1]

Ending balance, (in shares)

14,614,890

14,595,477

14,359,214

14,036,249

14,595,477

14,614,890

14,036,249

16,784,969

^[1]

14,215,302

^[1]

6,299,158

^[1]

Common Stock | ATM Equity Offering Program

Issuance of common stock (in shares)

168,000

106,781

633,464

274,781

^[1]

1,019,046

^[1]

189,453

^[1]

Common Stock | Follow-On Offering

Issuance of common stock (in shares)

6,428,571

^[1]

Additional Paid-In Capital

Beginning balance

$ 506,132

$ 503,276

$ 500,827

$ 472,193

$ 500,827

$ 459,636

$ 500,827

$ 459,636

$ 422,384

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

116

142

347

Stock-based compensation

1,705

2,247

2,175

2,210

7,419

9,379

11,553

Ending balance

507,789

506,132

503,276

498,401

506,132

507,789

498,401

512,773

500,827

459,636

Additional Paid-In Capital | ATM Equity Offering Program

Issuance of common stock, net of issuance costs

518

274

8,570

725

12,155

10,357

(48)

Additional Paid-In Capital | Follow-On Offering

Issuance of common stock, net of issuance costs

15,428

15,426

Accumulated Other Comprehensive Gain (Loss)

Beginning balance

(136)

(150)

(251)

(187)

(251)

(44)

(251)

(44)

Unrealized gain (loss) on available-for-sale marketable securities

101

(88)

227

(207)

(49)

Ending balance

(55)

(136)

(150)

(275)

(136)

(55)

(275)

(24)

(251)

(44)

Accumulated Deficit

Beginning balance

(465,228)

(449,772)

(444,493)

(432,076)

(444,493)

(400,024)

(444,493)

(400,024)

(339,299)

Net gain (loss)

(14,782)

(15,456)

(5,279)

(4,997)

(39,860)

(44,469)

(60,725)

Ending balance

(480,010)

(465,228)

(449,772)

(437,073)

(465,228)

(480,010)

(437,073)

(484,353)

(444,493)

(400,024)

As Previously Reported

Beginning balance

49,407

58,628

66,848

39,931

66,848

59,569

66,848

59,569

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

142

Stock-based compensation

2,055

2,361

2,270

2,210

9,379

Unrealized gain (loss) on available-for-sale marketable securities

101

(88)

(207)

Net gain (loss)

(15,289)

(12,205)

(10,865)

(13,708)

(23,070)

(38,362)

(45,758)

(59,927)

Ending balance

36,206

49,407

58,628

78,565

49,407

36,206

78,565

66,848

59,569

As Previously Reported | ATM Equity Offering Program

Issuance of common stock, net of issuance costs

518

274

8,570

12,155

(48)

As Previously Reported | Follow-On Offering

Issuance of common stock, net of issuance costs

41,650

41,648

As Previously Reported | Common Stock

Beginning balance

$ 1

Beginning balance, (in shares)

14,595,477

14,359,214

14,215,302

6,958,494

14,215,302

6,299,158

14,215,302

6,299,158

Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)

41,497

25,482

Vesting of restricted stock units, (in shares)

19,413

26,766

37,131

15,720

90,284

Ending balance

$ 1

Ending balance, (in shares)

14,614,890

14,595,477

14,359,214

14,036,249

14,595,477

14,614,890

14,036,249

14,215,302

6,299,158

As Previously Reported | Common Stock | ATM Equity Offering Program

Issuance of common stock (in shares)

168,000

106,781

633,464

1,019,046

As Previously Reported | Common Stock | Follow-On Offering

Issuance of common stock (in shares)

6,428,571

As Previously Reported | Additional Paid-In Capital

Beginning balance

$ 532,563

$ 529,593

$ 527,049

$ 472,193

$ 527,049

$ 459,636

$ 527,049

$ 459,636

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

142

Stock-based compensation

2,055

2,361

2,270

2,210

9,379

Ending balance

534,570

532,563

529,593

524,623

532,563

534,570

524,623

527,049

$ 459,636

As Previously Reported | Additional Paid-In Capital | ATM Equity Offering Program

Issuance of common stock, net of issuance costs

518

274

8,570

12,155

(48)

As Previously Reported | Additional Paid-In Capital | Follow-On Offering

Issuance of common stock, net of issuance costs

41,650

41,648

As Previously Reported | Accumulated Other Comprehensive Gain (Loss)

Beginning balance

(136)

(150)

(251)

(187)

(251)

(44)

(251)

(44)

Unrealized gain (loss) on available-for-sale marketable securities

101

(88)

(207)

Ending balance

(55)

(136)

(150)

(275)

(136)

(55)

(275)

(251)

(44)

As Previously Reported | Accumulated Deficit

Beginning balance

(483,021)

(470,816)

(459,951)

(432,076)

(459,951)

(400,024)

(459,951)

(400,024)

Net gain (loss)

(15,289)

(12,205)

(10,865)

(13,708)

(59,927)

Ending balance

(498,310)

(483,021)

(470,816)

(445,784)

(483,021)

(498,310)

(445,784)

(459,951)

$ (400,024)

Adjustment

Beginning balance

(8,638)

(5,273)

(10,764)

Stock-based compensation

(350)

(114)

(95)

Net gain (loss)

507

(3,251)

5,586

8,711

2,335

2,842

8,711

15,458

Ending balance

(8,481)

(8,638)

(5,273)

(17,511)

(8,638)

(8,481)

(17,511)

(10,764)

Adjustment | Follow-On Offering

Issuance of common stock, net of issuance costs

(26,222)

Adjustment | Additional Paid-In Capital

Beginning balance

(26,431)

(26,317)

(26,222)

Stock-based compensation

(350)

(114)

(95)

Ending balance

(26,781)

(26,431)

(26,317)

(26,222)

(26,431)

(26,781)

(26,222)

Adjustment | Additional Paid-In Capital | Follow-On Offering

Issuance of common stock, net of issuance costs

(26,222)

Adjustment | Accumulated Deficit

Beginning balance

17,793

21,044

15,458

$ 15,458

Net gain (loss)

507

(3,251)

5,586

8,711

15,458

Ending balance

$ 18,300

$ 17,793

$ 21,044

$ 8,711

$ 17,793

$ 18,300

$ 8,711

$ 15,458

[1]

Quarterly Financial Information (Unaudited) - Balance Sheets (Parenthetical) (Details) - $ / shares	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022
Convertible preferred stock, par value	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	10,000,000	10,000,000	10,000,000	10,000,000	10,000,000	10,000,000
Convertible preferred stock, shares issued	0	0	0	0	0	0
Convertible preferred stock, shares outstanding	0	0	0	0	0	0
Common stock, par value	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000	300,000,000	300,000,000	300,000,000	300,000,000
Common stock, shares issued	16,784,969	14,614,890	14,595,477	14,359,214	14,215,302	14,036,249
Common stock, shares outstanding	16,784,969	14,614,890	14,595,477	14,359,214	14,215,302	14,036,249

Statements of Operations and Comprehensive Loss (Parenthetical)	Oct. 19, 2022
Statement of Comprehensive Income [Abstract]
Reverse stock split ratio	0.1

Quarterly Financial Information (Unaudited)

12 Months Ended

Dec. 31, 2023

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information (Unaudited)

18. Quarterly Financial Information (Unaudited)

The previously reported financial information for the three and nine months ended September 30, 2022, the three months ended March 31, 2023, the three and six months ended June 30, 2023 and the three and nine months ended September 30, 2023, have been restated. Relevant restated financial information for each relevant period is included in this Annual Report on Form 10-K in the tables that follow. As part of the Warrants restatement (as noted below in the section titled ‘Warrant Adjustments’ for which the amounts restated are included with reference (a) in the table below), the Company has corrected certain other immaterial errors. While these other errors are quantitatively and qualitatively immaterial, individually and in the aggregate, because the Company is correcting for the material errors, the Company has corrected other errors as well. These adjustments are described in more detail in restated references (b), (c) and (d) in the section titled ‘Other Adjustments impacting only the interim periods for 2022 and 2023’.

Warrant Adjustment

(a) In March 2024, the Company concluded that it incorrectly classified certain warrants (the “Existing Warrants”) that were issued to investors in connection with a public offering of the Company’s common stock (“Common Stock”) in August 2022.

Historically, the Existing Warrants were reflected as a component of equity as opposed to liabilities on the balance sheet. Additionally, the Statements of Operations and Comprehensive Loss did not include the subsequent non-cash changes in the fair value of the Existing Warrants. The Company reassessed its accounting for the Existing Warrants and determined that the Existing Warrants should be classified as liabilities measured at fair value upon issuance with subsequent changes in fair value reported, as well as the issuance cost associated with the Existing Warrants, in the Company’s Statement of Operations and Comprehensive Loss.

Other Adjustments impacting only the interim periods for 2022 and 2023

The Company has corrected other immaterial errors. While these other errors are quantitatively and qualitatively immaterial, individually and in the aggregate, because the Company is correcting for the material errors, the Company has decided to correct these other errors as well. The adjustments to correct errors related to the out-of-period expenses are as follows:

(b) The Company had previously understated its accrued and other current liability and overstated its prepaid expenses and other current assets as of September 30, 2022 and understated its research and development operating expense for the three- and nine- months ended September 30, 2023 by $0.9 million.

The impact of the above other adjustment is reflected in the restatement tables below, as indicated by reference (b).

(c) The Company had previously overstated the amortization of debt issuance cost. This resulted in the understatement of the long-term debt liability as of June 30, 2023 and the overstatement of interest expense for the three- and six- months ended June 30, 2023 by $0.1 million.

The impact of the above other adjustment is reflected in the restatement tables below, as indicated by reference (c).

(d) The Company had previously overstated its stock-compensation expense in the three months ended March 31, 2023 by $0.1 million, three- and six- months ended June 30, 2023 by $0.1 million and $0.2 million, respectively, and for the three- and nine- months ended September 30, 2023 by $0.3 million and $0.6 million, respectively.

The impact of the above other adjustment is reflected in the restatement tables below as indicated by reference (d).

The unaudited interim financial statements reflect all adjustments which are, in the opinion of management, necessary for a fair statement of the results for the interim periods presented (in thousands).

Balance Sheets


	September 30, 2022 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Assets
Current assets:
Cash and cash equivalents	$	22,576		$	—			$	22,576
Short-term marketable securities		76,364			—				76,364
Prepaid expenses and other current asset		3,234			(150	)	b		3,084
Restricted cash		550			—				550
Total current assets		102,724			(150	)			102,574
Property and equipment, net		8,202			—				8,202
Operating lease right-of-use assets		19,515			—				19,515
Long-term marketable securities		4,980			—				4,980
Long-term restricted cash		896			—				896
Other long-term assets		76			—				76
Total assets	$	136,393		$	(150	)		$	136,243
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	2,444		$	—			$	2,444
Accrued compensation		2,961			—				2,961
Accrued and other current liabilities		4,593			728		b		5,321
Current portion of long-term debt		6,776			—				6,776
Total current liabilities		16,774			728		b		17,502
Operating lease liability, net of current portion		27,792			—				27,792
Long-term debt, net		13,262			—				13,262
Warrant liability		—			16,633		a		16,633
Total liabilities		57,828			17,361				75,189
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—				—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of September 30, 2022 ; 14,036,249 shares issued and outstanding as of September 30, 2022		1			—				1
Additional paid-in capital		524,623			(26,222	)	a		498,401
Accumulated other comprehensive loss		(275	)		—				(275	)
Accumulated deficit		(445,784	)		8,711		a,b		(437,073	)
Total stockholders’ equity		78,565			(17,511	)			61,054
Total liabilities and stockholders’ equity	$	136,393		$	(150	)		$	136,243


	March 31, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Assets
Current assets:
Cash and cash equivalents	$	22,972		$	—			$	22,972
Short-term marketable securities		60,420			—				60,420
Prepaid expenses and other current assets		2,989			—				2,989
Total current assets		86,381			—				86,381
Property and equipment, net		7,496			—				7,496
Operating lease right-of-use asset		18,557			—				18,557
Long-term deposits		896			—				896
Long-term restricted cash		896			—				896
Other long-term assets		29			—				29
Total assets	$	114,255		$	—			$	114,255
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	1,470		$	—			$	1,470
Accrued compensation		1,983			—				1,983
Accrued and other current liabilities		5,343			—				5,343
Current portion of long-term debt		13,062			—				13,062
Total current liabilities		21,858			—				21,858
Operating lease liability, net of current portion		26,150			—				26,150
Long-term debt, net		7,619			—				7,619
Warrant liability		—			5,273		a		5,273
Total liabilities		55,627			5,273				60,900
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—				—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of March 31, 2023; 14,359,214 shares issued and outstanding as of March 31, 2023		1			—				1
Additional paid-in capital		529,593			(26,317	)	a,d		503,276
Accumulated other comprehensive loss		(150	)		—				(150	)
Accumulated deficit		(470,816	)		21,044		a,d		(449,772	)
Total stockholders’ equity		58,628			(5,273	)			53,355
Total liabilities and stockholders’ equity	$	114,255		$	—			$	114,255


	June 30, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Assets
Current assets:
Cash and cash equivalents	$	19,118		$	—			$	19,118
Short-term marketable securities		49,974			—				49,974
Prepaid expenses and other current assets		3,874			—				3,874
Total current assets		72,966			—				72,966
Property and equipment, net		7,181			—				7,181
Operating lease right-of-use asset		18,061			—				18,061
Long-term marketable securities		1,899			—				1,899
Long-term restricted cash		896			—				896
Other long-term assets		5			—				5
Total assets	$	101,008		$	—			$	101,008
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	1,449		$	—			$	1,449
Accrued compensation		1,652			—				1,652
Accrued and other current liabilities		5,417			—				5,417
Current portion of long-term debt		13,704			(81	)	c		13,623
Total current liabilities		22,222			(81	)			22,141
Operating lease liability, net of current portion		25,297			—				25,297
Long-term debt, net		4,082			(15	)	c		4,067
Warrant liability		—			8,734		a		8,734
Total liabilities		51,601			8,638				60,239
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—				—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of June 30, 2023; 14,595,477 shares issued and outstanding as of June 30, 2023		1			—				1
Additional paid-in capital		532,563			(26,431	)	a,d		506,132
Accumulated other comprehensive loss		(136	)		—				(136	)
Accumulated deficit		(483,021	)		17,793		a,c,d		(465,228	)
Total stockholders’ equity		49,407			(8,638	)			40,769
Total liabilities and stockholders’ equity	$	101,008		$	—			$	101,008


	September 30, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Assets
Current assets:
Cash and cash equivalents	$	7,876		$	—			$	7,876
Short-term marketable securities		38,063			—				38,063
Prepaid expenses and other current assets		3,599			—				3,599
Total current assets		49,538			—				49,538
Property and equipment, net		5,314			—				5,314
Operating lease right-of-use asset		13,522			—				13,522
Long-term restricted cash		896			—				896
Total assets	$	69,270		$	—			$	69,270
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	1,149		$	—			$	1,149
Accrued compensation		2,226			—				2,226
Accrued and other current liabilities		5,258			—				5,258
Total current liabilities		8,633			—				8,633
Operating lease liability, net of current portion		24,431			—				24,431
Warrant liability		—			8,481		a		8,481
Total liabilities		33,064			8,481				41,545
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—				—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of September 30, 2023; 14,614,890 shares issued and outstanding as of September 30, 2023		1			—				1
Additional paid-in capital		534,570			(26,781	)	a,d		507,789
Accumulated other comprehensive loss		(55	)		—				(55	)
Accumulated deficit		(498,310	)		18,300		a,d		(480,010	)
Total stockholders’ equity		36,206			(8,481	)			27,725
Total liabilities and stockholders’ equity	$	69,270		$	—			$	69,270

Quarterly and Year to Date Statements of Operations and Comprehensive Loss


	Three Months Ended September 30, 2022 (unaudited)										Nine Months Ended September 30, 2022 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated			As Previously Reported			Adjustment			Reference	As Restated
Licensing revenue - related party	$	—		$	—			$	—		$	236		$	—			$	236
Operating expenses:
Research and development		8,208			878		b		9,086			28,222			878		b		29,100
General and administrative		4,922			—				4,922			15,669			—				15,669
Total operating expenses		13,130			878				14,008			43,891			878				44,769
Loss from operations		(13,130	)		(878	)			(14,008	)		(43,655	)		(878	)			(44,533	)
Interest income		329			—				329			416			—				416
Interest expense		(866	)		—				(866	)		(2,568	)		—				(2,568	)
Gain (loss) on warrant liability		—			10,974		a		10,974			—			10,974		a		10,974
Other expense, net		(41	)		(1,385	)	a		(1,426	)		49			(1,385	)	a		(1,336	)
Net loss		(13,708	)		8,711				(4,997	)		(45,758	)		8,711				(37,047	)
Other comprehensive loss
Unrealized loss on marketable debt securities		(88	)		—				(88	)		(231	)		—				(231	)
Comprehensive loss	$	(13,796	)	$	8,711			$	(5,085	)	$	(45,989	)	$	8,711			$	(37,278	)
Net loss per share, basic and diluted	$	(1.36	)	$	—			$	(0.50	)	$	(5.77	)	$	—			$	(4.67	)
Weighted average number of shares used in computing net loss per share, basic and diluted		10,072,077			—				10,072,077			7,928,729			—				7,928,729


	Three Months Ended March 31, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Operating expenses:
Research and development		5,835			(75	)	d		5,760
General and administrative		4,818			(20	)	d		4,798
Total operating expenses		10,653			(95	)			10,558
Loss from operations		(10,653	)		95				(10,558	)
Interest income		855			—				855
Interest expense		(1,002	)		—				(1,002	)
Gain (loss) on warrant liability		—			5,491		a		5,491
Other expense, net		(65	)		—				(65	)
Net loss		(10,865	)		5,586				(5,279	)
Other comprehensive gain
Unrealized gain on marketable debt securities		101			—				101
Comprehensive loss	$	(10,764	)	$	5,586			$	(5,178	)
Net loss per share, basic and diluted	$	(0.76	)	$	—			$	(0.37	)
Weighted average number of shares used in computing net loss per share, basic and diluted		14,312,887			—				14,312,887


	Three Months Ended June 30, 2023 (unaudited)										Six Months Ended June 30, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated			As Previously Reported			Adjustment			Reference	As Restated
Licensing revenue - related party	$	—		$	—			$	—		$	—		$	—			$	—
Operating expenses:
Research and development		6,529			(94	)	d		6,435			12,364			(169	)	d		12,195
General and administrative		5,433			(20	)	d		5,413			10,252			(40	)	d		10,212
Total operating expenses		11,962			(114	)			11,848			22,616			(209	)			22,407
Loss from operations		(11,962	)		114				(11,848	)		(22,616	)		209				(22,407	)
Interest income		805			—				805			1,660			—				1,660
Interest expense		(979	)		96		c		(883	)		(1,981	)		96		c		(1,885	)
Gain (loss) on warrant liability		—			(3,461	)	a		(3,461	)		—			2,030		a		2,030
Other expense, net		(69	)		—				(69	)		(133	)		—				(133	)
Net loss		(12,205	)		(3,251	)			(15,456	)		(23,070	)		2,335				(20,735	)
Other comprehensive gain
Unrealized gain on marketable debt securities		14			—				14			115			—				115
Comprehensive loss	$	(12,191	)	$	(3,251	)		$	(15,442	)	$	(22,955	)	$	2,335			$	(20,620	)
Net loss per share, basic and diluted	$	(0.85	)	$	—			$	(1.07	)	$	(1.61	)	$	—			$	(1.44	)
Weighted average number of shares used in computing net loss per share, basic and diluted		14,425,775			—				14,425,775			14,369,643			—				14,369,643


	Three Months Ended September 30, 2023 (unaudited)										Nine Months Ended September 30, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated			As Previously Reported			Adjustment			Reference	As Restated
Operating expenses:
Research and development		4,901			(269	)	d		4,632			17,266			(438	)	d		16,828
General and administrative		4,428			(81	)	d		4,347			14,681			(121	)	d		14,560
Impairment of long-lived assets		5,602			—				5,602			5,602			—				5,602
Total operating expenses		14,931			(350	)			14,581			37,549			(559	)			36,990
Loss from operations		(14,931	)		350				(14,581	)		(37,549	)		559				(36,990	)
Interest income		689			—				689			2,349			—				2,349
Interest expense		(470	)		(96	)	c		(566	)		(2,451	)		—				(2,451	)
Gain (loss) on warrant liability		—			253		a		253			—			2,283		a		2,283
Other expense, net		(577	)		—				(577	)		(711	)		—				(711	)
Net loss		(15,289	)		507				(14,782	)		(38,362	)		2,842				(35,520	)
Other comprehensive gain
Unrealized gain on marketable debt securities		81			—				81			196			—				196
Comprehensive loss	$	(15,208	)	$	507			$	(14,701	)	$	(38,166	)	$	2,842			$	(35,324	)
Net loss per share, basic and diluted	$	(1.05	)	$	—			$	(1.01	)	$	(2.66	)	$	—			$	(2.46	)
Weighted average number of shares used in computing net loss per share, basic and diluted		14,598,218			—				14,598,218			14,446,672			—				14,446,672

Statements of Changes in Stockholders' Equity


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at June 30, 2022		6,958,494	$	1	$	472,193		$	(187	)	$	(432,076	)	$	39,931
Issuance of common stock, net of issuance costs, under ATM equity offering program		633,464		—		8,570			—			—			8,570
Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs		6,428,571		—		41,650			—			—			41,650
Vesting of restricted stock units		15,720		—		—			—			—			—
Stock-based compensation		—		—		2,210			—			—			2,210
Unrealized loss on available-for-sale marketable securities		—		—		—			(88	)		—			(88	)
Net loss		—		—		—			—			(13,708	)		(13,708	)
Balances at September 30, 2022		14,036,249	$	1	$	524,623		$	(275	)	$	(445,784	)	$	78,565

Adjustment
Balances at June 30, 2022		—	$	—	$	—		$	—		$	—		$	—
Issuance of common stock, net of issuance costs, under ATM equity offering program		—		—		—			—			—			—
Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs		—		—		(26,222	)		—			—			(26,222	)
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		—			—			—			—
Unrealized loss on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			8,711			8,711
Balances at September 30, 2022		—	$	—	$	(26,222	)	$	—		$	8,711		$	(17,511	)

As Restated
Balances at June 30, 2022		6,958,494	$	1	$	472,193		$	(187	)	$	(432,076	)	$	39,931
Issuance of common stock, net of issuance costs, under ATM equity offering program		633,464		—		8,570			—			—			8,570
Sale of common stock under Follow-On Offering, net of issuance costs		6,428,571		—		15,428			—			—			15,428
Vesting of restricted stock units		15,720		—		—			—			—			—
Stock-based compensation		—		—		2,210			—			—			2,210
Unrealized loss on available-for-sale marketable securities		—		—		—			(88	)		—			(88	)
Net loss		—		—		—			—			(4,997	)		(4,997	)
Balances at September 30, 2022		14,036,249	$	1	$	498,401		$	(275	)	$	(437,073	)	$	61,054


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at December 31, 2022		14,215,302	$	1	$	527,049		$	(251	)	$	(459,951	)	$	66,848
Issuance of common stock, net of issuance costs, under ATM equity offering program		106,781		—		274			—			—			274
Vesting of restricted stock units		37,131		—		—			—			—			—
Stock-based compensation		—		—		2,270			—			—			2,270
Unrealized gain on available-for-sale marketable securities		—		—		—			101			—			101
Net loss		—		—		—			—			(10,865	)		(10,865	)
Balances at March 31, 2023		14,359,214	$	1	$	529,593		$	(150	)	$	(470,816	)	$	58,628

Adjustment
Balances at December 31, 2022		—	$	—	$	(26,222	)	$	—		$	15,458		$	(10,764	)
Issuance of common stock, net of issuance costs, under ATM equity offering program		—		—		—			—			—			—
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		(95	)		—			—			(95	)
Unrealized loss on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			5,586			5,586
Balances at March 31, 2023		—	$	—	$	(26,317	)	$	—		$	21,044		$	(5,273	)

As Restated
Balances at December 31, 2022		14,215,302	$	1	$	500,827		$	(251	)	$	(444,493	)	$	56,084
Issuance of common stock, net of issuance costs, under ATM equity offering program		106,781		—		274			—			—			274
Vesting of restricted stock units		37,131		—		—			—			—			—
Stock-based compensation		—		—		2,175			—			—			2,175
Unrealized gain on available-for-sale marketable securities		—		—		—			101			—			101
Net loss		—		—		—			—			(5,279	)		(5,279	)
Balances at March 31, 2023		14,359,214	$	1	$	503,276		$	(150	)	$	(449,772	)	$	53,355


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at March 31, 2023		14,359,214	$	1	$	529,593		$	(150	)	$	(470,816	)	$	58,628
Issuance of common stock, net of issuance costs, under ATM equity offering program		168,000		—		518			—			—			518
Issuance of common stock under 2018 ESPP		41,497		—		91			—			—			91
Vesting of restricted stock units		26,766		—		—			—			—			—
Stock-based compensation		—		—		2,361			—			—			2,361
Unrealized gain on available-for-sale marketable securities		—		—		—			14			—			14
Net loss		—		—		—			—			(12,205	)		(12,205	)
Balances at June 30, 2023		14,595,477	$	1	$	532,563		$	(136	)	$	(483,021	)	$	49,407

Adjustment
Balances at March 31, 2023		—	$	—	$	(26,317	)	$	—		$	21,044		$	(5,273	)
Issuance of common stock, net of issuance costs, under ATM equity offering program		—		—		—			—			—			—
Issuance of common stock under 2018 ESPP		—		—		—			—			—			—
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		(114	)		—			—			(114	)
Unrealized gain on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			(3,251	)		(3,251	)
Balances at June 30, 2023		—	$	—	$	(26,431	)	$	—		$	17,793		$	(8,638	)

As Restated
Balances at March 31, 2023		14,359,214	$	1	$	503,276		$	(150	)	$	(449,772	)	$	53,355
Issuance of common stock, net of issuance costs, under ATM equity offering program		168,000		—		518			—			—			518
Issuance of common stock under 2018 ESPP		41,497		—		91			—			—			91
Vesting of restricted stock units		26,766		—		—			—			—			—
Stock-based compensation		—		—		2,247			—			—			2,247
Unrealized gain on available-for-sale marketable securities		—		—		—			14			—			14
Net loss		—		—		—			—			(15,456	)		(15,456	)
Balances at June 30, 2023		14,595,477	$	1	$	506,132		$	(136	)	$	(465,228	)	$	40,769


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at June 30, 2023		14,595,477	$	1	$	532,563		$	(136	)	$	(483,021	)	$	49,407
Fees related to the ATM offering program		—		—		(48	)		—			—			(48	)
Vesting of restricted stock units		19,413		—		—			—			—			—
Stock-based compensation		—		—		2,055			—			—			2,055
Unrealized gain on available-for-sale marketable securities		—		—		—			81			—			81
Net loss		—		—		—			—			(15,289	)		(15,289	)
Balances at September 30, 2023		14,614,890	$	1	$	534,570		$	(55	)	$	(498,310	)	$	36,206

Adjustment
Balances at June 30, 2023		—	$	—	$	(26,431	)	$	—		$	17,793		$	(8,638	)
Fees related to the ATM offering program		—		—		—			—			—			—
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		(350	)		—			—			(350	)
Unrealized gain on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			507			507
Balances at September 30, 2023		—	$	—	$	(26,781	)	$	—		$	18,300		$	(8,481	)

As Restated
Balances at June 30, 2023		14,595,477	$	1	$	506,132		$	(136	)	$	(465,228	)	$	40,769
Fees related to the ATM offering program		—		—		(48	)		—			—			(48	)
Vesting of restricted stock units		19,413		—		—			—			—			—
Stock-based compensation		—		—		1,705			—			—			1,705
Unrealized gain on available-for-sale marketable securities		—		—		—			81			—			81
Net loss		—		—		—			—			(14,782	)		(14,782	)
Balances at September 30, 2023		14,614,890	$	1	$	507,789		$	(55	)	$	(480,010	)	$	27,725

Statements of Cash Flows


	Nine Months Ended September 30, 2022
	As Previously Reported			Adjustment			Reference	As Restated
Operating activities
Net loss	$	(45,758	)	$	8,711		a,b	$	(37,047	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		1,771			—				1,771
Amortization of debt issuance costs		989			—				989
Debt extinguishment gain upon conversion to equity		(199	)		—				(199	)
Net accretion and amortization of premium and discounts on marketable securities		155			—				155
Gain on disposal of property and equipment		(247	)		—				(247	)
Stock-based compensation		7,120			—				7,120
Non-cash rent expense		(1,891	)		—				(1,891	)
(Gain) loss on warrant liability		—			(10,974	)	a		(10,974	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(1,355	)		150		b		(1,205	)
Other long-term assets		15			—				15
Accounts payable		459			—				459
Accrued compensation		(1,067	)		—				(1,067	)
Accrued liabilities and other current liabilities		(632	)		728		b		96
Other long-term liabilities		(23	)		—				(23	)
Net cash used in operating activities		(40,663	)		(1,385	)			(42,048	)
Investing activities
Purchase of marketable securities		(86,567	)		—				(86,567	)
Maturities of marketable securities		62,000			—				62,000
Purchase of property and equipment		(59	)		—				(59	)
Sale of property and equipment		272			—				272
Net cash used in investing activities		(24,354	)		—				(24,354	)
Financing activities
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		12,003			—				12,003
Proceeds from sale of common stock and warrants under Follow-On Offering		41,650			3,350		a		45,000
Issuance costs for sale of common stock		—			(1,965	)	a		(1,965	)
Proceeds from issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		910			—				910
Proceeds from issuance of common stock under 2018 ESPP		125			—				125
Net cash provided by financing activities		54,688			1,385				56,073
Net decrease in cash, cash equivalents and restricted cash		(10,329	)		—				(10,329	)
Cash, cash equivalents and restricted cash at beginning of the period		34,351			—				34,351
Cash, cash equivalents and restricted cash at end of the period	$	24,022		$	—			$	24,022
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	1,577		$	—			$	1,577
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt	$	3,179		$	—			$	3,179

Cash and cash equivalents	$	22,576		$	—			$	22,576
Restricted cash		1,446			—			$	1,446
Total cash, cash equivalents and restricted cash	$	24,022		$	—			$	24,022


	Three Months Ended March 31, 2023
	As Previously Reported			Adjustment			Reference	As Restated
Operating activities
Net loss	$	(10,865	)	$	5,586		a,d	$	(5,279	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		329			—				329
Amortization of debt issuance costs		314			—				314
Net accretion and amortization of premium and discounts on marketable securities		(433	)		—				(433	)
Stock-based compensation		2,270			(95	)	d		2,175
Non-cash rent expense		(270	)		—				(270	)
(Gain) loss on warrant liability		—			(5,491	)	a		(5,491	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(1,249	)		—				(1,249	)
Other long-term assets		23			—				23
Accounts payable		(320	)		—				(320	)
Accrued compensation		(1,037	)		—				(1,037	)
Accrued liabilities and other current liabilities		(78	)		—				(78	)
Net cash used in operating activities		(11,316	)		—				(11,316	)
Investing activities
Purchase of marketable securities		(5,973	)		—				(5,973	)
Maturities of marketable securities		27,251			—				27,251
Net cash provided by investing activities		21,278			—				21,278
Financing activities
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		274			—				274
Net cash provided by financing activities		274			—				274
Net increase in cash, cash equivalents and restricted cash		10,236			—				10,236
Cash, cash equivalents and restricted cash at beginning of the period		13,632			—				13,632
Cash, cash equivalents and restricted cash at end of the period	$	23,868		$	—			$	23,868
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	680		$	—			$	680

Cash and cash equivalents	$	22,972		$	—			$	22,972
Restricted cash		896			—			$	896
Total cash, cash equivalents and restricted cash	$	23,868		$	—			$	23,868


	Six Months Ended June 30, 2023
	As Previously Reported			Adjustment			Reference	As Restated
Operating activities
Net loss	$	(23,070	)	$	2,335		a,c,d	$	(20,735	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		643			—				643
Amortization of debt issuance costs		653			(96	)	c		557
Net accretion and amortization of premium and discounts on marketable securities		(831	)		—				(831	)
Stock-based compensation		4,631			(209	)	d		4,422
Non-cash rent expense		(540	)		—				(540	)
(Gain) loss on warrant liability		—			(2,030	)	a		(2,030	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(2,134	)		—				(2,134	)
Other long-term assets		47			—				47
Accounts payable		(341	)		—				(341	)
Accrued compensation		(1,368	)		—				(1,368	)
Accrued liabilities and other current liabilities		(89	)		—				(89	)
Net cash used in operating activities		(22,399	)		—				(22,399	)
Investing activities
Purchase of marketable securities		(21,868	)		—				(21,868	)
Maturities of marketable securities		53,000			—				53,000
Net cash provided by investing activities		31,132			—				31,132
Financing activities
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		792			—				792
Repayment of term loan debt		(3,234	)		—				(3,234	)
Proceeds from issuance of common stock under 2018 ESPP		91			—				91
Net cash used in financing activities		(2,351	)		—				(2,351	)
Net increase in cash, cash equivalents and restricted cash		6,382			—				6,382
Cash, cash equivalents and restricted cash at beginning of the period		13,632			—				13,632
Cash, cash equivalents and restricted cash at end of the period	$	20,014		$	—			$	20,014
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	1,362		$	—			$	1,362

Cash and cash equivalents	$	19,118		$	—			$	19,118
Restricted cash		896			—			$	896
Total cash, cash equivalents and restricted cash	$	20,014		$	—			$	20,014


	Nine Months Ended September 30, 2023
	As Previously Reported			Adjustment			Reference	As Restated
Operating activities
Net loss	$	(38,362	)	$	2,842		a,d	$	(35,520	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		951			—				951
Amortization of debt issuance costs		705			—				705
Debt extinguishment loss upon paydown of principal		491			—				491
Net accretion and amortization of premium and discounts on marketable securities		(1,199	)		—				(1,199	)
Stock-based compensation		6,686			(559	)	d		6,127
Non-cash rent expense		(811	)		—				(811	)
Impairment of long-lived assets		5,602			—				5,602
(Gain) loss on warrant liability		—			(2,283	)	a		(2,283	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(1,858	)		—				(1,858	)
Other long-term assets		52			—				52
Accounts payable		(642	)		—				(642	)
Accrued compensation		(793	)		—				(793	)
Accrued liabilities and other current liabilities		(335	)		—				(335	)
Net cash used in operating activities		(29,513	)		—				(29,513	)
Investing activities
Purchase of marketable securities		(28,609	)		—				(28,609	)
Maturities of marketable securities		74,000			—				74,000
Purchase of property and equipment		(11	)		—				(11	)
Sale of property and equipment		1			—				1
Net cash provided by investing activities		45,381			—				45,381
Financing activities
Payment of debt principal		(20,000	)		—				(20,000	)
Payment of debt issuance costs		(1,563	)		—				(1,563	)
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		744			—				744
Proceeds from issuance of common stock under 2018 ESPP		91			—				91
Net cash used in financing activities		(20,728	)		—				(20,728	)
Net decrease in cash, cash equivalents and restricted cash		(4,860	)		—				(4,860	)
Cash, cash equivalents and restricted cash at beginning of the period		13,632			—				13,632
Cash, cash equivalents and restricted cash at end of the period	$	8,772		$	—			$	8,772
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	1,969		$	—			$	1,969

Cash and cash equivalents	$	7,876		$	—			$	7,876
Restricted cash		896			—			$	896
Total cash, cash equivalents and restricted cash	$	8,772		$	—			$	8,772

Fair Value Measurements - Sumarry of Roll forward of the fair value of level 3 Warrants (Details) - Warrant Liability - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning balance	$ 10,765
Warrants Issued	2,724	$ 27,607
Warrants Exercised	(1,361)
Change in fair value	(6,215)	(16,842)
Ending balance	$ 5,913	$ 10,765

Stock-Based Compensation - Additional Information (Details)			1 Months Ended							6 Months Ended	12 Months Ended
	May 11, 2023 USD ($) Employee $ / shares shares	May 04, 2023 $ / shares	Feb. 28, 2022 USD ($) Position shares	Jun. 30, 2021 USD ($) shares	Jan. 31, 2021 USD ($) $ / shares shares	Sep. 30, 2020 shares	Mar. 31, 2020 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) shares	Jun. 30, 2013	Feb. 28, 2018 $ / shares	Dec. 31, 2023 USD ($) Employee $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($)	Sep. 30, 2023 shares	Jun. 30, 2023 shares	Mar. 31, 2023 shares	Feb. 28, 2023 shares	Sep. 30, 2022 shares	Nov. 30, 2020 shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock, shares authorized											300,000,000	300,000,000		300,000,000	300,000,000	300,000,000		300,000,000
Intrinsic value of options exercised \| $											$ 0	$ 0
Weighted-average estimated fair value of stock options granted \| $ / shares											$ 2.79	$ 3.11
Exercisable, aggregate intrinsic value \| $											$ 0	$ 0
Number of shares authorized for issuance						320,000
Number of shares options granted to purchase an aggregate of common stock											446,200
Settlement of stock based compensation for liability awards											0	0
Incremental fair value on modification date \| $											$ 300,000	$ 0	$ 0
Stock option awards outstanding											1,913,345	1,609,938
Stock option awards, grant date fair value \| $											$ 5,000	$ 251,000
Stock-based compensation expense \| $											$ 7,419,000	9,379,000	11,553,000
Restructuring implementation date		May 04, 2023
Number of employees terminated \| Employee											5
Expected number of employees terminated			29								9
2018 Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance								53,624
Option purchase date price percentage lower of closing trading price per share								85.00%
Employees subscription rate during the offering period								15.00%
Maximum number of shares may be purchased by an employee								15,000
Maximum fair market value of shares may be purchased by an employee \| $								$ 25,000
Non Employee
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock-based compensation expense \| $											$ 400,000	200,000	$ 400,000
Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period, options						4 years
Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period, options						3 years
Performance and Market Contingent Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Trailing period				30 days
Stock option awards outstanding											3,336
Stock option awards, grant date fair value \| $											$ 100,000
Modification date fair value \| $				$ 102,000	$ 81,000
Implied service period for recognition				1 year 10 months 6 days
Performance and Market Contingent Stock Options \| Executive Team
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock option awards exercisable upon the achievement of performance goals				3,336	1,747
Performance and Market Contingent Stock Options \| Tranche One
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Volume-weighted average per Share closing trading price \| $ / shares					$ 180
Trailing period					30 days
Performance and Market Contingent Stock Options \| Tranche Two
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Volume-weighted average per Share closing trading price \| $ / shares					$ 360
Trailing period					30 days
Performance and Market Contingent Stock Options \| Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Implied service period for recognition					2 years 6 months 7 days
Performance and Market Contingent Stock Options \| Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Implied service period for recognition					1 year 5 months 15 days
Attaining valuation of certain amount \| $				$ 1,000,000,000
Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares authorized for issuance						25,000
Number of retention awards granted			189,333
Retention award grant date total fair value \| $			$ 2,000,000
RSUs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares authorized for issuance						295,985
Number of retention awards granted			46,332
Retention award grant date total fair value \| $			$ 500,000
RSUs and RSAs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total grant-date fair value of stock vested \| $											300,000	$ 600,000
Stock Options and RSAs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock-based compensation cost not yet amortized \| $											$ 3,900,000
Weighted-average period for recognition											10 months 24 days
2018 Incentive Award Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance								428,994
Vesting period, options								4 years
Common stock, shares authorized											2,182,500
2018 Incentive Award Plan \| Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period from the date of grant, options								10 years
2018 Incentive Award Plan \| Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Exercise price as a percentage of estimated fair value of the shares on the date of grant								100.00%
2020 Employment Inducement Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance							110,000										300,000		150,000
Vesting period, options							4 years
Common stock, shares authorized											542,000
2020 Employment Inducement Incentive Plan \| New Chief Executive Officer
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of common stock shares granted							110,000
2020 Employment Inducement Incentive Plan \| Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period from the date of grant, options							10 years
2020 Employment Inducement Incentive Plan \| Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Exercise price as a percentage of estimated fair value of the shares on the date of grant							100.00%
2020 Employment Inducement Incentive Plan \| PSUs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted-average period for recognition							4 years 3 months 18 days
Grant date fair value \| $							$ 700,000
Incremental fair value on modification date \| $					$ 31,000
Unamortized value of original grant \| $					$ 569,000
2020 Employment Inducement Incentive Plan \| PSUs \| New Chief Executive Officer
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of common stock shares granted							15,000
2020 Employment Inducement Incentive Plan \| PSUs \| Tranche One
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares to vest upon attainment of certain conditions					5,000		5,000
Volume-weighted average per Share closing trading price \| $ / shares					$ 180		$ 368.75
Trailing period					30 days		30 days
2020 Employment Inducement Incentive Plan \| PSUs \| Tranche Two
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares to vest upon attainment of certain conditions					10,000		10,000
Volume-weighted average per Share closing trading price \| $ / shares					$ 180
Trailing period					30 days		30 days
Price per share to holders of company's common stock \| $ / shares					$ 360		$ 368.75
Market capitalization trigger \| $							$ 2,500,000,000
2020 Employment Inducement Incentive Plan \| PSUs \| Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
New implied service period for recognition							2 years 9 months 14 days
2020 Employment Inducement Incentive Plan \| PSUs \| Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
New implied service period for recognition							1 year 7 months 17 days
2020 Employment Inducement Incentive Plan \| Stock Options \| New Chief Executive Officer
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares options granted to purchase an aggregate of common stock							80,000
2020 Employment Inducement Incentive Plan \| RSUs \| New Chief Executive Officer
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of common stock shares granted							12,000
2020 Employment Inducement Incentive Plan \| Restricted Stock Awards \| New Chief Executive Officer
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of common stock shares granted							3,000
2013 Equity Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period, options									4 years
Exercise price of an ISO and NSO granted to a stockholder, percentage									10.00%
Exercise price \| $ / shares										$ 3.42
Exercise price range, lower range limit \| $ / shares										3.95
Exercise price range, upper range limit \| $ / shares										$ 8.47
2013 Equity Incentive Plan \| Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period from the date of grant, options									10 years
2013 Equity Incentive Plan \| Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Exercise price as a percentage of estimated fair value of the shares on the date of grant									100.00%
Exercise price as a percentage of estimated grant date fair value of shares for a 10% shareholder									110.00%
2018 Incentive Award Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Exercise price \| $ / shares	$ 2.77	$ 6
Number of employees who met the eligibility terms \| Employee	26
Number of shares of common stock under option grants that met the eligibility criteria	444,273
Additional stock-based compensation from vested options \| $	$ 200,000
Number of vested options	251,821
Anticipated additional amount expensed \| $	$ 100,000
Number of unvested options	170,189

Income Taxes - Schedule of Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits at January 1	$ 17,605	$ 13,221	$ 7,142
Additions for tax positions taken in the current year	84	4,395	3,457
Reductions for tax positions taken in the prior year			2,622
Reductions for tax positions taken in the prior year	(232)	(11)
Gross unrecognized tax benefits at December 31	$ 17,457	$ 17,605	$ 13,221

Term Loan Facility

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Term Loan Facility

10. Term Loan Facility

On August 3, 2020, the Company entered into a Loan and Security Agreement (as amended, restated, supplemented or otherwise modified, the "Hercules Loan Agreement") with Hercules Capital, Inc. (“Hercules”), as administrative agent and collateral agent for the lenders, and certain banks and other financial institutions or entities from time to

time parties thereto, for an aggregate principal amount of up to $80.0 million secured term loan facility (the "Hercules Facility") subject to certain terms and conditions. The first tranche of $25.0 million was advanced to the Company on the date the Loan Agreement was executed. The maturity date under the Hercules Loan Agreement was August 1, 2024.

On September 6, 2023, the Company and Hercules entered into a payoff letter for a voluntary prepayment with respect to the Hercules Loan Agreement (the “Payoff Letter”). Pursuant to the Payoff Letter, the Company paid a total of $15.0 million to Hercules, representing the outstanding principal, accrued and unpaid interest, fees, costs and expenses due to Hercules under the Hercules Facility and the Hercules Loan Agreement and related loan documents, in repayment of the Company’s outstanding obligations under the Hercules Facility and the Hercules Loan Agreement and related loan documents, and thereby terminated the Hercules Loan Agreement and the Hercules Facility and related loan documents. Under the terms of the Hercules Loan Agreement, no early termination penalty was payable as a result of such prepayment and termination as of such date. The Company recorded a loss on extinguishment of debt of $0.5 million under "Other expense, net" in the financial statements for the year ended December 31, 2023 related to the write-off of the remaining balance of unamortized debt discount.

Pursuant to the Payoff Letter, the lenders’ commitments to extend further credit to the Company terminated. Hercules released and terminated all liens or security interests granted to secure the obligations under the Hercules Loan Agreement and the Company was unconditionally released from its respective guaranties and obligations under the Hercules Facility and the Hercules Loan Agreement and related loan documents without further action (other than with respect to customary provisions and agreements that are expressly specified to survive the termination). Hercules returned to the Company, for the benefit of the Company, all of the collateral that it had in its possession.

Interest expense relating to the term loan, which is included in interest expense in the Statements of Operations and Comprehensive Loss was $2.5 million, $3.6 million and $3.2 million for the years ended December 31, 2023, 2022 and 2021, respectively.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Summary of Significant Accounting Policies - Additional Information (Details)		12 Months Ended
	Oct. 19, 2022	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Reverse stock split ratio	0.1
Number of operating segment \| Segment		1
Off-balance sheet concentrations of credit risk description		As of December 31, 2023 and 2022, the Company had no off-balance sheet concentrations of credit risk.
Off-balance sheet concentrations of credit risk		$ 0	$ 0
Impairment loss		$ 5,600,000
ASU 2016-13
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Change in accounting principle, accounting standards update, adopted [true false]		true
Accounting standards, adoption date		Jan. 01, 2023
Change in accounting principle, accounting standards update, immaterial effect [true false]		true
ASU 2021-10
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Change in accounting principle, accounting standards update, adopted [true false]		true
Accounting standards, adoption date		Jan. 01, 2023

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):


	December 31,
	2023		2022
Prepaid research and development expenses	$	415	$	378
Prepaid insurance expenses		541		710
Tax credit receivable		1,493		—
Interest receivable		84		235
Other prepaid expenses and current assets		871		417
	$	3,404	$	1,740

Schedule of Property and Equipment, Net

Property and equipment, net, consists of the following (in thousands):


	December 31,
	2023			2022
Laboratory equipment	$	3,894		$	4,197
Computer equipment		303			412
Furniture and fixtures		627			726
Leasehold improvements		9,519			15,244
Total property and equipment		14,343			20,579
Less: accumulated depreciation and amortization		(9,261	)		(12,754	)
Total property and equipment, net	$	5,082		$	7,825

Schedule of Accrued and Other Current Liabilities

Accrued and other current liabilities consist of the following (in thousands):


	December 31,
	2023		2022
Operating lease liability - current portion	$	3,451	$	3,100
Accrued research and development		839		1,623
Liability related to early exercise shares		10		10
Accrued other		319		601
	$	4,619	$	5,334

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Summary of Components of Lease Expense

The following table summarizes the components of lease expense, which are included in operating expenses in the Company’s Statements of Operations and Comprehensive Loss (in thousands):


	Year ended December 31,
	2023			2022			2021
Operating lease expense	$	3,739		$	4,264		$	4,357
Variable lease expense		748			1,318			1,633
Sublease income		(3,988	)		(4,317	)		(2,578	)
Total lease expense	$	499		$	1,265		$	3,412

Summary of Supplemental Information Related to Operating Leases

The following table summarizes supplemental information related to operating leases (in thousands):


	Year ended December 31,
	2023			2022			2021
Cash paid for amounts included in the measurement of lease liabilities	$	4,810		$	6,283		$	6,653
Weighted-average remaining lease term (years)		6.0			7.0			7.7
Weighted-average discount rate (percentage)		6.0	%		6.0	%		5.9	%

Summary of Maturities of Lease Liabilities

The following table summarizes the maturities of lease liabilities as of December 31, 2023 (in thousands):


	Amount
2024	$	4,964
2025		5,123
2026		5,287
2027		5,457
2028		5,633
Thereafter		5,801
Total future minimum lease payments		32,265
Less: Amount representing interest		(5,275	)
Present value of future minimum lease payments		26,990
Less: Current portion of operating lease liability		(3,451	)
Noncurrent portion of operating lease liability	$	23,539

Related-Party Transactions - Additional Information (Details) - License Agreement - Jocasta Neuroscience, Inc. - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Upfront cash payments received			$ 5,000,000
Deferred revenue recognized	$ 0	$ 200,000	$ 4,800,000

Term Loan Facility - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 06, 2023	Aug. 03, 2020
Debt Instrument [Line Items]
Loss on extinguishment of debt								$ (500)
Interest expense	$ 566	$ 883	$ 1,002	$ 866	$ 1,885	$ 2,451	$ 2,568	2,452	$ 3,558	$ 3,177
Term Loan \| Loan Agreement \| Hercules Capital \| Interest And Other Expense
Debt Instrument [Line Items]
Interest expense								$ 2,500	$ 3,600	$ 3,200
Term Loan \| Payoff Letter Loan Agreement \| Hercules Capital
Debt Instrument [Line Items]
Debt payoff amount											$ 15,000
Secured Term Loan Facility \| Loan Agreement \| Hercules Capital
Debt Instrument [Line Items]
Principal amount of first tranche												$ 25,000
Long-term debt, maturity date												Aug. 01, 2024
Secured Term Loan Facility \| Loan Agreement \| Hercules Capital \| Maximum
Debt Instrument [Line Items]
Debt instrument aggregate principal amount												$ 80,000

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1.2	$ 2.2	$ 2.9

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Cash and cash equivalents	$ 19,803	$ 7,876	$ 19,118	$ 22,972	$ 12,736	$ 22,576	$ 32,905
Restricted cash	896				896		1,446
Total cash, cash equivalents, and restricted cash	$ 20,699	$ 8,772	$ 20,014	$ 23,868	$ 13,632	$ 24,022	$ 34,351	$ 19,253

Marketable Securities - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Realized gains or losses on available-for-sale debt securities	$ 0	$ 0
Allowance for credit loss	$ 0
Maximum
Marketable Securities [Line Items]
Available-for sale securities, remaining contractual maturity	1 year

Restatement of Previously Issued Financial Statements - Schedule of Restated Statement of Changes in Stockholders' Equity (Details) - USD ($)
$ in Thousands

1 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

16 Months Ended

Aug. 31, 2022

Sep. 30, 2021

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Sep. 30, 2022

Jun. 30, 2023

Sep. 30, 2023

Sep. 30, 2022

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Dec. 31, 2022

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance, (in shares)

14,595,477

14,359,214

14,215,302

Beginning balance

$ 40,769

$ 53,355

$ 56,084

$ 39,931

$ 56,084

$ 59,569

$ 56,084

$ 59,569

$ 82,881

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

116

142

347

Stock-based compensation

1,705

2,247

2,175

2,210

7,419

9,379

11,553

Unrealized (gain) loss on available-for-sale marketable securities

101

(88)

227

(207)

(49)

Net gain (loss)

$ (14,782)

$ (15,456)

$ (5,279)

$ (4,997)

$ (20,735)

$ (35,520)

$ (37,047)

$ (39,860)

$ (44,469)

(60,725)

Ending balance, (in shares)

14,614,890

14,595,477

14,359,214

14,036,249

14,595,477

14,614,890

14,036,249

16,784,969

14,215,302

Ending balance

$ 27,725

$ 40,769

$ 53,355

$ 61,054

$ 40,769

$ 27,725

$ 61,054

$ 28,398

$ 56,084

59,569

$ 56,084

At The Market Equity Offering Program

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

$ 518

$ 274

8,570

$ 725

12,155

10,357

Equity Purchase Agreement | Lincoln Park Capital Fund LLC

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

910

9,039

Issuance of common stock (in shares)

102,040

380,000

Follow-On Offering

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

$ 15,428

15,426

Warrant Inducement Agreement

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

$ 3,687

Loan Agreement | Hercules Capital

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

$ 3,179

$ 2,704

Common Stock

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance, (in shares)

14,595,477

14,359,214

14,215,302

^[1]

6,958,494

14,215,302

^[1]

14,215,302

^[1]

6,299,158

^[1]

14,215,302

^[1]

6,299,158

^[1]

5,325,288

^[1]

Beginning balance

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)

41,497

57,419

^[1]

25,482

^[1]

11,704

^[1]

Vesting of restricted stock units, (in shares)

19,413

26,766

37,131

15,720

94,467

^[1]

90,284

^[1]

96,269

^[1]

Ending balance, (in shares)

14,614,890

14,595,477

14,359,214

14,036,249

14,595,477

14,614,890

14,036,249

16,784,969

^[1]

14,215,302

^[1]

6,299,158

^[1]

14,215,302

^[1]

Ending balance

$ 1

$ 2

^[1]

$ 1

^[1]

$ 1

^[1]

$ 1

^[1]

Common Stock | At The Market Equity Offering Program

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock (in shares)

168,000

106,781

633,464

274,781

^[1]

1,019,046

^[1]

189,453

^[1]

Common Stock | Equity Purchase Agreement | Lincoln Park Capital Fund LLC

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock (in shares)

^[1]

90,000

417,286

Common Stock | Follow-On Offering

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock (in shares)

6,428,571

^[1]

Common Stock | Warrant Inducement Agreement

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

^[1]

$ 1

Issuance of common stock (in shares)

^[1]

2,143,000

Common Stock | Loan Agreement | Hercules Capital

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock (in shares)

^[1]

262,761

172,736

Additional Paid-In Capital

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

506,132

$ 503,276

$ 500,827

$ 472,193

500,827

459,636

$ 500,827

$ 459,636

$ 422,384

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

116

142

347

Stock-based compensation

1,705

2,247

2,175

2,210

7,419

9,379

11,553

Ending balance

507,789

506,132

503,276

498,401

506,132

507,789

498,401

512,773

500,827

459,636

500,827

Additional Paid-In Capital | At The Market Equity Offering Program

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

518

274

8,570

725

12,155

10,357

Additional Paid-In Capital | Equity Purchase Agreement | Lincoln Park Capital Fund LLC

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

910

9,039

Additional Paid-In Capital | Follow-On Offering

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

15,428

15,426

Additional Paid-In Capital | Warrant Inducement Agreement

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

3,686

Additional Paid-In Capital | Loan Agreement | Hercules Capital

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

3,179

2,704

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

(210)

Ending balance

Accumulated Other Comprehensive Gain (Loss)

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

(136)

(150)

(251)

(187)

(251)

(44)

(251)

(44)

Unrealized (gain) loss on available-for-sale marketable securities

101

(88)

227

(207)

(49)

Ending balance

(55)

(136)

(150)

(275)

(136)

(55)

(275)

(24)

(251)

(44)

(251)

Accumulated Deficit

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

(465,228)

(449,772)

(444,493)

(432,076)

(444,493)

(400,024)

(444,493)

(400,024)

(339,299)

Net gain (loss)

(14,782)

(15,456)

(5,279)

(4,997)

(39,860)

(44,469)

(60,725)

Ending balance

(480,010)

(465,228)

(449,772)

(437,073)

(465,228)

(480,010)

(437,073)

(484,353)

(444,493)

(400,024)

(444,493)

As Previously Reported

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

49,407

58,628

66,848

39,931

66,848

59,569

$ 66,848

59,569

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

142

Stock-based compensation

2,055

2,361

2,270

2,210

9,379

Unrealized (gain) loss on available-for-sale marketable securities

101

(88)

(207)

Net gain (loss)

(15,289)

(12,205)

(10,865)

(13,708)

(23,070)

(38,362)

(45,758)

(59,927)

Ending balance

$ 36,206

49,407

58,628

78,565

$ 49,407

$ 36,206

$ 78,565

66,848

$ 59,569

$ 66,848

As Previously Reported | At The Market Equity Offering Program

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

$ 518

$ 274

8,570

12,155

As Previously Reported | Equity Purchase Agreement | Lincoln Park Capital Fund LLC

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

910

As Previously Reported | Follow-On Offering

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

$ 41,650

41,648

As Previously Reported | Loan Agreement | Hercules Capital

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

$ 3,179

As Previously Reported | Common Stock

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance, (in shares)

14,595,477

14,359,214

14,215,302

6,958,494

14,215,302

6,299,158

14,215,302

6,299,158

Beginning balance

$ 1

Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)

41,497

25,482

Vesting of restricted stock units, (in shares)

19,413

26,766

37,131

15,720

90,284

Ending balance, (in shares)

14,614,890

14,595,477

14,359,214

14,036,249

14,595,477

14,614,890

14,036,249

14,215,302

6,299,158

14,215,302

Ending balance

$ 1

As Previously Reported | Common Stock | At The Market Equity Offering Program

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock (in shares)

168,000

106,781

633,464

1,019,046

As Previously Reported | Common Stock | Equity Purchase Agreement | Lincoln Park Capital Fund LLC

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock (in shares)

90,000

As Previously Reported | Common Stock | Follow-On Offering

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock (in shares)

6,428,571

As Previously Reported | Common Stock | Loan Agreement | Hercules Capital

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock (in shares)

262,761

As Previously Reported | Additional Paid-In Capital

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

532,563

$ 529,593

$ 527,049

$ 472,193

527,049

459,636

527,049

$ 459,636

Issuance of common stock under employee stock purchase plan (“2018 ESPP”)

142

Stock-based compensation

2,055

2,361

2,270

2,210

9,379

Ending balance

534,570

532,563

529,593

524,623

532,563

534,570

524,623

527,049

459,636

527,049

As Previously Reported | Additional Paid-In Capital | At The Market Equity Offering Program

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

518

274

8,570

12,155

As Previously Reported | Additional Paid-In Capital | Equity Purchase Agreement | Lincoln Park Capital Fund LLC

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

910

As Previously Reported | Additional Paid-In Capital | Follow-On Offering

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

41,650

41,648

As Previously Reported | Additional Paid-In Capital | Loan Agreement | Hercules Capital

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

3,179

As Previously Reported | Accumulated Other Comprehensive Gain (Loss)

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

(136)

(150)

(251)

(187)

(251)

(44)

(251)

(44)

Unrealized (gain) loss on available-for-sale marketable securities

101

(88)

(207)

Ending balance

(55)

(136)

(150)

(275)

(136)

(55)

(275)

(251)

(44)

(251)

As Previously Reported | Accumulated Deficit

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

(483,021)

(470,816)

(459,951)

(432,076)

(459,951)

(400,024)

(459,951)

(400,024)

Net gain (loss)

(15,289)

(12,205)

(10,865)

(13,708)

(59,927)

Ending balance

(498,310)

(483,021)

(470,816)

(445,784)

(483,021)

(498,310)

(445,784)

(459,951)

$ (400,024)

(459,951)

Adjustment

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

(8,638)

(5,273)

(10,764)

Stock-based compensation

(350)

(114)

(95)

Net gain (loss)

507

(3,251)

5,586

8,711

2,335

2,842

8,711

15,458

Ending balance

(8,481)

(8,638)

(5,273)

(17,511)

(8,638)

(8,481)

(17,511)

(10,764)

Adjustment | Follow-On Offering

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

(26,222)

Adjustment | Additional Paid-In Capital

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

(26,431)

(26,317)

(26,222)

Stock-based compensation

(350)

(114)

(95)

Ending balance

(26,781)

(26,431)

(26,317)

(26,222)

(26,431)

(26,781)

(26,222)

Adjustment | Additional Paid-In Capital | Follow-On Offering

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Issuance of common stock, net of issuance costs

(26,222)

Adjustment | Accumulated Deficit

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Beginning balance

17,793

21,044

15,458

$ 15,458

Net gain (loss)

507

(3,251)

5,586

8,711

15,458

Ending balance

$ 18,300

$ 17,793

$ 21,044

$ 8,711

$ 17,793

$ 18,300

$ 8,711

$ 15,458

[1]

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows (in thousands).


	December 31,
	2023		2022		2021
Cash and cash equivalents	$	19,803	$	12,736	$	32,905
Restricted cash		896		896		1,446
Total cash, cash equivalents, and restricted cash	$	20,699	$	13,632	$	34,351

Restatement of Previously Issued Financial Statements - Schedule of Restated Balance Sheet (Details) - USD ($)
$ in Thousands

Dec. 31, 2023

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Dec. 31, 2022

Sep. 30, 2022

Jun. 30, 2022

Dec. 31, 2021

Dec. 31, 2020

Current assets:

Cash and cash equivalents

$ 19,803

$ 7,876

$ 19,118

$ 22,972

$ 12,736

$ 22,576

$ 32,905

Short-term marketable securities

23,398

38,063

49,974

60,420

82,059

76,364

Prepaid expenses and other current assets

3,404

3,599

3,874

2,989

1,740

3,084

Restricted cash

550

Total current assets

46,605

49,538

72,966

86,381

96,535

102,574

Property and equipment, net

5,082

5,314

7,181

7,496

7,825

8,202

Operating lease right-of-use asset

12,981

13,522

18,061

18,557

19,042

19,515

Long-term restricted cash

896

Other long-term assets

126

Total assets

65,690

69,270

101,008

114,255

124,350

136,243

Current liabilities:

Accounts payable

1,380

1,149

1,449

1,470

1,790

2,444

Accrued compensation

1,841

2,226

1,652

1,983

3,020

2,961

Accrued and other current liabilities

4,619

5,258

5,417

5,343

5,334

5,321

Current portion of long-term debt

13,623

13,062

9,476

6,776

Total current liabilities

7,840

8,633

22,141

21,858

19,620

17,502

Operating lease liability, net of current portion

23,539

24,431

25,297

26,150

26,991

27,792

Long-term debt, net

4,067

7,619

10,891

13,262

Warrant liability

5,913

8,481

8,734

5,273

10,764

16,633

Total liabilities

37,292

41,545

60,239

60,900

68,266

75,189

Commitments and contingencies

Stockholders’ equity:

Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding

Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2022; 14,215,302 shares issued and outstanding as of December 31, 2022

^[1]

Additional paid-in capital

512,773

507,789

506,132

503,276

500,827

498,401

Accumulated other comprehensive loss

(24)

(55)

(136)

(150)

(251)

(275)

Accumulated deficit

(484,353)

(480,010)

(465,228)

(449,772)

(444,493)

(437,073)

Total stockholders’ equity

28,398

27,725

40,769

53,355

56,084

61,054

$ 39,931

59,569

$ 82,881

Total liabilities and stockholders’ equity

$ 65,690

69,270

101,008

114,255

124,350

136,243

As Previously Reported

Current assets:

Cash and cash equivalents

7,876

19,118

22,972

12,736

22,576

Short-term marketable securities

38,063

49,974

60,420

82,059

76,364

Prepaid expenses and other current assets

3,599

3,874

2,989

1,740

3,234

Restricted cash

550

Total current assets

49,538

72,966

86,381

96,535

102,724

Property and equipment, net

5,314

7,181

7,496

7,825

8,202

Operating lease right-of-use asset

13,522

18,061

18,557

19,042

19,515

Long-term restricted cash

896

Other long-term assets

Total assets

69,270

101,008

114,255

124,350

136,393

Current liabilities:

Accounts payable

1,149

1,449

1,470

1,790

2,444

Accrued compensation

2,226

1,652

1,983

3,020

2,961

Accrued and other current liabilities

5,258

5,417

5,343

5,334

4,593

Current portion of long-term debt

13,704

13,062

9,476

6,776

Total current liabilities

8,633

22,222

21,858

19,620

16,774

Operating lease liability, net of current portion

24,431

25,297

26,150

26,991

27,792

Long-term debt, net

4,082

7,619

10,891

13,262

Warrant liability

Total liabilities

33,064

51,601

55,627

57,502

57,828

Commitments and contingencies

Stockholders’ equity:

Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding

Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2022; 14,215,302 shares issued and outstanding as of December 31, 2022

Additional paid-in capital

534,570

532,563

529,593

527,049

524,623

Accumulated other comprehensive loss

(55)

(136)

(150)

(251)

(275)

Accumulated deficit

(498,310)

(483,021)

(470,816)

(459,951)

(445,784)

Total stockholders’ equity

36,206

49,407

58,628

66,848

78,565

$ 39,931

$ 59,569

Total liabilities and stockholders’ equity

69,270

101,008

114,255

124,350

136,393

Adjustment

Current assets:

Cash and cash equivalents

Short-term marketable securities

Prepaid expenses and other current assets

(150)

Restricted cash

Total current assets

(150)

Property and equipment, net

Operating lease right-of-use asset

Long-term restricted cash

Other long-term assets

Total assets

(150)

Current liabilities:

Accounts payable

Accrued compensation

Accrued and other current liabilities

728

Current portion of long-term debt

(81)

Total current liabilities

(81)

728

Operating lease liability, net of current portion

Long-term debt, net

(15)

Warrant liability

8,481

8,734

5,273

10,764

16,633

Total liabilities

8,481

8,638

5,273

10,764

17,361

Commitments and contingencies

Stockholders’ equity:

Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding

Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2022; 14,215,302 shares issued and outstanding as of December 31, 2022

Additional paid-in capital

(26,781)

(26,431)

(26,317)

(26,222)

Accumulated other comprehensive loss

Accumulated deficit

18,300

17,793

21,044

15,458

8,711

Total stockholders’ equity

(8,481)

(8,638)

(5,273)

(10,764)

(17,511)

Total liabilities and stockholders’ equity

$ 0

$ (150)

[1]

License Revenue, Agreements and Strategic Investment - Additional Information (Details) - USD ($)

1 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

Jun. 30, 2019

Jun. 30, 2023

Sep. 30, 2022

Jun. 30, 2023

Sep. 30, 2022

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Sep. 30, 2023

Mar. 31, 2023

Research And Development Arrangement Contract To Perform For Others [Line Items]

Revenue recognized

$ 0

$ 236,000

$ 0

$ 236,000

$ 4,784,000

Common stock, shares issued

14,595,477

14,036,249

14,595,477

14,036,249

16,784,969

14,215,302

14,614,890

14,359,214

Common stock value

$ 1,000

$ 2,000

^[1]

$ 1,000

^[1]

$ 1,000

Ascentage Pharma

Research And Development Arrangement Contract To Perform For Others [Line Items]

Compound library and option agreement execution month and year

2016-02

Compound library and option agreement expiration month and year

2022-02

Ascentage Pharma | Licensed Products

Research And Development Arrangement Contract To Perform For Others [Line Items]

Royalties due from sales

$ 0

License Agreement | Jocasta Neuroscience, Inc.

Research And Development Arrangement Contract To Perform For Others [Line Items]

Upfront cash payments received

5,000,000

Revenue recognized

200,000

$ 4,800,000

Other Licensing Agreements with Research Institutions

Research And Development Arrangement Contract To Perform For Others [Line Items]

Contingent consideration, milestone or royalty payments

$ 0

Other Licensing Agreements with Research Institutions | UCSF

Research And Development Arrangement Contract To Perform For Others [Line Items]

Common shares expected to be issued

3,400

Contingent consideration, milestone or royalty payments

$ 0

Maximum milestone payments for each product licensed under agreement

$ 13,600,000

Commercial Agreement | Affiliate of Clinical-Stage Biopharmaceutical Company

Research And Development Arrangement Contract To Perform For Others [Line Items]

Equity payments percentage

20.00%

Commercial Agreement | Ascentage Pharma

Research And Development Arrangement Contract To Perform For Others [Line Items]

Equity payments percentage

80.00%

Common stock, shares issued

Commercial Agreement | Ascentage Pharma | Maximum

Research And Development Arrangement Contract To Perform For Others [Line Items]

Contingent consideration additional common stock issued for one licensed product

93,333

Contingent consideration additional common stock issued for two or more licensed product

133,333

Milestone payments

$ 70,300,000

Commercial Agreement | Ascentage Pharma | Initial License Agreement

Research And Development Arrangement Contract To Perform For Others [Line Items]

License agreement termination month and year

2020-07

License agreement execution month and year

2016-02

Commercial Agreement | Ascentage Pharma | Second License Agreement

Research And Development Arrangement Contract To Perform For Others [Line Items]

License agreement execution month and year

2019-01

[1]

Fair Value Measurements

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

The Company determines the fair value of financial and non-financial assets and liabilities based on the assumptions that market participants would use in pricing the asset or liability in an orderly transaction between market participants at the measurement date. The identification of market participant assumptions provides a basis for determining what inputs are to be used for pricing each asset or liability. A fair value hierarchy has been established which gives precedence to fair value measurements calculated using observable inputs over those using unobservable inputs. This hierarchy prioritized the inputs into three broad levels as follows:

•

Level 1: Quoted prices in active markets for identical instruments

•

Level 2: Other significant observable inputs (including quoted prices in active markets for similar instruments)

•

Level 3: Significant unobservable inputs (including assumptions in determining the fair value of certain investments)

The carrying amounts of financial instruments such as cash and cash equivalents, restricted cash, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued and other current liabilities approximate to their related fair values due to the short-term nature of these instruments.

The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands):


	December 31, 2023
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	12,864	$	12,864	$	—	$	—
U.S. treasuries		2,989		—		2,989		—
Total cash equivalents		15,853		12,864		2,989		—
Short-term marketable securities:
U.S. treasuries		7,849		—		7,849		—
U.S. government debt securities		15,549		—		15,549		—
Total short-term marketable securities		23,398		—		23,398		—
Restricted Cash equivalents:
Money market funds		896		896		—		—
Total restricted cash equivalents		896		896		—		—
Total assets subject to fair value measurements on a recurring basis	$	40,147	$	13,760	$	26,387	$	—

Liabilities:
Warrant Liability	$	5,913	$	—	$	—	$	5,913
Total liabilities subject to fair value measurements on a recurring basis		5,913		—		—		5,913


	December 31, 2022
	(Restated)
	Total		Level 1		Level 2		Level 3 (Restated)
Assets:
Cash equivalents:
Money market funds	$	5,083	$	5,083	$	—	$	—
Total cash equivalents		5,083		5,083		—		—
Short-term marketable securities:
U.S. treasuries		30,758		—		30,758		—
U.S. government debt securities		51,301		—		51,301		—
Total short-term marketable securities		82,059		—		82,059		—
Total assets subject to fair value measurements on a recurring basis	$	87,142	$	5,083	$	82,059	$	—

Liabilities:
Warrant Liability (Restated)	$	10,764	$	—	$	—	$	10,764
Total liabilities subject to fair value measurements on a recurring basis		10,764		—		—		10,764

The Company estimates the fair value of its money market funds, U.S. treasuries, and U.S. government debt securities by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. See Note 5, “Marketable Securities,” for further information regarding the carrying value of the Company's financial instruments.

August 2022 Warrants ('Existing Warrants')

The common stock warrants are classified as a liability on the balance sheets and are measured at fair value with the change in fair value recorded within “Gain (loss) on warrant liability” on the Statement of Operations and Comprehensive Loss. The estimated fair value of the outstanding common warrants were $27.6 million, $16.6 million, $10.7 million, $5.3 million, $8.7 million, $8.4 million, and $2.8 million as of August 22, 2022 (i.e., the issuance date), September 30, 2022, December 31, 2022, March 31, 2023, June 30, 2023, September 30, 2023, and December 31, 2023, respectively. In November 2023, 2,143,000 shares of the common warrants were exercised through an Inducement Offer, for a reduced exercise price of $2.045. See Note 12, ‘Equity Financing’.

The Company estimates the fair value of its warrant liability using a Monte Carlo simulation model based on significant inputs not observable in the market, which represents a Level 3 measurement. The Company used the following key assumptions within its valuation. In all scenarios, the Company also applied the likelihood of a fundamental transaction and the related impact on the Company’s common stock price and volatility.


	August 22, 2022 (issuance)			September 30, 2022			December 31, 2022			March 31, 2023			June 30, 2023			September 30, 2023			November 14, 2023 (exercise)			December 31, 2023
Common stock price	$	6.10		$	3.95		$	2.74		$	1.63		$	2.55		$	2.40		$	1.72		$	1.93
Exercise price per share	$	8.50		$	8.50		$	8.50		$	8.50		$	8.50		$	8.50		$	2.045		$	8.50
Estimated volatility		87.5	%		90.0	%		95.0	%		100.0	%		95.0	%		100.0	%		80.0	%		80.0	%
Risk-free interest rate		3.17	%		4.07	%		4.03	%		3.66	%		4.28	%		4.71	%		4.42	%		3.85	%
Contractual term (in years)		5.00			4.89			4.64			4.39			4.14			3.89			3.77			3.64

November 2023 Inducement Offer ('New Warrants')

In November 2023, the Company issued common stock warrants to purchase an aggregate of 2,143,000 shares of common stock at an exercise price of $1.92 per warrant. Additionally, 128,580 common stock warrants were issued to the Placement Agent ("Placement Agent Warrants") at an exercise price of $2.5563 per warrant. The New Warrants and Placement Agent warrants are recorded for as a liability on the balance sheet and are adjusted to estimated fair value at period end through “Gain (loss) on warrant liability” on the Statement of Operations and Comprehensive Loss. The estimated fair value of the New Warrants were $2.7 million on November 14, 2023 (i.e., the issuance date) and $3.1 million as of December 31, 2023.

The Company estimates the fair value of its Level 3 warrant liabilities using a Monte Carlo simulation model. The Company used the following key assumptions within its valuation. In all scenarios, the Company also applied the likelihood of a fundamental transaction and the related impact on the Company’s common stock price and volatility.


		November 14, 2023 (issuance)				December 31, 2023
Common stock price	$	1.72			$	1.93
Exercise price per share	$	1.92-2.5563			$	1.92-2.5563
Expected volatility			80.0	%			80.0	%
Risk-free interest rate			4.42	%			3.85	%
Contractual term (in years)			5.00				4.87

The following is a roll forward of the fair value of Level 3 warrants:


	Warrant Liability Fair Value
Beginning balance at December 31, 2021	$	—
Warrants Issued		27,607
Change in fair value		(16,842	)
Ending balance at December 31, 2022 (Restated)		10,765
Warrants Issued		2,724
Warrants Exercised		(1,361	)
Change in fair value		(6,215	)
Balance at December 31, 2023	$	5,913

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

14. Stock-Based Compensation

Summary of Equity Incentive Plans

In March 2018, the Company’s board of directors adopted the Company’s 2018 Incentive Award Plan (the “2018 Plan”). The 2018 Plan was approved by the Company’s stockholders in April 2018 and became effective in May 2018. The 2018 Plan initially reserved 428,994 shares for the issuance of stock options as well as any automatic annual increases in the number of shares of common stock reserved for future issuance under the 2018 Plan. Awards granted under the 2018 Plan expire no later than ten years from the date of grant. For stock options, the option price shall not be less than 100% of the estimated fair value on the day of grant. Options granted typically vest over a four-year period but may be granted with different vesting terms. Unvested options not exercised at the time of an employee’s termination of employment are added back to the 2018 Plan.

Following the Company’s IPO and in connection with the effectiveness of the 2018 Plan, the 2013 Equity Incentive Plan (the “2013 Plan”) terminated and no further awards will be granted under that plan. All outstanding awards under the 2013 Plan will continue to be governed by their existing terms and the shares that remained outstanding for issuance under the 2013 Plan were transferred into the 2018 Plan. As of December 31, 2023, there were in aggregate 2,182,500 shares of common stock authorized for issuance under the 2018 Plan.

Prior to its termination, the 2013 Plan provided for the granting of incentive stock options (“ISOs”), non-statutory stock options (“NSOs”) and restricted shares to employees, directors, and consultants at the discretion of management and the board of directors. The exercise price of an ISO and NSO shall not be less than 100% of the estimated fair value of the shares on the date of grant, and the exercise price of an ISO and NSO granted to a 10% stockholder shall not be less than 110% of the estimated fair value of the shares on the date of grant. For awards granted between September 2017 and February 2018 with an exercise price of $3.42, a deemed fair value ranging from $3.95 to $8.47 per share was used in calculating stock-based compensation expense, which was determined using management hindsight. Options granted under the 2013 Plan expire no later than ten years from the date of grant and generally vest over a four-year period but may be granted with different vesting terms. Unvested options not exercised at the time of an employee’s termination of employment are added back to the 2018 Plan.

Under the 2013 Plan, the Company permitted early exercise of certain stock options prior to vesting. These unvested shares are subject to repurchase by the Company at the original issuance price in the event the optionee’s employment is terminated either voluntarily or involuntarily. The amounts paid for shares purchased under an early exercise of stock options and subject to repurchase by the Company are reported as a liability and reclassified into additional paid-in capital as the shares vest.

In March 2020, the Company’s board of directors approved the Company’s 2020 Employment Inducement Incentive Plan (“the 2020 Plan”), to provide for grants to newly hired employees as a material inducement for them to commence employment with the Company. The 2020 Plan initially reserved 110,000 shares for the issuance of stock options, and in November 2020, the Company reserved an additional 150,000 shares of common stock for future issuance under the 2020 Plan. In February 2023, the Company reserved an additional 300,000 shares of common stock for future issuance under the 2020 Plan. Awards granted under the 2020 Plan expire no later than ten years from the date of grant. For stock options, the option price shall not be less than 100% of the estimated fair value on the day of grant. Options granted typically vest over a four-year period but may be granted with different vesting terms. Unvested options not exercised at the time of an employee’s termination of employment are added back to the 2020 Plan. As of December 31, 2023, there were in aggregate 542,000 shares of common stock authorized for issuance under the 2020 Plan.

Equity Incentive Plan Activity

The following sections summarize activity under the Company’s equity incentive plans.

Stock Options and Restricted Stock Units (RSUs) Activity

A summary of the Company’s stock option activity under the 2013 Plan, 2018 Plan and 2020 Plan for the year ended December 31, 2023 is as follows:


	Shares Available for Grant			Outstanding Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contract Term		Aggregate Intrinsic Value
									(in Years)		(in thousands)
Balance at December 31, 2022		68,838			1,609,938		$	27.51		8.3	$	251
Shares added		1,010,831			—			—
Granted		(446,200	)		446,200			2.79
Exercised		—			—			—
Canceled		153,367			(142,793	)		7.96
Balance at December 31, 2023		786,836			1,913,345		$	14.23		7.1	$	5
Vested and exercisable at December 31, 2023					1,179,366		$	20.51		6.0	$	—
Vested and expected to vest at December 31, 2023					1,913,345		$	14.23		7.1	$	5

The total intrinsic value of options exercised was zero for the years ended December 31, 2023 and 2022, respectively. The weighted-average estimated fair value of stock options granted was $2.79 and $3.11 for the years ended December 31, 2023 and 2022, respectively.

The aggregate intrinsic value of options exercisable was zero as of December 31, 2023 and 2022.

In September 2020, the board of directors granted retention stock-based awards to employees covering an aggregate of 320,000 shares of common stock, including options to purchase an aggregate of 25,000 shares of common stock and 295,985 of restricted stock units. The awards are all time-based vesting and vest over three to four years.

During the years ended December 31, 2023 and 2022, there were no shares issued in settlement of stock-based compensation awards accounted for as liability awards.

The following table summarizes the Company’s RSU activity for the year ended December 31, 2023:


	Shares			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2022		146,333		$	27.66
Granted		—		$	—
Released		(94,534	)	$	28.39
Canceled		(10,574	)	$	11.27
Unvested at December 31, 2023		41,225		$	30.18

As of December 31, 2023, the total stock-based compensation cost related to options and RSUs granted but not yet amortized was $3.9 million and will be recognized over a weighted-average period of approximately 0.9 years. The total grant date fair value of RSUs and RSAs vested during the years ended December 31, 2023 and 2022 was approximately $0.3 million and $0.6 million, respectively.

In March 2020, the board of directors granted the Company’s newly hired Chief Executive Officer stock-based awards covering an aggregate of 110,000 shares of common stock, including options to purchase an aggregate of 80,000 shares of common stock, 12,000 RSUs, 15,000 PSUs, and 3,000 RSAs that immediately vested on the grant date. The stock-based awards were granted pursuant to the 2020 Employment Inducement Incentive Plan, which was approved

by the board of directors in March 2020 to provide for grants to newly hired employees as a material inducement for them to commence employment with the Company.

In February 2022, the Company’s board of directors approved the granting of retention awards to critical and important Company personnel. The awards consisted of 189,333 stock options and 46,332 restricted stock units with a grant date total fair value of $2.0 million and $0.5 million, respectively.

Valuation of Stock Options


	Year ended December 31,
	2023		2022		2021
Expected term of options (in years)	5.79		5.55		6.0
Expected stock price volatility	94.11%-98.92%		86.22%-93.17%		85.7%-88.5%
Risk-free interest rate	3.36%-4.13%		2.41%-4.01%		1.08%-1.35%
Expected dividend yield		—		—		—

The valuation assumptions were determined as follows:

Expected Term—The expected term represents the period that the options granted are expected to be outstanding and is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term) as the Company has concluded that its stock option exercise history does not provide a reasonable basis upon which to estimate expected term.

Expected Volatility—Due to limited historical data, the Company estimates stock price volatility based on a combined weighted-average of the Company’s historical average volatility and that of a selected peer group of comparable publicly traded companies within the biotechnology and pharmaceutical industry that were deemed to be representative of future stock price trends over the expected life of the award.

Risk-Free Interest Rate—The Company based the risk-free interest rate over the expected term of the options based on the constant maturity rate of U.S. Treasury securities with similar maturities as of the date of the grant.

Expected Dividend Yield—The Company has never paid any dividends and does not plan to pay dividends in the foreseeable future. Therefore, the expected dividend yield is zero.

The fair value of ESPP awards was not material for all periods presented.

Performance Stock Units

The PSUs were originally scheduled to vest as to 5,000 PSUs upon the attainment of (a) a volume-weighted average per share closing trading price of the Company’s common stock of at least $368.75 over a trailing 30-day period or (b) a change in control transaction in which the price per share to the holders of the Company’s common stock is at least $368.75 and as to 10,000 PSUs (x) at such time as the Company’s market capitalization reaches at least $2.5 billion, as measured based on the volume weighted-average closing trading price over a trailing 30 day period or (y) a change in control transaction in which the consideration paid to the Company’s stockholders is equal to at least $2.5 billion, as determined by the Company’s board of directors. In January 2021, the board of directors modified the PSUs to vest as to 5,000 PSUs upon the attainment of (a) a volume-weighted average per share closing trading price of the Company’s common stock of at least $180.00 over a trailing 30-day period or (b) a change in control transaction in which the price per share to the holders of the Company’s common stock is at least $180.00 and as to 10,000 PSUs upon the attainment of (x) a volume-weighted average per share closing trading price of the Company’s common stock of at least $360.00 over a trailing 30-day period or (y) a change in control transaction in which the price per share to the holders of the Company’s common stock is at least $360.00, as determined by the Company’s board of directors.

For the PSU awards, the Company used the Monte-Carlo option pricing model to determine the fair value of awards at the date of grant. The Monte-Carlo option pricing model uses similar input assumptions as the Black-Scholes model;

however, it further incorporates into the fair-value determination the possibility that the market condition may not be satisfied. Compensation costs related to awards with a market-based condition are recognized regardless of whether the market condition is ultimately satisfied. Compensation cost is not reversed if the achievement of the market condition does not occur. The total grant date fair value of the PSU awards was determined to be $0.7 million and will be recognized as compensation expense over the weighted-average derived service period of approximately 4.3 years. The incremental fair value of the PSUs on the modification date of $31,000 are added to the unamortized value of the original grant of $569,000 and will be amortized to expense over the new implied service periods of 1.63 years to 2.79 years.

Performance and Market Contingent Stock Options

In January 2021, the board of directors modified 1,747 performance and market contingent stock options with vesting conditions that required the combination of a liquidity event, change of control or IPO with a market condition at prescribed levels. The modification removed the performance condition and lowered the market conditions to a volume-weighted average per share closing trading price of the Company’s common stock of at least $180.00 over a trailing 30-day period for one tranche and at least $360.00 over a trailing 30-day period for the second tranche. The fair value of the options on the modification date of $81,000 will be amortized to expense over the implied service periods of 1.46 years to 2.52 years.

In June 2021, the board of directors modified 3,336 performance and market contingent stock options with vesting conditions that required the combination of a liquidity event, change of control or IPO with a market condition at prescribed levels. The modification removed the performance condition and adjusted the market conditions to a date on which the Company attains a valuation of at least one billion dollars measured by the volume-weighted average per share closing trading price of the Company’s common stock over a trailing 30-day period. The fair value of the options on the modification date of $102,000 will be amortized to expense over the implied service periods of 1.85 years.

As of December 31, 2023, there were 3,336 market contingent stock option awards outstanding with a total fair value of $0.1 million.

2018 Employee Stock Purchase Plan

In March 2018, the Company’s board of directors adopted the Company’s 2018 Employee Stock Purchase Plan (the “2018 ESPP”). The 2018 ESPP was approved by the Company’s stockholders in April 2018 and became effective on May 2, 2018. The 2018 ESPP reserved 53,624 shares of common stock for issuance pursuant to future awards, as well as any automatic increases in the number of shares of the Company’s common stock reserved for future issuance under this plan.

Under the 2018 ESPP, employees are offered the option to purchase the Company’s common stock at a discount during the offering periods, at semi-annual intervals, with their accumulated payroll deductions. The option purchase price will be 85% of the lower of the closing trading price per share at the beginning of the offering period or at the purchase date. The 2018 ESPP provides for consecutive offering periods and eligible employees may elect to withhold up to 15% of their compensation through payroll deductions during the offering period for the purchase of stock. The maximum number of shares that may be purchased by any one participant is limited to 15,000 shares in each offering period and $25,000 in fair market value during any calendar year per the Internal Revenue Code limits. The first offering period commenced on September 16, 2018.

Stock-Based Compensation Expense


	Year Ended December 31,
	2023		2022		2021
Research and development	$	1,947	$	3,526	$	4,809
General and administrative		5,472		5,853		6,744
Total	$	7,419	$	9,379	$	11,553

During the years ended December 31, 2023, 2022 and 2021, stock-based compensation expense recognized related to nonemployee options was $0.4 million, $0.2 million and $0.4 million, respectively.

Repricing

On May 4, 2023, and in accordance with the terms of the Company’s 2018 Plan, the Company’s Board of Directors approved a stock option repricing (the “Repricing”) for employees and certain service providers that were not affected by the reduction in its workforce, as well as affected employees and certain service providers entering into or subject to a continuing consulting agreement, as of May 11, 2023. Pursuant to the terms of the Repricing, the exercise price of each outstanding option to purchase shares of the Company's common stock granted under its 2018 Plan that had an original exercise price above $6.00, was reduced to an exercise price of $2.77, the closing price for the Company's common stock on May 11, 2023, the effective date of the Repricing.

On the effective date of the Repricing, 26 employees and certain service providers held 444,273 shares of the Company's common stock under option grants that met the eligibility criteria. Eligible outstanding options continue to remain outstanding in accordance with their current terms and conditions. On the effective date of the Repricing, the Company recognized $0.2 million of additional stock-based compensation from 251,821 shares of its common stock under vested options. The Company anticipates an additional $0.1 million will be expensed over the period from the effective date of the Repricing through 2025 relating to 170,189 shares of the Company's common stock under unvested options.

Stock option and awards modification

In connection with the corporate restructuring, the Company’s executed consulting agreements with five of the 9 employees that were terminated as part of the reduction in force. The consulting agreements allowed for the non-employee to continue vesting in their option and awards, resulting in a modification to all then vested and outstanding option and awards. The modification resulted in an incremental compensation charge recognized upfront on the date of modification of $0.3 million. These costs were recorded as part of the stock compensation expense within “Research and development” and “General and administrative” costs within the Statement of Operations and Comprehensive Loss. There was no material incremental compensation expense as a result of modifications during the year ended December 31, 2022 and 2021.

License Revenue, Agreements and Strategic Investment

12 Months Ended

Dec. 31, 2023

Research and Development [Abstract]

License Revenue, Agreements and Strategic Investment

6. License Revenue, Agreements and Strategic Investment

The Company has entered into license agreements with other pharmaceutical and biotechnology companies. The Company’s accounts receivable balances may contain billed and unbilled amounts from milestones and other contingent payments. The Company performs a regular review of its customers’ credit risk and payment histories, including payments made after period end. Historically, the Company has not experienced credit loss from its accounts receivable and, therefore, has not recorded a reserve for estimated credit losses as of December 31, 2023.

In accordance with the license agreements, the Company recognized revenue as follows:


	Year ended December 31,
	2023		2022		2021
Jocasta Neuroscience, Inc. (1)	$	—	$	236	$	4,784
	$	—	$	236	$	4,784

(1)

Jocasta Neuroscience, Inc. was deemed a related party at the effective time the agreement was made on December 17, 2021.

License Agreement with Jocasta Neuroscience, Inc.

In December 2021, the Company signed a License Agreement with Jocasta Neuroscience, Inc. (“the Jocasta Agreement”) to exclusively license its rights in the α-Klotho asset for development and commercialization, and included a sublicense agreement under the original license agreement with the University of California, San Francisco. Under the Jocasta Agreement, the Company received a $5.0 million upfront cash payment from Jocasta Neuroscience, Inc. The Company may also receive additional payments based on development milestones, approval milestones, and

sales-based royalties, per indication. The Jocasta agreement is recognized in accordance with ASC 606, Revenue from Contracts with Customers, and is classified under License Revenue.

Promises that the Company concluded were distinct performance obligations in the License Agreement included: (1) the license of intellectual property and delivery of know-how, and (2) the transfer of licensed compounds and materials.

In order to determine the transaction price, the Company evaluated all the payments to be received during the duration of the contract. Fixed consideration exists in the form of the upfront payment. Regulatory milestones and royalties were considered variable consideration. The estimated variable consideration is constrained until the Company determines it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur in future periods. Milestone payments are constrained and not included in the transaction price due to the uncertainties of research and development. The Company will re-evaluate the transaction price, including the estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. The Company determined that the initial transaction price consists of the upfront payment of $5.0 million. The allocation of the transaction price is performed based on standalone selling prices, which are based on estimated amounts that the Company would charge for a performance obligation if it were sold separately. The transaction price allocated to the license of intellectual property and delivery of know-how was recognized upon grant of license and delivery of know-how. The transaction price allocated the transfer of licensed compounds and materials, will be recognized over time as the materials are delivered. Consideration received in advance are recorded as deferred revenue and will be recognized as the performance obligations are satisfied.

For the years ended December 31, 2023, 2022 and 2021, the Company recognized zero, $0.2 million and $4.8 million, respectively, of license revenue related to the Jocasta Agreement.

License Agreements with Research Institutions

In May 2019, the Company entered into a license agreement with The Regents of the University of California on behalf its San Francisco campus (collectively, “UCSF”) which provides the Company the rights to certain patents and related know-how to make, use, sell, offer for sale and import certain products and practice certain methods for use in the development of human therapeutics, which excludes the provision of services to third parties for consideration of any kind. The license to the Company is subject to UCSF’s reserved rights under the licensed intellectual property for educational and non-commercial research purposes and a requirement to substantially manufacture any licensed products in the United States. The Company is obligated to use diligent efforts to develop and obtain regulatory approval for at least one product commercialized pursuant to the agreement, and must meet certain regulatory and development milestones. The Company is obligated to pay an annual license maintenance fee and may be obligated to make milestone payments or issue up to an additional 3,400 shares of its common stock upon the occurrence of specified development events, up to aggregate milestone payments of $13.6 million for each product licensed under the agreement, and upon commercialization, to make royalty payments in the low single digit percentages (subject to a specified minimum annual royalty) based on net sales of products commercialized pursuant to the agreement. None of these events had occurred and no milestone payments or royalty payments had been recognized as of December 31, 2023. In December 2021, the Company entered an agreement to exclusively license its rights in the α-Klotho asset to Jocasta Neuroscience, Inc. for development and commercialization. Under the license agreement, Jocasta Neuroscience, Inc. is, in addition to the payments due to the Company, required to make all payments due to UCSF from the Company under the UCSF License.

The Company has also entered into license agreements with various research institutions which have provided the Company with rights to patents, and in certain cases, research “know-how” and proprietary research tools to research, develop and commercialize drug candidates. In addition to upfront consideration paid to these various research institutions in either cash or shares of the Company’s common stock, the Company may be obligated to make milestone payments, payable in cash and/or the issuance of shares of the Company’s common stock upon achievement of certain specified clinical development and/or sales events. The contingent consideration liability considered to be a derivative associated with the potential issuance of common stock related to these license agreements was not

significant at December 31, 2023 and 2022. To date, none of these events has occurred and no contingent consideration, milestone or royalty payments have been recognized.

Ascentage Commercial Agreements

The Company was a party to three agreements (the "Commercial Agreements") with Ascentage Pharma: (a) a compound library and option agreement executed in February 2016, the Library Agreement, granting the Company the right to research and nominate an active compound from Ascentage’s library of Bcl compounds and subsequently nominate a development candidate from any active compound in order to begin GLP toxicology work for indications outside of oncology, which expired in February 2022; (b) a license agreement executed in February 2016 granting the Company rights to an Ascentage Pharma compound known as APG1252, or the APG1252 License Agreement, which the Company terminated in July 2020 due to the Company’s decision to prioritize the progression of UBX1325; and (c) a second license agreement executed in January 2019 granting the Company world-wide rights to develop and commercialize UBX0601, the active parent molecule of our lead drug candidate UBX1325, outside of Greater China, or the Original Bcl Agreement, for indications outside of oncology.

The Commercial Agreements referenced above include cash payments of up to $70.3 million as well as the equity payments of up to an aggregate of (a) 93,333 shares of common stock in the event there is only one licensed product, and (b) 133,333 shares of common stock in the event there are two or more licensed products, in each case to be issued based on the Company’s achievement of certain preclinical and clinical development and sales milestone events. The Company is required to make 80% of all equity payments to Ascentage Pharma and the remaining 20% to an academic institution from whom Ascentage Pharma had previously licensed the technology. The milestones include the advancement of additional compounds into Investigational New Drug application (“IND”) enabling studies, the filing of an IND, the commencement of clinical studies, Food and Drug Administration (“FDA”) and/or European Medicines Agency approval, and a net sales threshold. The Original Bcl License Agreement also includes tiered royalties in the low-single digits based on sales of licensed products. To date, no royalties were due from the sales of licensed products. The Company issued no shares pursuant to these agreements during the year ended December 31, 2023.

Income Taxes - Schedule of Components of Deferred Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Federal and state operating loss carryforwards	$ 81,094	$ 73,322
Research and development tax credits	9,552	8,646
Stock-based compensation	5,078	4,589
Accruals and other	320	587
Intangibles	1,343	5,329
Section 174 capitalization research expenses	10,117	6,624
Charitable contributions	0	12
Operating lease liabilities	6,280	6,908
Total deferred tax assets	113,784	106,017
Deferred tax liabilities:
Operating lease right-of-use asset	(3,041)	(4,371)
Fixed assets	(1,033)	(1,299)
Total deferred tax liabilities	(4,074)	(5,670)
Valuation allowance	(109,710)	(100,347)
Net deferred tax assets	$ 0	$ 0

Defined Contribution Plan - Additional Information (Details) - Defined Contribution Plan - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Contribution Plan Disclosure [Line Items]
Percent of employer matching contribution of employees' salary	4.00%
Defined Contribution Plan, Sponsor Location [Extensible Enumeration]	us-gaap:DomesticPlanMember
Matching contributions		$ 0.3	$ 0.4	$ 0.5

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research and development expenses	$ 415				$ 378
Prepaid insurance expenses	541				710
Tax credit receivable	1,493				0
Interest receivable	84				235
Other prepaid expenses and current assets	871				417
Total prepaid expenses & other current assets	$ 3,404	$ 3,599	$ 3,874	$ 2,989	$ 1,740	$ 3,084

Net Loss per Common Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Schedule of Reconciliation of Numerators and Denominators Used In Computing Net Loss From Continuing Operations Per Share

A reconciliation of the numerators and denominators used in computing net loss from continuing operations per share is as follows (in thousands, except per share amounts):


	Year ended December 31,
	2023			2022 (Restated)			2021
	(in thousands, except share and per share amounts)
Numerator:
Net loss	$	(39,860	)	$	(44,469	)	$	(60,725	)
Denominator:
Weighted average number of shares outstanding—basic and diluted		14,773,612			9,494,421			5,581,587
Net loss per share—basic and diluted	$	(2.70	)	$	(4.68	)	$	(10.88	)

Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Per Share

Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:


	Year ended December 31,
	2023		2022		2021
Options to purchase common stock		1,913,345		1,609,938		866,696
Outstanding warrants to purchase common stock		6,557,152		6,428,572		—
Early exercised common stock subject to future vesting		3,336		3,336		3,336
RSUs subject to future vesting		41,225		146,333		199,094
Shares subject to future vesting relating to the 2018 ESPP		47,389		65,939		14,774
Total		8,562,447		8,254,118		1,083,900

Restatement of Previously Issued Financial Statements

12 Months Ended

Dec. 31, 2023

Accounting Changes and Error Corrections [Abstract]

Restatement of Previously Issued Financial Statements

2. Restatement of Previously Issued Financial Statements

The Company has restated herein its audited financial statements for the fiscal year ended December 31, 2022, in accordance with Accounting Standards Codification (“ASC”) Topic 250, Accounting Changes and Error Corrections. In March 2024, the Company concluded the warrants issued in 2022 were incorrectly classified as equity and should have been recorded as liabilities.

Historically, the Existing Warrants were reflected as a component of equity as opposed to liabilities on the Balance Sheet. Additionally, the Statements of Operations and Comprehensive Loss did not include changes in the fair value of the Existing Warrants. The Company reassessed its accounting for the Existing Warrants and determined they should have been classified as liabilities and measured at fair value upon issuance with subsequent changes in fair value, as well as the issuance costs associated with the Existing Warrants, reported in the Company's Statement of Operations and Comprehensive Loss.

We have also restated interim financial statement periods for the third quarter of 2022 and the first, second and third quarters of 2023, as further described in Note 18.

Impact of the Restatement

Balance Sheet


	December 31, 2022
	As Previously Reported			Adjustment			As Restated
Assets
Current assets:
Cash and cash equivalents	$	12,736		$	—		$	12,736
Short-term marketable securities		82,059			—			82,059
Prepaid expenses and other current assets		1,740			—			1,740
Total current assets		96,535			—			96,535
Property and equipment, net		7,825			—			7,825
Operating lease right-of-use asset		19,042			—			19,042
Long-term restricted cash		896			—			896
Other long-term assets		52			—			52
Total assets	$	124,350		$	—		$	124,350
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	1,790		$	—		$	1,790
Accrued compensation		3,020			—			3,020
Accrued and other current liabilities		5,334			—			5,334
Current portion of long-term debt		9,476			—			9,476
Total current liabilities		19,620			—			19,620
Operating lease liability, net of current portion		26,991			—			26,991
Long-term debt, net		10,891			—			10,891
Warrant liability		—			10,764			10,764
Total liabilities		57,502			10,764			68,266
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—			—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2022; 14,215,302 shares issued and outstanding as of December 31, 2022		1			—			1
Additional paid-in capital		527,049			(26,222	)		500,827
Accumulated other comprehensive loss		(251	)		—			(251	)
Accumulated deficit		(459,951	)		15,458			(444,493	)
Total stockholders’ equity		66,848			(10,764	)		56,084
Total liabilities and stockholders’ equity	$	124,350		$	—		$	124,350

Statement of Operations and Comprehensive Loss


	Year Ended December 31, 2022
	As Previously Reported			Adjustment			As Restated
Licensing revenue - Related Party	$	236		$	—		$	236
Operating expenses:
Research and development		36,859			—			36,859
General and administrative		20,949			—			20,949
Total operating expenses		57,808			—			57,808
Loss from operations		(57,572	)		—			(57,572	)
Interest income		1,220			—			1,220
Interest expense		(3,558	)		—			(3,558	)
Gain (loss) on warrant liability		—			16,843			16,843
Other expense, net		(17	)		(1,385	)		(1,402	)
Net loss		(59,927	)		15,458			(44,469	)
Other comprehensive loss
Unrealized loss on marketable debt securities		(207	)		—			(207	)
Comprehensive loss	$	(60,134	)	$	15,458		$	(44,676	)
Net loss per share, basic and diluted	$	(6.31	)	$	—		$	(4.68	)
Weighted average number of shares used in computing net loss per share, basic and diluted		9,494,421			—			9,494,421

Statement of Changes in Stockholders' Equity


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at December 31, 2021		6,299,158	$	1	$	459,636		$	(44	)	$	(400,024	)	$	59,569
Issuance of common stock, net of issuance costs, under ATM equity offering program		1,019,046		—		12,155			—			—			12,155
Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs		6,428,571		—		41,648			—			—			41,648
Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		90,000		—		910			—			—			910
Issuance of common stock Hercules Capital, net of issuance costs		262,761		—		3,179			—			—			3,179
Issuance of common stock under 2018 ESPP		25,482		—		142			—			—			142
Vesting of restricted stock units		90,284		—		—			—			—			—
Stock-based compensation		—		—		9,379			—			—			9,379
Unrealized loss on available-for-sale marketable securities		—		—		—			(207	)		—			(207	)
Net loss		—		—		—			—			(59,927	)		(59,927	)
Balances at December 31, 2022		14,215,302	$	1	$	527,049		$	(251	)	$	(459,951	)	$	66,848

Adjustment
Balances at December 31, 2021		—	$	—	$	—		$	—		$	—		$	—
Issuance of common stock, net of issuance costs, under ATM equity offering program		—		—		—			—			—			—
Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs		—		—		(26,222	)		—			—			(26,222	)
Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		—		—		—			—			—			—
Issuance of common stock Hercules Capital, net of issuance costs		—		—		—			—			—			—
Issuance of common stock under 2018 ESPP		—		—		—			—			—			—
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		—			—			—			—
Unrealized loss on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			15,458			15,458
Balances at December 31, 2022		—	$	—	$	(26,222	)	$	—		$	15,458		$	(10,764	)

As Restated
Balances at December 31, 2021		6,299,158	$	1	$	459,636		$	(44	)	$	(400,024	)	$	59,569
Issuance of common stock, net of issuance costs, under ATM equity offering program		1,019,046		—		12,155			—			—			12,155
Sale of common stock under Follow-On Offering, net of issuance costs		6,428,571		—		15,426			—			—			15,426
Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		90,000		—		910			—			—			910
Issuance of common stock Hercules Capital, net of issuance costs		262,761		—		3,179			—			—			3,179
Issuance of common stock under 2018 ESPP		25,482		—		142			—			—			142
Vesting of restricted stock units		90,284		—		—			—			—			—
Stock-based compensation		—		—		9,379			—			—			9,379
Unrealized loss on available-for-sale marketable securities		—		—		—			(207	)		—			(207	)
Net loss		—		—		—			—			(44,469	)		(44,469	)
Balances at December 31, 2022		14,215,302	$	1	$	500,827		$	(251	)	$	(444,493	)	$	56,084

Statement of Cash Flow


	Year Ended December 31, 2022
	As Previously Reported			Adjustment			As Restated
Operating activities
Net loss	$	(59,927	)	$	15,458		$	(44,469	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		2,180			—			2,180
Amortization of debt issuance costs		1,318			—			1,318
Debt extinguishment gain upon conversion to equity		(199	)		—			(199	)
Net accretion and amortization of premium and discounts on marketable securities		(276	)		—			(276	)
Gain on disposal of property and equipment		(346	)		—			(346	)
Stock-based compensation		9,379			—			9,379
Non-cash rent expense		(2,136	)		—			(2,136	)
(Gain) loss on warrant liability		—			(16,843	)		(16,843	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		138			—			138
Other long-term assets		39			—			39
Accounts payable		(194	)		—			(194	)
Accrued compensation		(1,008	)		—			(1,008	)
Accrued liabilities and other current liabilities		26			—			26
Other long-term liabilities		(23	)		—			(23	)
Net cash used in operating activities		(51,029	)		(1,385	)		(52,414	)
Investing activities
Purchase of marketable securities		(98,827	)		—			(98,827	)
Maturities of marketable securities		74,000			—			74,000
Purchase of property and equipment		(96	)		—			(96	)
Sale of property and equipment		378			—			378
Net cash provided by (used in) investing activities		(24,545	)		—			(24,545	)
Financing activities
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		12,155			—			12,155
Proceeds from sale of common stock and warrants under Follow-On Offering		41,648			3,352			45,000
Issuance costs for sale of common stock		—			(1,967	)		(1,967	)
Proceeds from issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		910			—			910
Proceeds from issuance of common stock under 2018 ESPP		142			—			142
Net cash provided by financing activities		54,855			1,385			56,240
Net increase (decrease) in cash, cash equivalents and restricted cash		(20,719	)		—			(20,719	)
Cash, cash equivalents and restricted cash at beginning of the period		34,351			—			34,351
Cash, cash equivalents and restricted cash at end of the period	$	13,632		$	—		$	13,632
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	2,204		$	—		$	2,204
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt	$	3,179		$	—		$	3,179

The remainder of the notes to the Company's financial statements have been restated, as applicable, to reflect the impacts from the restatement discussed above.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation

The effective tax rate of the Company’s provision for income taxes differs from the federal statutory rate as follows:


	Year ended December 31,
	2023				2022 (Restated)				2021
Taxes at the U.S. statutory income tax rate		21.0		%		21.0		%		21.0		%
State tax, net of federal benefit		9.0				9.1				4.4
Other		0.5				(0.8	)			(0.4	)
Warrant activity		2.8				7.3				—
Stock-based compensation		(2.5	)			(6.6	)			(1.6	)
Research and development tax credits		1.8				2.9				3.2
Rate change		(8.8	)			4.7				3.8
ASC 740-10		—				(7.5	)			(4.2	)
Change in valuation allowance		(23.7	)			(30.1	)			(26.2	)
Total provision for income taxes		—		%		—		%		—		%

Schedule of Components of Deferred Income Taxes

The tax effects of significant items comprising the Company’s deferred income taxes are as follows:


	December 31,
	2023			2022
	(in thousands)
Deferred tax assets:
Federal and state operating loss carryforwards	$	81,094		$	73,322
Research and development tax credits		9,552			8,646
Stock-based compensation		5,078			4,589
Accruals and other		320			587
Intangibles		1,343			5,329
Section 174 capitalization research expenses		10,117			6,624
Charitable contributions		—			12
Operating lease liabilities		6,280			6,908
Total deferred tax assets		113,784			106,017
Deferred tax liabilities:
Operating lease right-of-use asset		(3,041	)		(4,371	)
Fixed assets		(1,033	)		(1,299	)
Total deferred tax liabilities		(4,074	)		(5,670	)
Valuation allowance		(109,710	)		(100,347	)
Net deferred tax assets	$	—		$	—

Summary of Net Operating Losses and Tax Credit Carryforwards

Net operating losses and tax credit carryforwards as of December 31, 2023 are as follows:


	Amount (in thousands)		Expiration Years
Net operating losses, federal (post December 31, 2017)	$	305,873	Do Not Expire
Net operating losses, federal (pre January 1, 2018)		64,136	2029 - 2037
Net operating losses, state		185,897	2034 - 2043
Research and development tax credits, federal		8,799	2034 - 2043
Research and development tax credits, California		7,070	Indefinite

Schedule of Reconciliation of Unrecognized Tax Benefits

The following table summarizes the activity related to the Company’s unrecognized tax benefits:


	Year ended December 31,
	2023			2022			2021
	(in thousands)
Gross unrecognized tax benefits at January 1	$	17,605		$	13,221		$	7,142
Additions for tax positions taken in the current year		84			4,395			3,457
Reductions for tax positions taken in the prior year		(232	)		(11	)		2,622
Gross unrecognized tax benefits at December 31	$	17,457		$	17,605		$	13,221

Quarterly Financial Information (Unaudited) - Balance Sheets (Details) - USD ($)
$ in Thousands

Dec. 31, 2023

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Dec. 31, 2022

Sep. 30, 2022

Jun. 30, 2022

Dec. 31, 2021

Dec. 31, 2020

Current assets:

Cash and cash equivalents

$ 19,803

$ 7,876

$ 19,118

$ 22,972

$ 12,736

$ 22,576

$ 32,905

Short-term marketable securities

23,398

38,063

49,974

60,420

82,059

76,364

Prepaid expenses and other current assets

3,404

3,599

3,874

2,989

1,740

3,084

Restricted cash

550

Total current assets

46,605

49,538

72,966

86,381

96,535

102,574

Property and equipment, net

5,082

5,314

7,181

7,496

7,825

8,202

Operating lease right-of-use asset

12,981

13,522

18,061

18,557

19,042

19,515

Long-term deposits

896

Long-term marketable securities

1,899

4,980

Long-term restricted cash

896

Other long-term assets

126

Total assets

65,690

69,270

101,008

114,255

124,350

136,243

Current liabilities:

Accounts payable

1,380

1,149

1,449

1,470

1,790

2,444

Accrued compensation

1,841

2,226

1,652

1,983

3,020

2,961

Accrued and other current liabilities

4,619

5,258

5,417

5,343

5,334

5,321

Current portion of long-term debt

13,623

13,062

9,476

6,776

Total current liabilities

7,840

8,633

22,141

21,858

19,620

17,502

Operating lease liability, net of current portion

23,539

24,431

25,297

26,150

26,991

27,792

Long-term debt, net

4,067

7,619

10,891

13,262

Warrant liability

5,913

8,481

8,734

5,273

10,764

16,633

Total liabilities

37,292

41,545

60,239

60,900

68,266

75,189

Commitments and contingencies

Stockholders’ equity:

Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding

Common stock value

^[1]

Additional paid-in capital

512,773

507,789

506,132

503,276

500,827

498,401

Accumulated other comprehensive loss

(24)

(55)

(136)

(150)

(251)

(275)

Accumulated deficit

(484,353)

(480,010)

(465,228)

(449,772)

(444,493)

(437,073)

Total stockholders’ equity

28,398

27,725

40,769

53,355

56,084

61,054

$ 39,931

59,569

$ 82,881

Total liabilities and stockholders’ equity

$ 65,690

69,270

101,008

114,255

124,350

136,243

As Previously Reported

Current assets:

Cash and cash equivalents

7,876

19,118

22,972

12,736

22,576

Short-term marketable securities

38,063

49,974

60,420

82,059

76,364

Prepaid expenses and other current assets

3,599

3,874

2,989

1,740

3,234

Restricted cash

550

Total current assets

49,538

72,966

86,381

96,535

102,724

Property and equipment, net

5,314

7,181

7,496

7,825

8,202

Operating lease right-of-use asset

13,522

18,061

18,557

19,042

19,515

Long-term deposits

896

Long-term marketable securities

1,899

4,980

Long-term restricted cash

896

Other long-term assets

Total assets

69,270

101,008

114,255

124,350

136,393

Current liabilities:

Accounts payable

1,149

1,449

1,470

1,790

2,444

Accrued compensation

2,226

1,652

1,983

3,020

2,961

Accrued and other current liabilities

5,258

5,417

5,343

5,334

4,593

Current portion of long-term debt

13,704

13,062

9,476

6,776

Total current liabilities

8,633

22,222

21,858

19,620

16,774

Operating lease liability, net of current portion

24,431

25,297

26,150

26,991

27,792

Long-term debt, net

4,082

7,619

10,891

13,262

Warrant liability

Total liabilities

33,064

51,601

55,627

57,502

57,828

Commitments and contingencies

Stockholders’ equity:

Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding

Common stock value

Additional paid-in capital

534,570

532,563

529,593

527,049

524,623

Accumulated other comprehensive loss

(55)

(136)

(150)

(251)

(275)

Accumulated deficit

(498,310)

(483,021)

(470,816)

(459,951)

(445,784)

Total stockholders’ equity

36,206

49,407

58,628

66,848

78,565

$ 39,931

$ 59,569

Total liabilities and stockholders’ equity

69,270

101,008

114,255

124,350

136,393

Adjustment

Current assets:

Cash and cash equivalents

Short-term marketable securities

Prepaid expenses and other current assets

(150)

Restricted cash

Total current assets

(150)

Property and equipment, net

Operating lease right-of-use asset

Long-term deposits

Long-term marketable securities

Long-term restricted cash

Other long-term assets

Total assets

(150)

Current liabilities:

Accounts payable

Accrued compensation

Accrued and other current liabilities

728

Current portion of long-term debt

(81)

Total current liabilities

(81)

728

Operating lease liability, net of current portion

Long-term debt, net

(15)

Warrant liability

8,481

8,734

5,273

10,764

16,633

Total liabilities

8,481

8,638

5,273

10,764

17,361

Commitments and contingencies

Stockholders’ equity:

Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding

Common stock value

Additional paid-in capital

(26,781)

(26,431)

(26,317)

(26,222)

Accumulated other comprehensive loss

Accumulated deficit

18,300

17,793

21,044

15,458

8,711

Total stockholders’ equity

(8,481)

(8,638)

(5,273)

(10,764)

(17,511)

Total liabilities and stockholders’ equity

$ 0

$ (150)

[1]

Restatement of Previously Issued Financial Statements - Schedule of Restated Statement of Statement of Operations and Comprehensive Loss (Parenthetical) (Details)	Oct. 19, 2022
Income Statement [Abstract]
Reverse stock split ratio	0.1

Quarterly Financial Information (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2023

Quarterly Financial Information Disclosure [Abstract]

Schedule of Balance Sheets

Balance Sheets


	September 30, 2022 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Assets
Current assets:
Cash and cash equivalents	$	22,576		$	—			$	22,576
Short-term marketable securities		76,364			—				76,364
Prepaid expenses and other current asset		3,234			(150	)	b		3,084
Restricted cash		550			—				550
Total current assets		102,724			(150	)			102,574
Property and equipment, net		8,202			—				8,202
Operating lease right-of-use assets		19,515			—				19,515
Long-term marketable securities		4,980			—				4,980
Long-term restricted cash		896			—				896
Other long-term assets		76			—				76
Total assets	$	136,393		$	(150	)		$	136,243
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	2,444		$	—			$	2,444
Accrued compensation		2,961			—				2,961
Accrued and other current liabilities		4,593			728		b		5,321
Current portion of long-term debt		6,776			—				6,776
Total current liabilities		16,774			728		b		17,502
Operating lease liability, net of current portion		27,792			—				27,792
Long-term debt, net		13,262			—				13,262
Warrant liability		—			16,633		a		16,633
Total liabilities		57,828			17,361				75,189
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—				—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of September 30, 2022 ; 14,036,249 shares issued and outstanding as of September 30, 2022		1			—				1
Additional paid-in capital		524,623			(26,222	)	a		498,401
Accumulated other comprehensive loss		(275	)		—				(275	)
Accumulated deficit		(445,784	)		8,711		a,b		(437,073	)
Total stockholders’ equity		78,565			(17,511	)			61,054
Total liabilities and stockholders’ equity	$	136,393		$	(150	)		$	136,243


	March 31, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Assets
Current assets:
Cash and cash equivalents	$	22,972		$	—			$	22,972
Short-term marketable securities		60,420			—				60,420
Prepaid expenses and other current assets		2,989			—				2,989
Total current assets		86,381			—				86,381
Property and equipment, net		7,496			—				7,496
Operating lease right-of-use asset		18,557			—				18,557
Long-term deposits		896			—				896
Long-term restricted cash		896			—				896
Other long-term assets		29			—				29
Total assets	$	114,255		$	—			$	114,255
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	1,470		$	—			$	1,470
Accrued compensation		1,983			—				1,983
Accrued and other current liabilities		5,343			—				5,343
Current portion of long-term debt		13,062			—				13,062
Total current liabilities		21,858			—				21,858
Operating lease liability, net of current portion		26,150			—				26,150
Long-term debt, net		7,619			—				7,619
Warrant liability		—			5,273		a		5,273
Total liabilities		55,627			5,273				60,900
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—				—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of March 31, 2023; 14,359,214 shares issued and outstanding as of March 31, 2023		1			—				1
Additional paid-in capital		529,593			(26,317	)	a,d		503,276
Accumulated other comprehensive loss		(150	)		—				(150	)
Accumulated deficit		(470,816	)		21,044		a,d		(449,772	)
Total stockholders’ equity		58,628			(5,273	)			53,355
Total liabilities and stockholders’ equity	$	114,255		$	—			$	114,255


	June 30, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Assets
Current assets:
Cash and cash equivalents	$	19,118		$	—			$	19,118
Short-term marketable securities		49,974			—				49,974
Prepaid expenses and other current assets		3,874			—				3,874
Total current assets		72,966			—				72,966
Property and equipment, net		7,181			—				7,181
Operating lease right-of-use asset		18,061			—				18,061
Long-term marketable securities		1,899			—				1,899
Long-term restricted cash		896			—				896
Other long-term assets		5			—				5
Total assets	$	101,008		$	—			$	101,008
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	1,449		$	—			$	1,449
Accrued compensation		1,652			—				1,652
Accrued and other current liabilities		5,417			—				5,417
Current portion of long-term debt		13,704			(81	)	c		13,623
Total current liabilities		22,222			(81	)			22,141
Operating lease liability, net of current portion		25,297			—				25,297
Long-term debt, net		4,082			(15	)	c		4,067
Warrant liability		—			8,734		a		8,734
Total liabilities		51,601			8,638				60,239
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—				—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of June 30, 2023; 14,595,477 shares issued and outstanding as of June 30, 2023		1			—				1
Additional paid-in capital		532,563			(26,431	)	a,d		506,132
Accumulated other comprehensive loss		(136	)		—				(136	)
Accumulated deficit		(483,021	)		17,793		a,c,d		(465,228	)
Total stockholders’ equity		49,407			(8,638	)			40,769
Total liabilities and stockholders’ equity	$	101,008		$	—			$	101,008


	September 30, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Assets
Current assets:
Cash and cash equivalents	$	7,876		$	—			$	7,876
Short-term marketable securities		38,063			—				38,063
Prepaid expenses and other current assets		3,599			—				3,599
Total current assets		49,538			—				49,538
Property and equipment, net		5,314			—				5,314
Operating lease right-of-use asset		13,522			—				13,522
Long-term restricted cash		896			—				896
Total assets	$	69,270		$	—			$	69,270
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	1,149		$	—			$	1,149
Accrued compensation		2,226			—				2,226
Accrued and other current liabilities		5,258			—				5,258
Total current liabilities		8,633			—				8,633
Operating lease liability, net of current portion		24,431			—				24,431
Warrant liability		—			8,481		a		8,481
Total liabilities		33,064			8,481				41,545
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding		—			—				—
Common stock, $0.0001 par value; 300,000,000 shares authorized as of September 30, 2023; 14,614,890 shares issued and outstanding as of September 30, 2023		1			—				1
Additional paid-in capital		534,570			(26,781	)	a,d		507,789
Accumulated other comprehensive loss		(55	)		—				(55	)
Accumulated deficit		(498,310	)		18,300		a,d		(480,010	)
Total stockholders’ equity		36,206			(8,481	)			27,725
Total liabilities and stockholders’ equity	$	69,270		$	—			$	69,270

Statements of Operations and Comprehensive Loss

Quarterly and Year to Date Statements of Operations and Comprehensive Loss


	Three Months Ended September 30, 2022 (unaudited)										Nine Months Ended September 30, 2022 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated			As Previously Reported			Adjustment			Reference	As Restated
Licensing revenue - related party	$	—		$	—			$	—		$	236		$	—			$	236
Operating expenses:
Research and development		8,208			878		b		9,086			28,222			878		b		29,100
General and administrative		4,922			—				4,922			15,669			—				15,669
Total operating expenses		13,130			878				14,008			43,891			878				44,769
Loss from operations		(13,130	)		(878	)			(14,008	)		(43,655	)		(878	)			(44,533	)
Interest income		329			—				329			416			—				416
Interest expense		(866	)		—				(866	)		(2,568	)		—				(2,568	)
Gain (loss) on warrant liability		—			10,974		a		10,974			—			10,974		a		10,974
Other expense, net		(41	)		(1,385	)	a		(1,426	)		49			(1,385	)	a		(1,336	)
Net loss		(13,708	)		8,711				(4,997	)		(45,758	)		8,711				(37,047	)
Other comprehensive loss
Unrealized loss on marketable debt securities		(88	)		—				(88	)		(231	)		—				(231	)
Comprehensive loss	$	(13,796	)	$	8,711			$	(5,085	)	$	(45,989	)	$	8,711			$	(37,278	)
Net loss per share, basic and diluted	$	(1.36	)	$	—			$	(0.50	)	$	(5.77	)	$	—			$	(4.67	)
Weighted average number of shares used in computing net loss per share, basic and diluted		10,072,077			—				10,072,077			7,928,729			—				7,928,729


	Three Months Ended March 31, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated
Operating expenses:
Research and development		5,835			(75	)	d		5,760
General and administrative		4,818			(20	)	d		4,798
Total operating expenses		10,653			(95	)			10,558
Loss from operations		(10,653	)		95				(10,558	)
Interest income		855			—				855
Interest expense		(1,002	)		—				(1,002	)
Gain (loss) on warrant liability		—			5,491		a		5,491
Other expense, net		(65	)		—				(65	)
Net loss		(10,865	)		5,586				(5,279	)
Other comprehensive gain
Unrealized gain on marketable debt securities		101			—				101
Comprehensive loss	$	(10,764	)	$	5,586			$	(5,178	)
Net loss per share, basic and diluted	$	(0.76	)	$	—			$	(0.37	)
Weighted average number of shares used in computing net loss per share, basic and diluted		14,312,887			—				14,312,887


	Three Months Ended June 30, 2023 (unaudited)										Six Months Ended June 30, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated			As Previously Reported			Adjustment			Reference	As Restated
Licensing revenue - related party	$	—		$	—			$	—		$	—		$	—			$	—
Operating expenses:
Research and development		6,529			(94	)	d		6,435			12,364			(169	)	d		12,195
General and administrative		5,433			(20	)	d		5,413			10,252			(40	)	d		10,212
Total operating expenses		11,962			(114	)			11,848			22,616			(209	)			22,407
Loss from operations		(11,962	)		114				(11,848	)		(22,616	)		209				(22,407	)
Interest income		805			—				805			1,660			—				1,660
Interest expense		(979	)		96		c		(883	)		(1,981	)		96		c		(1,885	)
Gain (loss) on warrant liability		—			(3,461	)	a		(3,461	)		—			2,030		a		2,030
Other expense, net		(69	)		—				(69	)		(133	)		—				(133	)
Net loss		(12,205	)		(3,251	)			(15,456	)		(23,070	)		2,335				(20,735	)
Other comprehensive gain
Unrealized gain on marketable debt securities		14			—				14			115			—				115
Comprehensive loss	$	(12,191	)	$	(3,251	)		$	(15,442	)	$	(22,955	)	$	2,335			$	(20,620	)
Net loss per share, basic and diluted	$	(0.85	)	$	—			$	(1.07	)	$	(1.61	)	$	—			$	(1.44	)
Weighted average number of shares used in computing net loss per share, basic and diluted		14,425,775			—				14,425,775			14,369,643			—				14,369,643


	Three Months Ended September 30, 2023 (unaudited)										Nine Months Ended September 30, 2023 (unaudited)
	As Previously Reported			Adjustment			Reference	As Restated			As Previously Reported			Adjustment			Reference	As Restated
Operating expenses:
Research and development		4,901			(269	)	d		4,632			17,266			(438	)	d		16,828
General and administrative		4,428			(81	)	d		4,347			14,681			(121	)	d		14,560
Impairment of long-lived assets		5,602			—				5,602			5,602			—				5,602
Total operating expenses		14,931			(350	)			14,581			37,549			(559	)			36,990
Loss from operations		(14,931	)		350				(14,581	)		(37,549	)		559				(36,990	)
Interest income		689			—				689			2,349			—				2,349
Interest expense		(470	)		(96	)	c		(566	)		(2,451	)		—				(2,451	)
Gain (loss) on warrant liability		—			253		a		253			—			2,283		a		2,283
Other expense, net		(577	)		—				(577	)		(711	)		—				(711	)
Net loss		(15,289	)		507				(14,782	)		(38,362	)		2,842				(35,520	)
Other comprehensive gain
Unrealized gain on marketable debt securities		81			—				81			196			—				196
Comprehensive loss	$	(15,208	)	$	507			$	(14,701	)	$	(38,166	)	$	2,842			$	(35,324	)
Net loss per share, basic and diluted	$	(1.05	)	$	—			$	(1.01	)	$	(2.66	)	$	—			$	(2.46	)
Weighted average number of shares used in computing net loss per share, basic and diluted		14,598,218			—				14,598,218			14,446,672			—				14,446,672

Statements of Changes in Stockholders' Equity


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at June 30, 2022		6,958,494	$	1	$	472,193		$	(187	)	$	(432,076	)	$	39,931
Issuance of common stock, net of issuance costs, under ATM equity offering program		633,464		—		8,570			—			—			8,570
Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs		6,428,571		—		41,650			—			—			41,650
Vesting of restricted stock units		15,720		—		—			—			—			—
Stock-based compensation		—		—		2,210			—			—			2,210
Unrealized loss on available-for-sale marketable securities		—		—		—			(88	)		—			(88	)
Net loss		—		—		—			—			(13,708	)		(13,708	)
Balances at September 30, 2022		14,036,249	$	1	$	524,623		$	(275	)	$	(445,784	)	$	78,565

Adjustment
Balances at June 30, 2022		—	$	—	$	—		$	—		$	—		$	—
Issuance of common stock, net of issuance costs, under ATM equity offering program		—		—		—			—			—			—
Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs		—		—		(26,222	)		—			—			(26,222	)
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		—			—			—			—
Unrealized loss on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			8,711			8,711
Balances at September 30, 2022		—	$	—	$	(26,222	)	$	—		$	8,711		$	(17,511	)

As Restated
Balances at June 30, 2022		6,958,494	$	1	$	472,193		$	(187	)	$	(432,076	)	$	39,931
Issuance of common stock, net of issuance costs, under ATM equity offering program		633,464		—		8,570			—			—			8,570
Sale of common stock under Follow-On Offering, net of issuance costs		6,428,571		—		15,428			—			—			15,428
Vesting of restricted stock units		15,720		—		—			—			—			—
Stock-based compensation		—		—		2,210			—			—			2,210
Unrealized loss on available-for-sale marketable securities		—		—		—			(88	)		—			(88	)
Net loss		—		—		—			—			(4,997	)		(4,997	)
Balances at September 30, 2022		14,036,249	$	1	$	498,401		$	(275	)	$	(437,073	)	$	61,054


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at December 31, 2022		14,215,302	$	1	$	527,049		$	(251	)	$	(459,951	)	$	66,848
Issuance of common stock, net of issuance costs, under ATM equity offering program		106,781		—		274			—			—			274
Vesting of restricted stock units		37,131		—		—			—			—			—
Stock-based compensation		—		—		2,270			—			—			2,270
Unrealized gain on available-for-sale marketable securities		—		—		—			101			—			101
Net loss		—		—		—			—			(10,865	)		(10,865	)
Balances at March 31, 2023		14,359,214	$	1	$	529,593		$	(150	)	$	(470,816	)	$	58,628

Adjustment
Balances at December 31, 2022		—	$	—	$	(26,222	)	$	—		$	15,458		$	(10,764	)
Issuance of common stock, net of issuance costs, under ATM equity offering program		—		—		—			—			—			—
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		(95	)		—			—			(95	)
Unrealized loss on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			5,586			5,586
Balances at March 31, 2023		—	$	—	$	(26,317	)	$	—		$	21,044		$	(5,273	)

As Restated
Balances at December 31, 2022		14,215,302	$	1	$	500,827		$	(251	)	$	(444,493	)	$	56,084
Issuance of common stock, net of issuance costs, under ATM equity offering program		106,781		—		274			—			—			274
Vesting of restricted stock units		37,131		—		—			—			—			—
Stock-based compensation		—		—		2,175			—			—			2,175
Unrealized gain on available-for-sale marketable securities		—		—		—			101			—			101
Net loss		—		—		—			—			(5,279	)		(5,279	)
Balances at March 31, 2023		14,359,214	$	1	$	503,276		$	(150	)	$	(449,772	)	$	53,355


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at March 31, 2023		14,359,214	$	1	$	529,593		$	(150	)	$	(470,816	)	$	58,628
Issuance of common stock, net of issuance costs, under ATM equity offering program		168,000		—		518			—			—			518
Issuance of common stock under 2018 ESPP		41,497		—		91			—			—			91
Vesting of restricted stock units		26,766		—		—			—			—			—
Stock-based compensation		—		—		2,361			—			—			2,361
Unrealized gain on available-for-sale marketable securities		—		—		—			14			—			14
Net loss		—		—		—			—			(12,205	)		(12,205	)
Balances at June 30, 2023		14,595,477	$	1	$	532,563		$	(136	)	$	(483,021	)	$	49,407

Adjustment
Balances at March 31, 2023		—	$	—	$	(26,317	)	$	—		$	21,044		$	(5,273	)
Issuance of common stock, net of issuance costs, under ATM equity offering program		—		—		—			—			—			—
Issuance of common stock under 2018 ESPP		—		—		—			—			—			—
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		(114	)		—			—			(114	)
Unrealized gain on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			(3,251	)		(3,251	)
Balances at June 30, 2023		—	$	—	$	(26,431	)	$	—		$	17,793		$	(8,638	)

As Restated
Balances at March 31, 2023		14,359,214	$	1	$	503,276		$	(150	)	$	(449,772	)	$	53,355
Issuance of common stock, net of issuance costs, under ATM equity offering program		168,000		—		518			—			—			518
Issuance of common stock under 2018 ESPP		41,497		—		91			—			—			91
Vesting of restricted stock units		26,766		—		—			—			—			—
Stock-based compensation		—		—		2,247			—			—			2,247
Unrealized gain on available-for-sale marketable securities		—		—		—			14			—			14
Net loss		—		—		—			—			(15,456	)		(15,456	)
Balances at June 30, 2023		14,595,477	$	1	$	506,132		$	(136	)	$	(465,228	)	$	40,769


	Common Stock				Additional Paid-In			Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital			Gain (Loss)			Deficit			Equity
As Previously Reported
Balances at June 30, 2023		14,595,477	$	1	$	532,563		$	(136	)	$	(483,021	)	$	49,407
Fees related to the ATM offering program		—		—		(48	)		—			—			(48	)
Vesting of restricted stock units		19,413		—		—			—			—			—
Stock-based compensation		—		—		2,055			—			—			2,055
Unrealized gain on available-for-sale marketable securities		—		—		—			81			—			81
Net loss		—		—		—			—			(15,289	)		(15,289	)
Balances at September 30, 2023		14,614,890	$	1	$	534,570		$	(55	)	$	(498,310	)	$	36,206

Adjustment
Balances at June 30, 2023		—	$	—	$	(26,431	)	$	—		$	17,793		$	(8,638	)
Fees related to the ATM offering program		—		—		—			—			—			—
Vesting of restricted stock units		—		—		—			—			—			—
Stock-based compensation		—		—		(350	)		—			—			(350	)
Unrealized gain on available-for-sale marketable securities		—		—		—			—			—			—
Net loss		—		—		—			—			507			507
Balances at September 30, 2023		—	$	—	$	(26,781	)	$	—		$	18,300		$	(8,481	)

As Restated
Balances at June 30, 2023		14,595,477	$	1	$	506,132		$	(136	)	$	(465,228	)	$	40,769
Fees related to the ATM offering program		—		—		(48	)		—			—			(48	)
Vesting of restricted stock units		19,413		—		—			—			—			—
Stock-based compensation		—		—		1,705			—			—			1,705
Unrealized gain on available-for-sale marketable securities		—		—		—			81			—			81
Net loss		—		—		—			—			(14,782	)		(14,782	)
Balances at September 30, 2023		14,614,890	$	1	$	507,789		$	(55	)	$	(480,010	)	$	27,725

Statements of Cash Flow

Statements of Cash Flows


	Nine Months Ended September 30, 2022
	As Previously Reported			Adjustment			Reference	As Restated
Operating activities
Net loss	$	(45,758	)	$	8,711		a,b	$	(37,047	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		1,771			—				1,771
Amortization of debt issuance costs		989			—				989
Debt extinguishment gain upon conversion to equity		(199	)		—				(199	)
Net accretion and amortization of premium and discounts on marketable securities		155			—				155
Gain on disposal of property and equipment		(247	)		—				(247	)
Stock-based compensation		7,120			—				7,120
Non-cash rent expense		(1,891	)		—				(1,891	)
(Gain) loss on warrant liability		—			(10,974	)	a		(10,974	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(1,355	)		150		b		(1,205	)
Other long-term assets		15			—				15
Accounts payable		459			—				459
Accrued compensation		(1,067	)		—				(1,067	)
Accrued liabilities and other current liabilities		(632	)		728		b		96
Other long-term liabilities		(23	)		—				(23	)
Net cash used in operating activities		(40,663	)		(1,385	)			(42,048	)
Investing activities
Purchase of marketable securities		(86,567	)		—				(86,567	)
Maturities of marketable securities		62,000			—				62,000
Purchase of property and equipment		(59	)		—				(59	)
Sale of property and equipment		272			—				272
Net cash used in investing activities		(24,354	)		—				(24,354	)
Financing activities
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		12,003			—				12,003
Proceeds from sale of common stock and warrants under Follow-On Offering		41,650			3,350		a		45,000
Issuance costs for sale of common stock		—			(1,965	)	a		(1,965	)
Proceeds from issuance of common stock to Lincoln Park Capital Fund, net of issuance costs		910			—				910
Proceeds from issuance of common stock under 2018 ESPP		125			—				125
Net cash provided by financing activities		54,688			1,385				56,073
Net decrease in cash, cash equivalents and restricted cash		(10,329	)		—				(10,329	)
Cash, cash equivalents and restricted cash at beginning of the period		34,351			—				34,351
Cash, cash equivalents and restricted cash at end of the period	$	24,022		$	—			$	24,022
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	1,577		$	—			$	1,577
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt	$	3,179		$	—			$	3,179

Cash and cash equivalents	$	22,576		$	—			$	22,576
Restricted cash		1,446			—			$	1,446
Total cash, cash equivalents and restricted cash	$	24,022		$	—			$	24,022


	Three Months Ended March 31, 2023
	As Previously Reported			Adjustment			Reference	As Restated
Operating activities
Net loss	$	(10,865	)	$	5,586		a,d	$	(5,279	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		329			—				329
Amortization of debt issuance costs		314			—				314
Net accretion and amortization of premium and discounts on marketable securities		(433	)		—				(433	)
Stock-based compensation		2,270			(95	)	d		2,175
Non-cash rent expense		(270	)		—				(270	)
(Gain) loss on warrant liability		—			(5,491	)	a		(5,491	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(1,249	)		—				(1,249	)
Other long-term assets		23			—				23
Accounts payable		(320	)		—				(320	)
Accrued compensation		(1,037	)		—				(1,037	)
Accrued liabilities and other current liabilities		(78	)		—				(78	)
Net cash used in operating activities		(11,316	)		—				(11,316	)
Investing activities
Purchase of marketable securities		(5,973	)		—				(5,973	)
Maturities of marketable securities		27,251			—				27,251
Net cash provided by investing activities		21,278			—				21,278
Financing activities
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		274			—				274
Net cash provided by financing activities		274			—				274
Net increase in cash, cash equivalents and restricted cash		10,236			—				10,236
Cash, cash equivalents and restricted cash at beginning of the period		13,632			—				13,632
Cash, cash equivalents and restricted cash at end of the period	$	23,868		$	—			$	23,868
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	680		$	—			$	680

Cash and cash equivalents	$	22,972		$	—			$	22,972
Restricted cash		896			—			$	896
Total cash, cash equivalents and restricted cash	$	23,868		$	—			$	23,868


	Six Months Ended June 30, 2023
	As Previously Reported			Adjustment			Reference	As Restated
Operating activities
Net loss	$	(23,070	)	$	2,335		a,c,d	$	(20,735	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		643			—				643
Amortization of debt issuance costs		653			(96	)	c		557
Net accretion and amortization of premium and discounts on marketable securities		(831	)		—				(831	)
Stock-based compensation		4,631			(209	)	d		4,422
Non-cash rent expense		(540	)		—				(540	)
(Gain) loss on warrant liability		—			(2,030	)	a		(2,030	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(2,134	)		—				(2,134	)
Other long-term assets		47			—				47
Accounts payable		(341	)		—				(341	)
Accrued compensation		(1,368	)		—				(1,368	)
Accrued liabilities and other current liabilities		(89	)		—				(89	)
Net cash used in operating activities		(22,399	)		—				(22,399	)
Investing activities
Purchase of marketable securities		(21,868	)		—				(21,868	)
Maturities of marketable securities		53,000			—				53,000
Net cash provided by investing activities		31,132			—				31,132
Financing activities
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		792			—				792
Repayment of term loan debt		(3,234	)		—				(3,234	)
Proceeds from issuance of common stock under 2018 ESPP		91			—				91
Net cash used in financing activities		(2,351	)		—				(2,351	)
Net increase in cash, cash equivalents and restricted cash		6,382			—				6,382
Cash, cash equivalents and restricted cash at beginning of the period		13,632			—				13,632
Cash, cash equivalents and restricted cash at end of the period	$	20,014		$	—			$	20,014
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	1,362		$	—			$	1,362

Cash and cash equivalents	$	19,118		$	—			$	19,118
Restricted cash		896			—			$	896
Total cash, cash equivalents and restricted cash	$	20,014		$	—			$	20,014


	Nine Months Ended September 30, 2023
	As Previously Reported			Adjustment			Reference	As Restated
Operating activities
Net loss	$	(38,362	)	$	2,842		a,d	$	(35,520	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		951			—				951
Amortization of debt issuance costs		705			—				705
Debt extinguishment loss upon paydown of principal		491			—				491
Net accretion and amortization of premium and discounts on marketable securities		(1,199	)		—				(1,199	)
Stock-based compensation		6,686			(559	)	d		6,127
Non-cash rent expense		(811	)		—				(811	)
Impairment of long-lived assets		5,602			—				5,602
(Gain) loss on warrant liability		—			(2,283	)	a		(2,283	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(1,858	)		—				(1,858	)
Other long-term assets		52			—				52
Accounts payable		(642	)		—				(642	)
Accrued compensation		(793	)		—				(793	)
Accrued liabilities and other current liabilities		(335	)		—				(335	)
Net cash used in operating activities		(29,513	)		—				(29,513	)
Investing activities
Purchase of marketable securities		(28,609	)		—				(28,609	)
Maturities of marketable securities		74,000			—				74,000
Purchase of property and equipment		(11	)		—				(11	)
Sale of property and equipment		1			—				1
Net cash provided by investing activities		45,381			—				45,381
Financing activities
Payment of debt principal		(20,000	)		—				(20,000	)
Payment of debt issuance costs		(1,563	)		—				(1,563	)
Proceeds from issuance of common stock under ATM offering program, net of issuance costs		744			—				744
Proceeds from issuance of common stock under 2018 ESPP		91			—				91
Net cash used in financing activities		(20,728	)		—				(20,728	)
Net decrease in cash, cash equivalents and restricted cash		(4,860	)		—				(4,860	)
Cash, cash equivalents and restricted cash at beginning of the period		13,632			—				13,632
Cash, cash equivalents and restricted cash at end of the period	$	8,772		$	—			$	8,772
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	$	1,969		$	—			$	1,969

Cash and cash equivalents	$	7,876		$	—			$	7,876
Restricted cash		896			—			$	896
Total cash, cash equivalents and restricted cash	$	8,772		$	—			$	8,772

Organization

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization

1. Organization

Description of Business

Unity Biotechnology, Inc. (the “Company”) is a biotechnology company engaged in the research and development of therapeutics to slow, halt, or reverse diseases of aging. The Company devotes substantially all of its time and efforts to performing research and development and raising capital. The Company’s headquarters are located in South San Francisco, California. The Company was incorporated in the State of Delaware in 2009.

Liquidity

The Company’s Financial Statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The Company has incurred operating losses and has an accumulated deficit as a result of ongoing efforts to develop drug product candidates, including conducting preclinical and clinical trials and providing general and administrative support for these operations. The Company had an accumulated deficit of $484.4 million as of December 31, 2023. During the year ended December 31, 2023, the Company incurred a net loss of $39.9 million and used $37.1 million of cash in operating activities. To date, none of the Company’s drug candidates have been approved for sale, and therefore, the Company has not generated any product revenue and does not expect positive cash flows from operations in the foreseeable future. The Company has financed its operations primarily through private placements of preferred stock and promissory notes, public equity issuances and more recently, from its ATM Offering Programs (as defined in Note 12), an Equity Purchase Agreement (as defined in Note 12), and the sale of common stock and warrants under a Follow-On Offering and the Inducement Offer (as defined in Note 12) and will continue to be dependent upon equity and/or debt financing until the Company is able to generate positive cash flows from its operations.

The Company anticipates operating losses and negative operating cash flows to continue for the foreseeable future. The Company had cash, cash equivalents and marketable securities of $43.2 million as of December 31, 2023. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations. Although the Company has been successful in raising capital in the past, there is no assurance that it will be successful in obtaining such additional financing. If sufficient funds on acceptable terms are not available when needed, the Company could be further required to significantly reduce its operating expenses and delay, reduce the scope of, or eliminate one or more of its development programs. Failure to manage discretionary spending or raise additional financing, as needed, may adversely impact the Company’s ability to achieve its intended business objectives, or the Company may be forced to liquidate assets where possible, or to cease operations or file for bankruptcy protection. The Company expects that its cash, cash equivalents, and marketable securities will be sufficient to fund its operations for a period of at least one year from the date the accompanying financial statements are filed with the Securities and Exchange Commission.

Statements of Operations and Comprehensive Loss - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Sep. 30, 2022

Jun. 30, 2023

Sep. 30, 2023

Sep. 30, 2022

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Statement of Comprehensive Income [Abstract]

Licensing revenue – Related Party

$ 0

$ 236

$ 0

$ 236

$ 4,784

Operating expenses:

Research and development

$ 4,632

6,435

$ 5,760

9,086

12,195

$ 16,828

29,100

20,099

36,859

38,393

General and administrative

4,347

5,413

4,798

4,922

10,212

14,560

15,669

18,966

20,949

23,056

Impairment of long-lived assets

5,602

Total operating expenses

14,581

11,848

10,558

14,008

22,407

36,990

44,769

44,667

57,808

61,449

Loss from operations

(14,581)

(11,848)

(10,558)

(14,008)

(22,407)

(36,990)

(44,533)

(44,667)

(57,572)

(56,665)

Interest income

689

805

855

329

1,660

2,349

416

2,874

1,220

100

Interest expense

(566)

(883)

(1,002)

(866)

(1,885)

(2,451)

(2,568)

(2,452)

(3,558)

(3,177)

Gain (loss) on warrant liability

6,215

16,843

Other expense, net

(577)

(69)

(65)

(1,426)

(133)

(711)

(1,336)

(1,830)

(1,402)

(983)

Net loss

(14,782)

(15,456)

(5,279)

(4,997)

(20,735)

(35,520)

(37,047)

(39,860)

(44,469)

(60,725)

Other comprehensive gain (loss)

Unrealized gain (loss) on marketable debt securities

101

(88)

115

196

(231)

227

(207)

(49)

Comprehensive loss

$ (14,701)

$ (15,442)

$ (5,178)

$ (5,085)

$ (20,620)

$ (35,324)

$ (37,278)

$ (39,633)

$ (44,676)

$ (60,774)

Net loss per share, basic

$ (1.01)

$ (1.07)

$ (0.37)

$ (0.5)

$ (1.44)

$ (2.46)

$ (4.67)

$ (2.7)

$ (4.68)

$ (10.88)

Net loss per share, diluted

$ (1.01)

$ (1.07)

$ (0.37)

$ (0.5)

$ (1.44)

$ (2.46)

$ (4.67)

$ (2.7)

$ (4.68)

$ (10.88)

Weighted average number of shares used in computing net loss per share, basic

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

14,773,612

^[1]

9,494,421

^[1]

5,581,587

^[1]

Weighted average number of shares used in computing net loss per share, diluted

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

14,773,612

^[1]

9,494,421

^[1]

5,581,587

^[1]

[1]

The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded up to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

License Revenue, Agreements and Strategic Investment (Tables)

12 Months Ended

Dec. 31, 2023

Research and Development [Abstract]

Schedule of Recognized Revenue of License Agreement

In accordance with the license agreements, the Company recognized revenue as follows:


	Year ended December 31,
	2023		2022		2021
Jocasta Neuroscience, Inc. (1)	$	—	$	236	$	4,784
	$	—	$	236	$	4,784

(1)

Jocasta Neuroscience, Inc. was deemed a related party at the effective time the agreement was made on December 17, 2021.

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

17. Income Taxes

The Company has incurred net operating losses for all the periods presented. The Company has not reflected the benefit of any such net operating loss carryforwards in the accompanying financial statements. The Company has established a full valuation allowance against its deferred tax assets due to the uncertainty surrounding the realization of such assets. All losses to date have been incurred domestically as the Company has no international operations or subsidiaries.

No provision for U.S. income taxes exists due to tax losses incurred in all periods presented. All losses incurred were U.S. based.

The effective tax rate for the years ended December 31, 2023, 2022 and 2021 is different from the federal statutory rate primarily due to the valuation allowance against deferred tax assets as a result of insufficient sources of income. The effective tax rate of the Company’s provision for income taxes differs from the federal statutory rate as follows:


	Year ended December 31,
	2023				2022 (Restated)				2021
Taxes at the U.S. statutory income tax rate		21.0		%		21.0		%		21.0		%
State tax, net of federal benefit		9.0				9.1				4.4
Other		0.5				(0.8	)			(0.4	)
Warrant activity		2.8				7.3				—
Stock-based compensation		(2.5	)			(6.6	)			(1.6	)
Research and development tax credits		1.8				2.9				3.2
Rate change		(8.8	)			4.7				3.8
ASC 740-10		—				(7.5	)			(4.2	)
Change in valuation allowance		(23.7	)			(30.1	)			(26.2	)
Total provision for income taxes		—		%		—		%		—		%

Deferred income taxes reflect the net tax effects of (a) temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes, and (b) operating losses and tax credit carryforwards.

The tax effects of significant items comprising the Company’s deferred income taxes are as follows:


	December 31,
	2023			2022
	(in thousands)
Deferred tax assets:
Federal and state operating loss carryforwards	$	81,094		$	73,322
Research and development tax credits		9,552			8,646
Stock-based compensation		5,078			4,589
Accruals and other		320			587
Intangibles		1,343			5,329
Section 174 capitalization research expenses		10,117			6,624
Charitable contributions		—			12
Operating lease liabilities		6,280			6,908
Total deferred tax assets		113,784			106,017
Deferred tax liabilities:
Operating lease right-of-use asset		(3,041	)		(4,371	)
Fixed assets		(1,033	)		(1,299	)
Total deferred tax liabilities		(4,074	)		(5,670	)
Valuation allowance		(109,710	)		(100,347	)
Net deferred tax assets	$	—		$	—

The tax benefit of net operating losses, temporary differences and credit carryforwards should be recorded as an asset to the extent that management assesses that their realization is "more likely than not." Realization of the future tax benefits is dependent on the Company's ability to generate sufficient taxable income within the carryforward period. Because of the Company's recent history of operating losses, management believes that recognition of the deferred tax assets arising from the above-mentioned future tax benefits is currently not likely to be realized and, accordingly, has provided a valuation allowance.

Realization of the net deferred tax assets is dependent upon future taxable income, if any, the amount and timing of which is uncertain. Based on the weight of available positive and negative objective evidence, management believes it more likely than not that the Company’s deferred tax assets are not realizable. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. The valuation allowance increased by $9.4 million and $13.4 million during the years ended December 31, 2023 and 2022, respectively.

Net operating losses and tax credit carryforwards as of December 31, 2023 are as follows:


	Amount (in thousands)		Expiration Years
Net operating losses, federal (post December 31, 2017)	$	305,873	Do Not Expire
Net operating losses, federal (pre January 1, 2018)		64,136	2029 - 2037
Net operating losses, state		185,897	2034 - 2043
Research and development tax credits, federal		8,799	2034 - 2043
Research and development tax credits, California		7,070	Indefinite

Federal and state laws impose restrictions on the utilization of net operating loss carryforwards and R&D credit carryforwards in the event of a change in ownership of the Company, which constitutes an 'ownership change' as defined by Internal Revenue Code Section 382 and 383. The Company experienced an ownership change in the past that impacts the availability of its net operating losses and tax credits. The amounts indicated in the above tables reflect the reduction of net operating losses and credit carryforwards as a result of previous ownership changes that the Company experienced. In August 2022, the Company's Follow-On Offering may have resulted in an ownership change, which could substantially restrict the ability to utilize existing net operating losses, credits and other attribute carryforwards as well. The Company is still analyzing the impact of the Follow-On Offering relative to Internal Revenue Code Sections 382 and 383.

The Inflation Reduction Act 2022 which incorporates a Corporate Alternative Minimum Tax (CAMT) was signed on August 16, 2022. The changes will be effective for the tax years beginning after December 31, 2022. The new tax will require companies to compute two separate calculations for federal income tax purposes and pay the greater of the new minimum tax or their regular tax liability. The IRA is not expected to have a material impact for the Company.

The Company determines its uncertain tax positions based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings is more likely than not to be sustained upon examination by the relevant income tax authorities.

The following table summarizes the activity related to the Company’s unrecognized tax benefits:


	Year ended December 31,
	2023			2022			2021
	(in thousands)
Gross unrecognized tax benefits at January 1	$	17,605		$	13,221		$	7,142
Additions for tax positions taken in the current year		84			4,395			3,457
Reductions for tax positions taken in the prior year		(232	)		(11	)		2,622
Gross unrecognized tax benefits at December 31	$	17,457		$	17,605		$	13,221

If recognized, none of the unrecognized tax benefits as of December 31, 2023 and 2022 would reduce the annual effective tax rate, primarily due to corresponding adjustments to the valuation allowance. The Company will recognize both accrued interest and penalties related to unrecognized benefits in income tax expense. As of December 31, 2023 and 2022, no liability has been recorded for potential interest or penalties. The Company does not expect the unrecognized tax benefits to change significantly over the next 12 months.

The Company files income tax returns in the U.S. federal jurisdiction and Arizona, California, Colorado, Delaware, Florida, Illinois, Massachusetts, Rhode Island and Washington. The Company is not currently under audit by the Internal Revenue Service or other similar state or local authorities. All tax years remain open to examination by major taxing jurisdictions to which the Company is subject.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Quarterly Financial Information (Unaudited) - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accrued and other current liabilities	$ 5,258	$ 5,417	$ 5,343	$ 5,321	$ 5,417	$ 5,258	$ 5,321	$ 4,619	$ 5,334
Prepaid expenses and other current assets	3,599	3,874	2,989	3,084	3,874	3,599	3,084	3,404	1,740
Accrued research and development liability								839	1,623
Research and development operating expense	4,632	6,435	5,760	9,086	12,195	16,828	29,100	20,099	36,859	$ 38,393
Amortization of debt issuance costs			314		557	705	989	705	1,318	813
Long-term debt liability		4,067	7,619	13,262	4,067		13,262	0	10,891
Interest expense	566	883	1,002	866	1,885	2,451	2,568	2,452	3,558	3,177
Stock-compensation expense			2,175		4,422	6,127	7,120	$ 7,419	$ 9,379	$ 11,553
Revision of Prior Period, Error Correction, Adjustment \| Understated
Accrued and other current liabilities				900			900
Research and development operating expense	900					900
Long-term debt liability		100			100
Revision of Prior Period, Error Correction, Adjustment \| Overstated
Prepaid expenses and other current assets				$ 900			$ 900
Amortization of debt issuance costs					100
Interest expense		100			100
Stock-compensation expense	$ 300	$ 100	$ 100		$ 200	$ 600

Restatement of Previously Issued Financial Statements - Schedule of Restated Balance Sheet (Parenthetical) (Details)	Oct. 19, 2022	Dec. 31, 2023 $ / shares shares	Sep. 30, 2023 $ / shares shares	Jun. 30, 2023 $ / shares shares	Mar. 31, 2023 $ / shares shares	Dec. 31, 2022 $ / shares shares	Sep. 30, 2022 $ / shares shares
Statement of Financial Position [Abstract]
Convertible preferred stock, par value \| $ / shares		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized		10,000,000	10,000,000	10,000,000	10,000,000	10,000,000	10,000,000
Convertible preferred stock, shares issued		0	0	0	0	0	0
Convertible preferred stock, shares outstanding		0	0	0	0	0	0
Common stock, par value \| $ / shares		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares authorized		300,000,000	300,000,000	300,000,000	300,000,000	300,000,000	300,000,000
Common stock, shares issued		16,784,969	14,614,890	14,595,477	14,359,214	14,215,302	14,036,249
Common stock, shares outstanding		16,784,969	14,614,890	14,595,477	14,359,214	14,215,302	14,036,249
Reverse stock split ratio	0.1

Marketable Securities

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

5. Marketable Securities

Marketable securities, which are classified as available-for-sale, consisted of the following (in thousands):


	December 31, 2023
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	12,864	$	—	$	—		$	12,864
U.S. treasuries		2,989		—		—			2,989
Total cash equivalents		15,853		—		—			15,853
Short-term marketable securities:
U.S. treasuries		7,853		4		(8	)		7,849
U.S. government debt securities		15,570		1		(22	)		15,549
Total short-term marketable securities		23,423		5		(30	)		23,398
Restricted Cash equivalents:
Money market funds		896		—		—		$	896
Total restricted cash equivalents		896		—		—			896
Total	$	40,172	$	5	$	(30	)	$	40,147


	December 31, 2022
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	5,083	$	—	$	—		$	5,083
Total cash equivalents		5,083		—		—			5,083
Short-term marketable securities:
U.S. treasuries		51,491		6		(196	)		51,301
U.S. government debt securities		30,820		1		(63	)		30,758
Total short-term marketable securities		82,311		7		(259	)		82,059
Total	$	87,394	$	7	$	(259	)	$	87,142

At December 31, 2023, the remaining contractual maturities of available-for-sale debt securities were less than a year. There have been no significant realized gains or losses on available-for-sale debt securities for the periods presented. As of December 31, 2023, the Company did not hold any individual securities in an unrealized loss position for 12 months or greater. The Company has the ability and intent to hold all marketable securities that have been in a continuous loss position until maturity or recovery. No significant facts or circumstances have arisen to indicate that there has been any significant deterioration in the creditworthiness of the issuers of the securities held by the Company. The Company considered the current and expected future economic and market conditions and determined that the estimate of credit losses was not significantly impacted. Thus, there has been no change in estimate of expected credit loss during the year ended December 31, 2023 and no allowance for credit loss was recorded at December 31, 2023. The Company will continue to assess the current and expected future economic and market conditions as further development arises.

See Note 4, “Fair Value Measurements,” for further information regarding the fair value of the Company's financial instruments.

Commitments and Contingencies - Summary of Supplemental Information Related to Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 4,810	$ 6,283	$ 6,653
Weighted-average remaining lease term (years)	6 years	7 years	7 years 8 months 12 days
Weighted-average discount rate (percentage)	6.00%	6.00%	5.90%

License Revenue, Agreements and Strategic Investment - Schedule of Recognized Revenue of License Agreement (Details) - Collaboration Agreement - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2022

Dec. 31, 2021

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized

$ 236

$ 4,784

Jocasta Neuroscience, Inc.

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized

^[1]

$ 236

$ 4,784

[1]	Jocasta Neuroscience, Inc. was deemed a related party at the effective time the agreement was made on December 17, 2021.

Balance Sheet Components

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

7. Balance Sheet Components

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):


	December 31,
	2023		2022
Prepaid research and development expenses	$	415	$	378
Prepaid insurance expenses		541		710
Tax credit receivable		1,493		—
Interest receivable		84		235
Other prepaid expenses and current assets		871		417
	$	3,404	$	1,740

Property and Equipment, Net

Property and equipment, net, consists of the following (in thousands):


	December 31,
	2023			2022
Laboratory equipment	$	3,894		$	4,197
Computer equipment		303			412
Furniture and fixtures		627			726
Leasehold improvements		9,519			15,244
Total property and equipment		14,343			20,579
Less: accumulated depreciation and amortization		(9,261	)		(12,754	)
Total property and equipment, net	$	5,082		$	7,825

Depreciation and amortization expense related to property and equipment was $1.2 million, $2.2 million and $2.9 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Accrued and Other Current Liabilities

Accrued and other current liabilities consist of the following (in thousands):


	December 31,
	2023		2022
Operating lease liability - current portion	$	3,451	$	3,100
Accrued research and development		839		1,623
Liability related to early exercise shares		10		10
Accrued other		319		601
	$	4,619	$	5,334

Marketable Securities - Summary of Marketable Securities Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	$ 40,172	$ 87,394
Unrealized Gains	5	7
Unrealized Losses	(30)	(259)
Fair Value	40,147	87,142
Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	15,853	5,083
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	15,853	5,083
Cash Equivalents \| Money market funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	12,864	5,083
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	12,864	5,083
Cash Equivalents \| U S Treasuries
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	2,989
Unrealized Gains	0
Unrealized Losses	0
Fair Value	2,989
Short Term Marketable Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	23,423	82,311
Unrealized Gains	5	7
Unrealized Losses	(30)	(259)
Fair Value	23,398	82,059
Short Term Marketable Securities \| U.S. government debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	15,570	30,820
Unrealized Gains	1	1
Unrealized Losses	(22)	(63)
Fair Value	15,549	30,758
Short Term Marketable Securities \| U S Treasuries
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	7,853	51,491
Unrealized Gains	4	6
Unrealized Losses	(8)	(196)
Fair Value	7,849	$ 51,301
Restricted Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	896
Unrealized Gains	0
Unrealized Losses	0
Fair Value	896
Restricted Cash Equivalents \| Money market funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	896
Unrealized Gains	0
Unrealized Losses	0
Fair Value	$ 896

Net Loss per Common Share - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	8,562,447	8,254,118	1,083,900
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	1,913,345	1,609,938	866,696
Outstanding warrants to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	6,557,152	6,428,572
Early Exercised Common Stock Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	3,336	3,336	3,336
RSUs Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	41,225	146,333	199,094
Shares Subject to Future Vesting Relating to the 2018 ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	47,389	65,939	14,774

Government Assistance Program - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Government Assistance [Line Items]
Employee retention credit receivable	$ 1.5	$ 0.0
CARES Act Member
Government Assistance [Line Items]
Refundable employee retention credit	1.5
Contra-expense to personnel related cost		$ 0.0
General and Administrative Expense \| CARES Act Member
Government Assistance [Line Items]
Contra-expense to personnel related cost	0.4
Research and Development Expense \| CARES Act Member
Government Assistance [Line Items]
Contra-expense to personnel related cost	$ 1.1

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2023	Apr. 08, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Registrant Name	Unity Biotechnology, Inc.
Entity Central Index Key	0001463361
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding		16,786,647
Entity Public Float			$ 34,108,688
Entity File Number	001-38470
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-4726035
Entity Address, Address Line One	285 East Grand Ave.
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	416-1192
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	false
Title of 12(b) Security	Common Stock, par value $0.0001
Security Exchange Name	NASDAQ
Trading Symbol	UBX
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	San Mateo, California
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the Registrant’s Definitive Proxy Statement relating to the 2024 Annual Meeting of Shareholders, scheduled to be held on June 21, 2024, are incorporated by reference into Part III of this Report. Such proxy statement will be filed with the Securities and Exchange Commission within 120 days of the end of the fiscal year covered by this Annual Report on Form 10-K.
Document Financial Statement Error Correction [Flag]	true
Document Financial Statement Restatement Recovery Analysis [Flag]	false

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Summary of Financial Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis and Level of Inputs Used in Measurements

The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands):


	December 31, 2023
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	12,864	$	12,864	$	—	$	—
U.S. treasuries		2,989		—		2,989		—
Total cash equivalents		15,853		12,864		2,989		—
Short-term marketable securities:
U.S. treasuries		7,849		—		7,849		—
U.S. government debt securities		15,549		—		15,549		—
Total short-term marketable securities		23,398		—		23,398		—
Restricted Cash equivalents:
Money market funds		896		896		—		—
Total restricted cash equivalents		896		896		—		—
Total assets subject to fair value measurements on a recurring basis	$	40,147	$	13,760	$	26,387	$	—

Liabilities:
Warrant Liability	$	5,913	$	—	$	—	$	5,913
Total liabilities subject to fair value measurements on a recurring basis		5,913		—		—		5,913


	December 31, 2022
	(Restated)
	Total		Level 1		Level 2		Level 3 (Restated)
Assets:
Cash equivalents:
Money market funds	$	5,083	$	5,083	$	—	$	—
Total cash equivalents		5,083		5,083		—		—
Short-term marketable securities:
U.S. treasuries		30,758		—		30,758		—
U.S. government debt securities		51,301		—		51,301		—
Total short-term marketable securities		82,059		—		82,059		—
Total assets subject to fair value measurements on a recurring basis	$	87,142	$	5,083	$	82,059	$	—

Liabilities:
Warrant Liability (Restated)	$	10,764	$	—	$	—	$	10,764
Total liabilities subject to fair value measurements on a recurring basis		10,764		—		—		10,764

Summary of Assumptions used in Fair Value Estimates of Level 3 Warrant Liabilities


	August 22, 2022 (issuance)			September 30, 2022			December 31, 2022			March 31, 2023			June 30, 2023			September 30, 2023			November 14, 2023 (exercise)			December 31, 2023
Common stock price	$	6.10		$	3.95		$	2.74		$	1.63		$	2.55		$	2.40		$	1.72		$	1.93
Exercise price per share	$	8.50		$	8.50		$	8.50		$	8.50		$	8.50		$	8.50		$	2.045		$	8.50
Estimated volatility		87.5	%		90.0	%		95.0	%		100.0	%		95.0	%		100.0	%		80.0	%		80.0	%
Risk-free interest rate		3.17	%		4.07	%		4.03	%		3.66	%		4.28	%		4.71	%		4.42	%		3.85	%
Contractual term (in years)		5.00			4.89			4.64			4.39			4.14			3.89			3.77			3.64


		November 14, 2023 (issuance)				December 31, 2023
Common stock price	$	1.72			$	1.93
Exercise price per share	$	1.92-2.5563			$	1.92-2.5563
Expected volatility			80.0	%			80.0	%
Risk-free interest rate			4.42	%			3.85	%
Contractual term (in years)			5.00				4.87

Sumarry of Roll forward of the fair value of level 3 Warrants

The following is a roll forward of the fair value of Level 3 warrants:


	Warrant Liability Fair Value
Beginning balance at December 31, 2021	$	—
Warrants Issued		27,607
Change in fair value		(16,842	)
Ending balance at December 31, 2022 (Restated)		10,765
Warrants Issued		2,724
Warrants Exercised		(1,361	)
Change in fair value		(6,215	)
Balance at December 31, 2023	$	5,913

Government Assistance Program

12 Months Ended

Dec. 31, 2023

Government Assistance [Abstract]

Government Assistance Program

8. Government Assistance Program

Under the CARES Act, the Company met eligibility criteria and was approved for a $1.5 million refundable employee retention credit. The Company recorded contra-expense to personnel related costs within general and administrative expense of $0.4 million and research and development expense of $1.1 million for the year ended December 31, 2023. No such amounts were recorded for the year ended December 31, 2022.

The Company had an employee retention credit receivable due from the U.S. Department of Treasury of $1.5 million in other current assets as of December 31, 2023 in the balance sheet. There was no employee retention credit receivable due from the U.S. Department of Treasury as of December 31, 2022.

Restatement of Previously Issued Financial Statements - Schedule of Restated Statement of Operations and Comprehensive Loss (Details) - USD ($)
$ / shares in Units, $ in Thousands

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Sep. 30, 2022

Jun. 30, 2023

Sep. 30, 2023

Sep. 30, 2022

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Licensing revenue – Related Party

$ 0

$ 236

$ 0

$ 236

$ 4,784

Operating expenses:

Research and development

$ 4,632

6,435

$ 5,760

9,086

12,195

$ 16,828

29,100

20,099

36,859

38,393

General and administrative

4,347

5,413

4,798

4,922

10,212

14,560

15,669

18,966

20,949

23,056

Total operating expenses

14,581

11,848

10,558

14,008

22,407

36,990

44,769

44,667

57,808

61,449

Loss from operations

(14,581)

(11,848)

(10,558)

(14,008)

(22,407)

(36,990)

(44,533)

(44,667)

(57,572)

(56,665)

Interest income

689

805

855

329

1,660

2,349

416

2,874

1,220

100

Interest expense

(566)

(883)

(1,002)

(866)

(1,885)

(2,451)

(2,568)

(2,452)

(3,558)

(3,177)

Gain (loss) on warrant liability

6,215

16,843

Other expense, net

(577)

(69)

(65)

(1,426)

(133)

(711)

(1,336)

(1,830)

(1,402)

(983)

Net loss

(14,782)

(15,456)

(5,279)

(4,997)

(20,735)

(35,520)

(37,047)

(39,860)

(44,469)

(60,725)

Other comprehensive loss

Unrealized loss on marketable debt securities

101

(88)

115

196

(231)

227

(207)

(49)

Comprehensive loss

$ (14,701)

$ (15,442)

$ (5,178)

$ (5,085)

$ (20,620)

$ (35,324)

$ (37,278)

$ (39,633)

$ (44,676)

$ (60,774)

Net loss per share, basic

$ (1.01)

$ (1.07)

$ (0.37)

$ (0.5)

$ (1.44)

$ (2.46)

$ (4.67)

$ (2.7)

$ (4.68)

$ (10.88)

Net loss per share, diluted

$ (1.01)

$ (1.07)

$ (0.37)

$ (0.5)

$ (1.44)

$ (2.46)

$ (4.67)

$ (2.7)

$ (4.68)

$ (10.88)

Weighted average number of shares used in computing net loss per share, basic

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

14,773,612

^[1]

9,494,421

^[1]

5,581,587

^[1]

Weighted average number of shares used in computing net loss per share, diluted

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

14,773,612

^[1]

9,494,421

^[1]

5,581,587

^[1]

As Previously Reported

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Licensing revenue – Related Party

$ 0

$ 236

Operating expenses:

Research and development

$ 4,901

6,529

$ 5,835

8,208

12,364

$ 17,266

28,222

36,859

General and administrative

4,428

5,433

4,818

4,922

10,252

14,681

15,669

20,949

Total operating expenses

14,931

11,962

10,653

13,130

22,616

37,549

43,891

57,808

Loss from operations

(14,931)

(11,962)

(10,653)

(13,130)

(22,616)

(37,549)

(43,655)

(57,572)

Interest income

689

805

855

329

1,660

2,349

416

1,220

Interest expense

(470)

(979)

(1,002)

(866)

(1,981)

(2,451)

(2,568)

(3,558)

Gain (loss) on warrant liability

Other expense, net

(577)

(69)

(65)

(41)

(133)

(711)

(17)

Net loss

(15,289)

(12,205)

(10,865)

(13,708)

(23,070)

(38,362)

(45,758)

(59,927)

Other comprehensive loss

Unrealized loss on marketable debt securities

101

(88)

115

196

(231)

(207)

Comprehensive loss

$ (15,208)

$ (12,191)

$ (10,764)

$ (13,796)

$ (22,955)

$ (38,166)

$ (45,989)

$ (60,134)

Net loss per share, basic

$ (1.05)

$ (0.85)

$ (0.76)

$ (1.36)

$ (1.61)

$ (2.66)

$ (5.77)

$ (6.31)

Net loss per share, diluted

$ (1.05)

$ (0.85)

$ (0.76)

$ (1.36)

$ (1.61)

$ (2.66)

$ (5.77)

$ (6.31)

Weighted average number of shares used in computing net loss per share, basic

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

9,494,421

Weighted average number of shares used in computing net loss per share, diluted

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

9,494,421

Adjustment

Error Corrections and Prior Period Adjustments Restatement [Line Items]

Licensing revenue – Related Party

$ 0

Operating expenses:

Research and development

$ (269)

(94)

$ (75)

878

(169)

$ (438)

878

General and administrative

(81)

(20)

(40)

(121)

Total operating expenses

(350)

(114)

(95)

878

(209)

(559)

878

Loss from operations

350

114

(878)

209

559

(878)

Interest income

Interest expense

(96)

Gain (loss) on warrant liability

16,843

Other expense, net

(1,385)

Net loss

507

(3,251)

5,586

8,711

2,335

2,842

8,711

15,458

Other comprehensive loss

Unrealized loss on marketable debt securities

Comprehensive loss

$ 507

$ (3,251)

$ 5,586

$ 8,711

$ 2,335

$ 2,842

$ 8,711

$ 15,458

Net loss per share, basic

$ 0

Net loss per share, diluted

$ 0

Weighted average number of shares used in computing net loss per share, basic

Weighted average number of shares used in computing net loss per share, diluted

[1]

The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded up to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Shares Available for Grant
Shares Available for Grant, Beginning Balance	68,838
Shares Available for Grant, Shares Added	1,010,831
Shares Available for Grant, Granted	(446,200)
Shares Available for Grant, Canceled	153,367
Shares Available for Grant, Ending Balance	786,836	68,838
Outstanding Options
Outstanding options, Beginning Balance	1,609,938
Outstanding options, Granted	446,200
Outstanding options, Canceled	(142,793)
Outstanding options, Ending Balance	1,913,345	1,609,938
Outstanding options, Vested and exercisable at December 31, 2023	1,179,366
Outstanding options. Vested and expected to vest at December 31, 2023	1,913,345
Weighted-Average Exercise Price
Weighted-Average Exercise Price, Beginning Balance	$ 27.51
Weighted-Average Exercise Price, Options granted	2.79
Weighted-Average Exercise Price, Options canceled	7.96
Weighted-Average Exercise Price, Ending Balance	14.23	$ 27.51
Weighted-Average Exercise Price, Vested exercisable as of December 31, 2023	20.51
Weighted-Average Exercise Price, Options vested and expected to vest as of December 31, 2023	$ 14.23
Weighted-Average Remaining Contract Term
Balance, weighted average remaining contractual term (Year)	7 years 1 month 6 days	8 years 3 months 18 days
Exercisable, weighted average remaining contractual term (Year)	6 years
Options vested or expected to vest at end of period, weighted average remaining contractual term (Year)	7 years 1 month 6 days
Aggregate Intrinsic Value
aggregate intrinsic value, Ending Balance	$ 5	$ 251
Aggregate intrinsic value Vested and expected to vest at December 31, 2023	$ 5

Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022
Property Plant And Equipment [Line Items]
Total property and equipment	$ 14,343				$ 20,579
Less: accumulated depreciation and amortization	(9,261)				(12,754)
Total property and equipment, net	5,082	$ 5,314	$ 7,181	$ 7,496	7,825	$ 8,202
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	3,894				4,197
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	303				412
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	627				726
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 9,519				$ 15,244

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

3. Summary of Significant Accounting Policies

Basis of Presentation

These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and the rules and regulations of Securities and Exchange Commission (“SEC”) for reporting.

The Company effected a reverse stock split on October 19, 2022 of its outstanding shares of common stock at a ratio of 1-for-10 pursuant to a Certificate of Amendment to the Company's Certificate of Incorporation filed with the Secretary of State of the State of Delaware. The reverse stock split was reflected on the Nasdaq Global Select Market beginning with the opening of trading on October 20, 2022. Accordingly, an amount equal to the par value of the decreased shares resulting from the reverse stock split was reclassified from "Additional paid-in capital" to "Common stock". Any fractional post-split shares as a result of the reverse stock split were rounded down to the nearest whole post-split share. The reverse stock split did not change the par value of the Company's common stock or the authorized number of shares of the Company's common stock. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Warrants

The Company determines the accounting classification of warrants that are issued, as either liability or equity, by first assessing whether the warrants meet liability classification in accordance with ASC 480-10, Distinguishing Liabilities from Equity, and then in accordance with ASC 815-40, Accounting for Derivative Financial Instruments Indexed to, and Potentially Settled in, a Company’s Own Stock. Under ASC 480-10, warrants are considered liability classified if the warrants are mandatorily redeemable, obligate the issuer to settle the warrants or the underlying shares by paying cash or other assets, or must or may require settlement by issuing variable number of shares.

If warrants do not meet liability classification under ASC 480-10, the Company assesses the requirements under ASC 815-40, which states that contracts that require or may require the issuer to settle the contract for cash are liabilities recorded at fair value, irrespective of the likelihood of the transaction occurring that triggers the net cash settlement feature. If the warrants do not require liability classification under ASC 815-40, in order to conclude equity classification, the Company assesses whether the warrants are indexed to its common stock and whether the warrants are classified as equity under ASC 815-40 or other applicable principles of GAAP. After all relevant assessments are made, the Company concludes whether the warrants are classified as liability or equity. Liability classified warrants are required to be accounted for at fair value both on the date of issuance and on subsequent accounting periods with changes in fair value recorded in the Statements of Operations and Comprehensive Loss under "Gain or (loss) on warrant liability".

If warrants are issued together with the sale of common stock, for the issuance costs that are not specifically attributed to either the common stock or warrants issued, the Company allocates the issuance costs between the common stock and warrants based on their relative fair value. The Company expenses issuance costs allocated to the warrants that are classified as liabilities and the issuance costs allocated to common stock or warrants that are classified as equity are recognized as reduction to the equity.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company bases its estimates on historical experience and market-specific or other relevant assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company’s balance sheets and the amount of expenses and income reported for each of the periods presented are affected by estimates and assumptions, which are used for, but are not limited to, determining the fair value of assets and liabilities, the fair value of right-of-use asset and lease liabilities, embedded derivatives and stock-based compensation. Actual results could differ from such estimates or assumptions.

Estimating fair values of liability-classified financial instruments requires the development of estimates that may, and are likely to, change over the duration of the instrument with related changes in internal and external market factors. In addition, derivatives liabilities are highly volatile and sensitive to changes in the market price of the Company’s common stock. Because liability-classified financial instruments are initially and subsequently carried at fair value, the Company’s financial results will reflect the volatility in these estimate and assumption changes. Changes in

estimated fair value are recognized as a component of "Other expense, net" in the Statements of Operations and Comprehensive Loss.

Segments

The Company has one operating segment. The Company’s chief operating decision maker, its Chief Executive Officer, manages the Company’s operations on a consolidated basis for the purposes of allocating resources.

Cash, Cash Equivalents, and Restricted Cash

The Company considers all highly liquid investments with original maturities of 90 days or less from the date of purchase to be cash equivalents. Cash equivalents primarily include money market funds that invest in U.S. Treasury obligations which are stated at fair value.

The Company has issued letters of credit under its lease agreements which have been collateralized. This cash is classified as noncurrent restricted cash on the balance sheet based on the term of the underlying lease.


	December 31,
	2023		2022		2021
Cash and cash equivalents	$	19,803	$	12,736	$	32,905
Restricted cash		896		896		1,446
Total cash, cash equivalents, and restricted cash	$	20,699	$	13,632	$	34,351

Marketable Securities

The Company generally invests its excess cash in investment grade, short to intermediate-term, fixed income securities. Such investments are considered available-for-sale debt securities and reported at fair value with unrealized gains and losses included as a component of stockholders’ equity. Marketable securities with original maturities of greater than 90 days from the date of purchase but less than one year from the balance sheet date that are available to be converted into cash to fund current operations are classified as short-term, while marketable securities with maturities in one year or beyond one year from the balance sheet date are classified as long-term. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in "Interest income" on the Statements of Operations and Comprehensive Loss. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on marketable securities are included in "Other expense, net". The cost of securities sold is determined using the specific identification method.

The Company periodically evaluates whether declines in fair values of its marketable securities below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the marketable security until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any marketable securities before recovery of its amortized cost basis. Factors considered include quoted market prices, recent financial results and operating trends, implied values from any recent transactions or offers of investee securities, credit quality of debt instrument issuers, other publicly available information that may affect the value of the marketable security, duration and severity of the decline in value, and management’s strategy and intentions for holding the marketable security. To date, the Company has not recorded any impairment charges on its marketable securities related to other-than-temporary declines in market value.

Fair Value Measurements

The Company’s financial instruments during the periods presented consist of cash and cash equivalents, restricted cash, marketable securities, strategic investments, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued and other current liabilities, derivative liabilities related to debt and long-term debt. Fair value estimates of these instruments are made at a specific point in time, based on relevant market information. Level 3 instruments incorporate certain unobservable inputs such as the selected discount rate of the related loan. These estimates may be subjective in nature and involve uncertainties and matters of judgment.

Revenue Recognition

The Company recognizes revenue in accordance with the provisions of Accounting Standards Codification Topic 606, Revenue from Contracts with Customers, or Topic 606. In determining the appropriate amount and timing of revenue to be recognized under this guidance, the Company performs the following five steps: (i) identifies the contract(s) with our customer; (ii) identifies the promised goods or services in the agreement and determine whether they are performance obligations, including whether they are distinct in the context of the agreement; (iii) measures the transaction price, including the constraint on variable consideration; (iv) allocates the transaction price to the performance obligations based on stand-alone selling prices; and (v) recognizes revenue when (or as) the Company satisfies each performance obligation.

A performance obligation is a promise in an agreement to transfer a distinct good or service to the customer and is the unit of account in Topic 606. Significant management judgment is required to determine the level of effort required and the period over which completion of the performance obligations is expected under an agreement. If reasonable estimates regarding when performance obligations are either complete or substantially complete cannot be made, then revenue recognition is deferred until a reasonable estimate can be made. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method.

The Company allocates the total transaction price to each performance obligation based on the estimated relative stand-alone selling prices of the promised goods or services underlying each performance obligation. The total consideration which the Company expects to collect in exchange for the Company’s products is an estimate and may be fixed or variable. The Company constrains the estimated variable consideration when it assesses it is probable that a significant reversal in the amount of cumulative revenue recognized may occur in future periods. The transaction price is re-evaluated, including the estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. The allocation of the transaction price is performed based on standalone selling prices, which are based on estimated amounts that the Company would charge for a performance obligation if it were sold separately. Revenue is recognized when, or as, performance obligations in the contracts are satisfied, in the amount reflecting the expected consideration to be received from the goods or services transferred to the customers. Consideration received in advance are recorded as deferred revenue and are recognized as the related performance obligation is satisfied.

Following is a description of the principal activities from which the Company generates revenue. License revenue primarily represent amounts earned under agreements that license our intellectual property to other companies. See Note 5, “License Revenue, Agreements and Strategic Investment” for further detail. Consideration under these contracts generally includes a nonrefundable upfront payment, development, regulatory and commercial milestones and royalties based on net sales of approved products.

Licenses of Intellectual Property. If the Company determines the license to intellectual property is distinct from the other performance obligations identified in the agreement and the licensee can use and benefit from the license, the Company recognizes revenue from the estimated transaction price that is allocated to the license. Licensing arrangements are analyzed to determine whether the promised goods or services, which may include licenses, transfer of know-how, transfer of materials, research and development services and governance committee services, are distinct or whether they must be accounted for as part of a combined performance obligation. If the license is considered not to be distinct, the license would then be combined with other promised goods or services as a combined performance obligation. If the Company is involved in a governance committee, it assesses whether its involvement constitutes a separate performance obligation. When governance committee services are determined to be separate performance obligations, the Company determines the fair value to be allocated to this promised service.

Milestone Payments: At the inception of each agreement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimate the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone is included in the transaction price. For milestones that the Company do not deem to be probable of being achieved, the associated milestone payments are fully constrained and the value of the milestone is excluded from the transaction price with no revenue being recognized. For example, milestone payments that are not within our control, such as regulatory-related accomplishments, are not considered probable of being achieved until those accomplishments have been communicated by the relevant regulatory authority. Once the assessment of probability of achievement becomes probable, the Company recognizes revenue for the milestone payment. At each reporting date, the Company assesses the probability of achievement of each milestone under our current agreements.

Royalties. For agreements with sales-based royalties, including milestone payments based on the level of sales, where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation, to which some or all of the royalty has been allocated, has been satisfied (or partially satisfied). At each reporting date, the Company estimates the sales incurred by each licensee during the reporting period based on historical experience and accrues the associated royalty amount.

Concentrations of Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, and marketable securities. Substantially all of the Company’s cash and cash equivalents and restricted cash is deposited in accounts with financial institutions that management believes are of high credit quality. Such deposits have and will continue to exceed federally insured limits. The Company maintains its cash with accredited financial institutions and accordingly, such funds are subject to minimal credit risk. The Company has not experienced any losses on its cash deposits.

The Company’s investment policy limits investments in marketable securities to certain types of securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents, restricted cash and marketable securities and issuers of marketable securities to the extent recorded on the balance sheets. As of December 31, 2023 and 2022, the Company had no off-balance sheet concentrations of credit risk.

The Company depends on third-party suppliers for key raw materials used in its manufacturing processes and is subject to certain risks related to the loss of these third-party suppliers or their inability to supply the Company with adequate raw materials.

Research and Development Expenses and Accruals

Costs related to research, design, and development of drug candidates are charged to research and development expense as incurred. Research and development costs include, but are not limited to, payroll and personnel expenses for personnel contributing to research and development activities, laboratory supplies, outside services, licenses acquired to be used in research and development, manufacturing of clinical material, pre-clinical testing and consultants and allocated overhead, including rent, equipment, depreciation, and utilities. Research and development costs are expensed as incurred unless there is an alternative future use in other research and development projects. Payments made prior to the receipt of goods or services to be used in research and development are deferred and recognized as expense in the period in which the related goods are received or services are rendered. Such payments are evaluated for current or long-term classification based on when they will be realized.

As part of the process of preparing its financial statements, the Company is required to estimate expenses resulting from its obligations under contracts with vendors and consultants and clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. The Company’s objective is to reflect the appropriate expenses in its financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of the production of clinical trial materials or based on progression of the clinical trial, as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates by taking into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of goods and services, or the services completed.

During the course of a clinical trial, the rate of expense recognition is adjusted if actual results differ from the Company’s estimates. The Company makes estimates of accrued expenses as of each balance sheet date in its financial statements based on the facts and circumstances known at that time. The clinical trial accrual is dependent in part upon the timely and accurate reporting of contract research organizations, contract manufacturers, and other third-party vendors. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting changes in estimates in any particular period. Adjustments to prior period estimates have not been material for the years ended December 31, 2023 and 2022.

Contingent Consideration Liability

The Company has entered into and may continue to enter into, license agreements to access and utilize certain technology. In each case, the Company evaluates whether the license agreement results in the acquisition of an asset or a business. To date, all of the Company’s license agreements have been considered acquisitions of assets and none have been considered acquisitions of a business. For license agreements that are considered to be acquisitions of assets, the upfront payments for such license, as well as any future milestone payments made before product approval, are immediately recognized as research and development expense when due, provided there is no alternative future use of the rights in other research and development projects. Some of the Company’s license agreements also include contingent consideration in the form of an obligation to issue additional shares of the Company’s common stock based on the achievement of certain milestones. The Company assesses on a continuous basis whether (i) such contingent consideration meets the definition of a derivative, and (ii) whether it can be classified within stockholders’ equity. Until such time when equity classification criteria are met or the milestones expire, the contingent consideration is classified as a liability. The derivative related to this contingent consideration is measured at fair value as of each balance sheet date with the related change in fair value being reflected in operating expenses. Upon a reassessment event that results in the contingent consideration no longer meeting the definition of a derivative and/or meeting equity classification criteria, the final change in fair value of the instrument is recorded within operating expenses and the liability is reclassified into stockholders’ equity.

Property and Equipment, Net

Property and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets, generally three years. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the term of the lease. Depreciation and amortization begin at the time the asset is placed in service. Maintenance and repairs are charged to expense as incurred and costs of improvement are capitalized.

Leases

The Company determines whether the arrangement is or contains a lease at the inception of the arrangement and if so, whether such a lease is classified as a financing lease or an operating lease. Operating leases are included in operating lease right-of-use asset, (“ROU asset”), operating lease liabilities, net of current portion, and accrued and other current liabilities on the Company’s balance sheets. The Company has elected not to recognize on the balance sheets leases with terms of one year or less. Operating lease ROU assets represent the Company’s right to use an underlying asset for the lease term and are considered long-lived assets for purposes of identifying, recognizing and measuring impairment. Operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of lease payments over the expected lease term. As the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment, in determining the present value of lease payments. The operating lease ROU asset also includes any lease payments made or incentives received and impairment charges if the Company determines the ROU asset is impaired and excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options to extend or terminate the lease. Lease expense for lease payments is recognized on a straight-line basis over the lease term.

The Company has elected to not separate lease and non-lease components for its leased assets and accounts for all lease and non-lease components of its agreements as a single lease component. The lease components resulting in a ROU asset have been recorded on the balance sheets and are amortized as lease expense on a straight-line basis over the lease term.

The Company has subleased a majority of its South San Francisco, California facility under agreements considered to be operating leases according to ASC 842. The Company has not been legally released from its primary obligations under the original leases and therefore it continues to account for the original leases as it did before commencement of the subleases. The Company records both fixed and variable payments received from the sublessee in its statements of operations on a straight-line basis as an offset to rent expense.

Impairment of Long-Lived Assets

The Company evaluates long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be fully recoverable. If indicators of impairment exist and the undiscounted future cash flows that the assets are expected to generate are less than the carrying value of the assets, the Company reduces the carrying amount of the assets through an impairment charge, to their estimated fair value based on a discounted cash flow approach or, when available and appropriate, to comparable market values. See Note 9, “Commitments and Contingencies”.

Determining estimated discounted cash flows for purposes of an impairment analysis requires the Company to make estimates and assumptions regarding the amount of market rent, timing of sublease income, and risk-adjusted discount rates. There are often risks and uncertainties associated with the intent to sublease offices and laboratory space. Consequently, the eventual realized sublease income may vary from estimates as of the impairment testing date and adjustments may occur in future periods.

Stock-Based Compensation

The Company measures compensation expense for all stock-based awards based on their grant date fair value. For stock-based awards with service conditions only, stock-based compensation expense is recognized over the requisite service period using the straight-line method. For awards with performance conditions, the Company evaluates the probability of achieving performance condition at each reporting date. The Company begins to recognize stock-based compensation expense using an accelerated attribution method when it is deemed probable that the performance condition will be met. Forfeitures are recognized as they occur.

The Company uses the Black-Scholes option-pricing model to estimate the fair value of stock option awards that do not contain market conditions. The Black-Scholes option-pricing model requires assumptions to be made related to the expected term of an award, expected dividends, expected volatility and risk-free rate.

The Company has used the Monte-Carlo option-pricing model to estimate the fair value of stock option awards that contain only market conditions. The Monte-Carlo option pricing model uses similar input assumptions as the Black-Scholes model; however, it further incorporates into the fair-value determination the possibility that the market condition may not be satisfied.

Embedded Derivatives of the Loan Agreement

The Company measures derivative liability related to debt at fair value. Estimated fair value of the derivative liability related to debt, initially measured and recorded on the date of the amendment of the loan and security agreement, is considered to be a Level 3 instrument. The fair value of the derivative liability related to debt is based on the term loan principal, the date of maturity, the contractual term loan interest rate, the convertible discount factor, and the selected discount rate of the loan. The derivative liability related to debt is recorded at fair value at the end of each reporting period with changes in estimated fair values recognized as a component of "Other expense, net" in the Statements of Operations and Comprehensive Loss.

Restructuring

The Company recognizes restructuring charges related to reorganization plans that have been committed to by management and when liabilities have been incurred. In connection with these activities, the Company records restructuring charges at fair value for a) contractual employee termination benefits when obligations are associated to services already rendered, rights to such benefits have vested, and payment of benefits is probable and can be reasonably estimated, and b) one-time employee termination benefits when management has committed to a plan of termination, the plan identifies the employees and their expected termination dates, the details of termination benefits are complete, it is unlikely changes to the plan will be made or the plan will be withdrawn and communication to such employees has occurred.

One-time employee termination benefits are recognized in their entirety when communication has occurred, and future services are not required. Contract termination costs to be incurred over the remaining contract term without economic benefit are recorded in their entirety when the contract is canceled.

The recognition of restructuring charges requires the Company to make certain judgments and estimates regarding the nature, timing and amount of costs associated with the planned reorganization plan. At the end of each reporting period, the Company evaluates the remaining accrued restructuring balances to ensure that no excess accruals are

retained, and the utilization of the provisions are for their intended purpose in accordance with developed restructuring plans.

Income Taxes

The Company uses the asset and liability method of accounting for income taxes, in which deferred tax assets and liabilities are recognized for future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be reversed. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as income in the period that includes the enactment date. A valuation allowance is established if it is more likely than not that all or a portion of the deferred tax asset will not be realized.

The Company’s tax positions are subject to income tax audits. The Company recognizes the tax benefit of an uncertain tax position only if it is more likely than not that the position is sustainable upon examination by the taxing authority, based on the technical merits. The tax benefit recognized is measured as the largest amount of benefit which is more likely than not to be realized upon settlement with the taxing authority. The Company recognizes interest accrued and penalties related to unrecognized tax benefits in its tax provision. The Company evaluates uncertain tax positions on a regular basis. The evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of the audit, and effective settlement of audit issues. The provision for income taxes includes the effects of any accruals that the Company believes are appropriate, as well as the related net interest and penalties.

Net Loss per Common Share

Basic net loss per share is calculated by dividing net loss by the weighted average number of shares outstanding for the period. Diluted net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding plus the effect of dilutive potential common shares outstanding during the period determined using the treasury-stock method.

In all periods presented, the Company’s outstanding stock options, convertible preferred stock, early exercised common stock subject to future vesting, warrants and presumed issuance of additional shares as contingent consideration were excluded from the calculation of diluted net loss per share because their effects were antidilutive.

Comprehensive Loss

Comprehensive loss includes net loss and certain changes in stockholders’ equity that are excluded from net loss, primarily unrealized losses on the Company’s marketable securities.

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments, as clarified in subsequent amendments. ASU 2016-13 changes the impairment model for certain financial instruments. The new model is a forward-looking expected loss model and will apply to financial assets subject to credit losses and measured at amortized cost and certain off-balance sheet credit exposures. This includes loans, held-to-maturity debt securities, loan commitments, financial guarantees and net investments in leases, as well as trade receivables. For available-for-sale debt securities with unrealized losses, credit losses will be measured in a manner similar to today, except that the losses will be recognized as allowances rather than reductions in the amortized cost of the securities. In October 2019, the FASB voted to delay the effective date of this standard. Topic 326 will be effective for the Company for fiscal years beginning after December 15, 2022. Early adoption is permitted. We adopted ASU 2016-13 on January 1, 2023 and the adoption did not have a material impact on the Company’s financial statements and related disclosures.

In November 2021, the FASB issued ASU 2021-10, Government Assistance, or Topic 832, which requires enhanced disclosures of transactions with governments that are accounted for by applying a grant or contribution model. The new pronouncement requires entities to provide information about the nature of the transaction, terms and conditions associated with the transaction and financial statement line items affected by the transaction. The Company adopted the standard for the annual period beginning January 1, 2023. The employee retention credit received under the CARES Act qualifies as a government assistance program under Topic 832 and resulted in enhanced required disclosures, as described in Note 7, "Government Assistance Program".

Recently Issued Accounting Pronouncements Not Yet Adopted

In December 2023, the Financial Accounting Standards Board (FASB) issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the disclosures required for income taxes in our annual financial statements. ASU 2023-09 is effective for the Company in its annual reporting for fiscal 2025 on a prospective basis. Early adoption and retrospective reporting are permitted. The Company is currently evaluating the impact of ASU 2023-09 on its Financial Statements.

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Increase in the valuation allowance	$ 9,400,000	$ 13,400,000
Unrecognized tax benefits that would impact effective tax rate	0	0
Liability recorded for potential interest or penalties	$ 0	$ 0

Net Loss per Common Share - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 shares
Maximum
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares contingently issued	3,390

Equity Financing

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Equity Financing

12. Equity Financing

On October 19, 2022, the Company effected a reverse stock split of its outstanding share of common stock at a ratio of 1-for-10 pursuant to a Certificate of Amendment to the Company's Certificate of Incorporation filed with the Secretary of State of the State of Delaware. The reverse stock split was reflected on the Nasdaq Global Select Market beginning with the opening of trading on October 20, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

The Company has 10,000,000 shares of convertible preferred stock authorized for issuance, par value of $0.0001 per share. As of December 31, 2023 and 2022, no shares of preferred stock were issued and outstanding.

The Company has 300,000,000 shares of common stock authorized for issuance, par value of $0.0001 per share. Holders of the Company’s common stock are entitled to one vote per share. As of December 31, 2023 and 2022, there were 16,784,969 and 14,215,302 shares, respectively, of common stock issued and outstanding.

Follow-On Offering (Restated)

In August 2022, the Company closed an underwritten offering (the “Follow-On Offering”) in which the Company issued and sold an aggregate of 6,428,571 of the Company’s common stock together with warrants (the "Existing Warrants”) to purchase up to 6,428,572 of the Company’s common stock at an offering price of at an aggregate

offering price of $7.00 per unit. The Existing Warrants have an exercise price of $8.50 per warrant. The gross proceeds to the Company were $45.0 million before deducting underwriting discounts and commissions and other offering expenses. The net proceeds of the Follow-On Offering were approximately $41.7 million.

The Existing Warrants are exercisable at any time after their original issuance and on or prior to the five-year anniversary of the original issuance date. A holder of Existing Warrants may not exercise the warrant if the holder, together with its affiliates, would beneficially own more than 4.99% of the number of shares of common stock outstanding immediately after giving effect to such exercise. As of December 31, 2023, 2,143,000 warrants have been exercised.

The Company recorded the Existing Warrants as liabilities based upon the guidance of ASC 480 and ASC 815. The Company evaluated the Existing Warrants under ASC 815-40 and concluded that they do not meet the criteria to be classified in stockholders’ equity. Specifically, the settlement value in a scenario of a fundamental transaction precluded the Existing Warrants from being indexed to the Company’s own stock and Company believes that the scope exception related to the occurrence of a fundamental transaction in ASC 815-40 is not met. Since the Existing Warrants meet the definition of a derivative, they are recorded as liabilities and measured at fair value at initial recognition. Any subsequent changes in their respective fair values is recognized in the Statement of Operations and Comprehensive Loss at each reporting date.

At issuance, the Company valued the Existing Warrants using a Monte-Carlo valuation model due to the more than de-minims probability of a fundamental transaction which triggered a settlement value that is not indexed to the Company's own stock. The Monte Carlo valuation model resulted in a fair value of $27.6 million on the Existing Warrant issuance date. The difference between the gross proceeds of $45.0 million and $27.6 million fair value of warrants issued, was recorded to the stockholders’ equity under Common stock and Additional paid-in capital. Additionally, the Company also incurred an issuance cost of $3.3 million which was allocated to Existing Warrants and common stock based on their relative fair value. The issuance cost of $1.4 million attributed to the Existing Warrants were expensed under "Other expense, net" in the Statement of Operations and Comprehensive Loss. The remaining issuance cost of $1.9 million attributed to the common stock was recorded as a reduction to Additional paid-in capital.

At December 31, 2023 and 2022, the Company updated the estimated fair value of the outstanding Existing Warrants using a Monte-Carlo valuation model resulting in an estimated fair value of $2.8 million (subsequent to the exercise of the Existing Warrants as described in the section below) and $10.7 million. The change in fair value for the year ended December 31, 2023 and 2022 of $6.6 million and $16.8 million was recorded as the Gain (loss) on warrant liability in the Statements of Operations and Comprehensive Loss for the year ended December 31, 2023 and 2022.

Inducement Offer

On November 9, 2023, the Company entered into an inducement offer letter agreement (the “Inducement Offer”) with certain holders (collectively, the “Holders”) of the Company's Existing Warrants to purchase up to an aggregate of 2,143,000 shares of common stock. The Holders agreed to exercise for cash their Existing Warrants to purchase an aggregate of 2,143,000 shares of common stock at a reduced exercise price of $2.045 per share in consideration of the Company’s agreement to issue new unregistered common stock purchase warrants (the “New Warrants”) to purchase up to an aggregate of 2,143,000 shares of the Company’s common stock.

Each New Warrant will have an exercise price equal to $1.92 per share. The New Warrants will be exercisable on or after the initial issue date until the five-year anniversary of such date. The exercise price and number of New Warrant Shares issuable upon exercise of the New Warrants is subject to appropriate adjustment in the event of stock dividends, stock splits, subsequent rights offerings, pro rata distributions, reorganizations, or similar events affecting the Company’s common stock and the exercise price.

The Company engaged H.C. Wainwright & Co., LLC (the “Placement Agent”) to act as its exclusive placement agent in connection with the transactions summarized above. The Company also issued to the Placement Agent or its designees warrants to purchase up to 128,580 shares of common stock. The Placement Agent Warrants have substantially the same terms as the New Warrants, except that the Placement Agent Warrants have an exercise price equal to $2.5563 per share.

The Company recorded the New Warrants and Placement Agent Warrants (together “2023 Warrants”) as liabilities based upon the guidance of ASC 480 and ASC 815. The Company evaluated the 2023 Warrants under ASC 815-40

and concluded that they do not meet the criteria to be classified in stockholders’ equity. Specifically, the settlement value in a scenario of a fundamental transaction precludes the 2023 Warrants from being indexed to the Company’s own stock and Company believes that the scope exception related to the occurrence of a fundamental transaction in ASC 815-40 is not met. Since the 2023 Warrants are recorded as liabilities on the balance sheet at fair value, any subsequent changes in their respective fair values are recognized in the statement of operations and comprehensive loss at each reporting date.

The Company received aggregate gross proceeds of $4.4 million from the exercise of the Existing Warrants by the Holders (the “Exercise”), before deducting placement agent fees and other offering expenses payable by the Company.

The Company issued common stock at fair value of $3.7 million and 2023 Warrants at fair value of $2.7 million. The extinguished the Existing Warrants Liability of $1.4 million. The issuance costs related to 2023 Warrants and loss on extinguishment of Existing Warrants Liability of $1.0 million were expensed under "Other expense, net" in the Statement of Operations and Comprehensive Loss.

At-the-Market Offering

In June 2019, the Company filed a Registration Statement on Form S-3 (the “Shelf Registration Statement”), covering the offering of up to $250.0 million of common stock, preferred stock, debt securities, warrants and units. The Shelf Registration Statement included a prospectus covering the offering, issuance and sale of up to $75.0 million of the Company’s common stock from time to time through an “at-the-market” offering under the Securities Act of 1933, as amended (the “Initial ATM Offering Program”). The SEC declared the Shelf Registration Statement effective on June 6, 2019.

In June 2019, the Company also entered into a sales agreement (the “June 2019 Sales Agreement”) with Cowen and Company, LLC (“Cowen”) to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $75.0 million, through the ATM Offering Program under which Cowen acts as its sales agent. Cowen is entitled to compensation for its services equal to up to 3.0% of the gross proceeds of any shares of common stock sold through Cowen under the June 2019 Sales Agreement. During the year ended December 31, 2020, the Company issued and sold 500,226 shares of its common stock through its ATM Offering Program and received net proceeds of approximately $37.3 million, after deducting commissions and other offering expenses of $1.3 million.

In July 2020, the Company filed an additional prospectus supplement to the Shelf Registration Statement. This prospectus supplement covers the offering, issuance and sale of up to an additional $50.0 million of the Company’s common stock from time to time through an additional “at-the-market” offering under the Securities Act of 1933, as amended (the “Additional ATM Offering Program”). The Initial ATM Offering Program and Additional ATM Offering Program are collectively called the “ATM Offering Programs”.

In July 2020, the Company entered into sales agreement (the “July 2020 Sales Agreements”) with Cowen to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $50.0 million, through the Additional ATM Offering Program under which Cowen will act as its sales agent. The issuance and sale of shares of common stock by the Company pursuant to the July 2020 Sales Agreement are also deemed an “at-the-market” offering under the Securities Act of 1933, as amended (the “Securities Act”). Cowen is entitled to compensation for its services equal to up to 3.0% of the gross proceeds of any shares of common stock sold through Cowen under the July 2020 Sales Agreement. During the year ended December 31, 2021, there were 118,707 shares of the Company’s common stock sold through the Initial ATM Offering Program and 70,746 shares of the Company’s common stock sold through the Additional ATM Offering Program and received total net proceeds of approximately $10.4 million, after deducting commissions and other offering expenses of $0.3 million.

In March 2022, the Company filed a Registration Statement on Form S-3 (the “March 2022 Shelf Registration Statement”), covering the offering of up to $125.0 million of common stock, preferred stock, debt securities, warrants, and units, which was declared effective by the SEC in May 2022. In March 2022, the Company also entered into a sales agreement (the “March 2022 Sales Agreement”) with Cowen and Company, LLC ("Cowen") as sales agent to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $50.0 million pursuant to the March 2022 Shelf Registration Statement as an “at-the-market” offering under the Securities Act (the "March 2022 ATM Offering Program"). Cowen is entitled to up to 3.0% of the gross proceeds of any shares of common stock sold under the March 2022 Sales Agreement. For so long as its public float is less than $75.0 million, it may not sell more than the equivalent of one-third of its public float during any 12 consecutive months pursuant to the "baby shelf" rules. During the year ended December 31, 2023, there were 274,781 shares of the Company's

common stock sold pursuant to the March 2022 Sales Agreement and the Company received total net proceeds of approximately $1.0 million, after deducting commissions and other offering expenses which were insignificant. On August 17, 2022, the Company entered into Amendment No. 1 (the “Amendment”) to the March 2022 Sales Agreement, which Amendment decreased the amount of the Company’s common stock that can be sold by the Company through Cowen under the March 2022 Sales Agreement, from an aggregate offering of up to $50.0 million to an aggregate offering of up to $25.0 million. Following the Amendment, $14.6 million of shares of common stock remained available for sale under the March 2022 Sales Agreement, as amended, as of December 31, 2023. On March 17, 2023, the Company entered into Amendment No. 2 (the "Second Amendment"), accompanied by a prospectus supplement, to the March 2022 Sales Agreement. The Second Amendment added the limitations imposed on the Program by General Instruction I.B.6 of Form S-3 (“Instruction I.B.6”) to the Sales Agreement. Pursuant to Instruction I.B.6, in no event will the Company sell ATM Shares through the Program with a value exceeding more than one-third of the Company’s “public float” (the market value of the Company’s outstanding common stock held by non-affiliates) in any twelve-month period so long as the Company’s public float remains below $75.0 million.

In October 2022, the Company filed a Registration Statement on Form S-3 (the “October 2022 Shelf Registration Statement”), covering the offering of up to $250.0 million of common stock, preferred stock, debt securities, warrants, and units. In October 2022, the Company also entered into a sales agreement (the “October 2022 Sales Agreement”) with Cowen as sales agent to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $50.0 million pursuant to the October 2022 Shelf Registration Statement as an “at-the-market” offering under the Securities Act. Cowen is entitled to up to 3.0% of the gross proceeds of any shares of common stock sold under the October 2022 Sales Agreement. During the year ended December 31, 2023, there were no shares of the Company's common stock sold pursuant to the October 2022 Sales Agreement.

Equity Purchase Agreement

In September 2021, the Company entered into an equity purchase agreement (the “Purchase Agreement” or “Equity Purchase Agreement”) and a registration rights agreement with Lincoln Park Capital Fund, LLC (“Lincoln Park” or “Investor”) which provides for the sale to Lincoln Park up to $30,000,000 of shares (the “Purchase Shares”) of its common stock over the thirty-six (36) month term of the Purchase Agreement. In connection with the Purchase Agreement, Lincoln Park purchased 102,040 Purchase Shares at a purchase price of $2.94 per share, for a total gross purchase price of $3.0 million (the “Initial Purchase”), and the Company issued 25,244 shares of common stock to Lincoln Park as a commitment fee in connection with entering into the Purchase Agreement. The Company recognized $0.8 million of other expense relating to the commitment fee share issuance. From the date of the agreement through December 31, 2022, the Company had initiated the purchase of an additional 380,000 shares of the Company’s common stock amounting to $6.2 million in gross proceeds. The Company has initiated no purchases through the Purchase Agreement for the year ended December 31, 2023.

Under the Purchase Agreement, the Company has sole discretion, subject to certain conditions, on any business day selected by the Company to require Lincoln Park to purchase up to 10,000 shares of common stock (the “Regular Purchase Amount”) at the Purchase Price (as defined below) per purchase notice (each such purchase, a “Regular Purchase”). The Regular Purchase Amount may be increased as follows: up to 15,000 shares if the closing price is not below $35.00, up to 20,000 shares if the closing price is not below $50.00, and up to 25,000 shares if the closing price is not below $70.00. Lincoln Park’s committed obligation under each Regular Purchase is capped at $2,000,000, unless the parties agree otherwise. The purchase price for Regular Purchases (the “Purchase Price”) shall be equal to the lesser of: (i) the lowest sale price of the common shares during the Purchase Date, or (ii) the average of the three (3) lowest closing sale prices of the common shares during the ten (10) business days prior to the Purchase Date.

In addition to Regular Purchases and subject to certain conditions and limitations, the Company in its sole discretion may require Lincoln Park on each Purchase Date to purchase on the following business day up to the lesser of (i) three (3) times the number of shares purchased pursuant to such Regular Purchase or (ii) 30% of the trading volume on the Accelerated Purchase Date (the “Accelerated Purchase”) (unless the Parties agree otherwise) at a purchase price equal to the lesser of 97% of (i) the closing sale price on the Accelerated Purchase Date, or (ii) the Accelerated Purchase Date’s volume weighted average price (the “Accelerated Purchase Price”). The Company has the sole right to set a minimum price threshold for each Accelerated Purchase in the notice provided with respect to such Accelerated Purchase and under certain circumstances and in accordance with the Purchase Agreement the Company may direct multiple Accelerated Purchases in a day.

The aggregate number of shares that the Company can sell to Lincoln Park under the Purchase Agreement may not exceed 1,106,580 shares of the common stock (which is equal to approximately 19.99% of the shares of the common

stock outstanding immediately prior to the execution of the Purchase Agreement) (the “Exchange Cap”), unless (i) shareholder approval is obtained to issue Purchase Shares above the Exchange Cap, in which the Exchange Cap will no longer apply, or (ii) the average price of all applicable sales of common stock to Lincoln Park under the Purchase Agreement equals or exceeds $29.40 per share; provided that at no time may Lincoln Park (together with its affiliates) beneficially own more than 9.99% of the Company’s issued and outstanding common stock.

The Purchase Agreement contains customary representations, warranties, covenants, closing conditions, indemnification and termination provisions. The Purchase Agreement may be terminated by the Company at any time, at its sole discretion, without any cost or penalty, by giving one business day notice to Lincoln Park. Further, Lincoln Park has covenanted not to engage in any direct or indirect short selling or hedging of the Common Shares. There are no limitations on the use of proceeds, financial or business covenants, restrictions on future financings (other than restrictions on the Company’s ability to enter into a similar type of agreement or Equity Line of Credit during the Term, excluding an At-The-Market transaction with a registered broker-dealer), rights of first refusal, participation rights, penalties or liquidated damages in the Purchase Agreement. Issuances under the Purchase Agreement were to be made pursuant to the Company's Registration Statement on Form S-3 filed in July 2019, which has since expired. The Company would need to file a new prospectus supplement covering issuances under the Purchase Agreement in order to continue using the facility.

- Definition

The entire disclosure for equity.

+ References

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+ Details

Quarterly Financial Information (Unaudited) - Statements of Operations and Comprehensive Loss (Parenthetical) (Details)	Oct. 19, 2022
Income Statement [Abstract]
Reverse stock split ratio	0.1

Stock-Based Compensation - Summary of Valuation Assumption to Estimate Fair Value of Stock Options (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term of options (in years)	5 years 9 months 14 days	5 years 6 months 18 days	6 years
Expected stock price volatility, Minimum	94.11%	86.22%	85.70%
Expected stock price volatility, Maximum	98.92%	93.17%	88.50%
Risk-free interest rate, Minimum	3.36%	2.41%	1.08%
Risk-free interest rate, Maximum	4.13%	4.01%	1.35%
Expected dividend yield	0.00%	0.00%	0.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
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-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

+ Details

Quarterly Financial Information (Unaudited) - Statements of Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net gain (loss)	$ (14,782)	$ (15,456)	$ (5,279)	$ (4,997)	$ (20,735)	$ (35,520)	$ (37,047)	$ (39,860)	$ (44,469)	$ (60,725)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization			329		643	951	1,771	1,182	2,180	2,880
Amortization of debt issuance costs			314		557	705	989	705	1,318	813
Debt extinguishment loss upon paydown of principal						491		491	0	0
Debt extinguishment gain upon conversion to equity							(199)	0	(199)	(123)
Net accretion and amortization of premium and discounts on marketable securities			(433)		(831)	(1,199)	155	(1,503)	(276)	1,043
Gain on disposal of property and equipment							(247)	(114)	(346)	0
Stock-based compensation			2,175		4,422	6,127	7,120	7,419	9,379	11,553
Non-cash rent expense			(270)		(540)	(811)	(1,891)	(1,072)	(2,136)	(2,152)
Impairment of long-lived assets	5,602					5,602		5,602	0	0
(Gain) loss on warrant liability, net of issuance costs			(5,491)		(2,030)	(2,283)	(10,974)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			(1,249)		(2,134)	(1,858)	(1,205)	(1,664)	138	1,288
Other long-term assets			23		47	52	15	(74)	39	(91)
Accounts payable			(320)		(341)	(642)	459	(410)	(194)	(573)
Accrued compensation			(1,037)		(1,368)	(793)	(1,067)	(1,180)	(1,008)	(1,327)
Accrued liabilities and other current liabilities			(78)		(89)	(335)	96	(1,063)	26	(1,131)
Other long-term liabilities							(23)	0	(23)	24
Net cash used in operating activities			(11,316)		(22,399)	(29,513)	(42,048)	(37,088)	(52,414)	(45,060)
Investing activities
Purchase of marketable securities			(5,973)		(21,868)	(28,609)	(86,567)	(28,609)	(98,827)	(81,492)
Maturities of marketable securities			27,251		53,000	74,000	62,000	89,000	74,000	121,000
Purchase of property and equipment						(11)	(59)	(11)	(96)	(195)
Sale of property and equipment						1	272	115	378	0
Net cash used in investing activities			21,278		31,132	45,381	(24,354)	60,495	(24,545)	39,313
Financing activities
Payment of debt principal						(20,000)		(20,000)	0	0
Payment of debt issuance costs						(1,563)		(1,563)	0	0
Issuance costs for sale of common stock							(1,965)	0	(1,967)	0
Repayment of term loan debt					(3,234)
Proceeds from issuance of common stock under the 2018 ESPP					91	91	125	116	142	347
Net cash provided by financing activities			274		(2,351)	(20,728)	56,073	(16,340)	56,240	20,845
Net decrease in cash, cash equivalents and restricted cash			10,236		6,382	(4,860)	(10,329)	7,067	(20,719)	15,098
Cash, cash equivalents and restricted cash at beginning of year	20,014	23,868	13,632		13,632	13,632	34,351	13,632	34,351	19,253
Cash, cash equivalents and restricted cash at end of year	8,772	20,014	23,868	24,022	20,014	8,772	24,022	20,699	13,632	34,351
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest			680		1,362	1,969	1,577	1,969	2,204	2,370
Cash and cash equivalents	7,876	19,118	22,972	22,576	19,118	7,876	22,576	19,803	12,736	32,905
Restricted cash	896	896	896	1,446	896	896	1,446
Total cash, cash equivalents, and restricted cash	8,772	20,014	23,868	24,022	20,014	8,772	24,022	20,699	13,632	34,351
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt							3,179	0	3,179	2,704
ATM Offering Program
Financing activities
Proceeds from issuance of common stock, net of issuance costs			274		792	744	12,003	725	12,155	10,357
Follow-on Offering
Financing activities
Proceeds from issuance of common stock, net of issuance costs							45,000	0	45,000	0
Lincoln Park Capital Fund Equity Purchase Agreement
Financing activities
Proceeds from issuance of common stock, net of issuance costs							910	0	910	8,215
As Previously Reported
Operating activities
Net gain (loss)	(15,289)	(12,205)	(10,865)	(13,708)	(23,070)	(38,362)	(45,758)		(59,927)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization			329		643	951	1,771		2,180
Amortization of debt issuance costs			314		653	705	989		1,318
Debt extinguishment loss upon paydown of principal						491
Debt extinguishment gain upon conversion to equity							(199)		(199)
Net accretion and amortization of premium and discounts on marketable securities			(433)		(831)	(1,199)	155		(276)
Gain on disposal of property and equipment							(247)		(346)
Stock-based compensation			2,270		4,631	6,686	7,120		9,379
Non-cash rent expense			(270)		(540)	(811)	(1,891)		(2,136)
Impairment of long-lived assets	5,602					5,602
(Gain) loss on warrant liability, net of issuance costs			0		0	0	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			(1,249)		(2,134)	(1,858)	(1,355)		138
Other long-term assets			23		47	52	15		39
Accounts payable			(320)		(341)	(642)	459		(194)
Accrued compensation			(1,037)		(1,368)	(793)	(1,067)		(1,008)
Accrued liabilities and other current liabilities			(78)		(89)	(335)	(632)		26
Other long-term liabilities							(23)		(23)
Net cash used in operating activities			(11,316)		(22,399)	(29,513)	(40,663)		(51,029)
Investing activities
Purchase of marketable securities			(5,973)		(21,868)	(28,609)	(86,567)		(98,827)
Maturities of marketable securities			27,251		53,000	74,000	62,000		74,000
Purchase of property and equipment						(11)	(59)		(96)
Sale of property and equipment						1	272		378
Net cash used in investing activities			21,278		31,132	45,381	(24,354)		(24,545)
Financing activities
Payment of debt principal						(20,000)
Payment of debt issuance costs						(1,563)
Issuance costs for sale of common stock							0		0
Repayment of term loan debt					(3,234)
Proceeds from issuance of common stock under the 2018 ESPP					91	91	125		142
Net cash provided by financing activities			274		(2,351)	(20,728)	54,688		54,855
Net decrease in cash, cash equivalents and restricted cash			10,236		6,382	(4,860)	(10,329)		(20,719)
Cash, cash equivalents and restricted cash at beginning of year	20,014	23,868	13,632		13,632	13,632	34,351	13,632	34,351
Cash, cash equivalents and restricted cash at end of year	8,772	20,014	23,868	24,022	20,014	8,772	24,022		13,632	34,351
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest			680		1,362	1,969	1,577		2,204
Cash and cash equivalents	7,876	19,118	22,972	22,576	19,118	7,876	22,576		12,736
Restricted cash	896	896	896	1,446	896	896	1,446
Total cash, cash equivalents, and restricted cash	8,772	20,014	23,868	24,022	20,014	8,772	24,022		13,632	34,351
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt							3,179
As Previously Reported \| ATM Offering Program
Financing activities
Proceeds from issuance of common stock, net of issuance costs			274		792	744	12,003		12,155
As Previously Reported \| Follow-on Offering
Financing activities
Proceeds from issuance of common stock, net of issuance costs							41,650		41,648
As Previously Reported \| Lincoln Park Capital Fund Equity Purchase Agreement
Financing activities
Proceeds from issuance of common stock, net of issuance costs							910		910
Adjustment
Operating activities
Net gain (loss)	507	(3,251)	5,586	8,711	2,335	2,842	8,711		15,458
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization			0		0	0	0		0
Amortization of debt issuance costs			0		(96)	0	0		0
Debt extinguishment loss upon paydown of principal						0
Debt extinguishment gain upon conversion to equity							0		0
Net accretion and amortization of premium and discounts on marketable securities			0		0	0	0		0
Gain on disposal of property and equipment							0		0
Stock-based compensation			(95)		(209)	(559)	0		0
Non-cash rent expense			0		0	0	0		0
Impairment of long-lived assets	0					0
(Gain) loss on warrant liability, net of issuance costs			(5,491)		(2,030)	(2,283)	(10,974)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			0		0	0	150		0
Other long-term assets			0		0	0	0		0
Accounts payable			0		0	0	0		0
Accrued compensation			0		0	0	0		0
Accrued liabilities and other current liabilities			0		0	0	728		0
Other long-term liabilities							0		0
Net cash used in operating activities			0		0	0	(1,385)		(1,385)
Investing activities
Purchase of marketable securities			0		0	0	0		0
Maturities of marketable securities			0		0	0	0		0
Purchase of property and equipment						0	0		0
Sale of property and equipment						0	0		0
Net cash used in investing activities			0		0	0	0		0
Financing activities
Payment of debt principal						0
Payment of debt issuance costs						0
Proceeds from issuance of common stock, net of issuance costs									0
Issuance costs for sale of common stock							(1,965)		(1,967)
Repayment of term loan debt					0
Proceeds from issuance of common stock under the 2018 ESPP					0	0	0
Net cash provided by financing activities			0		0	0	1,385		1,385
Net decrease in cash, cash equivalents and restricted cash			0		0	0	0		0
Cash, cash equivalents and restricted cash at beginning of year	0	0	0		0	0	0	$ 0	0
Cash, cash equivalents and restricted cash at end of year	0	0	0	0	0	0	0		0	0
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest			0		0	0	0		0
Cash and cash equivalents	0	0	0	0	0	0	0		0
Restricted cash	0	0	0	0	0	0	0
Total cash, cash equivalents, and restricted cash	$ 0	$ 0	0	$ 0	0	0	0		0	$ 0
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt							0
Adjustment \| ATM Offering Program
Financing activities
Proceeds from issuance of common stock, net of issuance costs			$ 0		$ 0	$ 0	0		0
Adjustment \| Follow-on Offering
Financing activities
Proceeds from issuance of common stock, net of issuance costs							3,350		3,352
Adjustment \| Lincoln Park Capital Fund Equity Purchase Agreement
Financing activities
Proceeds from issuance of common stock, net of issuance costs							$ 0		$ 0

Related Party Transactions

12 Months Ended

Dec. 31, 2023

Related-Party Transactions

11. Related Party Transactions

Licensing Revenue – Related Party

In December 2021, the Company entered into a license agreement with Jocasta Neuroscience, Inc. A member of the Board of Directors of the Company is also an affiliate of Jocasta Neuroscience, Inc. The agreement provides for an upfront fee of $5.0 million and the opportunity for future research and development services to be provided. The Company recognized zero, $0.2 million and $4.8 million of licensing revenue for the years ended December 31, 2023, 2022 and 2021, respectively.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-6

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

+ Details

Income Taxes - Summary of Net Operating Losses and Tax Credit Carryforwards (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Federal \| Post December 31, 2017
Income Taxes [Line Items]
Net operating losses	$ 305,873
Operating losses carryforwards expiration years	Do Not Expire
Federal \| Pre January 1, 2018
Income Taxes [Line Items]
Net operating losses	$ 64,136
Federal \| Pre January 1, 2018 \| Maximum
Income Taxes [Line Items]
Operating losses carryforwards expiration years	2037
Federal \| Pre January 1, 2018 \| Minimum
Income Taxes [Line Items]
Operating losses carryforwards expiration years	2029
Federal \| Research and Development Tax Credits
Income Taxes [Line Items]
Research and development tax credits	$ 8,799
Federal \| Research and Development Tax Credits \| Maximum
Income Taxes [Line Items]
Research and development tax credits carryforwards expiration years	2043
Federal \| Research and Development Tax Credits \| Minimum
Income Taxes [Line Items]
Research and development tax credits carryforwards expiration years	2034
State
Income Taxes [Line Items]
Net operating losses	$ 185,897
State \| Maximum
Income Taxes [Line Items]
Operating losses carryforwards expiration years	2043
State \| Minimum
Income Taxes [Line Items]
Operating losses carryforwards expiration years	2034
California \| Research and Development Tax Credits
Income Taxes [Line Items]
Research and development tax credits	$ 7,070
Research and development tax credits carryforwards expiration years	Indefinite

Balance Sheets (Parenthetical)	Oct. 19, 2022	Dec. 31, 2023 $ / shares shares	Sep. 30, 2023 $ / shares shares	Jun. 30, 2023 $ / shares shares	Mar. 31, 2023 $ / shares shares	Dec. 31, 2022 $ / shares shares	Sep. 30, 2022 $ / shares shares
Statement of Financial Position [Abstract]
Convertible preferred stock, par value \| $ / shares		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized		10,000,000	10,000,000	10,000,000	10,000,000	10,000,000	10,000,000
Convertible preferred stock, shares issued		0	0	0	0	0	0
Convertible preferred stock, shares outstanding		0	0	0	0	0	0
Common stock, par value \| $ / shares		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares authorized		300,000,000	300,000,000	300,000,000	300,000,000	300,000,000	300,000,000
Common stock, shares issued		16,784,969	14,614,890	14,595,477	14,359,214	14,215,302	14,036,249
Common stock, shares outstanding		16,784,969	14,614,890	14,595,477	14,359,214	14,215,302	14,036,249
Reverse stock split ratio	0.1

Net Loss per Common Share - Schedule of Reconciliation of Numerators and Denominators Used In Computing Net Loss From Continuing Operations Per Share (Details) - USD ($)
$ / shares in Units, $ in Thousands

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Sep. 30, 2022

Jun. 30, 2023

Sep. 30, 2023

Sep. 30, 2022

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Numerator:

Net gain (loss)

$ (14,782)

$ (15,456)

$ (5,279)

$ (4,997)

$ (20,735)

$ (35,520)

$ (37,047)

$ (39,860)

$ (44,469)

$ (60,725)

Denominator:

Weighted average number of shares outstanding-basic

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

14,773,612

^[1]

9,494,421

^[1]

5,581,587

^[1]

Weighted average number of shares outstanding-diluted

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

14,773,612

^[1]

9,494,421

^[1]

5,581,587

^[1]

Net loss per share-basic

$ (1.01)

$ (1.07)

$ (0.37)

$ (0.5)

$ (1.44)

$ (2.46)

$ (4.67)

$ (2.7)

$ (4.68)

$ (10.88)

Net loss per share-diluted

$ (1.01)

$ (1.07)

$ (0.37)

$ (0.5)

$ (1.44)

$ (2.46)

$ (4.67)

$ (2.7)

$ (4.68)

$ (10.88)

[1]

The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded up to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

Stock-Based Compensation - Summary of Restricted Stock Units Activity (Details) - RSUs	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares, Unvested at December 31, 2022 \| shares	146,333
Shares, Released \| shares	94,534
Shares, Canceled \| shares	(10,574)
Shares, Unvested at December 31, 2023 \| shares	41,225
Weighted Average Grant Date Fair Value, Unvested at December 31, 2022 \| $ / shares	$ 27.66
Weighted Average Grant Date Fair Value, Released \| $ / shares	28.39
Weighted Average Grant Date Fair Value, Canceled \| $ / shares	11.27
Weighted Average Grant Date Fair Value, Unvested at December 31, 2023 \| $ / shares	$ 30.18

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Income Taxes - Schedule of Effective Tax Rate of Provision for Income Taxes Differs From Federal Statutory Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Taxes at the U.S. statutory income tax rate	21.00%	21.00%	21.00%
State tax, net of federal benefit	9.00%	9.10%	4.40%
Other	0.50%	(0.80%)	(0.40%)
Warrant activity	2.80%	7.30%	0.00%
Stock-based compensation	(2.50%)	(6.60%)	(1.60%)
Research and development tax credits	1.80%	2.90%	3.20%
Rate change	(8.80%)	4.70%	3.80%
ASC 740-10	0.00%	(7.50%)	(4.20%)
Change in valuation allowance	(23.70%)	(30.10%)	(26.20%)
Total provision for income taxes	0.00%	0.00%	0.00%

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Summary of Marketable Securities Classified as Available-for-Sale

Marketable securities, which are classified as available-for-sale, consisted of the following (in thousands):


	December 31, 2023
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	12,864	$	—	$	—		$	12,864
U.S. treasuries		2,989		—		—			2,989
Total cash equivalents		15,853		—		—			15,853
Short-term marketable securities:
U.S. treasuries		7,853		4		(8	)		7,849
U.S. government debt securities		15,570		1		(22	)		15,549
Total short-term marketable securities		23,423		5		(30	)		23,398
Restricted Cash equivalents:
Money market funds		896		—		—		$	896
Total restricted cash equivalents		896		—		—			896
Total	$	40,172	$	5	$	(30	)	$	40,147


	December 31, 2022
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	5,083	$	—	$	—		$	5,083
Total cash equivalents		5,083		—		—			5,083
Short-term marketable securities:
U.S. treasuries		51,491		6		(196	)		51,301
U.S. government debt securities		30,820		1		(63	)		30,758
Total short-term marketable securities		82,311		7		(259	)		82,059
Total	$	87,394	$	7	$	(259	)	$	87,142

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
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-Paragraph 3
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Organization - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (480,010)	$ (465,228)	$ (449,772)	$ (437,073)	$ (465,228)	$ (480,010)	$ (437,073)	$ (484,353)	$ (444,493)
Net gain (loss)	$ (14,782)	$ (15,456)	(5,279)	$ (4,997)	(20,735)	(35,520)	(37,047)	(39,860)	(44,469)	$ (60,725)
Cash used in operations			$ (11,316)		$ (22,399)	$ (29,513)	$ (42,048)	(37,088)	$ (52,414)	$ (45,060)
Product revenue								0
Cash, cash equivalents and marketable securities								$ 43,200

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

- Definition

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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+ Details

Corporate Restructuring

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Corporate Restructuring

13. Corporate Restructuring

In February 2022, the Company implemented a corporate restructuring to align its resources to focus on its UBX1325 program while further extending operating capital. The restructuring resulted in an elimination of 29 positions, or approximately 50% of the Company’s workforce, in the first nine months of 2022. The Company incurred a one-time employee benefits and severance charge of approximately $1.9 million in operating expenses which was primarily recorded in the first nine months of 2022. Restructuring charges incurred under this plan primarily consisted of employee termination benefits. Employee termination benefits include $1.6 million of severance costs, $0.2 million of employee-related benefits, $0.1 million of payroll taxes and supplemental one-time termination payments. Charges and other costs related to the workforce reduction and structure realignment, and non-cash share-based compensation credits related to the forfeiture of stock options for $1.7 million, are included in operating expenses in the Statements of Operations and Comprehensive Loss. Of the total charge, $1.4 million was recorded to research and development expenses and $0.5 million was recorded to general and administrative expenses during the year ended December 31, 2022.

In May 2023, the Company implemented a reduction in its workforce to align operations with the changes in its corporate strategy to focus on resource optimization to enable the initiation and advancement of key data readouts. The reduction decreased its headcount by nine employees, or approximately 29% of the Company’s workforce, effective as of May 31, 2023. Six employees departed as of the effective date and three employees departed as of June 30, 2023. The Company recognized the employee benefits and severance charge of approximately $0.6 million in operating expenses in the second quarter of 2023. Restructuring charges primarily consisted of employee termination benefits, which included $0.5 million of severance costs, $0.1 million of employee-related benefits, and a negligible amount of payroll taxes. Charges and other costs related to the restructuring, and non-cash share-based compensation credits related to the forfeiture of stock options were negligible and are included in operating expenses in the Statements of Operations and Comprehensive Loss. Of the total charge, $0.4 million was recorded to research and development expenses and $0.2 million was recorded to general and administrative expenses during the year ended December 31, 2023.

Stock-Based Compensation - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 7,419	$ 9,379	$ 11,553
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,947	3,526	4,809
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 5,472	$ 5,853	$ 6,744

Fair Value Measurements - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2023	Nov. 30, 2023	Nov. 14, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Aug. 22, 2022
August 2022 Warrants ('Existing Warrants')
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of outstanding common warrants	$ 2.8			$ 8.4	$ 8.7	$ 5.3	$ 10.7	$ 16.6	$ 27.6
November 2023 Inducement Offer ('New Warrants')
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued to purchase common stock		2,143,000
November 2023 Inducement Offer ('New Warrants') \| Warrant Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of warrant liability	$ 3.1		$ 2.7
November 2023 Inducement Offer ('New Warrants') \| Placement Agent \| Placement Agent Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exercise price for warrant		$ 2.5563
Warrants issued to purchase common stock		128,580
November 2023 Inducement Offer ('New Warrants') \| Inducement Letter \| Holders \| Existing Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants exercised		2,143,000
Reduced exercise price of warrant		$ 2.045
Exercise price for warrant		$ 1.92

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

9. Commitments and Contingencies

Leases

In February 2019, the Company entered into a lease agreement for new office and laboratory space in South San Francisco, California. The term of the lease agreement commenced in May 2019. The lease has an initial term from occupancy of approximately ten years ending on December 31, 2029 with an option to extend the term for an additional eight years at then-market rental rates. The total base rent payment escalates annually based on a fixed percentage beginning from the 13th month of the lease agreement. The Company will also be responsible for the operating expenses and real estate taxes allocated to the building and common areas. Pursuant to the lease agreement, the landlord provided the Company with a tenant improvement allowance of $10.7 million, which was included in deferred rent and leasehold improvements on the balance sheet at December 31, 2019. In connection with the execution of the lease agreement, the Company delivered a letter of credit of approximately $0.9 million to the landlord.

The Company’s operating leases include various covenants, indemnities, defaults, termination rights, security deposits and other provisions customary for lease transactions of this nature.

The following table summarizes the components of lease expense, which are included in operating expenses in the Company’s Statements of Operations and Comprehensive Loss (in thousands):


	Year ended December 31,
	2023			2022			2021
Operating lease expense	$	3,739		$	4,264		$	4,357
Variable lease expense		748			1,318			1,633
Sublease income		(3,988	)		(4,317	)		(2,578	)
Total lease expense	$	499		$	1,265		$	3,412

Variable lease payments include amounts relating to common area maintenance, real estate taxes and insurance and are recognized in the Statements of Operations and Comprehensive Loss as incurred.

The following table summarizes supplemental information related to operating leases (in thousands):


	Year ended December 31,
	2023			2022			2021
Cash paid for amounts included in the measurement of lease liabilities	$	4,810		$	6,283		$	6,653
Weighted-average remaining lease term (years)		6.0			7.0			7.7
Weighted-average discount rate (percentage)		6.0	%		6.0	%		5.9	%

The following table summarizes the maturities of lease liabilities as of December 31, 2023 (in thousands):


	Amount
2024	$	4,964
2025		5,123
2026		5,287
2027		5,457
2028		5,633
Thereafter		5,801
Total future minimum lease payments		32,265
Less: Amount representing interest		(5,275	)
Present value of future minimum lease payments		26,990
Less: Current portion of operating lease liability		(3,451	)
Noncurrent portion of operating lease liability	$	23,539

In February 2021, the Company entered into an agreement to sublease the first floor of the Brisbane, California facility (the Company's previous offices and laboratory space), consisting of approximately 27,000 square feet, to Zymergen, Inc., through August 31, 2022. The base sublease rent rate is $3.53 per rental square foot per month and will increase by 3% on March 1, 2022 through expiration of the agreement. Additionally, the subtenant is required to pay approximately 41% of operating expenses and property management fees that the Company is required to pay under the lease for the Brisbane, California facility. In May 2021, the Company entered into an agreement to sublease the second floor of the Brisbane, California facility, consisting of approximately 11,500 square feet, to CareDx, Inc., through September 30, 2022. The base sublease rent rate is $1.00 per rental square foot per month through expiration of the agreement. Additionally, the subtenant is required to pay approximately 30% of operating expenses and property management fees that the Company is required to pay under the lease for the Brisbane, California facility. The Company incurred initial direct costs of $0.1 million in sublease commissions related to entering into the agreements to sublease the Brisbane, California facility. To account for the commissions, the Company capitalized the total commissions amount and will amortize the balance over the term of the sublease. Sublease income from this facility was zero, $1.3 million and $1.5 million for the years ended December 31, 2023, 2022 and 2021, respectively, which was offset against total rent expense.

In June 2021, the Company entered into an agreement to sublease a portion of the first floor of the South San Francisco facility, consisting of approximately 23,000 square feet, to Freenome Holdings, Inc., through July 31, 2024. The base sublease rent rate is $6.25 per rental square foot per month and will increase annually by 3.5% through expiration of the agreement. Additionally, the subtenant is required to pay approximately 37% of operating expenses and property management fees that the Company is required to pay under the lease for the South San Francisco, California facility. The Company incurred initial direct costs of $0.2 million in sublease commissions related to entering into the agreements to sublease the South San Francisco, California facility. To account for the commissions, the Company capitalized the total commissions amount and will amortize the balance over the term of the sublease. Sublease income related to this facility and this specific sub-tenant was $2.3 million, $2.2 million and $1.1 million for the years ended December 31, 2023, 2022 and 2021, respectively, which was offset against total rent expense.

In May 2022, the Company entered into an agreement to sublease a portion of the second floor of the South San Francisco, California facility, consisting of approximately 15,000 square feet, to Initial Therapeutics, Inc. ("Initial Therapeutics"). The original sublease term commenced on July 1, 2022 and continued through June 30, 2024 and further extended through June 30, 2026 upon execution of an amendment as defined below. The base sublease rent rate is $7.80 per rental square foot per month and will increase by 3.5% annually through the expiration of the agreement. Additionally, the subtenant is required to pay approximately 24% of operating expenses and property management fees that the Company is required to pay under the lease for the South San Francisco, California facility.

The Company incurred initial direct costs of $0.1 million in sublease commissions related to entering into the agreements to sublease the South San Francisco, California facility. To account for the commissions, the Company capitalized the total commissions amount and will amortize the balance over the term of the sublease.

On September 15, 2023, the Company entered into an amendment with Initial Therapeutics to sublease the remainder of the second floor of the South San Francisco, California facility, consisting of an additional 17,000 square feet. The sublease term commenced on October 1, 2023 and extends the existing sublease agreement that commenced on July 1, 2022 through June 30, 2026. The additional space will be subleased at a monthly rent rate of $1.00 per square foot starting a month after Initial Therapeutics first takes possession of the additional space through June 30, 2024. Starting July 1, 2024, the rent rate for the entirety of Initial Therapeutics' subleased space will be $6.02 per rental square foot per month and will increase 3.5% on December 1, 2024 and 2025. Additionally, Initial Therapeutics will be required to pay approximately 51% of operating expenses and property management fees that the Company is required to pay under the lease for the South San Francisco, California facility. The Company incurred initial direct costs of $0.3 million in sublease commissions. Sublease income related to this amendment was $1.7 million for the year ended December 31, 2023 which was offset against total rent expense.

On September 15, 2023, the Company entered into a sublease agreement with GT Biopharma, Inc. to sublease a portion of its first floor at 8000 Marina Boulevard, Brisbane, California, consisting of 4,500 square feet. The sub-sublease term will commence on October 6, 2023 through June 30, 2024. The space will be subleased at a rent rate of $2.00 per rent square feet.

Impairment of Operating Lease Right-of-Use Asset and Other Long-Lived Assets

As the Company is subleasing its South San Francisco facility through June 30, 2026, the Company determined an impairment indicator was present. The Company determined all of its long-lived assets represent entity wide asset group for the purpose of the long-lived asset impairment assessment. The Company concluded that the carrying value of the entity wide asset group was not recoverable as it exceeded the future net undiscounted cash flows that are expected to be generated from the use and eventual disposition of the assets within the asset group. To allocate and recognize the impairment loss, the Company determined the fair value of the Company using the adjusted net asset method under the cost approach. The implied allocated impairment loss to any individual asset within the long-lived asset group shall not reduce the carrying amount of that asset below its fair value. To determine the fair value of the individual assets within the asset group, the Company utilized the discounted cash flow method using the income approach. Based on this analysis, the Company recognized a non-cash impairment charge of $5.6 million, including $4.0 million for the right-of-use asset and $1.6 million for the leasehold improvements during the year ended December 31, 2023. This represents a Level 3 nonrecurring fair value measurement. Calculating the fair value of the assets involves significant estimates and assumptions. These estimates and assumptions include, among others, projected future cash flows, risk-adjusted discount rates and market rental rates. Changes in the factors and assumptions used could materially affect the amount of impairment loss recognized in the period the asset was considered impaired.

Indemnifications

The Company indemnifies each of its officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at the Company’s request in such capacity, as permitted under Delaware law and in accordance with the Company’s amended and restated certificate of incorporation and bylaws. The term of the indemnification period lasts as long as an officer or director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity.

The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director and officer liability insurance. This insurance allows the transfer of risk associated with the Company’s exposure and may enable the Company to recover a portion of any future amounts paid. The Company believes that the fair value of these potential indemnification obligations is minimal. Accordingly, the Company has not recognized any liabilities relating to these obligations for any period presented.

Commitments and Contingencies -Summary of Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease, Expense [Abstract]
Operating lease expense	$ 3,739	$ 4,264	$ 4,357
Variable lease expense	748	1,318	1,633
Sublease income	(3,988)	(4,317)	(2,578)
Total lease expense	$ 499	$ 1,265	$ 3,412

Commitments and Contingencies - Additional Information (Details)		1 Months Ended				12 Months Ended
	Sep. 15, 2023 USD ($) ft² $ / ft²	May 31, 2022 USD ($) ft² $ / ft²	Jun. 30, 2021 USD ($) ft² $ / ft²	May 31, 2021 USD ($) ft² $ / ft²	Feb. 28, 2021 ft² $ / ft²	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Feb. 28, 2019 USD ($)
Commitments And Contingencies [Line Items]
Impairment loss						$ 5,600,000
Impairment of operating lease right-of-use asset						4,000,000
Impairment of leasehold improvements						1,600,000
Sublease income						$ 3,988,000	$ 4,317,000	$ 2,578,000
South San Francisco, California
Commitments And Contingencies [Line Items]
Lessee, operating lease, description						In February 2019, the Company entered into a lease agreement for new office and laboratory space in South San Francisco, California. The term of the lease agreement commenced in May 2019. The lease has an initial term from occupancy of approximately ten years ending on December 31, 2029 with an option to extend the term for an additional eight years at then-market rental rates.
Operating lease, initial lease term						10 years
Operating lease, renewal term						8 years
Tenant improvement allowance									$ 10,700,000
Letter of credit, delivered in connection of lease agreement						$ 900,000
Lease commencement date						2019-05
Operating lease, option to extend description						option to extend the term for an additional eight years
Operating lease, existence of option to extend						true
Lease expiration date						Dec. 31, 2029
South San Francisco, California \| Office and Laboratory Space, First Floor
Commitments And Contingencies [Line Items]
Space subleased (in square feet) \| ft²			23,000
Sublease expiration date			Jul. 31, 2024
Sublease rent per square foot \| $ / ft²			6.25
Annual percentage increase in sublease base rent			3.50%
Percentage of operating expenses and property management fees to be paid by subtenant			37.00%
Incurred initial direct costs of sublease			$ 200,000
Sublease income						$ 2,300,000	2,200,000	1,100,000
South San Francisco, California \| Office and Laboratory Space, Second Floor
Commitments And Contingencies [Line Items]
Space subleased (in square feet) \| ft²	17,000	15,000
Sublease start date	Oct. 01, 2023	Jul. 01, 2022
Sublease expiration date	Jun. 30, 2026	Jun. 30, 2026
Sublease rent per square foot \| $ / ft²	1	7.8
Annual percentage increase in sublease base rent	3.50%	3.50%
Increase in sublease rent per square foot \| $ / ft²	6.02
Percentage of operating expenses and property management fees to be paid by subtenant	51.00%	24.00%
Incurred initial direct costs of sublease	$ 300,000	$ 100,000
Sublease income						1,700,000
Brisbane, California
Commitments And Contingencies [Line Items]
Space subleased (in square feet) \| ft²				11,500	27,000
Sublease expiration date				Sep. 30, 2022	Aug. 31, 2022
Sublease rent per square foot \| $ / ft²				1	3.53
Annual percentage increase in sublease base rent					3.00%
Percentage of operating expenses and property management fees to be paid by subtenant				30.00%	41.00%
Incurred initial direct costs of sublease				$ 100,000
Sublease income						$ 0	$ 1,300,000	$ 1,500,000
Brisbane, California \| Office and Laboratory Space, First Floor
Commitments And Contingencies [Line Items]
Space subleased (in square feet) \| ft²	4,500
Sublease expiration date	Jun. 30, 2024
Sublease rent per square foot \| $ / ft²	2

Commitments and Contingencies - Summary of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
2024	$ 4,964
2025	5,123
2026	5,287
2027	5,457
2028	5,633
Thereafter	5,801
Total future minimum lease payments	32,265
Less: Amount representing interest	(5,275)
Present value of future minimum lease payments	26,990
Less: Current portion of operating lease liability	(3,451)				$ (3,100)
Noncurrent portion of operating lease liability	$ 23,539	$ 24,431	$ 25,297	$ 26,150	$ 26,991	$ 27,792

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

Warrants

Use of Estimates

estimated fair value are recognized as a component of "Other expense, net" in the Statements of Operations and Comprehensive Loss.

Segments

Cash, Cash Equivalents, and Restricted Cash


	December 31,
	2023		2022		2021
Cash and cash equivalents	$	19,803	$	12,736	$	32,905
Restricted cash		896		896		1,446
Total cash, cash equivalents, and restricted cash	$	20,699	$	13,632	$	34,351

Marketable Securities

Fair Value Measurements

Revenue Recognition

Concentrations of Risk

Research and Development Expenses and Accruals

Contingent Consideration Liability

Property and Equipment, Net

Leases

Impairment of Long-Lived Assets

Stock-Based Compensation

Embedded Derivatives of the Loan Agreement

Restructurings

Restructuring

retained, and the utilization of the provisions are for their intended purpose in accordance with developed restructuring plans.

Income Taxes

Net Loss per Common Share

Comprehensive Loss

Comprehensive loss includes net loss and certain changes in stockholders’ equity that are excluded from net loss, primarily unrealized losses on the Company’s marketable securities.

Recently Issued Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Recently Issued Accounting Pronouncements Not Yet Adopted

Balance Sheet Components - Schedule of Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022
Payables and Accruals [Abstract]
Operating lease liability - current portion	$ 3,451				$ 3,100
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued and other current liabilities				Accrued and other current liabilities
Accrued research and development	$ 839				$ 1,623
Liability related to early exercise shares	10				10
Accrued other	319				601
Accrued and other current liabilities	$ 4,619	$ 5,258	$ 5,417	$ 5,343	$ 5,334	$ 5,321

Balance Sheets - USD ($)
$ in Thousands

Dec. 31, 2023

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Dec. 31, 2022

Sep. 30, 2022

Jun. 30, 2022

Dec. 31, 2021

Dec. 31, 2020

Current assets:

Cash and cash equivalents

$ 19,803

$ 7,876

$ 19,118

$ 22,972

$ 12,736

$ 22,576

$ 32,905

Short-term marketable securities

23,398

38,063

49,974

60,420

82,059

76,364

Prepaid expenses and other current assets

3,404

3,599

3,874

2,989

1,740

3,084

Total current assets

46,605

49,538

72,966

86,381

96,535

102,574

Property and equipment, net

5,082

5,314

7,181

7,496

7,825

8,202

Operating lease right-of-use asset

12,981

13,522

18,061

18,557

19,042

19,515

Long-term restricted cash

896

Other long-term assets

126

Total assets

65,690

69,270

101,008

114,255

124,350

136,243

Current liabilities:

Accounts payable

1,380

1,149

1,449

1,470

1,790

2,444

Accrued compensation

1,841

2,226

1,652

1,983

3,020

2,961

Accrued and other current liabilities

4,619

5,258

5,417

5,343

5,334

5,321

Current portion of long-term debt

13,623

13,062

9,476

6,776

Total current liabilities

7,840

8,633

22,141

21,858

19,620

17,502

Operating lease liability, net of current portion

23,539

24,431

25,297

26,150

26,991

27,792

Long-term debt, net

4,067

7,619

10,891

13,262

Warrant liability

5,913

8,481

8,734

5,273

10,764

16,633

Total liabilities

37,292

41,545

60,239

60,900

68,266

75,189

Commitments and contingencies (Note 9)

Stockholders’ equity:

Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding

Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2023 and 2022; 16,784,969 and 14,215,302 shares issued and outstanding as of December 31, 2023 and 2022, respectively

^[1]

Additional paid-in capital

512,773

507,789

506,132

503,276

500,827

498,401

Accumulated other comprehensive gain

(24)

(55)

(136)

(150)

(251)

(275)

Accumulated deficit

(484,353)

(480,010)

(465,228)

(449,772)

(444,493)

(437,073)

Total stockholders’ equity

28,398

27,725

40,769

53,355

56,084

61,054

$ 39,931

$ 59,569

$ 82,881

Total liabilities and stockholders’ equity

$ 65,690

$ 69,270

$ 101,008

$ 114,255

$ 124,350

$ 136,243

[1]

Fair Value Measurements - Summary of Assumptions used in Fair Value Estimates of Level 3 Warrant Liabilities (Details) - Level 3 - Fair Value, Recurring	Dec. 31, 2023 $ / shares	Nov. 14, 2023 $ / shares	Sep. 30, 2023 $ / shares	Jun. 30, 2023 $ / shares	Mar. 31, 2023 $ / shares	Dec. 31, 2022 $ / shares	Sep. 30, 2022 $ / shares	Aug. 22, 2022 $ / shares
August 2022 Warrants ('Existing Warrants')
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock price	$ 1.93	$ 1.72	$ 2.4	$ 2.55	$ 1.63	$ 2.74	$ 3.95	$ 6.1
Exercise price per share	$ 8.5	$ 2.045	$ 8.5	$ 8.5	$ 8.5	$ 8.5	$ 8.5	$ 8.5
Contractual terms	3 years 7 months 20 days	3 years 9 months 7 days	3 years 10 months 20 days	4 years 1 month 20 days	4 years 4 months 20 days	4 years 7 months 20 days	4 years 10 months 20 days	5 years
August 2022 Warrants ('Existing Warrants') \| Estimated Volatility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.80	0.80	1	0.95	1	0.95	0.90	0.875
August 2022 Warrants ('Existing Warrants') \| Risk-free Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.0385	0.0442	0.0471	0.0428	0.0366	0.0403	0.0407	0.0317
November 2023 Inducement Offer ('New Warrants')
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock price	$ 1.93	$ 1.72
Contractual terms	4 years 10 months 13 days	5 years
November 2023 Inducement Offer ('New Warrants') \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exercise price per share	$ 1.92	$ 1.92
November 2023 Inducement Offer ('New Warrants') \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exercise price per share	$ 2.5563	$ 2.5563
November 2023 Inducement Offer ('New Warrants') \| Estimated Volatility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.80	0.80
November 2023 Inducement Offer ('New Warrants') \| Risk-free Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.0385	0.0442

Net Loss per Common Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss per Common Share

15. Net Loss per Common Share

Basic net loss per share is calculated by dividing net loss by the weighted-average number of shares outstanding for the period. Diluted net loss per share is calculated by dividing net loss by the weighted-average number of shares of common stock and potential dilutive common stock equivalents outstanding during the period if the effect is dilutive.

The calculation of diluted earnings (loss) per share also requires the consideration of the effect of dilutive potential common shares outstanding during the period determined using the treasury-stock related to the warrants outstanding.

A reconciliation of the numerators and denominators used in computing net loss from continuing operations per share is as follows (in thousands, except per share amounts):


	Year ended December 31,
	2023			2022 (Restated)			2021
	(in thousands, except share and per share amounts)
Numerator:
Net loss	$	(39,860	)	$	(44,469	)	$	(60,725	)
Denominator:
Weighted average number of shares outstanding—basic and diluted		14,773,612			9,494,421			5,581,587
Net loss per share—basic and diluted	$	(2.70	)	$	(4.68	)	$	(10.88	)

The Company was in a net loss position for all periods presented, basic net loss per common share is the same as diluted net loss per common share as the inclusion of all potential securities outstanding would have been anti-dilutive.

Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:


	Year ended December 31,
	2023		2022		2021
Options to purchase common stock		1,913,345		1,609,938		866,696
Outstanding warrants to purchase common stock		6,557,152		6,428,572		—
Early exercised common stock subject to future vesting		3,336		3,336		3,336
RSUs subject to future vesting		41,225		146,333		199,094
Shares subject to future vesting relating to the 2018 ESPP		47,389		65,939		14,774
Total		8,562,447		8,254,118		1,083,900

Up to 3,390 shares may be contingently issued, if certain performance conditions are met under the Company’s in-licensing agreements. See Note 6, “License Revenue, Agreements and Strategic Investment”.

Restatement of Previously Issued Financial Statements - Schedule of Restated Statement of Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net gain (loss)	$ (14,782)	$ (15,456)	$ (5,279)	$ (4,997)	$ (20,735)	$ (35,520)	$ (37,047)	$ (39,860)	$ (44,469)	$ (60,725)
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization			329		643	951	1,771	1,182	2,180	2,880
Amortization of Debt Issuance Costs			314		557	705	989	705	1,318	813
Debt extinguishment gain upon conversion to equity							(199)	0	(199)	(123)
Net accretion and amortization of premium and discounts on marketable securities			(433)		(831)	(1,199)	155	(1,503)	(276)	1,043
Gain on disposal of property and equipment							(247)	(114)	(346)	0
Stock-based compensation			2,175		4,422	6,127	7,120	7,419	9,379	11,553
Non-cash rent expense			(270)		(540)	(811)	(1,891)	(1,072)	(2,136)	(2,152)
(Gain) loss on warrant liability	(253)	3,461	(5,491)	(10,974)	(2,030)	(2,283)	(10,974)	(6,215)	(16,843)	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			(1,249)		(2,134)	(1,858)	(1,205)	(1,664)	138	1,288
Other long-term assets			23		47	52	15	(74)	39	(91)
Accounts payable			(320)		(341)	(642)	459	(410)	(194)	(573)
Accrued compensation			(1,037)		(1,368)	(793)	(1,067)	(1,180)	(1,008)	(1,327)
Accrued liabilities and other current liabilities			(78)		(89)	(335)	96	(1,063)	26	(1,131)
Other long-term liabilities							(23)	0	(23)	24
Net cash used in operating activities			(11,316)		(22,399)	(29,513)	(42,048)	(37,088)	(52,414)	(45,060)
Investing activities
Purchase of marketable securities			(5,973)		(21,868)	(28,609)	(86,567)	(28,609)	(98,827)	(81,492)
Maturities of marketable securities			27,251		53,000	74,000	62,000	89,000	74,000	121,000
Purchase of property and equipment						(11)	(59)	(11)	(96)	(195)
Sale of property and equipment						1	272	115	378	0
Net cash used in investing activities			21,278		31,132	45,381	(24,354)	60,495	(24,545)	39,313
Financing activities
Issuance costs for sale of common stock							(1,965)	0	(1,967)	0
Proceeds from issuance of common stock under the 2018 ESPP					91	91	125	116	142	347
Net cash provided by financing activities			274		(2,351)	(20,728)	56,073	(16,340)	56,240	20,845
Net decrease in cash, cash equivalents and restricted cash			10,236		6,382	(4,860)	(10,329)	7,067	(20,719)	15,098
Cash, cash equivalents and restricted cash at beginning of year	20,014	23,868	13,632		13,632	13,632	34,351	13,632	34,351	19,253
Cash, cash equivalents and restricted cash at end of year	8,772	20,014	23,868	24,022	20,014	8,772	24,022	20,699	13,632	34,351
Supplemental Cash Flow Information [Abstract]
Cash paid for interest			680		1,362	1,969	1,577	1,969	2,204	2,370
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt									3,179
As Previously Reported
Operating activities
Net gain (loss)	(15,289)	(12,205)	(10,865)	(13,708)	(23,070)	(38,362)	(45,758)		(59,927)
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization			329		643	951	1,771		2,180
Amortization of Debt Issuance Costs			314		653	705	989		1,318
Debt extinguishment gain upon conversion to equity							(199)		(199)
Net accretion and amortization of premium and discounts on marketable securities			(433)		(831)	(1,199)	155		(276)
Gain on disposal of property and equipment							(247)		(346)
Stock-based compensation			2,270		4,631	6,686	7,120		9,379
Non-cash rent expense			(270)		(540)	(811)	(1,891)		(2,136)
(Gain) loss on warrant liability	0	0	0	0	0	0	0		0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			(1,249)		(2,134)	(1,858)	(1,355)		138
Other long-term assets			23		47	52	15		39
Accounts payable			(320)		(341)	(642)	459		(194)
Accrued compensation			(1,037)		(1,368)	(793)	(1,067)		(1,008)
Accrued liabilities and other current liabilities			(78)		(89)	(335)	(632)		26
Other long-term liabilities							(23)		(23)
Net cash used in operating activities			(11,316)		(22,399)	(29,513)	(40,663)		(51,029)
Investing activities
Purchase of marketable securities			(5,973)		(21,868)	(28,609)	(86,567)		(98,827)
Maturities of marketable securities			27,251		53,000	74,000	62,000		74,000
Purchase of property and equipment						(11)	(59)		(96)
Sale of property and equipment						1	272		378
Net cash used in investing activities			21,278		31,132	45,381	(24,354)		(24,545)
Financing activities
Issuance costs for sale of common stock							0		0
Proceeds from issuance of common stock under the 2018 ESPP					91	91	125		142
Net cash provided by financing activities			274		(2,351)	(20,728)	54,688		54,855
Net decrease in cash, cash equivalents and restricted cash			10,236		6,382	(4,860)	(10,329)		(20,719)
Cash, cash equivalents and restricted cash at beginning of year	20,014	23,868	13,632		13,632	13,632	34,351	13,632	34,351
Cash, cash equivalents and restricted cash at end of year	8,772	20,014	23,868	24,022	20,014	8,772	24,022		13,632	34,351
Supplemental Cash Flow Information [Abstract]
Cash paid for interest			680		1,362	1,969	1,577		2,204
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt									3,179
Adjustment
Operating activities
Net gain (loss)	507	(3,251)	5,586	8,711	2,335	2,842	8,711		15,458
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization			0		0	0	0		0
Amortization of Debt Issuance Costs			0		(96)	0	0		0
Debt extinguishment gain upon conversion to equity							0		0
Net accretion and amortization of premium and discounts on marketable securities			0		0	0	0		0
Gain on disposal of property and equipment							0		0
Stock-based compensation			(95)		(209)	(559)	0		0
Non-cash rent expense			0		0	0	0		0
(Gain) loss on warrant liability	(253)	3,461	(5,491)	(10,974)	(2,030)	(2,283)	(10,974)		(16,843)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			0		0	0	150		0
Other long-term assets			0		0	0	0		0
Accounts payable			0		0	0	0		0
Accrued compensation			0		0	0	0		0
Accrued liabilities and other current liabilities			0		0	0	728		0
Other long-term liabilities							0		0
Net cash used in operating activities			0		0	0	(1,385)		(1,385)
Investing activities
Purchase of marketable securities			0		0	0	0		0
Maturities of marketable securities			0		0	0	0		0
Purchase of property and equipment						0	0		0
Sale of property and equipment						0	0		0
Net cash used in investing activities			0		0	0	0		0
Financing activities
Proceeds from issuance of common stock, net of issuance costs									0
Issuance costs for sale of common stock							(1,965)		(1,967)
Proceeds from issuance of common stock under the 2018 ESPP					0	0	0
Net cash provided by financing activities			0		0	0	1,385		1,385
Net decrease in cash, cash equivalents and restricted cash			0		0	0	0		0
Cash, cash equivalents and restricted cash at beginning of year	0	0	0		0	0	0	0	0
Cash, cash equivalents and restricted cash at end of year	$ 0	$ 0	0	$ 0	0	0	0		0	0
Supplemental Cash Flow Information [Abstract]
Cash paid for interest			0		0	0	0		0
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common stock in payment of debt									0
ATM Offering Program
Financing activities
Proceeds from issuance of common stock, net of issuance costs			274		792	744	12,003	725	12,155	10,357
ATM Offering Program \| As Previously Reported
Financing activities
Proceeds from issuance of common stock, net of issuance costs			274		792	744	12,003		12,155
ATM Offering Program \| Adjustment
Financing activities
Proceeds from issuance of common stock, net of issuance costs			$ 0		$ 0	$ 0	0		0
Follow-on Offering
Financing activities
Proceeds from issuance of common stock, net of issuance costs							45,000	0	45,000	0
Follow-on Offering \| As Previously Reported
Financing activities
Proceeds from issuance of common stock, net of issuance costs							41,650		41,648
Follow-on Offering \| Adjustment
Financing activities
Proceeds from issuance of common stock, net of issuance costs							3,350		3,352
Lincoln Park Capital Fund Equity Purchase Agreement [Member]
Financing activities
Proceeds from issuance of common stock, net of issuance costs							910	$ 0	910	$ 8,215
Lincoln Park Capital Fund Equity Purchase Agreement [Member] \| As Previously Reported
Financing activities
Proceeds from issuance of common stock, net of issuance costs							910		910
Lincoln Park Capital Fund Equity Purchase Agreement [Member] \| Adjustment
Financing activities
Proceeds from issuance of common stock, net of issuance costs							$ 0		$ 0

Quarterly Financial Information (Unaudited) - Statements of Operations and Comprehensive Loss (Details) - USD ($)
$ / shares in Units, $ in Thousands

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Sep. 30, 2022

Jun. 30, 2023

Sep. 30, 2023

Sep. 30, 2022

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Licensing revenue – Related Party

$ 0

$ 236

$ 0

$ 236

$ 4,784

Operating expenses:

Research and development

$ 4,632

6,435

$ 5,760

9,086

12,195

$ 16,828

29,100

20,099

36,859

38,393

General and administrative

4,347

5,413

4,798

4,922

10,212

14,560

15,669

18,966

20,949

23,056

Impairment of long-lived assets

5,602

Total operating expenses

14,581

11,848

10,558

14,008

22,407

36,990

44,769

44,667

57,808

61,449

Loss from operations

(14,581)

(11,848)

(10,558)

(14,008)

(22,407)

(36,990)

(44,533)

(44,667)

(57,572)

(56,665)

Interest income

689

805

855

329

1,660

2,349

416

2,874

1,220

100

Interest expense

(566)

(883)

(1,002)

(866)

(1,885)

(2,451)

(2,568)

(2,452)

(3,558)

(3,177)

Gain (loss) on warrant liability

253

(3,461)

5,491

10,974

2,030

2,283

10,974

6,215

16,843

Other expense, net

(577)

(69)

(65)

(1,426)

(133)

(711)

(1,336)

(1,830)

(1,402)

(983)

Net loss

(14,782)

(15,456)

(5,279)

(4,997)

(20,735)

(35,520)

(37,047)

(39,860)

(44,469)

(60,725)

Other comprehensive gain (loss)

Unrealized loss on marketable debt securities

101

(88)

115

196

(231)

227

(207)

(49)

Comprehensive loss

$ (14,701)

$ (15,442)

$ (5,178)

$ (5,085)

$ (20,620)

$ (35,324)

$ (37,278)

$ (39,633)

$ (44,676)

$ (60,774)

Net loss per share, basic

$ (1.01)

$ (1.07)

$ (0.37)

$ (0.5)

$ (1.44)

$ (2.46)

$ (4.67)

$ (2.7)

$ (4.68)

$ (10.88)

Net loss per share, diluted

$ (1.01)

$ (1.07)

$ (0.37)

$ (0.5)

$ (1.44)

$ (2.46)

$ (4.67)

$ (2.7)

$ (4.68)

$ (10.88)

Weighted average number of shares used in computing net loss per share, diluted

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

14,773,612

^[1]

9,494,421

^[1]

5,581,587

^[1]

Weighted average number of shares used in computing net loss per share, basic

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

14,773,612

^[1]

9,494,421

^[1]

5,581,587

^[1]

As Previously Reported

Licensing revenue – Related Party

$ 0

$ 236

Operating expenses:

Research and development

$ 4,901

6,529

$ 5,835

8,208

12,364

$ 17,266

28,222

36,859

General and administrative

4,428

5,433

4,818

4,922

10,252

14,681

15,669

20,949

Impairment of long-lived assets

5,602

Total operating expenses

14,931

11,962

10,653

13,130

22,616

37,549

43,891

57,808

Loss from operations

(14,931)

(11,962)

(10,653)

(13,130)

(22,616)

(37,549)

(43,655)

(57,572)

Interest income

689

805

855

329

1,660

2,349

416

1,220

Interest expense

(470)

(979)

(1,002)

(866)

(1,981)

(2,451)

(2,568)

(3,558)

Gain (loss) on warrant liability

Other expense, net

(577)

(69)

(65)

(41)

(133)

(711)

(17)

Net loss

(15,289)

(12,205)

(10,865)

(13,708)

(23,070)

(38,362)

(45,758)

(59,927)

Other comprehensive gain (loss)

Unrealized loss on marketable debt securities

101

(88)

115

196

(231)

(207)

Comprehensive loss

$ (15,208)

$ (12,191)

$ (10,764)

$ (13,796)

$ (22,955)

$ (38,166)

$ (45,989)

$ (60,134)

Net loss per share, basic

$ (1.05)

$ (0.85)

$ (0.76)

$ (1.36)

$ (1.61)

$ (2.66)

$ (5.77)

$ (6.31)

Net loss per share, diluted

$ (1.05)

$ (0.85)

$ (0.76)

$ (1.36)

$ (1.61)

$ (2.66)

$ (5.77)

$ (6.31)

Weighted average number of shares used in computing net loss per share, diluted

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

9,494,421

Weighted average number of shares used in computing net loss per share, basic

14,598,218

14,425,775

14,312,887

10,072,077

14,369,643

14,446,672

7,928,729

9,494,421

Adjustment

Licensing revenue – Related Party

$ 0

Operating expenses:

Research and development

$ (269)

(94)

$ (75)

878

(169)

$ (438)

878

General and administrative

(81)

(20)

(40)

(121)

Impairment of long-lived assets

Total operating expenses

(350)

(114)

(95)

878

(209)

(559)

878

Loss from operations

350

114

(878)

209

559

(878)

Interest income

Interest expense

(96)

Gain (loss) on warrant liability

253

(3,461)

5,491

10,974

2,030

2,283

10,974

16,843

Other expense, net

(1,385)

Net loss

507

(3,251)

5,586

8,711

2,335

2,842

8,711

15,458

Other comprehensive gain (loss)

Unrealized loss on marketable debt securities

Comprehensive loss

$ 507

$ (3,251)

$ 5,586

$ 8,711

$ 2,335

$ 2,842

$ 8,711

$ 15,458

Net loss per share, basic

$ 0

Net loss per share, diluted

$ 0

Weighted average number of shares used in computing net loss per share, diluted

Weighted average number of shares used in computing net loss per share, basic

[1]

The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded up to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.