0000950170-24-091903 | 10-Q | XBRL Viewer

Prepaid expenses and other current assets

26,400

23,398

^[1]

1,862

3,404

^[1]

Total current assets

35,846

46,605

^[1]

Property and equipment, net

4,630

5,082

^[1]

Operating lease right-of-use assets

11,900

12,981

^[1]

Long-term restricted cash

896

^[1]

Other long-term assets

250

126

^[1]

Total assets

53,522

65,690

^[1]

Current liabilities:

Accounts payable

1,456

1,380

^[1]

Accrued compensation

1,385

1,841

^[1]

Accrued and other current liabilities

5,977

4,619

^[1]

Total current liabilities

8,818

7,840

^[1]

Operating lease liability, net of current portion

21,659

23,539

^[1]

Warrant liability

3,291

5,913

^[1]

Total liabilities

33,768

37,292

^[1]

Commitments and contingencies (Note 6)

Stockholders’ equity:

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

^[1]

Common stock, $0.0001 par value; 300,000,000 shares authorized as of June 30, 2024 and December 31, 2023; 16,847,622 and 16,784,969 shares issued and outstanding as of June 30, 2024 and December 31, 2023, respectively

^[1]

Additional paid-in capital

515,209

512,773

^[1]

Accumulated other comprehensive loss

(35)

(24)

^[1]

Accumulated deficit

(495,422)

(484,353)

^[1]

Total stockholders’ equity

19,754

28,398

^[1]

Total liabilities and stockholders’ equity

$ 53,522

$ 65,690

^[1]

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2024

Commitments and Contingencies Disclosure [Abstract]

Summary of Components of Lease Expense

The following table summarizes the components of lease expense and sublease income, which are included in operating expenses in the Company’s condensed statements of operations and comprehensive loss (in thousands):


	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Operating lease cost	$	926		$	930		$	1,864		$	2,151
Variable lease cost		202			140			474			707
Sublease income		(1,472	)		(965	)		(2,944	)		(2,014	)
Total lease (income) cost	$	(344	)	$	105		$	(606	)	$	844

Summary of Maturities of Lease Liabilities

The following table summarizes the maturities of lease liabilities as of June 30, 2024 (in thousands):


	Amount
2024 (remaining 6 months)	$	2,488
2025		5,123
2026		5,287
2027		5,457
2028		5,633
Thereafter		5,801
Total future minimum lease payments		29,789
Less: Amount representing interest		(4,492	)
Present value of future minimum lease payments		25,297
Less: Current portion of operating lease liability		(3,638	)
Noncurrent portion of operating lease liability	$	21,659

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2024

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

These condensed 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 the United States SEC for interim reporting.

Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted. Accordingly, the unaudited condensed financial statements should be

read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 filed with the SEC.

Unaudited Condensed Financial Statements

The accompanying financial information for the three and six months ended June 30, 2024 and 2023 are unaudited. The unaudited condensed financial statements have been prepared on the same basis as the annual audited financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s financial position as of June 30, 2024 and its results of operations for the three and six months ended June 30, 2024 and 2023 and cash flows for the six months ended June 30, 2024 and 2023. The results for interim periods are not necessarily indicative of the results expected for the full fiscal year or any other periods.

Use of Estimates

The condensed financial statements have been prepared in accordance with GAAP, which requires management to make estimates and assumptions that affect the amounts and disclosures reported in the condensed 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 condensed 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 assets and lease liabilities, 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. As 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 income (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.

Recently Issued Accounting Pronouncements Not Yet Adopted

There have been no new accounting pronouncements issued or effective that are expected to have a material impact on the Company's condensed financial statements.

Net Loss per Common Share (Tables)

6 Months Ended

Jun. 30, 2024

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 share and per share amounts):


	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Numerator:
Net loss	$	(5,279	)	$	(15,456	)	$	(11,069	)	$	(20,735	)
Denominator:
Weighted-average number of shares outstanding—basic and diluted		16,815,387			14,425,775			16,800,238			14,369,643
Net loss per share—basic and diluted	$	(0.31	)	$	(1.07	)	$	(0.66	)	$	(1.44	)

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:


	Six Months Ended June 30,
	2024		2023
Options to purchase common stock		2,398,340		2,006,544
Outstanding warrants to purchase common stock		6,557,152		6,428,572
Early exercised common stock subject to future vesting		—		3,336
RSUs subject to future vesting		393,595		78,778
Shares subject to future vesting relating to the 2018 ESPP		46,046		31,956
Total		9,395,133		8,549,186

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (5,279)	$ (5,790)	$ (15,456)	$ (5,279)	$ (11,069)	$ (20,735)

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

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Investments, Debt and Equity Securities [Abstract]

Marketable Securities

6 Months Ended

Jun. 30, 2024

Marketable Securities

4. Marketable Securities

Marketable securities, which are classified as available-for-sale, consisted of the following as of June 30, 2024 (in thousands):


	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	4,437	$	—	$	—		$	4,437
Total cash equivalents		4,437		—		—			4,437
Short-term marketable securities:
U.S. treasuries		20,941		—		(26	)		20,915
U.S. government debt securities		5,494		—		(9	)		5,485
Total short-term marketable securities		26,435		—		(35	)		26,400
Restricted cash equivalents:
Money market funds		896		—		—			896
Total restricted cash equivalents		896		—		—			896
Total	$	31,768	$	—	$	(35	)	$	31,733

Marketable securities, which are classified as available-for-sale, consisted of the following as of December 31, 2023 (in thousands):


	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		(7	)		7,850
U.S. government debt securities		15,570		1		(22	)		15,549
Total short-term marketable securities		23,423		5		(29	)		23,399
Restricted Cash equivalents:
Money market funds		896		—		—			896
Total restricted cash equivalents		896		—		—			896
Total	$	40,172	$	5	$	(29	)	$	40,148

At June 30, 2024, the remaining contractual maturities of available-for-sale securities were less than one year. There have been no significant realized gains or losses on available-for-sale securities for the periods presented. As of June 30, 2024, 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 three and six months ended June 30, 2024 and no allowance for credit loss was recorded at June 30, 2024. The Company will continue to assess the current and expected future economic and market conditions as further development arises.

Equity Financing

6 Months Ended

Jun. 30, 2024

Equity [Abstract]

Equity Financing

. Equity Financing

The Company has 10,000,000 shares of convertible preferred stock authorized for issuance, par value of $0.0001 per share. As of June 30, 2024 and December 31, 2023, 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 June 30, 2024 and December 31, 2023, there were 16,847,622 and 16,784,969 shares, respectively, of common stock issued and outstanding.

Follow-On Offering

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 June 30, 2024, 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 are recognized in the Statement of Operations and Comprehensive Loss at each reporting date.

At June 30, 2024 and December 31, 2023, 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 $1.4 million and $2.8 million (subsequent to the exercise of the Existing Warrants as described in the section below), respectively. The change in fair value for the three months ended June 30, 2024 and 2023 of $0.7 million and $3.5 million, respectively, and the six months ended June 30, 2024 and 2023 of $1.4 million and $2.0 million, respectively, was recorded as 'Gain (loss) on warrant liability' in the condensed Statements of Operations and Comprehensive Loss.

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.

At June 30, 2024 and December 31, 2023, the Company updated the estimated fair value of the outstanding New Warrants using a Monte-Carlo valuation model resulting in an estimated fair value of $1.9 million and $3.1 million (subsequent to the exercise of the Existing Warrants as described in the section below), respectively. The change in fair value for the three months ended June 30, 2024 and 2023 of $0.6 million and zero, respectively, and for the six months ended June 30, 2024 and 2023 of $1.2 million and zero, respectively, was recorded as 'Gain (loss) on warrant liability' in the condensed Statements of Operations and Comprehensive Loss.

The entire disclosure for equity.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Beginning balance at Dec. 31, 2022

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2024	Aug. 02, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Amendment Flag	false
Document Period End Date	Jun. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Trading Symbol	UBX
Entity Registrant Name	Unity Biotechnology, Inc.
Entity Central Index Key	0001463361
Current Fiscal Year End Date	--12-31
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Current Reporting Status	Yes
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		16,847,622
Entity Shell Company	false
Entity File Number	001-38470
Entity Tax Identification Number	26-4726035
Entity Incorporation, State or Country Code	DE
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
Title of 12(b) Security	Common Stock, par value $0.0001
Security Exchange Name	NASDAQ

Condensed Statements of Stockholders' Equity (Unaudited) - USD ($)

Total

ATM Equity Offering Program

Common Stock

ATM Equity Offering Program

Additional Paid-In Capital

ATM Equity Offering Program

Accumulated Other Comprehensive (Loss)

Accumulated Deficit

$ 56,084,000

$ 1,000

$ 500,827,000

$ (251,000)

$ (444,493,000)

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

14,215,302

Issuance of common stock, net of issuance costs

$ 274,000

Issuance of common stock (in shares)

106,781

37,131

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

2,175,000

101,000

Ending balance at Mar. 31, 2023

(5,279,000)

53,355,000

$ 1,000

503,276,000

(150,000)

(449,772,000)

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

14,359,214

Beginning balance at Dec. 31, 2022

56,084,000

$ 1,000

500,827,000

(251,000)

(444,493,000)

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

14,215,302

Ending balance at Jun. 30, 2023

(20,735,000)

40,769,000

$ 1,000

506,132,000

(136,000)

(465,228,000)

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

14,595,477

Beginning balance at Mar. 31, 2023

53,355,000

$ 1,000

503,276,000

(150,000)

(449,772,000)

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

14,359,214

Issuance of common stock, net of issuance costs

$ 518,000

Issuance of common stock (in shares)

168,000

Issuance of common stock under 2018 ESPP

91,000

Issuance of common stock under 2018 ESPP (in Shares)

41,497

26,766

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

2,247,000

14,000

Ending balance at Jun. 30, 2023

(15,456,000)

40,769,000

$ 1,000

506,132,000

(136,000)

(465,228,000)

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

14,595,477

Beginning balance at Dec. 31, 2023

$ 28,398,000

^[1]

$ 2,000

512,773,000

(24,000)

(484,353,000)

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

16,784,969

Repurchase of early exercised shares, (in shares)

(3,336)

5,014

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

$ 1,394,000

1,394,000

(14,000)

Ending balance at Mar. 31, 2024

(5,790,000)

23,988,000

$ 2,000

514,167,000

(38,000)

(490,143,000)

Ending balance, (in shares) at Mar. 31, 2024

16,786,647

Beginning balance at Dec. 31, 2023

$ 28,398,000

^[1]

$ 2,000

512,773,000

(24,000)

(484,353,000)

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

16,784,969

Ending balance at Jun. 30, 2024

$ (11,069,000)

$ 19,754,000

$ 2,000

515,209,000

(35,000)

(495,422,000)

Ending balance, (in shares) at Jun. 30, 2024

16,847,622

Beginning balance at Mar. 31, 2024

$ 23,988,000

$ 2,000

514,167,000

(38,000)

(490,143,000)

Beginning balance, (in shares) at Mar. 31, 2024

16,786,647

Issuance of common stock under 2018 ESPP

68,000

Issuance of common stock under 2018 ESPP (in Shares)

52,494

8,481

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

974,000

3,000

Ending balance at Jun. 30, 2024

(5,279,000)

$ 19,754,000

$ 2,000

$ 515,209,000

$ (35,000)

$ (495,422,000)

Ending balance, (in shares) at Jun. 30, 2024

16,847,622

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Fair Value Measurements - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Nov. 30, 2023
Warrant Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of warrant liability	$ 1.4	$ 2.8
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
Exercise price for warrant			$ 1.92
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	$ 1.9	$ 3.1
November 2023 Inducement Offer ('New Warrants') \| Placement Agent \| Placement Agent Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued to purchase common stock			128,580
Exercise price for warrant			$ 2.5563

Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2024

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 as of June 30, 2024 (in thousands):


	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	4,437	$	—	$	—		$	4,437
Total cash equivalents		4,437		—		—			4,437
Short-term marketable securities:
U.S. treasuries		20,941		—		(26	)		20,915
U.S. government debt securities		5,494		—		(9	)		5,485
Total short-term marketable securities		26,435		—		(35	)		26,400
Restricted cash equivalents:
Money market funds		896		—		—			896
Total restricted cash equivalents		896		—		—			896
Total	$	31,768	$	—	$	(35	)	$	31,733

Marketable securities, which are classified as available-for-sale, consisted of the following as of December 31, 2023 (in thousands):


	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		(7	)		7,850
U.S. government debt securities		15,570		1		(22	)		15,549
Total short-term marketable securities		23,423		5		(29	)		23,399
Restricted Cash equivalents:
Money market funds		896		—		—			896
Total restricted cash equivalents		896		—		—			896
Total	$	40,172	$	5	$	(29	)	$	40,148

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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Marketable Securities - Additional Information (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
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

Fair Value Measurements - Summary of Assumptions used in Fair Value Estimates of Level 3 Warrant Liabilities (Details) - Level 3 - Fair Value, Recurring	Jun. 30, 2024 $ / shares
August 2022 Warrants ('Existing Warrants')
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock price	$ 1.35
Exercise price per share	$ 8.5
Contractual terms	3 years 1 month 20 days
August 2022 Warrants ('Existing Warrants') \| Estimated Volatility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.80
August 2022 Warrants ('Existing Warrants') \| Risk-free Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.0451
November 2023 Inducement Offer ('New Warrants')
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock price	$ 1.35
Contractual terms	4 years 4 months 13 days
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
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
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
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	0.0439

Stock-Based Compensation - Summary of Restricted Stock Units ("RSUs") (Details) - Restricted Stock Units ("RSUs") [Member]	6 Months Ended
	Jun. 30, 2024 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Unvested at December 31, 2023 \| shares	41,225
Shares, Granted \| shares	407,725
Shares, Vested \| shares	(13,565)
Shares, Canceled \| shares	(41,790)
Shares, Unvested at June 30, 2024 \| shares	393,595
Weighted-Average Grant Date Fair Value, Unvested at December 31, 2023 \| $ / shares	$ 30.18
Weighted-Average Grant Date Fair Value, Granted \| $ / shares	1.67
Weighted-Average Grant Date Fair Value, Vested \| $ / shares	31.08
Weighted-Average Grant Date Fair Value, Canceled \| $ / shares	2.06
Weighted-Average Grant Date Fair Value, Unvested at June 30, 2024 \| $ / shares	$ 3.6

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
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Numerator:
Net loss	$ (5,279)	$ (5,790)	$ (15,456)	$ (5,279)	$ (11,069)	$ (20,735)
Denominator:
Weighted average number of shares outstanding-basic	16,815,387		14,425,775		16,800,238	14,369,643
Weighted average number of shares outstanding-diluted	16,815,387		14,425,775		16,800,238	14,369,643
Net loss per share-basic	$ (0.31)		$ (1.07)		$ (0.66)	$ (1.44)
Net loss per share-diluted	$ (0.31)		$ (1.07)		$ (0.66)	$ (1.44)

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

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.

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

Net Loss per Common Share

Commitments and Contingencies - Additional Information (Details) $ in Thousands		1 Months Ended			3 Months Ended		6 Months Ended
	Sep. 15, 2023 USD ($) ft² $ / ft²	May 31, 2022 USD ($) ft² $ / ft²	Jun. 30, 2021 USD ($) ft² $ / ft²	Feb. 28, 2019 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)
Commitments And Contingencies [Line Items]
Sublease income					$ 1,472	$ 965	$ 2,944	$ 2,014
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
Letter of credit, delivered in connection of lease agreement				$ 900
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, 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	$ 100
Sublease income					800	400	$ 1,600	800
Original sublease expiration date		Jun. 30, 2024
Existing sublease start date	Jul. 01, 2022
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
Sublease income					$ 600	$ 500	$ 1,300	$ 1,100
Brisbane, California \| Office And Laboratory Space First Floor
Commitments And Contingencies [Line Items]
Space subleased (in square feet) \| ft²	4,500
Sublease start date	Oct. 06, 2023
Sublease expiration date	Jun. 30, 2024
Sublease rent per square foot \| $ / ft²	2

Net Loss per Common Share

6 Months Ended

Jun. 30, 2024

Earnings Per Share [Abstract]

8. 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 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 share and per share amounts):


	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Numerator:
Net loss	$	(5,279	)	$	(15,456	)	$	(11,069	)	$	(20,735	)
Denominator:
Weighted-average number of shares outstanding—basic and diluted		16,815,387			14,425,775			16,800,238			14,369,643
Net loss per share—basic and diluted	$	(0.31	)	$	(1.07	)	$	(0.66	)	$	(1.44	)

Since 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 common shares 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:


	Six Months Ended June 30,
	2024		2023
Options to purchase common stock		2,398,340		2,006,544
Outstanding warrants to purchase common stock		6,557,152		6,428,572
Early exercised common stock subject to future vesting		—		3,336
RSUs subject to future vesting		393,595		78,778
Shares subject to future vesting relating to the 2018 ESPP		46,046		31,956
Total		9,395,133		8,549,186

Up to 3,390 shares may be contingently issued, if certain performance conditions are met under the Company’s in-licensing agreements.

Organization - Additional Information (Details) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 30, 2024

Mar. 31, 2024

Jun. 30, 2023

Mar. 31, 2023

Jun. 30, 2024

Jun. 30, 2023

Dec. 31, 2023

^[1]

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Accumulated deficit

$ (495,422)

$ (484,353)

Cash, cash equivalents and marketable securities

(5,279)

$ (5,790)

$ (15,456)

$ (5,279)

(11,069)

$ (20,735)

Cash used in operations

(9,767)

(22,399)

Product revenue

$ 0

$ 34,000

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

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

Amount of accumulated undistributed earnings (deficit).

+ References + Details

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.

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Commitments and Contingencies Disclosure [Abstract]

Summary of Significant Accounting Policies - Additional Information (Details)	6 Months Ended
	Jun. 30, 2024 Segment
Number of operating segment	1

Stock-Based Compensation - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 974	$ 2,247	$ 2,368	$ 4,422
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	117	714	438	1,396
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 857	$ 1,533	$ 1,930	$ 3,026

Commitments and Contingencies

6 Months Ended

Jun. 30, 2024

Commitments and Contingencies

5. 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.

In June 2021, the Company entered into an agreement to sublease a portion of the first floor of the South San Francisco, California 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 was $0.6 million and $0.5 million for the three months ended June 30, 2024 and 2023, respectively, and $1.3 million and $1.1 million for the six months ended June 30, 2024 and 2023, 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 will commence on October 1, 2023 and extends the existing sublease agreement that commenced on July 1, 2022 through June 30, 2026. The additional space was subleased at a monthly rent rate of $1.00 per square foot starting a month after Initial Therapeutics first took possession of the additional space through June 30, 2024. Starting July 1, 2024, the rent rate for the entirety of Initial Therapeutics' subleased space is $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 from Initial Therapeutics, Inc. was $0.8 million and $0.4 million for the three months ended June 30, 2024 and 2023, respectively, and $1.6 million and $0.8 million for the six months ended June 30, 2024 and 2023, respectively, which was offset against total rent expense.


	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Operating lease cost	$	926		$	930		$	1,864		$	2,151
Variable lease cost		202			140			474			707
Sublease income		(1,472	)		(965	)		(2,944	)		(2,014	)
Total lease (income) cost	$	(344	)	$	105		$	(606	)	$	844

Variable lease payments include amounts relating to common area maintenance, real estate taxes and insurance and are recognized in the condensed statements of operations and comprehensive loss as incurred.

The following table summarizes the maturities of lease liabilities as of June 30, 2024 (in thousands):


	Amount
2024 (remaining 6 months)	$	2,488
2025		5,123
2026		5,287
2027		5,457
2028		5,633
Thereafter		5,801
Total future minimum lease payments		29,789
Less: Amount representing interest		(4,492	)
Present value of future minimum lease payments		25,297
Less: Current portion of operating lease liability		(3,638	)
Noncurrent portion of operating lease liability	$	21,659

On September 15, 2023, the Company entered into a sub-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 commenced on October 6, 2023 and ended June 30, 2024. The space was subleased at a rent rate of $2.00 per rent square feet.

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.

Stock-Based Compensation - Summary of Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 2024 $ / shares shares
Number of Shares
Balances at December 31, 2023 \| shares	1,913,345
Granted \| shares	691,834
Canceled \| shares	(206,839)
Balances at June 30, 2024 \| shares	2,398,340
Weighted-Average Exercise Price
Balances at December 31, 2023 \| $ / shares	$ 14.23
Granted \| $ / shares	1.64
Canceled \| $ / shares	5.13
Balances at June 30, 2024 \| $ / shares	$ 11.38

Equity Financing - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended
	Nov. 09, 2023	Aug. 31, 2022	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Subsidiary Sale Of Stock [Line Items]
Number of stock, authorized for issuance			10,000,000		10,000,000			10,000,000
Number of stock, par value per share			$ 0.0001		$ 0.0001			$ 0.0001
Number of stock, shares issued			0		0			0
Number of stock, shares outstanding			0		0			0
Common stock, shares authorized			300,000,000		300,000,000			300,000,000
Common stock, par value per share			$ 0.0001		$ 0.0001			$ 0.0001
Common stock, shares issued			16,847,622		16,847,622			16,784,969
Common stock, shares outstanding			16,847,622		16,847,622			16,784,969
Gain (loss) on warrant liability					$ 2,622	$ 2,030
Inducement Offer
Subsidiary Sale Of Stock [Line Items]
Gain (loss) on warrant liability			$ 600	$ 0	1,200	$ 0
Estimated Fair Value of Common Warrants Outstanding			$ 1,900		$ 1,900			$ 3,100
Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock, shares outstanding			16,847,622	14,595,477	16,847,622	14,595,477	16,786,647	16,784,969	14,359,214	14,215,302
Existing Warrants \| Holders \| Inducement Offer
Subsidiary Sale Of Stock [Line Items]
Warrants issued to purchase ordinary shares	2,143,000
Reduced exercise price of warrant	$ 2.045
Expected aggregate gross proceeds from exercise of warrants	$ 4,400
New Warrants \| Holders \| Inducement Offer
Subsidiary Sale Of Stock [Line Items]
Exercise price for warrant	$ 1.92
Warrants issued to purchase ordinary shares	2,143,000
New Warrants \| Holders \| Inducement Offer \| Maximum
Subsidiary Sale Of Stock [Line Items]
Warrants exercisable term	5 years
Placement Agent Warrants \| H.C. Wainwright & Co.
Subsidiary Sale Of Stock [Line Items]
Exercise price for warrant	$ 2.5563
Warrants issued to purchase ordinary shares	128,580
Follow-On Offering
Subsidiary Sale Of Stock [Line Items]
Gross proceeds		$ 45,000
Gain (loss) on warrant liability			$ 700	$ 3,500	$ (1,400)	$ 2,000
Proceeds from sale of common stock		$ 41,700
Number of warrants exercised			2,143,000		2,143,000
Estimated Fair Value of Common Warrants Outstanding			$ 1,400		$ 1,400			$ 2,800
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)		6,428,571
Share purchase price		$ 7
Follow-On Offering \| Existing Warrants
Subsidiary Sale Of Stock [Line Items]
Exercise price for warrant		$ 8.5
Warrants issued to purchase ordinary shares		6,428,572

Condensed Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	10,000,000	10,000,000
Convertible preferred stock, shares issued	0	0
Convertible preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	16,847,622	16,784,969
Common stock, shares outstanding	16,847,622	16,784,969

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Operating activities
Net loss	$ (11,069)	$ (20,735)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	448	643
Amortization of debt issuance costs	0	557
Net accretion and amortization of premium and discounts on marketable securities	(474)	(831)
Gain on disposal of property and equipment	(16)	0
Stock-based compensation	2,368	4,422
Non-cash rent expense	(612)	(540)
Gain (loss) on warrant liability	(2,622)	(2,030)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,542	(2,134)
Other long-term assets	(124)	47
Accounts payable	76	(341)
Accrued compensation	(456)	(1,368)
Accrued liabilities and other current liabilities	1,172	(89)
Net cash used in operating activities	(9,767)	(22,399)
Investing activities
Purchase of marketable securities	(21,289)	(21,868)
Maturities of marketable securities	18,750	53,000
Sale of property and equipment	19	0
Net cash provided by (used in) investing activities	(2,520)	31,132
Financing activities
Repayment of term loan debt	0	(3,234)
Proceeds from issuance of common stock under 2018 ESPP	68	91
Net cash provided by financing activities	68	(2,351)
Net increase (decrease) in cash, cash equivalents and restricted cash	(12,219)	6,382
Cash, cash equivalents and restricted cash at beginning of the period	20,699	13,632
Cash, cash equivalents and restricted cash at end of the period	8,480	20,014
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	0	1,362
Cash and cash equivalents	7,584	19,118
Restricted cash	896	896
Total cash, cash equivalents and restricted cash	8,480	20,014
ATM Offering Program
Financing activities
Proceeds from issuance of common stock, net of issuance costs	$ 0	$ 792

Fair Value Measurements

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

3. Fair Value Measurements

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 the related fair values due to the short maturities of these instruments.

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


	June 30, 2024
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	4,437	$	4,437	$	—	$	—
Total cash equivalents		4,437		4,437		—		—
Short-term marketable securities:
U.S. treasuries		20,915		—		20,915		—
U.S. government debt securities		5,485		—		5,485		—
Total short-term marketable securities		26,400		—		26,400		—
Restricted cash equivalents:
Money market funds		896		896		—		—
Total restricted cash equivalents		896		896		—		—
Total assets subject to fair value measurements	$	31,733	$	5,333	$	26,400	$	—

Liabilities:
Warrant Liability	$	3,291	$	—	$	—	$	3,291
Total liabilities subject to fair value measurements on a recurring basis	$	3,291	$	—	$	—	$	3,291


	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	$	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

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.

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 stock warrants was $1.4 million and $2.8 million as of June 30, 2024 and December 31, 2023, respectively.


	June 30, 2024
Common stock price	$	1.35
Exercise price per share	$	8.50
Estimated volatility		80.0	%
Risk-free interest rate		4.51	%
Contractual term (in years)		3.14

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 as a liability on the Balance Sheet and are adjusted to estimated fair value at period end within “Gain (loss) on warrant liability” on the Statement of Operations and Comprehensive Loss. The estimated fair value of the New Warrants was $1.9 million and $3.1 million as of June 30, 2024 and December 31, 2023, respectively.


	June 30, 2024
Common stock price	$		1.35
Exercise price per share	$	1.92 - 2.5563
Expected volatility			80.0	%
Risk-free interest rate			4.39	%
Contractual term (in years)			4.37

The following is a roll forward of the fair value of Level 3 warrants for the three months ended June 30, 2024 (in thousands):


	Warrant Liability Fair Value
Balance at March 31, 2024	$	4,537
Change in fair value		(1,246	)
Balance at June 30, 2024	$	3,291

The following is a roll forward of the fair value of Level 3 warrants for the six months ended June 30, 2024 (in thousands):


	Warrant Liability Fair Value
Balance at December 31, 2023	$	5,913
Change in fair value		(2,622	)
Balance at June 30, 2024	$	3,291

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.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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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

Jun. 30, 2024

Dec. 31, 2023

Assets:

$ 26,400

$ 23,398

^[1]

896

^[1]

Fair Value, Recurring

Assets:

4,437

15,853

26,400

23,398

Total assets subject to fair value measurements

896

31,733

40,147

Total liabilities subject to fair value measurements on a recurring basis

3,291

5,913

Fair Value, Recurring | Level 1

Assets:

4,437

12,864

Total assets subject to fair value measurements

896

5,333

13,760

Fair Value, Recurring | Level 2

Assets:

2,989

Total assets subject to fair value measurements

26,400

23,398

26,400

26,387

Fair Value, Recurring | Level 3

Assets:

Total liabilities subject to fair value measurements on a recurring basis

3,291

5,913

Money market funds | Fair Value, Recurring

Assets:

4,437

12,864

Money market funds | Fair Value, Recurring | Level 1

896

Assets:

4,437

12,864

U.S. Treasuries | Fair Value, Recurring

896

Assets:

2,989

U.S. Treasuries | Fair Value, Recurring | Level 2

20,915

7,849

Assets:

2,989

U.S. government debt securities | Fair Value, Recurring

20,915

7,849

Assets:

U.S. government debt securities | Fair Value, Recurring | Level 2

5,485

15,549

Assets:

Warrant Liability | Fair Value, Recurring

5,485

15,549

Assets:

Total liabilities subject to fair value measurements on a recurring basis

3,291

5,913

Warrant Liability | Fair Value, Recurring | Level 3

Assets:

Total liabilities subject to fair value measurements on a recurring basis

$ 3,291

$ 5,913

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Commitments and Contingencies - Summary of Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Lease, Cost [Abstract]
Operating lease cost	$ 926	$ 930	$ 1,864	$ 2,151
Variable lease cost	202	140	474	707
Sublease income	(1,472)	(965)	(2,944)	(2,014)
Total lease (income) cost	$ (344)	$ 105	$ (606)	$ 844

Stock-Based Compensation

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

7. Stock-Based Compensation

Stock Options and Restricted Stock Units (RSUs) Activity

A summary of the Company’s stock option activity under the 2013 Equity Incentive Plan, 2018 Incentive Award Plan (the "2018 Plan"), and 2020 Employment Inducement Incentive Plan for the six months ended June 30, 2024 is as follows:


	Number of Shares			Weighted- Average Exercise Price
Balances at December 31, 2023		1,913,345		$	14.23
Granted		691,834		$	1.64
Canceled		(206,839	)	$	5.13
Balances at June 30, 2024		2,398,340		$	11.38

A summary of the Company’s restricted stock units (“RSUs”) activity for the six months ended June 30, 2024 is as follows:


	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2023		41,225		$	30.18
Granted		407,725		$	1.67
Vested		(13,565	)	$	31.08
Canceled		(41,790	)	$	2.06
Unvested at June 30, 2024		393,595		$	3.60

Stock Based Compensation Expense

The following table sets forth the total stock-based compensation expense for all options granted to employees and nonemployees, including shares sold through the issuance of non-recourse promissory notes which are considered to be options for accounting purposes, and costs associated with the Company’s 2018 Employee Stock Purchase Plan (“2018 ESPP”) included in the Company’s condensed statements of operations and comprehensive loss (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	117	$	714	$	438	$	1,396
General and administrative		857		1,533		1,930		3,026
Total	$	974	$	2,247	$	2,368	$	4,422

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Summary of Stock Option Activity


	Number of Shares			Weighted- Average Exercise Price
Balances at December 31, 2023		1,913,345		$	14.23
Granted		691,834		$	1.64
Canceled		(206,839	)	$	5.13
Balances at June 30, 2024		2,398,340		$	11.38

Summary of Restricted Stock Units ("RSUs")

A summary of the Company’s restricted stock units (“RSUs”) activity for the six months ended June 30, 2024 is as follows:


	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2023		41,225		$	30.18
Granted		407,725		$	1.67
Vested		(13,565	)	$	31.08
Canceled		(41,790	)	$	2.06
Unvested at June 30, 2024		393,595		$	3.60

Summary of Stock-based Compensation Expense


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	117	$	714	$	438	$	1,396
General and administrative		857		1,533		1,930		3,026
Total	$	974	$	2,247	$	2,368	$	4,422

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($)
$ in Thousands

Jun. 30, 2024

Dec. 31, 2023

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Total prepaid expenses & other current assets

$ 1,862

$ 3,404

^[1]

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Marketable Securities - Summary of Marketable Securities Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	$ 31,768	$ 40,172
Unrealized Gains	0	5
Unrealized Losses	(35)	(29)
Fair Value	31,733	40,148
Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	4,437	15,853
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	4,437	15,853
Cash Equivalents \| Money market funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	4,437	12,864
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	4,437	12,864
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	26,435	23,423
Unrealized Gains	0	5
Unrealized Losses	(35)	(29)
Fair Value	26,400	23,399
Short Term Marketable Securities \| U.S. government debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	5,494	15,570
Unrealized Gains	0	1
Unrealized Losses	(9)	(22)
Fair Value	5,485	15,549
Short Term Marketable Securities \| U S Treasuries
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	20,941	7,853
Unrealized Gains	0	4
Unrealized Losses	(26)	(7)
Fair Value	20,915	7,850
Restricted Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	896	896
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	896	896
Restricted Cash Equivalents \| Money market funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	896	896
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 896	$ 896

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Jun. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Commitments and Contingencies - Summary of Maturities of Lease Liabilities (Details) - USD ($)
$ in Thousands

Jun. 30, 2024

Dec. 31, 2023

^[1]

Commitments and Contingencies Disclosure [Abstract]

2024 (remaining 6 months)

$ 2,488

5,123

5,287

5,457

5,633

5,801

Total future minimum lease payments

29,789

Less: Amount representing interest

(4,492)

Present value of future minimum lease payments

25,297

Less: Current portion of operating lease liability

(3,638)

Noncurrent portion of operating lease liability

$ 21,659

$ 23,539

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These condensed 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 the United States SEC for interim reporting. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted. Accordingly, the unaudited condensed financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 filed with the SEC.
Unaudited Condensed Financial Statements	Unaudited Condensed Financial Statements The accompanying financial information for the three and six months ended June 30, 2024 and 2023 are unaudited. The unaudited condensed financial statements have been prepared on the same basis as the annual audited financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s financial position as of June 30, 2024 and its results of operations for the three and six months ended June 30, 2024 and 2023 and cash flows for the six months ended June 30, 2024 and 2023. The results for interim periods are not necessarily indicative of the results expected for the full fiscal year or any other periods.
Use of Estimates	Use of Estimates The condensed financial statements have been prepared in accordance with GAAP, which requires management to make estimates and assumptions that affect the amounts and disclosures reported in the condensed 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 condensed 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 assets and lease liabilities, 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. As 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 income (expense), net" in the Statements of Operations and Comprehensive Loss.
Segments	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.
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncements Not Yet Adopted There have been no new accounting pronouncements issued or effective that are expected to have a material impact on the Company's condensed financial statements.

Disclosure of accounting policy for segment reporting.

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