0001564590-22-010232 | 10-K | XBRL Viewer

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Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 32,905	$ 17,807
Short-term marketable securities	55,170	79,892
Prepaid expenses and other current assets	1,879	3,167
Restricted cash	550	0
Total current assets	90,504	100,866
Property and equipment, net	9,942	12,627
Operating lease right-of-use assets	21,286	23,509
Long-term marketable securities	1,993	17,871
Long-term restricted cash	896	1,446
Other long-term assets	91	0
Total assets	124,712	156,319
Current liabilities:
Accounts payable	1,985	2,558
Accrued compensation	4,028	5,355
Accrued and other current liabilities	6,370	6,550
Deferred revenue	216	0
Derivative liability related to debt	963	0
Current portion of long-term debt	3,055	0
Total current liabilities	16,617	14,463
Operating lease liability, net of current portion	30,094	34,468
Long-term debt, net	18,409	24,508
Other long-term liabilities	23	0
Total liabilities	65,143	73,439
Commitments and contingencies (Note 7)
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, 2021 and 2020; 62,991,906 and 53,253,213 shares issued and outstanding as of December 31, 2021 and 2020, respectively	6	5
Additional paid-in capital	459,631	422,379
Related party promissory notes for purchase of common stock		(210)
Accumulated other comprehensive gain	(44)	5
Accumulated deficit	(400,024)	(339,299)
Total stockholders’ equity	59,569	82,880
Total liabilities and stockholders’ equity	$ 124,712	$ 156,319

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
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	62,991,906	53,253,213
Common stock, shares outstanding	62,991,906	53,253,213

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Licensing revenue – Related Party	$ 4,784	$ 0	$ 0
Operating expenses:
Research and development	38,393	67,309	70,957
General and administrative	23,056	24,025	20,046
Change in fair value of contingent consideration	0	(33)	(1,352)
Impairment of long-lived assets	0	2,629	0
Total operating expenses	61,449	93,930	89,651
Loss from operations	(56,665)	(93,930)	(89,651)
Interest income	100	1,196	3,289
Interest expense	(3,177)	(1,292)	0
Other (expense) income, net	(983)	182	4,185
Net loss	(60,725)	(93,844)	(82,177)
Other comprehensive loss
Unrealized (loss) gain on marketable debt securities	(49)	(85)	185
Comprehensive loss	$ (60,774)	$ (93,929)	$ (81,992)
Net loss per share, basic and diluted	$ (1.09)	$ (1.84)	$ (1.88)
Weighted average number of shares used in computing net loss per share, basic and diluted	55,815,873	50,864,889	43,624,807

Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	At The Market Equity Offering Program	Equity Purchase Agreement Lincoln Park Capital Fund LLC	Loan Agreement Hercules Capital	Common Stock	Common Stock At The Market Equity Offering Program	Common Stock Equity Purchase Agreement Lincoln Park Capital Fund LLC	Common Stock Loan Agreement Hercules Capital	Additional Paid-In 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 Loan Agreement Hercules Capital	Related Party Promissory Notes for Purchase of Common Stock	Employee Promissory Notes for Purchase of Common Stock	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ 160,693				$ 4				$ 324,663				$ (201)	$ (400)	$ (95)	$ (163,278)
Beginning balance, (in shares) at Dec. 31, 2018					42,414,294
Issuance of common stock, net of issuance costs		$ 26,086				$ 1				$ 26,085
Issuance of common stock (in shares)						3,974,908
Issuance of common stock upon exercise of stock options	840								840
Issuance of common stock upon exercise of stock options (in shares)					505,226
Vesting of early exercised stock options	647								647
Stock-based compensation	10,852								10,852
Common stock issued to third parties	2,995								3,022				(9)	(18)
Common stock issued to third parties, (in shares)					253,334
Repurchased shares (in shares)					(4,281)
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)	586								586
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)					83,584
Unrealized gain (loss) on available-for-sale marketable securities	185														185
Net loss	(82,177)															(82,177)
Ending balance at Dec. 31, 2019	120,707				$ 5				366,695				(210)	(418)	90	(245,455)
Ending balance, (in shares) at Dec. 31, 2019					47,227,065
Issuance of common stock, net of issuance costs		37,270								37,270
Issuance of common stock (in shares)						5,002,257
Issuance of common stock upon exercise of stock options	1,510								1,510
Issuance of common stock upon exercise of stock options (in shares)					410,484
Issuance of common stock upon vesting of restricted stock units (in shares)					103,020
Vesting of early exercised stock options	216								216
Stock-based compensation	13,746								13,746
Common stock issued for services	100								100
Common stock issued for services (in shares)					43,550
Common stock issued to third parties for milestone payments	2,310								2,310
Common stock issued to third parties for milestone payments, (in shares)					361,644
Repayment of promissory note from employee from purchase of common stock	374													374
Repayment of promissory note from employee through repurchase of early exercise shares									(44)					$ 44
Repayment of promissory note from employee through repurchase of early exercise shares (in shares)					(12,909)
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)	576								576
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)					118,102
Unrealized gain (loss) on available-for-sale marketable securities	(85)														(85)
Net loss	(93,844)															(93,844)
Ending balance at Dec. 31, 2020	$ 82,880				$ 5				422,379				(210)		5	(339,299)
Ending balance, (in shares) at Dec. 31, 2020	53,253,213				53,253,213
Issuance of common stock, net of issuance costs		$ 10,357	$ 9,040	$ 2,704			$ 1			$ 10,357	$ 9,039	$ 2,704
Issuance of common stock (in shares)			2,900,000			1,894,527	4,172,855	1,727,361
Issuance of common stock upon exercise of stock options	$ 1,795								1,795
Issuance of common stock upon exercise of stock options (in shares)	430,047				497,538
Repurchase of early exercised shares, (in shares)					(33,370)
Vesting of restricted stock units, (in shares)					962,693
Stock-based compensation	$ 11,553								11,553
Common stock issued to third parties	1,457								1,457
Common stock issued to third parties, (in shares)					400,052
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								347
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)					117,037
Unrealized gain (loss) on available-for-sale marketable securities	(49)														(49)
Net loss	(60,725)															(60,725)
Ending balance at Dec. 31, 2021	$ 59,569				$ 6				$ 459,631						$ (44)	$ (400,024)
Ending balance, (in shares) at Dec. 31, 2021	62,991,906				62,991,906

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net loss	$ (60,725)	$ (93,844)	$ (82,177)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,880	3,449	2,663
Amortization of debt issuance costs	813	318	0
Debt extinguishment gain upon conversion to equity	(123)	0	0
Net accretion and amortization of premium and discounts on marketable securities	1,043	256	(1,151)
Other expense related to the commitment shares issued to Lincoln Park Capital Fund	825	0	0
Stock-based compensation	11,553	13,813	10,852
Common stock issued to third parties	1,457	1,211	965
Non-cash rent expense	(2,152)	(1,076)	0
Impairment of long-lived assets	0	2,629	0
Change in fair value of strategic investment	0	(502)	(4,507)
Accretion of tenant improvement allowance	0	0	(1,275)
Change in fair value of contingent consideration	0	(33)	(1,352)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,288	(1,168)	(169)
Other long-term assets	(91)	628	(31)
Accounts payable	(573)	(2,640)	(227)
Accrued compensation	(1,327)	(517)	2,114
Accrued liabilities and other current liabilities	(1,131)	(857)	(587)
Other long-term liabilities	24	0	0
Derivative liability related to debt	963	0	0
Deferred revenue	216	0	0
Deferred rent, net of current portion	0	0	2,461
Net cash used in operating activities	(45,060)	(78,333)	(72,421)
Investing activities
Purchase of marketable securities	(81,492)	(138,486)	(119,270)
Maturities of marketable securities	121,000	127,915	188,809
Sale of strategic investments	0	6,009	0
Purchase of property and equipment	(195)	(646)	(1,586)
Net cash provided by (used in) investing activities	39,313	(5,208)	67,953
Financing activities
Proceeds from repayment of employee promissory notes	210	374	0
Proceeds from long-term debt, net of issuance costs to lender	0	24,550	0
Payment of long-term debt non-lender issuance costs	0	(360)	0
Proceeds from issuance of common stock upon exercise of stock options, net of repurchases	1,784	1,510	840
Proceeds from issuance of common stock under the 2018 ESPP	347	576	586
Current portion of long-term debt arrangement	(68)	0	0
Payments made on capital lease obligations	0	(45)	(73)
Net cash provided by financing activities	20,845	63,875	27,438
Net increase (decrease) in cash, cash equivalents and restricted cash	15,098	(19,666)	22,970
Cash, cash equivalents and restricted cash at beginning of year	19,253	38,919	15,949
Cash, cash equivalents and restricted cash at end of year	34,351	19,253	38,919
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	2,370	773	0
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Issuance of common shares in payment of debt	2,704	0	0
Property and equipment included in accounts payable	0	13	565
Issuance of common stock in settlement of contingent consideration milestone	0	1,098	0
Issuance of shares in settlement of share-based liability	0	100	0
Right-of-use assets obtained in exchange for new operating lease liabilities	0	27,714	0
Lessor funded lease incentives included in property and equipment	0	0	10,651
Receipt of promissory note from related party for purchase of common stock	0	0	27
ATM Offering Program
Financing activities
Proceeds from issuance of common stock, net of issuance costs	10,357	37,270	26,085
Lincoln Park Capital Fund
Financing activities
Proceeds from issuance of common stock, net of issuance costs	$ 8,215	$ 0	$ 0

Organization

12 Months Ended

Dec. 31, 2021

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, raising capital, and recruiting personnel. The Company’s headquarters are located in South San Francisco, California. The Company was incorporated in the State of Delaware in 2009.

Liquidity

In accordance with Accounting Standards Update (“ASU”) No. 2014-15, Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40) (“ASU No. 2014-15”), management must evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management’s plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, management evaluates whether the mitigating effect of its plans sufficiently alleviates substantial doubt about the Company’s ability to continue as a going concern. The mitigating effect of management’s plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued. Generally, to be considered probable of being effectively implemented, the plans must have been approved before the date that the financial statements are issued.

The Company’s Financial Statements have been prepared on a going concern basis, which contemplates the continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary 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 $400.0 million as of December 31, 2021. During the year ended December 31, 2021, the Company incurred a net loss of $60.7 million and used $45.1 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 revenue from contracts with customers 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 Program (as defined in Note 10), the Term Loan Facility (as defined in Note 8) and an Equity Purchase Agreement (as defined in Note 10), 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 had cash, cash equivalents and marketable securities of $90.1 million as of December 31, 2021. As of March 15, 2022, the date of issuance of these Financial Statements, the Company expects that its cash and cash equivalents as of December 31, 2021 will not be sufficient to fund its current business plan including related operating expenses and capital expenditure requirements through at least 12 months from the date of issuance of these Financial Statements. These conditions raise substantial doubt about the Company’s ability to continue as a going concern. The Company plans to seek to address this condition by raising additional capital to finance its operations. 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. Therefore, it is not considered probable, as defined in ASU No. 2014-15, that the Company’s plans to raise additional capital will alleviate the substantial doubt regarding its ability to continue as a going concern.

Management expects operating losses to continue for the foreseeable future. As a result, the Company will need to raise additional capital. If sufficient funds on acceptable terms are not available when needed, the Company could be 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.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. 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.

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, contingent consideration liability, the fair value of right-of-use assets and lease liabilities, embedded derivatives and stock-based compensation. Actual results could differ from such estimates or assumptions.

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.

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,
	2021		2020		2019
Cash and cash equivalents	$	32,905	$	17,807	$	37,473
Restricted cash		1,446		1,446		1,446
Total cash, cash equivalents, and restricted cash	$	34,351	$	19,253	$	38,919

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. 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.

Strategic Investments

The Company has previously made investments in strategic partners and may do so again in the future. The Company does not intend to have a controlling interest or significant influence when it makes these strategic investments. Investments in equity securities of strategic partners with readily determinable fair values are measured using quoted market prices, with changes recorded through other income (expense), net in the statement of operations and comprehensive loss.

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, contingent consideration 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, 2021 and 2020, 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.

In March 2020, the World Health Organization declared the COVID-19 outbreak a pandemic. To date, the Company’s operations have not been materially impacted by the COVID-19 pandemic. However, the Company cannot at this time predict the specific extent, duration, or full impact that the COVID-19 pandemic will have on its financial condition and results of operations, including ongoing and planned clinical studies. The impact of the COVID-19 pandemic on the financial performance of the Company will depend on future developments. These developments and the impact of the COVID-19 pandemic on the financial markets and the overall economy are highly uncertain. The Company continues to monitor the impact the COVID-19 pandemic may have on the clinical

development of its product candidates, including potential delays or modifications to its ongoing and planned studies.

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, 2021 and 2020.

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

Prior to January 1, 2020, the Company accounted for its leases of office space and laboratory facilities under non-cancelable operating lease agreements and recognized related rent expense on a straight-line basis over the term of the lease. Incentives granted under the Company’s facilities lease, including allowances to fund leasehold improvements and rent holidays, were recognized as reductions to rental expense on a straight-line basis over the term of the lease. Lessor funded leasehold improvement incentives not yet received were recorded in prepaid expenses and other current assets on the balance sheets. The Company did not assume renewals in its determination of the lease term unless they were deemed to be reasonably assured at the inception of the lease and began recognizing rent expense on the date that it obtained the legal right to use and control the leased space. Deferred rent consisted of the difference between cash payments and the rent expense recognized. The Company recognized a liability for costs that would continue to be incurred under a lease contract for its remaining term without economic benefit at its fair value when the entity ceased using the right conveyed by the contract, which was when the space was completely vacated.

Subsequent to January 1, 2020, 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 assets, (“ROU assets”), 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 all of its Brisbane, California facility and a portion 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.

The Company does not have any material financing leases.

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. During the year ended December 31, 2020, the Company evaluated indicators of impairment for the ROU asset and related leasehold improvements considering the current economic environment and COVID-19 outbreak, its impact on subleasing activity and the exit of its previous headquarters located in Brisbane, California. The Company concluded the carrying value of these assets were not fully recoverable and recorded an impairment charge of $2.6 million. See Note 7, “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 and timing of sublease income. There are often risks and uncertainties associated with the intent to sublease offices and laboratory space. Consequently, the eventual realized sublease revenues may vary from estimates as of the impairment testing date and adjustments may occur in future

periods. Furthermore, the Company’s sublease assumptions could be further impacted by the uncertainties caused by the COVID-19 outbreak.

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 income (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.

On March 18, 2020, the Families First Coronavirus Response Act (“FFCR Act”), and on March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) were each enacted in response to the COVID-19 pandemic. The FFCR Act and the CARES Act contain numerous tax-related provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property.

On June 29, 2020 California State Assembly Bill 85 (the “Trailer Bill”) was enacted which suspends the use of California net operating loss (“NOL”) deductions and certain tax credits, including research and development tax credits, for the 2020, 2021, and 2022 tax years.

In December 2020, the Consolidated Appropriations Act, 2021 (the “CAA” ) was signed into law. The CAA included additional funding through tax credits as part of its economic package for 2021.

The FFCR Act, CARES Act, Trailer Bill and CAA did not have a material impact on the Company’s financial statements as of December 31, 2020; however, the Company continues to examine the impacts the FFCR Act, CARES Act and Trailer Bill may have on its business, results of operations, financial condition and liquidity.

On March 10, 2021, Congress passed the American Rescue Plan Act (“ARP Act”) of 2021. On March 11, 2021, President Biden signed the bill into law. The ARP contains employment-related provisions. The ARP is a follow-up to the CARES Act, and that part of the CAA Act of 2021 devoted to COVID-19 relief. The ARP includes Paycheck Protection Program (PPP) funding changes and expanded the Employee Retention Credit (ERC) provisions under the CAA. The Company did not apply for a PPP loan. Regarding the ERC, management has calculated that a total ERC of $535,504 for 2020 and $957,839 for 2021 are available. The Company does not expect the ARP to have a material impact on the Company’s financial statements. Any change to the deferred taxes as a result of the enactment of the ARP is expected to be fully offset to the valuation allowance.

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. Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share as the effects of potentially dilutive securities are antidilutive. The calculation of diluted loss per share also requires that, to the extent the presumed issuance of additional shares as contingent consideration is dilutive to loss per share for the period, adjustments to net loss used in the calculation are required to remove the change in fair value of the contingent consideration liability for the period. Likewise, adjustments to the denominator are required to reflect the related dilutive shares. In all periods presented, the Company’s outstanding stock options, convertible preferred stock, early exercised common stock subject to future vesting, restricted stock accounted for as options common and preferred stock 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 Issued Accounting Pronouncements Not Yet Adopted

In October 2020, the FASB issued ASU 2020-10, Codification Improvements. The ASU contains improvements to the Codification by ensuring that all guidance that requires or provides an option for an entity to provide information in the notes to financial statements is codified in the disclosure section of the Codification. The ASU also improves various topics in the Codification so that entities can apply guidance more consistently on codifications that are varied in nature where the original guidance may have been unclear. The amendments in ASU 2020-10 are effective for the Company for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is permitted. The Company does not expect the adoption of ASU 2020-10 to have a material impact on its financial statements and related disclosures.

In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity. ASU 2020-06 eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, ASU 2020-06 modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. The amendments in ASU 2020-06 are effective for smaller reporting companies as defined by the SEC for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020. The Company is currently evaluating the impact of ASU 2020-06 on its financial statements.

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. The Company is currently assessing the effect that this ASU will have on its financial position, results of operations, and disclosures.

Fair Value Measurements

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

3. 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 the related fair values due to the short maturities of these instruments. As the long-term debt is subject to variable interest rates that are based on market rates which are regularly reset, considering level 2 inputs, the Company believes the carrying value of the long-term debt approximates its fair value.

	December 31, 2021
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	21,421	$	21,421	$	—	$	—
Total cash equivalents		21,421		21,421		—		—
Short-term marketable securities:
U.S. treasuries		52,146		—		52,146		—
U.S. government debt securities		3,024		—		3,024		—
Total short-term marketable securities		55,170		—		55,170		—
Long-term marketable securities:
U.S. treasuries		1,993		—		1,993		—
Total long-term marketable securities		1,993		—		1,993		—
Total assets subject to fair value measurements on a recurring basis	$	78,584	$	21,421	$	57,163	$	—

	December 31, 2020
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	13,686	$	13,686	$	—	$	—
Total cash equivalents		13,686		13,686		—		—
Short-term marketable securities:
U.S. treasuries		55,349		—		55,349		—
U.S. and foreign commercial paper		11,999		—		11,999		—
U.S. and foreign corporate debt securities		1,001		—		1,001		—
U.S. government debt securities		11,543		—		11,543		—
Total short-term marketable securities		79,892		—		79,892		—
Long-term marketable securities
U.S. treasuries		7,370		—		7,370		—
U.S. government debt securities		10,501		—		10,501		—
Total long-term marketable securities		17,871		—		17,871		—
Total assets subject to fair value measurements on a recurring basis	$	111,449	$	13,686	$	97,763	$	—

The Company estimates the fair value of its money market funds, U.S. and foreign commercial paper, U.S. and foreign corporate debt securities, 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 4, “Marketable Securities,” for further information regarding the carrying value of the Company's financial instruments.

The Company had previously recorded a contingent consideration liability related to three agreements (the “Commercial Agreements”) with Ascentage Pharma Group Corp. Limited, a clinical-stage biopharmaceutical company based in Hong Kong China (“Ascentage Pharma”). See Note 5, “License Revenue, Agreements and Strategic Investment”. The fair value of the contingent consideration liability at December 31, 2019 included inputs not observable in the market and thus represented a Level 3 measurement. The probability of achieving the defined milestone events under the Commercial Agreements was estimated on a quarterly basis by the Company’s management using a probability-weighted valuation approach model which utilized current stock price and reflected the probability and timing of future issuances of shares. As a result of settlements and changes made to the Commercial Agreements, there was no contingent consideration liability at December 31, 2021 and 2020.

The following table provides a reconciliation of contingent consideration liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands):

	Contingent Consideration Liability Amount
Balance at December 31, 2019		1,131
Additions		—
Settlements		(1,098	)
Change in fair value		(33	)
Balance at December 31, 2020	$	—

In December 2021, the Company recorded a derivative liability relating to an amendment to its loan and security agreement. It comprised of a redemption conversion feature which met the definition of a derivative instrument, which terms are included in the amended loan and security agreement. See Note 8, “Term Loan Facility”. The Company classified this instrument as a liability on the balance sheet because the feature was not clearly and closely related to its host instrument and met the definition of a derivative. The derivative liability was initially recorded at fair value upon issuance of the loan amendment and is being subsequently remeasured to fair value at each reporting date. Changes in the fair value of the derivative liability are recognized as a component of other income (expense), net in the statements of operations. There were no adjustments to the fair value of the derivative as of December 31, 2021.

The following table provides a reconciliation of the derivative liability related to debt measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands):

	Derivative Liability related to Debt Conversion Feature⁽¹⁾
Balance at December 31, 2020	$	—
Additions		1,782
Conversion		(819	)
Change in fair value		—
Balance at December 31, 2021	$	963

⁽¹⁾	Transfers into Level 3 during the year ended December 31, 2021 relate to the call option with Hercules Capital, Inc, where the lender can convert principal debt into common stock. Transfers out of Level 3 during the year relate to the conversions calls of this option made by Hercules Capitals, Inc.

- 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

Marketable Securities

12 Months Ended

Dec. 31, 2021

Investments Debt And Equity Securities [Abstract]

Marketable Securities

4. Marketable Securities

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

	December 31, 2021
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	21,421	$	—	$	—		$	21,421
Total cash equivalents		21,421		—		—			21,421
Short-term marketable securities:
U.S. government debt securities		3,026		—		(2	)		3,024
U.S. treasuries		52,186		—		(40	)		52,146
Total short-term marketable securities		55,212		—		(42	)		55,170
Long-term marketable securities:
U.S. treasuries		1,995		—		(2	)		1,993
Total long-term marketable securities		1,995		—		(2	)		1,993
Total marketable securities	$	78,628	$	—	$	(44	)	$	78,584

	December 31, 2020
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	13,686	$	—	$	—		$	13,686
Total cash equivalents		13,686		—		—			13,686
Short-term marketable securities:
U.S. and foreign commercial paper		11,998		1		—			11,999
U.S. and foreign corporate debt securities		1,001		—		—			1,001
U.S. government debt securities		11,541		2		—			11,543
U.S. treasuries		55,350		2		(3	)		55,349
Total short-term marketable securities		79,890		5		(3	)		79,892
Long-term marketable securities
U.S. treasuries		7,369		1		—			7,370
U.S. government debt securities		10,498		3		—			10,501
Total long-term marketable securities		17,867		4		—			17,871
Total marketable securities	$	111,443	$	9	$	(3	)	$	111,449

At December 31, 2021, the remaining contractual maturities of available-for-sale debt securities were less than two years. There have been no significant realized gains or losses on available-for-sale debt securities for the periods presented. Available-for-sale debt securities that were in a continuous loss position but were not deemed to be other than temporarily impaired were immaterial at both December 31, 2021 and 2020. The Company does not intend to and believes it is not more likely than not that it will be required to sell these debt securities before their maturities.

See Note 3, “Fair Value Measurements,” for further information regarding the fair value of the Company's financial instruments.

License Revenue, Agreements and Strategic Investment

12 Months Ended

Dec. 31, 2021

Research And Development [Abstract]

License Revenue, Agreements and Strategic Investment

5. 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, 2021.

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

	Twelve Months Ended December 31,
	2021		2020		2019
Jocasta Neuroscience, Inc. ⁽¹⁾	$	4,784	$	—	$	—
	$	4,784	$	—	$	—

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

There have been no material changes to the Company’s license agreements in the three and twelve months ended December 31, 2021, except as described below.

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, 2021 and 2020, the Company recognized $4.8 million and zero, respectively, of license revenue, primarily related to the delivery of a performance obligation consisting of a license of intellectual property and related know-how which was delivered in 2021. For the year ended December 31, 2021, the Company recorded the $0.2 million as deferred revenue.

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. In June 2019, as part of this license agreement, the Company issued 120,000 shares of its common stock to UCSF. In addition, 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 34,000 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, 2021. The upfront issuance of 120,000 shares of the Company’s common stock was valued at $1.0 million and recorded as additional paid-in capital upon issuance in June 2019. 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. See above, “License Agreement with Jocasta Neuroscience, Inc.” for additional information on the Jocasta Agreement.

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, 2021 and 2020. To date, none of these events has occurred and no contingent consideration, milestone or royalty payments have been recognized.

License and Compound Library and Option Agreement

The Company is a party to three agreements, two active and one terminated, with Ascentage Pharma: (a) a compound library and option agreement executed in February 2016 granting the Company the right to identify and take licenses to research, develop, and seek and obtain marketing approval for library compounds for the treatment of indications outside of oncology (the “Library Agreement”), (b) an initial license agreement executed in February 2016 granting the Company rights to an initial Ascentage Pharma compound known as APG1252 (the “APG1252 License Agreement”), and (c) a second license agreement executed in January 2019 granting the Company rights to a second licensed compound (this second license agreement, the “Bcl License Agreement” and collectively with the Library Agreement and APG1252 License Agreement, the “Commercial Agreements”). On July 30, 2020, the Company notified Ascentage Pharma of its termination of the APG1252 License Agreement due to the Company’s decision to prioritize the progression of other compounds from Ascentage International’s library of Bcl-2 inhibitors, such as UBX1325, a Bcl-xL inhibitor.

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) 933,337 shares of common stock in the event there is only one licensed product, and (b) 1,333,338 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 Bcl License Agreement also includes tiered royalties in the low-single digits based on sales of licensed products.

As of December 31, 2021, pursuant to these agreements, the Company had issued 1,269,755 shares of common stock to Ascentage Pharma and 291,944 shares of common stock to the academic institution from whom Ascentage Pharma had previously licensed the technology. In May 2021, the Company initiated a Phase 2a proof-of-concept study of UBX1325 in patients with diabetic macular edema. As a result of the first patient dosed in the Phase 2a UBX1325 study in June 2021, the Company triggered a milestone payment of $2.0 million for Ascentage Pharma, which the Company elected to settle in shares of the Company’s common stock. At the instruction of Ascentage Pharma, the Company issued 294,775 shares of its common stock to Ascentage Pharma as of August 2021 with a fair market value of $1.1 million net of withholding taxes, and 105,277 shares of its common stock to the academic institution with a fair market value of $0.4 million at settlement date. The milestone payment was recognized as research and development expense in the statement of operations and comprehensive loss during the year ended December 31, 2021. The Company had previously issued 361,664 shares of its common stock with a value of $2.3 million to Ascentage Pharma as of December 31, 2020.

The Commercial Agreements included contingent consideration in the form of additional issuances of shares of the Company’s common stock based on the achievement of the specified milestones. Upon the July 2020 termination of the license to APG1252, the Company determined that the contingency no longer applied and adjusted the fair value of the contingent consideration liability to zero. To date, no royalties were due from the sales of licensed products.

Strategic Investment

The Company previously held an equity investment in Ascentage International, an affiliate of Ascentage Pharma. The equity interest represented an insignificant level of ownership in the investee and was recorded within strategic investment on the Company’s condensed balance sheets. The fair value of the Company’s equity investment in Ascentage International was zero as of December 31, 2021 and 2020. The change in fair value of this investment was zero and $0.5 million for the years ended December 31, 2021 and 2020, respectively, and was recorded in other expense on the statements of operations and comprehensive loss.

The Company agreed to provide funding to Ascentage Pharma for research and development work performed at a cost of up to $2.0 million through February 2020. During the year ended December 31, 2020, the research and development expense under the research services agreement was not material to the Company’s financial statements.

Balance Sheet Components

12 Months Ended

Dec. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

6. Balance Sheet Components

Property and Equipment, Net

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

	December 31,
	2021			2020
Laboratory equipment	$	5,718		$	5,960
Computer equipment		499			501
Furniture and fixtures		818			825
Leasehold improvements		15,158			15,083
Total property and equipment		22,193			22,369
Less: accumulated depreciation and amortization		(12,258	)		(9,742	)
Construction-in-progress		7			—
Total property and equipment, net	$	9,942		$	12,627

Depreciation and amortization expense related to property and equipment was $2.9 million, $3.4 million and $2.7 million for the years ended December 31, 2021, 2020 and 2019, respectively.

Accrued and Other Current Liabilities

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

	December 31,
	2021		2020
Operating lease liability - current portion	$	4,378	$	4,520
Accrued research and development		1,390		1,638
Liability related to early exercise shares		10		21
Accrued other		592		371
	$	6,370	$	6,550

Commitments and Contingencies

12 Months Ended

Dec. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. 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 13^th 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.

In May 2016, the Company executed a non-cancellable lease agreement for office and laboratory space in Brisbane, California which commenced in May 2016 and continues through October 2022. The lease agreement includes an escalation clause for increased rent and a renewal provision allowing the Company to extend this lease for an additional four years by giving the landlord written notice of the election to exercise the option at least fifteen months prior to the original expiration of the lease term. The lease provides for monthly base rent amounts escalating over the term of the lease and the lessor provided the Company a $3.9 million tenant improvement allowance to complete the laboratory and office renovation which was recorded as deferred rent liability and

leasehold improvements within property and equipment, net. In May 2017, the Company entered into an amendment to expand the leased space and received a three-month rent holiday for the expanded space.

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,
	2021			2020
Operating lease expense	$	4,357		$	4,721
Variable lease expense		1,633			1,168
Sublease income		(2,578	)		—
Impairment of operating lease right-of-use asset		—			1,409
Total lease expense	$	3,412		$	7,298

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. Rent expense for the year ended December 31, 2019 was $4.5 million.

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

	Year Ended December 31,
	2021			2020
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$	6,653		$	5,797
Weighted-average remaining lease term (years)
Operating leases		7.7			8.5
Weighted-average discount rate (percentage)
Operating leases		5.9	%		5.8	%

The following table summarizes the maturities of lease liabilities as of December 31, 2021 (in thousands):

	Amount
2022	$	6,286
2023		4,810
2024		4,964
2025		5,123
2026		5,287
Thereafter		16,892
Total future minimum lease payments		43,362
Less: Amount representing interest		(8,890	)
Present value of future minimum lease payments		34,472
Less: Current portion of operating lease liability		(4,378	)
Noncurrent portion of operating lease liability	$	30,094

In February 2020, the Company completed its move into the new office and laboratory space in South San Francisco, exited its previous offices and laboratory space in Brisbane, California, and began to actively market this space for sublease. Concurrent with this move and in consideration of real estate market conditions, in particular due to the COVID-19 pandemic in March 2020, the Company identified indicators of impairment in the related asset group, which included the leased ROU asset and related leasehold improvements associated with the lease. The Company subsequently evaluated and compared the net book value of the asset group to the estimated undiscounted future cash flows over the remaining term of the lease and concluded that an impairment had occurred. The discounted estimated future cash flows included estimates of sublease rentals through the end of the lease term, which ends on October 31, 2022, utilizing a discount rate of 3.5% based on the Company’s estimated incremental borrowing rate at that time. The estimated discounted cash flows were compared to the net book value of the ROU asset and leasehold improvements resulting in an impairment loss of $2.6 million during the year ended December 31, 2020, which was included in operating expense in the statements of operations and comprehensive loss. No impairment loss was recorded during the year ended December 31, 2021.

In February 2021, the Company entered into an agreement to sublease the first floor of the Brisbane, California facility, 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 was $1.5 million and zero for the years ended December 31, 2021 and 2020, 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 August 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 facility. No impairment loss was recorded during the year ended December 31, 2021. Sublease income was $1.1 million and zero for the years ended December 31, 2021 and 2020, respectively, which was offset against total rent expense.

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.

Term Loan Facility

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Term Loan Facility

8. Term Loan Facility

On August 3, 2020, the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with Hercules Capital, Inc. (“Hercules”). Under the Loan Agreement, Hercules provided the Company with access to a term loan with an aggregate principal amount of up to $80.0 million (the “Term Loan Facility”), available in four tranches, 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 milestones for the remaining tranches have not yet been reached and as of December 31, 2021 are not expected to be reached as they were dependent, in whole or in part, upon continued advancement in the clinical development of UBX0101 in patients with osteoarthritis of the knee.

On December 15, 2021, the Company entered into an amendment to the Loan and Security Agreement (“the Loan Amendment”). The Loan Amendment includes a Lender Optional Conversion where after the effective date and until the six-month anniversary of the execution date, the lender may elect to convert to equity of the Company all or any part of up to twenty percent (20%) of the original principal amount for a maximum amount of $5.0 million. As of December 31, 2021, the lender had elected to convert $2.3 million of the outstanding principal into equity. The Company incurred approximately $0.1 million in loan issuance costs relating to the amendment, which were offset against the loan proceeds and are accounted for as a loan discount.

The Company expects to make interest only payments through September 1, 2022 and expects to then repay the principal balance and interest in equal monthly installments through August 1, 2024. Pursuant to the Loan Amendment, the interest only period may extend up to a maximum of 9 months to June 1, 2023 should the company meet specific milestones related to its clinical trials and raising additional capital.

The Company may prepay advances under the Loan Agreement, in whole or in part, at any time subject to a prepayment charge of up to 1.50% of any amount prepaid, depending upon when the prepayment occurs. Upon prepayment or repayment of all or any of the term loans under the Term Loan Facility, the Company is required to pay an end of term fee (“End of Term Fee”) equal to 6.25% of the total aggregate amount of the term loans being prepaid or repaid, which has been recorded as a discount on the principal balance upon issuance.

Interest on the term loan accrues at a per annum rate equal to the greater of (i) the Wall Street Journal prime rate plus 6.10% and (ii) 9.35%. On December 31, 2021, the rate was 9.35%. Interest expense is calculated using the effective interest method and is inclusive of non-cash amortization of capitalized loan issuance costs. At December 31, 2021, the effective interest rate was 16.69%.

Under the terms of the Loan Agreement, the Company granted first priority liens and security interests in substantially all of the Company’s assets, other than intellectual property, as collateral for the obligations thereunder. The Company also granted Hercules the right, at their discretion, to participate in any closing of any single subsequent financing as defined up to a maximum aggregate amount of $2.0 million. The Loan Agreement also contains representations and warranties by the Company and Hercules, indemnification provisions in favor of Hercules and customary affirmative and negative covenants (including a liquidity covenant beginning July 1, 2021, requiring the Company to maintain at least $15.0 million in unrestricted cash), and events of default, including a material adverse change in the Company’s business, payment defaults, breaches of covenants following any applicable cure period, and a material impairment in the perfection or priority of Hercules’ security interest in the collateral. The substantial doubt regarding the Company’s ability to continue as a going concern does not constitute a material adverse event under the terms of the Loan Agreement. In the event of default by the Company under the Loan Agreement, the Company may be required to repay all amounts then outstanding under the Loan Agreement.

We have determined that the risk of subjective acceleration under the material adverse events clause included in the Loan Agreement is remote and, therefore, have classified the outstanding principal amount in current and long-term liabilities based on the timing of scheduled principal payments. As of December 31, 2021, and as of the date of the issuance of these financial statements, the Company was in compliance with all covenants and has not been notified of an event of default by the lender under the Loan Agreement.

As of December 31, 2021, the carrying value of the term loan consists of $22.7 million principal outstanding less the debt discount and issuance costs of approximately $2.8 million. The end of term fee of $1.6 million is recognized over the life of the term loan as interest expense using the effective interest method. The debt issuance costs have been recorded as a debt discount which are being accreted to interest expense through the maturity date of the term loan.

Interest expense relating to the term loan, which is included in interest expense in the statements of operations and comprehensive loss, was $3.2 million and $1.3 million for the years ended December 31, 2021 and 2020, respectively.

Future principal payments for the long-term debt are as follows (in thousands):

	December 31, 2021
2022	$	3,485
2023		11,144
2024		8,073
Total principal payments		22,702
End of term fee due at maturity in 2024		1,562
Total principal and end of term fee payments		24,264
Unamortized discount and debt issuance costs		(2,800	)
Present value of remaining debt payments		21,464
Current portion of long-term debt		(3,055	)
Long-term debt, net	$	18,409

- 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

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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 12: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Related Party Transactions

12 Months Ended

Dec. 31, 2021

Related-Party Transactions

9. 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 $4.8 million of licensing revenue for the year ended December 31, 2021.

Recourse Notes

In January 2018, the Company issued full-recourse promissory notes to a non-executive officer employee of the Company for an aggregate principal amount of $0.2 million with an interest rate of 2.5% per annum. All of the principal was used to early exercise options for 59,322 shares of the Company’s common stock. In December 2019, the full recourse note was deemed satisfied and superseded by a new full recourse promissory note agreement with a principal amount of $0.2 million and an interest rate of 1.51% per annum. In January 2021, the non-executive officer employee terminated his employment with the Company. As at March 31, 2021 the Company reclassified the $0.2 million recorded on the balance sheet in stockholders’ equity as ‘Related party promissory note for purchase of common stock’ to ‘Promissory notes for purchase of common stock’. The balance was repaid in full by June 30, 2021.

Equity Financing

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Equity Financing

10. 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 December 31, 2021 and 2020, 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, 2021 and 2020, there were 62,991906 and 53,253,213 shares of common stock issued and outstanding.

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 5,002,257 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 a second sales agreement (the “July 2020 Sales Agreement”) 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 1,187,068 shares of the Company’s common stock sold through the Initial ATM Offering Program and 707,459 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.

Equity Purchase Agreement

On September 29, 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 1,020,408 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 252,447 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. As of December 31, 2021, the Company had initiated the purchase of an additional 2.9 million shares of the Company’s common stock amounting to $5.3 million in gross proceeds.

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 100,000 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: to up to 150,000 shares if the closing price is not below $3.50, up to 200,000 shares if the closing price is not below $5.00, and up to 250,000 shares if the closing price is not below $7.00. 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 11,065,803 shares of the Common Shares (which is equal to approximately 19.99% of the shares of the Common Shares 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 Shares to Lincoln Park under the Purchase Agreement equals or exceeds $2.94 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 Shares.

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.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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 7: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Corporate Restructuring

12 Months Ended

Dec. 31, 2021

Restructuring And Related Activities [Abstract]

Corporate Restructuring

11. Corporate Restructuring

In September 2020, the Company’s board of directors implemented a corporate restructuring to align its resources on cellular senescence programs in ophthalmology and neurology while further extending operating capital. The restructuring resulted in an elimination of approximately 33 positions, or approximately 32% of the Company’s workforce, as of September 30, 2020. The Company incurred a one-time employee benefits and severance charge of approximately $1.8 million in operating expenses during the year ended December 31, 2020. The related accrual is recorded in accrued compensation on the balance sheet at December 31, 2020. Restructuring charges incurred under this plan primarily consisted of employee termination benefits. Employee termination benefits include severance costs, employee-related benefits, 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 are included in operating expenses in the statements of operations and comprehensive loss. Of the total charge, $1.5 million was recorded to research and development expenses and $0.3 million was recorded to general and administrative expenses during the year ended December 31, 2020. Substantially all cash payments were paid out in the first quarter of 2021. The Company may also incur additional costs not currently contemplated due to events that may occur as a result of, or that are associated with, the 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 is expected to result in an elimination of approximately 32 positions and the Company will incur a one-time employee benefits and severance charge of approximately $1.8 million in operating expenses in the first half of 2022.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

12. 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 4,289,936 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, 2021, there were in aggregate 13,271,831 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 1,100,000 shares for the issuance of

stock options, and in November 2020, the Company reserved an additional 1,500,000 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, 2021, there were in aggregate 2,530,000 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, Restricted Stock Units (RSUs) and Performance Stock Units (“PSUs”) 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, 2021 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, 2020		4,270,764			7,475,472		$	6.88
Shares added		2,942,007			—			—
Granted		(3,629,461	)		3,062,738			4.92
Exercised		—			(430,047	)		3.64
Canceled		1,730,141			(1,441,208	)		8.70
Balance at December 31, 2021		5,313,451			8,666,955		$	6.05		7.7	$	—
Vested and exercisable at December 31, 2021					4,204,083		$	6.55		6.4	$	—
Vested and expected to vest at December 31, 2021					8,666,955		$	6.05		7.7	$	—

The total intrinsic value of options exercised was $1.1 million and $1.5 million for the years ended December 31, 2021 and 2020, respectively. The weighted-average estimated fair value of stock options granted was $4.88 and $4.83 for the years ended December 31, 2021 and 2020, respectively.

The aggregate intrinsic value of options exercisable was zero and $4.1 million as of December 31, 2021 and 2020, respectively.

In September 2020, the board of directors granted retention stock-based awards to employees covering an aggregate of 3.2 million shares of common stock, including options to purchase an aggregate of 250,000 shares of common stock and 2,959,850 of restricted stock units. The awards are all time-based vesting and vest over three to four years.

During the year ended December 31, 2020 the Company issued 13,550 shares in settlement of stock-based compensation awards accounted for as liability awards. During the year ended December 31, 2021, 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, RSA and PSU activity for the year ended December 31, 2021:

	Shares			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2020		2,922,077		$	3.44
Granted		566,723		$	4.88
Released		(962,693	)	$	3.36
Canceled		(535,170	)	$	3.33
Unvested at December 31, 2021		1,990,937		$	3.92

As of December 31, 2021, the total stock-based compensation cost related to options, RSAs, RSUs and PSUs granted but not yet amortized was $23.1 million and will be recognized over a weighted-average period of approximately 3.2 years. The total grant date fair value of RSUs and RSAs vested during the years ended December 31, 2021 and 2020 was approximately $3.1 million and $1.2 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 1.1 million shares of common stock, including options to purchase an aggregate of 800,000 shares of common stock, 120,000 RSUs, 150,000 PSUs and 30,000 shares of common stock. The stock-based awards were granted pursuant to the 2020 Plan.

The 30,000 shares of common stock were fully vested on the date of grant and thus, the related compensation expense of $0.2 million was recognized on the grant date. The stock options and RSUs will vest subject to continued service through the applicable vesting date.

Valuation 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,
	2021		2020		2019
Expected term of options (in years)	6.0		6.1		6.1
Expected stock price volatility	85.7%-88.5%		92.6%-107.9%		99.4%-111.3%
Risk-free interest rate	1.08%-1.35%		0.29%-0.52%		1.59%-2.27%
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).

Expected Volatility—The Company used an average historical 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 public companies within the biotechnology and pharmaceutical industry that were deemed to be representative of future stock price trends as the Company does not have a sufficient historical trading history of its own common stock. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available.

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 50,000 PSUs upon the attainment of (a) a volume-weighted average per share closing trading price of the Company’s common stock of at least $36.875 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 $36.875 and as to 100,000 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 50,000 PSUs upon the attainment of (a) a volume-weighted average per share closing trading price of the Company’s common stock of at least $18 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 $18.00 and as to 100,000 PSUs upon the attainment of (x) a volume-weighted average per share closing trading price of the Company’s common stock of at least $36.00 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 $36.00, 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

As of December 31, 2020, there were 87,521 performance and market contingent stock option awards outstanding with a grant date total fair value of $0.3 million. As of December 31, 2020 the Company determined that the achievement of the requisite performance conditions was not probable and, as a result, no compensation cost was recognized for these awards.

In January 2021, the board of directors modified 17,479 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 $18.00 over a trailing 30-day period for one tranche and at least $36.00 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 33,370 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, 2021, there were 50,849 market contingent stock option awards outstanding with a modification date total fair value of $0.2 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 536,242 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

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 2018 ESPP included in the Company’s statement of operations (in thousands):

	Year Ended December 31,
	2021		2020		2019
Research and development	$	4,809	$	6,563	$	4,979
General and administrative		6,744		7,250		5,873
Total	$	11,553	$	13,813	$	10,852

Stock-based compensation for the year ended December 31, 2020 includes $0.1 million of expense related to awards accounted for as liability awards. There was no expense related to awards accounted for as liability awards included in stock-based compensation for the year ended December 31, 2021.

During the years ended December 31, 2021 and 2020, stock-based compensation expense recognized related to nonemployee options was $0.4 million and $0.3 million, respectively.

Net Loss per Common Share

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Net Loss per Common Share

13. 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 that, to the extent contingencies are satisfied during the period and the presumed issuance of additional shares as contingent consideration is dilutive to earnings (loss) per share for the period, adjustments to net income or net loss used in the calculation are required to remove the change in fair value of the contingent consideration liability for the period. Likewise, adjustments to the denominator are required to reflect the related dilutive shares. In all periods presented, the Company’s outstanding stock options, RSAs, RSUs (including PSUs), early exercised common stock subject to future vesting, restricted stock accounted for as options, shares subject to the 2018 ESPP 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.

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):

	December 31,
	2021			2020			2019
	(in thousands, except share and per share amounts)
Numerator:
Net loss	$	(60,725	)	$	(93,844	)	$	(82,177	)
Denominator:
Weighted average number of shares outstanding—basic and diluted		55,815,873			50,864,889			43,624,807
Net loss per share—basic and diluted	$	(1.09	)	$	(1.84	)	$	(1.88	)

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:

	Year Ended December 31,
	2021		2020		2019
Options to purchase common stock		8,666,955		7,540,472		6,906,898
Early exercised common stock subject to future vesting		33,370		66,741		146,915
RSUs		1,990,937		2,832,077		325,887
PSUs		—		150,000		—
Shares subject to the 2018 ESPP		147,741		111,383		47,597
Total		10,839,003		10,700,673		7,427,297

Up to 55,900 shares may be contingently issued, if certain performance conditions are met under the Company’s in-licensing agreements. See Note 5, “License Revenue, Agreements and Strategic Investment,” to the Company’s financial statements for additional information.

Defined Contribution Plan

12 Months Ended

Dec. 31, 2021

Compensation And Retirement Disclosure [Abstract]

Defined Contribution Plan

14. 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, 2021 and 2020, the Company recorded matching contributions of $0.5 million and $0.6 million, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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-Name Accounting Standards Codification
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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

15. 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, 2021, 2020 and 2019 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,
	2021				2020				2019
Taxes at the U.S. statutory income tax rate		21.0		%		21.0		%		21.0		%
State tax, net of federal benefit		0.9				—				(2.2	)
Other		(0.4	)			1.8				(0.9	)
Stock-based compensation		(1.6	)			(1.6	)			(0.5	)
Research and development tax credits		3.2				2.2				(0.2	)
Rate change		7.3				0.1				(3.9	)
ASC 740-10		(4.2	)			—				—
Change in valuation allowance		(26.2	)			(23.5	)			(13.3	)
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,
	2021			2020
	(in thousands)
Deferred tax assets:
Federal and state operating loss carryforwards	$	68,216		$	57,126
Research and development tax credits		7,356			5,411
Stock-based compensation		5,232			4,326
Accruals and other		837			1,145
Intangibles		3,581			1,181
Charitable contributions		266			254
Operating lease liabilities		7,608			8,203
Total deferred tax assets		93,096			77,646
Deferred tax liabilities:
Operating lease right-of-use assets		(4,698	)		(4,946	)
Fixed assets		(1,500	)		(1,750	)
Unrealized gain on equity investment		—			—
Total deferred tax liabilities		(6,198	)		(6,696	)
Valuation allowance		(86,898	)		(70,950	)
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 $15.9 million and $22.1 million during the years ended December 31, 2021 and 2020, respectively.

Net operating losses and tax credit carryforwards as of December 31, 2021 are as follows:

	Amount (in thousands)		Expiration Years
Net operating losses, federal (post December 31, 2017)	$	260,405	Do Not Expire
Net operating losses, federal (pre January 1, 2018)		64,136	2029-2037
Net operating losses, state		93,166	2029-2036
Research and development tax credits, federal		7,173	2034-2041
Research and development tax credits, California		6,040	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. Should there be additional ownership changes in the future, the Company's ability to utilize existing carryforwards could be substantially restricted.

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:

	December 31,
	2021		2020			2019
	(in thousands)
Gross unrecognized tax benefits at January 1	$	7,142	$	9,762		$	3,714
Additions for tax positions taken in the current year		3,457		255			6,221
Reductions for tax positions taken in the prior year		2,622		(2,875	)		(173	)
Gross unrecognized tax benefits at December 31	$	13,221	$	7,142		$	9,762

If recognized, none of the unrecognized tax benefits as of December 31, 2021 and 2020 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, 2021 and 2020, 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 California, Colorado, Delaware, Florida and Massachusetts. 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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-Section 50
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Subsequent Events

12 Months Ended

Dec. 31, 2021

Subsequent Events [Abstract]

Subsequent Events

16. Subsequent Events

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 is expected to result in an elimination of approximately 32 positions, or approximately 50% of the Company’s workforce, by the first half of 2022. The Company will incur a one-time employee benefits and severance charge of approximately $1.8 million in operating expenses in the first half of 2022.

During the first quarter of 2022, Hercules Capital, Inc. gave notice to convert the remaining convertible debt option into equity of the Company’s common stock. This resulted in the conversion of $2.7 million of principal debt into common stock, and reducing the outstanding principal under the first tranche to $20.0 million.

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 1,893,335 stock options and 463,328 restricted stock units with a grant date total fair value of $2.0 million and $0.5 million, respectively.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Segments

Cash, Cash Equivalents, and Restricted Cash

	December 31,
	2021		2020		2019
Cash and cash equivalents	$	32,905	$	17,807	$	37,473
Restricted cash		1,446		1,446		1,446
Total cash, cash equivalents, and restricted cash	$	34,351	$	19,253	$	38,919

Marketable Securities

Strategic Investments

Fair Value Measurements

Revenue Recognition

contracts generally includes a nonrefundable upfront payment, development, regulatory and commercial milestones and royalties based on net sales of approved products.

Concentrations of Risk

development of its product candidates, including potential delays or modifications to its ongoing and planned studies.

Research and Development Expenses and Accruals

Contingent Consideration Liability

Property and Equipment, Net

Leases

The Company does not have any material financing leases.

Impairment of Long-Lived Assets

periods. Furthermore, the Company’s sublease assumptions could be further impacted by the uncertainties caused by the COVID-19 outbreak.

Stock-Based Compensation

Embedded Derivatives of the Loan Agreement

Restructurings

Restructuring

Income Taxes

In December 2020, the Consolidated Appropriations Act, 2021 (the “CAA” ) was signed into law. The CAA included additional funding through tax credits as part of its economic package for 2021.

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 Not Yet Adopted

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash

	December 31,
	2021		2020		2019
Cash and cash equivalents	$	32,905	$	17,807	$	37,473
Restricted cash		1,446		1,446		1,446
Total cash, cash equivalents, and restricted cash	$	34,351	$	19,253	$	38,919

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

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

	December 31, 2021
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	21,421	$	21,421	$	—	$	—
Total cash equivalents		21,421		21,421		—		—
Short-term marketable securities:
U.S. treasuries		52,146		—		52,146		—
U.S. government debt securities		3,024		—		3,024		—
Total short-term marketable securities		55,170		—		55,170		—
Long-term marketable securities:
U.S. treasuries		1,993		—		1,993		—
Total long-term marketable securities		1,993		—		1,993		—
Total assets subject to fair value measurements on a recurring basis	$	78,584	$	21,421	$	57,163	$	—

	December 31, 2020
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	13,686	$	13,686	$	—	$	—
Total cash equivalents		13,686		13,686		—		—
Short-term marketable securities:
U.S. treasuries		55,349		—		55,349		—
U.S. and foreign commercial paper		11,999		—		11,999		—
U.S. and foreign corporate debt securities		1,001		—		1,001		—
U.S. government debt securities		11,543		—		11,543		—
Total short-term marketable securities		79,892		—		79,892		—
Long-term marketable securities
U.S. treasuries		7,370		—		7,370		—
U.S. government debt securities		10,501		—		10,501		—
Total long-term marketable securities		17,871		—		17,871		—
Total assets subject to fair value measurements on a recurring basis	$	111,449	$	13,686	$	97,763	$	—

Summary of Reconciliation of Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs

The following table provides a reconciliation of contingent consideration liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands):

	Contingent Consideration Liability Amount
Balance at December 31, 2019		1,131
Additions		—
Settlements		(1,098	)
Change in fair value		(33	)
Balance at December 31, 2020	$	—

The following table provides a reconciliation of the derivative liability related to debt measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands):

	Derivative Liability related to Debt Conversion Feature⁽¹⁾
Balance at December 31, 2020	$	—
Additions		1,782
Conversion		(819	)
Change in fair value		—
Balance at December 31, 2021	$	963

Transfers into Level 3 during the year ended December 31, 2021 relate to the call option with Hercules Capital, Inc, where the lender can convert principal debt into common stock. Transfers out of Level 3 during the year relate to the conversions calls of this option made by Hercules Capitals, Inc.

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2021

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, 2021
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	21,421	$	—	$	—		$	21,421
Total cash equivalents		21,421		—		—			21,421
Short-term marketable securities:
U.S. government debt securities		3,026		—		(2	)		3,024
U.S. treasuries		52,186		—		(40	)		52,146
Total short-term marketable securities		55,212		—		(42	)		55,170
Long-term marketable securities:
U.S. treasuries		1,995		—		(2	)		1,993
Total long-term marketable securities		1,995		—		(2	)		1,993
Total marketable securities	$	78,628	$	—	$	(44	)	$	78,584

	December 31, 2020
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	13,686	$	—	$	—		$	13,686
Total cash equivalents		13,686		—		—			13,686
Short-term marketable securities:
U.S. and foreign commercial paper		11,998		1		—			11,999
U.S. and foreign corporate debt securities		1,001		—		—			1,001
U.S. government debt securities		11,541		2		—			11,543
U.S. treasuries		55,350		2		(3	)		55,349
Total short-term marketable securities		79,890		5		(3	)		79,892
Long-term marketable securities
U.S. treasuries		7,369		1		—			7,370
U.S. government debt securities		10,498		3		—			10,501
Total long-term marketable securities		17,867		4		—			17,871
Total marketable securities	$	111,443	$	9	$	(3	)	$	111,449

License Revenue, Agreements and Strategic Investment (Tables)

12 Months Ended

Dec. 31, 2021

Research And Development [Abstract]

Schedule of Recognized Revenue of License Agreement

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

	Twelve Months Ended December 31,
	2021		2020		2019
Jocasta Neuroscience, Inc. ⁽¹⁾	$	4,784	$	—	$	—
	$	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 (Tables)

12 Months Ended

Dec. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Schedule of Property and Equipment, Net

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

	December 31,
	2021			2020
Laboratory equipment	$	5,718		$	5,960
Computer equipment		499			501
Furniture and fixtures		818			825
Leasehold improvements		15,158			15,083
Total property and equipment		22,193			22,369
Less: accumulated depreciation and amortization		(12,258	)		(9,742	)
Construction-in-progress		7			—
Total property and equipment, net	$	9,942		$	12,627

Schedule of Accrued and Other Current Liabilities

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

	December 31,
	2021		2020
Operating lease liability - current portion	$	4,378	$	4,520
Accrued research and development		1,390		1,638
Liability related to early exercise shares		10		21
Accrued other		592		371
	$	6,370	$	6,550

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2021

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,
	2021			2020
Operating lease expense	$	4,357		$	4,721
Variable lease expense		1,633			1,168
Sublease income		(2,578	)		—
Impairment of operating lease right-of-use asset		—			1,409
Total lease expense	$	3,412		$	7,298

Summary of Supplemental Information Related to Leases

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

	Year Ended December 31,
	2021			2020
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$	6,653		$	5,797
Weighted-average remaining lease term (years)
Operating leases		7.7			8.5
Weighted-average discount rate (percentage)
Operating leases		5.9	%		5.8	%

Summary of Maturities of Lease Liabilities

The following table summarizes the maturities of lease liabilities as of December 31, 2021 (in thousands):

	Amount
2022	$	6,286
2023		4,810
2024		4,964
2025		5,123
2026		5,287
Thereafter		16,892
Total future minimum lease payments		43,362
Less: Amount representing interest		(8,890	)
Present value of future minimum lease payments		34,472
Less: Current portion of operating lease liability		(4,378	)
Noncurrent portion of operating lease liability	$	30,094

Term Loan Facility (Tables)

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Schedule of Future Principal Payments for Long-Term Debt

Future principal payments for the long-term debt are as follows (in thousands):

	December 31, 2021
2022	$	3,485
2023		11,144
2024		8,073
Total principal payments		22,702
End of term fee due at maturity in 2024		1,562
Total principal and end of term fee payments		24,264
Unamortized discount and debt issuance costs		(2,800	)
Present value of remaining debt payments		21,464
Current portion of long-term debt		(3,055	)
Long-term debt, net	$	18,409

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option 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, 2021 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, 2020		4,270,764			7,475,472		$	6.88
Shares added		2,942,007			—			—
Granted		(3,629,461	)		3,062,738			4.92
Exercised		—			(430,047	)		3.64
Canceled		1,730,141			(1,441,208	)		8.70
Balance at December 31, 2021		5,313,451			8,666,955		$	6.05		7.7	$	—
Vested and exercisable at December 31, 2021					4,204,083		$	6.55		6.4	$	—
Vested and expected to vest at December 31, 2021					8,666,955		$	6.05		7.7	$	—

Summary of Restricted Stock Units, Performance Stock Units and Restricted Stock Awards Activity

The following table summarizes the Company’s RSU, RSA and PSU activity for the year ended December 31, 2021:

	Shares			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2020		2,922,077		$	3.44
Granted		566,723		$	4.88
Released		(962,693	)	$	3.36
Canceled		(535,170	)	$	3.33
Unvested at December 31, 2021		1,990,937		$	3.92

Summary of Valuation Assumption to Estimate Fair Value of Stock Options

	Year Ended December 31,
	2021		2020		2019
Expected term of options (in years)	6.0		6.1		6.1
Expected stock price volatility	85.7%-88.5%		92.6%-107.9%		99.4%-111.3%
Risk-free interest rate	1.08%-1.35%		0.29%-0.52%		1.59%-2.27%
Expected dividend yield		—		—		—

Summary of Stock-based Compensation Expense

	Year Ended December 31,
	2021		2020		2019
Research and development	$	4,809	$	6,563	$	4,979
General and administrative		6,744		7,250		5,873
Total	$	11,553	$	13,813	$	10,852

Net Loss per Common Share (Tables)

12 Months Ended

Dec. 31, 2021

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):

	December 31,
	2021			2020			2019
	(in thousands, except share and per share amounts)
Numerator:
Net loss	$	(60,725	)	$	(93,844	)	$	(82,177	)
Denominator:
Weighted average number of shares outstanding—basic and diluted		55,815,873			50,864,889			43,624,807
Net loss per share—basic and diluted	$	(1.09	)	$	(1.84	)	$	(1.88	)

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,
	2021		2020		2019
Options to purchase common stock		8,666,955		7,540,472		6,906,898
Early exercised common stock subject to future vesting		33,370		66,741		146,915
RSUs		1,990,937		2,832,077		325,887
PSUs		—		150,000		—
Shares subject to the 2018 ESPP		147,741		111,383		47,597
Total		10,839,003		10,700,673		7,427,297

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

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,
	2021				2020				2019
Taxes at the U.S. statutory income tax rate		21.0		%		21.0		%		21.0		%
State tax, net of federal benefit		0.9				—				(2.2	)
Other		(0.4	)			1.8				(0.9	)
Stock-based compensation		(1.6	)			(1.6	)			(0.5	)
Research and development tax credits		3.2				2.2				(0.2	)
Rate change		7.3				0.1				(3.9	)
ASC 740-10		(4.2	)			—				—
Change in valuation allowance		(26.2	)			(23.5	)			(13.3	)
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,
	2021			2020
	(in thousands)
Deferred tax assets:
Federal and state operating loss carryforwards	$	68,216		$	57,126
Research and development tax credits		7,356			5,411
Stock-based compensation		5,232			4,326
Accruals and other		837			1,145
Intangibles		3,581			1,181
Charitable contributions		266			254
Operating lease liabilities		7,608			8,203
Total deferred tax assets		93,096			77,646
Deferred tax liabilities:
Operating lease right-of-use assets		(4,698	)		(4,946	)
Fixed assets		(1,500	)		(1,750	)
Unrealized gain on equity investment		—			—
Total deferred tax liabilities		(6,198	)		(6,696	)
Valuation allowance		(86,898	)		(70,950	)
Net deferred tax assets	$	—		$	—

Summary of Net Operating Losses and Tax Credit Carryforwards

Net operating losses and tax credit carryforwards as of December 31, 2021 are as follows:

	Amount (in thousands)		Expiration Years
Net operating losses, federal (post December 31, 2017)	$	260,405	Do Not Expire
Net operating losses, federal (pre January 1, 2018)		64,136	2029-2037
Net operating losses, state		93,166	2029-2036
Research and development tax credits, federal		7,173	2034-2041
Research and development tax credits, California		6,040	Indefinite

Schedule of Reconciliation of Unrecognized Tax Benefits

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

	December 31,
	2021		2020			2019
	(in thousands)
Gross unrecognized tax benefits at January 1	$	7,142	$	9,762		$	3,714
Additions for tax positions taken in the current year		3,457		255			6,221
Reductions for tax positions taken in the prior year		2,622		(2,875	)		(173	)
Gross unrecognized tax benefits at December 31	$	13,221	$	7,142		$	9,762

Organization - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ 400,024	$ 339,299
Net loss	60,725	93,844	$ 82,177
Cash used in operations	45,060	$ 78,333	$ 72,421
Cash, cash equivalents and marketable securities	$ 90,100

- Definition

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

+ References

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+ Details

- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

+ References + Details

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) Segment	Dec. 31, 2020 USD ($)
Accounting Policies [Abstract]
Number of operating segment \| Segment	1
Off-balance sheet concentrations of credit risk description	As of December 31, 2021 and 2020, the Company had no off-balance sheet concentrations of credit risk.
Off-balance sheet concentrations of credit risk	$ 0
Impairment charge	2,600,000
Employee Retention Credit available amount	$ 957,839	$ 535,504

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 32,905	$ 17,807	$ 37,473
Restricted cash	1,446	1,446	1,446
Total cash, cash equivalents, and restricted cash	$ 34,351	$ 19,253	$ 38,919	$ 15,949

Fair Value Measurements - Summary of Financial Assets Subject to Fair Value Measurements on Recurring Basis and Level of Inputs Used in Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets:
Short-term marketable securities	$ 55,170	$ 79,892
Long-term marketable securities	1,993	17,871
Fair Value, Recurring
Assets:
Cash equivalents	21,421	13,686
Short-term marketable securities	55,170	79,892
Long-term marketable securities	1,993	17,871
Total assets subject to fair value measurements on a recurring basis	78,584	111,449
Fair Value, Recurring \| Level 1
Assets:
Cash equivalents	21,421	13,686
Total assets subject to fair value measurements on a recurring basis	21,421	13,686
Fair Value, Recurring \| Level 2
Assets:
Short-term marketable securities	55,170	79,892
Long-term marketable securities	1,993	17,871
Total assets subject to fair value measurements on a recurring basis	57,163	97,763
Money market funds \| Fair Value, Recurring
Assets:
Cash equivalents	21,421	13,686
Money market funds \| Fair Value, Recurring \| Level 1
Assets:
Cash equivalents	21,421	13,686
U.S. Treasuries \| Fair Value, Recurring
Assets:
Short-term marketable securities	52,146	55,349
Long-term marketable securities	1,993	7,370
U.S. Treasuries \| Fair Value, Recurring \| Level 2
Assets:
Short-term marketable securities	52,146	55,349
Long-term marketable securities	1,993	7,370
U.S. government debt securities \| Fair Value, Recurring
Assets:
Short-term marketable securities	3,024	11,543
Long-term marketable securities		10,501
U.S. government debt securities \| Fair Value, Recurring \| Level 2
Assets:
Short-term marketable securities	$ 3,024	11,543
Long-term marketable securities		10,501
U.S. and foreign commercial paper \| Fair Value, Recurring
Assets:
Short-term marketable securities		11,999
U.S. and foreign commercial paper \| Fair Value, Recurring \| Level 2
Assets:
Short-term marketable securities		11,999
U.S. and foreign corporate debt securities \| Fair Value, Recurring
Assets:
Short-term marketable securities		1,001
U.S. and foreign corporate debt securities \| Fair Value, Recurring \| Level 2
Assets:
Short-term marketable securities		$ 1,001

Fair Value Measurements - Summary of Reconciliation of Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - Fair Value, Recurring - Level 3 - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2021

Dec. 31, 2020

Contingent Consideration Liability Amount

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]

Beginning balance

$ 0

$ 1,131

Settlements

(1,098)

Change in fair value

(33)

Ending balance

Derivative Liability Related To Debt Conversion Feature

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]

Beginning balance

^[1]

Additions

^[1]

1,782

Conversion

^[1]

(819)

Ending balance

^[1]

$ 963

$ 0

[1]	Transfers into Level 3 during the year ended December 31, 2021 relate to the call option with Hercules Capital, Inc, where the lender can convert principal debt into common stock. Transfers out of Level 3 during the year relate to the conversions calls of this option made by Hercules Capitals, Inc.

Fair Value Measurements - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 USD ($)
Fair Value Disclosures [Abstract]
Adjustments to fair value of derivative	$ 0

Marketable Securities - Summary of Marketable Securities Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	$ 78,628	$ 111,443
Unrealized Gains	0	9
Unrealized Losses	(44)	(3)
Fair Value	78,584	111,449
Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	21,421	13,686
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	21,421	13,686
Cash Equivalents \| Money market funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	21,421	13,686
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	21,421	13,686
Short Term Marketable Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	55,212	79,890
Unrealized Gains	0	5
Unrealized Losses	(42)	(3)
Fair Value	55,170	79,892
Short Term Marketable Securities \| U.S. government debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	3,026	11,541
Unrealized Gains	0	2
Unrealized Losses	(2)	0
Fair Value	3,024	11,543
Short Term Marketable Securities \| U S Treasuries
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	52,186	55,350
Unrealized Gains	0	2
Unrealized Losses	(40)	(3)
Fair Value	52,146	55,349
Short Term Marketable Securities \| U.S. and foreign corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis		1,001
Unrealized Gains		0
Unrealized Losses		0
Fair Value		1,001
Short Term Marketable Securities \| U.S. and foreign commercial paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis		11,998
Unrealized Gains		1
Unrealized Losses		0
Fair Value		11,999
Long Term Marketable Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	1,995	17,867
Unrealized Gains	0	4
Unrealized Losses	(2)	0
Fair Value	1,993	17,871
Long Term Marketable Securities \| U.S. government debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis		10,498
Unrealized Gains		3
Unrealized Losses		0
Fair Value		10,501
Long Term Marketable Securities \| U S Treasuries
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	1,995	7,369
Unrealized Gains	0	1
Unrealized Losses	(2)	0
Fair Value	$ 1,993	$ 7,370

Marketable Securities - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 USD ($)
Marketable Securities [Line Items]
Realized gains or losses on available-for-sale debt securities	$ 0
Maximum
Marketable Securities [Line Items]
Available-for sale securities, remaining contractual maturity	2 years

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

12 Months Ended

Dec. 31, 2021

USD ($)

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized

$ 4,784

Jocasta Neuroscience, Inc.

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized

$ 4,784

^[1]

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

License Revenue, Agreements and Strategic Investment - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Aug. 31, 2021
Research And Development Arrangement Contract To Perform For Others [Line Items]
Compound library and option agreement execution month and year			2016-02
Common stock, shares issued			62,991,906	53,253,213
Common stock, value			$ 6,000	$ 5,000
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			5,000,000.0
Revenue recognized			4,800,000	0
Deferred revenue			200,000
Other Licensing Agreements with Research Institutions
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common shares expected to be issued		34,000
Contingent consideration, milestone or royalty payments			$ 0	$ 0
Maximum milestone payments for each product licensed under agreement		$ 13,600,000
Other Licensing Agreements with Research Institutions \| Common Stock
Research And Development Arrangement Contract To Perform For Others [Line Items]
Issuance of common stock		120,000
Other Licensing Agreements with Research Institutions \| Additional Paid-In Capital
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock issued to third parties		$ 1,000,000.0
Commercial Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone payments	$ 2,000,000.0
Equity payments percentage			20.00%
Common stock, shares issued			291,944	361,664	105,277
Common stock fair market value, net of withholding taxes					$ 1,100,000
Common stock fair market value					$ 400,000
Common stock, value				$ 2,300,000
Contingent consideration liability			$ 0
Strategic investments			0	0
Change in fair value of investment			$ 0	$ 500,000
Funding provided for the research and development under the agreement in period			2020-02
Commercial Agreement \| Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contingent consideration additional common stock issued for one licensed product			933,337
Contingent consideration additional common stock issued for two or more licensed product			1,333,338
Milestone payments			$ 70,300,000
Funding provided for the research and development under the agreement			$ 2,000,000.0
Commercial Agreement \| Initial License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
License agreement execution month and year			2016-02
Commercial Agreement \| Second License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
License agreement execution month and year			2019-01

Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 22,193	$ 22,369
Less: accumulated depreciation and amortization	(12,258)	(9,742)
Construction-in-progress	7
Total property and equipment, net	9,942	12,627
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	5,718	5,960
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	499	501
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	818	825
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 15,158	$ 15,083

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 2.9	$ 3.4	$ 2.7

Balance Sheet Components - Schedule of Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Operating lease liability - current portion	$ 4,378	$ 4,520
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Accrued research and development	$ 1,390	$ 1,638
Liability related to early exercise shares	10	21
Accrued other	592	371
Accrued and other current liabilities	$ 6,370	$ 6,550

Commitments and Contingencies - Additional Information (Details)	1 Months Ended			12 Months Ended
	Jun. 30, 2021 ft² $ / ft²	May 31, 2021 USD ($) ft² $ / ft²	Feb. 28, 2021 ft² $ / ft²	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Commitments And Contingencies [Line Items]
Rent expense						$ 4,500,000
Sublease income				$ 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
Estimated discount rate				3.50%
Impairment loss				$ 0	$ 2,600,000
Space subleased (in square feet) \| ft²	23,000
Sublease expiration date	Aug. 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%
Sublease income				$ 1,100,000	0
Brisbane, California
Commitments And Contingencies [Line Items]
Operating lease, renewal term				4 years
Tenant improvement allowance				$ 3,900,000
Lease commencement date				2016-05
Operating lease, option to extend description				The lease agreement includes an escalation clause for increased rent and a renewal provision allowing the Company to extend this lease for an additional four years by giving the landlord written notice of the election to exercise the option at least fifteen months prior to the original expiration of the lease term.
Operating lease, expiration date				2022-10
Operating leases rent holiday period for expanded space				3 months
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		1.00	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				$ 1,500,000	$ 0
Brisbane, California \| Minimum
Commitments And Contingencies [Line Items]
Operating lease option exercise notice period				15 months

Commitments and Contingencies -Summary of Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Lease, Expense [Abstract]
Operating lease expense	$ 4,357	$ 4,721
Variable lease expense	1,633	1,168
Sublease income	(2,578)
Impairment of operating lease right-of-use asset		1,409
Total lease expense	$ 3,412	$ 7,298

Commitments and Contingencies - Summary of Supplemental Information Related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Operating cash flows from operating leases	$ 6,653	$ 5,797
Operating leases, Weighted-average remaining lease term (years)	7 years 8 months 12 days	8 years 6 months
Operating leases, Weighted-average discount rate (percentage)	5.90%	5.80%

Commitments and Contingencies - Summary of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
2022	$ 6,286
2023	4,810
2024	4,964
2025	5,123
2026	5,287
Thereafter	16,892
Total future minimum lease payments	43,362
Less: Amount representing interest	(8,890)
Present value of future minimum lease payments	34,472
Less: Current portion of operating lease liability	(4,378)	$ (4,520)
Noncurrent portion of operating lease liability	$ 30,094	$ 34,468

Term Loan Facility - Additional Information (Details) $ in Thousands			12 Months Ended
	Dec. 15, 2021 USD ($)	Aug. 03, 2020 USD ($) Tranche	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 01, 2021 USD ($)
Debt Instrument [Line Items]
Debt instrument aggregate principal amount			$ 22,702
Total principal payments			22,702
Unamortized discount and debt issuance costs			2,800
End of term fee due at maturity			1,562
Interest expense			3,177	$ 1,292	$ 0
Term Loan \| Loan Agreement
Debt Instrument [Line Items]
Debt conversion, original debt amount			2,300
Loan issuance cost			100
Term Loan \| Loan Agreement \| Maximum
Debt Instrument [Line Items]
Loan amendment conversion effective month of anniversary	6 months
Debt conversion, original debt amount	$ 5,000
Debt conversion percentage of principal amount	20.00%
Term Loan \| Loan Agreement \| Hercules Capital
Debt Instrument [Line Items]
Debt instrument aggregate principal amount			$ 22,700
Number of tranches \| Tranche		4
Principal amount of first tranche		$ 25,000
Long-term debt, maturity date			Aug. 01, 2024
Final payment fee of the total term loan advanced			6.25%
Debt instrument, interest rate terms			Interest on the term loan accrues at a per annum rate equal to the greater of (i) the Wall Street Journal prime rate plus 6.10% and (ii) 9.35%. On December 31, 2021, the rate was 9.35%. Interest expense is calculated using the effective interest method and is inclusive of non-cash amortization of capitalized loan issuance costs. At December 31, 2021, the effective interest rate was 16.69%.
Debt instrument, interest rate, stated percentage			9.35%
Debt instrument, interest rate, effective percentage			16.69%
Maximum amount of debt that can be purchased by lender.			$ 2,000
Debt instrument, minimum unrestricted cash						$ 15,000
Total principal payments			22,700
Unamortized discount and debt issuance costs			2,800
End of term fee due at maturity			1,600
Term Loan \| Loan Agreement \| Hercules Capital \| Interest And Other Expense
Debt Instrument [Line Items]
Interest expense			$ 3,200	$ 1,300
Term Loan \| Loan Agreement \| Hercules Capital \| Wall Street Journal Prime Rate
Debt Instrument [Line Items]
Debt instrument, interest rate, basis spread on variable rate			6.10%
Term Loan \| Loan Agreement \| Hercules Capital \| Maximum
Debt Instrument [Line Items]
Debt instrument aggregate principal amount		80,000
Prepayment fee			1.50%
Total principal payments		$ 80,000

Term Loan Facility - Schedule of Future Principal Payments for Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
2022	$ 3,485
2023	11,144
2024	8,073
Total principal payments	22,702
End of term fee due at maturity in 2024	1,562
Total principal and end of term fee payments	24,264
Unamortized discount and debt issuance costs	(2,800)
Present value of remaining debt payments	21,464
Current portion of long-term debt	(3,055)	$ 0
Long-term debt, net	$ 18,409	$ 24,508

Related-Party Transactions - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Dec. 31, 2019	Jan. 31, 2018	Dec. 31, 2021	Mar. 31, 2021
Non-executive Officer \| Promissory Note
Related Party Transaction [Line Items]
Due from related parties	$ 0.2	$ 0.2
Promissory notes for purchase of common stock				$ 0.2
Interest rate	1.51%	2.50%
Non-executive Officer \| Promissory Note \| Common Stock
Related Party Transaction [Line Items]
Early exercise options in aggregate		59,322
License Agreement \| Jocasta Neuroscience, Inc.
Related Party Transaction [Line Items]
Upfront cash payments received			$ 5.0
Revenue recognized			$ 4.8

Equity Financing - Additional Information (Details) - USD ($)		1 Months Ended		12 Months Ended
	Sep. 29, 2021	Jul. 31, 2020	Jun. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Subsidiary Sale Of Stock [Line Items]
Number of stock, authorized for issuance				10,000,000	10,000,000
Number of stock, par value per share				$ 0.0001	$ 0.0001
Number of stock, shares issued				0	0
Number of stock, shares outstanding				0	0
Common stock, shares authorized				300,000,000	300,000,000
Common stock, par value per share				$ 0.0001	$ 0.0001
Common stock, shares issued				62,991,906	53,253,213
Common stock, shares outstanding				62,991,906	53,253,213
Equity financing, authorized amount			$ 250,000,000.0
Other expense related to the commitment shares issued to Lincoln Park Capital Fund				$ 825,000	$ 0	$ 0
Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock, shares outstanding				62,991,906	53,253,213	47,227,065	42,414,294
At The Market Equity Offering Program
Subsidiary Sale Of Stock [Line Items]
Proceeds from sale of common stock				$ 10,357,000	$ 37,270,000	$ 26,085,000
Issuance of common stock, value				10,357,000	$ 37,270,000	$ 26,086,000
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
At The Market Equity Offering Program \| Cowen \| Sales Agreement
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares)					5,002,257
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			$ 75,000,000.0
Percentage of gross sales proceeds of common stock payable as compensation			3.00%
At The Market Equity Offering Program \| Cowen \| July 2020 Sales Agreement
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares)				707,459
At The Market Equity Offering Program \| Cowen \| July 2020 Sales Agreement \| Maximum
Subsidiary Sale Of Stock [Line Items]
Equity financing, authorized amount		$ 50,000,000.0
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)				1,187,068
At The Market Equity Offering Program \| Common Stock
Subsidiary Sale Of Stock [Line Items]
Equity financing, authorized amount		$ 50,000,000.0	$ 75,000,000.0
Issuance of common stock (in shares)				1,894,527	5,002,257	3,974,908
Issuance of common stock, value						$ 1,000
Equity Purchase Agreement \| Lincoln Park Capital Fund LLC
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares)	1,020,408			2,900,000
Issuance of common stock, value				$ 9,040,000
Purchase agreement term	36 months
Share purchase price	$ 2.94
Total gross purchase price of share	$ 3,000,000.0
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	$ 2.94
Maximum percentage ownership of issued and outstanding shares	9.99%
Equity Purchase Agreement \| Lincoln Park Capital Fund LLC \| Tranche One
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount closing price per share	$ 3.50
Equity Purchase Agreement \| Lincoln Park Capital Fund LLC \| Tranche Two
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount closing price per share	5.00
Equity Purchase Agreement \| Lincoln Park Capital Fund LLC \| Tranche Three
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount closing price per share	$ 7.00
Equity Purchase Agreement \| Lincoln Park Capital Fund LLC \| Maximum
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares)	11,065,803
Issuance of common stock, value	$ 30,000,000
Equity Purchase Agreement \| Lincoln Park Capital Fund LLC \| Maximum \| Tranche One
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount shares	150,000
Equity Purchase Agreement \| Lincoln Park Capital Fund LLC \| Maximum \| Tranche Two
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount shares	200,000
Equity Purchase Agreement \| Lincoln Park Capital Fund LLC \| Maximum \| Tranche Three
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount shares	250,000
Equity Purchase Agreement \| Common Stock \| Lincoln Park Capital Fund LLC
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares)				4,172,855
Proceeds from sale of common stock				$ 5,300,000
Issuance of common stock, value				$ 1,000
Issuance of common stock as commitment fee	252,447
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 \| Maximum
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares)	100,000

Corporate Restructuring - Additional Information (Details) $ in Millions	1 Months Ended		6 Months Ended	12 Months Ended
	Feb. 28, 2022 Position	Sep. 30, 2020 Position	Jun. 30, 2022 USD ($)	Dec. 31, 2021	Dec. 31, 2020 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring implementation month and year				2020-09
Number of positions eliminated \| Position		33
Percentage of positions eliminated		32.00%
Severance charge in operating expenses					$ 1.8
Scenario Forecast
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses			$ 1.8
Subsequent Event
Restructuring Cost And Reserve [Line Items]
Restructuring implementation month and year	2022-02
Number of positions eliminated \| Position	32
Percentage of positions eliminated	50.00%
Research and Development Expense
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses					1.5
General and Administrative Expense
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses					$ 0.3

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended						6 Months Ended	12 Months Ended
	Jun. 30, 2021	Jan. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Mar. 31, 2018	Jun. 30, 2013	Feb. 28, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Nov. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares authorized								300,000,000	300,000,000
Intrinsic value of options exercised								$ 1,100,000	$ 1,500,000
Weighted-average estimated fair value of stock options granted								$ 4.88	$ 4.83
Exercisable, aggregate intrinsic value								$ 0	$ 4,100,000
Number of shares authorized for issuance			3,200,000
Settlement of stock based compensation for liability awards								0	13,550
Compensation cost recognized				$ 200,000
Stock option awards outstanding								8,666,955	7,475,472
Stock based compensation expense for liability awards								$ 0	$ 100,000
Stock-based compensation expense								11,553,000	13,813,000	$ 10,852,000
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance					536,242
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	300,000
Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting of restricted stock units, (in shares)								962,693
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]
Compensation cost recognized									$ 0
Trailing period	30 days
Stock option awards outstanding								50,849	87,521
Stock option awards, grant date fair value								$ 200,000	$ 300,000
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	33,370	17,479
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		$ 18.00
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		$ 36.00
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			250,000
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance			2,959,850
Stock Options, RSAs, RSUs and PSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation cost not yet amortized								$ 23,100,000
Weighted-average period for recognition								3 years 2 months 12 days
RSUs and RSAs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total grant-date fair value of stock vested								$ 3,100,000	$ 1,200,000
Stock Options and RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights				The stock options and RSUs will vest subject to continued service through the applicable vesting date
2018 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance					4,289,936
Vesting period, options					4 years
Common stock, shares authorized								13,271,831
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				1,100,000							1,500,000
Vesting period, options				4 years
Common stock, shares authorized								2,530,000
Number of shares authorized for issuance				1,100,000
Incremental fair value on modification date				$ 31,000				$ 31,000
Unamortized value of original grant				$ 569,000				$ 569,000
2020 Employment Inducement Incentive Plan \| Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance				30,000
Vesting of restricted stock units, (in shares)				30,000
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]
Number of shares authorized for issuance				150,000
Weighted-average period for recognition				4 years 3 months 18 days
Grant date fair value				$ 700,000
2020 Employment Inducement Incentive Plan \| PSUs \| Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance		50,000		50,000
Volume-weighted average per Share closing trading price		$ 18		$ 36.875
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 authorized for issuance		100,000		100,000
Trailing period		30 days		30 days
Price per share to holders of company's common stock		$ 36.00		$ 36.875
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
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance				800,000
2020 Employment Inducement Incentive Plan \| RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance				120,000
2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period, options						4 years
Exercise price							$ 3.42
Exercise price range, lower range limit							3.95
Exercise price range, upper range limit							$ 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%

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Shares Available for Grant
Shares Available for Grant, Beginning Balance	4,270,764
Shares Available for Grant, Shares Added	2,942,007
Shares Available for Grant, Granted	(3,629,461)
Shares Available for Grant, Canceled	1,730,141
Shares Available for Grant, Ending Balance	5,313,451	4,270,764
Outstanding Options
Outstanding options, Beginning Balance	7,475,472
Outstanding options, Granted	3,062,738
Outstanding options, Exercised	(430,047)
Outstanding options, Canceled	(1,441,208)
Outstanding options, Ending Balance	8,666,955	7,475,472
Outstanding options, Vested and exercisable at December 31, 2021	4,204,083
Outstanding options. Vested and expected to vest at December 31, 2021	8,666,955
Weighted-Average Exercise Price
Weighted-Average Exercise Price, Beginning Balance	$ 6.88
Weighted-Average Exercise Price, Options granted	4.92
Weighted-Average Exercise Price, Options exercised	3.64
Weighted-Average Exercise Price, Options canceled	8.70
Weighted-Average Exercise Price, Ending Balance	6.05	$ 6.88
Weighted-Average Exercise Price, Vested exercisable as of December 31, 2021	6.55
Weighted-Average Exercise Price, Options vested and expected to vest as of December 31, 2021	$ 6.05
Weighted-Average Remaining Contract Term
Balance at December 31, 2021	7 years 8 months 12 days
Exercisable, weighted average remaining contractual term (Year)	6 years 4 months 24 days
Options vested or expected to vest at end of period, weighted average remaining contractual term (Year)	7 years 8 months 12 days
Aggregate Intrinsic Value
Exercisable, aggregate intrinsic value	$ 0	$ 4,100,000

Stock-Based Compensation - Summary of Restricted Stock Units, Performance Stock Units and Restricted Stock Awards Activity (Details) - RSU, RSA and PSU	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Unvested at December 31, 2020 \| shares	2,922,077
Shares, Granted \| shares	566,723
Shares, Released \| shares	(962,693)
Shares, Canceled \| shares	(535,170)
Shares, Unvested at December 31, 2021 \| shares	1,990,937
Weighted Average Grant Date Fair Value, Unvested at December 31, 2020 \| $ / shares	$ 3.44
Weighted Average Grant Date Fair Value, Granted \| $ / shares	4.88
Weighted Average Grant Date Fair Value, Released \| $ / shares	3.36
Weighted Average Grant Date Fair Value, Canceled \| $ / shares	3.33
Weighted Average Grant Date Fair Value, Unvested at December 31, 2021 \| $ / shares	$ 3.92

Stock-Based Compensation - Summary of Valuation Assumption to Estimate Fair Value of Stock Options (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term of options (in years)	6 years	6 years 1 month 6 days	6 years 1 month 6 days
Expected stock price volatility, Minimum	85.70%	92.60%	99.40%
Expected stock price volatility, Maximum	88.50%	107.90%	111.30%
Risk-free interest rate, Minimum	1.08%	0.29%	1.59%
Risk-free interest rate, Maximum	1.35%	0.52%	2.27%
Expected dividend yield	0.00%	0.00%	0.00%

Stock-Based Compensation - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 11,553	$ 13,813	$ 10,852
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	4,809	6,563	4,979
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 6,744	$ 7,250	$ 5,873

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	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss	$ (60,725)	$ (93,844)	$ (82,177)
Denominator:
Weighted average number of shares outstanding—basic and diluted	55,815,873	50,864,889	43,624,807
Net loss per share—basic and diluted	$ (1.09)	$ (1.84)	$ (1.88)

- Definition

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

+ References

+ Details

Net Loss per Common Share - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	10,839,003	10,700,673	7,427,297
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	8,666,955	7,540,472	6,906,898
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	33,370	66,741	146,915
RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	1,990,937	2,832,077	325,887
PSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	0	150,000	0
Shares Subject 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	147,741	111,383	47,597

Net Loss per Common Share - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 shares
Maximum
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares contingently issued	55,900

Defined Contribution Plan - Additional Information (Details) - 401(k) Plan - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2021	Dec. 31, 2020
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		$ 0.5	$ 0.6

Income Taxes - Schedule of Effective Tax Rate of Provision for Income Taxes Differs From Federal Statutory Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
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	0.90%	0.00%	(2.20%)
Other	(0.40%)	1.80%	(0.90%)
Stock-based compensation	(1.60%)	(1.60%)	(0.50%)
Research and development tax credits	3.20%	2.20%	(0.20%)
Rate change	7.30%	0.10%	(3.90%)
ASC 740-10	(4.20%)	0.00%	0.00%
Change in valuation allowance	(26.20%)	(23.50%)	(13.30%)
Total provision for income taxes	0.00%	0.00%	0.00%

Income Taxes - Schedule of Components of Deferred Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Federal and state operating loss carryforwards	$ 68,216	$ 57,126
Research and development tax credits	7,356	5,411
Stock-based compensation	5,232	4,326
Accruals and other	837	1,145
Intangibles	3,581	1,181
Charitable contributions	266	254
Operating lease liabilities	7,608	8,203
Total deferred tax assets	93,096	77,646
Deferred tax liabilities:
Operating lease right-of-use assets	(4,698)	(4,946)
Fixed assets	(1,500)	(1,750)
Unrealized gain on equity investment	0	0
Total deferred tax liabilities	(6,198)	(6,696)
Valuation allowance	(86,898)	(70,950)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Increase in the valuation allowance	$ 15,900,000	$ 22,100,000
Unrecognized tax benefits that would impact effective tax rate	0	0
Liability recorded for potential interest or penalties	$ 0	$ 0

Income Taxes - Summary of Net Operating Losses and Tax Credit Carryforwards (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
Federal \| Post December 31, 2017
Income Taxes [Line Items]
Net operating losses	$ 260,405
Operating losses carryforwards expiration years	Do Not Expire
Federal \| Pre January 1, 2018
Income Taxes [Line Items]
Net operating losses	$ 64,136
Operating losses carryforwards expiration years	2029-2037
Federal \| Research and Development Tax Credits
Income Taxes [Line Items]
Research and development tax credits	$ 7,173
Research and development tax credits carryforwards expiration years	2034-2041
State
Income Taxes [Line Items]
Net operating losses	$ 93,166
Operating losses carryforwards expiration years	2029-2036
California \| Research and Development Tax Credits
Income Taxes [Line Items]
Research and development tax credits	$ 6,040
Research and development tax credits carryforwards expiration years	Indefinite

Income Taxes - Schedule of Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits at January 1	$ 7,142	$ 9,762	$ 3,714
Additions for tax positions taken in the current year	3,457	255	6,221
Reductions for tax positions taken in the prior year	2,622
Reductions for tax positions taken in the prior year		(2,875)	(173)
Gross unrecognized tax benefits at December 31	$ 13,221	$ 7,142	$ 9,762

Subsequent Events - Additional Information (Details) $ in Millions	1 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended
	Feb. 28, 2022 USD ($) Position shares	Sep. 30, 2020 Position	Mar. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares	Aug. 03, 2020 USD ($)
Subsequent Event [Line Items]
Restructuring implementation month and year					2020-09
Number of positions eliminated \| Position		33
Percentage of positions eliminated		32.00%
Severance charge in operating expenses						$ 1.8
Number of awards available for grant \| shares					5,313,451	4,270,764
Term Loan \| Loan Agreement
Subsequent Event [Line Items]
Debt conversion, original debt amount					$ 2.3
Term Loan \| Loan Agreement \| Hercules Capital
Subsequent Event [Line Items]
Principal amount of first tranche							$ 25.0
Scenario Forecast
Subsequent Event [Line Items]
Severance charge in operating expenses				$ 1.8
Scenario Forecast \| Term Loan \| Loan Agreement \| Hercules Capital
Subsequent Event [Line Items]
Debt conversion, original debt amount			$ 2.7
Principal amount of first tranche			$ 20.0
Subsequent Event
Subsequent Event [Line Items]
Restructuring implementation month and year	2022-02
Number of positions eliminated \| Position	32
Percentage of positions eliminated	50.00%
Subsequent Event \| Stock Options
Subsequent Event [Line Items]
Number of awards available for grant \| shares	1,893,335
Grant date total fair value	$ 2.0
Subsequent Event \| RSUs
Subsequent Event [Line Items]
Number of awards available for grant \| shares	463,328
Grant date total fair value	$ 0.5