0000950170-24-043399 | 10-K | XBRL Viewer

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Summary of Significant Accounting Policies - Summary of Property and Equipment Useful Lives (Details)	12 Months Ended
	Dec. 31, 2023
Leasehold Improvements [Member]
Property, Plant and Equipment, Estimated Useful Lives	Shorter of useful life of asset or lease term
Lab Equipment [Member]
Property, Plant and Equipment, Estimated Useful Lives	3 years
Furniture and Office Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment, Estimated Useful Lives	3 years
Furniture and Office Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment, Estimated Useful Lives	8 years
Computer equipment and software
Property, Plant and Equipment, Estimated Useful Lives	3 years

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

The Company’s consolidated financial statements and accompanying notes have been prepared in accordance with generally accepted accounting principles in the United States of America, or U.S. GAAP, as determined by the Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, and pursuant to the regulations of the U.S. Securities and Exchange Commission, or SEC. The consolidated financial statements include the accounts of the Company and its subsidiary. All intercompany transactions and balances have been eliminated.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions made in the accompanying consolidated financial statements include, impairment of long-lived assets, revenue recognition and certain accrued expenses for research and development activities. Management bases its estimates on historical

experience and on various other market-specific and relevant assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results could materially differ from those estimates.

Concentration of Credit Risk

Financial instruments, which potentially subject the Company to significant concentration of credit risk, consist of cash, cash equivalents and marketable securities. The Company’s cash is held by financial institutions that may at times exceed federally insured limits. However, the Company’s exposure to credit risk in the event of default by the financial institution is limited to the extent of amounts recorded on the consolidated balance sheets. The Company believes it is not exposed to significant credit risk on cash. The Company's cash equivalents and marketable securities were held in custodial accounts maintained by third party custodians. The Company's policy is to invest cash in institutional money market funds and marketable securities with high credit quality to limit the amount of credit exposure. The Company maintained a portfolio of cash equivalents and marketable securities in a variety of securities. The Company has not experienced any losses on its cash equivalents and marketable securities.

Cash and Cash Equivalents

Cash equivalents relate to securities having an original maturity of three months or less at the time of purchase. As of December 31, 2023 and 2022, cash and cash equivalents consisted of bank deposits, money market funds and U.S. government agency debt securities.

Restricted Cash

As of December 31, 2023, the Company had $0.7 million of restricted cash consisting of a letter of credit for the Company’s facility lease and the collateral associated with the Company’s credit card program. As of December 31, 2022, the Company had $0.4 million of restricted cash in the form of a letter of credit for the Company’s facility lease.

Marketable Securities

The Company invested its excess cash in marketable U.S. government bonds, commercial paper and corporate debt securities. All marketable securities were classified as available-for-sale and carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. The Company does not buy or hold securities principally for the purpose of selling them in the near future. The Company’s policy is focused on the preservation of capital, liquidity, and return. From time to time, the Company may sell certain securities, but the objectives are generally not to generate profits on short-term differences in price.

Short-term marketable securities have maturities less than or equal to one year as of the balance sheet date. These marketable securities were carried at estimated fair value with unrealized holding gains or losses included in accumulated other comprehensive loss in stockholders’ equity until realized. Gains and losses on marketable security transactions are reported on the specific-identification method. Interest income is recognized in the consolidated statements of operations and comprehensive loss when earned.

The Company periodically evaluates its available-for-sale marketable securities for credit losses. When the fair value of a marketable security is below its amortized cost basis, the amortized cost is reduced to its fair value if it is more likely than not that the Company is required to sell the security before recovery of its amortized cost, or the Company has the intention to sell the security. If neither of these conditions are met, the Company determines whether the decline in fair value is due to credit losses by comparing the present value of the expected cash flows of the security with its amortized cost basis. The amount of credit losses recognized is limited to the excess of the amortized cost basis over the fair value of the security. An allowance for credit losses for the excess of amortized cost basis over the expected cash flows, if any, is recorded in other income, net on the condensed consolidated statements of operations. Any losses from declines in fair value that are not credit-related are included in accumulated other comprehensive loss in stockholders’ equity.

Property and Equipment

Property and equipment, including leasehold improvements, are recorded at cost net of accumulated depreciation and amortization. Major replacements and improvements that extend the useful lives of assets are capitalized, while general repairs and maintenance are charged to expense as incurred. Property and equipment are depreciated and amortized using the straight-line method over the estimated useful lives of the assets as follows:


Asset		Estimated useful life
Leasehold improvements		Shorter of useful life of asset or lease term
Lab equipment		3 years
Furniture and office equipment		3-8 years
Computer equipment and software		3 years

When assets are retired or otherwise disposed of, the cost and related accumulated depreciation and amortization are removed from the consolidated balance sheet and the resulting gain or loss is recognized in the period realized.

Leases

Material leases with a term longer than one year are recognized as right-of-use, or ROU, assets and lease liabilities in the Company's consolidated balance sheets. The Company determines the lease classification and measurement of its ROU assets and lease liabilities at the lease commencement date and thereafter if modified. The Company uses its incremental borrowing rate, based on the information available at the commencement date, to determine the present value of lease payments if the rate implicit in the lease is not readily available. The ROU asset is based on the measurement of the lease liability and is adjusted for lease incentives provided by the landlord. Lease expense for the Company’s operating leases is recognized on a straight-line basis over the lease term. The lease term includes any renewal options and termination options that the Company is reasonably assured to exercise.

Impairment of Long-Lived Assets

The Company reviews long-lived assets, including property and equipment and operating lease right-of-use assets, for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be fully recoverable. Recoverability is measured by comparing the carrying amount to the future net undiscounted cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds their fair value.

Warrant Liabilities

The Company's warrants are classified as liabilities. At the end of each reporting period, any changes in fair value during the period are recognized in other income, net within the consolidated statements of operations and comprehensive loss. The Company will continue to adjust the warrant liabilities pertaining to the outstanding warrants for changes in the fair value until the earlier of a) the exercise or expiration of the warrants or b) the redemption of the warrants, at which time such warrants will be reclassified to additional paid-in capital.

Revenue Recognition

The Company recognizes revenue in accordance with ASC 606, Revenue from Contracts with Customers (Topic 606), when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the Company expects to receive in exchange for these goods or services. To determine revenue recognition for the arrangement that is within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract with the customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when or as the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services transferred to the customer.

At contract inception, the Company assesses the goods or services promised within the contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes revenue for the amount of the transaction price that is allocated to the respective performance obligations when or as the performance obligations are satisfied. The Company constrains its estimate of the transaction price up to the amount (the variable consideration constraint) that a significant reversal of recognized revenue is not probable.

The Company records accounts receivable for amounts billed to the customer for which the Company has an unconditional right to consideration. The Company assesses accounts receivable for credit losses and, to date, no credit losses have been recorded.

The Company has a Collaboration and License Agreement, or CLA, with Boehringer Ingelheim International GmbH, or BI, to which the Company licensed certain rights to its intellectual property that is determined within the scope of ASC 606. The terms of the CLA include payments to the Company of a non-refundable upfront payment, development, regulatory and commercial milestone payments and royalties on net sales of licensed products.

Licenses of Intellectual Property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable upfront fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promised goods or services, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable upfront fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Milestone Payments: At contract inception, the Company uses the most likely amount method evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price. If it is probable that a significant reversal of cumulative revenue would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received or the underlying activity has been completed. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenue in the period of adjustment.

Royalties: The Company recognizes sales-based royalties as revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalties that have been allocated have been satisfied (or partially satisfied).

The incremental costs of obtaining a customer contract are expensed as and when incurred if the amortization period of the asset that would have been recognized is one year or less.

Research and Development Expenses

Research and development costs are expensed as incurred. Research and development costs consist of external and internal expenses directly attributable to the conduct of research and development programs. The external expenses include the costs of services provided by outside contractors, clinical research organizations and contract manufacturing organizations. The internal expenses include the costs of salaries, bonus, payroll taxes, stock-based compensation, employee benefits, materials, supplies, depreciation on and maintenance of research equipment, and the allocated facility-related costs, such as rent, utilities, insurance, repairs and maintenance, and general support services.

The Company has entered into and may continue to enter into licensing or subscription arrangements to access and utilize certain technology. In each case, the Company evaluates if the license agreement results in the acquisition of an asset or a business. To date, none of the Company’s license agreements have been considered an acquisition of a business. For asset acquisitions, the upfront payments to acquire such licenses, as well as any future milestone payments made before product approval that do not meet the definition of a derivative, are immediately recognized as research and development expense when they are paid or become payable, provided there is no alternative future use of the rights in other research and development projects.

Accrued Research and Development Expenses

The Company records accruals for estimated costs of research, preclinical, clinical, and manufacturing development, which are significant components of research and development expenses, within accrued and other liabilities in the accompanying consolidated balance sheets. A substantial portion of the Company’s preclinical studies, clinical trials and contract manufacturing activities is conducted by third-party service providers. The Company accrues for estimated costs of research and development activities conducted by third-party service providers based upon the estimated services provided but not yet invoiced. We estimate the amounts incurred in each period based on the information available and our knowledge of the nature of the contractual activities generating such costs. Payments made to third parties under these arrangements in advance of the performance of the related services are recorded as prepaid expenses until the services are rendered.

If the actual timing of the performance of services or the level of effort varies from the estimate, the Company adjusts accrued expenses or prepaid expenses accordingly, which impacts research and development expenses. For the years ended December 31, 2023 and 2022, the Company did not have any material differences between accrued costs and actual costs incurred. 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 amounts that are too high or too low in any particular period.

Stock-Based Compensation

The Company recognizes stock-based compensation expense for all stock-based awards. For stock awards, stock-based compensation cost is estimated on the grant date based on the closing price of the Company's stock, with consideration of whether there is material nonpublic information that could impact the estimated fair value of awards. Stock-Based compensation cost is recognized as expense on a straight-line basis over the requisite service period. Under the Company's employee stock purchase plan, stock-based compensation cost is measured at the beginning of the offering period and recognized on a straight-line basis over the offering period. Forfeitures are accounted for as they occur.

The Company has elected to calculate the fair value of awards using the Black-Scholes option pricing model, or the Black-Scholes Model. The Black-Scholes Model requires the use of various assumptions including common stock valuation, expected option life and expected stock price volatility. The Company estimates the expected term for stock options using the simplified method as the midpoint between the vesting date and the contractual expiration date of the award as the Company has limited historical exercise information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock option grants. Due to the limited trading history of the Company’s stock, the Company estimates the volatility using volatilities of a group of public companies in a comparable industry, stage of life cycle, and size. The interest rate is derived from the U.S. Treasury instruments with maturities similar to the expected term of the options. The Company has not declared nor expects to declare dividends. Therefore, there is no dividend impact on the valuation of options.

Comprehensive Loss

The Company’s comprehensive loss consists of unrealized losses on available-for-sale securities.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss attributable to common stock by the weighted-average number of shares of common stock outstanding for the period, without consideration for potential dilutive securities. Since the Company was in a loss position for the periods presented, basic net loss per share is the same as diluted net loss per share as the effects of the potentially dilutive securities are antidilutive. The following table presents the potential common stock outstanding that were excluded from the computation of diluted net loss per share of common stock as of the periods presented because including them would have been antidilutive (in thousands):


	December 31,
	2023		2022
Common stock issuable upon exercise of stock options		311		260
Unvested restricted stock awards		4		7
Unvested restricted stock units		90		—
Unvested common stock subject to repurchase		—		1
Common stock issuable upon exercise of warrants		394		394
Total		799		662

Income Taxes

The Company accounts for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement carrying amounts and tax bases of assets and liabilities using enacted tax rates expected to be in effect for the year in which the differences are expected to reverse. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts more likely than not to be realized.

The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position’s sustainability and is measured at the largest amount of benefit that is more likely than not of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits require significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available.

The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to unrecognized tax benefits.

Emerging Growth Company Status

The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012, or the JOBS Act. Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with certain new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it is (i) no longer an emerging growth company or (ii) affirmatively and irrevocably opt out of the extended transition period provided in the JOBS Act. As a result, these consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.

Recent Accounting Pronouncements

In December 2023, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. The standard requires entities to disclose additional categories about federal, state and foreign income taxes in the effective tax rate reconciliation as well as provide annual income taxes paid disaggregated by federal, state and foreign taxes. The standard is effective for annual periods beginning after December 15, 2024. Early adoption is permitted. The Company is evaluating the impact of adopting this standard on its consolidated financial statements and related disclosures.

In November 2023, the FASB issued Accounting Standards Update 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The standard improves reportable segment disclosure requirements through enhanced disclosures about significant segment expenses and information used to assess segment performance. All disclosure requirements of the update are required for entities with a single reportable segment. The standard is effective for annual periods beginning after December 15, 2023, and interim periods beginning thereafter. Early adoption is permitted and requires retrospective application to all prior periods presented in the financial statements. The Company is evaluating the impact of adopting this standard on its consolidated financial statements and related disclosures.

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Accrued payroll and related expenses	$ 2,508	$ 3,964
Accrued research and development expenses	1,261	1,665
Accrued professional service fees	65	638
Liability for early exercised stock options	3	89
Other	289	492
Accrued and other liabilities	$ 4,126	$ 6,848

Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Summary of Lessee, Operating Lease, Liability, Maturity

Aggregate future minimum rental payments under the operating leases as of December 31, 2023, were as follows (in thousands):


Year ending December 31, 2024	$	2,670
Year ending December 31, 2025		891
Total lease payments		3,561
Less: Imputed interest		(182	)
Operating lease liabilities	$	3,379

Schedule of Supplemental Information Related to Operating Leases

The following represents supplemental information related to the Company’s operating leases:


	December 31,
	2023			2022
Cash paid for amounts included in the measurement of lease liabilities (in thousands)	$	2,596		$	2,743
Weighted-average remaining lease term (in years)		1.33			2.33
Weighted-average discount rate		8.48	%		8.48	%

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating activities:
Net loss	$ (43,042)	$ (36,004)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,911	1,955
Stock-based compensation	4,372	4,517
Non-cash operating lease expense	1,273	1,314
Amortization of (discount) premium on marketable securities, net	(732)	108
Non-cash impairment of long-lived assets	169	0
Change in fair value of warrant liabilities	(211)	(7,890)
Gain on foreign currency remeasurement	(174)
Other expense related to the commitment shares issued to Lincoln Park	0	273
Changes in operating assets and liabilities:
Accounts receivable	0	(1,978)
Prepaid expenses and other current assets	915	(50)
Other assets	62	(379)
Accounts payable	(133)	(2,038)
Accrued and other liabilities	(2,550)	(1,782)
Operating lease liabilities	(2,223)	(2,191)
Net cash used in operating activities	(40,363)	(44,145)
Investing activities:
Purchases of property and equipment	(398)	(728)
Purchases of marketable securities	(28,044)	(29,600)
Proceeds from maturities of marketable securities	80,165	68,637
Net cash provided by investing activities	51,723	38,309
Financing activities:
Proceeds from issuance of common stock upon exercise of stock options	3	0
Proceeds from issuance of common stock upon employee stock plan purchases	332	143
Repurchase and cancelation of common stock	0	(2,607)
Repurchase of warrants	0	(85)
Repurchase of early exercised stock options	(55)	(16)
Redemption of fractional shares due to reverse stock split	(4)	0
Net cash provided by (used in) financing activities	276	(2,565)
Net increase (decrease) in cash, cash equivalents and restricted cash	11,636	(8,401)
Cash, cash equivalents and restricted cash at beginning of year	25,095	33,496
Cash, cash equivalents and restricted cash at end of year	36,731	25,095
Supplemental disclosure of noncash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued expenses	0	85
Vesting of early exercises of stock options	32	101
Reconciliation Of Cash Cash Equivalents And Restricted Cash To Consolidated Balance Sheets Abstract
Cash and cash equivalents	36,043	24,690
Restricted cash	688	405
Cash, cash equivalents and restricted cash	$ 36,731	$ 25,095

Organization and Business

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization and Business

Note 1. Organization and Business

Organization

Surrozen, Inc., or the Company, is a clinical stage biotechnology company committed to discovering and developing drug candidates to selectively modulate the Wnt pathway, a critical mediator of tissue repair, in a broad range of organs and tissues. The Company, a Delaware corporation, is located in South San Francisco, California, and it operates and manages its business as one operating segment. Surrozen Netherlands, B.V. was incorporated in May 2022 and is located in Amsterdam, Netherlands as a wholly-owned subsidiary of the Company.

Liquidity

The Company has incurred net losses since inception. During the years ended December 31, 2023 and 2022, the Company incurred a net loss of $43.0 million and $36.0 million, respectively. During the years ended December 31, 2023 and 2022, the Company used $40.4 million and $44.1 million of cash in operations. As of December 31, 2023, the Company had cash and cash equivalents of $36.0 million and an accumulated deficit of approximately $221.7 million. The Company expects operating expenses to continue to be significant in connection with its ongoing clinical study and anticipates the need to raise additional capital to continue to execute its long-range business plan.

Management believes that the existing cash, cash equivalents and the gross proceeds of approximately $17.6 million received in April 2024 from the closing of the private placement (see Note 16), before deducting placement agent fees and other expenses, are sufficient for the Company to continue operating activities for at least the next 12 months from the date of issuance of its consolidated financial statements. However, if the Company’s anticipated cash burn is greater than anticipated, the Company could use its capital resources sooner than expected which may result in the need to reduce future planned expenditures and/or raise additional capital to continue to fund the operations.

Reverse Stock Split

On December 13, 2023, the Company filed a certificate of amendment to its certificate of incorporation to effect a 1-for-15 reverse stock split of the issued and outstanding common stock, or the Reverse Stock Split. As a result of the Reverse Stock Split, every 15 shares of issued and outstanding common stock was converted into one issued and outstanding share of common stock, without any change in par value per share. The Reverse Stock Split affected all shares of common stock outstanding immediately prior to the effectiveness of the Reverse Stock Split, as well as the number of shares of common stock available for issuance under the equity incentive plans and employee stock purchase plan. In addition, the Reverse Stock Split effected a reduction in the number of shares of common stock issuable upon the exercise of stock options, restricted stock units and warrants outstanding immediately prior to the effectiveness of the Reverse Stock Split with a corresponding increase in the exercise price per share applicable to such stock options and warrants. No fractional shares were issued because of the Reverse Stock Split. Stockholders who would otherwise be entitled to receive a fractional share received a cash payment in lieu thereof. All share and per share amounts in these consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to the Reverse Stock Split.

Subsequent Events (Additional Information) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2024	Apr. 30, 2024	Dec. 31, 2023
Subsequent Event [Line Items]
Number shares sold and issued	1,100,000
Common stock warrants exercise price per share			$ 172.5
Maximum [Member] \| Investors
Subsequent Event [Line Items]
Purchase Price	$ 15.5	$ 15.5
Minimum [Member] \| Investors
Subsequent Event [Line Items]
Purchase Price	$ 15.4999	15.4999
Subsequent Events \| Members Of Management
Subsequent Event [Line Items]
Number shares sold and issued	2,948,000,000
Purchase Price	$ 16.96	16.96
purchase price per share accompanying common stock warrants	1.25	$ 1.25
Subsequent Events \| Investors
Subsequent Event [Line Items]
Gross proceed		$ 17.6
Common stock warrants exercise price per share	0.0001	$ 0.0001
purchase price per share accompanying common stock warrants	$ 1.25	$ 1.25
Subsequent Events \| Maximum [Member] \| Investors
Subsequent Event [Line Items]
Warrants to purchase common stock	40,000	40,000
Subsequent Events \| Common Class A [Member] \| Members Of Management
Subsequent Event [Line Items]
Purchase price per share	$ 16.96	$ 16.96
Subsequent Events \| Common Class A [Member] \| Investors
Subsequent Event [Line Items]
Purchase price per share	$ 15.5	$ 15.5
Subsequent Events \| Common Class A [Member] \| Maximum [Member] \| Members Of Management
Subsequent Event [Line Items]
Warrants to purchase common stock	2,948,000,000	2,948,000,000
Subsequent Events \| Common Class A [Member] \| Maximum [Member] \| Investors
Subsequent Event [Line Items]
Warrants to purchase common stock	1,100,000	1,100,000
Proceeds from warrants exercised	$ 17.5
Subsequent Events \| Common Class B [Member] \| Members Of Management
Subsequent Event [Line Items]
Warrants to purchase common stock	3,206,000,000	3,206,000,000
Purchase price per share	$ 15.71	$ 15.71
Subsequent Events \| Common Class B [Member] \| Investors
Subsequent Event [Line Items]
Purchase price per share	$ 14.25	$ 14.25
Subsequent Events \| Common Class B [Member] \| Maximum [Member] \| Investors
Subsequent Event [Line Items]
Warrants to purchase common stock	1,200,000	1,200,000
Proceeds from warrants exercised	$ 17.5
Subsequent Events \| Common Class C [Member] \| Members Of Management
Subsequent Event [Line Items]
Warrants to purchase common stock	11,424,000,000	11,424,000,000
Purchase price per share	$ 16	$ 16
Subsequent Events \| Common Class C [Member] \| Investors
Subsequent Event [Line Items]
Purchase price per share	$ 16	$ 16
Subsequent Events \| Common Class C [Member] \| Maximum [Member] \| Investors
Subsequent Event [Line Items]
Warrants to purchase common stock	4,400,000	4,400,000
Proceeds from warrants exercised	$ 70.0
Subsequent Events \| Common Class D Member \| Members Of Management
Subsequent Event [Line Items]
Warrants to purchase common stock	11,424,000,000	11,424,000,000
Purchase price per share	$ 16	$ 16
Subsequent Events \| Common Class D Member \| Investors
Subsequent Event [Line Items]
Purchase price per share	$ 16	$ 16
Subsequent Events \| Common Class D Member \| Maximum [Member] \| Investors
Subsequent Event [Line Items]
Warrants to purchase common stock	4,400,000	4,400,000
Proceeds from warrants exercised	$ 70.0

Collaboration and License Agreements - (Additional Information) (Details) - Collaboration and License Agreement with BI [Member] - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Nov. 30, 2022	Oct. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Non-refundable upfront payment received		$ 12.5		$ 12.5
Success-based milestone payments		587.0
Upfront Payment	$ 10.5
Associated withholding tax		2.2
Transaction price		$ 12.5
Accounts Receivable [Member]
Associated withholding tax			$ 2.2	$ 2.2

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive loss	Accumulated deficit
Balance at the beginning at Dec. 31, 2021	$ 109,700		$ 252,468	$ (119)	$ (142,649)
Balance at the beginning (in shares) at Dec. 31, 2021		2,336
Issuance of common stock under Equity Purchase Agreement(Value)	273		273
Issuance of common stock under Equity Purchase Agreement (Share)		7
Issuance of common stock under employee stock purchase plan	143		143
Issuance of common stock under employee stock purchase plan (Share)		23
Repurchase of early exercised stock options, shares		(1)
Repurchase and cancelation of common stock	(2,607)		(2,607)
Repurchase and cancellation of common stock (Share)		(359)
Vesting of early exercised stock options	101		101
Stock-based compensation expense	4,517		4,517
Other comprehensive loss	(122)			(122)
Net loss	(36,004)				(36,004)
Balance at the end at Dec. 31, 2022	76,001		254,895	(241)	(178,653)
Balance at the end (in shares) at Dec. 31, 2022		2,006
Issuance of common stock under employee stock purchase plan	332		332
Issuance of common stock under employee stock purchase plan (Share)		58
Issuance of common stock upon option exercises	3		3
Redemption of fractional shares due to reverse stock split, value	(4)		(4)
Repurchase of early exercised stock options, shares		(1)
Repurchase and cancelation of common stock	0
Vesting of early exercised stock options	32		32
Stock-based compensation expense	4,372		4,372
Other comprehensive loss	241			$ 241
Net loss	(43,042)				(43,042)
Balance at the end at Dec. 31, 2023	$ 37,935		$ 259,630		$ (221,695)
Balance at the end (in shares) at Dec. 31, 2023		2,063

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables summarize the Company’s financial assets and liabilities that are measured at fair value on a recurring basis (in thousands):


	As of December 31, 2023
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds (1)	$	33,014	$	—	$	—	$	33,014
Total financial assets measured at fair value	$	33,014	$	—	$	—	$	33,014

Liabilities(2):
Public Warrants	$	53	$	—	$	—	$	53
PIPE Warrants		—		62		—		62
Total financial liabilities measured at fair value	$	53	$	62	$	—	$	115


	As of December 31, 2022
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds (1)	$	9,194	$	—	$	—	$	9,194
Commercial paper		—		22,549		—		22,549
Corporate bonds		—		10,797		—		10,797
Government bonds		—		17,802		—		17,802
Government agency debt securities(1)		—		3,982		—		3,982
Total financial assets measured at fair value	$	9,194	$	55,130	$	—	$	64,324

Liabilities(2):
Public Warrants	$	151	$	—	$	—	$	151
PIPE Warrants		—		175		—		175
Total financial liabilities measured at fair value	$	151	$	175	$	—	$	326

(1)

Included in cash and cash equivalents on the consolidated balance sheets as of December 31, 2023 and 2022.

(2)

See the definition and discussion of Public Warrants and PIPE Warrants in Note 11.

Schedule of Marketable Securities by Security Type

The following table provides the Company’s marketable securities by security type as of December 31, 2022 (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Commercial paper	$	22,549	$	—	$	—		$	22,549
Corporate bonds		10,817		1		(21	)		10,797
Government bonds		18,023		—		(221	)		17,802
Total short-term marketable securities	$	51,389	$	1	$	(242	)	$	51,148

Schedule Of Unrealized Loss On Investments

The following table indicates the length of the time that individual securities have been in a continuous unrealized loss position (dollars in thousands):


	As of December 31, 2022
			Less Than 12 Months
	Number of Investments		Fair Value		Unrealized Losses
Corporate bonds		4	$	9,719	$	21
Government bonds		3		17,802		221
Total		7	$	27,521	$	242

- Definition

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

+ References

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

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

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

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

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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

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

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

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

+ Details

Restructuring - Schedule of outstanding restructuring liabilities on the condensed consolidated balance sheets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 1,200
Employee Severance and Other Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring begining balance	$ 0	$ 0
Restructuring Charges		2,752
Cash payments		(2,678)
Restructuring ending balance		$ 74

- Definition

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

+ References + Details

Common Stock Warrants

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Common Stock Warrants

Note 11. Common Stock Warrants

The following table sets forth the common stock warrants outstanding as of December 31, 2023 and 2022 (in thousands, except exercise price per warrant):


Type	Classification	Expiration Date	Exercise Price per Share		Number of Warrants		Fair Value
Public Warrants	Liability	August 12, 2026	$	172.50		2,733	$	53
PIPE Warrants	Liability	August 12, 2026		172.50		3,174		62
Total						5,907	$	115

Public Warrants

Given the effect of the Reverse Stock Split as described in Note 1, every 15 shares of common stock that may be purchased pursuant to the Company’s outstanding warrants immediately prior to the Reverse Stock Split represents 1 share of common stock that may be purchased pursuant to such warrants immediately following the Reverse Stock Split at a price of $172.50 per share, at any time commencing on November 23, 2021 and terminating at the earlier of August 12, 2026 or upon redemption or liquidation. The exercise price and number of shares issuable upon exercise of the Public Warrants may be adjusted in the event of a share dividend, extraordinary dividend or recapitalization, reorganization, merger or consolidation. The Company would not be obligated to deliver any shares of common stock pursuant to the exercise of a Public Warrant and would have no obligation to settle such Public Warrant exercise unless a registration statement under the Securities Act with respect to the common stock underlying the Public Warrants is then effective. If the Company fails to have maintained an effective registration statement, the Public Warrant holders have the right to exercise the Public Warrants on a cashless basis until such time as there is an effective registration statement.

The Company may redeem the outstanding Public Warrants at a price of $0.01 per warrant if the closing price of common stock equals or exceeds $270.00 per share (as adjusted for share sub-divisions, share capitalizations, reorganizations, recapitalizations and similar transaction). Additionally, the Company may redeem the outstanding Public Warrants at a price of $0.10 per warrant if the closing price of common stock equals or exceeds $150.00 per share (as adjusted for share sub-divisions, share capitalizations, reorganizations, recapitalizations and similar transaction). Notice of redemption shall be mailed to the Public Warrant holders no less than 30 days prior to the redemption date, or the Redemption Period. If the closing price of common stock equals or exceeds $150.00 per share and is less than $270.00 per share, during the Redemption Period, the Public Warrant holders may elect to exercise their Public Warrants on a cashless basis based on a make-whole table.

In no event will the Company be required to net cash settle the Public Warrants. The Public Warrant holders do not have the rights or privileges of common stockholders and any voting rights until they exercise their Public Warrants and receive common stock.

PIPE Warrants

At December 31, 2023, the PIPE Warrants are the same in all respects as the Public Warrants. On March 31, 2023, the Company entered into an amended and restated warrant agreement with Continental Stock Transfer & Trust Company as warrant agent, or the PIPE Warrant Agreement. PIPE Warrants may be converted into Public Warrants on transfer pursuant to the terms of the PIPE Warrant Agreement. As of December 31, 2023, no PIPE Warrants were converted into Public Warrants.

Classification

The Public Warrants and PIPE Warrants are not considered indexed to the Company’s common stock as certain provisions of the warrant agreements could change the settlement amount of these warrants. As a result, they were classified as liabilities and recorded at fair value with subsequent change in their respective fair value recognized in other income, net within the consolidated statements of operations and comprehensive loss.

Leases - Summary Of Lessee, Operating Lease, Liability, Maturity (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Leases [Abstract]
Year ending December 31, 2024	$ 2,670
Year ending December 31, 2025	891
Total lease payments	3,561
Less: Imputed interest	(182)
Operating lease liabilities	$ 3,379

Organization and Business - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Apr. 30, 2024
Subsidiary Sale Of Stock [Line Items]
Net loss	$ (43,042)	$ (36,004)
Net cash used in Operation	40,363	44,145
Cash and cash equivalents	36,043	24,690
Accumulated deficit	$ (221,695)	$ (178,653)
Reverse stock split, description	On December 13, 2023, the Company filed a certificate of amendment to its certificate of incorporation to effect a 1-for-15 reverse stock split of the issued and outstanding common stock, or the Reverse Stock Split. As a result of the Reverse Stock Split, every 15 shares of issued and outstanding common stock was converted into one issued and outstanding share of common stock, without any change in par value per share.
Subsequent Events \| Private Placement
Subsidiary Sale Of Stock [Line Items]
Cash and cash equivalents			$ 17,600

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Restricted cash	$ 36,731	$ 25,095
Letter of Credit
Restricted cash	$ 700	$ 400

401(k) Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Retirement Benefits [Abstract]
Company's Contributions	$ 0.1	$ 0.2

Income Taxes - Schedule of Reconciliation of U.S. Federal Statutory Income Tax Rate TO Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	21.00%
State tax	0.00%	(2.12%)
Tax credits	0.64%	1.72%
Stock-based compensation	(1.74%)	2.26%
Change in valuation allowance	(19.95%)	(26.88%)
Gain on warrant liabilities	0.10%	4.60%
Other	(0.05%)	(0.30%)
Effective Income Tax Rate Reconciliation, Percent, Total	0.00%	0.00%

Stock Based Compensation Plans - Summary of RSA Activity (Details) - RSA [Member] shares in Thousands	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Beginning Balance \| shares	7
Number of Shares RSAs, Vested \| shares	(3)
Number of Shares RSAs, unvested, Ending Balance \| shares	4
Weighted Average Grant Date Fair Value RSAs, Unvested Beginning Balance \| $ / shares	$ 146.14
Weighted Average Grant Date Fair Value RSAs, Vested \| $ / shares	145.23
Weighted Average Grant Date Fair Value RSAs, Unvested Ending Balance \| $ / shares	$ 146.92

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-1D

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Paragraph 3
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 2
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Reference 4: 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 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 27: http://www.xbrl.org/2003/role/disclosureRef
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Reference 28: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Leases - Schedule of Supplemental Information Related to Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities (in thousands)	$ 2,596	$ 2,743
Weighted-average remaining lease term (in years)	1 year 3 months 29 days	2 years 3 months 29 days
Weighted-average discount rate	8.48%	8.48%

Stockholders' Equity (Additional Information) (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		12 Months Ended
	Dec. 12, 2022	Apr. 30, 2024	Feb. 28, 2022	Dec. 31, 2023	Dec. 31, 2022
Shares issued				2,063,000	2,006,000
Number shares sold and issued		1,100,000
Common stock issued				$ 0	$ 0
Share repurchased, shares	400,000
Purchase of common stock				0	2,607
Warrant liability	$ 100			$ 115	$ 326
Lincoln Park [Member]
Shares issued				0
Common stock with the fair value			$ 300
Common stock purchase commitment			$ 100
Common stock per share			$ 15
Description of common stock closing sale transaction				Any single purchase of the Company’s common stock shall not exceed $3.5 million.
Share issued, shares				0
Guggenheim Securities, LLC [Member]
Common stock issued				$ 23,000
Compensation payable				3.00%
Maximum [Member]
Sale of stock, consideration received on transaction			$ 3,500
Maximum [Member] \| Lincoln Park [Member]
Sale of stock, consideration received on transaction			50,000
Minimum [Member] \| Lincoln Park [Member]
Sale of stock, consideration received on transaction			$ 30,000

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization	$ 1,911	$ 1,955
Asset impairment charge	$ 100

Restructuring (Tables)

12 Months Ended

Dec. 31, 2023

Restructuring Reserve [Abstract]

Schedule Of Restructuring And Related Cost

The outstanding restructuring liabilities are included in accrued and other liabilities on the consolidated balance sheet. The following table summarizes activity during the year ended December 31, 2023 (in thousands):


	Employee Severance and Other Benefits
Balance, December 31, 2022	$	—
Restructuring charges		2,752
Cash payments		(2,678	)
Balance, December 31, 2023	$	74

Fair Value Measurement - Schedule of Marketable Securities by Security Type (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Current	$ 51,389
Gross Unrealized Gains, Current	1
Gross Unrealized Losses, Current	(242)
Debt Securities, Available-for-sale, Current, Total	51,148
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Current	22,549
Gross Unrealized Gains, Current	0
Gross Unrealized Losses, Current	0
Debt Securities, Available-for-sale, Current, Total	22,549
Corporate Bond
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Current	10,817
Gross Unrealized Gains, Current	1
Gross Unrealized Losses, Current	(21)
Debt Securities, Available-for-sale, Current, Total	10,797
Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Current	18,023
Gross Unrealized Gains, Current	0
Gross Unrealized Losses, Non-current	(221)
Debt Securities, Available-for-sale, Current, Total	$ 17,802

Common Stock Warrants - (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Class Of Warrant Or Right [Line Items]
Common Stock Warrants Expiration Date	Aug. 12, 2026
Common stock warrants exercise price per share \| $ / shares	$ 172.5
Common Stock Warrants Outstanding \| shares	5,907,000
Common Stock Warrants Fair Value \| $	$ 115
Public Warrants
Class Of Warrant Or Right [Line Items]
Common Stock Warrant Classification	Liability
Common Stock Warrants Expiration Date	Aug. 12, 2026
Common stock warrants exercise price per share \| $ / shares	$ 172.5
Common Stock Warrants Outstanding \| shares	2,733,000
Common Stock Warrants Fair Value \| $	$ 53
P I P E Warrants
Class Of Warrant Or Right [Line Items]
Common Stock Warrant Classification	Liability
Common Stock Warrants Expiration Date	Aug. 12, 2026
Common stock warrants exercise price per share \| $ / shares	$ 172.5
Common Stock Warrants Outstanding \| shares	3,174,000
Common Stock Warrants Fair Value \| $	$ 62

Leases

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Leases

Note 5. Leases

In August 2016, the Company entered into a lease agreement for office and lab space, which consists of approximately 32,813 square feet of rental space in South San Francisco, California. The office space lease is classified as an operating lease. The initial lease term commenced in May 2017 and ends in April 2025, with rent payments escalating each year. The Company has options to extend the lease for additional years, but the exercise of the option was not reasonably certain.

In connection with the lease, the Company maintains a letter of credit for the benefit of the landlord in the amount of $0.4 million, which is recorded as restricted cash in the consolidated balance sheets. On March 10, 2023, Silicon Valley Bank, or SVB, was closed by the California Department of Financial Protection and Innovation, which appointed the Federal Deposit Insurance Corporation, or FDIC, as a receiver. On March 27, 2023, First-Citizens Bank & Trust Company assumed all of SVB's customer deposits and certain other liabilities and acquired substantially all of SVB's loans and certain other assets from the FDIC. As required by the landlord, the Company replaced the letter of credit issued by SVB with a letter of credit from a different financial institution in 2023.

In January 2020, the Company entered into a lease agreement for a term of 18 months commencing June 2020 for approximately 6,478 square feet of office space. This office space lease, which was classified as an operating lease, was amended in September 2021 and expired in June 2022.

The operating lease expense for the years ended December 31, 2023 and 2022 was $1.6 million and $1.9 million, respectively. For the year ended December 31, 2023, the Company recorded an asset impairment charge of $0.1 million on its right-of-use assets. Refer to Note 3, Fair Value Measurement for more information.

Aggregate future minimum rental payments under the operating leases as of December 31, 2023, were as follows (in thousands):


Year ending December 31, 2024	$	2,670
Year ending December 31, 2025		891
Total lease payments		3,561
Less: Imputed interest		(182	)
Operating lease liabilities	$	3,379

The following represents supplemental information related to the Company’s operating leases:


	December 31,
	2023			2022
Cash paid for amounts included in the measurement of lease liabilities (in thousands)	$	2,596		$	2,743
Weighted-average remaining lease term (in years)		1.33			2.33
Weighted-average discount rate		8.48	%		8.48	%

401(K) Plan

12 Months Ended

Dec. 31, 2023

Retirement Benefits [Abstract]

401(K) Plan

Note 15. 401(k) Plan

The Company adopted a 401(k) retirement savings plan, or the 401(k) Plan for all eligible employees. Each participant may contribute pre- or post-tax compensation, up to annual statutory limits. The 401(k) Plan also permits the Company to make discretionary and matching contributions, subject to established limits and a vesting schedule. Each year, the Company may, at its sole discretion, make contributions to the plan. For the years ended December 31, 2023 and 2022, the Company's contributions were $0.1 million and $0.2 million, respectively.

Note 16. Subsequent Event

In April 2024, the Company entered into a securities purchase agreement with certain institutional investors (the “Investors”) and management (together with the Investors, the “Purchasers”) whereby the Company issued and sold in a private placement : (i) shares of common stock, (ii) pre-funded warrants to purchase shares of common stock, and (iii) warrants to purchase shares of common stock.

Pursuant to the agreement, the Company issued and sold to the Investors 1.1 million shares of common stock and pre-funded warrants to purchase up to 40,000 shares of common stock, at a purchase price of $15.50 and $15.4999, respectively, for aggregate gross proceeds of approximately $17.6 million, before deducting placement agent fees and other expenses. Each pre-funded warrant has an exercise price of $0.0001 per share, is exercisable immediately and will not expire until exercised in full. The purchase price per share and per pre-funded warrant includes $1.25 for the following accompanying common stock warrants:

•

Series A common stock warrants to purchase up to 1.1 million shares of common stock with an exercise price of $15.50 per share, for aggregate gross proceeds of up to approximately $17.5 million, exercisable immediately upon issuance for five years.

•

Series B common stock warrants to purchase up to 1.2 million shares of common stock with an exercise price of $14.25 per share, for aggregate gross proceeds of up to approximately $17.5 million, exercisable immediately upon issuance until the fifth trading day following the Company’s announcement that (i) it has completed the enrollment of at least 15 patients with a 30-day mortality rate less than 30% in the Company’s SZN-043 Phase 1b clinical trial for the treatment of severe alcohol-associated hepatitis, with no recommended changes by the safety review committee to the study design, including changes related to dose or schedule, and (ii) safety review committee approval for the Company to advance to a higher dose cohort.

•

Series C common stock warrants to purchase up to 4.4 million shares of common stock with an exercise price of $16.00 per share, for aggregate gross proceeds of up to approximately $70 million, exercisable for 30 days following the Company’s announcement of final data from the SZN-043 phase 1b clinical trial for the treatment of severe alcohol-associated hepatitis. The Series C common stock warrants will also become exercisable in the event of a fundamental transaction.

•

Series D common stock warrants to purchase up to 4.4 million shares of common stock with an exercise price of $16.00 per share, for aggregate gross proceeds of up to approximately $70 million, exercisable for 30 days following the Company’s announcement of the enrollment of at least 50 patients in the SZN-043 Phase 2/3 clinical trial for the treatment of severe alcohol-associated hepatitis. The Series D common stock warrants will also become exercisable in the event of a fundamental transaction.

The Company issued and sold to members of management an additional 2,948 shares of common stock at a purchase price of $16.96 per share. The purchase price per share includes $1.25 for the following accompanying common stock warrants:

•

Series A common stock warrants to purchase up to 2,948 shares of common stock with an exercise price of $16.96 per share.

•

Series B common stock warrants to purchase up to 3,206 shares of common stock with an exercise price of $15.71 per share.

•

Series C common stock warrants to purchase up to 11,424 shares of common stock with an exercise purchase price of $16.00 per share.

•

Series D common stock warrants to purchase up to 11,424 shares of common stock with an exercise price of $16.00 per share.

- Definition

The entire disclosure for retirement benefits.

+ References

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

Reference 2: http://www.xbrl.org/2003/role/exampleRef
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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 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

+ Details

License Agreement

12 Months Ended

Dec. 31, 2023

License Agreements [Abstract]

License Agreements

Note 7. License Agreements

Stanford License Agreements

In March 2016, the Company entered into a license agreement with Stanford University, or the 2016 Stanford Agreement, which was amended in July 2016, October 2016 and January 2021, pursuant to which the Company obtained from Stanford a worldwide, exclusive, sublicensable license under certain patents, rights, or licensed patents and technology related to its engineered Wnt surrogate molecules to make, use, import, offer to sell and sell products that are claimed by the licensed patents or that use or incorporate such technology, or licensed products, for the treatment, diagnosis and prevention of human and veterinary diseases. The Company agreed to pay Stanford (i) nominal annual license maintenance fees which are creditable against earned royalties owed to Stanford for the same year, (ii) an aggregate of up to $0.9 million for the achievement of specified development and regulatory milestones, and (iii) an aggregate of up to $5.0 million for achievement of specified sales milestones. Stanford is also entitled to receive royalties from the Company equal to a very low single digit percentage of the Company’s and its sublicensees’ net sales of licensed products that are covered by a valid claim of a licensed patent. Additionally, the Company agreed to pay Stanford a sub-teen double digit percentage of certain consideration the Company receives as a result of granting sublicenses to the licensed patents. However, the Company and Stanford may be able to negotiate a lower non-royalty sublicense percentage based on then-current value of the licensed patents for each sublicense product. If the Company is acquired, it agreed to pay a one-time change of control fee in the low six figures. Stanford retains the right under the 2016 Stanford Agreement, on behalf of itself, Stanford Hospital and Clinics, the University of Washington and all other non-profit research institutions, to practice the licensed patents and technology for any non-profit purpose. The licensed patents and technology are additionally subject to a non-exclusive, irrevocable, worldwide license held by the Howard Hughes Medical Institute to practice the licensed patents and technology for its research purposes, but with no right to assign or sublicense.

In June 2018, the Company entered into another license agreement with Stanford, or the 2018 Stanford Agreement, pursuant to which the Company obtained from Stanford a worldwide, exclusive, sublicensable license under certain patent rights related to its surrogate R-spondin proteins, or the licensed patents, to make, use, import, offer to sell and sell products that are claimed by the licensed patents, or licensed products, for the treatment, diagnosis and prevention of human and veterinary diseases, or the exclusive field. Additionally, Stanford granted the Company a worldwide, non-exclusive, sublicensable license under the licensed patents to make and use licensed products for research and development purposes in furtherance of the exclusive field and a worldwide, non-exclusive license to make, use and import, but not to offer to sell or sell licensed products in any other field of use. The Company agreed to pay Stanford an aggregate of up to $0.4 million for the achievement of specified development and regulatory milestones. Stanford is also entitled to receive royalties from the Company equal to a sub-single digit percentage of the Company’s and its sublicensees’ net sales of licensed products. Additionally, Stanford is entitled to receive a one-time payment in the low six figures for each sublicense of the licensed patents that the Company grants to a third party and, if the Company is acquired, a one-time nominal change of control fee.

For the year ended December 31, 2023, the Company incurred research and development expenses of approximately $0.1 million under the Stanford Agreements. For the year ended December 31, 2022, the Company incurred research and development expenses of approximately $0.2 million under the Stanford Agreements, pertaining to the sublicense fee in connection with the upfront payment received from BI. No milestones have been achieved as of December 31, 2023.

UCSF License and Option Agreements

In September and October 2016, the Company entered into two separate license and option agreements with The Regents of the University of California, or the UCSF Agreements, pursuant to which the Company obtained exclusive licenses from UCSF for internal research and antibody discovery purposes and an option to negotiate with UCSF to obtain an exclusive license under UCSF’s rights in the applicable library to make, use, sell, offer for sale and import products incorporating antibodies identified or resulting from the Company’s use of such library, or licensed products.

In January 2020, the Company amended and restated the UCSF Agreements to provide non-exclusive licenses to make and use a certain human Fab naïve phage display library and to make and use a certain phage display llama VHH single domain antibody library for internal research and antibody discovery purposes and an option to negotiate with UCSF to obtain a non-exclusive commercial license under UCSF’s rights in the applicable library to make, use, sell, offer for sale and import products incorporating antibodies identified or resulting from the Company’s use of such library, or licensed products.

In March 2022, the Company exercised the option under the UCSF Agreements and entered into a non-exclusive commercial license agreement to make and use licensed products derived from the phage display llama VHH single domain antibody library. Under the commercial license agreement, the Company paid UCSF a nominal license issue fee and agreed to pay a nominal annual license maintenance fee, five- to six-digit payments per licensed product upon achievement of a regulatory milestone, nominal minimum annual royalties and earned royalties equal to a sub-single digit percentage of the Company’s and the Company’s sublicensees’ net sales of licensed products.

For the year ended December 31, 2023, the Company incurred de minimis research and development expenses under the UCSF Agreements. For the year ended December 31, 2022, the Company incurred research and development expenses of $0.1 million under the UCSF Agreements as a result of the CLA. No milestones have been achieved as of December 31, 2023.

Distributed Bio Subscription Agreement

In September 2016, the Company entered into, and in January 2019 the Company amended, an antibody library subscription agreement with Charles River Laboratories International, Inc., formerly known as Distributed Bio, Inc., or the Distributed Bio Agreement, in which the Company obtained from Distributed Bio a non-exclusive license to use Distributed Bio’s antibody library to identify antibodies directed to an unlimited number of the Company’s proprietary targets and to make, use, sell, offer for sale, import and exploit products incorporating the antibodies that the Company identifies, or licensed products. In consideration for the rights granted to the Company under the Distributed Bio Agreement, the Company paid Distributed Bio a nominal upfront fee and an additional nominal fee upon entering into the amendment. The Company agreed to pay Distributed Bio an annual fee in the low six figures after the first three years. Additionally, the Company agreed to pay Distributed Bio an aggregate of $5.9 million for each licensed product that achieves specified development, regulatory and commercial milestones and royalties equal to a very low single digit percentage of the Company’s and its sublicensees’ net sales of licensed products. The Company’s obligation to pay royalties will end for each licensed product ten years after its first commercial sale.

In September 2023, the Company amended the Distributed Bio Agreement to cease its use of Distributed Bio’s antibody library and terminate the Company’s obligation to pay the respective annual fee. The obligations to make milestone and royalty payments for use of each licensed product remain in full force and effect.

For the years ended December 31, 2023 and 2022, the Company incurred research and development expenses of $0.2 million under the Distributed Bio Agreement, including the milestone payment of zero and $0.1 million, respectively, as the Company achieved milestones with regard to the Phase 1 clinical trial for SZN-1326.

Stock Based Compensation Plans - Additional Information (Details) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2022 Employees $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of options exercised		$ 1.2	$ 1.2
Weighted average grant date fair value/shares \| $ / shares		$ 9.47	$ 34.2
Unrecognized stock based compensation expense		$ 5.6
Weighted-average period		1 year 8 months 1 day
Shares issued \| shares		2,063,000	2,006,000
Stock options outstanding \| shares	85,000	311	260
Number of employees held stock options \| Employees	59
Weighted average exercise price \| $ / shares	$ 132.15
Incremental expense		$ 0.7
vested member
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incremental expense		0.3
unvested member
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incremental expense		0.4
RSA [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of RSAs vested		$ 0.2	$ 0.2
Employee stock purchase plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance \| shares		7,000
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture, Total \| shares		58,000	23,000
Percentage of discount payroll deductions		15.00%
Common stock trading description		The eligible employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the purchase day
2021 Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance \| shares		200,000
Weighted average exercise price \| $ / shares	$ 32.4
2021 Stock Plan [Member] \| Employee Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Description of modification of options		Options and restricted stock awards, or RSAs, under the 2021 Plan generally vest over four years. Restricted stock units, or RSUs, granted under the 2021 Plan generally vest in one year.
2021 Stock Plan [Member] \| Employee Stock \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period		10 years

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	799	662
Common Stock Issuable Upon Exercise of Stock Options [Member]
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	311	260
Unvested Restricted Stock Awards [Member]
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	4	7
Unvested Restricted Stock Units [Member]
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	90
Unvested Common Stock Subject to Repurchase [Member]
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share		1
Common Stock Issuable Upon Exercise of Warrants [Member]
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	394	394

Fair Value Measurement

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurement

Note 3. Fair Value Measurement

The Company records its financial assets and liabilities at fair value. The carrying amount of the Company's financial instruments, including cash and cash equivalents, accounts receivable, restricted cash, accounts payable, and accrued and other liabilities, approximate their fair value due to their short-term maturities. The accounting guidance for fair value establishes a framework for measuring fair value and a fair value hierarchy that prioritizes the inputs used in valuation techniques. The fair value hierarchy is based on three levels of inputs that may be used to measure fair value as follows:

Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2—Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active.

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The following tables summarize the Company’s financial assets and liabilities that are measured at fair value on a recurring basis (in thousands):


	As of December 31, 2023
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds (1)	$	33,014	$	—	$	—	$	33,014
Total financial assets measured at fair value	$	33,014	$	—	$	—	$	33,014

Liabilities(2):
Public Warrants	$	53	$	—	$	—	$	53
PIPE Warrants		—		62		—		62
Total financial liabilities measured at fair value	$	53	$	62	$	—	$	115


	As of December 31, 2022
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds (1)	$	9,194	$	—	$	—	$	9,194
Commercial paper		—		22,549		—		22,549
Corporate bonds		—		10,797		—		10,797
Government bonds		—		17,802		—		17,802
Government agency debt securities(1)		—		3,982		—		3,982
Total financial assets measured at fair value	$	9,194	$	55,130	$	—	$	64,324

Liabilities(2):
Public Warrants	$	151	$	—	$	—	$	151
PIPE Warrants		—		175		—		175
Total financial liabilities measured at fair value	$	151	$	175	$	—	$	326

(1)

Included in cash and cash equivalents on the consolidated balance sheets as of December 31, 2023 and 2022.

(2)

See the definition and discussion of Public Warrants and PIPE Warrants in Note 11.

Commercial paper, corporate bonds, government bonds and government agency debt securities are classified as Level 2 as they were valued based upon quoted market prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets.

The Public Warrants are classified as Level 1 due to the use of an observable market quote in an active market. The PIPE Warrants are classified as Level 2 due to the use of observable market data for identical or similar liabilities. The fair value of each PIPE Warrants is determined to be consistent with that of a Public Warrant because the PIPE Warrants are also subject to the make-whole redemption feature, which allows the Company to redeem both types of warrants on similar terms.

There were no changes to the valuation methods utilized, and there were no transfers of financial instruments for the years ended December 31, 2023 and 2022.

There were no marketable securities outstanding as of December 31, 2023. The following table provides the Company’s marketable securities by security type as of December 31, 2022 (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Commercial paper	$	22,549	$	—	$	—		$	22,549
Corporate bonds		10,817		1		(21	)		10,797
Government bonds		18,023		—		(221	)		17,802
Total short-term marketable securities	$	51,389	$	1	$	(242	)	$	51,148

The following table indicates the length of the time that individual securities have been in a continuous unrealized loss position (dollars in thousands):


	As of December 31, 2022
			Less Than 12 Months
	Number of Investments		Fair Value		Unrealized Losses
Corporate bonds		4	$	9,719	$	21
Government bonds		3		17,802		221
Total		7	$	27,521	$	242

All short-term marketable securities had maturities of one year or less. There have been no significant realized gains or losses on the marketable securities during the years ended December 31, 2023 and 2022. The Company periodically reviews the available-for-sale

investments for credit losses. All investments with unrealized losses had been in a loss position for less than 12 months. The Company determined that the unrealized loss was primarily attributed to changes in market interest rates and not to credit quality. Therefore, there were no allowance for credit losses recognized as of December 31, 2023.

Assets that are Measured at Fair Value on a Nonrecurring Basis

The Company's non-financial assets such as property and equipment and operating lease right-of-use assets, are adjusted to fair value on a nonrecurring basis when an impairment has occurred. As of December 31, 2023, the Company identified an indicator of impairment of its long-lived assets due to a sustained decline in the trading price of the Company’s common stock over the preceding year, resulting in the Company’s market capitalization being below its net asset value. As a result of the sustained decline in the Company’s stock price, the Company determined an impairment indicator was present. The Company determined all of its long-lived assets represent a single asset group for the purpose of the long-lived asset impairment assessment. The Company concluded that the carrying value of the single asset group was not recoverable as it exceeded the future net undiscounted cash flows that are expected to be generated from the use and eventual disposition of the assets within the asset group. The implied allocated impairment loss to any individual asset within the long-lived asset group shall not reduce the carrying amount of that asset below its fair value.

To determine the fair value of the individual assets within the asset group, the Company utilized the discounted cash flow method of the income approach based on market participant assumptions with Level 3 inputs. These represent a Level 3 nonrecurring fair value measurement. Calculating the fair value of the assets involves significant estimates and assumptions. These estimates and assumptions include, among others, projected future cash flows, risk-adjusted discount rates and market conditions. Changes in the factors and assumptions used could materially affect the amount of impairment loss recognized in the period the asset was considered impaired. For the year ended December 31, 2023, the Company recognized an impairment loss of $0.2 million, consisting of $0.1 million on the operating lease right-of-use asset and $0.1 million on the leasehold improvements, which is included in research and development expenses and general and administrative expenses in the accompanying consolidated statements of operations and comprehensive loss.

- 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

Recapitalization - Additional Information (Details) - shares	Dec. 31, 2023	Dec. 31, 2022
Subsidiary Sale Of Stock [Line Items]
Common shares, shares outstanding	2,063,000	2,006,000
Shares issued	2,063,000	2,006,000

Balance Sheet Components - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Total Property and equipment	$ 9,337	$ 14,985
Less: accumulated depreciation and amortization	(7,368)	(11,355)
Property and equipment, net	1,969	3,630
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total Property and equipment	1,116	7,052
Lab Equipment
Property Plant And Equipment [Line Items]
Total Property and equipment	7,703	7,515
Furniture and office equipment
Property Plant And Equipment [Line Items]
Total Property and equipment	316	299
Computer equipment and software
Property Plant And Equipment [Line Items]
Total Property and equipment	$ 202	$ 119

Fair Value Measurement - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details)) - Fair Value, Recurring - USD ($)
$ in Thousands

Dec. 31, 2023

Dec. 31, 2022

Assets:

Assets

$ 33,014

$ 64,324

Liabilities(2):

Liabilities

^[1]

115

326

Money Market Funds

Assets:

Assets

^[2]

33,014

9,194

Assets:

22,549

Assets:

10,797

Assets:

17,802

Assets:

^[2]

3,982

Public Warrants

Liabilities(2):

Liabilities

^[1]

151

P I P E Warrants

Liabilities(2):

Liabilities

^[1]

175

Level 1

Assets:

Assets

33,014

9,194

Liabilities(2):

Liabilities

^[1]

151

Level 1 | Money Market Funds

Assets:

Assets

^[2]

33,014

9,194

Level 1 | Commercial Paper

Assets:

Assets

Level 1 | Corporate Bond

Assets:

Assets

Level 1 | Government Bonds

Assets:

Assets

Level 1 | Foreign Bonds

Assets:

Assets

^[2]

Level 1 | Public Warrants

Liabilities(2):

Liabilities

^[1]

151

Level 1 | P I P E Warrants

Liabilities(2):

Liabilities

^[1]

Level 2

Assets:

Assets

55,130

Liabilities(2):

Liabilities

^[1]

175

Level 2 | Money Market Funds

Assets:

Assets

^[2]

Level 2 | Commercial Paper

Assets:

Assets

22,549

Level 2 | Corporate Bond

Assets:

Assets

10,797

Level 2 | Government Bonds

Assets:

Assets

17,802

Level 2 | Foreign Bonds

Assets:

Assets

^[2]

3,982

Level 2 | Public Warrants

Liabilities(2):

Liabilities

^[1]

Level 2 | P I P E Warrants

Liabilities(2):

Liabilities

^[1]

175

Level 3

Assets:

Assets

Liabilities(2):

Liabilities

^[1]

Level 3 | Money Market Funds

Assets:

Assets

^[2]

Level 3 | Commercial Paper

Assets:

Assets

Level 3 | Corporate Bond

Assets:

Assets

Level 3 | Government Bonds

Assets:

Assets

Level 3 | Foreign Bonds

Assets:

Assets

^[2]

Level 3 | Public Warrants

Liabilities(2):

Liabilities

^[1]

Level 3 | P I P E Warrants

Liabilities(2):

Liabilities

^[1]

$ 0

[1]	See the definition and discussion of Public Warrants and PIPE Warrants in Note 11.
[2]	Included in cash and cash equivalents on the consolidated balance sheets as of December 31, 2023 and 2022.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

Basis of Presentation

Use of Estimates

Concentration of Credit Risk

Cash and Cash Equivalents

Restricted Cash

Marketable Securities

Property and Equipment


Asset		Estimated useful life
Leasehold improvements		Shorter of useful life of asset or lease term
Lab equipment		3 years
Furniture and office equipment		3-8 years
Computer equipment and software		3 years

Leases

Impairment of Long-Lived Assets

Warrant Liabilities

Revenue Recognition

The incremental costs of obtaining a customer contract are expensed as and when incurred if the amortization period of the asset that would have been recognized is one year or less.

Research and Development Expenses

Accrued Research and Development Expenses

Stock-Based Compensation

Comprehensive Loss

The Company’s comprehensive loss consists of unrealized losses on available-for-sale securities.

Net Loss Per Share


	December 31,
	2023		2022
Common stock issuable upon exercise of stock options		311		260
Unvested restricted stock awards		4		7
Unvested restricted stock units		90		—
Unvested common stock subject to repurchase		—		1
Common stock issuable upon exercise of warrants		394		394
Total		799		662

Income Taxes

Emerging Growth Company Status

Recent Accounting Pronouncements

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenues:
Collaboration and license revenue	$ 0	$ 12,500
Operating expenses:
Research and development	27,230	37,013
General and administrative	15,798	19,826
Restructuring	2,752	0
Total operating expenses	45,780	56,839
Loss from operations	(45,780)	(44,339)
Interest income	2,340	781
Other income, net	398	7,554
Net loss	(43,042)	(36,004)
Unrealized gain (loss) on marketable securities, net of tax	241	(122)
Comprehensive loss	$ (42,801)	$ (36,126)
Net loss per share attributable to common stockholders, basic	$ (21.33)	$ (15.56)
Net loss per share attributable to common Stockholders, diluted	$ (21.33)	$ (15.56)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic	2,018	2,314
Weighted-average shares used in computing net loss per share attributable to common stockholders, diluted	2,018	2,314

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Summary of Net Deferred Tax Assets

Significant components of the Company’s net deferred tax assets consist of the following (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	36,398		$	32,985
Section 174 capitalized expense		12,047			6,812
Research and development credits		4,000			3,775
Lease liabilities		664			1,096
Accrual and reserves		471			739
Employee retention credits		64			271
Stock-based compensation		322			201
Capitalized intangible costs		160			176
Fixed assets		279			66
Other		6			3
Gross deferred tax assets		54,411			46,124
Less: valuation allowance		(53,962	)		(45,343	)
Deferred tax assets, net of valuation allowance		449			781
Deferred tax liabilities:
Right-of-use assets		(397	)		(686	)
Other		(52	)		(95	)
Gross deferred tax liabilities		(449	)		(781	)
Total net deferred tax assets	$	—		$	—

Summary of Unrecognized Tax Benefits

A reconciliation of the Company’s unrecognized tax benefits is as follows (in thousands):


	December 31,
	2023		2022

Balance at beginning of the year	$	1,628	$	974
Additions based on tax positions related to current year		—		654
Additions based on tax positions of prior years		97		—
Balance at end of the year	$	1,725	$	1,628

Schedule of Reconciliation of U.S. Federal Statutory Income Tax Rate TO Effective Income Tax Rate

A reconciliation of the statutory U.S. federal tax rate to the Company’s effective tax rate is as follows:


	December 31,
	2023			2022
Statutory rate		21.00	%		21.00	%
State tax		—			2.12
Tax credits		0.64			1.72
Stock-based compensation		(1.74	)		(2.26	)
Change in valuation allowance		(19.95	)		(26.88	)
Gain on warrant liabilities		0.10			4.60
Other		(0.05	)		(0.30	)
Total		0.00	%		0.00	%

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Property and Equipment Useful Lives


Asset		Estimated useful life
Leasehold improvements		Shorter of useful life of asset or lease term
Lab equipment		3 years
Furniture and office equipment		3-8 years
Computer equipment and software		3 years

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following table presents the potential common stock outstanding that were excluded from the computation of diluted net loss per share of common stock as of the periods presented because including them would have been antidilutive (in thousands):


	December 31,
	2023		2022
Common stock issuable upon exercise of stock options		311		260
Unvested restricted stock awards		4		7
Unvested restricted stock units		90		—
Unvested common stock subject to repurchase		—		1
Common stock issuable upon exercise of warrants		394		394
Total		799		662

Fair Value Measurement - Schedule of Individual Securities Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2022 USD ($) Investments
Debt Securities, Available-for-Sale [Line Items]
Number Of Positions \| Investments	7
Less then 12 Months, Fair Value	$ 27,521
Less then 12 Months, Unrealized Losses	$ 242
Corporate Bond
Debt Securities, Available-for-Sale [Line Items]
Number Of Positions \| Investments	4
Less then 12 Months, Fair Value	$ 9,719
Less then 12 Months, Unrealized Losses	$ 21
Government Bonds
Debt Securities, Available-for-Sale [Line Items]
Number Of Positions \| Investments	3
Less then 12 Months, Fair Value	$ 17,802
Less then 12 Months, Unrealized Losses	$ 221

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Name Accounting Standards Codification
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-Paragraph 2
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Section 50
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Collaboration and License Agreement

12 Months Ended

Dec. 31, 2023

Business Combination and Asset Acquisition [Abstract]

Collaboration and License Agreements

Note 6. Collaboration and License Agreements

Collaboration and License Agreement with Boehringer Ingelheim International GmbH

In October 2022, the Company executed the CLA with BI to research, develop and commercialize Fzd4 bi-specific antibodies designed using the Company’s SWAP technology, including SZN-413. The Company and BI are conducting partnership research focused on SZN-413 during a one-year period, which BI extended for an additional six month period. The Company granted BI an exclusive, royalty-bearing, worldwide, sublicensable license, under the applicable patents and know-how, to develop, manufacture and commercialize, for all uses, one lead and two back-up Fzd4 bi-specific antibodies selected by BI. After an initial period of joint research, BI shall be responsible for all further research, preclinical and clinical development, manufacturing, regulatory approvals, and commercialization of licensed products at its expense. Unless terminated earlier, the CLA will remain effective, on a country-by-country and product-by-product basis, until the expiration of BI's royalty obligations. BI has the right to terminate the CLA for any reason after a specified notice period. Each party has the right to terminate the CLA on account of the other party’s bankruptcy or material, uncured breach.

Under the terms of the CLA, BI agreed to pay a non-refundable upfront payment of $12.5 million less any applicable withholding tax, success-based milestone payments up to a total of $587.0 million and mid-single digit to low-double digit royalties on net sales of the licensed products should any reach commercialization. The royalty payments will be subject to reduction due to patent expiration, generic competition and payments made under certain licenses for third-party intellectual property. The Company received $10.5 million of the upfront payment from BI in November 2022. The associated withholding tax of $2.2 million is expected to be refunded to the Company in 2024.

The Company determined that the CLA is within the scope of ASC 606. The Company evaluated the promised goods and services and determined that the license to the Company's intellectual property granted to BI represented one performance obligation for the purposes of conducting the partnership research and further development on SZN-413. The transaction price was determined to be $12.5 million, which is the non-refundable upfront payment. Variable consideration related to future milestones was fully constrained because the Company cannot conclude that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur, given the inherent uncertainty of success with these future milestones. For sales-based royalties, the Company determined that the license is the predominant item to which the royalties relate to. Accordingly, the Company will recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all the royalty has been allocated has been satisfied (or partially satisfied). The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. During the year ended December 31, 2022, the Company recognized the non-refundable upfront payment of $12.5 million as collaboration and license revenue at a point in time upon delivery of the license. The associated withholding tax of $2.2 million to be refunded was recognized as accounts receivable as of December 31, 2023 and 2022.

Income Taxes - Summary of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets
Net operating loss carryforwards	$ 36,398	$ 32,985
Section 174 capitalized expense	12,047	6,812
Research and development credits	4,000	3,775
Lease liabilities	664	1,096
Accrual and reserves	471	739
Employee retention credits	64	271
Stock-based compensation	322	201
Capitalized intangible costs	160	176
Fixed assets	279	66
Other	6	3
Gross deferred tax assets	54,411	46,124
Less valuation allowance	(53,962)	(45,343)
Deferred tax assets, net of valuation allowance	449	781
Deferred tax liabilities
Right-of-use assets	(397)	(686)
Other	(52)	(95)
Gross deferred tax liabilities	(449)	(781)
Total net deferred tax assets	$ 0	$ 0

Common Stock Warrants - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 12, 2022
Common Stock Warrants Outstanding	5,907,000
Common Stock Warrants Expiration Date	Aug. 12, 2026
Class of warrants repurchased			87,000
Repurchased Outstanding Warrants	$ 115
Common Stock, Shares, Issued	2,063,000	2,006,000
Warrant Redemption Condition Minimum Share Price Scenario Two	$ 270
Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1	$ 172.5
Public Warrants
Common Stock Warrants Outstanding	2,733,000
Common Stock Warrants Expiration Date	Aug. 12, 2026
Warrant Redemption Period	30 days
Repurchased Outstanding Warrants	$ 53
Warrant Redemption Condition Minimum Share Price Scenario One	$ 150
Common Stock, Shares, Issued	1
Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1	$ 172.5
Public Warrants \| Common Stock
Common Stock Warrants Outstanding	15
Public Warrants \| Common Stock, Closing Price equals or Exceeds $18 Per Share [Member]
Redemption Price Per Public Warrant	$ 0.01
Issuance of common stock Per Share	270
Public Warrants \| Common Stock, Closing Price equals or Exceeds $10 Per Share [Member]
Redemption Price Per Public Warrant	0.1
Issuance of common stock Per Share	$ 150
P I P E Warrants
Common Stock Warrants Outstanding	3,174,000
Common Stock Warrants Expiration Date	Aug. 12, 2026
Repurchased Outstanding Warrants	$ 62
Stock Issued During Period, Shares, Conversion of Convertible Securities	0
Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1	$ 172.5

Restructuring

12 Months Ended

Dec. 31, 2023

Restructuring Reserve [Abstract]

Restructuring and Related

Note 8. Restructuring

In January 2023, the Company implemented a restructuring plan approved by the board of directors to prioritize and focus its resources on key clinical and discovery programs. The plan included a reduction of the Company’s overall workforce by approximately 25% in the first quarter of 2023. In connection with the workforce reduction, the Company incurred one-time restructuring charges, including employee severance and other termination benefits, of approximately $1.2 million in the first quarter of 2023.

In July 2023, the Company implemented a restructuring plan approved by the board of directors to further reduce its overall workforce by approximately 38% to better align its workforce with the business needs and focus more of its capital resources on its clinical stage programs. The Company substantially completed the workforce reduction by the end of 2023 and incurred one-time restructuring charges, including employee severance and other termination benefits, of approximately $1.6 million to be recognized ratably over the requisite service period.


	Employee Severance and Other Benefits
Balance, December 31, 2022	$	—
Restructuring charges		2,752
Cash payments		(2,678	)
Balance, December 31, 2023	$	74

Related Party Transactions (Additional Information) (Details) - USD ($) $ in Thousands	Dec. 12, 2022	Dec. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Share repurchased, shares	400,000
Class of warrants repurchased	87,000
Shares issued		2,063,000	2,006,000
Repurchase of warrants or repurchase price	$ 2,600
Common stock purchase price	2,700
Warrant liability	$ 100	$ 115	$ 326

- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

+ References + Details

- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References + Details

Stock Based Compensation Plans- Schedule of Weighted Average Assumptions Used to Estimate Fair Value of Options (Details) - Stock Option	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 10 months 6 days	6 years
Expected volatility	85.86%	81.07%
Risk-free rate	3.89%	2.03%
Dividend yield	0.00%	0.00%

- Definition

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

+ References

+ Details

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2023	Apr. 08, 2024	Jun. 30, 2023
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Registrant Name	Surrozen, Inc./DE
Entity Central Index Key	0001824893
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		3,198,786
Entity Public Float			$ 11.5
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
ICFR Auditor Attestation Flag	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Document Financial Statement Error Correction [Flag]	false
Entity File Number	001-39635
Entity Tax Identification Number	30-1374889
Entity Address, Address Line One	171 Oyster Point Blvd
Entity Address, Address Line Two	Suite 400
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	489-9000
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Document Transition Report	false
Auditor Firm ID	42
Auditor Location	San Francisco, California
Auditor Name	Ernst & Young LLP
Documents Incorporated by Reference	None.
Common Stock
Document Information [Line Items]
Trading Symbol	SRZN
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Redeemable Warrant
Document Information [Line Items]
Trading Symbol	SRZNW
Title of 12(b) Security	Redeemable warrants, each whole warrant exercisable for one-fifteenth of a share of Common Stock
Security Exchange Name	NASDAQ

Common Stock Warrants (Tables)

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Schedule of Common Stock Warrants Outstanding


Type	Classification	Expiration Date	Exercise Price per Share		Number of Warrants		Fair Value
Public Warrants	Liability	August 12, 2026	$	172.50		2,733	$	53
PIPE Warrants	Liability	August 12, 2026		172.50		3,174		62
Total						5,907	$	115

Related Party Transactions

12 Months Ended

Dec. 31, 2023

Related Party Transactions

Note 9. Related Party Transactions

Repurchase of Common Stock and Common Stock Warrants

On December 12, 2022, the Company entered into a securities purchase agreement with entities affiliated with Consonance Capital Management LP, collectively the Consonance Entities. Pursuant to the agreement, the Company repurchased 0.4 million shares of common stock and warrants to purchase an aggregate 87,000 shares of common stock from the Consonance Entities for an aggregate purchase price of approximately $2.7 million, or the Repurchase. Following the Repurchase, the Consonance Entities no longer hold any shares of common stock or warrants.

The shares of common stock repurchased were constructively retired and the common stock warrants repurchased were subsequently cancelled. The total purchase price was allocated to the repurchase of common stock warrants based on the fair value of the warrants remeasured on the repurchase date, resulting in the derecognition of warrant liabilities of $0.1 million. The remaining $2.6 million allocated to the repurchase of common stock was recorded as a reduction of equity on the consolidated balance sheets.

- Definition

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

+ References

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

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

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

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

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

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

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

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

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

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

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

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

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

+ Details

Balance Sheet Components - Prepaid expenses and other current assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid research and development expenses	$ 1,751	$ 1,657
Prepaid insurance	606	1,076
Other	580	756
Prepaid expenses and other current assets	$ 2,937	$ 3,489

Stock Based Compensation Plans - Summary of Stock Option Activity for Company's Stock Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options Outstanding Beginning Balance	260
Number of Options Granted	120
Number of options Forfeited	(44)
Number of Options Exercised	0
Number of Options Cancelled	(25)
Number of Options Outstanding Ending Balance	311	260
Number of Options outstanding and exercisable	163
Weighted Average Exercise Price Outstanding, Beginning Balance \| $ / shares	$ 36.43
Weighted Average Exercise Price Granted	12.86
Weighted Average Exercise Price Forfeited	35.85
Weighted Average Exercise Price Exercised	8.42
Weighted Average Exercise Price Cancelled	32.97
Weighted Average Exercise Price Outstanding, Ending Balance	27.7	$ 36.43
Weighted Average Exercise Price Options outstanding and exercisable	$ 28.56
Weighted Average Remaining Contractual Life (In Years)	7 years 11 months 26 days	8 years 5 months 8 days
Weighted Average Remaining Contractual Life, exercisable (In Years)	7 years 5 months 1 day
Aggregate Intrinsic Value	$ 28
Aggregate Intrinsic Value Options outstanding and exercisable	$ 15

Balance Sheet Components

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

Note 4. Balance Sheet Components

Prepaid Expenses and Other Current Assets

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


	December 31,
	2023		2022
Prepaid research and development expenses	$	1,751	$	1,657
Prepaid insurance		606		1,076
Other		580		756
Prepaid expenses and other current assets	$	2,937	$	3,489

Property and Equipment, Net

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


	December 31,
	2023			2022
Leasehold improvements	$	1,116		$	7,052
Lab equipment		7,703			7,515
Furniture and office equipment		316			299
Computer equipment and software		202			119
Total property and equipment		9,337			14,985
Less: accumulated depreciation and amortization		(7,368	)		(11,355	)
Property and equipment, net	$	1,969		$	3,630

Depreciation expenses for the years ended December 31, 2023 and 2022 was $1.9 million and $2.0 million, respectively. For the year ended December 31, 2023, the Company recorded an asset impairment charge of $0.1 million on its leasehold improvements. Refer to Note 3, Fair Value Measurement for more information.

Accrued and Other Liabilities

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


	December 31,
	2023		2022
Accrued payroll and related expenses	$	2,508	$	3,964
Accrued research and development expenses		1,261		1,665
Accrued professional service fees		65		638
Liability for early exercised stock options		3		89
Other		289		492
Accrued and other liabilities	$	4,126	$	6,848

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

Note 13. Income Taxes

No provision for income taxes was recorded for the years ended December 31, 2023 and 2022. The Company has incurred net operating losses for all the periods presented. The Company accounts for income taxes in accordance with the asset and liability method, which requires that the tax benefit of net operating losses, temporary differences and credit carryforwards be recorded as an asset to the extent that management assesses that 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 not likely to be realized and, accordingly, has provided a full valuation allowance.

Significant components of the Company’s net deferred tax assets consist of the following (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	36,398		$	32,985
Section 174 capitalized expense		12,047			6,812
Research and development credits		4,000			3,775
Lease liabilities		664			1,096
Accrual and reserves		471			739
Employee retention credits		64			271
Stock-based compensation		322			201
Capitalized intangible costs		160			176
Fixed assets		279			66
Other		6			3
Gross deferred tax assets		54,411			46,124
Less: valuation allowance		(53,962	)		(45,343	)
Deferred tax assets, net of valuation allowance		449			781
Deferred tax liabilities:
Right-of-use assets		(397	)		(686	)
Other		(52	)		(95	)
Gross deferred tax liabilities		(449	)		(781	)
Total net deferred tax assets	$	—		$	—

The net valuation allowance increased by $8.6 million and $9.7 million for the years ended December 31, 2023 and 2022, respectively.

As of December 31, 2023, the Company had net operating loss, or NOL, carryforwards of approximately $155.7 million and $53.0 million available to reduce future taxable income, if any, for federal and California state income tax purposes, respectively. NOL carryforwards generated after 2018 for federal tax reporting purposes of $143.2 million have an indefinite carryforward period. The remaining federal and state net operating loss carryforwards begin expiring in 2036.

As of December 31, 2023, the Company had research and development credit carryforwards of approximately $2.6 million and $3.8 million available to reduce future taxable income, if any, for federal and California state income tax purposes, respectively. The federal credit carryforwards begin expiring in 2036 and the state credits carry forward indefinitely.

Federal and state laws impose substantial restrictions on the utilization of net operating loss and tax credit carryforwards in the event of an ownership change for tax purposes, as defined in Section 382 of the Internal Revenue Code. As a result of such ownership changes, the Company’s ability to realize the potential future benefit of tax losses and tax credits that existed at the time of the ownership change may be limited and may expire unutilized. Such impairment of tax losses and tax credits would reduce the deferred tax asset and corresponding valuation allowance, as a result of the limitation. The Company completed an assessment of the available NOLs under Section 382 and determined that the Company underwent an ownership change in September 2020. As a result of the annual limitations caused by the ownership change, it was estimated the approximately $1.3 million of federal tax credit and $27.4 million of California

NOL will expire unrealized for income tax purposes, and such amounts are excluded from the carryforward balances as of December 31, 2023.

The Company recognizes uncertain income tax positions at the largest amount that is more likely than not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. The unrecognized tax benefits, if recognized, would not have an impact on the Company’s effective tax rate assuming the Company continues to maintain a full valuation allowance position. The Company does not expect its unrecognized tax benefits to change significantly over the next 12 months.

A reconciliation of the Company’s unrecognized tax benefits is as follows (in thousands):


	December 31,
	2023		2022

Balance at beginning of the year	$	1,628	$	974
Additions based on tax positions related to current year		—		654
Additions based on tax positions of prior years		97		—
Balance at end of the year	$	1,725	$	1,628

The Company files income tax returns in the U.S. federal and California tax jurisdictions. As of the date these financial statements were issued, the Company is not under examination by any income tax authority. The federal and state income tax returns from December 31, 2016 to December 31, 2022 remain subject to examination.

A reconciliation of the statutory U.S. federal tax rate to the Company’s effective tax rate is as follows:


	December 31,
	2023			2022
Statutory rate		21.00	%		21.00	%
State tax		—			2.12
Tax credits		0.64			1.72
Stock-based compensation		(1.74	)		(2.26	)
Change in valuation allowance		(19.95	)		(26.88	)
Gain on warrant liabilities		0.10			4.60
Other		(0.05	)		(0.30	)
Total		0.00	%		0.00	%

- Definition

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

+ References

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

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

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

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

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

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-Section 50
-Paragraph 1
-Publisher FASB
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

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

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Stock Based Compensation Plans

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation Plans

Note 12. Stock-Based Compensation Plans

The Company maintains the 2021 Equity Incentive Plan, or the 2021 Plan, which provides for the granting of stock awards to employees, directors and consultants. Options granted under the 2021 Plan may be either incentive stock options or nonqualified stock options. Options granted under the 2021 Plan expire no later than 10 years from the date of grant. Options and restricted stock awards, or RSAs, under the 2021 Plan generally vest over four years. Restricted stock units, or RSUs, granted under the 2021 Plan generally vest in one year. As of December 31, 2023, there were 0.2 million shares of common stock available for issuance under the 2021 Plan.

The Company maintains the 2021 Employee Stock Purchase Plan, or the ESPP, which allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to plan limitations. An offering period under the ESPP consists of four six-month purchase periods, unless otherwise determined by the Company. The eligible employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the purchase day. As of December 31, 2023, there were 7,000 shares of common stock available for issuance under the ESPP. During the years ended December 31, 2023 and 2022, 58,000 shares and 23,000 shares were issued under the ESPP.

Option Repricing

In October 2022, the Company’s compensation committee authorized and approved a stock option repricing whereby certain outstanding stock options held by 59 employees were repriced to the closing price of the Company’s common stock on the date of such approval. As a result of this repricing, 85,000 outstanding stock options, with a weighted average exercise price of $132.15 per share, were repriced to have an exercise price of $32.40 per share. The vesting terms and expiration dates of the new stock options remain unchanged from the original stock options.

The option repricing was treated as an option modification for accounting purposes and resulted in the incremental expense of $0.7 million. $0.3 million of the total incremental expense associated with the vested options was recognized on the modification date. The remaining $0.4 million associated with the unvested options as of the modification date will be recognized over the remainder of the original requisite service period.

Stock Options

A summary of stock option activity is set forth below (shares in thousands):


	Options Outstanding
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Number of			Exercise		Contractual Life		Value
	Options			Price		(In years)		(In thousands)
Outstanding – December 31, 2022		260		$	36.43		8.44
Granted		120			12.86
Exercised		—			8.42
Forfeited		(44	)		35.85
Expired		(25	)		32.97
Outstanding – December 31, 2023		311			27.70		7.99	$	28
Exercisable – December 31, 2023		163			28.56		7.42		15

The aggregate intrinsic value of options outstanding and exercisable is the difference between the exercise price of the options and the fair value of the Company’s common stock at December 31, 2023.

The intrinsic value of options exercised during the years ended December 31, 2023 and 2022 was de minimis and $1.2 million, respectively.

During the years ended December 31, 2023 and 2022, the Company granted options with a weighted-average grant-date fair value of $9.47 per share and $34.20 per share, respectively.

Fair Value of Options

The fair value of options is estimated at the grant date using the Black-Scholes option-pricing model with the following weighted-average assumptions:


	Year Ended December 31,
	2023			2022
Expected term (in years)		5.85			6.00
Expected volatility		85.86			81.07	%
Risk-free rate		3.89	%		2.03	%
Dividend yield		—			—

Restricted Stock Awards

The following table summarizes the Company’s RSAs activity (shares in thousands):


				Weighted
				Average
	Number of			Grant Date
	Shares			Fair Value
RSAs, unvested at December 31, 2022		7		$	146.14
Vested		(3	)		145.23
RSAs, unvested at December 31, 2023		4			146.92

The fair value of RSAs vested during the years ended December 31, 2023 and 2022 was de minimis and $0.2 million, respectively.

Restricted Stock Units

The following table summarizes the Company’s RSUs activity (shares in thousands):


			Weighted
			Average
	Number of		Grant Date
	Shares		Fair Value
RSUs, unvested at December 31, 2022		—	$	—
Granted		90		7.73
RSUs, unvested at December 31, 2023		90		7.73

Stock-Based Compensation

Total stock-based compensation expense recorded in the consolidated statements of operations and comprehensive loss was as follows (in thousands):


	Year Ended December 31,
	2023		2022
Research and development	$	1,272	$	1,612
General and administrative		3,100		2,905
Total stock-based compensation expense	$	4,372	$	4,517

As of December 31, 2023, there was approximately $5.6 million of stock-based compensation expense to be recognized over a weighted-average period of approximately 1.67 years.

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common shares, par value	$ 0.0001	$ 0.0001
common stock	500,000,000	500,000,000
Shares issued	2,063,000	2,006,000
Common shares, shares outstanding	2,063,000	2,006,000

Stock Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of stock option activity

A summary of stock option activity is set forth below (shares in thousands):


	Options Outstanding
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Number of			Exercise		Contractual Life		Value
	Options			Price		(In years)		(In thousands)
Outstanding – December 31, 2022		260		$	36.43		8.44
Granted		120			12.86
Exercised		—			8.42
Forfeited		(44	)		35.85
Expired		(25	)		32.97
Outstanding – December 31, 2023		311			27.70		7.99	$	28
Exercisable – December 31, 2023		163			28.56		7.42		15

Summary of RSU Activity

The following table summarizes the Company’s RSUs activity (shares in thousands):


			Weighted
			Average
	Number of		Grant Date
	Shares		Fair Value
RSUs, unvested at December 31, 2022		—	$	—
Granted		90		7.73
RSUs, unvested at December 31, 2023		90		7.73

Summary of RSA Activity

The following table summarizes the Company’s RSAs activity (shares in thousands):


				Weighted
				Average
	Number of			Grant Date
	Shares			Fair Value
RSAs, unvested at December 31, 2022		7		$	146.14
Vested		(3	)		145.23
RSAs, unvested at December 31, 2023		4			146.92

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The fair value of options is estimated at the grant date using the Black-Scholes option-pricing model with the following weighted-average assumptions:


	Year Ended December 31,
	2023			2022
Expected term (in years)		5.85			6.00
Expected volatility		85.86			81.07	%
Risk-free rate		3.89	%		2.03	%
Dividend yield		—			—

Schedule of Stock-Based Compensation Expense

Total stock-based compensation expense recorded in the consolidated statements of operations and comprehensive loss was as follows (in thousands):


	Year Ended December 31,
	2023		2022
Research and development	$	1,272	$	1,612
General and administrative		3,100		2,905
Total stock-based compensation expense	$	4,372	$	4,517

Fair Value Measurement - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Transfers of financial instruments	$ 0	$ 0
Debt Securities, Available-for-Sale, Total	0
Operating lease right-of-use assets	1,889	$ 3,268
Fair Value on a Nonrecurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment of Long-Lived Assets	200
Operating lease right-of-use assets	100
Leasehold Improvements	$ 100
P I P E Warrants \| Measurement Input, Expected Dividend Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative Investment, Measurement Input	0	0

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 14. Commitments and Contingencies

Indemnification

From time to time, the Company enters into certain types of contracts that contingently require the Company to indemnify various parties against claims from third parties. These contracts primarily relate to (i) the Company’s bylaws, under which the Company must indemnify directors and executive officers, and may indemnify other officers and employees, for liabilities arising out of their relationship with the Company, (ii) contracts under which the Company must indemnify directors and certain officers for liabilities arising out of their relationship with the Company, (iii) contracts under which the Company may be required to indemnify customers or partners against certain claims, including claims from third parties asserting, among other things, infringement of their intellectual property rights and (iv) procurement, consulting, or license agreements under which the Company may be required to indemnify vendors, consultants or licensors for certain claims, including claims that may be brought against them arising from acts or omissions with respect to the supplied products, technology or services. From time to time, the Company may receive indemnification claims under these contracts in the normal course of business. In addition, under these contracts the Company may have to modify the accused infringing intellectual property and/or refund amounts received.

In the event that one or more of these matters were to result in a claim against the Company, an adverse outcome, including a judgment or settlement, may cause a material adverse effect on the Company’s future business, operating results or financial condition. It is not

possible to determine the maximum potential amount under these contracts due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement.

The Company maintains director and officer insurance, which may cover certain liabilities arising from the Company’s obligation to indemnify its directors and certain officers.

To the date of the consolidated financial statements were issued, the Company has not incurred any material costs or accrued any liabilities related to indemnification obligations.

Litigation

The Company’s industry is characterized by frequent claims and litigation, including claims regarding intellectual property. As a result, the Company may be subject to various legal proceedings from time to time. The results of any future litigation cannot be predicted with certainty, and regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources and other factors. Management is not aware of any pending or threatened litigation.

License Agreements - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended			12 Months Ended
	Jun. 30, 2018	Sep. 30, 2016	Mar. 31, 2016	Dec. 31, 2023	Dec. 31, 2022
Research and development				$ 27,230	$ 37,013
Stanford License Agreements [Member] \| Stanford [Member]
Payments for milestone agreement or earned royalties on achievement of milestones			$ 5,000
Payments for achievement of specified development and regulatory milestones	$ 400
Research and development				100	200
Payments for milestone agreement on achievement of milestones				0
U C S F License And Option Agreements [Member] \| Stanford [Member]
Research and development					100
Payments for milestone agreement on achievement of milestones				0
Distributed Bio Subscription Agreement [Member]
Payments for milestone agreement or earned royalties on achievement of milestones					100
Payments for achievement of specified development and regulatory milestones		$ 5,900
Distributed Bio Subscription Agreement [Member] \| Stanford [Member]
Research and development				$ 200	$ 200
Maximum [Member] \| Stanford License Agreements [Member] \| Stanford [Member]
Payments for milestone agreement or earned royalties on achievement of milestones			$ 900

Stockholders' Equity

12 Months Ended

Dec. 31, 2023

Stockholders' Equity Note [Abstract]

Stockholders' Equity

Note 10. Stockholders’ Equity

Equity Purchase Agreement

In February 2022, the Company entered into a purchase agreement with Lincoln Park Capital Fund, LLC, or Lincoln Park, or the Equity Purchase Agreement, pursuant to which Lincoln Park is obligated to purchase up to $50.0 million shares of the Company’s common stock.

Upon execution of the Equity Purchase Agreement, the Company issued nominal shares of common stock to Lincoln Park with the fair value of $0.3 million as consideration for Lincoln Park’s commitment to purchase the Company’s common stock, which was included in other income, net on the consolidated statements of operations and comprehensive loss. In the event that the Company sells in an

aggregate of $30.0 million shares of its common stock under the Equity Purchase Agreement, the Company shall pay an additional commitment fee of $0.1 million in cash to Lincoln Park.

As contemplated by the Equity Purchase Agreement, and so long as the closing price of the Company’s common stock exceeds $15.00 per share, the Company may direct Lincoln Park, at its sole discretion, to purchase the Company's common stock within specific share limits. Any single purchase of the Company’s common stock shall not exceed $3.5 million. As of December 31, 2023, the Company has not sold any shares of common stock under the Equity Purchase Agreement.

At-the-Market Sales Agreement

In December 2022, the Company entered into a sales agreement with Guggenheim Securities, LLC to issue and sell up to $23.0 million shares of the Company’s common stock, or the 2022 ATM. The compensation payable to Guggenheim is equal to 3.0% of the gross sales price of any shares sold through it pursuant to the sales agreement. As of December 31, 2023, the Company has not sold any shares of common stock under the 2022 ATM.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

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

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

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481004/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-16

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating Loss Carryforwards [Line Items]
Tax credit carry forwards expiration start year	2036
Research and development credits	$ 4,000,000	$ 3,775,000
Uncertain income tax position, Description	An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained.
Income tax expense (benefit)	$ 0	0
Net valuation allowance increased	8,600,000	$ 9,700,000
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carry forward	1,300,000
Net operating loss carryforwards	$ 155,700,000
Domestic Tax Authority [Member] \| Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carry forwards expiration start year	2036
Research and development credits	$ 2,600,000
Domestic Tax Authority [Member] \| Indefinite Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	143,200,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carry forward	27,400,000
Research and development credits	3,800,000
Net operating loss carryforwards	$ 53,000,000
State and Local Jurisdiction [Member] \| Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carry forwards expiration start year	indefinitely

Stock Based Compensation Plans - Schedule of Stock-Based Compensation Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
General and administrative	$ 15,798	$ 19,826
Total stock-based compensation expense	4,372	4,517
Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Research and development	1,272	1,612
General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
General and administrative	$ 3,100	$ 2,905

- Definition

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

+ References

+ Details

Income Taxes - Summary of Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Balance at beginning of the year	$ 1,628	$ 974
Additions based on tax positions related to current year	0	654
Additions based on tax positions of prior years	(97)	0
Balance at end of the year	$ 1,725	$ 1,628

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Schedule of Prepaid Expense and Other Current Assets

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


	December 31,
	2023		2022
Prepaid research and development expenses	$	1,751	$	1,657
Prepaid insurance		606		1,076
Other		580		756
Prepaid expenses and other current assets	$	2,937	$	3,489

Schedule of Property and Equipment, Net

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


	December 31,
	2023			2022
Leasehold improvements	$	1,116		$	7,052
Lab equipment		7,703			7,515
Furniture and office equipment		316			299
Computer equipment and software		202			119
Total property and equipment		9,337			14,985
Less: accumulated depreciation and amortization		(7,368	)		(11,355	)
Property and equipment, net	$	1,969		$	3,630

Schedule of Accrued and Other Liabilities

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


	December 31,
	2023		2022
Accrued payroll and related expenses	$	2,508	$	3,964
Accrued research and development expenses		1,261		1,665
Accrued professional service fees		65		638
Liability for early exercised stock options		3		89
Other		289		492
Accrued and other liabilities	$	4,126	$	6,848

Share-Based Compensation plans - Summary of RSU Activity (Details) - Restricted Stock Units (RSUs) [Member] shares in Thousands	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Beginning Balance \| shares	0
Number of Shares RSAs, Granted \| shares	90
Number of Shares RSAs, unvested, Ending Balance \| shares	90
Weighted Average Grant Date Fair Value RSAs, Unvested Beginning Balance \| $ / shares	$ 0
Weighted Average Grant Date Fair Value RSU Granted \| $ / shares	7.73
Weighted Average Grant Date Fair Value RSAs, Unvested Ending Balance \| $ / shares	$ 7.73

- Definition

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

+ References

+ Details

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 36,043	$ 24,690
Accounts receivable	2,152	1,978
Short-term marketable securities	0	51,148
Prepaid expenses and other current assets	2,937	3,489
Total current assets	41,132	81,305
Property and equipment, net	1,969	3,630
Operating lease right-of-use assets	1,889	3,268
Restricted cash	688	405
Other assets	402	827
Total assets	46,080	89,435
Current liabilities:
Accounts payable	525	658
Accrued and other liabilities	4,126	6,848
Lease liabilities, current portion	2,497	2,226
Total current liabilities	7,148	9,732
Lease liabilities, noncurrent portion	882	3,376
Warrant liability	115	326
Total liabilities	8,145	13,434
Commitments and contingencies (Note 5 and Note 14)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 10,000 shares authorized; no shares issued and outstanding as of December 31, 2023 and 2022	0	0
Common stock, $0.0001 par value, 500,000 shares authorized as of December 31, 2023 and 2022; 2,063 and 2,006 shares issued and outstanding as of December 31, 2023 and 2022, respectively	0	0
Additional paid-in-capital	259,630	254,895
Accumulated other comprehensive loss	0	(241)
Accumulated deficit	(221,695)	(178,653)
Total stockholders’ equity	37,935	76,001
Total liabilities and stockholders’ equity	$ 46,080	$ 89,435

Restructuring (Additional Information) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2023
Restructuring Reserve [Abstract]
Reduction in workforce	25.00%	38.00%
Restructuring Charges	$ 1.2
Other Restructuring Costs		$ 1.6

Subsequent Events

12 Months Ended

Mar. 31, 2023

Subsequent Events [Abstract]

Subsequent Events

Note 16. Subsequent Event

•

Series A common stock warrants to purchase up to 2,948 shares of common stock with an exercise price of $16.96 per share.

•

Series B common stock warrants to purchase up to 3,206 shares of common stock with an exercise price of $15.71 per share.

•

Series C common stock warrants to purchase up to 11,424 shares of common stock with an exercise purchase price of $16.00 per share.

•

Series D common stock warrants to purchase up to 11,424 shares of common stock with an exercise price of $16.00 per share.

Leases - Additional Information (Details) m² in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jan. 31, 2020 m²	Aug. 31, 2016 ft²
Lessee Lease Description [Line Items]
Area of real estate property \| m²			6,478
Restricted cash	$ 688	$ 405
Operating lease term			18 months
Operating Lease, Expense	1,600	$ 1,900
Assets Impairment Charges on right-of-use assets	$ 100
CALIFORNIA \| Eight Years [Member]
Lessee Lease Description [Line Items]
Area of real estate property \| ft²				32,813
Operating lease month of expiry of lease	2025-04
Restricted cash	$ 400