Surrozen (SRZN) 10-Q6 Nov 242024 Q3 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2024	Nov. 04, 2024
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
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 Current Reporting Status	Yes
Entity Shell Company	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 Quarterly Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		3,249,798
Common Stock [Member]
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 [Member]
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

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 31,012	$ 36,043
Accounts receivable	12,196	2,152
Prepaid expenses and other current assets	2,078	2,937
Total current assets	45,286	41,132
Property and equipment, net	856	1,969
Operating lease right-of-use assets	817	1,889
Restricted cash	688	688
Other assets	351	402
Total assets	47,998	46,080
Current liabilities:
Accounts payable	276	525
Accrued and other liabilities	4,317	4,126
Lease liabilities, current portion	1,527	2,497
Total current liabilities	6,120	7,148
Lease liabilities, noncurrent portion	0	882
Warrant liabilities	36,211	115
Total liabilities	42,331	8,145
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 10,000 shares authorized; no shares issued and outstanding as of September 30, 2024 and December 31, 2023	0	0
Common stock, $0.0001 par value, 500,000 shares authorized as of September 30, 2024 and December 31, 2023; 3,250 and 2,063 shares issued and outstanding as of September 30, 2024 and December 31, 2023, respectively	0	0
Additional paid-in-capital	262,887	259,630
Accumulated deficit	(257,220)	(221,695)
Total stockholders' equity	5,667	37,935
Total liabilities and stockholders’ equity	$ 47,998	$ 46,080

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2024	Dec. 31, 2023
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 stock, par value	$ 0.0001	$ 0.0001
Common shares, shares authorized	500,000,000	500,000,000
Common stock shares issued	3,250,000	2,063,000
Common shares, shares outstanding	3,250,000	2,063,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Collaboration and license revenue	$ 10,000	$ 0	$ 10,000	$ 0
Operating expenses:
Research and development	5,200	6,112	15,782	21,135
General and administrative	3,568	3,572	11,165	12,209
Restructuring	0	1,505	0	2,712
Total operating expenses	8,768	11,189	26,947	36,056
Income (Loss) from operations	1,232	(11,189)	(16,947)	(36,056)
Interest income	431	661	1,306	1,831
Other (expense) income, net	(3,097)	83	513	96
Loss on issuance of common stock, pre-funded warrants and warrants	0	0	(20,397)	0
Net loss	(1,434)	(10,445)	(35,525)	(34,129)
Unrealized (loss) gain on marketable securities, net of tax	0	(4)	0	242
Comprehensive loss	$ (1,434)	$ (10,449)	$ (35,525)	$ (33,887)
Net loss per share attributable to common stockholders, basic	$ (0.44)	$ (5.14)	$ (12.57)	$ (16.96)
Net loss per share attributable to common stockholders, diluted	$ (0.44)	$ (5.14)	$ (12.57)	$ (16.96)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic	3,228	2,033	2,826	2,012
Weighted-average shares used in computing net loss per share attributable to common stockholders, diluted	3,228	2,033	2,826	2,012

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Common Stock Private Placement [Member]	Additional Paid-in Capital	Accumulated Other Comprehensive Income (loss)	Accumulated Deficit
Balance at the beginning at Dec. 31, 2022	$ 76,001			$ 254,895	$ (241)	$ (178,653)
Balance at the beginning (in shares) at Dec. 31, 2022		2,006
Repurchase of early exercised stock options, shares		(1)
Vesting of early exercised stock options	13			13
Stock-based compensation expense	1,129			1,129
Other comprehensive income	191				191
Net loss	(14,297)					(14,297)
Balance at the end at Mar. 31, 2023	63,037			256,037	(50)	(192,950)
Balance at the end (in shares) at Mar. 31, 2023		2,005
Balance at the beginning at Dec. 31, 2022	76,001			254,895	(241)	(178,653)
Balance at the beginning (in shares) at Dec. 31, 2022		2,006
Net loss	(34,129)
Balance at the end at Sep. 30, 2023	45,531			258,312	1	(212,782)
Balance at the end (in shares) at Sep. 30, 2023		2,038
Balance at the beginning at Mar. 31, 2023	63,037			256,037	(50)	(192,950)
Balance at the beginning (in shares) at Mar. 31, 2023		2,005
Issuance of common stock upon employee stock purchase plan, shares		33
Issuance of common stock upon employee stock purchase plan, value	187			187
Vesting of early exercised stock options	8			8
Stock-based compensation expense	1,158			1,158
Other comprehensive income	55				55
Net loss	(9,387)					(9,387)
Balance at the end at Jun. 30, 2023	55,058			257,390	5	(202,337)
Balance at the end (in shares) at Jun. 30, 2023		2,038
Issuance of common stock upon option exercises	3			3
Vesting of early exercised stock options	6			6
Stock-based compensation expense	913			913
Other comprehensive income	(4)				(4)
Net loss	(10,445)					(10,445)
Balance at the end at Sep. 30, 2023	45,531			258,312	$ 1	(212,782)
Balance at the end (in shares) at Sep. 30, 2023		2,038
Balance at the beginning at Dec. 31, 2023	37,935			259,630		(221,695)
Balance at the beginning (in shares) at Dec. 31, 2023		2,063
Vesting of restricted stock units		44
Vesting of early exercised stock options	1			1
Stock-based compensation expense	1,030			1,030
Net loss	(8,830)					(8,830)
Balance at the end at Mar. 31, 2024	30,136			260,661		(230,525)
Balance at the end (in shares) at Mar. 31, 2024		2,107
Balance at the beginning at Dec. 31, 2023	37,935			259,630		(221,695)
Balance at the beginning (in shares) at Dec. 31, 2023		2,063
Net loss	(35,525)
Balance at the end at Sep. 30, 2024	5,667			262,887		(257,220)
Balance at the end (in shares) at Sep. 30, 2024		3,250
Balance at the beginning at Mar. 31, 2024	30,136			260,661		(230,525)
Balance at the beginning (in shares) at Mar. 31, 2024		2,107
Issuance of common stock in the Private Placement, shares			1,092
Issuance of common stock upon employee stock purchase plan, shares		7
Issuance of common stock upon employee stock purchase plan, value	42			42
Stock-based compensation expense	1,145			1,145
Net loss	(25,261)					(25,261)
Balance at the end at Jun. 30, 2024	6,062			261,848		(255,786)
Balance at the end (in shares) at Jun. 30, 2024		3,206
Vesting of restricted stock units		44
Stock-based compensation expense	1,039			1,039
Net loss	(1,434)					(1,434)
Balance at the end at Sep. 30, 2024	$ 5,667			$ 262,887		$ (257,220)
Balance at the end (in shares) at Sep. 30, 2024		3,250

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Operating activities:
Net loss	$ (35,525)	$ (34,129)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,120	1,460
Stock-based compensation	3,214	3,200
Non-cash operating lease expense	1,072	937
Amortization of discount on marketable securities, net	0	(688)
Transaction costs allocated to pre-funded warrants and warrants in connection with the Private Placement	1,507	0
Loss on issuance of common stock, pre-funded warrants and warrants	20,397	0
Change in fair value of warrant liabilities	(1,851)	(83)
Loss on foreign currency remeasurement	(44)	0
Changes in operating assets and liabilities:
Accounts receivable	(10,000)	0
Prepaid expenses and other current assets	859	955
Other assets	51	38
Accounts payable	(249)	(371)
Accrued and other liabilities	192	(2,728)
Operating Lease liabilities	(1,852)	(1,643)
Net cash used in operating activities	(21,109)	(33,052)
Investing activities:
Purchases of property and equipment	(7)	(398)
Purchases of marketable securities	0	(28,044)
Proceeds from maturities of marketable securities	0	70,665
Net cash (used in) provided by investing activities	(7)	42,223
Financing activities:
Proceeds from issuance of common stock, pre-funded warrants and warrants in the Private Placement, net of transaction costs	16,043	0
Proceeds from issuance of common stock upon exercise of stock options	0	3
Proceeds from issuance of common stock upon employee stock plan purchases	42	187
Repurchase of early exercised stock options	0	(55)
Net cash provided by financing activities	16,085	135
Net increase in cash, cash equivalents and restricted cash	(5,031)	9,306
Cash, cash equivalents and restricted cash at beginning of period	36,731	25,095
Cash, cash equivalents and restricted cash at end of period	31,700	34,401
Supplemental disclosure of noncash investing and financing activities:
Vesting of early exercises of stock options	1	27
Reconciliation Of Cash Cash Equivalents And Restricted Cash To Consolidated Balance Sheets Abstract
Cash and cash equivalents	31,012	33,975
Restricted cash	688	426
Cash, cash equivalents and restricted cash	$ 31,700	$ 34,401

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (1,434)	$ (10,445)	$ (35,525)	$ (34,129)

Insider Trading Arrangements

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

Organization and Business

Organization and Business	9 Months Ended
Organization and Business	Sep. 30, 2024
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 in 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 three and nine months ended September 30, 2024, the Company incurred a net loss of $ 1.4 million and $ 35.5 million , respectively. For the three and nine months ended September 30, 2023, the Company incurred a net loss of $ 10.4 million and $ 34.1 million , respectively. For the nine months ended September 30, 2024 and 2023, the Company used $ 21.1 million and $ 33.1 million of cash in operations, respectively. As of September 30, 2024, the Company had cash and cash equivalents of $ 31.0 million and an accumulated deficit of approximately $ 257.2 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 and cash equivalents, plus a $ 10.0 million milestone payment received in October 2024 (see Note 5), are sufficient for the Company to continue operating activities for at least the next 12 months from the date of issuance of its unaudited condensed 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 unaudited condensed consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to the Reverse Stock Split.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies Basis of Presentation The Company’s unaudited condensed 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. As permitted under those rules, certain notes or other financial information that are normally required by U.S. GAAP have been condensed or omitted and accordingly, the consolidated balance sheet as of December 31, 2023 has been derived from the Company’s audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete consolidated financial statements. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting of normal recurring adjustments) that are necessary for a fair presentation of the Company’s consolidated financial statements. The results of operations for the three and nine months ended September 30, 2024 are not necessarily indicative of the results to be expected for the year ended December 31, 2024 or for any other interim period or future year. The unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiary. All intercompany transactions and balances have been eliminated. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2023 included in the Company’s Annual Report on Form 10-K , filed with the SEC on April 10 , 2024. Use of Estimates The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP r equires 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 unaudited condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions made in the accompanying unaudited condensed consolidated financial statements include certain accrued expenses for research and development activities and fair value of warrants issued in connection with the closing of a private placement in April 2024. 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 and cash equivalents. 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 unaudited condensed consolidated balance sheets. The Company believes it is not exposed to significant credit risk on cash. The Company’s cash equivalents were held in custodial accounts maintained by third-party custodians. The Company’s policy is to invest cash in institutional money market funds with high credit quality to limit the amount of credit exposure. The Company has not experienced any losses on its cash equivalents. Revenue Recognition 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. The Company determined that 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 the non-refundable upfront payment. Variable consideration related to future milestones is 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. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded as revenue on a cumulative catch-up basis during the period of adjustment. The Company will recognize 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). Warrant Liabilities The Company's warrants are classified as liabilities and measured at fair value. Transaction costs associated with the warrant liabilities are recognized as other expenses when incurred. At the end of each reporting period, any change in fair value during the period are recognized in other income, net within the unaudited consolidated statements of operations and comprehensive loss. The Company will continue to adjust the warrant liabilities 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. 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. Diluted net loss per share is calculated using the more dilutive of the two-class method or treasury method. The Company’s 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 s hares of 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): September 30, 2024 2023 Common stock issuable upon exercise of stock options 553 317 Unvested restricted stock awards 1 5 Unvested restricted stock units 40 90 Common stock issuable upon exercise of warrants 11,569 394 Total 12,163 806 Recent Accounting Pronouncements In August 2020, the FASB issued Accounting Standards Update 2020-06, Debt — Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging — Contracts in Entity’s Own Equity (Subtopic 815-40). This standard eliminates the beneficial conversion and cash conversion accounting models for convertible instruments, amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions, and modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted earning per share calculation. The standard is effective for annual periods beginning after December 15, 2023 for smaller reporting companies, and interim periods within those reporting periods. The Company adopted this standard effective January 1, 2024, using a modified retrospective method. The adoption of the standard did not have a material impact on the Company's unaudited condensed consolidated financial statements and related disclosures. In December 2023, the 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 unaudited condensed 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 within fiscal years beginning after December 15, 2024. 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 unaudited condensed consolidated financial statements and related disclosures .

Fair Value Measurement

Fair Value Measurement	9 Months Ended
Fair Value Measurement	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurement	Note 3. Fair Value Measurement 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 September 30, 2024 Level 1 Level 2 Level 3 Total Assets: Money market funds (1) $ 28,179 $ — $ — $ 28,179 Total financial assets measured at fair value $ 28,179 $ — $ — $ 28,179 Liabilities (2) : 2021 Public Warrants $ 50 $ — $ — $ 50 2021 PIPE Warrants — 11 — 11 2024 Pre-Funded Warrants — 479 — 479 2024 PIPE Warrants — — 35,671 35,671 Total financial liabilities measured at fair value $ 50 $ 490 $ 35,671 $ 36,211 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) : 2021 Public Warrants $ 53 $ — $ — $ 53 2021 PIPE Warrants — 62 — 62 Total financial liabilities measured at fair value $ 53 $ 62 $ — $ 115 (1) Included in cash and cash equivalents on the condensed consolidated balance sheets. (2) See Note 10. There were no changes to the valuation methods utilized and there were no transfers of financial instruments between Level 1, Level 2, and Level 3 during the nine months ended September 30, 2024. The 2021 Public Warrants (as defined in Note 10 below) are classified as Level 1 due to the use of an observable market quote in an active market. The 2021 PIPE Warrants (as defined in Note 10 below) are classified as Level 2 due to the use of observable market data for identical or similar liabilities. The fair value of each 2021 PIPE Warrant is determined to be consistent with that of a 2021 Public Warrant because the 2021 PIPE Warrants are also subject to the make-whole redemption feature, which allows the Company to redeem both types of warrants on similar terms. The 2024 Pre-Funded Warrants (as defined in Note 10 below) are classified as Level 2 due to the use of observable market data for similar instruments. The fair value of the 2024 Pre-Funded Warrants is determined to be consistent with the fair value of the Company’s common stock due to the nominal exercise price. The 2024 PIPE Warrants (as defined in Note 10 below) are classified as Level 3 because the fair value was measured based on significant inputs that are unobservable in the market. The 2024 PIPE Warrants were initially recorded at fair value and subsequently remeasured at each reporting period using the Black-Scholes option-pricing model. The significant unobservable inputs used in the fair value measurement of the warrants include the timing and probability of achieving the milestones and the expected volatility. The expected volatility was implied from a peer analysis. The expected term was estimated based on the timing of when the milestone is expected to be achieved, and the risk-free interest rate was based on the implied yield available on U.S. Treasury Securities with a maturity equivalent to the expected term. The dividend rate is based on the historical rate, which the Company anticipated remaining at zero. The fair value of the 2024 PIPE Warrants may change significantly as additional data is obtained, impacting the Company’s assumptions to estimate the fair value of the liabilities. In evaluating this information, considerable judgment is required to interpret the data used to develop the assumptions and estimates. Accordingly, the use of different market assumptions and/or different valuation techniques may have a material effect on the estimated fair value amounts, and such changes could materially impact the Company’s results of operations in future periods. The key inputs into the fair value measurement of the 2024 PIPE Warrants were as follows at the initial measurement and September 30, 2024: September 30, April 4, 2024 2024 Expected term (in years) 0.3 - 4.5 0.8 - 5.0 Expected volatility 95 % 100 % Risk-free interest rate 3.6 % - 4.8 % 4.4 % - 5.2 % Dividend yield — — 2024 PIPE Balance, December 31, 2023 $ — Issuance in the Private Placement 37,494 Change in fair value upon remeasurement (1) ( 5,004 ) Balance, June 30, 2024 32,490 Change in fair value upon remeasurement (1) 3,181 Balance, September, 30, 2024 $ 35,671 (1) Included in other (expense) income, net on the condensed consolidated statement of operations. 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 impairme nt 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. The Company concluded that the carrying value of its long-lived assets was not recoverable and recognized an impairment loss of $ 0.2 million during the fourth quarter of 2023 based on the fair value of the individual assets. To determine the fair value of the individual assets, 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. The Company is not aware of any identified events or changes in circumstances that would have a significant adverse effect on the carrying value of its long-lived assets for the nine months ended September 30, 2024 .

Balance Sheet Components

Balance Sheet Components	9 Months Ended
Balance Sheet Components	Sep. 30, 2024
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): September 30, December 31, 2024 2023 Prepaid research and development expenses $ 715 $ 1,751 Prepaid insurance 632 606 Other 731 580 Prepaid expenses and other current assets $ 2,078 $ 2,937 Accrued and Other Liabilities Accrued and other liabilities consist of the following (in thousands): September 30, December 31, 2024 2023 Accrued payroll and related expenses $ 2,443 $ 2,508 Accrued research and development expenses 1,626 1,261 Accrued professional service fees 87 65 Other 161 292 Accrued and other liabilities $ 4,317 $ 4,126

Collaboration and License Agree

Collaboration and License Agreements	9 Months Ended
Collaboration and License Agreements	Sep. 30, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Collaboration and License Agreements	Note 5. 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 Frizzled 4, or 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 $ 2.1 m illion is expected to be refunded to the Company in 2024 and recognized as accounts receivable. In September 2024, a milestone was achieved as BI decided to move forward with the development of SZN-413, which entitled the Company to receive a $ 10.0 million non-refundable and non-creditable payment from BI pursuant to the terms of the CLA. The milestone payment of $ 10.0 million was recognized as revenue and accounts receivable on the condensed consolidated financial statements for the nine months ended September 30, 2024 and was received in October 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 at the inception, which is the non-refundable upfront payment. Variable consideration related to future milestones is 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.

License Agreements

License Agreements	9 Months Ended
License Agreements	Sep. 30, 2024
License Agreements [Abstract]
License Agreements	Note 6. 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 three and nine months ended September 30, 2024 and 2023 , the Company incurred de minimis research and development expenses under the Stanford agreements. No milestones have been achieved as of September 30, 2024. 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. In August 2024, 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 human Fab naïve phage display library. Under the commercial license agreements, 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 three and nine months ended September 30, 2024 and 2023 the Company incurred de minimis research and development expenses under the UCSF Agreements and the commercial license agreement. No milestones have been achiev ed as of September 30, 2024. 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. 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 three and nine months ended September 30, 2024, the Company did not incur research and development expenses under the Distributed Bio Agreement, respectively. For the three and nine months ended September 30, 2023, the Company incurred $ 0.1 million and $ 0.2 million of research and development expenses under the Distributed Bio Agreement, respectively. The Company achieved a milestone with regard to the initiation of the Phase 1 clinical trial for SZN-1326 in May 2022.

Restructuring

Restructuring	9 Months Ended
Restructuring	Sep. 30, 2024
Restructuring Reserve [Abstract]
Restructuring	Note 7. 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 completed the workforce reduction in 2023 and incurred one-time restructuring charges, including employee severance and other termination benefits, of approximately $ 1.5 million to be recognized ratably over the requisite service period from July 2023 through March 2024. The outstanding restructuring liabilities are included in accrued and other liabilities on the condensed consolidated balance sheet. The following tables summarize activity during the three and nine months ended September 30, 2024 and 2023 (in thousands): Employee Severance and Other Benefits Balance, December 31, 2023 $ 74 Cash payments ( 44 ) Personnel adjustments ( 30 ) Balance, September 30, 2024 $ — Employee Severance and Other Benefits Balance, December 31, 2022 $ — Restructuring charges 1,207 Cash payments ( 726 ) Balance, March 31, 2023 481 Cash payments ( 457 ) Balance, June 30, 2023 24 Restructuring charges 1,505 Cash payments ( 1,304 ) Balance, September 30, 2023 $ 225

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 8. Commitments and Contingencies Lease Agreement 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 condensed consolidated balance sheets. The operating lease expense for each of the three and nine months ended September 30, 2024 and 2023 was $ 0.4 million, $ 1.2 million, $ 0.4 million and $ 1.2 million, respectively. Aggregate future minimum rental payments under the operating leases as of September 30, 2024, were as follows (in thousands): Remaining three months ending December 31, 2024 $ 668 Year ending December 31, 2025 891 Total lease payments 1,559 Less: Imputed interest ( 32 ) Operating lease liabilities $ 1,527

Stockholders' Equity

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2024
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Note 9. Stockholders’ Equity Private Placement In April 2024, the Company entered into a securities purchase agreement with certain institutional investors, or the Investors, and certain members of management whereby the Company issued and sold in a private placement, or the Private Placement: (i) 1.1 million shares of common stock, (ii) pre-funded warrants to purchase up to 40,000 shares of common stock, and (iii) warrants to purchase up to 11.1 million shares of common stock for aggregate gross proceeds of approximately $ 17.5 million. The purchase price of common stock and pre-funded warrants to the Investors was $ 15.50 per share and $ 15.4999 per share, respectively . The pre-funded warrants and warrants were issued with an initial fair value of $ 37.9 million, which was greater than the aggregate gross proceeds in the private placement. The excess of $ 20.4 million was recorded as loss on issuance of common stock, pre-funded warrants and warrants on the condensed consolidated statements of operations and comprehensive loss. The Company incurred transaction costs of $ 1.5 million, consisting of placement agent fees and other expenses, all of which were allocated to the warrant liabilities associated with the pre-funded warrants and warrants issued, and recognized the allocated transaction costs as other expenses when incurred. See Note 10 for more information regarding the warrants issued and sold to the Investors in the Private Placement and Note 11 for more information regarding the shares of the Company’s common stock and the warrants issued and sold to management in the Private Placement. 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. In the event that the Company sells 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 of September 30, 2024 , the Company has no t 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 September 30, 2024 , the Company has no t sold any shares of common stock under the 2022 ATM.

Common Stock Warrants

Common Stock Warrants	9 Months Ended
Common Stock Warrants	Sep. 30, 2024
Equity [Abstract]
Common Stock Warrants	Note 10. Common Stock Warrants The following table sets forth the common stock warrants outstanding as of September 30, 2024 and December 31, 2023 (in thousands, except exercise price per warrant): Exercise Price per Share — Exercise Price per Share — September 30, December 31, Type Classification Investor Management 2024 2023 2024 Pre-Funded Warrants Liability $ 0.0001 N/A 40 — 2024 PIPE Warrants – Series A Liability 15.50 $ 16.96 1,132 — 2024 PIPE Warrants – Series B Liability 14.25 15.71 1,231 — 2024 PIPE Warrants – Series C Liability 16.00 16.00 4,386 — 2024 PIPE Warrants – Series D Liability 16.00 16.00 4,386 — 2021 Public Warrants Liability 172.50 N/A 4,883 2,733 2021 PIPE Warrants Liability 172.50 N/A 1,024 3,174 Total 17,082 5,907 2024 Pre-Funded Warrants and 2024 PIPE Warrants As described in Note 9, in April 2024, the Company entered into a securities purchase agreement with Investors and certain members of management whereby the Company issued and sold in a private placement: (i) common stock, (ii) pre-funded warrants to purchase common stock, or the 2024 Pre-Funded Warrants, and (iii) warrants to purchase common stock, or the 2024 PIPE Warrants. The purchase price per share of common stock and per Pre-Funded Warrant includes $ 1.25 for the following accompanying common stock warrants issued to the Investors: • 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 as defined in the warrants. • 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 as defined in the warrants. The holders of the 2024 Pre-Funded Warrants and the 2024 PIPE Warrants are entitled to receive dividends if the Company declares or makes a dividend to holders of shares of common stock while such warrants are outstanding. If a purchaser fails to exercise such purchaser’s Series B common stock warrants in full, then all warrants issued to such purchaser are subject to mandatory transfer and to the extent not transferred shall automatically be cancelled and cease to be exercisable. If a purchaser fails to exercise such purchaser’s Series C common stock warrants in full, then the Series D common stock warrants issued to such purchaser shall automatically be cancelled and cease to be exercisable. 2021 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 public warrants, or the 2021 Public 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 2021 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 2021 Public Warrant and would have no obligation to settle such 2021 Public Warrant exercise unless a registration statement under the Securities Act with respect to the common stock underlying the 2021 Public Warrants is then effective. If the Company fails to have maintained an effective registration statement, the 2021 Public Warrant holders have the right to exercise the 2021 Public Warrants on a cashless basis until such time as there is an effective registration statement. The Company may redeem the outstanding 2021 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 transactions). Additionally, the Company may redeem the outstanding 2021 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 transactions). Notice of redemption shall be mailed to the 2021 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 2021 Public Warrant holders may elect to exercise their 2021 Public Warrants on a cashless basis based on a make-whole table. 2021 PIPE Warrants At September 30, 2024, the Company’s outstanding warrants that were issued in connection with a private placement occurring in 2021, or the 2021 PIPE Warrants, are the same in all respects as the 2021 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. The 2021 PIPE Warrants may be converted into 2021 Public Warrants on transfer pursuant to the terms of the PIPE Warrant Agreement. As of September 30, 2024 , 2.1 million 2021 PIPE Warrants had been converted into 2021 Public Warrants. Classification In no event will the Company be required to net cash settle outstanding warrants. The holders of all of the Company’s warrants do not have the rights or privileges of common stockholders and any voting rights until they exercise warrants and receive common stock. All of the Company’s outstanding warrants are classified as liabilities and recorded at fair value with subsequent change in their respective fair value recognized in other income, net within the unaudited condensed consolidated statements of operations and comprehensive loss. See Note 3 for discussion of warrant valuations.

Related Party Transactions

Related Party Transactions	9 Months Ended
Related Party Transactions	Sep. 30, 2024
Related Party Transactions [Abstract]
Related Party Transactions	Note 11. Related Party Transactions Private Placement As described in Note 9, the Company entered into a securities purchase agreement with Investors and certain members of management in April 2024, whereby the Company issued and sold to members of management 2,948 shares of common stock, at a purchase price of $ 16.96 per share for aggregate gross proceeds of $ 0.1 million. The purchase price per share of common stock includes $ 1.25 for the following 2024 PIPE 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. The terms of the 2024 PIPE Warrants held by management are the same as those held by the Investors. See Note 10 for the terms of the 2024 PIPE Warrants. Sublease In April 2024, the Company entered into a related party transaction with Nura Bio, Inc., or Nura Bio, to sublease approximately 6,102 square feet of the Company’s office and laboratory space. The sublease term is on a month-to-month basis and the monthly base rent is approximately $ 35,000 , escalating at 3 % per annum. Nura Bio is also responsible for its share of real estate taxes, utilities and other operating expenses applicable to the subleased space. During the three and nine months ended September 30, 2024 , the Company recognized sublease income of $ 0.2 million and $ 0.3 million, respectively, as reductions to operating expenses.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	9 Months Ended
Stock-Based Compensation Plans	Sep. 30, 2024
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 September 30, 2024, there were 0.1 million shares of common stock available for issuance unde r 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 September 30, 2024, there wer e 28,000 shares of common stock available for issuance under the ESPP. During the nine months ended September 30, 2024 , approximately 7,000 shares of common stock were issued under the ESPP. 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, 2023 311 $ 27.70 7.99 Granted 258 9.64 Forfeited ( 9 ) 24.31 Expired ( 7 ) 30.74 Outstanding – September 30, 2024 553 19.29 8.28 $ 786 Exercisable – September 30, 2024 240 25.72 7.16 224 The aggregate intrinsic value of options outstanding and exercisable are the difference between the exercise price of the options and the fair value of the Company’s common stock at September 30, 2024. During the nine months ended September 30, 2024 and 2023, the Company granted options with a weighted-average grant-date fair value of $ 7.45 and $ 9.47 pe r share. No options were exercised during the nine months ended September 30, 2024. During the nine months ended September 30, 2023, the intrinsic value of options exercised was de minimis. The fair value of options is estimated at the grant date using the Black-Scholes option-pricing model with the following weighted-average assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Expected term (in years) — 6.02 6.00 5.85 Expected volatility — 84.66 % 91.59 % 85.86 % Risk-free rate — 4.19 % 4.63 % 3.89 % 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, 2023 4 $ 146.92 Vested ( 3 ) 145.22 RSAs, unvested at September 30, 2024 1 149.95 The fair value of RSAs vested during the nine months ended September 30, 2024 and 2023 was de minimis in both periods. 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, 2023 90 $ 7.73 Granted 40 9.17 Vested ( 88 ) 7.73 Cancelled ( 2 ) 7.73 RSUs, unvested at September 30, 2024 40 9.17 The fair value of RSUs vested during the nine months ended September 30, 2024 and 2023 was $ 0.7 million and zero , respectively. Stock-Based Compensation Total stock-based compensation expense recorded in the unaudited condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Research and development $ 291 $ 215 $ 940 $ 882 General and administrative 748 698 2,274 2,318 Total stock-based compensation expense $ 1,039 $ 913 $ 3,214 $ 3,200 As of September 30, 2024 , there was approximately $ 4.3 million of stock-based compensation expense to be recognized over a weighted-average period of approximately 2.07 years.

Subsequent Events

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2024
Subsequent Events [Abstract]
Subsequent Events	Note 13. Subsequent Events In October 2024, the Company amended its existing lease agreement to extend the lease term from April 2025 to April 2029. The Company has an option to extend the lease for an additional four-year period and a one-time option to early terminate the lease effective as of April 30, 2026, subject to a termination fee of $ 0.4 million. The exercise of either option was not reasonably certain. The total future lease payments under the amendment are approximately $ 9.8 million.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s unaudited condensed 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. As permitted under those rules, certain notes or other financial information that are normally required by U.S. GAAP have been condensed or omitted and accordingly, the consolidated balance sheet as of December 31, 2023 has been derived from the Company’s audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete consolidated financial statements. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting of normal recurring adjustments) that are necessary for a fair presentation of the Company’s consolidated financial statements. The results of operations for the three and nine months ended September 30, 2024 are not necessarily indicative of the results to be expected for the year ended December 31, 2024 or for any other interim period or future year. The unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiary. All intercompany transactions and balances have been eliminated. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2023 included in the Company’s Annual Report on Form 10-K , filed with the SEC on April 10 , 2024.
Use of Estimates	Use of Estimates The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP r equires 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 unaudited condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions made in the accompanying unaudited condensed consolidated financial statements include certain accrued expenses for research and development activities and fair value of warrants issued in connection with the closing of a private placement in April 2024. 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	Concentration of Credit Risk Financial instruments, which potentially subject the Company to significant concentration of credit risk, consist of cash and cash equivalents. 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 unaudited condensed consolidated balance sheets. The Company believes it is not exposed to significant credit risk on cash. The Company’s cash equivalents were held in custodial accounts maintained by third-party custodians. The Company’s policy is to invest cash in institutional money market funds with high credit quality to limit the amount of credit exposure. The Company has not experienced any losses on its cash equivalents.
Revenue Recognition	Revenue Recognition 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. The Company determined that 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 the non-refundable upfront payment. Variable consideration related to future milestones is 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. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded as revenue on a cumulative catch-up basis during the period of adjustment. The Company will recognize 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).
Warrant Liabilities	Warrant Liabilities The Company's warrants are classified as liabilities and measured at fair value. Transaction costs associated with the warrant liabilities are recognized as other expenses when incurred. At the end of each reporting period, any change in fair value during the period are recognized in other income, net within the unaudited consolidated statements of operations and comprehensive loss. The Company will continue to adjust the warrant liabilities 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.
Net Loss Per Share	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. Diluted net loss per share is calculated using the more dilutive of the two-class method or treasury method. The Company’s 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 s hares of 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): September 30, 2024 2023 Common stock issuable upon exercise of stock options 553 317 Unvested restricted stock awards 1 5 Unvested restricted stock units 40 90 Common stock issuable upon exercise of warrants 11,569 394 Total 12,163 806
Recent Accounting Pronouncements	Recent Accounting Pronouncements In August 2020, the FASB issued Accounting Standards Update 2020-06, Debt — Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging — Contracts in Entity’s Own Equity (Subtopic 815-40). This standard eliminates the beneficial conversion and cash conversion accounting models for convertible instruments, amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions, and modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted earning per share calculation. The standard is effective for annual periods beginning after December 15, 2023 for smaller reporting companies, and interim periods within those reporting periods. The Company adopted this standard effective January 1, 2024, using a modified retrospective method. The adoption of the standard did not have a material impact on the Company's unaudited condensed consolidated financial statements and related disclosures. In December 2023, the 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 unaudited condensed 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 within fiscal years beginning after December 15, 2024. 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 unaudited condensed consolidated financial statements and related disclosures

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
Summary of Significant Accounting Policies (Tables)	Sep. 30, 2024
Accounting Policies [Abstract]
Schedule of Anti-dilutive Securities Excluded from Computation of Earnings Per Share	The following table presents the potential s hares of 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): September 30, 2024 2023 Common stock issuable upon exercise of stock options 553 317 Unvested restricted stock awards 1 5 Unvested restricted stock units 40 90 Common stock issuable upon exercise of warrants 11,569 394 Total 12,163 806

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	9 Months Ended
Fair Value Measurement (Tables)	Sep. 30, 2024
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 September 30, 2024 Level 1 Level 2 Level 3 Total Assets: Money market funds (1) $ 28,179 $ — $ — $ 28,179 Total financial assets measured at fair value $ 28,179 $ — $ — $ 28,179 Liabilities (2) : 2021 Public Warrants $ 50 $ — $ — $ 50 2021 PIPE Warrants — 11 — 11 2024 Pre-Funded Warrants — 479 — 479 2024 PIPE Warrants — — 35,671 35,671 Total financial liabilities measured at fair value $ 50 $ 490 $ 35,671 $ 36,211 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) : 2021 Public Warrants $ 53 $ — $ — $ 53 2021 PIPE Warrants — 62 — 62 Total financial liabilities measured at fair value $ 53 $ 62 $ — $ 115 (1) Included in cash and cash equivalents on the condensed consolidated balance sheets. (2) See Note 10.
Schedule of Fair Value Measurement Key Inputs	The key inputs into the fair value measurement of the 2024 PIPE Warrants were as follows at the initial measurement and September 30, 2024: September 30, April 4, 2024 2024 Expected term (in years) 0.3 - 4.5 0.8 - 5.0 Expected volatility 95 % 100 % Risk-free interest rate 3.6 % - 4.8 % 4.4 % - 5.2 % Dividend yield — —
Schedule of Fair Value Measurement of 2024 PIPE Warrants	2024 PIPE Balance, December 31, 2023 $ — Issuance in the Private Placement 37,494 Change in fair value upon remeasurement (1) ( 5,004 ) Balance, June 30, 2024 32,490 Change in fair value upon remeasurement (1) 3,181 Balance, September, 30, 2024 $ 35,671 (1) Included in other (expense) income, net on the condensed consolidated statement of operations.

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
Balance Sheet Components (Tables)	Sep. 30, 2024
Balance Sheet Related Disclosures [Abstract]
Schedule of Prepaid Expense and Other Current Assets	Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): September 30, December 31, 2024 2023 Prepaid research and development expenses $ 715 $ 1,751 Prepaid insurance 632 606 Other 731 580 Prepaid expenses and other current assets $ 2,078 $ 2,937
Schedule of Accrued Liabilities	Accrued and other liabilities consist of the following (in thousands): September 30, December 31, 2024 2023 Accrued payroll and related expenses $ 2,443 $ 2,508 Accrued research and development expenses 1,626 1,261 Accrued professional service fees 87 65 Other 161 292 Accrued and other liabilities $ 4,317 $ 4,126

Restructuring (Tables)

Restructuring (Tables)	9 Months Ended
Restructuring (Tables)	Sep. 30, 2024
Restructuring Reserve [Abstract]
Schedule Of Restructuring And Related Cost	The outstanding restructuring liabilities are included in accrued and other liabilities on the condensed consolidated balance sheet. The following tables summarize activity during the three and nine months ended September 30, 2024 and 2023 (in thousands): Employee Severance and Other Benefits Balance, December 31, 2023 $ 74 Cash payments ( 44 ) Personnel adjustments ( 30 ) Balance, September 30, 2024 $ — Employee Severance and Other Benefits Balance, December 31, 2022 $ — Restructuring charges 1,207 Cash payments ( 726 ) Balance, March 31, 2023 481 Cash payments ( 457 ) Balance, June 30, 2023 24 Restructuring charges 1,505 Cash payments ( 1,304 ) Balance, September 30, 2023 $ 225

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
Commitments and Contingencies (Tables)	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Summary of Lessee, Operating Lease, Liability, Maturity	Aggregate future minimum rental payments under the operating leases as of September 30, 2024, were as follows (in thousands): Remaining three months ending December 31, 2024 $ 668 Year ending December 31, 2025 891 Total lease payments 1,559 Less: Imputed interest ( 32 ) Operating lease liabilities $ 1,527

Common Stock Warrants (Tables)

Common Stock Warrants (Tables)	9 Months Ended
Common Stock Warrants (Tables)	Sep. 30, 2024
Equity [Abstract]
Schedule of Common Stock Warrants Outstanding	The following table sets forth the common stock warrants outstanding as of September 30, 2024 and December 31, 2023 (in thousands, except exercise price per warrant): Exercise Price per Share — Exercise Price per Share — September 30, December 31, Type Classification Investor Management 2024 2023 2024 Pre-Funded Warrants Liability $ 0.0001 N/A 40 — 2024 PIPE Warrants – Series A Liability 15.50 $ 16.96 1,132 — 2024 PIPE Warrants – Series B Liability 14.25 15.71 1,231 — 2024 PIPE Warrants – Series C Liability 16.00 16.00 4,386 — 2024 PIPE Warrants – Series D Liability 16.00 16.00 4,386 — 2021 Public Warrants Liability 172.50 N/A 4,883 2,733 2021 PIPE Warrants Liability 172.50 N/A 1,024 3,174 Total 17,082 5,907

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	9 Months Ended
Stock-Based Compensation Plans (Tables)	Sep. 30, 2024
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, 2023 311 $ 27.70 7.99 Granted 258 9.64 Forfeited ( 9 ) 24.31 Expired ( 7 ) 30.74 Outstanding – September 30, 2024 553 19.29 8.28 $ 786 Exercisable – September 30, 2024 240 25.72 7.16 224
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: Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Expected term (in years) — 6.02 6.00 5.85 Expected volatility — 84.66 % 91.59 % 85.86 % Risk-free rate — 4.19 % 4.63 % 3.89 % Dividend yield — — — —
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, 2023 4 $ 146.92 Vested ( 3 ) 145.22 RSAs, unvested at September 30, 2024 1 149.95
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, 2023 90 $ 7.73 Granted 40 9.17 Vested ( 88 ) 7.73 Cancelled ( 2 ) 7.73 RSUs, unvested at September 30, 2024 40 9.17
Schedule of Stock-Based Compensation Expense	Total stock-based compensation expense recorded in the unaudited condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Research and development $ 291 $ 215 $ 940 $ 882 General and administrative 748 698 2,274 2,318 Total stock-based compensation expense $ 1,039 $ 913 $ 3,214 $ 3,200

Organization and Business - Add

Organization and Business - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Subsidiary Sale Of Stock [Line Items]
Net loss		$ (1,434)	$ (10,445)	$ (35,525)	$ (34,129)
Net cash used in operation				(21,109)	(33,052)
Cash and cash equivalents		31,012	33,975	31,012	33,975	$ 36,043
Accumulated deficit		(257,220)		$ (257,220)		$ (221,695)
Stockholders' equity, 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.
Loss from operations		$ 1,232	$ (11,189)	$ (16,947)	$ (36,056)
Milestone Payments	$ 10,000			$ 10,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	12,163,000	806,000
Common stock issuable upon exercise of stock options [Member]
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	553,000	317,000
Unvested restricted stock awards [Member]
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	1,000	5,000
Unvested restricted stock units [Member]
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	40,000	90,000
Common stock issuable upon exercise of warrants [Member]
Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	11,569,000	394,000

Recapitalization - Additional I

Recapitalization - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Apr. 30, 2024	Dec. 31, 2023
Subsidiary Sale Of Stock [Line Items]
Shares issued, price per share			$ 15.5
Proceeds from issuance of common stock, pre-funded warrants and warrants in the Private Placement, net of transaction costs	$ 16,043	$ 0
Common shares, shares outstanding	3,250,000			2,063,000
Common stock shares issued	3,250,000			2,063,000

Fair Value Measurement - Schedu

Fair Value Measurement - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands		Sep. 30, 2024	Dec. 31, 2023
Assets:
Assets		$ 28,179	$ 33,014
Liabilities:
Liabilities	[1]	36,211	115
Money Market Funds [Member]
Assets:
Assets	[2]	28,179	33,014
2021 Public Warrants [Member]
Liabilities:
Liabilities	[1]	50	53
2021 PIPE Warrants [Member]
Liabilities:
Liabilities	[1]	11	62
2024 Pre-Funded Warrants [Member]
Liabilities:
Liabilities	[1]	479
2024 PIPE Warrants [Member]
Liabilities:
Liabilities	[1]	35,671
Level 1 [Member]
Assets:
Assets		28,179	33,014
Liabilities:
Liabilities	[1]	50	53
Level 1 [Member] \| Money Market Funds [Member]
Assets:
Assets	[2]	28,179	33,014
Level 1 [Member] \| 2021 Public Warrants [Member]
Liabilities:
Liabilities	[1]	50	53
Level 1 [Member] \| 2021 PIPE Warrants [Member]
Liabilities:
Liabilities	[1]	0	0
Level 1 [Member] \| 2024 Pre-Funded Warrants [Member]
Liabilities:
Liabilities	[1]	0
Level 1 [Member] \| 2024 PIPE Warrants [Member]
Liabilities:
Liabilities	[1]	0
Level 2 [Member]
Assets:
Assets		0	0
Liabilities:
Liabilities	[1]	490	62
Level 2 [Member] \| Money Market Funds [Member]
Assets:
Assets	[2]	0	0
Level 2 [Member] \| 2021 Public Warrants [Member]
Liabilities:
Liabilities	[1]	0	0
Level 2 [Member] \| 2021 PIPE Warrants [Member]
Liabilities:
Liabilities	[1]	11	62
Level 2 [Member] \| 2024 Pre-Funded Warrants [Member]
Liabilities:
Liabilities	[1]	479
Level 2 [Member] \| 2024 PIPE Warrants [Member]
Liabilities:
Liabilities	[1]	0
Level 3 [Member]
Assets:
Assets		0	0
Liabilities:
Liabilities	[1]	35,671	0
Level 3 [Member] \| Money Market Funds [Member]
Assets:
Assets	[2]	0	0
Level 3 [Member] \| 2021 Public Warrants [Member]
Liabilities:
Liabilities	[1]	0	0
Level 3 [Member] \| 2021 PIPE Warrants [Member]
Liabilities:
Liabilities	[1]	0	$ 0
Level 3 [Member] \| 2024 Pre-Funded Warrants [Member]
Liabilities:
Liabilities	[1]	0
Level 3 [Member] \| 2024 PIPE Warrants [Member]
Liabilities:
Liabilities	[1]	$ 35,671

[1] See Note 10. Included in cash and cash equivalents on the condensed consolidated balance sheets.

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Dec. 31, 2023 USD ($)	Sep. 30, 2024 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Transfers of financial instruments		$ 0
Fixed asset impairment loss	$ 200
Measurement Input, Dividend Yield [Member] \| 2021 PIPE Warrants [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment, measurement input		0

Fair Value Measurement - Sche_2

Fair Value Measurement - Schedule of Fair Value Measurement Key Inputs (Details)	Sep. 30, 2024	Apr. 04, 2024
Measurement Input, Expected Volatility [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input	0.95	1
Measurement Input, Dividend Yield [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input	0	0
Minimum [Member] \| Measurement Input, Expected Term [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Expected term (in years)	3 months 18 days	9 months 18 days
Minimum [Member] \| Measurement Input, Risk-free Interest Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input	0.036	0.044
Maximum [Member] \| Measurement Input, Expected Term [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Expected term (in years)	4 years 6 months	5 years
Maximum [Member] \| Measurement Input, Risk-free Interest Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input	0.048	0.052

Fair Value Measurement - Sche_3

Fair Value Measurement - Schedule of Fair Value Measurement of 2024 PIPE Warrants (Details) - 2024 PIPE Warrants [Member] - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
		Sep. 30, 2024	Jun. 30, 2024
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Balance, beginning of period		$ 32,490	$ 0
Issuance in the Private Placement			37,494
Change in fair value upon remeasurement	[1]	3,181	(5,004)
Balance, end of period		$ 35,671	$ 32,490

[1] Included in other (expense) income, net on the condensed consolidated statement of operations.

Balance Sheet Component - Sched

Balance Sheet Component - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Prepaid research and development expenses	$ 715	$ 1,751
Prepaid insurance	632	606
Others	731	580
Prepaid expenses and other current assets	$ 2,078	$ 2,937

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Accrued payroll and related expenses	$ 2,443	$ 2,508
Accrued research and development expenses	1,626	1,261
Accrued professional service fees	87	65
Other	161	292
Accrued and other liabilities	$ 4,317	$ 4,126

Restructuring (Additional Infor

Restructuring (Additional Information) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Mar. 31, 2024	Sep. 30, 2023	Mar. 31, 2023	Mar. 31, 2024
Restructuring Reserve [Abstract]
Restructuring Charges		$ 1,505	$ 1,207
Other Restructuring Costs				$ 1,500
Reduction in workforce	38%		25%

Restructuring - Schedule of out

Restructuring - Schedule of outstanding restructuring liabilities on the condensed consolidated balance sheets (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024
Restructuring Cost and Reserve [Line Items]
Restructuring begining balance				$ 0
Cash payments		$ (1,304)	$ (457)	(726)
Restructuring Charges		1,505		1,207
Restructuring ending balance		$ 225	$ 24	$ 481
Employee Severance and Other Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring begining balance					$ 74
Cash payments	$ (44)				(44)
Personnel adjustment	(30)				(30)
Restructuring ending balance	$ 0				$ 0

Collaboration and License Agr_2

Collaboration and License Agreements (Additional Information) (Details) - USD ($) $ in Millions	1 Months Ended			9 Months Ended
	Oct. 31, 2024	Nov. 30, 2022	Oct. 31, 2022	Sep. 30, 2024
Research and Development Arrangement, Contract to Perform for Others [Line Items
Milestone Payments	$ 10			$ 10
Collaboration and License Agreement with BI [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items
Non-refundable upfront payment received			$ 12.5	$ 10
Success-based milestone payments			587
Upfront payment		$ 10.5
Associated withholding tax			2.1
Transaction price			$ 12.5

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Aug. 31, 2016 ft²
Lessee, Lease, Description [Line Items]
Operating Lease, Expense	$ 0.4	$ 0.4	$ 1.2	$ 1.2
CALIFORNIA \| Eight Years [Member]
Lessee, Lease, Description [Line Items]
Area of Real Estate Property \| ft²					32,813
Restricted Cash	$ 0.4		$ 0.4

Commitments and Contingencies_2

Commitments and Contingencies - Summary Of Lessee, Operating Lease, Liability, Maturity (Detail) $ in Thousands	Sep. 30, 2024 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Remaining three months ending December 31, 2024	$ 668
Year ending December 31, 2025	891
Total lease payments	1,559
Less: Imputed interest	(32)
Operating lease liabilities	$ 1,527

License Agreements - Additional

License Agreements - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended
	Jun. 30, 2018	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
License Agreements [Line Items]
Research and development expense				$ 5,200	$ 6,112	$ 15,782	$ 21,135
Stanford License Agreements [Member] \| Stanford [Member]
License Agreements [Line Items]
Payments for milestone agreement or earned royalties on achievement of milestones			$ 5,000
Payments for achievement of specified development and regulatory milestones	$ 400
Payments for milestone agreement on achievement of milestones						0
Stanford License Agreements [Member] \| Stanford [Member] \| Maximum
License Agreements [Line Items]
Payments for milestone agreement or earned royalties on achievement of milestones			$ 900
UCSF License And Option Agreements [Member]
License Agreements [Line Items]
Payments for milestone agreement on achievement of milestones						$ 0
Distributed Bio Subscription Agreement [Member]
License Agreements [Line Items]
Payments for achievement of specified development and regulatory milestones		$ 5,900
Distributed Bio Subscription Agreement [Member] \| Stanford [Member]
License Agreements [Line Items]
Research and development expense					$ 100		$ 200

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		9 Months Ended
	Apr. 30, 2024	Apr. 30, 2024	Feb. 28, 2022	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Equity Financing shares		1,100,000
Warrants issued to purchase common stock	40,000	40,000		17,082,000		5,907,000
Warrants to purchase common stock ,value	11,100,000	11,100,000
Fair value of warrants issued	$ 37,900
Gross Proceeds From Issuance Of Common Stock		$ 17,500
Purchase price per share	$ 15.5	$ 15.5
Pre-Funded Warrants Purchase Price	$ 15.4999	$ 15.4999
Other expenses	$ 1,500
Common stock shares issued				3,250,000		2,063,000
Common stock issued				$ 0		$ 0
Loss on issuance of common stock, pre-funded warrants and warrants		$ 20,400		$ 20,397	$ 0
Lincoln Park [Member]
Common stock shares issued				0
Common stock with the fair value			$ 300
Payments of Stock Issuance Costs			100
Stock issued during period shares new shares				0
Lincoln Park [Member] \| Maximum
Sale of Stock, Consideration Received on Transaction			50,000
Lincoln Park [Member] \| Minimum
Sale of Stock, Consideration Received on Transaction			$ 30,000
Guggenheim Securities, LLC [Member]
Common stock issued							$ 23,000
Compensation payable							3%

Common Stock Warrants - Additio

Common Stock Warrants - Additional Information (Details) $ / shares in Units, $ in Millions		9 Months Ended
	Apr. 30, 2024 USD ($) Patient $ / shares shares	Sep. 30, 2024 $ / shares shares	Dec. 31, 2023 shares
Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1 \| $ / shares		$ 172.5
Common Stock Warrants Expiration Date		Aug. 12, 2026
Warrants issued to purchase common stock	40,000	17,082,000	5,907,000
Warrant Redemption Condition Minimum Share Price Scenario Two \| $ / shares		$ 270
Common stock shares issued		3,250,000	2,063,000
Warrants to purchase common stock ,value	11,100,000
Common Stock
Purchase price per share accompanying common stock warrants \| $ / shares	$ 1.25
2024 PIPE Warrants - Series A [Member]
Warrants issued to purchase common stock		1,132,000	0
2024 PIPE Warrants - Series A [Member] \| Common Stock
Warrants or Rights Exercisable, Period	5 years
2024 PIPE Warrants - Series A [Member] \| Common Stock \| Private Placement [Member]
Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1 \| $ / shares	$ 15.5
Warrants to purchase common stock ,value	1,100,000
2024 PIPE Warrants - Series A [Member] \| Maximum [Member] \| Common Stock \| Private Placement [Member]
Proceeds from issuance of warrants \| $	$ 17.5
2024 PIPE Warrants - Series B [Member]
Warrants issued to purchase common stock		1,231,000	0
2024 PIPE Warrants - Series B [Member] \| Common Stock
Warrants or Rights Exercisable, Period	5 days
2024 PIPE Warrants - Series B [Member] \| Common Stock \| Private Placement [Member]
Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1 \| $ / shares	$ 14.25
Warrants to purchase common stock ,value	1,200,000
2024 PIPE Warrants - Series B [Member] \| Minimum [Member] \| Common Stock
Number of patients enrolled \| Patient	15
2024 PIPE Warrants - Series B [Member] \| Maximum [Member] \| Common Stock \| Private Placement [Member]
Proceeds from issuance of warrants \| $	$ 17.5
2024 PIPE Warrants - Series C [Member]
Warrants issued to purchase common stock		4,386,000	0
2024 PIPE Warrants - Series C [Member] \| Common Stock
Warrants or Rights Exercisable, Period	30 days
2024 PIPE Warrants - Series C [Member] \| Common Stock \| Private Placement [Member]
Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1 \| $ / shares	$ 16
Warrants to purchase common stock ,value	4,400,000
2024 PIPE Warrants - Series C [Member] \| Maximum [Member] \| Common Stock \| Private Placement [Member]
Proceeds from issuance of warrants \| $	$ 70
2024 PIPE Warrants - Series D [Member]
Warrants issued to purchase common stock		4,386,000	0
2024 PIPE Warrants - Series D [Member] \| Common Stock
Warrants or Rights Exercisable, Period	30 days
2024 PIPE Warrants - Series D [Member] \| Common Stock \| Private Placement [Member]
Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1 \| $ / shares	$ 16
Warrants to purchase common stock ,value	4,400,000
2024 PIPE Warrants - Series D [Member] \| Minimum [Member] \| Common Stock
Number of patients enrolled \| Patient	50
2024 PIPE Warrants - Series D [Member] \| Maximum [Member] \| Common Stock \| Private Placement [Member]
Proceeds from issuance of warrants \| $	$ 70
2021 Public Warrants [Member]
Warrant Redemption Period		30 days
Warrants issued to purchase common stock		4,883,000	2,733,000
Warrant redemption condition minimum share price scenario one \| $ / shares		$ 150
Common stock shares issued		1
2021 Public Warrants [Member] \| Common Stock, Closing Price equals or Exceeds $270.00 Per Share [Member]
Redemption Price Per Public Warrant \| $ / shares		$ 0.01
Common stock Purchase price \| $ / shares		270
2021 Public Warrants [Member] \| Common Stock, Closing Price equals or Exceeds $150.00 Per Share [Member]
Redemption Price Per Public Warrant \| $ / shares		0.1
Common stock Purchase price \| $ / shares		$ 150
2021 Public Warrants [Member] \| Common Stock
Warrants issued to purchase common stock		15
2021 PIPE Warrants [Member]
Warrants issued to purchase common stock		1,024,000	3,174,000
Number of Converted Warrants		2,100,000

Common Stock Warrants - Schedul

Common Stock Warrants - Schedule of Common Stock Warrants Outstanding (Details) - $ / shares	9 Months Ended
	Sep. 30, 2024	Apr. 30, 2024	Dec. 31, 2023
Class Of Warrant Or Right [Line Items]
Common Stock Warrants Expiration Date	Aug. 12, 2026
Common stock warrants exercise price per share	$ 172.5
Common stock warrants outstanding	17,082,000	40,000	5,907,000
2024 Pre-Funded Warrants [Member]
Class Of Warrant Or Right [Line Items]
Common Stock Warrant Classification	Liability
Common stock warrants outstanding	40,000		0
2024 Pre-Funded Warrants [Member] \| Investor [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 0.0001
2024 PIPE Warrants - Series A [Member]
Class Of Warrant Or Right [Line Items]
Common Stock Warrant Classification	Liability
Common stock warrants outstanding	1,132,000		0
2024 PIPE Warrants - Series A [Member] \| Investor [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 15.5
2024 PIPE Warrants - Series A [Member] \| Management [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 16.96
2024 PIPE Warrants - Series B [Member]
Class Of Warrant Or Right [Line Items]
Common Stock Warrant Classification	Liability
Common stock warrants outstanding	1,231,000		0
2024 PIPE Warrants - Series B [Member] \| Investor [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 14.25
2024 PIPE Warrants - Series B [Member] \| Management [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 15.71
2024 PIPE Warrants - Series C [Member]
Class Of Warrant Or Right [Line Items]
Common Stock Warrant Classification	Liability
Common stock warrants outstanding	4,386,000		0
2024 PIPE Warrants - Series C [Member] \| Investor [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 16
2024 PIPE Warrants - Series C [Member] \| Management [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 16
2024 PIPE Warrants - Series D [Member]
Class Of Warrant Or Right [Line Items]
Common Stock Warrant Classification	Liability
Common stock warrants outstanding	4,386,000		0
2024 PIPE Warrants - Series D [Member] \| Investor [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 16
2024 PIPE Warrants - Series D [Member] \| Management [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 16
2021 Public Warrants [Member]
Class Of Warrant Or Right [Line Items]
Common Stock Warrant Classification	Liability
Common stock warrants outstanding	4,883,000		2,733,000
2021 Public Warrants [Member] \| Investor [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 172.5
2021 PIPE Warrants [Member]
Class Of Warrant Or Right [Line Items]
Common Stock Warrant Classification	Liability
Common stock warrants outstanding	1,024,000		3,174,000
2021 PIPE Warrants [Member] \| Investor [Member]
Class Of Warrant Or Right [Line Items]
Common stock warrants exercise price per share	$ 172.5

Related Party Transactions (Add

Related Party Transactions (Additional Information) (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	Apr. 30, 2024 USD ($) ft² $ / shares shares	Sep. 30, 2024 USD ($)	Sep. 30, 2024 USD ($)
Nura Bio \| Sublease Agreement
Sublease office and laboratory space \| ft²	6,102
Sublease term	month-to-month
Rental income \| $	$ 35,000
Percentage of increase in base rent	3%
Sublease Income \| $		$ 200	$ 300
Series A Common Stock \| Private Placement [Member] \| 2024 PIPE Warrants
Warrant exercise price	$ 16.96
Series A Common Stock \| Private Placement [Member] \| 2024 PIPE Warrants \| Maximum
Warrants to purchase common stock \| shares	2,948
Series B Common Stock \| Private Placement [Member] \| 2024 PIPE Warrants
Warrant exercise price	$ 15.71
Series B Common Stock \| Private Placement [Member] \| 2024 PIPE Warrants \| Maximum
Warrants to purchase common stock \| shares	3,206
Series C Common Stock \| Private Placement [Member] \| 2024 PIPE Warrants
Warrant exercise price	$ 16
Series C Common Stock \| Private Placement [Member] \| 2024 PIPE Warrants \| Maximum
Warrants to purchase common stock \| shares	11,424
Series D Common Stock \| Private Placement [Member] \| 2024 PIPE Warrants
Warrant exercise price	$ 16
Series D Common Stock \| Private Placement [Member] \| 2024 PIPE Warrants \| Maximum
Warrants to purchase common stock \| shares	11,424
Members of Management \| Private Placement [Member]
Number of shares sold and issued \| shares	2,948
Purchase price	$ 16.96
Proceeds from sale of shares \| $	$ 100
Purchase price per share accompanying common stock warrants	$ 1.25

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value/shares	$ 7.45	$ 9.47
Unrecognized stock based compensation expense	$ 4.3
Weighted-average period	2 years 25 days
RSU [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of RSU vested	$ 0.7	$ 0
2021 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance	100,000
Options \| 2021 Stock Plan
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.
Options \| Maximum \| 2021 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period	10 years
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance	28,000
Shares Issued under ESPP	7,000
Percentage of discount payroll deductions	15%
Common Stock Trading Discription	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

Stock-Based Compensation Plansn

Stock-Based Compensation Plansn - Summary of Stock Option Activity for Company's Stock Option Plans (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of Options Outstanding Beginning Balance	311
Number of Options Granted	258
Number of Options Forfeited	(9)
Number of Options Expired	(7)
Number of Options Outstanding Ending Balance	553	311
Number of Options outstanding and Exercisable	240
Weighted Average Exercise Price Outstanding, Beginning Balance	$ 27.7
Weighted Average Exercise Price Granted	9.64
Weighted Average Exercise Price Forfeited	24.31
Weighted Average Exercise Price Expired	30.74
Weighted Average Exercise Price Outstanding, Ending Balance	19.29	$ 27.7
Weighted Average Exercise Price Options Outstanding and Exercisable	$ 25.72
Weighted Average Remaining Contractual Life (In Years)	8 years 3 months 10 days	7 years 11 months 26 days
Weighted Average Remaining Contractual Life, Exercisable (In Years)	7 years 1 month 28 days
Aggregate Intrinsic Value	$ 786
Aggregate Intrinsic Value Options outstanding and exercisable	$ 224

Stock-Based Compensation Plan_3

Stock-Based Compensation Plans - Schedule of Weighted Average Assumptions Used to Estimate Fair Value of Options (Details) - Stock Option	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (in years)		6 years 7 days	6 years	5 years 10 months 6 days
Expected volatility	0%	84.66%	91.59%	85.86%
Risk-free rate	0%	4.19%	4.63%	3.89%
Dividend yield	0%	0%	0%	0%

Stock-Based Compensation Plan_4

Stock-Based Compensation Plans - Summary of RSA Activity (Details) - RSA [Member] shares in Thousands	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares RSA, unvested, Beginning Balance \| shares	4
Weighted Average Grant Date Fair Value, RSA Unvested Beginning Balance \| $ / shares	$ 146.92
Number of Shares RSAs, Vested \| shares	(3)
Weighted Average Grant Date Fair Value RSUs, Vested \| $ / shares	$ 145.22
Number of Shares RSA, unvested, Ending Balance \| shares	1
Weighted Average Grant Date Fair Value RSA, Unvested Ending Balance \| $ / shares	$ 149.95

Stock-Based Compensation Plan_5

Stock-Based Compensation Plans - Summary of RSU Activity (Details) (Details) - Restricted Stock Units (RSUs) [Member] shares in Thousands	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of Shares RSA, unvested, Beginning Balance \| shares	90
Weighted Average Grant Date Fair Value, RSA Unvested Beginning Balance \| $ / shares	$ 7.73
Number of Shares RSU, Granted \| shares	40
Weighted Average Grant Date Fair Value, Granted \| $ / shares	$ 9.17
Number of Shares RSAs, Vested \| shares	(88)
Weighted Average Grant Date Fair Value RSUs, Vested \| $ / shares	$ 7.73
Number of shared ,RSU, cancelled \| shares	(2)
Weighted average grant date fair value, cancelled \| $ / shares	7.73
Number of Shares RSA, unvested, Ending Balance \| shares	40
Weighted Average Grant Date Fair Value RSA, Unvested Ending Balance \| $ / shares	$ 9.17

Stock-Based Compensation Plan_6

Stock-Based Compensation Plans - Schedule of Stock-Based Compensation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
General and administrative	$ 3,568	$ 3,572	$ 11,165	$ 12,209
Total stock-based compensation expense	1,039	913	3,214	3,200
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Research and development	291	215	940	882
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
General and administrative	$ 748	$ 698	$ 2,274	$ 2,318

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Subsequent Event [Line Items]
Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1		$ 172.5		$ 172.5
Research and Development Expense		$ 5,200	$ 6,112	$ 15,782	$ 21,135
Total lease payments		$ 1,559		$ 1,559
Subsequent Event [Member] \| TCGFB, Inc [Member]
Subsequent Event [Line Items]
Warrant Issue	3.4
Exercise Price	$ 0.0001
Company Research Services	$ 6,000
Four Years [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Extended lease term	four-year
Termination fee	$ 400
Total lease payments	$ 9,800