Unity Biotechnology (UBX) 10-K 15 Apr 24 2023 FY Annual report Financial data

Document and Entity Information

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

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023		Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022		Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 19,803		$ 7,876	$ 19,118	$ 22,972	$ 12,736		$ 22,576		$ 32,905
Short-term marketable securities	23,398		38,063	49,974	60,420	82,059		76,364
Prepaid expenses and other current assets	3,404		3,599	3,874	2,989	1,740		3,084
Total current assets	46,605		49,538	72,966	86,381	96,535		102,574
Property and equipment, net	5,082		5,314	7,181	7,496	7,825		8,202
Operating lease right-of-use asset	12,981		13,522	18,061	18,557	19,042		19,515
Long-term restricted cash	896		896	896	896	896		896
Other long-term assets	126			5	29	52		76
Total assets	65,690		69,270	101,008	114,255	124,350		136,243
Current liabilities:
Accounts payable	1,380		1,149	1,449	1,470	1,790		2,444
Accrued compensation	1,841		2,226	1,652	1,983	3,020		2,961
Accrued and other current liabilities	4,619		5,258	5,417	5,343	5,334		5,321
Current portion of long-term debt	0			13,623	13,062	9,476		6,776
Total current liabilities	7,840		8,633	22,141	21,858	19,620		17,502
Operating lease liability, net of current portion	23,539		24,431	25,297	26,150	26,991		27,792
Long-term debt, net	0			4,067	7,619	10,891		13,262
Warrant liability	5,913		8,481	8,734	5,273	10,764		16,633
Total liabilities	37,292		41,545	60,239	60,900	68,266		75,189
Commitments and contingencies (Note 9)
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding	0		0	0	0	0		0
Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2023 and 2022; 16,784,969 and 14,215,302 shares issued and outstanding as of December 31, 2023 and 2022, respectively	2	[1]	1	1	1	1	[1]	1
Additional paid-in capital	512,773		507,789	506,132	503,276	500,827		498,401
Accumulated other comprehensive gain	(24)		(55)	(136)	(150)	(251)		(275)
Accumulated deficit	(484,353)		(480,010)	(465,228)	(449,772)	(444,493)		(437,073)
Total stockholders’ equity	28,398		27,725	40,769	53,355	56,084		61,054	$ 39,931	$ 59,569	$ 82,881
Total liabilities and stockholders’ equity	$ 65,690		$ 69,270	$ 101,008	$ 114,255	$ 124,350		$ 136,243
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Balance Sheets (Parenthetical)

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

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Licensing revenue – Related Party		$ 0		$ 0	$ 0		$ 236	$ 0		$ 236		$ 4,784
Operating expenses:
Research and development	$ 4,632	6,435	$ 5,760	9,086	12,195	$ 16,828	29,100	20,099		36,859		38,393
General and administrative	4,347	5,413	4,798	4,922	10,212	14,560	15,669	18,966		20,949		23,056
Impairment of long-lived assets	5,602					5,602		5,602		0		0
Total operating expenses	14,581	11,848	10,558	14,008	22,407	36,990	44,769	44,667		57,808		61,449
Loss from operations	(14,581)	(11,848)	(10,558)	(14,008)	(22,407)	(36,990)	(44,533)	(44,667)		(57,572)		(56,665)
Interest income	689	805	855	329	1,660	2,349	416	2,874		1,220		100
Interest expense	(566)	(883)	(1,002)	(866)	(1,885)	(2,451)	(2,568)	(2,452)		(3,558)		(3,177)
Gain (loss) on warrant liability								6,215		16,843		0
Other expense, net	(577)	(69)	(65)	(1,426)	(133)	(711)	(1,336)	(1,830)		(1,402)		(983)
Net loss	(14,782)	(15,456)	(5,279)	(4,997)	(20,735)	(35,520)	(37,047)	(39,860)		(44,469)		(60,725)
Other comprehensive gain (loss)
Unrealized gain (loss) on marketable debt securities	81	14	101	(88)	115	196	(231)	227		(207)		(49)
Comprehensive loss	$ (14,701)	$ (15,442)	$ (5,178)	$ (5,085)	$ (20,620)	$ (35,324)	$ (37,278)	$ (39,633)		$ (44,676)		$ (60,774)
Net loss per share, basic	$ (1.01)	$ (1.07)	$ (0.37)	$ (0.5)	$ (1.44)	$ (2.46)	$ (4.67)	$ (2.7)		$ (4.68)		$ (10.88)
Net loss per share, diluted	$ (1.01)	$ (1.07)	$ (0.37)	$ (0.5)	$ (1.44)	$ (2.46)	$ (4.67)	$ (2.7)		$ (4.68)		$ (10.88)
Weighted average number of shares used in computing net loss per share, basic	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729	14,773,612	[1]	9,494,421	[1]	5,581,587	[1]
Weighted average number of shares used in computing net loss per share, diluted	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729	14,773,612	[1]	9,494,421	[1]	5,581,587	[1]
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded up to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Statements of Operations and _2

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

Statements of Stockholders' Equ

Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	At The Market Equity Offering Program	Equity Purchase Agreement Lincoln Park Capital Fund LLC	Follow-On Offering	Warrant Inducement Agreement	Loan Agreement Hercules Capital	Common Stock		Common Stock At The Market Equity Offering Program		Common Stock Equity Purchase Agreement Lincoln Park Capital Fund LLC	Common Stock Follow-On Offering	Common Stock Warrant Inducement Agreement	[1]	Common Stock Loan Agreement Hercules Capital	Additional Paid-In Capital	Additional Paid-In Capital At The Market Equity Offering Program	Additional Paid-In Capital Equity Purchase Agreement Lincoln Park Capital Fund LLC	Additional Paid-In Capital Follow-On Offering	Additional Paid-In Capital Warrant Inducement Agreement	Additional Paid-In Capital Loan Agreement Hercules Capital	Related Party Promissory Notes for Purchase of Common Stock	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2020		$ 82,881						$ 1	[1]								$ 422,384						$ (210)	$ 5	$ (339,299)
Beginning balance, (in shares) at Dec. 31, 2020	[1]							5,325,288
Issuance of common stock, net of issuance costs			$ 10,357	$ 9,039			$ 2,704											$ 10,357	$ 9,039			$ 2,704
Issuance of common stock (in shares)	[1]									189,453		417,286				172,736
Issuance of common stock upon exercise of stock options		1,795															1,795
Issuance of common stock upon exercise of stock options (in shares)	[1]							49,754
Repurchase of early exercised shares, (in shares)	[1]							(3,337)
Vesting of restricted stock units, (in shares)	[1]							96,269
Stock-based compensation		11,553															11,553
Common stock granted to third party		1,457															1,457
Common stock issued to third parties, (in shares)	[1]							40,005
Repayment of promissory note from employee from purchase of common stock		210																					$ 210
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)		347															347
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)	[1]							11,704
Unrealized gain (loss) on available-for-sale marketable securities		(49)																						(49)
Net gain (loss)		(60,725)																							(60,725)
Ending balance at Dec. 31, 2021		59,569						$ 1	[1]								459,636							(44)	(400,024)
Ending balance, (in shares) at Dec. 31, 2021	[1]							6,299,158
Net gain (loss)		(37,047)
Ending balance at Sep. 30, 2022		$ 61,054						$ 1									498,401							(275)	(437,073)
Ending balance, (in shares) at Sep. 30, 2022		14,036,249						14,036,249
Beginning balance at Dec. 31, 2021		$ 59,569						$ 1	[1]								459,636							(44)	(400,024)
Beginning balance, (in shares) at Dec. 31, 2021	[1]							6,299,158
Issuance of common stock, net of issuance costs			12,155	$ 910	$ 15,426		$ 3,179											12,155	$ 910	$ 15,426		$ 3,179
Issuance of common stock (in shares)	[1]									1,019,046		90,000	6,428,571			262,761
Vesting of restricted stock units, (in shares)	[1]							90,284
Stock-based compensation		9,379															9,379
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)		142															142
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)	[1]							25,482
Unrealized gain (loss) on available-for-sale marketable securities		(207)																						(207)
Net gain (loss)		(44,469)																							(44,469)
Ending balance at Dec. 31, 2022		$ 56,084						$ 1	[1]								500,827							(251)	(444,493)
Ending balance, (in shares) at Dec. 31, 2022		14,215,302						14,215,302	[1]
Beginning balance at Jun. 30, 2022		$ 39,931						$ 1									472,193							(187)	(432,076)
Beginning balance, (in shares) at Jun. 30, 2022								6,958,494
Issuance of common stock, net of issuance costs			8,570		$ 15,428													8,570		$ 15,428
Issuance of common stock (in shares)										633,464			6,428,571
Vesting of restricted stock units, (in shares)								15,720
Stock-based compensation		2,210															2,210
Unrealized gain (loss) on available-for-sale marketable securities		(88)																						(88)
Net gain (loss)		(4,997)																							(4,997)
Ending balance at Sep. 30, 2022		$ 61,054						$ 1									498,401							(275)	(437,073)
Ending balance, (in shares) at Sep. 30, 2022		14,036,249						14,036,249
Beginning balance at Dec. 31, 2022		$ 56,084						$ 1	[1]								500,827							(251)	(444,493)
Beginning balance, (in shares) at Dec. 31, 2022		14,215,302						14,215,302	[1]
Issuance of common stock, net of issuance costs			274															274
Issuance of common stock (in shares)										106,781
Vesting of restricted stock units, (in shares)								37,131
Stock-based compensation		$ 2,175															2,175
Unrealized gain (loss) on available-for-sale marketable securities		101																						101
Net gain (loss)		(5,279)																							(5,279)
Ending balance at Mar. 31, 2023		$ 53,355						$ 1									503,276							(150)	(449,772)
Ending balance, (in shares) at Mar. 31, 2023		14,359,214						14,359,214
Beginning balance at Dec. 31, 2022		$ 56,084						$ 1	[1]								500,827							(251)	(444,493)
Beginning balance, (in shares) at Dec. 31, 2022		14,215,302						14,215,302	[1]
Net gain (loss)		$ (20,735)
Ending balance at Jun. 30, 2023		$ 40,769						$ 1									506,132							(136)	(465,228)
Ending balance, (in shares) at Jun. 30, 2023		14,595,477						14,595,477
Beginning balance at Dec. 31, 2022		$ 56,084						$ 1	[1]								500,827							(251)	(444,493)
Beginning balance, (in shares) at Dec. 31, 2022		14,215,302						14,215,302	[1]
Net gain (loss)		$ (35,520)
Ending balance at Sep. 30, 2023		$ 27,725						$ 1									507,789							(55)	(480,010)
Ending balance, (in shares) at Sep. 30, 2023		14,614,890						14,614,890
Beginning balance at Dec. 31, 2022		$ 56,084						$ 1	[1]								500,827							(251)	(444,493)
Beginning balance, (in shares) at Dec. 31, 2022		14,215,302						14,215,302	[1]
Issuance of common stock, net of issuance costs			725			$ 3,687								$ 1				725			$ 3,686
Issuance of common stock (in shares)				0						274,781	[1]			2,143,000
Vesting of restricted stock units, (in shares)	[1]							94,467
Stock-based compensation		$ 7,419															7,419
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)		116															116
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)	[1]							57,419
Unrealized gain (loss) on available-for-sale marketable securities		227																						227
Net gain (loss)		(39,860)																							(39,860)
Ending balance at Dec. 31, 2023		$ 28,398						$ 2	[1]								512,773							(24)	(484,353)
Ending balance, (in shares) at Dec. 31, 2023		16,784,969						16,784,969	[1]
Beginning balance at Mar. 31, 2023		$ 53,355						$ 1									503,276							(150)	(449,772)
Beginning balance, (in shares) at Mar. 31, 2023		14,359,214						14,359,214
Issuance of common stock, net of issuance costs			$ 518															$ 518
Issuance of common stock (in shares)										168,000
Vesting of restricted stock units, (in shares)								26,766
Stock-based compensation		$ 2,247															2,247
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)		91															91
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)								41,497
Unrealized gain (loss) on available-for-sale marketable securities		14																						14
Net gain (loss)		(15,456)																							(15,456)
Ending balance at Jun. 30, 2023		$ 40,769						$ 1									506,132							(136)	(465,228)
Ending balance, (in shares) at Jun. 30, 2023		14,595,477						14,595,477
Vesting of restricted stock units, (in shares)								19,413
Stock-based compensation		$ 1,705															1,705
Unrealized gain (loss) on available-for-sale marketable securities		81																						81
Net gain (loss)		(14,782)																							(14,782)
Ending balance at Sep. 30, 2023		$ 27,725						$ 1									$ 507,789							$ (55)	$ (480,010)
Ending balance, (in shares) at Sep. 30, 2023		14,614,890						14,614,890
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Statements of Cash Flows

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

Organization

Organization	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Description of Business Unity Biotechnology, Inc. (the “Company”) is a biotechnology company engaged in the research and development of therapeutics to slow, halt, or reverse diseases of aging. The Company devotes substantially all of its time and efforts to performing research and development and raising capital. The Company’s headquarters are located in South San Francisco, California. The Company was incorporated in the State of Delaware in 2009. Liquidity The Company’s Financial Statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The Company has incurred operating losses and has an accumulated deficit as a result of ongoing efforts to develop drug product candidates, including conducting preclinical and clinical trials and providing general and administrative support for these operations. The Company had an accumulated deficit of $ 484.4 million as of December 31, 2023. During the year ended December 31, 2023, the Company incurred a net loss of $ 39.9 million and used $ 37.1 million of cash in operating activities. To date, none of the Company’s drug candidates have been approved for sale, and therefore, the Company has no t generated any product revenue and does not expect positive cash flows from operations in the foreseeable future. The Company has financed its operations primarily through private placements of preferred stock and promissory notes, public equity issuances and more recently, from its ATM Offering Programs (as defined in Note 12), an Equity Purchase Agreement (as defined in Note 12), and the sale of common stock and warrants under a Follow-On Offering and the Inducement Offer (as defined in Note 12) and will continue to be dependent upon equity and/or debt financing until the Company is able to generate positive cash flows from its operations. The Company anticipates operating losses and negative operating cash flows to continue for the foreseeable future. The Company had cash, cash equivalents and marketable securities of $ 43.2 million as of December 31, 2023. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations. Although the Company has been successful in raising capital in the past, there is no assurance that it will be successful in obtaining such additional financing. If sufficient funds on acceptable terms are not available when needed, the Company could be further required to significantly reduce its operating expenses and delay, reduce the scope of, or eliminate one or more of its development programs. Failure to manage discretionary spending or raise additional financing, as needed, may adversely impact the Company’s ability to achieve its intended business objectives, or the Company may be forced to liquidate assets where possible, or to cease operations or file for bankruptcy protection. The Company expects that its cash, cash equivalents, and marketable securities will be sufficient to fund its operations for a period of at least one year from the date the accompanying financial statements are filed with the Securities and Exchange Commission.

Restatement of Previously Issue

Restatement of Previously Issued Financial Statements	12 Months Ended
	Dec. 31, 2023
Accounting Changes and Error Corrections [Abstract]
Restatement of Previously Issued Financial Statements	2. Restatement of Previously Issued Financial Statements The Company has restated herein its audited financial statements for the fiscal year ended December 31, 2022, in accordance with Accounting Standards Codification (“ASC”) Topic 250, Accounting Changes and Error Corrections . In March 2024, the Company concluded the warrants issued in 2022 were incorrectly classified as equity and should have been recorded as liabilities. Historically, the Existing Warrants were reflected as a component of equity as opposed to liabilities on the Balance Sheet. Additionally, the Statements of Operations and Comprehensive Loss did not include changes in the fair value of the Existing Warrants. The Company reassessed its accounting for the Existing Warrants and determined they should have been classified as liabilities and measured at fair value upon issuance with subsequent changes in fair value, as well as the issuance costs associated with the Existing Warrants, reported in the Company's Statement of Operations and Comprehensive Loss. We have also restated interim financial statement periods for the third quarter of 2022 and the first, second and third quarters of 2023, as further described in Note 18. Impact of the Restatement The following tables represent the restated amounts in the Balance Sheet, Statement of Operations and Comprehensive Loss, Statement of Changes in Stockholders’ Equity and Statement of Cash Flows for the year ended December 31, 2022. The amounts as previously reported for fiscal year 2022 was derived from the Annual Report on Form 10-K for the fiscal year ended December 31, 2022, filed on March 15, 2023 (Original Report). These amounts are labeled as “As Previously Reported” in the tables below. The amounts labeled “Adjustment” represent the effects of this restatement described above. Balance Sheet December 31, 2022 As Previously Reported Adjustment As Restated Assets Current assets: Cash and cash equivalents $ 12,736 $ — $ 12,736 Short-term marketable securities 82,059 — 82,059 Prepaid expenses and other current assets 1,740 — 1,740 Total current assets 96,535 — 96,535 Property and equipment, net 7,825 — 7,825 Operating lease right-of-use asset 19,042 — 19,042 Long-term restricted cash 896 — 896 Other long-term assets 52 — 52 Total assets $ 124,350 $ — $ 124,350 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 1,790 $ — $ 1,790 Accrued compensation 3,020 — 3,020 Accrued and other current liabilities 5,334 — 5,334 Current portion of long-term debt 9,476 — 9,476 Total current liabilities 19,620 — 19,620 Operating lease liability, net of current portion 26,991 — 26,991 Long-term debt, net 10,891 — 10,891 Warrant liability — 10,764 10,764 Total liabilities 57,502 10,764 68,266 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,215,302 shares issued and outstanding as of December 31, 2022 1 — 1 Additional paid-in capital 527,049 ( 26,222 ) 500,827 Accumulated other comprehensive loss ( 251 ) — ( 251 ) Accumulated deficit ( 459,951 ) 15,458 ( 444,493 ) Total stockholders’ equity 66,848 ( 10,764 ) 56,084 Total liabilities and stockholders’ equity $ 124,350 $ — $ 124,350 Statement of Operations and Comprehensive Loss Year Ended As Previously Reported Adjustment As Restated Licensing revenue - Related Party $ 236 $ — $ 236 Operating expenses: Research and development 36,859 — 36,859 General and administrative 20,949 — 20,949 Total operating expenses 57,808 — 57,808 Loss from operations ( 57,572 ) — ( 57,572 ) Interest income 1,220 — 1,220 Interest expense ( 3,558 ) — ( 3,558 ) Gain (loss) on warrant liability — 16,843 16,843 Other expense, net ( 17 ) ( 1,385 ) ( 1,402 ) Net loss ( 59,927 ) 15,458 ( 44,469 ) Other comprehensive loss Unrealized loss on marketable debt securities ( 207 ) — ( 207 ) Comprehensive loss $ ( 60,134 ) $ 15,458 $ ( 44,676 ) Net loss per share, basic and diluted $ ( 6.31 ) $ — $ ( 4.68 ) Weighted average number of shares used in computing net loss per share, basic and diluted 9,494,421 — 9,494,421 Statement of Changes in Stockholders' Equity Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at December 31, 2021 6,299,158 $ 1 $ 459,636 $ ( 44 ) $ ( 400,024 ) $ 59,569 Issuance of common stock, net of issuance costs, 1,019,046 — 12,155 — — 12,155 Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs 6,428,571 — 41,648 — — 41,648 Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs 90,000 — 910 — — 910 Issuance of common stock Hercules Capital, net of issuance costs 262,761 — 3,179 — — 3,179 Issuance of common stock under 2018 ESPP 25,482 — 142 — — 142 Vesting of restricted stock units 90,284 — — — — — Stock-based compensation — — 9,379 — — 9,379 Unrealized loss on available-for-sale marketable securities — — — ( 207 ) — ( 207 ) Net loss — — — — ( 59,927 ) ( 59,927 ) Balances at December 31, 2022 14,215,302 $ 1 $ 527,049 $ ( 251 ) $ ( 459,951 ) $ 66,848 Adjustment Balances at December 31, 2021 — $ — $ — $ — $ — $ — Issuance of common stock, net of issuance costs, — — — — — — Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs — — ( 26,222 ) — — ( 26,222 ) Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs — — — — — — Issuance of common stock Hercules Capital, net of issuance costs — — — — — — Issuance of common stock under 2018 ESPP — — — — — — Vesting of restricted stock units — — — — — — Stock-based compensation — — — — — — Unrealized loss on available-for-sale marketable securities — — — — — — Net loss — — — — 15,458 15,458 Balances at December 31, 2022 — $ — $ ( 26,222 ) $ — $ 15,458 $ ( 10,764 ) As Restated Balances at December 31, 2021 6,299,158 $ 1 $ 459,636 $ ( 44 ) $ ( 400,024 ) $ 59,569 Issuance of common stock, net of issuance costs, 1,019,046 — 12,155 — — 12,155 Sale of common stock under Follow-On Offering, net of issuance costs 6,428,571 — 15,426 — — 15,426 Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs 90,000 — 910 — — 910 Issuance of common stock Hercules Capital, net of issuance costs 262,761 — 3,179 — — 3,179 Issuance of common stock under 2018 ESPP 25,482 — 142 — — 142 Vesting of restricted stock units 90,284 — — — — — Stock-based compensation — — 9,379 — — 9,379 Unrealized loss on available-for-sale marketable securities — — — ( 207 ) — ( 207 ) Net loss — — — — ( 44,469 ) ( 44,469 ) Balances at December 31, 2022 14,215,302 $ 1 $ 500,827 $ ( 251 ) $ ( 444,493 ) $ 56,084 Statement of Cash Flow Year Ended As Previously Reported Adjustment As Restated Operating activities Net loss $ ( 59,927 ) $ 15,458 $ ( 44,469 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 2,180 — 2,180 Amortization of debt issuance costs 1,318 — 1,318 Debt extinguishment gain upon conversion to equity ( 199 ) — ( 199 ) Net accretion and amortization of premium and discounts on ( 276 ) — ( 276 ) Gain on disposal of property and equipment ( 346 ) — ( 346 ) Stock-based compensation 9,379 — 9,379 Non-cash rent expense ( 2,136 ) — ( 2,136 ) (Gain) loss on warrant liability — ( 16,843 ) ( 16,843 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets 138 — 138 Other long-term assets 39 — 39 Accounts payable ( 194 ) — ( 194 ) Accrued compensation ( 1,008 ) — ( 1,008 ) Accrued liabilities and other current liabilities 26 — 26 Other long-term liabilities ( 23 ) — ( 23 ) Net cash used in operating activities ( 51,029 ) ( 1,385 ) ( 52,414 ) Investing activities Purchase of marketable securities ( 98,827 ) — ( 98,827 ) Maturities of marketable securities 74,000 — 74,000 Purchase of property and equipment ( 96 ) — ( 96 ) Sale of property and equipment 378 — 378 Net cash provided by (used in) investing activities ( 24,545 ) — ( 24,545 ) Financing activities Proceeds from issuance of common stock under ATM offering program, net of issuance costs 12,155 — 12,155 Proceeds from sale of common stock and warrants under Follow-On Offering 41,648 3,352 45,000 Issuance costs for sale of common stock — ( 1,967 ) ( 1,967 ) Proceeds from issuance of common stock to Lincoln Park Capital Fund, net of issuance costs 910 — 910 Proceeds from issuance of common stock under 2018 ESPP 142 — 142 Net cash provided by financing activities 54,855 1,385 56,240 Net increase (decrease) in cash, cash equivalents and restricted cash ( 20,719 ) — ( 20,719 ) Cash, cash equivalents and restricted cash at beginning of the period 34,351 — 34,351 Cash, cash equivalents and restricted cash at end of the period $ 13,632 $ — $ 13,632 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 2,204 $ — $ 2,204 Supplemental Disclosures of Non-Cash Investing and Financing Issuance of common stock in payment of debt $ 3,179 $ — $ 3,179 The remainder of the notes to the Company's financial statements have been restated, as applicable, to reflect the impacts from the restatement discussed above.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and the rules and regulations of Securities and Exchange Commission (“SEC”) for reporting. The Company effected a reverse stock split on October 19, 2022 of its outstanding shares of common stock at a ratio of 1-for-10 pursuant to a Certificate of Amendment to the Company's Certificate of Incorporation filed with the Secretary of State of the State of Delaware. The reverse stock split was reflected on the Nasdaq Global Select Market beginning with the opening of trading on October 20, 2022. Accordingly, an amount equal to the par value of the decreased shares resulting from the reverse stock split was reclassified from "Additional paid-in capital" to "Common stock". Any fractional post-split shares as a result of the reverse stock split were rounded down to the nearest whole post-split share. The reverse stock split did not change the par value of the Company's common stock or the authorized number of shares of the Company's common stock. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented. Warrants The Company determines the accounting classification of warrants that are issued, as either liability or equity, by first assessing whether the warrants meet liability classification in accordance with ASC 480-10, Distinguishing Liabilities from Equity , and then in accordance with ASC 815-40, Accounting for Derivative Financial Instruments Indexed to, and Potentially Settled in, a Company’s Own Stock . Under ASC 480-10, warrants are considered liability classified if the warrants are mandatorily redeemable, obligate the issuer to settle the warrants or the underlying shares by paying cash or other assets, or must or may require settlement by issuing variable number of shares. If warrants do not meet liability classification under ASC 480-10, the Company assesses the requirements under ASC 815-40, which states that contracts that require or may require the issuer to settle the contract for cash are liabilities recorded at fair value, irrespective of the likelihood of the transaction occurring that triggers the net cash settlement feature. If the warrants do not require liability classification under ASC 815-40, in order to conclude equity classification, the Company assesses whether the warrants are indexed to its common stock and whether the warrants are classified as equity under ASC 815-40 or other applicable principles of GAAP. After all relevant assessments are made, the Company concludes whether the warrants are classified as liability or equity. Liability classified warrants are required to be accounted for at fair value both on the date of issuance and on subsequent accounting periods with changes in fair value recorded in the Statements of Operations and Comprehensive Loss under "Gain or (loss) on warrant liability". If warrants are issued together with the sale of common stock, for the issuance costs that are not specifically attributed to either the common stock or warrants issued, the Company allocates the issuance costs between the common stock and warrants based on their relative fair value. The Company expenses issuance costs allocated to the warrants that are classified as liabilities and the issuance costs allocated to common stock or warrants that are classified as equity are recognized as reduction to the equity. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company bases its estimates on historical experience and market-specific or other relevant assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company’s balance sheets and the amount of expenses and income reported for each of the periods presented are affected by estimates and assumptions, which are used for, but are not limited to, determining the fair value of assets and liabilities, the fair value of right-of-use asset and lease liabilities, embedded derivatives and stock-based compensation. Actual results could differ from such estimates or assumptions. Estimating fair values of liability-classified financial instruments requires the development of estimates that may, and are likely to, change over the duration of the instrument with related changes in internal and external market factors. In addition, derivatives liabilities are highly volatile and sensitive to changes in the market price of the Company’s common stock. Because liability-classified financial instruments are initially and subsequently carried at fair value, the Company’s financial results will reflect the volatility in these estimate and assumption changes. Changes in estimated fair value are recognized as a component of "Other expense, net" in the Statements of Operations and Comprehensive Loss. Segments The Company has one operating segment. The Company’s chief operating decision maker, its Chief Executive Officer, manages the Company’s operations on a consolidated basis for the purposes of allocating resources. Cash, Cash Equivalents, and Restricted Cash The Company considers all highly liquid investments with original maturities of 90 days or less from the date of purchase to be cash equivalents. Cash equivalents primarily include money market funds that invest in U.S. Treasury obligations which are stated at fair value. The Company has issued letters of credit under its lease agreements which have been collateralized. This cash is classified as noncurrent restricted cash on the balance sheet based on the term of the underlying lease. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows (in thousands). December 31, 2023 2022 2021 Cash and cash equivalents $ 19,803 $ 12,736 $ 32,905 Restricted cash 896 896 1,446 Total cash, cash equivalents, and restricted cash $ 20,699 $ 13,632 $ 34,351 Marketable Securities The Company generally invests its excess cash in investment grade, short to intermediate-term, fixed income securities. Such investments are considered available-for-sale debt securities and reported at fair value with unrealized gains and losses included as a component of stockholders’ equity. Marketable securities with original maturities of greater than 90 days from the date of purchase but less than one year from the balance sheet date that are available to be converted into cash to fund current operations are classified as short-term, while marketable securities with maturities in one year or beyond one year from the balance sheet date are classified as long-term. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in "Interest income" on the Statements of Operations and Comprehensive Loss. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on marketable securities are included in "Other expense, net". The cost of securities sold is determined using the specific identification method . The Company periodically evaluates whether declines in fair values of its marketable securities below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the marketable security until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any marketable securities before recovery of its amortized cost basis. Factors considered include quoted market prices, recent financial results and operating trends, implied values from any recent transactions or offers of investee securities, credit quality of debt instrument issuers, other publicly available information that may affect the value of the marketable security, duration and severity of the decline in value, and management’s strategy and intentions for holding the marketable security. To date, the Company has not recorded any impairment charges on its marketable securities related to other-than-temporary declines in market value. Fair Value Measurements The Company’s financial instruments during the periods presented consist of cash and cash equivalents, restricted cash, marketable securities, strategic investments, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued and other current liabilities, derivative liabilities related to debt and long-term debt. Fair value estimates of these instruments are made at a specific point in time, based on relevant market information. Level 3 instruments incorporate certain unobservable inputs such as the selected discount rate of the related loan. These estimates may be subjective in nature and involve uncertainties and matters of judgment. Revenue Recognition The Company recognizes revenue in accordance with the provisions of Accounting Standards Codification Topic 606, Revenue from Contracts with Customers, or Topic 606. In determining the appropriate amount and timing of revenue to be recognized under this guidance, the Company performs the following five steps: (i) identifies the contract(s) with our customer; (ii) identifies the promised goods or services in the agreement and determine whether they are performance obligations, including whether they are distinct in the context of the agreement; (iii) measures the transaction price, including the constraint on variable consideration; (iv) allocates the transaction price to the performance obligations based on stand-alone selling prices; and (v) recognizes revenue when (or as) the Company satisfies each performance obligation. A performance obligation is a promise in an agreement to transfer a distinct good or service to the customer and is the unit of account in Topic 606. Significant management judgment is required to determine the level of effort required and the period over which completion of the performance obligations is expected under an agreement. If reasonable estimates regarding when performance obligations are either complete or substantially complete cannot be made, then revenue recognition is deferred until a reasonable estimate can be made. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. The Company allocates the total transaction price to each performance obligation based on the estimated relative stand-alone selling prices of the promised goods or services underlying each performance obligation. The total consideration which the Company expects to collect in exchange for the Company’s products is an estimate and may be fixed or variable. The Company constrains the estimated variable consideration when it assesses it is probable that a significant reversal in the amount of cumulative revenue recognized may occur in future periods. The transaction price is re-evaluated, including the estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. The allocation of the transaction price is performed based on standalone selling prices, which are based on estimated amounts that the Company would charge for a performance obligation if it were sold separately. Revenue is recognized when, or as, performance obligations in the contracts are satisfied, in the amount reflecting the expected consideration to be received from the goods or services transferred to the customers. Consideration received in advance are recorded as deferred revenue and are recognized as the related performance obligation is satisfied. Following is a description of the principal activities from which the Company generates revenue. License revenue primarily represent amounts earned under agreements that license our intellectual property to other companies. See Note 5, “License Revenue, Agreements and Strategic Investment” for further detail. Consideration under these contracts generally includes a nonrefundable upfront payment, development, regulatory and commercial milestones and royalties based on net sales of approved products. Licenses of Intellectual Property. If the Company determines the license to intellectual property is distinct from the other performance obligations identified in the agreement and the licensee can use and benefit from the license, the Company recognizes revenue from the estimated transaction price that is allocated to the license. Licensing arrangements are analyzed to determine whether the promised goods or services, which may include licenses, transfer of know-how, transfer of materials, research and development services and governance committee services, are distinct or whether they must be accounted for as part of a combined performance obligation. If the license is considered not to be distinct, the license would then be combined with other promised goods or services as a combined performance obligation. If the Company is involved in a governance committee, it assesses whether its involvement constitutes a separate performance obligation. When governance committee services are determined to be separate performance obligations, the Company determines the fair value to be allocated to this promised service. Milestone Payments : At the inception of each agreement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimate the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone is included in the transaction price. For milestones that the Company do not deem to be probable of being achieved, the associated milestone payments are fully constrained and the value of the milestone is excluded from the transaction price with no revenue being recognized. For example, milestone payments that are not within our control, such as regulatory-related accomplishments, are not considered probable of being achieved until those accomplishments have been communicated by the relevant regulatory authority. Once the assessment of probability of achievement becomes probable, the Company recognizes revenue for the milestone payment. At each reporting date, the Company assesses the probability of achievement of each milestone under our current agreements. Royalties . For agreements with sales-based royalties, including milestone payments based on the level of sales, where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation, to which some or all of the royalty has been allocated, has been satisfied (or partially satisfied). At each reporting date, the Company estimates the sales incurred by each licensee during the reporting period based on historical experience and accrues the associated royalty amount. Concentrations of Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, and marketable securities. Substantially all of the Company’s cash and cash equivalents and restricted cash is deposited in accounts with financial institutions that management believes are of high credit quality. Such deposits have and will continue to exceed federally insured limits. The Company maintains its cash with accredited financial institutions and accordingly, such funds are subject to minimal credit risk. The Company has not experienced any losses on its cash deposits. The Company’s investment policy limits investments in marketable securities to certain types of securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents, restricted cash and marketable securities and issuers of marketable securities to the extent recorded on the balance sheets. As of December 31, 2023 and 2022, the Company had no off-balance sheet concentrations of credit risk. The Company depends on third-party suppliers for key raw materials used in its manufacturing processes and is subject to certain risks related to the loss of these third-party suppliers or their inability to supply the Company with adequate raw materials. Research and Development Expenses and Accruals Costs related to research, design, and development of drug candidates are charged to research and development expense as incurred. Research and development costs include, but are not limited to, payroll and personnel expenses for personnel contributing to research and development activities, laboratory supplies, outside services, licenses acquired to be used in research and development, manufacturing of clinical material, pre-clinical testing and consultants and allocated overhead, including rent, equipment, depreciation, and utilities. Research and development costs are expensed as incurred unless there is an alternative future use in other research and development projects. Payments made prior to the receipt of goods or services to be used in research and development are deferred and recognized as expense in the period in which the related goods are received or services are rendered. Such payments are evaluated for current or long-term classification based on when they will be realized. As part of the process of preparing its financial statements, the Company is required to estimate expenses resulting from its obligations under contracts with vendors and consultants and clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. The Company’s objective is to reflect the appropriate expenses in its financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of the production of clinical trial materials or based on progression of the clinical trial, as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates by taking into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of goods and services, or the services completed. During the course of a clinical trial, the rate of expense recognition is adjusted if actual results differ from the Company’s estimates. The Company makes estimates of accrued expenses as of each balance sheet date in its financial statements based on the facts and circumstances known at that time. The clinical trial accrual is dependent in part upon the timely and accurate reporting of contract research organizations, contract manufacturers, and other third-party vendors. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting changes in estimates in any particular period. Adjustments to prior period estimates have not been material for the years ended December 31, 2023 and 2022. Contingent Consideration Liability The Company has entered into and may continue to enter into, license agreements to access and utilize certain technology. In each case, the Company evaluates whether the license agreement results in the acquisition of an asset or a business. To date, all of the Company’s license agreements have been considered acquisitions of assets and none have been considered acquisitions of a business. For license agreements that are considered to be acquisitions of assets, the upfront payments for such license, as well as any future milestone payments made before product approval, are immediately recognized as research and development expense when due, provided there is no alternative future use of the rights in other research and development projects. Some of the Company’s license agreements also include contingent consideration in the form of an obligation to issue additional shares of the Company’s common stock based on the achievement of certain milestones. The Company assesses on a continuous basis whether (i) such contingent consideration meets the definition of a derivative, and (ii) whether it can be classified within stockholders’ equity. Until such time when equity classification criteria are met or the milestones expire, the contingent consideration is classified as a liability. The derivative related to this contingent consideration is measured at fair value as of each balance sheet date with the related change in fair value being reflected in operating expenses. Upon a reassessment event that results in the contingent consideration no longer meeting the definition of a derivative and/or meeting equity classification criteria, the final change in fair value of the instrument is recorded within operating expenses and the liability is reclassified into stockholders’ equity. Property and Equipment, Net Property and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets, generally three years. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the term of the lease. Depreciation and amortization begin at the time the asset is placed in service. Maintenance and repairs are charged to expense as incurred and costs of improvement are capitalized. Leases The Company determines whether the arrangement is or contains a lease at the inception of the arrangement and if so, whether such a lease is classified as a financing lease or an operating lease. Operating leases are included in operating lease right-of-use asset, (“ROU asset”), operating lease liabilities, net of current portion, and accrued and other current liabilities on the Company’s balance sheets. The Company has elected not to recognize on the balance sheets leases with terms of one year or less. Operating lease ROU assets represent the Company’s right to use an underlying asset for the lease term and are considered long-lived assets for purposes of identifying, recognizing and measuring impairment. Operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of lease payments over the expected lease term. As the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment, in determining the present value of lease payments. The operating lease ROU asset also includes any lease payments made or incentives received and impairment charges if the Company determines the ROU asset is impaired and excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options to extend or terminate the lease. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company has elected to not separate lease and non-lease components for its leased assets and accounts for all lease and non-lease components of its agreements as a single lease component. The lease components resulting in a ROU asset have been recorded on the balance sheets and are amortized as lease expense on a straight-line basis over the lease term. The Company has subleased a majority of its South San Francisco, California facility under agreements considered to be operating leases according to ASC 842. The Company has not been legally released from its primary obligations under the original leases and therefore it continues to account for the original leases as it did before commencement of the subleases. The Company records both fixed and variable payments received from the sublessee in its statements of operations on a straight-line basis as an offset to rent expense. Impairment of Long-Lived Assets The Company evaluates long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be fully recoverable. If indicators of impairment exist and the undiscounted future cash flows that the assets are expected to generate are less than the carrying value of the assets, the Company reduces the carrying amount of the assets through an impairment charge, to their estimated fair value based on a discounted cash flow approach or, when available and appropriate, to comparable market values. See Note 9, “Commitments and Contingencies”. Determining estimated discounted cash flows for purposes of an impairment analysis requires the Company to make estimates and assumptions regarding the amount of market rent, timing of sublease income, and risk-adjusted discount rates. There are often risks and uncertainties associated with the intent to sublease offices and laboratory space. Consequently, the eventual realized sublease income may vary from estimates as of the impairment testing date and adjustments may occur in future periods . Stock-Based Compensation The Company measures compensation expense for all stock-based awards based on their grant date fair value. For stock-based awards with service conditions only, stock-based compensation expense is recognized over the requisite service period using the straight-line method. For awards with performance conditions, the Company evaluates the probability of achieving performance condition at each reporting date. The Company begins to recognize stock-based compensation expense using an accelerated attribution method when it is deemed probable that the performance condition will be met. Forfeitures are recognized as they occur. The Company uses the Black-Scholes option-pricing model to estimate the fair value of stock option awards that do not contain market conditions. The Black-Scholes option-pricing model requires assumptions to be made related to the expected term of an award, expected dividends, expected volatility and risk-free rate. The Company has used the Monte-Carlo option-pricing model to estimate the fair value of stock option awards that contain only market conditions. The Monte-Carlo option pricing model uses similar input assumptions as the Black-Scholes model; however, it further incorporates into the fair-value determination the possibility that the market condition may not be satisfied. Embedded Derivatives of the Loan Agreement The Company measures derivative liability related to debt at fair value. Estimated fair value of the derivative liability related to debt, initially measured and recorded on the date of the amendment of the loan and security agreement, is considered to be a Level 3 instrument. The fair value of the derivative liability related to debt is based on the term loan principal, the date of maturity, the contractual term loan interest rate, the convertible discount factor, and the selected discount rate of the loan. The derivative liability related to debt is recorded at fair value at the end of each reporting period with changes in estimated fair values recognized as a component of "Other expense, net" in the Statements of Operations and Comprehensive Loss. Restructuring The Company recognizes restructuring charges related to reorganization plans that have been committed to by management and when liabilities have been incurred. In connection with these activities, the Company records restructuring charges at fair value for a) contractual employee termination benefits when obligations are associated to services already rendered, rights to such benefits have vested, and payment of benefits is probable and can be reasonably estimated, and b) one-time employee termination benefits when management has committed to a plan of termination, the plan identifies the employees and their expected termination dates, the details of termination benefits are complete, it is unlikely changes to the plan will be made or the plan will be withdrawn and communication to such employees has occurred. One-time employee termination benefits are recognized in their entirety when communication has occurred, and future services are not required. Contract termination costs to be incurred over the remaining contract term without economic benefit are recorded in their entirety when the contract is canceled. The recognition of restructuring charges requires the Company to make certain judgments and estimates regarding the nature, timing and amount of costs associated with the planned reorganization plan. At the end of each reporting period, the Company evaluates the remaining accrued restructuring balances to ensure that no excess accruals are retained, and the utilization of the provisions are for their intended purpose in accordance with developed restructuring plans. Income Taxes The Company uses the asset and liability method of accounting for income taxes, in which deferred tax assets and liabilities are recognized for future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be reversed. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as income in the period that includes the enactment date. A valuation allowance is established if it is more likely than not that all or a portion of the deferred tax asset will not be realized. The Company’s tax positions are subject to income tax audits. The Company recognizes the tax benefit of an uncertain tax position only if it is more likely than not that the position is sustainable upon examination by the taxing authority, based on the technical merits. The tax benefit recognized is measured as the largest amount of benefit which is more likely than not to be realized upon settlement with the taxing authority. The Company recognizes interest accrued and penalties related to unrecognized tax benefits in its tax provision. The Company evaluates uncertain tax positions on a regular basis. The evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of the audit, and effective settlement of audit issues. The provision for income taxes includes the effects of any accruals that the Company believes are appropriate, as well as the related net interest and penalties. Net Loss per Common Share Basic net loss per share is calculated by dividing net loss by the weighted average number of shares outstanding for the period. Diluted net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding plus the effect of dilutive potential common shares outstanding during the period determined using the treasury-stock method. In all periods presented, the Company’s outstanding stock options, convertible preferred stock, early exercised common stock subject to future vesting, warrants and presumed issuance of additional sh

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The Company determines the fair value of financial and non-financial assets and liabilities based on the assumptions that market participants would use in pricing the asset or liability in an orderly transaction between market participants at the measurement date. The identification of market participant assumptions provides a basis for determining what inputs are to be used for pricing each asset or liability. A fair value hierarchy has been established which gives precedence to fair value measurements calculated using observable inputs over those using unobservable inputs. This hierarchy prioritized the inputs into three broad levels as follows: • Level 1: Quoted prices in active markets for identical instruments • Level 2: Other significant observable inputs (including quoted prices in active markets for similar instruments) • Level 3: Significant unobservable inputs (including assumptions in determining the fair value of certain investments) The carrying amounts of financial instruments such as cash and cash equivalents, restricted cash, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued and other current liabilities approximate to their related fair values due to the short-term nature of these instruments. The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands): December 31, 2023 Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 12,864 $ 12,864 $ — $ — U.S. treasuries 2,989 — 2,989 — Total cash equivalents 15,853 12,864 2,989 — Short-term marketable securities: U.S. treasuries 7,849 — 7,849 — U.S. government debt securities 15,549 — 15,549 — Total short-term marketable securities 23,398 — 23,398 — Restricted Cash equivalents: Money market funds 896 896 — — Total restricted cash equivalents 896 896 — — Total assets subject to fair value measurements $ 40,147 $ 13,760 $ 26,387 $ — Liabilities: Warrant Liability $ 5,913 $ — $ — $ 5,913 Total liabilities subject to fair value measurements 5,913 — — 5,913 December 31, 2022 (Restated) Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 5,083 $ 5,083 $ — $ — Total cash equivalents 5,083 5,083 — — Short-term marketable securities: U.S. treasuries 30,758 — 30,758 — U.S. government debt securities 51,301 — 51,301 — Total short-term marketable securities 82,059 — 82,059 — Total assets subject to fair value measurements $ 87,142 $ 5,083 $ 82,059 $ — Liabilities: Warrant Liability (Restated) $ 10,764 $ — $ — $ 10,764 Total liabilities subject to fair value measurements 10,764 — — 10,764 The Company estimates the fair value of its money market funds, U.S. treasuries, and U.S. government debt securities by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. See Note 5, “Marketable Securities,” for further information regarding the carrying value of the Company's financial instruments. August 2022 Warrants ('Existing Warrants') The common stock warrants are classified as a liability on the balance sheets and are measured at fair value with the change in fair value recorded within “Gain (loss) on warrant liability” on the Statement of Operations and Comprehensive Loss. The estimated fair value of the outstanding common warrants were $ 27.6 million, $ 16.6 million, $ 10.7 million, $ 5.3 million, $ 8.7 million, $ 8.4 million, and $ 2.8 million as of August 22, 2022 (i.e., the issuance date), September 30, 2022, December 31, 2022, March 31, 2023, June 30, 2023, September 30, 2023, and December 31, 2023, respectively. In November 2023, 2,143,000 shares of the common warrants were exercised through an Inducement Offer, for a reduced exercise price of $ 2.045 . See Note 12, ‘Equity Financing’. The Company estimates the fair value of its warrant liability using a Monte Carlo simulation model b ased on significant inputs not observable in the market, which represents a Level 3 measurement. The Company used the following key assumptions within its valuation. In all scenarios, the Company also applied the likelihood of a fundamental transaction and the related impact on the Company’s common stock price and volatility. August 22, 2022 September 30, 2022 December 31, 2022 March 31, 2023 June 30, 2023 September 30, 2023 November 14, 2023 December 31, 2023 Common stock price $ 6.10 $ 3.95 $ 2.74 $ 1.63 $ 2.55 $ 2.40 $ 1.72 $ 1.93 Exercise price per share $ 8.50 $ 8.50 $ 8.50 $ 8.50 $ 8.50 $ 8.50 $ 2.045 $ 8.50 Estimated volatility 87.5 % 90.0 % 95.0 % 100.0 % 95.0 % 100.0 % 80.0 % 80.0 % Risk-free interest rate 3.17 % 4.07 % 4.03 % 3.66 % 4.28 % 4.71 % 4.42 % 3.85 % Contractual term (in years) 5.00 4.89 4.64 4.39 4.14 3.89 3.77 3.64 November 2023 Inducement Offer ('New Warrants') In November 2023, the Company issued common stock warrants to purchase an aggregate of 2,143,000 shares of common stock at an exercise price of $ 1.92 per warrant. Additionally, 128,580 common stock warrants were issued to the Placement Agent ("Placement Agent Warrants") at an exercise price of $ 2.5563 per warrant. The New Warrants and Placement Agent warrants are recorded for as a liability on the balance sheet and are adjusted to estimated fair value at period end through “Gain (loss) on warrant liability” on the Statement of Operations and Comprehensive Loss. The estimated fair value of the New Warrants were $ 2.7 million on November 14, 2023 (i.e., the issuance date) and $ 3.1 million as of December 31, 2023. The Company estimates the fair value of its Level 3 warrant liabilities using a Monte Carlo simulation model. The Company used the following key assumptions within its valuation. In all scenarios, the Company also applied the likelihood of a fundamental transaction and the related impact on the Company’s common stock price and volatility. November 14, 2023 December 31, 2023 Common stock price $ 1.72 $ 1.93 Exercise price per share $ 1.92 - 2.5563 $ 1.92 - 2.5563 Expected volatility 80.0 % 80.0 % Risk-free interest rate 4.42 % 3.85 % Contractual term (in years) 5.00 4.87 The following is a roll forward of the fair value of Level 3 warrants: Warrant Liability Beginning balance at December 31, 2021 $ — Warrants Issued 27,607 Change in fair value ( 16,842 ) Ending balance at December 31, 2022 (Restated) 10,765 Warrants Issued 2,724 Warrants Exercised ( 1,361 ) Change in fair value ( 6,215 ) Balance at December 31, 2023 $ 5,913

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	5. Marketable Securities Marketable securities, which are classified as available-for-sale, consisted of the following (in thousands): December 31, 2023 Amortized Unrealized Unrealized Fair Cash equivalents: Money market funds $ 12,864 $ — $ — $ 12,864 U.S. treasuries 2,989 — — 2,989 Total cash equivalents 15,853 — — 15,853 Short-term marketable securities: U.S. treasuries 7,853 4 ( 8 ) 7,849 U.S. government debt securities 15,570 1 ( 22 ) 15,549 Total short-term marketable securities 23,423 5 ( 30 ) 23,398 Restricted Cash equivalents: Money market funds 896 — — $ 896 Total restricted cash equivalents 896 — — 896 Total $ 40,172 $ 5 $ ( 30 ) $ 40,147 December 31, 2022 Amortized Unrealized Unrealized Fair Cash equivalents: Money market funds $ 5,083 $ — $ — $ 5,083 Total cash equivalents 5,083 — — 5,083 Short-term marketable securities: U.S. treasuries 51,491 6 ( 196 ) 51,301 U.S. government debt securities 30,820 1 ( 63 ) 30,758 Total short-term marketable securities 82,311 7 ( 259 ) 82,059 Total $ 87,394 $ 7 $ ( 259 ) $ 87,142 At December 31, 2023, the remaining contractual maturities of available-for-sale debt securities were less than a year . There have been no significant realized gains or losses on available-for-sale debt securities for the periods presented. As of December 31, 2023, the Company did not hold any individual securities in an unrealized loss position for 12 months or greater. The Company has the ability and intent to hold all marketable securities that have been in a continuous loss position until maturity or recovery. No significant facts or circumstances have arisen to indicate that there has been any significant deterioration in the creditworthiness of the issuers of the securities held by the Company. The Company considered the current and expected future economic and market conditions and determined that the estimate of credit losses was not significantly impacted. Thus, there has been no change in estimate of expected credit loss during the year ended December 31, 2023 and no allowance for credit loss was recorded at December 31, 2023. The Company will continue to assess the current and expected future economic and market conditions as further development arises. See Note 4, “Fair Value Measurements,” for further information regarding the fair value of the Company's financial instruments.

License Revenue, Agreements and

License Revenue, Agreements and Strategic Investment	12 Months Ended
	Dec. 31, 2023
Research and Development [Abstract]
License Revenue, Agreements and Strategic Investment	6. License Revenue, Agreements and Strategic Investment The Company has entered into license agreements with other pharmaceutical and biotechnology companies. The Company’s accounts receivable balances may contain billed and unbilled amounts from milestones and other contingent payments. The Company performs a regular review of its customers’ credit risk and payment histories, including payments made after period end. Historically, the Company has not experienced credit loss from its accounts receivable and, therefore, has not recorded a reserve for estimated credit losses as of December 31, 2023. In accordance with the license agreements, the Company recognized revenue as follows: Year ended December 31, 2023 2022 2021 Jocasta Neuroscience, Inc. (1) $ — $ 236 $ 4,784 $ — $ 236 $ 4,784 (1) Jocasta Neuroscience, Inc. was deemed a related party at the effective time the agreement was made on December 17, 2021. License Agreement with Jocasta Neuroscience, Inc. In December 2021, the Company signed a License Agreement with Jocasta Neuroscience, Inc. (“the Jocasta Agreement”) to exclusively license its rights in the α-Klotho asset for development and commercialization, and included a sublicense agreement under the original license agreement with the University of California, San Francisco. Under the Jocasta Agreement, the Company received a $ 5.0 million upfront cash payment from Jocasta Neuroscience, Inc. The Company may also receive additional payments based on development milestones, approval milestones, and sales-based royalties, per indication. The Jocasta agreement is recognized in accordance with ASC 606, Revenue from Contracts with Customers , and is classified under License Revenue. Promises that the Company concluded were distinct performance obligations in the License Agreement included: (1) the license of intellectual property and delivery of know-how, and (2) the transfer of licensed compounds and materials. In order to determine the transaction price, the Company evaluated all the payments to be received during the duration of the contract. Fixed consideration exists in the form of the upfront payment. Regulatory milestones and royalties were considered variable consideration. The estimated variable consideration is constrained until the Company determines it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur in future periods. Milestone payments are constrained and not included in the transaction price due to the uncertainties of research and development. The Company will re-evaluate the transaction price, including the estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. The Company determined that the initial transaction price consists of the upfront payment of $ 5.0 million. The allocation of the transaction price is performed based on standalone selling prices, which are based on estimated amounts that the Company would charge for a performance obligation if it were sold separately. The transaction price allocated to the license of intellectual property and delivery of know-how was recognized upon grant of license and delivery of know-how. The transaction price allocated the transfer of licensed compounds and materials, will be recognized over time as the materials are delivered. Consideration received in advance are recorded as deferred revenue and will be recognized as the performance obligations are satisfied. For the years ended December 31, 2023, 2022 and 2021, the Company recognized zero , $ 0.2 million and $ 4.8 million, respectively, of license revenue related to the Jocasta Agreement. License Agreements with Research Institutions In May 2019, the Company entered into a license agreement with The Regents of the University of California on behalf its San Francisco campus (collectively, “UCSF”) which provides the Company the rights to certain patents and related know-how to make, use, sell, offer for sale and import certain products and practice certain methods for use in the development of human therapeutics, which excludes the provision of services to third parties for consideration of any kind. The license to the Company is subject to UCSF’s reserved rights under the licensed intellectual property for educational and non-commercial research purposes and a requirement to substantially manufacture any licensed products in the United States. The Company is obligated to use diligent efforts to develop and obtain regulatory approval for at least one product commercialized pursuant to the agreement, and must meet certain regulatory and development milestones. The Company is obligated to pay an annual license maintenance fee and may be obligated to make milestone payments or issue up to an additional 3,400 shares of its common stock upon the occurrence of specified development events, up to aggregate milestone payments of $ 13.6 million for each product licensed under the agreement, and upon commercialization, to make royalty payments in the low single digit percentages (subject to a specified minimum annual royalty) based on net sales of products commercialized pursuant to the agreement. None of these events had occurred and no milestone payments or royalty payments had been recognized as of December 31, 2023. In December 2021, the Company entered an agreement to exclusively license its rights in the α-Klotho asset to Jocasta Neuroscience, Inc. for development and commercialization. Under the license agreement, Jocasta Neuroscience, Inc. is, in addition to the payments due to the Company, required to make all payments due to UCSF from the Company under the UCSF License. The Company has also entered into license agreements with various research institutions which have provided the Company with rights to patents, and in certain cases, research “know-how” and proprietary research tools to research, develop and commercialize drug candidates. In addition to upfront consideration paid to these various research institutions in either cash or shares of the Company’s common stock, the Company may be obligated to make milestone payments, payable in cash and/or the issuance of shares of the Company’s common stock upon achievement of certain specified clinical development and/or sales events. The contingent consideration liability considered to be a derivative associated with the potential issuance of common stock related to these license agreements was not significant at December 31, 2023 and 2022. To date, none of these events has occurred and no contingent consideration, milestone or royalty payments have been recognized. Ascentage Commercial Agreements The Company was a party to three agreements (the "Commercial Agreements") with Ascentage Pharma: (a) a compound library and option agreement executed in February 2016 , the Library Agreement, granting the Company the right to research and nominate an active compound from Ascentage’s library of Bcl compounds and subsequently nominate a development candidate from any active compound in order to begin GLP toxicology work for indications outside of oncology, which expired in February 2022 ; (b) a license agreement executed in February 2016 granting the Company rights to an Ascentage Pharma compound known as APG1252, or the APG1252 License Agreement, which the Company terminated in July 2020 due to the Company’s decision to prioritize the progression of UBX1325; and (c) a second license agreement executed in January 2019 granting the Company world-wide rights to develop and commercialize UBX0601, the active parent molecule of our lead drug candidate UBX1325, outside of Greater China, or the Original Bcl Agreement, for indications outside of oncology. The Commercial Agreements referenced above include cash payments of up to $ 70.3 million as well as the equity payments of up to an aggregate of (a) 93,333 shares of common stock in the event there is only one licensed product, and (b) 133,333 shares of common stock in the event there are two or more licensed products, in each case to be issued based on the Company’s achievement of certain preclinical and clinical development and sales milestone events. The Company is required to make 80 % of all equity payments to Ascentage Pharma and the remaining 20 % to an academic institution from whom Ascentage Pharma had previously licensed the technology. The milestones include the advancement of additional compounds into Investigational New Drug application (“IND”) enabling studies, the filing of an IND, the commencement of clinical studies, Food and Drug Administration (“FDA”) and/or European Medicines Agency approval, and a net sales threshold. The Original Bcl License Agreement also includes tiered royalties in the low-single digits based on sales of licensed products. To date, no royalties were due from the sales of licensed products. The Company issued no shares pursuant to these agreements during the year ended December 31, 2023.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	7. Balance Sheet Components Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): December 31, 2023 2022 Prepaid research and development expenses $ 415 $ 378 Prepaid insurance expenses 541 710 Tax credit receivable 1,493 — Interest receivable 84 235 Other prepaid expenses and current assets 871 417 $ 3,404 $ 1,740 Property and Equipment, Net Property and equipment, net, consists of the following (in thousands): December 31, 2023 2022 Laboratory equipment $ 3,894 $ 4,197 Computer equipment 303 412 Furniture and fixtures 627 726 Leasehold improvements 9,519 15,244 Total property and equipment 14,343 20,579 Less: accumulated depreciation and amortization ( 9,261 ) ( 12,754 ) Total property and equipment, net $ 5,082 $ 7,825 Depreciation and amortization expense related to property and equipment was $ 1.2 million, $ 2.2 million and $ 2.9 million for the years ended December 31, 2023, 2022 and 2021, respectively. Accrued and Other Current Liabilities Accrued and other current liabilities consist of the following (in thousands): December 31, 2023 2022 Operating lease liability - current portion $ 3,451 $ 3,100 Accrued research and development 839 1,623 Liability related to early exercise shares 10 10 Accrued other 319 601 $ 4,619 $ 5,334

Government Assistance Program

Government Assistance Program	12 Months Ended
	Dec. 31, 2023
Government Assistance [Abstract]
Government Assistance Program	8. Government Assistance Program Under the CARES Act, the Company met eligibility criteria and was approved for a $ 1.5 million refundable employee retention credit. The Company recorded contra-expense to personnel related costs within general and administrative expense of $ 0.4 million and research and development expense of $ 1.1 million for the year ended December 31, 2023. No such amounts were recorded for the year ended December 31, 2022. The Company had an employee retention credit receivable due from the U.S. Department of Treasury of $ 1.5 million in other current assets as of December 31, 2023 in the balance sheet. There was no employee retention credit receivable due from the U.S. Department of Treasury as of December 31, 2022.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9 . Commitments and Contingencies Leases In February 2019, the Company entered into a lease agreement for new office and laboratory space in South San Francisco, California. The term of the lease agreement commenced in May 2019 . The lease has an initial term from occupancy of approximately ten years ending on December 31, 2029 with an option to extend the term for an additional eight years at then-market rental rates. The total base rent payment escalates annually based on a fixed percentage beginning from the 13 th month of the lease agreement. The Company will also be responsible for the operating expenses and real estate taxes allocated to the building and common areas. Pursuant to the lease agreement, the landlord provided the Company with a tenant improvement allowance of $ 10.7 million, which was included in deferred rent and leasehold improvements on the balance sheet at December 31, 2019. In connection with the execution of the lease agreement, the Company delivered a letter of credit of approximately $ 0.9 million to the landlord. The Company’s operating leases include various covenants, indemnities, defaults, termination rights, security deposits and other provisions customary for lease transactions of this nature. The following table summarizes the components of lease expense, which are included in operating expenses in the Company’s Statements of Operations and Comprehensive Loss (in thousands): Year ended December 31, 2023 2022 2021 Operating lease expense $ 3,739 $ 4,264 $ 4,357 Variable lease expense 748 1,318 1,633 Sublease income ( 3,988 ) ( 4,317 ) ( 2,578 ) Total lease expense $ 499 $ 1,265 $ 3,412 Variable lease payments include amounts relating to common area maintenance, real estate taxes and insurance and are recognized in the Statements of Operations and Comprehensive Loss as incurred. The following table summarizes supplemental information related to operating leases (in thousands): Year ended December 31, 2023 2022 2021 Cash paid for amounts included in the measurement of lease liabilities $ 4,810 $ 6,283 $ 6,653 Weighted-average remaining lease term (years) 6.0 7.0 7.7 Weighted-average discount rate (percentage) 6.0 % 6.0 % 5.9 % The following table summarizes the maturities of lease liabilities as of December 31, 2023 (in thousands): Amount 2024 $ 4,964 2025 5,123 2026 5,287 2027 5,457 2028 5,633 Thereafter 5,801 Total future minimum lease payments 32,265 Less: Amount representing interest ( 5,275 ) Present value of future minimum lease payments 26,990 Less: Current portion of operating lease liability ( 3,451 ) Noncurrent portion of operating lease liability $ 23,539 In February 2021, the Company entered into an agreement to sublease the first floor of the Brisbane, California facility (the Company's previous offices and laboratory space), consisting of approximately 27,000 square feet, to Zymergen, Inc., through August 31, 2022 . The base sublease rent rate is $ 3.53 per rental square foot per month and will increase by 3 % on March 1, 2022 through expiration of the agreement. Additionally, the subtenant is required to pay approximately 41 % of operating expenses and property management fees that the Company is required to pay under the lease for the Brisbane, California facility. In May 2021, the Company entered into an agreement to sublease the second floor of the Brisbane, California facility, consisting of approximately 11,500 square feet, to CareDx, Inc., through September 30, 2022 . The base sublease rent rate is $ 1.00 per rental square foot per month through expiration of the agreement. Additionally, the subtenant is required to pay approximately 30 % of operating expenses and property management fees that the Company is required to pay under the lease for the Brisbane, California facility. The Company incurred initial direct costs of $ 0.1 million in sublease commissions related to entering into the agreements to sublease the Brisbane, California facility. To account for the commissions, the Company capitalized the total commissions amount and will amortize the balance over the term of the sublease. Sublease income from this facility was zero , $ 1.3 million and $ 1.5 million for the years ended December 31, 2023, 2022 and 2021, respectively, which was offset against total rent expense. In June 2021, the Company entered into an agreement to sublease a portion of the first floor of the South San Francisco facility, consisting of approximately 23,000 square feet, to Freenome Holdings, Inc., through July 31, 2024 . The base sublease rent rate is $ 6.25 per rental square foot per month and will increase annually by 3.5 % through expiration of the agreement. Additionally, the subtenant is required to pay approximately 37 % of operating expenses and property management fees that the Company is required to pay under the lease for the South San Francisco, California facility. The Company incurred initial direct costs of $ 0.2 million in sublease commissions related to entering into the agreements to sublease the South San Francisco, California facility. To account for the commissions, the Company capitalized the total commissions amount and will amortize the balance over the term of the sublease. Sublease income related to this facility and this specific sub-tenant was $ 2.3 million, $ 2.2 million and $ 1.1 million for the years ended December 31, 2023, 2022 and 2021, respectively, which was offset against total rent expense. In May 2022, the Company entered into an agreement to sublease a portion of the second floor of the South San Francisco, California facility, consisting of approximately 15,000 square feet, to Initial Therapeutics, Inc. ("Initial Therapeutics"). The original sublease term commenced on July 1, 2022 and continued through June 30, 2024 and further extended through June 30, 2026 upon execution of an amendment as defined below. The base sublease rent rate is $ 7.80 per rental square foot per month and will increase by 3.5 % annually through the expiration of the agreement. Additionally, the subtenant is required to pay approximately 24 % of operating expenses and property management fees that the Company is required to pay under the lease for the South San Francisco, California facility. The Company incurred initial direct costs of $ 0.1 million in sublease commissions related to entering into the agreements to sublease the South San Francisco, California facility. To account for the commissions, the Company capitalized the total commissions amount and will amortize the balance over the term of the sublease. On September 15, 2023, the Company entered into an amendment with Initial Therapeutics to sublease the remainder of the second floor of the South San Francisco, California facility, consisting of an additional 17,000 square feet. The sublease term commenced on October 1, 2023 and extends the existing sublease agreement that commenced on July 1, 2022 through June 30, 2026 . The additional space will be subleased at a monthly rent rate of $ 1.00 per square foot starting a month after Initial Therapeutics first takes possession of the additional space through June 30, 2024. Starting July 1, 2024, the rent rate for the entirety of Initial Therapeutics' subleased space will be $ 6.02 per rental square foot per month and will increase 3.5 % on December 1, 2024 and 2025. Additionally, Initial Therapeutics will be required to pay approximately 51 % of operating expenses and property management fees that the Company is required to pay under the lease for the South San Francisco, California facility. The Company incurred initial direct costs of $ 0.3 million in sublease commissions. Sublease income related to this amendment was $ 1.7 million for the year ended December 31, 2023 which was offset against total rent expense. On September 15, 2023, the Company entered into a sublease agreement with GT Biopharma, Inc. to sublease a portion of its first floor at 8000 Marina Boulevard, Brisbane, California, consisting of 4,500 square feet. The sub-sublease term will commence on October 6, 2023 through June 30, 2024 . The space will be subleased at a rent rate of $ 2.00 per rent square feet. Impairment of Operating Lease Right-of-Use Asset and Other Long-Lived Assets As the Company is subleasing its South San Francisco facility through June 30, 2026, the Company determined an impairment indicator was present. The Company determined all of its long-lived assets represent entity wide asset group for the purpose of the long-lived asset impairment assessment. The Company concluded that the carrying value of the entity wide asset group was not recoverable as it exceeded the future net undiscounted cash flows that are expected to be generated from the use and eventual disposition of the assets within the asset group. To allocate and recognize the impairment loss, the Company determined the fair value of the Company using the adjusted net asset method under the cost approach. The implied allocated impairment loss to any individual asset within the long-lived asset group shall not reduce the carrying amount of that asset below its fair value. To determine the fair value of the individual assets within the asset group, the Company utilized the discounted cash flow method using the income approach. Based on this analysis, the Company recognized a non-cash impairment charge of $ 5.6 million, including $ 4.0 million for the right-of-use asset and $ 1.6 million for the leasehold improvements during the year ended December 31, 2023. This represents a Level 3 nonrecurring fair value measurement. Calculating the fair value of the assets involves significant estimates and assumptions. These estimates and assumptions include, among others, projected future cash flows, risk-adjusted discount rates and market rental rates. Changes in the factors and assumptions used could materially affect the amount of impairment loss recognized in the period the asset was considered impaired. Indemnifications The Company indemnifies each of its officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at the Company’s request in such capacity, as permitted under Delaware law and in accordance with the Company’s amended and restated certificate of incorporation and bylaws. The term of the indemnification period lasts as long as an officer or director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director and officer liability insurance. This insurance allows the transfer of risk associated with the Company’s exposure and may enable the Company to recover a portion of any future amounts paid. The Company believes that the fair value of these potential indemnification obligations is minimal. Accordingly, the Company has not recognized any liabilities relating to these obligations for any period presented.

Term Loan Facility

Term Loan Facility	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Term Loan Facility	10. Term Loan Facility On August 3, 2020, the Company entered into a Loan and Security Agreement (as amended, restated, supplemented or otherwise modified, the "Hercules Loan Agreement") with Hercules Capital, Inc. (“Hercules”), as administrative agent and collateral agent for the lenders, and certain banks and other financial institutions or entities from time to time parties thereto, for an aggregate principal amount of up to $ 80.0 million secured term loan facility (the "Hercules Facility") subject to certain terms and conditions. The first tranche of $ 25.0 million was advanced to the Company on the date the Loan Agreement was executed. The maturity date under the Hercules Loan Agreement was August 1, 2024 . On September 6, 2023, the Company and Hercules entered into a payoff letter for a voluntary prepayment with respect to the Hercules Loan Agreement (the “Payoff Letter”). Pursuant to the Payoff Letter, the Company paid a total of $ 15.0 million to Hercules, representing the outstanding principal, accrued and unpaid interest, fees, costs and expenses due to Hercules under the Hercules Facility and the Hercules Loan Agreement and related loan documents, in repayment of the Company’s outstanding obligations under the Hercules Facility and the Hercules Loan Agreement and related loan documents, and thereby terminated the Hercules Loan Agreement and the Hercules Facility and related loan documents. Under the terms of the Hercules Loan Agreement, no early termination penalty was payable as a result of such prepayment and termination as of such date. The Company recorded a loss on extinguishment of debt of $ 0.5 million under "Other expense, net" in the financial statements for the year ended December 31, 2023 related to the write-off of the remaining balance of unamortized debt discount. Pursuant to the Payoff Letter, the lenders’ commitments to extend further credit to the Company terminated. Hercules released and terminated all liens or security interests granted to secure the obligations under the Hercules Loan Agreement and the Company was unconditionally released from its respective guaranties and obligations under the Hercules Facility and the Hercules Loan Agreement and related loan documents without further action (other than with respect to customary provisions and agreements that are expressly specified to survive the termination). Hercules returned to the Company, for the benefit of the Company, all of the collateral that it had in its possession. Interest expense relating to the term loan, which is included in interest expense in the Statements of Operations and Comprehensive Loss was $ 2.5 million, $ 3.6 million and $ 3.2 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related-Party Transactions	11. Related Party Transactions Licensing Revenue – Related Party In December 2021, the Company entered into a license agreement with Jocasta Neuroscience, Inc. A member of the Board of Directors of the Company is also an affiliate of Jocasta Neuroscience, Inc. The agreement provides for an upfront fee of $ 5.0 million and the opportunity for future research and development services to be provided. The Company recognized zero , $ 0.2 million and $ 4.8 million of licensing revenue for the years ended December 31, 2023, 2022 and 2021, respectively.

Equity Financing

Equity Financing	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Equity Financing	12. Equity Financing On October 19, 2022, the Company effected a reverse stock split of its outstanding share of common stock at a ratio of 1-for-10 pursuant to a Certificate of Amendment to the Company's Certificate of Incorporation filed with the Secretary of State of the State of Delaware. The reverse stock split was reflected on the Nasdaq Global Select Market beginning with the opening of trading on October 20, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented. The Company has 10,000,000 shares of convertible preferred stock authorized for issuance, par value of $ 0.0001 per share. As of December 31, 2023 and 2022, no shares of preferred stock were issued and outstanding. The Company has 300,000,000 shares of common stock authorized for issuance, par value of $ 0.0001 per share. Holders of the Company’s common stock are entitled to one vote per share. As of December 31, 2023 and 2022, there were 16,784,969 and 14,215,302 shares, respectively, of common stock issued and outstanding. Follow-On Offering (Restated) In August 2022, the Company closed an underwritten offering (the “Follow-On Offering”) in which the Company issued and sold an aggregate of 6,428,571 of the Company’s common stock together with warrants (the "Existing Warrants”) to purchase up to 6,428,572 of the Company’s common stock at an offering price of at an aggregate offering price of $ 7.00 per unit. The Existing Warrants have an exercise price of $ 8.50 per warrant. The gross proceeds to the Company were $ 45.0 million before deducting underwriting discounts and commissions and other offering expenses. The net proceeds of the Follow-On Offering were approximately $ 41.7 million. The Existing Warrants are exercisable at any time after their original issuance and on or prior to the five-year anniversary of the original issuance date. A holder of Existing Warrants may not exercise the warrant if the holder, together with its affiliates, would beneficially own more than 4.99 % of the number of shares of common stock outstanding immediately after giving effect to such exercise. As of December 31, 2023, 2,143,000 warrants have been exercised. The Company recorded the Existing Warrants as liabilities based upon the guidance of ASC 480 and ASC 815. The Company evaluated the Existing Warrants under ASC 815-40 and concluded that they do not meet the criteria to be classified in stockholders’ equity. Specifically, the settlement value in a scenario of a fundamental transaction precluded the Existing Warrants from being indexed to the Company’s own stock and Company believes that the scope exception related to the occurrence of a fundamental transaction in ASC 815-40 is not met. Since the Existing Warrants meet the definition of a derivative, they are recorded as liabilities and measured at fair value at initial recognition. Any subsequent changes in their respective fair values is recognized in the Statement of Operations and Comprehensive Loss at each reporting date. At issuance, the Company valued the Existing Warrants using a Monte-Carlo valuation model due to the more than de-minims probability of a fundamental transaction which triggered a settlement value that is not indexed to the Company's own stock. The Monte Carlo valuation model resulted in a fair value of $ 27.6 million on the Existing Warrant issuance date. The difference between the gross proceeds of $ 45.0 million and $ 27.6 million fair value of warrants issued, was recorded to the stockholders’ equity under Common stock and Additional paid-in capital. Additionally, the Company also incurred an issuance cost of $ 3.3 million which was allocated to Existing Warrants and common stock based on their relative fair value. The issuance cost of $ 1.4 million attributed to the Existing Warrants were expensed under "Other expense, net" in the Statement of Operations and Comprehensive Loss. The remaining issuance cost of $ 1.9 million attributed to the common stock was recorded as a reduction to Additional paid-in capital. At December 31, 2023 and 2022, the Company updated the estimated fair value of the outstanding Existing Warrants using a Monte-Carlo valuation model resulting in an estimated fair value of $ 2.8 million (subsequent to the exercise of the Existing Warrants as described in the section below) and $ 10.7 million. The change in fair value for the year ended December 31, 2023 and 2022 of $ 6.6 million and $ 16.8 million was recorded as the Gain (loss) on warrant liability in the Statements of Operations and Comprehensive Loss for the year ended December 31, 2023 and 2022. Inducement Offer On November 9, 2023, the Company entered into an inducement offer letter agreement (the “Inducement Offer”) with certain holders (collectively, the “Holders”) of the Company's Existing Warrants to purchase up to an aggregate of 2,143,000 shares of common stock. The Holders agreed to exercise for cash their Existing Warrants to purchase an aggregate of 2,143,000 shares of common stock at a reduced exercise price of $ 2.045 per share in consideration of the Company’s agreement to issue new unregistered common stock purchase warrants (the “New Warrants”) to purchase up to an aggregate of 2,143,000 shares of the Company’s common stock. Each New Warrant will have an exercise price equal to $ 1.92 per share. The New Warrants will be exercisable on or after the initial issue date until the five-year anniversary of such date. The exercise price and number of New Warrant Shares issuable upon exercise of the New Warrants is subject to appropriate adjustment in the event of stock dividends, stock splits, subsequent rights offerings, pro rata distributions, reorganizations, or similar events affecting the Company’s common stock and the exercise price. The Company engaged H.C. Wainwright & Co., LLC (the “Placement Agent”) to act as its exclusive placement agent in connection with the transactions summarized above. The Company also issued to the Placement Agent or its designees warrants to purchase up to 128,580 shares of common stock. The Placement Agent Warrants have substantially the same terms as the New Warrants, except that the Placement Agent Warrants have an exercise price equal to $ 2.5563 per share. The Company recorded the New Warrants and Placement Agent Warrants (together “2023 Warrants”) as liabilities based upon the guidance of ASC 480 and ASC 815. The Company evaluated the 2023 Warrants under ASC 815-40 and concluded that they do not meet the criteria to be classified in stockholders’ equity. Specifically, the settlement value in a scenario of a fundamental transaction precludes the 2023 Warrants from being indexed to the Company’s own stock and Company believes that the scope exception related to the occurrence of a fundamental transaction in ASC 815-40 is not met. Since the 2023 Warrants are recorded as liabilities on the balance sheet at fair value, any subsequent changes in their respective fair values are recognized in the statement of operations and comprehensive loss at each reporting date. The Company received aggregate gross proceeds of $ 4.4 million from the exercise of the Existing Warrants by the Holders (the “Exercise”), before deducting placement agent fees and other offering expenses payable by the Company. The Company issued common stock at fair value of $ 3.7 million and 2023 Warrants at fair value of $ 2.7 million. The extinguished the Existing Warrants Liability of $ 1.4 million. The issuance costs related to 2023 Warrants and loss on extinguishment of Existing Warrants Liability of $ 1.0 million were expensed under "Other expense, net" in the Statement of Operations and Comprehensive Loss. At-the-Market Offering In June 2019, the Company filed a Registration Statement on Form S-3 (the “Shelf Registration Statement”), covering the offering of up to $ 250.0 million of common stock, preferred stock, debt securities, warrants and units. The Shelf Registration Statement included a prospectus covering the offering, issuance and sale of up to $ 75.0 million of the Company’s common stock from time to time through an “at-the-market” offering under the Securities Act of 1933, as amended (the “Initial ATM Offering Program”). The SEC declared the Shelf Registration Statement effective on June 6, 2019. In June 2019, the Company also entered into a sales agreement (the “June 2019 Sales Agreement”) with Cowen and Company, LLC (“Cowen”) to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $ 75.0 million, through the ATM Offering Program under which Cowen acts as its sales agent. Cowen is entitled to compensation for its services equal to up to 3.0 % of the gross proceeds of any shares of common stock sold through Cowen under the June 2019 Sales Agreement. During the year ended December 31, 2020, the Company issued and sold 500,226 shares of its common stock through its ATM Offering Program and received net proceeds of approximately $ 37.3 million, after deducting commissions and other offering expenses of $ 1.3 million. In July 2020, the Company filed an additional prospectus supplement to the Shelf Registration Statement. This prospectus supplement covers the offering, issuance and sale of up to an additional $ 50.0 million of the Company’s common stock from time to time through an additional “at-the-market” offering under the Securities Act of 1933, as amended (the “Additional ATM Offering Program”). The Initial ATM Offering Program and Additional ATM Offering Program are collectively called the “ATM Offering Programs”. In July 2020, the Company entered into sales agreement (the “July 2020 Sales Agreements”) with Cowen to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $ 50.0 million, through the Additional ATM Offering Program under which Cowen will act as its sales agent. The issuance and sale of shares of common stock by the Company pursuant to the July 2020 Sales Agreement are also deemed an “at-the-market” offering under the Securities Act of 1933, as amended (the “Securities Act”). Cowen is entitled to compensation for its services equal to up to 3.0 % of the gross proceeds of any shares of common stock sold through Cowen under the July 2020 Sales Agreement. During the year ended December 31, 2021, there were 118,707 shares of the Company’s common stock sold through the Initial ATM Offering Program and 70,746 shares of the Company’s common stock sold through the Additional ATM Offering Program and received total net proceeds of approximately $ 10.4 million, after deducting commissions and other offering expenses of $ 0.3 million. In March 2022, the Company filed a Registration Statement on Form S-3 (the “March 2022 Shelf Registration Statement”), covering the offering of up to $ 125.0 million of common stock, preferred stock, debt securities, warrants, and units, which was declared effective by the SEC in May 2022. In March 2022, the Company also entered into a sales agreement (the “March 2022 Sales Agreement”) with Cowen and Company, LLC ("Cowen") as sales agent to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $ 50.0 million pursuant to the March 2022 Shelf Registration Statement as an “at-the-market” offering under the Securities Act (the "March 2022 ATM Offering Program"). Cowen is entitled to up to 3.0 % of the gross proceeds of any shares of common stock sold under the March 2022 Sales Agreement. For so long as its public float is less than $ 75.0 million, it may not sell more than the equivalent of one-third of its public float during any 12 consecutive months pursuant to the "baby shelf" rules. During the year ended December 31, 2023, there were 274,781 shares of the Company's common stock sold pursuant to the March 2022 Sales Agreement and the Company received total net proceeds of approximately $ 1.0 million, after deducting commissions and other offering expenses which were insignificant. On August 17, 2022, the Company entered into Amendment No. 1 (the “Amendment”) to the March 2022 Sales Agreement, which Amendment decreased the amount of the Company’s common stock that can be sold by the Company through Cowen under the March 2022 Sales Agreement, from an aggregate offering of up to $ 50.0 million to an aggregate offering of up to $ 25.0 million. Following the Amendment, $ 14.6 million of shares of common stock remained available for sale under the March 2022 Sales Agreement, as amended, as of December 31, 2023. On March 17, 2023, the Company entered into Amendment No. 2 (the "Second Amendment"), accompanied by a prospectus supplement, to the March 2022 Sales Agreement. The Second Amendment added the limitations imposed on the Program by General Instruction I.B.6 of Form S-3 (“Instruction I.B.6”) to the Sales Agreement. Pursuant to Instruction I.B.6, in no event will the Company sell ATM Shares through the Program with a value exceeding more than one-third of the Company’s “public float” (the market value of the Company’s outstanding common stock held by non-affiliates) in any twelve-month period so long as the Company’s public float remains below $ 75.0 million. In October 2022, the Company filed a Registration Statement on Form S-3 (the “October 2022 Shelf Registration Statement”), covering the offering of up to $ 250.0 million of common stock, preferred stock, debt securities, warrants, and units. In October 2022, the Company also entered into a sales agreement (the “October 2022 Sales Agreement”) with Cowen as sales agent to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $ 50.0 million pursuant to the October 2022 Shelf Registration Statement as an “at-the-market” offering under the Securities Act. Cowen is entitled to up to 3.0 % of the gross proceeds of any shares of common stock sold under the October 2022 Sales Agreement. During the year ended December 31, 2023, there were no shares of the Company's common stock sold pursuant to the October 2022 Sales Agreement. Equity Purchase Agreement In September 2021, the Company entered into an equity purchase agreement (the “Purchase Agreement” or “Equity Purchase Agreement”) and a registration rights agreement with Lincoln Park Capital Fund, LLC (“Lincoln Park” or “Investor”) which provides for the sale to Lincoln Park up to $ 30,000,000 of shares (the “Purchase Shares”) of its common stock over the thirty-six ( 36 ) month term of the Purchase Agreement. In connection with the Purchase Agreement, Lincoln Park purchased 102,040 Purchase Shares at a purchase price of $ 2.94 per share, for a total gross purchase price of $ 3.0 million (the “Initial Purchase”), and the Company issued 25,244 shares of common stock to Lincoln Park as a commitment fee in connection with entering into the Purchase Agreement. The Company recognized $ 0.8 million of other expense relating to the commitment fee share issuance. From the date of the agreement through December 31, 2022, the Company had initiated the purchase of an additional 380,000 shares of the Company’s common stock amounting to $ 6.2 million in gross proceeds. The Company has initiated no purchases through the Purchase Agreement for the year ended December 31, 2023. Under the Purchase Agreement, the Company has sole discretion, subject to certain conditions, on any business day selected by the Company to require Lincoln Park to purchase up to 10,000 shares of common stock (the “Regular Purchase Amount”) at the Purchase Price (as defined below) per purchase notice (each such purchase, a “Regular Purchase”). The Regular Purchase Amount may be increased as follows: up to 15,000 shares if the closing price is not below $ 35.00 , up to 20,000 shares if the closing price is not below $ 50.00 , and up to 25,000 shares if the closing price is not below $ 70.00 . Lincoln Park’s committed obligation under each Regular Purchase is capped at $ 2,000,000 , unless the parties agree otherwise. The purchase price for Regular Purchases (the “Purchase Price”) shall be equal to the lesser of: (i) the lowest sale price of the common shares during the Purchase Date, or (ii) the average of the three (3) lowest closing sale prices of the common shares during the ten (10) business days prior to the Purchase Date. In addition to Regular Purchases and subject to certain conditions and limitations, the Company in its sole discretion may require Lincoln Park on each Purchase Date to purchase on the following business day up to the lesser of (i) three (3) times the number of shares purchased pursuant to such Regular Purchase or (ii) 30 % of the trading volume on the Accelerated Purchase Date (the “Accelerated Purchase”) (unless the Parties agree otherwise) at a purchase price equal to the lesser of 97 % of (i) the closing sale price on the Accelerated Purchase Date, or (ii) the Accelerated Purchase Date’s volume weighted average price (the “Accelerated Purchase Price”). The Company has the sole right to set a minimum price threshold for each Accelerated Purchase in the notice provided with respect to such Accelerated Purchase and under certain circumstances and in accordance with the Purchase Agreement the Company may direct multiple Accelerated Purchases in a day. The aggregate number of shares that the Company can sell to Lincoln Park under the Purchase Agreement may not exceed 1,106,580 shares of the common stock (which is equal to approximately 19.99 % of the shares of the common stock outstanding immediately prior to the execution of the Purchase Agreement) (the “Exchange Cap”), unless (i) shareholder approval is obtained to issue Purchase Shares above the Exchange Cap, in which the Exchange Cap will no longer apply, or (ii) the average price of all applicable sales of common stock to Lincoln Park under the Purchase Agreement equals or exceeds $ 29.40 per share; provided that at no time may Lincoln Park (together with its affiliates) beneficially own more than 9.99 % of the Company’s issued and outstanding common stock. The Purchase Agreement contains customary representations, warranties, covenants, closing conditions, indemnification and termination provisions. The Purchase Agreement may be terminated by the Company at any time, at its sole discretion, without any cost or penalty, by giving one business day notice to Lincoln Park. Further, Lincoln Park has covenanted not to engage in any direct or indirect short selling or hedging of the Common Shares. There are no limitations on the use of proceeds, financial or business covenants, restrictions on future financings (other than restrictions on the Company’s ability to enter into a similar type of agreement or Equity Line of Credit during the Term, excluding an At-The-Market transaction with a registered broker-dealer), rights of first refusal, participation rights, penalties or liquidated damages in the Purchase Agreement. Issuances under the Purchase Agreement were to be made pursuant to the Company's Registration Statement on Form S-3 filed in July 2019, which has since expired. The Company would need to file a new prospectus supplement covering issuances under the Purchase Agreement in order to continue using the facility.

Corporate Restructuring

Corporate Restructuring	12 Months Ended
	Dec. 31, 2023
Restructuring and Related Activities [Abstract]
Corporate Restructuring	13. Corporate Restructuring In February 2022 , the Company implemented a corporate restructuring to align its resources to focus on its UBX1325 program while further extending operating capital. The restructuring resulted in an elimination of 29 positions, or approximately 50 % of the Company’s workforce, in the first nine months of 2022. The Company incurred a one-time employee benefits and severance charge of approximately $ 1.9 million in operating expenses which was primarily recorded in the first nine months of 2022. Restructuring charges incurred under this plan primarily consisted of employee termination benefits. Employee termination benefits include $ 1.6 million of severance costs, $ 0.2 million of employee-related benefits, $ 0.1 million of payroll taxes and supplemental one-time termination payments. Charges and other costs related to the workforce reduction and structure realignment, and non-cash share-based compensation credits related to the forfeiture of stock options for $ 1.7 million, are included in operating expenses in the Statements of Operations and Comprehensive Loss. Of the total charge, $ 1.4 million was recorded to research and development expenses and $ 0.5 million was recorded to general and administrative expenses during the year ended December 31, 2022. In May 2023 , the Company implemented a reduction in its workforce to align operations with the changes in its corporate strategy to focus on resource optimization to enable the initiation and advancement of key data readouts. The reduction decreased its headcount by nine employees, or approximately 29 % of the Company’s workforce, effective as of May 31, 2023. Six employees departed as of the effective date and three employees departed as of June 30, 2023. The Company recognized the employee benefits and severance charge of approximately $ 0.6 million in operating expenses in the second quarter of 2023. Restructuring charges primarily consisted of employee termination benefits, which included $ 0.5 million of severance costs, $ 0.1 million of employee-related benefits, and a negligible amount of payroll taxes. Charges and other costs related to the restructuring, and non-cash share-based compensation credits related to the forfeiture of stock options were negligible and are included in operating expenses in the Statements of Operations and Comprehensive Loss. Of the total charge, $ 0.4 million was recorded to research and development expenses and $ 0.2 million was recorded to general and administrative expenses during the year ended December 31, 2023.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	14. Stock-Based Compensation Summary of Equity Incentive Plans In March 2018, the Company’s board of directors adopted the Company’s 2018 Incentive Award Plan (the “2018 Plan”). The 2018 Plan was approved by the Company’s stockholders in April 2018 and became effective in May 2018. The 2018 Plan initially reserved 428,994 shares for the issuance of stock options as well as any automatic annual increases in the number of shares of common stock reserved for future issuance under the 2018 Plan. Awards granted under the 2018 Plan expire no later than ten years from the date of grant. For stock options, the option price shall not be less than 100 % of the estimated fair value on the day of grant. Options granted typically vest over a four-year period but may be granted with different vesting terms. Unvested options not exercised at the time of an employee’s termination of employment are added back to the 2018 Plan. Following the Company’s IPO and in connection with the effectiveness of the 2018 Plan, the 2013 Equity Incentive Plan (the “2013 Plan”) terminated and no further awards will be granted under that plan. All outstanding awards under the 2013 Plan will continue to be governed by their existing terms and the shares that remained outstanding for issuance under the 2013 Plan were transferred into the 2018 Plan. As of December 31, 2023, there were in aggregate 2,182,500 shares of common stock authorized for issuance under the 2018 Plan. Prior to its termination, the 2013 Plan provided for the granting of incentive stock options (“ISOs”), non-statutory stock options (“NSOs”) and restricted shares to employees, directors, and consultants at the discretion of management and the board of directors. The exercise price of an ISO and NSO shall not be less than 100 % of the estimated fair value of the shares on the date of grant, and the exercise price of an ISO and NSO granted to a 10 % stockholder shall not be less than 110 % of the estimated fair value of the shares on the date of grant. For awards granted between September 2017 and February 2018 with an exercise price of $ 3.42 , a deemed fair value ranging from $ 3.95 to $ 8.47 per share was used in calculating stock-based compensation expense, which was determined using management hindsight. Options granted under the 2013 Plan expire no later than ten years from the date of grant and generally vest over a four-year period but may be granted with different vesting terms. Unvested options not exercised at the time of an employee’s termination of employment are added back to the 2018 Plan. Under the 2013 Plan, the Company permitted early exercise of certain stock options prior to vesting. These unvested shares are subject to repurchase by the Company at the original issuance price in the event the optionee’s employment is terminated either voluntarily or involuntarily. The amounts paid for shares purchased under an early exercise of stock options and subject to repurchase by the Company are reported as a liability and reclassified into additional paid-in capital as the shares vest. In March 2020, the Company’s board of directors approved the Company’s 2020 Employment Inducement Incentive Plan (“the 2020 Plan”), to provide for grants to newly hired employees as a material inducement for them to commence employment with the Company. The 2020 Plan initially reserved 110,000 shares for the issuance of stock options, and in November 2020, the Company reserved an additional 150,000 shares of common stock for future issuance under the 2020 Plan. In February 2023, the Company reserved an additional 300,000 shares of common stock for future issuance under the 2020 Plan. Awards granted under the 2020 Plan expire no later than ten years from the date of grant. For stock options, the option price shall not be less than 100 % of the estimated fair value on the day of grant. Options granted typically vest over a four-year period but may be granted with different vesting terms. Unvested options not exercised at the time of an employee’s termination of employment are added back to the 2020 Plan. As of December 31, 2023, there were in aggregate 542,000 shares of common stock authorized for issuance under the 2020 Plan. Equity Incentive Plan Activity The following sections summarize activity under the Company’s equity incentive plans. Stock Options and Restricted Stock Units (RSUs) Activity A summary of the Company’s stock option activity under the 2013 Plan, 2018 Plan and 2020 Plan for the year ended December 31, 2023 is as follows: Shares Outstanding Weighted- Weighted- Aggregate (in Years) (in thousands) Balance at December 31, 2022 68,838 1,609,938 $ 27.51 8.3 $ 251 Shares added 1,010,831 — — Granted ( 446,200 ) 446,200 2.79 Exercised — — — Canceled 153,367 ( 142,793 ) 7.96 Balance at December 31, 2023 786,836 1,913,345 $ 14.23 7.1 $ 5 Vested and exercisable at December 31, 2023 1,179,366 $ 20.51 6.0 $ — Vested and expected to vest at December 31, 2023 1,913,345 $ 14.23 7.1 $ 5 The total intrinsic value of options exercised was zero for the years ended December 31, 2023 and 2022, respectively. The weighted-average estimated fair value of stock options granted was $ 2.79 and $ 3.11 for the years ended December 31, 2023 and 2022, respectively. The aggregate intrinsic value of options exercisable was zero as of December 31, 2023 and 2022. In September 2020, the board of directors granted retention stock-based awards to employees covering an aggregate of 320,000 shares of common stock, including options to purchase an aggregate of 25,000 shares of common stock and 295,985 of restricted stock units. The awards are all time-based vesting and vest over three to four years . During the years ended December 31, 2023 and 2022, there were no shares issued in settlement of stock-based compensation awards accounted for as liability awards. The following table summarizes the Company’s RSU activity for the year ended December 31, 2023: Shares Weighted- Unvested at December 31, 2022 146,333 $ 27.66 Granted — $ — Released ( 94,534 ) $ 28.39 Canceled ( 10,574 ) $ 11.27 Unvested at December 31, 2023 41,225 $ 30.18 As of December 31, 2023, the total stock-based compensation cost related to options and RSUs granted but not yet amortized was $ 3.9 million and will be recognized over a weighted-average period of approximately 0.9 years. The total grant date fair value of RSUs and RSAs vested during the years ended December 31, 2023 and 2022 was approximately $ 0.3 million and $ 0.6 million, respectively. In March 2020, the board of directors granted the Company’s newly hired Chief Executive Officer stock-based awards covering an aggregate of 110,000 shares of common stock, including options to purchase an aggregate of 80,000 shares of common stock, 12,000 RSUs, 15,000 PSUs, and 3,000 RSAs that immediately vested on the grant date. The stock-based awards were granted pursuant to the 2020 Employment Inducement Incentive Plan, which was approved by the board of directors in March 2020 to provide for grants to newly hired employees as a material inducement for them to commence employment with the Company. In February 2022, the Company’s board of directors approved the granting of retention awards to critical and important Company personnel. The awards consisted of 189,333 stock options and 46,332 restricted stock units with a grant date total fair value of $ 2.0 million and $ 0.5 million, respectively. Valuation of Stock Options The Company uses the Black-Scholes option-pricing model for determining the estimated fair value and stock-based compensation related to stock options and ESPP awards. The fair value of stock options granted to employees was estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Year ended December 31, 2023 2022 2021 Expected term of options (in years) 5.79 5.55 6.0 Expected stock price volatility 94.11 %- 98.92 % 86.22 %- 93.17 % 85.7 %- 88.5 % Risk-free interest rate 3.36 %- 4.13 % 2.41 %- 4.01 % 1.08 %- 1.35 % Expected dividend yield — — — The valuation assumptions were determined as follows: Expected Term —The expected term represents the period that the options granted are expected to be outstanding and is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term) as the Company has concluded that its stock option exercise history does not provide a reasonable basis upon which to estimate expected term. Expected Volatility —Due to limited historical data, the Company estimates stock price volatility based on a combined weighted-average of the Company’s historical average volatility and that of a selected peer group of comparable publicly traded companies within the biotechnology and pharmaceutical industry that were deemed to be representative of future stock price trends over the expected life of the award. Risk-Free Interest Rate —The Company based the risk-free interest rate over the expected term of the options based on the constant maturity rate of U.S. Treasury securities with similar maturities as of the date of the grant. Expected Dividend Yield —The Company has never paid any dividends and does not plan to pay dividends in the foreseeable future. Therefore, the expected dividend yield is zero. The fair value of ESPP awards was not material for all periods presented. Performance Stock Units The PSUs were originally scheduled to vest as to 5,000 PSUs upon the attainment of (a) a volume-weighted average per share closing trading price of the Company’s common stock of at least $ 368.75 over a trailing 30 -day period or (b) a change in control transaction in which the price per share to the holders of the Company’s common stock is at least $ 368.75 and as to 10,000 PSUs (x) at such time as the Company’s market capitalization reaches at least $ 2.5 billion, as measured based on the volume weighted-average closing trading price over a trailing 30 day period or (y) a change in control transaction in which the consideration paid to the Company’s stockholders is equal to at least $ 2.5 billion, as determined by the Company’s board of directors. In January 2021, the board of directors modified the PSUs to vest as to 5,000 PSUs upon the attainment of (a) a volume-weighted average per share closing trading price of the Company’s common stock of at least $ 180.00 over a trailing 30 -day period or (b) a change in control transaction in which the price per share to the holders of the Company’s common stock is at least $ 180.00 and as to 10,000 PSUs upon the attainment of (x) a volume-weighted average per share closing trading price of the Company’s common stock of at least $ 360.00 over a trailing 30 -day period or (y) a change in control transaction in which the price per share to the holders of the Company’s common stock is at least $ 360.00 , as determined by the Company’s board of directors . For the PSU awards, the Company used the Monte-Carlo option pricing model to determine the fair value of awards at the date of grant. The Monte-Carlo option pricing model uses similar input assumptions as the Black-Scholes model; however, it further incorporates into the fair-value determination the possibility that the market condition may not be satisfied. Compensation costs related to awards with a market-based condition are recognized regardless of whether the market condition is ultimately satisfied. Compensation cost is not reversed if the achievement of the market condition does not occur. The total grant date fair value of the PSU awards was determined to be $ 0.7 million and will be recognized as compensation expense over the weighted-average derived service period of approximately 4.3 years. The incremental fair value of the PSUs on the modification date of $ 31,000 are added to the unamortized value of the original grant of $ 569,000 and will be amortized to expense over the new implied service periods of 1.63 years to 2.79 years. Performance and Market Contingent Stock Options In January 2021, the board of directors modified 1,747 performance and market contingent stock options with vesting conditions that required the combination of a liquidity event, change of control or IPO with a market condition at prescribed levels. The modification removed the performance condition and lowered the market conditions to a volume-weighted average per share closing trading price of the Company’s common stock of at least $ 180.00 over a trailing 30 -day period for one tranche and at least $ 360.00 over a trailing 30 -day period for the second tranche. The fair value of the options on the modification date of $ 81,000 will be amortized to expense over the implied service periods of 1.46 years to 2.52 years. In June 2021, the board of directors modified 3,336 performance and market contingent stock options with vesting conditions that required the combination of a liquidity event, change of control or IPO with a market condition at prescribed levels. The modification removed the performance condition and adjusted the market conditions to a date on which the Company attains a valuation of at least one billion dollars measured by the volume-weighted average per share closing trading price of the Company’s common stock over a trailing 30 -day period. The fair value of the options on the modification date of $ 102,000 will be amortized to expense over the implied service periods of 1.85 years. As of December 31, 2023, there were 3,336 market contingent stock option awards outstanding with a total fair value of $ 0.1 million. 2018 Employee Stock Purchase Plan In March 2018, the Company’s board of directors adopted the Company’s 2018 Employee Stock Purchase Plan (the “2018 ESPP”). The 2018 ESPP was approved by the Company’s stockholders in April 2018 and became effective on May 2, 2018. The 2018 ESPP reserved 53,624 shares of common stock for issuance pursuant to future awards, as well as any automatic increases in the number of shares of the Company’s common stock reserved for future issuance under this plan. Under the 2018 ESPP, employees are offered the option to purchase the Company’s common stock at a discount during the offering periods, at semi-annual intervals, with their accumulated payroll deductions. The option purchase price will be 85 % of the lower of the closing trading price per share at the beginning of the offering period or at the purchase date. The 2018 ESPP provides for consecutive offering periods and eligible employees may elect to withhold up to 15 % of their compensation through payroll deductions during the offering period for the purchase of stock. The maximum number of shares that may be purchased by any one participant is limited to 15,000 shares in each offering period and $ 25,000 in fair market value during any calendar year per the Internal Revenue Code limits. The first offering period commenced on September 16, 2018. Stock-Based Compensation Expense The following table sets forth the total stock-based compensation expense for all options granted to employees and nonemployees and costs associated with the 2018 ESPP included in the Company’s statement of operations (in thousands): Year Ended December 31, 2023 2022 2021 Research and development $ 1,947 $ 3,526 $ 4,809 General and administrative 5,472 5,853 6,744 Total $ 7,419 $ 9,379 $ 11,553 During the years ended December 31, 2023, 2022 and 2021, stock-based compensation expense recognized related to nonemployee options was $ 0.4 million, $ 0.2 million and $ 0.4 million, respectively. Repricing On May 4, 2023 , and in accordance with the terms of the Company’s 2018 Plan, the Company’s Board of Directors approved a stock option repricing (the “Repricing”) for employees and certain service providers that were not affected by the reduction in its workforce, as well as affected employees and certain service providers entering into or subject to a continuing consulting agreement, as of May 11, 2023. Pursuant to the terms of the Repricing, the exercise price of each outstanding option to purchase shares of the Company's common stock granted under its 2018 Plan that had an original exercise price above $ 6.00 , was reduced to an exercise price of $ 2.77 , the closing price for the Company's common stock on May 11, 2023, the effective date of the Repricing. On the effective date of the Repricing, 26 employees and certain service providers held 444,273 shares of the Company's common stock under option grants that met the eligibility criteria. Eligible outstanding options continue to remain outstanding in accordance with their current terms and conditions. On the effective date of the Repricing, the Company recognized $ 0.2 million of additional stock-based compensation from 251,821 shares of its common stock under vested options. The Company anticipates an additional $ 0.1 million will be expensed over the period from the effective date of the Repricing through 2025 relating to 170,189 shares of the Company's common stock under unvested options. Stock option and awards modification In connection with the corporate restructuring, the Company’s executed consulting agreements with five of the 9 employees that were terminated as part of the reduction in force. The consulting agreements allowed for the non-employee to continue vesting in their option and awards, resulting in a modification to all then vested and outstanding option and awards. The modification resulted in an incremental compensation charge recognized upfront on the date of modification of $ 0.3 million. These costs were recorded as part of the stock compensation expense within “Research and development” and “General and administrative” costs within the Statement of Operations and Comprehensive Loss. There was no material incremental compensation expense as a result of modifications during the year ended December 31, 2022 and 2021.

Net Loss per Common Share

Net Loss per Common Share	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Loss per Common Share	15. Net Loss per Common Share Basic net loss per share is calculated by dividing net loss by the weighted-average number of shares outstanding for the period. Diluted net loss per share is calculated by dividing net loss by the weighted-average number of shares of common stock and potential dilutive common stock equivalents outstanding during the period if the effect is dilutive. The calculation of diluted earnings (loss) per share also requires the consideration of the effect of dilutive potential common shares outstanding during the period determined using the treasury-stock related to the warrants outstanding. A reconciliation of the numerators and denominators used in computing net loss from continuing operations per share is as follows (in thousands, except per share amounts): Year ended December 31, 2023 2022 (Restated) 2021 (in thousands, except share and per share amounts) Numerator: Net loss $ ( 39,860 ) $ ( 44,469 ) $ ( 60,725 ) Denominator: Weighted average number of shares outstanding—basic 14,773,612 9,494,421 5,581,587 Net loss per share—basic and diluted $ ( 2.70 ) $ ( 4.68 ) $ ( 10.88 ) The Company was in a net loss position for all periods presented, basic net loss per common share is the same as diluted net loss per common share as the inclusion of all potential securities outstanding would have been anti-dilutive. Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: Year ended December 31, 2023 2022 2021 Options to purchase common stock 1,913,345 1,609,938 866,696 Outstanding warrants to purchase common stock 6,557,152 6,428,572 — Early exercised common stock subject to future vesting 3,336 3,336 3,336 RSUs subject to future vesting 41,225 146,333 199,094 Shares subject to future vesting relating to the 2018 ESPP 47,389 65,939 14,774 Total 8,562,447 8,254,118 1,083,900 Up to 3,390 shares may be contingently issued, if certain performance conditions are met under the Company’s in-licensing agreements. See Note 6, “License Revenue, Agreements and Strategic Investment”.

Defined Contribution Plan

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

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	17. Income Taxes The Company has incurred net operating losses for all the periods presented. The Company has not reflected the benefit of any such net operating loss carryforwards in the accompanying financial statements. The Company has established a full valuation allowance against its deferred tax assets due to the uncertainty surrounding the realization of such assets. All losses to date have been incurred domestically as the Company has no international operations or subsidiaries. No provision for U.S. income taxes exists due to tax losses incurred in all periods presented. All losses incurred were U.S. based. The effective tax rate for the years ended December 31, 2023, 2022 and 2021 is different from the federal statutory rate primarily due to the valuation allowance against deferred tax assets as a result of insufficient sources of income. The effective tax rate of the Company’s provision for income taxes differs from the federal statutory rate as follows: Year ended December 31, 2023 2022 (Restated) 2021 Taxes at the U.S. statutory income tax rate 21.0 % 21.0 % 21.0 % State tax, net of federal benefit 9.0 9.1 4.4 Other 0.5 ( 0.8 ) ( 0.4 ) Warrant activity 2.8 7.3 — Stock-based compensation ( 2.5 ) ( 6.6 ) ( 1.6 ) Research and development tax credits 1.8 2.9 3.2 Rate change ( 8.8 ) 4.7 3.8 ASC 740-10 — ( 7.5 ) ( 4.2 ) Change in valuation allowance ( 23.7 ) ( 30.1 ) ( 26.2 ) Total provision for income taxes — % — % — % Deferred income taxes reflect the net tax effects of (a) temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes, and (b) operating losses and tax credit carryforwards. The tax effects of significant items comprising the Company’s deferred income taxes are as follows: December 31, 2023 2022 (in thousands) Deferred tax assets: Federal and state operating loss carryforwards $ 81,094 $ 73,322 Research and development tax credits 9,552 8,646 Stock-based compensation 5,078 4,589 Accruals and other 320 587 Intangibles 1,343 5,329 Section 174 capitalization research expenses 10,117 6,624 Charitable contributions — 12 Operating lease liabilities 6,280 6,908 Total deferred tax assets 113,784 106,017 Deferred tax liabilities: Operating lease right-of-use asset ( 3,041 ) ( 4,371 ) Fixed assets ( 1,033 ) ( 1,299 ) Total deferred tax liabilities ( 4,074 ) ( 5,670 ) Valuation allowance ( 109,710 ) ( 100,347 ) Net deferred tax assets $ — $ — The tax benefit of net operating losses, temporary differences and credit carryforwards should be recorded as an asset to the extent that management assesses that their realization is "more likely than not." Realization of the future tax benefits is dependent on the Company's ability to generate sufficient taxable income within the carryforward period. Because of the Company's recent history of operating losses, management believes that recognition of the deferred tax assets arising from the above-mentioned future tax benefits is currently not likely to be realized and, accordingly, has provided a valuation allowance. Realization of the net deferred tax assets is dependent upon future taxable income, if any, the amount and timing of which is uncertain. Based on the weight of available positive and negative objective evidence, management believes it more likely than not that the Company’s deferred tax assets are not realizable. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. The valuation allowance increased by $ 9.4 million and $ 13.4 million during the years ended December 31, 2023 and 2022, respectively. Net operating losses and tax credit carryforwards as of December 31, 2023 are as follows: Amount Expiration Years Net operating losses, federal (post December 31, 2017) $ 305,873 Do Not Expire Net operating losses, federal (pre January 1, 2018) 64,136 2029 - 2037 Net operating losses, state 185,897 2034 - 2043 Research and development tax credits, federal 8,799 2034 - 2043 Research and development tax credits, California 7,070 Indefinite Federal and state laws impose restrictions on the utilization of net operating loss carryforwards and R&D credit carryforwards in the event of a change in ownership of the Company, which constitutes an 'ownership change' as defined by Internal Revenue Code Section 382 and 383. The Company experienced an ownership change in the past that impacts the availability of its net operating losses and tax credits. The amounts indicated in the above tables reflect the reduction of net operating losses and credit carryforwards as a result of previous ownership changes that the Company experienced. In August 2022, the Company's Follow-On Offering may have resulted in an ownership change, which could substantially restrict the ability to utilize existing net operating losses, credits and other attribute carryforwards as well. The Company is still analyzing the impact of the Follow-On Offering relative to Internal Revenue Code Sections 382 and 383. The Inflation Reduction Act 2022 which incorporates a Corporate Alternative Minimum Tax (CAMT) was signed on August 16, 2022. The changes will be effective for the tax years beginning after December 31, 2022. The new tax will require companies to compute two separate calculations for federal income tax purposes and pay the greater of the new minimum tax or their regular tax liability. The IRA is not expected to have a material impact for the Company. The Company determines its uncertain tax positions based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings is more likely than not to be sustained upon examination by the relevant income tax authorities. The following table summarizes the activity related to the Company’s unrecognized tax benefits: Year ended December 31, 2023 2022 2021 (in thousands) Gross unrecognized tax benefits at January 1 $ 17,605 $ 13,221 $ 7,142 Additions for tax positions taken in the current year 84 4,395 3,457 Reductions for tax positions taken in the prior year ( 232 ) ( 11 ) 2,622 Gross unrecognized tax benefits at December 31 $ 17,457 $ 17,605 $ 13,221 If recognized, no ne of the unrecognized tax benefits as of December 31, 2023 and 2022 would reduce the annual effective tax rate, primarily due to corresponding adjustments to the valuation allowance. The Company will recognize both accrued interest and penalties related to unrecognized benefits in income tax expense. As of December 31, 2023 and 2022, no liability has been recorded for potential interest or penalties. The Company does not expect the unrecognized tax benefits to change significantly over the next 12 months. The Company files income tax returns in the U.S. federal jurisdiction and Arizona, California, Colorado, Delaware, Florida, Illinois, Massachusetts, Rhode Island and Washington. The Company is not currently under audit by the Internal Revenue Service or other similar state or local authorities. All tax years remain open to examination by major taxing jurisdictions to which the Company is subject.

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2023
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (Unaudited)	18. Quarterly Financial Information (Unaudited) The previously reported financial information for the three and nine months ended September 30, 2022, the three months ended March 31, 2023, the three and six months ended June 30, 2023 and the three and nine months ended September 30, 2023, have been restated. Relevant restated financial information for each relevant period is included in this Annual Report on Form 10-K in the tables that follow. As part of the Warrants restatement (as noted below in the section titled ‘ Warrant Adjustments ’ for which the amounts restated are included with reference (a) in the table below), the Company has corrected certain other immaterial errors. While these other errors are quantitatively and qualitatively immaterial, individually and in the aggregate, because the Company is correcting for the material errors, the Company has corrected other errors as well. These adjustments are described in more detail in restated references (b), (c) and (d) in the section titled ‘ Other Adjustments impacting only the interim periods for 2022 and 2023’ . Warrant Adjustment (a) In March 2024, the Company concluded that it incorrectly classified certain warrants (the “Existing Warrants”) that were issued to investors in connection with a public offering of the Company’s common stock (“Common Stock”) in August 2022. Historically, the Existing Warrants were reflected as a component of equity as opposed to liabilities on the balance sheet. Additionally, the Statements of Operations and Comprehensive Loss did not include the subsequent non-cash changes in the fair value of the Existing Warrants. The Company reassessed its accounting for the Existing Warrants and determined that the Existing Warrants should be classified as liabilities measured at fair value upon issuance with subsequent changes in fair value reported, as well as the issuance cost associated with the Existing Warrants, in the Company’s Statement of Operations and Comprehensive Loss. Other Adjustments impacting only the interim periods for 2022 and 2023 The Company has corrected other immaterial errors. While these other errors are quantitatively and qualitatively immaterial, individually and in the aggregate, because the Company is correcting for the material errors, the Company has decided to correct these other errors as well. The adjustments to correct errors related to the out-of-period expenses are as follows: (b) The Company had previously understated its accrued and other current liability and overstated its prepaid expenses and other current assets as of September 30, 2022 and understated its research and development operating expense for the three- and nine- months ended September 30, 2023 by $ 0.9 million. The impact of the above other adjustment is reflected in the restatement tables below, as indicated by reference (b). (c) The Company had previously overstated the amortization of debt issuance cost. This resulted in the understatement of the long-term debt liability as of June 30, 2023 and the overstatement of interest expense for the three- and six- months ended June 30, 2023 by $ 0.1 million. The impact of the above other adjustment is reflected in the restatement tables below, as indicated by reference (c). (d) The Company had previously overstated its stock-compensation expense in the three months ended March 31, 2023 by $ 0.1 million, three- and six- months ended June 30, 2023 by $ 0.1 million and $ 0.2 million, respectively, and for the three- and nine- months ended September 30, 2023 by $ 0.3 million and $ 0.6 million, respectively. The impact of the above other adjustment is reflected in the restatement tables below as indicated by reference (d). The unaudited interim financial statements reflect all adjustments which are, in the opinion of management, necessary for a fair statement of the results for the interim periods presented (in thousands). Balance Sheets September 30, 2022 (unaudited) As Previously Reported Adjustment Reference As Restated Assets Current assets: Cash and cash equivalents $ 22,576 $ — $ 22,576 Short-term marketable securities 76,364 — 76,364 Prepaid expenses and other current asset 3,234 ( 150 ) b 3,084 Restricted cash 550 — 550 Total current assets 102,724 ( 150 ) 102,574 Property and equipment, net 8,202 — 8,202 Operating lease right-of-use assets 19,515 — 19,515 Long-term marketable securities 4,980 — 4,980 Long-term restricted cash 896 — 896 Other long-term assets 76 — 76 Total assets $ 136,393 $ ( 150 ) $ 136,243 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 2,444 $ — $ 2,444 Accrued compensation 2,961 — 2,961 Accrued and other current liabilities 4,593 728 b 5,321 Current portion of long-term debt 6,776 — 6,776 Total current liabilities 16,774 728 b 17,502 Operating lease liability, net of current portion 27,792 — 27,792 Long-term debt, net 13,262 — 13,262 Warrant liability — 16,633 a 16,633 Total liabilities 57,828 17,361 75,189 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,036,249 shares issued and outstanding as of September 30, 2022 1 — 1 Additional paid-in capital 524,623 ( 26,222 ) a 498,401 Accumulated other comprehensive loss ( 275 ) — ( 275 ) Accumulated deficit ( 445,784 ) 8,711 a,b ( 437,073 ) Total stockholders’ equity 78,565 ( 17,511 ) 61,054 Total liabilities and stockholders’ equity $ 136,393 $ ( 150 ) $ 136,243 March 31, 2023 (unaudited) As Previously Reported Adjustment Reference As Restated Assets Current assets: Cash and cash equivalents $ 22,972 $ — $ 22,972 Short-term marketable securities 60,420 — 60,420 Prepaid expenses and other current assets 2,989 — 2,989 Total current assets 86,381 — 86,381 Property and equipment, net 7,496 — 7,496 Operating lease right-of-use asset 18,557 — 18,557 Long-term deposits 896 — 896 Long-term restricted cash 896 — 896 Other long-term assets 29 — 29 Total assets $ 114,255 $ — $ 114,255 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 1,470 $ — $ 1,470 Accrued compensation 1,983 — 1,983 Accrued and other current liabilities 5,343 — 5,343 Current portion of long-term debt 13,062 — 13,062 Total current liabilities 21,858 — 21,858 Operating lease liability, net of current portion 26,150 — 26,150 Long-term debt, net 7,619 — 7,619 Warrant liability — 5,273 a 5,273 Total liabilities 55,627 5,273 60,900 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,359,214 shares issued and outstanding as of March 31, 2023 1 — 1 Additional paid-in capital 529,593 ( 26,317 ) a,d 503,276 Accumulated other comprehensive loss ( 150 ) — ( 150 ) Accumulated deficit ( 470,816 ) 21,044 a,d ( 449,772 ) Total stockholders’ equity 58,628 ( 5,273 ) 53,355 Total liabilities and stockholders’ equity $ 114,255 $ — $ 114,255 June 30, 2023 (unaudited) As Previously Reported Adjustment Reference As Restated Assets Current assets: Cash and cash equivalents $ 19,118 $ — $ 19,118 Short-term marketable securities 49,974 — 49,974 Prepaid expenses and other current assets 3,874 — 3,874 Total current assets 72,966 — 72,966 Property and equipment, net 7,181 — 7,181 Operating lease right-of-use asset 18,061 — 18,061 Long-term marketable securities 1,899 — 1,899 Long-term restricted cash 896 — 896 Other long-term assets 5 — 5 Total assets $ 101,008 $ — $ 101,008 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 1,449 $ — $ 1,449 Accrued compensation 1,652 — 1,652 Accrued and other current liabilities 5,417 — 5,417 Current portion of long-term debt 13,704 ( 81 ) c 13,623 Total current liabilities 22,222 ( 81 ) 22,141 Operating lease liability, net of current portion 25,297 — 25,297 Long-term debt, net 4,082 ( 15 ) c 4,067 Warrant liability — 8,734 a 8,734 Total liabilities 51,601 8,638 60,239 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,595,477 shares issued and outstanding as of June 30, 2023 1 — 1 Additional paid-in capital 532,563 ( 26,431 ) a,d 506,132 Accumulated other comprehensive loss ( 136 ) — ( 136 ) Accumulated deficit ( 483,021 ) 17,793 a,c,d ( 465,228 ) Total stockholders’ equity 49,407 ( 8,638 ) 40,769 Total liabilities and stockholders’ equity $ 101,008 $ — $ 101,008 September 30, 2023 (unaudited) As Previously Reported Adjustment Reference As Restated Assets Current assets: Cash and cash equivalents $ 7,876 $ — $ 7,876 Short-term marketable securities 38,063 — 38,063 Prepaid expenses and other current assets 3,599 — 3,599 Total current assets 49,538 — 49,538 Property and equipment, net 5,314 — 5,314 Operating lease right-of-use asset 13,522 — 13,522 Long-term restricted cash 896 — 896 Total assets $ 69,270 $ — $ 69,270 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 1,149 $ — $ 1,149 Accrued compensation 2,226 — 2,226 Accrued and other current liabilities 5,258 — 5,258 Total current liabilities 8,633 — 8,633 Operating lease liability, net of current portion 24,431 — 24,431 Warrant liability — 8,481 a 8,481 Total liabilities 33,064 8,481 41,545 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,614,890 shares issued and outstanding as of September 30, 2023 1 — 1 Additional paid-in capital 534,570 ( 26,781 ) a,d 507,789 Accumulated other comprehensive loss ( 55 ) — ( 55 ) Accumulated deficit ( 498,310 ) 18,300 a,d ( 480,010 ) Total stockholders’ equity 36,206 ( 8,481 ) 27,725 Total liabilities and stockholders’ equity $ 69,270 $ — $ 69,270 Quarterly and Year to Date Statements of Operations and Comprehensive Loss Three Months Ended Nine Months Ended As Previously Reported Adjustment Reference As Restated As Previously Reported Adjustment Reference As Restated Licensing revenue - related party $ — $ — $ — $ 236 $ — $ 236 Operating expenses: Research and development 8,208 878 b 9,086 28,222 878 b 29,100 General and administrative 4,922 — 4,922 15,669 — 15,669 Total operating expenses 13,130 878 14,008 43,891 878 44,769 Loss from operations ( 13,130 ) ( 878 ) ( 14,008 ) ( 43,655 ) ( 878 ) ( 44,533 ) Interest income 329 — 329 416 — 416 Interest expense ( 866 ) — ( 866 ) ( 2,568 ) — ( 2,568 ) Gain (loss) on warrant liability — 10,974 a 10,974 — 10,974 a 10,974 Other expense, net ( 41 ) ( 1,385 ) a ( 1,426 ) 49 ( 1,385 ) a ( 1,336 ) Net loss ( 13,708 ) 8,711 ( 4,997 ) ( 45,758 ) 8,711 ( 37,047 ) Other comprehensive loss Unrealized loss on marketable debt securities ( 88 ) — ( 88 ) ( 231 ) — ( 231 ) Comprehensive loss $ ( 13,796 ) $ 8,711 $ ( 5,085 ) $ ( 45,989 ) $ 8,711 $ ( 37,278 ) Net loss per share, basic and diluted $ ( 1.36 ) $ — $ ( 0.50 ) $ ( 5.77 ) $ — $ ( 4.67 ) Weighted average number of shares used in computing net loss per share, basic and diluted 10,072,077 — 10,072,077 7,928,729 — 7,928,729 Three Months Ended As Previously Reported Adjustment Reference As Restated Operating expenses: Research and development 5,835 ( 75 ) d 5,760 General and administrative 4,818 ( 20 ) d 4,798 Total operating expenses 10,653 ( 95 ) 10,558 Loss from operations ( 10,653 ) 95 ( 10,558 ) Interest income 855 — 855 Interest expense ( 1,002 ) — ( 1,002 ) Gain (loss) on warrant liability — 5,491 a 5,491 Other expense, net ( 65 ) — ( 65 ) Net loss ( 10,865 ) 5,586 ( 5,279 ) Other comprehensive gain Unrealized gain on marketable debt securities 101 — 101 Comprehensive loss $ ( 10,764 ) $ 5,586 $ ( 5,178 ) Net loss per share, basic and diluted $ ( 0.76 ) $ — $ ( 0.37 ) Weighted average number of shares used in computing net loss per share, basic and diluted 14,312,887 — 14,312,887 Three Months Ended Six Months Ended As Previously Reported Adjustment Reference As Restated As Previously Reported Adjustment Reference As Restated Licensing revenue - related party $ — $ — $ — $ — $ — $ — Operating expenses: Research and development 6,529 ( 94 ) d 6,435 12,364 ( 169 ) d 12,195 General and administrative 5,433 ( 20 ) d 5,413 10,252 ( 40 ) d 10,212 Total operating expenses 11,962 ( 114 ) 11,848 22,616 ( 209 ) 22,407 Loss from operations ( 11,962 ) 114 ( 11,848 ) ( 22,616 ) 209 ( 22,407 ) Interest income 805 — 805 1,660 — 1,660 Interest expense ( 979 ) 96 c ( 883 ) ( 1,981 ) 96 c ( 1,885 ) Gain (loss) on warrant liability — ( 3,461 ) a ( 3,461 ) — 2,030 a 2,030 Other expense, net ( 69 ) — ( 69 ) ( 133 ) — ( 133 ) Net loss ( 12,205 ) ( 3,251 ) ( 15,456 ) ( 23,070 ) 2,335 ( 20,735 ) Other comprehensive gain Unrealized gain on marketable debt securities 14 — 14 115 — 115 Comprehensive loss $ ( 12,191 ) $ ( 3,251 ) $ ( 15,442 ) $ ( 22,955 ) $ 2,335 $ ( 20,620 ) Net loss per share, basic and diluted $ ( 0.85 ) $ — $ ( 1.07 ) $ ( 1.61 ) $ — $ ( 1.44 ) Weighted average number of shares used in computing net loss per share, basic and diluted 14,425,775 — 14,425,775 14,369,643 — 14,369,643 Three Months Ended Nine Months Ended As Previously Reported Adjustment Reference As Restated As Previously Reported Adjustment Reference As Restated Operating expenses: Research and development 4,901 ( 269 ) d 4,632 17,266 ( 438 ) d 16,828 General and administrative 4,428 ( 81 ) d 4,347 14,681 ( 121 ) d 14,560 Impairment of long-lived assets 5,602 — 5,602 5,602 — 5,602 Total operating expenses 14,931 ( 350 ) 14,581 37,549 ( 559 ) 36,990 Loss from operations ( 14,931 ) 350 ( 14,581 ) ( 37,549 ) 559 ( 36,990 ) Interest income 689 — 689 2,349 — 2,349 Interest expense ( 470 ) ( 96 ) c ( 566 ) ( 2,451 ) — ( 2,451 ) Gain (loss) on warrant liability — 253 a 253 — 2,283 a 2,283 Other expense, net ( 577 ) — ( 577 ) ( 711 ) — ( 711 ) Net loss ( 15,289 ) 507 ( 14,782 ) ( 38,362 ) 2,842 ( 35,520 ) Other comprehensive gain Unrealized gain on marketable debt securities 81 — 81 196 — 196 Comprehensive loss $ ( 15,208 ) $ 507 $ ( 14,701 ) $ ( 38,166 ) $ 2,842 $ ( 35,324 ) Net loss per share, basic and diluted $ ( 1.05 ) $ — $ ( 1.01 ) $ ( 2.66 ) $ — $ ( 2.46 ) Weighted average number of shares used in computing net loss per share, basic and diluted 14,598,218 — 14,598,218 14,446,672 — 14,446,672 Statements of Changes in Stockholders' Equity Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at June 30, 2022 6,958,494 $ 1 $ 472,193 $ ( 187 ) $ ( 432,076 ) $ 39,931 Issuance of common stock, net of issuance costs, 633,464 — 8,570 — — 8,570 Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs 6,428,571 — 41,650 — — 41,650 Vesting of restricted stock units 15,720 — — — — — Stock-based compensation — — 2,210 — — 2,210 Unrealized loss on available-for-sale marketable securities — — — ( 88 ) — ( 88 ) Net loss — — — — ( 13,708 ) ( 13,708 ) Balances at September 30, 2022 14,036,249 $ 1 $ 524,623 $ ( 275 ) $ ( 445,784 ) $ 78,565 Adjustment Balances at June 30, 2022 — $ — $ — $ — $ — $ — Issuance of common stock, net of issuance costs, — — — — — — Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs — — ( 26,222 ) — — ( 26,222 ) Vesting of restricted stock units — — — — — — Stock-based compensation — — — — — — Unrealized loss on available-for-sale marketable securities — — — — — — Net loss — — — — 8,711 8,711 Balances at September 30, 2022 — $ — $ ( 26,222 ) $ — $ 8,711 $ ( 17,511 ) As Restated Balances at June 30, 2022 6,958,494 $ 1 $ 472,193 $ ( 187 ) $ ( 432,076 ) $ 39,931 Issuance of common stock, net of issuance costs, 633,464 — 8,570 — — 8,570 Sale of common stock under Follow-On Offering, net of issuance costs 6,428,571 — 15,428 — — 15,428 Vesting of restricted stock units 15,720 — — — — — Stock-based compensation — — 2,210 — — 2,210 Unrealized loss on available-for-sale marketable securities — — — ( 88 ) — ( 88 ) Net loss — — — — ( 4,997 ) ( 4,997 ) Balances at September 30, 2022 14,036,249 $ 1 $ 498,401 $ ( 275 ) $ ( 437,073 ) $ 61,054 Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at December 31, 2022 14,215,302 $ 1 $ 527,049 $ ( 251 ) $ ( 459,951 ) $ 66,848 Issuance of common stock, net of issuance costs, 106,781 — 274 — — 274 Vesting of restricted stock units 37,131 — — — — — Stock-based compensation — — 2,270 — — 2,270 Unrealized gain on available-for-sale marketable securities — — — 101 — 101 Net loss — — — — ( 10,865 ) ( 10,865 ) Balances at March 31, 2023 14,359,214 $ 1 $ 529,593 $ ( 150 ) $ ( 470,816 ) $ 58,628 Adjustment Balances at December 31, 2022 — $ — $ ( 26,222 ) $ — $ 15,458 $ ( 10,764 ) Issuance of common stock, net of issuance costs, — — — — — — Vesting of restricted stock units — — — — — — Stock-based compensation — — ( 95 ) — — ( 95 ) Unrealized loss on available-for-sale marketable securities — — — — — — Net loss — — — — 5,586 5,586 Balances at March 31, 2023 — $ — $ ( 26,317 ) $ — $ 21,044 $ ( 5,273 ) As Restated Balances at December 31, 2022 14,215,302 $ 1 $ 500,827 $ ( 251 ) $ ( 444,493 ) $ 56,084 Issuance of common stock, net of issuance costs, 106,781 — 274 — — 274 Vesting of restricted stock units 37,131 — — — — — Stock-based compensation — — 2,175 — — 2,175 Unrealized gain on available-for-sale marketable securities — — — 101 — 101 Net loss — — — — ( 5,279 ) ( 5,279 ) Balances at March 31, 2023 14,359,214 $ 1 $ 503,276 $ ( 150 ) $ ( 449,772 ) $ 53,355 Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at March 31, 2023 14,359,214 $ 1 $ 529,593 $ ( 150 ) $ ( 470,816 ) $ 58,628 Issuance of common stock, net of issuance costs, 168,000 — 518 — — 518 Issuance of common stock under 2018 ESPP 41,497 — 91 — — 91 Vesting of restricted stock units 26,766 — — — — — Stock-based compensation — — 2,361 — — 2,361 Unrealized gain on available-for-sale marketable securities — — — 14 — 14 Net loss — — — — ( 12,205 ) ( 12,205 ) Balances at June 30, 2023 14,595,477 $ 1 $ 532,563 $ ( 136 ) $ ( 483,021 ) $ 49,407 Adjustment Balances at March 31, 2023 — $ — $ ( 26,317 ) $ — $ 21,044 $ ( 5,273 ) Issuance of common stock, net of issuance costs, — — — — — — Issuance of common stock under 2018 ESPP — — — — — — Vesting of restricted stock units — — — — — — Stock-based compensation — — ( 114 ) — — ( 114 ) Unrealized gain on available-for-sale marketable securities — — — — — — Net loss — — — — ( 3,251 ) ( 3,251 ) Balances at June 30, 2023 — $ — $ ( 26,431 ) $ — $ 17,793 $ ( 8,638 ) As Restated Balances at March 31, 2023 14,359,214 $ 1 $ 503,276 $ ( 150 ) $ ( 449,772 ) $ 53,355 Issuance of common stock, net of issuance costs, 168,000 — 518 — — 518 Issuance of common stock under 2018 ESPP 41,497 — 91 — — 91 Vesting of restricted stock units 26,766 — — — — — Stock-based compensation — — 2,247 — — 2,247 Unrealized gain on available-for-sale marketable securities — — — 14 — 14 Net loss — — — — ( 15,456 ) ( 15,456 ) Balances at June 30, 2023 14,595,477 $ 1 $ 506,132 $ ( 136 ) $ ( 465,228 ) $ 40,769 Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at June 30, 2023 14,595,477 $ 1 $ 532,563 $ ( 136 ) $ ( 483,021 ) $ 49,407 Fees related to the ATM offering program — — ( 48 ) — — ( 48 ) Vesting of restricted stock units 19,413 — — — — — Stock-based compensation — — 2,055 — — 2,055 Unrealized gain on available-for-sale marketable securities — — — 81 — 81 Net loss — — — — ( 15,289 ) ( 15,289 ) Balances at September 30, 2023 14,614,890 $ 1 $ 534,570 $ ( 55 ) $ ( 498,310 ) $ 36,206 Adjustment Balances at June 30, 2023 — $ — $ ( 26,431 ) $ — $ 17,793 $ ( 8,638 ) Fees related to the ATM offering program — — — — — — Vesting of restricted stock units — — — — — — Stock-based compensation — — ( 350 ) — — ( 350 ) Unrealized gain on available-for-sale marketable securities — — — — — — Net loss — — — — 507 507 Balances at September 30, 2023 — $ — $ ( 26,781 ) $ — $ 18,300 $ ( 8,481 ) As Restated Balances at June 30, 2023 14,595,477 $ 1 $ 506,132 $ ( 136 ) $ ( 465,228 ) $ 40,769 Fees related to the ATM offering program — — ( 48 ) — — ( 48 ) Vesting of restricted stock units 19,413 — — — — — Stock-based compensation — — 1,705 — — 1,705 Unrealized gain on available-for-sale marketable securities — — — 81 — 81 Net loss — — — — ( 14,782 ) ( 14,782 ) Balances at September 30, 2023 14,614,890 $ 1 $ 507,789 $ ( 55 ) $ ( 480,010 ) $ 27,725 Statements of Cash Flows Nine Months Ended September 30, 2022 As Previously Reported Adjustment Reference As Restated Operating activities Net loss $ ( 45,758 ) $ 8,711 a,b $ ( 37,047 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 1,771 — 1,771 Amortization of debt issuance costs 989 — 989 Debt extinguishment gain upon conversion to equity ( 199 ) — ( 199 ) Net accretion and amortization of premium and discounts on marketable securities 155 — 155 Gain on disposal of property and equipment ( 247 ) — ( 247 ) Stock-based compensation 7,120 — 7,120 Non-cash rent expense ( 1,891 ) — ( 1,891 ) (Gain) loss on warrant liability — ( 10,974 ) a ( 10,974 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets ( 1,355 ) 150 b ( 1,205 ) Other long-term assets 15 — 15 Accounts payable 459 — 459 Accrued compensation ( 1,067 ) — ( 1,067 ) Accrued liabilities and other current liabilities ( 632 ) 728 b 96 Other long-term liabilities ( 23 ) — ( 23 ) Net cash used in operating activities ( 40,663 ) ( 1,385 ) ( 42,048 ) Investing activities Purchase of marketable securities ( 86,567 ) — ( 86,567 ) Maturities of marketable securities 62,000 — 62,000 Purchase of property and equipment ( 59 ) — ( 59 ) Sale of property and equipment 272 — 272 Net cash used in investing activities ( 24,354 ) — ( 24,354 ) Financing activities Proceeds from issuance of common stock under ATM offering program, net of issuance costs 12,003 — 12,003 Proceeds from sale of common stock and warrants under Follow-On Offering 41,650 3,350 a 45,000 Issuance costs for sale of common stock — ( 1,965 ) a ( 1,965 ) Proceeds from issuance of common stock to Lincoln Park Capital Fund, net of issuance costs 910 — 910 Proceeds from issuance of common stock under 2018 ESPP 125 — 125 Net cash provided by financing activities 54,688 1,385 56,073 Net decrease in cash, cash equivalents and restricted cash ( 10,329 ) — ( 10,329 ) Cash, cash equivalents and restricted cash at beginning of the period 34,351 — 34,351 Cash, cash equivalents and restricted cash at end of the period $ 24,022 $ — $ 24,022 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 1,577 $ — $ 1,577 Supplemental Disclosures of Non-Cash Investing and Financing Issuance of common stock in payment of debt $ 3,179 $ — $ 3,179 Cash and cash equivalents $ 22,576 $ — $ 22,576 Restricted cash 1,446 — $ 1,446 Total cash, cash equivalents and restricted cash $ 24,022 $ — $ 24,022 Three Months Ended March 31, 2023 As Previously Reported Adjustment Reference As Restated Operating activities Net loss $ ( 10,865 ) $ 5,586 a,d $ ( 5,279 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 329 — 329 Amortization of debt issuance costs 314 — 314 Net accretion and amortization of premium and discounts on marketable securities ( 433 ) — ( 433 ) Stock-based compensation 2,270 ( 95 ) d 2,175 Non-cash rent expense ( 270 ) — ( 270 ) (Gain) loss on warrant liability — ( 5,491 ) a ( 5,491 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets ( 1,249 ) — ( 1,249 ) Other long-term assets 23 — 23 Accounts payable ( 320 ) — ( 320 ) Accrued compensation ( 1,037 ) — ( 1,037 ) Accrued liabilities and other current liabilities ( 78 ) — ( 78 ) Net cash used in operating activities ( 11,316 ) — ( 11,316 ) Investing activities Purchase of marketable securities ( 5,973 ) — ( 5,973 ) Maturities of marketable securities 27,251 — 27,251 Net cash provided by investing activities 21,278 — 21,278 Financing activities Proceeds from issuance of common stock under ATM offering program, net of issuance costs 274 — 274 Net cash provided by financing activities 274 — 274 Net increase in cash, cash equivalents and restricted cash 10,236 — 10,236 Cash, cash equivalents and restricted cash at beginning of the period 13,632 — 13,632 Cash, cash equivalents and restricted cash at end of the period $ 23,868 $ — $ 23,868 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 680 $ — $ 680 Cash and cash equivalents $ 22,972 $ — $ 22,972 Restricted cash 896 — $ 896 Total cash, cash equivalents and restricted cash $ 23,868 $ — $ 23,868 Six Months Ended June 30, 2023 As Previously Reported Adjustment Reference As Restated Operating activities Net loss $ ( 23,070 ) $ 2,335 a,c,d $ ( 20,735 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 643 — 643 Amortization of debt issuance costs 653 ( 96 ) c 557 Net accretion and amortization of premium and discounts on marketable securities ( 831 ) — ( 831 ) Stock-based compensation 4,631 ( 209 ) d 4,422 Non-cash rent expense ( 540 ) — ( 540 ) (Gain) loss on warrant liability — ( 2,030 ) a ( 2,030 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets ( 2,134 ) — ( 2,134 ) Other long-term assets 47 — 47 Accounts payable ( 341 ) — ( 341 ) Accrued compensation ( 1,368 ) — ( 1,368 ) Accrued liabilities and other current liabilities ( 89 ) — ( 89 ) Net cash used in operating activities ( 22,399 ) — ( 22,399 ) Investing activities Purchase of marketable securities ( 21,868 ) — ( 21,868 ) Maturities of marketable securities 53,000 — 53,000 Net cash provided by investing activities 31,132 — 31,132 Financing activities Proceeds from issuance of common stock under ATM offering program, net of issuance costs 792 — 792 Repayment of term loan debt ( 3,234 ) — ( 3,234 ) Proceeds from issuance of common stock under 2018 ESPP 91 — 91 Net cash used in financing activities ( 2,351 ) — ( 2,351 ) Net increase in cash, cash equivalents and restricted cash 6,382 — 6,382 Cash, cash equivalents and restricted cash at beginning of the period 13,632 — 13,632 Cash, cash equivalents and restricted cash at end of the period $ 20,014 $ — $ 20,014 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 1,362 $ — $ 1,362 Cash and cash equivalents $ 19,118 $ — $ 19,118 Restricted cash 896 — $ 896 Total cash, cash equivalents and restricted cash $ 20,014 $ — $ 20,014 Nine Months Ended September 30, 2023 As Previously Reported Adjustment Reference As Restated Operating activities Net loss $ ( 38,362 ) $ 2,842 a,d $ ( 35,520 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 951 — 951 Amortization of debt issuance costs 705 — 705 Debt extinguishment loss upon paydown of principal 491 — 491 Net accretion and amortization of premium and discounts on marketable securities ( 1,199 ) — ( 1,199 ) Stock-based compensation 6,686 ( 559 ) d 6,127 Non-cash rent expense ( 811 ) — ( 811 ) Impairment of long-lived assets 5,602 — 5,602 (Gain) loss on warrant liability — ( 2,283 ) a ( 2,283 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets ( 1,858 ) — ( 1,858 ) Other long-term assets 52 — 52 Accounts payable ( 642 ) — ( 642 ) Accrued compensation ( 793 ) — ( 793 ) Accrued liabilities and other current liabilities ( 335 ) — ( 335 ) Net cash used in operating activities ( 29,513 ) — ( 29,513 ) Investing activities Purchase of marketable securities ( 28,609 ) — ( 28,609 ) Maturities of marketable securities 74,000 — 74,000 Purchase of property and equipment ( 11 ) — ( 11 ) Sale of property and equipment 1 — 1 Net cash provided by investing activities 45,381 — 45,381 Financing activities Payment of debt principal ( 20,000 ) — ( 20,000 ) Payment of debt issuance costs ( 1,563 ) — ( 1,563 ) Proceeds from issuance of common stock under ATM offering program, net of issuance costs 744 — 744 Proceeds from issuance of common stock under 2018 ESPP 91 — 91 Net cash used in financing activities ( 20,728 ) — ( 20,728 ) Net decrease in cash, cash equivalents and restricted cash ( 4,860 ) — ( 4,860 ) Cash, cash equivalents and restricted cash at beginning of the period 13,632 — 13,632 Cash, cash equivalents and restricted cash at end of the period $ 8,772 $ — $ 8,772 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 1,969 $ — $ 1,969 Cash and cash equivalents $ 7,876 $ — $ 7,876 Restricted cash 896 — $ 896 Total cash, cash equivalents and restricted cash $ 8,772 $ — $ 8,772

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and the rules and regulations of Securities and Exchange Commission (“SEC”) for reporting. The Company effected a reverse stock split on October 19, 2022 of its outstanding shares of common stock at a ratio of 1-for-10 pursuant to a Certificate of Amendment to the Company's Certificate of Incorporation filed with the Secretary of State of the State of Delaware. The reverse stock split was reflected on the Nasdaq Global Select Market beginning with the opening of trading on October 20, 2022. Accordingly, an amount equal to the par value of the decreased shares resulting from the reverse stock split was reclassified from "Additional paid-in capital" to "Common stock". Any fractional post-split shares as a result of the reverse stock split were rounded down to the nearest whole post-split share. The reverse stock split did not change the par value of the Company's common stock or the authorized number of shares of the Company's common stock. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.
Warrants	Warrants The Company determines the accounting classification of warrants that are issued, as either liability or equity, by first assessing whether the warrants meet liability classification in accordance with ASC 480-10, Distinguishing Liabilities from Equity , and then in accordance with ASC 815-40, Accounting for Derivative Financial Instruments Indexed to, and Potentially Settled in, a Company’s Own Stock . Under ASC 480-10, warrants are considered liability classified if the warrants are mandatorily redeemable, obligate the issuer to settle the warrants or the underlying shares by paying cash or other assets, or must or may require settlement by issuing variable number of shares. If warrants do not meet liability classification under ASC 480-10, the Company assesses the requirements under ASC 815-40, which states that contracts that require or may require the issuer to settle the contract for cash are liabilities recorded at fair value, irrespective of the likelihood of the transaction occurring that triggers the net cash settlement feature. If the warrants do not require liability classification under ASC 815-40, in order to conclude equity classification, the Company assesses whether the warrants are indexed to its common stock and whether the warrants are classified as equity under ASC 815-40 or other applicable principles of GAAP. After all relevant assessments are made, the Company concludes whether the warrants are classified as liability or equity. Liability classified warrants are required to be accounted for at fair value both on the date of issuance and on subsequent accounting periods with changes in fair value recorded in the Statements of Operations and Comprehensive Loss under "Gain or (loss) on warrant liability". If warrants are issued together with the sale of common stock, for the issuance costs that are not specifically attributed to either the common stock or warrants issued, the Company allocates the issuance costs between the common stock and warrants based on their relative fair value. The Company expenses issuance costs allocated to the warrants that are classified as liabilities and the issuance costs allocated to common stock or warrants that are classified as equity are recognized as reduction to the equity.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company bases its estimates on historical experience and market-specific or other relevant assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company’s balance sheets and the amount of expenses and income reported for each of the periods presented are affected by estimates and assumptions, which are used for, but are not limited to, determining the fair value of assets and liabilities, the fair value of right-of-use asset and lease liabilities, embedded derivatives and stock-based compensation. Actual results could differ from such estimates or assumptions. Estimating fair values of liability-classified financial instruments requires the development of estimates that may, and are likely to, change over the duration of the instrument with related changes in internal and external market factors. In addition, derivatives liabilities are highly volatile and sensitive to changes in the market price of the Company’s common stock. Because liability-classified financial instruments are initially and subsequently carried at fair value, the Company’s financial results will reflect the volatility in these estimate and assumption changes. Changes in estimated fair value are recognized as a component of "Other expense, net" in the Statements of Operations and Comprehensive Loss.
Segments	Segments The Company has one operating segment. The Company’s chief operating decision maker, its Chief Executive Officer, manages the Company’s operations on a consolidated basis for the purposes of allocating resources.
Cash, Cash Equivalents, and Restricted Cash	Cash, Cash Equivalents, and Restricted Cash The Company considers all highly liquid investments with original maturities of 90 days or less from the date of purchase to be cash equivalents. Cash equivalents primarily include money market funds that invest in U.S. Treasury obligations which are stated at fair value. The Company has issued letters of credit under its lease agreements which have been collateralized. This cash is classified as noncurrent restricted cash on the balance sheet based on the term of the underlying lease. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows (in thousands). December 31, 2023 2022 2021 Cash and cash equivalents $ 19,803 $ 12,736 $ 32,905 Restricted cash 896 896 1,446 Total cash, cash equivalents, and restricted cash $ 20,699 $ 13,632 $ 34,351
Marketable Securities	Marketable Securities The Company generally invests its excess cash in investment grade, short to intermediate-term, fixed income securities. Such investments are considered available-for-sale debt securities and reported at fair value with unrealized gains and losses included as a component of stockholders’ equity. Marketable securities with original maturities of greater than 90 days from the date of purchase but less than one year from the balance sheet date that are available to be converted into cash to fund current operations are classified as short-term, while marketable securities with maturities in one year or beyond one year from the balance sheet date are classified as long-term. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in "Interest income" on the Statements of Operations and Comprehensive Loss. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on marketable securities are included in "Other expense, net". The cost of securities sold is determined using the specific identification method . The Company periodically evaluates whether declines in fair values of its marketable securities below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the marketable security until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any marketable securities before recovery of its amortized cost basis. Factors considered include quoted market prices, recent financial results and operating trends, implied values from any recent transactions or offers of investee securities, credit quality of debt instrument issuers, other publicly available information that may affect the value of the marketable security, duration and severity of the decline in value, and management’s strategy and intentions for holding the marketable security. To date, the Company has not recorded any impairment charges on its marketable securities related to other-than-temporary declines in market value.
Fair Value Measurements	Fair Value Measurements The Company’s financial instruments during the periods presented consist of cash and cash equivalents, restricted cash, marketable securities, strategic investments, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued and other current liabilities, derivative liabilities related to debt and long-term debt. Fair value estimates of these instruments are made at a specific point in time, based on relevant market information. Level 3 instruments incorporate certain unobservable inputs such as the selected discount rate of the related loan. These estimates may be subjective in nature and involve uncertainties and matters of judgment.
Revenue Recognition	Revenue Recognition The Company recognizes revenue in accordance with the provisions of Accounting Standards Codification Topic 606, Revenue from Contracts with Customers, or Topic 606. In determining the appropriate amount and timing of revenue to be recognized under this guidance, the Company performs the following five steps: (i) identifies the contract(s) with our customer; (ii) identifies the promised goods or services in the agreement and determine whether they are performance obligations, including whether they are distinct in the context of the agreement; (iii) measures the transaction price, including the constraint on variable consideration; (iv) allocates the transaction price to the performance obligations based on stand-alone selling prices; and (v) recognizes revenue when (or as) the Company satisfies each performance obligation. A performance obligation is a promise in an agreement to transfer a distinct good or service to the customer and is the unit of account in Topic 606. Significant management judgment is required to determine the level of effort required and the period over which completion of the performance obligations is expected under an agreement. If reasonable estimates regarding when performance obligations are either complete or substantially complete cannot be made, then revenue recognition is deferred until a reasonable estimate can be made. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. The Company allocates the total transaction price to each performance obligation based on the estimated relative stand-alone selling prices of the promised goods or services underlying each performance obligation. The total consideration which the Company expects to collect in exchange for the Company’s products is an estimate and may be fixed or variable. The Company constrains the estimated variable consideration when it assesses it is probable that a significant reversal in the amount of cumulative revenue recognized may occur in future periods. The transaction price is re-evaluated, including the estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. The allocation of the transaction price is performed based on standalone selling prices, which are based on estimated amounts that the Company would charge for a performance obligation if it were sold separately. Revenue is recognized when, or as, performance obligations in the contracts are satisfied, in the amount reflecting the expected consideration to be received from the goods or services transferred to the customers. Consideration received in advance are recorded as deferred revenue and are recognized as the related performance obligation is satisfied. Following is a description of the principal activities from which the Company generates revenue. License revenue primarily represent amounts earned under agreements that license our intellectual property to other companies. See Note 5, “License Revenue, Agreements and Strategic Investment” for further detail. Consideration under these contracts generally includes a nonrefundable upfront payment, development, regulatory and commercial milestones and royalties based on net sales of approved products. Licenses of Intellectual Property. If the Company determines the license to intellectual property is distinct from the other performance obligations identified in the agreement and the licensee can use and benefit from the license, the Company recognizes revenue from the estimated transaction price that is allocated to the license. Licensing arrangements are analyzed to determine whether the promised goods or services, which may include licenses, transfer of know-how, transfer of materials, research and development services and governance committee services, are distinct or whether they must be accounted for as part of a combined performance obligation. If the license is considered not to be distinct, the license would then be combined with other promised goods or services as a combined performance obligation. If the Company is involved in a governance committee, it assesses whether its involvement constitutes a separate performance obligation. When governance committee services are determined to be separate performance obligations, the Company determines the fair value to be allocated to this promised service. Milestone Payments : At the inception of each agreement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimate the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone is included in the transaction price. For milestones that the Company do not deem to be probable of being achieved, the associated milestone payments are fully constrained and the value of the milestone is excluded from the transaction price with no revenue being recognized. For example, milestone payments that are not within our control, such as regulatory-related accomplishments, are not considered probable of being achieved until those accomplishments have been communicated by the relevant regulatory authority. Once the assessment of probability of achievement becomes probable, the Company recognizes revenue for the milestone payment. At each reporting date, the Company assesses the probability of achievement of each milestone under our current agreements. Royalties . For agreements with sales-based royalties, including milestone payments based on the level of sales, where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation, to which some or all of the royalty has been allocated, has been satisfied (or partially satisfied). At each reporting date, the Company estimates the sales incurred by each licensee during the reporting period based on historical experience and accrues the associated royalty amount.
Concentrations of Risk	Concentrations of Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, and marketable securities. Substantially all of the Company’s cash and cash equivalents and restricted cash is deposited in accounts with financial institutions that management believes are of high credit quality. Such deposits have and will continue to exceed federally insured limits. The Company maintains its cash with accredited financial institutions and accordingly, such funds are subject to minimal credit risk. The Company has not experienced any losses on its cash deposits. The Company’s investment policy limits investments in marketable securities to certain types of securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents, restricted cash and marketable securities and issuers of marketable securities to the extent recorded on the balance sheets. As of December 31, 2023 and 2022, the Company had no off-balance sheet concentrations of credit risk. The Company depends on third-party suppliers for key raw materials used in its manufacturing processes and is subject to certain risks related to the loss of these third-party suppliers or their inability to supply the Company with adequate raw materials.
Research and Development Expenses and Accruals	Research and Development Expenses and Accruals Costs related to research, design, and development of drug candidates are charged to research and development expense as incurred. Research and development costs include, but are not limited to, payroll and personnel expenses for personnel contributing to research and development activities, laboratory supplies, outside services, licenses acquired to be used in research and development, manufacturing of clinical material, pre-clinical testing and consultants and allocated overhead, including rent, equipment, depreciation, and utilities. Research and development costs are expensed as incurred unless there is an alternative future use in other research and development projects. Payments made prior to the receipt of goods or services to be used in research and development are deferred and recognized as expense in the period in which the related goods are received or services are rendered. Such payments are evaluated for current or long-term classification based on when they will be realized. As part of the process of preparing its financial statements, the Company is required to estimate expenses resulting from its obligations under contracts with vendors and consultants and clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. The Company’s objective is to reflect the appropriate expenses in its financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of the production of clinical trial materials or based on progression of the clinical trial, as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates by taking into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of goods and services, or the services completed. During the course of a clinical trial, the rate of expense recognition is adjusted if actual results differ from the Company’s estimates. The Company makes estimates of accrued expenses as of each balance sheet date in its financial statements based on the facts and circumstances known at that time. The clinical trial accrual is dependent in part upon the timely and accurate reporting of contract research organizations, contract manufacturers, and other third-party vendors. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting changes in estimates in any particular period. Adjustments to prior period estimates have not been material for the years ended December 31, 2023 and 2022.
Contingent Consideration Liability	Contingent Consideration Liability The Company has entered into and may continue to enter into, license agreements to access and utilize certain technology. In each case, the Company evaluates whether the license agreement results in the acquisition of an asset or a business. To date, all of the Company’s license agreements have been considered acquisitions of assets and none have been considered acquisitions of a business. For license agreements that are considered to be acquisitions of assets, the upfront payments for such license, as well as any future milestone payments made before product approval, are immediately recognized as research and development expense when due, provided there is no alternative future use of the rights in other research and development projects. Some of the Company’s license agreements also include contingent consideration in the form of an obligation to issue additional shares of the Company’s common stock based on the achievement of certain milestones. The Company assesses on a continuous basis whether (i) such contingent consideration meets the definition of a derivative, and (ii) whether it can be classified within stockholders’ equity. Until such time when equity classification criteria are met or the milestones expire, the contingent consideration is classified as a liability. The derivative related to this contingent consideration is measured at fair value as of each balance sheet date with the related change in fair value being reflected in operating expenses. Upon a reassessment event that results in the contingent consideration no longer meeting the definition of a derivative and/or meeting equity classification criteria, the final change in fair value of the instrument is recorded within operating expenses and the liability is reclassified into stockholders’ equity.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets, generally three years. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the term of the lease. Depreciation and amortization begin at the time the asset is placed in service. Maintenance and repairs are charged to expense as incurred and costs of improvement are capitalized.
Leases	Leases The Company determines whether the arrangement is or contains a lease at the inception of the arrangement and if so, whether such a lease is classified as a financing lease or an operating lease. Operating leases are included in operating lease right-of-use asset, (“ROU asset”), operating lease liabilities, net of current portion, and accrued and other current liabilities on the Company’s balance sheets. The Company has elected not to recognize on the balance sheets leases with terms of one year or less. Operating lease ROU assets represent the Company’s right to use an underlying asset for the lease term and are considered long-lived assets for purposes of identifying, recognizing and measuring impairment. Operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of lease payments over the expected lease term. As the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment, in determining the present value of lease payments. The operating lease ROU asset also includes any lease payments made or incentives received and impairment charges if the Company determines the ROU asset is impaired and excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options to extend or terminate the lease. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company has elected to not separate lease and non-lease components for its leased assets and accounts for all lease and non-lease components of its agreements as a single lease component. The lease components resulting in a ROU asset have been recorded on the balance sheets and are amortized as lease expense on a straight-line basis over the lease term. The Company has subleased a majority of its South San Francisco, California facility under agreements considered to be operating leases according to ASC 842. The Company has not been legally released from its primary obligations under the original leases and therefore it continues to account for the original leases as it did before commencement of the subleases. The Company records both fixed and variable payments received from the sublessee in its statements of operations on a straight-line basis as an offset to rent expense.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company evaluates long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be fully recoverable. If indicators of impairment exist and the undiscounted future cash flows that the assets are expected to generate are less than the carrying value of the assets, the Company reduces the carrying amount of the assets through an impairment charge, to their estimated fair value based on a discounted cash flow approach or, when available and appropriate, to comparable market values. See Note 9, “Commitments and Contingencies”. Determining estimated discounted cash flows for purposes of an impairment analysis requires the Company to make estimates and assumptions regarding the amount of market rent, timing of sublease income, and risk-adjusted discount rates. There are often risks and uncertainties associated with the intent to sublease offices and laboratory space. Consequently, the eventual realized sublease income may vary from estimates as of the impairment testing date and adjustments may occur in future periods .
Stock-Based Compensation	Stock-Based Compensation The Company measures compensation expense for all stock-based awards based on their grant date fair value. For stock-based awards with service conditions only, stock-based compensation expense is recognized over the requisite service period using the straight-line method. For awards with performance conditions, the Company evaluates the probability of achieving performance condition at each reporting date. The Company begins to recognize stock-based compensation expense using an accelerated attribution method when it is deemed probable that the performance condition will be met. Forfeitures are recognized as they occur. The Company uses the Black-Scholes option-pricing model to estimate the fair value of stock option awards that do not contain market conditions. The Black-Scholes option-pricing model requires assumptions to be made related to the expected term of an award, expected dividends, expected volatility and risk-free rate. The Company has used the Monte-Carlo option-pricing model to estimate the fair value of stock option awards that contain only market conditions. The Monte-Carlo option pricing model uses similar input assumptions as the Black-Scholes model; however, it further incorporates into the fair-value determination the possibility that the market condition may not be satisfied.
Embedded Derivatives of the Loan Agreement	Embedded Derivatives of the Loan Agreement The Company measures derivative liability related to debt at fair value. Estimated fair value of the derivative liability related to debt, initially measured and recorded on the date of the amendment of the loan and security agreement, is considered to be a Level 3 instrument. The fair value of the derivative liability related to debt is based on the term loan principal, the date of maturity, the contractual term loan interest rate, the convertible discount factor, and the selected discount rate of the loan. The derivative liability related to debt is recorded at fair value at the end of each reporting period with changes in estimated fair values recognized as a component of "Other expense, net" in the Statements of Operations and Comprehensive Loss.
Restructurings	Restructuring The Company recognizes restructuring charges related to reorganization plans that have been committed to by management and when liabilities have been incurred. In connection with these activities, the Company records restructuring charges at fair value for a) contractual employee termination benefits when obligations are associated to services already rendered, rights to such benefits have vested, and payment of benefits is probable and can be reasonably estimated, and b) one-time employee termination benefits when management has committed to a plan of termination, the plan identifies the employees and their expected termination dates, the details of termination benefits are complete, it is unlikely changes to the plan will be made or the plan will be withdrawn and communication to such employees has occurred. One-time employee termination benefits are recognized in their entirety when communication has occurred, and future services are not required. Contract termination costs to be incurred over the remaining contract term without economic benefit are recorded in their entirety when the contract is canceled. The recognition of restructuring charges requires the Company to make certain judgments and estimates regarding the nature, timing and amount of costs associated with the planned reorganization plan. At the end of each reporting period, the Company evaluates the remaining accrued restructuring balances to ensure that no excess accruals are retained, and the utilization of the provisions are for their intended purpose in accordance with developed restructuring plans.
Income Taxes	Income Taxes The Company uses the asset and liability method of accounting for income taxes, in which deferred tax assets and liabilities are recognized for future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be reversed. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as income in the period that includes the enactment date. A valuation allowance is established if it is more likely than not that all or a portion of the deferred tax asset will not be realized. The Company’s tax positions are subject to income tax audits. The Company recognizes the tax benefit of an uncertain tax position only if it is more likely than not that the position is sustainable upon examination by the taxing authority, based on the technical merits. The tax benefit recognized is measured as the largest amount of benefit which is more likely than not to be realized upon settlement with the taxing authority. The Company recognizes interest accrued and penalties related to unrecognized tax benefits in its tax provision. The Company evaluates uncertain tax positions on a regular basis. The evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of the audit, and effective settlement of audit issues. The provision for income taxes includes the effects of any accruals that the Company believes are appropriate, as well as the related net interest and penalties.
Net Loss per Common Share	Net Loss per Common Share Basic net loss per share is calculated by dividing net loss by the weighted average number of shares outstanding for the period. Diluted net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding plus the effect of dilutive potential common shares outstanding during the period determined using the treasury-stock method. In all periods presented, the Company’s outstanding stock options, convertible preferred stock, early exercised common stock subject to future vesting, warrants and presumed issuance of additional shares as contingent consideration were excluded from the calculation of diluted net loss per share because their effects were antidilutive.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss and certain changes in stockholders’ equity that are excluded from net loss, primarily unrealized losses on the Company’s marketable securities.
Recently Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments, as clarified in subsequent amendments. ASU 2016-13 changes the impairment model for certain financial instruments. The new model is a forward-looking expected loss model and will apply to financial assets subject to credit losses and measured at amortized cost and certain off-balance sheet credit exposures. This includes loans, held-to-maturity debt securities, loan commitments, financial guarantees and net investments in leases, as well as trade receivables. For available-for-sale debt securities with unrealized losses, credit losses will be measured in a manner similar to today, except that the losses will be recognized as allowances rather than reductions in the amortized cost of the securities. In October 2019, the FASB voted to delay the effective date of this standard. Topic 326 will be effective for the Company for fiscal years beginning after December 15, 2022. Early adoption is permitted. We adopted ASU 2016-13 on January 1, 2023 and the adoption did no t have a material impact on the Company’s financial statements and related disclosures. In November 2021, the FASB issued ASU 2021-10, Government Assistance, or Topic 832, which requires enhanced disclosures of transactions with governments that are accounted for by applying a grant or contribution model. The new pronouncement requires entities to provide information about the nature of the transaction, terms and conditions associated with the transaction and financial statement line items affected by the transaction. The Company adopted the standard for the annual period beginning January 1, 2023 . The employee retention credit received under the CARES Act qualifies as a government assistance program under Topic 832 and resulted in enhanced required disclosures, as described in Note 7, "Government Assistance Program". Recently Issued Accounting Pronouncements Not Yet Adopted In December 2023, the Financial Accounting Standards Board (FASB) issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the disclosures required for income taxes in our annual financial statements. ASU 2023-09 is effective for the Company in its annual reporting for fiscal 2025 on a prospective basis. Early adoption and retrospective reporting are permitted. The Company is currently evaluating the impact of ASU 2023-09 on its Financial Statements.

Restatement of Previously Iss_2

Restatement of Previously Issued Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2023
Prior Period Adjustment [Abstract]
Schedule Of Restated And Reconciliation From The Prior Period As Previously Reported To The Restated Amounts In Financial Statments	The following tables represent the restated amounts in the Balance Sheet, Statement of Operations and Comprehensive Loss, Statement of Changes in Stockholders’ Equity and Statement of Cash Flows for the year ended December 31, 2022. The amounts as previously reported for fiscal year 2022 was derived from the Annual Report on Form 10-K for the fiscal year ended December 31, 2022, filed on March 15, 2023 (Original Report). These amounts are labeled as “As Previously Reported” in the tables below. The amounts labeled “Adjustment” represent the effects of this restatement described above. Balance Sheet December 31, 2022 As Previously Reported Adjustment As Restated Assets Current assets: Cash and cash equivalents $ 12,736 $ — $ 12,736 Short-term marketable securities 82,059 — 82,059 Prepaid expenses and other current assets 1,740 — 1,740 Total current assets 96,535 — 96,535 Property and equipment, net 7,825 — 7,825 Operating lease right-of-use asset 19,042 — 19,042 Long-term restricted cash 896 — 896 Other long-term assets 52 — 52 Total assets $ 124,350 $ — $ 124,350 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 1,790 $ — $ 1,790 Accrued compensation 3,020 — 3,020 Accrued and other current liabilities 5,334 — 5,334 Current portion of long-term debt 9,476 — 9,476 Total current liabilities 19,620 — 19,620 Operating lease liability, net of current portion 26,991 — 26,991 Long-term debt, net 10,891 — 10,891 Warrant liability — 10,764 10,764 Total liabilities 57,502 10,764 68,266 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,215,302 shares issued and outstanding as of December 31, 2022 1 — 1 Additional paid-in capital 527,049 ( 26,222 ) 500,827 Accumulated other comprehensive loss ( 251 ) — ( 251 ) Accumulated deficit ( 459,951 ) 15,458 ( 444,493 ) Total stockholders’ equity 66,848 ( 10,764 ) 56,084 Total liabilities and stockholders’ equity $ 124,350 $ — $ 124,350 Statement of Operations and Comprehensive Loss Year Ended As Previously Reported Adjustment As Restated Licensing revenue - Related Party $ 236 $ — $ 236 Operating expenses: Research and development 36,859 — 36,859 General and administrative 20,949 — 20,949 Total operating expenses 57,808 — 57,808 Loss from operations ( 57,572 ) — ( 57,572 ) Interest income 1,220 — 1,220 Interest expense ( 3,558 ) — ( 3,558 ) Gain (loss) on warrant liability — 16,843 16,843 Other expense, net ( 17 ) ( 1,385 ) ( 1,402 ) Net loss ( 59,927 ) 15,458 ( 44,469 ) Other comprehensive loss Unrealized loss on marketable debt securities ( 207 ) — ( 207 ) Comprehensive loss $ ( 60,134 ) $ 15,458 $ ( 44,676 ) Net loss per share, basic and diluted $ ( 6.31 ) $ — $ ( 4.68 ) Weighted average number of shares used in computing net loss per share, basic and diluted 9,494,421 — 9,494,421 Statement of Changes in Stockholders' Equity Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at December 31, 2021 6,299,158 $ 1 $ 459,636 $ ( 44 ) $ ( 400,024 ) $ 59,569 Issuance of common stock, net of issuance costs, 1,019,046 — 12,155 — — 12,155 Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs 6,428,571 — 41,648 — — 41,648 Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs 90,000 — 910 — — 910 Issuance of common stock Hercules Capital, net of issuance costs 262,761 — 3,179 — — 3,179 Issuance of common stock under 2018 ESPP 25,482 — 142 — — 142 Vesting of restricted stock units 90,284 — — — — — Stock-based compensation — — 9,379 — — 9,379 Unrealized loss on available-for-sale marketable securities — — — ( 207 ) — ( 207 ) Net loss — — — — ( 59,927 ) ( 59,927 ) Balances at December 31, 2022 14,215,302 $ 1 $ 527,049 $ ( 251 ) $ ( 459,951 ) $ 66,848 Adjustment Balances at December 31, 2021 — $ — $ — $ — $ — $ — Issuance of common stock, net of issuance costs, — — — — — — Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs — — ( 26,222 ) — — ( 26,222 ) Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs — — — — — — Issuance of common stock Hercules Capital, net of issuance costs — — — — — — Issuance of common stock under 2018 ESPP — — — — — — Vesting of restricted stock units — — — — — — Stock-based compensation — — — — — — Unrealized loss on available-for-sale marketable securities — — — — — — Net loss — — — — 15,458 15,458 Balances at December 31, 2022 — $ — $ ( 26,222 ) $ — $ 15,458 $ ( 10,764 ) As Restated Balances at December 31, 2021 6,299,158 $ 1 $ 459,636 $ ( 44 ) $ ( 400,024 ) $ 59,569 Issuance of common stock, net of issuance costs, 1,019,046 — 12,155 — — 12,155 Sale of common stock under Follow-On Offering, net of issuance costs 6,428,571 — 15,426 — — 15,426 Issuance of common stock to Lincoln Park Capital Fund, net of issuance costs 90,000 — 910 — — 910 Issuance of common stock Hercules Capital, net of issuance costs 262,761 — 3,179 — — 3,179 Issuance of common stock under 2018 ESPP 25,482 — 142 — — 142 Vesting of restricted stock units 90,284 — — — — — Stock-based compensation — — 9,379 — — 9,379 Unrealized loss on available-for-sale marketable securities — — — ( 207 ) — ( 207 ) Net loss — — — — ( 44,469 ) ( 44,469 ) Balances at December 31, 2022 14,215,302 $ 1 $ 500,827 $ ( 251 ) $ ( 444,493 ) $ 56,084 Statement of Cash Flow Year Ended As Previously Reported Adjustment As Restated Operating activities Net loss $ ( 59,927 ) $ 15,458 $ ( 44,469 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 2,180 — 2,180 Amortization of debt issuance costs 1,318 — 1,318 Debt extinguishment gain upon conversion to equity ( 199 ) — ( 199 ) Net accretion and amortization of premium and discounts on ( 276 ) — ( 276 ) Gain on disposal of property and equipment ( 346 ) — ( 346 ) Stock-based compensation 9,379 — 9,379 Non-cash rent expense ( 2,136 ) — ( 2,136 ) (Gain) loss on warrant liability — ( 16,843 ) ( 16,843 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets 138 — 138 Other long-term assets 39 — 39 Accounts payable ( 194 ) — ( 194 ) Accrued compensation ( 1,008 ) — ( 1,008 ) Accrued liabilities and other current liabilities 26 — 26 Other long-term liabilities ( 23 ) — ( 23 ) Net cash used in operating activities ( 51,029 ) ( 1,385 ) ( 52,414 ) Investing activities Purchase of marketable securities ( 98,827 ) — ( 98,827 ) Maturities of marketable securities 74,000 — 74,000 Purchase of property and equipment ( 96 ) — ( 96 ) Sale of property and equipment 378 — 378 Net cash provided by (used in) investing activities ( 24,545 ) — ( 24,545 ) Financing activities Proceeds from issuance of common stock under ATM offering program, net of issuance costs 12,155 — 12,155 Proceeds from sale of common stock and warrants under Follow-On Offering 41,648 3,352 45,000 Issuance costs for sale of common stock — ( 1,967 ) ( 1,967 ) Proceeds from issuance of common stock to Lincoln Park Capital Fund, net of issuance costs 910 — 910 Proceeds from issuance of common stock under 2018 ESPP 142 — 142 Net cash provided by financing activities 54,855 1,385 56,240 Net increase (decrease) in cash, cash equivalents and restricted cash ( 20,719 ) — ( 20,719 ) Cash, cash equivalents and restricted cash at beginning of the period 34,351 — 34,351 Cash, cash equivalents and restricted cash at end of the period $ 13,632 $ — $ 13,632 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 2,204 $ — $ 2,204 Supplemental Disclosures of Non-Cash Investing and Financing Issuance of common stock in payment of debt $ 3,179 $ — $ 3,179 The remainder of the notes to the Company's financial statements have been restated, as applicable, to reflect the impacts from the restatement discussed above.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows (in thousands). December 31, 2023 2022 2021 Cash and cash equivalents $ 19,803 $ 12,736 $ 32,905 Restricted cash 896 896 1,446 Total cash, cash equivalents, and restricted cash $ 20,699 $ 13,632 $ 34,351

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis and Level of Inputs Used in Measurements	The carrying amounts of financial instruments such as cash and cash equivalents, restricted cash, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued and other current liabilities approximate to their related fair values due to the short-term nature of these instruments. The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands): December 31, 2023 Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 12,864 $ 12,864 $ — $ — U.S. treasuries 2,989 — 2,989 — Total cash equivalents 15,853 12,864 2,989 — Short-term marketable securities: U.S. treasuries 7,849 — 7,849 — U.S. government debt securities 15,549 — 15,549 — Total short-term marketable securities 23,398 — 23,398 — Restricted Cash equivalents: Money market funds 896 896 — — Total restricted cash equivalents 896 896 — — Total assets subject to fair value measurements $ 40,147 $ 13,760 $ 26,387 $ — Liabilities: Warrant Liability $ 5,913 $ — $ — $ 5,913 Total liabilities subject to fair value measurements 5,913 — — 5,913 December 31, 2022 (Restated) Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 5,083 $ 5,083 $ — $ — Total cash equivalents 5,083 5,083 — — Short-term marketable securities: U.S. treasuries 30,758 — 30,758 — U.S. government debt securities 51,301 — 51,301 — Total short-term marketable securities 82,059 — 82,059 — Total assets subject to fair value measurements $ 87,142 $ 5,083 $ 82,059 $ — Liabilities: Warrant Liability (Restated) $ 10,764 $ — $ — $ 10,764 Total liabilities subject to fair value measurements 10,764 — — 10,764
Summary of Assumptions used in Fair Value Estimates of Level 3 Warrant Liabilities	The Company estimates the fair value of its warrant liability using a Monte Carlo simulation model b ased on significant inputs not observable in the market, which represents a Level 3 measurement. The Company used the following key assumptions within its valuation. In all scenarios, the Company also applied the likelihood of a fundamental transaction and the related impact on the Company’s common stock price and volatility. August 22, 2022 September 30, 2022 December 31, 2022 March 31, 2023 June 30, 2023 September 30, 2023 November 14, 2023 December 31, 2023 Common stock price $ 6.10 $ 3.95 $ 2.74 $ 1.63 $ 2.55 $ 2.40 $ 1.72 $ 1.93 Exercise price per share $ 8.50 $ 8.50 $ 8.50 $ 8.50 $ 8.50 $ 8.50 $ 2.045 $ 8.50 Estimated volatility 87.5 % 90.0 % 95.0 % 100.0 % 95.0 % 100.0 % 80.0 % 80.0 % Risk-free interest rate 3.17 % 4.07 % 4.03 % 3.66 % 4.28 % 4.71 % 4.42 % 3.85 % Contractual term (in years) 5.00 4.89 4.64 4.39 4.14 3.89 3.77 3.64 The Company estimates the fair value of its Level 3 warrant liabilities using a Monte Carlo simulation model. The Company used the following key assumptions within its valuation. In all scenarios, the Company also applied the likelihood of a fundamental transaction and the related impact on the Company’s common stock price and volatility. November 14, 2023 December 31, 2023 Common stock price $ 1.72 $ 1.93 Exercise price per share $ 1.92 - 2.5563 $ 1.92 - 2.5563 Expected volatility 80.0 % 80.0 % Risk-free interest rate 4.42 % 3.85 % Contractual term (in years) 5.00 4.87
Sumarry of Roll forward of the fair value of level 3 Warrants	The following is a roll forward of the fair value of Level 3 warrants: Warrant Liability Beginning balance at December 31, 2021 $ — Warrants Issued 27,607 Change in fair value ( 16,842 ) Ending balance at December 31, 2022 (Restated) 10,765 Warrants Issued 2,724 Warrants Exercised ( 1,361 ) Change in fair value ( 6,215 ) Balance at December 31, 2023 $ 5,913

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Summary of Marketable Securities Classified as Available-for-Sale	Marketable securities, which are classified as available-for-sale, consisted of the following (in thousands): December 31, 2023 Amortized Unrealized Unrealized Fair Cash equivalents: Money market funds $ 12,864 $ — $ — $ 12,864 U.S. treasuries 2,989 — — 2,989 Total cash equivalents 15,853 — — 15,853 Short-term marketable securities: U.S. treasuries 7,853 4 ( 8 ) 7,849 U.S. government debt securities 15,570 1 ( 22 ) 15,549 Total short-term marketable securities 23,423 5 ( 30 ) 23,398 Restricted Cash equivalents: Money market funds 896 — — $ 896 Total restricted cash equivalents 896 — — 896 Total $ 40,172 $ 5 $ ( 30 ) $ 40,147 December 31, 2022 Amortized Unrealized Unrealized Fair Cash equivalents: Money market funds $ 5,083 $ — $ — $ 5,083 Total cash equivalents 5,083 — — 5,083 Short-term marketable securities: U.S. treasuries 51,491 6 ( 196 ) 51,301 U.S. government debt securities 30,820 1 ( 63 ) 30,758 Total short-term marketable securities 82,311 7 ( 259 ) 82,059 Total $ 87,394 $ 7 $ ( 259 ) $ 87,142

License Revenue, Agreements a_2

License Revenue, Agreements and Strategic Investment (Tables)	12 Months Ended
	Dec. 31, 2023
Research and Development [Abstract]
Schedule of Recognized Revenue of License Agreement	In accordance with the license agreements, the Company recognized revenue as follows: Year ended December 31, 2023 2022 2021 Jocasta Neuroscience, Inc. (1) $ — $ 236 $ 4,784 $ — $ 236 $ 4,784 (1) Jocasta Neuroscience, Inc. was deemed a related party at the effective time the agreement was made on December 17, 2021.

Balance Sheet Components (Tabl

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): December 31, 2023 2022 Prepaid research and development expenses $ 415 $ 378 Prepaid insurance expenses 541 710 Tax credit receivable 1,493 — Interest receivable 84 235 Other prepaid expenses and current assets 871 417 $ 3,404 $ 1,740
Schedule of Property and Equipment, Net	Property and equipment, net, consists of the following (in thousands): December 31, 2023 2022 Laboratory equipment $ 3,894 $ 4,197 Computer equipment 303 412 Furniture and fixtures 627 726 Leasehold improvements 9,519 15,244 Total property and equipment 14,343 20,579 Less: accumulated depreciation and amortization ( 9,261 ) ( 12,754 ) Total property and equipment, net $ 5,082 $ 7,825
Schedule of Accrued and Other Current Liabilities	Accrued and other current liabilities consist of the following (in thousands): December 31, 2023 2022 Operating lease liability - current portion $ 3,451 $ 3,100 Accrued research and development 839 1,623 Liability related to early exercise shares 10 10 Accrued other 319 601 $ 4,619 $ 5,334

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Summary of Components of Lease Expense	The following table summarizes the components of lease expense, which are included in operating expenses in the Company’s Statements of Operations and Comprehensive Loss (in thousands): Year ended December 31, 2023 2022 2021 Operating lease expense $ 3,739 $ 4,264 $ 4,357 Variable lease expense 748 1,318 1,633 Sublease income ( 3,988 ) ( 4,317 ) ( 2,578 ) Total lease expense $ 499 $ 1,265 $ 3,412
Summary of Supplemental Information Related to Operating Leases	The following table summarizes supplemental information related to operating leases (in thousands): Year ended December 31, 2023 2022 2021 Cash paid for amounts included in the measurement of lease liabilities $ 4,810 $ 6,283 $ 6,653 Weighted-average remaining lease term (years) 6.0 7.0 7.7 Weighted-average discount rate (percentage) 6.0 % 6.0 % 5.9 %
Summary of Maturities of Lease Liabilities	The following table summarizes the maturities of lease liabilities as of December 31, 2023 (in thousands): Amount 2024 $ 4,964 2025 5,123 2026 5,287 2027 5,457 2028 5,633 Thereafter 5,801 Total future minimum lease payments 32,265 Less: Amount representing interest ( 5,275 ) Present value of future minimum lease payments 26,990 Less: Current portion of operating lease liability ( 3,451 ) Noncurrent portion of operating lease liability $ 23,539

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Summary of Stock Option Activity	A summary of the Company’s stock option activity under the 2013 Plan, 2018 Plan and 2020 Plan for the year ended December 31, 2023 is as follows: Shares Outstanding Weighted- Weighted- Aggregate (in Years) (in thousands) Balance at December 31, 2022 68,838 1,609,938 $ 27.51 8.3 $ 251 Shares added 1,010,831 — — Granted ( 446,200 ) 446,200 2.79 Exercised — — — Canceled 153,367 ( 142,793 ) 7.96 Balance at December 31, 2023 786,836 1,913,345 $ 14.23 7.1 $ 5 Vested and exercisable at December 31, 2023 1,179,366 $ 20.51 6.0 $ — Vested and expected to vest at December 31, 2023 1,913,345 $ 14.23 7.1 $ 5
Summary of Restricted Stock Units Activity	The following table summarizes the Company’s RSU activity for the year ended December 31, 2023: Shares Weighted- Unvested at December 31, 2022 146,333 $ 27.66 Granted — $ — Released ( 94,534 ) $ 28.39 Canceled ( 10,574 ) $ 11.27 Unvested at December 31, 2023 41,225 $ 30.18
Summary of Valuation Assumption to Estimate Fair Value of Stock Options	The Company uses the Black-Scholes option-pricing model for determining the estimated fair value and stock-based compensation related to stock options and ESPP awards. The fair value of stock options granted to employees was estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Year ended December 31, 2023 2022 2021 Expected term of options (in years) 5.79 5.55 6.0 Expected stock price volatility 94.11 %- 98.92 % 86.22 %- 93.17 % 85.7 %- 88.5 % Risk-free interest rate 3.36 %- 4.13 % 2.41 %- 4.01 % 1.08 %- 1.35 % Expected dividend yield — — —
Summary of Stock-based Compensation Expense	The following table sets forth the total stock-based compensation expense for all options granted to employees and nonemployees and costs associated with the 2018 ESPP included in the Company’s statement of operations (in thousands): Year Ended December 31, 2023 2022 2021 Research and development $ 1,947 $ 3,526 $ 4,809 General and administrative 5,472 5,853 6,744 Total $ 7,419 $ 9,379 $ 11,553

Net Loss per Common Share (Tabl

Net Loss per Common Share (Tables)	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Schedule of Reconciliation of Numerators and Denominators Used In Computing Net Loss From Continuing Operations Per Share	A reconciliation of the numerators and denominators used in computing net loss from continuing operations per share is as follows (in thousands, except per share amounts): Year ended December 31, 2023 2022 (Restated) 2021 (in thousands, except share and per share amounts) Numerator: Net loss $ ( 39,860 ) $ ( 44,469 ) $ ( 60,725 ) Denominator: Weighted average number of shares outstanding—basic 14,773,612 9,494,421 5,581,587 Net loss per share—basic and diluted $ ( 2.70 ) $ ( 4.68 ) $ ( 10.88 )
Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Per Share	Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: Year ended December 31, 2023 2022 2021 Options to purchase common stock 1,913,345 1,609,938 866,696 Outstanding warrants to purchase common stock 6,557,152 6,428,572 — Early exercised common stock subject to future vesting 3,336 3,336 3,336 RSUs subject to future vesting 41,225 146,333 199,094 Shares subject to future vesting relating to the 2018 ESPP 47,389 65,939 14,774 Total 8,562,447 8,254,118 1,083,900

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The effective tax rate of the Company’s provision for income taxes differs from the federal statutory rate as follows: Year ended December 31, 2023 2022 (Restated) 2021 Taxes at the U.S. statutory income tax rate 21.0 % 21.0 % 21.0 % State tax, net of federal benefit 9.0 9.1 4.4 Other 0.5 ( 0.8 ) ( 0.4 ) Warrant activity 2.8 7.3 — Stock-based compensation ( 2.5 ) ( 6.6 ) ( 1.6 ) Research and development tax credits 1.8 2.9 3.2 Rate change ( 8.8 ) 4.7 3.8 ASC 740-10 — ( 7.5 ) ( 4.2 ) Change in valuation allowance ( 23.7 ) ( 30.1 ) ( 26.2 ) Total provision for income taxes — % — % — %
Schedule of Components of Deferred Income Taxes	The tax effects of significant items comprising the Company’s deferred income taxes are as follows: December 31, 2023 2022 (in thousands) Deferred tax assets: Federal and state operating loss carryforwards $ 81,094 $ 73,322 Research and development tax credits 9,552 8,646 Stock-based compensation 5,078 4,589 Accruals and other 320 587 Intangibles 1,343 5,329 Section 174 capitalization research expenses 10,117 6,624 Charitable contributions — 12 Operating lease liabilities 6,280 6,908 Total deferred tax assets 113,784 106,017 Deferred tax liabilities: Operating lease right-of-use asset ( 3,041 ) ( 4,371 ) Fixed assets ( 1,033 ) ( 1,299 ) Total deferred tax liabilities ( 4,074 ) ( 5,670 ) Valuation allowance ( 109,710 ) ( 100,347 ) Net deferred tax assets $ — $ —
Summary of Net Operating Losses and Tax Credit Carryforwards	Net operating losses and tax credit carryforwards as of December 31, 2023 are as follows: Amount Expiration Years Net operating losses, federal (post December 31, 2017) $ 305,873 Do Not Expire Net operating losses, federal (pre January 1, 2018) 64,136 2029 - 2037 Net operating losses, state 185,897 2034 - 2043 Research and development tax credits, federal 8,799 2034 - 2043 Research and development tax credits, California 7,070 Indefinite
Schedule of Reconciliation of Unrecognized Tax Benefits	The following table summarizes the activity related to the Company’s unrecognized tax benefits: Year ended December 31, 2023 2022 2021 (in thousands) Gross unrecognized tax benefits at January 1 $ 17,605 $ 13,221 $ 7,142 Additions for tax positions taken in the current year 84 4,395 3,457 Reductions for tax positions taken in the prior year ( 232 ) ( 11 ) 2,622 Gross unrecognized tax benefits at December 31 $ 17,457 $ 17,605 $ 13,221

Quarterly Financial Informati_2

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2023
Quarterly Financial Information Disclosure [Abstract]
Schedule of Balance Sheets	Balance Sheets September 30, 2022 (unaudited) As Previously Reported Adjustment Reference As Restated Assets Current assets: Cash and cash equivalents $ 22,576 $ — $ 22,576 Short-term marketable securities 76,364 — 76,364 Prepaid expenses and other current asset 3,234 ( 150 ) b 3,084 Restricted cash 550 — 550 Total current assets 102,724 ( 150 ) 102,574 Property and equipment, net 8,202 — 8,202 Operating lease right-of-use assets 19,515 — 19,515 Long-term marketable securities 4,980 — 4,980 Long-term restricted cash 896 — 896 Other long-term assets 76 — 76 Total assets $ 136,393 $ ( 150 ) $ 136,243 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 2,444 $ — $ 2,444 Accrued compensation 2,961 — 2,961 Accrued and other current liabilities 4,593 728 b 5,321 Current portion of long-term debt 6,776 — 6,776 Total current liabilities 16,774 728 b 17,502 Operating lease liability, net of current portion 27,792 — 27,792 Long-term debt, net 13,262 — 13,262 Warrant liability — 16,633 a 16,633 Total liabilities 57,828 17,361 75,189 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,036,249 shares issued and outstanding as of September 30, 2022 1 — 1 Additional paid-in capital 524,623 ( 26,222 ) a 498,401 Accumulated other comprehensive loss ( 275 ) — ( 275 ) Accumulated deficit ( 445,784 ) 8,711 a,b ( 437,073 ) Total stockholders’ equity 78,565 ( 17,511 ) 61,054 Total liabilities and stockholders’ equity $ 136,393 $ ( 150 ) $ 136,243 March 31, 2023 (unaudited) As Previously Reported Adjustment Reference As Restated Assets Current assets: Cash and cash equivalents $ 22,972 $ — $ 22,972 Short-term marketable securities 60,420 — 60,420 Prepaid expenses and other current assets 2,989 — 2,989 Total current assets 86,381 — 86,381 Property and equipment, net 7,496 — 7,496 Operating lease right-of-use asset 18,557 — 18,557 Long-term deposits 896 — 896 Long-term restricted cash 896 — 896 Other long-term assets 29 — 29 Total assets $ 114,255 $ — $ 114,255 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 1,470 $ — $ 1,470 Accrued compensation 1,983 — 1,983 Accrued and other current liabilities 5,343 — 5,343 Current portion of long-term debt 13,062 — 13,062 Total current liabilities 21,858 — 21,858 Operating lease liability, net of current portion 26,150 — 26,150 Long-term debt, net 7,619 — 7,619 Warrant liability — 5,273 a 5,273 Total liabilities 55,627 5,273 60,900 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,359,214 shares issued and outstanding as of March 31, 2023 1 — 1 Additional paid-in capital 529,593 ( 26,317 ) a,d 503,276 Accumulated other comprehensive loss ( 150 ) — ( 150 ) Accumulated deficit ( 470,816 ) 21,044 a,d ( 449,772 ) Total stockholders’ equity 58,628 ( 5,273 ) 53,355 Total liabilities and stockholders’ equity $ 114,255 $ — $ 114,255 June 30, 2023 (unaudited) As Previously Reported Adjustment Reference As Restated Assets Current assets: Cash and cash equivalents $ 19,118 $ — $ 19,118 Short-term marketable securities 49,974 — 49,974 Prepaid expenses and other current assets 3,874 — 3,874 Total current assets 72,966 — 72,966 Property and equipment, net 7,181 — 7,181 Operating lease right-of-use asset 18,061 — 18,061 Long-term marketable securities 1,899 — 1,899 Long-term restricted cash 896 — 896 Other long-term assets 5 — 5 Total assets $ 101,008 $ — $ 101,008 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 1,449 $ — $ 1,449 Accrued compensation 1,652 — 1,652 Accrued and other current liabilities 5,417 — 5,417 Current portion of long-term debt 13,704 ( 81 ) c 13,623 Total current liabilities 22,222 ( 81 ) 22,141 Operating lease liability, net of current portion 25,297 — 25,297 Long-term debt, net 4,082 ( 15 ) c 4,067 Warrant liability — 8,734 a 8,734 Total liabilities 51,601 8,638 60,239 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,595,477 shares issued and outstanding as of June 30, 2023 1 — 1 Additional paid-in capital 532,563 ( 26,431 ) a,d 506,132 Accumulated other comprehensive loss ( 136 ) — ( 136 ) Accumulated deficit ( 483,021 ) 17,793 a,c,d ( 465,228 ) Total stockholders’ equity 49,407 ( 8,638 ) 40,769 Total liabilities and stockholders’ equity $ 101,008 $ — $ 101,008 September 30, 2023 (unaudited) As Previously Reported Adjustment Reference As Restated Assets Current assets: Cash and cash equivalents $ 7,876 $ — $ 7,876 Short-term marketable securities 38,063 — 38,063 Prepaid expenses and other current assets 3,599 — 3,599 Total current assets 49,538 — 49,538 Property and equipment, net 5,314 — 5,314 Operating lease right-of-use asset 13,522 — 13,522 Long-term restricted cash 896 — 896 Total assets $ 69,270 $ — $ 69,270 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $ 1,149 $ — $ 1,149 Accrued compensation 2,226 — 2,226 Accrued and other current liabilities 5,258 — 5,258 Total current liabilities 8,633 — 8,633 Operating lease liability, net of current portion 24,431 — 24,431 Warrant liability — 8,481 a 8,481 Total liabilities 33,064 8,481 41,545 Commitments and contingencies Stockholders’ equity: Convertible preferred stock, $ 0.0001 par value; 10,000,000 shares no shares issued and outstanding — — — Common stock, $ 0.0001 par value; 300,000,000 shares 14,614,890 shares issued and outstanding as of September 30, 2023 1 — 1 Additional paid-in capital 534,570 ( 26,781 ) a,d 507,789 Accumulated other comprehensive loss ( 55 ) — ( 55 ) Accumulated deficit ( 498,310 ) 18,300 a,d ( 480,010 ) Total stockholders’ equity 36,206 ( 8,481 ) 27,725 Total liabilities and stockholders’ equity $ 69,270 $ — $ 69,270
Statements of Operations and Comprehensive Loss	Quarterly and Year to Date Statements of Operations and Comprehensive Loss Three Months Ended Nine Months Ended As Previously Reported Adjustment Reference As Restated As Previously Reported Adjustment Reference As Restated Licensing revenue - related party $ — $ — $ — $ 236 $ — $ 236 Operating expenses: Research and development 8,208 878 b 9,086 28,222 878 b 29,100 General and administrative 4,922 — 4,922 15,669 — 15,669 Total operating expenses 13,130 878 14,008 43,891 878 44,769 Loss from operations ( 13,130 ) ( 878 ) ( 14,008 ) ( 43,655 ) ( 878 ) ( 44,533 ) Interest income 329 — 329 416 — 416 Interest expense ( 866 ) — ( 866 ) ( 2,568 ) — ( 2,568 ) Gain (loss) on warrant liability — 10,974 a 10,974 — 10,974 a 10,974 Other expense, net ( 41 ) ( 1,385 ) a ( 1,426 ) 49 ( 1,385 ) a ( 1,336 ) Net loss ( 13,708 ) 8,711 ( 4,997 ) ( 45,758 ) 8,711 ( 37,047 ) Other comprehensive loss Unrealized loss on marketable debt securities ( 88 ) — ( 88 ) ( 231 ) — ( 231 ) Comprehensive loss $ ( 13,796 ) $ 8,711 $ ( 5,085 ) $ ( 45,989 ) $ 8,711 $ ( 37,278 ) Net loss per share, basic and diluted $ ( 1.36 ) $ — $ ( 0.50 ) $ ( 5.77 ) $ — $ ( 4.67 ) Weighted average number of shares used in computing net loss per share, basic and diluted 10,072,077 — 10,072,077 7,928,729 — 7,928,729 Three Months Ended As Previously Reported Adjustment Reference As Restated Operating expenses: Research and development 5,835 ( 75 ) d 5,760 General and administrative 4,818 ( 20 ) d 4,798 Total operating expenses 10,653 ( 95 ) 10,558 Loss from operations ( 10,653 ) 95 ( 10,558 ) Interest income 855 — 855 Interest expense ( 1,002 ) — ( 1,002 ) Gain (loss) on warrant liability — 5,491 a 5,491 Other expense, net ( 65 ) — ( 65 ) Net loss ( 10,865 ) 5,586 ( 5,279 ) Other comprehensive gain Unrealized gain on marketable debt securities 101 — 101 Comprehensive loss $ ( 10,764 ) $ 5,586 $ ( 5,178 ) Net loss per share, basic and diluted $ ( 0.76 ) $ — $ ( 0.37 ) Weighted average number of shares used in computing net loss per share, basic and diluted 14,312,887 — 14,312,887 Three Months Ended Six Months Ended As Previously Reported Adjustment Reference As Restated As Previously Reported Adjustment Reference As Restated Licensing revenue - related party $ — $ — $ — $ — $ — $ — Operating expenses: Research and development 6,529 ( 94 ) d 6,435 12,364 ( 169 ) d 12,195 General and administrative 5,433 ( 20 ) d 5,413 10,252 ( 40 ) d 10,212 Total operating expenses 11,962 ( 114 ) 11,848 22,616 ( 209 ) 22,407 Loss from operations ( 11,962 ) 114 ( 11,848 ) ( 22,616 ) 209 ( 22,407 ) Interest income 805 — 805 1,660 — 1,660 Interest expense ( 979 ) 96 c ( 883 ) ( 1,981 ) 96 c ( 1,885 ) Gain (loss) on warrant liability — ( 3,461 ) a ( 3,461 ) — 2,030 a 2,030 Other expense, net ( 69 ) — ( 69 ) ( 133 ) — ( 133 ) Net loss ( 12,205 ) ( 3,251 ) ( 15,456 ) ( 23,070 ) 2,335 ( 20,735 ) Other comprehensive gain Unrealized gain on marketable debt securities 14 — 14 115 — 115 Comprehensive loss $ ( 12,191 ) $ ( 3,251 ) $ ( 15,442 ) $ ( 22,955 ) $ 2,335 $ ( 20,620 ) Net loss per share, basic and diluted $ ( 0.85 ) $ — $ ( 1.07 ) $ ( 1.61 ) $ — $ ( 1.44 ) Weighted average number of shares used in computing net loss per share, basic and diluted 14,425,775 — 14,425,775 14,369,643 — 14,369,643 Three Months Ended Nine Months Ended As Previously Reported Adjustment Reference As Restated As Previously Reported Adjustment Reference As Restated Operating expenses: Research and development 4,901 ( 269 ) d 4,632 17,266 ( 438 ) d 16,828 General and administrative 4,428 ( 81 ) d 4,347 14,681 ( 121 ) d 14,560 Impairment of long-lived assets 5,602 — 5,602 5,602 — 5,602 Total operating expenses 14,931 ( 350 ) 14,581 37,549 ( 559 ) 36,990 Loss from operations ( 14,931 ) 350 ( 14,581 ) ( 37,549 ) 559 ( 36,990 ) Interest income 689 — 689 2,349 — 2,349 Interest expense ( 470 ) ( 96 ) c ( 566 ) ( 2,451 ) — ( 2,451 ) Gain (loss) on warrant liability — 253 a 253 — 2,283 a 2,283 Other expense, net ( 577 ) — ( 577 ) ( 711 ) — ( 711 ) Net loss ( 15,289 ) 507 ( 14,782 ) ( 38,362 ) 2,842 ( 35,520 ) Other comprehensive gain Unrealized gain on marketable debt securities 81 — 81 196 — 196 Comprehensive loss $ ( 15,208 ) $ 507 $ ( 14,701 ) $ ( 38,166 ) $ 2,842 $ ( 35,324 ) Net loss per share, basic and diluted $ ( 1.05 ) $ — $ ( 1.01 ) $ ( 2.66 ) $ — $ ( 2.46 ) Weighted average number of shares used in computing net loss per share, basic and diluted 14,598,218 — 14,598,218 14,446,672 — 14,446,672
Statements of Changes in Stockholders' Equity	Statements of Changes in Stockholders' Equity Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at June 30, 2022 6,958,494 $ 1 $ 472,193 $ ( 187 ) $ ( 432,076 ) $ 39,931 Issuance of common stock, net of issuance costs, 633,464 — 8,570 — — 8,570 Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs 6,428,571 — 41,650 — — 41,650 Vesting of restricted stock units 15,720 — — — — — Stock-based compensation — — 2,210 — — 2,210 Unrealized loss on available-for-sale marketable securities — — — ( 88 ) — ( 88 ) Net loss — — — — ( 13,708 ) ( 13,708 ) Balances at September 30, 2022 14,036,249 $ 1 $ 524,623 $ ( 275 ) $ ( 445,784 ) $ 78,565 Adjustment Balances at June 30, 2022 — $ — $ — $ — $ — $ — Issuance of common stock, net of issuance costs, — — — — — — Sale of common stock and warrants to purchase common shares under Follow-On Offering, net of issuance costs — — ( 26,222 ) — — ( 26,222 ) Vesting of restricted stock units — — — — — — Stock-based compensation — — — — — — Unrealized loss on available-for-sale marketable securities — — — — — — Net loss — — — — 8,711 8,711 Balances at September 30, 2022 — $ — $ ( 26,222 ) $ — $ 8,711 $ ( 17,511 ) As Restated Balances at June 30, 2022 6,958,494 $ 1 $ 472,193 $ ( 187 ) $ ( 432,076 ) $ 39,931 Issuance of common stock, net of issuance costs, 633,464 — 8,570 — — 8,570 Sale of common stock under Follow-On Offering, net of issuance costs 6,428,571 — 15,428 — — 15,428 Vesting of restricted stock units 15,720 — — — — — Stock-based compensation — — 2,210 — — 2,210 Unrealized loss on available-for-sale marketable securities — — — ( 88 ) — ( 88 ) Net loss — — — — ( 4,997 ) ( 4,997 ) Balances at September 30, 2022 14,036,249 $ 1 $ 498,401 $ ( 275 ) $ ( 437,073 ) $ 61,054 Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at December 31, 2022 14,215,302 $ 1 $ 527,049 $ ( 251 ) $ ( 459,951 ) $ 66,848 Issuance of common stock, net of issuance costs, 106,781 — 274 — — 274 Vesting of restricted stock units 37,131 — — — — — Stock-based compensation — — 2,270 — — 2,270 Unrealized gain on available-for-sale marketable securities — — — 101 — 101 Net loss — — — — ( 10,865 ) ( 10,865 ) Balances at March 31, 2023 14,359,214 $ 1 $ 529,593 $ ( 150 ) $ ( 470,816 ) $ 58,628 Adjustment Balances at December 31, 2022 — $ — $ ( 26,222 ) $ — $ 15,458 $ ( 10,764 ) Issuance of common stock, net of issuance costs, — — — — — — Vesting of restricted stock units — — — — — — Stock-based compensation — — ( 95 ) — — ( 95 ) Unrealized loss on available-for-sale marketable securities — — — — — — Net loss — — — — 5,586 5,586 Balances at March 31, 2023 — $ — $ ( 26,317 ) $ — $ 21,044 $ ( 5,273 ) As Restated Balances at December 31, 2022 14,215,302 $ 1 $ 500,827 $ ( 251 ) $ ( 444,493 ) $ 56,084 Issuance of common stock, net of issuance costs, 106,781 — 274 — — 274 Vesting of restricted stock units 37,131 — — — — — Stock-based compensation — — 2,175 — — 2,175 Unrealized gain on available-for-sale marketable securities — — — 101 — 101 Net loss — — — — ( 5,279 ) ( 5,279 ) Balances at March 31, 2023 14,359,214 $ 1 $ 503,276 $ ( 150 ) $ ( 449,772 ) $ 53,355 Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at March 31, 2023 14,359,214 $ 1 $ 529,593 $ ( 150 ) $ ( 470,816 ) $ 58,628 Issuance of common stock, net of issuance costs, 168,000 — 518 — — 518 Issuance of common stock under 2018 ESPP 41,497 — 91 — — 91 Vesting of restricted stock units 26,766 — — — — — Stock-based compensation — — 2,361 — — 2,361 Unrealized gain on available-for-sale marketable securities — — — 14 — 14 Net loss — — — — ( 12,205 ) ( 12,205 ) Balances at June 30, 2023 14,595,477 $ 1 $ 532,563 $ ( 136 ) $ ( 483,021 ) $ 49,407 Adjustment Balances at March 31, 2023 — $ — $ ( 26,317 ) $ — $ 21,044 $ ( 5,273 ) Issuance of common stock, net of issuance costs, — — — — — — Issuance of common stock under 2018 ESPP — — — — — — Vesting of restricted stock units — — — — — — Stock-based compensation — — ( 114 ) — — ( 114 ) Unrealized gain on available-for-sale marketable securities — — — — — — Net loss — — — — ( 3,251 ) ( 3,251 ) Balances at June 30, 2023 — $ — $ ( 26,431 ) $ — $ 17,793 $ ( 8,638 ) As Restated Balances at March 31, 2023 14,359,214 $ 1 $ 503,276 $ ( 150 ) $ ( 449,772 ) $ 53,355 Issuance of common stock, net of issuance costs, 168,000 — 518 — — 518 Issuance of common stock under 2018 ESPP 41,497 — 91 — — 91 Vesting of restricted stock units 26,766 — — — — — Stock-based compensation — — 2,247 — — 2,247 Unrealized gain on available-for-sale marketable securities — — — 14 — 14 Net loss — — — — ( 15,456 ) ( 15,456 ) Balances at June 30, 2023 14,595,477 $ 1 $ 506,132 $ ( 136 ) $ ( 465,228 ) $ 40,769 Common Stock Additional Accumulated Accumulated Total Shares Amount Capital Gain (Loss) Deficit Equity As Previously Reported Balances at June 30, 2023 14,595,477 $ 1 $ 532,563 $ ( 136 ) $ ( 483,021 ) $ 49,407 Fees related to the ATM offering program — — ( 48 ) — — ( 48 ) Vesting of restricted stock units 19,413 — — — — — Stock-based compensation — — 2,055 — — 2,055 Unrealized gain on available-for-sale marketable securities — — — 81 — 81 Net loss — — — — ( 15,289 ) ( 15,289 ) Balances at September 30, 2023 14,614,890 $ 1 $ 534,570 $ ( 55 ) $ ( 498,310 ) $ 36,206 Adjustment Balances at June 30, 2023 — $ — $ ( 26,431 ) $ — $ 17,793 $ ( 8,638 ) Fees related to the ATM offering program — — — — — — Vesting of restricted stock units — — — — — — Stock-based compensation — — ( 350 ) — — ( 350 ) Unrealized gain on available-for-sale marketable securities — — — — — — Net loss — — — — 507 507 Balances at September 30, 2023 — $ — $ ( 26,781 ) $ — $ 18,300 $ ( 8,481 ) As Restated Balances at June 30, 2023 14,595,477 $ 1 $ 506,132 $ ( 136 ) $ ( 465,228 ) $ 40,769 Fees related to the ATM offering program — — ( 48 ) — — ( 48 ) Vesting of restricted stock units 19,413 — — — — — Stock-based compensation — — 1,705 — — 1,705 Unrealized gain on available-for-sale marketable securities — — — 81 — 81 Net loss — — — — ( 14,782 ) ( 14,782 ) Balances at September 30, 2023 14,614,890 $ 1 $ 507,789 $ ( 55 ) $ ( 480,010 ) $ 27,725
Statements of Cash Flow	Statements of Cash Flows Nine Months Ended September 30, 2022 As Previously Reported Adjustment Reference As Restated Operating activities Net loss $ ( 45,758 ) $ 8,711 a,b $ ( 37,047 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 1,771 — 1,771 Amortization of debt issuance costs 989 — 989 Debt extinguishment gain upon conversion to equity ( 199 ) — ( 199 ) Net accretion and amortization of premium and discounts on marketable securities 155 — 155 Gain on disposal of property and equipment ( 247 ) — ( 247 ) Stock-based compensation 7,120 — 7,120 Non-cash rent expense ( 1,891 ) — ( 1,891 ) (Gain) loss on warrant liability — ( 10,974 ) a ( 10,974 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets ( 1,355 ) 150 b ( 1,205 ) Other long-term assets 15 — 15 Accounts payable 459 — 459 Accrued compensation ( 1,067 ) — ( 1,067 ) Accrued liabilities and other current liabilities ( 632 ) 728 b 96 Other long-term liabilities ( 23 ) — ( 23 ) Net cash used in operating activities ( 40,663 ) ( 1,385 ) ( 42,048 ) Investing activities Purchase of marketable securities ( 86,567 ) — ( 86,567 ) Maturities of marketable securities 62,000 — 62,000 Purchase of property and equipment ( 59 ) — ( 59 ) Sale of property and equipment 272 — 272 Net cash used in investing activities ( 24,354 ) — ( 24,354 ) Financing activities Proceeds from issuance of common stock under ATM offering program, net of issuance costs 12,003 — 12,003 Proceeds from sale of common stock and warrants under Follow-On Offering 41,650 3,350 a 45,000 Issuance costs for sale of common stock — ( 1,965 ) a ( 1,965 ) Proceeds from issuance of common stock to Lincoln Park Capital Fund, net of issuance costs 910 — 910 Proceeds from issuance of common stock under 2018 ESPP 125 — 125 Net cash provided by financing activities 54,688 1,385 56,073 Net decrease in cash, cash equivalents and restricted cash ( 10,329 ) — ( 10,329 ) Cash, cash equivalents and restricted cash at beginning of the period 34,351 — 34,351 Cash, cash equivalents and restricted cash at end of the period $ 24,022 $ — $ 24,022 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 1,577 $ — $ 1,577 Supplemental Disclosures of Non-Cash Investing and Financing Issuance of common stock in payment of debt $ 3,179 $ — $ 3,179 Cash and cash equivalents $ 22,576 $ — $ 22,576 Restricted cash 1,446 — $ 1,446 Total cash, cash equivalents and restricted cash $ 24,022 $ — $ 24,022 Three Months Ended March 31, 2023 As Previously Reported Adjustment Reference As Restated Operating activities Net loss $ ( 10,865 ) $ 5,586 a,d $ ( 5,279 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 329 — 329 Amortization of debt issuance costs 314 — 314 Net accretion and amortization of premium and discounts on marketable securities ( 433 ) — ( 433 ) Stock-based compensation 2,270 ( 95 ) d 2,175 Non-cash rent expense ( 270 ) — ( 270 ) (Gain) loss on warrant liability — ( 5,491 ) a ( 5,491 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets ( 1,249 ) — ( 1,249 ) Other long-term assets 23 — 23 Accounts payable ( 320 ) — ( 320 ) Accrued compensation ( 1,037 ) — ( 1,037 ) Accrued liabilities and other current liabilities ( 78 ) — ( 78 ) Net cash used in operating activities ( 11,316 ) — ( 11,316 ) Investing activities Purchase of marketable securities ( 5,973 ) — ( 5,973 ) Maturities of marketable securities 27,251 — 27,251 Net cash provided by investing activities 21,278 — 21,278 Financing activities Proceeds from issuance of common stock under ATM offering program, net of issuance costs 274 — 274 Net cash provided by financing activities 274 — 274 Net increase in cash, cash equivalents and restricted cash 10,236 — 10,236 Cash, cash equivalents and restricted cash at beginning of the period 13,632 — 13,632 Cash, cash equivalents and restricted cash at end of the period $ 23,868 $ — $ 23,868 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 680 $ — $ 680 Cash and cash equivalents $ 22,972 $ — $ 22,972 Restricted cash 896 — $ 896 Total cash, cash equivalents and restricted cash $ 23,868 $ — $ 23,868 Six Months Ended June 30, 2023 As Previously Reported Adjustment Reference As Restated Operating activities Net loss $ ( 23,070 ) $ 2,335 a,c,d $ ( 20,735 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 643 — 643 Amortization of debt issuance costs 653 ( 96 ) c 557 Net accretion and amortization of premium and discounts on marketable securities ( 831 ) — ( 831 ) Stock-based compensation 4,631 ( 209 ) d 4,422 Non-cash rent expense ( 540 ) — ( 540 ) (Gain) loss on warrant liability — ( 2,030 ) a ( 2,030 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets ( 2,134 ) — ( 2,134 ) Other long-term assets 47 — 47 Accounts payable ( 341 ) — ( 341 ) Accrued compensation ( 1,368 ) — ( 1,368 ) Accrued liabilities and other current liabilities ( 89 ) — ( 89 ) Net cash used in operating activities ( 22,399 ) — ( 22,399 ) Investing activities Purchase of marketable securities ( 21,868 ) — ( 21,868 ) Maturities of marketable securities 53,000 — 53,000 Net cash provided by investing activities 31,132 — 31,132 Financing activities Proceeds from issuance of common stock under ATM offering program, net of issuance costs 792 — 792 Repayment of term loan debt ( 3,234 ) — ( 3,234 ) Proceeds from issuance of common stock under 2018 ESPP 91 — 91 Net cash used in financing activities ( 2,351 ) — ( 2,351 ) Net increase in cash, cash equivalents and restricted cash 6,382 — 6,382 Cash, cash equivalents and restricted cash at beginning of the period 13,632 — 13,632 Cash, cash equivalents and restricted cash at end of the period $ 20,014 $ — $ 20,014 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 1,362 $ — $ 1,362 Cash and cash equivalents $ 19,118 $ — $ 19,118 Restricted cash 896 — $ 896 Total cash, cash equivalents and restricted cash $ 20,014 $ — $ 20,014 Nine Months Ended September 30, 2023 As Previously Reported Adjustment Reference As Restated Operating activities Net loss $ ( 38,362 ) $ 2,842 a,d $ ( 35,520 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 951 — 951 Amortization of debt issuance costs 705 — 705 Debt extinguishment loss upon paydown of principal 491 — 491 Net accretion and amortization of premium and discounts on marketable securities ( 1,199 ) — ( 1,199 ) Stock-based compensation 6,686 ( 559 ) d 6,127 Non-cash rent expense ( 811 ) — ( 811 ) Impairment of long-lived assets 5,602 — 5,602 (Gain) loss on warrant liability — ( 2,283 ) a ( 2,283 ) Changes in operating assets and liabilities: Prepaid expenses and other current assets ( 1,858 ) — ( 1,858 ) Other long-term assets 52 — 52 Accounts payable ( 642 ) — ( 642 ) Accrued compensation ( 793 ) — ( 793 ) Accrued liabilities and other current liabilities ( 335 ) — ( 335 ) Net cash used in operating activities ( 29,513 ) — ( 29,513 ) Investing activities Purchase of marketable securities ( 28,609 ) — ( 28,609 ) Maturities of marketable securities 74,000 — 74,000 Purchase of property and equipment ( 11 ) — ( 11 ) Sale of property and equipment 1 — 1 Net cash provided by investing activities 45,381 — 45,381 Financing activities Payment of debt principal ( 20,000 ) — ( 20,000 ) Payment of debt issuance costs ( 1,563 ) — ( 1,563 ) Proceeds from issuance of common stock under ATM offering program, net of issuance costs 744 — 744 Proceeds from issuance of common stock under 2018 ESPP 91 — 91 Net cash used in financing activities ( 20,728 ) — ( 20,728 ) Net decrease in cash, cash equivalents and restricted cash ( 4,860 ) — ( 4,860 ) Cash, cash equivalents and restricted cash at beginning of the period 13,632 — 13,632 Cash, cash equivalents and restricted cash at end of the period $ 8,772 $ — $ 8,772 Supplemental Disclosures of Cash Flow Information: Cash paid for interest $ 1,969 $ — $ 1,969 Cash and cash equivalents $ 7,876 $ — $ 7,876 Restricted cash 896 — $ 896 Total cash, cash equivalents and restricted cash $ 8,772 $ — $ 8,772

Organization - Additional Infor

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

Restatement of Previously Iss_3

Restatement of Previously Issued Financial Statements - Schedule of Restated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2023		Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022		Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 19,803		$ 7,876	$ 19,118	$ 22,972	$ 12,736		$ 22,576		$ 32,905
Short-term marketable securities	23,398		38,063	49,974	60,420	82,059		76,364
Prepaid expenses and other current assets	3,404		3,599	3,874	2,989	1,740		3,084
Restricted cash								550
Total current assets	46,605		49,538	72,966	86,381	96,535		102,574
Property and equipment, net	5,082		5,314	7,181	7,496	7,825		8,202
Operating lease right-of-use asset	12,981		13,522	18,061	18,557	19,042		19,515
Long-term restricted cash	896		896	896	896	896		896
Other long-term assets	126			5	29	52		76
Total assets	65,690		69,270	101,008	114,255	124,350		136,243
Current liabilities:
Accounts payable	1,380		1,149	1,449	1,470	1,790		2,444
Accrued compensation	1,841		2,226	1,652	1,983	3,020		2,961
Accrued and other current liabilities	4,619		5,258	5,417	5,343	5,334		5,321
Current portion of long-term debt	0			13,623	13,062	9,476		6,776
Total current liabilities	7,840		8,633	22,141	21,858	19,620		17,502
Operating lease liability, net of current portion	23,539		24,431	25,297	26,150	26,991		27,792
Long-term debt, net	0			4,067	7,619	10,891		13,262
Warrant liability	5,913		8,481	8,734	5,273	10,764		16,633
Total liabilities	37,292		41,545	60,239	60,900	68,266		75,189
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding	0		0	0	0	0		0
Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2022; 14,215,302 shares issued and outstanding as of December 31, 2022	2	[1]	1	1	1	1	[1]	1
Additional paid-in capital	512,773		507,789	506,132	503,276	500,827		498,401
Accumulated other comprehensive loss	(24)		(55)	(136)	(150)	(251)		(275)
Accumulated deficit	(484,353)		(480,010)	(465,228)	(449,772)	(444,493)		(437,073)
Total stockholders’ equity	28,398		27,725	40,769	53,355	56,084		61,054	$ 39,931	59,569	$ 82,881
Total liabilities and stockholders’ equity	$ 65,690		69,270	101,008	114,255	124,350		136,243
As Previously Reported
Current assets:
Cash and cash equivalents			7,876	19,118	22,972	12,736		22,576
Short-term marketable securities			38,063	49,974	60,420	82,059		76,364
Prepaid expenses and other current assets			3,599	3,874	2,989	1,740		3,234
Restricted cash								550
Total current assets			49,538	72,966	86,381	96,535		102,724
Property and equipment, net			5,314	7,181	7,496	7,825		8,202
Operating lease right-of-use asset			13,522	18,061	18,557	19,042		19,515
Long-term restricted cash			896	896	896	896		896
Other long-term assets				5	29	52		76
Total assets			69,270	101,008	114,255	124,350		136,393
Current liabilities:
Accounts payable			1,149	1,449	1,470	1,790		2,444
Accrued compensation			2,226	1,652	1,983	3,020		2,961
Accrued and other current liabilities			5,258	5,417	5,343	5,334		4,593
Current portion of long-term debt				13,704	13,062	9,476		6,776
Total current liabilities			8,633	22,222	21,858	19,620		16,774
Operating lease liability, net of current portion			24,431	25,297	26,150	26,991		27,792
Long-term debt, net				4,082	7,619	10,891		13,262
Warrant liability			0	0	0	0		0
Total liabilities			33,064	51,601	55,627	57,502		57,828
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding			0	0	0	0		0
Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2022; 14,215,302 shares issued and outstanding as of December 31, 2022			1	1	1	1		1
Additional paid-in capital			534,570	532,563	529,593	527,049		524,623
Accumulated other comprehensive loss			(55)	(136)	(150)	(251)		(275)
Accumulated deficit			(498,310)	(483,021)	(470,816)	(459,951)		(445,784)
Total stockholders’ equity			36,206	49,407	58,628	66,848		78,565	$ 39,931	$ 59,569
Total liabilities and stockholders’ equity			69,270	101,008	114,255	124,350		136,393
Adjustment
Current assets:
Cash and cash equivalents			0	0	0	0		0
Short-term marketable securities			0	0	0	0		0
Prepaid expenses and other current assets			0	0	0	0		(150)
Restricted cash								0
Total current assets			0	0	0	0		(150)
Property and equipment, net			0	0	0	0		0
Operating lease right-of-use asset			0	0	0	0		0
Long-term restricted cash			0	0	0	0		0
Other long-term assets				0	0	0		0
Total assets			0	0	0	0		(150)
Current liabilities:
Accounts payable			0	0	0	0		0
Accrued compensation			0	0	0	0		0
Accrued and other current liabilities			0	0	0	0		728
Current portion of long-term debt				(81)	0	0		0
Total current liabilities			0	(81)	0	0		728
Operating lease liability, net of current portion			0	0	0	0		0
Long-term debt, net				(15)	0	0		0
Warrant liability			8,481	8,734	5,273	10,764		16,633
Total liabilities			8,481	8,638	5,273	10,764		17,361
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding			0	0	0	0		0
Common stock, $0.0001 par value; 300,000,000 shares authorized as of December 31, 2022; 14,215,302 shares issued and outstanding as of December 31, 2022			0	0	0	0		0
Additional paid-in capital			(26,781)	(26,431)	(26,317)	(26,222)		(26,222)
Accumulated other comprehensive loss			0	0	0	0		0
Accumulated deficit			18,300	17,793	21,044	15,458		8,711
Total stockholders’ equity			(8,481)	(8,638)	(5,273)	(10,764)		(17,511)
Total liabilities and stockholders’ equity			$ 0	$ 0	$ 0	$ 0		$ (150)
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Restatement of Previously Iss_4

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

Restatement of Previously Iss_5

Restatement of Previously Issued Financial Statements - Schedule of Restated Statement of Operations and Comprehensive Loss (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Licensing revenue – Related Party		$ 0		$ 0	$ 0		$ 236	$ 0		$ 236		$ 4,784
Operating expenses:
Research and development	$ 4,632	6,435	$ 5,760	9,086	12,195	$ 16,828	29,100	20,099		36,859		38,393
General and administrative	4,347	5,413	4,798	4,922	10,212	14,560	15,669	18,966		20,949		23,056
Total operating expenses	14,581	11,848	10,558	14,008	22,407	36,990	44,769	44,667		57,808		61,449
Loss from operations	(14,581)	(11,848)	(10,558)	(14,008)	(22,407)	(36,990)	(44,533)	(44,667)		(57,572)		(56,665)
Interest income	689	805	855	329	1,660	2,349	416	2,874		1,220		100
Interest expense	(566)	(883)	(1,002)	(866)	(1,885)	(2,451)	(2,568)	(2,452)		(3,558)		(3,177)
Gain (loss) on warrant liability								6,215		16,843		0
Other expense, net	(577)	(69)	(65)	(1,426)	(133)	(711)	(1,336)	(1,830)		(1,402)		(983)
Net loss	(14,782)	(15,456)	(5,279)	(4,997)	(20,735)	(35,520)	(37,047)	(39,860)		(44,469)		(60,725)
Other comprehensive loss
Unrealized loss on marketable debt securities	81	14	101	(88)	115	196	(231)	227		(207)		(49)
Comprehensive loss	$ (14,701)	$ (15,442)	$ (5,178)	$ (5,085)	$ (20,620)	$ (35,324)	$ (37,278)	$ (39,633)		$ (44,676)		$ (60,774)
Net loss per share, basic	$ (1.01)	$ (1.07)	$ (0.37)	$ (0.5)	$ (1.44)	$ (2.46)	$ (4.67)	$ (2.7)		$ (4.68)		$ (10.88)
Net loss per share, diluted	$ (1.01)	$ (1.07)	$ (0.37)	$ (0.5)	$ (1.44)	$ (2.46)	$ (4.67)	$ (2.7)		$ (4.68)		$ (10.88)
Weighted average number of shares used in computing net loss per share, basic	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729	14,773,612	[1]	9,494,421	[1]	5,581,587	[1]
Weighted average number of shares used in computing net loss per share, diluted	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729	14,773,612	[1]	9,494,421	[1]	5,581,587	[1]
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Licensing revenue – Related Party		$ 0		$ 0	$ 0		$ 236			$ 236
Operating expenses:
Research and development	$ 4,901	6,529	$ 5,835	8,208	12,364	$ 17,266	28,222			36,859
General and administrative	4,428	5,433	4,818	4,922	10,252	14,681	15,669			20,949
Total operating expenses	14,931	11,962	10,653	13,130	22,616	37,549	43,891			57,808
Loss from operations	(14,931)	(11,962)	(10,653)	(13,130)	(22,616)	(37,549)	(43,655)			(57,572)
Interest income	689	805	855	329	1,660	2,349	416			1,220
Interest expense	(470)	(979)	(1,002)	(866)	(1,981)	(2,451)	(2,568)			(3,558)
Gain (loss) on warrant liability										0
Other expense, net	(577)	(69)	(65)	(41)	(133)	(711)	49			(17)
Net loss	(15,289)	(12,205)	(10,865)	(13,708)	(23,070)	(38,362)	(45,758)			(59,927)
Other comprehensive loss
Unrealized loss on marketable debt securities	81	14	101	(88)	115	196	(231)			(207)
Comprehensive loss	$ (15,208)	$ (12,191)	$ (10,764)	$ (13,796)	$ (22,955)	$ (38,166)	$ (45,989)			$ (60,134)
Net loss per share, basic	$ (1.05)	$ (0.85)	$ (0.76)	$ (1.36)	$ (1.61)	$ (2.66)	$ (5.77)			$ (6.31)
Net loss per share, diluted	$ (1.05)	$ (0.85)	$ (0.76)	$ (1.36)	$ (1.61)	$ (2.66)	$ (5.77)			$ (6.31)
Weighted average number of shares used in computing net loss per share, basic	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729			9,494,421
Weighted average number of shares used in computing net loss per share, diluted	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729			9,494,421
Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Licensing revenue – Related Party		$ 0		$ 0	$ 0		$ 0			$ 0
Operating expenses:
Research and development	$ (269)	(94)	$ (75)	878	(169)	$ (438)	878			0
General and administrative	(81)	(20)	(20)	0	(40)	(121)	0			0
Total operating expenses	(350)	(114)	(95)	878	(209)	(559)	878			0
Loss from operations	350	114	95	(878)	209	559	(878)			0
Interest income	0	0	0	0	0	0	0			0
Interest expense	(96)	96	0	0	96	0	0			0
Gain (loss) on warrant liability										16,843
Other expense, net	0	0	0	(1,385)	0	0	(1,385)			(1,385)
Net loss	507	(3,251)	5,586	8,711	2,335	2,842	8,711			15,458
Other comprehensive loss
Unrealized loss on marketable debt securities	0	0	0	0	0	0	0			0
Comprehensive loss	$ 507	$ (3,251)	$ 5,586	$ 8,711	$ 2,335	$ 2,842	$ 8,711			$ 15,458
Net loss per share, basic	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Net loss per share, diluted	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Weighted average number of shares used in computing net loss per share, basic	0	0	0	0	0	0	0
Weighted average number of shares used in computing net loss per share, diluted	0	0	0	0	0	0	0
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded up to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Restatement of Previously Iss_6

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

Restatement of Previously Iss_7

Restatement of Previously Issued Financial Statements - Schedule of Restated Statement of Changes in Stockholders' Equity (Details) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended					6 Months Ended		9 Months Ended				12 Months Ended						16 Months Ended
		Aug. 31, 2022	Sep. 30, 2021	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023		Sep. 30, 2022	Jun. 30, 2023		Sep. 30, 2023		Sep. 30, 2022		Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021		Dec. 31, 2022
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance, (in shares)				14,595,477	14,359,214	14,215,302			14,215,302		14,215,302				14,215,302
Beginning balance				$ 40,769	$ 53,355	$ 56,084		$ 39,931	$ 56,084		$ 56,084		$ 59,569		$ 56,084		$ 59,569		$ 82,881
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)					91										116		142		347
Stock-based compensation				1,705	2,247	2,175		2,210							7,419		9,379		11,553
Unrealized (gain) loss on available-for-sale marketable securities				81	14	101		(88)							227		(207)		(49)
Net gain (loss)				$ (14,782)	$ (15,456)	$ (5,279)		$ (4,997)	$ (20,735)		$ (35,520)		$ (37,047)		$ (39,860)		$ (44,469)		(60,725)
Ending balance, (in shares)				14,614,890	14,595,477	14,359,214		14,036,249	14,595,477		14,614,890		14,036,249		16,784,969		14,215,302				14,215,302
Ending balance				$ 27,725	$ 40,769	$ 53,355		$ 61,054	$ 40,769		$ 27,725		$ 61,054		$ 28,398		$ 56,084		59,569		$ 56,084
At The Market Equity Offering Program
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs					$ 518	$ 274		8,570							$ 725		12,155		10,357
Equity Purchase Agreement | Lincoln Park Capital Fund LLC
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs																	910		9,039
Issuance of common stock (in shares)			102,040												0						380,000
Follow-On Offering
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs								$ 15,428									15,426
Warrant Inducement Agreement
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs															$ 3,687
Loan Agreement | Hercules Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs																	$ 3,179		$ 2,704
Common Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance, (in shares)				14,595,477	14,359,214	14,215,302	[1]	6,958,494	14,215,302	[1]	14,215,302	[1]	6,299,158	[1]	14,215,302	[1]	6,299,158	[1]	5,325,288	[1]
Beginning balance				$ 1	$ 1	$ 1	[1]	$ 1	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)					41,497										57,419	[1]	25,482	[1]	11,704	[1]
Vesting of restricted stock units, (in shares)				19,413	26,766	37,131		15,720							94,467	[1]	90,284	[1]	96,269	[1]
Ending balance, (in shares)				14,614,890	14,595,477	14,359,214		14,036,249	14,595,477		14,614,890		14,036,249		16,784,969	[1]	14,215,302	[1]	6,299,158	[1]	14,215,302	[1]
Ending balance				$ 1	$ 1	$ 1		$ 1	$ 1		$ 1		$ 1		$ 2	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]
Common Stock | At The Market Equity Offering Program
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock (in shares)					168,000	106,781		633,464							274,781	[1]	1,019,046	[1]	189,453	[1]
Common Stock | Equity Purchase Agreement | Lincoln Park Capital Fund LLC
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock (in shares)	[1]																90,000		417,286
Common Stock | Follow-On Offering
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock (in shares)		6,428,571						6,428,571									6,428,571	[1]
Common Stock | Warrant Inducement Agreement
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs	[1]														$ 1
Issuance of common stock (in shares)	[1]														2,143,000
Common Stock | Loan Agreement | Hercules Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock (in shares)	[1]																262,761		172,736
Additional Paid-In Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				506,132	$ 503,276	$ 500,827		$ 472,193	500,827		500,827		459,636		$ 500,827		$ 459,636		$ 422,384
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)					91										116		142		347
Stock-based compensation				1,705	2,247	2,175		2,210							7,419		9,379		11,553
Ending balance				507,789	506,132	503,276		498,401	506,132		507,789		498,401		512,773		500,827		459,636		500,827
Additional Paid-In Capital | At The Market Equity Offering Program
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs					518	274		8,570							725		12,155		10,357
Additional Paid-In Capital | Equity Purchase Agreement | Lincoln Park Capital Fund LLC
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs																	910		9,039
Additional Paid-In Capital | Follow-On Offering
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs								15,428									15,426
Additional Paid-In Capital | Warrant Inducement Agreement
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs															3,686
Additional Paid-In Capital | Loan Agreement | Hercules Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs																	3,179		2,704
Related Party Promissory Notes for Purchase of Common Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance																			(210)
Ending balance
Accumulated Other Comprehensive Gain (Loss)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				(136)	(150)	(251)		(187)	(251)		(251)		(44)		(251)		(44)		5
Unrealized (gain) loss on available-for-sale marketable securities				81	14	101		(88)							227		(207)		(49)
Ending balance				(55)	(136)	(150)		(275)	(136)		(55)		(275)		(24)		(251)		(44)		(251)
Accumulated Deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				(465,228)	(449,772)	(444,493)		(432,076)	(444,493)		(444,493)		(400,024)		(444,493)		(400,024)		(339,299)
Net gain (loss)				(14,782)	(15,456)	(5,279)		(4,997)							(39,860)		(44,469)		(60,725)
Ending balance				(480,010)	(465,228)	(449,772)		(437,073)	(465,228)		(480,010)		(437,073)		(484,353)		(444,493)		(400,024)		(444,493)
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				49,407	58,628	66,848		39,931	66,848		66,848		59,569		$ 66,848		59,569
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)					91												142
Stock-based compensation				2,055	2,361	2,270		2,210									9,379
Unrealized (gain) loss on available-for-sale marketable securities				81	14	101		(88)									(207)
Net gain (loss)				(15,289)	(12,205)	(10,865)		(13,708)	(23,070)		(38,362)		(45,758)				(59,927)
Ending balance				$ 36,206	49,407	58,628		78,565	$ 49,407		$ 36,206		$ 78,565				66,848		$ 59,569		$ 66,848
As Previously Reported | At The Market Equity Offering Program
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs					$ 518	$ 274		8,570									12,155
As Previously Reported | Equity Purchase Agreement | Lincoln Park Capital Fund LLC
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs																	910
As Previously Reported | Follow-On Offering
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs								$ 41,650									41,648
As Previously Reported | Loan Agreement | Hercules Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs																	$ 3,179
As Previously Reported | Common Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance, (in shares)				14,595,477	14,359,214	14,215,302		6,958,494	14,215,302		14,215,302		6,299,158		14,215,302		6,299,158
Beginning balance				$ 1	$ 1	$ 1		$ 1	$ 1		$ 1		$ 1		$ 1		$ 1
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)					41,497												25,482
Vesting of restricted stock units, (in shares)				19,413	26,766	37,131		15,720									90,284
Ending balance, (in shares)				14,614,890	14,595,477	14,359,214		14,036,249	14,595,477		14,614,890		14,036,249				14,215,302		6,299,158		14,215,302
Ending balance				$ 1	$ 1	$ 1		$ 1	$ 1		$ 1		$ 1				$ 1		$ 1		$ 1
As Previously Reported | Common Stock | At The Market Equity Offering Program
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock (in shares)					168,000	106,781		633,464									1,019,046
As Previously Reported | Common Stock | Equity Purchase Agreement | Lincoln Park Capital Fund LLC
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock (in shares)																	90,000
As Previously Reported | Common Stock | Follow-On Offering
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock (in shares)								6,428,571									6,428,571
As Previously Reported | Common Stock | Loan Agreement | Hercules Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock (in shares)																	262,761
As Previously Reported | Additional Paid-In Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				532,563	$ 529,593	$ 527,049		$ 472,193	527,049		527,049		459,636		527,049		$ 459,636
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)					91												142
Stock-based compensation				2,055	2,361	2,270		2,210									9,379
Ending balance				534,570	532,563	529,593		524,623	532,563		534,570		524,623				527,049		459,636		527,049
As Previously Reported | Additional Paid-In Capital | At The Market Equity Offering Program
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs					518	274		8,570									12,155
As Previously Reported | Additional Paid-In Capital | Equity Purchase Agreement | Lincoln Park Capital Fund LLC
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs																	910
As Previously Reported | Additional Paid-In Capital | Follow-On Offering
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs								41,650									41,648
As Previously Reported | Additional Paid-In Capital | Loan Agreement | Hercules Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs																	3,179
As Previously Reported | Accumulated Other Comprehensive Gain (Loss)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				(136)	(150)	(251)		(187)	(251)		(251)		(44)		(251)		(44)
Unrealized (gain) loss on available-for-sale marketable securities				81	14	101		(88)									(207)
Ending balance				(55)	(136)	(150)		(275)	(136)		(55)		(275)				(251)		(44)		(251)
As Previously Reported | Accumulated Deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				(483,021)	(470,816)	(459,951)		(432,076)	(459,951)		(459,951)		(400,024)		(459,951)		(400,024)
Net gain (loss)				(15,289)	(12,205)	(10,865)		(13,708)									(59,927)
Ending balance				(498,310)	(483,021)	(470,816)		(445,784)	(483,021)		(498,310)		(445,784)				(459,951)		$ (400,024)		(459,951)
Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				(8,638)	(5,273)	(10,764)			(10,764)		(10,764)				(10,764)
Stock-based compensation				(350)	(114)	(95)
Net gain (loss)				507	(3,251)	5,586		8,711	2,335		2,842		8,711				15,458
Ending balance				(8,481)	(8,638)	(5,273)		(17,511)	(8,638)		(8,481)		(17,511)				(10,764)				(10,764)
Adjustment | Follow-On Offering
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs								(26,222)
Adjustment | Additional Paid-In Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				(26,431)	(26,317)	(26,222)			(26,222)		(26,222)				(26,222)
Stock-based compensation				(350)	(114)	(95)
Ending balance				(26,781)	(26,431)	(26,317)		(26,222)	(26,431)		(26,781)		(26,222)				(26,222)				(26,222)
Adjustment | Additional Paid-In Capital | Follow-On Offering
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Issuance of common stock, net of issuance costs								(26,222)									(26,222)
Adjustment | Accumulated Deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance				17,793	21,044	15,458			15,458		15,458				$ 15,458
Net gain (loss)				507	(3,251)	5,586		8,711									15,458
Ending balance				$ 18,300	$ 17,793	$ 21,044		$ 8,711	$ 17,793		$ 18,300		$ 8,711				$ 15,458				$ 15,458
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Restatement of Previously Iss_8

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

Restatement of Previously Iss_9

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

Summary of Significant Accoun_4

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

Summary of Significant Accoun_5

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

Fair Value Measurements - Summa

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

Fair Value Measurements - Addit

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

Fair Value Measurements - Sum_2

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

Fair Value Measurements - Sumar

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

Marketable Securities - Summary

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

Marketable Securities - Additio

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

License Revenue, Agreements a_3

License Revenue, Agreements and Strategic Investment - Schedule of Recognized Revenue of License Agreement (Details) - Collaboration Agreement - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized		$ 236	$ 4,784
Jocasta Neuroscience, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized	[1]	$ 236	$ 4,784
[1] Jocasta Neuroscience, Inc. was deemed a related party at the effective time the agreement was made on December 17, 2021.

License Revenue, Agreements a_4

License Revenue, Agreements and Strategic Investment - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2022	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021	Sep. 30, 2023	Mar. 31, 2023
Research And Development Arrangement Contract To Perform For Others [Line Items]
Revenue recognized		$ 0	$ 0	$ 0	$ 236,000	$ 0		$ 236,000		$ 4,784,000
Common stock, shares issued		14,595,477	14,036,249	14,595,477	14,036,249	16,784,969		14,215,302			14,614,890	14,359,214
Common stock value		$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 2,000	[1]	$ 1,000	[1]		$ 1,000	$ 1,000
Ascentage Pharma
Research And Development Arrangement Contract To Perform For Others [Line Items]
Compound library and option agreement execution month and year						2016-02
Compound library and option agreement expiration month and year						2022-02
Ascentage Pharma | Licensed Products
Research And Development Arrangement Contract To Perform For Others [Line Items]
Royalties due from sales						$ 0
License Agreement | Jocasta Neuroscience, Inc.
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront cash payments received										5,000,000
Revenue recognized						0		200,000		$ 4,800,000
Other Licensing Agreements with Research Institutions
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contingent consideration, milestone or royalty payments						0		$ 0
Other Licensing Agreements with Research Institutions | UCSF
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common shares expected to be issued	3,400
Contingent consideration, milestone or royalty payments						$ 0
Maximum milestone payments for each product licensed under agreement	$ 13,600,000
Commercial Agreement | Affiliate of Clinical-Stage Biopharmaceutical Company
Research And Development Arrangement Contract To Perform For Others [Line Items]
Equity payments percentage						20%
Commercial Agreement | Ascentage Pharma
Research And Development Arrangement Contract To Perform For Others [Line Items]
Equity payments percentage						80%
Common stock, shares issued						0
Commercial Agreement | Ascentage Pharma | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contingent consideration additional common stock issued for one licensed product						93,333
Contingent consideration additional common stock issued for two or more licensed product						133,333
Milestone payments						$ 70,300,000
Commercial Agreement | Ascentage Pharma | Initial License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
License agreement termination month and year						2020-07
License agreement execution month and year						2016-02
Commercial Agreement | Ascentage Pharma | Second License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
License agreement execution month and year						2019-01
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Balance Sheet Components - Sche

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

Balance Sheet Components - Sc_2

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

Balance Sheet Components - Addi

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

Balance Sheet Components - Sc_3

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

Government Assistance Program -

Government Assistance Program - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Government Assistance [Line Items]
Employee retention credit receivable	$ 1.5	$ 0
CARES Act Member
Government Assistance [Line Items]
Refundable employee retention credit	1.5
Contra-expense to personnel related cost		$ 0
General and Administrative Expense | CARES Act Member
Government Assistance [Line Items]
Contra-expense to personnel related cost	0.4
Research and Development Expense | CARES Act Member
Government Assistance [Line Items]
Contra-expense to personnel related cost	$ 1.1

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)		1 Months Ended				12 Months Ended
	Sep. 15, 2023 USD ($) ft² $ / ft²	May 31, 2022 USD ($) ft² $ / ft²	Jun. 30, 2021 USD ($) ft² $ / ft²	May 31, 2021 USD ($) ft² $ / ft²	Feb. 28, 2021 ft² $ / ft²	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Feb. 28, 2019 USD ($)
Commitments And Contingencies [Line Items]
Impairment loss						$ 5,600,000
Impairment of operating lease right-of-use asset						4,000,000
Impairment of leasehold improvements						1,600,000
Sublease income						$ 3,988,000	$ 4,317,000	$ 2,578,000
South San Francisco, California
Commitments And Contingencies [Line Items]
Lessee, operating lease, description						In February 2019, the Company entered into a lease agreement for new office and laboratory space in South San Francisco, California. The term of the lease agreement commenced in May 2019. The lease has an initial term from occupancy of approximately ten years ending on December 31, 2029 with an option to extend the term for an additional eight years at then-market rental rates.
Operating lease, initial lease term						10 years
Operating lease, renewal term						8 years
Tenant improvement allowance									$ 10,700,000
Letter of credit, delivered in connection of lease agreement						$ 900,000
Lease commencement date						2019-05
Operating lease, option to extend description						option to extend the term for an additional eight years
Operating lease, existence of option to extend						true
Lease expiration date						Dec. 31, 2029
South San Francisco, California | Office and Laboratory Space, First Floor
Commitments And Contingencies [Line Items]
Space subleased (in square feet) | ft²			23,000
Sublease expiration date			Jul. 31, 2024
Sublease rent per square foot | $ / ft²			6.25
Annual percentage increase in sublease base rent			3.50%
Percentage of operating expenses and property management fees to be paid by subtenant			37%
Incurred initial direct costs of sublease			$ 200,000
Sublease income						$ 2,300,000	2,200,000	1,100,000
South San Francisco, California | Office and Laboratory Space, Second Floor
Commitments And Contingencies [Line Items]
Space subleased (in square feet) | ft²	17,000	15,000
Sublease start date	Oct. 01, 2023	Jul. 01, 2022
Sublease expiration date	Jun. 30, 2026	Jun. 30, 2026
Sublease rent per square foot | $ / ft²	1	7.8
Annual percentage increase in sublease base rent	3.50%	3.50%
Increase in sublease rent per square foot | $ / ft²	6.02
Percentage of operating expenses and property management fees to be paid by subtenant	51%	24%
Incurred initial direct costs of sublease	$ 300,000	$ 100,000
Sublease income						1,700,000
Brisbane, California
Commitments And Contingencies [Line Items]
Space subleased (in square feet) | ft²				11,500	27,000
Sublease expiration date				Sep. 30, 2022	Aug. 31, 2022
Sublease rent per square foot | $ / ft²				1	3.53
Annual percentage increase in sublease base rent					3%
Percentage of operating expenses and property management fees to be paid by subtenant				30%	41%
Incurred initial direct costs of sublease				$ 100,000
Sublease income						$ 0	$ 1,300,000	$ 1,500,000
Brisbane, California | Office and Laboratory Space, First Floor
Commitments And Contingencies [Line Items]
Space subleased (in square feet) | ft²	4,500
Sublease expiration date	Jun. 30, 2024
Sublease rent per square foot | $ / ft²	2

Commitments and Contingencies_2

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

Commitments and Contingencies_3

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

Commitments and Contingencies_4

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

Term Loan Facility - Additional

Term Loan Facility - Additional Information (Details) - USD ($) $ in Thousands

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2023

Jun. 30, 2023

Mar. 31, 2023

Sep. 30, 2022

Jun. 30, 2023

Sep. 30, 2023

Sep. 30, 2022

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Sep. 06, 2023

Aug. 03, 2020

Debt Instrument [Line Items]

Loss on extinguishment of debt

$ (500)

Interest expense

$ 566

$ 883

$ 1,002

$ 866

$ 1,885

$ 2,451

$ 2,568

2,452

$ 3,558

$ 3,177

Term Loan | Loan Agreement | Hercules Capital | Interest And Other Expense

Debt Instrument [Line Items]

Interest expense

$ 2,500

$ 3,600

$ 3,200

Term Loan | Payoff Letter Loan Agreement | Hercules Capital

Debt Instrument [Line Items]

Debt payoff amount

$ 15,000

Secured Term Loan Facility | Loan Agreement | Hercules Capital

Debt Instrument [Line Items]

Principal amount of first tranche

$ 25,000

Long-term debt, maturity date

Aug. 01, 2024

Secured Term Loan Facility | Loan Agreement | Hercules Capital | Maximum

Debt Instrument [Line Items]

Debt instrument aggregate principal amount

$ 80,000

Related-Party Transactions - Ad

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

Equity Financing - Additional I

Equity Financing - Additional Information (Details)						1 Months Ended					3 Months Ended					6 Months Ended	9 Months Ended		12 Months Ended								16 Months Ended
		Nov. 09, 2023 USD ($) $ / shares shares	Oct. 19, 2022	Aug. 31, 2022 USD ($) $ / shares shares	Aug. 17, 2022 USD ($)	Oct. 31, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($) $ / shares shares	Jul. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2023 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) $ / shares shares	Mar. 31, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($) $ / shares shares	Mar. 31, 2022 USD ($)	Jun. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares		Dec. 31, 2022 USD ($) $ / shares shares		Dec. 31, 2021 USD ($) shares		Dec. 31, 2020 USD ($) shares		Dec. 31, 2022 USD ($) $ / shares shares		Jun. 30, 2022 shares
Subsidiary Sale Of Stock [Line Items]
Reverse stock split ratio			0.1
Number of stock, authorized for issuance | shares																			10,000,000		10,000,000						10,000,000
Number of stock, par value per share | $ / shares																			$ 0.0001		$ 0.0001						$ 0.0001
Number of stock, shares issued | shares																			0		0						0
Number of stock, shares outstanding | shares																			0		0						0
Common stock, shares authorized | shares											300,000,000	300,000,000	300,000,000	300,000,000		300,000,000	300,000,000	300,000,000	300,000,000		300,000,000						300,000,000
Common stock, par value per share | $ / shares											$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001		$ 0.0001						$ 0.0001
Common stock, shares issued | shares											14,614,890	14,595,477	14,359,214	14,036,249		14,595,477	14,614,890	14,036,249	16,784,969		14,215,302						14,215,302
Common stock, shares outstanding | shares											14,614,890	14,595,477	14,359,214	14,036,249		14,595,477	14,614,890	14,036,249	16,784,969		14,215,302						14,215,302
Equity financing, authorized amount						$ 250,000,000	$ 125,000,000			$ 250,000,000
Common stock value											$ 1,000	$ 1,000	$ 1,000	$ 1,000		$ 1,000	$ 1,000	$ 1,000	$ 2,000	[1]	$ 1,000	[1]					$ 1,000	[1]
Issuance cost																		1,965,000	0		1,967,000		$ 0
Other expense related to the commitment shares issued to Lincoln Park Capital Fund																			0		0		825,000
Gain (loss) on warrant liability											$ 253,000	$ (3,461,000)	$ 5,491,000	$ 10,974,000		$ 2,030,000	$ 2,283,000	$ 10,974,000	$ 6,215,000		$ 16,843,000		$ 0
Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock, shares outstanding | shares											14,614,890	14,595,477	14,359,214	14,036,249		14,595,477	14,614,890	14,036,249	16,784,969	[2]	14,215,302	[2]	6,299,158	[2]	5,325,288	[2]	14,215,302	[2]	6,958,494
New Warrants | Holders | Inducement Offer
Subsidiary Sale Of Stock [Line Items]
Exercise price for warrant | $ / shares		$ 1.92
Warrants issued to purchase ordinary shares | shares		2,143,000
New Warrants | Holders | Inducement Offer | Maximum
Subsidiary Sale Of Stock [Line Items]
Warrants exercisable term		5 years
Existing Warrants | Inducement Offer
Subsidiary Sale Of Stock [Line Items]
Fair value of common stock																			$ 3,700,000
Fair value of common warrants issued																			2,700,000
Issuance costs and loss on extinguishment of warrants																			1,000,000
Warrant liability																			1,400,000
Existing Warrants | Holders | Inducement Offer
Subsidiary Sale Of Stock [Line Items]
Warrants issued to purchase ordinary shares | shares		2,143,000
Reduced exercise price of warrant | $ / shares		$ 2.045
Expected aggregate gross proceeds from exercise of warrants		$ 4,400,000
Placement Agent Warrants | H.C. Wainwright & Co.
Subsidiary Sale Of Stock [Line Items]
Exercise price for warrant | $ / shares		$ 2.5563
Warrants issued to purchase ordinary shares | shares		128,580
At The Market Equity Offering Program
Subsidiary Sale Of Stock [Line Items]
Proceeds from sale of common stock													$ 274,000			$ 792,000	$ 744,000	$ 12,003,000	725,000		$ 12,155,000		$ 10,357,000
Issuance of common stock, value												$ 518,000	$ 274,000	$ 8,570,000					$ 725,000		$ 12,155,000		$ 10,357,000
Remaining issuance cost of additional paid-in capital											$ 48,000
At The Market Equity Offering Program | Cowen | Sales Agreement
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares) | shares																									500,226
Proceeds from sale of common stock																									$ 37,300,000
Payments for other offering expenses																									$ 1,300,000
At The Market Equity Offering Program | Cowen | Sales Agreement | Maximum
Subsidiary Sale Of Stock [Line Items]
Equity financing, authorized amount										$ 75,000,000
Percentage of gross sales proceeds of common stock payable as compensation										3%
At The Market Equity Offering Program | Cowen | June 2019 Sales Agreement
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares) | shares																							118,707
At The Market Equity Offering Program | Common Stock
Subsidiary Sale Of Stock [Line Items]
Equity financing, authorized amount										$ 75,000,000
Issuance of common stock (in shares) | shares												168,000	106,781	633,464					274,781	[2]	1,019,046	[2]	189,453	[2]
Additional At The Market Equity Offering Program | Cowen
Subsidiary Sale Of Stock [Line Items]
Proceeds from sale of common stock																							$ 10,400,000
Payments for other offering expenses																							$ 300,000
Additional At The Market Equity Offering Program | Cowen | July 2020 Sales Agreement
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares) | shares																							70,746
Additional At The Market Equity Offering Program | Cowen | July 2020 Sales Agreement | Maximum
Subsidiary Sale Of Stock [Line Items]
Equity financing, authorized amount									$ 50,000,000
Percentage of gross sales proceeds of common stock payable as compensation									3%
Additional At The Market Equity Offering Program | Common Stock
Subsidiary Sale Of Stock [Line Items]
Equity financing, authorized amount									$ 50,000,000
March 2022 ATM Offering Program | Common Stock | Cowen | March 2022 Sales Agreement
Subsidiary Sale Of Stock [Line Items]
Percentage of gross sales proceeds of common stock payable as compensation							3%
Issuance of common stock (in shares) | shares																			274,781
Proceeds from sale of common stock																			$ 1,000,000
Maximum Public Float							$ 75,000,000								$ 75,000,000
March 2022 ATM Offering Program | Common Stock | Cowen | March 2022 Sales Agreement | Maximum
Subsidiary Sale Of Stock [Line Items]
Equity financing, authorized amount							$ 50,000,000								$ 50,000,000
March 2022 ATM Offering Program Amendment | March 2022 Sales Agreement
Subsidiary Sale Of Stock [Line Items]
Common stock, capital shares reserved for future issuance | shares																			14,600,000
March 2022 ATM Offering Program Amendment | Common Stock | Cowen | March 2022 Sales Agreement | Maximum
Subsidiary Sale Of Stock [Line Items]
Equity financing, authorized amount					$ 25,000,000
October 2022 At The Market Equity Offering Program | Cowen | October 2022 Sales Agreement
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares) | shares																					0
October 2022 At The Market Equity Offering Program | Cowen | October 2022 Sales Agreement | Maximum
Subsidiary Sale Of Stock [Line Items]
Equity financing, authorized amount						$ 50,000,000
Percentage of gross sales proceeds of common stock payable as compensation						3%
Equity Purchase Agreement | Lincoln Park Capital Fund LLC
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares) | shares								102,040											0								380,000
Issuance of common stock, value																					$ 910,000		$ 9,039,000
Purchase agreement term								36 months
Share purchase price | $ / shares								$ 2.94
Total gross purchase price of share								$ 3,000,000
Regular purchase capped amount								$ 2,000,000
Percentage of trading volume								30%
Percentage of purchase price								97%
Percentage of shares issued to common shares outstanding immediately prior to the execution of the purchase agreement								19.99%
Purchase agreement price per share | $ / shares								$ 29.4
Maximum percentage ownership of issued and outstanding shares								9.99%
Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Purchase Agreement 35.00 Closing Price
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount closing price per share | $ / shares								$ 35
Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Purchase Agreement 50.00 Closing Price
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount closing price per share | $ / shares								50
Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Purchase Agreement 70.00 Closing Price
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount closing price per share | $ / shares								$ 70
Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Maximum
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares) | shares								1,106,580
Issuance of common stock, value								$ 30,000,000
Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Maximum | Purchase Agreement 35.00 Closing Price
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount shares | shares								15,000
Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Maximum | Purchase Agreement 50.00 Closing Price
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount shares | shares								20,000
Equity Purchase Agreement | Lincoln Park Capital Fund LLC | Maximum | Purchase Agreement 70.00 Closing Price
Subsidiary Sale Of Stock [Line Items]
Regular purchase amount shares | shares								25,000
Equity Purchase Agreement | Common Stock | Lincoln Park Capital Fund LLC
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares) | shares	[2]																				90,000		417,286
Proceeds from sale of common stock																											$ 6,200,000
Issuance of common stock as commitment fee | shares								25,244
Other expense related to the commitment shares issued to Lincoln Park Capital Fund								$ 800,000
Equity Purchase Agreement | Common Stock | Lincoln Park Capital Fund LLC | Regular Purchase Amount | Maximum
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares) | shares								10,000
Follow-On Offering
Subsidiary Sale Of Stock [Line Items]
Gross proceeds				$ 45,000,000
Proceeds from sale of common stock				$ 41,700,000
Number of warrants exercised | shares																			2,143,000
Issuance of common stock, value														$ 15,428,000							$ 15,426,000
Estimated fair value of common warrants exercised																			$ 2,800,000		10,700,000
Gain (loss) on warrant liability																			6,600,000		$ 16,800,000
Follow-On Offering | Maximum
Subsidiary Sale Of Stock [Line Items]
Warrants exercisable term				5 years
Warrant exercise percentage of ordinary shares outstanding beneficially owned				4.99%
Follow-On Offering | Common Stock
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock (in shares) | shares				6,428,571										6,428,571							6,428,571	[2]
Share purchase price | $ / shares				$ 7
Follow-On Offering | Existing Warrants
Subsidiary Sale Of Stock [Line Items]
Exercise price for warrant | $ / shares				$ 8.5
Warrants issued to purchase ordinary shares | shares				6,428,572
Gross proceeds																			45,000,000
Fair value of common warrants issued																			27,600,000
Issuance cost																			3,300,000
Remaining issuance cost of additional paid-in capital																			1,900,000
Follow-On Offering | Existing Warrants | Other Income (Expense)
Subsidiary Sale Of Stock [Line Items]
Issuance cost																			$ 1,400,000
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented. The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Corporate Restructuring - Addit

Corporate Restructuring - Additional Information (Details) $ in Millions			1 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2023 Employee	May 31, 2023 Employee	May 31, 2023 Employee	Feb. 28, 2022 Position	Jun. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2023 USD ($) Employee	Dec. 31, 2022 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring implementation date		2023-05		2022-02
Number of positions eliminated				29			9
Percentage of positions eliminated		29%		50%
Severance charge in operating expenses						$ 1.9
Non-cash share-based payment compensation credits to forfeiture of stock options								$ 1.7
Expected number of employees departing | Employee	3	9	6
Operating Expenses
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses					$ 0.6
Employee Termination Benefits
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses							$ 0.5	1.6
Employee Termination Benefits | Research and Development Expense
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses							0.4	1.4
Employee Termination Benefits | Employee-Related Benefits
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses							0.1	0.2
Employee Termination Benefits | General and Administrative Expense
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses							$ 0.2	0.5
Employee Termination Benefits | Payroll Taxes
Restructuring Cost And Reserve [Line Items]
Severance charge in operating expenses								$ 0.1

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details)

1 Months Ended

6 Months Ended

12 Months Ended

May 11, 2023 USD ($) Employee $ / shares shares

May 04, 2023 $ / shares

Feb. 28, 2022 USD ($) Position shares

Jun. 30, 2021 USD ($) shares

Jan. 31, 2021 USD ($) $ / shares shares

Sep. 30, 2020 shares

Mar. 31, 2020 USD ($) $ / shares shares

Mar. 31, 2018 USD ($) shares

Jun. 30, 2013

Feb. 28, 2018 $ / shares

Dec. 31, 2023 USD ($) Employee $ / shares shares

Dec. 31, 2022 USD ($) $ / shares shares

Dec. 31, 2021 USD ($)

Sep. 30, 2023 shares

Jun. 30, 2023 shares

Mar. 31, 2023 shares

Feb. 28, 2023 shares

Sep. 30, 2022 shares

Nov. 30, 2020 shares

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Common stock, shares authorized

300,000,000

300,000,000

300,000,000

300,000,000

300,000,000

300,000,000

Intrinsic value of options exercised | $

$ 0

$ 0

Weighted-average estimated fair value of stock options granted | $ / shares

$ 2.79

$ 3.11

Exercisable, aggregate intrinsic value | $

$ 0

$ 0

Number of shares authorized for issuance

320,000

Number of shares options granted to purchase an aggregate of common stock

446,200

Settlement of stock based compensation for liability awards

0

0

Incremental fair value on modification date | $

$ 300,000

$ 0

$ 0

Stock option awards outstanding

1,913,345

1,609,938

Stock option awards, grant date fair value | $

$ 5,000

$ 251,000

Stock-based compensation expense | $

$ 7,419,000

9,379,000

11,553,000

Restructuring implementation date

May 04, 2023

Number of employees terminated | Employee

5

Expected number of employees terminated

29

9

2018 Employee Stock Purchase Plan

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Common stock, capital shares reserved for future issuance

53,624

Option purchase date price percentage lower of closing trading price per share

85%

Employees subscription rate during the offering period

15%

Maximum number of shares may be purchased by an employee

15,000

Maximum fair market value of shares may be purchased by an employee | $

$ 25,000

Non Employee

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Stock-based compensation expense | $

$ 400,000

200,000

$ 400,000

Maximum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Vesting period, options

4 years

Minimum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Vesting period, options

3 years

Performance and Market Contingent Stock Options

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Trailing period

30 days

Stock option awards outstanding

3,336

Stock option awards, grant date fair value | $

$ 100,000

Modification date fair value | $

$ 102,000

$ 81,000

Implied service period for recognition

1 year 10 months 6 days

Performance and Market Contingent Stock Options | Executive Team

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Stock option awards exercisable upon the achievement of performance goals

3,336

1,747

Performance and Market Contingent Stock Options | Tranche One

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Volume-weighted average per Share closing trading price | $ / shares

$ 180

Trailing period

30 days

Performance and Market Contingent Stock Options | Tranche Two

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Volume-weighted average per Share closing trading price | $ / shares

$ 360

Trailing period

30 days

Performance and Market Contingent Stock Options | Maximum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Implied service period for recognition

2 years 6 months 7 days

Performance and Market Contingent Stock Options | Minimum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Implied service period for recognition

1 year 5 months 15 days

Attaining valuation of certain amount | $

$ 1,000,000,000

Stock Options

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of shares authorized for issuance

25,000

Number of retention awards granted

189,333

Retention award grant date total fair value | $

$ 2,000,000

RSUs

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of shares authorized for issuance

295,985

Number of retention awards granted

46,332

Retention award grant date total fair value | $

$ 500,000

RSUs and RSAs

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Total grant-date fair value of stock vested | $

300,000

$ 600,000

Stock Options and RSAs

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Stock-based compensation cost not yet amortized | $

$ 3,900,000

Weighted-average period for recognition

10 months 24 days

2018 Incentive Award Plan

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Common stock, capital shares reserved for future issuance

428,994

Vesting period, options

4 years

Common stock, shares authorized

2,182,500

2018 Incentive Award Plan | Maximum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Expiration period from the date of grant, options

10 years

2018 Incentive Award Plan | Minimum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Exercise price as a percentage of estimated fair value of the shares on the date of grant

100%

2020 Employment Inducement Incentive Plan

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Common stock, capital shares reserved for future issuance

110,000

300,000

150,000

Vesting period, options

4 years

Common stock, shares authorized

542,000

2020 Employment Inducement Incentive Plan | New Chief Executive Officer

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of common stock shares granted

110,000

2020 Employment Inducement Incentive Plan | Maximum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Expiration period from the date of grant, options

10 years

2020 Employment Inducement Incentive Plan | Minimum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Exercise price as a percentage of estimated fair value of the shares on the date of grant

100%

2020 Employment Inducement Incentive Plan | PSUs

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Weighted-average period for recognition

4 years 3 months 18 days

Grant date fair value | $

$ 700,000

Incremental fair value on modification date | $

$ 31,000

Unamortized value of original grant | $

$ 569,000

2020 Employment Inducement Incentive Plan | PSUs | New Chief Executive Officer

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of common stock shares granted

15,000

2020 Employment Inducement Incentive Plan | PSUs | Tranche One

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of shares to vest upon attainment of certain conditions

5,000

5,000

Volume-weighted average per Share closing trading price | $ / shares

$ 180

$ 368.75

Trailing period

30 days

30 days

2020 Employment Inducement Incentive Plan | PSUs | Tranche Two

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of shares to vest upon attainment of certain conditions

10,000

10,000

Volume-weighted average per Share closing trading price | $ / shares

$ 180

Trailing period

30 days

30 days

Price per share to holders of company's common stock | $ / shares

$ 360

$ 368.75

Market capitalization trigger | $

$ 2,500,000,000

2020 Employment Inducement Incentive Plan | PSUs | Maximum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

New implied service period for recognition

2 years 9 months 14 days

2020 Employment Inducement Incentive Plan | PSUs | Minimum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

New implied service period for recognition

1 year 7 months 17 days

2020 Employment Inducement Incentive Plan | Stock Options | New Chief Executive Officer

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of shares options granted to purchase an aggregate of common stock

80,000

2020 Employment Inducement Incentive Plan | RSUs | New Chief Executive Officer

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of common stock shares granted

12,000

2020 Employment Inducement Incentive Plan | Restricted Stock Awards | New Chief Executive Officer

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of common stock shares granted

3,000

2013 Equity Incentive Plan

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Vesting period, options

4 years

Exercise price of an ISO and NSO granted to a stockholder, percentage

10%

Exercise price | $ / shares

$ 3.42

Exercise price range, lower range limit | $ / shares

3.95

Exercise price range, upper range limit | $ / shares

$ 8.47

2013 Equity Incentive Plan | Maximum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Expiration period from the date of grant, options

10 years

2013 Equity Incentive Plan | Minimum

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Exercise price as a percentage of estimated fair value of the shares on the date of grant

100%

Exercise price as a percentage of estimated grant date fair value of shares for a 10% shareholder

110%

2018 Incentive Award Plan

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Exercise price | $ / shares

$ 2.77

$ 6

Number of employees who met the eligibility terms | Employee

26

Number of shares of common stock under option grants that met the eligibility criteria

444,273

Additional stock-based compensation from vested options | $

$ 200,000

Number of vested options

251,821

Anticipated additional amount expensed | $

$ 100,000

Number of unvested options

170,189

Stock-Based Compensation - Summ

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

Stock-Based Compensation - Su_2

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

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Valuation Assumption to Estimate Fair Value of Stock Options (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term of options (in years)	5 years 9 months 14 days	5 years 6 months 18 days	6 years
Expected stock price volatility, Minimum	94.11%	86.22%	85.70%
Expected stock price volatility, Maximum	98.92%	93.17%	88.50%
Risk-free interest rate, Minimum	3.36%	2.41%	1.08%
Risk-free interest rate, Maximum	4.13%	4.01%	1.35%
Expected dividend yield	0%	0%	0%

Stock-Based Compensation - Su_4

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

Net Loss per Common Share - Sch

Net Loss per Common Share - Schedule of Reconciliation of Numerators and Denominators Used In Computing Net Loss From Continuing Operations Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Numerator:
Net gain (loss)	$ (14,782)	$ (15,456)	$ (5,279)	$ (4,997)	$ (20,735)	$ (35,520)	$ (37,047)	$ (39,860)		$ (44,469)		$ (60,725)
Denominator:
Weighted average number of shares outstanding-basic	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729	14,773,612	[1]	9,494,421	[1]	5,581,587	[1]
Weighted average number of shares outstanding-diluted	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729	14,773,612	[1]	9,494,421	[1]	5,581,587	[1]
Net loss per share-basic	$ (1.01)	$ (1.07)	$ (0.37)	$ (0.5)	$ (1.44)	$ (2.46)	$ (4.67)	$ (2.7)		$ (4.68)		$ (10.88)
Net loss per share-diluted	$ (1.01)	$ (1.07)	$ (0.37)	$ (0.5)	$ (1.44)	$ (2.46)	$ (4.67)	$ (2.7)		$ (4.68)		$ (10.88)
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded up to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Net Loss per Common Share - Sum

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

Net Loss per Common Share - Add

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

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Details) - Defined Contribution Plan - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Contribution Plan Disclosure [Line Items]
Percent of employer matching contribution of employees' salary	4%
Defined Contribution Plan, Sponsor Location [Extensible Enumeration]	us-gaap:DomesticPlanMember
Matching contributions		$ 0.3	$ 0.4	$ 0.5

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Tax Rate of Provision for Income Taxes Differs From Federal Statutory Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Taxes at the U.S. statutory income tax rate	21%	21%	21%
State tax, net of federal benefit	9%	9.10%	4.40%
Other	0.50%	(0.80%)	(0.40%)
Warrant activity	2.80%	7.30%	0%
Stock-based compensation	(2.50%)	(6.60%)	(1.60%)
Research and development tax credits	1.80%	2.90%	3.20%
Rate change	(8.80%)	4.70%	3.80%
ASC 740-10	0%	(7.50%)	(4.20%)
Change in valuation allowance	(23.70%)	(30.10%)	(26.20%)
Total provision for income taxes	0%	0%	0%

Income Taxes - Schedule of Comp

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

Income Taxes - Additional Infor

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

Income Taxes - Summary of Net O

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

Income Taxes - Schedule of Reco

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

Quarterly Financial Informati_3

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

Quarterly Financial Informati_4

Quarterly Financial Information (Unaudited) - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2023		Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022		Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 19,803		$ 7,876	$ 19,118	$ 22,972	$ 12,736		$ 22,576		$ 32,905
Short-term marketable securities	23,398		38,063	49,974	60,420	82,059		76,364
Prepaid expenses and other current assets	3,404		3,599	3,874	2,989	1,740		3,084
Restricted cash								550
Total current assets	46,605		49,538	72,966	86,381	96,535		102,574
Property and equipment, net	5,082		5,314	7,181	7,496	7,825		8,202
Operating lease right-of-use asset	12,981		13,522	18,061	18,557	19,042		19,515
Long-term deposits					896
Long-term marketable securities				1,899				4,980
Long-term restricted cash	896		896	896	896	896		896
Other long-term assets	126			5	29	52		76
Total assets	65,690		69,270	101,008	114,255	124,350		136,243
Current liabilities:
Accounts payable	1,380		1,149	1,449	1,470	1,790		2,444
Accrued compensation	1,841		2,226	1,652	1,983	3,020		2,961
Accrued and other current liabilities	4,619		5,258	5,417	5,343	5,334		5,321
Current portion of long-term debt	0			13,623	13,062	9,476		6,776
Total current liabilities	7,840		8,633	22,141	21,858	19,620		17,502
Operating lease liability, net of current portion	23,539		24,431	25,297	26,150	26,991		27,792
Long-term debt, net	0			4,067	7,619	10,891		13,262
Warrant liability	5,913		8,481	8,734	5,273	10,764		16,633
Total liabilities	37,292		41,545	60,239	60,900	68,266		75,189
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding	0		0	0	0	0		0
Common stock value	2	[1]	1	1	1	1	[1]	1
Additional paid-in capital	512,773		507,789	506,132	503,276	500,827		498,401
Accumulated other comprehensive loss	(24)		(55)	(136)	(150)	(251)		(275)
Accumulated deficit	(484,353)		(480,010)	(465,228)	(449,772)	(444,493)		(437,073)
Total stockholders’ equity	28,398		27,725	40,769	53,355	56,084		61,054	$ 39,931	59,569	$ 82,881
Total liabilities and stockholders’ equity	$ 65,690		69,270	101,008	114,255	124,350		136,243
As Previously Reported
Current assets:
Cash and cash equivalents			7,876	19,118	22,972	12,736		22,576
Short-term marketable securities			38,063	49,974	60,420	82,059		76,364
Prepaid expenses and other current assets			3,599	3,874	2,989	1,740		3,234
Restricted cash								550
Total current assets			49,538	72,966	86,381	96,535		102,724
Property and equipment, net			5,314	7,181	7,496	7,825		8,202
Operating lease right-of-use asset			13,522	18,061	18,557	19,042		19,515
Long-term deposits					896
Long-term marketable securities				1,899				4,980
Long-term restricted cash			896	896	896	896		896
Other long-term assets				5	29	52		76
Total assets			69,270	101,008	114,255	124,350		136,393
Current liabilities:
Accounts payable			1,149	1,449	1,470	1,790		2,444
Accrued compensation			2,226	1,652	1,983	3,020		2,961
Accrued and other current liabilities			5,258	5,417	5,343	5,334		4,593
Current portion of long-term debt				13,704	13,062	9,476		6,776
Total current liabilities			8,633	22,222	21,858	19,620		16,774
Operating lease liability, net of current portion			24,431	25,297	26,150	26,991		27,792
Long-term debt, net				4,082	7,619	10,891		13,262
Warrant liability			0	0	0	0		0
Total liabilities			33,064	51,601	55,627	57,502		57,828
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding			0	0	0	0		0
Common stock value			1	1	1	1		1
Additional paid-in capital			534,570	532,563	529,593	527,049		524,623
Accumulated other comprehensive loss			(55)	(136)	(150)	(251)		(275)
Accumulated deficit			(498,310)	(483,021)	(470,816)	(459,951)		(445,784)
Total stockholders’ equity			36,206	49,407	58,628	66,848		78,565	$ 39,931	$ 59,569
Total liabilities and stockholders’ equity			69,270	101,008	114,255	124,350		136,393
Adjustment
Current assets:
Cash and cash equivalents			0	0	0	0		0
Short-term marketable securities			0	0	0	0		0
Prepaid expenses and other current assets			0	0	0	0		(150)
Restricted cash								0
Total current assets			0	0	0	0		(150)
Property and equipment, net			0	0	0	0		0
Operating lease right-of-use asset			0	0	0	0		0
Long-term deposits					0
Long-term marketable securities				0				0
Long-term restricted cash			0	0	0	0		0
Other long-term assets				0	0	0		0
Total assets			0	0	0	0		(150)
Current liabilities:
Accounts payable			0	0	0	0		0
Accrued compensation			0	0	0	0		0
Accrued and other current liabilities			0	0	0	0		728
Current portion of long-term debt				(81)	0	0		0
Total current liabilities			0	(81)	0	0		728
Operating lease liability, net of current portion			0	0	0	0		0
Long-term debt, net				(15)	0	0		0
Warrant liability			8,481	8,734	5,273	10,764		16,633
Total liabilities			8,481	8,638	5,273	10,764		17,361
Commitments and contingencies
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding			0	0	0	0		0
Common stock value			0	0	0	0		0
Additional paid-in capital			(26,781)	(26,431)	(26,317)	(26,222)		(26,222)
Accumulated other comprehensive loss			0	0	0	0		0
Accumulated deficit			18,300	17,793	21,044	15,458		8,711
Total stockholders’ equity			(8,481)	(8,638)	(5,273)	(10,764)		(17,511)
Total liabilities and stockholders’ equity			$ 0	$ 0	$ 0	$ 0		$ (150)
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Quarterly Financial Informati_5

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

Quarterly Financial Informati_6

Quarterly Financial Information (Unaudited) - Statements of Operations and Comprehensive Loss (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Licensing revenue – Related Party		$ 0		$ 0	$ 0		$ 236	$ 0		$ 236		$ 4,784
Operating expenses:
Research and development	$ 4,632	6,435	$ 5,760	9,086	12,195	$ 16,828	29,100	20,099		36,859		38,393
General and administrative	4,347	5,413	4,798	4,922	10,212	14,560	15,669	18,966		20,949		23,056
Impairment of long-lived assets	5,602					5,602		5,602		0		0
Total operating expenses	14,581	11,848	10,558	14,008	22,407	36,990	44,769	44,667		57,808		61,449
Loss from operations	(14,581)	(11,848)	(10,558)	(14,008)	(22,407)	(36,990)	(44,533)	(44,667)		(57,572)		(56,665)
Interest income	689	805	855	329	1,660	2,349	416	2,874		1,220		100
Interest expense	(566)	(883)	(1,002)	(866)	(1,885)	(2,451)	(2,568)	(2,452)		(3,558)		(3,177)
Gain (loss) on warrant liability	253	(3,461)	5,491	10,974	2,030	2,283	10,974	6,215		16,843		0
Other expense, net	(577)	(69)	(65)	(1,426)	(133)	(711)	(1,336)	(1,830)		(1,402)		(983)
Net loss	(14,782)	(15,456)	(5,279)	(4,997)	(20,735)	(35,520)	(37,047)	(39,860)		(44,469)		(60,725)
Other comprehensive gain (loss)
Unrealized loss on marketable debt securities	81	14	101	(88)	115	196	(231)	227		(207)		(49)
Comprehensive loss	$ (14,701)	$ (15,442)	$ (5,178)	$ (5,085)	$ (20,620)	$ (35,324)	$ (37,278)	$ (39,633)		$ (44,676)		$ (60,774)
Net loss per share, basic	$ (1.01)	$ (1.07)	$ (0.37)	$ (0.5)	$ (1.44)	$ (2.46)	$ (4.67)	$ (2.7)		$ (4.68)		$ (10.88)
Net loss per share, diluted	$ (1.01)	$ (1.07)	$ (0.37)	$ (0.5)	$ (1.44)	$ (2.46)	$ (4.67)	$ (2.7)		$ (4.68)		$ (10.88)
Weighted average number of shares used in computing net loss per share, diluted	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729	14,773,612	[1]	9,494,421	[1]	5,581,587	[1]
Weighted average number of shares used in computing net loss per share, basic	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729	14,773,612	[1]	9,494,421	[1]	5,581,587	[1]
As Previously Reported
Licensing revenue – Related Party		$ 0		$ 0	$ 0		$ 236			$ 236
Operating expenses:
Research and development	$ 4,901	6,529	$ 5,835	8,208	12,364	$ 17,266	28,222			36,859
General and administrative	4,428	5,433	4,818	4,922	10,252	14,681	15,669			20,949
Impairment of long-lived assets	5,602					5,602
Total operating expenses	14,931	11,962	10,653	13,130	22,616	37,549	43,891			57,808
Loss from operations	(14,931)	(11,962)	(10,653)	(13,130)	(22,616)	(37,549)	(43,655)			(57,572)
Interest income	689	805	855	329	1,660	2,349	416			1,220
Interest expense	(470)	(979)	(1,002)	(866)	(1,981)	(2,451)	(2,568)			(3,558)
Gain (loss) on warrant liability	0	0	0	0	0	0	0			0
Other expense, net	(577)	(69)	(65)	(41)	(133)	(711)	49			(17)
Net loss	(15,289)	(12,205)	(10,865)	(13,708)	(23,070)	(38,362)	(45,758)			(59,927)
Other comprehensive gain (loss)
Unrealized loss on marketable debt securities	81	14	101	(88)	115	196	(231)			(207)
Comprehensive loss	$ (15,208)	$ (12,191)	$ (10,764)	$ (13,796)	$ (22,955)	$ (38,166)	$ (45,989)			$ (60,134)
Net loss per share, basic	$ (1.05)	$ (0.85)	$ (0.76)	$ (1.36)	$ (1.61)	$ (2.66)	$ (5.77)			$ (6.31)
Net loss per share, diluted	$ (1.05)	$ (0.85)	$ (0.76)	$ (1.36)	$ (1.61)	$ (2.66)	$ (5.77)			$ (6.31)
Weighted average number of shares used in computing net loss per share, diluted	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729			9,494,421
Weighted average number of shares used in computing net loss per share, basic	14,598,218	14,425,775	14,312,887	10,072,077	14,369,643	14,446,672	7,928,729			9,494,421
Adjustment
Licensing revenue – Related Party		$ 0		$ 0	$ 0		$ 0			$ 0
Operating expenses:
Research and development	$ (269)	(94)	$ (75)	878	(169)	$ (438)	878			0
General and administrative	(81)	(20)	(20)	0	(40)	(121)	0			0
Impairment of long-lived assets	0					0
Total operating expenses	(350)	(114)	(95)	878	(209)	(559)	878			0
Loss from operations	350	114	95	(878)	209	559	(878)			0
Interest income	0	0	0	0	0	0	0			0
Interest expense	(96)	96	0	0	96	0	0			0
Gain (loss) on warrant liability	253	(3,461)	5,491	10,974	2,030	2,283	10,974			16,843
Other expense, net	0	0	0	(1,385)	0	0	(1,385)			(1,385)
Net loss	507	(3,251)	5,586	8,711	2,335	2,842	8,711			15,458
Other comprehensive gain (loss)
Unrealized loss on marketable debt securities	0	0	0	0	0	0	0			0
Comprehensive loss	$ 507	$ (3,251)	$ 5,586	$ 8,711	$ 2,335	$ 2,842	$ 8,711			$ 15,458
Net loss per share, basic	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Net loss per share, diluted	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Weighted average number of shares used in computing net loss per share, diluted	0	0	0	0	0	0	0
Weighted average number of shares used in computing net loss per share, basic	0	0	0	0	0	0	0
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded up to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Quarterly Financial Informati_7

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

Quarterly Financial Informati_8

Quarterly Financial Information (Unaudited) - Statements of Changes in Stockholders' Equity (Details) - USD ($) $ in Thousands		3 Months Ended					6 Months Ended		9 Months Ended				12 Months Ended
	Aug. 31, 2022	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023		Sep. 30, 2022	Jun. 30, 2023		Sep. 30, 2023		Sep. 30, 2022		Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Beginning balance		$ 40,769	$ 53,355	$ 56,084		$ 39,931	$ 56,084		$ 56,084		$ 59,569		$ 56,084		$ 59,569		$ 82,881
Beginning balance, (in shares)		14,595,477	14,359,214	14,215,302			14,215,302		14,215,302				14,215,302
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)			$ 91										$ 116		142		347
Stock-based compensation		$ 1,705	2,247	$ 2,175		2,210							7,419		9,379		11,553
Unrealized gain (loss) on available-for-sale marketable securities		81	14	101		(88)							227		(207)		(49)
Net gain (loss)		(14,782)	(15,456)	(5,279)		(4,997)	$ (20,735)		$ (35,520)		(37,047)		(39,860)		(44,469)		(60,725)
Ending balance		$ 27,725	$ 40,769	$ 53,355		$ 61,054	$ 40,769		$ 27,725		$ 61,054		$ 28,398		$ 56,084		59,569
Ending balance, (in shares)		14,614,890	14,595,477	14,359,214		14,036,249	14,595,477		14,614,890		14,036,249		16,784,969		14,215,302
ATM Equity Offering Program
Issuance of common stock, net of issuance costs			$ 518	$ 274		$ 8,570							$ 725		$ 12,155		10,357
Fees related to the ATM offering program		$ (48)
Follow-On Offering
Issuance of common stock, net of issuance costs						15,428									15,426
Common Stock
Beginning balance		$ 1	$ 1	$ 1	[1]	$ 1	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]
Beginning balance, (in shares)		14,595,477	14,359,214	14,215,302	[1]	6,958,494	14,215,302	[1]	14,215,302	[1]	6,299,158	[1]	14,215,302	[1]	6,299,158	[1]	5,325,288	[1]
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)			41,497										57,419	[1]	25,482	[1]	11,704	[1]
Vesting of restricted stock units, (in shares)		19,413	26,766	37,131		15,720							94,467	[1]	90,284	[1]	96,269	[1]
Ending balance		$ 1	$ 1	$ 1		$ 1	$ 1		$ 1		$ 1		$ 2	[1]	$ 1	[1]	$ 1	[1]
Ending balance, (in shares)		14,614,890	14,595,477	14,359,214		14,036,249	14,595,477		14,614,890		14,036,249		16,784,969	[1]	14,215,302	[1]	6,299,158	[1]
Common Stock | ATM Equity Offering Program
Issuance of common stock (in shares)			168,000	106,781		633,464							274,781	[1]	1,019,046	[1]	189,453	[1]
Fees related to the ATM offering program (in shares)		0
Common Stock | Follow-On Offering
Issuance of common stock (in shares)	6,428,571					6,428,571									6,428,571	[1]
Additional Paid-In Capital
Beginning balance		$ 506,132	$ 503,276	$ 500,827		$ 472,193	$ 500,827		$ 500,827		$ 459,636		$ 500,827		$ 459,636		$ 422,384
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)			91										116		142		347
Stock-based compensation		1,705	2,247	2,175		2,210							7,419		9,379		11,553
Ending balance		507,789	506,132	503,276		498,401	506,132		507,789		498,401		512,773		500,827		459,636
Additional Paid-In Capital | ATM Equity Offering Program
Issuance of common stock, net of issuance costs			518	274		8,570							725		12,155		10,357
Fees related to the ATM offering program		(48)
Additional Paid-In Capital | Follow-On Offering
Issuance of common stock, net of issuance costs						15,428									15,426
Accumulated Other Comprehensive Gain (Loss)
Beginning balance		(136)	(150)	(251)		(187)	(251)		(251)		(44)		(251)		(44)		5
Unrealized gain (loss) on available-for-sale marketable securities		81	14	101		(88)							227		(207)		(49)
Ending balance		(55)	(136)	(150)		(275)	(136)		(55)		(275)		(24)		(251)		(44)
Accumulated Deficit
Beginning balance		(465,228)	(449,772)	(444,493)		(432,076)	(444,493)		(444,493)		(400,024)		(444,493)		(400,024)		(339,299)
Net gain (loss)		(14,782)	(15,456)	(5,279)		(4,997)							(39,860)		(44,469)		(60,725)
Ending balance		(480,010)	(465,228)	(449,772)		(437,073)	(465,228)		(480,010)		(437,073)		(484,353)		(444,493)		(400,024)
As Previously Reported
Beginning balance		49,407	58,628	66,848		39,931	66,848		66,848		59,569		66,848		59,569
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)			91												142
Stock-based compensation		2,055	2,361	2,270		2,210									9,379
Unrealized gain (loss) on available-for-sale marketable securities		81	14	101		(88)									(207)
Net gain (loss)		(15,289)	(12,205)	(10,865)		(13,708)	(23,070)		(38,362)		(45,758)				(59,927)
Ending balance		36,206	49,407	58,628		78,565	49,407		36,206		78,565				66,848		59,569
As Previously Reported | ATM Equity Offering Program
Issuance of common stock, net of issuance costs			518	274		8,570									12,155
Fees related to the ATM offering program		(48)
As Previously Reported | Follow-On Offering
Issuance of common stock, net of issuance costs						41,650									41,648
As Previously Reported | Common Stock
Beginning balance		$ 1	$ 1	$ 1		$ 1	$ 1		$ 1		$ 1		$ 1		$ 1
Beginning balance, (in shares)		14,595,477	14,359,214	14,215,302		6,958,494	14,215,302		14,215,302		6,299,158		14,215,302		6,299,158
Issuance of common stock under employee stock purchase plan ("2018 ESPP") (in Shares)			41,497												25,482
Vesting of restricted stock units, (in shares)		19,413	26,766	37,131		15,720									90,284
Ending balance		$ 1	$ 1	$ 1		$ 1	$ 1		$ 1		$ 1				$ 1		$ 1
Ending balance, (in shares)		14,614,890	14,595,477	14,359,214		14,036,249	14,595,477		14,614,890		14,036,249				14,215,302		6,299,158
As Previously Reported | Common Stock | ATM Equity Offering Program
Issuance of common stock (in shares)			168,000	106,781		633,464									1,019,046
As Previously Reported | Common Stock | Follow-On Offering
Issuance of common stock (in shares)						6,428,571									6,428,571
As Previously Reported | Additional Paid-In Capital
Beginning balance		$ 532,563	$ 529,593	$ 527,049		$ 472,193	$ 527,049		$ 527,049		$ 459,636		$ 527,049		$ 459,636
Issuance of common stock under employee stock purchase plan (“2018 ESPP”)			91												142
Stock-based compensation		2,055	2,361	2,270		2,210									9,379
Ending balance		534,570	532,563	529,593		524,623	532,563		534,570		524,623				527,049		$ 459,636
As Previously Reported | Additional Paid-In Capital | ATM Equity Offering Program
Issuance of common stock, net of issuance costs			518	274		8,570									12,155
Fees related to the ATM offering program		(48)
As Previously Reported | Additional Paid-In Capital | Follow-On Offering
Issuance of common stock, net of issuance costs						41,650									41,648
As Previously Reported | Accumulated Other Comprehensive Gain (Loss)
Beginning balance		(136)	(150)	(251)		(187)	(251)		(251)		(44)		(251)		(44)
Unrealized gain (loss) on available-for-sale marketable securities		81	14	101		(88)									(207)
Ending balance		(55)	(136)	(150)		(275)	(136)		(55)		(275)				(251)		(44)
As Previously Reported | Accumulated Deficit
Beginning balance		(483,021)	(470,816)	(459,951)		(432,076)	(459,951)		(459,951)		(400,024)		(459,951)		(400,024)
Net gain (loss)		(15,289)	(12,205)	(10,865)		(13,708)									(59,927)
Ending balance		(498,310)	(483,021)	(470,816)		(445,784)	(483,021)		(498,310)		(445,784)				(459,951)		$ (400,024)
Adjustment
Beginning balance		(8,638)	(5,273)	(10,764)			(10,764)		(10,764)				(10,764)
Stock-based compensation		(350)	(114)	(95)
Net gain (loss)		507	(3,251)	5,586		8,711	2,335		2,842		8,711				15,458
Ending balance		(8,481)	(8,638)	(5,273)		(17,511)	(8,638)		(8,481)		(17,511)				(10,764)
Adjustment | Follow-On Offering
Issuance of common stock, net of issuance costs						(26,222)
Adjustment | Additional Paid-In Capital
Beginning balance		(26,431)	(26,317)	(26,222)			(26,222)		(26,222)				(26,222)
Stock-based compensation		(350)	(114)	(95)
Ending balance		(26,781)	(26,431)	(26,317)		(26,222)	(26,431)		(26,781)		(26,222)				(26,222)
Adjustment | Additional Paid-In Capital | Follow-On Offering
Issuance of common stock, net of issuance costs						(26,222)									(26,222)
Adjustment | Accumulated Deficit
Beginning balance		17,793	21,044	15,458			15,458		15,458				$ 15,458
Net gain (loss)		507	(3,251)	5,586		8,711									15,458
Ending balance		$ 18,300	$ 17,793	$ 21,044		$ 8,711	$ 17,793		$ 18,300		$ 8,711				$ 15,458
[1] The Company effected a reverse stock split of its outstanding shares of common stock on October 19, 2022 where every ten shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were rounded down to the nearest whole post-split share. Shareholders of the Company previously authorized the Board of Directors to approve a reverse stock split at the annual meeting on October 18, 2022. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis in all periods presented.

Quarterly Financial Informati_9

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