LENZ Therapeutics (LENZ) S-4 6 Dec 23 Registration of securities issued in business combination transactions Financial data

Cover Page

Cover Page	9 Months Ended
	Sep. 30, 2023
Document Type	S-4
Amendment Flag	false
Entity Registrant Name	Graphite Bio, Inc.
Entity Central Index Key	0001815776
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Incorporation State Country Code	DE
Entity Address Address Line1	611 Gateway Blvd
Entity Address, Address Line Two	Suite 120
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	484-0886
Entity Tax Identification Number	84-4867570
Entity Primary SIC Number	2836
Business Contact [Member]
Contact Personnel Name	Kimberlee C. Drapkin
Entity Address Address Line1	611 Gateway Blvd
Entity Address, Address Line Two	Suite 120
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	484-0886

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 182,988	$ 47,730	$ 376,976
Investments in marketable securities, current	50,998	220,499	0
Assets held for sale	20	0
Prepaid expenses and other current assets	4,777	7,136	4,760
Total current assets	238,783	275,365	381,736
Restricted cash	1,716	1,716	1,716
Investments in marketable securities, non-current	0	15,322	0
Property and equipment, net	12,534	22,630	6,507
Operating lease right-of-use assets	13,195	5,580	11,574
Other assets	0	1,289	454
Total assets	266,228	321,902	401,987
Current liabilities:
Accounts payable	3,753	2,608	2,453
Accrued compensation	1,899	3,799	2,689
Accrued research costs	30	720	633
Accrued expenses and other current liabilities	3,416	1,871	886
Operating lease liabilities, current	3,439	4,045	5,482
Total current liabilities	12,537	13,043	12,143
Operating lease liabilities, non-current	49,672	1,749	5,794
Other long- term liabilities	0	10,819	0
Total liabilities	62,209	25,611	17,937
Commitments and contingencies (Note 7)
Stockholders' equity:
Preferred stock, $0.00001 par value, 10,000,000 shares authorized as of September 30, 2023 and December 31, 2022; and no shares issued and outstanding as of September 30, 2023 and December 31, 2022	0	0	0
Common stock, $0.00001 par value, 300,000,000 shares authorized as of September 30, 2023 and December 31, 2022; 57,971,910 and 58,221,760 shares issued and outstanding as of September 30, 2023 and December 31, 2022, respectively	1	1	1
Additional paid-in-capital	548,249	539,741	525,400
Accumulated other comprehensive loss	(95)	(1,048)	0
Accumulated deficit	(344,136)	(242,403)	(141,351)
Total stockholders' equity	204,019	296,291	384,050
Total liabilities and stockholders' equity	$ 266,228	$ 321,902	$ 401,987

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Preferred stock, par or stated value per share	$ 0.00001	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	10,000,000	10,000,000	10,000,000
Preferred stock, shares issued	0	0	0
Preferred stock, shares outstanding	0	0	0
Common stock, par or stated value per share	$ 0.00001	$ 0.00001	$ 0.00001
Common stock, shares authorized	300,000,000	300,000,000	300,000,000
Common stock, shares, issued	57,971,910	58,221,760	58,010,823
Common stock, shares, outstanding	57,971,910	58,221,760	58,010,823

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Operating expenses:
Research and development	$ 2,384	$ 18,302	$ 32,136	$ 54,325	$ 72,787	$ 37,932
General and administrative	11,294	7,852	26,372	24,563	32,852	22,511
Restructuring and impairment costs	11,349	0	51,128	0
Total operating expenses	25,027	26,154	109,636	78,888	105,639	60,443
Loss from operations	(25,027)	(26,154)	(109,636)	(78,888)	(105,639)	(60,443)
Other income (expense), net:
Interest income, net	2,955	1,472	8,387	2,435	4,587	24
Change in fair value of the Series A redeemable convertible preferred stock tranche liability					0	(10,341)
Loss on disposal of assets	0	0	(71)	0
Other income (expense), net:	(413)	0	(413)	0
Total other income, net	2,542	1,472	7,903	2,435	4,587	(10,317)
Net loss	(22,485)	(24,682)	(101,733)	(76,453)	(101,052)	(70,760)
Unrealized loss on investments in marketable securities	176	(563)	953	(1,596)	(1,048)	0
Comprehensive loss	$ (22,309)	$ (25,245)	$ (100,780)	$ (78,049)	$ (102,100)	$ (70,760)
Net loss per share attributable to common stockholders-basic	$ (0.39)	$ (0.45)	$ (1.79)	$ (1.4)	$ (1.84)	$ (2.45)
Net loss per share attributable to common stockholders-diluted	$ (0.39)	$ (0.45)	$ (1.79)	$ (1.4)	$ (1.84)	$ (2.45)
Weighted-average shares used in computing net loss per share-basic	57,257,241	55,206,139	56,748,995	54,591,593	54,873,675	28,919,255
Weighted-average shares used in computing net loss per share-diluted	57,257,241	55,206,139	56,748,995	54,591,593	54,873,675	28,919,255

Condensed Statements of Stockho

Condensed Statements of Stockholders' Equity (unaudited) - USD ($)	Total	Initial Public Offering	Series A Redeemable Convertible Preferred Stock	Series A Redeemable Convertible Preferred Stock Initial Public Offering	Series B Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock Initial Public Offering	Common Stock	Common Stock Initial Public Offering	Common Stock License Agreement with Stanford	Additional Paid in Capital	Additional Paid in Capital Initial Public Offering	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2020	$ (65,408,000)									$ 5,183,000		$ (70,591,000)
Temporary equity, Beginning balance, Shares at Dec. 31, 2020			30,019,945
Temporary equity, Beginning balance at Dec. 31, 2020			$ 55,608,000
Beginning balance, Shares at Dec. 31, 2020							10,279,102
Common stock issued upon exercise of options	42,000									42,000
Common stock issued upon exercise of options, Shares							33,906
Common stock issued upon early exercise of options, Shares							918,825
Common stock issued under ESPP	306,000									306,000
Common stock issued under ESPP, Shares							39,894
Issuance of redeemable convertible preferred stock for cash			$ 14,997,000		$ 150,524,000
Issuance of redeemable convertible preferred stock for cash, Shares			15,000,000		29,792,487
Reclassification of tranche liability upon settlement			$ 39,403,000
Issuance of common stock		$ 251,323,000									$ 251,323,000
Issuance of common stock, Shares								16,100,000	640,861
Repurchase of founders' shares, shares									624,845
Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering		$ 260,532,000						$ 1,000			$ 260,531,000
Temporary equity, Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering, Shares				(45,019,945)		(29,792,487)
Temporary equity, Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering				$ (110,008,000)		$ (150,524,000)
Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering, Shares								30,761,676
Stock-based compensation expense	7,871,000									7,871,000
Vesting of early exercised stock options	144,000									144,000
Repurchase of unvested early exercised shares, Shares							138,596
Net loss	(70,760,000)											(70,760,000)
Ending balance at Dec. 31, 2021	384,050,000						$ 1,000			525,400,000		(141,351,000)
Ending balance, Shares at Dec. 31, 2021							58,010,823
Stock-based compensation expense	3,342,000									3,342,000
Unrealized gain (loss) on investments in marketable securities	(309,000)												$ (309,000)
Vesting of early exercised stock options	51,000									51,000
Net loss	(25,835,000)											(25,835,000)
Ending balance at Mar. 31, 2022	361,299,000						$ 1,000			528,793,000		(167,186,000)	(309,000)
Ending balance, Shares at Mar. 31, 2022							58,010,823
Beginning balance at Dec. 31, 2021	384,050,000						$ 1,000			525,400,000		(141,351,000)
Beginning balance, Shares at Dec. 31, 2021							58,010,823
Net loss	(76,453,000)
Ending balance at Sep. 30, 2022	316,453,000						$ 1,000			535,852,000		(217,804,000)	(1,596,000)
Ending balance, Shares at Sep. 30, 2022							58,149,317
Beginning balance at Dec. 31, 2021	384,050,000						$ 1,000			525,400,000		(141,351,000)
Beginning balance, Shares at Dec. 31, 2021							58,010,823
Common stock issued upon exercise of options	20,000									20,000
Common stock issued upon exercise of options, Shares							67,196
Common stock issued under ESPP	656,000									656,000
Common stock issued under ESPP, Shares							333,155
Stock-based compensation expense	13,534,000									13,534,000
Unrealized gain (loss) on investments in marketable securities	(1,048,000)												(1,048,000)
Vesting of early exercised stock options	131,000									131,000
Repurchase of unvested early exercised shares, Shares							189,414
Net loss	(101,052,000)											(101,052,000)
Ending balance at Dec. 31, 2022	296,291,000						$ 1,000			539,741,000		(242,403,000)	(1,048,000)
Ending balance, Shares at Dec. 31, 2022							58,221,760
Beginning balance at Mar. 31, 2022	361,299,000						$ 1,000			528,793,000		(167,186,000)	(309,000)
Beginning balance, Shares at Mar. 31, 2022							58,010,823
Common stock issued upon exercise of options	13,000									13,000
Common stock issued upon exercise of options, Shares							43,945
Common stock issued under ESPP	414,000									414,000
Common stock issued under ESPP, Shares							207,137
Stock-based compensation expense	3,360,000									3,360,000
Unrealized gain (loss) on investments in marketable securities	(724)												(724)
Vesting of early exercised stock options	30,000									30,000
Repurchase of unvested early exercised shares, Shares							(50,713)
Net loss	(25,936,000)											(25,936,000)
Ending balance at Jun. 30, 2022	338,456,000						$ 1,000			532,610,000		(193,122,000)	(1,033,000)
Ending balance, Shares at Jun. 30, 2022							58,211,192
Common stock issued upon exercise of options	5,000									5,000
Common stock issued upon exercise of options, Shares							17,000
Stock-based compensation expense	3,210,000									3,210,000
Unrealized gain (loss) on investments in marketable securities	(563)												(563)
Vesting of early exercised stock options	27,000									27,000
Repurchase of unvested early exercised shares, Shares							(78,875)
Net loss	(24,682,000)											(24,682,000)
Ending balance at Sep. 30, 2022	316,453,000						$ 1,000			535,852,000		(217,804,000)	(1,596,000)
Ending balance, Shares at Sep. 30, 2022							58,149,317
Beginning balance at Dec. 31, 2022	296,291,000						$ 1,000			539,741,000		(242,403,000)	(1,048,000)
Beginning balance, Shares at Dec. 31, 2022							58,221,760
Stock-based compensation expense	3,263,000									3,263,000
Unrealized gain (loss) on investments in marketable securities	579,000												579,000
Vesting of early exercised stock options	25,000									25,000
Repurchase of unvested early exercised shares, Shares							(26,942)
Net loss	(23,934,000)											(23,934,000)
Ending balance at Mar. 31, 2023	276,224,000						$ 1,000			543,029,000		(266,337,000)	(469,000)
Ending balance, Shares at Mar. 31, 2023							58,194,818
Beginning balance at Dec. 31, 2022	296,291,000						$ 1,000			539,741,000		(242,403,000)	(1,048,000)
Beginning balance, Shares at Dec. 31, 2022							58,221,760
Net loss	(101,733,000)
Ending balance at Sep. 30, 2023	204,019,000						$ 1,000			548,249,000		(344,136,000)	(95,000)
Ending balance, Shares at Sep. 30, 2023							57,971,910
Beginning balance at Mar. 31, 2023	276,224,000						$ 1,000			543,029,000		(266,337,000)	(469,000)
Beginning balance, Shares at Mar. 31, 2023							58,194,818
Common stock issued upon exercise of options	18,000									18,000
Common stock issued upon exercise of options, Shares							55,047
Common stock issued under ESPP	157,000									157,000
Common stock issued under ESPP, Shares							65,222
Repurchase of founders' shares, shares							(152,694)
Stock-based compensation expense	2,845,000									2,845,000
Unrealized gain (loss) on investments in marketable securities	198,000												198,000
Vesting of early exercised stock options	18,000									18,000
Repurchase of unvested early exercised shares, Shares							(173,120)
Net loss	(55,314,000)											(55,314,000)
Ending balance at Jun. 30, 2023	224,146,000						$ 1,000			546,067,000		(321,651,000)	(271,000)
Ending balance, Shares at Jun. 30, 2023							57,989,273
Common stock issued upon exercise of options	16,000									16,000
Common stock issued upon exercise of options, Shares							10,367
Stock-based compensation expense	2,161,000									2,161,000
Unrealized gain (loss) on investments in marketable securities	176,000												176,000
Vesting of early exercised stock options	5,000									5,000
Repurchase of unvested early exercised shares, Shares							(27,730)
Net loss	(22,485,000)											(22,485,000)
Ending balance at Sep. 30, 2023	$ 204,019,000						$ 1,000			$ 548,249,000		$ (344,136,000)	$ (95,000)
Ending balance, Shares at Sep. 30, 2023							57,971,910

Condensed Statements of Stock_2

Condensed Statements of Stockholders' Equity (unaudited) (Parenthetical) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Series A Redeemable Convertible Preferred Stock
Stock issuance costs		$ 4	$ 200
Series B Redeemable Convertible Preferred Stock
Stock issuance costs	$ 200	$ 226

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (101,733)	$ (76,453)	$ (101,052)	$ (70,760)
Adjustments to reconcile net loss to net cash used in operating activities:
Net amortization of premiums and discounts on investments in marketable securities	(3,422)	(479)	(1,600)	0
Depreciation and amortization	2,265	1,670	2,352	734
Non-cash lease expense	3,860	4,454	5,994	1,460
Stock-based compensation expense	8,269	9,912	13,534	7,871
Loss on disposal of assets	71	0
Impairment of assets	43,276	0
Change in fair value of the Series A redeemable convertible preferred stock tranche liability			0	10,341
Changes in assets and liabilities:
Assets held for sale	(20)	0
Prepaid expenses and other current assets and other assets	4,884	(2,437)	(3,211)	(3,914)
Accounts payable	1,145	1,275	194	1,825
Accrued compensation	(1,900)	657	1,110	2,223
Accrued research costs	(690)	(280)	87	(1,131)
Accrued expenses and other current liabilities and other liabilities	2,479	399	94	257
Operating lease liabilities	(2,614)	(4,269)	(5,482)	(1,758)
Net cash used in operating activities	(44,130)	(65,551)	(87,980)	(52,852)
Cash flows from investing activities:
Purchases of property and equipment	(10,806)	(5,573)	(6,594)	(5,740)
Proceeds from sales of property and equipment	1,225	0
Purchases of investments in marketable securities	(28,130)	(339,814)	(405,519)	0
Proceeds from maturities of marketable securities	216,975	90,000	170,250	0
Net cash provided by (used in) investing activities	179,264	(255,387)	(241,863)	(5,740)
Cash flows from financing activities:
Proceeds from issuance of common stock upon exercise of vested stock options	34	18	20	28
Proceeds from employee stock purchase plan	157	414	656	306
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs			0	165,521
Proceeds from initial public offering, net of issuance costs			0	251,323
Proceeds from issuance of common stock upon early exercises of stock options			0	289
Repurchase of unvested early exercised shares and founders' shares	(67)	(79)	(79)	0
Net cash provided by financing activities	124	353	597	417,467
Net increase (decrease) in cash, cash equivalents and restricted cash	135,258	(320,585)	(329,246)	358,875
Cash, cash equivalents and restricted cash, at beginning of period	49,446	378,692	378,692	19,817
Cash, cash equivalents and restricted cash, at end of period	184,704	58,107	49,446	378,692
Reconciliation of cash, cash equivalents and restricted cash to statement of financial position:
Cash and cash equivalents	182,988	56,391	47,730	376,976
Restricted cash	1,716	1,716	1,716	1,716
Cash, cash equivalents and restricted cash in statement of financial position	184,704	58,107	49,446	378,692
Supplemental disclosures of non-cash investing and financing information:
Property and equipment purchases in accounts payable and accrued expenses	0	(319)	(36)	(75)
Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering			0	260,532
Settlement of redeemable convertible preferred stock tranche liability			0	(39,403)
Lessor funded lease incentive additions included in property and equipment	7,193	2,616	11,920	0
Repurchase of unvested early exercised shares included in accounts payable			(17)	(42)
Proceeds from issuance of common stock upon exercise of stock options included in accounts receivable				(14)
Proceeds from sale of property and equipment in accounts receivable	449	0
Additions to ROU assets from new operating lease liabilities	31,974	0	0	13,034
Vesting of early exercised stock options	$ 48	$ 108	$ 131	$ 144

Description of Business, Organi

Description of Business, Organization and Liquidity	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business, Organization and Liquidity	1. Description of Business, Organization and Liquidity Organization and Business Graphite Bio, Inc. (the “Company”) has historically been a clinical-stage, next-generation gene editing company. In January 2023, the Company announced a voluntary pause of its Phase 1/2 CEDAR study of nulabeglogene autogedtemcel (“nula-cel”), The Company was incorporated in Ontario, Canada in June 2017 as Longbow Therapeutics Inc., and was reincorporated in the State of Delaware in October 2019. In February 2020, the Company changed its name to Integral Medicines, Inc., and again in August 2020, changed the name to Graphite Bio, Inc. Research and development of the Company’s initial technology ceased at the end of 2018, and the Company did not have any significant operations or any research and development activities in 2019. In March 2020, the Company identified new gene editing technology which the Company sought to further develop, and the Company licensed the related intellectual property rights from The Board of Trustees of the Leland Stanford Junior University (“Stanford”) in December 2020 (Note 6). In February 2023, the Company announced its decision to discontinue the development of nula-cel The Company had previously disclosed its intention to continue research activities associated with its pre-clinical non-genotoxic pre-clinical non-genotoxic nula-cel pre-clinical From its inception in 2017, the Company’s primary activities have been to perform research and development, undertake preclinical studies and enable manufacturing activities in support of its product development efforts, organize and staff the Company, establish its intellectual property portfolio, and raise capital to support and expand such activities. Liquidity Matters The Company has incurred significant operating losses since inception and has primarily relied on private equity and convertible debt financings to fund its operations. As of September 30, 2023, the Company had an accumulated deficit of $344.1 million. The Company expects to continue to incur substantial losses. The Company may never achieve profitability, and unless and until then, the Company will need to continue to raise additional capital. Management expects that the existing cash, cash equivalents, and marketable securities of $234.0 million as of September 30, 2023 will be sufficient to fund the Company’s current operating plan for at least the next 12 months from the date of issuance of these unaudited condensed financial statements. On July 21, 2022, the Company filed a shelf registration statement on Form S-3 SM “at-the-market”	1. Description of Business, Organization and Liquidity Organization and Business Graphite Bio, Inc. (the “Company”) is a clinical-stage, next-generation gene editing company harnessing high-efficiency targeted gene integration to develop a new class of therapies to potentially cure a wide range of serious and life-threatening diseases. The Company is pioneering a precision gene editing approach to achieve one of medicine’s most elusive goals: to precisely “find & replace” any gene in the genome. The Company’s next-generation gene editing platform was designed to allow the Company to precisely correct mutations, replace entire disease-causing genes with normal genes, or insert new genes into predetermined, safe locations. In January 2023, the Company announced a voluntary pause of our Phase 1/2 CEDAR study of nulabeglogene autogedtemcel (nula-cel, Nula-cel nula-cel The Company was incorporated in Ontario, Canada in June 2017 as Longbow Therapeutics Inc., and was reincorporated in the State of Delaware in October 2019. In February 2020, the Company changed its name to Integral Medicines, Inc., and again in August 2020, changed the name to Graphite Bio, Inc. Research and development of the Company’s initial technology ceased at the end of 2018, and the Company did not have any significant operations or any research and development activities in 2019. In March 2020, the Company identified new gene editing technology which the Company sought to further develop, and the Company licensed the related intellectual property rights from The Board of Trustees of the Leland Stanford Junior University (“Stanford”) in December 2020 (Note 6). Reverse Stock Split On June 18, 2021, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse stock split of the Company’s issued and outstanding common stock at a 1 for 2.432 Initial Public Offering On June 24, 2021, the Company’s registration statement on Form S-1 underwriting discounts and commissions of $19.1 million and offering costs of approximately $3.2 million. Prior to the completion of the IPO, all shares of redeemable convertible preferred stock then outstanding were converted into 30,761,676 shares of common stock. Liquidity Matters The accompanying financial statements have been prepared assuming that the Company will continue as a going concern. The Company’s operations have historically been financed through the issuance of common and redeemable convertible preferred stock. The Company has incurred significant operating losses and negative net cash flows from operations since inception. During the year ended December 31, 2022, the Company incurred a net loss of $101.1 million and had negative net cash flows from operating activities of $88 million. The Company had an accumulated deficit of $242.4 million as of December 31, 2022 and will continue to require substantial additional capital for research and development activities. The Company anticipates incurring additional losses until such time, if ever, that it can generate significant sales of its drug candidates currently in development. As of December 31, 2022, the Company had cash and cash equivalents and investments in marketable securities of $283.6 million. On July 21, 2022, the Company filed a shelf registration statement on Form S-3 Offering SM “at-the-market” Management believes that its existing cash, cash equivalents and investments in marketable securities are sufficient to continue operating activities for at least 12 months following the issuance date of these financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Unaudited Interim Condensed Financial Statements The interim condensed balance sheet as of September 30, 2023 and the condensed statements of operations and comprehensive loss and stockholders’ equity for the three and nine months ended September 30, 2023 and 2022 and the condensed statements of cash flows for the nine months ended September 30, 2023 and 2022 are unaudited. The unaudited interim condensed financial statements have been prepared on the same basis as the annual financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair statement of the Company’s financial position as of September 30, 2023 and its results of operations for the three and nine months ended September 30, 2023 and cash flows for the nine months ended September 30, 2023 and 2022. The financial data and the other financial information disclosed in these notes to the financial statements related to the three and nine month periods are also unaudited. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results to be expected for the year ending December 31, 2023 or for any other future annual or interim period. The condensed balance sheet as of December 31, 2022 included herein was derived from the audited financial statements as of that date. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from these interim financial statements. These condensed financial statements should be read in conjunction with the Company’s audited financial statements and the related notes thereto for the year ended December 31, 2022, which are included in the Company’s Annual Report on Form 10-K Significant Accounting Policies The significant accounting policies used in preparation of these condensed financial statements for the three and nine months ended September 30, 2023 are consistent with those discussed in Note 2 to the condensed financial statements included in the Company’s Annual Report on Form 10-K Use of Estimates The preparation of condensed financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed financial statements, and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates estimates and assumptions, including but not limited to those related to the fair value of the marketable securities, stock-based compensation expense, accruals for research and development costs, lease assets and liabilities, the valuation of deferred tax assets, valuation of uncertain income tax positions, and impairment of long-lived assets. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other Principles of Consolidation The Company assesses entities for consolidation based on the specific facts and circumstances surrounding that entity. The Company first considers whether an entity is considered a variable interest entity (“VIE”) and therefore whether to apply the consolidation guidance under the VIE model. Entities that do not qualify as VIEs are assessed for consolidation as voting interest entities (“VOE”) under the voting interest model. An entity is considered to be a VIE if any of the following conditions exist: (i) the equity investment at risk is not sufficient to finance the activities of the entity without additional subordinated financial support, (ii) as a group, the holders of the equity investment at risk lack the power to direct the activities that most significantly impact the entity’s economic performance or the obligation to absorb the expected losses or right to receive the expected residual returns, and (iii) the voting rights of some holders of the equity investment at risk are disproportionate to their obligation to absorb losses or right to receive returns, and substantially all of the activities are conducted on behalf of the holder of equity investment at risk with disproportionately few voting rights. The Company consolidates all VIEs in which it is the primary beneficiary. An entity is determined to be the primary beneficiary if it holds a controlling financial interest in a VIE. The consolidation guidance requires an analysis to determine (i) whether an entity in which the Company holds a variable interest is a VIE and (ii) whether the Company’s involvement, through holding interest directly or indirectly in the entity or contractually through other variable interests, would give it a controlling financial interest. Performance of that analysis requires judgment. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with a maturity of three months or less at the date of purchase to be cash equivalents. As of September 30, 2023 and December 31, 2022, cash and cash equivalents consisted of cash, money market funds, and commercial paper. Restricted Cash Restricted cash of $1.7 million as of September 30, 2023 and December 31, 2022 represented security deposits in the form of letters of credit issued in connection with the lease of 233 E. Grand Ave, which was to be the company’s headquarters. A lease amendment was executed in October 2023, whereby the Company will have no further rent obligations to the landlord following the effective date, and the landlord will return the Company’s letter of credit within 60 days following the amendment’s effective date (Note 14). The letter of credit will be returned to the Company per the lease amendment. Marketable Securities The Company’s marketable securities are accounted for as available-for-sale The Company reviews its investment portfolio to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee and the Company’s intent and ability Operating Leases The Company accounts for its operating leases by recording right-of-use Right-of-use Recently Issued and Adopted Accounting Pronouncements The Company is a smaller reporting company and an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Under the JOBS Act, emerging growth companies can delay the adoption of new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. Thus, the Company has elected to use the extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that (i) the Company is no longer an emerging growth company or (ii) the Company affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. The Company may early adopt certain accounting standards, as the JOBS Act does not preclude an emerging growth company from adopting a new or revised accounting standard earlier than the time that such standard applies to private companies to the extent early adoption is permitted.	2. Summary of Significant Accounting Policies Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates estimates and assumptions, including but not limited to those related to the fair value of the marketable securities, the fair value of redeemable convertible preferred stock and common stock, stock-based compensation expense, accruals for research and development costs, lease assets and liabilities, the valuation of deferred tax assets, and uncertain income tax positions. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates. Concentration of Credit Risk Cash and cash equivalents are financial instruments that potentially subject the Company to concentrations of credit risk. Substantially all of the Company’s cash and cash equivalents are deposited in accounts with major financial institution and amounts may exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of the depository institution in which the cash and cash equivalents are held. The Company has not experienced any losses on deposits of cash and cash equivalents. Risks and Uncertainties The Company is subject to certain risks and uncertainties, including, but not limited to, changes in any of the following areas that the Company believes could have a material adverse effect on the future financial position or results of operations: the timing of, and the Company’s ability to advance its current and future product candidates into and through clinical development; costs and timelines associated with the manufacture of clinical supplies of the Company’s product candidates; regulatory approval and market acceptance of, and reimbursement for its product candidates; performance of third-party CROs and CMOs; competition from pharmaceutical companies with greater financial resources or expertise; protection of the intellectual property; litigation or claims against the Company based on intellectual property or other factors; and its ability to attract and retain employees necessary to support its growth. Disruption from CROs’, CMOs’ or suppliers’ operations would likely have a negative impact on the Company’s business, financial position and results of operations. Segment and Geographical Information The Company operates and manages its business as one reportable and operating segment. The chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. All of the Company’s long-lived assets are based in the United States. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with a maturity of three months or less at the date of purchase to be cash equivalents. As of December 31, 2022 and 2021, cash and cash equivalents consisted of cash, money market funds, and commercial paper. Restricted Cash Restricted cash of $1.7 million as of December 31, 2022 and 2021 represented security deposits in the form of letters of credit issued in connection with the leases of the Company’s headquarters (Notes 6 and 8). Marketable Securities The Company’s marketable securities are accounted for as available-for-sale The Company reviews its investment portfolio to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The carrying amounts of financial instruments, including restricted cash, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued expenses, and other liabilities, approximate fair value due to their short-term maturities Property and Equipment, Net Property and equipment are recorded at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three Leases Effective January 1, 2021, the Company adopted ASC Topic 842, Leases On January 27, 2021, the Company entered into a lease agreement for office and lab space in South San Francisco, CA that included two office suites. The lease terms for the office suites commenced in July and August 2021, respectively. Upon commencement of the leases, the Company recognized operating lease right-of-use On August 30, 2021, the Company entered into a service agreement with The Laboratory for Cell and Gene Medicine (“LCGM”) that included an embedded operating lease as the manufacturing suite in LCGM’s facility is designated for the Company’s exclusive use though April 30, 2023. Upon commencement of the agreement, the Company recognized operating lease right-of-use On November 10, 2021, the Company entered into a sublease agreement for office space in Brisbane, CA. The lease terms for the sublease commenced in December 2021. Upon commencement of the lease, the Company recognized operating lease right-of-use On November 17, 2021, the Company entered into a service agreement with Explora BioLabs, Inc (“Explora”) that included an embedded operating lease as the vivarium space is designated for the Company’s exclusive use through November 2023. Upon commencement of the lease, the Company recognized operating lease right-of-use The Company determines the initial classification and measurement of its right-of-use payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its incremental borrowing rate. The incremental borrowing rate is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment. Fixed lease expense for operating leases is recognized on a straight-line basis, unless the right-of-use For operating leases for which the right-of-use right-of-use For all leases, rent payments that are based on a fixed index or rate at the lease commencement date are included in the measurement of lease assets and lease liabilities at the lease commencement date. The Company has elected the practical expedient to not separate lease and non-lease non-lease Asset Acquisitions The Company measures and recognizes asset acquisitions that are not deemed to be business combinations based on the cost to acquire the assets, which includes transaction costs. Goodwill is not recognized in asset acquisitions. In an asset acquisition, the cost allocated to acquire in-process Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparing the carrying amount to the future undiscounted net cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured as the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows generated by the assets. There have been no such impairments of long-lived assets in the years ended December 31, 2022 and 2021. Research and Development Expenses Research and development costs are expensed as incurred. Research and development costs include salaries, stock-based compensation, and benefits for employees performing research and development activities, an allocation of facility and overhead expenses, expenses incurred under agreements with consultants, CMOs, CROs and investigative sites that conduct preclinical studies, other supplies and costs associated with product development efforts, preclinical activities, and regulatory operations. Accrued Research and Development Expenses The Company has entered into various agreements with outsourced vendors, CROs and CMOs. Research and development accruals are estimated based on the level of services performed, progress of the studies, including the phase or completion of events, and contracted costs. The estimated costs of research and development services provided, but not yet invoiced, are included in accrued research costs on the balance sheets. If the actual timing of the performance of services or the level of effort varies from the original estimates, the Company will adjust the accrual accordingly. Payments made under these arrangements in advance of the performance of the related services are recorded as prepaid expenses and other current assets until the services are rendered. To date, there have been no material differences between estimates of such expenses and the amounts actually Tax Credit Receivable The Company is eligible for federal and California research and development credits for its research and development activities performed within the United States and California, respectively. The credits are, generally, available to offset federal and California income tax liabilities as applicable. The Company has applied $0.1 million of federal research and development credits to offset its federal payroll tax expenses as of the year ended December 31, 2022 due to its small business status. The Company is electing to utilize $0.3 million of current year R&D credit generated against the employer portion of the payroll tax. Income Taxes The Company accounts for income taxes using the asset and liability method. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. In evaluating the ability to recover deferred income tax assets, the Company considers all available positive and negative evidence, including operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction-by-jurisdiction Tax benefits related to uncertain tax positions are recognized when it is more likely than not that a tax position will be sustained during an audit. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax. Stock-Based Compensation Expense The Company’s stock-based equity awards include restricted stock awards and stock options that are granted to employees and consultants that are accounted at fair value on the award grant date. Stock-based compensation expense is recognized over the awards’ vesting period on a straight-line basis and recorded as either research and development or general and administrative expenses in the statements of operations and comprehensive loss based on the function to which the related services are provided. Forfeitures are accounted for as they occur. As there was no public market for the Company’s common stock prior to the initial public offering of its common stock in June 2021, the estimated fair value of common stock was determined by the Company’s board of directors as of the date of each option grant, with input from management, considering third-party valuations of its common stock, as well as the Company’s board of directors’ assessment of additional objective and subjective factors that it believed were relevant, and which may have changed from the date of the most recent third-party valuation through the date of the grant. These third-party valuations were performed in accordance with the guidance outlined in the American Institute of Certified Public Accountants’ Accounting and Valuation Guide, Valuation of Privately Held Company Equity Securities Issued as Compensation. Following the closing of the initial public offering, the fair value of the Company’s common stock is determined based on the quoted market price of common stock. The Company also lacks company-specific historical and implied volatility information for its stock. The Company estimates its expected stock price volatility and expected term based on the historical volatility and expected term of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. There is no expected dividend yield since the Company Employee Stock Purchase Plan The Company recognizes stock-based expense related to shares issued pursuant to its Employee Stock Purchase Plan on a straight-line basis over the offering period, which is typically 6 months. The first offering period commenced on June 25, 2021 and ended on November 30, 2021. The second, third, and fourth offering periods commenced on December 1, 2021, June 1, 2022, and December 1, 2022, respectively. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a 15 percent discount on the lower price of either (i) the offering period begin date or (ii) the purchase date. The Company estimates the fair value of shares to be issued under the ESPP using the Black-Scholes option-pricing model. Comprehensive Loss Comprehensive loss is defined as the change in equity of a business during a period from transactions and other events and circumstances from non-owner Net Loss Per Share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common stock outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, redeemable convertible preferred stock, common stock subject to repurchase, restricted common shares issued, and stock options are considered to be potentially dilutive securities. Basic and diluted net loss attributable to common stockholders per share is presented in conformity with the two-class Adopted and Recent Accounting Pronouncements The Company is a smaller reporting company and an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Under the JOBS Act, emerging growth companies can delay the adoption of new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. Thus, the Company has elected to use the extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that (i) the Company is no longer an emerging growth company or (ii) the Company affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. However as described below, the Company early adopted certain accounting standards, as the JOBS Act does not preclude an emerging growth company from adopting a new or revised accounting standard earlier than the time that such standard applies to private companies to the extent early adoption is permitted Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Credit Losses available-for-sale available-for-sale In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) 815-40): 2020-06) if-converted

Fair Value Measurements

Fair Value Measurements	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value of Financial Assets Assets and liabilities recorded at fair value on a recurring basis in the condensed balance sheets, as well as assets and liabilities measured at fair value on a non-recurring The accounting guidance also establishes a three-level valuation hierarchy that prioritizes the inputs to valuation techniques used to measure fair value based upon whether such inputs are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect market assumptions made by the reporting entity. The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows: Level 1 — Level 2 — inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level 3 — Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. An assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. Changes in the ability to observe valuation inputs may result in a reclassification of levels of certain securities within the fair value hierarchy. The Company recognizes transfers into and out of levels within the fair value hierarchy in the period in which the actual event or change in circumstances that caused the transfer occurs. As of September 30, 2023 and December 31, 2022, Level 1 securities consist of U.S. Treasury and money market funds, for which the carrying amounts are based on the quoted market prices in active markets. As of September 30, 2023 and December 31, 2022, Level 2 securities consist of highly rated commercial paper, U.S. agency securities, and asset-backed securities, for which fair value is determined through the use of models or other valuation methodologies. During the periods presented, the Company did not have any Level 3 securities. The following tables set forth the financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy as of September 30, 2023 and December 31, 2022 (in thousands): September 30, 2023 Total Fair Value Level 1 Level 2 Level 3 Cash equivalents: Money market funds (1) $ 182,988 $ 182,988 $ — $ — Commercial paper (1) — — — — Total cash equivalents 182,988 182,988 — — Marketable securities: U.S. treasuries(2) 4,456 4,456 — — Commercial paper(2) 7,937 — 7,937 — U.S. agency securities(2) 36,626 — 36,626 — Asset-backed securities(2) 1,979 — 1,979 — Total marketable securities 50,998 4,456 46,542 — Total cash equivalents and marketable securities $ 233,986 $ 187,444 $ 46,542 $ — December 31, 2022 Total Fair Value Level 1 Level 2 Level 3 Cash equivalents: Money market funds (1) $ 45,739 $ 45,739 $ — $ — Commercial paper (1) 1,991 — 1,991 — Total cash equivalents 47,730 45,739 1,991 — Marketable securities: U.S. treasuries(2) 65,391 65,391 — — Commercial paper(2) 115,061 — 115,061 — U.S. agency securities(2) 53,455 — 53,455 — Asset-backed securities(2) 1,914 — 1,914 — Total marketable securities 235,821 65,391 170,430 — Total cash equivalents and marketable securities $ 283,551 $ 111,130 $ 172,421 $ — (1) Included within cash and cash equivalents on the condensed balance sheets. (2) non-current	3. Fair Value Measurements Assets and liabilities recorded at fair value on a recurring basis in the balance sheets, as well as assets and liabilities measured at fair value on a non-recurring The accounting guidance also establishes a three-level valuation hierarchy that prioritizes the inputs to valuation techniques used to measure fair value based upon whether such inputs are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect market assumptions made by the reporting entity. The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows: Level 1 Level 2 Level 3 — Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. An assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. Changes in the ability to observe valuation inputs may result in a reclassification of levels of certain securities within the fair value hierarchy. The Company recognizes transfers into and out of levels within the fair value hierarchy in the period in which the actual event or change in circumstances that caused the transfer occurs. As of December 31, 2022 and 2021, Level 1 securities consist of U.S. Treasury and money market funds, for which the carrying amounts are based on the quoted market prices in active markets As of December 31, 2022, Level 2 securities consist of highly rated commercial paper, U.S. agency securities, and asset-backed securities, for which fair value is determined through the use of models or other valuation methodologies. As of December 31, 2022, the Company had an immaterial amount of unrealized gains on its Level 2 securities. During the periods presented, the Company did not have any Level 3 securities. The following tables set forth the financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy as of December 31, 2022 and 2021 (in thousands): December 31, 2022 Total Fair Value Level 1 Level 2 Level 3 Cash equivalents: Money market funds (1) $ 45,739 $ 45,739 $ — $ — Commercial paper (1) 1,991 — 1,991 — Total cash equivalents 47,730 45,739 1,991 — Marketable securities: U.S. treasuries 65,391 65,391 — — Commercial paper 115,061 — 115,061 — U.S. agency securities(2) 53,455 — 53,455 — Asset-backed securities(2) 1,914 — 1,914 — Total marketable securities 235,821 65,391 170,430 — Total cash equivalents and marketable securities $ 283,551 $ 111,130 $ 172,421 $ — December 31, 2021 Total Fair Value Level 1 Level 2 Level 3 Money market funds (1) $ 376,976 $ 376,976 $ — $ — (1) Included within cash and cash equivalents on the balance sheet.(2)Included within investments in marketable securities, current and investments in marketable securities, non-current

Marketable Securities

Marketable Securities	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	4. Marketable Securities All marketable securities were considered available-for-sale marketable September 30, 2023 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Available-for-sale U.S. treasuries $ 4,469 $ — $ (13 ) $ 4,456 Commercial paper 7,942 — (5 ) 7,937 U.S. agency securities 36,700 — (74 ) 36,626 Asset-backed securities 1,982 — (3 ) 1,979 Total available-for-sale $ 51,093 $ — $ (95 ) $ 50,998 December 31, 2022 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Available-for-sale U.S. treasuries $ 65,807 $ — $ (416 ) $ 65,391 Commercial paper 115,381 13 (333 ) 115,061 U.S. agency securities 53,767 15 (327 ) 53,455 Asset-backed securities 1,914 — — 1,914 Total available-for-sale $ 236,869 $ 28 $ (1,076 ) $ 235,821 The amortized cost of available-for-sale the intent and ability to hold such securities until recovery and has determined that there has been no material change to its credit risk. As a result, the Company determined it did not hold any investments with a credit loss at September 30, 2023. There were no realized gains or losses recognized on the sale or maturity of available-for-sale	4. Marketable Securities All marketable securities were considered available-for-sale December 31, 2022 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Available-for-sale U.S. treasuries $ 65,807 $ — $ (416 ) $ 65,391 Commercial paper 115,381 13 (333 ) 115,061 U.S. agency securities 53,767 15 (327 ) 53,455 Asset-backed securities 1,914 — — 1,914 Total available-for-sale $ 236,869 $ 28 $ (1,076 ) $ 235,821 The amortized cost of available-for-sale There were no realized gains or losses recognized on the sale or maturity of available-for-sale The Company did not hold any marketable securities as of December 31, 2021.

Balance Sheet Components

Balance Sheet Components	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Balance Sheet Components	5. Balance Sheet Components Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets as of September 30, 2023 and December 31, 2022 consisted of the following (in thousands): September 30, 2023 December 31, 2022 Advances to suppliers $ — $ 2,486 Prepaid insurance 1,227 1,343 Other prepaid expenses 3,550 3,307 Total prepaid expenses and other current assets $ 4,777 $ 7,136 Property and Equipment, Net Property and equipment, net as of September 30, 2023 and December 31, 2022 consisted of the following (in thousands): September 30, 2023 December 31, 2022 Furniture and fixtures $ 1,264 $ 321 Computers and network equipment — 251 Lab equipment — 12,521 Leasehold improvements 12,108 304 Construction-in-progress — 12,440 Total property and equipment 13,372 25,837 Less: accumulated depreciation (838 ) (3,207 ) Total property and equipment, net 12,534 22,630 Depreciation expense for the three and nine months ended September 30, 2023 was $0.8 million and $2.3 million, respectively. Depreciation expense for the three and nine months ended September 30, 2022 was $0.7 million and $1.7 million, respectively. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities as of September 30, 2023 and December 31, 2022 consisted of the following (in thousands): September 30, 2023 December 31, 2022 Professional fees $ 178 $ 367 Early exercise liability 34 150 Other accrued expenses 221 1,354 Accrued employee termination benefits 2,983 — Total accrued expenses and other current liabilities $ 3,416 $ 1,871	5. Balance Sheet Components Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets as of December 31, 2022 and 2021 consisted of the following (in thousands): December 31, 2022 December 31, 2021 Advances to suppliers $ 2,486 $ 1,834 Prepaid insurance 1,343 1,543 Other prepaid expenses 3,307 1,383 Total prepaid expenses and other current assets $ 7,136 $ 4,760 Property and Equipment, Net Property and equipment, net as of December 31, 2022 and 2021 consisted of the following (in thousands): December 31, 2022 December 31, 2021 Furniture and fixtures $ 321 $ 3 Computers and network equipment 251 108 Lab equipment 12,521 6,680 Leasehold improvements 304 94 Construction-in-progress 12,440 477 Total property and equipment 25,837 7,362 Less: accumulated depreciation (3,207 ) (855 ) Total property and equipment, net $ 22,630 $ 6,507 Depreciation expense for the years ended December 31, 2022 and 2021 was $2.4 and $0.7 million, respectively. Accrued Expenses Accrued expenses as of December 31, 2022 and 2021 consisted of the following (in thousands): December 31, 2022 December 31, 2021 Professional fees $ 367 $ 186 Early exercise liability 150 337 Other accrued expenses 1,354 363 Total accrued expenses and other current liabilities $ 1,871 $ 886

Significant Agreements

Significant Agreements	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Significant Agreements [Abstract]
Significant Agreements	6. Significant Agreements Stanford Exclusive License Agreement and Option Agreement In December 2020, the Company entered into an exclusive license agreement (the “License Agreement”) with The Board of Trustees of the Leland Stanford Junior University (Stanford), pursuant to which Stanford granted the Company a worldwide license to specified technology and patent rights to develop, manufacture and commercialize human prophylactic and therapeutic products. Other than with respect to specified, broadly applicable assays and procedures and subject to retained rights by Stanford, the license is exclusive with respect to human prophylactic and therapeutic products for the treatment of SCD, XSCID and beta thalassemia. The license is non-exclusive Pursuant to the License Agreement, the Company paid an upfront license fee of $50.0 thousand and as additional consideration for the license, the Company agreed to issue to Stanford approximately 0.6 million shares of common stock. As of December 31, 2020, the Company recorded its obligations to issue Stanford shares of common stock at an estimated fair value of $2.8 million to additional paid in capital. The shares of common stock were expected to be issued when Stanford provided the inventors’ names for allocation of the shares. Stanford also received an option to purchase up to 10% of newly issued shares in the future private financings at the price paid by other participating investors. During the year ended December 31, 2021, the Company entered into an amendment to the License Agreement, pursuant to which it extended the time when the shares would be issued to May 7, 2021. On May 7, 2021, the Company issued an aggregate of 640,861 shares of the Company’s common stock to Stanford and certain individuals designated by Stanford in consideration for rights granted to the Company under the Company’s exclusive license agreement. On June 18, 2021, the Company exercised its right to repurchase an aggregate of 624,845 shares from each founder and investor under the Stanford Adjustment Repurchase Right as described below. The acquisition of the exclusive license, including patent rights and know-how, In connection with the License Agreement, the Company reimbursed Stanford $0.2 million for previously incurred patent costs, which were recorded in general and administrative expenses for the year ended December 31, 2020 and in addition, is obligated to reimburse future patent costs. The Company is also obligated to pay annual maintenance fees as follows: $5.0 thousand in the first year, $10.0 thousand in each year 2 and 3, $25.0 thousand in each year 3 through 6, $50.0 thousand each subsequent year until first commercial sale and $200.0 thousand each subsequent year after the first commercial sale. No fees were recorded during the three and nine months ended September 30, 2023. The Company did not record any patent fees during the three and nine months ended September 30, 2023. The Company is obligated to make future development and regulatory milestone payments in total of up to $5.3 million, sales based milestone payments of up to $7.5 million and royalties on future sales at percentage rates ranging in the low single digits. In addition, if the Company receives any sublicense income, it is required to share it with Stanford as a certain percentage defined for each milestone in the License Agreement. The Company will record the maintenance fees, when payable, and will record milestones when contingencies are resolved and milestones are due. No milestones were achieved and recorded as of September 30, 2023. In January 2021, the Company entered into an option agreement (the “First Option Agreement”) with Stanford, pursuant to which Stanford granted the Company the right to obtain a license to specified patent rights relating to human prophylactic and therapeutic products. The Company may exercise the option in whole or in part to obtain a license under one or more of the optioned patent rights. Subject to the Company’s exercise of the option under the First Option Agreement and its execution of an amendment to the License Agreement that incorporates the optioned patent rights and any optioned technology, the Company has agreed to issue to Stanford 132,137 shares of its common stock and pay a license execution fee of $10.0 thousand. The term of the First Option Agreement expires 18 months after its effective date, subject to the Company’s right to extend such expiration date by up to an additional one year upon notice to Stanford and by another additional one year upon the reasonable agreement of Stanford. The First Option Agreement will terminate if the License Agreement terminates. On June 23, 2022, the Company exercised its right to extend the term of the First Option Agreement for an additional year. On June 6, 2023, the Company and Stanford agreed to extend the term of the First Option Agreement for another additional year. As of September 30, 2023, the Company had not exercised the option under the First Option Agreement and no fees have been paid for the First Option Agreement. In April 2021, the Company entered into an option agreement (the “Second Option Agreement”) with Stanford to negotiate the license for additional technologies from Stanford. Pursuant to the Second Option Agreement, the Company agreed to pay Stanford option fees in an aggregate amount of $30.0 thousand over the term of the option. On April 13, 2022, the Company entered into an amendment to the Second Option Agreement which extended the term for an additional year. On March 8, 2023, the Company terminated the Second Option Agreement without exercising the option to negotiate a license for additional technologies from Stanford. No maintenance fees were paid during the three and nine months ended September 30, 2023. LCGM Service Agreement On August 30, 2021, the Company entered into a Master Manufacturing and Service Agreement with the Laboratory for Cell & Gene Medicine at Stanford (“LCGM MSA”). Pursuant to the LCGM MSA, LCGM will conduct clinical manufacturing, release testing, and product release for nula-cel IDT License Agreement On June 7, 2021, the Company entered into a License Agreement (“IDT License Agreement”) with Integrated DNA Technologies, Inc. (“IDT”). Pursuant to the IDT License Agreement, IDT granted the Company and its affiliates a worldwide, non-exclusive, In consideration of the licenses and rights granted to the Company under the IDT License Agreement, the Company agreed to pay to IDT an upfront payment in the amount of $3.0 million and up to $5.3 million (or $8.8 million if the Company elects to expand the Field as described above to include both the beta thalassemia and lysosomal storage disorders fields) in total regulatory milestone payments. Each regulatory milestone payment is payable once on an indication-by-indication The IDT License Agreement remains in effect on a country-by-country product-by-product During the three and nine months ended September 30, 2023, the Company has not recognized any research and development expense in connection with the IDT License Agreement. There are no milestones probable as of September 30, 2023 and 2022; therefore, no milestone payments have been recognized in the three and nine months ended September 30, 2023 and 2022. As of September 30, 2023, the Company does not expect to incur any additional expenses associated with the IDT License Agreement. Sale of Non-Genotoxic On August 1, 2023, the Company entered into an asset purchase agreement (the “APA”) with a third party pursuant to which the Company sold to the counterparty, concurrently with the execution of the APA, certain assets related to the Company’s non-genotoxic The disposal of certain assets sold pursuant to the APA was accounted for as a deconsolidation of a subsidiary or group of assets in accordance with ASC 810. During the three and nine months ended September 30, 2023, the Company recognized a loss on disposal of $0.1 million, which was recorded in other income. The Company will record amounts related to the contingent milestone payments, royalties, and potential transaction fees when contingencies are resolved and amounts are due in accordance with ASC 450. No contingencies were resolved and recorded as of September 30, 2023. License and Option to Acquire Nula-Cel Assets On August 4, 2023, the Company entered into an LOA with a third party pursuant to which the Company exclusively licensed to the counterparty, and granted the counterparty, an option to acquire certain intellectual property and materials related to the Company’s nula-cel pre-clinical The Company assessed the entity under the VIE model to assess whether to apply the consolidation guidance in accordance with ASC 810. The Company holds variable interests in the entity, and the entity was determined to be a VIE which is not consolidated as it is determined the Company lacks the power to direct the activities that most significantly impact the entity’s economic performance. The condensed balance sheets do not contain assets and liabilities related to the Company’s interest in the non-consolidated The 20% equity interest in the counterparty had minimal value upon execution of the LOA and the Company did not record any amount related to the equity interest as of September 30, 2023 or for the three and nine months ended September 30, 2023. As of September 30, 2023, the counterparty has not achieved the financial milestone and does not have the right to exercise the option.	6. Significant Agreements Stanford Exclusive License Agreement In December 2020, the Company entered into an exclusive license agreement (the “License Agreement”), with The Board of Trustees of the Leland Stanford Junior University (Stanford), pursuant to which Stanford granted us a worldwide license to specified technology and patent rights to develop, manufacture and commercialize human prophylactic and therapeutic products. Other than with respect to specified, broadly applicable assays and procedures and subject to retained rights by Stanford, the license is exclusive with respect to human prophylactic and therapeutic products for the treatment of SCD, XSCID and beta thalassemia. The license is non-exclusive Pursuant to the License Agreement, the Company paid an upfront license fee of $50.0 thousand, and as additional consideration for the license, the Company agreed to issue to Stanford approximately 640,861 shares of our common stock. As of December 31, 2020, the Company recorded its obligations to issue Stanford shares of common stock at an estimated fair value of $2.8 million to additional paid in capital. The common shares are expected to be issued when Stanford provides the inventors’ names for allocation of the shares. Stanford also had an option to buy up to 10% of newly issued shares in the future private financings at the price paid by other participating investors. During the year ended December 31, 2021, the Company entered into amendments to the License Agreement, pursuant to which it extended the time when the shares will be issued to May 7, 2021. On May 7, 2021, the Company issued an aggregate of 640,861 shares of the Company’s common stock to Stanford and certain individuals designated by Stanford in consideration for rights granted to the Company under the Company’s exclusive license agreement. On June 18, 2021, the Company exercised its right to repurchase an aggregate of 624,845 shares from each founder and investor under the Stanford Adjustment Repurchase Right as described below. The acquisition of the exclusive license, including patent rights and know-how, In connection with the License Agreement, the Company reimbursed Stanford $0.2 million for previously incurred patent costs, which were recorded in general and administrative expenses for the year ended December 31, 2020 and, in addition, is obligated to reimburse future patent costs. During the year ended December 31, 2021, the reimbursements of patent costs to Stanford were minimal. During the year ended December 31, 2021, the Company has recognized a minimal amount in research and development expense in connection with the License Agreement The Company is also obligated to pay annual maintenance fees as follows: $5.0 thousand in the first year, $10.0 thousand in each year 2 and 3, $25.0 thousand in each year 3 through 6, $50.0 thousand each subsequent year until first commercial sale and $200.0 thousand each subsequent year after the first commercial sale. The Company is also obligated to make future development and regulatory milestone payments in total of up to $5.3 million, sales-based milestone payments of up to $7.5 million and royalties on future sales at percentage rates ranging in the low single digits. In addition, if the Company receives any sublicense income, it is required to share it with Stanford as a certain percentage defined for each milestone in the License Agreement. The Company will record the maintenance fees, when payable, and will record milestones when contingencies are resolved, and milestones are due. No milestones were achieved and recorded as of December 31, 2022 and 2021. The term of the License Agreement expires on the later of (a) the expiration of the last patent or abandonment of the last patent application within the license patent rights or (b) the expiration of all royalty terms with respect to Licensed Products. The Stanford License terminates on a product by product and country by country basis on the latest to occur of (i) expiration of the last valid claim of a licensed patent that covers the sale or manufacture of the applicable licensed product in such country, (ii) expiration of any period of regulatory exclusivity granted with respect to such licensed product in such country or (iii) ten years after the first commercial sale of such licensed product in a country Stanford also has a right to terminate the agreement if milestones plan is rejected by Stanford as specified in the License Agreement. In January 2021, the Company entered into an option agreement (the “First Option Agreement”), with Stanford, pursuant to which Stanford granted the Company the right to obtain a license to specified patent rights relating to human prophylactic and therapeutic products. The Company may exercise the option in whole or in part to obtain a license under one or more of the optioned patent rights. Subject to the Company’s exercise of the option under the First Option Agreement and its execution of an amendment to the License Agreement that incorporates the optioned patent rights and any optioned technology, the Company has agreed to issue to Stanford 132,137 shares of its common stock and pay a license execution fee of $10.0 thousand. The term of the First Option Agreement expires 18 months after its effective date, subject to the Company’s right to extend such expiration date by up to an additional one year upon notice to Stanford and by another additional one year upon the reasonable agreement of Stanford. The First Option Agreement will terminate if the License Agreement terminates. On June 23, 2022, the Company exercised its right to extend the term of the First Option Agreement for an additional year. As of December 31, 2022, the Company had not exercised the option under the First Option Agreement and no fees have been paid for the First Option Agreement. In April 2021, the Company entered into an option agreement (the “Second Option Agreement”) with Stanford to negotiate the license for additional technologies from Stanford. Pursuant to the Second Option Agreement, the Company agreed to pay Stanford option fees in an aggregate amount of $30.0 thousand over the term of the option. On April 13, 2022, the Company entered into an amendment to the Second Option Agreement which extended the term for an additional year and the maintenance fee of $10.0 thousand for the extension was paid in the year ended December 31, 2022. As of December 31, 2022, the Company had not exercised the option under the Second Option Agreement. LCGM Service Agreement On August 30, 2021, the Company entered into a Master Manufacturing and Service Agreement with the Laboratory for Cell & Gene Medicine at Stanford (“LCGM MSA”). Pursuant to the LCGM MSA, LCGM will conduct clinical manufacturing, release testing, and product release for nula-cel IDT License Agreement On June 7, 2021, the Company entered into a License Agreement (“IDT License Agreement”) with Integrated DNA Technologies, Inc. (“IDT”). Pursuant to the IDT License Agreement, IDT granted the Company and its affiliates a worldwide, non-exclusive, In consideration of the licenses and rights granted to the Company under the IDT License Agreement, the Company agreed to pay to IDT an upfront payment in the amount of $3.0 million and up to $5.3 million (or $8.8 million if the Company elects to expand the Field as described above to include both the beta thalassemia and lysosomal storage disorders fields) in total regulatory milestone payments. Each regulatory milestone payment is payable once on an indication-by-indication The IDT License Agreement remains in effect on a country-by-country product-by-product During the years ended December 31, 2022 and 2021, the Company has recognized $0.0 and $3.0 million, respectively, in research and development expense in connection with the IDT License Agreement. There are no milestones probable as of December 31, 2022 and 2021; therefore, no milestone payments have been recognized in the years ended December 31, 2022 and 2021. Master Development and Manufacturing Services Agreement (for cell therapy services) In November 2022, we entered into a master development and manufacturing services agreement, with the WuXi Agreement, pursuant to which we may engage WuXi, at our discretion, to provide services under separate work orders for cell therapy services. To date, pursuant to the WuXi Agreement, we have entered into three work orders for cell therapy services. Following our decision to discontinue the development of nula-cel, Bayside Lease On December 16, 2021, the Company entered into a lease agreement with Bayside Area Development, LLC (“Bayside”) for 85,165 square feet of office and laboratory space at 233 E Grand Avenue, South San Francisco (the “Bayside Lease Agreement”). Pursuant to the Bayside Lease Agreement, the Company is expected to commence the lease on or before September 15, 2023 with a total term of 120 months. Future minimum lease payments under the Bayside Lease Agreement total $81.0 million, which does not include lease payments related to the Company’s one-time As of December 31, 2022 and 2021, the Company posted a security deposit in the amount of $1.6 million in the form of a letter of credit in connection with the Bayside Lease Agreement, which is classified as restricted cash, non-current construction-in-progress As of December 31, 2022 and 2021, there was no right-of-use

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Research and Development Agreements The Company enters into contracts in the normal course of business with CROs for clinical trials, with CMOs or other vendors for preclinical and clinical studies, supplies and other services and products for operating purposes. These contracts generally provide for termination on notice or may have a potential termination fee if a purchase order is cancelled within a specified time. As of September 30, 2023 and December 31, 2022, there were no amounts accrued related to termination and cancellation charges and the Company does not expect to incur any additional expenses associated with termination and cancellation charges. License Agreements The Company enters into license agreements (Note 6), pursuant to which the Company may acquire or license other patents, patent applications or know-how Legal Contingencies From time to time, the Company may become involved in legal proceedings arising from the ordinary course of business. The Company records a liability for such matters when it is probable that future losses will be incurred and that such losses can be reasonably estimated. Significant judgment by the Company is required to determine both probability and the estimated amount. Management is currently not aware of any legal matters that could have a material adverse effect on its financial position, results of operations or cash flows. Guarantees and Indemnifications In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnification. Its exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To the extent permitted under Delaware law, the Company has agreed to indemnify its directors and officers for certain events or occurrences while the director or officer is, or was serving, at a request in such capacity. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. As of September 30, 2023 and December 31, 2022, the Company did not have any material indemnification claims that were probable or reasonably possible and consequently has not recorded related liabilities.	7. Commitments and Contingencies Research and Development Agreements The Company enters into contracts in the normal course of business with CROs for clinical trials, with CMOS or other vendors for preclinical studies, supplies and other services and products for operating purposes. These contracts generally provide for termination on notice or may have a potential termination fee if a purchase order is cancelled within a specified time. As of December 31, 2022 and 2021, there were no amounts accrued related to termination and cancellation charges as the Company has not determined cancellation to be probable. License Agreements The Company entered into the license agreements (Note 6), pursuant to which the Company is required to pay certain cash milestones contingent upon the achievement of specific events. No such milestones were achieved or probable as of December 31, 2022 and 2021. The Company is required to pay royalties on sales of products developed under this agreement. All products are in development as of December 31, 2022 and 2021 and no such royalties were due. Legal Contingencies From time to time, the Company may become involved in legal proceedings arising from the ordinary course of business. The Company records a liability for such matters when it is probable that future losses will be incurred and that such losses can be reasonably estimated. Significant judgment by the Company is required to determine both probability and the estimated amount. Management is currently not aware of any legal matters that could have a material adverse effect on the Company’s financial position, results of operations or cash flows. Guarantees and Indemnifications In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnification. Its exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To the extent permitted under Delaware law, the Company has agreed to indemnify its directors and officers for certain events or occurrences while the director or officer is, or was serving, at a request in such capacity. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. As of December 31, 2022 and 2021, the Company did not have any material indemnification claims that were probable or reasonably possible and consequently has not recorded related liabilities.

Operating Leases

Operating Leases	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Leases [Abstract]
Operating Leases	8. Operating Leases As of September 30, 2023, the current and non-current Facility leases On January 27, 2021, the Company entered into a new lease agreement for office and lab space in South San Francisco, California that included two office suites. The lease terms for the two office suites commenced during July August 2021 right-of-use In August 2023, the Company subleased one of its office suites in the South San Francisco lease for 20 months starting from August 2023 for aggregate sublease payments of $0.5 million. The sublease income, while it reduces the rent expense, is not considered in the value of the right-of-use On November 10, 2021, the Company entered into a sublease agreement for office and lab space located in Brisbane, California. The sublease expires on December 6, 2023. The corresponding right-of-use On December 16, 2021, the Company entered into a lease agreement with Bayside Area Development, LLC (“Bayside”) for 85,165 square feet of office and laboratory space in South San Francisco, CA. The lease for the office and laboratory space commenced in April 2023. The term of the lease is 120 months with the option to extend the term up to an additional ten years. This option to extend the lease term was not determined to be reasonably certain and therefore has not been included in the Company’s calculation of the associated operating lease liability under ASC 842. During the second quarter of 2023, the Company took possession of the Bayside lease and recognized a $32.0 million right-of-use In October 2023, the Company entered into a sublease agreement and amendment to the original master lease with the landlord to accelerate the termination date of the Bayside lease, and in November 2023, the Company entered into an amendment to the original lease agreement to reassign the second suite of the South San Francisco lease (Note 14). As of September 30, 2023, the Company had operating lease right-of-use Embedded leases On May 10, 2021 and August 30, 2021, the Company and LCGM entered into the LCGM MSA and Statement of Work #3 (“SOW #3”), respectively, for the exclusive use of a manufacturing suite at the LCGM facility. Pursuant to the terms of SOW #3, LCGM agreed to provide the Company with certain dedicated space for the clinical manufacturing, release testing, and product release in the Company’s Phase 1/2 CEDAR clinical trial to treat sickle cell disease. The Company concluded that the agreement contains an embedded lease as the Company controls the use of a dedicated manufacturing suite and the equipment therein. The agreement includes fixed lease payments of $5.6 million from inception of lease through April 30, 2023, the expiration date of SOW #3. As of September 30, 2023, the Company has paid all fixed lease payments on the LCGM embedded lease. The Company and Explora BioLabs, Inc. (“Explora”) entered into a License Service Agreement and Master Services Agreement (together, the “Explora Agreements”) on November 17, 2021 and December 16, 2021, respectively. Pursuant to the terms of the Explora Agreements, Explora agreed to provide a certain dedicated space to perform in vitro or in vivo studies, obtain or house research animals, and provide scientific or technical consultation to the Company. The Company concluded that the Explora Agreements contain an embedded lease as the Company controls the use of a dedicated manufacturing suite and the equipment therein. The Explora Agreements contain fixed lease payments of $0.7 million from inception of lease through November 2023 As of September 30, 2023, the Company did not have any operating lease right-of-use Operating Lease Obligations As of September 30, 2023, the future minimum lease payments for the Company’s operating leases for each of the years ending December 31 were as follows (in thousands): Amount 2023 (Remaining three months) $ 2,155 2024 9,177 2025 8,336 2026 8,223 2027 8,493 Thereafter 50,103 Total undiscounted lease payments 86,487 Present value adjustment (33,376 ) Total net lease liabilities $ 53,111 Lease expense was $2.4 million and $6.4 million for the three and nine months ended September 30, 2023, respectively. Lease expense was $1.7 million and $5.0 million for the three and nine months ended September 30, 2022, respectively. Under the terms of the remaining lease agreements, the Company is also responsible for certain variable lease payments that are not included in the measurement of the lease liability. Variable lease payments for operating leases were $0.8 million and $1.8 million for the three and nine months ended September 30, 2023, respectively, including non-lease The following information represents supplemental disclosure for the statement of cash flows related to the operating leases (in thousands): September 30, 2023 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows under operating leases $ 4,817	8. Operating Leases In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2016-02, Leases right-of-use right-of-use non-lease non-lease As of December 31, 2022, the current and non-current Facility leases In April 2020, the Company entered into a one-year COVID-19 On January 27, 2021, the Company entered into a new lease agreement for office and lab space in South San Francisco, California that included office suites. The lease terms for the two office suites commenced during July and August 2021 , respectively. The term of the lease is 44 months for the first office suite and 43 months for the second office suite with an option to extend the term for an additional two years on the same terms and conditions. This option to extend the lease term was not determined to be reasonably certain and therefore has not been included in the Company’s calculation of the associated operating lease liability under ASC 842. The corresponding right-of-use assets and lease liabilities related to the two office suites were recorded on the Company’s balance sheet upon the lease commencement date, which was the date the Company was deemed to have obtained control of the premises. On November 10, 2021, the Company entered a sublease agreement for office and lab space located at Brisbane, California. The sublease expires on December 6, 2023. The corresponding right-of-use As of December 31, 2022, the Company had operating lease right-of-use Embedded leases The Company evaluated its vendor contracts to identify embedded leases, if any, and determined that two agreements with contract manufacturing suppliers constituted a lease under ASC 842 as the Company has the right to substantially all of the economic benefits from the use of the asset and can direct the use of the asset. On May 10, 2021 and August 30, 2021, the Company and LCGM entered into the LCGM MSA and SOW #3, respectively, for the exclusive use of a manufacturing suite at the LCGM facility. Pursuant to the terms of SOW #3, LCGM agreed to provide the Company with certain dedicated space for the clinical manufacturing, release testing, and product release in the Company’s Phase 1 clinical trial to treat Sickle Cell Disease. The Company concluded that the agreement contains an embedded lease as the Company controls the use of a dedicated manufacturing suite and the equipment therein. The agreement includes fixed lease payments of $5.6 million through April 30, 2023, the expiration date of SOW #3. The Company and Explora BioLabs, Inc. (“Explora”) entered into a License Service Agreement and Master Services Agreement (together, the “Explora Agreements”) on November 17, 2021 and December 16, 2021, respectively. Pursuant to the terms of the Explora Agreements, Explora agreed to provide a certain dedicated space to perform in vitro or in vivo studies, obtain or house research animals, and provide scientific or technical consultation to the Company. The Company concluded that the agreement contains an embedded lease as the Company controls the use of a dedicated manufacturing suite and the equipment therein. The Explora Agreements contain fixed lease payments of $0.7 million through November 2023 As of December 31, 2022, the Company had operating lease right-of-use Operating Lease Obligations As of December 31, 2022, the future minimum lease payments for the Company’s operating leases for each of the years ending December 31 were as follows (in thousands): Amount 2023 $ 4,331 2024 1,468 2025 375 Thereafter — Total undiscounted lease payments 6,174 Present value adjustment (380 ) Total net lease liabilities $ 5,794 Lease expense was $6.7 and $1.9 million for the years ended December 31, 2022 and 2021, respectively. Under the terms of the remaining lease agreements, the Company is also responsible for certain variable lease payments that are not included in the measurement of the lease liability. Variable lease payments for operating leases were $1.3 and $0.2 million for the years ended December 31, 2022 and 2021, respectively, including non-lease The following information represents supplemental disclosure for the statement of cash flows related to the operating leases (in thousands): December 31, 2022 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows under operating leases $ 6,172

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2022
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	9. Redeemable Convertible Preferred Stock In June 2021, immediately prior to the completion of the Company’s IPO (Note 1), all outstanding shares of redeemable convertible preferred stock were automatically converted into 30,761,676 shares of common stock. Upon conversion into common stock, the carrying value of the redeemable convertible preferred stock of $260.5 million was reclassified to equity. Series A Redeemable Convertible Preferred Stock In June 2020, the Company issued 10,000,000 shares of its Series A redeemable convertible preferred stock at a price of $1.00 per share for gross cash proceeds of $10.0 million and issued 5,019,949 shares of its Series A redeemable convertible preferred stock upon the conversion of the outstanding convertible note and accrued interest. In connection with the initial issuance of the shares of its Series A redeemable convertible preferred stock, the Company had an obligation to sell and the holders had the obligation to purchase the additional 30,000,000 shares of Series A redeemable convertible preferred stock at $1.00 per share upon the achievement of certain milestones as determined by the Board and approved by at least one of the investors, or upon the waiver of such milestones by the holders of at least 75% of the outstanding shares of Series A redeemable convertible preferred stock, in two equal tranches of $15.0 million each. The Company determined that the obligation to sell additional shares is a freestanding financing instrument and a liability. The Company estimated the fair value of the liability to be $3.3 million and recorded it as a reduction to redeemable convertible preferred stock and as a derivative redeemable convertible preferred stock tranche liability in its balance sheet at the issuance date. In December 2020, the requisite holders waived the second tranche milestone event and the Company issued 15,000,000 shares of its Series A redeemable convertible preferred stock for gross cash proceeds of $15.0 million. The redeemable convertible preferred stock tranche liability related to the second tranche shares was remeasured to fair value of $29.1 million and reclassified to redeemable convertible preferred shares upon the settlement. In connection with the issuance of Series A redeemable convertible preferred stock, in the year ended December 31, 2020, the Company incurred issuance costs of $0.2 million. As of December 31, 2020, the redeemable convertible preferred stock tranche liability related to the third tranche shares was remeasured at fair value of $29.1 million and continued to be reported in current liabilities. The Company settled the third tranche in February 2021 and issued 15,000,000 shares of its Series A redeemable convertible preferred stock for gross cash proceeds of $15.0 million. The Company recognized a total of $54.8 million as other loss in the statements of operations and comprehensive loss related to the changes in the fair value of the redeemable convertible preferred stock tranche liabilities during the year ended December 31, 2020. Prior to the closing of the third tranche of the Series A preferred stock financing in February 2021, the remaining tranche liability was remeasured at a fair value of $39.4 million. The Company recognized a loss of $10.3 million in the statements of operations and comprehensive loss related to the change in the fair value of the redeemable convertible preferred stock tranche liability during the year ended December 31, 2021. In connection with the closing of the third tranche of Series A redeemable convertible preferred stock, the Company incurred issuance costs of $4.0 thousand during the year ended December 31, 2021. Series B Redeemable Convertible Preferred Stock In March 2021, the Company issued 29,792,487 shares of the Series B redeemable convertible preferred stock at $5.06 per share for gross cash proceeds of $150.7 million. The Company incurred issuance costs of $0.2 million.

Common Stock

Common Stock	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Equity [Abstract]
Common Stock	9. Common Stock As of September 30, 2023 and December 31, 2022, the Company was authorized to issue 300,000,000 shares of its common stock with $0.00001 par value per share. Each share of the Company’s common stock is entitled to one vote. In connection with the IPO in June 2021, all outstanding shares of redeemable convertible preferred stock were converted into 30,761,676 shares of common stock. The IPO closed on June 29, 2021, pursuant to which the Company issued and sold 14,000,000 shares of its common stock at a public offering price of $17.00 per share. On June 29, 2021, the underwriters also exercised their option to purchase an additional 2,100,000 shares of common stock at the IPO price, less the underwriting discounts and commissions. The closing of the offering of the additional shares occurred on July 2, 2021. The Company issued and sold 2,100,000 shares of its common stock at a public offering price of $17.00 per share. Shares Reserved for Future Issuance As of September 30, 2023 and December 31, 2022, the Company reserved common stock for future issuances as follows: September 30, 2023 December 31, 2022 Outstanding stock option awards 6,380,515 7,755,303 Shares available for future stock option grants 9,831,161 5,382,907 ESPP shares available for future grants 1,253,729 754,951 Total shares reserved for future issuance 17,465,405 13,893,161 Founders’ and Investor’s Restricted Common Stock In March 2020, the Board approved and in April 2020, the Company issued 6,081,413 shares of its common stock to its founders and 2,467,104 shares of its common stock to its investor at the purchase price of $0.00002 per share. As of December 31, 2020, the investor’s shares were fully vested and a portion of the shares issued were subject to the Company’s option to repurchase per the Stanford Adjustment Repurchase Right, as described below. The shares of the Company’s common stock issued to its founders for their services as an employee, advisor, or consultant vest monthly over four years with one year cliff from the vesting commencement date. The vesting commencement date was the date of the initial closing of the Series A preferred stock financing or June 24, 2020. Pursuant to the restricted stock purchase agreements with each of the founders, the vesting of the founders’ common stock shares could be accelerated upon the occurrence of certain events, including signing of the term sheet for the license with Stanford, a change in control, or if the founder’s service is terminated by the Company without cause. The Company signed the term sheet with Stanford in June 2020, and as a result, an aggregate of 912,212 shares of founders’ common stock vested pursuant to the acceleration terms. As of September 30, 2023, certain founder agreements were terminated without cause and shares were accelerated. If a founder terminates the service relationship with the Company during the vesting period, the Company may repurchase any unvested restricted common stock at the price per share equal to the lower of (i) the original purchase price, subject to adjustment in the event of any reorganization, recapitalization, reclassification, stock dividend, stock split, reverse stock split, or (ii) the current fair market value as of the date the Company elects to exercise its Stanford Adjustment Repurchase Right, as described below. The repurchase right lapses in 180 days after the termination of the founder’s service or employment. During the vesting term, holders of founders’ common stock awards are deemed to be common stockholders and have the right to receive dividends and voting rights. The founders’ shares of common stock are also subject to the Company’s option to repurchase per the Stanford Adjustment Repurchase Right, as described below. The Company accounts for shares issued to founders as equity compensation awards and the estimated fair value at the grant date was minimal. The Company did not repurchase any founders’ common stock awards during the three months ended September 30, 2023. During the nine months ended September 30, 2023, the Company repurchased 152,694 shares of founders’ common stock awards. 647,803 and 1,938,430 shares of founders’ common stock awards were unvested and expected to vest in 0.7 years and 1.5 years as of September 30, 2023 and December 31, 2022, respectively. Stanford Adjustment Repurchase Right Upon the issuance of shares of common stock to Stanford pursuant to the License Agreement, as discussed in Note 6, the Company has a right to repurchase from each founder and an investor a number of shares of common stock equal to the number of shares issued to Stanford multiplied by the applicable number of shares issued to the founder or investor, as applicable, divided by 7,273,848 shares (a fully diluted number of shares of the Company at the end of March 2020, after the founders’ and investor’s shares were approved by the board of directors). The Stanford Adjustment Repurchase Right may be exercised by the Company within six months following the date of the issuance of the shares of common stock to Stanford. The repurchase price per share is equal to the lower of (i) the purchase price, subject to adjustment in the event of any reorganization, recapitalization, reclassification, etc., or (ii) the current fair market value as of the date the Company elects to exercise its Stanford Adjustment Repurchase Right. On May 7, 2021, the Company issued an aggregate of 640,861 shares of the Company’s common stock to Stanford and certain individuals designated by Stanford in consideration for rights granted to the Company under the Company’s exclusive license agreement. On June 18, 2021, the Company exercised its right to repurchase an aggregate of 624,845 shares from each founder and investor under the Stanford Adjustment Repurchase Right. As of September 30, 2023, the Company has not exercised the right to repurchase the remaining 16,016 shares. The Company accounts for the founders and investor’s shares of restricted common stock as equity share-based awards.	10. Common Stock As of December 31, 2022 and 2021, the Company was authorized to issue 300,000,000 shares of its common stock with $0.00001 par value per share. Each share of the Company’s common stock is entitled to one vote. In connection with the IPO in June 2021, all outstanding shares of redeemable convertible preferred stock were converted into 30,761,676 shares of common stock. The IPO closed on June 29, 2021, pursuant to which the Company issued and sold 14,000,000 shares of its common stock at a public offering price of $17.00 per share. On June 29, 2021, the underwriters also exercised their option to purchase an additional 2,100,000 shares of common stock at the IPO price, less the underwriting discounts and commissions. The closing of the offering of the additional shares occurred on July 2, 2021. The Company issued and sold 2,100,000 shares of its common stock at a public offering price of $17.00 per share. Shares Reserved for Future Issuance As of December 31, 2022 and 2021, the Company reserved common stock for future issuances as follows: December 31, 2022 December 31, 2021 Outstanding stock option awards 7,755,303 5,056,743 Shares available for future stock option grants 5,382,907 4,454,004 ESPP shares available for future grants 754,951 524,106 Total shares reserved for future issuance 13,893,161 10,034,853 Founders’ and Investor’s Restricted Common Stock In March 2020, the Board approved and in April 2020, the Company issued 6,081,413 shares of its common stock to its founders and 2,467,104 shares of its common stock to its investor at the purchase price of $0.00002 per share. As of December 31, 2020, the investor’s shares were fully vested and a portion of the shares issued were subject to the Company’s option to repurchase per the Stanford Adjustment Repurchase Right, as described below. The shares of the Company’s common stock issued to its founders for their services as an employee, advisor, or consultant vest monthly over four years with one year cliff from the vesting commencement date. The vesting commencement date was the date of the initial closing of the Series A preferred stock financing or June 24, 2020. Pursuant to the restricted stock purchase agreements with each of the founders, the vesting of the founders’ common stock shares could be accelerated upon the occurrence of certain events, including signing of the term sheet for the license with Stanford, a change in control, or if the founder’s service is terminated by the Company without cause. The Company signed the term sheet with Stanford in June 2020, and as a result, an aggregate of 912,212 shares of founders’ common stock vested pursuant to the acceleration terms. If a founder terminates the service relationship with the Company during the vesting period, the Company may repurchase any unvested restricted common stock at the price per share equal to the lower of (i) the original purchase price, subject to adjustment in the event of any reorganization, recapitalization, reclassification, stock dividend, stock split, reverse stock split, or (ii) the current fair market value as of the date the Company elects to exercise its Stanford Adjustment Repurchase Right, as described below. The repurchase right lapses in 180 days after the termination of the founder’s service or employment. During the vesting term, holders of founders’ common stock awards are deemed to be common stockholders and have the right to receive dividends and voting rights. The founders’ shares of common stock are also subject to the Company’s option to repurchase per the Stanford Adjustment Repurchase Right, as described below. The Company accounts for shares issued to founders as equity compensation awards and the estimated fair value at the grant date was minimal. 1,938,430 and 3,230,746 shares of founders’ common stock awards were unvested and expected to vest in 1.5 years and 2.5 years as of December 31, 2022 and 2021, respectively. Stanford Adjustment Repurchase Right Upon the issuance of shares of common stock to Stanford pursuant to the License Agreement, as discussed in Note 5, the Company has a right to repurchase from each founder and an investor a number of shares of common stock equal to the number of shares issued to Stanford multiplied the applicable number of shares issued to the founder or investor, as applicable, divided by 7,273,848 shares (a fully diluted number of shares of the Company at the end of March 2020, after founders and the investor’s shares were approved by the board of directors). The Stanford Adjustment Repurchase Right may be exercised by the Company within six months following the date of the issuance of the shares of common stock to Stanford. The repurchase price per share is equal to the lower of (i) the purchase price, subject to adjustment in the event of any reorganization, recapitalization, reclassification, etc., or (ii) the current fair market value as of the date the Company elects to exercise its Stanford Adjustment Repurchase Right. On May 7, 2021, the Company issued an aggregate of 640,861 shares of the Company’s common stock to Stanford and certain individuals designated by Stanford in consideration for rights granted to the Company under the Company’s exclusive license agreement. On June 18, 2021, the Company exercised its right to repurchase an aggregate of 624,845 shares from each founder and investor under the Stanford Adjustment Repurchase Right. As of December 31, 2022, the Company has not exercised the right to purchase the remaining 16,016 shares. The Company accounts for the founders and investor’s shares of restricted common stock as equity share-based awards.

Equity Incentive Plans

Equity Incentive Plans	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Equity Incentive Plans	10. Equity Incentive Plans 2020 Stock Option and Grant Plan Prior to the effectiveness of the registration statement on Form S-1 No. 333-256838) and at prices no less than 100.0% of the estimated fair value of the shares on the date of grant as determined by the Board, provided, however, that the exercise price of an incentive stock option granted to a 10.0% stockholder shall not be less than 110.0% of the estimated fair value of the shares on the date of grant and the option is not exercisable after the expiration of five years from the date of grant. Options generally vest monthly over four years with or without one year cliff vesting. Per the 2020 Plan, granted options may be early exercised prior to vesting and the Company will issue shares of restricted stock upon the early exercise with vesting terms consistent with the original grant. Upon completion of the Company’s IPO, the remaining shares available for issuance under the 2020 Plan were retired, and the Company no longer grants awards pursuant to the 2020 Plan. 2021 Stock Option and Incentive Plan In June 2021, the Company’s board of directors approved the 2021 Stock Option and Incentive Plan (the “2021 Plan”) that became effective immediately prior to the date when the Company’s prospectus was declared effective by the SEC on June 24, 2021. The Company initially reserved 5,636,000 shares of common stock for issuance of awards under the 2021 Plan. The 2021 Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2022, by 5% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. On January 1, 2022 and 2023, the number of shares of common stock available under the 2021 Plan increased by 2,900,541 shares and 2,911,088 shares, respectively pursuant to this evergreen provision of the 2021 Plan. The option exercise price of each option will be determined by the Company’s compensation committee but generally may not be less than 100% of the fair market value of the Company’s common stock on the date of grant. The term of each option will be fixed by the Company’s compensation committee and may not exceed ten years from the date of grant. The grant date fair value of all awards made under the 2021 Plan and all other cash compensation paid by the Company to any non-employee non-employee As of September 30, 2023, there were 9,831,161 shares available for future issuance under the 2021 Plan. Restricted Stock Awards During the year ended December 31, 2020, the Company issued 832,983 shares as restricted stock awards under the 2020 Plan. The purchase price of the restricted common stock awards was fair value as determined by the Board at the issuance date. The shares vest monthly over four years with the one-year The Company accounted for restricted stock awards as early exercised options and recognized a liability in other liabilities when cash was received for the purchase of shares of restricted stock awards. As shares of restricted stock awards vest, the Company reclassified the liability to common stock and additional paid in capital. As of September 30, 2023 and December 31, 2022, the Company recorded a minimal liability for restricted stock awards included in other liabilities. There were 1,542 and 11,136 restricted stock award shares canceled and repurchased during the three and nine months ended September 30, 2023, respectively. There were 5,140 shares canceled and repurchased during the three and nine months ended September 30, 2022. There were 703,035 and 553,443 shares of restricted stock vested as of September 30, 2023 and December 31, 2022, respectively. Employee Stock Purchase Plan In June 2021, the Company’s board of directors and stockholders approved the 2021 Employee Stock Purchase Plan (the “ESPP”) which became effective upon the IPO. Pursuant to the ESPP, certain employees of the Company, excluding consultants and non-employee $ and at a purchase price of % of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the applicable purchase date, which will be the final trading day of the applicable purchase period. The ESPP has two annual purchase periods extending from June to November and December to May. The Company recorded a minimal liability for ESPP in accrued liabilities as of September 30, 2023 and December 31, 2022. The Company did not issue any shares during the three months ended September 30, 2023 and 2022. The Company issued 65,222 shares and 207,137 shares under the ESPP during the nine months ended September 30, 2023 and 2022, respectively. Incentive Stock Options and Nonqualified Stock Options Stock options issued under the 2020 Plan and 2021 Plan generally vest over a four-year period and expire ten years from the date of grant. Certain options provide for accelerated vesting if there is a change in control, as defined in the individual award agreements. A summary of option activity under the 2020 Plan and the 2021 Plan during the nine months ended September 30, 2023 is as follows: Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2022 7,755,303 $ 8.47 8.67 $ 794 Options granted—2021 Plan 3,223,400 $ 2.22 Options exercised (65,414 ) $ 0.52 Options cancelled (4,532,774 ) $ 6.50 Outstanding as of September 30, 2023 6,380,515 $ 6.79 5.6 $ 695 Exercisable 4,231,849 $ 6.86 4.4 $ 472 Vested and expected to vest as of September 30, 2023 6,380,515 $ 6.79 5.6 $ 695 Aggregate intrinsic value represents the difference between the fair value of the underlying common stock and the exercise price as of September 30, 2023. The weighted-average grant date fair value of options granted during the three and nine months ended September 30, 2023 was $1.89 and $1.56 per share, respectively. There were 10,367 and 65,414 stock options exercised during the three and nine months ended September 30, 2023, respectively. Early Exercise of Stock Options The terms of the 2020 Plan permit the exercise of options granted prior to vesting, subject to required approvals. The unvested shares are subject to the repurchase right upon termination of employment at the original purchase price. The repurchase right lapses in 180 days after the termination of the employee’s employment. Shares purchased by employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be issued until those shares vest according to their respective vesting schedules. Cash received for early exercised stock options is recorded as other liabilities on the balance sheet and is reclassified to common stock and additional paid-in capital as such shares vest. During the three and nine months ended September 30, 2023, the Company repurchased As of September 30, 2023 and December 31, 2022, 111,600 and 554,695 shares, respectively, remained subject to the right of repurchase as a result of the early exercised stock options. As of September 30, 2023, the Company has a minimal remaining liability related to early exercised shares, which is recorded within accrued expenses and other liabilities on the Company’s condensed balance sheets. Stock-Based Compensation Expense The following table presents the components of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Restricted stock awards and founders’ common stock awards $ 1 $ 2 $ 5 $ 6 ESPP 1 58 96 316 Stock options 2,159 3,150 8,168 9,590 Total stock-based compensation expense $ 2,161 $ 3,210 $ 8,269 $ 9,912 The above stock-based compensation expense also includes the expenses of $0.4 million and $1.1 million related to stock options issued to non-employees non-employees The following table presents the classification of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Research and development expenses $ 37 $ 1,249 $ 1,904 $ 3,881 General and administrative expenses 2,124 1,961 6,365 6,031 Total stock-based compensation expense $ 2,161 $ 3,210 $ 8,269 $ 9,912 As of September 30, 2023 and December 31, 2022 there was $9.9 million and $31.0 million of unrecognized stock-based compensation expense related to the employee and non-employee	11. Equity Incentive Plans 2020 Stock Option and Grant Plan The Company grants share-based awards under the 2020 Stock Option Plan, as amended (the “2020 Plan”). The Company may grant under the 2020 Plan incentive stock options, nonqualified stock options, restricted stock awards, restricted stock units and other share-based awards to the Company’s officers, employees, directors and consultants. Options under the 2020 Plan may be granted for periods of up to years and at prices no less than % of the estimated fair value of the shares on the date of grant as determined by the Board, provided, however, that the exercise price of an incentive stock option granted to a % stockholder shall not be less than % of the estimated fair value of the shares on the date of grant and the option is not exercisable after the expiration of from the date of grant. Options generally vest monthly over with or without one year cliff vesting. Per the 2020 Plan, granted options maybe early exercised prior to vesting and the Company will issue shares of restricted stock upon the early exercise with vesting terms consistent with the original grant. Upon completion of the Company’s IPO, the remaining shares available for issuance under the 2020 Plan were retired. 2021 Stock Option and Grant Plan In June 2021, the Company’s Board of Directors approved the 2021 Stock Option and Incentive Plan (the “2021 Plan”) that became effective immediately prior to the date when the Company’s prospectus was declared effective by the SEC on June 24, 2021. The Company initially reserved 5,636,000 shares of common stock for issuance of awards under the 2021 Plan. The 2021 Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2022, by 5% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. On January 1, 2022, the number of shares of common stock available under the 2021 Plan increased by 2,900,541 shares pursuant to this evergreen provision of the 2021 Plan. The option exercise price of each option will be determined by the Company’s compensation committee but generally may not be less than 100% of the fair market value of the Company’s common stock on the date of grant. The term of each option will be fixed by the Company’s compensation committee and may not exceed ten years from the date of grant. The grant date fair value of all awards made under the 2021 Plan and all other cash compensation paid by the Company to any non-employee non-employee As of December 31, 2022, there were 5,382,907 shares available for future issuance under the 2021 Plan. Restricted Stock Awards During the year ended December 31, 2020, the Company issued 832,983 shares as restricted stock awards under the 2020 Plan. The purchase price of the restricted common stock awards was fair value as determined by the Board at the issuance date. The shares vest monthly over four years with the one-year The Company accounted for restricted stock awards as early exercised options and recognized a liability in other liabilities when cash was received for the purchase of shares of restricted stock awards. As shares of restricted stock awards vest, the Company reclassified the liability to common stock and additional paid in capital. As of December 31, 2022 and 2021, the Company recorded a minimal liability for restricted stock awards included in accrued expenses and other current liabilities. There were shares of restricted stock award shares canceled and repurchased as of December 31, 2022. restricted stock award shares were cancelled or repurchased as of December 31, 2021. There were and shares of restricted stock vested as of December 31, 2022 and 2021, respectively. Employee Stock Purchase Plan In June 2021, the Company’s board of directors and stockholders approved the 2021 Employee Stock Purchase Plan (the “2021 ESPP”) which became effective upon the IPO. The 2021 ESPP is intended to qualify as an employee stock purchase plan under Section 423 of the Internal Revenue Code of 1986, as amended, and is administered by the Company’s board of directors and the Compensation Committee of the board of directors. Under the 2021 ESPP, 564,000 shares of the Company’s common stock have been initially reserved for employee purchases of the Company’s common stock. The 2021 ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation. At the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock at the beginning of the offering period or at the end of each applicable purchase period. The first purchase period commenced upon the completion of the Company’s IPO and ended on November 30, 2021 and the subsequent offering periods commenced on December 1, 2021, June 1, 2022, and December 1, 2022. The Company recorded $0.1 million in accrued liabilities as of December 31, 2022. Effective January 1, 2022, the number of shares of common stock available under the 2021 ESPP increased by 564,000 shares pursuant to the evergreen provision of the 2021 ESPP. Year Ended December 31, 2022 2021 Expected volatility 73.00% - 75.00 % 72.00% - 74.00 % Expected dividend yield 0 % 0 % Expected term (in years) 0.5 0.44 - 0.5 Risk-free interest rate 0.10% - 4.65 % 0.10% - 1.00 % Incentive Stock Options and Nonqualified Stock Options Stock options issued under the 2020 Plan and 2021 Plan, generally, vest over a four-year period and expire ten years from the date of grant. Certain options provide for accelerated vesting if there is a change in control, as defined in the individual award agreements. The Company used the Black-Scholes option pricing model to estimate stock-based compensation expense for stock option awards granted during the periods presented, with the following assumptions. Year Ended December 31, 2022 2021 Expected volatility 74.00% - 75.00 % 72.00% - 77.74 % Expected dividend yield 0 % 0 % Expected term (in years) 5.97 - 6.01 5.48 - 6.04 Risk-free interest rate 1.91% - 4.23 % 0.56% - 1.34 % A summary of option activity under the 2020 Plan and the 2021 Plan during the year ended December 31, 2022 is as follows: Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2021 5,056,743 $ 8.77 9.2 $ 18,503 Options granted—2021 Plan 3,292,702 $ 7.91 Options exercised (67,196 ) $ 0.30 Options cancelled (526,946 ) $ 8.99 Outstanding as of December 31, 2022 7,755,303 $ 8.47 8.7 $ 794 Exercisable 2,330,389 $ 8.74 8.3 $ 388 Vested and expected to vest as of December 31, 2022 7,755,303 $ 8.47 8.7 $ 794 Aggregate intrinsic value represents the difference between the fair value of the underlying common stock and the exercise price as of December 31, 2022. The weighted-average grant date fair value of options granted during the year ended December 31, 2022 was $5.21 per share. The intrinsic value of the stock options exercised was $0.2 and $5.0 million for the years ended December 31, 2022 and 2021, respectively. Early Exercise of Stock Options The terms of the 2020 Plan permit the exercise of options granted prior to vesting, subject to required approvals. The unvested shares are subject to the repurchase right upon termination of employment at the original purchase price. The repurchase right lapses in 180 days after the termination of the employee’s employment. Shares purchased by employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be issued until those shares vest according to their respective vesting schedules. Cash received for early exercised stock options is recorded as other liabilities on the balance sheet and is reclassified to common stock and additional paid-in At December 31, 2022 and 2021, 554,695 and 1,195,631 shares, respectively, remained subject to the right of repurchase as a result of the early exercised stock options. The remaining liability related to early exercised shares as of December 31, 2022 and 2021 was $0.1 and $0.3 million, respectively, and was recorded in accrued expenses and other current liabilities, respectively, in the balance sheets. Stock-Based Compensation Expense The following table presents the components of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands): Year Ended December 31, 2022 2021 Restricted stock awards and founders’ common stock awards $ 11 $ 9 ESPP 391 215 Stock options 13,132 7,647 Total stock-based compensation expense $ 13,534 $ 7,871 The above stock-based compensation expense also includes the expenses of $2.2 and $0.3 million related to stock options issued to non-employees The following table presents the classification of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands): Year Ended December 31, 2022 2021 Research and development expenses $ 5,317 $ 2,685 General and administrative expenses 8,217 5,186 Total stock-based compensation expense $ 13,534 $ 7,871 As of the years ended December 31, 2022 and 2021, there was $31.0 and $30.5 million, respectively, of unrecognized stock-based compensation expense related to the employee and non-employee

Restructuring Activities

Restructuring Activities	9 Months Ended
	Sep. 30, 2023
Restructuring and Related Activities [Abstract]
Restructuring Activities	11. Restructuring Activities In February 2023, the Company’s board of directors approved a restructuring plan (the “First Restructuring Plan”) to reduce the Company’s operating costs and better align its workforce with the needs of its business. The First Restructuring Plan eliminated approximately 50% of the Company’s workforce. Employees affected by the First Restructuring Plan obtained involuntary termination benefits that are provided pursuant to a one-time beyond a minimum retention period to receive their one-time termination benefits, the Company recognized the termination benefits ratably over their future service periods. The service periods began in February 2023 and ended at various dates through June 2023. The Company has incurred approximately In August 2023, the Company’s board of directors approved a second restructuring plan (the “Second Restructuring Plan”; together with the First Restructuring Plan, the “Restructuring Plans”) to further reduce the Company’s operating costs and align its workforce with the needs of its business. The Second Restructuring Plan eliminated approximately an additional 33.1% of its total workforce, and in aggregate, 78.1 % of its total workforce. Employees affected by the Second Restructuring Plan obtained involuntary termination benefits that are provided to an ongoing benefit arrangement. Accordingly, the Company is recognizing termination benefits upon announcement of termination to all employees. The Company expects to incur approximately $3.5 million of employee termination benefits expense to implement the Second Restructuring Plan. In addition, the Company determined that as of September 30, 2023, it was reasonably likely to incur additional employee termination benefits expense for its remaining employees within the next twelve months. Accordingly, it recognized termination benefits for the remaining employees totaling $1.0 million. The following table summarizes the Company’s restructuring liability that is included in accrued expenses and other current liabilities in the accompanying condensed balance sheet: Nine Months Ended September 30, 2023 Accrued employee termination benefits beginning balance $ — Employee termination benefits charges incurred during the period 7,883 Amounts paid or otherwise settled during the period (4,900 ) Accrued employee termination benefits as of September 30, 2023 $ 2,983 In addition, the board of directors determined that it was in the best interests of the Company and its stockholders to put in place arrangements designed to provide that the Company will have the continued dedication and commitment of those employees, including executives, determined to be key to the Company’s planned go-forward In June 2023, the Company committed to a plan to sell certain of its lab equipment associated with the Restructuring Plan. During the three months ended September 30, 2023, the Company implemented a plan to sell its remaining lab equipment as well as other fixed assets not transferred to the Bayside lease. As of September 30, 2023, it disposed of the majority of its assets, with a minimal amount of assets on the condensed balance sheet meeting the criteria of held for sale. These assets are recognized at the lower of cost or fair value less cost to sell using market approach. The fair value of these assets are classified as Level 3 in the fair value hierarchy due to a mix of unobservable inputs utilized such as independent research in the market as well as actual quotes from market participants. Subsequent changes to the estimated selling price of assets held for sale are recorded as gains or losses to the condensed statements of operations and comprehensive loss wherein the recognition of subsequent gains is limited to the cumulative loss previously recognized. During the three and nine months ended September 30, 2023, the Company recorded impairment charges and loss on disposal of assets, which was included in restructuring and impairment costs in the condensed statements of operations and comprehensive loss, of In connection with the Restructuring Plans, the Company has determined that it will not utilize the Bayside and South San Francisco leases for purposes of its own operations. In August 2023, the Company subleased one of its office suites in the South San Francisco lease for 20 months starting from August 2023 for aggregate sublease payments of $0.5 million. In October 2023, the Company entered into a sublease agreement and amendment to the original master lease with the landlord to accelerate the termination date of the Bayside lease and in November 2023, the Company entered into an amendment to the original lease agreement to reassign the second suite of the South San Francisco lease (Note 14). The Company performed a recoverability test by comparing the future cash flows attributable to the asset group to the carrying value of the long-lived assets. Future cash flows were estimated using comparable laboratory and office facilities discounted at a market discount rate over the remaining term of the Company’s lease. During the three and nine months ended September 30, 2023, the Company recorded a non-cash right-of-use The Company entered into an asset purchase agreement with a third party pursuant to which the Company sold to the counterparty, concurrently with the execution of the APA, certain assets related to the Company’s non-genotoxic In addition, the Company also entered into an LOA with another third party pursuant to which the Company exclusively licensed to the counterparty, and granted the counterparty an option to acquire, certain intellectual property and materials related to the Company’s nulabeglogene autogedtemcel (nula-cel) pre-clinical

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	12. Net Loss Per Share Attributable to Common Stockholders The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders, which excludes shares which are legally outstanding, but subject to repurchase by the Company (in thousands, except share and per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Numerator: Net loss $ (22,485 ) $ (24,682 ) $ (101,733 ) $ (76,453 ) Denominator: Weighted-average common shares outstanding 57,977,907 58,189,211 58,064,472 58,085,711 Less: weighted-average unvested restricted shares and shares subject to repurchase (720,666 ) (2,983,072 ) (1,315,477 ) (3,494,118 ) Weighted-average shares used to compute basic and diluted net loss per share attributable to common stockholders 57,257,241 55,206,139 56,748,995 54,591,593 Net loss per share attributable to common stockholders—basic and diluted: $ (0.39 ) $ (0.45 ) $ (1.79 ) $ (1.40 ) Anti-dilutive Outstanding Shares or Equivalents The following outstanding options, unvested shares, and ESPP shares were excluded (as common stock equivalents) from the computation of diluted net loss per common share for the periods presented as their effect would have been anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Options to purchase common stock 6,380,515 7,849,590 6,380,515 7,849,590 Common stock subject to vesting or repurchase 873,062 3,236,152 873,062 3,236,152 Employee Stock Purchase Plan shares 10,437 128,888 10,437 128,888 Total 7,264,014 11,214,630 7,264,014 11,214,630	12. Net Loss Per Share Attributable to Common Stockholders The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders, which excludes shares which are legally outstanding, but subject to repurchase by the Company (in thousands, except share and per share amounts): Year Ended December 31, 2022 2021 Numerator: Net loss $ (101,052 ) $ (70,760 ) Denominator: Weighted-average common shares outstanding 58,111,437 35,121,114 Less: weighted-average unvested restricted shares and shares subject to repurchase (3,237,762 ) (6,201,859 ) Weighted-average shares used to compute basic and diluted net loss per share attributable to common stockholders 54,873,675 28,919,255 Net loss per share attributable to common stockholders—basic and diluted: $ (1.84 ) $ (2.45 ) Anti-dilutive Outstanding Shares or Equivalents The following outstanding options, unvested shares, and ESPP shares were excluded (as common stock equivalents) from the computation of diluted net loss per common share for the periods presented as their effect would have been antidilutive (in thousands): Year Ended December 31, 2022 2021 Options to purchase common stock 7,755,303 5,056,743 Common stock subject to vesting or repurchase 2,767,526 4,774,798 Employee Stock Purchase Plan shares 168,080 99,252 Total 10,690,909 9,930,793

Income Taxes

Income Taxes	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes During the nine months ended September 30, 2023 and 2022, the Company recorded a full valuation allowance on federal and state deferred tax assets since management does not forecast the Company to be in a taxable position in the near future.	13. Income Taxes No provision for income taxes was recorded for the years ended December 31, 2022 and 2021. The Company has incurred net operating losses only in the United States since its inception. The Company has not reflected any benefit of such net operating loss carryforwards in the financial statements. A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate was as follows: Year Ended December 31, 2022 2021 Federal statutory income tax rate ate 21.00 % 21.00 % State taxes 1.10 1.94 Others (0.69 ) (0.26 ) Research and development credits 1.11 1.01 Cancellation of debt income — — Tranche liability — (3.06 ) Interest expense — — Stock-based compensation (0.97 ) (0.96 ) Change in valuation allowance (21.55 ) (19.67 ) Provision for taxes 0.00 % 0.00 % Net deferred tax assets and liabilities consisted of the following (in thousands): Year Ended December 31, 2022 2021 Deferred tax assets: Net operating losses—non-current $ 15,940 $ 12,006 Capitalized R&D 13,815 — General business credit—non-current 5,699 2,682 Operating lease right-of-use 1,220 2,368 Stock based compensation 1,703 784 Accruals and reserves 735 525 Fixed assets 170 396 Other 3 2 Gross deferred tax assets 39,285 18,763 Valuation allowance (38,110 ) (16,332 ) Net deferred tax assets 1,175 2,431 Fixed asset basis — — Operating lease liabilities (1,175 ) (2,431 ) Other — — Gross deferred tax liabilities (1,175 ) (2,431 ) Valuation allowance $ — $ — Net operating losses and tax credit carryforwards were as follows as of December 31, 2022 (dollars in thousands): Year Ended December 31, 2022 Amount Expiration Years Net operating losses, federal (starting from January 1, 2018) $ 75,730 Do Not Expire Net operating losses, state 3,195 2039 - 2042 Tax credits, federal 5,309 2041 - 2042 Tax credits, state 592 Do Not Expire Utilization of the net operating loss carryforwards and research credit carryforwards may be subject to an annual limitation due to the ownership percentage change limitations provided by the Internal Revenue Code, as amended, (“IRC”), and similar state provisions. Annual limitations may result in the expiration of the net operating losses and tax credit carryforwards before they are utilized. The Company did not perform an IRC Section 382 analysis and any previous ownership changes may result in a limitation that will reduce the total amount of net operating loss and tax credit carryforwards disclosed that can be utilized. Subsequent ownership changes may affect the limitation in future years. During the years ended December 31, 2022 and 2021, the Company recorded a full valuation allowance on federal and state deferred balances since management does not forecast the Company to be in a profitable position in the near future. Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2022 and 2021 related primarily to the increases in net operating loss carryforwards and research and development tax credit carryforwards and were as follows (in thousands): Year Ended December 31, 2022 2021 Valuation allowance at the beginning of the year $ 16,332 $ 2,414 Increases recorded to income tax provision 21,778 13,918 Valuation allowance at the end of the year $ 38,110 $ 16,332 The Company’s U.S. federal and state income tax returns are generally subject to tax examinations for the tax years from inception through December 31, 2021. There are currently no pending income tax examinations. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service and state tax authorities to the extent utilized in a future period. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Year Ended December 31, 2022 2021 Balance at beginning of year $ 1,407 $ — Additions based on tax positions related to current year 1,862 1,258 Increase (reduction) for prior period positions (568 ) 149 Unrecognized tax benefit-December 31 $ 2,701 $ 1,407 The entire amount of the unrecognized tax benefits would not impact the Company’s effective tax rate if recognized. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision. The Company has elected to include interest and penalties as a component of tax expense. During the years ended December 31, 2022 and 2021, the Company did not recognize accrued interest and penalties related to unrecognized tax benefits. The Company does not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease during the next 12 months.

Subsequent Events

Subsequent Events	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events Amendment to Lease Agreement and Sublease of Company’s Premises In October 2023, the Company entered into a sublease agreement (the “Sublease”) with Soleil Labs, LLC (“Tenant”) for certain premises constituting approximately 32,113 square feet of space in the building located at 233 E. Grand Avenue, South San Francisco, California (the “Premises”). The Company currently leases approximately square feet of office space in the Premises pursuant to a Lease dated as of December , (as amended, the “Master Lease”), by and between the Company and Bayside Area Development, LLC (the “Landlord”). The term of the Sublease commenced on October , and expires on December , . Pursuant to the Sublease, Tenant agrees to make rent payments directly to the Landlord in the amount of $ 183,044.10 per month for the first twelve months and $ 189,450.64 per month for the remainder of the Term. The rights and obligations of Tenant under the Sublease are subject to the terms of the Master Lease. On October 26, 2023, the Company also entered into a First Amendment to Lease with the Landlord (the “Lease Amendment”) to adjust the timeline for certain payments under the Master Lease and to effect the acceleration of the termination date of the Master Lease. The Lease Amendment provides that the Master Lease will terminate on December 31, 2024, and that the Landlord may further accelerate the termination date for the premises not subject to the Sublease by delivering written notice and paying the Company $20,000 per month for each month of further acceleration. At signing, the Company prepaid all remaining amounts payable during the term of the Master Lease (including the difference between the rent obligations due under the Master Lease and the rent to be paid by Tenant under the Sublease for the Premises), in an amount equal to $15.9 million, as well as a lease termination payment of approximately $20.8 million. Partial Lease and Assignment Agreement In addition, in November 2023, the Company entered into a sublease agreement with a third party for certain premises constituting approximately 15,212 square feet of space in the building located at 201 Haskins Way, South San Francisco, California (the “Subleased Haskins Premises”). The Company currently leases approximately 19,000 square feet of office space at the location of the Subleased Haskins Premises pursuant to a lease dated as of February 26, 2021 (as amended, the “ARE Master Lease”), by and between the Company and ARE-San	14. Subsequent Events In February 2023, we announced a workforce reduction plan (the “Plan”) intended to realign our investments to accelerate our growth strategy and further optimize our operations and cost structure. The Plan is expected to result in reductions to our headcount of approximately 50% during 2023. In connection with the Plan, we currently estimate that we will incur charges consisting primarily of cash termination benefits and other employee-related costs. We are continuing to evaluate the amount of these charges and expect that the majority of these charges will be recognized during the second quarter of 2023.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
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 (“U.S. GAAP”).	Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”).
Use of Estimates	Use of Estimates The preparation of condensed financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed financial statements, and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates estimates and assumptions, including but not limited to those related to the fair value of the marketable securities, stock-based compensation expense, accruals for research and development costs, lease assets and liabilities, the valuation of deferred tax assets, valuation of uncertain income tax positions, and impairment of long-lived assets. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates estimates and assumptions, including but not limited to those related to the fair value of the marketable securities, the fair value of redeemable convertible preferred stock and common stock, stock-based compensation expense, accruals for research and development costs, lease assets and liabilities, the valuation of deferred tax assets, and uncertain income tax positions. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates.
Concentration of Credit Risk		Concentration of Credit Risk Cash and cash equivalents are financial instruments that potentially subject the Company to concentrations of credit risk. Substantially all of the Company’s cash and cash equivalents are deposited in accounts with major financial institution and amounts may exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of the depository institution in which the cash and cash equivalents are held. The Company has not experienced any losses on deposits of cash and cash equivalents.
Risks And Uncertainties		Risks and Uncertainties The Company is subject to certain risks and uncertainties, including, but not limited to, changes in any of the following areas that the Company believes could have a material adverse effect on the future financial position or results of operations: the timing of, and the Company’s ability to advance its current and future product candidates into and through clinical development; costs and timelines associated with the manufacture of clinical supplies of the Company’s product candidates; regulatory approval and market acceptance of, and reimbursement for its product candidates; performance of third-party CROs and CMOs; competition from pharmaceutical companies with greater financial resources or expertise; protection of the intellectual property; litigation or claims against the Company based on intellectual property or other factors; and its ability to attract and retain employees necessary to support its growth. Disruption from CROs’, CMOs’ or suppliers’ operations would likely have a negative impact on the Company’s business, financial position and results of operations.
Segment and Geographical Information		Segment and Geographical Information The Company operates and manages its business as one reportable and operating segment. The chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. All of the Company’s long-lived assets are based in the United States.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with a maturity of three months or less at the date of purchase to be cash equivalents. As of September 30, 2023 and December 31, 2022, cash and cash equivalents consisted of cash, money market funds, and commercial paper.	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with a maturity of three months or less at the date of purchase to be cash equivalents. As of December 31, 2022 and 2021, cash and cash equivalents consisted of cash, money market funds, and commercial paper.
Restricted Cash	Restricted Cash Restricted cash of $1.7 million as of September 30, 2023 and December 31, 2022 represented security deposits in the form of letters of credit issued in connection with the lease of 233 E. Grand Ave, which was to be the company’s headquarters. A lease amendment was executed in October 2023, whereby the Company will have no further rent obligations to the landlord following the effective date, and the landlord will return the Company’s letter of credit within 60 days following the amendment’s effective date (Note 14). The letter of credit will be returned to the Company per the lease amendment.	Restricted Cash Restricted cash of $1.7 million as of December 31, 2022 and 2021 represented security deposits in the form of letters of credit issued in connection with the leases of the Company’s headquarters (Notes 6 and 8).
Marketable Securities	Marketable Securities The Company’s marketable securities are accounted for as available-for-sale The Company reviews its investment portfolio to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee and the Company’s intent and ability	Marketable Securities The Company’s marketable securities are accounted for as available-for-sale The Company reviews its investment portfolio to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value.
Fair Value Measurements		Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The carrying amounts of financial instruments, including restricted cash, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued expenses, and other liabilities, approximate fair value due to their short-term maturities
Property and Equipment Net		Property and Equipment, Net Property and equipment are recorded at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three
Operating Leases	Operating Leases The Company accounts for its operating leases by recording right-of-use Right-of-use	Leases Effective January 1, 2021, the Company adopted ASC Topic 842, Leases On January 27, 2021, the Company entered into a lease agreement for office and lab space in South San Francisco, CA that included two office suites. The lease terms for the office suites commenced in July and August 2021, respectively. Upon commencement of the leases, the Company recognized operating lease right-of-use On August 30, 2021, the Company entered into a service agreement with The Laboratory for Cell and Gene Medicine (“LCGM”) that included an embedded operating lease as the manufacturing suite in LCGM’s facility is designated for the Company’s exclusive use though April 30, 2023. Upon commencement of the agreement, the Company recognized operating lease right-of-use On November 10, 2021, the Company entered into a sublease agreement for office space in Brisbane, CA. The lease terms for the sublease commenced in December 2021. Upon commencement of the lease, the Company recognized operating lease right-of-use On November 17, 2021, the Company entered into a service agreement with Explora BioLabs, Inc (“Explora”) that included an embedded operating lease as the vivarium space is designated for the Company’s exclusive use through November 2023. Upon commencement of the lease, the Company recognized operating lease right-of-use The Company determines the initial classification and measurement of its right-of-use payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its incremental borrowing rate. The incremental borrowing rate is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment. Fixed lease expense for operating leases is recognized on a straight-line basis, unless the right-of-use For operating leases for which the right-of-use right-of-use For all leases, rent payments that are based on a fixed index or rate at the lease commencement date are included in the measurement of lease assets and lease liabilities at the lease commencement date. The Company has elected the practical expedient to not separate lease and non-lease non-lease
Asset Acquisitions		Asset Acquisitions The Company measures and recognizes asset acquisitions that are not deemed to be business combinations based on the cost to acquire the assets, which includes transaction costs. Goodwill is not recognized in asset acquisitions. In an asset acquisition, the cost allocated to acquire in-process
Impairment of Long-Lived Assets		Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparing the carrying amount to the future undiscounted net cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured as the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows generated by the assets. There have been no such impairments of long-lived assets in the years ended December 31, 2022 and 2021.
Research and Development Expenses		Research and Development Expenses Research and development costs are expensed as incurred. Research and development costs include salaries, stock-based compensation, and benefits for employees performing research and development activities, an allocation of facility and overhead expenses, expenses incurred under agreements with consultants, CMOs, CROs and investigative sites that conduct preclinical studies, other supplies and costs associated with product development efforts, preclinical activities, and regulatory operations.
Accrued Research and Development Expenses		Accrued Research and Development Expenses The Company has entered into various agreements with outsourced vendors, CROs and CMOs. Research and development accruals are estimated based on the level of services performed, progress of the studies, including the phase or completion of events, and contracted costs. The estimated costs of research and development services provided, but not yet invoiced, are included in accrued research costs on the balance sheets. If the actual timing of the performance of services or the level of effort varies from the original estimates, the Company will adjust the accrual accordingly. Payments made under these arrangements in advance of the performance of the related services are recorded as prepaid expenses and other current assets until the services are rendered. To date, there have been no material differences between estimates of such expenses and the amounts actually
Tax Credit Receivable		Tax Credit Receivable The Company is eligible for federal and California research and development credits for its research and development activities performed within the United States and California, respectively. The credits are, generally, available to offset federal and California income tax liabilities as applicable. The Company has applied $0.1 million of federal research and development credits to offset its federal payroll tax expenses as of the year ended December 31, 2022 due to its small business status. The Company is electing to utilize $0.3 million of current year R&D credit generated against the employer portion of the payroll tax.
Income Taxes		Income Taxes The Company accounts for income taxes using the asset and liability method. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. In evaluating the ability to recover deferred income tax assets, the Company considers all available positive and negative evidence, including operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction-by-jurisdiction Tax benefits related to uncertain tax positions are recognized when it is more likely than not that a tax position will be sustained during an audit. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax.
Stock-Based Compensation Expense		Stock-Based Compensation Expense The Company’s stock-based equity awards include restricted stock awards and stock options that are granted to employees and consultants that are accounted at fair value on the award grant date. Stock-based compensation expense is recognized over the awards’ vesting period on a straight-line basis and recorded as either research and development or general and administrative expenses in the statements of operations and comprehensive loss based on the function to which the related services are provided. Forfeitures are accounted for as they occur. As there was no public market for the Company’s common stock prior to the initial public offering of its common stock in June 2021, the estimated fair value of common stock was determined by the Company’s board of directors as of the date of each option grant, with input from management, considering third-party valuations of its common stock, as well as the Company’s board of directors’ assessment of additional objective and subjective factors that it believed were relevant, and which may have changed from the date of the most recent third-party valuation through the date of the grant. These third-party valuations were performed in accordance with the guidance outlined in the American Institute of Certified Public Accountants’ Accounting and Valuation Guide, Valuation of Privately Held Company Equity Securities Issued as Compensation. Following the closing of the initial public offering, the fair value of the Company’s common stock is determined based on the quoted market price of common stock. The Company also lacks company-specific historical and implied volatility information for its stock. The Company estimates its expected stock price volatility and expected term based on the historical volatility and expected term of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. There is no expected dividend yield since the Company
Employee Stock Purchase Plan		Employee Stock Purchase Plan The Company recognizes stock-based expense related to shares issued pursuant to its Employee Stock Purchase Plan on a straight-line basis over the offering period, which is typically 6 months. The first offering period commenced on June 25, 2021 and ended on November 30, 2021. The second, third, and fourth offering periods commenced on December 1, 2021, June 1, 2022, and December 1, 2022, respectively. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a 15 percent discount on the lower price of either (i) the offering period begin date or (ii) the purchase date. The Company estimates the fair value of shares to be issued under the ESPP using the Black-Scholes option-pricing model.
Comprehensive Loss		Comprehensive Loss Comprehensive loss is defined as the change in equity of a business during a period from transactions and other events and circumstances from non-owner
Net Loss Per Share		Net Loss Per Share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common stock outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, redeemable convertible preferred stock, common stock subject to repurchase, restricted common shares issued, and stock options are considered to be potentially dilutive securities. Basic and diluted net loss attributable to common stockholders per share is presented in conformity with the two-class
Recently Issued and Adopted Accounting Pronouncements	Recently Issued and Adopted Accounting Pronouncements The Company is a smaller reporting company and an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Under the JOBS Act, emerging growth companies can delay the adoption of new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. Thus, the Company has elected to use the extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that (i) the Company is no longer an emerging growth company or (ii) the Company affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. The Company may early adopt certain accounting standards, as the JOBS Act does not preclude an emerging growth company from adopting a new or revised accounting standard earlier than the time that such standard applies to private companies to the extent early adoption is permitted.	Adopted and Recent Accounting Pronouncements The Company is a smaller reporting company and an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Under the JOBS Act, emerging growth companies can delay the adoption of new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. Thus, the Company has elected to use the extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that (i) the Company is no longer an emerging growth company or (ii) the Company affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. However as described below, the Company early adopted certain accounting standards, as the JOBS Act does not preclude an emerging growth company from adopting a new or revised accounting standard earlier than the time that such standard applies to private companies to the extent early adoption is permitted Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Credit Losses available-for-sale available-for-sale In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) 815-40): 2020-06) if-converted
Unaudited Interim Condensed Financial Statements	Unaudited Interim Condensed Financial Statements The interim condensed balance sheet as of September 30, 2023 and the condensed statements of operations and comprehensive loss and stockholders’ equity for the three and nine months ended September 30, 2023 and 2022 and the condensed statements of cash flows for the nine months ended September 30, 2023 and 2022 are unaudited. The unaudited interim condensed financial statements have been prepared on the same basis as the annual financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair statement of the Company’s financial position as of September 30, 2023 and its results of operations for the three and nine months ended September 30, 2023 and cash flows for the nine months ended September 30, 2023 and 2022. The financial data and the other financial information disclosed in these notes to the financial statements related to the three and nine month periods are also unaudited. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results to be expected for the year ending December 31, 2023 or for any other future annual or interim period. The condensed balance sheet as of December 31, 2022 included herein was derived from the audited financial statements as of that date. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from these interim financial statements. These condensed financial statements should be read in conjunction with the Company’s audited financial statements and the related notes thereto for the year ended December 31, 2022, which are included in the Company’s Annual Report on Form 10-K
Significant Accounting Policies	Significant Accounting Policies The significant accounting policies used in preparation of these condensed financial statements for the three and nine months ended September 30, 2023 are consistent with those discussed in Note 2 to the condensed financial statements included in the Company’s Annual Report on Form 10-K
Principles of Consolidation	Principles of Consolidation The Company assesses entities for consolidation based on the specific facts and circumstances surrounding that entity. The Company first considers whether an entity is considered a variable interest entity (“VIE”) and therefore whether to apply the consolidation guidance under the VIE model. Entities that do not qualify as VIEs are assessed for consolidation as voting interest entities (“VOE”) under the voting interest model. An entity is considered to be a VIE if any of the following conditions exist: (i) the equity investment at risk is not sufficient to finance the activities of the entity without additional subordinated financial support, (ii) as a group, the holders of the equity investment at risk lack the power to direct the activities that most significantly impact the entity’s economic performance or the obligation to absorb the expected losses or right to receive the expected residual returns, and (iii) the voting rights of some holders of the equity investment at risk are disproportionate to their obligation to absorb losses or right to receive returns, and substantially all of the activities are conducted on behalf of the holder of equity investment at risk with disproportionately few voting rights. The Company consolidates all VIEs in which it is the primary beneficiary. An entity is determined to be the primary beneficiary if it holds a controlling financial interest in a VIE. The consolidation guidance requires an analysis to determine (i) whether an entity in which the Company holds a variable interest is a VIE and (ii) whether the Company’s involvement, through holding interest directly or indirectly in the entity or contractually through other variable interests, would give it a controlling financial interest. Performance of that analysis requires judgment.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments Measured at Fair Value on a Recurring Basis	The following tables set forth the financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy as of September 30, 2023 and December 31, 2022 (in thousands): September 30, 2023 Total Fair Value Level 1 Level 2 Level 3 Cash equivalents: Money market funds (1) $ 182,988 $ 182,988 $ — $ — Commercial paper (1) — — — — Total cash equivalents 182,988 182,988 — — Marketable securities: U.S. treasuries(2) 4,456 4,456 — — Commercial paper(2) 7,937 — 7,937 — U.S. agency securities(2) 36,626 — 36,626 — Asset-backed securities(2) 1,979 — 1,979 — Total marketable securities 50,998 4,456 46,542 — Total cash equivalents and marketable securities $ 233,986 $ 187,444 $ 46,542 $ — December 31, 2022 Total Fair Value Level 1 Level 2 Level 3 Cash equivalents: Money market funds (1) $ 45,739 $ 45,739 $ — $ — Commercial paper (1) 1,991 — 1,991 — Total cash equivalents 47,730 45,739 1,991 — Marketable securities: U.S. treasuries(2) 65,391 65,391 — — Commercial paper(2) 115,061 — 115,061 — U.S. agency securities(2) 53,455 — 53,455 — Asset-backed securities(2) 1,914 — 1,914 — Total marketable securities 235,821 65,391 170,430 — Total cash equivalents and marketable securities $ 283,551 $ 111,130 $ 172,421 $ — (1) Included within cash and cash equivalents on the condensed balance sheets. (2) non-current	The following tables set forth the financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy as of December 31, 2022 and 2021 (in thousands): December 31, 2022 Total Fair Value Level 1 Level 2 Level 3 Cash equivalents: Money market funds (1) $ 45,739 $ 45,739 $ — $ — Commercial paper (1) 1,991 — 1,991 — Total cash equivalents 47,730 45,739 1,991 — Marketable securities: U.S. treasuries 65,391 65,391 — — Commercial paper 115,061 — 115,061 — U.S. agency securities(2) 53,455 — 53,455 — Asset-backed securities(2) 1,914 — 1,914 — Total marketable securities 235,821 65,391 170,430 — Total cash equivalents and marketable securities $ 283,551 $ 111,130 $ 172,421 $ — December 31, 2021 Total Fair Value Level 1 Level 2 Level 3 Money market funds (1) $ 376,976 $ 376,976 $ — $ — (1) Included within cash and cash equivalents on the balance sheet.(2)Included within investments in marketable securities, current and investments in marketable securities, non-current

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Summary of Amortized Cost Gross Unrealized Holding Gains or Losses and Fair Value of Marketable Securities	All marketable securities were considered available-for-sale marketable September 30, 2023 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Available-for-sale U.S. treasuries $ 4,469 $ — $ (13 ) $ 4,456 Commercial paper 7,942 — (5 ) 7,937 U.S. agency securities 36,700 — (74 ) 36,626 Asset-backed securities 1,982 — (3 ) 1,979 Total available-for-sale $ 51,093 $ — $ (95 ) $ 50,998 December 31, 2022 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Available-for-sale U.S. treasuries $ 65,807 $ — $ (416 ) $ 65,391 Commercial paper 115,381 13 (333 ) 115,061 U.S. agency securities 53,767 15 (327 ) 53,455 Asset-backed securities 1,914 — — 1,914 Total available-for-sale $ 236,869 $ 28 $ (1,076 ) $ 235,821	December 31, 2022 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Available-for-sale U.S. treasuries $ 65,807 $ — $ (416 ) $ 65,391 Commercial paper 115,381 13 (333 ) 115,061 U.S. agency securities 53,767 15 (327 ) 53,455 Asset-backed securities 1,914 — — 1,914 Total available-for-sale $ 236,869 $ 28 $ (1,076 ) $ 235,821

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets as of September 30, 2023 and December 31, 2022 consisted of the following (in thousands): September 30, 2023 December 31, 2022 Advances to suppliers $ — $ 2,486 Prepaid insurance 1,227 1,343 Other prepaid expenses 3,550 3,307 Total prepaid expenses and other current assets $ 4,777 $ 7,136	Prepaid expenses and other current assets as of December 31, 2022 and 2021 consisted of the following (in thousands): December 31, 2022 December 31, 2021 Advances to suppliers $ 2,486 $ 1,834 Prepaid insurance 1,343 1,543 Other prepaid expenses 3,307 1,383 Total prepaid expenses and other current assets $ 7,136 $ 4,760
Summary of Property and Equipment, Net	Property and equipment, net as of September 30, 2023 and December 31, 2022 consisted of the following (in thousands): September 30, 2023 December 31, 2022 Furniture and fixtures $ 1,264 $ 321 Computers and network equipment — 251 Lab equipment — 12,521 Leasehold improvements 12,108 304 Construction-in-progress — 12,440 Total property and equipment 13,372 25,837 Less: accumulated depreciation (838 ) (3,207 ) Total property and equipment, net 12,534 22,630	Property and equipment, net as of December 31, 2022 and 2021 consisted of the following (in thousands): December 31, 2022 December 31, 2021 Furniture and fixtures $ 321 $ 3 Computers and network equipment 251 108 Lab equipment 12,521 6,680 Leasehold improvements 304 94 Construction-in-progress 12,440 477 Total property and equipment 25,837 7,362 Less: accumulated depreciation (3,207 ) (855 ) Total property and equipment, net $ 22,630 $ 6,507
Schedule of Accrued Expenses	Accrued expenses and other current liabilities as of September 30, 2023 and December 31, 2022 consisted of the following (in thousands): September 30, 2023 December 31, 2022 Professional fees $ 178 $ 367 Early exercise liability 34 150 Other accrued expenses 221 1,354 Accrued employee termination benefits 2,983 — Total accrued expenses and other current liabilities $ 3,416 $ 1,871	Accrued expenses as of December 31, 2022 and 2021 consisted of the following (in thousands): December 31, 2022 December 31, 2021 Professional fees $ 367 $ 186 Early exercise liability 150 337 Other accrued expenses 1,354 363 Total accrued expenses and other current liabilities $ 1,871 $ 886

Operating Leases (Tables)

Operating Leases (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Leases [Abstract]
Summary of Maturity of Operating Lease Liability	As of September 30, 2023, the future minimum lease payments for the Company’s operating leases for each of the years ending December 31 were as follows (in thousands): Amount 2023 (Remaining three months) $ 2,155 2024 9,177 2025 8,336 2026 8,223 2027 8,493 Thereafter 50,103 Total undiscounted lease payments 86,487 Present value adjustment (33,376 ) Total net lease liabilities $ 53,111	As of December 31, 2022, the future minimum lease payments for the Company’s operating leases for each of the years ending December 31 were as follows (in thousands): Amount 2023 $ 4,331 2024 1,468 2025 375 Thereafter — Total undiscounted lease payments 6,174 Present value adjustment (380 ) Total net lease liabilities $ 5,794
Summary of Supplemental Disclosure for Statement of Cash Flows Related to Operating Lease	The following information represents supplemental disclosure for the statement of cash flows related to the operating leases (in thousands): September 30, 2023 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows under operating leases $ 4,817	The following information represents supplemental disclosure for the statement of cash flows related to the operating leases (in thousands): December 31, 2022 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows under operating leases $ 6,172

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Equity [Abstract]
Schedule of Reserved Common Stock for Future Issuances	As of September 30, 2023 and December 31, 2022, the Company reserved common stock for future issuances as follows: September 30, 2023 December 31, 2022 Outstanding stock option awards 6,380,515 7,755,303 Shares available for future stock option grants 9,831,161 5,382,907 ESPP shares available for future grants 1,253,729 754,951 Total shares reserved for future issuance 17,465,405 13,893,161	As of December 31, 2022 and 2021, the Company reserved common stock for future issuances as follows: December 31, 2022 December 31, 2021 Outstanding stock option awards 7,755,303 5,056,743 Shares available for future stock option grants 5,382,907 4,454,004 ESPP shares available for future grants 754,951 524,106 Total shares reserved for future issuance 13,893,161 10,034,853

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Summary of Assumptions under Employee Stock Purchase Plan		Effective January 1, 2022, the number of shares of common stock available under the 2021 ESPP increased by 564,000 shares pursuant to the evergreen provision of the 2021 ESPP. Year Ended December 31, 2022 2021 Expected volatility 73.00% - 75.00 % 72.00% - 74.00 % Expected dividend yield 0 % 0 % Expected term (in years) 0.5 0.44 - 0.5 Risk-free interest rate 0.10% - 4.65 % 0.10% - 1.00 %
Summary of Assumptions under Black-Scholes Option Pricing Model to Estimate Stock-based Compensation Expense for Stock Option Awards		The Company used the Black-Scholes option pricing model to estimate stock-based compensation expense for stock option awards granted during the periods presented, with the following assumptions. Year Ended December 31, 2022 2021 Expected volatility 74.00% - 75.00 % 72.00% - 77.74 % Expected dividend yield 0 % 0 % Expected term (in years) 5.97 - 6.01 5.48 - 6.04 Risk-free interest rate 1.91% - 4.23 % 0.56% - 1.34 %
Summary of Option Activity	A summary of option activity under the 2020 Plan and the 2021 Plan during the nine months ended September 30, 2023 is as follows: Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2022 7,755,303 $ 8.47 8.67 $ 794 Options granted—2021 Plan 3,223,400 $ 2.22 Options exercised (65,414 ) $ 0.52 Options cancelled (4,532,774 ) $ 6.50 Outstanding as of September 30, 2023 6,380,515 $ 6.79 5.6 $ 695 Exercisable 4,231,849 $ 6.86 4.4 $ 472 Vested and expected to vest as of September 30, 2023 6,380,515 $ 6.79 5.6 $ 695	A summary of option activity under the 2020 Plan and the 2021 Plan during the year ended December 31, 2022 is as follows: Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2021 5,056,743 $ 8.77 9.2 $ 18,503 Options granted—2021 Plan 3,292,702 $ 7.91 Options exercised (67,196 ) $ 0.30 Options cancelled (526,946 ) $ 8.99 Outstanding as of December 31, 2022 7,755,303 $ 8.47 8.7 $ 794 Exercisable 2,330,389 $ 8.74 8.3 $ 388 Vested and expected to vest as of December 31, 2022 7,755,303 $ 8.47 8.7 $ 794
Components of Stock-based Compensation Expense	The following table presents the components of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Restricted stock awards and founders’ common stock awards $ 1 $ 2 $ 5 $ 6 ESPP 1 58 96 316 Stock options 2,159 3,150 8,168 9,590 Total stock-based compensation expense $ 2,161 $ 3,210 $ 8,269 $ 9,912	The following table presents the components of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands): Year Ended December 31, 2022 2021 Restricted stock awards and founders’ common stock awards $ 11 $ 9 ESPP 391 215 Stock options 13,132 7,647 Total stock-based compensation expense $ 13,534 $ 7,871
Classification of Stock-based Compensation Expense	The following table presents the classification of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Research and development expenses $ 37 $ 1,249 $ 1,904 $ 3,881 General and administrative expenses 2,124 1,961 6,365 6,031 Total stock-based compensation expense $ 2,161 $ 3,210 $ 8,269 $ 9,912	The following table presents the classification of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands): Year Ended December 31, 2022 2021 Research and development expenses $ 5,317 $ 2,685 General and administrative expenses 8,217 5,186 Total stock-based compensation expense $ 13,534 $ 7,871

Restructuring Activities (Table

Restructuring Activities (Tables)	9 Months Ended
	Sep. 30, 2023
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs [Table Text Block]	The following table summarizes the Company’s restructuring liability that is included in accrued expenses and other current liabilities in the accompanying condensed balance sheet: Nine Months Ended September 30, 2023 Accrued employee termination benefits beginning balance $ — Employee termination benefits charges incurred during the period 7,883 Amounts paid or otherwise settled during the period (4,900 ) Accrued employee termination benefits as of September 30, 2023 $ 2,983

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Earnings Per Share [Abstract]
Summary of Computation of Basic and Diluted Net Loss Per Share	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders, which excludes shares which are legally outstanding, but subject to repurchase by the Company (in thousands, except share and per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Numerator: Net loss $ (22,485 ) $ (24,682 ) $ (101,733 ) $ (76,453 ) Denominator: Weighted-average common shares outstanding 57,977,907 58,189,211 58,064,472 58,085,711 Less: weighted-average unvested restricted shares and shares subject to repurchase (720,666 ) (2,983,072 ) (1,315,477 ) (3,494,118 ) Weighted-average shares used to compute basic and diluted net loss per share attributable to common stockholders 57,257,241 55,206,139 56,748,995 54,591,593 Net loss per share attributable to common stockholders—basic and diluted: $ (0.39 ) $ (0.45 ) $ (1.79 ) $ (1.40 )	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders, which excludes shares which are legally outstanding, but subject to repurchase by the Company (in thousands, except share and per share amounts): Year Ended December 31, 2022 2021 Numerator: Net loss $ (101,052 ) $ (70,760 ) Denominator: Weighted-average common shares outstanding 58,111,437 35,121,114 Less: weighted-average unvested restricted shares and shares subject to repurchase (3,237,762 ) (6,201,859 ) Weighted-average shares used to compute basic and diluted net loss per share attributable to common stockholders 54,873,675 28,919,255 Net loss per share attributable to common stockholders—basic and diluted: $ (1.84 ) $ (2.45 )
Schedule of Anti-dilutive Outstanding Shares or Equivalents	The following outstanding options, unvested shares, and ESPP shares were excluded (as common stock equivalents) from the computation of diluted net loss per common share for the periods presented as their effect would have been anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Options to purchase common stock 6,380,515 7,849,590 6,380,515 7,849,590 Common stock subject to vesting or repurchase 873,062 3,236,152 873,062 3,236,152 Employee Stock Purchase Plan shares 10,437 128,888 10,437 128,888 Total 7,264,014 11,214,630 7,264,014 11,214,630	The following outstanding options, unvested shares, and ESPP shares were excluded (as common stock equivalents) from the computation of diluted net loss per common share for the periods presented as their effect would have been antidilutive (in thousands): Year Ended December 31, 2022 2021 Options to purchase common stock 7,755,303 5,056,743 Common stock subject to vesting or repurchase 2,767,526 4,774,798 Employee Stock Purchase Plan shares 168,080 99,252 Total 10,690,909 9,930,793

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Summary of Reconciliation of U.S. Federal Statutory Income Tax Rate to Company's Effective Income Tax Rate	A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate was as follows: Year Ended December 31, 2022 2021 Federal statutory income tax rate ate 21.00 % 21.00 % State taxes 1.10 1.94 Others (0.69 ) (0.26 ) Research and development credits 1.11 1.01 Cancellation of debt income — — Tranche liability — (3.06 ) Interest expense — — Stock-based compensation (0.97 ) (0.96 ) Change in valuation allowance (21.55 ) (19.67 ) Provision for taxes 0.00 % 0.00 %
Summary of Net Deferred Tax Assets and Liabilities	Net deferred tax assets and liabilities consisted of the following (in thousands): Year Ended December 31, 2022 2021 Deferred tax assets: Net operating losses—non-current $ 15,940 $ 12,006 Capitalized R&D 13,815 — General business credit—non-current 5,699 2,682 Operating lease right-of-use 1,220 2,368 Stock based compensation 1,703 784 Accruals and reserves 735 525 Fixed assets 170 396 Other 3 2 Gross deferred tax assets 39,285 18,763 Valuation allowance (38,110 ) (16,332 ) Net deferred tax assets 1,175 2,431 Fixed asset basis — — Operating lease liabilities (1,175 ) (2,431 ) Other — — Gross deferred tax liabilities (1,175 ) (2,431 ) Valuation allowance $ — $ —
Summary of Net Operating Losses and Tax Credit Carryforwards	Net operating losses and tax credit carryforwards were as follows as of December 31, 2022 (dollars in thousands): Year Ended December 31, 2022 Amount Expiration Years Net operating losses, federal (starting from January 1, 2018) $ 75,730 Do Not Expire Net operating losses, state 3,195 2039 - 2042 Tax credits, federal 5,309 2041 - 2042 Tax credits, state 592 Do Not Expire
Changes in Valuation Allowance for Deferred Tax Assets	During the years ended December 31, 2022 and 2021, the Company recorded a full valuation allowance on federal and state deferred balances since management does not forecast the Company to be in a profitable position in the near future. Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2022 and 2021 related primarily to the increases in net operating loss carryforwards and research and development tax credit carryforwards and were as follows (in thousands): Year Ended December 31, 2022 2021 Valuation allowance at the beginning of the year $ 16,332 $ 2,414 Increases recorded to income tax provision 21,778 13,918 Valuation allowance at the end of the year $ 38,110 $ 16,332
Summary of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Year Ended December 31, 2022 2021 Balance at beginning of year $ 1,407 $ — Additions based on tax positions related to current year 1,862 1,258 Increase (reduction) for prior period positions (568 ) 149 Unrecognized tax benefit-December 31 $ 2,701 $ 1,407

Description of Business, Orga_2

Description of Business, Organization and Liquidity - Additional Information (Details) $ / shares in Units, $ in Thousands						2 Months Ended	3 Months Ended						9 Months Ended		12 Months Ended
	Jul. 21, 2022 USD ($)	Jul. 02, 2021 $ / shares shares	Jun. 29, 2021 $ / shares shares	Jun. 28, 2021 shares	Jun. 21, 2021	Jul. 31, 2021 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) shares	Jun. 30, 2020 $ / shares
Description Of Business Organization And Liquidity Disclosure [Line Items]
Public offering price per share | $ / shares																	$ 1
Net proceeds from initial public offering															$ 0	$ 251,323
IPO closed date															Jun. 29, 2021
Net loss							$ 22,485	$ 55,314	$ 23,934	$ 24,682	$ 25,936	$ 25,835	$ 101,733	$ 76,453	$ 101,052	70,760
Net cash flows from operating activities													44,130	$ 65,551	87,980	52,852
Accumulated deficit							344,136						344,136		242,403	$ 141,351
Existing cash, cash equivalents, and marketable securities							$ 234,000						$ 234,000		$ 283,600
Initial Public Offering
Description Of Business Organization And Liquidity Disclosure [Line Items]
Net proceeds from initial public offering	$ 300,000
Common Stock
Description Of Business Organization And Liquidity Disclosure [Line Items]
Reverse stock split, description															On June 18, 2021, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse stock split of the Company’s issued and outstanding common stock at a 1 for 2.432 ratio, which was effected on June 21, 2021.
Stock split, conversion ratio					0.000002432
Offering costs	$ 75,000
Conversion of stock | shares				30,761,676
Common Stock | Initial Public Offering
Description Of Business Organization And Liquidity Disclosure [Line Items]
Issuance of common stock, Shares | shares		2,100,000	14,000,000													16,100,000
Public offering price per share | $ / shares		$ 17	$ 17
Net proceeds from initial public offering						$ 251,300
Underwriting discounts and commissions						19,100
Offering costs						$ 3,200
Conversion of stock | shares				30,761,676
Common Stock | Underwriters
Description Of Business Organization And Liquidity Disclosure [Line Items]
Issuance of common stock, Shares | shares		2,100,000	2,100,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands		9 Months Ended	12 Months Ended
	Jan. 27, 2021 OfficeSuite	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($) OfficeSuite Segment	Dec. 31, 2021 USD ($)	Nov. 17, 2021 USD ($)	Aug. 30, 2021 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segments | Segment			1
Restricted cash		$ 1,700	$ 1,700
Operating lease right-of-use assets		13,195	5,580	$ 11,574
Operating lease liability		53,111	5,794
Impairment of long lived assets			0	$ 0
Research and development credits to offset payroll tax expenses			100
Research and development credit generated against employer portion payroll tax			$ 300
ESPP
Summary Of Significant Accounting Policies [Line Items]
Offering period commenced date			Jun. 25, 2021
Offering period end date			Nov. 30, 2021
Offering period term of contract			6 months
Common stock, percent			15%
Offering period description terms			The second, third, and fourth offering periods commenced on December 1, 2021, June 1, 2022, and December 1, 2022, respectively.
Lease Agreement
Summary Of Significant Accounting Policies [Line Items]
Number of office suites | OfficeSuite	2
Operating lease right-of-use assets		13,200	$ 4,200
Operating lease liability		$ 53,100	$ 4,500
Maximum
Summary Of Significant Accounting Policies [Line Items]
Liquid investments maturity period		3 months	3 months
Property and equipment estimated useful life			5 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			3 years
Accounting Standards Update 2016-02 | Lease Agreement
Summary Of Significant Accounting Policies [Line Items]
Number of office suites | OfficeSuite			2
Operating lease right-of-use assets			$ 4,100
Operating lease liability			4,100
Accounting Standards Update 2016-02 | Service Agreement
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets					$ 600	$ 5,300
Operating lease liability					$ 600	$ 5,300
Accounting Standards Update 2016-02 | Sublease Agreement
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets			3,200
Operating lease liability			$ 3,200
Accounting Standards Update 2016-13
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]			true
Change in Accounting Principle, Accounting Standards Update, Adoption Date			Jan. 01, 2022
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]			true

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands		Sep. 30, 2023		Dec. 31, 2022		Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		$ 50,998		$ 235,821
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents		182,988		45,739
Marketable securities		4,456		65,391
Total financial assets		187,444		111,130
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents		0		1,991
Marketable securities		46,542		170,430
Total financial assets		46,542		172,421
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents		0		0
Marketable securities		0		0
Total financial assets		0		0
Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents		182,988		47,730
Marketable securities		50,998		235,821
Total financial assets		233,986		283,551
U.S. Treasuries
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		4,456		65,391
U.S. Treasuries | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[1]	4,456		65,391
U.S. Treasuries | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[1]	0		0
U.S. Treasuries | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[1]	0		0
U.S. Treasuries | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[1]	4,456		65,391
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		7,937		115,061
Commercial Paper | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	[2]	0		0	[3]
Marketable securities	[1]	0		0
Commercial Paper | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	[2]	0		1,991	[3]
Marketable securities	[1]	7,937		115,061
Commercial Paper | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	[2]	0		0	[3]
Marketable securities	[1]	0		0
Commercial Paper | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	[2]	0		1,991	[3]
Marketable securities	[1]	7,937		115,061
U.S. agency securities | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[4]			0
U.S. agency securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[4]			53,455
U.S. agency securities | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[4]			0
U.S. agency securities | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[4]			53,455
Asset Backed Securities Member
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		1,979		1,914
Asset Backed Securities Member | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		0	[1]	0	[4]
Asset Backed Securities Member | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		1,979	[1]	1,914	[4]
Asset Backed Securities Member | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		0	[1]	0	[4]
Asset Backed Securities Member | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		1,979	[1]	1,914	[4]
Money Market Funds | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	[2]	182,988		45,739
Money Market Funds | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents		0	[2]	0	[2],[3]	$ 0	[3]
Money Market Funds | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents		0	[2]	0	[2],[3]	0	[3]
Money Market Funds | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents		182,988	[2]	45,739	[2],[3]	376,976	[3]
Money Market Funds | Fair Value, Recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	[3]			45,739		$ 376,976
U.S. agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		36,626		53,455
U.S. agency securities | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[1]	0		0
U.S. agency securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[1]	36,626		53,455
U.S. agency securities | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[1]	0		0
U.S. agency securities | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	[1]	$ 36,626		$ 53,455
[1]Included within investments in marketable securities, current and investments in marketable securities, non-current on the condensed balance sheets.[2]Included within cash and cash equivalents on the condensed balance sheets.[3]Included within cash and cash equivalents on the balance sheet.[4]Included within investments in marketable securities, current and investments in marketable securities, non-current on the balance sheet.

Marketable Securities - Summary

Marketable Securities - Summary of Amortized Cost Gross Unrealized Holding Gains or Losses, and Fair Value of Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	$ 51,093	$ 236,869
Unrealized Gains	0	28
Unrealized Losses	(95)	(1,076)
Marketable securities	50,998	235,821
U.S. Treasuries
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	4,469	65,807
Unrealized Gains	0	0
Unrealized Losses	(13)	(416)
Marketable securities	4,456	65,391
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	7,942	115,381
Unrealized Gains	0	13
Unrealized Losses	(5)	(333)
Marketable securities	7,937	115,061
Asset Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	1,982	1,914
Unrealized Gains	0	0
Unrealized Losses	(3)	0
Marketable securities	1,979	1,914
U.S. agency securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	36,700	53,767
Unrealized Gains	0	15
Unrealized Losses	(74)	(327)
Marketable securities	$ 36,626	$ 53,455

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Dec. 31, 2021	Dec. 31, 2022
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Aggregate fair value of unrealized loss positions less than one year	$ 51,000	$ 51,000		$ 220,500
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer				15,300
Investments with credit losses	0	0		$ 0
Realized gains or losses recognized	0	0	$ 0
Reclassification out of Accumulated Other Comprehensive Gain (Loss)
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Available-for-sale, reclassifications out of accumulated other comprehensive gain (loss)	$ 0	$ 0	$ 0

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Prepaid Expense and Other Assets, Current [Abstract]
Advances to suppliers	$ 0	$ 2,486	$ 1,834
Prepaid insurance	1,227	1,343	1,543
Other prepaid expenses	3,550	3,307	1,383
Total prepaid expenses and other current assets	$ 4,777	$ 7,136	$ 4,760

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Total property and equipment	$ 13,372	$ 25,837	$ 7,362
Less: accumulated depreciation	(838)	(3,207)	(855)
Total property and equipment, net	12,534	22,630	6,507
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	1,264	321	3
Computers and Network Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	0	251	108
Lab Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	0	12,521	6,680
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	12,108	304	94
Construction in Progress
Property Plant And Equipment [Line Items]
Total property and equipment	$ 0	$ 12,440	$ 477

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation	$ 0.8	$ 0.7	$ 2.3	$ 1.7	$ 2.4	$ 0.7

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Accrued Liabilities and Other Liabilities [Abstract]
Professional fees	$ 178	$ 367	$ 186
Early exercise liability	34	150	337
Other accrued expenses	221	1,354	363
Accrued employee termination benefits	2,983	0
Total accrued expenses and other current liabilities	$ 3,416	$ 1,871	$ 886

Significant Agreements - Additi

Significant Agreements - Additional Information (Details)								1 Months Ended			3 Months Ended			9 Months Ended		12 Months Ended
	Aug. 04, 2023	Aug. 01, 2023 USD ($)	Dec. 16, 2021 USD ($)	Dec. 16, 2021 USD ($) ft²	Dec. 16, 2021 USD ($) OfficeSuite	Jun. 18, 2021 shares	Jun. 07, 2021 USD ($)	Apr. 30, 2021 USD ($)	Jan. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares	Sep. 30, 2023 USD ($) shares	Jun. 30, 2023 shares	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) shares	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares	May 07, 2021 shares
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock, shares, issued | shares											57,971,910			57,971,910		58,221,760	58,010,823
Research and development											$ 2,384,000		$ 18,302,000	$ 32,136,000	$ 54,325,000	$ 72,787,000	$ 37,932,000
General and administrative											11,294,000		7,852,000	26,372,000	24,563,000	32,852,000	22,511,000
Option agreement fees paid														0
Options fee														0
Future minimum lease payments											86,487,000			86,487,000		6,174,000
Operating lease liability											53,111,000			53,111,000		5,794,000
Contingencies Recorded
Common Stock
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock shares, repurchase | shares												152,694
Stanford Exclusive License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront license fees received										$ 50,000
Common stock, shares, issued | shares										640,861								640,861	640,861
Common stock additional paid in capital										$ 2,800,000								$ 2,800,000
Purchase of shares in private financings percentage										10%
Common stock shares, repurchase | shares						624,845
Research and development																		2,800,000
General and administrative																		200,000
Annual maintenance fees														0
First commercial sale																		50,000
Subsequent year commercial sale																		200,000
Maximum future development and regulatory milestone payments																5,300,000
Sale-based milestone payments																7,500,000
Milestone payments																0
License execution fee																	$ 0
Maximum future development and regulatory milestones payments														5,300,000
Sale-based milestones payments														7,500,000
Stanford Exclusive License Agreement | Patents Fees Member
Research And Development Arrangement Contract To Perform For Others [Line Items]
General and administrative														0
Annual maintenance fees											0
Stanford Exclusive License Agreement | First Year
Research And Development Arrangement Contract To Perform For Others [Line Items]
Annual maintenance fees																		5,000
Stanford Exclusive License Agreement | Second Year
Research And Development Arrangement Contract To Perform For Others [Line Items]
Annual maintenance fees																		10,000
Stanford Exclusive License Agreement | Third Year
Research And Development Arrangement Contract To Perform For Others [Line Items]
Annual maintenance fees																		10,000
Stanford Exclusive License Agreement | Fourth Year
Research And Development Arrangement Contract To Perform For Others [Line Items]
Annual maintenance fees																		25,000
Stanford Exclusive License Agreement | Fifth Year
Research And Development Arrangement Contract To Perform For Others [Line Items]
Annual maintenance fees																		25,000
Stanford Exclusive License Agreement | Sixth Year
Research And Development Arrangement Contract To Perform For Others [Line Items]
Annual maintenance fees																		$ 25,000
License Agreement with Stanford | Common Stock
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock shares, repurchase | shares						624,845											(624,845)
First Option Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock, shares, issued | shares									132,137
License execution fee									$ 10,000
Option agreement expiration term									18 months
Second Option Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Annual maintenance fees																10,000
Options fee								$ 30,000
LCGM Service Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development													1,700,000	1,100,000	4,500,000	6,100,000	$ 2,700,000
IDT License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development											0			0		0	3,000,000
Milestone payments											0		0	0	0	0	0
Option agreement fees paid														0
Exercise fee							$ 500,000
Upfront payment							3,000,000
Milestones probable											0		$ 0	0	$ 0
IDT License Agreement | Research and Development Expenses
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total consideration																	3,000,000
IDT License Agreement | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront payment							5,300,000
IDT License Agreement | Beta Thalassemia and Lysosomal Storage Disorders Fields
Research And Development Arrangement Contract To Perform For Others [Line Items]
Exercise fee							1,000,000
Upfront payment							$ 8,800,000
Bayside Lease
Research And Development Arrangement Contract To Perform For Others [Line Items]
Tenant improvement allowance														14,900,000		14,900,000
Milestones probable																0	0
Lease commencement date			Sep. 15, 2023
Office and Laboratory Space				85,165	85,165
Lease term			120 months	120 months	120 months
Security deposit																1,600,000	1,600,000
Future minimum lease payments			$ 81,000,000	$ 81,000,000	$ 81,000,000
Term of contract			10 years	10 years	10 years
Operating lease liability											32,000,000			32,000,000		0	$ 0
Tenant Improvements											12,200,000			12,200,000		$ 12,200,000
Asset Purchase Agreement (APA)
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone payments		$ 1,000,000
Exchange Amount Of Asset		500,000												500,000
Loss on Disposal Other Income														100,000
Contingencies Recorded											$ 0			0
Reimbursement of Research and Development Amount		$ 600,000												$ 600,000
LOA to Acquire Nula-Cel Assets
Research And Development Arrangement Contract To Perform For Others [Line Items]
Equity Interest Outstanding Shares	20%
LOA to Acquire Nula-Cel Assets | License And Option Agreement [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Equity Interset	20%										20%			20%

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Accrued termination and cancellation charges	$ 0	$ 0
Royalty payment due	$ 0	$ 0

Operating Leases - Additional I

Operating Leases - Additional Information (Details) $ in Thousands							3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 16, 2021 OfficeSuite	Dec. 16, 2021 ft²	Nov. 17, 2021 USD ($)	Nov. 10, 2021	May 10, 2021 USD ($)	Jan. 27, 2021 OfficeSuite	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Aug. 31, 2023 USD ($)	Aug. 01, 2023 USD ($)
Lessee Lease Description [Line Items]
Term of contract											1 year
Lessee, operating lease, option to extend											The original term of the lease was from May 11, 2020 to June 30, 2021 with an option to renew. In March 2021, the Company entered into an amendment to the lease agreement and extended the term of the lease to September 30, 2021.
Operating lease right-of-use assets							$ 13,195		$ 13,195		$ 5,580	$ 11,574
Operating lease liability							53,111		53,111		5,794
Current portions of operating lease liability							3,439		3,439		4,045	5,482
Non-current portions of operating lease liability							$ 49,672		$ 49,672		$ 1,749	5,794
Remaining lease term on operating leases							110 months		110 months		19 months
Weighted average incremental borrowing rate on operating lease							10.90%		10.90%		8.50%
Lease expense							$ 2,400	$ 1,700	$ 6,400	$ 5,000	$ 6,700	1,900
Variable lease payments							800	$ 300	1,800	$ 1,000	1,300	200
Explora BioLabs, Inc
Lessee Lease Description [Line Items]
Operating lease right-of-use assets											1,400
Operating lease liability							0		$ 0		$ 1,200
Lease Agreement
Lessee Lease Description [Line Items]
Lessee, operating lease, option to extend									The term of the lease is 44 months for the first office suite and 43 months for the second office suite with an option to extend the term for an additional two years on the same terms and conditions.		the first office suite and 43 months for the second office suite with an option to extend the term for an additional two years on the same terms and conditions.
Number of office suites | OfficeSuite						2
Operating lease right-of-use assets							13,200		$ 13,200		$ 4,200
Operating lease liability							53,100		$ 53,100		4,500
First Office Suite
Lessee Lease Description [Line Items]
Operating lease commencement date				Nov. 10, 2021		Jul. 31, 2021
Sublease expire date				Dec. 06, 2023
Second Office Suite
Lessee Lease Description [Line Items]
Operating lease commencement date						Aug. 31, 2021
Embedded Lease Agreement | Laboratory For Cell And Gene Medicine
Lessee Lease Description [Line Items]
Finance lease maturity date					Apr. 30, 2023
Fixed lease payments					$ 5,600
License Service Agreement and Master Services Agreement | Explora BioLabs, Inc
Lessee Lease Description [Line Items]
Finance lease maturity date			Nov. 30, 2023
Fixed lease payments			$ 700
Bayside Lease [Member]
Lessee Lease Description [Line Items]
Term of contract	120 months	120 months											20 months	20 months
Lessee, operating lease, option to extend									The term of the lease is 120 months with the option to extend the term up to an additional ten years.
Operating lease liability							32,000		$ 32,000		0	$ 0
Office And Laboratory Space	85,165	85,165
Leasehold improvements							27,200		27,200
Leasehold tenant improvement allowance									14,900		$ 14,900
Leasehold improvements liability utilized and recorded							14,900		$ 14,900
Sublease payments													$ 500	$ 500
Sublease Income							$ 100

Operating Leases - Summary of M

Operating Leases - Summary of Maturity of Operating Lease Liability (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Leases [Abstract]
2023 (Remaining three months)	$ 2,155
2024	9,177
2025\2023	8,336	$ 4,331
2026/2024	8,223	1,468
2027\2025	8,493	375
Thereafter	50,103
Total undiscounted lease payments	86,487	6,174
Present value adjustment	(33,376)	(380)
Total net lease liabilities	$ 53,111	$ 5,794

Operating Leases - Summary of S

Operating Leases - Summary of Supplemental Disclosure for Statement of Cash Flows Related to Operating Lease (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Leases [Abstract]
Operating cash flows under operating leases	$ 4,817	$ 6,172

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock - Additional Information (Details)			1 Months Ended			12 Months Ended
	Jun. 28, 2021 USD ($) shares	Feb. 28, 2021 USD ($) shares	Mar. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) Tranche shares	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) Tranche shares
Redeemable Convertible Preferred Stock [Line Items]
Redeemable convertible preferred stock reclassified to equity	$ 260,500,000
Temporary equity, shares issued | shares					10,000,000
Preferred stock value, per share | $ / shares					$ 1
Gross proceeds from issuance of convertible preferred stock					$ 10,000,000	$ 0	$ 165,521,000
Preferred stock additional shares issued | shares					30,000,000
Series A Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock [Line Items]
Preferred stock value, per share | $ / shares					$ 1
Preferred stock shares issued upon conversion of outstanding convertible notes and accrued interest | shares					5,019,949
Minimum percentage of preferred stock milestone achievement approval or waiver					75%
Number of tranches | Tranche				2				2
Estimated fair value liability					$ 3,300,000
Stock issuance costs							4,000	$ 200,000
Series A Redeemable Convertible Preferred Stock | Tranche One
Redeemable Convertible Preferred Stock [Line Items]
Gross proceeds from issuance of convertible preferred stock					$ 15,000,000
Series A Redeemable Convertible Preferred Stock | Tranche Two
Redeemable Convertible Preferred Stock [Line Items]
Gross proceeds from issuance of convertible preferred stock				$ 15,000,000
Preferred stock additional shares issued | shares				15,000,000				15,000,000
Remeasured fair value liability upon settlement				$ 29,100,000
Series A Redeemable Convertible Preferred Stock | Tranche Three
Redeemable Convertible Preferred Stock [Line Items]
Gross proceeds from issuance of convertible preferred stock		$ 15,000,000
Preferred stock additional shares issued | shares		15,000,000
Stock issuance costs							4,000
Remeasured fair value reported in current liability				$ 29,100,000				$ 29,100,000
Fair value, changes in fair value other loss		$ 10,300,000						$ 54,800,000
Remaining remeasured fair value liability		$ 39,400,000
Series B Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock [Line Items]
Conversion of stock | shares			29,792,487
Preferred stock value, per share | $ / shares			$ 5.06
Gross proceeds from issuance of convertible preferred stock			$ 150,700,000
Stock issuance costs			$ 200,000				$ 226,000
Common Stock
Redeemable Convertible Preferred Stock [Line Items]
Conversion of stock | shares	30,761,676

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - $ / shares

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

Jul. 02, 2021

Jun. 29, 2021

Jun. 28, 2021

Jun. 18, 2021

Jun. 30, 2021

Jun. 30, 2020

Mar. 31, 2020

Jun. 30, 2023

Sep. 30, 2023

Dec. 31, 2022

Dec. 31, 2021

May 07, 2021

Dec. 31, 2020

Apr. 30, 2020

Class Of Stock [Line Items]

Common stock, shares authorized

300,000,000

300,000,000

300,000,000

Common stock, par or stated value per share

$ 0.00001

$ 0.00001

$ 0.00001

Common stock voting rights

one

one

Public offering price per share

$ 1

Common stock, shares, issued

57,971,910

58,221,760

58,010,823

Vesting period description

The shares of the Company’s common stock issued to its founders for their services as an employee, advisor, or consultant vest monthly over four years with one year cliff from the vesting commencement date.

The shares of the Company’s common stock issued to its founders for their services as an employee, advisor, or consultant vest monthly over four years with one year cliff from the vesting commencement date.

Aggregate Common Stock Vested

912,212

Diluted number of shares

7,273,848

Stanford Exclusive License Agreement

Class Of Stock [Line Items]

Common stock, shares, issued

640,861

640,861

Common stock shares, repurchase

624,845

Remaining shares not exercised right to purchase

16,016

16,016

Number of Common stock shares, repurchase

624,845

Founder

Class Of Stock [Line Items]

Common stock nonvested number of shares

647,803

1,938,430

3,230,746

Common stock awards were unvested and expected to vest

8 months 12 days

1 year 6 months

2 years 6 months

Common stock shares, repurchase

152,694

Number of Common stock shares, repurchase

152,694

Founder | Restricted Common Stock

Class Of Stock [Line Items]

Public offering price per share

$ 0.00002

Common stock, shares, issued

6,081,413

Investor | Restricted Common Stock

Class Of Stock [Line Items]

Public offering price per share

$ 0.00002

Common stock, shares, issued

2,467,104

Common Stock

Class Of Stock [Line Items]

Conversion of stock

30,761,676

Common stock shares, repurchase

152,694

Number of Common stock shares, repurchase

152,694

Common Stock | IPO [Member]

Class Of Stock [Line Items]

Conversion of stock

30,761,676

Issuance of common stock, Shares

2,100,000

14,000,000

16,100,000

Public offering price per share

$ 17

$ 17

Common Stock | Underwriters

Class Of Stock [Line Items]

Issuance of common stock, Shares

2,100,000

2,100,000

Redeemable Convertible Preferred Stock | IPO [Member]

Class Of Stock [Line Items]

Conversion of stock

30,761,676

Common Stock - Schedule of Rese

Common Stock - Schedule of Reserved Common Stock for Future Issuances (Details) - shares	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Shares reserved for future issuance	17,465,405	13,893,161	10,034,853
Outstanding Stock Option Awards
Class Of Stock [Line Items]
Shares reserved for future issuance	6,380,515	7,755,303	5,056,743
Shares Available for Future Stock Option Grants
Class Of Stock [Line Items]
Shares reserved for future issuance	9,831,161	5,382,907	4,454,004
ESPP Shares Available for Future Grants
Class Of Stock [Line Items]
Shares reserved for future issuance	1,253,729	754,951	524,106

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Details) - USD ($)			3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 01, 2023	Jan. 01, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance			17,465,405		17,465,405		13,893,161	10,034,853
Increase in shares available for issuance		564,000
Early exercise of stock options repurchase right lapse period					180 days		180 days
Weighted-average grant date fair value of options granted			$ 1.89		$ 1.56		$ 5.21
Intrinsic value of the stock options exercised			$ 10,367		$ 65,414		$ 200,000	$ 5,000,000
Stock Issued During Period Shares Stock Options Exercised And Repurchased			26,188	73,735	216,656	124,448	189,414	138,596
Shares remained subject to the right of repurchase as a result of the early exercised stock options			111,600		111,600		554,695	1,195,631
Remaining liability related to early exercised shares							$ 100,000	$ 300,000
Stock-based compensation expense			$ 2,161,000	$ 3,210,000	$ 8,269,000	$ 9,912,000	$ 13,534,000	$ 7,871,000
Shares issued			57,971,910		57,971,910		58,221,760	58,010,823
Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense							$ 30,500,000
Unrecognized stock-based compensation expense, expected to be recognized period							3 years 3 months 18 days
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance							564,000
Percentage of lower of the fair market value of common stock at the beginning of the offering period or at the end of each applicable purchase period							85%
Accrued liabilities							$ 100,000
Shares issued			65,222	207,137	65,222	207,137
Maximum | 2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of eligible compensation to purchase shares of the Company's common stock at a discount through payroll deductions							15%
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock vesting period									4 years
Restricted stock awards granted					0	0	0	0
Share-based compensation, liabilities for restricted stock awards, cancelled			1,542	5,140	11,136	5,140	5,140	0
Share-based compensation, liabilities for restricted stock awards, vested					703,035		553,443	345,966
Outstanding Stock Option Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense			$ 2,159,000	$ 3,150,000	$ 8,168,000	$ 9,590,000	$ 13,132,000	$ 7,647,000
Unrecognized stock-based compensation expense			9,900,000		$ 9,900,000		$ 31,000,000
Unrecognized stock-based compensation expense, expected to be recognized period					1 year 10 months 24 days		2 years 7 months 6 days
Outstanding Stock Option Awards | Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense							$ 2.2	$ 300,000
Outstanding Stock Option Awards | Non Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense			$ 400,000	$ 800,000	$ 1,100,000	$ 900,000
2020 Stock Option and Grant Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, granted period							10 years
Share based compensation arrangement by share based payment award, exercise price percentage							10%
Common stock vesting period							4 years
2020 Stock Option and Grant Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage							100%
2020 Stock Option and Grant Plan | Stock Option Grant to 10.0% Stockholder
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock vesting period							5 years
2020 Stock Option and Grant Plan | Stock Option Grant to 10.0% Stockholder | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage							110%
2020 Stock Option and Grant Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock awards granted									832,983
2021 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, granted period							10 years
Common stock vesting period					4 years		4 years
Shares reserved for future issuance			5,636,000		5,636,000		5,636,000
Shares reserved and available for issuance							5%
Increase in shares available for issuance		2,900,541			9,831,161		5,382,907
Grant date fair value of year one							$ 1,000,000
Grant date fair value of year thereafter					$ 750,000		$ 750,000
Percentage of lower of the fair market value of common stock at the beginning of the offering period or at the end of each applicable purchase period					85%
Grant date fair value of year one					$ 1,000,000
ESPP compensation expenses					$ 25,000,000
2021 Stock Option and Incentive Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage					100%		100%
2020 Stock Option and Grant Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, granted period					10 years
Share based compensation arrangement by share based payment award, exercise price percentage					10%
Common stock vesting period					4 years
Shares reserved and available for issuance					5%
2020 Stock Option and Grant Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage					100%
2020 Stock Option and Grant Plan | Stock Option Grant to 10.0% Stockholder
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock vesting period					5 years
2020 Stock Option and Grant Plan | Stock Option Grant to 10.0% Stockholder | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage					110%
2020 Stock Option and Grant Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock awards granted									832,983
2021 Stock Option And Grant Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, granted period					10 years
Common stock vesting period					10 years
Increase in shares available for issuance	2,911,088	2,900,541

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Assumptions under Employee Stock Purchase Plan (Details) - 2021 Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	73%	72%
Expected volatility, Maximum	75%	74%
Expected dividend yield	0%	0%
Expected term (in years)	6 months
Risk-free interest rate, Minimum	0.10%	0.10%
Risk-free interest rate, Maximum	4.65%	1%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		5 months 8 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		6 months

Equity Incentive Plans - Summ_2

Equity Incentive Plans - Summary of Assumptions under Black-Scholes Option Pricing Model to Estimate Stock-based Compensation Expense for Stock Option Awards (Details) - Outstanding Stock Option Awards	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	74%	72%
Expected volatility, Maximum	75%	77.74%
Expected dividend yield	0%	0%
Risk-free interest rate, Minimum	1.91%	0.56%
Risk-free interest rate, Maximum	4.23%	1.34%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 11 months 19 days	5 years 5 months 23 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 3 days	6 years 14 days

Equity Incentive Plans - Summ_3

Equity Incentive Plans - Summary of Option Activity (Details) - 2020 and 2021 Plan - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, Beginning Balance	7,755,303	5,056,743
Number of Options, Granted		3,292,702
Options exercised		(67,196)
Number of Options, cancelled		(526,946)
Number of Options, Ending Balance		7,755,303	5,056,743
Number of Options, Exercisable		2,330,389
Number of Options, Vested and expected to vest		7,755,303
Weighted Average Exercise Price Per Share, Beginning balance	$ 8.47	$ 8.77
Weighted Average Exercise Price Per Share, granted		7.91
Weighted Average Exercise Price Per Share, exercised		0.3
Weighted Average Exercise Price Per Share, cancelled		8.99
Weighted Average Exercise Price Per Share, Ending balance		8.47	$ 8.77
Weighted Average Exercise Price Per Share, exercisable		8.74
Weighted Average Exercise Price Per Share, Vested and expected to vest		$ 8.47
Weighted Average Remaining Contractual Term, Outstanding		8 years 8 months 12 days	9 years 2 months 12 days
Weighted Average Remaining Contractual Term, exercisable		8 years 3 months 18 days
Weighted Average Remaining Contractual Term, Vested and expected to vest		8 years 8 months 12 days
Aggregate Intrinsic Value, Outstanding	$ 794	$ 18,503
Aggregate Intrinsic Value, Exercisable		388
Aggregate Intrinsic Value, Vested and expected to vest		794
Aggregate Intrinsic Value, Outstanding		$ 794	$ 18,503
Number of Options, Beginning Balance	7,755,303
Number of Options, Granted	3,223,400
Options exercised	(65,414)
Number of Options, cancelled	(4,532,774)
Number of Options, Ending Balance	6,380,515	7,755,303
Number of Options, Exercisable	4,231,849
Number of Options, Vested and expected to vest	6,380,515
Weighted Average Exercise Price Per Share, Beginning balance	$ 8.47
Weighted Average Exercise Price Per Share, granted	2.22
Weighted Average Exercise Price Per Share, exercised	0.52
Weighted Average Exercise Price Per Share, cancelled	6.5
Weighted Average Exercise Price Per Share, Ending balance	6.79	$ 8.47
Weighted Average Exercise Price Per Share, exercisable	6.86
Weighted Average Exercise Price Per Share, Vested and expected to vest	$ 6.79
Weighted Average Remaining Contractual Term, Outstanding	5 years 7 months 6 days	8 years 8 months 1 day
Weighted Average Remaining Contractual Term, exercisable	4 years 4 months 24 days
Weighted Average Remaining Contractual Term, Vested and expected to vest	5 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding	$ 794
Aggregate Intrinsic Value, Exercisable	472
Aggregate Intrinsic Value, Vested and expected to vest	695
Aggregate Intrinsic Value, Outstanding	$ 695	$ 794

Equity Incentive Plans - Compon

Equity Incentive Plans - Components of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 2,161	$ 3,210	$ 8,269	$ 9,912	$ 13,534	$ 7,871
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1	58	96	316	391	215
Restricted stock awards and founders' common stock awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1	2	5	6	11	9
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 2,159	$ 3,150	$ 8,168	$ 9,590	$ 13,132	$ 7,647

Equity Incentive Plans - Classi

Equity Incentive Plans - Classification of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 2,161	$ 3,210	$ 8,269	$ 9,912	$ 13,534	$ 7,871
Research and Development Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	37	1,249	1,904	3,881	5,317	2,685
General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 2,124	$ 1,961	$ 6,365	$ 6,031	$ 8,217	$ 5,186

Restructuring Activities - Sche

Restructuring Activities - Schedule Of Restructuring Liability Of Company (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($)
Restructuring and Related Activities [Abstract]
Accrued employee termination benefits beginning balance	$ 0
Employee termination benefits charges incurred during the period	7,883
Amounts paid or otherwise settled during the period	(4,900)
Accrued employee termination benefits as of September 30, 2023	$ 2,983

Restructuring Activities - Addi

Restructuring Activities - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Aug. 01, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Aug. 31, 2023	Dec. 31, 2022	Dec. 16, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring Costs		$ 11,349	$ 0	$ 51,128	$ 0
Employees Retention Bonus Payable				4,200
Employees Retention Bonus Accrued		2,800		4,000
Term of contract							1 year
Recognized termination benefits				1,000
Non cash impairment of assests		1,400		36,400
Restructuring and impairment charges		$ 5,300		6,800
Bayside Lease
Restructuring Cost and Reserve [Line Items]
Term of contract	20 months					20 months		120 months
Sublease payments	$ 500					$ 500
Asset Purchase Agreement (APA)
Restructuring Cost and Reserve [Line Items]
Contingent milestone payment				1,000
Exchange amount of assets and milestone payment	500			500
Reimbursement of research and development amount	$ 600			$ 600
LOA to Acquire Nula-Cel Assets
Restructuring Cost and Reserve [Line Items]
Equity interested diluted percentage		20%		20%
Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Costs				$ 3,400
Restructuring Plan eliminated				50%
Second Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs				$ 3,500
Retention Bonuses		$ 2,100
Second Restructuring Plan [Member] | Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Plan eliminated				78.10%
Second Restructuring Plan [Member] | Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Plan eliminated				33.10%

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Summary of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss	$ (22,485)	$ (55,314)	$ (23,934)	$ (24,682)	$ (25,936)	$ (25,835)	$ (101,733)	$ (76,453)	$ (101,052)	$ (70,760)
Denominator:
Weighted-average common shares outstanding	57,977,907			58,189,211			58,064,472	58,085,711	58,111,437	35,121,114
Less: weighted-average unvested restricted shares and shares subject to repurchase	(720,666)			(2,983,072)			(1,315,477)	(3,494,118)	(3,237,762)	(6,201,859)
Weighted-average shares used to compute basic net loss per share attributable to common stockholders	57,257,241			55,206,139			56,748,995	54,591,593	54,873,675	28,919,255
Weighted-average shares used to compute diluted net loss per share attributable to common stockholders	57,257,241			55,206,139			56,748,995	54,591,593	54,873,675	28,919,255
Net loss per share attributable to common stockholders-basic	$ (0.39)			$ (0.45)			$ (1.79)	$ (1.4)	$ (1.84)	$ (2.45)
Net loss per share attributable to common stockholders-diluted	$ (0.39)			$ (0.45)			$ (1.79)	$ (1.4)	$ (1.84)	$ (2.45)

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Schedule of Anti-dilutive Outstanding Shares or Equivalents (Details) - shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive outstanding shares or equivalents	7,264,014	11,214,630	7,264,014	11,214,630	10,690,909,000	9,930,793,000
Options To Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive outstanding shares or equivalents	6,380,515	7,849,590	6,380,515	7,849,590	7,755,303,000	5,056,743,000
Common Stock Subject To Vesting Or Repurchase
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive outstanding shares or equivalents	873,062	3,236,152	873,062	3,236,152	2,767,526,000	4,774,798,000
Employee Stock Purchase Plan shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive outstanding shares or equivalents	10,437	128,888	10,437	128,888	168,080,000	99,252,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 0	$ 0
Income tax examination, description		The Company’s U.S. federal and state income tax returns are generally subject to tax examinations for the tax years from inception through December 31, 2021. There are currently no pending income tax examinations. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service and state tax authorities to the extent utilized in a future period.
Accrued interest and penalties related to unrecognized tax benefits	$ 0	$ 0

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Federal statutory income tax rate ate	21%	21%
State taxes	1.10%	1.94%
Others	(0.69%)	(0.26%)
Research and development credits	1.11%	1.01%
Cancellation of debt income	0%	0%
Tranche liability	0%	(3.06%)
Interest expense	0%	0%
Stock-based compensation	(0.97%)	(0.96%)
Change in valuation allowance	(21.55%)	(19.67%)
Provision for taxes	0%	0%

Income Taxes - Summary of Net D

Income Taxes - Summary of Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating losses - non-current	$ 15,940	$ 12,006
Capitalized R&D	13,815	0
General business credit - non-current	5,699	2,682
Operating lease right-of-use assets	1,220	2,368
Stock based compensation	1,703	784
Accruals and reserves	735	525
Fixed assets	170	396
Other	3	2
Gross deferred tax assets	39,285	18,763
Valuation allowance	(38,110)	(16,332)	$ (2,414)
Net deferred tax assets	1,175	2,431
Fixed asset basis	0	0
Operating lease liabilities	(1,175)	(2,431)
Other	0	0
Gross deferred tax liabilities	$ (1,175)	$ (2,431)

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, 2022 USD ($)
Federal
Income Taxes [Line Items]
Tax credits, Amount	$ 5,309
Federal | Maximum [Member]
Income Taxes [Line Items]
Net operating loss carryforwards expiration year	2042
Tax credit carryforwards expiration year	2042
Federal | Minimum [Member]
Income Taxes [Line Items]
Net operating loss carryforwards expiration year	2039
Tax credit carryforwards expiration year	2041
Federal | Starting from January 1, 2018
Income Taxes [Line Items]
Net operating losses, Amount	$ 75,730
Net operating losses, Expiration Years description	Do Not Expire
State
Income Taxes [Line Items]
Net operating losses, Amount	$ 3,195
Tax credits, Amount	$ 592
Tax credits, Expiration Years Description	Do Not Expire

Income Taxes - Changes in Valua

Income Taxes - Changes in Valuation Allowance for Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Valuation allowance at the beginning of the year	$ 16,332	$ 2,414
Increases recorded to income tax provision	21,778	13,918
Valuation allowance at the end of the year	$ 38,110	$ 16,332

Income Taxes - Summary of Rec_2

Income Taxes - Summary of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 1,407	$ 0
Additions based on tax positions related to current year	1,862	1,258
Increase (reduction) for prior period positions	(568)	(149)
Unrecognized tax benefit-December 31	$ 2,701	$ 1,407

Subsequent Events - Additional

Subsequent Events - Additional Information (Details)		1 Months Ended
	Oct. 26, 2023 USD ($)	Nov. 30, 2023 USD ($) ft²	Oct. 31, 2023 USD ($) ft²	Oct. 26, 2023 USD ($)
Forecast [Member] | Sublease [Member]
Subsequent Event [Line Items]
Premises space | ft²		15,212
Payment of assumption costs		$ 1,400,000
Forecast [Member] | ARE San Francisco No 65 LLC [Member] | Sublease [Member]
Subsequent Event [Line Items]
Premises space | ft²			19,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Lease termination payment	$ (20,800,000)
Subsequent Event [Member] | Lease Amendment [Member]
Subsequent Event [Line Items]
Rent payments				$ 20,000
Subsequent Event [Member] | Sublease [Member]
Subsequent Event [Line Items]
Payments directly to the landlord			$ 18,304,410
Prepaid remaining amounts payable	$ 15,900,000
Rent payments			$ 18,945,064
Subsequent Event [Member] | Soleil Labs, LLC [Member] | Sublease [Member]
Subsequent Event [Line Items]
Premises space | ft²			32,113
Subsequent Event [Member] | Bayside Area Development, LLC [Member] | Sublease [Member]
Subsequent Event [Line Items]
Premises space | ft²			85,165