4D Molecular Therapeutics (FDMT) 10-Q 8 Nov 22 2022 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2022	Nov. 02, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Document Quarterly Report	true
Document Transition Report	false
Entity Registrant Name	4D Molecular Therapeutics, Inc.
Entity Central Index Key	0001650648
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		32,392,378
Entity Interactive Data Current	Yes
Entity File Number	001-39782
Entity Tax Identification Number	47-3506994
Entity Address, Address Line One	5858 Horton Street #455
Entity Address, City or Town	Emeryville
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94608
City Area Code	(510)
Local Phone Number	505-2680
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	FDMT
Security Exchange Name	NASDAQ

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 108,298	$ 153,001
Marketable securities	119,417	94,776
Accounts receivable	0	47
Prepaid expenses and other current assets (includes $0 and $285 at September 30, 2022 and December 31, 2021, respectively, attributable to related parties)	4,763	8,456
Total current assets	232,478	256,280
Marketable securities, long-term	11,122	67,652
Property and equipment, net	22,052	14,391
Operating lease right-of-use assets	13,459	14,562
Other assets	1,053	602
Total assets	280,164	353,487
Current liabilities
Accounts payable	1,480	4,764
Accrued and other current liabilities	7,244	7,744
Deferred revenue	2,207	2,599
Operating lease liabilities, current portion	2,633	1,231
Total current liabilities	13,564	16,338
Deferred revenue, net of current portion	1,001	2,491
Derivative liability	213	214
Operating lease liabilities, long-term portion	13,919	15,217
Other liabilities	23	120
Total liabilities	28,720	34,380
Commitments and contingencies (Notes 7, 8 and 9)
Stockholders’ equity
Common stock, $0.0001 par value, 300,000,000 shares authorized at September 30, 2022 and December 31, 2021; 32,392,378 and 32,224,524 shares issued and outstanding at September 30, 2022 and December 31, 2021, respectively	3	3
Additional paid-in-capital	540,403	526,523
Accumulated other comprehensive loss	(1,851)	(423)
Accumulated deficit	(287,111)	(206,996)
Total stockholders’ equity	251,444	319,107
Total liabilities and stockholders’ equity	$ 280,164	$ 353,487

Condensed Balance Sheets (Una_2

Condensed Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Prepaid expenses to related parties	$ 0	$ 285
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares, issued	32,392,378	32,224,524
Common stock, shares, outstanding	32,392,378	32,224,524

Condensed Statements of Operati

Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenue:
Collaboration and license revenue	$ 500	$ 1,366	$ 1,882	$ 17,946
Total revenue	500	1,366	1,882	17,946
Operating expenses:
Research and development (includes $0 and $263 for the three months ended September 30, 2022 and 2021, respectively, and $134 and $672 for the nine months ended September 30, 2022 and 2021, respectively, attributable to related parties)	18,940	15,840	58,753	43,832
General and administrative	8,055	8,187	24,441	20,683
Total operating expenses	26,995	24,027	83,194	64,515
Loss from operations	(26,495)	(22,661)	(81,312)	(46,569)
Other income (expense):
Interest income	795	435	1,235	449
Other income (expense), net	9	(13)	(38)	(114)
Total other income (expense), net	804	422	1,197	335
Net loss	$ (25,691)	$ (22,239)	$ (80,115)	$ (46,234)
Net loss per share, basic	$ (0.79)	$ (0.82)	$ (2.48)	$ (1.72)
Net loss per share, diluted	$ (0.79)	$ (0.82)	$ (2.48)	$ (1.72)
Weighted-average shares outstanding used in computing net loss per share, basic	32,385,791	27,022,380	32,305,074	26,818,595
Weighted-average shares outstanding used in computing net loss per share, diluted	32,385,791	27,022,380	32,305,074	26,818,595

Condensed Statements of Opera_2

Condensed Statements of Operations (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
Research and development expense, related party	$ 0	$ 263	$ 134	$ 672

Condensed Statements of Compreh

Condensed Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (25,691)	$ (22,239)	$ (80,115)	$ (46,234)
Other comprehensive loss:
Net unrealized loss on marketable securities	(24)	(195)	(1,428)	(195)
Total Comprehensive loss	$ (25,715)	$ (22,434)	$ (81,543)	$ (46,429)

Condensed Statements of Stockho

Condensed Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Stockholders' Equity, beginning balances at Dec. 31, 2020	$ 256,387	$ 3	$ 392,063		$ (135,679)
Stockholders' Equity, beginning balances (in shares) at Dec. 31, 2020		26,681,983
Issuance of common stock upon exercise of stock options	99		99
Issuance of common stock upon exercise of stock options (in shares)		12,396
Stock-based compensation expense	2,329		2,329
Vesting of common stock warrants issued for services	22		22
Net loss	(16,406)				(16,406)
Stockholders' Equity, ending balances at Mar. 31, 2021	242,431	$ 3	394,513		(152,085)
Stockholders' Equity, ending balances (in shares) at Mar. 31, 2021		26,694,379
Stockholders' Equity, beginning balances at Dec. 31, 2020	256,387	$ 3	392,063		(135,679)
Stockholders' Equity, beginning balances (in shares) at Dec. 31, 2020		26,681,983
Net loss	(46,234)
Stockholders' Equity, ending balances at Sep. 30, 2021	224,134	$ 3	406,239	$ (195)	(181,913)
Stockholders' Equity, ending balances (in shares) at Sep. 30, 2021		27,165,577
Stockholders' Equity, beginning balances at Mar. 31, 2021	242,431	$ 3	394,513		(152,085)
Stockholders' Equity, beginning balances (in shares) at Mar. 31, 2021		26,694,379
Issuance of common stock upon exercise of stock options and warrants	820		820
Issuance of common stock upon exercise of stock options and warrants (in shares)		197,478
Stock-based compensation expense	3,816		3,816
Issuance of common stock warrant	1,146		1,146
Vesting of common stock warrants issued for services	22		22
Net loss	(7,589)				(7,589)
Stockholders' Equity, ending balances at Jun. 30, 2021	240,646	$ 3	400,317		(159,674)
Stockholders' Equity, ending balances (in shares) at Jun. 30, 2021		26,891,857
Issuance of common stock upon exercise of stock options and warrants	1,977		1,977
Issuance of common stock upon exercise of stock options and warrants (in shares)		273,720
Stock-based compensation expense	3,923		3,923
Vesting of common stock warrants issued for services	22		22
Net unrealized loss on marketable securities	(195)			(195)
Net loss	(22,239)				(22,239)
Stockholders' Equity, ending balances at Sep. 30, 2021	224,134	$ 3	406,239	(195)	(181,913)
Stockholders' Equity, ending balances (in shares) at Sep. 30, 2021		27,165,577
Stockholders' Equity, beginning balances at Dec. 31, 2021	319,107	$ 3	526,523	(423)	(206,996)
Stockholders' Equity, beginning balances (in shares) at Dec. 31, 2021		32,224,524
Issuance of common stock upon exercise of stock options	330		330
Issuance of common stock upon exercise of stock options (in shares)		39,541
Stock-based compensation expense	3,933		3,933
Vesting of common stock warrants issued for services	22		22
Net unrealized loss on marketable securities	(998)			(998)
Net loss	(26,338)				(26,338)
Stockholders' Equity, ending balances at Mar. 31, 2022	296,056	$ 3	530,808	(1,421)	(233,334)
Stockholders' Equity, ending balances (in shares) at Mar. 31, 2022		32,264,065
Stockholders' Equity, beginning balances at Dec. 31, 2021	$ 319,107	$ 3	526,523	(423)	(206,996)
Stockholders' Equity, beginning balances (in shares) at Dec. 31, 2021		32,224,524
Issuance of common stock upon exercise of stock options (in shares)	106,302
Net loss	$ (80,115)
Stockholders' Equity, ending balances at Sep. 30, 2022	251,444	$ 3	540,403	(1,851)	(287,111)
Stockholders' Equity, ending balances (in shares) at Sep. 30, 2022		32,392,378
Stockholders' Equity, beginning balances at Mar. 31, 2022	296,056	$ 3	530,808	(1,421)	(233,334)
Stockholders' Equity, beginning balances (in shares) at Mar. 31, 2022		32,264,065
Issuance of common stock upon exercise of stock options	138		138
Issuance of common stock upon exercise of stock options (in shares)		51,261
Stock-based compensation expense	4,322		4,322
Issuance of common stock - 2020 ESPP	471		471
Issuance of common stock - 2020 ESPP (in shares)		61,552
Vesting of common stock warrants issued for services	22		22
Net unrealized loss on marketable securities	(406)			(406)
Net loss	(28,086)				(28,086)
Stockholders' Equity, ending balances at Jun. 30, 2022	272,517	$ 3	535,761	(1,827)	(261,420)
Stockholders' Equity, ending balances (in shares) at Jun. 30, 2022		32,376,878
Issuance of common stock upon exercise of stock options	100		100
Issuance of common stock upon exercise of stock options (in shares)		15,500
Stock-based compensation expense	4,520		4,520
Vesting of common stock warrants issued for services	22		22
Net unrealized loss on marketable securities	(24)			(24)
Net loss	(25,691)				(25,691)
Stockholders' Equity, ending balances at Sep. 30, 2022	$ 251,444	$ 3	$ 540,403	$ (1,851)	$ (287,111)
Stockholders' Equity, ending balances (in shares) at Sep. 30, 2022		32,392,378

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities
Net loss	$ (80,115)	$ (46,234)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	12,775	10,068
Vesting of common stock warrants	66	66
Change in fair value of derivative liability	(1)	92
Depreciation and amortization	1,389	1,133
Loss on disposition of property and equipment	0	2
Amortization of right-of-use assets	1,103	1,117
Net amortization (accretion) of premium (discount) on marketable securities	1,290	0
Changes in operating assets and liabilities
Accounts receivable	47	695
Prepaid expenses and other current assets	3,693	1,177
Other assets	(451)	0
Accounts payable	(3,151)	623
Accrued and other liabilities	662	154
Deferred revenue	(1,882)	(15,074)
Operating lease liabilities	104	(1,117)
Net cash used in operating activities	(64,471)	(47,298)
Cash flows from investing activities
Purchase of marketable securities	(253,821)	(136,375)
Maturities of marketable securities	282,993	0
Acquisition of property and equipment	(10,443)	(4,014)
Net cash provided by (used in) investing activities	18,729	(140,389)
Cash flows from financing activities
Payment of offering costs	0	(946)
Proceeds from the exercise of stock options and warrants	568	2,896
Issuance of common stock through 2020 ESPP	471	0
Net cash provided by financing activities	1,039	1,950
Net decrease in cash and cash equivalents	(44,703)	(185,737)
Cash and cash equivalents, beginning of period	153,001	276,726
Cash and cash equivalents, end of period	108,298	90,989
Supplemental disclosures of noncash investing and financing information
Decrease in right-of-use assets due to reduction in operating lease liabilities upon modification	0	(478)
Issuance of common stock warrant to settle liability	0	1,146
Purchases of property and equipment in accounts payable and accrued and other liabilities	$ 297	$ 1,303

The Company

The Company	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company	1. The Company 4D Molecular Therapeutics, Inc. (the “Company”) was formed as a limited liability company in September 2013 under the name 4D Molecular Therapeutics, LLC. The Company changed its name and converted into a corporation which was incorporated in the state of Delaware in March 2015. The Company is a clinical-stage gene therapy company pioneering the development of product candidates using its targeted and evolved adeno-associated virus (“AAV”) vectors. Initial Public Offering In December 2020, the Company sold and issued 9,660,000 shares of common stock at a price to the public of $ 23.00 per share, which included shares sold upon the underwriters’ exercise of their overallotment option to purchase 1,260,000 additional shares. The Company received an aggregate of $ 204.7 million in net proceeds, after deducting underwriting discounts and commissions, and offering costs. Upon the closing of the Company’s initial public offering in December 2020 (the “IPO”), all outstanding shares of redeemable convertible preferred stock automatically converted into 11,575,984 shares of common stock. Subsequent to the closing of the IPO, there were no shares of redeemable convertible preferred stock outstanding. Follow On Public Offering In November 2021, the Company completed its second underwritten public offering ("Follow-on Offering") in which 4,750,000 shares of the Company's common stock were sold at an offering price of $ 25.00 per share pursuant to an effective Registration Statement on Form S-1. The net proceeds from the Follow-on Offering were $ 111.1 million, after deducting underwriting discounts and commissions and offering expenses. Liquidity The Company has incurred significant losses and negative cash flows from operations and had an accumulated deficit of $ 287.1 million as of September 30, 2022. The Company believes that its cash and cash equivalents and marketable securities as of September 30, 2022 are sufficient for the Company to fund planned operations for at least one year from the issuance date of these unaudited condensed financial statements. The Company has historically financed its operations primarily through the sale of equity securities, and to a lesser extent, from cash received pursuant to its collaboration and license agreements. To date, none of the Company’s product candidates have been approved for sale, and therefore, the Company has not generated any revenue from product sales. Management expects operating losses and negative cash flows from operations to continue for the foreseeable future. The Company plans to raise additional funding as required based on the status of its clinical trials and projected cash flows. There can be no assurance that, in the event the Company requires additional financing, such financing will be available on terms acceptable to the Company, if at all. Failure to generate sufficient cash flows from operations, raise additional capital and reduce discretionary spending should additional capital not become available could have a material adverse effect on the Company’s ability to achieve its business objectives.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with United States Generally Accepted Accounting Principles (“U.S. GAAP”) and the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for interim reporting. Our condensed balance sheet for the year ended December 31, 2021 was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. Certain information and note disclosures normally included in annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. Accordingly, the unaudited condensed financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021 filed with the SEC. The accompanying financial information for the three and nine months ended September 30, 2022 and 2021 are unaudited. The unaudited condensed financial statements have been prepared on the same basis as the annual audited financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s financial position as of September 30, 2022 and December 31, 2021 and its results of operations and cash flows for the nine months ended September 30, 2022 and 2021. The results for interim periods are not necessarily indicative of the results expected for the full fiscal year or any other periods. Use of Estimates and Judgements The preparation of the condensed financial statements in conformity with U.S. GAAP requires management to make estimates and judgements that affect the reported amounts of assets, liabilities, revenue and expenses and disclosure of contingent assets and liabilities as of the date of the financial statements. Such estimates include the determination of useful lives for property and equipment, the contract term, transaction price and costs of collaboration agreements, as well as estimates of the fair value of common stock (prior to the IPO), stock options, derivative instrument and income tax uncertainties. Actual results could differ from those estimates. Due to the coronavirus (“COVID-19”) pandemic, there has been uncertainty and disruption in the global economy and financial markets. The Company is not aware of any specific event or circumstance that would require an update to its estimates or judgments or a revision of the carrying value of its assets or liabilities as of September 30, 2022. While there was not a material impact to the Company's unaudited condensed financial statements as of September 30, 2022, these estimates may change, as new events occur and additional information is obtained, as well as other factors related to the COVID-19 pandemic that could result in material impacts to the unaudited condensed financial statements in future reporting periods. Segment Information The Company operates and manages its business as one reportable and operating segment. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on a company-wide basis for purposes of allocating resources and assessing financial performance. Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents, marketable securities and accounts receivable. The Company’s cash is held at two financial institutions in the United States of America. The Company’s cash equivalents are invested in money market funds. The Company also invests in U.S. Treasuries, U.S. Government sponsored agency, commercial paper and corporate bonds. The Company has not experienced any losses on its deposits of cash and cash equivalents. Such deposits may, at times, exceed federally insured limits. The Company’s partners in collaboration and license agreements who represent 10% or more of the Company’s total revenue are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Customer A * 94 % * 96 % Customer B 99 % * 98 % * Total 99 % 94 % 98 % 96 % * Less than 10% The Company’s partners in collaboration and license agreements who represent 10% or more of the Company’s total accounts receivable are as follows: September 30, December 31, Customer A 0 % 100 % Total 0 % 100 % The Company’s total revenues by geographic region, based on the location of the customer, are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Netherlands $ 497 $ 64 $ 1,849 $ 724 Switzerland — 1,290 — 17,190 United States 3 12 33 32 Total revenue $ 500 $ 1,366 $ 1,882 $ 17,946 Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents. Cash equivalents consist of money market funds. Marketable Securities Marketable securities consist of commercial paper, corporate bonds, U.S. Treasuries and U.S. Government sponsored agencies and are included in current and noncurrent assets. The Company classifies its marketable securities as available-for-sale and carries them at fair value on its condensed balance sheet. Fair value is estimated using independent pricing sources based on quoted prices in active markets for similar securities. Unrealized gains and losses on the marketable securities are reported as a component of stockholders' equity in accumulated other comprehensive loss. The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in interest income on the condensed statements of operations. Realized gains and losses are included in interest income on the condensed statements of operations. The Company periodically evaluates its marketable securities to assess whether those with unrealized loss positions are other than temporarily impaired. The Company considers various factors in determining whether to recognize an impairment charge. If the Company determines that the decline in an investment's fair value is other-than-temporary, the difference is recognized as an impairment loss in the condensed statements of operations. Other Risks and Uncertainties The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, protection of proprietary technology, dependence on key personnel, suppliers for key raw materials, contract manufacturing organizations (“CMOs”) and contract research organizations (“CROs”), compliance with government regulations and the need to obtain additional financing to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical studies, clinical trials and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance and reporting. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained or maintained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from other pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees, consultants and other third parties (including for clinical trials and some aspects of research and preclinical testing). The extent of the impact of the COVID-19 pandemic on the Company’s business will depend upon the duration and spread of the outbreak and the extent and severity of the impact on the Company’s clinical trial activities, research activities and suppliers, all of which are uncertain and cannot be predicted. The extent to which the coronavirus outbreak may materially impact the Company’s financial condition, liquidity or results of operations is uncertain. Fair Value Measurements The Company applies fair value accounting for all financial assets and liabilities and nonfinancial assets and liabilities that are recognized or disclosed at fair value in the unaudited condensed financial statements on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on 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. As a basis for considering such assumptions, a three-level fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows: • Level 1 — Observable inputs that reflect unadjusted quoted market prices in active markets for identical assets or liabilities that are accessible at the measurement date. • Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company accounts for transfers of financial instruments between levels of the fair value hierarchy on the date of the event or change in circumstance that caused the transfer. Common Stock Warrants The Company accounts for common stock warrants which meet the definition of a derivative as liabilities if the warrant requires net cash settlement or gives the holder the option of net cash settlement. The Company accounts for common stock warrants as equity if the contract requires physical settlement or net physical settlement or if the Company has the option of physical settlement or net physical settlement. Common stock warrants classified as liabilities are initially recorded at fair value and remeasured at fair value each condensed balance sheet date with the offset adjustments recorded in other income (expense), net within the condensed statements of operations. Common stock warrants classified as equity are initially measured at fair value on the grant date and are not subsequently remeasured. Leases On December 31, 2021, the Company adopted Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842), (" ASC 842 ") using the alternative modified transition method effective as of January 1, 2021. As a result, the Company has retrospectively changed its previously issued unaudited condensed financial statements as of September 30, 2021 and for the three and nine months ended September 30, 2021 as presented within the Company's September 30, 2021 Quarterly Report on Form 10-Q to reflect the adoption of ASC 842 on January 1, 2021 . The condensed financial statements for the three and nine months ended September 30, 2021 presented herein differ from the Company's condensed financial statements included in the Company's September 30, 2021 Quarterly Report on Form 10-Q as those unaudited condensed financial statements were prepared using the former accounting standard referred to as ASC Topic 840, Leases. The impact of adoption on ASC 842 on the condensed statements of operations for the nine months ended September 30, 2021 was immaterial. The following table summarizes the effect of the adoption of ASC 842 on the condensed statement of cash flows for the nine months ended September 30, 2021 (in thousands): Pre ASC 842 After ASC 842 Nine Months Ended ASC 842 Nine Months Ended September 30, 2021 Adjustments September 30, 2021 Adjustments to reconcile net loss to net cash Amortization of right-of-use assets $ — $ 1,117 $ 1,117 Changes in operating assets and liabilities Operating lease liabilities — ( 1,117 ) ( 1,117 ) Supplemental disclosures of noncash investing and financing information Decrease in right-of-use assets due to reduction in operating lease liabilities upon modification — ( 478 ) ( 478 ) At contract inception, the Company determines if an arrangement is or contains a lease. A contract is or contains a lease if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. If determined to be or contain a lease, the lease is assessed for classification as either an operating or finance lease at the lease commencement date, defined as the date on which the leased asset is made available for use by the Company, based on the economic characteristics of the lease. A right-of-use asset represents the economic benefit conveyed to the Company by the right to use the underlying asset over the lease term. A lease liability represents the obligation to make lease payments arising from the lease. Operating lease right-of-use assets represent the Company's right to use an underlying asset for the lease term and operating lease liabilities represent the Company's obligation to make payments arising from the lease. Operating right-of-use assets and liabilities are recognized at the commencement date of the lease and are measured at the present value of the fixed payments due over the expected lease term less the present value of any incentives, rebates, or abatements the Company expects to receive from the lessor. The Company records amortization of operating right-of-use assets and accretion of lease liabilities as a single lease cost on a straight-line basis over the lease term. No lease renewal options are recognized as part of the right-of-use assets and lease liabilities. The Company's operating leases are presented in the condensed balance sheets as operating lease right-of-use assets, classified as noncurrent assets, and operating lease liabilities, classified as current and noncurrent based on the discounted lease payments to be made within the preceding twelve months. As the Company’s leases do not provide an implicit interest rate, the Company uses its incremental borrowing rate to discount lease payments. The incremental borrowing rate represents an estimated rate of interest that the Company would have to pay to borrow equivalent funds on a collateralized basis at the lease commencement date. Revenue Recognition The Company determines revenue recognition for arrangements within the scope of Accounting Standards Update 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASC 606") by performing the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company’s revenue is primarily derived through its license, research, development and commercialization agreements. The terms of these types of agreements may include (i) licenses to the Company’s technology, (ii) research and development services, and (iii) services or obligations in connection with participation in research or steering committees. Payments to the Company under these arrangements typically include one or more of the following: nonrefundable upfront and license fees, research funding, milestone and other contingent payments to the Company for the achievement of defined collaboration objectives and certain preclinical, clinical, regulatory and sales-based events, as well as royalties on sales of any commercialized products. Arrangements that include upfront payments are recorded as deferred revenue upon receipt or when due and are recognized as revenue as the performance conditions are met. The event-based milestone payments, royalties and cost reimbursements represent variable consideration, and the Company uses the most likely amount method to estimate this variable consideration. Royalty payments are recognized when earned or as the sales occur. The Company records cost reimbursements as accounts receivable when right to consideration is unconditional. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC 606. The Company allocates the total transaction price to each performance obligation based on the estimated standalone selling price and recognizes revenue when, or as, the performance obligation is satisfied. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. At the end of each reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Significant management judgment is required to determine the level of effort required under an arrangement and the period over which the Company expects to complete its performance obligations under the arrangement. Changes in these estimates can have a material effect on revenue recognized. Embedded Derivative Embedded derivatives that are required to be bifurcated from the underlying host instrument are accounted for and valued as a separate financial instrument. An embedded derivative exists in the award agreement with the Cystic Fibrosis Foundation (“CFF”). As described in Note 14, the embedded derivative has been bifurcated and is classified as a liability on the condensed balance sheets and is separately accounted for at its fair value. The derivative liability is subject to remeasurement to fair value each reporting period. Changes in the fair value of the derivative liability are recognized as a component of other income (expense), net within the condensed statements of operations. Net Loss Per Share, Basic and Diluted Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by giving effect to all potentially dilutive common shares outstanding for the period. For purposes of this calculation, stock options to acquire shares of common stock and common stock warrants are considered potentially dilutive common shares, but have been excluded from the calculation of diluted net loss per share as their effect is antidilutive. Recent Accounting Pronouncement New Accounting Pronouncement Not Yet Adopted As an “emerging growth company,” the Jumpstart Our Business Startups Act (“JOBS Act”) allows the Company to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are made applicable to private companies. The Company has elected to use this extended transition period under the JOBS Act. The adoption dates discussed below reflect this election. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments , as clarified in subsequent amendments. ASU 2016-13 changes the impairment model for certain financial instruments. The new model is a forward-looking expected loss model and will apply to financial assets subject to credit losses and measured at amortized cost and certain off-balance sheet credit exposures. This includes loans, held-to-maturity debt securities, loan commitments, financial guarantees and net investments in leases, as well as trade receivables. For available-for-sale debt securities with unrealized losses, credit losses will be measured in a manner similar to today, except that the losses will be recognized as allowances rather than reductions in the amortized cost of the securities. In October 2019, the FASB voted to delay the effective date of this standard. Topic 326 will be effective for the Company for fiscal years beginning after December 15, 2022. Early adoption is permitted. The Company is currently evaluating the effects of this ASU on its financial statements and related disclosures and does not expect there to be a material impact.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The following tables represent the Company’s fair value hierarchy for financial assets and financial liabilities measured at fair value on a recurring basis as of September 30, 2022 and December 31, 2021 (in thousands): Basis for Fair Value Measurements Fair Value as of Level 1 Level 2 Level 3 September 30, 2022 Assets Cash equivalents: Money market funds $ 87,704 $ — $ — $ 87,704 US treasuries — 5,461 — 5,461 Marketable securities: Commercial paper — 9,860 — 9,860 Corporate bonds — 46,862 — 46,862 US treasuries — 71,654 — 71,654 US government sponsored agencies — 2,163 — 2,163 Total $ 87,704 $ 136,000 $ — $ 223,704 Liabilities Derivative liability $ — $ — $ 213 $ 213 Total $ — $ — $ 213 $ 213 Basis for Fair Value Measurements Fair Value as of Level 1 Level 2 Level 3 December 31, 2021 Assets Cash equivalents: Money market funds $ 36,556 $ — $ — $ 36,556 Marketable securities: Commercial paper — 37,535 — 37,535 Corporate bonds — 94,864 — 94,864 US treasuries — 30,029 — 30,029 Total $ 36,556 $ 162,428 $ — $ 198,984 Liabilities Derivative liability $ — $ — $ 214 $ 214 Total $ — $ — $ 214 $ 214 Level 3 Inputs The fair value of the derivative liability is based on significant inputs no t observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The fair value of the derivative liability was determined using a present value analysis with multiple scenarios. In determining the fair value of the derivative liability, the inputs impacting fair value include the change of control payment to CFF, the probability of a change of control event, the product status at time of a change of control event and the discount rate. See Note 14 for further discussion on the embedded derivative. There were no transfers between Level 1, 2 and 3 during the periods presented. The following tables set forth a summary of the changes in the fair value of the Company’s Level 3 financial instrument during the nine-month periods ended September 30, 2022 and 2021 (in thousands): Derivative Balance as of December 31, 2021 $ 214 Change in fair value included in other income (expense), net ( 1 ) Balance as of September 30, 2022 $ 213 Derivative Balance as of December 31, 2020 $ 122 Change in fair value included in other income (expense), net 92 Balance as of September 30, 2021 $ 214

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	4. Marketable Securities Marketable securities, which are classified as available-for-sale, consisted of the following as of September 30, 2022 and December 31, 2021 (in thousands): Amortized Cost Basis Gross Unrealized Gains Gross Unrealized Losses Fair Value as of September 30, 2022 Short-term marketable securities: Commercial paper $ 5,025 $ — $ ( 55 ) $ 4,970 Corporate bonds 41,357 — ( 727 ) 40,630 US treasuries 72,314 4 ( 664 ) 71,654 US government sponsored agencies 2,200 — ( 37 ) 2,163 Total short-term marketable securities $ 120,896 $ 4 $ ( 1,483 ) $ 119,417 Long-term marketable securities: Commercial paper $ 5,082 $ — $ ( 192 ) $ 4,890 Corporate bonds 6,413 — ( 181 ) 6,232 Total long-term marketable securities $ 11,495 $ — $ ( 373 ) $ 11,122 Amortized Cost Basis Gross Unrealized Gains Gross Unrealized Losses Fair Value as of December 31, 2021 Short-term marketable securities: Commercial paper $ 32,471 $ — $ ( 4 ) $ 32,467 Corporate bonds 57,315 — ( 79 ) 57,236 US treasuries 5,082 — ( 9 ) 5,073 Total short-term marketable securities $ 94,868 $ — $ ( 92 ) $ 94,776 Long-term marketable securities: Commercial paper $ 5,089 $ — $ ( 21 ) $ 5,068 Corporate bonds 37,821 — ( 193 ) 37,628 US treasuries 25,073 — ( 117 ) 24,956 Total long-term marketable securities $ 67,983 $ — $ ( 331 ) $ 67,652 All marketable securities held as of September 30, 2022 and December 31, 2021 had contractual maturities of less than two years . There was an immaterial realized loss on marketable securities for the nine-month period ended September 30, 2022. As of September 30, 2022 and December 31, 2021, the aggregate fair value of securities held by the Company in a continuous unrealized loss position for less than twelve months was $ 64.6 million and $ 162.4 million, respectively. As of September 30, 2022 and December 31, 2021, the aggregate fair value of securities held by the Company in a continuous unrealized loss position for more than twelve months was $ 60.5 million and $ 0 million, respectively. The Company determined that it has the ability and intent to hold all marketable securities that have been in a continuous loss position until maturity or recovery, thus there has been no recognition of any other-than-temporary impairment in the three and nine months ended September 30, 2022.

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2022
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	5. Property and Equipment, Net Property and equipment, net, consisted of the following (in thousands): September 30, December 31, Machinery and equipment $ 9,952 $ 5,971 Leasehold improvements 16,380 2,527 Furniture and fixtures 566 566 Office equipment 240 165 Computer equipment and software 616 421 Construction in progress 1,012 10,066 Total property and equipment 28,766 19,716 Less: Accumulated depreciation and amortization ( 6,714 ) ( 5,325 ) Property and equipment, net $ 22,052 $ 14,391 All property and equipment are maintained in the United States. Depreciation expense was $ 0.5 million and $ 0.4 million for the three months ended September 30, 2022 and 2021, respectively, and $ 1.4 million and $ 1.1 million for the nine months ended September 30, 2022 and 2021, respectively.

Accrued and Other Current Liabi

Accrued and Other Current Liabilities	9 Months Ended
	Sep. 30, 2022
Payables and Accruals [Abstract]
Accrued and Other Current Liabilities	6. Accrued and Other Current Liabilities Accrued and other current liabilities consisted of the following (in thousands): September 30, December 31, Payroll and related expenses $ 4,161 $ 3,994 Accrued clinical and preclinical study costs 1,346 407 Consulting and professional 1,549 1,573 Other accrued expenses 188 1,770 Total accrued and other current liabilities $ 7,244 $ 7,744

Research and Collaboration Arra

Research and Collaboration Arrangements	9 Months Ended
	Sep. 30, 2022
Research And Collaboration Arrangements [Abstract]
Research and Collaboration Arrangements	7. Research and Collaboration Arrangements Collaboration and license revenue for each period was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 uniQure $ 497 $ 64 $ 1,849 $ 724 Roche — 1,290 — 17,190 CFF 3 12 33 32 Total revenue $ 500 $ 1,366 $ 1,882 $ 17,946 Deferred revenue is summarized as follows (in thousands): September 30, December 31, uniQure $ 1,812 $ 3,661 CFF 1,396 1,429 Total deferred revenue $ 3,208 $ 5,090 The total amount of revenue in the nine months ended September 30, 2022, which was included in deferred revenue at January 1, 2022, was $ 1.9 million. The total amount of revenue in the nine months ended September 30, 2021, which was included in deferred revenue at January 1, 2021, was $ 15.1 million. uniQure In January 2014, the Company and uniQure biopharma B.V. (“uniQure”) entered into a Collaboration and License Agreement (the “uniQure Agreement”) to collaborate on the discovery and non-clinical research activities related to the Company’s Therapeutic Vector Evolution platform in order to generate and validate vectors for gene delivery to treat diseases within the central nervous system and liver (together, the “uniQure Field”). The uniQure Agreement provided uniQure with a research license as well as an exclusive development and commercialization license for each project variant selected for further development. The initial research term was three years and uniQure exercised a one-time option to extend the research term for an additional year to January 2018. Once the Company’s research plan concluded, uniQure was solely responsible for the continued development, manufacturing and commercialization of the project variants as potential product candidates. The Company was also required to work exclusively with uniQure in the uniQure Field (the “uniQure Exclusivity Clause”). Pursuant to the uniQure Agreement, the Company received upfront payments of $ 0.2 million and was entitled to receive (i) contingent payments for the achievement of research and development milestones of up to $ 5.0 million for each licensed product selected under the arrangement, and (ii) royalties in the single digit percentage rate range on future sales of the potential product candidates and sublicense consideration in the low teens to low thirties percentage rate range on any future sublicensing arrangements. In connection with the performance obligations under the uniQure Agreement, the founders of 4D Molecular Therapeutics, LLC received equity options to purchase an aggregate of 609,744 of uniQure ordinary shares that vested over the initial three-year term of the agreement. The upfront payment of $ 0.2 million was recorded as deferred revenue and was recognized on a ratable basis over the estimated performance period of four years . Payments and reimbursements for research costs were recognized on an as-incurred basis. The options to purchase uniQure shares were deemed to be a noncash component of the arrangement consideration as the vesting of options is linked to the uniQure Agreement and there is a requirement for the holders of the options to provide services under the uniQure Agreement. The fair value of the uniQure options, which was estimated to be $ 10.6 million, was recognized ratably as revenue over the estimated performance period of four years and the associated compensation expense related to the stock options was recorded as research and development expense. In August 2019, the Company and uniQure entered into an Amended and Restated Collaboration and License Agreement (the “Amended uniQure Agreement”), which amended and restated the uniQure Agreement, and a separate Collaboration and License Agreement (the “Second uniQure Agreement”). Under these agreements, the Company agreed to transfer incremental rights and services to uniQure in exchange for uniQure eliminating the uniQure Exclusivity Clause and transferring other rights back to the Company. Under the Amended uniQure Agreement, uniQure continues to have an exclusive license to select AAV capsid variants (the “Selected Variants”) in the uniQure Field. uniQure continues to be solely responsible, at its cost, to develop and commercialize the compounds and products containing the Selected Variants. The amended uniQure Agreement eliminated the uniQure Exclusivity Clause in the uniQure Agreement. Furthermore, the contingent payments that the Company was entitled to receive from uniQure for the achievement of research and development milestones of up to $ 5.0 million for each licensed product selected under the uniQure Agreement were eliminated and sublicense consideration on any future sublicensing arrangements was reduced from the low teens to low thirties percentages to mid-single digit to mid-twenties percentages. Under the Second uniQure Agreement, the parties agreed to research and develop new AAV capsid variants (the “New Variants”) that are not Selected Variants that affect certain targets selected by uniQure (the “uniQure Targets”) in the uniQure Field. The Company is solely responsible, at its cost, for the research of the New Variants. The Company granted uniQure an exclusive license to a certain number of the New Variants (the “uniQure New Variants”) that affect the uniQure Targets. uniQure is solely responsible, at its cost, to develop and commercialize the compounds and products containing the uniQure New Variants that affect the uniQure Targets (the “Licensed Products”). The Company retains all rights to New Variants in the uniQure Field that affect targets other than the uniQure Targets. Under both the Amended uniQure Agreement and the Second uniQure Agreement, uniQure will be required to pay the Company royalties on worldwide annual net sales of Licensed Products at a mid-single digit percentage rate, subject to certain specified reductions. uniQure will also be required to pay the Company sublicensing consideration for sublicensing the Company’s intellectual property rights licensed under the Amended uniQure Agreement or the Second uniQure Agreement to third parties at a rate between the mid-single digit to mid-twenties. The Company has reciprocal obligations, at the same percentage rates as uniQure, to pay uniQure royalties and sublicensing consideration for sublicensing certain intellectual property rights licensed under the Amended uniQure Agreement or the Second uniQure Agreement to third parties. The Company concluded that the Amended uniQure Agreement and the Second uniQure Agreement should be accounted for as one combined contract but separate from the uniQure Agreement given that the incremental licensed intellectual property rights and research and development services are distinct from the rights and services previously transferred to uniQure under the uniQure Agreement and the transaction price increased by an amount that equals the standalone selling price of the incremental rights and services to be transferred to uniQure under the Amended uniQure Agreement and Second uniQure Agreement. Neither party was required to pay monetary consideration in connection with the execution of the Amended uniQure Agreement or the Second uniQure Agreement or for subsequent performance by the parties under those agreements, notwithstanding the potential future royalty and sublicense consideration described above. The fair value of the non-monetary consideration given by uniQure to the Company, for the intellectual property right was $ 5.1 million. This intellectual property right is considered to be an in-process research and development asset with no alternative future use and, accordingly, was written off as acquired in-process research and development expense in the year ended December 31, 2019. The incremental transaction price described in the paragraph above was recorded as deferred revenue given that the Company identified one single combined performance obligation under ASC 606, which includes the licenses to the New Variants, research services and participation in the joint steering committee (“JSC”). Revenue is recognized using the input method based on actual costs incurred as a percentage of total budgeted costs as the Company completes its performance obligation. Based on the current estimated timelines, the deferred revenue is expected to be recognized as revenue over approximately one year from September 30, 2022. The Company determined the transaction price using the risk adjusted net present value analysis (“rNPV”) methodology to value the elimination of the uniQure exclusivity clause and other material rights received by the Company, including the potential royalties the Company would receive from uniQure. The rNPVs incorporate estimates and assumptions including the number of products the Company and uniQure would develop, the risk-adjusted probability of successfully developing a biopharmaceutical product, the probability that uniQure will develop a product, the research and development costs, the potential worldwide sales and associated commercialization costs, corporate tax rate, and discount rate. During the three months ended September 30, 2022 and 2021, the Company recognized revenue of $ 0.5 million and $ 0.1 million under both of the Amended uniQure Agreement and the Second uniQure Agreement, respectively. During the nine months ended September 30, 2022 and 2021, the Company recognized revenue of $ 1.8 million and $ 0.7 million under both of the Amended uniQure Agreement and the Second uniQure Agreement, respectively. During the nine months ended September 30, 2022 the decrease in total budgeted costs for the remaining performance obligation resulted in a $ 1.8 million increase in revenue recognized related to the performance obligation partially satisfied prior to January 1, 2022. As of September 30, 2022 and December 31, 2021, deferred revenue relating to uniQure was $ 1.8 million and $ 3.7 million, respectively. There were no amounts due from uniQure under the uniQure Agreement, Amended uniQure Agreement or Second uniQure Agreement as of September 30, 2022 and December 31, 2021. As of September 30, 2022 and December 31, 2021, the aggregate amount of the transaction price allocated to the remaining performance obligation was $ 1.8 million and $ 3.7 million, respectively. CRF In November 2015, the Company entered into a research funding and collaboration agreement (the “CRF Agreement”) with the Choroideremia Research Foundation (“CRF”), a non-profit organization dedicated to finding a cure for choroideremia, a rare inherited disorder that causes progressive vision loss, ultimately leading to complete blindness. The goal of the CRF Agreement is for CRF to contribute funding to help with the advancement of the Company’s choroideremia research program. The Company is responsible for all decision making and execution of any and all of the related activities to be completed in its sole discretion. The initial term of the CRF Research Plan is two years . The agreement includes contribution by the Company to CRF of up to $ 2.5 million upon certain development or approval milestones. The overall arrangement has automatic extensions of up to three additional years. As of September 30, 2022, no milestones have been achieved. Revenue was fully recognized for this agreement in the year ended December 31, 2017. There was no deferred revenue relating to the CRF Agreement as of September 30, 2022 and December 31, 2021. No amount was due from or to CRF under the CRF Agreement as of September 30, 2022 and December 31, 2021. Roche In November 2017, the Company entered into a collaboration and license agreement with F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (together, “Roche”) to discover and develop products containing optimized next generation AAV Vectors focused on ophthalmological diseases and disorders excluding select criteria (the “2017 Roche Agreement”). The Company and Roche both had the ability to nominate products to discover, develop and commercialize. At the effective date of the 2017 Roche Agreement, choroideremia was designated a Roche product class and the 4D-110 product was licensed to Roche. The Company was responsible for conducting research and development services prior to pivotal clinical studies, and Roche was responsible for conducting subsequent development and commercialization activities. In addition, Roche agreed to pay for research and development services at the agreed upon full-time employee rate for work performed for choroideremia under the 2017 Roche Agreement, and certain external costs, except for the costs associated with the manufacturing work for choroideremia. Under the 2017 Roche Agreement, Roche had an option exercisable prior to pivotal clinical studies, to license 4D-125 (for the treatment of XLRP), which was not exercised. Pursuant to the 2017 Roche Agreement, the Company received a non-refundable upfront payment of $ 21.0 million as consideration. In addition, the Company was entitled to contingent payments including (i) $ 1.0 million for each Roche nominated product beyond the first three, (ii) up to $ 30.0 million upon exercise of the option to convert a product the Company nominated and developed prior to pivotal clinical studies, (iii) development milestone payments of up to $ 223.0 million, of which $ 86.0 million related to choroideremia and the rest related to other licensed products; and (iv) sales-based milestones of up to $ 123.0 million in connection with licensed products. Through June 30, 2022, the Company received $ 10.0 million for development milestone payments that are non-refundable. The 2017 Roche Agreement also included provisions that entitled the Company to receive royalty payments ranging from the mid-single digits to the mid-teens for the net sales of the licensed products, in each case subject to the reductions in accordance with the terms of the agreement. The Company identified a single combined performance obligation for the license, research services and participation in the JSC and concluded that Roche’s option did not represent a material right. The Company’s contract with Roche did not include a significant financing component. The Company further concluded that the transaction price should not include the variable consideration related to development milestones as they were considered to be constrained as it was probable that the inclusion of such variable consideration could result in a significant reversal of cumulative revenue in the future. The Company excluded any consideration related to sales-based milestones, including royalties, which would be recognized when the related sales occur. The transaction price and estimated period of performance are re-evaluated at each reporting period and adjusted as needed to reflect changes in the scope of the project, reimbursable expenses and other conditions affecting variable consideration. In June 2021, the Company received from Roche notice of termination without cause of the 2017 Roche Agreement. The licenses granted by the Company to Roche under the 2017 Roche Agreement terminated in their entirety on September 16, 2021. Therefore, as of September 16, 2021, Roche no longer has a license for 4D-110 for the treatment of choroideremia or any other product class, and the Company is no longer entitled to receive any further milestones or royalties from Roche. In July 2021, the Company notified Roche of the Company’s election to continue development of choroideremia. As a result, in accordance with the terms of the agreement, all rights to 4D-110 data and intellectual property generated under the collaboration reverted to the Company. Under the 2017 Roche Agreement, if the Company is required to initiate a new Phase 1/2a clinical trial for 4D-110, the Company would not owe any royalty to Roche on net sales of 4D-110. If, however, the Company moves directly to a pivotal trial of 4D-110, without first being required to conduct a new Phase 1/2a clinical trial, the Company must pay Roche a mid-single digits percentage royalty on the net sales of 4D-110. As a result of the termination of the 2017 Roche Agreement, an adjustment of $ 8.7 million was made to the transaction price for the nine months ended September 30, 2021. During the three and nine months ended September 30, 2021, the Company recognized revenue of $ 1.3 million and $ 17.2 million, respectively. The Company did no t recognize any revenue under the 2017 Roche Agreement during the three and nine months ended September 30, 2022. As of September 30, 2022 and December 31, 2021, there was no deferred revenue and no accounts receivable from Roche relating to the 2017 Roche Agreement. As of December 31, 2021, the Company had no remaining performance obligation under the 2017 Roche Agreement. CFF In September 2016, the Company entered into an award agreement for the Optimized Adeno-Associated Virus for Lung Epithelia Gene Delivery Development Program with CFF, a non-profit organization dedicated to finding a cure for cystic fibrosis, an inherited disorder that causes disease in the pulmonary airways leading to morbidity and mortality. Under this agreement, CFF contributes funding to help advance the Company’s CF research program. The agreement was subsequently amended in September 2017, August 2018 and February 2021 (all four agreements are collectively referred to as the “CFF Agreement”). The total amount of the award under the CFF Agreement is $ 3.5 million. As of September 30, 2022 and December 31, 2021, the Company achieved milestones totaling $ 1.8 million, under the CFF Agreement. The remaining award amount will be paid by CFF based on the achievement of certain development milestones by the Company. The Company expects to make payments to CFF equal to six times the actual award received by the Company in three installments within the first four years of the first commercial sale of a product developed under this agreement. The Company also has agreed to make future sales-based milestone payments to CFF of up to three times the actual award received upon achieving specified commercialization milestones with respect to the first of any product developed utilizing any compound covered under the CFF Agreement. The CFF Agreement also requires the Company to pay to CFF royalties of a mid-single digit percentage, up to six times the actual award received, on any amounts received by the Company from the sale, license or transfer to a third-party of rights in the technology developed as a result of this collaboration. Any such royalty payments shall be credited against the payments owed by the Company upon first commercial sale. In the event of a change of control of the Company, CFF will receive certain payments, depending on the timing of the change of control and the size of the transaction. To date, the Company has not developed a commercial product in connection with the CFF Agreement, and it has not licensed, sold or otherwise transferred to another party the product developed under the CFF Agreement or the underlying technology. If at any time prior to the first commercial sale of a product developed as a result of the CFF Agreement, the Company ceases to use commercially reasonable efforts to develop or commercialize any product under the CFF Agreement for a continuous period of 180 consecutive days and fails to present a reasonable plan to resume commercially reasonable efforts, the Company will grant to CFF an irrevocable, exclusive worldwide interruption license under all of the Company’s interest in the research plan technology to exploit such product. Any third-party license granted by the Company shall be subject to such interruption license. Under ASC 606, the Company identified one performance obligation within the CFF grant agreement for research activities. The Company’s contract with CFF does not include a significant financing component. The Company concluded that the transaction price should not include the variable consideration related to future research milestones as they were considered to be constrained as it is probable that the inclusion of such variable consideration could result in a significant reversal of cumulative revenue in the future. The Company re-evaluates the transaction price and estimated period of performance at each reporting date. Revenue recognized during the three and nine months ended September 30, 2022 and 2021 was immaterial. As of September 30, 2022 and December 31, 2021, deferred revenue relating to the CFF Agreement was $ 1.4 million. There were no accounts receivable from CFF under the CFF Agreement as of September 30, 2022 and December 31, 2021. As of September 30, 2022 and December 31, 2021, the aggregate amount of the transaction price allocated to the remaining performance obligation was $ 1.4 million. Based on current timelines, the deferred revenue is expected to be recognized as revenue over the next two to four years as the Company performs research services through the completion of IND-enabling studies. The obligation to make payments to CFF upon a change of control meets the definition of an embedded derivative that is required to be bifurcated and separately accounted for as a derivative liability. See Note 14 for further discussion of the embedded derivative.

License Arrangements

License Arrangements	9 Months Ended
	Sep. 30, 2022
License Arrangements [Abstract]
License Arrangements	8. License Arrangements The Company has exclusive, worldwide license agreements (the “UC Agreements”) with the Regents of the University of California (the “UC Regents”) relating to the use of certain patents and intellectual property surrounding its core technologies, including Therapeutic Vector Evolution. Pursuant to each of the UC Agreements executed prior to January 2019, the Company was obligated to pay a (i) non-refundable license fee of $ 5,000 upon execution, (ii) a non-refundable license fee of $ 5,000 each year thereafter, until sales of a licensed product are made and royalties are paid to the UC Regents, (iii) reimbursement of domestic and foreign patent filing, prosecution and maintenance fees, and (iv) either $ 50,000 or issuance of a 3 % equity interest in the Company upon the closing of the first qualified financing at the option of the UC Regents. The Company’s first qualified financing occurred in 2015 and at the election of the UC Regents, the Company issued the UC Regents in January 2016 an amount of common stock equal to 6 % of the equity interests in the Company pursuant to the applicable clause in each of the UC Agreements. Pursuant to an agreement with the UC Regents executed in January 2019 the Company paid a non-refundable license fee of $ 50,000 to the UC Regents upon execution of the agreement. The Company is obligated to pay a non-refundable license fee of $ 5,000 on the one-year anniversary of the contract effective date and each year thereafter, until sales of a licensed product are made and royalties are paid to the UC Regents. In addition, the Company is obligated to make certain contingent payments including (i) development milestones up to $ 3.1 million, (ii) low single digit royalties on the net sales of its developed products that consists of a minimum annual royalty of up to $ 0.1 million per year for the term of the Agreement beginning in the first calendar year after the year in which net sales first occurred and (iii) sublicense consideration in the mid-teens to the mid-twenties range on any future sublicensing arrangements the Company may enter into with third-party licensees. In July 2021, the Company entered into an exclusive license agreement with the UC Regents and the Trustees of the University Pennsylvania to license intellectual property related to certain vectors. In July 2021, the Company paid a non-refundable license fee of $ 100,000 to the UC Regents upon execution of the agreement. The Company is obligated to pay a non-refundable license maintenance fee of $ 10,000 on the one-year anniversary of the contract effective date and each year thereafter, except years for which the Company has paid royalties on the net sales of a licensed product. In addition, the Company is obligated to make certain contingent payments including (i) development milestones up to $ 3.9 million, (ii) low single digit percentage rate royalties on the net sales of its licensed products that consists of a minimum annual royalty of up to $ 0.1 million per year for the term of the Agreement beginning in the first calendar year after the year in which net sales first occurred and (iii) sublicense consideration in the mid-single digits to the low twenties percentage rate range on any future sublicensing arrangements the Company may enter into with third-party licensees. During each of the three and nine months ended September 30, 2022 and 2021, the Company incurred immaterial expenses under the provisions of the outstanding license arrangements.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Operating Lease Commitments 5980 Horton Street Building Lease In May 2015, the Company executed a lease agreement for office and laboratory space in Emeryville, California. In January 2016, the Company executed the first amendment to the lease agreement for additional rentable office and laboratory space which extended the lease term to March 31, 2023 and updated the option to renew the lease at market rent from the prior additional term of three years to five years . In October 2018, the Company executed a second amendment to extend the lease to September 2026 . Additionally, the second amendment provided a tenant improvement allowance of $ 0.2 million, which was paid to the Company in November 2018. The 5980 Horton Street Building Lease is considered an operating lease under ASC 842 as it does not meet the criteria of a finance lease. As of September 30, 2022, the operating lease right-of-use asset and operating lease liability were $ 1.7 million and $ 2.0 million, respectively. As of December 31, 2021, the operating lease right-of-use asset and operating lease liability were $ 1.9 million and $ 2.3 million, respectively. The discount rate used to determine the lease liability was 7.5 %. 5858 Horton Street Building Lease and Expansion In October 2018, the Company executed a second lease agreement for additional office and laboratory space in Emeryville, California. The new lease has an initial term of 87 months beginning on the rent commencement date with the option to renew the lease for one additional term of five years at market rent. The Company did not have to pay rent until October 2019. This lease agreement also provided for a tenant improvement allowance of $ 0.4 million, which was paid to the Company in December 2019. The Company amortizes the tenant improvement allowance on a straight-line basis over the remaining term of the lease as a reduction of rent expense. In May 2019, the Company amended the second lease agreement executed in October 2018 to add additional office, manufacturing and laboratory space (the “Expansion”). The amendment extended the term of the lease to December 31, 2029 . The Company did not have to pay rent until December 2019. The lease agreement also included a tenant improvement allowance, which was increased to $ 2.3 million in February 2021 pursuant to a second amendment to the second lease agreement. As of September 30, 2022 the Company has received $ 1.9 million of this tenant improvement allowance. The tenant improvement allowance funds improvements to the additional office, manufacturing and laboratory space, which the Company has determined to be lessee owned. The allowance is treated as a reduction of lease payments used to measure the lease liability. The 5858 Horton Street Building Lease and Expansion are considered operating leases under ASC 842 as they do not meet the criteria of a finance lease. As of September 30, 2022, the operating lease right-of-use asset and operating lease liability were $ 11.8 million and $ 14.6 million, respectively. As of December 31, 2021, the operating lease right-of-use asset and operating lease liability were $ 12.6 million and $ 14.2 million, respectively. The discount rate used to determine the lease liability was 7.8 %. Neither of the leases include a general option for the Company to terminate the leases. The following table summarizes the components of lease expense for the three and nine months ended September 30, 2022 and 2021 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Operating lease cost $ 697 $ 697 $ 2,090 $ 1,934 Variable lease cost 260 220 751 695 Total $ 957 $ 917 $ 2,841 $ 2,629 Variable lease payments include amounts relating to common area maintenance and are recognized in the condensed statements of operations as incurred. The following table summarizes supplemental information related to operating leases: September 30, December 31, Weighted-average remaining lease term (in years): 6.9 7.6 Weighted-average discount rate: 7.8 % 7.8 % For the nine months ended September 30, 2022, cash provided for amounts included in the measurement of operating lease liabilities included in cash flows used in operating activities was $ 0.1 million. For the nine months ended September 30, 2021, cash paid for amounts included in the measurement of operating lease liabilities included in cash flows used in operating activities was $ 1.1 million. The following table summarizes the maturities of lease liabilities as of September 30, 2022 (in thousands): 2022 (remaining three months) $ 348 2023 3,058 2024 3,149 2025 3,244 2026 3,135 Thereafter 8,685 Total future minimum lease payments 21,619 Less: Amount representing interest ( 5,067 ) Present value of future minimum lease payments 16,552 Less: Current portion of operating lease liabilities 2,633 Long-term portion of operating lease liabilities $ 13,919 Indemnification Agreements In the ordinary course of business, the Company enters into agreements that may include indemnification provisions, such as with vendors and other parties. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third-party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into indemnification agreements with its directors and officers that require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company currently maintains directors’ and officers’ liability insurance that would generally enable it to recover a portion of any future amounts paid. The Company believes the estimated fair value of its indemnification agreements in excess of applicable insurance coverage is not material. Legal Proceedings From time to time, the Company may become involved in legal proceedings arising from the ordinary course of its business. If applicable, the Company records a legal liability when it believes that it is both probable that a liability may be imputed, and the amount of the liability can be reasonably estimated. Significant judgment by the Company is required to determine both probability and the estimated amount. There are no material legal proceedings outstanding at September 30, 2022. See Note 12 for details of a settlement with a former employee in April 2021.

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Common Stock	10. Common Stock As of September 30, 2022 and December 31, 2021, the Company’s certificate of incorporation authorized the Company to issue 300,000,000 shares of common stock, at the par value of $ 0.0001 per share. The holder of each share of common stock is entitled to one vote per share . Common stockholders are entitled to dividends, if and when declared by the board of directors. To date, no dividends on common stock have been declared by the board of directors. As of September 30, 2022 and December 31, 2021, the Company has reserved common stock, on an as-converted basis, for future issuance as follows: September 30, December 31, Issuance of common stock under the 2020 Equity Incentive Award Plan 2,040,839 2,690,097 Issuance of common stock under the Employee Stock Purchase Plan 462,195 498,747 Exercise of options issued and outstanding 6,035,456 3,881,274 Exercise of common stock warrants 53,669 53,669 Total common stock reserved for future issuance 8,592,159 7,123,787

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Stock-based Compensation	11. Stock-based Compensation 2020 Equity Incentive Award Plan In December 2020, the Company adopted the 2020 Incentive Award Plan (“2020 Plan”), which became effective on December 10, 2020. The 2020 Plan initially reserved 2,606,546 shares of common stock for the issuance of stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance bonus awards, performance stock units, dividend equivalents or other stock or cash based award granted to employees, directors and consultants of the Company. The number of shares reserved for future issuance under the 2020 Plan will increase annually on the first day of each fiscal year beginning in 2021 and ending in 2030 by the lesser of (i) 5 % of the shares of common stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (ii) such number of shares of common stock as determined by the Company's board of directors, provided, however, no more than 18,000,000 shares of the Company's common stock may be issued upon the exercise of incentive stock options. In 2022, an additional 1,611,226 shares of the Company's common stock became available for issuance under the 2020 Plan, as a result of the operation of the automatic annual increase provision. All options are exercisable over a period not to exceed the contractual term of ten years from the date the stock options were issued. As of September 30, 2022 there were 1,859,923 shares available for grant under the 2020 Plan. 2015 Equity Incentive Plan Following the effectiveness of the 2020 Plan, the Company will not make any further grants under the 2015 Equity Incentive Plan (the "2015 Plan"). However, the 2015 Plan continues to govern the terms of options that remain outstanding under the 2015 Plan. All outstanding grants under the 2015 Plan that are repurchased, forfeited, expire or are returned back to the 2015 Plan are not available for grant under the 2020 Plan. The 2015 Plan provided for grants of stock options, stock appreciation rights, restricted stock and restricted stock unit awards to employees, directors and consultants of the Company. As of September 30, 2022, options to purchase 2,343,729 shares of the Company's common stock were outstanding under the 2015 Plan. All options are exercisable over a period not to exceed the contractual term of ten years from the date the stock options were issued and are granted at prices not less than the estimated fair market value of the Company’s common stock on the grant date as determined by the Company's board of directors. If an individual owns stock representing more than 10 % of the Company’s outstanding shares, the exercise price of each share shall be at least 110 % of the fair market value on the date of grant. Employee Stock Purchase Plan In December 2020, the Company adopted the 2020 Employee Stock Purchase Plan (the “2020 ESPP”). Under the 2020 ESPP, 252,337 shares of the Company's common stock were initially reserved for employee purchases of the Company's common stock under terms and provisions established by the Company's board of directors and approved by the Company's stockholders. The number of shares reserved for future issuance under the 2020 ESPP will increase annually on the first day of each fiscal year beginning in 2021 and ending in 2030 by the lesser of (i) 1 % of the shares of the Company's common stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (ii) such number of shares of common stock as determined by the Company's board of directors, provided, however, no more than 15,000,000 shares of the Company's common stock may be issued under the 2020 ESPP. On March 28, 2022, an additional 25,000 shares of the Company's common stock became available for future issuance under the 2020 ESPP, as a result of the operation of this automatic annual increase provision. Under the 2020 ESPP the Company's employees may purchase common stock through payroll deductions at a price equal to 85 % of the lower of the fair market value of the stock at the beginning of the offering period or at the end of each applicable purchase period. The 2020 ESPP provides for a series of overlapping 24 -month offering periods comprised of four six-month purchase periods. The initial offering period under the ESPP is longer than 24 months, commencing February 15, 2021 and ending on May 14, 2023. Contributions under the 2020 ESPP are limited to a maximum of 15 % of an employee's eligible compensation. Stock Options The following table summarizes the stock options activity for the nine months ended September 30, 2022: Number of Number of Balances at December 31, 2021 2,690,097 3,881,274 Options authorized 1,611,226 — Options granted ( 2,641,637 ) 2,641,637 Options exercised — ( 106,302 ) Options expired 82,627 ( 82,627 ) Options forfeited 298,526 ( 298,526 ) Balances at September 30, 2022 2,040,839 6,035,456 Options exercisable at September 30, 2022 2,280,409 Options vested and expected to vest at September 30, 2022 6,035,456 The Company estimates the fair value of stock options using the Black-Scholes option pricing model. The fair value of employee and nonemployee options is recognized on a straight-line basis over the requisite service period of the awards. The fair value of the Company’s stock options was estimated using the following assumptions for the three and nine months ended September 30, 2022 and 2021. Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Expected term 5.9 - 6.1 years 6.0 - 6.1 years 5.9 - 6.1 years 5.8 - 6.3 years Expected volatility 81.3 % - 81.9 % 80.4 % - 82.8 % 80.0 % - 81.9 % 80.4 % - 84.3 % Risk-free interest rate 2.9 % - 3.9 % 0.8 % - 1.1 % 1.5 % - 3.9 % 0.6 % - 1.1 % Expected dividend yield — % — % — % — % Expected Term . The expected term for employee options is calculated using the simplified method as the Company does not have sufficient historical information to provide a basis for this estimate. The simplified method is based on the average of the vesting tranches and the contractual life of each grant. The expected term for nonemployee options is the contractual term of the options. Expected Volatility . The expected volatility is based on a mix of the Company's historical volatility and the historical volatility of comparable companies with similar attributes to the Company, including industry, stage of life cycle, size and financial leverage. For each grant, the Company measured historical volatility over a period equivalent to the expected term. Risk-free Interest Rate. The risk-free interest rate is based on the yield available on U.S. Treasury zero-coupon issues whose term is similar in duration to the expected term of the respective stock option. Expected Dividend Yield . The Company has not paid and does not anticipate paying any dividends on its common stock in the future. Accordingly, the Company has estimated the dividend yield to be zero . Stock-Based Compensation Expense The following table is a summary of stock-based compensation expense incurred for employees and nonemployees by function (in thousands): Three Months Ended Nine Months Ended 2022 2021 2022 2021 Research and development $ 2,438 $ 1,893 $ 6,931 $ 4,901 General and administrative 2,082 2,030 5,844 5,167 Total stock-based compensation expense $ 4,520 $ 3,923 $ 12,775 $ 10,068

Common Stock Warrants

Common Stock Warrants	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Common Stock Warrants	12. Common Stock Warrants In 2016, the Company issued a warrant for 45,000 shares of the Company’s common stock to a service provider with an exercise price of $ 1.14 per share, of which 15,000 warrant shares become exercisable upon completion of an offering of securities in a private placement by the Company with net proceeds in excess of $ 25.0 million and 30,000 warrant shares become exercisable upon completion of an IPO by the Company. The fair value of the warrant was determined at the issuance date using the Black-Scholes option pricing model. 15,000 of these warrant shares became exercisable upon the completion of the Series B financing in 2018 and 30,000 of these warrants became exercisable upon completion of the IPO in 2020. All 45,000 shares of this warrant were exercised in October 2021 . In May 2018, the Company issued a warrant for 23,669 shares of the Company’s common stock to a service provider with an exercise price of $ 3.19 per share. The fair value of the warrant was determined at the issuance date using the Black-Scholes option pricing model, expires in 2025 and upon issuance was fully vested. In December 2020, the Company issued a warrant for 30,000 shares of the Company’s common stock to a service provider with an exercise price of $ 18.00 per share. This warrant vests over a period of four years and expires in 2027 . The fair value of the warrant was determined at the issuance date using the Black-Scholes option pricing model. In April 2021, the Company issued a warrant for 40,000 shares of the Company’s common stock to a former employee with an exercise price of $ 9.41 per share as a result of a settlement agreement with such former employee. The warrant was exercised in May 2021 . There was no material expense related to the above warrant shares during the three and nine months ended September 30, 2022 and 2021.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	13. Net Loss Per Share, Basic and Diluted The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Numerator Net loss $ ( 25,691 ) $ ( 22,239 ) $ ( 80,115 ) $ ( 46,234 ) Denominator Weighted-average shares outstanding used in computing net loss per share, basic and diluted 32,385,791 27,022,380 32,305,074 26,818,595 Net loss per share, basic and diluted $ ( 0.79 ) $ ( 0.82 ) $ ( 2.48 ) $ ( 1.72 ) The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive: September 30, 2022 2021 Options issued and outstanding 6,035,456 4,082,539 ESPP shares expected to be issued — 97,155 Common stock warrants 53,669 98,669 Total 6,089,125 4,278,363

Derivative Liability

Derivative Liability	9 Months Ended
	Sep. 30, 2022
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Liability	14. Derivative Liability The Company identified an embedded derivative resulting from the change of control provision in the CFF Agreement. Embedded derivatives that are required to be bifurcated from the underlying host instrument are accounted for and valued as separate financial instruments. At the inception of the derivative in 2017, the Company recognized this derivative as a liability, and revenue was reduced by the initial fair value of the derivative liability. The Company remeasures the derivative liability to fair value at each reporting period and records the change in fair value of the derivative liability as other income (expense), net. The Company uses a present value analysis with multiple scenarios, which incorporates assumptions and estimates to value the derivative instrument. The Company assesses these assumptions and estimates on a periodic basis as additional information impacting the assumptions is obtained. Estimates and assumptions impacting the fair value measurement include the change of control payment to CFF (range of $ 0.0 million to $ 10.6 million at September 30, 2022 and December 31, 2021), the probability of a change of control event, the probability of the product achieving development or commercial status at time of change of control (range of 4.8 % to 17.2 % at September 30, 2022 and December 31, 2021) and the discount rate ( 15.0 % and 14.0 % at September 30, 2022 and December 31, 2021, respectively). The Company determined the estimated fair value of this liability as of the inception date of the CFF Agreement and concluded that the amount was immaterial. The Company determined the fair value of this derivative liability was $ 0.2 million as of September 30, 2022 and December 31, 2021.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2022
Related Party Transactions [Abstract]
Related Party Transactions	15. Related Party Transactions During the three months and nine months ended September 30, 2021, the Company paid $ 21,000 and $ 64,000 , respectively, to David Schaffer, Ph.D., a co-founder, and former director and Chief Scientific Advisor of the Company for consulting services while Dr. Schaffer was a director. The Company made no payments to Dr. Schaffer during the three and nine months ended September 30, 2022 other than fees earned in his capacity as a member of our Board of Directors. In April 2019, the Company entered into two sponsored research agreements (“SRAs”) with the UC Regents to conduct research in a research facility on the U.C. Berkeley campus, under the direction of Dr. Schaffer. The SRAs had a three year term that ended in May 2022. Under the SRAs, the Company had an option to license (on a royalty-bearing basis) all intellectual property generated under the SRAs. Any patent prosecution costs incurred under the SRAs will also be borne by the Company. The Company could terminate the SRAs for convenience and without cause with 60 days’ notice. The total amount the Company is committed to pay to the UC Regents under the SRAs is $ 1.5 million, which was fully paid as of September 30, 2022. In March 2021, the Company entered into another sponsored research agreement with the UC Regents to conduct research in laboratories on the U.C. Berkeley campus that are under the direction of Dr. Schaffer and another U.C. Berkeley professor covering investigations into how machine learning approaches may enhance AAV capsid engineering (the “Machine Learning SRA”). Pursuant to the Machine Learning SRA, the Company committed to pay the UC Regents a total of $ 1.4 million, of which $ 0.4 million was paid as of September 30, 2022. The Machine Learning SRA has a three-year term ending in 2024. Any patent prosecution costs incurred under the SRAs will also be borne by the Company. The Company can terminate the SRAs for convenience and without cause with 60 days’ notice. While the Machine Learning SRA is between the Company and the UC Regents, the payments under the SRA will be used to fund the lab under the direction of Dr. Schaffer. As of September 30, 2022 and December 31, 2021, accounts payable related to the SRAs and Machine Learning SRA was $ 0.0 million. The Machine Learning SRA was terminated by the Company in March 2022 . As of February 2022, the SRAs ceased to be related party transactions upon the resignation of Dr. Schaffer from the board of directors of the Company.

401(K) Plan

401(K) Plan	9 Months Ended
	Sep. 30, 2022
Retirement Benefits [Abstract]
401(K) Plan	16. 401(k) Plan In 2014, the Company adopted a 401(k) plan for all employees who have met certain eligibility requirements. The 401(k) plan allows employees to make pre-tax and post-tax contributions up to the maximum allowable amount set by the Internal Revenue Service. The Company made contributions to the 401(k) plan for all eligible participants and recorded contribution expenses of $ 0.2 million and $ 0.1 million for the three months ended September 30, 2022 and 2021. For the nine months ended September 30, 2022 and 2021, the Company recorded contribution expenses of $ 0.7 million and $ 0.4 million, respectively.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with United States Generally Accepted Accounting Principles (“U.S. GAAP”) and the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for interim reporting. Our condensed balance sheet for the year ended December 31, 2021 was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. Certain information and note disclosures normally included in annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. Accordingly, the unaudited condensed financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021 filed with the SEC. The accompanying financial information for the three and nine months ended September 30, 2022 and 2021 are unaudited. The unaudited condensed financial statements have been prepared on the same basis as the annual audited financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s financial position as of September 30, 2022 and December 31, 2021 and its results of operations and cash flows for the nine months ended September 30, 2022 and 2021. The results for interim periods are not necessarily indicative of the results expected for the full fiscal year or any other periods.
Use of Estimates and Judgements	Use of Estimates and Judgements The preparation of the condensed financial statements in conformity with U.S. GAAP requires management to make estimates and judgements that affect the reported amounts of assets, liabilities, revenue and expenses and disclosure of contingent assets and liabilities as of the date of the financial statements. Such estimates include the determination of useful lives for property and equipment, the contract term, transaction price and costs of collaboration agreements, as well as estimates of the fair value of common stock (prior to the IPO), stock options, derivative instrument and income tax uncertainties. Actual results could differ from those estimates. Due to the coronavirus (“COVID-19”) pandemic, there has been uncertainty and disruption in the global economy and financial markets. The Company is not aware of any specific event or circumstance that would require an update to its estimates or judgments or a revision of the carrying value of its assets or liabilities as of September 30, 2022. While there was not a material impact to the Company's unaudited condensed financial statements as of September 30, 2022, these estimates may change, as new events occur and additional information is obtained, as well as other factors related to the COVID-19 pandemic that could result in material impacts to the unaudited condensed financial statements in future reporting periods.
Segment Information	Segment Information The Company operates and manages its business as one reportable and operating segment. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on a company-wide basis for purposes of allocating resources and assessing financial performance.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents, marketable securities and accounts receivable. The Company’s cash is held at two financial institutions in the United States of America. The Company’s cash equivalents are invested in money market funds. The Company also invests in U.S. Treasuries, U.S. Government sponsored agency, commercial paper and corporate bonds. The Company has not experienced any losses on its deposits of cash and cash equivalents. Such deposits may, at times, exceed federally insured limits. The Company’s partners in collaboration and license agreements who represent 10% or more of the Company’s total revenue are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Customer A * 94 % * 96 % Customer B 99 % * 98 % * Total 99 % 94 % 98 % 96 % * Less than 10% The Company’s partners in collaboration and license agreements who represent 10% or more of the Company’s total accounts receivable are as follows: September 30, December 31, Customer A 0 % 100 % Total 0 % 100 % The Company’s total revenues by geographic region, based on the location of the customer, are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Netherlands $ 497 $ 64 $ 1,849 $ 724 Switzerland — 1,290 — 17,190 United States 3 12 33 32 Total revenue $ 500 $ 1,366 $ 1,882 $ 17,946
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents. Cash equivalents consist of money market funds.
Marketable Securities	Marketable Securities Marketable securities consist of commercial paper, corporate bonds, U.S. Treasuries and U.S. Government sponsored agencies and are included in current and noncurrent assets. The Company classifies its marketable securities as available-for-sale and carries them at fair value on its condensed balance sheet. Fair value is estimated using independent pricing sources based on quoted prices in active markets for similar securities. Unrealized gains and losses on the marketable securities are reported as a component of stockholders' equity in accumulated other comprehensive loss. The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in interest income on the condensed statements of operations. Realized gains and losses are included in interest income on the condensed statements of operations. The Company periodically evaluates its marketable securities to assess whether those with unrealized loss positions are other than temporarily impaired. The Company considers various factors in determining whether to recognize an impairment charge. If the Company determines that the decline in an investment's fair value is other-than-temporary, the difference is recognized as an impairment loss in the condensed statements of operations.
Other Risks and Uncertainties	Other Risks and Uncertainties The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, protection of proprietary technology, dependence on key personnel, suppliers for key raw materials, contract manufacturing organizations (“CMOs”) and contract research organizations (“CROs”), compliance with government regulations and the need to obtain additional financing to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical studies, clinical trials and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance and reporting. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained or maintained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from other pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees, consultants and other third parties (including for clinical trials and some aspects of research and preclinical testing). The extent of the impact of the COVID-19 pandemic on the Company’s business will depend upon the duration and spread of the outbreak and the extent and severity of the impact on the Company’s clinical trial activities, research activities and suppliers, all of which are uncertain and cannot be predicted. The extent to which the coronavirus outbreak may materially impact the Company’s financial condition, liquidity or results of operations is uncertain.
Fair Value Measurements	Fair Value Measurements The Company applies fair value accounting for all financial assets and liabilities and nonfinancial assets and liabilities that are recognized or disclosed at fair value in the unaudited condensed financial statements on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on 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. As a basis for considering such assumptions, a three-level fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows: • Level 1 — Observable inputs that reflect unadjusted quoted market prices in active markets for identical assets or liabilities that are accessible at the measurement date. • Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company accounts for transfers of financial instruments between levels of the fair value hierarchy on the date of the event or change in circumstance that caused the transfer.
Common Stock Warrants	Common Stock Warrants The Company accounts for common stock warrants which meet the definition of a derivative as liabilities if the warrant requires net cash settlement or gives the holder the option of net cash settlement. The Company accounts for common stock warrants as equity if the contract requires physical settlement or net physical settlement or if the Company has the option of physical settlement or net physical settlement. Common stock warrants classified as liabilities are initially recorded at fair value and remeasured at fair value each condensed balance sheet date with the offset adjustments recorded in other income (expense), net within the condensed statements of operations. Common stock warrants classified as equity are initially measured at fair value on the grant date and are not subsequently remeasured.
Leases	Leases On December 31, 2021, the Company adopted Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842), (" ASC 842 ") using the alternative modified transition method effective as of January 1, 2021. As a result, the Company has retrospectively changed its previously issued unaudited condensed financial statements as of September 30, 2021 and for the three and nine months ended September 30, 2021 as presented within the Company's September 30, 2021 Quarterly Report on Form 10-Q to reflect the adoption of ASC 842 on January 1, 2021 . The condensed financial statements for the three and nine months ended September 30, 2021 presented herein differ from the Company's condensed financial statements included in the Company's September 30, 2021 Quarterly Report on Form 10-Q as those unaudited condensed financial statements were prepared using the former accounting standard referred to as ASC Topic 840, Leases. The impact of adoption on ASC 842 on the condensed statements of operations for the nine months ended September 30, 2021 was immaterial. The following table summarizes the effect of the adoption of ASC 842 on the condensed statement of cash flows for the nine months ended September 30, 2021 (in thousands): Pre ASC 842 After ASC 842 Nine Months Ended ASC 842 Nine Months Ended September 30, 2021 Adjustments September 30, 2021 Adjustments to reconcile net loss to net cash Amortization of right-of-use assets $ — $ 1,117 $ 1,117 Changes in operating assets and liabilities Operating lease liabilities — ( 1,117 ) ( 1,117 ) Supplemental disclosures of noncash investing and financing information Decrease in right-of-use assets due to reduction in operating lease liabilities upon modification — ( 478 ) ( 478 ) At contract inception, the Company determines if an arrangement is or contains a lease. A contract is or contains a lease if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. If determined to be or contain a lease, the lease is assessed for classification as either an operating or finance lease at the lease commencement date, defined as the date on which the leased asset is made available for use by the Company, based on the economic characteristics of the lease. A right-of-use asset represents the economic benefit conveyed to the Company by the right to use the underlying asset over the lease term. A lease liability represents the obligation to make lease payments arising from the lease. Operating lease right-of-use assets represent the Company's right to use an underlying asset for the lease term and operating lease liabilities represent the Company's obligation to make payments arising from the lease. Operating right-of-use assets and liabilities are recognized at the commencement date of the lease and are measured at the present value of the fixed payments due over the expected lease term less the present value of any incentives, rebates, or abatements the Company expects to receive from the lessor. The Company records amortization of operating right-of-use assets and accretion of lease liabilities as a single lease cost on a straight-line basis over the lease term. No lease renewal options are recognized as part of the right-of-use assets and lease liabilities. The Company's operating leases are presented in the condensed balance sheets as operating lease right-of-use assets, classified as noncurrent assets, and operating lease liabilities, classified as current and noncurrent based on the discounted lease payments to be made within the preceding twelve months. As the Company’s leases do not provide an implicit interest rate, the Company uses its incremental borrowing rate to discount lease payments. The incremental borrowing rate represents an estimated rate of interest that the Company would have to pay to borrow equivalent funds on a collateralized basis at the lease commencement date.
Revenue Recognition	Revenue Recognition The Company determines revenue recognition for arrangements within the scope of Accounting Standards Update 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASC 606") by performing the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company’s revenue is primarily derived through its license, research, development and commercialization agreements. The terms of these types of agreements may include (i) licenses to the Company’s technology, (ii) research and development services, and (iii) services or obligations in connection with participation in research or steering committees. Payments to the Company under these arrangements typically include one or more of the following: nonrefundable upfront and license fees, research funding, milestone and other contingent payments to the Company for the achievement of defined collaboration objectives and certain preclinical, clinical, regulatory and sales-based events, as well as royalties on sales of any commercialized products. Arrangements that include upfront payments are recorded as deferred revenue upon receipt or when due and are recognized as revenue as the performance conditions are met. The event-based milestone payments, royalties and cost reimbursements represent variable consideration, and the Company uses the most likely amount method to estimate this variable consideration. Royalty payments are recognized when earned or as the sales occur. The Company records cost reimbursements as accounts receivable when right to consideration is unconditional. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC 606. The Company allocates the total transaction price to each performance obligation based on the estimated standalone selling price and recognizes revenue when, or as, the performance obligation is satisfied. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. At the end of each reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Significant management judgment is required to determine the level of effort required under an arrangement and the period over which the Company expects to complete its performance obligations under the arrangement. Changes in these estimates can have a material effect on revenue recognized.
Embedded Derivative	Embedded Derivative Embedded derivatives that are required to be bifurcated from the underlying host instrument are accounted for and valued as a separate financial instrument. An embedded derivative exists in the award agreement with the Cystic Fibrosis Foundation (“CFF”). As described in Note 14, the embedded derivative has been bifurcated and is classified as a liability on the condensed balance sheets and is separately accounted for at its fair value. The derivative liability is subject to remeasurement to fair value each reporting period. Changes in the fair value of the derivative liability are recognized as a component of other income (expense), net within the condensed statements of operations.
Net Loss Per Share, Basic and Diluted	Net Loss Per Share, Basic and Diluted Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by giving effect to all potentially dilutive common shares outstanding for the period. For purposes of this calculation, stock options to acquire shares of common stock and common stock warrants are considered potentially dilutive common shares, but have been excluded from the calculation of diluted net loss per share as their effect is antidilutive.
Recent Accounting Pronouncement	Recent Accounting Pronouncement New Accounting Pronouncement Not Yet Adopted As an “emerging growth company,” the Jumpstart Our Business Startups Act (“JOBS Act”) allows the Company to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are made applicable to private companies. The Company has elected to use this extended transition period under the JOBS Act. The adoption dates discussed below reflect this election. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments , as clarified in subsequent amendments. ASU 2016-13 changes the impairment model for certain financial instruments. The new model is a forward-looking expected loss model and will apply to financial assets subject to credit losses and measured at amortized cost and certain off-balance sheet credit exposures. This includes loans, held-to-maturity debt securities, loan commitments, financial guarantees and net investments in leases, as well as trade receivables. For available-for-sale debt securities with unrealized losses, credit losses will be measured in a manner similar to today, except that the losses will be recognized as allowances rather than reductions in the amortized cost of the securities. In October 2019, the FASB voted to delay the effective date of this standard. Topic 326 will be effective for the Company for fiscal years beginning after December 15, 2022. Early adoption is permitted. The Company is currently evaluating the effects of this ASU on its financial statements and related disclosures and does not expect there to be a material impact.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Schedule of Concentration of Risk	The Company’s partners in collaboration and license agreements who represent 10% or more of the Company’s total revenue are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Customer A * 94 % * 96 % Customer B 99 % * 98 % * Total 99 % 94 % 98 % 96 % * Less than 10% The Company’s partners in collaboration and license agreements who represent 10% or more of the Company’s total accounts receivable are as follows: September 30, December 31, Customer A 0 % 100 % Total 0 % 100 %
Schedule of Revenues by Geographic Region	The Company’s total revenues by geographic region, based on the location of the customer, are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Netherlands $ 497 $ 64 $ 1,849 $ 724 Switzerland — 1,290 — 17,190 United States 3 12 33 32 Total revenue $ 500 $ 1,366 $ 1,882 $ 17,946
Schedule of Impact of Adoption of New Accounting Standard	The following table summarizes the effect of the adoption of ASC 842 on the condensed statement of cash flows for the nine months ended September 30, 2021 (in thousands): Pre ASC 842 After ASC 842 Nine Months Ended ASC 842 Nine Months Ended September 30, 2021 Adjustments September 30, 2021 Adjustments to reconcile net loss to net cash Amortization of right-of-use assets $ — $ 1,117 $ 1,117 Changes in operating assets and liabilities Operating lease liabilities — ( 1,117 ) ( 1,117 ) Supplemental disclosures of noncash investing and financing information Decrease in right-of-use assets due to reduction in operating lease liabilities upon modification — ( 478 ) ( 478 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Fair Value Hierarchy for Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis	The following tables represent the Company’s fair value hierarchy for financial assets and financial liabilities measured at fair value on a recurring basis as of September 30, 2022 and December 31, 2021 (in thousands): Basis for Fair Value Measurements Fair Value as of Level 1 Level 2 Level 3 September 30, 2022 Assets Cash equivalents: Money market funds $ 87,704 $ — $ — $ 87,704 US treasuries — 5,461 — 5,461 Marketable securities: Commercial paper — 9,860 — 9,860 Corporate bonds — 46,862 — 46,862 US treasuries — 71,654 — 71,654 US government sponsored agencies — 2,163 — 2,163 Total $ 87,704 $ 136,000 $ — $ 223,704 Liabilities Derivative liability $ — $ — $ 213 $ 213 Total $ — $ — $ 213 $ 213 Basis for Fair Value Measurements Fair Value as of Level 1 Level 2 Level 3 December 31, 2021 Assets Cash equivalents: Money market funds $ 36,556 $ — $ — $ 36,556 Marketable securities: Commercial paper — 37,535 — 37,535 Corporate bonds — 94,864 — 94,864 US treasuries — 30,029 — 30,029 Total $ 36,556 $ 162,428 $ — $ 198,984 Liabilities Derivative liability $ — $ — $ 214 $ 214 Total $ — $ — $ 214 $ 214
Summary of Changes in Fair Value of Level 3 Financial Instruments	The following tables set forth a summary of the changes in the fair value of the Company’s Level 3 financial instrument during the nine-month periods ended September 30, 2022 and 2021 (in thousands): Derivative Balance as of December 31, 2021 $ 214 Change in fair value included in other income (expense), net ( 1 ) Balance as of September 30, 2022 $ 213 Derivative Balance as of December 31, 2020 $ 122 Change in fair value included in other income (expense), net 92 Balance as of September 30, 2021 $ 214

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Summary of Available for Sale Securities	Marketable securities, which are classified as available-for-sale, consisted of the following as of September 30, 2022 and December 31, 2021 (in thousands): Amortized Cost Basis Gross Unrealized Gains Gross Unrealized Losses Fair Value as of September 30, 2022 Short-term marketable securities: Commercial paper $ 5,025 $ — $ ( 55 ) $ 4,970 Corporate bonds 41,357 — ( 727 ) 40,630 US treasuries 72,314 4 ( 664 ) 71,654 US government sponsored agencies 2,200 — ( 37 ) 2,163 Total short-term marketable securities $ 120,896 $ 4 $ ( 1,483 ) $ 119,417 Long-term marketable securities: Commercial paper $ 5,082 $ — $ ( 192 ) $ 4,890 Corporate bonds 6,413 — ( 181 ) 6,232 Total long-term marketable securities $ 11,495 $ — $ ( 373 ) $ 11,122 Amortized Cost Basis Gross Unrealized Gains Gross Unrealized Losses Fair Value as of December 31, 2021 Short-term marketable securities: Commercial paper $ 32,471 $ — $ ( 4 ) $ 32,467 Corporate bonds 57,315 — ( 79 ) 57,236 US treasuries 5,082 — ( 9 ) 5,073 Total short-term marketable securities $ 94,868 $ — $ ( 92 ) $ 94,776 Long-term marketable securities: Commercial paper $ 5,089 $ — $ ( 21 ) $ 5,068 Corporate bonds 37,821 — ( 193 ) 37,628 US treasuries 25,073 — ( 117 ) 24,956 Total long-term marketable securities $ 67,983 $ — $ ( 331 ) $ 67,652

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2022
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net, consisted of the following (in thousands): September 30, December 31, Machinery and equipment $ 9,952 $ 5,971 Leasehold improvements 16,380 2,527 Furniture and fixtures 566 566 Office equipment 240 165 Computer equipment and software 616 421 Construction in progress 1,012 10,066 Total property and equipment 28,766 19,716 Less: Accumulated depreciation and amortization ( 6,714 ) ( 5,325 ) Property and equipment, net $ 22,052 $ 14,391

Accrued and Other Current Lia_2

Accrued and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2022
Payables and Accruals [Abstract]
Summary of Accrued and Other Current Liabilities	Accrued and other current liabilities consisted of the following (in thousands): September 30, December 31, Payroll and related expenses $ 4,161 $ 3,994 Accrued clinical and preclinical study costs 1,346 407 Consulting and professional 1,549 1,573 Other accrued expenses 188 1,770 Total accrued and other current liabilities $ 7,244 $ 7,744

Research and Collaboration Ar_2

Research and Collaboration Arrangements (Tables)	9 Months Ended
	Sep. 30, 2022
Research And Collaboration Arrangements [Abstract]
Summary of Collaboration and License Revenue	Collaboration and license revenue for each period was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 uniQure $ 497 $ 64 $ 1,849 $ 724 Roche — 1,290 — 17,190 CFF 3 12 33 32 Total revenue $ 500 $ 1,366 $ 1,882 $ 17,946
Summary of Deferred Revenue	Deferred revenue is summarized as follows (in thousands): September 30, December 31, uniQure $ 1,812 $ 3,661 CFF 1,396 1,429 Total deferred revenue $ 3,208 $ 5,090

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Summary of Components of Lease Expense	The following table summarizes the components of lease expense for the three and nine months ended September 30, 2022 and 2021 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Operating lease cost $ 697 $ 697 $ 2,090 $ 1,934 Variable lease cost 260 220 751 695 Total $ 957 $ 917 $ 2,841 $ 2,629
Summary of Supplemental Information Related to Leases	The following table summarizes supplemental information related to operating leases: September 30, December 31, Weighted-average remaining lease term (in years): 6.9 7.6 Weighted-average discount rate: 7.8 % 7.8 % For the nine months ended September 30, 2022, cash provided for amounts included in the measurement of operating lease liabilities included in cash flows used in operating activities was $ 0.1 million. For the nine months ended September 30, 2021, cash paid for amounts included in the measurement of operating lease liabilities included in cash flows used in operating activities was $ 1.1 million.
Summary of Future Minimum Commitments Under Lease Contracts	The following table summarizes the maturities of lease liabilities as of September 30, 2022 (in thousands): 2022 (remaining three months) $ 348 2023 3,058 2024 3,149 2025 3,244 2026 3,135 Thereafter 8,685 Total future minimum lease payments 21,619 Less: Amount representing interest ( 5,067 ) Present value of future minimum lease payments 16,552 Less: Current portion of operating lease liabilities 2,633 Long-term portion of operating lease liabilities $ 13,919

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Schedule of Common Share Reserved for Future Issuance	As of September 30, 2022 and December 31, 2021, the Company has reserved common stock, on an as-converted basis, for future issuance as follows: September 30, December 31, Issuance of common stock under the 2020 Equity Incentive Award Plan 2,040,839 2,690,097 Issuance of common stock under the Employee Stock Purchase Plan 462,195 498,747 Exercise of options issued and outstanding 6,035,456 3,881,274 Exercise of common stock warrants 53,669 53,669 Total common stock reserved for future issuance 8,592,159 7,123,787

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Summary of Stock Options Activity	The following table summarizes the stock options activity for the nine months ended September 30, 2022: Number of Number of Balances at December 31, 2021 2,690,097 3,881,274 Options authorized 1,611,226 — Options granted ( 2,641,637 ) 2,641,637 Options exercised — ( 106,302 ) Options expired 82,627 ( 82,627 ) Options forfeited 298,526 ( 298,526 ) Balances at September 30, 2022 2,040,839 6,035,456 Options exercisable at September 30, 2022 2,280,409 Options vested and expected to vest at September 30, 2022 6,035,456
Schedule of Assumptions Used in Black-Scholes Valuation Model to Estimate Fair Value of Stock Options	The Company estimates the fair value of stock options using the Black-Scholes option pricing model. The fair value of employee and nonemployee options is recognized on a straight-line basis over the requisite service period of the awards. The fair value of the Company’s stock options was estimated using the following assumptions for the three and nine months ended September 30, 2022 and 2021. Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Expected term 5.9 - 6.1 years 6.0 - 6.1 years 5.9 - 6.1 years 5.8 - 6.3 years Expected volatility 81.3 % - 81.9 % 80.4 % - 82.8 % 80.0 % - 81.9 % 80.4 % - 84.3 % Risk-free interest rate 2.9 % - 3.9 % 0.8 % - 1.1 % 1.5 % - 3.9 % 0.6 % - 1.1 % Expected dividend yield — % — % — % — %
Summary of Stock-based Compensation Expense for Employees and Nonemployees by Function	The following table is a summary of stock-based compensation expense incurred for employees and nonemployees by function (in thousands): Three Months Ended Nine Months Ended 2022 2021 2022 2021 Research and development $ 2,438 $ 1,893 $ 6,931 $ 4,901 General and administrative 2,082 2,030 5,844 5,167 Total stock-based compensation expense $ 4,520 $ 3,923 $ 12,775 $ 10,068

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share	The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Numerator Net loss $ ( 25,691 ) $ ( 22,239 ) $ ( 80,115 ) $ ( 46,234 ) Denominator Weighted-average shares outstanding used in computing net loss per share, basic and diluted 32,385,791 27,022,380 32,305,074 26,818,595 Net loss per share, basic and diluted $ ( 0.79 ) $ ( 0.82 ) $ ( 2.48 ) $ ( 1.72 )
Outstanding Shares of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive: September 30, 2022 2021 Options issued and outstanding 6,035,456 4,082,539 ESPP shares expected to be issued — 97,155 Common stock warrants 53,669 98,669 Total 6,089,125 4,278,363

The Company - Additional Inform

The Company - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended
	Nov. 30, 2021	Dec. 31, 2020	Sep. 30, 2022	Dec. 31, 2021
Organization And Nature Of Business [Line Items]
Outstanding shares of redeemable convertible preferred stock		0
Accumulated deficit			$ 287,111	$ 206,996
Common Stock | Initial Public Offering
Organization And Nature Of Business [Line Items]
Number of shares sold and issued		9,660,000
Stock sold and issued price per share		$ 23
Aggregate net proceeds, after deducting underwriting discounts and commissions and offering costs		$ 204,700
Number shares issued upon conversion of redeemable convertible preferred shares		11,575,984
Common Stock | Excess of Overallotment Option
Organization And Nature Of Business [Line Items]
Number of shares sold and issued		1,260,000
Common Stock | Follow-On Offering
Organization And Nature Of Business [Line Items]
Number of shares priced under public offering	4,750,000
Stock sold and issued price per share	$ 25
Aggregate net proceeds, after deducting underwriting discounts and commissions and offering costs	$ 111,100

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2022 Financial_Institution Segment	Dec. 31, 2021
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segments	1
Number of operating segments	1
Number of financial institutions cash is held | Financial_Institution	2
Accounting Standards Update [Extensible Enumeration]		Accounting Standards Update 2016-02 [Member]
Change in accounting principle accounting standards update, adopted		true
Change in accounting principle accounting standards update, adoption date		Jan. 01, 2021

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Concentration of Risk (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Revenue | Customer Concentration Risk | Customer A
Concentration Risk [Line Items]
Concentration risk, percentage		94%		96%
Revenue | Customer Concentration Risk | Customer B
Concentration Risk [Line Items]
Concentration risk, percentage	99%		98%
Revenue | Customer Concentration Risk | Customer
Concentration Risk [Line Items]
Concentration risk, percentage	99%	94%	98%	96%
Accounts Receivable | Credit Concentration Risk | Customer A
Concentration Risk [Line Items]
Concentration risk, percentage			0%		100%
Accounts Receivable | Credit Concentration Risk | Customer
Concentration Risk [Line Items]
Concentration risk, percentage			0%		100%

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Revenues by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation Of Revenue [Line Items]
Total revenue	$ 500	$ 1,366	$ 1,882	$ 17,946
Netherlands
Disaggregation Of Revenue [Line Items]
Total revenue	497	64	1,849	724
Switzerland
Disaggregation Of Revenue [Line Items]
Total revenue	0	1,290	0	17,190
United States
Disaggregation Of Revenue [Line Items]
Total revenue	$ 3	$ 12	$ 33	$ 32

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Summary of Adoption of ASC 842 on condensed statement of cash flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Summary Of Significant Accounting Policies [Line Items]
Amortization of right-of-use assets	$ 1,103	$ 1,117
Operating lease liabilities	104	(1,117)
Decrease in right-of-use assets due to reduction in operating lease liabilities upon modification	$ 0	(478)
Revision of Prior Period, Accounting Standards Update, Adjustment | ASC 842 Adjustments
Summary Of Significant Accounting Policies [Line Items]
Amortization of right-of-use assets		1,117
Operating lease liabilities		(1,117)
Decrease in right-of-use assets due to reduction in operating lease liabilities upon modification		$ (478)

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Hierarchy for Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value on Recurring Basis - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	$ 223,704	$ 198,984
Liabilities	213	214
Derivative Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities	213	214
US treasuries
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	5,461
Cash Equivalents | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	87,704	36,556
Marketable Securities | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	9,860	37,535
Marketable Securities | Corporate Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	46,862	94,864
Marketable Securities | US treasuries
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	71,654	30,029
Marketable Securities | US government Sponsored Agency
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	2,163
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	87,704	36,556
Level 1 | Cash Equivalents | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	87,704	36,556
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	136,000	162,428
Level 2 | Cash Equivalents | US treasuries
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	5,461
Level 2 | Marketable Securities | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	9,860	37,535
Level 2 | Marketable Securities | Corporate Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	46,862	94,864
Level 2 | Marketable Securities | US treasuries
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	71,654	30,029
Level 2 | Marketable Securities | US government Sponsored Agency
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	2,163
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities	213	214
Level 3 | Derivative Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities	$ 213	$ 214

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Assets, Level 1 and Level 2 transfers	$ 0	$ 0
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	0	0
Liabilities, Level 1 and Level 2 transfers	0	0
Liabilities, Transfers into Level 3	0	0
Liabilities, Transfers out of Level 3	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Fair Value of Level 3 Financial Instruments (Details) - Derivative Liability - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 214	$ 122
Change in fair value included in other income (expense), net	$ (1)	$ 92
Fair Value, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Income [Extensible List]	Other income (expense), net	Other income (expense), net
Ending Balance	$ 213	$ 214

Marketable Securities - Summary

Marketable Securities - Summary of Available for Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Short-term Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	$ 120,896	$ 94,868
Gross Unrealized Gains	4	0
Gross Unrealized Losses	(1,483)	(92)
Fair Value	119,417	94,776
Long-term Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	11,495	67,983
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(373)	(331)
Fair Value	11,122	67,652
Commercial Paper | Short-term Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	5,025	32,471
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(55)	(4)
Fair Value	4,970	32,467
Commercial Paper | Long-term Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	5,082	5,089
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(192)	(21)
Fair Value	4,890	5,068
Corporate Bonds | Short-term Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	41,357	57,315
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(727)	(79)
Fair Value	40,630	57,236
Corporate Bonds | Long-term Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	6,413	37,821
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(181)	(193)
Fair Value	6,232	37,628
US treasuries | Short-term Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	72,314	5,082
Gross Unrealized Gains	4	0
Gross Unrealized Losses	(664)	(9)
Fair Value	71,654	5,073
US treasuries | Long-term Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis		25,073
Gross Unrealized Gains		0
Gross Unrealized Losses		(117)
Fair Value		$ 24,956
US government Sponsored Agency | Short-term Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	2,200
Gross Unrealized Gains	0
Gross Unrealized Losses	(37)
Fair Value	$ 2,163

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Aggregate fair value of securities held in a continuous unrealized loss position for less than twelve months	$ 64,600,000	$ 64,600,000	$ 162,400,000
Aggregate fair value of securities held in a continuous unrealized loss position for more than twelve months	60,500,000	60,500,000	$ 0
Other-than-temporary impairment on investment in debt securities available-for-sale	$ 0	$ 0
Maximum
Debt Securities, Available-for-sale [Line Items]
Maturity period of marketable securities	2 years	2 years

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Total property and equipment	$ 28,766	$ 19,716
Less: Accumulated depreciation and amortization	(6,714)	(5,325)
Property and equipment, net	22,052	14,391
Machinery and Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	9,952	5,971
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	16,380	2,527
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	566	566
Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	240	165
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Total property and equipment	616	421
Construction in Progress
Property Plant And Equipment [Line Items]
Total property and equipment	$ 1,012	$ 10,066

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 0.5	$ 0.4	$ 1.4	$ 1.1

Accrued and Other Current Lia_3

Accrued and Other Current Liabilities - Summary of Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Payroll and related expenses	$ 4,161	$ 3,994
Accrued clinical and preclinical study costs	1,346	407
Consulting and professional	1,549	1,573
Other accrued expenses	188	1,770
Total accrued and other current liabilities	$ 7,244	$ 7,744

Research and Collaboration Ar_3

Research and Collaboration Arrangements - Summary of Collaboration and License Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue	$ 500	$ 1,366	$ 1,882	$ 17,946
Collaboration and License Revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue	500	1,366	1,882	17,946
Collaboration and License Revenue | uniQure
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue	497	64	1,849	724
Collaboration and License Revenue | Roche
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue	0	1,290	0	17,190
Collaboration and License Revenue | CFF
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue	$ 3	$ 12	$ 33	$ 32

Research and Collaboration Ar_4

Research and Collaboration Arrangements - Summary of Deferred Revenue (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total deferred revenue	$ 3,208	$ 5,090
uniQure
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total deferred revenue	1,812	3,661
CFF
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total deferred revenue	$ 1,396	$ 1,429

Research and Collaboration Ar_5

Research and Collaboration Arrangements - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2014	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Aug. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized				$ 1,900,000	$ 15,100,000
Deferred revenue		$ 3,208,000		3,208,000		$ 5,090,000
Accounts receivable		0		0		47,000
uniQure
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue		1,812,000		1,812,000		3,661,000
Accounts receivable		0		0		0
uniQure | uniQure Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Increase in revenue recognized related to performance obligations partially satisfied in the beginning of the current year				1,800,000
Collaborative arrangement, initial research term	3 years
Upfront payments received	$ 200,000
Options to purchase ordinary shares	609,744
Ordinary shares vesting period	3 years
Fair value of options	$ 10,600,000
uniQure | uniQure Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payments entitled to receive for achievement of research and development milestones	$ 5,000,000
uniQure | Amended uniQure Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized		500,000	$ 100,000	1,800,000	$ 700,000
Fair value of non monetary consideration of intellectual property right							$ 5,100,000
Remaining performance obligations		$ 1,800,000		$ 1,800,000		$ 3,700,000
uniQure | Amended uniQure Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payments eliminated							$ 5,000,000

Research and Collaboration Ar_6

Research and Collaboration Arrangements - Additional Information (Details 1)	Sep. 30, 2022	Jan. 31, 2014
uniQure | uniQure Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-10-01
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue, estimated performance period	1 year	4 years

Research and Collaboration Ar_7

Research and Collaboration Arrangements - CRF Agreement - Additional Information (Details) - USD ($)	1 Months Ended	9 Months Ended
	Nov. 30, 2015	Sep. 30, 2022	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable		$ 0	$ 47,000
Accounts payable		1,480,000	4,764,000
CRF Agreement | CRF
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement, initial research term	2 years
Collaborative arrangement contribution upon development milestone	$ 2,500,000
Collaborative arrangement additional research term	3 years
Collaborative arrangement achieved milestones		0
Deferred revenue		0	0
Accounts receivable		0	0
Accounts payable		$ 0	$ 0

Research and Collaboration Ar_8

Research and Collaboration Arrangements - Roche Agreement - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended
	Nov. 30, 2017	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2022	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 500,000	$ 1,366,000		$ 1,882,000	$ 17,946,000
Roche | 2017 Roche Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-refundable upfront payments received	$ 21,000,000
Contingent payment for each nominated product beyond the first three	1,000,000
Maximum contingent payment upon exercise of the option to convert a product	30,000,000
Maximum development milestone payments	223,000,000
Development milestone payments relating to Choroideremia	86,000,000
Maximum sales-based milestone payments	$ 123,000,000
Collaborative arrangement adjustment to transaction price						8,700,000
Non-refundable development milestone payments received				$ 10,000,000
Revenues		0	$ 1,300,000		0	$ 17,200,000
Deferred revenue		0			0		$ 0
Accounts receivable		0			0		0
Remaining performance obligations		$ 0			$ 0		$ 0

Research and Collaboration Ar_9

Research and Collaboration Arrangements - CFF - Additional Information (Details) - CFF	1 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) Installment	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement total amount of award	$ 3,500,000
Collaborative arrangement achieved milestones		$ 1,800,000	$ 1,800,000
Number of installments to pay actual award | Installment	3
Actual award payment period upon first commercial sale of product	4 years
Collaborative arrangements special term	If at any time prior to the first commercial sale of a product developed as a result of the CFF Agreement, the Company ceases to use commercially reasonable efforts to develop or commercialize any product under the CFF Agreement for a continuous period of 180 consecutive days and fails to present a reasonable plan to resume commercially reasonable efforts, the Company will grant to CFF an irrevocable, exclusive worldwide interruption license under all of the Company’s interest in the research plan technology to exploit such product. Any third-party license granted by the Company shall be subject to such interruption license.
Deferred revenue		1,400,000	1,400,000
Accounts receivable		0	0
Aggregate amount of transaction price allocated to remaining performance obligation		$ 1,400,000	$ 1,400,000
Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Expected payments percentage to equal actual award received	600%
Future sales-based milestone payments percentage	300%
Royalties percentage on actual award received	600%

Research and Collaboration A_10

Research and Collaboration Arrangements - CFF - Additional Information (Details 1) - CFF - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-10-01	Sep. 30, 2022
Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue, estimated performance period	2 years
Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue, estimated performance period	4 years

License Arrangements - Addition

License Arrangements - Additional Information (Details) - UC Agreements - USD ($)	1 Months Ended
	Jul. 31, 2021	Jan. 31, 2019	Jan. 31, 2016	Dec. 31, 2018
Research And Development Arrangement Contract To Perform For Others [Line Items]
Non-refundable license fee payable upon execution				$ 5,000
Non-refundable license fee payable upon execution every year thereafter until sales of a licensed product and payment of royalties				5,000
Amount obligated to pay upon closing first qualified financing at option of UC Regents				$ 50,000
Percentage of equity interest upon closing of first qualified financing at option of UC Regents				3%
Percentage of equity interests issued as common stock			6%
Amount paid non-refundable license fee	$ 100,000	$ 50,000
Non-refundable license fee payable annually	10,000	5,000
Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contingent payments development milestones	3,900,000	3,100,000
Minimum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Annual royalty	$ 100,000	$ 100,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended						9 Months Ended
	Feb. 28, 2021	Dec. 31, 2019	May 31, 2019	Nov. 30, 2018	Oct. 31, 2018	May 31, 2015	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Jan. 31, 2016
Commitment And Contingencies [Line Items]
Operating lease right-of-use ("ROU") assets							$ 13,459		$ 14,562
Operating lease liability							16,552
Operating lease payments							100	$ 1,100
5980 Horton Street Building Lease
Commitment And Contingencies [Line Items]
Lease extended term date						Mar. 31, 2023
Tenant improvement allowance				$ 200
Operating lease right-of-use ("ROU") assets							1,700		1,900
Operating lease liability							$ 2,000		$ 2,300
Operating lease, discount rate							7.50%		7.50%
Lease extended term period					2026-09
5858 Horton Street Building Lease and Expansion
Commitment And Contingencies [Line Items]
Lease extended term date			Dec. 31, 2029
Maximum tenant improvement allowance available	$ 2,300
Tenant improvement allowance		$ 400					$ 1,900
Operating lease right-of-use ("ROU") assets							11,800		$ 12,600
Operating lease liability							$ 14,600		$ 14,200
Operating lease, discount rate							7.80%		7.80%
Lease initial term					87 months
Lease option to renew term description							The new lease has an initial term of 87 months beginning on the rent commencement date with the option to renew the lease for one additional term of five years at market rent.
Lease existence of option to renew term					true
Lease renewal term					5 years
Maximum | 5980 Horton Street Building Lease
Commitment And Contingencies [Line Items]
Lease renewal term										5 years
Minimum | 5980 Horton Street Building Lease
Commitment And Contingencies [Line Items]
Lease renewal term										3 years

Commitments and Contingencies-

Commitments and Contingencies- Summary of Components of Lease Expense - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 697	$ 697	$ 2,090	$ 1,934
Variable lease cost	260	220	751	695
Lease, Cost, Total	$ 957	$ 917	$ 2,841	$ 2,629

Commitments and Contingencies_2

Commitments and Contingencies -Summary of Supplemental Information Related to Leases - (Details)	Sep. 30, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (in years)	6 years 10 months 24 days	7 years 7 months 6 days
Weighted-average discount rate	7.80%	7.80%

Commitments and Contingencies_3

Commitments and Contingencies - Summary of Future Minimum Commitments Under Lease Contracts (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
2022 (remaining three months)	$ 348
2023	3,058
2024	3,149
2025	3,244
2026	3,135
Thereafter	8,685
Total future minimum lease payments	21,619
Less: Amount representing interest	(5,067)
Present value of future minimum lease payments	16,552
Less: Current portion of operating lease liabilities	2,633	$ 1,231
Operating lease liabilities, long-term portion	$ 13,919	$ 15,217

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Equity [Abstract]
Common stock, shares authorized	300,000,000	300,000,000
Common stock, par value	$ 0.0001	$ 0.0001
Common stock voting rights	one vote per share
Common stock dividend	$ 0	$ 0

Common Stock - Schedule of Comm

Common Stock - Schedule of Common Share Reserved for Future Issuance (Details) - shares	Sep. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Common stock reserved	8,592,159	7,123,787
2020 Equity Incentive Award Plan
Class Of Stock [Line Items]
Common stock reserved	2,040,839	2,690,097	2,606,546
Employee Stock Purchase Plan
Class Of Stock [Line Items]
Common stock reserved	462,195	498,747
Options Issued and Outstanding
Class Of Stock [Line Items]
Common stock reserved	6,035,456	3,881,274
Common Stock Warrants
Class Of Stock [Line Items]
Common stock reserved	53,669	53,669

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - shares	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Mar. 28, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance		8,592,159		8,592,159		7,123,787
Number of shares available for grant		2,040,839		2,040,839		2,690,097
Number of options outstanding		6,035,456		6,035,456		3,881,274
Expected dividend yield		0%	0%	0%	0%
2020 Equity Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance	2,606,546	2,040,839		2,040,839		2,690,097
Number of shares authorized and reserved for issuance		1,611,226		1,611,226
Percentage of aggregate number of shares of common stock outstanding reserved for future issuance				5%		5%
Number of shares available for grant		1,859,923		1,859,923
2020 Equity Incentive Award Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for grant		18,000,000		18,000,000		18,000,000
Options exercisable period				10 years		10 years
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options exercisable period				10 years
Number of options outstanding		2,343,729		2,343,729
Minimum percentage of outstanding shares held by individual				10%
Exercise price as percentage of fair market value, minimum				110%
2020 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized and reserved for issuance	252,337						25,000
Percentage of aggregate number of shares of common stock outstanding reserved for future issuance				1%
Employee purchase price of common stock as percentage of fair market value	85%
Common stock overlapping offering period	24 months
Duration of purchase period	6 months
Percentage of maximum contributions of employee's eligible compensation	15%
2020 ESPP | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for grant		15,000,000		15,000,000

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Options Activity (Details) - shares	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Number of Shares Available for Grant, Balances at December 31, 2021	2,690,097
Number of Shares Available for Grant, Options authorized	1,611,226
Number of Shares Available for Grant, Options granted	(2,641,637)
Number of Shares Available for Grant, Options expired	82,627
Number of Shares Available for Grant, Options forfeited	298,526
Number of Shares Available for Grant, Balances at September 30, 2022	2,040,839
Number of Shares Underlying Outstanding Options, Balances at December 31, 2021	3,881,274
Number of Shares Underlying Outstanding Options, granted	2,641,637
Number of Shares Underlying Outstanding Options, exercised	(106,302)
Number of Shares Underlying Outstanding Options, expired	(82,627)
Number of Shares Underlying Outstanding Options, forfeited	(298,526)
Number of Shares Underlying Outstanding Options, Balances at September 30, 2022	6,035,456
Number of Shares Underlying Outstanding Options, Options exercisable at September 30, 2022	2,280,409
Number of Shares Underlying Outstanding Options, Options vested and expected to vest at September 30, 2022	6,035,456

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Assumptions Used in Black-Scholes Valuation Model to Estimate Fair Value of Stock Options (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	81.30%	80.40%	80%	80.40%
Expected volatility, maximum	81.90%	82.80%	81.90%	84.30%
Risk-free interest rate, minimum	2.90%	0.80%	1.50%	0.60%
Risk-free interest rate, maximum	3.90%	1.10%	3.90%	1.10%
Expected dividend yield	0%	0%	0%	0%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	5 years 10 months 24 days	6 years	5 years 10 months 24 days	5 years 9 months 18 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days	6 years 3 months 18 days

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Stock-based Compensation Expense for Employees and Nonemployees by Function (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,520	$ 3,923	$ 12,775	$ 10,068
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2,438	1,893	6,931	4,901
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,082	$ 2,030	$ 5,844	$ 5,167

Common Stock Warrants - Additio

Common Stock Warrants - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2021	May 31, 2018	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2016	Dec. 31, 2018
Class Of Warrant Or Right [Line Items]
Number of warrant shares issued	40,000	23,669					30,000	45,000
Exercise price	$ 9.41	$ 3.19					$ 18	$ 1.14
Warrant shares become exercisable								45,000
Warrant expiration year		2025					2027
Warrant shares, expense recognized			0	0	0	0
Warrant vesting period							4 years
Warrant exercised month and year	2021-05							2021-10
Series B Financing
Class Of Warrant Or Right [Line Items]
Warrant shares become exercisable									15,000
Private Placement
Class Of Warrant Or Right [Line Items]
Warrant shares become exercisable								15,000
Proceeds from offering of securities in a private placement								$ 25
Initial Public Offering
Class Of Warrant Or Right [Line Items]
Warrant shares become exercisable							30,000

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator
Net loss	$ (25,691)	$ (22,239)	$ (80,115)	$ (46,234)
Denominator
Weighted-average shares outstanding used in computing net loss per share, basic	32,385,791	27,022,380	32,305,074	26,818,595
Weighted-average shares outstanding used in computing net loss per share, diluted	32,385,791	27,022,380	32,305,074	26,818,595
Net loss per share, basic	$ (0.79)	$ (0.82)	$ (2.48)	$ (1.72)
Net loss per share, diluted	$ (0.79)	$ (0.82)	$ (2.48)	$ (1.72)

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Outstanding Potentially Dilutive Securities Excluded From Computation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	6,089,125	4,278,363
ESPP Shares Expected to be Issued
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	0	97,155
Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	6,035,456	4,082,539
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	53,669	98,669

Derivative Liability - Addition

Derivative Liability - Additional Information (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Change in control discount rate	15%	14%
Estimated fair value of derivative liability	$ 0.2	$ 0.2
Minimum
Derivative [Line Items]
Change of control payment	$ 0	$ 0
Change in control event percentage	4.80%	4.80%
Maximum
Derivative [Line Items]
Change of control payment	$ 10.6	$ 10.6
Change in control event percentage	17.20%	17.20%

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details)	1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2021 USD ($)	Apr. 30, 2019 USD ($) Agreement	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
UC Regents | SRAs
Related Party Transaction [Line Items]
Number of sponsored research agreements entered | Agreement		2
Agreement term		3 years
Amount due to related party		$ 1,500,000
UC Regents | SRAs and Machine Learning SRA
Related Party Transaction [Line Items]
Accounts payable, related party			$ 0		$ 0		$ 0
UC Regents | Machine Learning SRA
Related Party Transaction [Line Items]
Agreement term	3 years
Amount due to related party	$ 1,400,000
Payment to related party			400,000		$ 400,000
Agreement terminated					2022-03
David Schaffer, Ph.D. | Consulting Services and Services as Board of Director
Related Party Transaction [Line Items]
Related party expenses			$ 0	$ 21,000	$ 0	$ 64,000

401(K) Plan - Additional Inform

401(K) Plan - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
2014 401(k) Plan
Defined Contribution Plan Disclosure [Line Items]
Employer contribution	$ 0.2	$ 0.1	$ 0.7	$ 0.4