Voyager Therapeutics (VYGR) 10-K 7 Mar 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 01, 2023	Jun. 30, 2022
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2022
Entity File Number	001-37625
Entity Registrant Name	Voyager Therapeutics, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-3003182
Entity Address, Address Line One	64 Sidney Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	857
Local Phone Number	259-5340
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	VYGR
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Central Index Key	0001640266
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Public Float			$ 113.6
Entity Common Stock, Shares Outstanding		43,293,369
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Boston, Massachusetts

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 98,959	$ 117,433
Marketable securities	19,889	15,106
Related party collaboration receivable	257	732
Prepaid expenses and other current assets	5,394	3,427
Total current assets	124,499	136,698
Property and equipment, net	17,857	21,920
Deposits and other non-current assets	1,515	1,779
Operating lease, right-of-use assets	15,485	33,458
Total assets	159,356	193,855
Current liabilities:
Accounts payable	2,566	574
Accrued expenses	7,816	10,950
Other current liabilities	2,832	5,571
Deferred revenue, current	59,377	33,886
Total current liabilities	72,591	50,981
Deferred revenue, non-current	6,450	8,210
Other non-current liabilities	21,295	39,609
Total liabilities	100,336	98,800
Commitments and contingencies (see note 9)
Stockholders' equity:
Preferred stock, $0.001 par value: 5,000,000 shares authorized; no shares issued and outstanding at December 31, 2022 and 2021
Common stock, $0.001 par value: 120,000,000 shares authorized; 38,613,891 and 37,918,395 shares issued and outstanding at December 31, 2022 and 2021, respectively	38	38
Additional paid-in capital	452,713	442,259
Accumulated other comprehensive loss	(219)	(138)
Accumulated deficit	(393,512)	(347,104)
Total stockholders' equity	59,020	95,055
Total liabilities and stockholders' equity	$ 159,356	$ 193,855

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Consolidated Balance Sheets
Preferred Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred Stock, Shares Authorized	5,000,000	5,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, Shares Authorized	120,000,000	120,000,000
Common Stock, Shares, Issued	38,613,891	37,918,395
Common Stock, Shares, Outstanding	38,613,891	37,918,395

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive (Loss) Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Consolidated Statements of Operations and Comprehensive (Loss) Income
Collaboration revenue	$ 40,907	$ 37,415	$ 171,128
Operating expenses:
Research and development	60,764	73,787	108,753
General and administrative	30,980	37,246	34,991
Total operating expenses	91,744	111,033	143,744
Operating (loss) income	(50,837)	(73,618)	27,384
Other income, net:
Interest income (expense)	1,792	(390)	1,659
Other income	2,653	2,811	7,698
Total other income, net	4,445	2,421	9,357
(Loss) income before income taxes	(46,392)	(71,197)	36,741
Income tax provision	16
Net (loss) income	(46,408)	(71,197)	36,741
Other comprehensive (loss) income
Net unrealized loss on available-for-sale-securities	(81)	(4)	(30)
Total other comprehensive loss	(81)	(4)	(30)
Comprehensive (loss) income	$ (46,489)	$ (71,201)	$ 36,711
Net (loss) income per share, basic	$ (1.21)	$ (1.89)	$ 0.99
Net (loss) income per share, diluted	$ (1.21)	$ (1.89)	$ 0.98
Weighted-average common shares outstanding, basic	38,356,810	37,668,947	37,132,447
Weighted-average common shares outstanding, diluted	38,356,810	37,668,947	37,348,514

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Stockholders' Equity, Beginning Balance at Dec. 31, 2019	$ 37	$ 412,227	$ (104)	$ (312,648)	$ 99,512
Shares, Outstanding, Beginning Balance at Dec. 31, 2019	36,865,116
Exercises of vested stock options		2,319			2,319
Exercises of vested stock options (in shares)	228,436
Vesting of restricted stock units (in shares)	170,367
Issuance of common stock under ESPP		1,279			1,279
Issuance of common stock under ESPP (in shares)	104,108
Stock based compensation expense		14,499			14,499
Net unrealized loss on available-for-sale-securities			(30)		(30)
Net income (loss)				36,741	36,741
Stockholders' Equity, Ending Balance at Dec. 31, 2020	$ 37	430,324	(134)	(275,907)	154,320
Shares, Outstanding, Ending Balance at Dec. 31, 2020	37,368,027
Exercises of vested stock options	$ 1	27			28
Exercises of vested stock options (in shares)	3,811
Vesting of restricted stock units (in shares)	346,551
Issuance of common stock under ESPP		918			918
Issuance of common stock under ESPP (in shares)	200,006
Stock based compensation expense		10,990			10,990
Net unrealized loss on available-for-sale-securities			(4)		(4)
Net income (loss)				(71,197)	(71,197)
Stockholders' Equity, Ending Balance at Dec. 31, 2021	$ 38	442,259	(138)	(347,104)	95,055
Shares, Outstanding, Ending Balance at Dec. 31, 2021	37,918,395
Exercises of vested stock options		629			$ 629
Exercises of vested stock options (in shares)	89,012				89,012
Vesting of restricted stock units (in shares)	456,219
Issuance of common stock under ESPP		672			$ 672
Issuance of common stock under ESPP (in shares)	150,265
Stock based compensation expense		9,153			9,153
Net unrealized loss on available-for-sale-securities			(81)		(81)
Net income (loss)				(46,408)	(46,408)
Stockholders' Equity, Ending Balance at Dec. 31, 2022	$ 38	$ 452,713	$ (219)	$ (393,512)	$ 59,020
Shares, Outstanding, Ending Balance at Dec. 31, 2022	38,613,891

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flow from operating activities
Net (loss) income	$ (46,408)	$ (71,197)	$ 36,741
Adjustments to reconcile net (loss) income to net cash used in operating activities:
Stock-based compensation expense	9,344	11,324	14,934
Depreciation	6,191	5,165	3,817
Amortization of premiums and discounts on marketable securities	(16)	349	27
Gain on Lease Termination	(2,468)
Change in fair value of common stock and warrants to purchase equity securities		(2,460)	(7,698)
Loss on disposal of fixed assets	377
Changes in operating assets and liabilities:
Related party collaboration receivable	475	7,280	10,484
Prepaid expenses and other assets	(1,967)	1,883	(551)
Operating lease, right-of-use assets	3,462	2,606	(7,592)
Other non-current assets	(152)	69	275
Accounts payable	1,992	(60)	(3,436)
Accrued expenses	(3,148)	(3,335)	(6,480)
Operating lease liabilities	(3,922)	(3,428)	13,439
Deferred revenue	23,731	(1,721)	(150,676)
Net cash used in operating activities	(12,509)	(53,525)	(96,716)
Cash flow from investing activities
Purchases of property and equipment	(2,491)	(1,609)	(12,097)
Purchases of marketable securities	(54,848)	(15,117)	(70,403)
Proceeds from sales and maturities of marketable securities	50,000	82,632	195,495
Net cash (used in) provided by investing activities	(7,339)	65,906	112,995
Cash flow from financing activities
Proceeds from the exercise of stock options	629	28	2,319
Proceeds from the purchase of common stock under ESPP	481	584	844
Net cash provided by financing activities	1,110	612	3,163
Net (decrease) increase in cash and cash equivalents	(18,738)	12,993	19,442
Cash, cash equivalents, and restricted cash beginning of period	119,212	106,219	86,777
Cash, cash equivalents, and restricted cash end of period	100,474	119,212	106,219
Supplemental disclosure of cash and non-cash activities
Operating lease right-of-use assets obtained in exchange for operating lease liabilities		664	10,818
Capital expenditures incurred but not yet paid	$ 14	$ 80	$ 831

Nature of business

Nature of business	12 Months Ended
	Dec. 31, 2022
Nature of business
Nature of business	​ 1. Nature of business Voyager Therapeutics, Inc. (the “Company”) is a biotechnology company dedicated to breaking through barriers in gene therapy and neurology. The Company focuses on leveraging its expertise in capsid discovery and neuropharmacology to address the delivery hurdles that have constrained the gene therapy and neurology disciplines, with the goal of either halting or slowing disease progression or reduce symptom severity, therefore providing clinically meaningful impact to patients. The Company’s gene therapy platforms enable it to engineer, optimize, manufacture and deliver its adeno-associated virus (“AAV”) based gene therapies that it believes have the potential to safely provide durable efficacy. The Company’s team of experts in the field of AAV gene therapy and neuroscience first identifies and selects diseases in which the Company believes an AAV gene therapy or other biological therapy will answer a high unmet medical need, be supported by target validation, offer an efficient path to human proof of biology, present robust preclinical pharmacology, and offer strong commercial potential. The Company then engineers and optimizes an AAV vector or other biological therapy for activity in, efficacy in, or delivery to, the targeted tissue or cells. ​ The Company is identifying proprietary AAV capsids, the outer viral protein shells that enclose genetic material that makes up the vector payload. The Company’s team has developed a proprietary AAV capsid discovery platform called TRACER TM in vivo ​ The Company has a history of incurring annual net operating losses. As of December 31, 2022, the Company had an accumulated deficit of $393.5 million. The Company has not generated any product revenue and has financed its operations primarily through public offerings and private placements of its equity securities and funding from fees, milestone payments, and cost reimbursements associated with its prior collaborations with Sanofi Genzyme Corporation (“Sanofi Genzyme”) and AbbVie Biotechnology Ltd and AbbVie Ireland Unlimited Company (collectively, “AbbVie”), and its ongoing collaborations with Neurocrine Biosciences, Inc. (“Neurocrine”), its option and license agreement with Pfizer, Inc. (“Pfizer”), and its option and license agreement with Novartis Pharma AG (“Novartis”). ​ As of December 31, 2022, the Company had cash, cash equivalents, and marketable securities of $118.8 million. Based upon its current operating plan, the Company expects that its existing cash, cash equivalents, and marketable securities at December 31, 2022, together with the upfront payment received in February 2023 in connection with the Collaboration and License Agreement by and between the Company and Neurocrine dated as of January 8, 2023 (the “2023 Neurocrine Collaboration Agreement”), along with amounts expected to be received as reimbursement for development costs under the Company’s collaboration and license agreements with Neurocrine, will be sufficient to meet the Company’s planned operating expenses and capital expenditure requirements into 2025. ​ There can be no assurance that the Company will be able to obtain additional debt or equity financing on terms acceptable to the Company or generate product revenue or revenue from collaboration partners, on a timely basis or at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations, and financial condition.

Summary of significant accounti

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2022
Summary of significant accounting policies
Summary of significant accounting policies	2. Summary of significant accounting policies and basis of presentation

Fair value measurements

Fair value measurements	12 Months Ended
	Dec. 31, 2022
Fair value measurements
Fair value measurements	3. Fair value measurements ​ Assets and liabilities measured at fair value on a recurring basis as of December 31, 2022 and 2021 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted Prices ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ ​ ​ ​ ​ Identical Assets ​ Inputs ​ Inputs ​ Assets Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) December 31, 2022 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents ​ $ 91,724 ​ $ 91,724 ​ $ — ​ $ — ​ Marketable securities- U.S. Treasury notes ​ ​ 19,889 ​ ​ 19,889 ​ ​ — ​ ​ — ​ Total ​ $ 111,613 ​ $ 111,613 ​ $ — ​ $ — ​ December 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents $ 100,305 ​ $ 100,305 ​ $ — ​ $ — ​ Marketable securities- U.S. Treasury notes ​ ​ 15,106 ​ ​ 15,106 ​ ​ ​ ​ ​ ​ ​ Total ​ $ 115,411 ​ $ 115,411 ​ $ — ​ $ — ​ ​ The Company measures the fair value of money market funds and U.S. Treasuries based on quoted prices in active markets for identical securities.

Prepaid expenses and other curr

Prepaid expenses and other current assets	12 Months Ended
	Dec. 31, 2022
Prepaid expense and other current assets
Prepaid expenses and other current assets	4. Prepaid expenses and other current assets ​ Prepaid expenses and other current assets consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2022 2021 ​ ​ (in thousands) ​ Other current assets ​ $ 4,233 ​ $ 1,701 ​ Prepaid insurance ​ 696 ​ 1,360 ​ Prepaid research and development contracts 83 ​ ​ 350 ​ Accrued interest receivable ​ ​ 382 ​ ​ 16 ​ Total ​ $ 5,394 ​ $ 3,427 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Property and equipment, net

Property and equipment, net	12 Months Ended
	Dec. 31, 2022
Property and equipment, net
Property and equipment, net	5. Property and equipment, net ​ Property and equipment, net consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Laboratory equipment ​ $ 19,675 ​ $ 19,384 ​ Leasehold improvements ​ ​ 12,554 ​ ​ 15,695 ​ Furniture and office equipment ​ 2,333 ​ 2,524 ​ Other ​ ​ 502 ​ 230 ​ Total property and equipment ​ 35,064 ​ 37,833 ​ Less: accumulated depreciation ​ (17,207) ​ (15,913) ​ Property and equipment, net ​ $ 17,857 ​ $ 21,920 ​ ​ The Company recorded $6.2 million, $5.2 million, and $3.8 million in depreciation expense during the years ended December 31, 2022, 2021, and 2020, respectively.

Accrued expenses

Accrued expenses	12 Months Ended
	Dec. 31, 2022
Accrued expenses
Accrued expenses	6. Accrued expenses ​ Accrued expenses consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Employee compensation costs ​ $ 4,559 ​ $ 5,022 ​ Research and development costs ​ ​ 1,895 ​ ​ 3,719 ​ Accrued goods and services ​ 636 ​ 1,482 ​ Professional services ​ 726 ​ 727 ​ Total ​ $ 7,816 ​ $ 10,950 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Lease obligation

Lease obligation	12 Months Ended
	Dec. 31, 2022
Lease obligation
Lease obligation	7. Lease obligation ​ Operating Leases ​ As of December 31, 2022, the Company has a lease for office and laboratory space at 64 Sidney Street in Cambridge, Massachusetts through November 30, 2026 and a lease for additional laboratory and office space at 75 Hayden Avenue in Lexington, Massachusetts through January 31, 2031. ​ In September 2021, the Company entered into an agreement with BioNTech US, Inc. (“BioNTech US”) to sublease part of the office and laboratory space leased by the Company at 75 Sidney Street in Cambridge, Massachusetts (the “Sublease Agreement”) at that time. The sublease term was for approximately 3.3 years. The sublease did not relieve the Company of its original obligation under the lease, and therefore the Company did not adjust the operating lease right-of-use asset as a result of the sublease and accounted for the sublease as a separate lease. ​ On June 22, 2022 the Company entered into a Lease Termination Agreement (the “Lease Termination Agreement”) and terminated the lease for office and laboratory space at 75 Sidney Street (the “75 Sidney Street Lease”), effective immediately. In connection with the Lease Termination Agreement, the Company also entered into a Sublease Termination Agreement (the “Sublease Termination Agreement”) and terminated the Sublease Agreement with BioNTech US. The Company did not incur any termination penalties in connection with the Lease Termination Agreement or Sublease Termination Agreement. The Company derecognized the related right-of-use asset of approximately $14.5 million and the operating lease liabilities of $17.0 million, accordingly, resulting in a gain of $2.5 million in the three-month period ended June 30, 2022. ​ The Company’s lease agreements require the Company to maintain a cash deposit or irrevocable letter of credit in the aggregate amount of $1.5 million payable to its landlords as security for the performance of its obligations under the leases. These amounts are recorded as restricted cash and are included in deposits and other non-current assets in the accompanying consolidated balance sheets. ​ Total lease cost for operating leases of approximately $4.6 million, $6.8 million, and $6.2 million was incurred during the years ended December 31, 2022, 2021 and 2020, respectively. As of December 31, 2022, the weighted average remaining lease term was 6 years and the weighted average incremental borrowing rate used to determine the operating lease liabilities was 7.4%. ​ The following table summarizes the operating sublease income generated under the Sublease Agreement which was recorded within operating expenses for the years ended December 31, 2022 and 2021. ​ ​ ​ ​ ​ ​ ​ ​ ​ Years ended ​ ​ December 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Operating sublease income $ 1,380 ​ $ 838 ​ ​

Other liabilities

Other liabilities	12 Months Ended
	Dec. 31, 2022
Other liabilities
Other liabilities	8. Other liabilities ​ As of December 31, 2022 and 2021, other current and non-current liabilities consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Other current liabilities ​ ​ ​ ​ ​ ​ Lease liabilities ​ 2,832 ​ ​ 5,571 ​ Total other current liabilities $ 2,832 ​ $ 5,571 ​ ​ ​ ​ ​ ​ ​ ​ Other non-current liabilities ​ ​ ​ ​ ​ ​ Lease liabilities $ 20,294 ​ $ 38,608 ​ Other ​ 1,001 ​ ​ 1,001 ​ Total other non-current liabilities $ 21,295 ​ $ 39,609 ​ ​ Strategic Restructuring ​ On August 6, 2021, the board of directors of the Company approved a strategic restructuring plan to eliminate a portion of its workforce as part of an initiative to reduce expenses and enhance operations. The strategic restructuring plan was approved in connection with its portfolio reevaluation efforts and its strategic shift to invest additional resources in the Company’s TRACER capsid development efforts. ​ During the year ended December 31, 2021, the Company incurred restructuring costs of approximately $2.6 million, which consists of severance-related costs. These costs are reported within our research and development expenses and general and administrative expenses. Substantially all costs have been paid as of December 31, 2022.

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2022
Commitments and contingencies
Commitments and contingencies	9. Commitments and contingencies Significant Agreements ​ 2019 Neurocrine Collaboration Agreement ​ Summary of Agreement ​ Effective March 2019, the Company entered into a collaboration agreement with Neurocrine (the “2019 Neurocrine Collaboration Agreement”) for the research, development and commercialization of certain of its AAV gene therapy products. Under the 2019 Neurocrine Collaboration Agreement, the Company agreed to collaborate on the conduct of four collaboration programs (the “2019 Neurocrine Programs”) which include: (a) VY-AADC (NBIb-1817) for Parkinson’s disease (the “VY-AADC Program”), (b) VY-FXN01 for Friedreich’s ataxia (the “FA Program”) (collectively, with the VY-AADC Program, the “Legacy Programs”), and (c) two programs to be determined by the Company and Neurocrine at a later date (the “2019 Discovery Programs”) ​ In June 2019, in conjunction with the termination of the collaboration agreement with Sanofi Genzyme (the “Sanofi Genzyme Collaboration Agreement”), the Company gained ex-U.S. rights to the FA Program. The Company’s ex-U.S. rights to the FA Program were subsequently transferred to Neurocrine under the terms of the 2019 Neurocrine Collaboration Agreement. To facilitate the transfer of the ex-U.S. rights to the FA Program to Neurocrine, the Company and Neurocrine executed an amendment to the 2019 Neurocrine Collaboration Agreement (the “June 2019 Modification”), and Neurocrine paid $5.0 million to the Company. There were no other changes in pricing or scope of the obligations required to be performed under the 2019 Neurocrine Collaboration Agreement. ​ In February 2021, Neurocrine notified the Company that it had elected to terminate the 2019 Neurocrine Collaboration Agreement solely with regards to the VY-AADC Program, effective August 2, 2021 (the “Neurocrine VY-AADC Program Termination Effective Date”). The 2019 Neurocrine Collaboration Agreement remains in full force and effect for each other program thereunder. As a result of the termination, Neurocrine is no longer obligated to reimburse the Company for research and development activities related to the VY-AADC Program. ​ Under the terms of the 2019 Neurocrine Collaboration Agreement, the Company originally agreed to collaborate with Neurocrine on, and to grant, exclusive, royalty-bearing, non-transferable, sublicensable licenses to certain of its intellectual property rights, for all human and veterinary diagnostic, prophylactic, and therapeutic uses, for the research, development, and commercialization of gene therapy products (the “ 2019 Collaboration Products”) under (a) the VY-AADC Program on a worldwide basis; (b) the FA Program in the United States and, all countries in the world in which the 2019 Neurocrine Collaboration Agreement remains in effect with respect to the FA Program; and (c) each 2019 Discovery Program on a worldwide basis. As a result of the termination of the 2019 Neurocrine Collaboration Agreement with regards to the VY-AADC Program, in accordance with the terms of the 2019 Neurocrine Collaboration Agreement, the licenses granted by the Company to Neurocrine regarding the VY-AADC Program have expired, and the Company has regained worldwide intellectual property rights regarding the VY-AADC Program, in each case as of the VY-AADC Termination Effective Date. ​ Pursuant to development plans agreed by the parties, which are overseen by a joint steering committee (“JSC”), the Company has operational responsibility, subject to certain exceptions, for the conduct of each 2019 Neurocrine Program prior to the occurrence of a specified event for such 2019 Neurocrine Program (a “2019 Transition Event”), as described below, and is required to use commercially reasonable efforts to develop the corresponding 2019 Collaboration Products. Neurocrine has agreed to be responsible for all costs incurred by the Company in conducting these activities for each 2019 Neurocrine Program, in accordance with an agreed budget for each 2019 Neurocrine Program. If the Company breaches its development responsibilities or in certain circumstances upon a change in control, Neurocrine has the right but not the obligation to assume the activities under such 2019 Neurocrine Program. ​ Upon the occurrence of a 2019 Transition Event for each 2019 Neurocrine Program, Neurocrine has agreed to assume responsibility for development, manufacturing and commercialization activities for such 2019 Neurocrine Program from the Company and to pay milestones and royalties on future net sales as described further below. As a result of Neurocrine’s termination of the 2019 Neurocrine Collaboration Agreement with respect to the VY-AADC Program, the 2019 Transition Event with respect to the VY-AADC Program is no longer applicable. The 2019 Transition Events for the remaining programs are (a) with respect to the FA Program, the Company’s receipt of topline data for the initial Phase 1 clinical trial for an FA Program product candidate; and (b) with respect to each 2019 Discovery Program, the preparation by the Company and the approval by Neurocrine of an IND application to be filed with the U.S. Food and Drug Administration (the “FDA”) by Neurocrine for the first development candidate in such 2019 Discovery Program. For the FA Program, the Company was granted the option (the “2019 FA Co-Co Option”) to co-develop and co-commercialize the FA Program upon the occurrence of a specified event (a “2019 FA Co-Co Trigger Event”). The Company agreed, upon its exercise of the FA Co-Co Option, to enter into a cost- and profit-sharing arrangement with Neurocrine (the “2019 FA Co-Co Agreement”), and (a) jointly develop and commercialize the 2019 Collaboration Products for the FA Program (“FA Collaboration Products”), (b) share in its costs, profits and losses, and (c) forfeit certain milestones and royalties on net sales in the United States during the effective period of the 2019 FA Co-Co Agreement. The 2019 FA Co-Co Trigger Event is the receipt of topline data for the initial Phase 1 clinical trial for a FA Program product candidate. ​ Under the 2019 Neurocrine Collaboration Agreement, subject to exceptions specified therein, the Company and Neurocrine agreed that profits and losses under the Company’s 2019 FA Co-Co Option would be allocated 60% to Neurocrine and 40% to the Company for any FA Collaboration Product. The parties agreed that 2019 FA Co-Co Agreement would provide the Company the right to terminate for any reason upon prior written notice to Neurocrine and Neurocrine the right to terminate in certain circumstances upon change of control. ​ The Company’s research and development activities under the 2019 Neurocrine Collaboration Agreement are conducted pursuant to plans agreed to by the parties, on a program-by-program basis, and overseen by the JSC, as detailed in the 2019 Neurocrine Collaboration Agreement. ​ Under the 2019 Neurocrine Collaboration Agreement, the parties committed to agree on a list of up to eight target genes (the “Targets”) from which Neurocrine had the right to nominate Targets for the two 2019 Discovery Programs. The Company and Neurocrine completed the nomination process, and the JSC has approved the two Targets for development under the 2019 Discovery Programs. The two Targets are currently under development. ​ The 2019 Neurocrine Collaboration Agreement provides for an upfront non-refundable payment of $115.0 million, as well as for aggregate development and regulatory milestone payments from Neurocrine to the Company for 2019 Collaboration Products under (a) the VY-AADC Program of up to $170.0 million, which the Company is no longer eligible to receive in light of the partial termination of the 2019 Neurocrine Collaboration Agreement; (b) the FA Program of up to $195.0 million, and (c) each of the two 2019 Discovery Programs of up to $130.0 million per 2019 Discovery Program. The Company may be entitled to receive aggregate commercial milestone payments for each 2019 Collaboration Product of up to $275.0 million, subject to an aggregate cap on commercial milestone payments across all 2019 Neurocrine Programs of $1.1 billion. Furthermore, in connection with the 2019 Neurocrine Collaboration Agreement, Neurocrine purchased 4,179,728 shares of the Company’s common stock at a price of $11.9625 per share, for an aggregate purchase price of $50.0 million. ​ Neurocrine also agreed to pay the Company royalties, based on future net sales of the 2019 Collaboration Products. Such royalty percentages, for net sales in and outside the United States, as applicable, range (a) for the VY-AADC Program, from the mid-teens to low thirties and the low-teens to low twenties, respectively, which the Company is no longer eligible to receive in light of the partial termination of the 2019 Neurocrine Collaboration Agreement; (b) for the FA Program, from the low-teens to high-teens and high-single digits to mid-teens, respectively; and (c) for each 2019 Discovery Program, from the high-single digits to mid-teens and mid-single digits to low-teens, respectively. On a country-by-country and program-by-program basis, royalty payments would commence on the first commercial sale of a 2019 Collaboration Product and terminate on the later of (a) the expiration of the last patent covering the 2019 Collaboration Product or its method of use in such country, (b) ten years from the first commercial sale of the 2019 Collaboration Product in such country and (c) the expiration of regulatory exclusivity in such country (the “2019 Royalty Term”). Royalty payments may be reduced by up to 50% in specified circumstances, including expiration of patents rights related to a 2019 Collaboration Product, approval of biosimilar products in a given country or required payment of licensing fees to third parties related to the development and commercialization of any 2019 Collaboration Product. As a result of Neurocrine’s termination of the 2019 Neurocrine Collaboration Agreement with respect to the VY-AADC Program, the Company is no longer entitled to receive royalties related to the VY-AADC Program. Additionally, the licenses granted to Neurocrine shall automatically convert to fully paid-up, non-royalty bearing, perpetual, irrevocable, exclusive licenses on a country-by-country and product-by-product basis upon the expiration of the 2019 Royalty Term applicable to such 2019 Collaboration Product in such country. ​ Under the terms of the 2019 Neurocrine Collaboration Agreement and subject to specified exceptions therein, each party owns the entire right, title and interest in and to all intellectual property rights made solely by its employees or agents in the course of the collaboration. The parties jointly own all rights, title and interest in and to all intellectual property rights made or invented jointly by employees or agents of both parties . ​ During the term of the 2019 Neurocrine Collaboration Agreement, neither party nor any of its respective affiliates is permitted to directly or indirectly exploit any AAV-based gene therapy products directed to a Target to which a 2019 Collaboration Product is directed, subject to specified exceptions, including the parties’ conduct of basic research activities. ​ Unless earlier terminated, the 2019 Neurocrine Collaboration Agreement expires on the later of (a) the expiration of the last to expire 2019 Royalty Term with respect to a 2019 Collaboration Product in all countries in the relevant territory or (b) the expiration or termination of any 2019 FA Co-Co Agreement. Neurocrine may terminate the 2019 Neurocrine Collaboration Agreement in its entirety or on a program-by-program or country-by-country basis by providing at least (x) 180-day advance notice if such notice is provided prior to the first commercial sale of the 2019 Collaboration Product to which the termination applies or (y) one-year advance notice if such notice is provided after the first commercial sale of the 2019 Collaboration Product to which the termination applies. The Company may terminate the 2019 Neurocrine Collaboration Agreement, subject to specified conditions, if Neurocrine challenges the validity or enforceability of certain of the Company’s intellectual property rights. Subject to a cure period, either party may terminate the 2019 Neurocrine Collaboration Agreement in the event of a material breach by the other party in whole or in part, subject to specified conditions. ​ Upon termination in certain cases, Neurocrine has agreed to grant to the Company licenses to certain Neurocrine intellectual property, subject to a negotiation between the parties to establish royalty rates for use of such intellectual property. In the event of a breach by the Company with respect to a 2019 Neurocrine Program, if such termination were to occur after a 2019 Transition Event, then (a) with respect to the FA Program, if a 2019 FA Co-Co Agreement is in effect, Neurocrine can terminate the 2019 FA Co-Co Agreement for such program and the Company would no longer have co-development and co-commercialization rights with respect to the FA Collaboration Products and (b) subject to any license agreements, Neurocrine would no longer have any obligations with respect to any 2019 Collaboration Products resulting from such program. ​ Termination of VY-AADC Program ​ As described above, as of the Neurocrine VY-AADC Program Termination Effective Date, the license granted by the Company to Neurocrine thereunder regarding the VY-AADC Program expired, the Company regained worldwide intellectual property rights regarding the VY-AADC Program, and the restrictions on the Company to develop, manufacture or commercialize a gene therapy product directed to the target of the VY-AADC Program terminated, in each case in accordance with the terms of the 2019 Neurocrine Collaboration Agreement. As of the Neurocrine VY-AADC Program Termination Effective Date, Neurocrine no longer is obligated to reimburse the Company for research and development activities related to the VY-AADC Program, and the Company is no longer entitled to receive future milestone or royalty payments related to the VY-AADC Program. ​ Accounting Analysis ​ At inception, the Company determined the 2019 Neurocrine Collaboration Agreement was a contract with a customer under ASC 606, and included the following performance obligations: (a) research and development services for each Legacy Program combined with a development and commercialization license for each such program and (b) research and development services for each 2019 Discovery Program combined with a development and commercialization license for each program. The research services and license on a program-by-program basis are not distinct as Neurocrine cannot benefit from such license on its own or from other resources commonly available in the industry, without the corresponding research services due to the unique and specialized expertise of the Company that is not readily available in the marketplace. ​ The Company identified $92.4 million of fixed transaction price consisting of the $115.0 million upfront fee and $5.0 million payment from the June 2019 Modification, offset by a discount of $27.6 million related to the $50.0 million equity investment of 4,179,728 shares when measured at fair value on the date of issuance. The Company is also entitled to reimbursement of costs incurred by the Company prior to the 2019 Transition Events associated with each 2019 Neurocrine Program. These amounts are determinable based on program plans and budgets, and the Company has a contractual right to the payment of cost incurred under the agreed upon program plans. The Company utilized the most likely amount approach and estimated the expected cost reimbursement to be $431.1 million at inception. The Company concluded that these amounts do not require a constraint and are included in the transaction price at inception. The Company considers this estimate at each reporting date and updates the estimate based on information available. During the fourth quarter of 2021, the Company revised the estimate of the expected reimbursement to approximately $80.0 million based on expectations as a result from decisions made at the JSC meeting held in the fourth quarter of 2021, which resulted in significantly less research and development services to be provided by the Company under the 2019 Neurocrine Collaboration Agreement. During the fourth quarter of 2022, the Company further revised the estimate of the expected reimbursement to approximately $81.7 million, based on expectations resulting from decisions made at the JSC meeting held in the fourth quarter of 2022. Additional consideration to be paid to the Company upon reaching certain milestones are excluded from the transaction price at inception due to the uncertainty of achieving the development and regulatory milestones. ​ The Company allocated the fixed transaction price to the separate performance obligations based on the relative standalone selling price of each performance obligation or in the case of certain variable consideration to one or more performance obligations. The estimated standalone selling prices for performance obligations, which include a license and research services, were developed using the estimated selling price of the license, using comparable and market data, and an estimate of the overall effort to perform the research services along with a reasonable profit for research services. ​ The total variable consideration allocated to each program related to the expected cost reimbursement was as follows as of December 31, 2022: ​ ​ ​ ​ ​ ​ Performance Obligation ​ Amount ​ ​ ​ (in thousands) ​ Variable Consideration ​ ​ ​ VY-AADC Program ​ $ 53,863 ​ FA Program ​ ​ 18,868 ​ 2019 Discovery Program 1 ​ ​ 5,336 ​ 2019 Discovery Program 2 ​ ​ 3,605 ​ Total ​ $ 81,671 ​ ​ ​ ​ ​ ​ ​ Based on the relative standalone selling price allocation, the allocation of the transaction price, exclusive of the variable consideration allocated to the individual performance obligations, to the separate performance obligations was as follows: ​ ​ ​ ​ ​ ​ Performance Obligation ​ Amount ​ ​ ​ (in thousands) ​ Fixed Consideration ​ ​ ​ VY-AADC Program ​ $ 49,045 ​ FA Program ​ ​ 20,647 ​ 2019 Discovery Program 1 ​ ​ 14,443 ​ 2019 Discovery Program 2 ​ ​ 8,247 ​ Total ​ $ 92,382 ​ ​ ​ ​ ​ ​ ​ The Company recognizes the transaction price associated with each performance obligation on a proportional performance basis over the period of service using input-based measurements such as costs incurred to date, to estimate proportion performed, and remeasures its progress towards completion at the end of each reporting period. ​ The Company determined the partial termination of the 2019 Neurocrine Collaboration Agreement with respect to the VY-AADC Program represented a modification of the arrangement under ASC 606 and that the remaining fixed transaction price at the Neurocrine VY-AADC Program Termination Effective Date of $42.2 million should be re-allocated to the FA Program and 2019 Discovery Program 1 and 2 based on their standalone selling prices. Accordingly, the Company recorded a cumulative adjustment to revenue of approximately $0.9 million on the partially satisfied remaining performance obligations, as the remaining services to be performed under each of the performance obligations are not distinct from the services prior to the modification. The Company determined that reasonable changes to the Company’s estimates of standalone selling prices for the FA Program, 2019 Discovery Program 1 and 2019 Discovery Program 2 performance obligations did not have a material impact on the re-allocation or the amount of revenue recorded pursuant to the cumulative catch-up adjustment. ​ During the years ended December 31, 2022 and 2021, the Company recognized $0.9 million and $37.4 million of revenue, respectively, associated with its collaboration with Neurocrine related to research and development services performed during the period and the corresponding cost reimbursement receivable. As of December 31, 2022, there was $11.8 million of deferred revenue related to the 2019 Neurocrine Collaboration Agreement, which is classified as either current or non-current in the accompanying consolidated balance sheet based on the period the services are expected to be delivered. Additionally, as of December 31, 2022, there was $0.3 million of collaboration receivables related to reimbursable costs expected to be received from Neurocrine for research and development services performed. ​ The following table presents changes in the balances of the Company’s related party collaboration receivables and contract liabilities during the year ended December 31, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ Balance at ​ ​ ​ December 31, 2021 ​ Additions ​ Deductions ​ December 31, 2022 ​ ​ ​ ​ ( in thousands) ​ Related party collaboration receivable ​ $ 732 ​ $ 907 ​ $ (1,382) ​ $ 257 ​ Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue ​ $ 12,096 ​ $ — ​ $ (269) ​ $ 11,827 ​ ​ The change in the receivables balance for the year ended December 31, 2022 is primarily driven by amounts owed to the Company for research and development services provided, offset by amounts collected from Neurocrine during the period. ​ Costs incurred relating to the Company’s collaboration programs under the 2019 Neurocrine Collaboration Agreement consist of internal and external research and development costs, which primarily include: salaries and benefits, laboratory supplies, preclinical research studies, clinical studies, consulting services, and commercial development. These costs are included in research and development expenses in the Company’s consolidated statements of operations. ​ The Company incurred approximately $0.8 million of costs to obtain the 2019 Neurocrine Collaboration Agreement which were payable only upon the close of the deal and therefore considered incremental costs of obtaining a contract with a customer and capitalized. The costs are recorded in prepaid expenses and other non-current assets and are being amortized over the period in which the research services will be provided. ​ Pfizer Option and License Agreement ​ Summary of Agreement ​ On October 1, 2021, the Company entered into an option and license agreement with Pfizer (the “Pfizer Agreement”), pursuant to which the Company granted Pfizer options to receive an exclusive license (the “Pfizer License Options”) to certain TRACER capsids to develop and commercialize certain AAV gene therapy candidates comprised of a capsid and specified Pfizer transgenes (the “Pfizer Transgenes”). Under the terms of the Pfizer Agreement, during an initial research term that ended as of October 1, 2022 (the “Pfizer Research Term”), Pfizer had the right to evaluate the potential use of the capsids in combination with up to two Pfizer Transgenes to help treat respective central nervous system (“CNS”) and cardiovascular diseases. ​ During the Pfizer Research Term, the Company agreed to provide Pfizer with certain quantities of materials encoding specified existing capsids for Pfizer’s evaluation. Further, during the Pfizer Research Term, the Company agreed to disclose to Pfizer, on a rolling basis, the performance characteristics identified during the Pfizer Research Term for all such capsid candidates. Pfizer had the right, in its sole discretion, to select any capsid candidate for evaluation to determine its interest in exercising a Pfizer License Option with respect to such capsid candidate. Pfizer had the right to exercise up to two Pfizer License Options, provided that it could exercise only one Pfizer License Option for each Pfizer Transgene. ​ Effective as of September 30, 2022, Pfizer exercised its Pfizer License Option with respect to a capsid for the specified Pfizer Transgene for potential treatment of a rare neurological disease. Pfizer did not exercise its option to license a capsid for the potential treatment of a cardiovascular disease. As result, Pfizer’s right to exercise a Pfizer License Option for a cardiovascular disease has terminated in accordance with the terms of the Pfizer Agreement and all rights to capsids for that cardiovascular disease have reverted to the Company. Pfizer’s exercise of a Pfizer License Option extends the Pfizer Research Term to October 1, 2024, during which period the Company may, at its sole discretion and expense, conduct additional research activities to identify additional proprietary capsids that may be useful for AAV gene therapies for the treatment of the rare neurological disease associated with the exercise of the applicable Pfizer License Option. ​ Pursuant to the exercise of the Pfizer License Option, the Company granted Pfizer an exclusive, worldwide license, with the right to sublicense, under certain of the Company’s intellectual property, the rights to develop and commercialize rare neurological disease products utilizing the capsid candidate and incorporating the corresponding Pfizer Transgene (the “Pfizer Licensed CNS Products”). Until October 1, 2024, while the Company is not obligated to conduct additional research activities to identify additional proprietary capsids that may be useful for AAV gene therapies for the treatment of rare neurological diseases, it has agreed to continue to disclose to Pfizer, on a rolling basis, the performance characteristics identified for all such capsid candidates, if and when available. Pfizer may, during the Pfizer Research Term, conduct additional evaluations of such capsid candidates and has the right to substitute any other capsid candidate for the capsid it previously elected to license when it exercised the Pfizer License Option. ​ Under the Pfizer Agreement, Pfizer is solely responsible for, and has sole decision-making authority with respect to, development and commercialization of the Pfizer Licensed CNS Products. Pfizer is required to use commercially reasonable efforts to develop and obtain regulatory approval for at least ​ Under the terms of the Pfizer Agreement, Pfizer paid the Company an upfront payment of $30.0 million in October 2021. Following the exercise of the Pfizer License Option, Pfizer paid the Company a fee of $10.0 million and the Company is also eligible to receive specified development, regulatory, and commercialization milestone payments of up to an aggregate of $115.0 million for the first corresponding Pfizer Licensed CNS Product to achieve the corresponding milestone. On a Pfizer Licensed CNS Product-by-Pfizer Licensed CNS Product basis, the Company is also eligible to receive (a) specified sales milestone payments of up to an aggregate of $175.0 million per Pfizer Licensed CNS Product and (b) tiered, escalating royalties in the mid- to high-single-digit percentages of annual net sales of each Pfizer Licensed CNS Product. The royalties are subject to potential reductions in customary circumstances including patent claim expiration, payments for certain third-party licenses, and biosimilar market penetration, subject to specified limits. ​ Under the terms of the Pfizer Agreement, each of the Company and Pfizer owns the entire right, title, and interest in and to all patents or know-how controlled by such party and existing as of or before the effective date of the Pfizer Agreement, or invented, developed, created, generated or acquired solely by or on behalf of such party after such effective date. ​ Subject to certain specified exceptions, any patents and know-how that are invented or otherwise developed jointly by or on behalf of the parties during the term of the Pfizer Agreement and in the course of the Company’s and Pfizer’s activities under the Pfizer Agreement will follow inventorship under U.S. patent law. Subject to certain limitations and exceptions, the Company agreed (a) during the Pfizer Research Term, not to conduct any internal program or program on behalf of a third party that is directed to development or commercialization of any capsid candidates, or grant any third party or affiliate any right or license under the Company’s rights in such capsid candidates to exploit any therapeutic product, in combination with any Pfizer Transgene in any indication for therapeutic, diagnostic and prophylactic human and veterinary use; and (b) after Pfizer’s exercise of a Pfizer License Option, not to grant any third party or affiliate any right or license under the Company’s patents to exploit any licensed capsid in combination with any Pfizer Transgene. ​ Unless earlier terminated, the Pfizer Agreement expires on the expiration of the last-to-expire royalty term with respect to all Pfizer Licensed CNS Products in all countries. Subject to a cure period, either party may terminate the Pfizer Agreement, in whole or in part, subject to specified conditions, in the event of the other party’s uncured material breach. Pfizer may also terminate the Pfizer Agreement, in whole or in part, subject to specified conditions, for the Company’s insolvency, the occurrence of a violation of global trade control laws, or for the Company’s noncompliance with certain anti-bribery or anti-corruption covenants. Pfizer may also terminate the Pfizer Agreement, in whole or in part, for any or no reason upon ninety days’ written notice to us. ​ Upon certain terminations for cause by Pfizer, the license that the Company has granted to Pfizer under the Pfizer Agreement shall become irrevocable and perpetual, and all milestone payments and royalties that would have otherwise been payable by Pfizer under such license had the Pfizer Agreement remained in effect would be substantially reduced. ​ Accounting Analysis ​ At inception, the Company determined the Pfizer Agreement was a contract with a customer under ASC 606. The Company assessed the promised goods and services under the Pfizer Agreement, in accordance with ASC 606, and determined that the Pfizer Agreement contains two performance obligations consisting of two material rights, one for each of the Pfizer License Options. The Company concluded that each Pfizer License Option provides a material right as consideration for each option is less than the amount that the Company would otherwise have expected to receive outside the context of the contract. The promises at inception do not include the underlying goods or services that would be delivered upon exercise of the option, but rather represent the value to the customer of having the right to exercise the Pfizer License Option at the specified exercise fee. Upon the exercise of a Pfizer License Option, until October 1, 2024, while the Company is not obligated to conduct additional research activities upon option exercise to identify additional proprietary capsids that may be useful for AAV gene therapies for the treatment of central nervous system or cardiovascular diseases, it has agreed to continue to disclose to Pfizer, on a rolling basis, the performance characteristics identified for all such capsid candidates, if and when available. Pfizer may, conduct additional evaluations of such capsid candidates and has the right to substitute any other capsid candidate for the capsid it previously elected to license when it exercised the Pfizer License Option. The Company determined that this promise to provide Pfizer the ability to evaluate and potentially substitute other capsid candidates for the capsid it previously elected to license when it exercised the Pfizer License Option, if and when available, is an additional performance obligation in the arrangement (“the Pfizer Substitution Right Performance Obligation”). ​ The Company received a nonrefundable, upfront payment of $30.0 million as consideration under the Pfizer Agreement, which represents the transaction price at inception. Additional consideration to be paid to the Company upon exercise of the Pfizer License Option or upon reaching certain milestones are excluded from the transaction price as they relate to option fees and milestones that could only be achieved subsequent to an option exercise. ​ The Company allocated the transaction price to the Pfizer License Options based on their relative standalone selling prices. The estimated standalone selling price for each material right was based on an adjusted market assessment approach. The Company concluded that the market would be willing to pay an equal amount for each Pfizer License Option on a standalone basis. The Company reached this conclusion after considering (a) the downstream economics including option fees, milestones and royalties related to each Pfizer License Option being identical and (b)

Common stock

Common stock	12 Months Ended
	Dec. 31, 2022
Common stock.
Common stock	10. Common stock ​ As of December 31, 2022 and 2021, the Company had authorized 120,000,000 shares of common stock, at $0.001 par value per share. ​ General ​ The voting, dividend and liquidation rights of the holders of the common stock are subject to and qualified by the rights, powers and preferences of the holders of preferred stock. The common stock has the following characteristics: ​ Liquidation ​ The holders of shares of common stock are entitled to share ratably in the Company’s remaining assets available for distribution to its stockholders in the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or upon occurrence of a deemed liquidation event. ​ Shares Reserved For Future Issuance ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 Shares reserved for vesting of restricted stock awards under the Founder Agreements 45,000 ​ 137,255 ​ Shares reserved for exercise of outstanding stock options 6,199,571 ​ 5,013,193 Shares reserved for vesting of outstanding restricted stock units 1,112,563 ​ 806,379 Shares reserved for issuances under the 2015 Stock Option Plan ​ 3,536,932 ​ 4,374,539 ​ Shares reserved for issuances under the 2015 Employee Stock Purchase Plan ​ 1,884,309 ​ 1,659,574 ​ ​ 12,778,375 ​ 11,990,940 ​

Stock-based compensation

Stock-based compensation	12 Months Ended
	Dec. 31, 2022
Stock-based compensation
Stock-based compensation	11. Stock-based compensation ​ 2014 Stock Option and Grant Plan ​ In January 2014, the Company adopted the 2014 Stock Option and Grant Plan (the “2014 Plan”), under which it could grant incentive stock options, non-qualified stock options, restricted stock awards, unrestricted stock awards, or restricted stock units to purchase up to 823,529 shares of common stock to employees, officers, directors and consultants of the Company. ​ The terms of stock option agreements, including vesting requirements, were determined by the Board of Directors and were subject to the provisions of the 2014 Plan. Restricted stock awards granted by the Company generally vest based on each grantee’s continued service with the Company during a specified period following grant. Stock options granted to employees generally vest over four years, with 25% vesting on the one year anniversary and 75% vesting ratably, on a monthly basis, over the remaining three years. Stock options granted to non-employee consultants generally vest monthly over a period of one ​ Founder Awards ​ In January 2014, the Company issued 1,188,233 shares of restricted stock to its founders (each, a “Founder”) at an original issuance price of $0.0425 per share. Of the total restricted shares awarded to the Founders, 835,292 shares were slated to vest over one ​ The remainder of the restricted stock awards were slated to vest upon the achievement of certain performance objectives as well as continued service to the Company, as set forth in the agreements. Stock-based compensation expense associated with these performance-based awards is recognized when the achievement of the performance condition is considered probable, using management’s best estimates. The Company has modified certain of the awards, including repurchasing a total of 131,470 shares underlying the awards through December 31, 2022, and modifying the vesting provisions such that the modified awards vest over time rather than based on performance. The stock-based compensation expense recorded related to these awards during the years ended December 31, 2022, 2021, and 2020 were immaterial to the Company’s consolidated financial statements. ​ 2015 Stock Option Plan ​ In October 2015, the Company s board of directors and stockholders The 2015 Stock Option Plan replaced the 2014 Plan. Any options or awards outstanding under the 2014 Plan remained outstanding and effective. The number of shares initially reserved for issuance under the 2015 Stock Option Plan is the sum of (a) 1,311,812 shares of common stock and (b) the number of shares under the 2014 Plan that are not needed to fulfill the Company s obligations for awards issued under the 2014 Plan as a result of forfeiture, expiration, cancellation, termination or net issuances of awards thereunder. The number of shares of common stock that may be issued under the 2015 Stock Option Plan is also subject to increase on the first day of each fiscal year by up to 4% of the Company s issued and outstanding shares of common stock on the immediately preceding December 31. ​ Effective January 1, 2016 and every anniversary thereafter an additional 4% of outstanding common stock was added to the Company’s 2015 Stock Option Plan pursuant to its “evergreen” provision, for future issuance. This has accumulated to a total of 10,771,368 shares through January 1, 2023. During the year ended December 31, 2022, the Company granted options to purchase 3,291,075 shares of common stock to employees and directors under the 2015 Stock Option Plan. As of December 31, 2022, there were 3,536,932 shares available for future issuance under the 2015 Stock Option Plan. ​ 2015 Employee Stock Purchase Plan ​ In October 2015, the Company’s board of directors and stockholders approved the 2015 Employee Stock Purchase Plan (the “2015 ESPP”). Under the 2015 ESPP, all full-time employees of the Company are eligible to purchase common stock of the Company twice per year, at the end of each six-month payment period. During each payment period, eligible employees who so elect, may authorize payroll deductions in an amount of 1% to 10% (whole percentages only) of the employee’s base pay for each payroll period. At the end of each payment period, the accumulated deductions are used to purchase shares of common stock from the Company at a discount. A total of 262,362 shares of common stock were initially authorized for issuance under this plan. ​ The 2015 ESPP became effective upon the completion of the IPO. Effective January 1, 2016 and every anniversary thereafter an additional 1% of outstanding common stock was added to the 2015 ESPP, pursuant to its evergreen provision, for future issuance . This has accumulated to a total of 2,692,838 shares through January 1, 2023. The Company issued 150,265 and 200,006 shares of common stock under the 2015 ESPP in the years ended December 31, 2022 and 2021. As of December 31, 2022, there were 1,884,309 shares available for future purchase under the 2015 ESPP. ​ Inducement Awards ​ In the years ended December 31, 2022, 2021, and 2020, the Company issued non-statutory stock options to purchase an aggregate of 390,000, 76,500 and 172,500 shares of the Company’s common stock and restricted stock unit awards for an aggregate of 163,000, 13,000 and 29,000 shares of the Company’s common stock, respectively, in each case outside of the Company’s 2015 Stock Option Plan as an inducement material to certain individuals’ acceptance of an offer of employment with the Company in accordance with Nasdaq Listing Rule 5635(c)(4). ​ The stock options will vest over a four-year period, with 25% of the shares underlying the option award vesting on the first anniversary of the award and the remaining 75% of the shares underlying the award vesting monthly thereafter over the subsequent 36-month period. The restricted stock units vest over a three-year period, with 33% of the restricted stock units vesting on the first anniversary of the award, 33% of the restricted stock units vesting on the second anniversary, and the remaining restricted stock units vesting on the third anniversary. ​ Stock-based Compensation Expense ​ Total compensation cost recognized for all stock-based compensation awards in the statements of operations and comprehensive (loss) income is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2022 2021 2020 ​ ​ (in thousands) General and administrative ​ $ 6,398 ​ $ 7,191 ​ $ 8,577 ​ Research and development ​ 2,946 ​ 4,133 ​ 6,357 ​ Total stock-based compensation expense ​ $ 9,344 ​ $ 11,324 ​ $ 14,934 ​ ​ Stock-based compensation expense by type of award included within the consolidated statements of operations and ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ ​ 2022 2021 2020 ​ ​ ​ (in thousands) ​ Stock options ​ $ 5,938 ​ $ 7,438 ​ $ 11,387 ​ Restricted stock awards and units ​ ​ 3,215 ​ ​ 3,551 ​ ​ 3,110 ​ Employee stock purchase plan awards ​ 191 ​ 335 ​ 437 ​ Total stock-based compensation expense ​ $ 9,344 ​ $ 11,324 ​ $ 14,934 ​ ​ Restricted Stock Units ​ A summary of the status of and changes in unvested restricted stock unit activity under the Company’s equity award plans for the year ended December 31, 2022 was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ Grant Date ​ ​ ​ ​ ​ Fair Value ​ ​ ​ Units Per Unit ​ Unvested restricted stock units as of December 31, 2021 ​ 806,379 ​ $ 7.26 ​ Awarded ​ 964,480 ​ $ 4.29 ​ Vested ​ (436,611) ​ $ 6.92 ​ Forfeited ​ (221,685) ​ $ 5.05 ​ Unvested restricted stock units as of December 31, 2022 ​ 1,112,563 ​ $ 5.27 ​ ​ Stock-based compensation of restricted stock units is based on the fair value of the Company’s common stock on the date of grant and recognized over the vesting period. In the year ended December 31, 2022, the Company granted 864,480 restricted stock units vesting in equal amounts, annually over three years, and 100,000 restricted stock units vesting in equal amounts, annually over four years. The stock-based compensation expense was $2.9 million, $3.3 million, and $2.8 million for the years ended December 31, 2022, 2021, and 2020, respectively. ​ As of December 31, 2022, the Company had unrecognized stock-based compensation expense related to its unvested restricted stock units of $3.7 million which is expected to be recognized over the remaining weighted average vesting period of 1.9 years. ​ Stock Options ​ A summary of the status of, and changes in, stock options was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Remaining Aggregate ​ ​ ​ ​ ​ Average ​ Contractual ​ Intrinsic ​ ​ ​ ​ ​ Exercise ​ Life ​ Value ​ ​ Shares Price (in years) (in thousands) ​ Outstanding at December 31, 2021 5,013,193 ​ $ 12.69 ​ ​ ​ ​ ​ Granted ​ 3,681,075 ​ $ 5.17 ​ ​ ​ ​ ​ ​ Exercised ​ (89,012) ​ $ 7.07 ​ ​ ​ ​ ​ ​ Cancelled or forfeited ​ (2,405,685) ​ $ 13.15 ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2022 ​ 6,199,571 ​ $ 8.12 ​ 7.9 ​ $ 6,095 ​ Exercisable at December 31, 2022 2,744,489 ​ $ 10.56 6.5 ​ $ 2,287 ​ ​ Using the Black-Scholes option pricing model, the weighted average fair value of options granted during the year ended December 31, 2022 was $3.60. The stock-based compensation expense related to stock option awards granted was $5.8 million, $7.3 million, and $11.2 million for the years ended December 31, 2022, 2021, and 2020, respectively. ​ The fair value of each option was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2022 2021 2020 ​ Risk-free interest rate 2.2 % 0.9 % ​ 1.0 % ​ Expected dividend yield — % — % ​ — % ​ Expected term (in years) 6.0 ​ 6.0 ​ ​ 6.0 ​ ​ Expected volatility 79.4 % 75.0 % ​ 73.7 % ​ ​ As of December 31, 2022, the Company had unrecognized stock-based compensation expense related to its unvested stock options of $12.8 million which is expected to be recognized over the remaining weighted average vesting period of 2.9 years.

401(k) Savings plan

401(k) Savings plan	12 Months Ended
	Dec. 31, 2022
401(k) Savings plan
401(k) Savings plan	12. 401(k) Savings plan The Company has a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements, and allows participants to defer a portion of their annual compensation on a pretax basis. The Company expensed approximately $0.9 million, $1.1 million, and $1.1 million related to employer contributions made during the years ended December 31, 2022, 2021, and 2020, respectively.

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2022
Income taxes
Income taxes	13. Income taxes The Company recognized deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the Company’s financial statements or tax returns. Under this method, deferred tax assets and liabilities are determined based on differences between the financial statement carrying amounts and the tax bases of the assets and liabilities using the enacted tax rates in effect in the years in which the differences are expected to reverse. A valuation allowance against deferred tax assets is recorded if, based on the weight of the available evidence, it is more likely than not that some or all the deferred tax assets will not be realized. The Company accounts for uncertain tax positions using a more-likely-than-not threshold for recognizing and resolving uncertain tax positions. The evaluation of uncertain tax positions is based on factors including, but not limited to, changes in the law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity, and changes in facts or circumstances related to a tax position. The Company evaluates its tax positions on an annual basis. The provision for incomes taxes is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2022 ​ 2021 ​ 2020 ​ (in thousands) ​ ​ ​ Current ​ ​ ​ ​ ​ ​ ​ ​ Federal $ — ​ $ — ​ $ — State ​ 16 ​ ​ — ​ ​ — Total current ​ 16 ​ ​ — ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ — ​ ​ — ​ ​ — State ​ — ​ ​ — ​ ​ — Total deferred ​ — ​ ​ — ​ ​ — Total tax provision $ 16 ​ $ — ​ $ — ​ A reconciliation of the expected income tax provision computed using the federal statutory income tax rate at the Company’s effective tax rate for the years ended December 31, 2022, 2021, and 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2022 ​ 2021 ​ 2020 ​ Income tax computed at federal statutory tax rate ​ 21.0 % ​ 21.0 % ​ 21.0 % ​ State taxes, net of federal benefit ​ 5.2 % ​ 6.6 % ​ (2.3) % ​ Provision to return ​ 3.2 % ​ 4.9 % ​ — % ​ General business credit carryovers ​ (3.5) % ​ 3.2 % ​ (20.6) % ​ Non-deductible expenses ​ (4.6) % ​ (3.8) % ​ 5.0 % ​ Other ​ — % ​ — % ​ 1.9 % ​ Change in valuation allowance ​ (21.3) % ​ (31.9) % ​ (5.0) % ​ Total ​ — % ​ — % ​ — % ​ ​ The Company has historically incurred net operating losses (“NOLs”). As of December 31, 2022, the Company had federal and state net operating loss carryforwards of $175.1 million and $166.5 million, respectively. As of December 31, 2022, the Company had federal and state research and development tax credit carryforwards of $24.0 million and $9.6 million, respectively, which expire beginning in 2033. As of December 31, 2021, the Company had state investment credits of $0.5 million, which expire beginning in 2023. ​ The significant components of the Company’s deferred tax assets and (liabilities) as of December 31, 2022 and 2021 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 ​ 2021 ​ (in thousands) ​ Deferred tax assets: ​ ​ ​ ​ ​ ​ Net operating loss carryforward $ 47,282 ​ $ 56,756 ​ Tax credit carryforward 32,060 ​ 30,122 ​ Lease liability ​ 6,318 ​ ​ 12,012 ​ Deferred revenue ​ 17,984 ​ ​ 11,485 ​ Stock compensation ​ 4,630 ​ ​ 7,784 ​ Non-deductible accruals and reserves 1,603 ​ 1,507 ​ Capitalized research expenses ​ 14,351 ​ ​ — ​ Intangibles 610 ​ 664 ​ Other temporary differences ​ (1) ​ ​ — ​ Total deferred tax assets 124,837 ​ 120,330 ​ Less valuation allowance (117,416) ​ (107,563) ​ Net deferred tax assets 7,421 ​ 12,767 ​ Deferred tax liabilities ​ ​ ​ ​ ​ Right of use assets ​ (4,231) ​ (9,128) ​ Depreciation and amortization ​ (3,190) ​ ​ (3,632) ​ Other temporary differences ​ — ​ ​ (7) ​ Net deferred taxes $ — ​ $ — ​ ​ As required by ASC 740, management has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which principally comprise NOL carryforwards, research and development credit carryforwards, and lease liability. Management has determined that it is more likely than not that the Company will not recognize the benefits of its federal and state deferred tax assets, and as a result, a valuation allowance of $117.4 million and $107.6 million has been established at December 31, 2022 and 2021, respectively. The change in valuation allowance was $9.8 million for the year ended December 31, 2022. The primary reason for the difference between the income tax provision recorded by the Company and the amount of income tax provision at statutory income tax rates was the change in the valuation allowance. ​ At December 31, 2022 and 2021, the Company had no unrecognized tax benefits. The Company has not as yet conducted a study of its research and development credit carryforwards. This study may result in an adjustment to the Company’s research and development credit carryforwards; however, until a study is completed, and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s research and development credits, and if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the balance sheets or statements of operations if an adjustment were required. ​ Interest and penalty charges, if any, related to unrecognized tax benefits would be classified as income tax expense in the accompanying statements of operations. As of December 31, 2022 and 2021, the Company has no accrued interest related to uncertain tax positions. Since the Company is in a loss carryforward position, it is generally subject to examination by the U.S. federal, state, and local income tax authorities for all tax years in which a loss carryforward is available.

Related party transactions

Related party transactions	12 Months Ended
	Dec. 31, 2022
Related party transactions
Related party transactions	14. Related-party transactions ​ During the years ended December 31, 2022, 2021, and 2020, the Company received board and scientific advisory services from two of its prior executives, Steven M. Paul, M.D., the Company’s former President and Chief Executive Officer, and Dinah Sah, Ph.D., the Company’s former Chief Scientific Officer. As of December 31, 2020, Dr. Paul’s consulting agreement was complete. The total amount of fees paid to Dr. Paul for services provided during the year ended December 31, 2020 was $0.2 million. The total amount of fees paid to Dr. Sah for services provided during the years ended December 31, 2022, 2021 and 2020 was $0.5 million, $0.2 million, and $0.4 million, respectively. ​ During the year ended December 31, 2022, the Company received advisory services related to strategic planning, operations, and management from Alfred Sandrock, M.D., Ph.D., the Company’s current President and Chief Executive Officer and a member of the Company’s Board of Directors, before he commenced service in the capacity of President and Chief Executive Officer in March 2022. The total amount of fees paid to Dr. Sandrock for services provided was $60,000 for the year ended December 31, 2022. ​ Under the 2019 Neurocrine Collaboration Agreement, the Company and Neurocrine have agreed to conduct research, development and commercialization activities for certain of the Company’s AAV gene therapy products (Note 9). Amounts due from Neurocrine are reflected as related party collaboration receivables. As of December 31, 2022, the Company recorded approximately $0.3 million in related party collaboration receivables. ​

Subsequent event

Subsequent event	12 Months Ended
	Dec. 31, 2022
Subsequent event
Subsequent event	15. Subsequent events ​ 2023 Neurocrine Collaboration ​ On January 8, 2023, the Company entered into the 2023 Neurocrine Collaboration Agreement, with Neurocrine for the research, development, manufacture and commercialization of gene therapy products directed to the gene that encodes glucosylceramidase beta 1 (“GBA1”) for the treatment of Parkinson’s disease and other diseases associated with GBA1 (the “GBA1 Program”) and three new programs focused on the research, development, manufacture and commercialization of gene therapies designed to address central nervous system diseases or conditions associated with rare genetic targets (the “2023 Discovery Programs” and, collectively with the GBA1 Program, the "2023 Neurocrine Programs”). ​ Under the terms of the 2023 Neurocrine Collaboration Agreement, Neurocrine paid to the Company an upfront payment of approximately $136.0 million (the “Upfront Collaboration Payment”) and approximately $39.0 million as consideration (the “Share Consideration”) for an equity purchase of 4,395,588 shares of the Company’s common stock (the “Shares”) in February 2023. The 2023 Collaboration Agreement also provides for aggregate development milestone payments from Neurocrine for gene therapy products arising under the 2023 Neurocrine Programs (the “2023 Collaboration Products”) under (a) the GBA1 Program of up to $985.0 million; and (b) each of the three 2023 Discovery Programs of up to $175.0 million for each 2023 Discovery Program. The Company may be entitled to receive aggregate commercial milestone payments for up to two 2023 Collaboration Products under the GBA1 Program of up to $950.0 million per 2023 Collaboration Product and for one 2023 Collaboration Product under each 2023 Discovery Program of up to $275.0 million per 2023 Discovery Program. ​ The 2023 Neurocrine Collaboration Agreement became effective on February 21, 2023, upon expiration of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended. On February 23, 2023, the Company received the Upfront Collaboration Agreement and the Share Consideration and issued and sold to Neurocrine the Shares pursuant to the applicable stock purchase agreement. ​ In connection with the execution of the 2023 Neurocrine Collaboration Agreement, the Company amended and restated their existing investor agreement on January 8, 2023 (the “2023 Neurocrine Amended and Restated Investor Agreement”), providing for standstill and lock-up restrictions and a voting agreement with respect to shares of the Company owned by Neurocrine. ​ Novartis Option Exercises ​ Effective as of March 1, 2023, Novartis exercised its Novartis License Options to license novel capsids generated from the Company’s TRACER capsid discovery platform for use in gene therapy programs against two undisclosed Initial Novartis Targets. With Novartis’ option exercise on two Initial Novartis Targets, the Company will receive a $25.0 million option exercise payment during the first half of 2023, and is eligible to receive associated potential development, regulatory, and commercial milestone payments, as well as mid- to high-single-digit tiered royalties based on net sales of the Novartis Licensed Products incorporating the Novartis Licensed Capsids. The two Initial Novartis Targets licensed are distinct from targets in the Company’s internal and partnered pipeline. In addition, over the next 18 months, Novartis retains the right to expand the agreement to include options to license capsids for up to two Additional Novartis Targets, subject to their availability, for a fee of $18.0 million per Additional Novartis Target. Under such an expansion, the Company would be eligible to receive a $12.5 million license option exercise fee for each Additional Novartis Target exercised, as well as future potential milestone payments per Additional Novartis Target and tiered mid- to high-single digit royalties on the Novartis Licensed Products incorporating the Novartis Licensed Capsids. ​ Novartis elected not to license a capsid for one Initial Novartis Target under the Novartis Agreement prior to the expiration of the applicable Novartis License Option. As a result, the non-exclusive research license that we granted to Novartis in connection with this Initial Novartis Target has terminated, the Novartis Research Term for this Initial Novartis Target has expired, and we are no longer eligible to receive development, regulatory, and commercial milestone payments or royalties in connection with this Initial Novartis Target. All capsid rights with respect to that Initial Novartis Target have returned to the Company.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2022
Summary of significant accounting policies
Basis of Presentation	Basis of presentation ​ The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) for reporting on Form 10-K. The Company’s consolidated financial statements include the accounts of Voyager Therapeutics, Inc. and its wholly-owned subsidiary, Voyager Securities Corporation. All intercompany balances and transactions have been eliminated. ​
Use of Estimates	Use of Estimates ​ The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, accrued expenses, stock-based compensation expense, and income taxes. The Company bases its estimates on historical experience and other market specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.
Fair Value of Financial Instruments	​ Fair Value of Financial Instruments ​ ASC Topic 820, Fair Value Measurement ​ ASC 820 identifies fair value as the exchange price, or 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. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: ​ ● Level 1 —Quoted market prices in active markets for identical assets or liabilities. ● Level 2 —Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates, and yield curves. ● Level 3 —Unobservable inputs developed using estimates of assumptions developed by the Company, which reflect those that a market participant would use. ​ To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. ​ The carrying amounts reflected in the balance sheets for cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature. ​
Cash and Cash Equivalents	Cash and Cash Equivalents ​ The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include cash held in banks and amounts held in money market funds. ​
Marketable Securities	Marketable Securities ​ The Company classifies marketable securities with a remaining maturity of greater than three months when purchased as available-for-sale. Marketable securities with a remaining maturity date greater than one year and marketable equity securities are classified as non-current where the Company has the intent and ability to hold these securities for at least the next 12 months. ​ All available for sale debt securities are carried at fair value with the unrealized gains and losses included in other comprehensive (loss) income as a component of stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense. Realized gains and losses are determined using the specific identification method and are included in other income. If any adjustment to fair value reflects a decline in value of the investment, the Company uses a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available-for-sale debt securities. No other than temporary losses have been recognized. ​ Cash, cash equivalents, and marketable securities as of December 31, 2022 and 2021 consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (in thousands) As of December 31, 2022 ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents $ 91,724 ​ ​ — ​ ​ — ​ $ 91,724 ​ Marketable securities- U.S. Treasury notes 19,980 ​ ​ — ​ ​ (91) ​ 19,889 ​ Total money market funds and marketable securities $ 111,704 ​ $ — ​ $ (91) ​ $ 111,613 ​ As of December 31, 2021 ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents $ 100,305 ​ $ — ​ $ — ​ $ 100,305 ​ Marketable securities- U.S. Treasury notes ​ 15,117 ​ ​ — ​ ​ (11) ​ ​ 15,106 ​ Total money market funds and marketable securities $ 115,422 ​ $ — ​ $ (11) ​ $ 115,411 ​ ​ All of the Company’s marketable securities at December 31, 2022 and 2021 have a contractual maturity of one year or less. ​
Restricted Cash	Restricted Cash ​ As of December 31, 2022 and 2021, the Company maintained restricted cash totaling approximately $1.5 million and $1.8 million, respectively, held in the form of money market accounts as collateral for the Company’s facility lease obligations. The balance is included within deposits and other non-current assets in the accompanying consolidated balance sheets. The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the consolidated balance sheets that sum to the total of the same such amounts shown in the statements of cash flows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ ​ 2022 2021 2020 ​ ​ ​ (in thousands) ​ Cash and cash equivalents ​ $ 98,959 ​ $ 117,433 ​ $ 104,440 ​ Restricted cash included in deposits and other non-current assets ​ ​ 1,515 ​ ​ 1,779 ​ ​ 1,779 ​ Total cash, cash equivalents, and restricted cash ​ $ 100,474 ​ $ 119,212 ​ $ 106,219 ​ ​
Property and Equipment	Property and Equipment ​ Property and equipment consists of laboratory equipment, furniture and office equipment, and leasehold improvements and is stated at cost, less accumulated depreciation. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred; while costs of major additions and betterments are capitalized. Depreciation is calculated over the estimated useful lives of the assets using the straight-line method. ​
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets ​ The Company evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book values of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book values of the assets exceed their fair value. The Company has not recognized any impairment losses from inception through December 31, 2022. ​
Revenue Recognition	Revenue Recognition ​ The Company enters into license, option, and collaboration agreements which are within the scope of ASC 606, Revenue from Contracts with Customers ​ The promised goods or services in the Company’s arrangements typically consist of license rights to the Company’s intellectual property and research and development services. The Company provides options to additional items in the contracts, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. The Company evaluates the customer options for material rights, or options to acquire additional goods or services for free or at a discount. If the customer options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (a) the customer can benefit from the good or service on its own or together with other readily available resources and (b) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract. ​ The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of potential payments and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected amount method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration which is included in the transaction price may be constrained, and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. ​ The Company’s contracts often include development and regulatory milestone payments which are assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenue in the period of adjustment. To date, the Company has not recognized any consideration related to the achievement of development, regulatory, or commercial milestone revenue resulting from any of the Company’s collaboration or license arrangements. ​ For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any consideration related to sales-based royalty revenue resulting from any of the Company’s collaboration or license arrangements. ​ The Company allocates the transaction price based on the estimated stand-alone selling price of each of the performance obligations. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price for service obligations, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Additionally, in determining the standalone selling price for material rights, the Company utilizes comparable transactions, clinical trial success probabilities, and estimates of option exercise likelihood. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation. ​ The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. ​ Upfront payments and fees are recorded as contract liabilities within deferred revenue on the consolidated balance sheets until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. A significant portion of revenue recognized from the 2019 Neurocrine Collaboration Agreement is related to performance obligations pursuant to which revenue is recognized using a proportional performance model. Revenue is recognized using input-based measurements, which involves the measurement of progress toward each performance obligation based on the actual costs incurred compared to total projected costs. The Company estimates the expected remaining costs to complete the research and development services for each performance obligation. The Company evaluates the measure of progress each reporting period and, if necessary, adjust the measure and related revenue recognition. ​
Research and Development	Research and Development ​ Research and development costs are charged to expense as incurred in performing research and development activities. The costs include employee compensation costs, external research, consultant costs, sponsored research, license fees, process development and facilities costs. Facilities costs primarily include the allocation of rent, utilities and depreciation. ​
Leases	Leases ​ The Company determines if an arrangement is or contains a lease at inception under Accounting Standards Codification (ASC) 842 Leases ​ Right-of-use assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. As the Company’s leases typically do not provide an implicit rate, the Company uses an estimate of its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. Operating lease right-of-use assets also include the effect of any lease prepaid or deferred lease payments and are reduced by lease incentives. The lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term. ​ The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. Non-lease components as it pertains to the Company's leased premises generally refer to common area maintenance charges related to the premises. ​
Research Contract Costs and Accruals	Research Contract Costs and Accruals ​ The Company has entered into various research and development contracts with research institutions and other companies. These agreements are generally cancelable. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs. ​
Patent Costs	Patent Costs ​ The Company expenses patent application and related legal costs as incurred and classifies such costs as general and administrative expenses in the accompanying statements of operations. ​
Stock-Based Compensation Expense	Stock-Based Compensation Expense ​ The Company accounts for its stock-based compensation awards in accordance with ASC Topic 718 Compensation—Stock Compensation ​ The Black-Scholes option pricing model requires inputs based on certain subjective assumptions, including (a) the expected stock price volatility, (b) the expected term of the award, (c) the risk-free interest rate and (d) expected dividends. The Company bases the estimate of expected volatility on the historical volatility of its common stock. The historical volatility is calculated based on a period of time commensurate with the expected term assumption. The Company uses the simplified method as prescribed by the SEC Staff Accounting Bulletin No. 107, Share-Based Payment ​ The Company expenses the fair value of its stock-based compensation awards on a straight-line basis over the associated service period, which is generally the period in which the related services are received, adjusted for actual forfeitures of unvested awards as they occur. ​ The Company records the expense for stock-based compensation awards subject to performance conditions over the remaining service period when management determines that achievement of the performance condition is probable. Management evaluates when the achievement of a performance condition is probable based on the expected satisfaction of the performance conditions as of the reporting date. ​
Income Taxes	Income Taxes ​ Income taxes are recorded in accordance with ASC Topic 740, Income Taxes ​ The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2022, the Company does not have any significant uncertain tax positions. ​
Comprehensive (Loss) Income	Comprehensive (Loss) Income ​ Comprehensive (loss) income is comprised of net (loss) income and other comprehensive income or loss. Other comprehensive income or loss consists of unrealized gains or losses on marketable securities. ​
Net (Loss) Income Per Share	Net (Loss) Income Per Share ​ Basic net (loss) income per share is calculated by dividing the net (loss) income by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net (loss) income per share is computed by dividing the net (loss) income by the weighted-average number of shares of common stock and potentially dilutive securities outstanding for the period determined using the treasury-stock and if-converted methods. ​ For purposes of the diluted net (loss) income per share, unvested restricted common stock and outstanding stock options are considered to be potentially dilutive securities. Unvested restricted common stock and outstanding stock options were excluded from the calculation of diluted net loss per share in the years ended December 31, 2022 and 2021, because their effect would be anti-dilutive and therefore, basic and diluted net loss per share were the same for the years ended December 31, 2022 and 2021. ​ The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net (loss) income per share because to do so would be anti-dilutive: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ ​ 2022 ​ 2021 ​ 2020 ​ Unvested restricted common stock awards ​ 45,000 ​ 137,255 ​ 156,863 ​ Unvested restricted common stock units ​ ​ 1,112,563 ​ ​ 806,379 ​ ​ 527,625 ​ Outstanding stock options ​ 6,199,571 ​ 5,013,193 ​ 5,379,856 ​ Total ​ 7,357,134 ​ 5,956,827 ​ 6,064,344 ​ ​ Basic net (loss) income and diluted weighted-average shares outstanding are as follows for the years ended December 31, 2022, 2021, and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2022 ​ 2021 ​ 2020 ​ ​ ​ (in thousands, except share data) ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income ​ $ (46,408) ​ $ (71,197) ​ $ 36,741 ​ Denominator for basic net (loss) income per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average shares outstanding-basic ​ ​ 38,356,810 ​ ​ 37,668,947 ​ ​ 37,132,447 ​ Denominator for diluted net (loss) income per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average shares outstanding ​ ​ 38,356,810 ​ ​ 37,668,947 ​ ​ 37,132,447 ​ Common stock options and restricted stock units ​ ​ — ​ ​ — ​ ​ 216,068 ​ Weighted average shares outstanding-diluted ​ ​ 38,356,810 ​ ​ 37,668,947 ​ ​ 37,348,514 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Concentrations of Credit Risk and Significant Suppliers	Concentrations of Credit Risk and Significant Suppliers ​ The Company has no financial instruments with off-balance sheet risk such as foreign exchange contracts, option contracts or other foreign currency hedging arrangements. Financial instruments that potentially subject the Company to a concentration of credit risk are cash and cash equivalents. The Company’s cash is held in accounts at financial institutions that may exceed federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. ​ The Company is dependent on third-party manufacturers to supply certain products for research and development activities in its programs. In particular, the Company relies on a sole manufacturer to supply it with specific vectors related to the Company’s research and development programs. ​
Segment Information	Segment Information ​ Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker in deciding how to allocate resources and assess performance. The Company and the Company’s chief operating decision maker, the Company’s Chief Executive Officer, view the Company’s operations and manages its business as a single operating segment, which is the business of developing and commercializing gene therapies. ​
Recent Accounting Pronouncements	Recent Accounting Pronouncements ​ In August 2020, the FASB issued ASU No. 2020-06, Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40)

Summary of significant accoun_3

Summary of significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2022
Summary of significant accounting policies
Schedule of money market funds and marketable securities	Cash, cash equivalents, and marketable securities as of December 31, 2022 and 2021 consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (in thousands) As of December 31, 2022 ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents $ 91,724 ​ ​ — ​ ​ — ​ $ 91,724 ​ Marketable securities- U.S. Treasury notes 19,980 ​ ​ — ​ ​ (91) ​ 19,889 ​ Total money market funds and marketable securities $ 111,704 ​ $ — ​ $ (91) ​ $ 111,613 ​ As of December 31, 2021 ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents $ 100,305 ​ $ — ​ $ — ​ $ 100,305 ​ Marketable securities- U.S. Treasury notes ​ 15,117 ​ ​ — ​ ​ (11) ​ ​ 15,106 ​ Total money market funds and marketable securities $ 115,422 ​ $ — ​ $ (11) ​ $ 115,411 ​ ​
Reconciliation of cash, cash equivalents, and restricted cash	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ ​ 2022 2021 2020 ​ ​ ​ (in thousands) ​ Cash and cash equivalents ​ $ 98,959 ​ $ 117,433 ​ $ 104,440 ​ Restricted cash included in deposits and other non-current assets ​ ​ 1,515 ​ ​ 1,779 ​ ​ 1,779 ​ Total cash, cash equivalents, and restricted cash ​ $ 100,474 ​ $ 119,212 ​ $ 106,219 ​ ​
Outstanding potentially dilutive securities excluded in the calculation of diluted net income (loss) per share	The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net (loss) income per share because to do so would be anti-dilutive: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ ​ 2022 ​ 2021 ​ 2020 ​ Unvested restricted common stock awards ​ 45,000 ​ 137,255 ​ 156,863 ​ Unvested restricted common stock units ​ ​ 1,112,563 ​ ​ 806,379 ​ ​ 527,625 ​ Outstanding stock options ​ 6,199,571 ​ 5,013,193 ​ 5,379,856 ​ Total ​ 7,357,134 ​ 5,956,827 ​ 6,064,344 ​ ​
Schedule of weighted average number of shares, basic and diluted	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2022 ​ 2021 ​ 2020 ​ ​ ​ (in thousands, except share data) ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income ​ $ (46,408) ​ $ (71,197) ​ $ 36,741 ​ Denominator for basic net (loss) income per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average shares outstanding-basic ​ ​ 38,356,810 ​ ​ 37,668,947 ​ ​ 37,132,447 ​ Denominator for diluted net (loss) income per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average shares outstanding ​ ​ 38,356,810 ​ ​ 37,668,947 ​ ​ 37,132,447 ​ Common stock options and restricted stock units ​ ​ — ​ ​ — ​ ​ 216,068 ​ Weighted average shares outstanding-diluted ​ ​ 38,356,810 ​ ​ 37,668,947 ​ ​ 37,348,514 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
	Dec. 31, 2022
Fair value measurements
Assets and liabilities measured at fair value on a recurring basis	Assets and liabilities measured at fair value on a recurring basis as of December 31, 2022 and 2021 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted Prices ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ ​ ​ ​ ​ Identical Assets ​ Inputs ​ Inputs ​ Assets Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) December 31, 2022 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents ​ $ 91,724 ​ $ 91,724 ​ $ — ​ $ — ​ Marketable securities- U.S. Treasury notes ​ ​ 19,889 ​ ​ 19,889 ​ ​ — ​ ​ — ​ Total ​ $ 111,613 ​ $ 111,613 ​ $ — ​ $ — ​ December 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents $ 100,305 ​ $ 100,305 ​ $ — ​ $ — ​ Marketable securities- U.S. Treasury notes ​ ​ 15,106 ​ ​ 15,106 ​ ​ ​ ​ ​ ​ ​ Total ​ $ 115,411 ​ $ 115,411 ​ $ — ​ $ — ​ ​

Prepaid expenses and other cu_2

Prepaid expenses and other current assets (Tables)	12 Months Ended
	Dec. 31, 2022
Prepaid expense and other current assets
Schedule of prepaid expense and other current assets	Prepaid expenses and other current assets consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2022 2021 ​ ​ (in thousands) ​ Other current assets ​ $ 4,233 ​ $ 1,701 ​ Prepaid insurance ​ 696 ​ 1,360 ​ Prepaid research and development contracts 83 ​ ​ 350 ​ Accrued interest receivable ​ ​ 382 ​ ​ 16 ​ Total ​ $ 5,394 ​ $ 3,427 ​ ​ ​ ​ ​ ​ ​ ​ ​

Property and equipment, net (Ta

Property and equipment, net (Tables)	12 Months Ended
	Dec. 31, 2022
Property and equipment, net
Schedule of property and equipment, net	Property and equipment, net consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Laboratory equipment ​ $ 19,675 ​ $ 19,384 ​ Leasehold improvements ​ ​ 12,554 ​ ​ 15,695 ​ Furniture and office equipment ​ 2,333 ​ 2,524 ​ Other ​ ​ 502 ​ 230 ​ Total property and equipment ​ 35,064 ​ 37,833 ​ Less: accumulated depreciation ​ (17,207) ​ (15,913) ​ Property and equipment, net ​ $ 17,857 ​ $ 21,920 ​ ​

Accrued expenses (Tables)

Accrued expenses (Tables)	12 Months Ended
	Dec. 31, 2022
Accrued expenses
Schedule of accrued expenses	Accrued expenses consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Employee compensation costs ​ $ 4,559 ​ $ 5,022 ​ Research and development costs ​ ​ 1,895 ​ ​ 3,719 ​ Accrued goods and services ​ 636 ​ 1,482 ​ Professional services ​ 726 ​ 727 ​ Total ​ $ 7,816 ​ $ 10,950 ​ ​ ​ ​ ​ ​ ​ ​ ​

Lease obligation (Tables)

Lease obligation (Tables)	12 Months Ended
	Dec. 31, 2022
Lease obligation
Summary of operating sublease income	​ ​ ​ ​ ​ ​ ​ ​ ​ Years ended ​ ​ December 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Operating sublease income $ 1,380 ​ $ 838 ​

Other liabilities (Tables)

Other liabilities (Tables)	12 Months Ended
	Dec. 31, 2022
Other liabilities
Summary of other current and non-current liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Other current liabilities ​ ​ ​ ​ ​ ​ Lease liabilities ​ 2,832 ​ ​ 5,571 ​ Total other current liabilities $ 2,832 ​ $ 5,571 ​ ​ ​ ​ ​ ​ ​ ​ Other non-current liabilities ​ ​ ​ ​ ​ ​ Lease liabilities $ 20,294 ​ $ 38,608 ​ Other ​ 1,001 ​ ​ 1,001 ​ Total other non-current liabilities $ 21,295 ​ $ 39,609 ​ ​

Commitments and contingencies (

Commitments and contingencies (Tables)	12 Months Ended
	Dec. 31, 2022
Schedule of collaboration receivables and contract liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ Balance at ​ ​ ​ December 31, 2021 ​ Additions ​ Deductions ​ December 31, 2022 ​ ​ ​ ​ ( in thousands) ​ Related party collaboration receivable ​ $ 732 ​ $ 907 ​ $ (1,382) ​ $ 257 ​ Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue ​ $ 12,096 ​ $ — ​ $ (269) ​ $ 11,827 ​ ​
Neurocrine Collaboration Agreement
Schedule of allocation of variable consideration	​ ​ ​ ​ ​ ​ Performance Obligation ​ Amount ​ ​ ​ (in thousands) ​ Variable Consideration ​ ​ ​ VY-AADC Program ​ $ 53,863 ​ FA Program ​ ​ 18,868 ​ 2019 Discovery Program 1 ​ ​ 5,336 ​ 2019 Discovery Program 2 ​ ​ 3,605 ​ Total ​ $ 81,671 ​ ​ ​ ​ ​ ​
Schedule of allocation of fixed consideration	​ ​ ​ ​ ​ ​ Performance Obligation ​ Amount ​ ​ ​ (in thousands) ​ Fixed Consideration ​ ​ ​ VY-AADC Program ​ $ 49,045 ​ FA Program ​ ​ 20,647 ​ 2019 Discovery Program 1 ​ ​ 14,443 ​ 2019 Discovery Program 2 ​ ​ 8,247 ​ Total ​ $ 92,382 ​ ​ ​ ​ ​ ​

Common stock (Tables)

Common stock (Tables)	12 Months Ended
	Dec. 31, 2022
Common stock.
Schedule of shares reserved for future issuance	​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 Shares reserved for vesting of restricted stock awards under the Founder Agreements 45,000 ​ 137,255 ​ Shares reserved for exercise of outstanding stock options 6,199,571 ​ 5,013,193 Shares reserved for vesting of outstanding restricted stock units 1,112,563 ​ 806,379 Shares reserved for issuances under the 2015 Stock Option Plan ​ 3,536,932 ​ 4,374,539 ​ Shares reserved for issuances under the 2015 Employee Stock Purchase Plan ​ 1,884,309 ​ 1,659,574 ​ ​ 12,778,375 ​ 11,990,940

Stock-based compensation (Table

Stock-based compensation (Tables)	12 Months Ended
	Dec. 31, 2022
Stock-based compensation
Compensation cost recognized for all stock-based compensation awards	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2022 2021 2020 ​ ​ (in thousands) General and administrative ​ $ 6,398 ​ $ 7,191 ​ $ 8,577 ​ Research and development ​ 2,946 ​ 4,133 ​ 6,357 ​ Total stock-based compensation expense ​ $ 9,344 ​ $ 11,324 ​ $ 14,934 ​ ​
Summary of stock-based compensation expense by type of award	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ ​ 2022 2021 2020 ​ ​ ​ (in thousands) ​ Stock options ​ $ 5,938 ​ $ 7,438 ​ $ 11,387 ​ Restricted stock awards and units ​ ​ 3,215 ​ ​ 3,551 ​ ​ 3,110 ​ Employee stock purchase plan awards ​ 191 ​ 335 ​ 437 ​ Total stock-based compensation expense ​ $ 9,344 ​ $ 11,324 ​ $ 14,934 ​ ​
Summary of status and changes in unvested restricted stock	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ Grant Date ​ ​ ​ ​ ​ Fair Value ​ ​ ​ Units Per Unit ​ Unvested restricted stock units as of December 31, 2021 ​ 806,379 ​ $ 7.26 ​ Awarded ​ 964,480 ​ $ 4.29 ​ Vested ​ (436,611) ​ $ 6.92 ​ Forfeited ​ (221,685) ​ $ 5.05 ​ Unvested restricted stock units as of December 31, 2022 ​ 1,112,563 ​ $ 5.27 ​ ​
Summary of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Remaining Aggregate ​ ​ ​ ​ ​ Average ​ Contractual ​ Intrinsic ​ ​ ​ ​ ​ Exercise ​ Life ​ Value ​ ​ Shares Price (in years) (in thousands) ​ Outstanding at December 31, 2021 5,013,193 ​ $ 12.69 ​ ​ ​ ​ ​ Granted ​ 3,681,075 ​ $ 5.17 ​ ​ ​ ​ ​ ​ Exercised ​ (89,012) ​ $ 7.07 ​ ​ ​ ​ ​ ​ Cancelled or forfeited ​ (2,405,685) ​ $ 13.15 ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2022 ​ 6,199,571 ​ $ 8.12 ​ 7.9 ​ $ 6,095 ​ Exercisable at December 31, 2022 2,744,489 ​ $ 10.56 6.5 ​ $ 2,287 ​ ​
Summary of weighted-average assumptions	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2022 2021 2020 ​ Risk-free interest rate 2.2 % 0.9 % ​ 1.0 % ​ Expected dividend yield — % — % ​ — % ​ Expected term (in years) 6.0 ​ 6.0 ​ ​ 6.0 ​ ​ Expected volatility 79.4 % 75.0 % ​ 73.7 % ​

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income taxes
Schedule of components of income expense (benefit)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2022 ​ 2021 ​ 2020 ​ (in thousands) ​ ​ ​ Current ​ ​ ​ ​ ​ ​ ​ ​ Federal $ — ​ $ — ​ $ — State ​ 16 ​ ​ — ​ ​ — Total current ​ 16 ​ ​ — ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ — ​ ​ — ​ ​ — State ​ — ​ ​ — ​ ​ — Total deferred ​ — ​ ​ — ​ ​ — Total tax provision $ 16 ​ $ — ​ $ — ​
Schedule of reconciliation of the expected income tax (benefit) computed using the federal statutory income tax rate to the effective income tax rate	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2022 ​ 2021 ​ 2020 ​ Income tax computed at federal statutory tax rate ​ 21.0 % ​ 21.0 % ​ 21.0 % ​ State taxes, net of federal benefit ​ 5.2 % ​ 6.6 % ​ (2.3) % ​ Provision to return ​ 3.2 % ​ 4.9 % ​ — % ​ General business credit carryovers ​ (3.5) % ​ 3.2 % ​ (20.6) % ​ Non-deductible expenses ​ (4.6) % ​ (3.8) % ​ 5.0 % ​ Other ​ — % ​ — % ​ 1.9 % ​ Change in valuation allowance ​ (21.3) % ​ (31.9) % ​ (5.0) % ​ Total ​ — % ​ — % ​ — % ​ ​
Schedule of principal components of the Company's deferred tax assets and liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 ​ 2021 ​ (in thousands) ​ Deferred tax assets: ​ ​ ​ ​ ​ ​ Net operating loss carryforward $ 47,282 ​ $ 56,756 ​ Tax credit carryforward 32,060 ​ 30,122 ​ Lease liability ​ 6,318 ​ ​ 12,012 ​ Deferred revenue ​ 17,984 ​ ​ 11,485 ​ Stock compensation ​ 4,630 ​ ​ 7,784 ​ Non-deductible accruals and reserves 1,603 ​ 1,507 ​ Capitalized research expenses ​ 14,351 ​ ​ — ​ Intangibles 610 ​ 664 ​ Other temporary differences ​ (1) ​ ​ — ​ Total deferred tax assets 124,837 ​ 120,330 ​ Less valuation allowance (117,416) ​ (107,563) ​ Net deferred tax assets 7,421 ​ 12,767 ​ Deferred tax liabilities ​ ​ ​ ​ ​ Right of use assets ​ (4,231) ​ (9,128) ​ Depreciation and amortization ​ (3,190) ​ ​ (3,632) ​ Other temporary differences ​ — ​ ​ (7) ​ Net deferred taxes $ — ​ $ — ​ ​

Nature of business (Details)

Nature of business (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Nature of business
Accumulated deficit	$ (393,512)	$ (347,104)
Cash, cash equivalents, and marketable debt securities	$ 118,800

Summary of significant accoun_4

Summary of significant accounting policies - Cash, Cash Equivalents, and Marketable Securities - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost Basis [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 98,959	$ 117,433	$ 104,440
Total money market funds and marketable securities	111,704	115,422
Fair Value Disclosure [Abstract]
Total money market funds and marketable securities	111,613	115,411
Unrealized Gain and Loss [Abstract]
Total money market funds and marketable securities	(91)	(11)
Other than temporary losses	0
Money market funds
Amortized Cost Basis [Abstract]
Cash and Cash Equivalents, at Carrying Value	91,724	100,305
Fair Value Disclosure [Abstract]
Cash and cash equivalents	91,724	100,305
U.S. Treasury notes
Amortized Cost Basis [Abstract]
Marketable securities, amortized cost	19,980	15,117
Fair Value Disclosure [Abstract]
Marketable securities, fair value	19,889	15,106
Unrealized Gain and Loss [Abstract]
Marketable securities, unrealized losses	$ (91)	$ (11)
Maximum
Unrealized Gain and Loss [Abstract]
Debt securities, contractual maturity period	1 year	1 year

Summary of significant accoun_5

Summary of significant accounting policies - Restricted Cash - (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Summary of significant accounting policies
Cash and cash equivalents	$ 98,959	$ 117,433	$ 104,440
Restricted cash included in deposits and other noncurrent assets	1,515	1,779	1,779
Total cash, cash equivalents, and restricted cash	$ 100,474	$ 119,212	$ 106,219	$ 86,777

Summary of significant accoun_6

Summary of significant accounting policies - Stock Based Compensation Expense - (Details)	12 Months Ended
	Dec. 31, 2022
Summary of significant accounting policies
Expected dividend yield	0%

Summary of significant accoun_7

Summary of significant accounting policies - Net income (loss) per share - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	7,357,134	5,956,827	6,064,344
Numerator:
Net (loss) income	$ (46,408)	$ (71,197)	$ 36,741
Denominator for basic net income (loss) per share:
Weighted average shares outstanding-basic	38,356,810	37,668,947	37,132,447
Denominator for diluted net income (loss) per share:
Weighted average shares outstanding-basic	38,356,810	37,668,947	37,132,447
Common stock options and restricted stock units			216,068
Weighted average shares outstanding-diluted	38,356,810	37,668,947	37,348,514
Financial instruments with off-balance sheet risk	$ 0
Unvested restricted common stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	45,000	137,255	156,863
Unvested restricted common stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	1,112,563	806,379	527,625
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	6,199,571	5,013,193	5,379,856

Fair value measurements - Asset

Fair value measurements - Assets and liabilities measured on a recurring basis - (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	$ 98,959	$ 117,433	$ 104,440
Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value	111,613	115,411
Level 1 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value	111,613	115,411
U.S. Treasury notes | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	19,889	15,106
U.S. Treasury notes | Level 1 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	19,889	15,106
Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	91,724	100,305
Money market funds | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	91,724	100,305
Money market funds | Level 1 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	$ 91,724	$ 100,305

Prepaid expenses and other cu_3

Prepaid expenses and other current assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Prepaid expense and other current assets
Other current assets	$ 4,233	$ 1,701
Prepaid insurance	696	1,360
Prepaid research and development contracts	83	350
Accrued interest receivable	382	16
Total	$ 5,394	$ 3,427

Property and equipment, net (De

Property and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 35,064	$ 37,833
Less: accumulated depreciation	(17,207)	(15,913)
Property and equipment, net	17,857	21,920
Depreciation expense	6,191	5,165	$ 3,817
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	19,675	19,384
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	12,554	15,695
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,333	2,524
Other
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 502	$ 230

Accrued expenses (Details)

Accrued expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accrued expenses
Employee compensation costs	$ 4,559	$ 5,022
Research and development costs	1,895	3,719
Accrued goods and services	636	1,482
Professional services	726	727
Total	$ 7,816	$ 10,950

Lease obligation (Details)

Lease obligation (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Jun. 22, 2022	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021
Change in operating lease, right-of-use assets			$ (3,462)	$ (2,606)	$ 7,592
Change in operating lease liabilities			(3,922)	(3,428)	13,439
Gain on termination of lease			2,468
Restricted cash included in deposits and other noncurrent assets			1,515	1,779	1,779
Lease expense			$ 4,600	$ 6,800	$ 6,200
Weighted average remaining lease term			6 years
Weighted average incremental borrowing rate			7.40%
Total minimum lease payments
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]			Other Liabilities, Current	Other Liabilities, Current
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]			Other Liabilities, Noncurrent	Other Liabilities, Noncurrent
75 Sidney Street
Sublease term						3 years 3 months 18 days
Change in operating lease, right-of-use assets	$ (14,500)
Change in operating lease liabilities		$ (17,000)
Gain on termination of lease		$ 2,500
Restricted cash included in deposits and other noncurrent assets			$ 1,500

Lease obligation - Operating su

Lease obligation - Operating sublease income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Lease obligation
Operating sublease income	$ 1,380	$ 838
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration]	Operating Expenses	Operating Expenses

Other liabilities (Details)

Other liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2022
Other current liabilities
Lease liabilities	$ 5,571	$ 2,832
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Total other current liabilities	Total other current liabilities
Total other current liabilities	$ 5,571	$ 2,832
Other non-current liabilities
Lease liabilities	$ 38,608	$ 20,294
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Total other non-current liabilities	Total other non-current liabilities
Other	$ 1,001	$ 1,001
Total other non-current liabilities	39,609	$ 21,295
Restructuring costs	$ 2,600

Commitments and contingencies -

Commitments and contingencies - Neurocrine Collaboration Agreement - (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		12 Months Ended
	Jun. 30, 2019 USD ($) shares	Mar. 31, 2019 USD ($) item Program $ / shares shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Allocation of Transaction Price
Revenue recognized					$ 269
Deferred revenue			$ 11,827	$ 12,096	11,827	$ 12,096
Neurocrine Collaboration Agreement | FA Program
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of profit or loss under co-co option		40%
Neurocrine Collaboration Agreement | Neurocrine
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of collaboration programs | item		4
Number of discovery programs | Program		2
Programs added later | item		2
Discovery programs under development | item		2
Number of targets | item		8
Upfront payment	$ 115,000	$ 115,000
Purchase of common stock, shares | shares	4,179,728	4,179,728
Purchase of common stock	$ 5,000	$ 50,000
Price per share | $ / shares		$ 11.9625
Aggregate maximum milestone payments to be received from collaborative partner		$ 170,000
Estimated cost reimbursement	431,100		81,700	$ 80,000
Termination period		10 years
Period of advance notice for termination prior to first commercial sale		180 days
Period of advance notice for termination after first commercial sale		1 year
Discount related to equity investment	27,600
Equity investment	50,000
Allocation of Transaction Price
Allocation of variable consideration			81,671		81,671
Allocation of fixed consideration	92,400		92,382		92,382
Cumulative catch up of revenue recognized					900
Reimbursement costs expected to be received					300
Costs to obtain collaboration agreement			800		800
Consideration received	$ 5,000
Revenue recognized					900	$ 37,400
Deferred revenue			11,800		11,800
Neurocrine Collaboration Agreement | Neurocrine | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of reduction in royalty payments		50%
Neurocrine Collaboration Agreement | Neurocrine | VY-AADC
Allocation of Transaction Price
Allocation of variable consideration			53,863		53,863
Allocation of fixed consideration			49,045		49,045
Neurocrine Collaboration Agreement | Neurocrine | FA Program
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of profit or loss under co-co option		60%
Allocation of Transaction Price
Allocation of variable consideration			18,868		18,868
Allocation of fixed consideration			20,647		20,647
Neurocrine Collaboration Agreement | Neurocrine | Discovery and FA Programs
Allocation of Transaction Price
Allocation of fixed consideration			42,200		42,200
Neurocrine Collaboration Agreement | Neurocrine | Discovery program 1
Allocation of Transaction Price
Allocation of variable consideration			5,336		5,336
Allocation of fixed consideration			14,443		14,443
Neurocrine Collaboration Agreement | Neurocrine | Discovery program 2
Allocation of Transaction Price
Allocation of variable consideration			3,605		3,605
Allocation of fixed consideration			$ 8,247		$ 8,247
Neurocrine Collaboration Agreement | Neurocrine | Development and regulatory milestones | FA Program
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner		$ 195,000
Neurocrine Collaboration Agreement | Neurocrine | Development and regulatory milestones | Discovery program 1
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner		130,000
Neurocrine Collaboration Agreement | Neurocrine | Commercial Milestone
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Per Milestone, maximum milestone payments to be received from collaborative partner		275,000
Aggregate maximum milestone payments to be received from collaborative partner		$ 1,100,000

Commitments and contingencies_2

Commitments and contingencies - Collaboration receivables and contract liabilities - (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Commitments and contingencies
Related party collaboration receivables, beginning balance	$ 732
Additions	907
Deductions	(1,382)
Related party collaboration receivables, ending balance	257
Deferred revenue, beginning balance	12,096
Deductions	(269)
Deferred revenue, ending balance	$ 11,827

Commitments and contingencies_3

Commitments and contingencies - Pfizer Option and License Agreement - (Details) $ in Thousands		12 Months Ended
	Oct. 01, 2021 USD ($) item	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized		$ 269
Collaboration revenue		40,907	$ 37,415	$ 171,128
Pfizer | Option and license agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of transgenes | item	2
Number of options | item	1
Number of performance obligations | item	2
Number of material rights | item	2
Upfront payment	$ 30,000
Non-refundable upfront payment received	$ 30,000
Number of license options | item	1
Allocation of transaction price	$ 15,000
Aggregate milestone payments, if exercise rights	$ 10,000	10,000
Revenue recognized		40,000
Collaboration revenue		40,000
Pfizer | First Material Right
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allocation of transaction price		25,000
Pfizer | Second Material Right
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allocation of transaction price		$ 15,000
Number of days written notice required by reporting entity to terminate agreement	90 days
Pfizer | Development, regulatory and commercialization milestone | Option and license agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner	$ 115,000
Pfizer | Sales milestone | Option and license agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner	$ 175,000
Minimum | Pfizer | Option and license agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of countries received regulatory approval | item	1
Number of major market countries received regulatory approval | item	1

Commitments and contingencies_4

Commitments and contingencies - Novartis Option and License Agreement (Details) $ in Thousands			12 Months Ended
	Mar. 04, 2023 USD ($) item	Apr. 03, 2022 USD ($) item	Dec. 31, 2022 USD ($) item
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized | $			$ 269
Novartis Pharma, AG | Novartis License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of transgenes		3
Number of additional targets	2	2
Upfront payment | $		$ 54,000
Number of license options		3	2
Number of license options on additional targets		5
Number of license option exercise for each target		1
Number of Alliance Managers		2
Number of options		1
Number of major market countries received regulatory approval		3
Number of days written notice required by reporting entity to terminate agreement		90 days
Number of performance obligations		3
Number of material rights		3
Allocation of transaction price | $		$ 18,000
Revenue recognized | $			$ 54,000
Novartis Pharma, AG | Novartis License Agreement | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of license options		1
Novartis Pharma, AG | Forecast | Novartis License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of additional targets	2
Upfront payment | $	$ 54,000

Commitments and Contingencies_5

Commitments and Contingencies - Touchlight IP Ltd License Agreement (Details) $ in Millions	Dec. 31, 2022 USD ($)
Touchlight IP Ltd License Agreement | Touchlight IP Ltd
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Non-refundable technology access fee payable	$ 5

Commitments and contingencies_6

Commitments and contingencies - Other Agreements - (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) multiple	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingency [Abstract]
Contingency reserves for litigation liabilities		$ 0	$ 0
Non-profit organization agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum funding	$ 4
Funding multiple | multiple	2.6
Milestone payment liability				$ 1

Common stock (Details)

Common stock (Details) - $ / shares	Dec. 31, 2022	Dec. 31, 2021	Oct. 31, 2015
Class of Stock [Line Items]
Common Stock, Shares Authorized	120,000,000	120,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Shares available for future issuance (in shares)	12,778,375	11,990,940
2015 Stock Option Plan
Class of Stock [Line Items]
Shares available for future issuance (in shares)	3,536,932	4,374,539	1,311,812
2015 Employee Stock Purchase Plan.
Class of Stock [Line Items]
Shares available for future issuance (in shares)	1,884,309	1,659,574
Stock options
Class of Stock [Line Items]
Shares available for future issuance (in shares)	6,199,571	5,013,193
Unvested restricted common stock units
Class of Stock [Line Items]
Shares available for future issuance (in shares)	1,112,563	806,379
Founders restricted stock
Class of Stock [Line Items]
Shares available for future issuance (in shares)	45,000	137,255

Stock-based compensation (Detai

Stock-based compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended			84 Months Ended
	Oct. 31, 2015	Jan. 31, 2014	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)			12,778,375	11,990,940		12,778,375
Stock options granted (in shares)			3,681,075
Stock-based compensation.			$ 9,344	$ 11,324	$ 14,934
2014 Stock Option and Grant Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for stock-based compensation plan (in shares)		823,529
2015 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)			1,884,309			1,884,309
Percentage of outstanding common stock						1%
Common stock shares authorized for issuance						2,692,838
New stock options issued			150,265	200,006
Number of shares authorized for stock-based compensation plan (in shares)	262,362
Period to purchase shares			6 months
2015 Employee Stock Purchase Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of payroll deduction	1%
2015 Employee Stock Purchase Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of payroll deduction	10%
2015 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)	1,311,812		3,536,932	4,374,539		3,536,932
Percentage limit of issued and outstanding shares up to which additional shares may be issued	4%
Percentage of outstanding common stock						4%
Common stock shares authorized for issuance						10,771,368
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)			6,199,571	5,013,193		6,199,571
Stock-based compensation.			$ 5,938	$ 7,438	11,387
Stock options | Inducement Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Stock options | Inducement Awards | Vesting period, tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25%
Stock options | Inducement Awards | Vesting period, tranche two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			36 months
Vesting percentage			75%
Unvested restricted common stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)			1,112,563	806,379		1,112,563
Stock-based compensation.			$ 3,215	$ 3,551	$ 3,110
Restricted stock granted, original issued price (in dollars per share)			$ 4.29
Unvested restricted common stock units | Vesting period, tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Unvested restricted common stock units | Vesting period, tranche two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Unvested restricted common stock units | Inducement Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New stock options issued			163,000	13,000	29,000
Vesting period			3 years
Unvested restricted common stock units | Inducement Awards | Vesting period, tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			33%
Unvested restricted common stock units | Inducement Awards | Vesting period, tranche two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			33%
Performance based milestone awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining number of shares authorized to be repurchased			131,470			131,470
Founders restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)			45,000	137,255		45,000
Restricted stock granted (in shares)		1,188,233
Restricted stock granted, original issued price (in dollars per share)		$ 0.0425
Founders restricted stock | Vesting period, tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock granted (in shares)		835,292
Founders restricted stock | Minimum | Vesting period, tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		1 year
Founders restricted stock | Maximum | Vesting period, tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
Non-statutory stock options | Inducement Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New stock options issued			390,000	76,500	172,500
Employees and directors stock options | 2014 Stock Option and Grant Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Employees and directors stock options | 2014 Stock Option and Grant Plan | Vesting period, tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			1 year
Vesting percentage			25%
Employees and directors stock options | 2014 Stock Option and Grant Plan | Vesting period, tranche two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Vesting percentage			75%
Employees and directors stock options | 2015 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)			3,291,075
Non-employees stock options | 2014 Stock Option and Grant Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			1 year
Non-employees stock options | 2014 Stock Option and Grant Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Share-based Payment Arrangement, Employee | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.			$ 5,800	$ 7,300	$ 11,200
Share-based Payment Arrangement, Employee | Unvested restricted common stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.			2,900	3,300	2,800
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.			2,946	4,133	6,357
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.			$ 6,398	$ 7,191	$ 8,577

Stock-based compensation - Comp

Stock-based compensation - Compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 9,344	$ 11,324	$ 14,934
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	5,938	7,438	11,387
Restricted stock awards and units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	3,215	3,551	3,110
Employee stock purchase plan awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	191	335	437
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	2,946	4,133	6,357
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 6,398	$ 7,191	$ 8,577

Stock-based compensation - Rest

Stock-based compensation - Restricted Stock - (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Restricted stock disclosures
Stock-based compensation.	$ 9,344	$ 11,324	$ 14,934
Unvested restricted common stock units
Shares
Balance, beginning (in shares)	806,379
Granted (in shares)	964,480
Vested (in shares)	(436,611)
Forfeited (in shares)	(221,685)
Balance, ending (in shares)	1,112,563	806,379
Weighted Average Grant Date Fair Value Per Share
Balance, beginning (in dollars per share)	$ 7.26
Granted (in dollars per share)	4.29
Vested (in dollars per share)	6.92
Forfeited (in dollars per share)	5.05
Balance, ending (in dollars per share)	$ 5.27	$ 7.26
Restricted stock disclosures
Stock-based compensation.	$ 3,215	$ 3,551	3,110
Unrecognized stock-based compensation expense	$ 3,700
Remaining weighted-average remaining vesting period	1 year 10 months 24 days
Share-based Payment Arrangement, Employee | Unvested restricted common stock units
Restricted stock disclosures
Stock-based compensation.	$ 2,900	$ 3,300	$ 2,800
Vesting period, tranche one | Unvested restricted common stock units
Shares
Granted (in shares)	864,480
Restricted stock disclosures
Vesting period	3 years
Vesting period, tranche two | Unvested restricted common stock units
Shares
Granted (in shares)	100,000
Restricted stock disclosures
Vesting period	4 years

Stock-based compensation - Stoc

Stock-based compensation - Stock Options - (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning balance (in shares) | shares	5,013,193
Granted (in shares) | shares	3,681,075
Exercised (in shares) | shares	(89,012)
Cancelled or forfeited (in shares) | shares	(2,405,685)
Outstanding, ending balance (in shares) | shares	6,199,571
Exercisable (in shares) | shares	2,744,489
Weighted Average Exercise Price
Outstanding (in dollars per share)	$ 12.69
Granted (in dollars per share)	5.17
Exercised (in dollars per share)	7.07
Cancelled or forfeited (in dollars per share)	13.15
Outstanding (in dollars per share)	8.12
Exercisable (in dollars per share)	$ 10.56
Remaining Contractual Life
Outstanding	7 years 10 months 24 days
Exercisable	6 years 6 months
Aggregate Intrinsic Value
Outstanding | $	$ 6,095
Exercisable | $	$ 2,287
Stock options
Options disclosures
Weighted average fair value of grants (in dollars per share)	$ 3.60
Unrecognized stock-based compensation expense | $	$ 12,800
Remaining weighted-average remaining vesting period	2 years 10 months 24 days

Stock-based compensation - Unre

Stock-based compensation - Unrecognized expense and weighted-average period (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fair value assumptions
Expected dividend yield	0%
Stock options
Options disclosures
Weighted average fair value of grants (in dollars per share)	$ 3.60
Employees and directors stock options
Fair value assumptions
Risk-free interest rate	2.20%	0.90%	1%
Expected term	6 years	6 years	6 years
Expected volatility	79.40%	75%	73.70%

401(k) Savings plan (Details)

401(k) Savings plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
401(k) Savings plan
Employer contribution expense	$ 0.9	$ 1.1	$ 1.1

Income taxes (Details)

Income taxes (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Current
State	$ 16
Total current	16
Total tax expense	$ 16

Income taxes - Net operating lo

Income taxes - Net operating loss carryforwards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Loss Carryforwards [Line Items]
Valuation Allowance	$ 117,416	$ 107,563
Change in the valuation allowance	$ 9,800
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income tax computed at federal statutory tax rate	21%	21%	21%
State taxes, net of federal benefit	5.20%	6.60%	(2.30%)
Provision to return	3.20%	4.90%
General business credit carryovers	(3.50%)	3.20%	(20.60%)
Nondeductible expenses	(4.60%)	(3.80%)	5%
Other			1.90%
Change in valuation allowance	(21.30%)	(31.90%)	(5.00%)
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 175,100
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	166,500
Investment tax credit	500
Research and development tax credits carryforwards | Federal
Operating Loss Carryforwards [Line Items]
Tax credits carryforwards	24,000
Research and development tax credits carryforwards | State
Operating Loss Carryforwards [Line Items]
Tax credits carryforwards	$ 9,600

Income taxes - Deferred tax ass

Income taxes - Deferred tax assets (liabilities) and unrecognized tax benefits (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Income taxes
Unrecognized tax benefits	$ 0	$ 0
Amounts in uncertain tax position	0	0
Accrued interest	0	0
Deferred tax assets:
Net operating loss carryforwards	47,282	56,756
Tax credit carryforwards	32,060	30,122
Lease liability	6,318	12,012
Deferred revenue	17,984	11,485
Stock compensation	4,630	7,784
Non-deductible accruals and reserves	1,603	1,507
Capitalized research expenses	14,351
Intangibles	610	664
Other temporary differences	(1)
Total deferred tax assets	124,837	120,330
Less valuation allowance	(117,416)	(107,563)
Net deferred tax assets	7,421	12,767
Deferred tax liabilities
Right of use assets	(4,231)	(9,128)
Depreciation and amortization	$ (3,190)	(3,632)
Other temporary differences		$ (7)

Related party transactions (Det

Related party transactions (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) item	Dec. 31, 2021 USD ($) item	Dec. 31, 2020 USD ($) item
Related party transactions
Related party collaboration receivable	$ 257,000	$ 732,000
Former Executives | Board and scientific advisory services
Related party transactions
Number of individuals providing services | item	2	2	2
Dr. Paul | Board and scientific advisory services
Related party transactions
Total amount of services received			$ 200,000
Dr. Sah | Board and scientific advisory services
Related party transactions
Total amount of services received	$ 500,000	$ 200,000	$ 400,000
Dr. Sandrock | Consulting and advisor services
Related party transactions
Total amount of services received	60,000
Neurocrine | Collaboration arrangement
Related party transactions
Related party collaboration receivable	$ 300,000

Subsequent event - (Details)

Subsequent event - (Details) $ in Millions					1 Months Ended
	Mar. 04, 2023 item	Mar. 01, 2023 USD ($) item	Jan. 08, 2023 USD ($) item Program shares	Apr. 03, 2022 USD ($) item	Jun. 30, 2019 USD ($) shares	Mar. 31, 2019 USD ($) item Program shares
Neurocrine | Neurocrine Collaboration Agreement
Subsequent events
Number of collaboration programs | item						4
Purchase of common stock					$ 5	$ 50
Purchase of common stock, shares | shares					4,179,728	4,179,728
Aggregate maximum milestone payments to be received from collaborative partner						$ 170
Number of discovery programs | Program						2
Number of targets | item						8
Upfront payment					$ 115	$ 115
Neurocrine | Neurocrine Collaborative Agreement 2023 | Subsequent Event.
Subsequent events
Number of collaboration programs | item			3
Purchase of common stock			$ 39
Purchase of common stock, shares | shares			4,395,588
Upfront payment			$ 136
Neurocrine | Neurocrine Collaborative Agreement 2023 | Subsequent Event. | GBA1
Subsequent events
Aggregate maximum milestone payments to be received from collaborative partner			$ 985
Number of products | item			2
Neurocrine | Neurocrine Collaborative Agreement 2023 | Subsequent Event. | Discovery Programs 2023
Subsequent events
Aggregate maximum milestone payments to be received from collaborative partner			$ 175
Number of discovery programs | Program			3
Per Milestone, maximum milestone payments to be received from collaborative partner			$ 275
Number of products | item			1
Neurocrine | Commercial Milestone | Neurocrine Collaboration Agreement
Subsequent events
Aggregate maximum milestone payments to be received from collaborative partner						1,100
Per Milestone, maximum milestone payments to be received from collaborative partner						$ 275
Neurocrine | Commercial Milestone | Neurocrine Collaborative Agreement 2023 | Subsequent Event. | GBA1
Subsequent events
Per Milestone, maximum milestone payments to be received from collaborative partner			$ 950
Novartis Pharma, AG | Novartis License Agreement
Subsequent events
Number of transgenes | item				3
Number of targets | item	2			2
Upfront payment				$ 54
Number of options | item				1
Novartis Pharma, AG | Novartis License Agreement | Subsequent Event.
Subsequent events
Number of royalties | item		2
Number of targets not elected to license a capsid | item		1
Number of targets | item		2
Upfront payment		$ 25
Period to retain rights		18 months
Additional fee agreed to pay		$ 18
Aggregate milestone payments, if exercise rights		$ 12.5