Voyager Therapeutics (VYGR) 10-Q 10 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 05, 2021
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
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	75 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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0001640266
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Common Stock, Shares Outstanding		37,728,183

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 117,799	$ 104,440
Marketable securities	43,707	76,698
Related party collaboration receivable	4,253	8,012
Prepaid expenses and other current assets	10,078	8,619
Total current assets	175,837	197,769
Property and equipment, net	24,520	25,435
Deposits and other non-current assets	2,247	2,316
Operating lease, right-of-use assets	35,113	36,064
Total assets	237,717	261,584
Current liabilities:
Accounts payable	3,177	634
Accrued expenses	10,535	14,205
Other current liabilities	4,596	4,198
Deferred revenue, current	6,443	7,729
Total current liabilities	24,751	26,766
Deferred revenue, non-current	33,614	36,088
Other non-current liabilities	43,144	44,410
Total liabilities	101,509	107,264
Commitments and contingencies (see note 8)
Stockholders' equity:
Preferred stock $0.001 par value: 5,000,000 shares authorized at March 31, 2021 and December 31, 2020; no shares issued and outstanding at March 31, 2021 and December 31, 2020
Common stock, $0.001 par value: 120,000,000 shares authorized at March 31, 2021 and December 31, 2020; 37,556,055 and 37,368,027 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	38	37
Additional paid-in capital	433,849	430,324
Accumulated other comprehensive loss	(123)	(134)
Accumulated deficit	(297,556)	(275,907)
Total stockholders' equity	136,208	154,320
Total liabilities and stockholders' equity	$ 237,717	$ 261,584

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Condensed 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	37,556,055	37,368,027
Common Stock, Shares, Outstanding	37,556,055	37,368,027

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Condensed Consolidated Statements of Operations and Comprehensive Loss
Collaboration revenue	$ 6,501	$ 18,067
Operating expenses:
Research and development	22,346	32,294
General and administrative	9,744	10,206
Total operating expenses	32,090	42,500
Operating loss	(25,589)	(24,433)
Other income:
Interest income	19	978
Other income (expense)	3,921	(808)
Total other income	3,940	170
Net loss	(21,649)	(24,263)
Other comprehensive income
Net unrealized gain on available-for-sale-securities	11	525
Total other comprehensive income	11	525
Comprehensive loss	$ (21,638)	$ (23,738)
Net loss per share, basic and diluted	$ (0.58)	$ (0.66)
Weighted-average common shares outstanding, basic and diluted	37,501,065	36,963,255

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	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		34			34
Exercises of vested stock options (in shares)	3,035
Vesting of restricted stock units (in shares)	108,600
Stock based compensation expense		3,949			3,949
Unrealized gain on available for-sale securities, net of tax			525		525
Net loss				(24,263)	(24,263)
Stockholders' Equity, Ending Balance at Mar. 31, 2020	$ 37	416,210	421	(336,911)	79,757
Shares, Outstanding, Ending Balance at Mar. 31, 2020	36,976,751
Stockholders' Equity, Beginning Balance at Dec. 31, 2020	$ 37	430,324	(134)	(275,907)	154,320
Shares, Outstanding, Beginning 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				3,811
Vesting of restricted stock units (in shares)	184,217
Stock based compensation expense		3,498			$ 3,498
Unrealized gain on available for-sale securities, net of tax			11		11
Net loss				(21,649)	(21,649)
Stockholders' Equity, Ending Balance at Mar. 31, 2021	$ 38	$ 433,849	$ (123)	$ (297,556)	$ 136,208
Shares, Outstanding, Ending Balance at Mar. 31, 2021	37,556,055

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flow from operating activities
Net loss	$ (21,649)	$ (24,263)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	3,601	4,040
Depreciation	1,274	842
Amortization of premiums and discounts on marketable securities	102	(188)
Other non-cash items	(3,882)	808
Changes in operating assets and liabilities:
Related party collaboration receivable	3,759	2,213
Prepaid expenses and other current assets	323	(55)
Operating lease, right-of-use assets	951	734
Non-current assets	69	69
Accounts payable	2,543	745
Accrued expenses	(3,757)	(4,626)
Operating lease liabilities	(868)	(774)
Deferred revenue	(3,760)	(8,343)
Net cash used in operating activities	(21,294)	(28,798)
Cash flow from investing activities
Purchases of property and equipment	(375)	(1,507)
Proceeds from maturities of marketable securities	35,000	110,500
Net cash provided by investing activities	34,625	108,993
Cash flow from financing activities
Proceeds from the exercise of stock options	28	34
Net cash provided by financing activities	28	34
Net increase in cash and cash equivalents	13,359	80,229
Cash, cash equivalents, and restricted cash beginning of period	106,219	86,777
Cash, cash equivalents, and restricted cash end of period	119,578	167,006
Supplemental disclosure of cash and non-cash activities
Capital expenditures incurred but not yet paid	$ 17	$ 65

Nature of business

Nature of business	3 Months Ended
	Mar. 31, 2021
Nature of business
Nature of business	VOYAGER THERAPEUTICS INC. NOTE S TO UNAUDITED CONDENSED CONSOLIDATED FINANCIAL STATEMENTS ​ 1. Nature of business Voyager Therapeutics, Inc. (the “Company”) is a clinical-stage gene therapy company focused on developing life-changing treatments for patients suffering from serious neurological diseases. The Company is focused on neurological diseases where it believes an adeno-associated virus (“AAV”) gene therapy approach that either increases or decreases the production of a specific protein can slow or reduce the symptoms experienced by patients, and therefore have a clinically meaningful impact. The Company has built a gene therapy platform that it believes positions itself to be a leading company at the intersection of AAV gene therapy and severe neurological disease. The Company’s gene therapy platform enables it to engineer, optimize, manufacture and deliver its AAV-based gene therapies that have the potential to provide durable efficacy following a single administration. Additionally, the Company is working to identify novel AAV capsids, which are the outer viral protein shells that enclose the genetic material of the virus payload. The Company’s team of experts in the fields of AAV gene therapy and neuroscience first identifies and selects severe neurological diseases that are well-suited for treatment using AAV gene therapy. The Company then engineers and optimizes AAV vectors for delivery of the virus payload to the targeted tissue or cells. The Company’s manufacturing process employs an established system that it believes will enable production of high quality AAV vectors at commercial-scale. I The Company’s business strategy focuses on discovering, developing, manufacturing and commercializing its gene therapy programs. As part of this strategy, the Company has developed core competencies specific to AAV gene therapy development and manufacturing and is beginning to build its commercial infrastructure. This business strategy also includes business development activities that may include in-licensing activities or partnering certain programs in certain geographies with collaborators, as the Company has demonstrated through its ongoing collaboration with Neurocrine Biosciences, Inc. (the “Neurocrine Collaboration Agreement”). The Company is devoting substantially all of its efforts to product research and development, market development, and raising capital. The Company is subject to risks common to companies in the biotechnology and gene therapy industries, including but not limited to, the need to obtain sufficient capital to continue to fund its operations, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval for its product candidates, the need to successfully commercialize and gain market acceptance of its product candidates, dependence on key personnel, protection of proprietary information and technology, protection against data breaches and other cybersecurity threats, compliance with government regulations, development by competitors of technological innovations, and ability to transition from pilot-scale manufacturing to large-scale production of products. The Company has a history of incurring annual net operating losses. As of March 31, 2021, the Company had an accumulated deficit of $297.6 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 its prior collaborations with Sanofi Genzyme Corporation (“Sanofi Genzyme”), AbbVie Biotechnology Ltd and AbbVie Ireland Unlimited Company (collectively, “AbbVie”), and its ongoing collaboration with Neurocrine Biosciences, Inc. (“Neurocrine”) Through March 31, 2021, the Company has raised approximately $640.0 million of proceeds from sales of convertible preferred stock and common stock, including its initial public offering and follow-on public offering, and from its collaboration agreements. As of March 31, 2021, the Company had cash, cash equivalents, and marketable debt securities Based upon its current operating plan, the Company expects that its existing cash, cash equivalents, and marketable debt securities, as well as ongoing reimbursement amounts expected from development costs related to the Neurocrine Collaboration Agreement, will enable the Company to meet its planned operating expenses and capital expenditure requirements into mid-2022 . There can be no assurance that the Company will be able to obtain additional debt or equity financing or generate product revenue or revenue from collaboration partners on terms acceptable to the Company, 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	3 Months Ended
	Mar. 31, 2021
Summary of significant accounting policies
Summary of significant accounting policies	2. Summary of significant accounting policies and basis of presentation Basis of Presentation The accompanying unaudited condensed consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. For further information, refer to the consolidated financial statements and footnotes included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020 as filed with the Securities and Exchange Commission (“SEC”) on February 25, 2021. These interim condensed consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the periods presented. Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). See “ Recently Adopted Accounting Pronouncements Principles of Consolidation The unaudited interim consolidated financial statements include the accounts of the Company and its wholly owned subsidiary as disclosed in Note 2, Summary of Significant Accounting Policies and Basis of Presentation, within the “Notes to Consolidated Financial Statements” accompanying the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020. Intercompany accounts and transactions have been eliminated. 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. Certain reclassifications have been made to prior periods to conform to current period presentation. Summary of Significant Accounting Policies There have been no changes in the Company's significant accounting policies as described in Note 1, Summary of Significant Accounting Policies

Fair value measurements

Fair value measurements	3 Months Ended
	Mar. 31, 2021
Fair value measurements
Fair value measurements	3. Fair value measurements Assets and liabilities measured at fair value on a recurring basis as of March 31, 2021 and December 31, 2020 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) March 31, 2021 ​ (in thousands) Money market funds included in cash and cash equivalents $ 109,155 $ 109,155 $ — $ — ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury notes ​ 35,251 ​ 35,251 ​ — ​ — ​ Equity securities ​ ​ 8,456 ​ ​ 8,456 ​ ​ — ​ ​ — ​ Total marketable securities ​ $ 43,707 ​ $ 43,707 ​ $ — ​ $ — ​ Warrants to purchase equity securities ​ ​ 5,638 ​ ​ — ​ ​ 5,638 ​ ​ — ​ Total ​ $ 158,500 ​ $ 152,862 ​ $ 5,638 ​ $ — ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents $ 103,992 $ 103,992 $ — $ — ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury notes ​ 70,342 ​ 70,342 ​ — ​ — ​ Equity securities ​ ​ 6,356 ​ ​ 6,356 ​ ​ — ​ ​ — ​ Total marketable securities ​ $ 76,698 ​ $ 76,698 ​ $ — ​ $ — ​ Warrants to purchase equity securities ​ ​ 3,816 ​ ​ — ​ ​ 3,816 ​ ​ — ​ Total ​ $ 184,506 ​ $ 180,690 ​ $ 3,816 ​ $ — ​ ​ The Company measures the fair value of money market funds, U.S. Treasury notes and equity securities based on quoted prices in active markets for identical securities. The Level 2 equity securities include warrants used to purchase equity securities that are valued using the Black-Scholes model. The Black-Scholes option pricing model requires inputs based on certain subjective assumptions, including (a) the expected stock price volatility, (b) the calculation of expected term of the awards, (c) the risk-free interest rate, and (d) expected dividends. The assumptions utilized to value the warrants to purchase equity securities as of March 31, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ As of December 31, ​ ​ 2021 2020 ​ Risk-free interest rate 0.1 % 0.1 % ​ Expected dividend yield — % — % ​ Expected term (in years) 0.4 ​ 0.7 ​ ​ Expected volatility 87.0 % 89.2 % ​ ​ The expected volatility is based on the historic volatility for the equity securities underlying the warrants and is calculated based on a period of time commensurate with the expected term assumption. The expected term is based on the remaining contractual life of the warrants on each measurement date. The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected term of the warrants. The expected dividend yield is assumed to be zero as the entity that issued the warrants has never paid and has not indicated any intention to pay dividends.

Cash, cash equivalents, restric

Cash, cash equivalents, restricted cash, and available-for-sale marketable securities	3 Months Ended
	Mar. 31, 2021
Cash, cash equivalents, restricted cash, and available-for-sale marketable securities
Cash, cash equivalents, restricted cash, and available-for-sale marketable securities	4. Cash, cash equivalents, restricted cash, and available-for-sale marketable securities Cash, cash equivalents, and marketable securities included the following at March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ ​ Cost Gains Losses Value ​ ​ ​ (in thousands) ​ As of March 31, 2021 ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents ​ $ 109,155 ​ $ — ​ $ — ​ $ 109,155 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury notes ​ 35,246 ​ 5 ​ — ​ 35,251 ​ Equity securities ​ ​ 1,220 ​ ​ 7,236 ​ ​ — ​ ​ 8,456 ​ Total marketable securities ​ $ 36,466 ​ $ 7,241 ​ $ — ​ $ 43,707 ​ Total money market funds and marketable securities ​ $ 145,621 ​ $ 7,241 ​ $ — ​ $ 152,862 ​ As of December 31, 2020 ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents ​ $ 103,992 ​ $ — ​ $ — ​ $ 103,992 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury notes ​ 70,348 ​ ​ — ​ ​ 6 ​ 70,342 ​ Equity securities ​ ​ 1,220 ​ ​ 5,136 ​ ​ — ​ ​ 6,356 ​ Total marketable securities ​ $ 71,568 ​ $ 5,136 ​ $ 6 ​ $ 76,698 ​ Total money market funds and marketable securities ​ $ 175,560 ​ $ 5,136 ​ $ 6 ​ $ 180,690 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ All of the Company’s marketable debt securities at March 31, 2021, have a contractual maturity of one year or less. The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the condensed consolidated balance sheets that sum to the total of the same such amounts shown in the condensed consolidated statements of cash flows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ ​ ​ 2021 2020 ​ ​ ​ (in thousands) ​ Cash and cash equivalents ​ $ 117,799 ​ $ 165,227 ​ Restricted cash included in deposits and other non-current assets ​ ​ 1,779 ​ ​ 1,779 ​ Total cash, cash equivalents, and restricted cash ​ $ 119,578 ​ $ 167,006 ​ ​

Accrued expenses

Accrued expenses	3 Months Ended
	Mar. 31, 2021
Accrued expenses
Accrued expenses	5. Accrued expenses Accrued expenses as of March 31, 2021 and December 31, 2020 consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ As of December 31, ​ 2021 2020 ​ ​ (in thousands) Research and development costs ​ $ 6,134 ​ $ 6,624 Employee compensation costs ​ 2,963 ​ 5,857 Professional services ​ 1,279 ​ 1,228 Accrued goods and services ​ ​ 159 ​ ​ 496 Total ​ $ 10,535 ​ $ 14,205 ​

Lease obligation

Lease obligation	3 Months Ended
	Mar. 31, 2021
Lease obligation
Lease obligation	6. Lease obligation Operating Leases As of March 31, 2021 the Company has leases for office and lab space at 75 and 64 Sidney Street in Cambridge, Massachusetts through November 30, 2026. In March 2020, the Company entered into an agreement to lease additional laboratory and office space at 75 Hayden Avenue in Lexington, Massachusetts through January 31, 2031. The Company gained control of and occupied the space in November 2020. The Company has received leasehold improvement incentives from the landlord totaling $5.3 million for the 75 Sidney Street and 64 Sidney Street leases. The Company also received $5.6 million of leasehold improvement incentives for the 75 Hayden Avenue lease. The leasehold improvements have been capitalized as fixed assets and the Company recorded the incentives as a component of its right-of-use assets and is amortizing them as a reduction of lease expense over the life of the lease. The Company’s lease agreements require the Company to maintain a cash deposit or irrevocable letter of credit in the aggregate amount of $1.8 million payable to the landlords as security for the performance of its obligations under the leases. These amounts are recorded as restricted cash and included in deposits and other non-current assets in the accompanying condensed consolidated balance sheets. The following table summarizes the Company’s significant contractual obligations under operating leases as of payment due date by period at March 31, 2021: ​ ​ ​ ​ ​ ​ ​ Total Minimum ​ Lease Payments ​ ​ (in thousands) ​ 2021 (remainder of year) ​ 6,016 ​ 2022 ​ 8,469 ​ 2023 ​ 8,723 ​ 2024 ​ ​ 8,985 ​ 2025 ​ ​ 9,644 ​ Thereafter ​ ​ 19,945 ​ Total future minimum lease payments ​ $ 61,783 ​ Less: imputed interest ​ ​ (15,044) ​ Total lease liability ​ $ 46,739 ​ Reported as: ​ ​ ​ ​ Other current liabilities ​ $ 4,596 ​ Other non-current liabilities ​ ​ 42,143 ​ Total lease liability ​ $ 46,739 ​ ​ During each of the three months ended March 31, 2021 and 2020, the Company incurred lease expense of $1.8 million for operating leases. As of March 31, 2021, the weighted average remaining lease term was 6.6 years and the weighted average incremental borrowing rate used to determine the operating lease liability was 8.0%.

Other liabilities

Other liabilities	3 Months Ended
	Mar. 31, 2021
Other liabilities
Other liabilities	7. Other liabilities As of March 31, 2021 and December 31, 2020, other current and non-current liabilities consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ As of December 31, ​ ​ 2021 ​ 2020 ​ ​ (in thousands) ​ Other current liabilities ​ ​ ​ ​ ​ ​ Lease liability ​ 4,596 ​ ​ 4,198 ​ Total other current liabilities $ 4,596 ​ $ 4,198 ​ ​ ​ ​ ​ ​ ​ ​ Other non-current liabilities ​ ​ ​ ​ ​ ​ Lease liability $ 42,143 ​ $ 43,409 ​ Other ​ 1,001 ​ ​ 1,001 ​ Total other non-current liabilities $ 43,144 ​ $ 44,410 ​ ​ ​ ​ ​ ​ ​ ​ ​

Commitments and contingencies

Commitments and contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and contingencies
Commitments and contingencies	8. Commitments and contingencies Significant Agreements Neurocrine Collaboration Agreement Summary of Agreement In March 2019, the Company entered into the Neurocrine Collaboration Agreement for the research, development and commercialization of certain of its AAV gene therapy products. Under the Neurocrine Collaboration Agreement, the Company agreed to collaborate on the conduct of four collaboration programs (the “Neurocrine Programs”) which include: (i) VY-AADC (NBIb-1817) for Parkinson’s disease (the “VY-AADC Program”), (ii) the VY-FXN01 for Friedreich’s ataxia (the “FA Program”) (collectively, the “Legacy Programs”); and (iii) two programs to be determined by the Company and Neurocrine at a later date (the “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 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 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 Neurocrine Collaboration Agreement. In February 2021, Neurocrine notified the Company that it had elected to terminate the Neurocrine Collaboration Agreement solely with regards to the VY-AADC Program, effective August 2, 2021 (the “Neurocrine VY-AADC Program Termination Effective Date”). The Neurocrine Collaboration Agreement remains in full force and effect for each other program thereunder. As a result of the termination, subsequent to the Neurocrine VY-AADC Program Termination Effective Date, Neurocrine will no longer reimburse the Company for research and development activities related to the VY-AADC Program. Under the terms of the 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 “Collaboration Products”) on a worldwide basis under (i) the VY-AADC Program; (ii) the FA Program; and (iii) each Discovery Program. As a result of the termination of the Neurocrine Collaboration Agreement with regards to the VY-AADC Program, in accordance with the terms of the Neurocrine Collaboration Agreement, the licenses granted by the Company to Neurocrine regarding the VY-AADC Program will expire and the Company will regain worldwide intellectual property rights regarding the VY-AADC Program, effective upon 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 Neurocrine Program prior to the occurrence of a specified event for such Neurocrine Program (a “Transition Event”), as described below, and is required to use commercially reasonable efforts to develop the corresponding Collaboration Products. Neurocrine has agreed to be responsible for all costs incurred by the Company in conducting these activities for each Neurocrine Program, in accordance with an agreed budget for each 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 Neurocrine Program. Upon the occurrence of a Transition Event for each Neurocrine Program, Neurocrine has agreed to assume responsibility for development, manufacturing and commercialization activities for such Neurocrine Program from the Company and to pay milestones and royalties on future net sales as described further below. The Transition Events are (i) with respect to the VY-AADC Program, the Company’s receipt of topline data for the RESTORE-1 Phase 2 clinical trial for VY-AAD C (NBIb-1817) C (NBIb-1817) with respect to the FA Program, the receipt of topline data for the initial Phase 1 clinical trial for an FA Program product candidate. As a result of the termination of the Neurocrine Collaboration Agreement with respect to the VY-AADC Program, the Transition Event and the Co-Co Trigger Event with respect to the VY-AADC Program will no longer apply upon the Neurocrine VY-AADC Program Termination Effective Date. Under the Neurocrine Collaboration Agreement, subject to exceptions specified therein, the Company and Neurocrine agreed that profits and losses under the Company’s Co-Co Option would be allocated (i) 50% to Neurocrine and 50% to the Company for a Collaboration Product from the VY-AADC Program and (ii) 60% to Neurocrine and 40% to the Company for a Collaboration Product from the FA Program; provided, however, that Neurocrine would have the right to elect, within a specified period following the acceptance for filing of a biologics license application from the FDA, to pay a $35.0 million rate-shifting fee to the Company to change the allocation for the VY-AADC Program to 55% to Neurocrine and 45% to the Company. The parties agreed that each 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. As a result of the termination of the Neurocrine Collaboration Agreement with respect to the VY-AADC Program, the Co-Co Option with respect to the VY-AADC Program will terminate upon the Neurocrine VY-AADC Program Termination Effective Date. The Company’s research and development activities under the 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 Neurocrine Collaboration Agreement. The parties have committed to agree on a list of up to eight target genes (the “Targets”) from which Neurocrine has the right to nominate Targets for the two Discovery Programs. The Targets nominated for the Discovery Programs were approved by a consensus of the JSC or the executive officers. The 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 Collaboration Products under (i) the VY-AADC Program of up to $170.0 million; (ii) the FA Program of up to $195.0 million, and (iii) each of the two Discovery Programs of up to $130.0 million per Discovery Program. The Company may be entitled to receive aggregate commercial milestone payments for each Collaboration Product of up to $275.0 million, subject to an aggregate cap on commercial milestone payments across all Neurocrine Programs of $1.1 billion. As a result of the termination of the Neurocrine Collaboration Agreement with respect to the VY-AADC Program, the Company is no longer entitled to receive the development, regulatory and commercial milestone payments related to the VY-AADC Program upon the achievement of specified milestones. Furthermore, in connection with the 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 Collaboration Products. Such royalty percentages, for net sales in and outside the United States, as applicable, range (i) for the VY-AADC Program, from the mid-teens to low thirties and the low-teens to low twenties, respectively; (ii) for the FA Program, from the low-teens to high-teens and high-single digits to mid-teens, respectively; and (iii) for each 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 Collaboration Product and terminate on the later of (a) the expiration of the last patent covering the Collaboration Product or its method of use in such country, (b) ten years from the first commercial sale of the Collaboration Product in such country and (c) the expiration of regulatory exclusivity in such country, or the Royalty Term. Royalty payments may be reduced by up to 50% in specified circumstances, including expiration of patents rights related to a 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 Collaboration Product. As a result of the termination of the 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 Royalty Term applicable to such Collaboration Product in such country. Under the terms of the 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 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 Collaboration Product is directed, subject to specified exceptions, including the parties’ conduct of basic research activities. Unless earlier terminated, the Neurocrine Collaboration Agreement expires on the later of (i) the expiration of the last to expire royalty term with respect to a Collaboration Product in all countries in the relevant territory or (ii) the expiration or termination of all Co-Co Agreements. Neurocrine may terminate the 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 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 Collaboration Product to which the termination applies. The Company may terminate the 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 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 Neurocrine Program, if such termination were to occur after a Transition Event, then (i) if a Co-Co Agreement is in effect with respect to such program, Neurocrine can terminate the Co-Co Agreement for such program and the Company would no longer have co-development and co-commercialization rights with respect to the Collaboration Product and (ii) subject to any license agreements, Neurocrine would no longer have any obligations with respect to any 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 shall expire and the Company shall regain worldwide intellectual property rights regarding the VY-AADC Program, in each case in accordance with the terms of the Neurocrine Collaboration Agreement. As of the Neurocrine VY-AADC Program Termination Effective Date, Neurocrine will no longer 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. The Company continues to believe that the VY-AADC program holds significant promise for Parkinson’s disease patients as evidenced by the positive multi-year safety and efficacy data from the two Phase 1b clinical trials presented in September 2020 at the MDS Virtual Congress. As a result of the prioritization of new programs enabled by novel capsids in the Company’s preclinical portfolio and its focus on the clinical efforts for the VY-HTT01 program to treat Huntington’s disease, the Company has determined that it will not advance the VY-AADC program on its own following the termination of that portion of the Neurocrine Collaboration Agreement. Instead, the Company expects to turn the future development and commercialization of VY-AADC over to a partner once the potential path forward for the program is determined. Accounting Analysis At inception, the Neurocrine Collaboration Agreement included the following performance obligations: (i) research and development services for each Legacy Program combined with a development and commercialization license for each such program and (ii) research and development services for each 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 Transition Events associated with each 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 three months ended March 31, 2021, the Company changed the estimate of the expected reimbursement to $270.2 million, based upon expectations as of March 31, 2021. 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, that 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 Company concluded that the variable consideration related to the cost reimbursement of each program will be allocated to each respective program as the cost reimbursement relates specifically to the respective program services being performed under the Neurocrine Collaboration Agreement. The reimbursement of research services is considered to be at a market rate and the allocation of the fixed consideration to all of the performance obligations depicts the estimated amounts in which it would expect to receive for these obligations, absent the variable consideration related to the research reimbursement. The total variable consideration allocated to each program related to the expected cost reimbursement was as follows at March 31, 2021: ​ ​ ​ ​ ​ ​ Performance Obligation ​ Amount ​ ​ ​ (in thousands) ​ Variable Consideration ​ ​ ​ ​ VY-AADC Program ​ $ 53,397 ​ FA Program ​ ​ 80,408 ​ Discovery Program 1 ​ ​ 69,572 ​ Discovery Program 2 ​ ​ 66,831 ​ Total ​ $ 270,208 ​ ​ 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 ​ Discovery Program 1 ​ ​ 14,443 ​ 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 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 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, Discovery Program 1 and 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 three months ended March 31, 2021 and 2020, the Company recognized $6.5 million and $14.5 million, respectively, of revenue associated with its collaboration with Neurocrine related to research and development services performed during the period and the corresponding cost reimbursement receivable. As of March 31, 2021, there was $40.1 million of deferred revenue related to the Neurocrine Collaboration Agreement, which is classified as either current or non-current in the accompanying condensed consolidated balance sheet based on the period the services are expected to be delivered. Additionally, as of March 31, 2021, there was $4.3 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 three months ended March 31, 2021. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ Balance at ​ ​ ​ December 31, 2020 ​ Additions ​ Deductions ​ March 31, 2021 ​ ​ ​ ​ ( in thousands) ​ Related party collaboration receivables ​ $ 8,012 ​ $ 3,363 ​ $ (7,122) ​ $ 4,253 ​ Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue ​ $ 43,689 ​ $ — ​ $ (3,632) ​ $ 40,057 ​ ​ The change in the receivables balance for the three months ended March 31, 2021 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 Neurocrine Collaboration Agreement consist of internal and external research and development costs, which primarily include: salaries and benefits, lab supplies, preclinical research studies, clinical studies, consulting services, and commercial development. These costs are included in research and development expenses in the Company’s condensed consolidated statements of operations during the three months ended March 31, 2021 and 2020. The Company incurred approximately $0.8 million of costs to obtain the 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. Other Agreements The Company has entered into various agreements with contract research organizations and institutions to license intellectual property. In consideration for the rights licensed under such agreements, the Company generally made upfront payments, which were recorded as research and development expense as the acquired technologies were considered in-process research and development. The license agreements obligate the Company to make additional payments that are contingent upon specific clinical trial and regulatory approval milestones being achieved as well as royalties on future product sales. The agreements to license intellectual property include potential milestone payments that are dependent upon the development of products licensed under the agreements and contingent upon the achievement of clinical trial or regulatory approval milestones. The Company reached a milestone related to first patient dosing on the RESTORE-1 Phase 2 clinical trial which resulted in a $0.1 million milestone payment to one of its licensors in 2019. The Company can generally terminate the license agreements upon 30 to 90 days prior written notice. Additionally, certain license agreements require the Company to reimburse the licensor for certain past and ongoing patent related expenses. During the year ended December 31, 2016, the Company entered into a research and development funding arrangement with a non-profit organization that provides up to $4.0 million in funding to the Company upon the achievement of clinical and development milestones. The agreement provides that the Company repay amounts received under certain circumstances including termination of the agreement, and to pay an amount up to 2.6 times the funding received upon successful development and commercialization of any products developed. During the year ended December 31, 2017, the Company earned a milestone payment of $1.0 million. The Company has evaluated the arrangement and has concluded that it represents a research and development financing arrangement as it is probable that the Company will repay amounts received under the arrangement. As a result, the $1.0 million earned to date is recorded as a non-current liability in the condensed consolidated balance sheet. Litigation The Company was not a party to any material legal matters or claims and did not have contingency reserves established for any litigation liabilities as of December 31, 2020. On January 22, 2021, a putative class action lawsuit was filed in the U.S. District Court for the Eastern District of New York against the Company and certain of its current and former officers and directors, captioned Karp v. Voyager Therapeutics, Inc. et al. , interest, attorneys’ and expert fees and costs. On April 19, 2021, the court appointed the lead plaintiff for the action, and on April 30, 2021, the action was transferred to the U.S. District Court for the District of Massachusetts (where it has been assigned case number 1:21-cv-10727). The Company denies any allegations of wrongdoing and believes it has a valid defense against these claims and, therefore, intends to vigorously defend itself against this lawsuit.

Stock-based compensation

Stock-based compensation	3 Months Ended
	Mar. 31, 2021
Stock-based compensation
Stock-based compensation	9. Stock-based compensation Stock-Based Compensation Expense Total compensation cost recognized for all stock-based compensation awards in the condensed consolidated statements of operations and comprehensive loss is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ 2021 2020 ​ ​ (in thousands) ​ Research and development ​ $ 1,371 ​ $ 1,685 ​ General and administrative ​ 2,230 ​ 2,355 ​ Total stock-based compensation expense ​ $ 3,601 ​ $ 4,040 ​ ​ Stock-based compensation expense by type of award included within the condensed consolidated statements of operations and comprehensive loss was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ ​ ​ (in thousands) ​ Stock options ​ $ 2,523 ​ $ 3,208 ​ Restricted stock awards and units ​ ​ 975 ​ ​ 741 ​ Employee stock purchase plan awards ​ 103 ​ 91 ​ Total stock-based compensation expense ​ $ 3,601 ​ $ 4,040 ​ ​ 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 three months ended March 31, 2021 was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ Grant Date ​ ​ ​ ​ ​ Fair Value ​ ​ Units Per Unit ​ Unvested restricted stock units as of December 31, 2020 638,471 ​ $ 12.74 ​ Granted 1,203,684 ​ $ 6.28 ​ Vested (184,217) ​ $ 11.55 ​ Forfeited (50,607) ​ $ 9.40 ​ Unvested restricted stock units as of March 31, 2021 1,607,331 ​ $ 8.15 ​ ​ 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. Restricted stock units granted by the Company typically vest in equal amounts, annually over three years. In the three months ended March 31, 2021, the Company granted 503,684 restricted stock units vesting in equal amounts, annually over three years, and 700,000 restricted stock units vesting in equal amounts, annually over two years. All of the restricted stock units granted in the three months ended March 31, 2020 vest in equal amounts, annually over three years. The stock-based compensation expense related to restricted stock units and awards was $ 0.9 As of March 31, 2021, the Company had unrecognized stock-based compensation expense related to its unvested restricted stock units of $11.8 million, which is expected to be recognized over the remaining weighted-average vesting period of 2.2 years. Stock Options The following is a summary of stock option activity for the three months ended March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Remaining Aggregate ​ ​ ​ ​ ​ Average ​ Contractual ​ Intrinsic ​ ​ ​ ​ ​ Exercise ​ Life ​ Value ​ ​ Shares Price (in years) (in thousands) ​ Outstanding at December 31, 2020 5,485,078 ​ $ 14.77 ​ ​ ​ ​ ​ ​ Granted 1,031,704 ​ $ 7.42 ​ ​ ​ ​ ​ ​ Exercised (3,811) ​ $ 7.27 ​ ​ ​ ​ ​ ​ Cancelled or forfeited (261,109) ​ $ 14.01 ​ ​ ​ ​ ​ ​ Outstanding at March 31, 2021 6,251,862 ​ $ 13.59 ​ 7.7 ​ $ — ​ Exercisable at March 31, 2021 3,165,450 ​ $ 15.18 ​ 6.5 ​ $ — ​ ​ Using the Black ‑ The fair value of each option issued to employees and directors was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ ​ 2021 2020 ​ Risk-free interest rate 0.7 % 1.4 % Expected dividend yield — % — % Expected term (in years) 6.0 ​ 6.0 ​ Expected volatility 74.8 % 72.3 % ​ There were no new stock options granted to non ‑ ‑ As of March 31, 2021, the Company had unrecognized stock-based compensation expense related to its unvested stock options of $22.0 million which is expected to be recognized over the remaining weighted-average vesting period of 2.8 years .

Net loss per share

Net loss per share	3 Months Ended
	Mar. 31, 2021
Net loss per share
Net loss per share	10. Net loss per share The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to so include them would be anti-dilutive: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ ​ 2021 2020 ​ Unvested restricted common stock awards 156,863 176,471 ​ Unvested restricted common stock units ​ 1,607,331 ​ 747,427 ​ Outstanding stock options 6,251,862 6,065,155 ​ Total 8,016,056 6,989,053 ​ ​ Basic net loss per share for the three months ended March 31, 2021 and 2020, is the same as diluted net loss per share as shown on the Company’s condensed consolidated statement of operations and comprehensive loss.

Related party transactions

Related party transactions	3 Months Ended
	Mar. 31, 2021
Related party transactions
Related party transactions	11. Related-party transactions During the three months ended March 31, 2021 and 2020, the Company received board and scientific advisory services from one of its former executives, Dinah Sah, Ph.D., the Company’s former Chief Scientific Officer. The total amount of fees paid to Dr. Sah for services provided was Under the collaboration agreement, the Company and Neurocrine have agreed to conduct research, development and commercialization of certain of the Company’s AAV gene therapy products (Note 8). Amounts due from Neurocrine are reflected as related party collaboration receivables. As of March 31, 2021, the Company had approximately $4.3 million in related party collaboration receivable associated with Neurocrine.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	3 Months Ended
	Mar. 31, 2021
Summary of significant accounting policies
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. For further information, refer to the consolidated financial statements and footnotes included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020 as filed with the Securities and Exchange Commission (“SEC”) on February 25, 2021. These interim condensed consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the periods presented. Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). See “ Recently Adopted Accounting Pronouncements
Principles of Consolidation	Principles of Consolidation The unaudited interim consolidated financial statements include the accounts of the Company and its wholly owned subsidiary as disclosed in Note 2, Summary of Significant Accounting Policies and Basis of Presentation, within the “Notes to Consolidated Financial Statements” accompanying the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020. Intercompany accounts 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. Certain reclassifications have been made to prior periods to conform to current period presentation.
Recent Accounting Pronouncements	Summary of Significant Accounting Policies There have been no changes in the Company's significant accounting policies as described in Note 1, Summary of Significant Accounting Policies

Fair value measurements (Tables

Fair value measurements (Tables)	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 and December 31, 2020 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) March 31, 2021 ​ (in thousands) Money market funds included in cash and cash equivalents $ 109,155 $ 109,155 $ — $ — ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury notes ​ 35,251 ​ 35,251 ​ — ​ — ​ Equity securities ​ ​ 8,456 ​ ​ 8,456 ​ ​ — ​ ​ — ​ Total marketable securities ​ $ 43,707 ​ $ 43,707 ​ $ — ​ $ — ​ Warrants to purchase equity securities ​ ​ 5,638 ​ ​ — ​ ​ 5,638 ​ ​ — ​ Total ​ $ 158,500 ​ $ 152,862 ​ $ 5,638 ​ $ — ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents $ 103,992 $ 103,992 $ — $ — ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury notes ​ 70,342 ​ 70,342 ​ — ​ — ​ Equity securities ​ ​ 6,356 ​ ​ 6,356 ​ ​ — ​ ​ — ​ Total marketable securities ​ $ 76,698 ​ $ 76,698 ​ $ — ​ $ — ​ Warrants to purchase equity securities ​ ​ 3,816 ​ ​ — ​ ​ 3,816 ​ ​ — ​ Total ​ $ 184,506 ​ $ 180,690 ​ $ 3,816 ​ $ — ​
Summary of fair value assumptions	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ As of December 31, ​ ​ 2021 2020 ​ Risk-free interest rate 0.1 % 0.1 % ​ Expected dividend yield — % — % ​ Expected term (in years) 0.4 ​ 0.7 ​ ​ Expected volatility 87.0 % 89.2 % ​

Cash, cash equivalents, restr_2

Cash, cash equivalents, restricted cash, and available-for-sale marketable securities (Tables)	3 Months Ended
	Mar. 31, 2021
Cash, cash equivalents, restricted cash, and available-for-sale marketable securities
Cash, cash equivalents and marketable securities	Cash, cash equivalents, and marketable securities included the following at March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ ​ Cost Gains Losses Value ​ ​ ​ (in thousands) ​ As of March 31, 2021 ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents ​ $ 109,155 ​ $ — ​ $ — ​ $ 109,155 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury notes ​ 35,246 ​ 5 ​ — ​ 35,251 ​ Equity securities ​ ​ 1,220 ​ ​ 7,236 ​ ​ — ​ ​ 8,456 ​ Total marketable securities ​ $ 36,466 ​ $ 7,241 ​ $ — ​ $ 43,707 ​ Total money market funds and marketable securities ​ $ 145,621 ​ $ 7,241 ​ $ — ​ $ 152,862 ​ As of December 31, 2020 ​ ​ ​ ​ ​ Money market funds included in cash and cash equivalents ​ $ 103,992 ​ $ — ​ $ — ​ $ 103,992 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury notes ​ 70,348 ​ ​ — ​ ​ 6 ​ 70,342 ​ Equity securities ​ ​ 1,220 ​ ​ 5,136 ​ ​ — ​ ​ 6,356 ​ Total marketable securities ​ $ 71,568 ​ $ 5,136 ​ $ 6 ​ $ 76,698 ​ Total money market funds and marketable securities ​ $ 175,560 ​ $ 5,136 ​ $ 6 ​ $ 180,690 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Reconciliation of cash, cash equivalents, and restricted cash	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ ​ ​ 2021 2020 ​ ​ ​ (in thousands) ​ Cash and cash equivalents ​ $ 117,799 ​ $ 165,227 ​ Restricted cash included in deposits and other non-current assets ​ ​ 1,779 ​ ​ 1,779 ​ Total cash, cash equivalents, and restricted cash ​ $ 119,578 ​ $ 167,006 ​

Accrued expenses (Tables)

Accrued expenses (Tables)	3 Months Ended
	Mar. 31, 2021
Accrued expenses
Schedule of accrued expenses	Accrued expenses as of March 31, 2021 and December 31, 2020 consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ As of December 31, ​ 2021 2020 ​ ​ (in thousands) Research and development costs ​ $ 6,134 ​ $ 6,624 Employee compensation costs ​ 2,963 ​ 5,857 Professional services ​ 1,279 ​ 1,228 Accrued goods and services ​ ​ 159 ​ ​ 496 Total ​ $ 10,535 ​ $ 14,205

Lease obligation (Tables)

Lease obligation (Tables)	3 Months Ended
	Mar. 31, 2021
Lease obligation
Summary of significant contractual obligations under operating leases	​ ​ ​ ​ ​ ​ ​ Total Minimum ​ Lease Payments ​ ​ (in thousands) ​ 2021 (remainder of year) ​ 6,016 ​ 2022 ​ 8,469 ​ 2023 ​ 8,723 ​ 2024 ​ ​ 8,985 ​ 2025 ​ ​ 9,644 ​ Thereafter ​ ​ 19,945 ​ Total future minimum lease payments ​ $ 61,783 ​ Less: imputed interest ​ ​ (15,044) ​ Total lease liability ​ $ 46,739 ​ Reported as: ​ ​ ​ ​ Other current liabilities ​ $ 4,596 ​ Other non-current liabilities ​ ​ 42,143 ​ Total lease liability ​ $ 46,739 ​

Other liabilities (Tables)

Other liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
Other liabilities
Summary of other current and non-current liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ As of December 31, ​ ​ 2021 ​ 2020 ​ ​ (in thousands) ​ Other current liabilities ​ ​ ​ ​ ​ ​ Lease liability ​ 4,596 ​ ​ 4,198 ​ Total other current liabilities $ 4,596 ​ $ 4,198 ​ ​ ​ ​ ​ ​ ​ ​ Other non-current liabilities ​ ​ ​ ​ ​ ​ Lease liability $ 42,143 ​ $ 43,409 ​ Other ​ 1,001 ​ ​ 1,001 ​ Total other non-current liabilities $ 43,144 ​ $ 44,410 ​ ​ ​ ​ ​ ​ ​ ​

Commitments and contingencies (

Commitments and contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
Schedule of collaboration receivables and contract liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ Balance at ​ ​ ​ December 31, 2020 ​ Additions ​ Deductions ​ March 31, 2021 ​ ​ ​ ​ ( in thousands) ​ Related party collaboration receivables ​ $ 8,012 ​ $ 3,363 ​ $ (7,122) ​ $ 4,253 ​ Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue ​ $ 43,689 ​ $ — ​ $ (3,632) ​ $ 40,057 ​
Neurocrine Collaboration Agreement
Schedule of allocation of variable consideration	​ ​ ​ ​ ​ ​ Performance Obligation ​ Amount ​ ​ ​ (in thousands) ​ Variable Consideration ​ ​ ​ ​ VY-AADC Program ​ $ 53,397 ​ FA Program ​ ​ 80,408 ​ Discovery Program 1 ​ ​ 69,572 ​ Discovery Program 2 ​ ​ 66,831 ​ Total ​ $ 270,208 ​
Schedule of allocation of fixed consideration	​ ​ ​ ​ ​ ​ Performance Obligation ​ Amount ​ ​ ​ (in thousands) ​ Fixed Consideration ​ ​ ​ ​ VY-AADC Program ​ $ 49,045 ​ FA Program ​ ​ 20,647 ​ Discovery Program 1 ​ ​ 14,443 ​ Discovery Program 2 ​ ​ 8,247 ​ Total ​ $ 92,382 ​

Stock-based compensation (Table

Stock-based compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Stock-based compensation
Compensation cost recognized for all stock-based compensation awards	Total compensation cost recognized for all stock-based compensation awards in the condensed consolidated statements of operations and comprehensive loss is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ 2021 2020 ​ ​ (in thousands) ​ Research and development ​ $ 1,371 ​ $ 1,685 ​ General and administrative ​ 2,230 ​ 2,355 ​ Total stock-based compensation expense ​ $ 3,601 ​ $ 4,040 ​
Summary of stock-based compensation expense by classification	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ ​ ​ (in thousands) ​ Stock options ​ $ 2,523 ​ $ 3,208 ​ Restricted stock awards and units ​ ​ 975 ​ ​ 741 ​ Employee stock purchase plan awards ​ 103 ​ 91 ​ Total stock-based compensation expense ​ $ 3,601 ​ $ 4,040 ​
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, 2020 638,471 ​ $ 12.74 ​ Granted 1,203,684 ​ $ 6.28 ​ Vested (184,217) ​ $ 11.55 ​ Forfeited (50,607) ​ $ 9.40 ​ Unvested restricted stock units as of March 31, 2021 1,607,331 ​ $ 8.15 ​
Summary of stock option activity	The following is a summary of stock option activity for the three months ended March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Remaining Aggregate ​ ​ ​ ​ ​ Average ​ Contractual ​ Intrinsic ​ ​ ​ ​ ​ Exercise ​ Life ​ Value ​ ​ Shares Price (in years) (in thousands) ​ Outstanding at December 31, 2020 5,485,078 ​ $ 14.77 ​ ​ ​ ​ ​ ​ Granted 1,031,704 ​ $ 7.42 ​ ​ ​ ​ ​ ​ Exercised (3,811) ​ $ 7.27 ​ ​ ​ ​ ​ ​ Cancelled or forfeited (261,109) ​ $ 14.01 ​ ​ ​ ​ ​ ​ Outstanding at March 31, 2021 6,251,862 ​ $ 13.59 ​ 7.7 ​ $ — ​ Exercisable at March 31, 2021 3,165,450 ​ $ 15.18 ​ 6.5 ​ $ — ​
Summary of weighted-average assumptions	The fair value of each option issued to employees and directors was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ ​ 2021 2020 ​ Risk-free interest rate 0.7 % 1.4 % Expected dividend yield — % — % Expected term (in years) 6.0 ​ 6.0 ​ Expected volatility 74.8 % 72.3 %

Net loss per share (Tables)

Net loss per share (Tables)	3 Months Ended
	Mar. 31, 2021
Net loss per share
Outstanding potentially dilutive securities excluded in the calculation of diluted net loss per share	​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, ​ ​ 2021 2020 ​ Unvested restricted common stock awards 156,863 176,471 ​ Unvested restricted common stock units ​ 1,607,331 ​ 747,427 ​ Outstanding stock options 6,251,862 6,065,155 ​ Total 8,016,056 6,989,053 ​

Nature of business (Details)

Nature of business (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Nature of business
Accumulated deficit	$ (297,556)	$ (275,907)
Proceeds raised	640,000
Cash, cash equivalents, and marketable debt securities	$ 153,100

Fair value measurements - Asset

Fair value measurements - Assets measured on a recurring basis - (Details) $ in Thousands	Mar. 31, 2021USD ($)item	Dec. 31, 2020USD ($)item	Mar. 31, 2020USD ($)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	$ 117,799	$ 104,440	$ 165,227
Measurement Input, Risk-Free Interest Rate
Fair value assumptions
Warrants, measurement input	0.001	0.001
Measurement Input, Expected Term
Fair value assumptions
Warrants, measurement input | item	0.004	0.007
Measurement Input, Expected Volatility
Fair value assumptions
Warrants, measurement input | item	0.870	0.892
Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	$ 43,707	$ 76,698
Total assets measured at fair value	158,500	184,506
Level 1 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	43,707	76,698
Total assets measured at fair value	152,862	180,690
Level 2 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value	5,638	3,816
U.S. Treasury notes | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	35,251	70,342
U.S. Treasury notes | Level 1 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	35,251	70,342
Equity securities | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	8,456	6,356
Equity securities | Level 1 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	8,456	6,356
Warrants | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Warrants to purchase equity securities	5,638	3,816
Warrants | Level 2 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Warrants to purchase equity securities	5,638	3,816
Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	109,155	103,992
Money market funds | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	109,155	103,992
Money market funds | Level 1 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	$ 109,155	$ 103,992

Cash, cash equivalents, restr_3

Cash, cash equivalents, restricted cash and available-for-sale marketable securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Amortized Cost
Cash and cash equivalents	$ 117,799	$ 104,440	$ 165,227
Marketable securities, amortized cost	36,466	71,568
Total money market funds and marketable securities	145,621	175,560
Fair Value
Marketable securities, fair value	43,707	76,698
Total money market funds and marketable securities	152,862	180,690
Unrealized Gains and Losses
Marketable securities, unrealized gains	7,241	5,136
Total money market funds and marketable securities	$ 7,241	5,136
Marketable securities, unrealized losses		6
Total money market funds and marketable securities		6
Debt securities, contractual maturity period	1 year
Money market funds
Amortized Cost
Cash and cash equivalents	$ 109,155	103,992
Fair Value
Cash and cash equivalents	109,155	103,992
U.S. Treasury notes
Amortized Cost
Marketable securities, amortized cost	35,246	70,348
Fair Value
Marketable securities, fair value	35,251	70,342
Unrealized Gains and Losses
Marketable securities, unrealized gains	5
Marketable securities, unrealized losses		6
Equity securities
Amortized Cost
Marketable securities, amortized cost	1,220	1,220
Fair Value
Marketable securities, fair value	8,456	6,356
Unrealized Gains and Losses
Marketable securities, unrealized gains	$ 7,236	$ 5,136

Cash, cash equivalents, restr_4

Cash, cash equivalents, restricted cash and available-for-sale marketable securities - Reconciliation of cash, cash equivalents, and restricted cash (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Cash, cash equivalents, restricted cash, and available-for-sale marketable securities
Cash and cash equivalents	$ 117,799	$ 104,440	$ 165,227
Restricted cash included in deposits and other noncurrent assets	1,779		1,779
Total cash, cash equivalents, and restricted cash	$ 119,578	$ 106,219	$ 167,006	$ 86,777

Accrued expenses (Details)

Accrued expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accrued expenses
Research and development costs	$ 6,134	$ 6,624
Employee compensation costs	2,963	5,857
Professional services	1,279	1,228
Accrued goods and services	159	496
Total	$ 10,535	$ 14,205

Lease obligation (Details)

Lease obligation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Lease expense	$ 1,800	$ 1,800
Restricted cash included in deposits and other noncurrent assets	$ 1,779	$ 1,779
Weighted average remaining lease term	6 years 7 months 6 days
Weighted average incremental borrowing rate	8.00%
Total minimum lease payments
2021 (remainder of year)	$ 6,016
2022	8,469
2023	8,723
2024	8,985
2025	9,644
Thereafter	19,945
Total future minimum lease payments	61,783
Less: imputed interest	(15,044)
Total lease liability	46,739
Current lease liabilities	$ 4,596		$ 4,198
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherCurrentLiabilitiesMember
Non-current lease liabilities	$ 42,143		$ 43,409
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherNoncurrentLiabilitiesMember
75 and 64 Sidney Street Leases
Leasehold improvements	$ 5,300
75 Hayden Avenue
Leasehold improvements	5,600
Deposits and other non-current assets
Restricted cash included in deposits and other noncurrent assets	$ 1,800

Other liabilities (Details)

Other liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Other current liabilities
Lease liability	$ 4,596	$ 4,198
Total other current liabilities	4,596	4,198
Other non-current liabilities
Lease liability	42,143	43,409
Other	1,001	1,001
Total other non-current liabilities	$ 43,144	$ 44,410

Commitments and contingencies -

Commitments and contingencies - Neurocrine Collaboration Agreement - (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended
	Jun. 30, 2019USD ($)shares	Mar. 31, 2019USD ($)item$ / sharesshares	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)
Allocation of Transaction Price
Revenue recognized			$ 3,632
Deferred revenue			40,057		$ 43,689
Related party collaboration receivable			4,253		$ 8,012
Neurocrine | FA Program
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of profit or loss under co-co option		60.00%
Neurocrine Collaboration Agreement
Allocation of Transaction Price
Related party collaboration receivable			4,300
Neurocrine Collaboration Agreement | VY-AADC
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of profit or loss under co-co option		50.00%
Percentage of profit or loss under co-co option after paying rate-shifting fee		45.00%
Neurocrine Collaboration Agreement | FA Program
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of profit or loss under co-co option		40.00%
Neurocrine Collaboration Agreement | Neurocrine
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of collaboration programs | item		4
Number of discovery programs | item		2
Programs added later | 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		270,200
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			270,208
Allocation of fixed consideration	92,400		92,382
Revenue recognized			6,500	$ 14,500
Cumulative catch up of revenue recognized			900
Deferred revenue			40,100
Related party collaboration receivable			4,300
Costs to obtain collaboration agreement			800
Consideration received	$ 5,000
Neurocrine Collaboration Agreement | Neurocrine | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of reduction in royalty payments		50.00%
Neurocrine Collaboration Agreement | Neurocrine | VY-AADC
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of profit or loss under co-co option		50.00%
Rate-shifting fee		$ 35,000
Percentage of profit or loss under co-co option after paying rate-shifting fee		55.00%
Allocation of Transaction Price
Allocation of variable consideration			53,397
Allocation of fixed consideration			49,045
Neurocrine Collaboration Agreement | Neurocrine | FA Program
Allocation of Transaction Price
Allocation of variable consideration			80,408
Allocation of fixed consideration			20,647
Neurocrine Collaboration Agreement | Neurocrine | Discovery and FA Programs
Allocation of Transaction Price
Allocation of fixed consideration			42,200
Neurocrine Collaboration Agreement | Neurocrine | Discovery program 1
Allocation of Transaction Price
Allocation of variable consideration			69,572
Allocation of fixed consideration			14,443
Neurocrine Collaboration Agreement | Neurocrine | Discovery program 2
Allocation of Transaction Price
Allocation of variable consideration			66,831
Allocation of fixed consideration			$ 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	3 Months Ended
	Mar. 31, 2021USD ($)
Commitments and contingencies
Related party collaboration receivables, beginning balance	$ 8,012
Additions	3,363
Deductions	(7,122)
Related party collaboration receivables, ending balance	4,253
Deferred revenue, beginning balance	43,689
Deductions	(3,632)
Deferred revenue, ending balance	$ 40,057

Commitments and contingencies_3

Commitments and contingencies - Other Agreements - (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2016USD ($)multiple	Dec. 31, 2020USD ($)	Dec. 31, 2017USD ($)
Loss Contingency [Abstract]
Contingency reserves for litigation liabilities	$ 0			$ 0
Various contract research organizations and institutions
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payable upon achievement		$ 0.1
Various contract research organizations and institutions | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of days written notice required by reporting entity to terminate agreement	30 days
Various contract research organizations and institutions | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of days written notice required by reporting entity to terminate agreement	90 days
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

Stock-based compensation - Comp

Stock-based compensation - Compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.	$ 3,601	$ 4,040
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.	2,523	3,208
Unvested restricted common stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.	975	741
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.	103	91
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.	1,371	1,685
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation.	$ 2,230	$ 2,355

Stock-based compensation - Rest

Stock-based compensation - Restricted Stock - (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Restricted stock disclosures
Stock-based compensation.	$ 3,601	$ 4,040
Unvested restricted common stock units
Shares
Balance, beginning (in shares)	638,471
Granted (in shares)	1,203,684
Vested (in shares)	(184,217)
Forfeited (in shares)	(50,607)
Balance, ending (in shares)	1,607,331
Weighted Average Grant Date Fair Value Per Share
Balance, beginning (in dollars per share)	$ 12.74
Granted (in dollars per share)	6.28
Vested (in dollars per share)	11.55
Forfeited (in dollars per share)	9.40
Balance, ending (in dollars per share)	$ 8.15
Restricted stock disclosures
Vesting period	3 years	3 years
Stock-based compensation.	$ 975	$ 741
Unrecognized stock-based compensation expense	$ 11,800
Remaining weighted-average remaining vesting period	2 years 2 months 12 days
Vesting period, tranche one | Unvested restricted common stock units
Shares
Granted (in shares)	503,684
Restricted stock disclosures
Vesting period	3 years
Vesting period, tranche two | Unvested restricted common stock units
Shares
Granted (in shares)	700,000
Restricted stock disclosures
Vesting period	2 years

Stock-based compensation - Stoc

Stock-based compensation - Stock Options - (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning balance (in shares)	5,485,078
Granted (in shares)	1,031,704
Exercised (in shares)	(3,811)
Cancelled or forfeited (in shares)	(261,109)
Outstanding, ending balance (in shares)	6,251,862
Exercisable (in shares)	3,165,450
Weighted Average Exercise Price
Outstanding (in dollars per share)	$ 14.77
Granted (in dollars per share)	7.42
Exercised (in dollars per share)	7.27
Cancelled or forfeited (in dollars per share)	14.01
Outstanding (in dollars per share)	13.59
Exercisable (in dollars per share)	$ 15.18
Remaining Contractual Life
Outstanding	7 years 8 months 12 days
Exercisable	6 years 6 months
Options disclosures
Stock-based compensation.	$ 3,601	$ 4,040
Stock options
Options disclosures
Stock-based compensation.	$ 2,523	3,208
Share-based Payment Arrangement, Employee | Stock options
Options disclosures
Weighted average fair value of grants (in dollars per share)	$ 4.81
Stock-based compensation.	$ 2,500	$ 3,200
Share-based Payment Arrangement, Nonemployee | Stock options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Granted (in shares)	0	0

Stock-based compensation - Unre

Stock-based compensation - Unrecognized expense and weighted-average period (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Options disclosures
Stock-based compensation.	$ 3,601	$ 4,040
Stock options
Options disclosures
Stock-based compensation.	2,523	$ 3,208
Unrecognized stock-based compensation expense	$ 22,000
Remaining weighted-average remaining vesting period	2 years 9 months 18 days
Share-based Payment Arrangement, Employee | Stock options
Fair value assumptions
Risk-free interest rate	0.70%	1.40%
Expected term	6 years	6 years
Expected volatility	74.80%	72.30%
Options disclosures
Weighted average fair value of grants (in dollars per share)	$ 4.81
Stock-based compensation.	$ 2,500	$ 3,200

Net loss per share (Details)

Net loss per share (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	8,016,056	6,989,053
Unvested restricted common stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	156,863	176,471
Unvested restricted common stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	1,607,331	747,427
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	6,251,862	6,065,155

Related party transactions (Det

Related party transactions (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)individual	Mar. 31, 2020USD ($)individual	Dec. 31, 2020USD ($)
Related party transactions
Related party collaboration receivable	$ 4,253		$ 8,012
Dr. Sah | Board and scientific advisory services
Related party transactions
Number of individuals providing services | individual	1	1
Total amount of services received	$ 100	$ 100
Neurocrine Collaboration Agreement
Related party transactions
Related party collaboration receivable	$ 4,300