Rocket Pharmaceuticals (RCKT) 10-Q 5 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 04, 2021
Cover page [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Document Transition Report	false
Entity File Number	001-36829
Entity Registrant Name	Rocket Pharmaceuticals, Inc.
Entity Central Index Key	0001281895
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3475813
Entity Address, Address Line One	9 Cedarbrook Drive
Entity Address, City or Town	Cranbury
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08512
City Area Code	646
Local Phone Number	440-9100
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	RCKT
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		64,442,601

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 245,644	$ 297,098
Investments	175,815	185,621
Prepaid expenses and other current assets	3,610	4,626
Total current assets	425,069	487,345
Property and equipment, net	22,090	19,206
Goodwill	30,815	30,815
Restricted cash	1,334	1,568
Deposits	455	455
Operating lease right-of-use assets	1,467	914
Finance lease right-of-use asset	49,011	50,521
Total assets	530,241	590,824
Current liabilities:
Accounts payable and accrued expenses	22,008	25,472
Convertible notes, net of unamortized discount, current	0	4,875
Operating lease liabilities, current	804	626
Finance lease liability, current	1,677	1,644
Total current liabilities	24,489	32,617
Convertible notes, net of unamortized discount, non-current	0	35,066
Operating lease liabilities, non-current	891	498
Finance lease liability, non-current	19,109	18,988
Other liabilities	94	136
Total liabilities	44,583	87,305
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $0.01 par value, 120,000,000 shares authorized; 64,442,601 and 60,996,367 shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively	644	610
Additional paid-in capital	932,776	825,794
Accumulated other comprehensive loss	(97)	(42)
Accumulated deficit	(447,665)	(322,843)
Total stockholders' equity	485,658	503,519
Total liabilities and stockholders' equity	530,241	590,824
Series A Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock	0	0
Series B Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock	$ 0	$ 0

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Stockholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	120,000,000	120,000,000
Common stock, shares issued (in shares)	64,442,601	60,996,367
Common stock, shares outstanding (in shares)	64,442,601	60,996,367
Series A Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock, shares authorized (in shares)	300,000	300,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Series B Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock, shares authorized (in shares)	300,000	300,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Consolidated Statements of Operations [Abstract]
Revenue	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	39,975	21,657	93,315	55,345
General and administrative	9,671	5,730	29,600	19,720
Total operating expenses	49,646	27,387	122,915	75,065
Loss from operations	(49,646)	(27,387)	(122,915)	(75,065)
Research and development incentives	0	0	500	0
Interest expense	(534)	(1,967)	(2,514)	(5,326)
Interest and other income - net	806	518	2,218	1,913
Amortization of premium on investments - net	(744)	(244)	(2,111)	(306)
Net loss	$ (50,118)	$ (29,080)	$ (124,822)	$ (78,784)
Net loss per share attributable to common stockholders - basic (in dollars per share)	$ (0.79)	$ (0.53)	$ (1.99)	$ (1.43)
Net loss per share attributable to common stockholders - diluted (in dollars per share)	$ (0.79)	$ (0.53)	$ (1.99)	$ (1.43)
Weighted-average common shares outstanding - basic (in shares)	63,825,429	55,188,956	62,828,601	55,077,254
Weighted-average common shares outstanding - diluted (in shares)	63,825,429	55,188,956	62,828,601	55,077,254

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Consolidated Statements of Comprehensive Loss [Abstract]
Net loss	$ (50,118)	$ (29,080)	$ (124,822)	$ (78,784)
Other comprehensive loss
Net unrealized (loss) gain on investments	(16)	(160)	(55)	49
Total comprehensive loss	$ (50,134)	$ (29,240)	$ (124,877)	$ (78,735)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Total
Beginning Balance at Dec. 31, 2019	$ 548	$ (53)	$ 489,925	$ 20	$ (183,143)	$ 307,297
Beginning Balance (in shares) at Dec. 31, 2019	54,773,061
Issuance of common stock pursuant to exercise of stock options	$ 4	0	(4)	0	0	0
Issuance of common stock pursuant to exercise of stock options (in shares)	386,974
Share repurchase	$ 0	0	(72)	0	0	(72)
Share repurchase (in shares)	(3,000)
Sale of treasury stock	$ 0	53	0	0	0	53
Sale of treasury stock (in shares)	0
Issuance of treasury stock pursuant to exercise of stock options	$ 0	(429)	0	0	0	(429)
Issuance of treasury stock pursuant to exercise of stock options (in shares)	0
Unrealized comprehensive gain (loss) on investments	$ 0	0	0	(95)	0	(95)
Share-based compensation	0	0	3,961	0	0	3,961
Net loss	0	0	0	0	(24,664)	(24,664)
Ending Balance at Mar. 31, 2020	$ 552	(429)	493,810	(75)	(207,807)	286,051
Ending Balance (in shares) at Mar. 31, 2020	55,157,035
Beginning Balance at Dec. 31, 2019	$ 548	(53)	489,925	20	(183,143)	307,297
Beginning Balance (in shares) at Dec. 31, 2019	54,773,061
Unrealized comprehensive gain (loss) on investments						49
Net loss						(78,784)
Ending Balance at Sep. 30, 2020	$ 552	(76)	503,223	69	(261,927)	241,841
Ending Balance (in shares) at Sep. 30, 2020	55,204,127
Beginning Balance at Mar. 31, 2020	$ 552	(429)	493,810	(75)	(207,807)	286,051
Beginning Balance (in shares) at Mar. 31, 2020	55,157,035
Issuance of common stock pursuant to exercise of stock options	$ 0	0	290	0	0	290
Issuance of common stock pursuant to exercise of stock options (in shares)	12,968
Sale of treasury stock	$ 0	538	0	0	0	538
Sale of treasury stock (in shares)	0
Issuance of treasury stock pursuant to exercise of stock options	$ 0	(109)	0	0	0	(109)
Issuance of treasury stock pursuant to exercise of stock options (in shares)	0
Unrealized comprehensive gain (loss) on investments	$ 0	0	0	304	0	304
Share-based compensation	0	0	4,489	0	0	4,489
Net loss	0	0	0	0	(25,040)	(25,040)
Ending Balance at Jun. 30, 2020	$ 552	0	498,589	229	(232,847)	266,523
Ending Balance (in shares) at Jun. 30, 2020	55,170,003
Issuance of common stock pursuant to exercise of stock options	$ 0	0	587	0	0	587
Issuance of common stock pursuant to exercise of stock options (in shares)	34,124
Issuance of treasury stock pursuant to exercise of stock options	$ 0	(76)	0	0	0	(76)
Issuance of treasury stock pursuant to exercise of stock options (in shares)	0
Unrealized comprehensive gain (loss) on investments	$ 0	0	0	(160)	0	(160)
Share-based compensation	0	0	4,047	0	0	4,047
Net loss	0	0	0	0	(29,080)	(29,080)
Ending Balance at Sep. 30, 2020	$ 552	(76)	503,223	69	(261,927)	241,841
Ending Balance (in shares) at Sep. 30, 2020	55,204,127
Beginning Balance at Dec. 31, 2020	$ 610	0	825,794	(42)	(322,843)	503,519
Beginning Balance (in shares) at Dec. 31, 2020	60,996,367
Issuance of common stock pursuant to exercise of stock options	$ 9	0	8,783	0	0	8,792
Issuance of common stock pursuant to exercise of stock options (in shares)	991,432
Unrealized comprehensive gain (loss) on investments	$ 0	0	0	(33)	0	(33)
Share-based compensation	0	0	7,900	0	0	7,900
Net loss	0	0	0	0	(40,179)	(40,179)
Ending Balance at Mar. 31, 2021	$ 619	0	842,477	(75)	(363,022)	479,999
Ending Balance (in shares) at Mar. 31, 2021	61,987,799
Beginning Balance at Dec. 31, 2020	$ 610	0	825,794	(42)	(322,843)	503,519
Beginning Balance (in shares) at Dec. 31, 2020	60,996,367
Unrealized comprehensive gain (loss) on investments						(55)
Net loss						(124,822)
Ending Balance at Sep. 30, 2021	$ 644	0	932,776	(97)	(447,665)	485,658
Ending Balance (in shares) at Sep. 30, 2021	64,442,601
Beginning Balance at Mar. 31, 2021	$ 619	0	842,477	(75)	(363,022)	479,999
Beginning Balance (in shares) at Mar. 31, 2021	61,987,799
Issuance of common stock pursuant to exercise of stock options	$ 2	0	1,113	0	0	1,115
Issuance of common stock pursuant to exercise of stock options (in shares)	133,838
Issuance of common stock pursuant to conversion of notes	$ 13	0	35,530	0	0	35,543
Issuance of common stock pursuant to conversion of notes (in shares)	1,326,432
Unrealized comprehensive gain (loss) on investments	$ 0	0	0	(6)	0	(6)
Share-based compensation	0	0	7,311	0	0	7,311
Net loss	0	0	0	0	(34,525)	(34,525)
Ending Balance at Jun. 30, 2021	$ 634	0	886,431	(81)	(397,547)	489,437
Ending Balance (in shares) at Jun. 30, 2021	63,448,069
Issuance of common stock pursuant to exercise of stock options	$ 0	0	284	0	0	284
Issuance of common stock pursuant to exercise of stock options (in shares)	21,402
Issuance of common stock pursuant to conversion of notes	$ 2	0	5,148	0	0	5,150
Issuance of common stock pursuant to conversion of notes (in shares)	160,614
Issuance of common stock, net of issuance costs	$ 8	0	26,346	0	0	26,354
Issuance of common stock, net of issuance costs (in shares)	812,516
Warrant issuance	$ 0	0	7,578	0	0	7,578
Unrealized comprehensive gain (loss) on investments	0	0	0	(16)	0	(16)
Share-based compensation	0	0	6,989	0	0	6,989
Net loss	0	0	0	0	(50,118)	(50,118)
Ending Balance at Sep. 30, 2021	$ 644	$ 0	$ 932,776	$ (97)	$ (447,665)	$ 485,658
Ending Balance (in shares) at Sep. 30, 2021	64,442,601

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating Activities:
Net loss	$ (124,822)	$ (78,784)
Adjustments to reconcile net loss to net cash used in operating activities:
Accretion of discount on convertible notes	752	2,085
Depreciation and amortization expense	2,188	515
Write down of property and equipment	0	62
Stock-based compensation	22,200	12,497
Accretion of discount on investments, net	2,089	306
Expense in connection with warrant issuance	7,578	0
Changes in operating assets and liabilities:
Prepaid expenses and other assets	1,016	(1,415)
Accounts payable and accrued expenses	(2,842)	1,752
Operating lease liabilities	17	(114)
Finance lease liability	1,644	1,565
Other long term liabilities	(42)	0
Net cash used in operating activities	(90,222)	(61,531)
Investing activities:
Purchases of investments	(226,484)	(132,101)
Proceeds from maturities of investments	234,146	104,111
Payments made to acquire right of use asset	(18)	(6,539)
Purchases of property and equipment	(4,907)	(6,954)
Purchases of internal use software	(748)	(646)
Net cash provided by (used in) investing activities	1,989	(42,129)
Financing activities:
Issuance of common stock, pursuant to exercise of stock options	10,191	874
Issuance of common stock, net of issuance costs	26,354	0
Common stock repurchase	0	(72)
Proceeds from sale of treasury stock	0	591
Proceeds from exercise of options	0	4
Payment of withholding tax on option exercises	0	(614)
Convertible notes refinancing costs to the lender	0	(237)
Net cash provided by financing activities	36,545	546
Net change in cash, cash equivalents and restricted cash	(51,688)	(103,114)
Cash, cash equivalents and restricted cash at beginning of period	298,666	186,908
Cash, cash equivalents and restricted cash at end of period	246,978	83,794
Supplemental disclosure of non-cash financing and investing activities:
Accrued purchases of property and equipment	1,106	5,627
Accrued purchases of internal use software	26	100
Unrealized (loss) gain on investments	(55)	49
Conversion of 2021 and 2022 convertible notes into common stock	(40,693)	0
Finance lease right of use asset and lease liability	0	20,179
Reclassification of construction in process to finance right of use asset	39	26,465
Supplemental cash flow information:
Cash paid for interest	$ 148	$ 2,960

Nature of Business

Nature of Business	9 Months Ended
	Sep. 30, 2021
Nature of Business [Abstract]
Nature of Business	1. Nature of Business Rocket Pharmaceuticals, Inc. (“Rocket” or the “Company”) is a clinical-stage, multi-platform biotechnology company focused on the development of first, only and best-in-class gene therapies, with direct on-target mechanism of action and clear clinical endpoints, for rare and devastating diseases. Rocket has four ex vivo ” in vivo

Risks and Liquidity

Risks and Liquidity	9 Months Ended
	Sep. 30, 2021
Risks and Liquidity [Abstract]
Risks and Liquidity	2. Risks and Liquidity T he Company has not generated any revenue and has incurred losses since inception. The Company’s operations are subject to certain risks and uncertainties, including, among others, uncertainty of drug candidate development, technological uncertainty, uncertainty regarding patents and proprietary rights, the absence of commercial manufacturing experience, marketing or sales capability or experience, dependency on key personnel, compliance with government regulations and the need to obtain additional financing. Drug candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance-reporting capabilities. The Company’s product candidates are in the development and clinical stage. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary government approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companie The Company’s consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities in the ordinary course of business. The Company has experienced negative cash flows from operations and had an accumulated deficit of $447.7 million as of September 30, 2021. As of September 30, 2021, the Company had $421.5 million of cash, cash equivalents and investments. In August 2021, the Company issued and sold 812,516 shares of its common stock at a purchase price of $32.48 per share for aggregate net proceeds of approximately $26.4 million in a private placement transaction to a fund affiliated with RTW Investments, LP, the Company’s largest shareholder (see Note 14). The Company expects such resources will be sufficient to fund its operating expenses and capital expenditure requirements into the second half of 2023. In April 2021, the Company called for the redemption of the remaining $ million principal balance of its , 2022 Convertible Senior Notes due 2022 which were converted into common stock. On August 2, 2021, holders of $ million of the 2021 Convertible Notes converted the $ million remaining balance of the 2021 Convertible Notes into common stock (see Note 7). As of September 30, 2021, ne of the 2021 Convertible Notes or 2022 Convertible Notes were outstanding. In the longer term, the future viability of the Company is dependent on its ability to generate cash from operating activities or to raise additional capital to finance its operations. The Company’s failure to raise capital as and when needed could have a negative impact on its financial condition and ability to pursue its business strategies.

Basis of Presentation, Principl

Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies [Abstract]
Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies	3. Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies Basis of Presentation T he accompanying unaudited interim consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements for the year ended December 31, 2020 included in the Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 1, 2021 (“2020 Form 10-K”). The unaudited interim consolidated financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s consolidated financial position as of September 30, 2021 and the results of its operations and its cash flows for the three and nine months ended September 30, 2021 and 2020. The financial data and other information disclosed in these consolidated notes related to the three and nine months ended September 30, 2021 and 2020 are unaudited. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021 and any other interim periods or any future year or perio d. Principles of Consolidation The consolidated financial statements represent the consolidation of the accounts of the Company and its subsidiaries in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”). All intercompany accounts have been eliminated in consolidation. Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include but are not limited to goodwill impairment, the accrual of research and development (“R&D”) expenses, the valuation of equity transactions and stock-based awards. Changes in estimates and assumptions are reflected in reported results in the period in which they become known. Actual results could differ from those estimates. Cash, Cash Equivalents and Restricted Cash Cash, cash equivalents and restricted cash consists of bank deposits, certificates of deposit and money market accounts with financial institutions. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of months or less from the date of purchase to be cash equivalents. The Company’s cash and cash equivalent accounts, at times, exceeds federally insured limits. The Company has not experienced any losses in such accounts. Restricted cash consists of deposits collateralizing letters of credit issued by a bank in connection with the Company’s finance and operating leases (see Note “Commitments and Contingencies” for additional disclosures) and a deposit collateralizing a letter of credit issued by a bank supporting the Company’s Corporate Credit Card. Cash, cash equivalents and restricted cash consist of the following: September 30, 2021 December 31 2020 Cash and cash equivalents $ 245,644 $ 297,098 Restricted cash 1,334 1,568 $ 246,978 $ 298,666 Significant Accounting Policies T he significant accounting policies used in the preparation of these consolidated financial statements for the three and nine months ended September 30, 2021 are consistent with those disclosed in Note 3 to the consolidated financial statements in the 2020 Form 10-K, except as noted belo w. NYS Life Sciences Research and Development Tax Credit N ew York State allows investors and owners of emerging technology companies focused on biotechnology to claim a tax credit against their New York State Tax return for certain expenditures incurred in New York State, including applicable R&D related expenditures. The credit is recognized as research and development incentives when the eligibility and amount has been approved by New York State. During the three and nine months ended September 30, 2021, the Compan respectively. During the three and nine months ended September 30, 2020, the Company . Recent Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements (“ASU 2016-13”). The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The targeted transition relief standard allows filers an option to irrevocably elect the fair value option of ASC 825-10, Financial Instruments-Overall, applied on an instrument-by-instrument basis for eligible instruments. The new standard was effective beginning January 1, 2021. The adoption of ASU 2016-13, and related updates, did not have a material impact on the Company’s consolidated financial position and results of operations. There were no other recent accounting pronouncements that impacted the Company or are expected to have a significant effect on the consolidated financial statements

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2021
Fair Value of Financial Instruments [Abstract]
Fair Value of Financial Instruments	4. Fair Value of Financial Instruments Items measured at fair value on a recurring basis are the Company’s investments. The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy: Fair Value Measurements as of September 30 2021 Level 1 Level 2 Level 3 Total Assets: Cash and cash equivalents: Money market mutual funds $ 180,084 $ - $ - $ 180,084 180,084 - - 180,084 Investments: United States Treasury securities 67,686 - - 67,686 Corporate Bonds - 92,817 - 92,817 Municipal Bonds - 6,000 - 6,000 Agency Bonds - 9,312 - 9,312 67,686 108,129 - 175,815 $ 247,770 $ 108,129 $ - $ 355,899 Fair Value Measurements as of December 31, 2020 Using: Level 1 Level 2 Level 3 Total Assets: Cash and cash equivalents: Money market mutual funds $ 193,312 $ - $ - $ 193,312 United States Treasury securities 62,497 - - 62,497 Corporate Bonds - 501 - 501 Agency Bonds - 8,015 - 8,015 255,809 8,516 - 264,325 Investments: United States Treasury securities 112,328 - - 112,328 Corporate Bonds - 63,710 - 63,710 Municipal Bonds - 6,000 - 6,000 Agency Bonds - 3,583 - 3,583 112,328 73,293 - 185,621 $ 368,137 $ 81,809 $ - $ 449,946 The Company classifies its money market mutual funds and U.S. Treasury securities as Level assets under the fair value hierarchy, as these assets have been valued using quoted market prices in active markets without any valuation adjustment. The Company classifies its Corporate, Municipal and Agency Bonds as Level assets as these assets are not traded in an active market and have been valued through a -party pricing service based on quoted prices for similar assets. As of September 30, 2021, both the 2021 Convertible Notes and the 2022 Convertible Notes have been fully redeemed or converted The fair value of the 2021 Convertible Notes and 2022 Convertible Notes as of December 31, 2020 was $ million and $ million, respectively (see Note 7 .

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2021
Property and Equipment, Net [Abstract]
Property and Equipment, Net	5. Property and Equipment, Net The Company’s property and equipment consisted of the following: September 30, 2021 December 31, 2020 Laboratory equipment $ 12,120 $ 7,807 Machinery and equipment 10,065 9,933 Computer equipment 218 218 Furniture and fixtures 1,955 1,880 Leasehold improvements 106 29 Internal use software 1,860 1,385 26,324 21,252 Less: accumulated depreciation and amortization (4,234 ) (2,046 ) $ 22,090 $ 19,206 During the three and nine months ended September 30, 2021 During the three and nine months ended September 30, 202 million and $ million of depreciation and amortization expense, respectively

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	9 Months Ended
	Sep. 30, 2021
Accounts Payable and Accrued Expenses [Abstract]
Accounts Payable and Accrued Expenses	6. Accounts Payable and Accrued Expenses At September 30, 2021 and December 31, 2020, the Company’s accounts payable and accrued expenses consisted of the following: September 30, December 31, 2021 2020 Research and development $ 14,617 $ 14,962 Property and equipment 1,106 1,456 Employee compensation 3,815 4,875 Accrued interest - 1,122 Government grant payable 597 590 Professional fees 1,196 1,332 Internal use software 26 300 Other 651 835 $ 22,008 $ 25,472

Convertible Notes

Convertible Notes	9 Months Ended
	Sep. 30, 2021
Convertible Notes [Abstract]
Convertible Notes	7. Convertible Notes 2021 Convertible Notes On January 4, 2018, in connection with its reverse merger with Inotek Pharmaceuticals, Corporation (“Inotek”), the Company assumed the obligations of Inotek under its outstanding convertible notes, with an aggregate original principal amount of $52.0 million, (the “2021 Convertible Notes”). The 2021 Convertible Notes were issued in 2016 and were scheduled to mature on August 1, 2021 (the “Maturity Date”). The 2021 Convertible Notes were unsecured and accrue interest at a rate of 5.75% per annum and interest is payable semi-annually on February 1 and August 1 of each year. Each holder of the 2021 Convertible Notes (“Holder”) had the option until the close of business on the second business day immediately preceding the Maturity Date to convert all, or any portion, of the 2021 Convertible Notes held by it at a conversion rate of 31.1876 shares of the Company’s common stock per $1.00 principal amount of 2021 Convertible Notes (the “Conversion Rate”) which is $32.08 per share. On , holders of the Convertible Notes converted the $ million remaining balance of the Convertible Notes into shares , ne of the Convertible Notes were outstanding. 2022 Convertible Notes On February 20, 2020, and , August 2022 Additionally, the Company repurchased shares of its common stock that have been retired for an aggregate amount of $ from certain holders of the Convertible Notes participating in the exchange transactions in privately negotiated, private transactions. Also pursuant to the Exchange Agreements, on , the Company exchanged $ million aggregate principal amount of the Convertible Notes for (a) $ million aggregate principal amount of its newly issued Convertible Senior Notes due (an exchange ratio equal to Convertible Notes per exchanged Convertible Notes) and (b) approximately $ to pay the accrued and unpaid interest on the exchanged Convertible Notes from, and including, , to, but excluding, the closing date of the exchange transaction, adjusted to take into account the unearned accrued interest on the Convertible Notes from, and including, , to, but excluding, the closing date of the exchange transaction. The conversion rate for the 2022 Convertible Notes was initially 31.1876 shares of the Company’s common stock per 1.00 principal amount of 2022 Convertible Notes, which was equivalent to an initial conversion price of approximately $32.06 per share of common stock and was subject to adjustment under the terms of the 2022 Convertible Notes. The Company may have redeemed for cash all or any portion of the 2022 Convertible Notes, at its option, if the last reported sale price of its common stock was equal to or greater than 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending within the five In December 2020, $8.5 million principal amount, representing a carrying value of $7.6 million of the 2022 Convertible Notes was converted into 298,562 shares of the Company’s common stock. On April 26, 2021, the Company called for the redemption of the remaining $38.4 million principal amount of the 2022 Convertible Notes as the Company’s stock price traded above the Conversion Rate for at least 20 trading days during a 30-day consecutive trading period. On , the Company redeemed in full the Convertible Notes prior to the redemption date. Holders of approximately $ remaining million principal amount of the Convertible Notes converted such notes in accordance with the terms of the Exchange Agreements into approximately million shares of the Company’s common stock and cash in lieu of fractional shares. In accordance with ASC - Debt , the settlement of the Convertible Notes is accounted for as a conversion since the Convertible Notes did not include a beneficial conversion feature and the carrying amount of the Convertible Notes, including any unamortized premium or discount, was credited to additional paid in capital upon conversion to reflect the common stock issued and no gain or loss is recognized. The principal amount of $ million and any unamortized discount was recorded to additional paid in capital upon redemption. The table below summarizes the carrying value of the 2021 Convertible Notes as of September 30, 2021 and December 31, 2020: September 30, 2021 December 31, 2020 Principal amount $ - $ 5,150 Discount - (275 ) Carrying value $ - $ 4,875

Stock Based Compensation

Stock Based Compensation	9 Months Ended
	Sep. 30, 2021
Stock Based Compensation [Abstract]
Stock Based Compensation	8. Stock Based Compensation Stock Option Valuation The weighted average assumptions that the Company used in the Black-Scholes pricing model to determine the fair value of the stock options granted to employees, non-employees and directors were as follows: Nine September 30 2021 2020 Risk-free interest rate 0.78 % 1.07 % Expected term (in years) 5.84 5.83 Expected volatility 69.31 % 76.74 % Expected dividend yield 0.00 % 0.00 % Exercise price $ 53.98 $ 21.97 Fair value of common stock $ 53.98 $ 21.97 The following table summarizes stock option activity for the nine months ended September 30, 2021, under the Second Amended and Restated 2014 Stock Option and Incentive Plan: Number of Shares Weighted Average Exercise Price Weighted Average Contractual Term (Years) Aggregate Intrinsic Value Outstanding as of December 31, 2020 11,050,931 $ 9.10 6.55 $ 504,079 Granted 1,506,009 53.98 8.96 Exercised (1,146,672 ) 8.84 53,871 Cancelled (302,026 ) 33.88 Outstanding as of September 30 2021 11,108,242 $ 14.55 6.15 $ 203,781 Options vested and exercisable as of September 30 2021 8,468,030 $ 6.88 5.25 $ 194,593,951 Options unvested as of September 30 2021 2,640,212 $ 39.11 9.04 The weighted average grant-date fair value per share of stock options granted during the nine months ended September 30, 2021 and 2020 was $32.74 and $14.42, respectively. The total fair value of options vested during the nine months ended September 30, 2021, and 2020 was $18.2 million and $12.7 million, respectively. Stock-Based Compensation Stock-based compensation expense recognized by award type was as follows: Three Months Ended September 30, Nine September 30 2021 2020 2021 2020 Stock options $ 6,831 $ 4,047 $ 21,872 $ 12,497 Restricted stock units 158 - 328 - Total share based compensation expense $ 6,989 $ 4,047 $ 22,200 $ 12,497 Stock-based compensation expense by classification included within the consolidated statements of operations and comprehensive loss was as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development $ 3,084 $ 1,780 $ 9,148 $ 5,194 General and administrative 3,905 2,267 13,052 7,303 Total share based compensation expense $ 6,989 $ 4,047 $ 22,200 $ 12,497 In addition, on August 9, 2021, pursuant to a consulting agreement with a related party, the Company issued a warrant to purchase 301,291 shares of its common stock to such party for a non-cash research and development expense of $7.6 million (see Note 14- Related Party Transactions). Restricted Stock The following table summarizes the Company’s RSU activity for the nine months ended September 30, 2021: Number of Shares Weighted Average Grant Date Fair Value Unvested as of December 31, 2020 20,000 $ 25.06 Granted 3,500 62.32 Unvested as of September 30, 2021 23,500 30.61 As of September 30, 2021, the Company had an aggregate of $52.6 million of unrecognized stock-based compensation expense related to both stock options and RSU grants

Warrants

Warrants	9 Months Ended
	Sep. 30, 2021
Warrants [Abstract]
Warrants	9. Warrants As of , respectively.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2021
Net Loss Per Share [Abstract]
Net Loss Per Share	10. Net Loss Per Share Basic and diluted net loss per share attributable to common stockholders was calculated as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Numerator: Net loss attributable to common stockholders $ (50,118 ) $ (29,080 ) $ (124,822 ) $ (78,784 ) Denominator: Weighted-average common shares outstanding - basic and diluted 63,825,429 55,188,956 62,828,601 55,077,254 Net loss per share attributable to common stockholders $ (0.79 ) $ (0.53 ) $ (1.99 ) $ (1.43 ) The Company excluded the following potential shares of common stock, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: Three and Nine Months Ended September 30, 2021 2020 Shares issuable upon conversion of the 2021 Convertible Notes - 160,536 Shares issuable upon conversion of the 2022 Convertible Notes - 1,460,412 Warrants exercisable for common shares 911,728 14,102 Restricted stock units exercisable for common shares 23,500 - Options to purchase common shares 11,108,242 10,922,678 12,043,470 12,557,728

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies The Company determines if an arrangement is a lease at inception. Operating and finance leases are presented in the Company’s consolidated balance sheet as right-of-use assets from leases, current lease liabilities and long-term lease liabilities. Certain of the Company’s lease agreements contain renewal options; however, the Company does not recognize right-of-use assets or lease liabilities for renewal periods unless it is determined that the Company is reasonably certain of renewing the lease at inception or when a triggering event occurs. As the Company’s leases do not provide an implicit rate, the Company estimated the incremental borrowing rate in calculating the present value of the lease payments using an estimate of the Company’s collateralized borrowing rate for debt with a similar term. The Company has utilized its incremental borrowing rate based on the long-term borrowing costs of comparable companies in the biotechnology industry. Since the Company elected to account for each lease component and its associated non-lease components as a single combined lease component, all contract consideration was allocated to the combined lease component. Some of the Company’s lease agreements contain rent escalation clauses (including index-based escalations). The Company recognizes the minimum rental expense on a straight-line basis based on the fixed components of a lease arrangement. The Company will amortize this expense over the term of the lease beginning with the lease commencement date. Variable lease components represent amounts that are not fixed in nature and are not tied to an index or rate and are recognized as incurred. Finance Lease The Company has a lease for a facility in Cranbury, New Jersey, consisting of 103,720 square feet of space including areas for offices, process development, research and development laboratories and 50,000 square feet dedicated to AAV Current Good Manufacturing Practice (“cGMP”) manufacturing facilities to support the Company’s pipeline. A smaller area within this facility was originally leased in August 2018, and the lease was amended in June 2019 to include the full building (such lease, as amended, the “NJ Lease Agreement”). The NJ Lease Agreement has a 15-year term from September 1, 2019, with an option to renew for two consecutive five-year renewal terms. Estimated rent payments for the NJ Lease Agreement are $1.2 million per annum, payable in monthly installments and subject to annual base rent increases of 3%. The total commitment under the NJ Lease Agreement is estimated to be approximately $29.3 million over the 15-year term of the NJ Lease Agreement. The Company paid a cash security deposit of $0.3 million to the landlord in connection with the NJ Lease Agreement which has been reflected in deposits in the consolidated balance sheets as of September 30, 2021 and December 31, 2020. The Company determined the lease commencement date was reached on March 15, 2020 when the construction of all landlord owned improvements had been substantially completed and when the Company began including its leasehold improvements on the consolidated balance sheet and move equipment into the space. Upon commencement of the NJ Lease Agreement in March 2020, the Company recognized total right-of-use assets of $47.7 million, with a corresponding lease liability of $20.2 million. The Company reclassified $26.5 million of construction costs in progress and $1.1 million of prepaid rent as part of the right of use asset upon the lease commencement date o f . During the months ended , the Company reclassified an additional $ million bringing the aggregate reclassification to $ million of construction costs in progress as part of the right of use asset Interest associated with the financing lease was $ million and $ million for the three and nine months ended September 30, 2021, respectively. Interest associated with the financing lease was $ million and $ million for the three and nine months ended September 30, 2020, respectively. This is recorded as interest expense on the consolidated statements of operations. Operating Leases On June 7, 2018, the Company entered into a three-year lease agreement for office space in the Empire State Building in New York, NY (the “ESB Lease Agreement”). In connection with the ESB Lease Agreement, the Company established an irrevocable standby letter of credit (the “Empire LOC”) for $0.9 million. On March 26, 2021, the Company entered in Amendment No. 1 to the ESB Lease Agreement (“ESB Lease Amendment”) that extended the term of the lease agreement to June 30, 2024, reduced the rent payments going forward, and reduced the Empire LOC to $0.8 million. The Empire LOC serves as the Company’s security deposit on the lease in which the landlord is the beneficiary and expires . The Company has a certificate of deposit of $0.8 million and $0.9 million with a bank as collateral for the Empire LOC which is classified as part of restricted cash in the consolidated balance sheets as of September 30, 2021 and December 31, 2020, respectively. On January 4, 2018, in connection with the Reverse Merger, the Company assumed an operating lease for Inotek’s former headquarters in Lexington, Massachusetts, with a term ending in February 2023 Rental income received under the sublease agreement totaled $ million and $ million for the three and nine months ended September 30, 2021, respectively. Rental income received under the same agreement totaled $ million and $ million for the three and nine months ended September 30, 2020, respectively. Rental income is netted against rent expense in the consolidated statement of operations. Rent expense was $ million and $ million for the three and nine months ended September 30, 2021, respectively. Rent expense was $ million and $ million for the three and nine months ended September 30, 2020, respectively. The total restricted cash balance for the Company’s operating and finance leases at and was $ million and $ million, respectively. Lease cost September 30, 2021 Operating lease cost $ 457 Finance lease cost Amortization of right of use assets 1,605 Interest on lease liabilities 1,382 Total lease cost $ 3,444 The following table summarizes the maturity of the Company’s operating and finance lease liabilities on an undiscounted cash flow basis and a reconciliation to the operating and finance lease liabilities as of September 30, 2021: Maturity of operating lease liabilities September 30, 2021 2021 $ 215 2022 860 2023 488 2024 207 Total lease payments $ 1,770 Less: interest (75 ) Total operating lease liabilities $ 1,695 Maturity of finance lease liability September 30, 2021 2021 $ 416 2022 1,689 2023 1,736 2024 1,791 2025 1,856 Thereafter 46,912 Total lease payments $ 54,400 Less: interest (33,614 ) Total finance lease liability $ 20,786 Leases September 30, 2021 Operating right-of-use assets $ 1,467 Operating current lease liabilities 804 Operating noncurrent lease liabilities 891 Total operating lease liabilities $ 1,695 Finance right-of-use assets $ 49,011 Finance current lease liability 1,677 Finance noncurrent lease liability 19,109 Total finance lease liability $ 20,786 Other information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 439 Cash flows from finance lease $ 1,227 Weighted-average remaining lease term - operating leases 2.3 Weighted-average remaining lease term - finance lease 22.9 Weighted-average discount rate - operating leases 4.67 % Weighted-average discount rate - finance lease 8.96 % Litigation From time to time, the Company may be subject to other various legal proceedings and claims that arise in the ordinary course of its business activities. Although the results of litigation and claims cannot be predicted with certainty, the Company does not believe it is party to any other claim or litigation the outcome of which, if determined adversely to the Company, would individually or in the aggregate be reasonably expected to have a material adverse effect on its business. Regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources and other factors. Indemnification Arrangements Pursuant to its bylaws and as permitted under Delaware law, the Company has indemnification obligations to directors, officers, employees or agents of the Company or anyone serving in these capacities. The maximum potential amount of future payments the Company could be required to pay is unlimited. The Company has insurance that reduces its monetary exposure and would enable it to recover a portion of any future amounts paid. As a result, the Company believes that the estimated fair value of these indemnification commitments is minimal. Throughout the normal course of business, the Company has agreements with vendors that provide goods and services required by the Company to run its business. In some instances, vendor agreements include language that requires the Company to indemnify the vendor from certain damages caused by the Company’s use of the vendor’s goods and/or services. The Company has insurance that would allow it to recover a portion of any future amounts that could arise from these indemnifications. As a result, the Company believes that the estimated fair value of these indemnification commitments is minimal.

Agreements Related to Intellect

Agreements Related to Intellectual Property	9 Months Ended
	Sep. 30, 2021
Agreements Related to Intellectual Property [Abstract]
Agreements Related to Intellectual Property	12. Agreements Related to Intellectual Property The Company has various license and research and collaboration arrangements. The transactions principally resulted in the acquisition of rights to intellectual property which is in the preclinical phase and has not been tested for safety or feasibility. In all cases, the Company did not acquire tangible assets, processes, protocols, or operating systems. The Company expenses the acquired intellectual property rights as of the acquisition date on the basis that the cost of intangible assets purchased from others for use in research and development activities has no alternative future uses.

CIRM Grants

CIRM Grants	9 Months Ended
	Sep. 30, 2021
CIRM Grants [Abstract]
CIRM Grants	13. CIRM Grants LAD-I CIRM Grant On April 30, 2019, the California Institute for Regenerative Medicine (“CIRM”) awarded the Company up to $6.5 million under a CLIN2 grant award to support the clinical development of gene therapy for LAD-I. Proceeds from the grant will help fund clinical trial costs as well as manufactured drug product for Phase I/II patients enrolled at the U.S. clinical site, University of California, Los Angeles (“UCLA”) Mattel Children’s Hospital, led by principal investigator Donald Kohn, M.D., UCLA Professor of Microbiology, Immunology and Molecular Genetics, Pediatrics (Hematology/Oncology), Molecular and Medical Pharmacology and member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA. In 2019, the Company , 2020 , the Company met the next CIRM milestone and recorded a receivable, included in prepaid and other assets in the consolidated balance sheet, and a reduction of research and development expenses of $ million IMO CIRM Grant On November 12, 2020, the CIRM awarded the Company up to $3.7 million under a CLIN2 grant award to support the clinical development of its lentiviral vector (LVV)-based gene therapy, RP-L401, for the treatment of IMO. The Company received a $1.0 million pursuant to the grant on January 4, 2021 related to the CIRM IMO award and recorded a receivable, included in prepaid and other assets in the consolidated balance sheet, and a reduction of research and development expenses of $0.9 million as of December 31, 2020. The Company recorded a reduction of research and development expense of $0.1 million for the three and nine months ended September 30, 2021. As of September 30, 2021, the Company did not meet the next milestone and no receivable has been recorded.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	14. Related Party Transactions During April 2018 , the Company entered into an agreement with a member of the Board of Directors for business development consulting services. Payments for the services under the agreement are $27.5 per quarter, and the Company may terminate the agreement with 14 days’ notice. The Company incurred expenses of $27.5 and $82.5 during the three and nine months ended September 30, 2021 and 2020, relating to services provided under this agreement In September 2021 , the Company entered into a consulting agreement with a member of the Board of Directors for pipeline development, new asset evaluation, and corporate strategy. In lieu of cash for services to be provided under the consulting agreement during its term, the Company granted the board member options to purchase shares of the Company’s common stock with a fair value of $ million. In October 2020 , the Company entered into a consulting agreement with the spouse of of the Company’s executive officers for information technology advisory services. In exchange for the services provided under the agreement, the Company granted restricted stock units which vest over a period. On August 27, 2021, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement”) with a fund affiliated with RTW Investments, LP, the Company’s largest shareholder (the “Purchaser”), pursuant to which it agreed to sell and issue to the Purchaser, in a private placement (the “Private Placement”), 812,516 shares of the Company’s common stock at a purchase price of $32.48 per share for aggregate net proceeds of approximately $26.4 million to the Company before deducting estimated offering expenses payable by the Company. The Private Placement closed on August 31, 2021. In addition, concurrently with the execution of the Purchase Agreement, the Company entered into a registration rights agreement with the Purchaser, pursuant to which the Company agreed, following demand by the Purchaser, to file with the Securities and Exchange Commission a Registration Statement on Form S-3 covering the resale of shares of common stock held by the Purchaser as promptly as reasonably practicable following such demand, and in any event within 60 days of such demand. In December 2020, the Company entered into a consulting agreement with a related party. Pursuant to the consulting agreement, the related party provides certain business development and asset identification consulting services to the Company. The term of the consulting agreement is three years and may be terminated with 60 days’ notice by either party. In exchange for the business development services to be provided under the agreement, the Company issued a warrant exercisable for 603,386 shares of common stock. Pursuant to the consulting agreement, the related party is entitled to receive additional warrants exercisable for common stock upon identification of new assets for the Company to in-license. On August 9, 2021, the Company issued a warrant exercisable for 301,291 shares of common stock to the same related party for business development and asset identification consulting services. The Company recorded a non-cash R&D expense of $7.6 million during the three and nine months ended September 30, 2021 related to the issuance of the warrant. The fair value of the warrant was calculated using the Black-Scholes fair value pricing model with the following inputs: Nine Months Ended September 30, 2021 Year Ended December 31, 2020 Risk-free interest rate 1.33 % 0.95 % Expected term (in years) 10.00 10.00 Expected volatility 69.40 % 74.20 % Expected dividend yield 0.00 % 0.00 % Exercise price $ 33.63 $ 57.11 Fair value of common stock $ 33.63 $ 57.11

401(k) Savings Plan

401(k) Savings Plan	9 Months Ended
	Sep. 30, 2021
401(k) Savings Plan [Abstract]
401(k) Savings Plan	15. 401(k) Savings Plan The Company has a defined contribution savings plan (the “Plan”) under Section 401(k) of the Internal Revenue Code of 1986. This Plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Company contributions to the Plan may be made at the discretion of the Company’s Board of Directors. The Company has elected to the safe harbor match of of employee contributions to the Plan, subject to certain limitations. The Company’s matching contribution for the three and nine months ended September 30, 2021 was $ million and $ million, respectively. The Company’s matching contribution for the three and nine months ended September 30, 2020 was $ million and $ million, respectively.

Basis of Presentation, Princi_2

Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation T he accompanying unaudited interim consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements for the year ended December 31, 2020 included in the Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 1, 2021 (“2020 Form 10-K”). The unaudited interim consolidated financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s consolidated financial position as of September 30, 2021 and the results of its operations and its cash flows for the three and nine months ended September 30, 2021 and 2020. The financial data and other information disclosed in these consolidated notes related to the three and nine months ended September 30, 2021 and 2020 are unaudited. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021 and any other interim periods or any future year or perio d.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements represent the consolidation of the accounts of the Company and its subsidiaries in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”). All intercompany accounts have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include but are not limited to goodwill impairment, the accrual of research and development (“R&D”) expenses, the valuation of equity transactions and stock-based awards. Changes in estimates and assumptions are reflected in reported results in the period in which they become known. Actual results could differ from those estimates.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash, cash equivalents and restricted cash consists of bank deposits, certificates of deposit and money market accounts with financial institutions. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of months or less from the date of purchase to be cash equivalents. The Company’s cash and cash equivalent accounts, at times, exceeds federally insured limits. The Company has not experienced any losses in such accounts. Restricted cash consists of deposits collateralizing letters of credit issued by a bank in connection with the Company’s finance and operating leases (see Note “Commitments and Contingencies” for additional disclosures) and a deposit collateralizing a letter of credit issued by a bank supporting the Company’s Corporate Credit Card. Cash, cash equivalents and restricted cash consist of the following: September 30, 2021 December 31 2020 Cash and cash equivalents $ 245,644 $ 297,098 Restricted cash 1,334 1,568 $ 246,978 $ 298,666
Significant Accounting Policies	Significant Accounting Policies T he significant accounting policies used in the preparation of these consolidated financial statements for the three and nine months ended September 30, 2021 are consistent with those disclosed in Note 3 to the consolidated financial statements in the 2020 Form 10-K, except as noted belo w.
NYS Life Sciences Research and Development Tax Credit	NYS Life Sciences Research and Development Tax Credit N ew York State allows investors and owners of emerging technology companies focused on biotechnology to claim a tax credit against their New York State Tax return for certain expenditures incurred in New York State, including applicable R&D related expenditures. The credit is recognized as research and development incentives when the eligibility and amount has been approved by New York State. During the three and nine months ended September 30, 2021, the Compan respectively. During the three and nine months ended September 30, 2020, the Company .
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements (“ASU 2016-13”). The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The targeted transition relief standard allows filers an option to irrevocably elect the fair value option of ASC 825-10, Financial Instruments-Overall, applied on an instrument-by-instrument basis for eligible instruments. The new standard was effective beginning January 1, 2021. The adoption of ASU 2016-13, and related updates, did not have a material impact on the Company’s consolidated financial position and results of operations. There were no other recent accounting pronouncements that impacted the Company or are expected to have a significant effect on the consolidated financial statements

Basis of Presentation, Princi_3

Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies [Abstract]
Cash, Cash Equivalents and Restricted Cash	Restricted cash consists of deposits collateralizing letters of credit issued by a bank in connection with the Company’s finance and operating leases (see Note “Commitments and Contingencies” for additional disclosures) and a deposit collateralizing a letter of credit issued by a bank supporting the Company’s Corporate Credit Card. Cash, cash equivalents and restricted cash consist of the following: September 30, 2021 December 31 2020 Cash and cash equivalents $ 245,644 $ 297,098 Restricted cash 1,334 1,568 $ 246,978 $ 298,666

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value of Financial Instruments [Abstract]
Fair Value of Financial Instruments Measured on Recurring Basis	Items measured at fair value on a recurring basis are the Company’s investments. The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy: Fair Value Measurements as of September 30 2021 Level 1 Level 2 Level 3 Total Assets: Cash and cash equivalents: Money market mutual funds $ 180,084 $ - $ - $ 180,084 180,084 - - 180,084 Investments: United States Treasury securities 67,686 - - 67,686 Corporate Bonds - 92,817 - 92,817 Municipal Bonds - 6,000 - 6,000 Agency Bonds - 9,312 - 9,312 67,686 108,129 - 175,815 $ 247,770 $ 108,129 $ - $ 355,899 Fair Value Measurements as of December 31, 2020 Using: Level 1 Level 2 Level 3 Total Assets: Cash and cash equivalents: Money market mutual funds $ 193,312 $ - $ - $ 193,312 United States Treasury securities 62,497 - - 62,497 Corporate Bonds - 501 - 501 Agency Bonds - 8,015 - 8,015 255,809 8,516 - 264,325 Investments: United States Treasury securities 112,328 - - 112,328 Corporate Bonds - 63,710 - 63,710 Municipal Bonds - 6,000 - 6,000 Agency Bonds - 3,583 - 3,583 112,328 73,293 - 185,621 $ 368,137 $ 81,809 $ - $ 449,946

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2021
Property and Equipment, Net [Abstract]
Property and Equipment	The Company’s property and equipment consisted of the following: September 30, 2021 December 31, 2020 Laboratory equipment $ 12,120 $ 7,807 Machinery and equipment 10,065 9,933 Computer equipment 218 218 Furniture and fixtures 1,955 1,880 Leasehold improvements 106 29 Internal use software 1,860 1,385 26,324 21,252 Less: accumulated depreciation and amortization (4,234 ) (2,046 ) $ 22,090 $ 19,206

Accounts Payable and Accrued _2

Accounts Payable and Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2021
Accounts Payable and Accrued Expenses [Abstract]
Accounts Payable and Accrued Expenses	At September 30, 2021 and December 31, 2020, the Company’s accounts payable and accrued expenses consisted of the following: September 30, December 31, 2021 2020 Research and development $ 14,617 $ 14,962 Property and equipment 1,106 1,456 Employee compensation 3,815 4,875 Accrued interest - 1,122 Government grant payable 597 590 Professional fees 1,196 1,332 Internal use software 26 300 Other 651 835 $ 22,008 $ 25,472

Convertible Notes (Tables)

Convertible Notes (Tables)	9 Months Ended
	Sep. 30, 2021
2021 Convertible Notes [Member]
Debt Instrument [Line Items]
Carrying Value of Convertible Notes	The table below summarizes the carrying value of the 2021 Convertible Notes as of September 30, 2021 and December 31, 2020: September 30, 2021 December 31, 2020 Principal amount $ - $ 5,150 Discount - (275 ) Carrying value $ - $ 4,875

Stock Based Compensation (Table

Stock Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Stock Based Compensation [Abstract]
Weighted-Average Assumptions for Stock Options	The weighted average assumptions that the Company used in the Black-Scholes pricing model to determine the fair value of the stock options granted to employees, non-employees and directors were as follows: Nine September 30 2021 2020 Risk-free interest rate 0.78 % 1.07 % Expected term (in years) 5.84 5.83 Expected volatility 69.31 % 76.74 % Expected dividend yield 0.00 % 0.00 % Exercise price $ 53.98 $ 21.97 Fair value of common stock $ 53.98 $ 21.97
Stock Option Activity	The following table summarizes stock option activity for the nine months ended September 30, 2021, under the Second Amended and Restated 2014 Stock Option and Incentive Plan: Number of Shares Weighted Average Exercise Price Weighted Average Contractual Term (Years) Aggregate Intrinsic Value Outstanding as of December 31, 2020 11,050,931 $ 9.10 6.55 $ 504,079 Granted 1,506,009 53.98 8.96 Exercised (1,146,672 ) 8.84 53,871 Cancelled (302,026 ) 33.88 Outstanding as of September 30 2021 11,108,242 $ 14.55 6.15 $ 203,781 Options vested and exercisable as of September 30 2021 8,468,030 $ 6.88 5.25 $ 194,593,951 Options unvested as of September 30 2021 2,640,212 $ 39.11 9.04
Stock-Based Compensation Expense by Award Type	Stock-based compensation expense recognized by award type was as follows: Three Months Ended September 30, Nine September 30 2021 2020 2021 2020 Stock options $ 6,831 $ 4,047 $ 21,872 $ 12,497 Restricted stock units 158 - 328 - Total share based compensation expense $ 6,989 $ 4,047 $ 22,200 $ 12,497
Stock-Based Compensation Expense	Stock-based compensation expense by classification included within the consolidated statements of operations and comprehensive loss was as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development $ 3,084 $ 1,780 $ 9,148 $ 5,194 General and administrative 3,905 2,267 13,052 7,303 Total share based compensation expense $ 6,989 $ 4,047 $ 22,200 $ 12,497
RSU Activity	The following table summarizes the Company’s RSU activity for the nine months ended September 30, 2021: Number of Shares Weighted Average Grant Date Fair Value Unvested as of December 31, 2020 20,000 $ 25.06 Granted 3,500 62.32 Unvested as of September 30, 2021 23,500 30.61

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Net Loss Per Share [Abstract]
Basic and Diluted Net Loss Per Share	Basic and diluted net loss per share attributable to common stockholders was calculated as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Numerator: Net loss attributable to common stockholders $ (50,118 ) $ (29,080 ) $ (124,822 ) $ (78,784 ) Denominator: Weighted-average common shares outstanding - basic and diluted 63,825,429 55,188,956 62,828,601 55,077,254 Net loss per share attributable to common stockholders $ (0.79 ) $ (0.53 ) $ (1.99 ) $ (1.43 )
Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The Company excluded the following potential shares of common stock, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: Three and Nine Months Ended September 30, 2021 2020 Shares issuable upon conversion of the 2021 Convertible Notes - 160,536 Shares issuable upon conversion of the 2022 Convertible Notes - 1,460,412 Warrants exercisable for common shares 911,728 14,102 Restricted stock units exercisable for common shares 23,500 - Options to purchase common shares 11,108,242 10,922,678 12,043,470 12,557,728

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies [Abstract]
Lease Cost	Lease cost September 30, 2021 Operating lease cost $ 457 Finance lease cost Amortization of right of use assets 1,605 Interest on lease liabilities 1,382 Total lease cost $ 3,444
Maturities of Operating Lease Liabilities	The following table summarizes the maturity of the Company’s operating and finance lease liabilities on an undiscounted cash flow basis and a reconciliation to the operating and finance lease liabilities as of September 30, 2021: Maturity of operating lease liabilities September 30, 2021 2021 $ 215 2022 860 2023 488 2024 207 Total lease payments $ 1,770 Less: interest (75 ) Total operating lease liabilities $ 1,695
Maturity of Finance Lease Liability	Maturity of finance lease liability September 30, 2021 2021 $ 416 2022 1,689 2023 1,736 2024 1,791 2025 1,856 Thereafter 46,912 Total lease payments $ 54,400 Less: interest (33,614 ) Total finance lease liability $ 20,786
Balance Sheet Information Related to Leases	Leases September 30, 2021 Operating right-of-use assets $ 1,467 Operating current lease liabilities 804 Operating noncurrent lease liabilities 891 Total operating lease liabilities $ 1,695 Finance right-of-use assets $ 49,011 Finance current lease liability 1,677 Finance noncurrent lease liability 19,109 Total finance lease liability $ 20,786
Lease Related to Cash Flow Information, Lease Term and Discount Rate	Other information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 439 Cash flows from finance lease $ 1,227 Weighted-average remaining lease term - operating leases 2.3 Weighted-average remaining lease term - finance lease 22.9 Weighted-average discount rate - operating leases 4.67 % Weighted-average discount rate - finance lease 8.96 %

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Fair Value of Warrant	The fair value of the warrant was calculated using the Black-Scholes fair value pricing model with the following inputs: Nine Months Ended September 30, 2021 Year Ended December 31, 2020 Risk-free interest rate 1.33 % 0.95 % Expected term (in years) 10.00 10.00 Expected volatility 69.40 % 74.20 % Expected dividend yield 0.00 % 0.00 % Exercise price $ 33.63 $ 57.11 Fair value of common stock $ 33.63 $ 57.11

Nature of Business (Details)

Nature of Business (Details)	9 Months Ended
	Sep. 30, 2021Program
Nature of Business [Abstract]
Number of clinical-stage programs	4

Risks and Liquidity (Details)

Risks and Liquidity (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 27, 2021	Aug. 02, 2021	Apr. 26, 2021	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jun. 30, 2021	Mar. 31, 2021	Jun. 12, 2020	Feb. 20, 2020	Jan. 04, 2018
Risks and Liquidity [Abstract]
Accumulated deficit				$ (447,665)	$ (447,665)		$ (322,843)
Cash, cash equivalents and investments				421,500	421,500
Shareholders' Equity Disclosure [Abstract]
Issuance of common stock, net of issuance costs					26,354	$ 0
Conversion of convertible notes into common stock					$ 40,693	$ 0
2022 Convertible Notes [Member]
Shareholders' Equity Disclosure [Abstract]
Redemption of principal balance									$ 38,400		$ 39,350
Convertible senior notes, interest rate, stated percentage			6.25%								6.25%
Debt instrument maturity date					Aug. 31, 2022
Conversion of convertible notes into common stock			$ 38,400				7,600
Outstanding amount				0	$ 0
2021 Convertible Notes [Member]
Shareholders' Equity Disclosure [Abstract]
Redemption of principal balance				$ 0	$ 0		$ 5,150	$ 5,150		$ 7,500		$ 52,000
Convertible senior notes, interest rate, stated percentage				5.75%	5.75%					6.25%
Debt instrument maturity date					Aug. 1, 2021
Conversion of convertible notes into common stock		$ 5,150
Outstanding amount				$ 0	$ 0
Common Stock [Member]
Shareholders' Equity Disclosure [Abstract]
Common stock shares issued and sold (in shares)				812,516
Private Placement [Member]
Shareholders' Equity Disclosure [Abstract]
Issuance of common stock, net of issuance costs	$ 26,400
Private Placement [Member] | Common Stock [Member]
Shareholders' Equity Disclosure [Abstract]
Common stock shares issued and sold (in shares)	812,516
Share price (in dollars per share)	$ 32.48

Basis of Presentation, Princi_4

Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and cash equivalents	$ 245,644		$ 245,644		$ 297,098
Restricted cash	1,334		1,334		1,568
Total	246,978	$ 83,794	246,978	$ 83,794	$ 298,666	$ 186,908
NYS Life Sciences Research and Development Tax Credit [Abstract]
Research and development incentive income	$ 0	$ 0	$ 500	$ 0

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
2021 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note		$ 9,500
2022 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note		65,600
Recurring [Member]
Assets [Abstract]
Cash and cash equivalents	$ 180,084	264,325
Investments	175,815	185,621
Fair value of financial instruments	355,899	449,946
Recurring [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	180,084	193,312
Recurring [Member] | United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		62,497
Investments	67,686	112,328
Recurring [Member] | Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		501
Investments	92,817	63,710
Recurring [Member] | Municipal Bonds [Member]
Assets [Abstract]
Investments	6,000	6,000
Recurring [Member] | Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		8,015
Investments	9,312	3,583
Recurring [Member] | Level 1 [Member]
Assets [Abstract]
Cash and cash equivalents	180,084	255,809
Investments	67,686	112,328
Fair value of financial instruments	247,770	368,137
Recurring [Member] | Level 1 [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	180,084	193,312
Recurring [Member] | Level 1 [Member] | United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		62,497
Investments	67,686	112,328
Recurring [Member] | Level 1 [Member] | Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] | Level 1 [Member] | Municipal Bonds [Member]
Assets [Abstract]
Investments	0	0
Recurring [Member] | Level 1 [Member] | Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] | Level 2 [Member]
Assets [Abstract]
Cash and cash equivalents	0	8,516
Investments	108,129	73,293
Fair value of financial instruments	108,129	81,809
Recurring [Member] | Level 2 [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] | Level 2 [Member] | United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] | Level 2 [Member] | Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		501
Investments	92,817	63,710
Recurring [Member] | Level 2 [Member] | Municipal Bonds [Member]
Assets [Abstract]
Investments	6,000	6,000
Recurring [Member] | Level 2 [Member] | Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		8,015
Investments	9,312	3,583
Recurring [Member] | Level 3 [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Investments	0	0
Fair value of financial instruments	0	0
Recurring [Member] | Level 3 [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] | Level 3 [Member] | United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] | Level 3 [Member] | Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] | Level 3 [Member] | Municipal Bonds [Member]
Assets [Abstract]
Investments	0	0
Recurring [Member] | Level 3 [Member] | Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	$ 0	$ 0

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property and Equipment [Abstract]
Property and equipment, gross	$ 26,324		$ 26,324		$ 21,252
Less: accumulated depreciation and amortization	(4,234)		(4,234)		(2,046)
Property and equipment, net	22,090		22,090		19,206
Depreciation and amortization expense	800	$ 300	2,188	$ 515
Laboratory Equipment [Member]
Property and Equipment [Abstract]
Property and equipment, gross	12,120		12,120		7,807
Machinery and Equipment [Member]
Property and Equipment [Abstract]
Property and equipment, gross	10,065		10,065		9,933
Computer Equipment [Member]
Property and Equipment [Abstract]
Property and equipment, gross	218		218		218
Furniture and Fixtures [Member]
Property and Equipment [Abstract]
Property and equipment, gross	1,955		1,955		1,880
Leasehold Improvements [Member]
Property and Equipment [Abstract]
Property and equipment, gross	106		106		29
Internal use Software [Member]
Property and Equipment [Abstract]
Property and equipment, gross	$ 1,860		$ 1,860		$ 1,385

Accounts Payable and Accrued _3

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accounts Payable and Accrued Expenses [Abstract]
Research and development	$ 14,617	$ 14,962
Property and equipment	1,106	1,456
Employee compensation	3,815	4,875
Accrued interest	0	1,122
Government grant payable	597	590
Professional fees	1,196	1,332
Internal use software	26	300
Other	651	835
Total	$ 22,008	$ 25,472

Convertible Notes (Details)

Convertible Notes (Details)	Aug. 02, 2021USD ($)shares	Apr. 26, 2021USD ($)dshares	Feb. 20, 2020USD ($)$ / sharesshares	Mar. 31, 2020USD ($)shares	Sep. 30, 2021USD ($)d$ / shares	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)shares	Jun. 30, 2021USD ($)	Mar. 31, 2021USD ($)	Jun. 12, 2020USD ($)	Jan. 04, 2018USD ($)
Debt [Abstract]
Aggregate amount of common stock shares repurchased				$ 72,000
Conversion of convertible notes into common stock					$ 40,693,000	$ 0
Convertible notes converted					40,693,000	$ 0
Principal amount recorded to additional paid in capital					932,776,000		$ 825,794,000
Carrying value of convertible notes [Abstract]
Carrying value					$ 0		35,066,000
Common Stock [Member]
Debt [Abstract]
Number of common stock shares repurchased (in shares) | shares				3,000
Aggregate amount of common stock shares repurchased				$ 0
2021 Convertible Notes [Member]
Debt [Abstract]
Debt instrument maturity date					Aug. 1, 2021
Convertible senior notes, interest rate, stated percentage					5.75%					6.25%
Debt conversion ratio					31.1876
Conversion per principal amount of debt					$ 1,000
Convertible Note exchange										1
Conversion price (in dollars per share) | $ / shares					$ 32.08
Debt instrument, aggregate principal amount exchanged			$ 39,350,000							$ 7,500,000
Debt instrument, percentage of aggregate outstanding principal			76.00%
Accrued and unpaid interest			$ 100,000							11,000,000
Number of common stock shares repurchased (in shares) | shares			3,000
Aggregate amount of common stock shares repurchased			$ 71,670,000
Conversion of convertible notes into common stock	$ 5,150,000
Convertible notes converted	$ 5,150,000
Convertible notes, outstanding					$ 0
Redemption of principal balance					0		5,150,000	$ 5,150,000		7,500,000	$ 52,000,000
Carrying value of convertible notes [Abstract]
Principal amount					0		5,150,000	$ 5,150,000		$ 7,500,000	$ 52,000,000
Discount					0		(275,000)
Carrying value					$ 0		4,875,000
2021 Convertible Notes [Member] | Common Stock [Member]
Debt [Abstract]
Convertible Notes converted into shares of common stock (in shares) | shares	160,614
2022 Convertible Notes [Member]
Debt [Abstract]
Debt instrument maturity date					Aug. 31, 2022
Convertible senior notes, interest rate, stated percentage		6.25%	6.25%
Debt conversion ratio			31.1876
Conversion per principal amount of debt			$ 1,000
Convertible Note exchange			1
Conversion price (in dollars per share) | $ / shares			$ 32.06
Percentage of common stock conversion price			130.00%
Number of trading days, not consecutive | d		20			20
Number of consecutive trading days | d		30			30
Number of trading days immediately preceding notice of redemption					5 days
Conversion of convertible notes into common stock, principal amount							8,500,000
Conversion of convertible notes into common stock		$ 38,400,000					7,600,000
Convertible notes converted		38,400,000					$ 7,600,000
Convertible notes, outstanding					$ 0
Redemption of principal balance			$ 39,350,000						$ 38,400,000
Principal amount recorded to additional paid in capital		$ 38,400,000
Carrying value of convertible notes [Abstract]
Principal amount			$ 39,350,000						$ 38,400,000
2022 Convertible Notes [Member] | Common Stock [Member]
Debt [Abstract]
Convertible Notes converted into shares of common stock (in shares) | shares		1,300,000					298,562

Stock Based Compensation, Share

Stock Based Compensation, Share Option Valuation (Details) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Stock Option Activity [Roll Forward]
Outstanding at beginning of period (in shares)	11,050,931
Granted (in shares)	1,506,009
Exercised (in shares)	(1,146,672)
Cancelled (in shares)	(302,026)
Outstanding at end of period (in shares)	11,108,242		11,050,931
Options vested and exercisable at end of period (in shares)	8,468,030
Options unvested at ending of period (in shares)	2,640,212
Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period (in dollars per share)	$ 9.10
Granted (in dollars per share)	53.98
Exercised (in dollars per share)	8.84
Cancelled (in dollars per share)	33.88
Outstanding at end of period (in dollars per share)	14.55		$ 9.10
Options vested and exercisable at end of period (in dollars per share)	6.88
Options unvested at ending (in dollars per share)	$ 39.11
Weighted-Average Remaining Contractual Term [Abstract]
Outstanding	6 years 1 month 24 days		6 years 6 months 18 days
Granted	8 years 11 months 15 days
Options vested and exercisable	5 years 3 months
Options unvested	9 years 14 days
Aggregate Intrinsic Value [Abstract]
Outstanding at beginning of period	$ 504,079
Exercised	53,871
Outstanding at end of period	203,781		$ 504,079
Options vested and exercisable	$ 194,593,951
Weighted average grant date fair value of shares granted (in dollars per share)	$ 32.74	$ 14.42
Total fair value of options vested	$ 18,200	$ 12,700
Employees and Directors [Member]
Weighted-Average Assumptions [Abstract]
Risk-free interest rate	0.78%	1.07%
Expected term	5 years 10 months 2 days	5 years 9 months 29 days
Expected volatility	69.31%	76.74%
Expected dividend yield	0.00%	0.00%
Exercise price (in dollars per share)	$ 53.98	$ 21.97
Fair value of common stock (in dollars per share)	$ 53.98	$ 21.97

Stock Based Compensation, Stock

Stock Based Compensation, Stock-Based Compensation (Details) - USD ($) $ in Thousands	Aug. 09, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense		$ 6,989	$ 4,047	$ 22,200	$ 12,497
Agreement with Related Party [Abstract]
Expense in connection with warrant issue				7,578	0
Common Stock [Member] | Consulting Agreement [Member]
Agreement with Related Party [Abstract]
Warrant issued (in shares)	301,291					603,386
Common Stock Warrant [Member]
Agreement with Related Party [Abstract]
Expense in connection with warrant issue	$ 7,600	7,600		7,600
Research and Development [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense		3,084	1,780	9,148	5,194
General and Administrative [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense		3,905	2,267	13,052	7,303
Stock Options [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense		6,831	4,047	21,872	12,497
Restricted Stock Units [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense		$ 158	$ 0	$ 328	$ 0

Stock Based Compensation, Restr

Stock Based Compensation, Restricted Stock Units (Details) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares
Stock-Based Compensation Expense [Abstract]
Weighted average period expected to recognize unrecognized share-based compensation cost	1 year 11 months 1 day
Stock Options [Member]
Stock-Based Compensation Expense [Abstract]
Unrecognized share-based compensation cost | $	$ 52.6
Restricted Stock Units (RSU) [Member]
Number of Shares [Roll Forward]
Unvested, beginning balance (in shares) | shares	20,000
Granted (in shares) | shares	3,500
Unvested, ending balance (in shares) | shares	23,500
Weighted Average Grant Date Fair Value [Abstract]
Unvested, beginning balance (in dollars per share) | $ / shares	$ 25.06
Granted (in dollars per share) | $ / shares	62.32
Unvested, ending balance (in dollars per share) | $ / shares	$ 30.61
Stock-Based Compensation Expense [Abstract]
Unrecognized share-based compensation cost | $	$ 52.6

Warrants (Details)

Warrants (Details) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Warrant One [Member]
Warrants [Abstract]
Exercise price of warrants (in dollars per share)	$ 24.82	$ 24.82
Warrant One [Member] | Common Stock [Member]
Warrants [Abstract]
Number of common stock shares called by warrants (in shares)	7,051	7,051
Warrant Two [Member]
Warrants [Abstract]
Exercise price of warrants (in dollars per share)	$ 57.11	$ 57.11
Warrant Two [Member] | Common Stock [Member]
Warrants [Abstract]
Number of common stock shares called by warrants (in shares)	603,386	603,386
Warrant Three [Member]
Warrants [Abstract]
Exercise price of warrants (in dollars per share)	$ 33.63
Warrant Three [Member] | Common Stock [Member]
Warrants [Abstract]
Number of common stock shares called by warrants (in shares)	301,291

Net Loss Per Share (Details)

Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator [Abstract]
Net loss attributable to common stockholders	$ (50,118)	$ (29,080)	$ (124,822)	$ (78,784)
Denominator [Abstract]
Weighted-average common shares outstanding - basic (in shares)	63,825,429	55,188,956	62,828,601	55,077,254
Weighted-average common shares outstanding - diluted (in shares)	63,825,429	55,188,956	62,828,601	55,077,254
Net loss per share attributable to common stockholders - basic (in dollars per share)	$ (0.79)	$ (0.53)	$ (1.99)	$ (1.43)
Net loss per share attributable to common stockholders - diluted (in dollars per share)	$ (0.79)	$ (0.53)	$ (1.99)	$ (1.43)
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Warrants exercisable for common shares (in shares)	911,728	14,102	911,728	14,102
Restricted stock units exercisable for common shares (in shares)	23,500	0	23,500	0
Options to purchase common shares (in shares)	11,108,242	10,922,678	11,108,242	10,922,678
Weighted average number diluted shares outstanding (in shares)	12,043,470	12,557,728	12,043,470	12,557,728
Convertible Notes 2021 [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Shares issuable upon conversion of Convertible Notes (in shares)	0	160,536	0	160,536
Convertible Notes 2022 [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Shares issuable upon conversion of Convertible Notes (in shares)	0	1,460,412	0	1,460,412

Commitments and Contingencies,

Commitments and Contingencies, Finance Lease (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)ft²LeaseAgreement	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Mar. 15, 2020USD ($)
Finance Lease [Abstract]
Total lease payments	$ 54,400		$ 54,400
Cash security deposit	455		455		$ 455
Finance right-of-use assets	49,011		49,011		50,521
Finance lease, liability	$ 20,786		20,786
Finance lease, interest expense			$ 1,382
NJ Lease Agreement [Member]
Finance Lease [Abstract]
Area of lease | ft²			103,720
Term of finance lease agreement	15 years		15 years
Number of options to renew lease agreement | LeaseAgreement			2
Term of renewal of finance lease agreement	5 years		5 years
Estimated rent payments			$ 1,200
Percentage of annual increase in base rent			3.00%
Total lease payments	$ 29,300		$ 29,300
Cash security deposit	300		300		$ 300
Finance right-of-use assets						$ 47,700
Finance lease, liability						20,200
Reclassification of construction costs in progress to right-of-use assets	100		100			26,500
Reclassification of prepaid rent to right-of-use assets						$ 1,100
Aggregate amount for reclassification of construction costs in progress to right-of-use assets	32,100		32,100
Finance lease, interest expense	$ 500	$ 500	$ 1,400	$ 1,100
AAV Current Good Manufacturing Practice (cGMP) [Member]
Finance Lease [Abstract]
Area of lease | ft²			50,000

Commitments and Contingencies_2

Commitments and Contingencies, Operating Leases (Details) - USD ($) $ in Thousands	Mar. 26, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jun. 07, 2018
Operating Leases [Abstract]
Rent expense		$ 200	$ 400	$ 800	$ 900
Restricted cash		$ 1,334		$ 1,334		$ 1,568
ESB Lease Agreement [Member]
Operating Leases [Abstract]
Term of lease agreement		3 years		3 years
Letter of credit							$ 900
Lease expiration date				Aug. 29, 2024
Certificate of deposit		$ 800		$ 800		900
ESB Lease Agreement Amendment [Member]
Operating Leases [Abstract]
Letter of credit		800		$ 800
Lease expiration date				Jun. 30, 2024
Operating lease right of use asset, adjustment	$ 1,100
Inotek Lexington Massachusetts Lease Agreement [Member]
Operating Leases [Abstract]
Lease expiration date				Feb. 28, 2023
Rental income received under sublease agreement		100	$ 100	$ 300	$ 300
Operating and Finance Leases [Member]
Operating Leases [Abstract]
Restricted cash		$ 1,000		$ 1,000		$ 1,100

Commitments and Contingencies_3

Commitments and Contingencies, Details of Operating and Finance Lease (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Lease cost [Abstract]
Operating lease cost	$ 457
Finance lease cost [Abstract]
Amortization of right of use assets	1,605
Interest on lease liabilities	1,382
Total lease cost	3,444
Maturity of operating lease liabilities [Abstract]
2021	215
2022	860
2023	488
2024	207
Total lease payments	1,770
Less: interest	(75)
Total operating lease liabilities	1,695
Maturity of finance lease liability [Abstract]
2021	416
2022	1,689
2023	1,736
2024	1,791
2025	1,856
Thereafter	46,912
Total lease payments	54,400
Less: interest	(33,614)
Total finance lease liability	20,786
Lease assets and liabilities [Abstract]
Operating right-of-use assets	1,467	$ 914
Operating current lease liabilities	804	626
Operating noncurrent lease liabilities	891	498
Total operating lease liabilities	1,695
Finance right-of-use assets	49,011	50,521
Finance current lease liability	1,677	1,644
Finance noncurrent lease liability	19,109	$ 18,988
Total finance lease liability	20,786
Cash paid for amounts included in the measurement of lease liabilities [Abstract]
Operating cash flows from operating leases	439
Cash flows from finance lease	$ 1,227
Weighted-average remaining lease term - operating leases	2 years 3 months 18 days
Weighted-average remaining lease term - finance lease	22 years 10 months 24 days
Weighted-average discount rate - operating leases	4.67%
Weighted-average discount rate - finance lease	8.96%

CIRM Grants (Details)

CIRM Grants (Details) $ in Millions	Apr. 01, 2021USD ($)	Jan. 04, 2021USD ($)	Sep. 30, 2021USD ($)	Mar. 31, 2021USD ($)	Sep. 30, 2021USD ($)	Dec. 31, 2019USD ($)Grant	Dec. 31, 2020USD ($)	Nov. 12, 2020USD ($)	Apr. 30, 2019USD ($)
LAD-I CIRM Grant [Member]
CIRM Grants [Abstract]
Grant award for clinical development support									$ 6.5
Number of grants | Grant						2
Amount received from grant for eligible costs incurred						$ 1.2
Grant receivable included in prepaid and other assets							$ 1.1
Milestone payments received	$ 1	$ 1.1
Decrease in research and development expense				$ (1)
IMO CIRM Grant [Member]
CIRM Grants [Abstract]
Grant award for clinical development support								$ 3.7
Amount received from grant for eligible costs incurred		$ 1
Grant receivable included in prepaid and other assets							$ 0.9
Decrease in research and development expense			$ (0.1)		$ (0.1)

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	Aug. 27, 2021	Aug. 09, 2021	Oct. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Transaction [Abstract]
Issuance of common stock, net of issuance costs						$ 26,354,000	$ 0
Expense in connection with warrant issue						7,578,000	0
Private Placement [Member]
Related Party Transaction [Abstract]
Issuance of common stock, net of issuance costs	$ 26,400,000
Period to file S-3 following demand by purchaser	60 days
Common Stock [Member]
Related Party Transaction [Abstract]
Issuance of common stock (in shares)				812,516
Common Stock [Member] | Private Placement [Member]
Related Party Transaction [Abstract]
Issuance of common stock (in shares)	812,516
Share price (in dollars per share)	$ 32.48
Common Stock Warrant [Member]
Related Party Transaction [Abstract]
Expense in connection with warrant issue		$ 7,600,000		$ 7,600,000		$ 7,600,000
Fair Value Assumptions [Abstract]
Risk-free interest rate						1.33%		0.95%
Expected term						10 years		10 years
Expected volatility						69.40%		74.20%
Expected dividend yield						0.00%		0.00%
Exercise price (in dollars per share)				$ 33.63		$ 33.63		$ 57.11
Fair value of common stock (in dollars per share)				$ 33.63		$ 33.63		$ 57.11
Restricted Stock Units [Member]
Related Party Transaction [Abstract]
Shares granted (in shares)						3,500
Consulting Agreement, Business Development Services [Member]
Related Party Transaction [Abstract]
Termination notice period for business development consulting services agreement						60 days
Term of consulting agreement						3 years
Consulting Agreement, Business Development Services [Member] | Common Stock [Member]
Related Party Transaction [Abstract]
Number of common stock shares called by warrants (in shares)		301,291						603,386
Member of the Board of Directors - One [Member]
Related Party Transaction [Abstract]
Business development consulting services expense (per quarter)						$ 27,500
Termination notice period for business development consulting services agreement						14 days
Related party expenses				$ 27,500	$ 27,500	$ 82,500	$ 82,500
Member of the Board of Directors - Two [Member]
Related Party Transaction [Abstract]
Term of consulting agreement						1 year
Number of options granted to purchase common stock (in shares)						20,000
Fair value amount of options granted						$ 400,000
Spouse of Executive officer [Member] | Restricted Stock Units [Member]
Related Party Transaction [Abstract]
Shares granted (in shares)			10,000
Vesting period						3 years

401(k) Savings Plan (Details)

401(k) Savings Plan (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
401(k) Savings Plan [Abstract]
Percentage of matching employee contributions			4.00%
Matching employee contributions	$ 0.1	$ 0.1	$ 0.4	$ 0.3