Editas Medicine (EDIT) 10-Q 9 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 05, 2021
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2021
Entity File Number	001-37687
Entity Registrant Name	EDITAS MEDICINE, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-4097528
Entity Address, Address Line One	11 Hurley Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02141
City Area Code	617
Local Phone Number	401-9000
Title of 12(b) Security	Common Stock
Trading Symbol	EDIT
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		68,398,540
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001650664
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 259,884	$ 139,682
Marketable securities	297,957	262,428
Accounts receivable	251	6,048
Prepaid expenses and other current assets	9,516	10,929
Total current assets	567,608	419,087
Marketable securities	99,198	109,664
Property and equipment, net	15,631	14,020
Right-of-use assets	27,801	25,128
Restricted cash and other non-current assets	6,781	4,703
Total assets	717,019	572,602
Current liabilities:
Accounts payable	3,402	6,408
Accrued expenses	14,575	24,046
Deferred revenue, current	22,667	20,943
Operating lease liabilities	10,263	6,811
Total current liabilities	50,907	58,208
Operating lease liabilities, net of current portion	18,430	19,324
Deferred revenue, net of current portion	60,888	73,984
Other non-current liabilities		27,500
Total liabilities	130,225	179,016
Stockholders' equity
Preferred stock, $0.0001 par value per share: 5,000,000 shares authorized; no shares issued or outstanding
Common stock, $0.0001 par value per share: 195,000,000 shares authorized; 68,392,659 and 62,689,457 shares issued, and 68,320,659 and 62,563,457 shares outstanding at September 30, 2021 and December 31, 2020, respectively	7	6
Additional paid-in capital	1,403,114	1,058,823
Accumulated other comprehensive loss	(64)	(46)
Accumulated deficit	(816,263)	(665,197)
Total stockholders' equity	586,794	393,586
Total liabilities and stockholders' equity	$ 717,019	$ 572,602

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Condensed Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	195,000,000	195,000,000
Common stock, shares issued	68,392,659	62,689,457
Common stock, shares outstanding	68,320,659	62,563,457

Condensed Consolidated Statemen

Condensed Consolidated Statement of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Condensed Consolidated Statement of Operations
Collaboration and other research and development revenues	$ 6,197	$ 62,841	$ 13,075	$ 79,313
Revenue type	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember
Operating expenses:
Research and development	$ 29,265	$ 33,916	$ 104,954	$ 96,492
General and administrative	16,185	19,936	59,657	51,789
Total operating expenses	45,450	53,852	164,611	148,281
Operating (loss) income	(39,253)	8,989	(151,536)	(68,968)
Other income (expense), net:
Other income (expense), net	19	(1,396)	38	13,114
Interest income, net	152	226	432	2,377
Total other income (expense), net	171	(1,170)	470	15,491
Net (loss) income	$ (39,082)	$ 7,819	$ (151,066)	$ (53,477)
Net (loss) income per share, basic (in dollars per share)	$ (0.57)	$ 0.13	$ (2.24)	$ (0.93)
Net (loss) income per share, diluted (in dollars per share)	$ (0.57)	$ 0.12	$ (2.24)	$ (0.93)
Weighted-average common shares outstanding, basic (in shares)	68,219,742	62,144,118	67,371,246	57,377,581
Weighted-average common shares outstanding, diluted (in shares)	68,219,742	62,697,173	67,371,246	57,377,581

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Condensed Consolidated Statements of Comprehensive (Loss) Income
Net (loss) income	$ (39,082)	$ 7,819	$ (151,066)	$ (53,477)
Other comprehensive (loss) income:
Unrealized gain (loss) on marketable debt securities	7	(231)	(18)	(155)
Comprehensive (loss) income	$ (39,075)	$ 7,588	$ (151,084)	$ (53,632)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total
Balance, beginning of period at Dec. 31, 2019	$ 5	$ 811,546	$ (549,221)	$ 107	$ 262,437
Balance, beginning of period (in shares) at Dec. 31, 2019	54,355,798
Statement of Stockholders' Equity (Deficit)
Exercise of stock options		3,047			3,047
Exercise of stock options (in shares)	233,208
Stock-based compensation expense		6,220			6,220
Vesting of restricted common stock awards (in shares)	213,393
Unrealized gain (loss) on marketable debt securities				587	587
Net income (loss)			(37,724)		(37,724)
Balance, end of period at Mar. 31, 2020	$ 5	820,813	(586,945)	694	234,567
Balance, end of period (in shares) at Mar. 31, 2020	54,802,399
Balance, beginning of period at Dec. 31, 2019	$ 5	811,546	(549,221)	107	262,437
Balance, beginning of period (in shares) at Dec. 31, 2019	54,355,798
Statement of Stockholders' Equity (Deficit)
Net income (loss)					(53,477)
Balance, end of period at Sep. 30, 2020	$ 6	1,043,892	(602,698)	(48)	441,152
Balance, end of period (in shares) at Sep. 30, 2020	62,187,700
Balance, beginning of period at Mar. 31, 2020	$ 5	820,813	(586,945)	694	234,567
Balance, beginning of period (in shares) at Mar. 31, 2020	54,802,399
Statement of Stockholders' Equity (Deficit)
Issuance of common stock for public offering	$ 1	203,681			203,682
Issuance of common stock for public offering (in shares)	6,900,000
Exercise of stock options		6,839			6,839
Exercise of stock options (in shares)	355,812
Stock-based compensation expense		5,417			5,417
Vesting of restricted common stock awards (in shares)	30,194
Purchase of common stock under benefit plans		350			350
Purchase of common stock under benefit plans (in shares)	15,244
Unrealized gain (loss) on marketable debt securities				(511)	(511)
Net income (loss)			(23,572)		(23,572)
Balance, end of period at Jun. 30, 2020	$ 6	1,037,100	(610,517)	183	426,772
Balance, end of period (in shares) at Jun. 30, 2020	62,103,649
Statement of Stockholders' Equity (Deficit)
Exercise of stock options		947			947
Exercise of stock options (in shares)	48,312
Stock-based compensation expense		5,845			5,845
Vesting of restricted common stock awards (in shares)	35,739
Unrealized gain (loss) on marketable debt securities				(231)	(231)
Net income (loss)			7,819		7,819
Balance, end of period at Sep. 30, 2020	$ 6	1,043,892	(602,698)	(48)	441,152
Balance, end of period (in shares) at Sep. 30, 2020	62,187,700
Balance, beginning of period at Dec. 31, 2020	$ 6	1,058,823	(665,197)	(46)	393,586
Balance, beginning of period (in shares) at Dec. 31, 2020	62,563,457
Statement of Stockholders' Equity (Deficit)
Issuance of common stock for public offering	$ 1	249,458			249,459
Issuance of common stock for public offering (in shares)	4,025,000
Issuance of common stock for success payment		27,500			27,500
Issuance of common stock for success payment (in shares)	303,599
Exercise of stock options		12,002			12,002
Exercise of stock options (in shares)	501,162
Stock-based compensation expense		12,204			12,204
Vesting of restricted common stock awards (in shares)	79,397
Unrealized gain (loss) on marketable debt securities				(27)	(27)
Net income (loss)			(56,728)		(56,728)
Balance, end of period at Mar. 31, 2021	$ 7	1,359,987	(721,925)	(73)	637,996
Balance, end of period (in shares) at Mar. 31, 2021	67,472,615
Balance, beginning of period at Dec. 31, 2020	$ 6	1,058,823	(665,197)	(46)	393,586
Balance, beginning of period (in shares) at Dec. 31, 2020	62,563,457
Statement of Stockholders' Equity (Deficit)
Net income (loss)					(151,066)
Balance, end of period at Sep. 30, 2021	$ 7	1,403,114	(816,263)	(64)	586,794
Balance, end of period (in shares) at Sep. 30, 2021	68,320,659
Balance, beginning of period at Mar. 31, 2021	$ 7	1,359,987	(721,925)	(73)	637,996
Balance, beginning of period (in shares) at Mar. 31, 2021	67,472,615
Statement of Stockholders' Equity (Deficit)
Exercise of stock options		16,567			16,567
Exercise of stock options (in shares)	629,973
Stock-based compensation expense		13,526			13,526
Vesting of restricted common stock awards (in shares)	37,790
Purchase of common stock under benefit plans		526			526
Purchase of common stock under benefit plans (in shares)	19,408
Unrealized gain (loss) on marketable debt securities				2	2
Net income (loss)			(55,256)		(55,256)
Balance, end of period at Jun. 30, 2021	$ 7	1,390,606	(777,181)	(71)	613,361
Balance, end of period (in shares) at Jun. 30, 2021	68,159,786
Statement of Stockholders' Equity (Deficit)
Exercise of stock options		2,496			2,496
Exercise of stock options (in shares)	86,985
Stock-based compensation expense		10,012			10,012
Vesting of restricted common stock awards (in shares)	73,888
Unrealized gain (loss) on marketable debt securities				7	7
Net income (loss)			(39,082)		(39,082)
Balance, end of period at Sep. 30, 2021	$ 7	$ 1,403,114	$ (816,263)	$ (64)	$ 586,794
Balance, end of period (in shares) at Sep. 30, 2021	68,320,659

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flow from operating activities
Net loss	$ (151,066)	$ (53,477)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	35,742	17,483
Depreciation	3,542	2,776
Unrealized gain on corporate equity securities		(13,109)
Other non-cash items, net	1,332	(285)
Changes in operating assets and liabilities:
Accounts receivable	5,797	(637)
Prepaid expenses and other current assets	1,414	(4,181)
Right-of-use assets	7,080	2,363
Other non-current assets	(2,077)	106
Accounts payable	(2,978)	(447)
Accrued expenses	(9,439)	(2,391)
Deferred revenue	(11,372)	(86,026)
Operating lease liabilities	(7,196)	(2,371)
Other current and non-current liabilities		453
Net cash used in operating activities	(129,221)	(139,743)
Cash flow from investing activities
Purchases of property and equipment	(5,132)	(5,786)
Proceeds from the sale of equipment		21
Purchases of marketable securities	(304,570)	(300,363)
Proceeds from maturities of marketable securities	278,076	274,500
Net cash used in investing activities	(31,626)	(31,628)
Cash flow from financing activities
Proceeds from offering of common stock, net of issuance costs	249,458	203,839
Proceeds from exercise of stock options	31,065	10,833
Issuance of common stock under benefit plans	526	350
Net cash provided by financing activities	281,049	215,022
Net increase in cash, cash equivalents, and restricted cash	120,202	43,651
Cash, cash equivalents, and restricted cash, beginning of period	143,559	239,802	$ 239,802
Cash, cash equivalents, and restricted cash, end of period	263,761	283,453	$ 143,559
Supplemental disclosure of cash and non-cash activities:
Fixed asset additions included in accounts payable and accrued expenses	597	910
Cash paid in connection with operating lease liabilities	8,918	7,757
Offering costs included in accounts payable and accrued expenses		$ 158
Right-of-use assets obtained in exchange of operating lease obligations	$ 9,753

Nature of Business

Nature of Business	9 Months Ended
	Sep. 30, 2021
Nature of Business
Nature of Business	1. Nature of Business ​ Editas Medicine, Inc. (the “Company”) is a leading, clinical stage genome editing company dedicated to developing potentially transformative genomic medicines to treat a broad range of serious diseases. The Company was incorporated in the state of Delaware in September 2013. Its principal offices are in Cambridge, Massachusetts. Since its inception, the Company has devoted substantially all of its efforts to business planning, research and development, recruiting management and technical staff, and raising capital. The Company has primarily financed its operations through various equity financings, payments received under a research collaboration with Juno Therapeutics, a wholly-owned subsidiary of the Bristol Myers Squibb Company (“Juno Therapeutics”), and payments received under a strategic alliance and option agreement with Allergan Pharmaceuticals International Limited (together with its affiliates, “Allergan”), which was terminated in August 2020. The Company is subject to risks common to companies in the biotechnology industry, including but not limited to, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval for any drug product candidate that it may identify and develop, the need to successfully commercialize and gain market acceptance of its product candidates, dependence on key personnel, protection of proprietary technology, compliance with government regulations, development by competitors of technological innovations and ability to transition from pilot-scale manufacturing to large-scale production of products. Liquidity ​ In May 2021, the Company entered into a common stock sales agreement with Cowen and Company, LLC (“Cowen”), under which the Company from time to time can issue and sell shares of its common stock through Cowen in at-the-market offerings for aggregate gross sale proceeds of up to $300.0 million (the “ATM Facility”). As of September 30, 2021, the Company has not sold any shares of its common stock under the ATM Facility. ​ In January 2021, the Company completed a public offering whereby it sold 3,500,000 shares of its common stock and received net proceeds of approximately $216.9 million. In February 2021, the underwriters in the public offering exercised their option to purchase an additional 525,000 shares, resulting in additional net proceeds to the Company of approximately $32.6 million. ​ The Company has incurred annual net operating losses in every year since its inception. The Company expects that its existing cash, cash equivalents and marketable securities at September 30, 2021 and anticipated interest income will enable it to fund its operating expenses and capital expenditure requirements well into 2023 . The Company had an accumulated deficit of $816.3 million at September 30, 2021, and will require substantial additional capital to fund its operations. The Company has never generated any product revenue. There can be no assurance that the Company will be able to obtain additional debt or equity financing or generate product revenue or revenues from collaborative partners, on terms acceptable to the Company, on a timely basis or at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations, and financial condition.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies ​ Unaudited Interim Financial Information ​ The condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020 (the “Annual Report”). ​ The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Editas Securities Corporation. All intercompany transactions and balances of the subsidiary have been eliminated in consolidation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The three months ended September 30, 2021 and 2020 are referred to as the third quarter of 2021 and 2020, respectively. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. ​ Summary of Significant Accounting Policies ​ The Company’s significant accounting policies are described in Note 2, “Summary of significant accounting policies,” to the consolidated financial statements included in the Annual Report. There have been no material changes to the significant accounting policies previously disclosed in the Annual Report. ​ ​

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	9 Months Ended
	Sep. 30, 2021
Cash Equivalents and Marketable Securities
Cash Equivalents and Marketable Securities	3. Cash Equivalents and Marketable Securities ​ Cash equivalents and marketable securities consisted of the following at September 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ for Credit ​ ​ Unrealized ​ Unrealized ​ Fair September 30, 2021 ​ Cost ​ Losses ​ ​ Gains ​ Losses ​ Value Cash equivalents and marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 259,884 ​ $ — ​ ​ $ — ​ $ — ​ $ 259,884 U.S. Treasuries ​ ​ 109,060 ​ ​ — ​ ​ ​ 4 ​ ​ (15) ​ ​ 109,049 Government agency securities ​ ​ 118,708 ​ ​ — ​ ​ ​ 1 ​ ​ (17) ​ ​ 118,692 Commercial Paper ​ ​ 101,167 ​ ​ — ​ ​ ​ 3 ​ ​ (6) ​ ​ 101,164 Corporate notes/bonds ​ ​ 68,284 ​ ​ — ​ ​ ​ 2 ​ ​ (36) ​ ​ 68,250 Total ​ $ 657,103 ​ $ — ​ ​ $ 10 ​ $ (74) ​ $ 657,039 ​ Cash equivalents and marketable securities consisted of the following at December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ for Credit ​ ​ Unrealized ​ Unrealized ​ Fair December 31, 2020 ​ Cost ​ Losses ​ ​ Gains ​ Losses ​ Value Cash equivalents and marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 139,682 ​ $ — ​ ​ $ — ​ $ — ​ $ 139,682 U.S. Treasuries ​ ​ 180,376 ​ ​ — ​ ​ ​ 8 ​ ​ (11) ​ ​ 180,373 Government agency securities ​ ​ 107,665 ​ ​ — ​ ​ ​ — ​ ​ (20) ​ ​ 107,645 Commercial paper ​ ​ 41,912 ​ ​ — ​ ​ ​ — ​ ​ (8) ​ ​ 41,904 Corporate notes/bonds ​ ​ 42,185 ​ ​ — ​ ​ ​ 10 ​ ​ (25) ​ ​ 42,170 Total ​ $ 511,820 ​ $ — ​ ​ $ 18 ​ $ (64) ​ $ 511,774 ​ As of September 30, 2021, the Company did not hold any marketable securities that had been in an unrealized loss position for more than twelve months. Furthermore, the Company has determined that there were no material changes in the credit risk of the debt securities. As of September 30, 2021, the Company holds 29 securities with an aggregate fair value of $99.2 million that had remaining maturities between one ​ There were no realized gains or losses on available-for-sale securities during the nine months ended September 30, 2021 or 2020.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Measurements
Fair Value Measurements	4. Fair Value Measurements ​ Assets measured at fair value on a recurring basis as of September 30, 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted Prices Significant ​ ​ ​ ​ ​ ​ ​ in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ ​ September 30, ​ Identical Assets ​ Inputs ​ Inputs Financial Assets ​ 2021 ​ (Level 1) ​ (Level 2) ​ (Level 3) Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 259,884 ​ $ 259,884 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasuries ​ ​ 109,049 ​ ​ 109,049 ​ ​ — ​ ​ — Government agency securities ​ ​ 118,692 ​ ​ — ​ ​ 118,692 ​ ​ — Commercial paper ​ ​ 101,164 ​ ​ — ​ ​ 101,164 ​ ​ — Corporate notes/bonds ​ ​ 68,250 ​ ​ — ​ ​ 68,250 ​ ​ — Restricted cash and other non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ ​ 3,877 ​ ​ 3,877 ​ ​ — ​ ​ — Total financial assets ​ $ 660,916 ​ $ 372,810 ​ $ 288,106 ​ $ — ​ Assets measured at fair value on a recurring basis as of December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted Prices Significant ​ ​ ​ ​ ​ ​ ​ in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ ​ December 31, ​ Identical Assets ​ Inputs ​ Inputs Financial Assets ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 139,682 ​ $ 139,682 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasuries ​ ​ 180,373 ​ ​ 180,373 ​ ​ — ​ ​ — Government agency securities ​ ​ 107,645 ​ ​ — ​ ​ 107,645 ​ ​ — Commercial paper ​ ​ 41,904 ​ ​ — ​ ​ 41,904 ​ ​ — Corporate bonds ​ ​ 42,170 ​ ​ — ​ ​ 42,170 ​ ​ — Restricted cash and other non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ ​ 3,877 ​ ​ 3,877 ​ ​ — ​ ​ — Total financial assets ​ $ 515,651 ​ $ 323,932 ​ $ 191,719 ​ $ — ​

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2021
Accrued Expenses
Accrued Expenses	5. Accrued Expenses ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ September 30, ​ December 31, ​ 2021 2020 Employee related expenses ​ $ 9,639 ​ $ 5,323 External research and development expenses ​ ​ 2,381 ​ 12,820 Intellectual property and patent related fees ​ ​ 1,606 ​ ​ 4,240 Professional service expenses ​ ​ 640 ​ ​ 533 Other expenses ​ ​ 271 ​ ​ 359 Sublicensing expenses ​ ​ 38 ​ ​ 771 Total accrued expenses ​ $ 14,575 ​ $ 24,046 ​ ​ ​ ​ ​ ​ ​ ​

Property and Equipment, net

Property and Equipment, net	9 Months Ended
	Sep. 30, 2021
Property and Equipment, net
Property and Equipment, net	6. Property and Equipment, net ​ Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ September 30, ​ December 31, ​ 2021 2020 Laboratory equipment ​ $ 20,647 ​ $ 18,433 Leasehold improvements ​ ​ 5,427 ​ ​ 4,967 Construction-in-progress ​ 2,360 ​ 500 Computer equipment ​ ​ 858 ​ ​ 858 Furniture and office equipment ​ ​ 264 ​ ​ 239 Software ​ 118 ​ 118 Total property and equipment ​ 29,674 ​ 25,115 Less: accumulated depreciation ​ (14,043) ​ (11,095) Property and equipment, net ​ $ 15,631 ​ $ 14,020 ​

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies
Commitments and Contingencies	7. Commitments and Contingencies ​ ​ Licensor Expense Reimbursement ​ The Company is obligated to reimburse The Broad Institute, Inc. (“Broad”) and the President and Fellows of Harvard College (“Harvard”) for expenses incurred by each of them associated with the prosecution and maintenance of the patent rights that the Company licenses from them pursuant to the license agreement by and among the Company, Broad and Harvard, including the interference and opposition proceedings involving patents licensed to the Company under the license agreement, and other license agreements between the Company and Broad. As such, the Company anticipates that it has a substantial commitment in connection with these proceedings until such time as these proceedings have been resolved, but the amount of such commitment is not determinable. The Company incurred an aggregate of $1.8 million and $9.0 million in expense during the three and nine months ended September 30, 2021, respectively, for such reimbursement. The Company incurred an aggregate of $2.6 million and $9.3 million in expense during the three and nine months ended September 30, 2020, respectively, for such reimbursement.

Collaboration and Profit-Sharin

Collaboration and Profit-Sharing Agreements	9 Months Ended
	Sep. 30, 2021
Collaboration and Profit-Sharing Agreements
Collaboration and Profit-Sharing Agreements	8 Collaboration and Profit-Sharing Agreements ​ The Company has entered into multiple collaborations, out-licenses and strategic alliances with third parties that typically involve payments to or from the Company, including up-front payments, payments for research and development services, option payments, milestone payments and royalty payments to or from the Company. The terms and conditions as well as the accounting analysis for the Company’s significant collaborations, out-licenses and strategic alliances are described in Note 9, “Collaboration and Profit-Sharing Agreements” to the consolidated financial statements included in the Annual Report. There have been no material changes to the terms and conditions, or the accounting conclusions, previously disclosed in the Annual Report. ​ ​ ​ Collaboration Revenue ​ As of September 30, 2021, the Company’s contract liabilities were primarily related to the Company’s collaboration with Juno Therapeutics. The following table presents changes in the Company’s accounts receivable and contract liabilities for the nine months ended September 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the nine months ended September 30, 2021 Balance at December 31, 2020 ​ Additions ​ Deductions ​ Balance at September 30, 2021 Accounts receivable $ 6,048 ​ $ 390 ​ $ (6,187) ​ $ 251 Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue $ 94,927 ​ $ — ​ $ (11,372) ​ $ 83,555 ​ During the three and nine months ended September 30, 2021, the Company recognized the following collaboration revenue (in thousands): ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended Revenue recognized in the period from: September 30, 2021 Amounts included in deferred revenue at the beginning of the period $ 5,666 ​ $ 11,372 Performance obligations satisfied in previous periods $ — ​ $ — ​

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2021
Stock-Based Compensation
Stock-Based Compensation	9 Stock-based Compensation ​ Total compensation cost recognized for all stock-based compensation awards in the condensed consolidated statements of operations was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Research and development ​ $ 4,552 ​ $ 2,938 ​ $ 12,689 ​ $ 8,668 General and administrative ​ 5,460 ​ 2,908 ​ 23,053 ​ 8,815 Total stock-based compensation expense ​ $ 10,012 ​ $ 5,846 ​ $ 35,742 ​ $ 17,483 ​ Restricted Stock and Restricted Stock Unit Awards ​ The following is a summary of restricted stock and restricted stock unit awards activity for the nine months ended September 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ ​ ​ Grant Date ​ ​ ​ ​ Fair Value ​ ​ Shares ​ Per Share Unvested restricted stock and restricted stock unit awards as of December 31, 2020 507,450 ​ $ 27.35 Issued 614,775 ​ $ 48.12 Vested (191,075) ​ $ 31.08 Forfeited ​ (180,694) ​ $ 38.70 Unvested restricted stock and restricted stock unit awards as of September 30, 2021 750,456 ​ $ 41.33 ​ ​ As of September 30, 2021, total unrecognized compensation expense related to unvested restricted stock and restricted stock unit awards was $18.7 million, which the Company expects to recognize over a remaining weighted-average period of 2.1 years. ​ Stock Options ​ The following is a summary of stock option activity for the nine months ended September 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Average Remaining Aggregate Intrinsic ​ ​ Shares ​ Exercise Price ​ Contractual Life (years) ​ Value (in thousands) Outstanding at December 31, 2020 3,912,257 ​ $ 27.26 ​ 7.9 ​ $ 167,640 Granted ​ 1,206,841 ​ $ 45.58 ​ ​ ​ ​ ​ Exercised ​ (1,218,120) ​ $ 25.50 ​ ​ ​ ​ ​ Cancelled ​ (817,563) ​ $ 30.83 ​ ​ ​ ​ ​ Outstanding at September 30, 2021 3,083,415 ​ $ 34.18 ​ 7.8 ​ $ 28,399 Exercisable at September 30, 2021 1,318,174 ​ $ 28.58 ​ 7.0 ​ $ 17,411 ​ The stock options granted in the nine months ended September 30, 2021 include option grants to the Company’s Chief Executive Officer to purchase 196,637 and 341,978 shares of the Company’s common stock that contained market-based vesting provisions and performance-based vesting provisions, respectively. The Company recognizes the fair value of the market-based options over the earlier of the derived service period, valued using the Monte-Carlo simulation model, or when the market-based vesting conditions are met. The Company recognizes the fair value of the performance-based options through the expected achievement date if the performance-based vesting provisions are deemed probable. ​ As of September 30, 2021, total unrecognized compensation expense related to stock options was $33.3 million, which the Company expects to recognize over a remaining weighted-average period of 2.5 years.

Net (Loss) Income per Share

Net (Loss) Income per Share	9 Months Ended
	Sep. 30, 2021
Net (Loss) Income per Share
Net (Loss) Income per Share	10. Net (Loss) Income per Share ​ Basic net (loss) income per common share is calculated by dividing the net (loss) income attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net (loss) income per share is computed by dividing the net (loss) income attributable to common stockholders by the weighted average number of shares of common stock and potentially dilutive securities outstanding for the period determined using the treasury stock and if converted methods. Contingently issuable shares are included in the calculation of basic (loss) income per share as of the beginning of the period in which all the necessary conditions have been satisfied. Contingently issuable shares are included in diluted (loss) income per share based on the number of shares, if any, that would be issuable under the terms of the arrangement if the end of the reporting period was the end of the contingency period, if the results are dilutive. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Net (loss) income ​ $ (39,082) ​ $ 7,819 ​ $ (151,066) ​ $ (53,477) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares outstanding, basic ​ 68,219,742 ​ ​ 62,144,118 ​ ​ 67,371,246 ​ ​ 57,377,581 Dilutive effect of outstanding stock options ​ ​ — ​ ​ 414,640 ​ ​ — ​ ​ — Dilutive effect of unvested restricted stock and restricted stock unit awards ​ — ​ 138,415 ​ — ​ — Weighted average common shares outstanding, diluted ​ ​ 68,219,742 ​ ​ 62,697,173 ​ ​ 67,371,246 ​ ​ 57,377,581 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income per share, basic ​ $ (0.57) ​ $ 0.13 ​ $ (2.24) ​ $ (0.93) Net (loss) income per share, diluted ​ $ (0.57) ​ $ 0.12 ​ $ (2.24) ​ $ (0.93) ​ ​ The following common stock equivalents were excluded from the calculation of diluted net (loss) income per share allocable to common stockholders because their inclusion would have been anti-dilutive: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ Nine months Ended ​ ​ September 30, ​ September 30, ​ 2021 ​ 2020 ​ 2021 2020 Unvested restricted stock and restricted stock unit awards 750,456 ​ 371,463 ​ 750,456 509,878 Outstanding stock options 3,083,415 ​ 3,626,151 ​ 3,083,415 4,040,791 Total 3,833,871 ​ 3,997,614 ​ 3,833,871 4,550,669 ​

Cash Equivalents and Marketab_2

Cash Equivalents and Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Cash Equivalents and Marketable Securities
Schedule of cash equivalents and marketable securities	Cash equivalents and marketable securities consisted of the following at September 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ for Credit ​ ​ Unrealized ​ Unrealized ​ Fair September 30, 2021 ​ Cost ​ Losses ​ ​ Gains ​ Losses ​ Value Cash equivalents and marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 259,884 ​ $ — ​ ​ $ — ​ $ — ​ $ 259,884 U.S. Treasuries ​ ​ 109,060 ​ ​ — ​ ​ ​ 4 ​ ​ (15) ​ ​ 109,049 Government agency securities ​ ​ 118,708 ​ ​ — ​ ​ ​ 1 ​ ​ (17) ​ ​ 118,692 Commercial Paper ​ ​ 101,167 ​ ​ — ​ ​ ​ 3 ​ ​ (6) ​ ​ 101,164 Corporate notes/bonds ​ ​ 68,284 ​ ​ — ​ ​ ​ 2 ​ ​ (36) ​ ​ 68,250 Total ​ $ 657,103 ​ $ — ​ ​ $ 10 ​ $ (74) ​ $ 657,039 ​ Cash equivalents and marketable securities consisted of the following at December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ for Credit ​ ​ Unrealized ​ Unrealized ​ Fair December 31, 2020 ​ Cost ​ Losses ​ ​ Gains ​ Losses ​ Value Cash equivalents and marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 139,682 ​ $ — ​ ​ $ — ​ $ — ​ $ 139,682 U.S. Treasuries ​ ​ 180,376 ​ ​ — ​ ​ ​ 8 ​ ​ (11) ​ ​ 180,373 Government agency securities ​ ​ 107,665 ​ ​ — ​ ​ ​ — ​ ​ (20) ​ ​ 107,645 Commercial paper ​ ​ 41,912 ​ ​ — ​ ​ ​ — ​ ​ (8) ​ ​ 41,904 Corporate notes/bonds ​ ​ 42,185 ​ ​ — ​ ​ ​ 10 ​ ​ (25) ​ ​ 42,170 Total ​ $ 511,820 ​ $ — ​ ​ $ 18 ​ $ (64) ​ $ 511,774

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Measurements
Schedule of assets measured at fair value on a recurring basis	Assets measured at fair value on a recurring basis as of September 30, 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted Prices Significant ​ ​ ​ ​ ​ ​ ​ in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ ​ September 30, ​ Identical Assets ​ Inputs ​ Inputs Financial Assets ​ 2021 ​ (Level 1) ​ (Level 2) ​ (Level 3) Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 259,884 ​ $ 259,884 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasuries ​ ​ 109,049 ​ ​ 109,049 ​ ​ — ​ ​ — Government agency securities ​ ​ 118,692 ​ ​ — ​ ​ 118,692 ​ ​ — Commercial paper ​ ​ 101,164 ​ ​ — ​ ​ 101,164 ​ ​ — Corporate notes/bonds ​ ​ 68,250 ​ ​ — ​ ​ 68,250 ​ ​ — Restricted cash and other non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ ​ 3,877 ​ ​ 3,877 ​ ​ — ​ ​ — Total financial assets ​ $ 660,916 ​ $ 372,810 ​ $ 288,106 ​ $ — ​ Assets measured at fair value on a recurring basis as of December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted Prices Significant ​ ​ ​ ​ ​ ​ ​ in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ ​ December 31, ​ Identical Assets ​ Inputs ​ Inputs Financial Assets ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 139,682 ​ $ 139,682 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasuries ​ ​ 180,373 ​ ​ 180,373 ​ ​ — ​ ​ — Government agency securities ​ ​ 107,645 ​ ​ — ​ ​ 107,645 ​ ​ — Commercial paper ​ ​ 41,904 ​ ​ — ​ ​ 41,904 ​ ​ — Corporate bonds ​ ​ 42,170 ​ ​ — ​ ​ 42,170 ​ ​ — Restricted cash and other non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ ​ 3,877 ​ ​ 3,877 ​ ​ — ​ ​ — Total financial assets ​ $ 515,651 ​ $ 323,932 ​ $ 191,719 ​ $ —

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2021
Accrued Expenses
Schedule of accrued expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ September 30, ​ December 31, ​ 2021 2020 Employee related expenses ​ $ 9,639 ​ $ 5,323 External research and development expenses ​ ​ 2,381 ​ 12,820 Intellectual property and patent related fees ​ ​ 1,606 ​ ​ 4,240 Professional service expenses ​ ​ 640 ​ ​ 533 Other expenses ​ ​ 271 ​ ​ 359 Sublicensing expenses ​ ​ 38 ​ ​ 771 Total accrued expenses ​ $ 14,575 ​ $ 24,046 ​ ​ ​ ​ ​ ​ ​

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	9 Months Ended
	Sep. 30, 2021
Property and Equipment, net
Schedule of property and equipment, net	Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ September 30, ​ December 31, ​ 2021 2020 Laboratory equipment ​ $ 20,647 ​ $ 18,433 Leasehold improvements ​ ​ 5,427 ​ ​ 4,967 Construction-in-progress ​ 2,360 ​ 500 Computer equipment ​ ​ 858 ​ ​ 858 Furniture and office equipment ​ ​ 264 ​ ​ 239 Software ​ 118 ​ 118 Total property and equipment ​ 29,674 ​ 25,115 Less: accumulated depreciation ​ (14,043) ​ (11,095) Property and equipment, net ​ $ 15,631 ​ $ 14,020

Collaboration and Profit-Shar_2

Collaboration and Profit-Sharing Agreements (Tables)	9 Months Ended
	Sep. 30, 2021
Collaboration and Profit-Sharing Agreements
Schedule of accounts receivable and contract liabilities	The following table presents changes in the Company’s accounts receivable and contract liabilities for the nine months ended September 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the nine months ended September 30, 2021 Balance at December 31, 2020 ​ Additions ​ Deductions ​ Balance at September 30, 2021 Accounts receivable $ 6,048 ​ $ 390 ​ $ (6,187) ​ $ 251 Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue $ 94,927 ​ $ — ​ $ (11,372) ​ $ 83,555
Schedule of change in contract assets and contract liabilities	During the three and nine months ended September 30, 2021, the Company recognized the following collaboration revenue (in thousands): ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended Revenue recognized in the period from: September 30, 2021 Amounts included in deferred revenue at the beginning of the period $ 5,666 ​ $ 11,372 Performance obligations satisfied in previous periods $ — ​ $ —

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Stock-Based Compensation
Schedule of stock-based compensation expense	Total compensation cost recognized for all stock-based compensation awards in the condensed consolidated statements of operations was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Research and development ​ $ 4,552 ​ $ 2,938 ​ $ 12,689 ​ $ 8,668 General and administrative ​ 5,460 ​ 2,908 ​ 23,053 ​ 8,815 Total stock-based compensation expense ​ $ 10,012 ​ $ 5,846 ​ $ 35,742 ​ $ 17,483
Schedule of changes in unvested restricted stock	The following is a summary of restricted stock and restricted stock unit awards activity for the nine months ended September 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ ​ ​ Grant Date ​ ​ ​ ​ Fair Value ​ ​ Shares ​ Per Share Unvested restricted stock and restricted stock unit awards as of December 31, 2020 507,450 ​ $ 27.35 Issued 614,775 ​ $ 48.12 Vested (191,075) ​ $ 31.08 Forfeited ​ (180,694) ​ $ 38.70 Unvested restricted stock and restricted stock unit awards as of September 30, 2021 750,456 ​ $ 41.33
Schedule of stock option activity	The following is a summary of stock option activity for the nine months ended September 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Average Remaining Aggregate Intrinsic ​ ​ Shares ​ Exercise Price ​ Contractual Life (years) ​ Value (in thousands) Outstanding at December 31, 2020 3,912,257 ​ $ 27.26 ​ 7.9 ​ $ 167,640 Granted ​ 1,206,841 ​ $ 45.58 ​ ​ ​ ​ ​ Exercised ​ (1,218,120) ​ $ 25.50 ​ ​ ​ ​ ​ Cancelled ​ (817,563) ​ $ 30.83 ​ ​ ​ ​ ​ Outstanding at September 30, 2021 3,083,415 ​ $ 34.18 ​ 7.8 ​ $ 28,399 Exercisable at September 30, 2021 1,318,174 ​ $ 28.58 ​ 7.0 ​ $ 17,411

Net (Loss) Income per Share (Ta

Net (Loss) Income per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Net (Loss) Income per Share
Schedule of Basic and Diluted Net Income (Loss) Per Share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Net (loss) income ​ $ (39,082) ​ $ 7,819 ​ $ (151,066) ​ $ (53,477) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares outstanding, basic ​ 68,219,742 ​ ​ 62,144,118 ​ ​ 67,371,246 ​ ​ 57,377,581 Dilutive effect of outstanding stock options ​ ​ — ​ ​ 414,640 ​ ​ — ​ ​ — Dilutive effect of unvested restricted stock and restricted stock unit awards ​ — ​ 138,415 ​ — ​ — Weighted average common shares outstanding, diluted ​ ​ 68,219,742 ​ ​ 62,697,173 ​ ​ 67,371,246 ​ ​ 57,377,581 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income per share, basic ​ $ (0.57) ​ $ 0.13 ​ $ (2.24) ​ $ (0.93) Net (loss) income per share, diluted ​ $ (0.57) ​ $ 0.12 ​ $ (2.24) ​ $ (0.93)
Schedule of anti-dilutive common stock equivalents	The following common stock equivalents were excluded from the calculation of diluted net (loss) income per share allocable to common stockholders because their inclusion would have been anti-dilutive: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ Nine months Ended ​ ​ September 30, ​ September 30, ​ 2021 ​ 2020 ​ 2021 2020 Unvested restricted stock and restricted stock unit awards 750,456 ​ 371,463 ​ 750,456 509,878 Outstanding stock options 3,083,415 ​ 3,626,151 ​ 3,083,415 4,040,791 Total 3,833,871 ​ 3,997,614 ​ 3,833,871 4,550,669

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ in Thousands	1 Months Ended		5 Months Ended
	Feb. 28, 2021	Jan. 31, 2021	Sep. 30, 2021	May 31, 2021	Dec. 31, 2020
Liquidity
Accumulated deficit			$ 816,263		$ 665,197
At Market Offering
Liquidity
Number of common stock issued			0
Sales agreement amount of aggregate sale proceeds of common stock agreed to be issued				$ 300,000
Public Offering
Liquidity
Number of common stock issued		3,500,000
Aggregate net proceeds		$ 216,900
Overallotment Option
Liquidity
Number of common stock issued	525,000
Aggregate net proceeds	$ 32,600

Cash Equivalents and Marketab_3

Cash Equivalents and Marketable Securities (Details) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021USD ($)securityitem	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Cash Equivalents and Marketable Securities
Amortized Cost	$ 657,103		$ 511,820
Gross Unrealized Gains	10		18
Gross Unrealized Losses	(74)		(64)
Fair Value	$ 657,039		511,774
Equity securities included in other non-current assets:
Gross Unrealized Gains		$ 13,109
Number of securities in an unrealized loss position for more than 12 months | item	0
Number of noncurrent securities | security	29
Noncurrent marketable securities	$ 99,198		109,664
Realized gains (losses) on available-for-sale securities	$ 0	$ 0
Minimum
Equity securities included in other non-current assets:
Remaining maturity term	1 year
Maximum
Equity securities included in other non-current assets:
Remaining maturity term	2 years
U.S. Treasuries
Cash Equivalents and Marketable Securities
Amortized Cost	$ 109,060		180,376
Gross Unrealized Gains	4		8
Gross Unrealized Losses	(15)		(11)
Fair Value	109,049		180,373
Government agency securities.
Cash Equivalents and Marketable Securities
Amortized Cost	118,708		107,665
Gross Unrealized Gains	1
Gross Unrealized Losses	(17)		(20)
Fair Value	118,692		107,645
Commercial paper
Cash Equivalents and Marketable Securities
Amortized Cost	101,167		41,912
Gross Unrealized Gains	3
Gross Unrealized Losses	(6)		(8)
Fair Value	101,164		41,904
Corporate notes/bonds
Cash Equivalents and Marketable Securities
Amortized Cost	68,284
Gross Unrealized Gains	2
Gross Unrealized Losses	(36)
Fair Value	68,250
Equity securities included in other non-current assets:
Amortized Cost			42,185
Gross Unrealized Gains			10
Gross Unrealized Losses			(25)
Fair Value			42,170
Money market funds
Cash Equivalents and Marketable Securities
Amortized Cost	259,884		139,682
Fair Value	$ 259,884		$ 139,682

Fair Value Measurements - Recur

Fair Value Measurements - Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financial Assets
Marketable securities	$ 657,039	$ 511,774
U.S. Treasuries
Financial Assets
Marketable securities	109,049	180,373
Commercial paper
Financial Assets
Marketable securities	101,164	41,904
Corporate notes/bonds
Financial Assets
Equity securities		42,185
Marketable securities	68,250
Money market funds
Financial Assets
Marketable securities	259,884	139,682
Recurring
Financial Assets
Total financial assets	660,916	515,651
Recurring | Restricted cash and other non-current assets
Financial Assets
Restricted cash	3,877	3,877
Recurring | U.S. Treasuries
Financial Assets
Marketable securities	109,049	180,373
Recurring | Government agency securities
Financial Assets
Marketable securities	118,692	107,645
Recurring | Commercial paper
Financial Assets
Marketable securities	101,164	41,904
Recurring | Corporate notes/bonds
Financial Assets
Marketable securities	68,250	42,170
Recurring | Money market funds
Financial Assets
Cash and cash equivalents	259,884	139,682
Recurring | Level 1
Financial Assets
Total financial assets	372,810	323,932
Recurring | Level 1 | Restricted cash and other non-current assets
Financial Assets
Restricted cash	3,877	3,877
Recurring | Level 1 | U.S. Treasuries
Financial Assets
Marketable securities	109,049	180,373
Recurring | Level 1 | Money market funds
Financial Assets
Cash and cash equivalents	259,884	139,682
Recurring | Level 2
Financial Assets
Total financial assets	288,106	191,719
Recurring | Level 2 | Government agency securities
Financial Assets
Marketable securities	118,692	107,645
Recurring | Level 2 | Commercial paper
Financial Assets
Marketable securities	101,164	41,904
Recurring | Level 2 | Corporate notes/bonds
Financial Assets
Marketable securities	$ 68,250	$ 42,170

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accrued Expenses
Employee related expenses	$ 9,639	$ 5,323
External research and development expenses	2,381	12,820
Intellectual property and patent related fees	1,606	4,240
Professional service expenses	640	533
Other expenses	271	359
Sublicensing expenses	38	771
Total accrued expenses	$ 14,575	$ 24,046

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property and equipment disclosures
Total property and equipment	$ 29,674	$ 25,115
Less: accumulated depreciation	(14,043)	(11,095)
Property and equipment, net	15,631	14,020
Laboratory equipment
Property and equipment disclosures
Total property and equipment	20,647	18,433
Leasehold improvements
Property and equipment disclosures
Total property and equipment	5,427	4,967
Construction-in-progress
Property and equipment disclosures
Total property and equipment	2,360	500
Computer equipment
Property and equipment disclosures
Total property and equipment	858	858
Furniture and office equipment
Property and equipment disclosures
Total property and equipment	264	239
Software
Property and equipment disclosures
Total property and equipment	$ 118	$ 118

Commitments and Contingencies -

Commitments and Contingencies - Licensor Expense Reimbursement (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Licensor Expense Reimbursement
Commitments and contingencies
Expense for prosecution and maintenance of patent rights	$ 1.8	$ 2.6	$ 9	$ 9.3

Collaboration and Profit-Shar_3

Collaboration and Profit-Sharing Agreements - Revenue Recognition (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Accounts receivable
Accounts receivable, Balance at Beginning of Period	$ 6,048
Accounts Receivable, Additions	390
Accounts Receivable, Deductions	(6,187)
Accounts receivable, Balance at End of Period	251
Contract liabilities:
Deferred Revenue, Balance at Beginning of Period	94,927
Deferred revenue, Deductions	(11,372)
Deferred Revenue, Balance at End of Period	$ 83,555

Collaboration and Profit-Shar_4

Collaboration and Profit-Sharing Agreements - Contract Assets and Liability (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Change in contract asset and contract liability balances
Amounts included in deferred revenue at the beginning of the period	$ 5,666	$ 11,372

Stock-Based Compensation - Expe

Stock-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-based compensation disclosures
Compensation expense	$ 10,012	$ 5,846	$ 35,742	$ 17,483
Research and development
Stock-based compensation disclosures
Compensation expense	4,552	2,938	12,689	8,668
General and administrative
Stock-based compensation disclosures
Compensation expense	$ 5,460	$ 2,908	$ 23,053	$ 8,815

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock and Stock Options (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Restricted Stock
Changes in unvested restricted stock
Unvested restricted shares, beginning of period (in shares)	507,450
Issued (in shares)	614,775
Vested (in shares)	(191,075)
Forfeited (in shares)	(180,694)
Unvested restricted shares, end of period(in shares)	750,456	507,450
Weighted Average Grant Date Fair Value
Balance, beginning of period | $ / shares	$ 27.35
Issued (in dollars per share) | $ / shares	48.12
Vested (in dollars per share) | $ / shares	31.08
Forfeited (in dollars per share) | $ / shares	38.70
Balance, ending of period | $ / shares	$ 41.33	$ 27.35
Unrecognized stock-based compensation expense | $	$ 18,700
Period for recognition	2 years 1 month 6 days
Performance based awards
Changes in unvested restricted stock
Issued (in shares)	226,747
Stock options
Weighted Average Grant Date Fair Value
Unrecognized stock-based compensation expense | $	$ 33,300
Period for recognition	2 years 6 months
Changes in unvested stock options
Outstanding, beginning of period (in shares)	3,912,257
Granted (in shares)	1,206,841
Exercised (in shares)	(1,218,120)
Cancelled (in shares)	(817,563)
Outstanding, end of period (in shares)	3,083,415	3,912,257
Exercisable (in shares)	1,318,174
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 27.26
Granted (in dollars per share) | $ / shares	45.58
Exercised (in dollars per share) | $ / shares	25.50
Cancelled (in dollars per share) | $ / shares	30.83
Outstanding, end of period (in dollars per share) | $ / shares	34.18	$ 27.26
Exercisable (in dollar per share) | $ / shares	$ 28.58
Remaining contractual life	7 years 9 months 18 days	7 years 10 months 24 days
Exercisable, remaining contractual life	7 years
Aggregate intrinsic value | $	$ 28,399	$ 167,640
Exercisable, aggregated intrinsic value | $	$ 17,411
Stock options | Chief Executive Officer | Vesting Provision One
Changes in unvested stock options
Granted (in shares)	196,637
Stock options | Chief Executive Officer | Vesting Provision Two
Changes in unvested stock options
Granted (in shares)	341,978

Net Income (Loss) per Share - B

Net Income (Loss) per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Net Income (Loss) per share
Net (loss) income	$ (39,082)	$ (55,256)	$ (56,728)	$ 7,819	$ (23,572)	$ (37,724)	$ (151,066)	$ (53,477)
Weighted-average common shares outstanding, basic (in shares)	68,219,742			62,144,118			67,371,246	57,377,581
Weighted-average common shares outstanding, diluted (in shares)	68,219,742			62,697,173			67,371,246	57,377,581
Net (loss) income per share, basic (in dollars per share)	$ (0.57)			$ 0.13			$ (2.24)	$ (0.93)
Net (loss) income per share, diluted (in dollars per share)	$ (0.57)			$ 0.12			$ (2.24)	$ (0.93)
Stock options
Net Income (Loss) per share
Dilutive effect				414,640
Restricted Stock
Net Income (Loss) per share
Dilutive effect				138,415

Net Loss per Share - Anti-dilut

Net Loss per Share - Anti-dilutive (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Potentially dilutive securities
Anti-dilutive common stock equivalent shares	3,833,871	3,997,614	3,833,871	4,550,669
Restricted Stock
Potentially dilutive securities
Anti-dilutive common stock equivalent shares	750,456	371,463	750,456	509,878
Stock options
Potentially dilutive securities
Anti-dilutive common stock equivalent shares	3,083,415	3,626,151	3,083,415	4,040,791