Editas Medicine (EDIT) 10-K 24 Feb 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 14, 2022	Jun. 30, 2021
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,147,336,173
Entity Common Stock, Shares Outstanding		68,518,971
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Boston, Massachusetts
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0001650664
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 203,519	$ 139,682
Marketable securities	296,326	262,428
Accounts receivable	267	6,048
Prepaid expenses and other current assets	7,198	10,929
Total current assets	507,310	419,087
Marketable securities	120,071	109,664
Property and equipment, net	17,118	14,020
Right-of-use assets	26,173	25,128
Restricted cash and other non-current assets	6,811	4,703
Total assets	677,483	572,602
Current liabilities:
Accounts payable	5,050	6,408
Accrued expenses	20,192	24,046
Deferred revenue, current	11,333	20,943
Operating lease liabilities	10,309	6,811
Total current liabilities	46,884	58,208
Operating lease liabilities, net of current portion	16,069	19,324
Deferred revenue, net of current portion	60,888	73,984
Other non-current liabilities		27,500
Total liabilities	123,841	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; 68,489,257 and 62,689,457 shares issued, and 68,435,257 and 62,563,457 shares outstanding at December 31, 2021 and December 31, 2020, respectively	7	6
Additional paid-in capital	1,411,827	1,058,823
Accumulated other comprehensive loss	(493)	(46)
Accumulated deficit	(857,699)	(665,197)
Total stockholders' equity	553,642	393,586
Total liabilities and stockholders' equity	$ 677,483	$ 572,602

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
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	68,489,257	62,689,457
Common stock, shares outstanding	68,435,257	62,563,457

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Consolidated Statements of Operations
Collaboration and other research and development revenues	$ 25,544	$ 90,732	$ 20,531
Revenue type	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember
Operating expenses:
Research and development	$ 142,507	$ 157,996	$ 96,898
General and administrative	76,183	67,576	64,555
Total operating expenses	218,690	225,572	161,453
Operating loss	(193,146)	(134,840)	(140,922)
Other income, net:
Other (expense) income, net	(1,698)	16,259	(137)
Interest income, net	2,342	2,605	7,313
Total other income, net	644	18,864	7,176
Net loss	(192,502)	(115,976)	(133,746)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss, basic	(192,502)	(115,976)	(133,746)
Net loss, diluted	$ (191,499)	$ (115,976)	$ (133,746)
Net loss per share, basic (in dollars per share)	$ (2.85)	$ (1.98)	$ (2.68)
Net loss per share, diluted (in dollars per share)	$ (2.83)	$ (1.98)	$ (2.68)
Weighted-average common shares outstanding, basic (in shares)	67,619,388	58,609,389	49,983,329
Weighted-average common shares outstanding, diluted (in shares)	67,619,388	58,609,389	49,983,329

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Consolidated Statements of Comprehensive Loss
Net loss	$ (192,502)	$ (115,976)	$ (133,746)
Other comprehensive loss:
Unrealized (loss) gain on marketable debt securities	(447)	(153)	136
Comprehensive loss	$ (192,949)	$ (116,129)	$ (133,610)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common StockAt The Market Offering	Common Stock	Additional Paid-In CapitalAt The Market Offering	Additional Paid-In Capital	Accumulated DeficitCumulative effect adjustment for adoption of new accounting guidance	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Cumulative effect adjustment for adoption of new accounting guidance	At The Market Offering	Total
Balance, beginning of period at Dec. 31, 2018		$ 5		$ 652,464		$ (416,278)	$ (29)			$ 236,162
Balance, beginning of period (in shares) at Dec. 31, 2018		48,758,951
Statement of Stockholders' Equity (Deficit)
Issuance of common stock, net of issuance costs			$ 116,356						$ 116,356
Issuance of common stock, net of issuance costs (in shares)	4,341,428
Exercise of stock options				14,863						14,863
Exercise of stock options (in shares)		1,120,186
Stock-based compensation expense				27,243						27,243
Vesting of restricted common stock awards (in shares)		99,919
Purchase of common stock under benefit plans				620						620
Purchase of common stock under benefit plans (in shares)		35,314
Unrealized gain (loss) on marketable debt securities							136			136
Net loss						(133,746)				(133,746)
Balance, end of period at Dec. 31, 2019		$ 5		811,546	$ 803	(549,221)	107	$ 803		262,437
Balance, end of period (in shares) at Dec. 31, 2019		54,355,798
Statement of Stockholders' Equity (Deficit)
Issuance of common stock, net of issuance costs		$ 1		203,725						203,726
Issuance of common stock, net of issuance costs (in shares)		6,900,000
Exercise of stock options				19,500						19,500
Exercise of stock options (in shares)		964,412
Stock-based compensation expense				23,156						23,156
Vesting of restricted common stock awards (in shares)		304,638
Purchase of common stock under benefit plans				896						896
Purchase of common stock under benefit plans (in shares)		38,609
Unrealized gain (loss) on marketable debt securities							(153)			(153)
Net loss						(115,976)				(115,976)
Balance, end of period at Dec. 31, 2020		$ 6		1,058,823		(665,197)	(46)			393,586
Balance, end of period (in shares) at Dec. 31, 2020		62,563,457
Statement of Stockholders' Equity (Deficit)
Issuance of common stock, net of issuance costs		$ 1		249,458						249,459
Issuance of common stock, net of issuance costs (in shares)		4,025,000							0
Issuance of common stock for repayment of notes payable				27,500						27,500
Issuance of common stock for repayment of notes payable (in shares)		303,599
Exercise of stock options				31,495						31,495
Exercise of stock options (in shares)		1,233,958
Stock-based compensation expense				43,399						43,399
Vesting of restricted common stock awards (in shares)		267,268
Purchase of common stock under benefit plans				1,152						1,152
Purchase of common stock under benefit plans (in shares)		41,975
Unrealized gain (loss) on marketable debt securities							(447)			(447)
Net loss						(192,502)				(192,502)
Balance, end of period at Dec. 31, 2021		$ 7		$ 1,411,827		$ (857,699)	$ (493)			$ 553,642
Balance, end of period (in shares) at Dec. 31, 2021		68,435,257

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock issuance costs	$ 0.3	$ 0.1
At The Market Offering
Stock issuance costs			$ 0.2

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flow from operating activities
Net loss	$ (192,502)	$ (115,976)	$ (133,746)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	43,399	23,156	27,243
Depreciation	5,053	3,959	2,830
Realized gain on corporate equity securities		(16,366)
Non-cash research and development expenses		27,500
Other non-cash items, net	1,657	104	(2,928)
Changes in operating assets and liabilities:
Accounts receivable	5,781	(5,630)	(388)
Prepaid expenses and other current assets	3,731	(4,643)	(495)
Right-of-use assets	9,691	3,633	(9,300)
Other non-current assets	(2,108)	(719)	(15)
Accounts payable	(1,139)	855	274
Accrued expenses	(4,166)	1,707	9,485
Deferred revenue	(22,706)	(91,794)	55,395
Operating lease liabilities	(10,494)	(2,946)	9,324
Other current and non-current liabilities		(2,683)	1,652
Net cash used in operating activities	(163,803)	(179,843)	(40,669)
Cash flow from investing activities
Purchases of property and equipment	(7,977)	(7,162)	(6,167)
Proceeds from the sale of equipment		12	102
Purchases of marketable securities	(408,891)	(458,404)	(342,183)
Proceeds from maturities of marketable securities	362,402	305,000	360,500
Proceeds from sale of corporate equity securities		20,032
Net cash (used in) provided by investing activities	(54,466)	(140,522)	12,252
Cash flow from financing activities
Proceeds from offering of common stock, net of issuance costs	249,459	203,726	116,341
Proceeds from exercise of stock options	31,495	19,501	14,863
Issuance of common stock under benefit plans	1,152	895	620
Net cash provided by financing activities	282,106	224,122	131,824
Net increase (decrease) in cash, cash equivalents, and restricted cash	63,837	(96,243)	103,407
Cash, cash equivalents, and restricted cash, beginning of period	143,559	239,802	136,395
Cash, cash equivalents, and restricted cash, end of period	207,396	143,559	239,802
Supplemental disclosure of cash and non-cash activities:
Fixed asset additions included in accounts payable and accrued expenses	749	656	728
Cash paid in connection with operating lease liabilities	13,094	9,760	5,970
Offering costs included in accounts payable and accrued expenses			15
Right-of-use assets obtained in exchange of operating lease obligations	$ 10,736		$ 19,461
Issuance of common stock for settlement of success payments (see Note 8)		$ 27,500

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 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”). 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 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. ​ 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 December 31, 2021 the Company has not sold any shares of its common stock under the ATM Facility. ​ The Company has incurred annual net operating losses in every year since its inception. The Company has an accumulated deficit of $857.7 million at December 31, 2021. The Company expects that its existing cash, cash equivalents and marketable securities on December 31, 2021 will enable it to fund its operating expenses and capital expenditure requirements through 2023.The Company 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	12 Months Ended
	Dec. 31, 2021
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Principles of Consolidation The accompanying consolidated financial statements include the accounts of Editas Medicine, Inc. and its wholly owned subsidiary, Editas Securities Corporation, which is a Delaware subsidiary created to buy, sell and hold securities. All intercompany transactions and balances have been eliminated. Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, stock-based compensation expense, the accrual for research and development expenses, valuations of in-process research and development assets and deferred tax valuation allowances. The Company bases its estimates on historical experience and other market-specific or relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. Fair Value of Financial Instruments ASC Topic 820, Fair Value Measurement ASC 820 identifies fair value as the exchange price representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: ● Level 1 – Quoted market prices in active markets for identical assets or liabilities. ● Level 2 – Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates, and yield curves. ● Level 3 – Unobservable inputs developed using estimates of assumptions developed by the Company, which reflect those that a market participant would use. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, restricted cash, marketable securities, accounts receivable, prepaid expenses and other current assets, accounts payable, accrued expenses, and other current liabilities approximate their fair values, due to their short-term nature. Cash, Cash Equivalents, and Restricted Cash The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include cash held in banks and amounts held in money market funds. The Company has restricted cash of $3.9 million held as collateral for the Company’s office and lab facilities and credit card program. The restricted funds are maintained in a traditional bank account. The following table presents cash, cash equivalents, and restricted cash as reported on the consolidated balance sheets that equal the total amounts on the consolidated statements of cash flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2021 ​ 2020 Cash and cash equivalents ​ $ 619,916 ​ $ 511,774 Restricted cash included in "Restricted cash and other non-current assets" ​ ​ 3,877 ​ ​ 3,877 Total cash, cash equivalents, and restricted cash ​ $ 623,793 ​ $ 515,651 ​ Marketable Securities The Company classifies marketable securities with a remaining maturity when purchased of greater than three months and less than one year from the balance sheet date as current. Marketable securities are classified as long-term assets on the consolidated balance sheets if the contractual maturity exceeds one year and the Company does not intend to utilize the marketable securities to fund current operations. As of December 31, 2021, the Company’s marketable securities consisted of investments in available-for-sale debt securities. Available-for-sale debt securities are carried at fair value with the unrealized gains and losses included in other comprehensive loss as a component of stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the of the underlying security. Realized gains and losses are included in other income (expense). At each reporting date, the Company records an allowance for credit losses and reports it as credit loss expense which is included in “Other income (expense), net” in the Company’s consolidated statement of operations. The estimate for credit losses includes a measure of the expected risk of credit loss even if the risk is remote. When assessing financial assets for credit losses, the Company pools financial assets with similar risk characteristics and performs a collective evaluation. A credit loss on an available-for-sale debt security is limited to the difference in fair value and the amortized cost. A previously recognized credit loss may be increased or decreased in subsequent periods if the Company’s estimate of fair value changes. To determine whether to record a credit loss, the Company considers issuer or vendor specific credit ratings and historical losses as well as current economic conditions and its expectations for future economic conditions. To date, the Company has not had any credit losses, and the Company did not have an allowance for credit losses as of December 31, 2021 and 2020. During 2020, the Company’s marketable securities also included corporate equity securities. The Company classified investments in equity securities that had a readily determinable fair value as marketable securities in the Company’s consolidated balance sheets. The fair value of these securities were based on a quoted price for an identical equity security. If the equity security had a restriction that was determined to be an attribute of the security that would transfer to a market participant, the fair value of the security was measured based on the quoted price for an otherwise identical unrestricted equity security, adjusted for the effect of the restriction. The adjustment reflects the discount that a market participant would demand for the risk relating to the inability to dispose of the security for a specified period of time. The Company recorded changes in the fair value of its equity securities in “Other income (expense), net” in the Company’s consolidated statement of operations. Accounts Receivable The Company makes judgments as to its ability to collect outstanding receivables and provides an allowance for receivables when collection becomes doubtful. The Company's receivables primarily relate to amounts reimbursed under its collaboration agreements. The Company believes that credit risk associated with its collaborations partners is not significant. To date, the Company has not had any write-offs of bad debt, and the Company did not have an allowance for doubtful accounts as of December 31, 2021 and 2020. Concentrations of Credit Risk and Off-Balance Sheet Risk The Company has no financial instruments with off-balance sheet risk such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Financial instruments that potentially subject the Company to a concentration of credit risk are cash, cash equivalents, marketable securities and receivables owed to the Company from collaboration partners. The Company’s cash, cash equivalents and marketable securities are held in accounts at a financial institution that may exceed federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. Property and Equipment Property and equipment consists of computers, laboratory equipment, furniture and office equipment, and leasehold improvements and is stated at cost, less accumulated depreciation. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred, while costs of major additions and betterments are capitalized. Depreciation is calculated over the estimated useful lives of the assets using the straight-line method. The Company capitalizes laboratory equipment used for research and development if it has alternative future use in research and development or otherwise. ​ ​ ​ ​ ​ Asset: Estimated Useful life Lab equipment 5 years ​ Computer equipment and software 3 years ​ Furniture and equipment 5 years ​ Leasehold improvements Shorter of useful life or remaining lease term ​ ​ Impairment of Long-lived Assets The Company evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book values of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book values of the assets exceed their fair value. The Company has not recognized any impairment losses from inception through December 31, 2021. Profit-Sharing Arrangements The Company considers the nature and contractual terms of the arrangements and assesses whether such arrangements involve a joint operating activity pursuant to which the Company is an active participant and is exposed to significant risks and rewards with respect to such arrangement. If the Company is an active participant and is exposed to significant risks and rewards with respect to such arrangement, the Company accounts for such arrangement as a collaboration under ASC Topic 808, Collaborative Arrangements Payments received from a collaboration partner to which this policy applies are recorded as contra-expense in the applicable period and may include development costs or patent expense reimbursements. The Company classifies payments made under the cost sharing provisions of such arrangements as a component of research and development expenses to reflect the joint risk sharing nature of such profit-sharing arrangements. The Company classifies payments owed or receivables recorded as other current liabilities or prepaid expenses and other current assets, respectively, in the Company’s consolidated balance sheets. The Company had one agreement that was accounted for in accordance with ASC 808 prior to the termination of the arrangement during the year ended 2020. The arrangements and payments are described more fully in Note 9. Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer. The promised goods or services in the Company’s arrangements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. The Company provides options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised good or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract. The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. The Company’s contracts often include development and regulatory milestone payments that are as assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration and other research and development revenues in the period of adjustment. For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of the Company’s collaboration or strategic alliance arrangements. The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation. The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. ​ ​ Research and Development Expenses Research and development expenses are charged to expense as incurred in performing research and development activities. The costs include employee-related expenses including salaries, benefits, and stock-based compensation expense, costs of funding research performed by third parties that conduct research and development and preclinical and clinical activities on the Company’s behalf, the cost of purchasing lab supplies and non-capital equipment used in preclinical and clinical activities and in manufacturing preclinical and clinical study materials, consultant fees, facility costs including rent, depreciation, and maintenance expenses, and fees for acquiring and maintaining licenses under third party licensing agreements which are typically expensed when incurred if the technology licensed has no alternate future uses, including any sublicensing or success payments made to the Company’s licensors. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the Company’s estimate, the accrual or prepaid is adjusted accordingly. The Company defers and capitalizes non-refundable advance payments made by the Company for research and development activities until the related goods are received or the related services are performed. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. In-process Research and Development Assets In-process research and development assets that are acquired in a transaction that does not qualify as a business combination under GAAP and that do not have an alternative future use are expensed in the period in which the assets are acquired. Patent Costs The Company expenses patent and patent application costs and related legal costs for the prosecution and maintenance of such patents and patent applications, including patents and patent applications the Company in-licenses, as incurred, and classifies such costs as general and administrative expenses in the accompanying consolidated statements of operations. Leases The Company accounts for leases in accordance with ASC 842. At the inception of an arrangement the Company determines whether the arrangement contains a lease. If a lease is identified in an arrangement, the Company recognizes a right-of-use asset and liability on its balance sheet and determines whether the lease should be classified as a finance or operating lease. The Company does not recognize assets or liabilities for leases with lease terms of less than 12 months. Lease payments for short-term leases are recorded to operating expense on a straight-line basis over the lease term and variable lease payments are recorded in the period in which the obligation for those payments is incurred. A lease qualifies as a finance lease if any of the following criteria are met at the inception of the lease: (i) there is a transfer of ownership of the leased asset to the Company by the end of the lease term, (ii) the Company holds an option to purchase the leased asset that it is reasonably certain to exercise, (iii) the lease term is for a major part of the remaining economic life of the leased asset, (iv) the present value of the sum of lease payments equals or exceeds substantially all of the fair value of the leased asset, and (v) the nature of the leased asset is specialized to the point that it is expected to provide the lessor no alternative use at the end of the lease term. All other leases are recorded as operating leases. Finance and operating lease assets and liabilities are recognized at the lease commencement date based on the present value of the lease payments over the lease term using the discount rate implicit in the lease. If the rate is not readily determinable, the Company utilizes its incremental borrowing rate at the lease commencement date. Operating lease assets are further adjusted for prepaid or accrued lease payments. Operating lease payments are expensed using the straight-line method as an operating expense over the lease term. Finance lease assets are amortized to depreciation expense using the straight-line method over the shorter of the useful life of the related asset or the lease term. Finance lease payments are bifurcated into (i) a portion that is recorded as imputed interest expense and (ii) a portion that reduces the finance liability associated with the lease. The Company does not separate lease and non-lease components when determining which lease payments to include in the calculation of its lease assets and liabilities. Variable lease payments are expensed as incurred. If a lease includes an option to extend or terminate the lease, the Company reflects the option in the lease term if it is reasonably certain it will exercise the option. Stock-based Compensation Expense The Company accounts for all stock-based awards granted to employees and non-employees as stock-based compensation expense at fair value in accordance with FASB ASC Topic 718 Compensation—Stock Compensation (“ASC 718”). The Company estimates the grant date fair value of restricted stock based on the market value of the Company’s common stock on the date of the grant. The Company estimates the grant date fair value of each option award using the Black-Scholes option-pricing model. The Black-Scholes option pricing model requires the input of certain subjective assumptions, including (1) the expected stock price volatility, (2) the calculation of expected term of the award, (3) the risk-free interest rate, and (4) the expected dividend yield. Because there had been no public market for the Company’s common stock prior to its initial public offering, there was a lack of company-specific historical and implied volatility data. Accordingly, the Company based its estimates of expected volatility on the historical volatility of a group of similar companies that are publicly traded. The Company calculates historical volatility based on a period of time commensurate with the expected term. The Company computes expected volatility based on the historical volatility of a representative group of companies with similar characteristics to the Company, including their stages of product development and focus on the life science industry. The Company uses the simplified method as prescribed by the Securities and Exchange Commission’s Staff Accounting Bulletin No. 107, Share-Based Payment, to calculate the expected term for options granted to employees as the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. For options granted to non-employees, the Company utilizes the contractual term of the arrangement as the basis for the expected term. The Company determines the risk-free interest rate based on a treasury instrument whose term is consistent with the expected term of the stock options. The Company uses an assumed dividend yield of zero as the Company has never paid dividends and does not have current plans to pay any dividends on its common stock. Restricted stock awards (“RSAs”) are subject to repurchase rights. Accordingly, the Company has recorded the proceeds from the issuance of RSAs as a liability in the consolidated balance sheets. The restricted stock liability is reclassified into stockholders’ equity as the restricted stock vests. ​ Service-Based Awards For stock-based awards issued to employees, non-employee service providers and members of the Company’s board of directors (the “Board”), the Company recognizes the grant date fair value of the service-based options, RSAs or restricted stock unit awards (“RSUs”) on a straight-line basis over the requisite service period, which is generally the vesting period of the respective award. If an employee or non-employee service requirement is concluded to be non-substantive, the stock-based compensation expense would be expensed immediately. Market-Based Awards For market-based awards, the Company recognizes the grant date fair value of the market-based options over the earlier of the derived service period, pursuant to a Monte-Carlo simulation model, or when the market-based vesting conditions are met. The Company estimates an award's derived service period based on the best estimate of the period over which an award's vesting condition(s) will be achieved. If the market-based vesting conditions are met ahead of the derived service period, the expense will be accelerated. If the market-based vesting conditions are not met and the market-based award is cancelled, the expense will not be reversed unless the market-based award is forfeited. Performance-Based Awards For performance-based awards, the Company recognizes the grant date fair value of the performance-based options or RSUs over the requisite service period using the accelerated attribution method to the extent achievement of the performance condition is probable. Certain awards are subject to both performance and continued service conditions. ​ The Company classifies stock-based compensation expense in its consolidated statement of operations and comprehensive loss in the same manner in which the award recipient’s salary or service payments are classified. Forfeitures are recorded as they occur. If factors change or different assumptions are used, the Company’s stock-based compensation expense could be materially different in the future Success Payments, Research Funding Payments and Notes Payables Income taxes Income taxes are recorded in accordance with ASC Topic 740, Income Taxes The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. The Company assesses the impact of various tax reform proposals and modifications to existing tax treaties in all jurisdictions where they have operations to determine the potential effect on the Company’s business and any assumptions they have made about their future taxable income. The Company cannot predict whether any specific proposals will be enacted, the terms of any such proposals or what effect, if any, such proposals would have on the Company if they were to be enacted. Beginning in 2022, the Tax Cut and Jobs Act of 2017 eliminates the currently available option to deduct research and development expenditures and requires taxpayers to amortize them over five years. The U.S. Congress is considering legislation that would defer the amortization requirement to future periods, however, the Company has no assurance that the provision will be repealed or otherwise modified. Comprehensive Loss Comprehensive loss currently consists of net loss and changes in unrealized gains and losses on marketable securities. Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker in deciding how to allocate resources and assess performance. The Company and the Company’s chief operating decision maker, the Company’s Chief Executive Officer, view the Company’s operations and manage the Company’s business as a single operating segment, which is the business of developing and commercializing genome editing technology. ​

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 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 December 31, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ for Credit ​ ​ Unrealized ​ Unrealized ​ Fair December 31, 2021 ​ Cost ​ Losses ​ ​ Gains ​ Losses ​ Value Cash equivalents and marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 203,519 ​ $ — ​ ​ $ — ​ $ — ​ $ 203,519 U.S. Treasuries ​ ​ 124,016 ​ ​ — ​ ​ ​ 1 ​ ​ (84) ​ ​ 123,933 Government agency securities ​ ​ 126,927 ​ ​ — ​ ​ ​ — ​ ​ (228) ​ ​ 126,699 Commercial paper ​ ​ 89,699 ​ ​ — ​ ​ ​ 1 ​ ​ (13) ​ ​ 89,687 Corporate notes/bonds ​ ​ 76,248 ​ ​ — ​ ​ ​ — ​ ​ (170) ​ ​ 76,078 Total ​ $ 620,409 ​ $ — ​ ​ $ 2 ​ $ (495) ​ $ 619,916 ​ 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 ​ ​ — ​ ​ ​ 10 ​ ​ (8) ​ ​ 41,914 Corporate notes/bonds ​ ​ 42,185 ​ ​ — ​ ​ ​ — ​ ​ (25) ​ ​ 42,160 Total ​ $ 511,820 ​ $ — ​ ​ $ 18 ​ $ (64) ​ $ 511,774 ​ As of December 31, 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 December 31, 2021, the Company holds 51 securities with an aggregate fair value of $120.1 million that had remaining maturities between one and two years .

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Measurements
Fair Value Measurements	4. Fair Value Measurements Assets measured at fair value on a recurring basis as of December 31, 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted Prices Significant ​ ​ ​ ​ ​ ​ ​ in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ ​ December 31, ​ Identical Assets ​ Inputs ​ Inputs Financial Assets ​ 2021 ​ (Level 1) ​ (Level 2) ​ (Level 3) Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 203,519 ​ $ 203,519 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasuries ​ ​ 123,933 ​ ​ 123,933 ​ ​ — ​ ​ — Government agency securities ​ ​ 126,699 ​ ​ — ​ ​ 126,699 ​ ​ — Commercial paper ​ ​ 89,687 ​ ​ — ​ ​ 89,687 ​ ​ — Corporate bonds ​ ​ 76,078 ​ ​ — ​ ​ 76,078 ​ ​ — Restricted cash and other non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ ​ 3,877 ​ ​ 3,877 ​ ​ — ​ ​ — Total financial assets ​ $ 623,793 ​ $ 331,329 ​ $ 292,464 ​ $ — ​ 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 ​ $ — ​ During the year ended December 31, 2020, the Company held an investment in Beam Therapeutics Inc. (“Beam Therapeutics”) consisting of shares of Beam Therapeutics’ common stock. Prior to Beam Therapeutics’ initial public offering in February 2020, the Company valued such investment based on the cost of the equity securities adjusted for any observable market transactions. Following the initial public offering, the equity securities had a readily determinable fair value, and were included in marketable securities on the consolidated balance sheet. The Company sold this investment in October 2020, resulting in a realized gain of $16.4 million recorded in other income (expense), net on the consolidated statements of operations.

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2021
Property and Equipment, net
Property and Equipment, net	5. Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ December 31, ​ December 31, ​ 2021 2020 Laboratory equipment ​ $ 21,579 ​ $ 18,433 ​ Leasehold improvements ​ ​ 8,162 ​ ​ 4,967 ​ Construction-in-progress ​ 1,529 ​ 858 ​ Computer equipment ​ ​ 876 ​ ​ 500 ​ Furniture and office equipment ​ ​ 264 ​ ​ 239 ​ Software ​ 215 ​ 118 ​ Total property and equipment ​ 32,625 ​ 25,115 ​ Less: accumulated depreciation ​ (15,507) ​ (11,095) ​ Property and equipment, net ​ $ 17,118 ​ $ 14,020 ​ ​ The Company recorded $5.1 million, $4.0 million, and $2.8 million in depreciation expense during the years ended December 31, 2021, 2020 and 2019, respectively.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2021
Accrued Expenses
Accrued Expenses	6. Accrued Expenses Accrued expenses consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ December 31, ​ 2021 2020 Employee related expenses ​ $ 10,159 ​ $ 5,323 External research and development expenses ​ ​ 5,614 ​ ​ 12,820 Professional service expenses ​ ​ 2,345 ​ ​ 533 Intellectual property and patent related fees ​ ​ 1,408 ​ ​ 4,240 Other expenses ​ ​ 666 ​ ​ 1,130 Total accrued expenses ​ $ 20,192 ​ $ 24,046 ​

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases
Leases	​ 7. Leases ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ December 31, ​ December 31, ​ 2021 2020 Right-of-use assets $ 26,173 ​ $ 25,128 Operating lease liabilities, current $ (10,309) ​ $ (6,811) Operating lease liabilities, noncurrent $ (16,069) ​ $ (19,324) ​ ​ ​ ​ ​ ​ ​ ​ Year Ended Maturity of lease liabilities: ​ December 31, 2021 2022 $ 12,021 2023 $ 11,932 2024 $ 4,510 2025 $ 506 2026 $ 110 Thereafter $ — Total minimum lease payments $ 29,079 Less: imputed interest $ (2,751) Total operating lease liabilities at December 31, 2021 $ 26,328 ​ ​ Hurley Street In 2016, the Company entered into a lease agreement for 59,783 square feet of office and laboratory space located on Hurley Street in Cambridge, Massachusetts. The term of the lease began on October 1, 2016 and continues until October 2023. In connection with the lease and as a security deposit, the Company deposited with the landlord a letter of credit in the amount of approximately $1.6 million. Subject to the terms of the lease and certain reduction requirements specified therein, the $1.6 million security deposit may decrease over time. The letter of credit, which is collateralized by the Company, is recorded in restricted cash and other non-current assets in the accompanying consolidated balance sheets as of December 31, 2021 and December 31, 2020. ​ One Main Street ​ ​

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies
Commitments and Contingencies	8. Commitments and Contingencies The Company is a party to a number of license agreements under which the Company licenses patents, patent applications and other intellectual property from third parties. As such, the Company is obligated to reimburse licensors for various costs including upfront licenses fees, annual license fees, certain licensor expense reimbursements, success payments, research funding payments, and milestones triggerable upon certain development, regulatory, and commercial events as well as royalties on future products. These contracts are generally cancellable, with notice, at the Company’s option and do not have significant cancellation penalties. Broad Sponsored Research Agreement In 2018, the Company entered into a sponsored research agreement (the “Sponsored Research Agreement”) with The Broad Institute, Inc. (“Broad”). The Sponsored Research Agreement provides for Broad to conduct research useful or relevant to genome editing in the field of genomic medicines for the prevention or treatment of human disease with funding from the Company. Under the Sponsored Research Agreement, Broad granted to the Company an exclusive right of first negotiation for licenses from Broad with respect to patentable inventions developed by Broad in the course of the sponsored research, subject to certain limitations and retained rights (“Sponsored Invention Licenses”). Under the Sponsored Research Agreement, the Company is obligated to make payments (“Market Cap Research Funding”) in the event the Company’s market capitalization reaches certain amounts for a specified period of time. Unless the Company has undergone a change in control, Market Cap Research Funding is payable by the Company in cash, in shares of common stock, or in the form of promissory notes, which may be settled in shares of common stock at the election of the Company. In aggregate, the Company has triggered $25.0 million in Market Cap Research Funding and has primarily settled these amounts through the issuance of shares of its common stock. The remaining $100.0 million in Market Cap Research Funding may be triggered when the Company’s market capitalization reaches various low-ten to eleven dollar amounts or in the event of a Company sale. The Company is not required to make additional Market Cap Research Funding payments if the Company, whether directly or through its affiliates or sublicensees, is not researching, developing, or commercializing products based on or incorporating inventions exclusively licensed to the Company from Broad subject to certain exclusions. The Sponsored Research Agreement is terminable by each party upon the occurrence of specified bankruptcy events of the other party and otherwise will continue in effect until the remaining Market Cap Research Funding payments are received by Broad and such time as the Company has no further rights of first negotiation for Sponsored Invention Licenses, unless otherwise mutually agreed between the parties. Broad & Harvard License Agreements that the Company is not, directly or through any of its affiliates, sublicensees, or collaborators, researching, developing, or commercializing a product directed toward the same gene target, or can demonstrate to Broad’s and/or Harvard’s, as applicable, reasonable satisfaction that the Company is interested in researching, developing, and commercializing a product directed toward the same gene target, that the Company has a commercially reasonable research, development, and commercialization plan to do so, and the Company commences and continues reasonable commercial efforts under such plan Milestones Royalties ​ Licensor Expense Reimbursements The Company is obligated to reimburse to Broad and 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 $10.6 million, $13.1 million, and $13.5 million in expense during the years ended December 31, 2021, 2020 and 2019, respectively, for such reimbursement. Success Payments Under the Cpf1 License Agreement and Cas9-II License Agreement, the Company is obligated to make payments (“Success Payments”) in the event the Company’s market capitalization reaches certain thresholds for a specified period of time, or in the event of a change in control of the Company, if the consideration is in excess of those thresholds. Unless the Company has undergone a change in control, Success Payments are payable by the Company in cash or in the form of promissory notes, which may be settled in shares of common stock at the election of the Company. In the event of a change in control of the Company, the Success Payments are required to be paid in cash. The Success Payments under the Cpf1 License Agreement are triggered when the Company’s market capitalization reaches certain amounts ranging from $750.0 million to $10.0 billion for a specified period of time. The Success Payments under the Cas9-II License Agreement are triggered when the Company’s market capitalization reaches certain amounts ranging from $1.0 billion to $9.0 billion for a specified period of time. In aggregate, the Company has triggered $25.0 million and $7.5 million of Success Payments under the Cpf1 License Agreement and Cas9-II License Agreement, respectively. The Company has primarily settled these amounts through the issuance of shares of its common stock. The remaining $100.0 million and $22.5 million in Success Payments under the Cpf1 License Agreement and Cas9-II License Agreement, respectively are only payable if the market capitalization threshold are met and the Company or any affiliate or sublicensee has at least one product candidate covered by a claim of a patent right licensed to the Company that is or was subject of a clinical trial. Other Payments Litigation The Company is not a party to any litigation and did not have contingency reserves established for any litigation liabilities as of December 31, 2021 or 2020.

Collaboration Agreements

Collaboration Agreements	12 Months Ended
	Dec. 31, 2021
Collaboration Agreements
Collaboration Agreements	9. Collaboration Agreements Collaboration Revenue ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, 2021 Balance at December 31, 2020 ​ Additions ​ Deductions ​ Balance at December 31, 2021 Accounts receivable $ 6,048 ​ $ 406 ​ $ (6,187) ​ $ 267 Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue $ 94,927 ​ $ — ​ $ (22,706) ​ $ 72,221 ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Year Ended Revenue recognized in the period from: December 31, 2021 Amounts included in deferred revenue at the beginning of the period $ 11,334 ​ $ 22,706 Performance obligations satisfied in previous periods $ — ​ $ — ​ Juno Therapeutics Collaboration Agreemen t In 2019, the Company entered into an amended and restated collaboration agreement (“Juno Collaboration Agreement”) and license agreement (“Juno License Agreement”) with Juno Therapeutics to focus on the research, development, and commercialization of autologous and allogenic alpha-beta T cell medicines for the treatment of all diseases, subject to certain exceptions. The Company and Juno Therapeutics started their collaboration in 2015 and have amended the agreement twice. The Company received a $70.0 million up-front, non-refundable, non-creditable cash payment (“Amendment Fee”) in connection with the execution of the 2019 amendment. The Company may develop genome editing tools, specific to a gene target and enzyme combination (or a “Program”) that, following the exercise of its option and the Company’s grant of a license, Juno Therapeutics may use in its development of gene edited alpha-beta T-cell therapies and certain other T-cell derived from pluripotent stem cells or any other precursor cell for the treatment of all diseases, subject to certain exceptions (the “Juno Field”). To assess the Programs prior to opt-in, the Company granted Juno Therapeutics a non-exclusive perpetual research license in the Juno Field. If Juno Therapeutics exercises their option to the Program, they receive an exclusive, worldwide, development and commercialization license in the Juno Field for a nominal option exercise fee. The Juno License Agreement provided that the Company would manufacture clinical grade materials through a Phase 1 clinical trial if requested by Juno Therapeutics at an incremental cost to be negotiated by the parties. However, Juno Therapeutics has sole responsibility, at its own cost, for the worldwide research, development, manufacturing, and commercialization of its products. They must use commercially reasonable efforts and meet certain regulatory and commercial diligence requirements. The first development and commercialization license was delivered to Juno Therapeutics at the onset of the amended arrangement for which the Company received $0.5 million in consideration for the license (the “First Development and Commercialization License). ​ On a product-by-product basis, the Company is eligible to receive up to $27.5 million in development milestones and $107.5 million in regulatory milestones. The Company is also eligible to receive up to an aggregate of $60.0 million for the first two licensed products to reach certain sales milestones. The Company is entitled to a high-single digit to low double-digit percentage of royalties on net sales of licensed products, subject to reductions in certain circumstances, through the later of the expiration of the patent(s) related to the licensed products or six years post-first commercial sale of such licensed products. ​ The amended term of the Juno Collaboration Agreement is five years, which is subject to two one-year extension periods. During the term, including the extension periods, the Company may not alone, or with a third party, research, develop, manufacture, or commercialize a product in the Juno Field. Juno Therapeutics has the right to terminate the Juno Collaboration Agreement at any time upon no less than six months prior written notice. Per the termination provisions of the Juno License Agreement, Juno Therapeutics has the right to terminate the License Agreement either on a licensed product-by-product basis or in its entirety for any reason at any time upon ninety days prior written notice. If Juno Therapeutics terminates the license agreement without cause, the exclusive licenses granted to Juno Therapeutics automatically revert back to the Company. ​ Accounting Assessment ​ ​ The Company identified the following performance obligations: (i) First Development and Commercialization License and (ii) seventeen material rights for additional development and commercialization licenses for other Programs. The Company also evaluated the (i) the research license, (ii) contract term extensions, (iii) clinical supply arrangement, (iv) participation by employees on the oversight committee, alliance and technology transfer teams and (v) certain intellectual property rights and concluded that none of these met the definition of a performance obligation as a result of the promise being quantitively and qualitatively immaterial in the context of the arrangement or the promise did not convey a material right to Juno Therapeutics. The Company also concluded that there was not an implicit promise to perform research and development services. ​ As of December 31, 2021 the total transaction price was approximately $110.0 million comprised of the following: (i) $70.0 million Amendment Fee, (ii) $32.0 million in remaining deferred revenue balance that was not recognized pursuant the 2018 amendment agreement (iii) $3.0 million related to option exercise fees for delivered licenses and (iv) $5.0 million related to a development milestone payment that was received by the Company. The outstanding milestone payments and extension term fees were fully constrained as of December 31, 2021, as a result of the uncertainty of whether any of the milestones will be achieved or the term would be extended. The assessment of the constraint utilizing the most likely amount method considers the stage of development and the risks associated with the remaining development required to achieve the milestones, as well as whether the achievement of the milestone is outside the control of the Company or Juno Therapeutics. The Company has determined that any commercial milestones and sales-based royalties will be recognized when the related sales occurs. The Company reevaluates the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. ​ The Company concluded that rights and attributes of each of the development and commercialization licenses are identical for both the license granted at inception and the licenses that may be issued in the future upon exercise of the associated option. The Company has considered the early stage of the science and the uncertainty of success and concluded that the probability of scientific success and opt-in is equal amongst all Programs. In addition, each Program is multi-functional, and a combination of Programs can be utilized in the development of a product candidate. As such, the Company concluded that the standalone selling price of each material right is the same. The Company will recognize the transaction price allocated to each material right when the material right is exercised, lapsed or expired. ​ During the year ended December 31, 2021 and 2020, the Company recognized $24.7 million and $11.3 million of revenue related to Juno Therapeutics. As of December 31, 2021, the Company recorded $68.0 million of deferred revenue, of which $56.7 million is classified as long-term on our condensed consolidated balance sheet. As of December 31, 2020, the $73.7 million was classified as long-term in the accompanying consolidated balance sheets. There were no material sublicense fees paid to licensors in connection with the consideration received pursuant to the Juno Collaboration Agreement for the year ended December 31, 2021 and 2020. ​ Allergan Pharmaceuticals Strategic Alliance and Profit-Sharing Agreement In March 2017, the Company entered into a Strategic Alliance and Option Agreement with Allergan to discover, develop, and commercialize new gene editing medicines for a range of ocular disorders (the “Allergan Agreement”). Under the terms of the Allergan Agreement, the Company received a $90.0 million up-front, non-refundable, non-creditable cash payment to primarily fund the Company’s ocular research and development efforts to provide Allergan with the option to exclusively exercise the worldwide development and commercialization rights to five ocular development programs meeting certain criteria. Subsequently Allergan and the Company entered into an agreement (the “Profit-Sharing Agreement”) to equally split U.S. profit and losses of EDIT-101, an experimental medicine or leber congenital amaurosis 10 or LCA10 that was the only program licensed to Allergan under the Allergan Agreement. In August 2020, the Company and Allergan agreed to terminate the Allergan Agreement and the Profit-Sharing Agreement (together with the Allergan Agreement, the “Initial Agreements”). In connection with the termination, the Company entered into a transition services agreement with Allergan (together with the termination agreement, the ‘Termination Agreements”), primarily to facilitate the transfer of EDIT-101 back to the Company. Pursuant to the Termination Agreements, the Company regained full global rights to research, develop, manufacture, and commercialize its ocular medicines, including EDIT-101. Allergan has no further obligations pursuant to the Initial Agreements, all unexercised options and contingent payments contemplated under the Initial Agreements have terminated, which includes Allergan’s worldwide developmental and commercialization rights to EDIT-101. Under the Termination Agreements, Allergan granted the Company a non-exclusive license to certain know-how that is necessary to develop, manufacture and commercialize EDIT-101 and transferred to the Company certain materials produced under the Initial Agreements. The Company will use commercially reasonable efforts to develop and commercialize products directed at four collaboration targets, one of which is LCA10. In connection with the Termination Agreements, the Company agreed to make a $20.0 million payment to Allergan, $17.5 million of which was paid as of December 31, 2020. In addition, the Company will make certain payments on achievements of clinical and regulatory milestones up to $20.0 million for each target program and aggregated sales milestones for all products covered by the Termination Agreement up to $90.0 million. Allergan is also entitled to royalties in a low-single digit percentage, subject to reduction under specified circumstances, on net sales of specified products. The Company’s obligation to pay royalties will expire on a country-by-country and product-by-product basis upon the later of the expiration of regulatory-based exclusivity with respect to such product in such country and the tenth anniversary of the first commercial sale of such product.  Accounting Assessment The Company evaluated the Termination Agreements in accordance with the provisions ASC 606 and concluded that they resulted in a modification followed by a termination of the Initial Agreements. Upon execution of the Termination Agreements, the Company is no longer obligated to transfer control of any goods or services to Allergan, and therefore there are no remaining performance obligations. As part of this assessment, the Company considered that Allergan relinquished its right to the remaining exclusive license options under the Allergan Agreement and the Company reacquired the development and commercialization rights to EDIT-101. Allergan no longer has any involvement in the development activities of the collaboration targets. Since there are no remaining performance obligations, the Company accounted for the modification as part of the existing contract with a cumulative catch-up adjustment. The Company concluded that $5.0 million of the $20.0 million payment that was paid to Allergan was for re-acquired rights to EDIT-101 that had no alternative future use, and as such the Company recorded it as in-process research and development expenses as of December 31, 2020. The remainder of the $20.0 million payment was recorded as a reduction to the contract liability and partially offset the recognition of $77.1 million in previously deferred revenue that was received under the Initial Agreements that was recognized on the termination date. The contingent payments associated with the collaboration targets not previously licensed by Allergan under the Allergan Agreement did not impact the amount of deferred revenue recognized upon termination because it is not probable that a significant reversal of revenue will occur. The contingent milestone and royalty payments associated with EDIT-101 qualify for scope exceptions from derivative accounting, and therefore there is no accounting for the contingent payments upon termination. During the year ended December 31, 2020, the Company recognized revenue related to Allergan of approximately $70.6 million. There was no revenue recognized related to Allergan for the year ended December 31, 2021. Beam Therapeutics License Agreement In 2018, the Company entered into a license agreement with Beam Therapeutics Inc. (“Beam,” and such agreement, the “Beam License Agreement”). Pursuant to the Beam License Agreement, the Company granted to Beam a worldwide, exclusive (subject to certain exceptions), sublicensable (subject to certain conditions), development and commercialization license under certain intellectual property controlled by the Company for the use of base editing therapies for the treatment of any field of human diseases and conditions, such to certain exceptions. Additionally, the Company granted Beam a non-exclusive research license. Lastly, the Company provided to Beam with an exclusive option to obtain three development and commercialization licenses to additional groups of intellectual property owned or controlled by the Company, on a group-by-group basis, during the specified option period, subject to certain exceptions. The Company received preferred stock valued at $3.6 million and received a nominal upfront cash payment. The Company subsequently sold its equity investment in Beam following Beam’s initial public offering in 2021. The Company is also eligible to receive additional consideration if Beam exercises its option to obtain additional licenses for a fee ranging from a mid-teen million-dollar amount to a low to mid-eight-digit dollar amount per license, depending on the timing of the option exercise. To the extent that any products are commercialized, the Company would be entitled to receive tiered low single-digit royalty payments, plus any royalties that would be due from the Company to any applicable licensors related to the sale of such licensed products. Unless earlier terminated by either party pursuant to the terms of the agreement, the Beam License Agreement will continue in full force and effect and will expire on a licensed product-by-licensed product and country-by-country basis upon the expiration of the royalty term with respect to such licensed product in such country. Beam has the right, at its sole discretion, at any time to terminate the Beam License Agreement in its entirety or on a group-by-group of intellectual property basis, upon ninety days written notice to the Company. Upon termination, all rights and licenses granted by the Company will immediately terminate. Accounting Assessment The Company identified the following performance obligations (i) the research license and (ii) the initial development and commercialization license. In addition, the Company concluded that the three options for the additional development and commercialization licenses are not discounted and therefore they do not represent material rights. During the years ended December 31, 2021 and 2020, the Company recognized revenue under the Beam License Agreement of approximately $0.3 million and $0.2 million, respectively. ​

Preferred Stock

Preferred Stock	12 Months Ended
	Dec. 31, 2021
Preferred Stock
Preferred Stock	10. Preferred Stock The Company’s amended and restated certificate of incorporation authorized 5,000,000 shares of undesignated preferred stock that may be issued from time to time by the Company’s board of directors in one or more series. As of December 31, 2021

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2021
Common Stock.
Common Stock	11. Common Stock The voting, dividend, and liquidation rights of the holders of the common stock are subject to and qualified by the rights, powers, and preferences of holders of the preferred stock that may be issued from time to time. The common stock had the following characteristics as of December 31, 2021: Voting The holders of shares of common stock are entitled to one vote for each share of common stock held at any meeting of stockholders and at the time of any written action in lieu of a meeting. Dividends The holders of shares of common stock are entitled to receive dividends, if and when declared by the Company’s board of directors. Cash dividends may not be declared or paid to holders of shares of common stock until all unpaid dividends on the redeemable convertible preferred stock have been paid in accordance with their terms. No dividends have been declared or paid by the Company since its inception. 2013 Stock Incentive Plan In September 2013, the board of directors adopted the 2013 Stock Incentive Plan, which was subsequently amended (as amended, the “2013 Plan”), which provides for the grant of incentive stock options and nonqualified stock options or other awards including restricted stock awards, unrestricted stock awards, and restricted stock units to the Company’s employees, officers, directors, advisors, and consultants for the purchase of up to 1,057,692 shares of the Company’s common stock, which has been amended several times, and as of July 2015, a total of 6,317,769 shares were reserved. The terms of stock awards agreements, including vesting requirements, are determined by the board of directors and are subject to the provisions of the 2013 Plan. The stock options granted to employees generally vest over a four-year period and expire ten years from the date of grant. Certain awards contain performance based vesting criteria. There has only been one such award to date. Certain options provide for accelerated vesting in the event of a change in control, as defined in the applicable options. Awards granted to non-employee consultants generally vest monthly over a period of one 2015 Stock Incentive Plan The Company’s board of directors adopted and the Company’s stockholders approved the 2015 stock incentive plan (the “2015 Plan”). The 2015 Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards. The Company’s employees, officers, directors and consultants and advisors are eligible to receive awards under the 2015 Plan. The number of shares reserved for issuance under the 2015 Plan is subject to further increases for (a) any additional shares of the Company’s common stock subject to outstanding awards under the 2013 Plan that expire, terminate, or are otherwise surrendered, cancelled, forfeited, or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right and (b) annual increases, to be added as of the first day of each fiscal year, from January 1, 2017 until, and including, January 1, 2026, equal to the lowest of 2,923,076 shares of common stock, 4% of the number of shares of common stock outstanding on such first day of the fiscal year in question and an amount determined by the Company’s board of directors. In January 2022, the shares under the 2015 Plan were increased by 2,738,110 shares pursuant to the annual increase described in the prior sentence. 2015 Employee Stock Purchase Plan The Company’s board of directors adopted and the Company’s stockholders approved the 2015 employee stock purchase plan (the “2015 ESPP”). The number of shares reserved for issuance under the 2015 ESPP is subject to annual increases, to be added as of the first day of each fiscal year, from January 1, 2017 until, and including, January 1, 2026, in an amount equal to the least of (a) 769,230 shares of common stock, (b) 1% of the total number of shares of common stock outstanding on the first day of the applicable year, and (c) an amount determined by the board of directors. The first offering under the 2015 ESPP opened on December 1, 2017. In January 2022, the shares under the 2015 ESPP Plan were increased by 684,527 shares pursuant to the annual increase described in the prior sentence. Inducement Awards From time to time the Company’s board of directors approves inducement awards to certain employees outside of the existing equity compensation plans in connection with such employees commencing employment with the Company. Inducement awards are typically a service-based option and a restricted stock unit and are subject to the Company’s typical vesting terms and the employee’s continued service relationship with the Company through the applicable vesting dates. In June 2021, the Company’s board of directors approved two inducement grants to the Company’s recently hired Chief Scientific Officer and Chief Regulatory Officer. The inducement grant for the Chief Medical Officer, granted in November 2020, was cancelled upon her departure from the Company in February 2022. Shares Reserved for Future Issuance ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2021 2020 Shares reserved for outstanding stock option awards under the 2013 Stock Incentive Plan, as amended 145,255 174,362 Shares reserved for outstanding stock option awards and restricted stock units under the 2015 Stock Incentive Plan 3,036,797 3,839,345 Shares reserved for outstanding inducement stock option award and restricted stock units 408,765 280,000 Remaining shares reserved, but unissued, for future awards under the 2015 Stock Incentive Plan 7,524,431 5,599,450 Remaining shares reserved, but unissued, for future awards under the 2015 Employee Stock Purchase Plan 2,722,040 ​ 2,137,127 ​ ​ 13,837,288 12,030,284 ​

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2021
Stock-Based Compensation
Stock-Based Compensation	12. Stock-Based Compensation Total compensation cost recognized for all stock-based compensation awards in the consolidated statements of operations was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ ​ ​ 2021 ​ 2020 Research and development ​ ​ $ 16,553 ​ $ 11,580 General and administrative ​ ​ 26,846 ​ 11,576 Total stock-based compensation expense ​ ​ $ 43,399 ​ $ 23,156 ​ Restricted Stock and Restricted Stock Unit Awards ​ The following table summarizes restricted stock and restricted stock unit awards activity for the instruments discussed above as of December 31, 2020 and 2021 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 629,797 ​ $ 47.79 Vested (267,268) ​ $ 33.79 Forfeited ​ (241,247) ​ $ 39.29 Unvested restricted stock and restricted stock unit awards as of December 31, 2021 628,732 ​ $ 41.28 ​ The expense related to restricted stock and restricted stock unit awards granted for the years ended December 31, 2021, 2020 and 2019 was $14.6 million, $4.4 million, and $6.4 million, respectively. 2.0 years. ​ Stock Options The following is a summary of stock option activity for the year ended December 31, 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 ​ 1,299,997 ​ $ 44.85 ​ ​ ​ ​ ​ Exercised ​ (1,233,958) ​ $ 25.52 ​ ​ ​ ​ ​ Cancelled ​ (962,211) ​ $ 31.38 ​ ​ ​ ​ ​ Outstanding at December 31, 2021 3,016,085 ​ $ 34.24 ​ 7.5 ​ $ 5,052,469 Exercisable at December 31, 2021 1,449,990 ​ $ 29.30 ​ 6.6 ​ $ 4,594,818 ​ Using the Black-Scholes option pricing model, the weighted average fair value of options containing service-based vesting granted during the years ended December 31, 2021, 2020, and 2019 was $17.54, $16.60, and $15.67, respectively. The expense related to options containing service-based vesting was $18.8 million, $16.1 million, and $18.1 million for the years ended December 31, 2021, 2020, and 2019, respectively. The fair value of each service-based vesting option issued was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ ​ ​ 2021 ​ 2020 2019 Expected volatility 61.2 % ​ 60.0 % ​ 73.8 % Expected option term (in years) 6.25 ​ ​ 6.25 ​ ​ 6.25 ​ Risk free interest rate 1.5 % ​ 1.5 % ​ 2.0 % Expected dividend yield — ​ ​ — ​ ​ — ​ ​ ​ The stock options granted in the year ended December 31, 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 and performance-based vesting provisions, respectively. The total expense for the year ended December 31, 2021 related to awards containing market-based and performance-based vesting provisions was $4.3 million and $5.3 million, respectively. ​ As of December 31, 2021, total unrecognized compensation expense related to stock options was $27.9 million, which the Company expects to recognize over a remaining weighted-average period of 2.5 years.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2021
401(k) Savings Plan
401(k) Savings Plan	13. 401(k) Savings Plan The Company has a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code of 1986, as amended (the “401(k) Plan”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements, and allows participants to defer a portion of their annual compensation on a pretax basis. Effective in 2017, the Company will provide a 200% match of employee contributions up to a limit on the Company’s contributions of the lesser of $6,000 and 3% of the employee’s salary. The Company made $1.2 million, $1.1 million, and $0.8 million in contributions to the 401(k) Plan for the years ended December 31, 2021, 2020 and 2019, respectively. ​

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Taxes
Income Taxes	14. Income Taxes ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2021 ​ 2020 Income tax computed at federal statutory tax rate 21 % 21 % State taxes, net of federal benefit 8.89 % 5.20 % General business credit carryovers 2.95 % 4.80 % 162m Limitation ​ (1.44) % — % Stock Options 1.12 % (1.8) % Non-deductible expenses 0.24 % (0.1) % Tax Rate Changes ​ 5.03 % — % Change in valuation allowance (37.80) % (29.10) % ​ — % — % ​ The principal components of the Company’s deferred tax assets and liabilities consist of the following at December 31, 2021 and 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2021 ​ 2020 Deferred tax assets: ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 127,092 ​ $ 70,751 Tax credit carryforwards ​ 25,028 ​ 19,353 Accrued expenses ​ 3,991 ​ 11,372 Capitalized patent costs ​ 63,093 ​ 46,197 Lease Liabilities ​ 7,929 ​ 7,083 Deferred revenue ​ 21,709 ​ 25,724 Other ​ 10,431 ​ 5,204 Total deferred tax assets ​ ​ 259,273 ​ ​ 185,684 Less valuation allowance ​ ​ (251,071) ​ ​ (178,307) Net deferred tax assets ​ ​ 8,202 ​ ​ 7,377 Deferred tax liabilities ​ ​ (8,202) ​ ​ (7,377) Depreciation and amortization ​ ​ (335) ​ ​ (567) Right-of-use assets ​ ​ (7,867) ​ ​ (6,810) Net deferred taxes ​ $ — ​ $ — ​ The Company has incurred net operating losses (“NOL”) since inception. At December 31, 2021 and 2020, the Company had federal net operating loss carryforwards of $447.4 million and $261.9 million, respectively. Of the amount as of December 31, 2021, $371.9 million will carryforward indefinitely while $75.5 million will expire beginning in 2033 and will continue to expire through 2037. As of December 31, 2021, and 2020, the Company also had state net operating loss carryforwards of approximately $507.1 million and $258.4 million, respectively, which may be available to offset future income tax liabilities and will expire beginning in 2035 and will continue to expire through 2040. Loss generated in 2021 expires in 2041. ​ Under the provisions of the Internal Revenue Code of 1986, as amended (the “Code”), the NOL and tax credit carryforward are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. NOL and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Code, respectively, as well as other similar state provisions. The Company conducted an analysis under Section 382 to determine if historical changes in ownership through December 31, 2019 would limit or otherwise restrict its ability to utilize its NOL and research and development credit carryforwards. As a result of this analysis, the Company does not believe there are any significant limitations on its ability to utilize these carryforwards. However, future changes in ownership occurring after December 31, 2019 could affect the limitation in future years, and any limitation may result in expiration of a portion of the NOL or research and development credit carryforwards before utilization. Management has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which principally comprise of NOL carryforwards, research and development credit carryforwards and capitalized license and patent costs. The Company’s management has determined that it is more likely than not that the Company will not recognize the benefits of its federal and state deferred tax assets, and as a result, a valuation allowance of $251.1 million and $178.3 million has been established at December 31, 2021 and 2020, respectively. The increase in the valuation allowance of $72.8 million for the year ended December 31, 2021 was primarily due to current period pre-tax losses incurred and research tax credits generated. The Company applies ASC 740 related to accounting for uncertainty in income taxes. The Company’s reserves related to income taxes are based on a determination of whether, and how much of, a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized following resolution of any potential contingencies present related to the tax benefit. At December 31, 2021 and 2020, the Company had no unrecognized tax benefits. Interest and penalty charges, if any, related to unrecognized tax benefits would be classified as income tax expense in the accompanying statements of operations. The Company has not as of yet conducted a study of its research and development credit carry forwards. This study may result in an adjustment to the Company’s research and development credit carryforwards; however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s research and development credits, and if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the consolidated balance sheets or statements of operations if an adjustment were required. The Company files income tax returns in the U.S. federal tax jurisdiction, the Massachusetts state jurisdiction, the California state jurisdiction and the Colorado state jurisdiction. Since the Company is in a loss carryforward position, the Company is generally subject to examination by the U.S. federal, state and local income tax authorities for all tax years in which a loss carryforward is available. The Company did not have any international operations as of December 31, 2021. The Company is currently under examination by the Internal Revenue Service ("IRS") for the period ended December 31, 2018 related to its R&D tax credits.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2021
Net Loss per Share
Net Loss per Share	15. Net Loss per Share Basic net loss per common share is calculated by dividing the net loss 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 per share is computed by dividing the net loss 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 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 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. For purposes of the diluted net loss per share calculation, stock options are considered to be common stock equivalents, but they were excluded from the Company’s calculation of diluted net loss per share allocable to common stockholders because their inclusion would have been anti-dilutive. Therefore, basic and diluted net loss per share applicable to common stockholders was the same for all periods presented. The following common stock equivalents were excluded from the calculation of diluted net loss per share allocable to common stockholders because their inclusion would have been anti-dilutive: ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2021 ​ 2020 Unvested restricted stock and restricted stock unit awards 628,732 ​ 507,450 Outstanding stock options 3,016,085 ​ 3,912,257 Estimated number of shares issuable for convertible notes (1) ​ — ​ 392,240 Total 3,644,817 ​ 4,811,947 (1) Represents the number of shares that would have been issued if the Company had elected to pay the success payment that was triggered in the fourth quarter of 2020 as discussed in Note 8, in shares of the Company’s common stock, based on the closing price of the common stock on December 31, 2020. The number of shares issued, for purposes of this presentation, is calculated by dividing the principal of the notes payable, including accrued interest, by the stock price per share ​ The table above reflects restricted stock issued upon exercise of unvested stock options as exercised on the dates that the shares are no longer subject to repurchase.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2021
Subsequent Events
Subsequent Events	16. Subsequent Events ​ None.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Summary of Significant Accounting Policies
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of Editas Medicine, Inc. and its wholly owned subsidiary, Editas Securities Corporation, which is a Delaware subsidiary created to buy, sell and hold securities. All intercompany transactions and balances have been eliminated.
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”).
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, stock-based compensation expense, the accrual for research and development expenses, valuations of in-process research and development assets and deferred tax valuation allowances. The Company bases its estimates on historical experience and other market-specific or relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.
Fair Value of Financial Instruments	Fair Value of Financial Instruments ASC Topic 820, Fair Value Measurement ASC 820 identifies fair value as the exchange price representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: ● Level 1 – Quoted market prices in active markets for identical assets or liabilities. ● Level 2 – Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates, and yield curves. ● Level 3 – Unobservable inputs developed using estimates of assumptions developed by the Company, which reflect those that a market participant would use. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, restricted cash, marketable securities, accounts receivable, prepaid expenses and other current assets, accounts payable, accrued expenses, and other current liabilities approximate their fair values, due to their short-term nature.
Cash, Cash Equivalents, and Restricted Cash	Cash, Cash Equivalents, and Restricted Cash The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include cash held in banks and amounts held in money market funds. The Company has restricted cash of $3.9 million held as collateral for the Company’s office and lab facilities and credit card program. The restricted funds are maintained in a traditional bank account. The following table presents cash, cash equivalents, and restricted cash as reported on the consolidated balance sheets that equal the total amounts on the consolidated statements of cash flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2021 ​ 2020 Cash and cash equivalents ​ $ 619,916 ​ $ 511,774 Restricted cash included in "Restricted cash and other non-current assets" ​ ​ 3,877 ​ ​ 3,877 Total cash, cash equivalents, and restricted cash ​ $ 623,793 ​ $ 515,651
Marketable Securities	Marketable Securities The Company classifies marketable securities with a remaining maturity when purchased of greater than three months and less than one year from the balance sheet date as current. Marketable securities are classified as long-term assets on the consolidated balance sheets if the contractual maturity exceeds one year and the Company does not intend to utilize the marketable securities to fund current operations. As of December 31, 2021, the Company’s marketable securities consisted of investments in available-for-sale debt securities. Available-for-sale debt securities are carried at fair value with the unrealized gains and losses included in other comprehensive loss as a component of stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the of the underlying security. Realized gains and losses are included in other income (expense). At each reporting date, the Company records an allowance for credit losses and reports it as credit loss expense which is included in “Other income (expense), net” in the Company’s consolidated statement of operations. The estimate for credit losses includes a measure of the expected risk of credit loss even if the risk is remote. When assessing financial assets for credit losses, the Company pools financial assets with similar risk characteristics and performs a collective evaluation. A credit loss on an available-for-sale debt security is limited to the difference in fair value and the amortized cost. A previously recognized credit loss may be increased or decreased in subsequent periods if the Company’s estimate of fair value changes. To determine whether to record a credit loss, the Company considers issuer or vendor specific credit ratings and historical losses as well as current economic conditions and its expectations for future economic conditions. To date, the Company has not had any credit losses, and the Company did not have an allowance for credit losses as of December 31, 2021 and 2020. During 2020, the Company’s marketable securities also included corporate equity securities. The Company classified investments in equity securities that had a readily determinable fair value as marketable securities in the Company’s consolidated balance sheets. The fair value of these securities were based on a quoted price for an identical equity security. If the equity security had a restriction that was determined to be an attribute of the security that would transfer to a market participant, the fair value of the security was measured based on the quoted price for an otherwise identical unrestricted equity security, adjusted for the effect of the restriction. The adjustment reflects the discount that a market participant would demand for the risk relating to the inability to dispose of the security for a specified period of time. The Company recorded changes in the fair value of its equity securities in “Other income (expense), net” in the Company’s consolidated statement of operations.
Accounts Receivable	Accounts Receivable The Company makes judgments as to its ability to collect outstanding receivables and provides an allowance for receivables when collection becomes doubtful. The Company's receivables primarily relate to amounts reimbursed under its collaboration agreements. The Company believes that credit risk associated with its collaborations partners is not significant. To date, the Company has not had any write-offs of bad debt, and the Company did not have an allowance for doubtful accounts as of December 31, 2021 and 2020.
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk The Company has no financial instruments with off-balance sheet risk such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Financial instruments that potentially subject the Company to a concentration of credit risk are cash, cash equivalents, marketable securities and receivables owed to the Company from collaboration partners. The Company’s cash, cash equivalents and marketable securities are held in accounts at a financial institution that may exceed federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds.
Property and Equipment	Property and Equipment Property and equipment consists of computers, laboratory equipment, furniture and office equipment, and leasehold improvements and is stated at cost, less accumulated depreciation. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred, while costs of major additions and betterments are capitalized. Depreciation is calculated over the estimated useful lives of the assets using the straight-line method. The Company capitalizes laboratory equipment used for research and development if it has alternative future use in research and development or otherwise. ​ ​ ​ ​ ​ Asset: Estimated Useful life Lab equipment 5 years ​ Computer equipment and software 3 years ​ Furniture and equipment 5 years ​ Leasehold improvements Shorter of useful life or remaining lease term ​
Impairment of Long-lived Assets	Impairment of Long-lived Assets The Company evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book values of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book values of the assets exceed their fair value. The Company has not recognized any impairment losses from inception through December 31, 2021.
Profit-Sharing Arrangements	Profit-Sharing Arrangements The Company considers the nature and contractual terms of the arrangements and assesses whether such arrangements involve a joint operating activity pursuant to which the Company is an active participant and is exposed to significant risks and rewards with respect to such arrangement. If the Company is an active participant and is exposed to significant risks and rewards with respect to such arrangement, the Company accounts for such arrangement as a collaboration under ASC Topic 808, Collaborative Arrangements Payments received from a collaboration partner to which this policy applies are recorded as contra-expense in the applicable period and may include development costs or patent expense reimbursements. The Company classifies payments made under the cost sharing provisions of such arrangements as a component of research and development expenses to reflect the joint risk sharing nature of such profit-sharing arrangements. The Company classifies payments owed or receivables recorded as other current liabilities or prepaid expenses and other current assets, respectively, in the Company’s consolidated balance sheets. The Company had one agreement that was accounted for in accordance with ASC 808 prior to the termination of the arrangement during the year ended 2020. The arrangements and payments are described more fully in Note 9.
Revenue Recognition	Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer. The promised goods or services in the Company’s arrangements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. The Company provides options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised good or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract. The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. The Company’s contracts often include development and regulatory milestone payments that are as assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration and other research and development revenues in the period of adjustment. For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of the Company’s collaboration or strategic alliance arrangements. The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation. The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional.
Research and Development Expenses	Research and Development Expenses Research and development expenses are charged to expense as incurred in performing research and development activities. The costs include employee-related expenses including salaries, benefits, and stock-based compensation expense, costs of funding research performed by third parties that conduct research and development and preclinical and clinical activities on the Company’s behalf, the cost of purchasing lab supplies and non-capital equipment used in preclinical and clinical activities and in manufacturing preclinical and clinical study materials, consultant fees, facility costs including rent, depreciation, and maintenance expenses, and fees for acquiring and maintaining licenses under third party licensing agreements which are typically expensed when incurred if the technology licensed has no alternate future uses, including any sublicensing or success payments made to the Company’s licensors. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the Company’s estimate, the accrual or prepaid is adjusted accordingly. The Company defers and capitalizes non-refundable advance payments made by the Company for research and development activities until the related goods are received or the related services are performed. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense.
In-process Research and Development Assets	In-process Research and Development Assets In-process research and development assets that are acquired in a transaction that does not qualify as a business combination under GAAP and that do not have an alternative future use are expensed in the period in which the assets are acquired.
Patent Costs	Patent Costs The Company expenses patent and patent application costs and related legal costs for the prosecution and maintenance of such patents and patent applications, including patents and patent applications the Company in-licenses, as incurred, and classifies such costs as general and administrative expenses in the accompanying consolidated statements of operations.
Leases	Leases The Company accounts for leases in accordance with ASC 842. At the inception of an arrangement the Company determines whether the arrangement contains a lease. If a lease is identified in an arrangement, the Company recognizes a right-of-use asset and liability on its balance sheet and determines whether the lease should be classified as a finance or operating lease. The Company does not recognize assets or liabilities for leases with lease terms of less than 12 months. Lease payments for short-term leases are recorded to operating expense on a straight-line basis over the lease term and variable lease payments are recorded in the period in which the obligation for those payments is incurred. A lease qualifies as a finance lease if any of the following criteria are met at the inception of the lease: (i) there is a transfer of ownership of the leased asset to the Company by the end of the lease term, (ii) the Company holds an option to purchase the leased asset that it is reasonably certain to exercise, (iii) the lease term is for a major part of the remaining economic life of the leased asset, (iv) the present value of the sum of lease payments equals or exceeds substantially all of the fair value of the leased asset, and (v) the nature of the leased asset is specialized to the point that it is expected to provide the lessor no alternative use at the end of the lease term. All other leases are recorded as operating leases. Finance and operating lease assets and liabilities are recognized at the lease commencement date based on the present value of the lease payments over the lease term using the discount rate implicit in the lease. If the rate is not readily determinable, the Company utilizes its incremental borrowing rate at the lease commencement date. Operating lease assets are further adjusted for prepaid or accrued lease payments. Operating lease payments are expensed using the straight-line method as an operating expense over the lease term. Finance lease assets are amortized to depreciation expense using the straight-line method over the shorter of the useful life of the related asset or the lease term. Finance lease payments are bifurcated into (i) a portion that is recorded as imputed interest expense and (ii) a portion that reduces the finance liability associated with the lease. The Company does not separate lease and non-lease components when determining which lease payments to include in the calculation of its lease assets and liabilities. Variable lease payments are expensed as incurred. If a lease includes an option to extend or terminate the lease, the Company reflects the option in the lease term if it is reasonably certain it will exercise the option.
Stock-based Compensation Expense	Stock-based Compensation Expense The Company accounts for all stock-based awards granted to employees and non-employees as stock-based compensation expense at fair value in accordance with FASB ASC Topic 718 Compensation—Stock Compensation (“ASC 718”). The Company estimates the grant date fair value of restricted stock based on the market value of the Company’s common stock on the date of the grant. The Company estimates the grant date fair value of each option award using the Black-Scholes option-pricing model. The Black-Scholes option pricing model requires the input of certain subjective assumptions, including (1) the expected stock price volatility, (2) the calculation of expected term of the award, (3) the risk-free interest rate, and (4) the expected dividend yield. Because there had been no public market for the Company’s common stock prior to its initial public offering, there was a lack of company-specific historical and implied volatility data. Accordingly, the Company based its estimates of expected volatility on the historical volatility of a group of similar companies that are publicly traded. The Company calculates historical volatility based on a period of time commensurate with the expected term. The Company computes expected volatility based on the historical volatility of a representative group of companies with similar characteristics to the Company, including their stages of product development and focus on the life science industry. The Company uses the simplified method as prescribed by the Securities and Exchange Commission’s Staff Accounting Bulletin No. 107, Share-Based Payment, to calculate the expected term for options granted to employees as the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. For options granted to non-employees, the Company utilizes the contractual term of the arrangement as the basis for the expected term. The Company determines the risk-free interest rate based on a treasury instrument whose term is consistent with the expected term of the stock options. The Company uses an assumed dividend yield of zero as the Company has never paid dividends and does not have current plans to pay any dividends on its common stock. Restricted stock awards (“RSAs”) are subject to repurchase rights. Accordingly, the Company has recorded the proceeds from the issuance of RSAs as a liability in the consolidated balance sheets. The restricted stock liability is reclassified into stockholders’ equity as the restricted stock vests. ​ Service-Based Awards For stock-based awards issued to employees, non-employee service providers and members of the Company’s board of directors (the “Board”), the Company recognizes the grant date fair value of the service-based options, RSAs or restricted stock unit awards (“RSUs”) on a straight-line basis over the requisite service period, which is generally the vesting period of the respective award. If an employee or non-employee service requirement is concluded to be non-substantive, the stock-based compensation expense would be expensed immediately. Market-Based Awards For market-based awards, the Company recognizes the grant date fair value of the market-based options over the earlier of the derived service period, pursuant to a Monte-Carlo simulation model, or when the market-based vesting conditions are met. The Company estimates an award's derived service period based on the best estimate of the period over which an award's vesting condition(s) will be achieved. If the market-based vesting conditions are met ahead of the derived service period, the expense will be accelerated. If the market-based vesting conditions are not met and the market-based award is cancelled, the expense will not be reversed unless the market-based award is forfeited. Performance-Based Awards For performance-based awards, the Company recognizes the grant date fair value of the performance-based options or RSUs over the requisite service period using the accelerated attribution method to the extent achievement of the performance condition is probable. Certain awards are subject to both performance and continued service conditions. ​ The Company classifies stock-based compensation expense in its consolidated statement of operations and comprehensive loss in the same manner in which the award recipient’s salary or service payments are classified. Forfeitures are recorded as they occur. If factors change or different assumptions are used, the Company’s stock-based compensation expense could be materially different in the future
Success Payments, Research Funding Payments and Notes Payables	Success Payments, Research Funding Payments and Notes Payables
Income taxes	Income taxes Income taxes are recorded in accordance with ASC Topic 740, Income Taxes The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. The Company assesses the impact of various tax reform proposals and modifications to existing tax treaties in all jurisdictions where they have operations to determine the potential effect on the Company’s business and any assumptions they have made about their future taxable income. The Company cannot predict whether any specific proposals will be enacted, the terms of any such proposals or what effect, if any, such proposals would have on the Company if they were to be enacted. Beginning in 2022, the Tax Cut and Jobs Act of 2017 eliminates the currently available option to deduct research and development expenditures and requires taxpayers to amortize them over five years. The U.S. Congress is considering legislation that would defer the amortization requirement to future periods, however, the Company has no assurance that the provision will be repealed or otherwise modified.
Comprehensive Loss	Comprehensive Loss Comprehensive loss currently consists of net loss and changes in unrealized gains and losses on marketable securities.
Segment Information	Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker in deciding how to allocate resources and assess performance. The Company and the Company’s chief operating decision maker, the Company’s Chief Executive Officer, view the Company’s operations and manage the Company’s business as a single operating segment, which is the business of developing and commercializing genome editing technology.

Summary of significant accoun_3

Summary of significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2021
Summary of Significant Accounting Policies
Schedule of cash, cash equivalents, and restricted cash	The following table presents cash, cash equivalents, and restricted cash as reported on the consolidated balance sheets that equal the total amounts on the consolidated statements of cash flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2021 ​ 2020 Cash and cash equivalents ​ $ 619,916 ​ $ 511,774 Restricted cash included in "Restricted cash and other non-current assets" ​ ​ 3,877 ​ ​ 3,877 Total cash, cash equivalents, and restricted cash ​ $ 623,793 ​ $ 515,651
Schedule of estimated useful lives of property, plant and equipment	​ ​ ​ ​ ​ Asset: Estimated Useful life Lab equipment 5 years ​ Computer equipment and software 3 years ​ Furniture and equipment 5 years ​ Leasehold improvements Shorter of useful life or remaining lease term ​

Cash Equivalents and Marketab_2

Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2021
Cash Equivalents and Marketable Securities
Schedule of cash equivalents and marketable securities	Cash equivalents and marketable securities consisted of the following at December 31, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ for Credit ​ ​ Unrealized ​ Unrealized ​ Fair December 31, 2021 ​ Cost ​ Losses ​ ​ Gains ​ Losses ​ Value Cash equivalents and marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 203,519 ​ $ — ​ ​ $ — ​ $ — ​ $ 203,519 U.S. Treasuries ​ ​ 124,016 ​ ​ — ​ ​ ​ 1 ​ ​ (84) ​ ​ 123,933 Government agency securities ​ ​ 126,927 ​ ​ — ​ ​ ​ — ​ ​ (228) ​ ​ 126,699 Commercial paper ​ ​ 89,699 ​ ​ — ​ ​ ​ 1 ​ ​ (13) ​ ​ 89,687 Corporate notes/bonds ​ ​ 76,248 ​ ​ — ​ ​ ​ — ​ ​ (170) ​ ​ 76,078 Total ​ $ 620,409 ​ $ — ​ ​ $ 2 ​ $ (495) ​ $ 619,916 ​ 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 ​ ​ — ​ ​ ​ 10 ​ ​ (8) ​ ​ 41,914 Corporate notes/bonds ​ ​ 42,185 ​ ​ — ​ ​ ​ — ​ ​ (25) ​ ​ 42,160 Total ​ $ 511,820 ​ $ — ​ ​ $ 18 ​ $ (64) ​ $ 511,774

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 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 December 31, 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted Prices Significant ​ ​ ​ ​ ​ ​ ​ in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ ​ December 31, ​ Identical Assets ​ Inputs ​ Inputs Financial Assets ​ 2021 ​ (Level 1) ​ (Level 2) ​ (Level 3) Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 203,519 ​ $ 203,519 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasuries ​ ​ 123,933 ​ ​ 123,933 ​ ​ — ​ ​ — Government agency securities ​ ​ 126,699 ​ ​ — ​ ​ 126,699 ​ ​ — Commercial paper ​ ​ 89,687 ​ ​ — ​ ​ 89,687 ​ ​ — Corporate bonds ​ ​ 76,078 ​ ​ — ​ ​ 76,078 ​ ​ — Restricted cash and other non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ ​ 3,877 ​ ​ 3,877 ​ ​ — ​ ​ — Total financial assets ​ $ 623,793 ​ $ 331,329 ​ $ 292,464 ​ $ — ​ 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 ​ $ —

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2021
Property and Equipment, net
Schedule of property and equipment, net	Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ December 31, ​ December 31, ​ 2021 2020 Laboratory equipment ​ $ 21,579 ​ $ 18,433 ​ Leasehold improvements ​ ​ 8,162 ​ ​ 4,967 ​ Construction-in-progress ​ 1,529 ​ 858 ​ Computer equipment ​ ​ 876 ​ ​ 500 ​ Furniture and office equipment ​ ​ 264 ​ ​ 239 ​ Software ​ 215 ​ 118 ​ Total property and equipment ​ 32,625 ​ 25,115 ​ Less: accumulated depreciation ​ (15,507) ​ (11,095) ​ Property and equipment, net ​ $ 17,118 ​ $ 14,020 ​ ​

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2021
Accrued Expenses
Schedule of accrued expenses	Accrued expenses consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ December 31, ​ 2021 2020 Employee related expenses ​ $ 10,159 ​ $ 5,323 External research and development expenses ​ ​ 5,614 ​ ​ 12,820 Professional service expenses ​ ​ 2,345 ​ ​ 533 Intellectual property and patent related fees ​ ​ 1,408 ​ ​ 4,240 Other expenses ​ ​ 666 ​ ​ 1,130 Total accrued expenses ​ $ 20,192 ​ $ 24,046

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases
Summary of leases included on its consolidated balance sheet	The Company’s leases are included on its consolidated balance sheet as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ As of ​ December 31, ​ December 31, ​ 2021 2020 Right-of-use assets $ 26,173 ​ $ 25,128 Operating lease liabilities, current $ (10,309) ​ $ (6,811) Operating lease liabilities, noncurrent $ (16,069) ​ $ (19,324)
Summary of maturities of lease liabilities	Maturities of the Company’s lease liabilities as of December 31, 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ Year Ended Maturity of lease liabilities: ​ December 31, 2021 2022 $ 12,021 2023 $ 11,932 2024 $ 4,510 2025 $ 506 2026 $ 110 Thereafter $ — Total minimum lease payments $ 29,079 Less: imputed interest $ (2,751) Total operating lease liabilities at December 31, 2021 $ 26,328

Collaboration Agreements (Table

Collaboration Agreements (Tables)	12 Months Ended
	Dec. 31, 2021
Collaboration Agreements
Schedule of accounts receivable and contract liabilities	The following table presents changes in the Company’s accounts receivable and contract liabilities for the year ended December 31, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, 2021 Balance at December 31, 2020 ​ Additions ​ Deductions ​ Balance at December 31, 2021 Accounts receivable $ 6,048 ​ $ 406 ​ $ (6,187) ​ $ 267 Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue $ 94,927 ​ $ — ​ $ (22,706) ​ $ 72,221
Schedule of change in contract assets and contract liabilities	During the three and twelve months ended December 31, 2021, the Company recognized the following collaboration revenue (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Year Ended Revenue recognized in the period from: December 31, 2021 Amounts included in deferred revenue at the beginning of the period $ 11,334 ​ $ 22,706 Performance obligations satisfied in previous periods $ — ​ $ —

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2021
Common Stock.
Schedule of shares reserved for future issuance	​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2021 2020 Shares reserved for outstanding stock option awards under the 2013 Stock Incentive Plan, as amended 145,255 174,362 Shares reserved for outstanding stock option awards and restricted stock units under the 2015 Stock Incentive Plan 3,036,797 3,839,345 Shares reserved for outstanding inducement stock option award and restricted stock units 408,765 280,000 Remaining shares reserved, but unissued, for future awards under the 2015 Stock Incentive Plan 7,524,431 5,599,450 Remaining shares reserved, but unissued, for future awards under the 2015 Employee Stock Purchase Plan 2,722,040 ​ 2,137,127 ​ ​ 13,837,288 12,030,284

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Stock-Based Compensation
Schedule of stock-based compensation expense	Total compensation cost recognized for all stock-based compensation awards in the consolidated statements of operations was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ ​ ​ 2021 ​ 2020 Research and development ​ ​ $ 16,553 ​ $ 11,580 General and administrative ​ ​ 26,846 ​ 11,576 Total stock-based compensation expense ​ ​ $ 43,399 ​ $ 23,156 ​
Schedule of changes in unvested restricted stock	​ ​ ​ ​ ​ ​ ​ ​ ​ 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 629,797 ​ $ 47.79 Vested (267,268) ​ $ 33.79 Forfeited ​ (241,247) ​ $ 39.29 Unvested restricted stock and restricted stock unit awards as of December 31, 2021 628,732 ​ $ 41.28
Schedule of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 ​ 1,299,997 ​ $ 44.85 ​ ​ ​ ​ ​ Exercised ​ (1,233,958) ​ $ 25.52 ​ ​ ​ ​ ​ Cancelled ​ (962,211) ​ $ 31.38 ​ ​ ​ ​ ​ Outstanding at December 31, 2021 3,016,085 ​ $ 34.24 ​ 7.5 ​ $ 5,052,469 Exercisable at December 31, 2021 1,449,990 ​ $ 29.30 ​ 6.6 ​ $ 4,594,818
Schedule of assumptions used to value stock options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ ​ ​ 2021 ​ 2020 2019 Expected volatility 61.2 % ​ 60.0 % ​ 73.8 % Expected option term (in years) 6.25 ​ ​ 6.25 ​ ​ 6.25 ​ Risk free interest rate 1.5 % ​ 1.5 % ​ 2.0 % Expected dividend yield — ​ ​ — ​ ​ — ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Taxes
Schedule of reconciliation of effective income tax rate	​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2021 ​ 2020 Income tax computed at federal statutory tax rate 21 % 21 % State taxes, net of federal benefit 8.89 % 5.20 % General business credit carryovers 2.95 % 4.80 % 162m Limitation ​ (1.44) % — % Stock Options 1.12 % (1.8) % Non-deductible expenses 0.24 % (0.1) % Tax Rate Changes ​ 5.03 % — % Change in valuation allowance (37.80) % (29.10) % ​ — % — %
Schedule of components of deferred tax assets and liabilities	The principal components of the Company’s deferred tax assets and liabilities consist of the following at December 31, 2021 and 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ ​ 2021 ​ 2020 Deferred tax assets: ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 127,092 ​ $ 70,751 Tax credit carryforwards ​ 25,028 ​ 19,353 Accrued expenses ​ 3,991 ​ 11,372 Capitalized patent costs ​ 63,093 ​ 46,197 Lease Liabilities ​ 7,929 ​ 7,083 Deferred revenue ​ 21,709 ​ 25,724 Other ​ 10,431 ​ 5,204 Total deferred tax assets ​ ​ 259,273 ​ ​ 185,684 Less valuation allowance ​ ​ (251,071) ​ ​ (178,307) Net deferred tax assets ​ ​ 8,202 ​ ​ 7,377 Deferred tax liabilities ​ ​ (8,202) ​ ​ (7,377) Depreciation and amortization ​ ​ (335) ​ ​ (567) Right-of-use assets ​ ​ (7,867) ​ ​ (6,810) Net deferred taxes ​ $ — ​ $ —

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2021
Net Loss per Share
Schedule of anti-dilutive common stock equivalents	​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2021 ​ 2020 Unvested restricted stock and restricted stock unit awards 628,732 ​ 507,450 Outstanding stock options 3,016,085 ​ 3,912,257 Estimated number of shares issuable for convertible notes (1) ​ — ​ 392,240 Total 3,644,817 ​ 4,811,947 (1) Represents the number of shares that would have been issued if the Company had elected to pay the success payment that was triggered in the fourth quarter of 2020 as discussed in Note 8, in shares of the Company’s common stock, based on the closing price of the common stock on December 31, 2020. The number of shares issued, for purposes of this presentation, is calculated by dividing the principal of the notes payable, including accrued interest, by the stock price per share

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Feb. 28, 2021	Jan. 31, 2021	Dec. 31, 2021	May 31, 2021	Dec. 31, 2020
Liquidity
Accumulated deficit			$ 857,699		$ 665,197
At The 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

Summary Of Significant Accoun_4

Summary Of Significant Accounting Policies - Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Cash, Cash Equivalents, and Restricted Cash
Restricted cash	$ 3,900
Cash and cash equivalents	619,916	$ 511,774
Restricted cash included in "Restricted cash and other non-current assets"	3,877	3,877
Total cash, cash equivalents, and restricted cash	$ 623,793	$ 515,651

Summary Of Significant Accoun_5

Summary Of Significant Accounting Policies - Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Accounts Receivable
Bad debt write-offs	$ 0	$ 0
Allowance for doubtful accounts	$ 0	$ 0

Summary Of Significant Accoun_6

Summary Of Significant Accounting Policies - Property And Equipment (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Property and equipment policy
Impairment losses	$ 0
Laboratory equipment
Property and equipment policy
Estimated useful life	5 years
Computer equipment and software
Property and equipment policy
Estimated useful life	3 years
Furniture and office equipment
Property and equipment policy
Estimated useful life	5 years

Summary Of Significant Accoun_7

Summary Of Significant Accounting Policies - Success Payments, Research Funding Payments and Notes Payables (Details) - Promissory Notes	12 Months Ended
	Dec. 31, 2021
Recent Accounting Pronouncements
Interest rate (as a percentage)	4.80%
Period of outstanding principal and accrued interest payable	5 months

Cash Equivalents and Marketab_3

Cash Equivalents and Marketable Securities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)securityitem	Dec. 31, 2020USD ($)
Cash Equivalents and Marketable Securities
Amortized Cost	$ 620,409	$ 511,820
Gross Unrealized Gains	2	18
Gross Unrealized Losses	(495)	(64)
Fair Value	$ 619,916	511,774
Number of securities in an unrealized loss position for more than 12 months | item	0
Number of noncurrent securities | security	51
Noncurrent marketable securities	$ 120,071	109,664
Minimum
Cash Equivalents and Marketable Securities
Remaining maturity term	1 year
Maximum
Cash Equivalents and Marketable Securities
Remaining maturity term	2 years
U.S. Treasuries
Cash Equivalents and Marketable Securities
Amortized Cost	$ 124,016	180,376
Gross Unrealized Gains	1	8
Gross Unrealized Losses	(84)	(11)
Fair Value	123,933	180,373
Government agency securities.
Cash Equivalents and Marketable Securities
Amortized Cost	126,927	107,665
Gross Unrealized Losses	(228)	(20)
Fair Value	126,699	107,645
Commercial paper
Cash Equivalents and Marketable Securities
Amortized Cost	89,699	41,912
Gross Unrealized Gains	1	10
Gross Unrealized Losses	(13)	(8)
Fair Value	89,687	41,914
Corporate notes/bonds
Cash Equivalents and Marketable Securities
Amortized Cost	76,248	42,185
Gross Unrealized Losses	(170)	(25)
Fair Value	76,078	42,160
Money market funds
Cash Equivalents and Marketable Securities
Amortized Cost	203,519	139,682
Fair Value	$ 203,519	$ 139,682

Fair Value Measurements - Recur

Fair Value Measurements - Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financial Assets
Marketable securities	$ 619,916	$ 511,774
U.S. Treasuries
Financial Assets
Marketable securities	123,933	180,373
Commercial paper
Financial Assets
Marketable securities	89,687	41,914
Corporate notes/bonds
Financial Assets
Marketable securities	76,078	42,160
Money market funds
Financial Assets
Marketable securities	203,519	139,682
Recurring
Financial Assets
Total financial assets	623,793	515,651
Recurring | U.S. Treasuries
Financial Assets
Marketable securities	123,933	180,373
Recurring | Government agency securities
Financial Assets
Marketable securities	126,699	107,645
Recurring | Commercial paper
Financial Assets
Marketable securities	89,687	41,904
Recurring | Corporate notes/bonds
Financial Assets
Marketable securities	76,078	42,170
Recurring | Money market funds
Financial Assets
Cash and cash equivalents	203,519	139,682
Restricted cash	3,877	3,877
Recurring | Level 1
Financial Assets
Total financial assets	331,329	323,932
Recurring | Level 1 | U.S. Treasuries
Financial Assets
Marketable securities	123,933	180,373
Recurring | Level 1 | Money market funds
Financial Assets
Cash and cash equivalents	203,519	139,682
Restricted cash	3,877	3,877
Recurring | Level 2
Financial Assets
Total financial assets	292,464	191,719
Recurring | Level 2 | Government agency securities
Financial Assets
Marketable securities	126,699	107,645
Recurring | Level 2 | Commercial paper
Financial Assets
Marketable securities	89,687	41,904
Recurring | Level 2 | Corporate notes/bonds
Financial Assets
Marketable securities	$ 76,078	$ 42,170

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Dec. 31, 2020
Fair Value Measurements
Realized gain on corporate equity securities	$ 16,400	$ 16,366

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property and equipment disclosures
Total property and equipment	$ 32,625	$ 25,115
Less: accumulated depreciation	(15,507)	(11,095)
Property and equipment, net	17,118	14,020
Depreciation	5,053	3,959	$ 2,830
Laboratory equipment
Property and equipment disclosures
Total property and equipment	21,579	18,433
Leasehold improvements
Property and equipment disclosures
Total property and equipment	8,162	4,967
Construction-in-progress
Property and equipment disclosures
Total property and equipment	1,529	858
Computer equipment
Property and equipment disclosures
Total property and equipment	876	500
Furniture and office equipment
Property and equipment disclosures
Total property and equipment	264	239
Software
Property and equipment disclosures
Total property and equipment	$ 215	$ 118

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued Expenses
Employee related expenses	$ 10,159	$ 5,323
External research and development expenses	5,614	12,820
Professional service expenses	2,345	533
Intellectual property and patent related fees	1,408	4,240
Other expenses	666	1,130
Total accrued expenses	$ 20,192	$ 24,046

Leases - Right of Use Asset and

Leases - Right of Use Asset and Lease Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases are included on its condensed consolidated balance sheet
Right-of-use assets	$ 26,173	$ 25,128
Operating lease liabilities, current	(10,309)	(6,811)
Operating lease liabilities, noncurrent	(16,069)	(19,324)
Operating lease costs	10,900	10,500
Variable lease costs	$ 2,100	$ 1,100

Leases - Maturities of Lease Li

Leases - Maturities of Lease Liabilities (Details) $ in Thousands	Dec. 31, 2021USD ($)
Maturity of lease liabilities:
2022	$ 12,021
2023	11,932
2024	4,510
2025	506
2026	110
Total minimum lease payments	29,079
Less: imputed interest	(2,751)
Total operating lease liabilities	$ 26,328
Weighted average remaining lease term	2 years 4 months 24 days
Weighted average discount rate	8.30%

Leases - Operating Leases (Deta

Leases - Operating Leases (Details) $ in Millions	Oct. 01, 2016USD ($)ft²	Dec. 31, 2019USD ($)ft²
Hurley Street Lease
Leases
Leased space ( in square feet) | ft²	59,783
Security deposit | $	$ 1.6
Lessee, Operating Lease, Existence of Option to Extend	true
Extended lease option (in years)	5 years
One Main Street
Leases
Leased space ( in square feet) | ft²		31,571
Security deposit | $		$ 0.8
Lessee, Operating Lease, Existence of Option to Extend		true
Extended lease option (in years)		5 years

Commitments and Contingencies -

Commitments and Contingencies - Research Funding Payments (Details) - Sponsored Research Agreement - Broad	12 Months Ended
	Dec. 31, 2018USD ($)
Commitments and contingencies
First research funding amount due and payable	$ 25,000,000
Second research funding amount due and payable	100,000,000
Maximum
Commitments and contingencies
Market cap research funding limit	11
Minimum
Commitments and contingencies
Market cap research funding limit	$ 10

Commitments and Contingencies_2

Commitments and Contingencies - Milestones (Details) $ in Millions	Dec. 31, 2021USD ($)item
Harvard
Commitments and Contingencies [Line Items]
Minimum number of product candidate covered by claim or patent right | item	1
Cas-9 License Agreement
Commitments and Contingencies [Line Items]
License agreement, sales milestone payments payable	$ 54
Cas-9 License Agreement | Product or service prevents or treats
Commitments and Contingencies [Line Items]
License agreement, clinical and regulatory milestone payments payable	4.1
License agreement, sales milestone payments payable	36
Cas-9 License Agreement | Maximum
Commitments and Contingencies [Line Items]
License agreement, clinical and regulatory milestone payments payable	14.8
Cpf1 License Agreement
Commitments and Contingencies [Line Items]
License agreement, sales milestone payments payable	54
Cpf1 License Agreement | Product or service prevents or treats
Commitments and Contingencies [Line Items]
License agreement, clinical and regulatory milestone payments payable	5.5
License agreement, sales milestone payments payable	36
Cpf1 License Agreement | Maximum
Commitments and Contingencies [Line Items]
License agreement, clinical and regulatory milestone payments payable	20
Cas9-II License Agreement
Commitments and Contingencies [Line Items]
License agreement, sales milestone payments payable	13.5
Cas9-II License Agreement | Product or service prevents or treats
Commitments and Contingencies [Line Items]
License agreement, clinical and regulatory milestone payments payable	1.1
License agreement, sales milestone payments payable	9
Cas9-II License Agreement | Maximum
Commitments and Contingencies [Line Items]
License agreement, clinical and regulatory milestone payments payable	$ 3.7

Commitments and Contingencies_3

Commitments and Contingencies - Licensor Expense Reimbursements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Licensor Expense Reimbursements
Commitments and contingencies
Expense for prosecution and maintenance of patent rights	$ 10.6	$ 13.1	$ 13.5

Commitments and Contingencies_4

Commitments and Contingencies - Royalties and Success Payments (Details) - Harvard $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)
Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalties credit paid to third party (as a percent)	50.00%
Cpf1 License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Success payments	$ 25
Success payment accrued	100
Cpf1 Success Payments | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Success payments	10,000
Cpf1 Success Payments | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Success payments	750
Cas9-II License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Success payments	7.5
Success payment accrued	22.5
Cas9-II License Agreement | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Success payments	9,000
Cas9-II License Agreement | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Success payments	$ 1,000

Collaboration Agreements - Reve

Collaboration Agreements - Revenue Recognition (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Accounts receivable
Accounts receivable, Balance at Beginning of Period	$ 6,048
Accounts Receivable, Additions	406
Accounts Receivable, Deductions	(6,187)
Accounts receivable, Balance at End of Period	267
Contract liabilities:
Deferred Revenue, Balance at Beginning of Period	94,927
Deferred revenue, Deductions	(22,706)
Deferred Revenue, Balance at End of Period	$ 72,221

Collaboration Agreements - Cont

Collaboration Agreements - Contract Assets and Liability (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021
Change in contract asset and contract liability balances
Amounts included in deferred revenue at the beginning of the period	$ 11,334	$ 22,706

Collaboration Agreements - Summ

Collaboration Agreements - Summary of Agreements (Details) $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Nov. 30, 2019USD ($)item	Mar. 31, 2017USD ($)item	Dec. 31, 2021USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Revenue recognized			$ 11,334	$ 22,706
Deferred revenue			72,221	72,221	$ 94,927
Deferred revenue, long-term			60,888	60,888	73,984
Allergan
Revenue recognized				0	70,600
Amended Collaboration Agreement 2019 | Juno Therapeutics
Agreement term	5 years
Extensions | item	2
Extension period	1 year
Upfront fee received	$ 70,000
Potential development milestone payments	27,500		3,000	3,000
Potential regulatory milestone payments	107,500
Potential licensed products milestone payments	60,000
Total transaction price				110,000
Amendment fee				70,000
License Agreement, Exercise Fee				5,000
Revenue recognized				24,700	11,300
Deferred revenue			68,000	68,000
Deferred revenue, long-term			56,700	56,700	73,700
First development and commercialization license payment received	$ 500
Sublicense fees paid				0	0
Amended Collaboration Agreement 2018 | Juno Therapeutics
Deferred revenue			$ 32,000	$ 32,000
Strategic Alliance | Allergan
Upfront fee received		$ 90,000
Deferred revenue					$ 77,100
Number of Collaboration Development Programs | item		5

Collaboration Agreements - Alle

Collaboration Agreements - Allegran pharmaceuticals strategic alliance and profit sharing agreement (Details) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 31, 2020item	Dec. 31, 2021USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue		$ 72,221	$ 72,221	$ 94,927
Revenue recognized		$ 11,334	22,706
Allergan
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognized			$ 0	70,600
Allergan | Termination Agreement
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Termination Agreements, final amount				5,000
Termination Agreements, amount payable to Allergan				20,000
Termination Agreements, payment made to Allergan				17,500
Number of collaboration targets | item	4
Allergan | Termination Agreement | Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Clinical and regulatory milestone payments for each target program				20,000
Aggregated sales milestones payments				90,000
Allergan | Strategic Alliance
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue				$ 77,100

Collaboration Agreements - Beam

Collaboration Agreements - Beam Therapeutics (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration and other research and development revenues	$ 25,544	$ 90,732	$ 20,531
Revenue type	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember
Beam Therapeutics, Inc | License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Non-cash consideration aggregate fair value received				$ 3,600
Contract termination notice				90 days
Total transaction price				$ 3,800
Collaboration and other research and development revenues	$ 300	$ 200
Revenue type	us-gaap:ServiceMember	us-gaap:ServiceMember

Preferred Stock (Details)

Preferred Stock (Details) - shares	Dec. 31, 2021	Dec. 31, 2020	Feb. 08, 2016
Preferred Stock
Authorized common stock	195,000,000	195,000,000
Authorized preferred stock	5,000,000	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Common Stock (Details)

Common Stock (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)Voteshares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)	Jun. 30, 2021item	Jul. 31, 2015shares
Number of inducement grants | item				2
Common Stock, Capital Shares Reserved for Future Issuance	13,837,288	12,030,284
Common Stock
Voting rights per share | Vote	1
Dividends, Common Stock | $	$ 0	$ 0	$ 0
Inducement stock option award and restricted stock units
Common Stock, Capital Shares Reserved for Future Issuance	408,765	280,000
2013 Plan
Common Stock, Capital Shares Reserved for Future Issuance					6,317,769
2013 Plan | Stock options | Common Stock
Common Stock, Capital Shares Reserved for Future Issuance	145,255	174,362
2015 Plan | Common Stock
Common Stock, Capital Shares Reserved for Future Issuance	7,524,431	5,599,450
2015 Plan | Stock options | Common Stock
Common Stock, Capital Shares Reserved for Future Issuance	3,036,797	3,839,345
2015 Employee Stock Purchase Plan | Common Stock
Common Stock, Capital Shares Reserved for Future Issuance	2,722,040	2,137,127

Common Stock - Stock Incentive

Common Stock - Stock Incentive Plan (Details)	1 Months Ended	12 Months Ended
	Jan. 31, 2022shares	Dec. 31, 2021itemshares	Dec. 31, 2020shares	Jul. 31, 2015shares	Sep. 30, 2013shares
Stock-based compensation disclosures
Shares reserved for future awards		13,837,288	12,030,284
2013 Plan
Stock-based compensation disclosures
Shares authorized					1,057,692
Shares reserved for future awards				6,317,769
2013 Plan | Stock options
Stock-based compensation disclosures
Vesting period		4 years
Expiration period		10 years
2013 Plan | Performance based awards
Stock-based compensation disclosures
Number of awards with performance vesting criteria | item		1
2015 Plan | Subsequent Event
Stock-based compensation disclosures
Increase to number of shares authorized	2,738,110
2015 Employee Stock Purchase Plan | Subsequent Event
Stock-based compensation disclosures
Increase to number of shares authorized	684,527
Maximum | 2013 Plan | Stock options
Stock-based compensation disclosures
Vesting period		4 years
Maximum | 2015 Plan
Stock-based compensation disclosures
Shares reserved for future awards		2,923,076
Percent of shares outstanding reserved for future awards (as a percent)		4.00%
Maximum | 2015 Employee Stock Purchase Plan
Stock-based compensation disclosures
Shares reserved for future awards		769,230
Percent of shares outstanding reserved for future awards (as a percent)		1.00%
Minimum | 2013 Plan | Stock options
Stock-based compensation disclosures
Vesting period		1 year

Stock-Based Compensation - Expe

Stock-Based Compensation - Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Stock-based compensation disclosures
Compensation expense	$ 43,399	$ 23,156
Research and development
Stock-based compensation disclosures
Compensation expense	16,553	11,580
General and administrative
Stock-based compensation disclosures
Compensation expense	$ 26,846	$ 11,576

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock and Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Weighted Average Grant Date Fair Value
Compensation expense	$ 43,399	$ 23,156
Restricted Stock
Changes in unvested restricted stock
Unvested restricted shares, beginning of period (in shares)	507,450
Issued (in shares)	629,797
Vested (in shares)	(267,268)
Forfeited (in shares)	(241,247)
Unvested restricted shares, end of period(in shares)	628,732	507,450
Weighted Average Grant Date Fair Value
Balance, beginning of period	$ 27.35
Issued (in dollars per share)	47.79
Vested (in dollars per share)	33.79
Forfeited (in dollars per share)	39.29
Balance, ending of period	$ 41.28	$ 27.35
Unrecognized stock-based compensation expense	$ 13,900
Period for recognition	2 years
Compensation expense	$ 14,600	$ 4,400	$ 6,400
Performance based awards | Employees
Changes in unvested restricted stock
Issued (in shares)	226,747
Weighted Average Grant Date Fair Value
Compensation expense	$ 4,000
Stock options
Weighted Average Grant Date Fair Value
Unrecognized stock-based compensation expense	$ 27,900
Period for recognition	2 years 6 months
Compensation expense	$ 18,800	$ 16,100	18,100
Changes in unvested stock options
Outstanding, beginning of period (in shares)	3,912,257
Granted (in shares)	1,299,997
Exercised (in shares)	(1,233,958)
Cancelled (in shares)	(962,211)
Outstanding, end of period (in shares)	3,016,085	3,912,257
Exercisable (in shares)	1,449,990
Outstanding, beginning of period (in dollars per share)	$ 27.26
Granted (in dollars per share)	44.85
Exercised (in dollars per share)	25.52
Cancelled (in dollars per share)	31.38
Outstanding, end of period (in dollars per share)	34.24	$ 27.26
Exercisable (in dollar per share)	$ 29.30
Remaining contractual life	7 years 6 months	7 years 10 months 24 days
Exercisable, remaining contractual life	6 years 7 months 6 days
Aggregate intrinsic value	$ 5,052,469	$ 167,640
Exercisable, aggregated intrinsic value	4,594,818
Intrinsic value of options exercised	$ 27,200	$ 15,600	$ 14,600
Weighted average fair value of options granted (per share)	$ 17.54	$ 16.60	$ 15.67
Stock options | Chief Executive Officer | Vesting Provision One
Weighted Average Grant Date Fair Value
Compensation expense	$ 4,300
Changes in unvested stock options
Granted (in shares)	196,637
Stock options | Chief Executive Officer | Vesting Provision Two
Weighted Average Grant Date Fair Value
Compensation expense	$ 5,300
Changes in unvested stock options
Granted (in shares)	341,978

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions (Details) - Stock options - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Assumptions
Expected volatility	61.20%	60.00%	73.80%
Expected option term (in years)	6 years 3 months	6 years 3 months	6 years 3 months
Risk free interest rate	1.50%	1.50%	2.00%
Unrecognized stock-based compensation expense	$ 27.9
Period for recognition	2 years 6 months

401(K) Savings Plan (Details)

401(K) Savings Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
401(k) Savings Plan
Employer match (as a percent)	200.00%
Maximum employee contributions eligible for matching contributions	$ 6,000
Maximum employee contributions eligible for matching contributions (as a percent)	3.00%
Contributions to the 401(k) Plan	$ 1,200,000	$ 1,100,000	$ 800,000

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of income tax rate
Income tax computed at federal statutory tax rate	21.00%	21.00%
State taxes, net of federal benefit	8.89%	5.20%
General business credit carryovers	2.95%	4.80%
162m Limitation	(1.44%)
Stock Options	1.12%	(1.80%)
Non-deductible expenses	0.24%	(0.10%)
Tax Rate Changes	5.03%
Change in valuation allowance	(37.80%)	(29.10%)

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 127,092	$ 70,751
Tax credit carryforwards	25,028	19,353
Accrued expenses	3,991	11,372
Capitalized patent costs	63,093	46,197
Lease Liabilities	7,929	7,083
Deferred revenue	21,709	25,724
Other	10,431	5,204
Total deferred tax assets	259,273	185,684
Less valuation allowance	(251,071)	(178,307)
Net deferred tax assets	8,202	7,377
Deferred tax liabilities	(8,202)	(7,377)
Deferred tax liabilities - depreciation and amortization	(335)	(567)
Deferred tax liabilities - Right-of-use assets	$ (7,867)	$ (6,810)

Income Taxes - Net Operating Lo

Income Taxes - Net Operating Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 251,071	$ 178,307
Change in the valuation allowance	72,800
Unrecognized tax benefits	0	0
Federal
Operating Loss Carryforwards [Line Items]
Net operating losses	447,400	261,900
Net operating losses carryforward indefinitely	371,900
Net operating losses with expiration	75,500
State
Operating Loss Carryforwards [Line Items]
Net operating losses	$ 507,100	$ 258,400

Net Loss per Share - Anti-dilut

Net Loss per Share - Anti-dilutive (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Potentially dilutive securities
Anti-dilutive common stock equivalent shares	3,644,817	4,811,947
Restricted Stock
Potentially dilutive securities
Anti-dilutive common stock equivalent shares	628,732	507,450
Stock options
Potentially dilutive securities
Anti-dilutive common stock equivalent shares	3,016,085	3,912,257
Convertible notes
Potentially dilutive securities
Anti-dilutive common stock equivalent shares		392,240