Editas Medicine (EDIT) 10-Q 8 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Document and Entity Information
Entity Registrant Name	Editas Medicine, Inc.
Entity Central Index Key	1,650,664
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		42,119,611
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 86,542	$ 185,323
Marketable securities	209,149
Accounts receivable	695	88
Prepaid expenses and other current assets	2,030	1,772
Total current assets	298,416	187,183
Property and equipment, net	39,092	40,378
Restricted cash and other non-current assets	1,619	1,621
Total assets	339,127	229,182
Current liabilities:
Accounts payable	6,976	4,640
Accrued expenses	8,450	17,439
Notes payable		10,000
Deferred revenue, current	13,239	256
Other current liabilities	831	748
Total current liabilities	29,496	33,083
Deferred revenue, net of current portion	97,851	26,000
Construction financing lease obligation, net of current portion	33,667	35,096
Other non-current liabilities	325	396
Total liabilities	161,339	94,575
Commitments and contingencies (see note 7)
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; 42,109,822 and 36,662,724 shares issued, and 41,840,122 and 35,818,131 shares outstanding at September 30, 2017 and December 31, 2016, respectively	4	4
Additional paid-in capital	447,468	320,129
Accumulated other comprehensive loss	(23)
Accumulated deficit	(269,661)	(185,526)
Total stockholders’ equity	177,788	134,607
Total liabilities and stockholders’ equity	$ 339,127	$ 229,182

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Condensed Consolidated Balance Sheet
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	42,109,822	36,662,724
Common stock, shares outstanding	41,840,122	35,818,131

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Consolidated Statements of Operations
Collaboration and other research and development revenues	$ 6,282	$ 962	$ 10,061	$ 5,155
Operating expenses:
Research and development	20,396	10,832	56,735	30,144
General and administrative	12,635	11,295	36,817	33,215
Total operating expenses	33,031	22,127	93,552	63,359
Operating loss	(26,749)	(21,165)	(83,491)	(58,204)
Other income (expense), net:
Other income (expense), net	196	3	458	(22)
Interest income (expense), net	(46)	142	(1,102)	419
Total other income (expense), net	150	145	(644)	397
Net loss	(26,599)	(21,020)	(84,135)	(57,807)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(26,599)	(21,020)	(84,135)	(57,807)
Accretion of redeemable convertible preferred stock to redemption value				(47)
Net loss attributable to common stockholders	$ (26,599)	$ (21,020)	$ (84,135)	$ (57,854)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.64)	$ (0.59)	$ (2.13)	$ (1.86)
Weighted-average common shares outstanding, basic and diluted	41,307,092	35,505,429	39,558,553	31,040,670

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Consolidated Statements of Comprehensive Loss
Net loss	$ (26,599)	$ (21,020)	$ (84,135)	$ (57,807)
Other comprehensive loss:
Unrealized gain (loss) on available-for-sale securities	44		(23)
Comprehensive loss	$ (26,555)	$ (21,020)	$ (84,158)	$ (57,807)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flow from operating activities
Net loss	$ (84,135)	$ (57,807)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Stock-based compensation expense	15,287	13,099
Depreciation	1,966	714
Non-cash research and development expense	5,000
Re-measurement of warrant to purchase redeemable securities		87
Other non-cash items, net	(17)	265
Changes in operating assets and liabilities:
Accounts receivable	(607)	(103)
Prepaid expenses and other current assets	(258)	(1,667)
Other non-current assets	2	2,235
Accounts payable	2,563	2,095
Accrued expenses	(8,962)	4,034
Deferred revenue	84,834	479
Other current and non-current liabilities	(21)
Net cash provided by (used in) operating activities	15,652	(36,569)
Cash flow from investing activities
Purchases of property and equipment	(1,770)	(2,817)
Proceeds from the sale of equipment	15
Purchases of marketable securities	(298,233)
Proceeds from maturities of marketable securities	89,500
Changes in restricted cash		(1,619)
Net cash used in investing activities	(210,488)	(4,436)
Cash flow from financing activities
Proceeds from public offering of common stock, net of issuance costs	96,685	97,488
Payments of notes payable	(600)
Proceeds from exercise of stock options	535	211
Payments on construction financing lease obligation	(565)
Net cash provided by financing activities	96,055	97,699
Net (decrease) increase in cash and cash equivalents	(98,781)	56,694
Cash and cash equivalents, beginning of period	185,323	143,180
Cash and cash equivalents, end of period	86,542	199,874
Supplemental disclosure of cash and non-cash activities:
Accretion of redeemable convertible preferred stock to redemption value		47
Fixed asset additions included in accounts payable and accrued expenses	234	244
Reclassification of warrants to additional paid in capital		376
Conversion of preferred stock to common stock upon closing of the initial public offering		199,915
Reclassification of liability for common stock subject to repurchase	9	$ 8
Issuance of common stock for settlement of notes payable	$ 14,823

Nature of Business

Nature of Business	9 Months Ended
	Sep. 30, 2017
Nature of Business
Nature of Business	Editas Medicine, Inc. Notes to Condensed Consolidated Financial Statements (unaudited) 1. Nature of Business Editas Medicine, Inc. (the “Company”) is a research stage company dedicated to treating patients with genetically defined diseases by correcting their disease‑causing genes. 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 and debt financings, including the initial public offering of its common stock (the “IPO”), its follow-on public offering of its common stock in March 2017 and private placements of preferred stock, from upfront, milestone and research and development fees paid under a research collaboration with Juno Therapeutics, Inc. (“Juno Therapeutics”), and from an upfront payment paid under a strategic alliance and option agreement with Allergan Pharmaceuticals International Limited (“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 February 2016, the Company completed its IPO whereby the Company sold 6,785,000 shares of its common stock, inclusive of 885,000 shares of common stock sold by the Company pursuant to the full exercise of an overallotment option granted to the underwriters in connection with the offering, at a price to the public of $16.00 per share. The shares began trading on the NASDAQ Global Select Market on February 3, 2016. The aggregate net proceeds received by the Company from the offering were $97.5 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. In March 2017, the Company completed a follow-on offering whereby the Company sold 4,600,000 shares of its common stock, inclusive of 600,000 shares of common stock sold by the Company pursuant to the full exercise of an option granted to the underwriters in connection with the offering, at a price to the public of $22.50 per share (the “March Offering”). The aggregate net proceeds received by the Company from the March Offering were $96.7 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. The significant increase in shares outstanding in the first quarter of 2017 as a result of the March Offering is expected to impact the year-over-year comparability of the Company’s net loss per share calculations for the next six months. As of September 30, 2017, there were 41,840,122 shares of common stock outstanding. The Company has incurred annual net operating losses in every year since its inception. The Company expects that its existing cash, cash equivalents, and marketable securities at September 30, 2017, anticipated interest income, and anticipated research support under the Company’s collaboration agreement with Juno Therapeutics will enable it to fund its operating expenses and capital expenditure requirements for at least the next 24 months. The Company had an accumulated deficit of $269.7 million at September 30, 2017, and will require substantial additional capital to fund its operations. The Company has not generated any product revenue. There can be no assurance that the Company will be able to obtain additional debt or equity financing or generate product revenue or revenues from collaborative partners, on terms acceptable to the Company, on a timely basis or at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations, and financial condition.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Unaudited Interim Financial Information The condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016 (the “Annual Report”). The unaudited condensed consolidated financial statements include the accounts of Editas Medicine, Inc. and its wholly owned subsidiary, Editas Securities Corporation. All intercompany transactions and balances of the subsidiary have been eliminated in consolidation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The three months ended September 30, 2017 and 2016 are referred to as the third quarter of 2017 and 2016, respectively. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. Use of Estimates The preparation of condensed consolidated financial statements in conformity with Summary of Significant Accounting Policies The Company’s significant accounting policies are described in Note 2, “Summary of Significant Accounting Policies,” to the Consolidated Financial Statements included in the Annual Report. There have been no material changes to the significant accounting policies previously disclosed in the Annual Report other than as noted below. 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 with a remaining maturity date greater than one year are classified as non-current. The Company classifies all of its marketable securities as available-for-sale securities. Available-for-sale 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). If any adjustment to fair value reflects a decline in value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is “other-than-temporary.” To determine whether an impairment is other-than-temporary, the Company considers whether it has the ability and intent to hold the investment until a market price recovery and considers whether evidence indicating the cost of the investment is recoverable outweighs evidence to the contrary. The Company does not intend to sell the investments and it is not likely that the Company will be required to sell the investments before recovery of their amortized cost bases, which may be maturity. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), which supersedes the revenue recognition requirements in Accounts Standards Codification (“ASC”) 605, Revenue Recognition , and most industry-specific guidance. The new standard requires that an entity recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The update also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017 and should be applied retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying this update recognized at the date of initial application. Early adoption is permitted beginning after December 15, 2016, including interim reporting periods within those years. In April 2016, the FASB issued ASU No. 2016-10 , Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing (“ASU 2016-10”), which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”), related to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration and the presentation of sales and other similar taxes collected from customers. These standards have the same effective date and transition date as ASU 2014-09. The Company has three revenue arrangements, its license and collaboration with Juno Therapeutics, its award arrangement with the Cystic Fibrosis Foundation Therapeutics, Inc. (“CFFT”), and its strategic alliance with Allergan, pursuant to which it has recognized since inception a total of $11.8 million, $0.3 million, and $5.6 million, respectively, through September 30, 2017. The Company is analyzing the potential impact that ASU 2014-09, ASU 2016-10 and ASU 2016-12 may have on its historical revenue recognition under these three arrangements. This analysis includes, but is not limited to, reviewing variable consideration as it relates to its agreements, reviewing the method and timing of recognition of the upfront license payments, research funding and the two $2.5 million milestones received from Juno Therapeutics, assessing potential disclosures and evaluating the impact of each potential method of adoption on the Company’s consolidated financial statements. The Company will adopt the new standard effective January 1, 2018 and anticipates using the modified retrospective approach with a cumulative-effect adjustment to retained earnings in the period of initial application. The adoption of ASU 2014-09 may have a material impact on revenue recognition and notes to consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASU 2016-02”), which applies to all leases and will require lessees to record most leases on the balance sheet, but recognize expense in a manner similar to the current standard. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 and interim periods within those years. Entities are required to use a modified retrospective approach of adoption for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. Full retrospective application is prohibited. The Company is evaluating the potential impact that the adoption of ASU 2016-02 will have on the Company’s consolidated financial statements. In March 2016, the FASB, issued ASU No. 2016-09, Compensation - Stock Compensation (“ASU 2016-09”). ASU 2016-09 simplifies several aspects of the accounting for employee share-based payment transactions, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. Under this guidance, a company recognizes all excess tax benefits and tax deficiencies as income tax expense or benefit in the income statement as the awards vest or are settled. ASU 2016-09 is effective for public companies for annual reporting periods beginning after December 15, 2016, including interim periods within those annual reporting periods. Upon adoption of this standard on January 1, 2017, the Company recognized previously unrecognized excess tax benefits using the modified retrospective transition method, which resulted in a cumulative-effect increase of $179,000 to deferred tax assets which is offset by a corresponding decrease to the valuation allowance. The implementation of ASU 2016-09 does not have a material impact on stock-based compensation expense. As part of the adoption of ASU 2016-09, the Company elected to record forfeitures as they occur. In October 2016, the FASB issued ASU No. 2016-18, Restricted Cash (“ASU 2016-18”), which requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and restricted cash or restricted cash equivalents. Therefore, amounts described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 is effective for fiscal years beginning after December 15, 2017, and interim periods within those years. Early adoption is permitted. The Company is evaluating the potential impact that the adoption of ASU 2016-18 will have on the Company’s consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (“ASU 2017-01”), which clarified the definition of a business and provides a screen to determine when an integrated set of assets and activities is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. This new standard will be effective for fiscal years beginning after December 15, 2017, and interim periods within those years. Early adoption is permitted. The Company has adopted this new standard as of January 1, 2017, with prospective application to any business development transactions. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (“ASU 2017-09”), which provided guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The new guidance requires modification accounting if the vesting condition, fair value or award classification is not the same both before and after a change to the terms and conditions of the award. This new standard will be effective for fiscal years beginning after December 15, 2017, and interim periods within those years. Early adoption is permitted. The Company does not anticipate a material impact to its consolidated financial statements as a result of the adoption of this standard.

Cash Equivalents & Marketable S

Cash Equivalents & Marketable Securities	9 Months Ended
	Sep. 30, 2017
Cash Equivalents & Marketable Securities
Cash Equivalents & Marketable Securities	3. Cash Equivalents & Marketable Securities Cash equivalents and marketable securities consisted of the following at September 30, 2017 (in thousands): Gross Gross Amortized Unrealized Unrealized Fair September 30, 2017 Cost Gains Losses Value Cash equivalents: Money market funds $ 66,797 $ — $ — $ 66,797 U.S. Treasuries 8,497 — — 8,497 Government agency securities 8,498 — — 8,498 Marketable securities: U.S. Treasuries 126,222 — — 126,222 Government agency securities 82,950 — (23) 82,927 Total cash equivalents and marketable securities $ 292,964 $ — $ (23) $ 292,941 Cash equivalents and marketable securities consisted of the following at December 31, 2016 (in thousands): Gross Gross Amortized Unrealized Unrealized Fair December 31, 2016 Cost Gains Losses Value Cash equivalents: Money market funds $ 185,323 $ — $ — $ 185,323 Total cash equivalents and marketable securities $ 185,323 $ — $ — $ 185,323 At September 30, 2017, the Company held 21 securities that were in an unrealized loss position. The aggregate fair value of securities held by the Company in an unrealized loss position for less than 12 months at September 30, 2017 was $135.2 million, and there were no securities held by the Company in an unrealized loss position for more than 12 months. As of September 30, 2017, the Company did not intend to sell, and would not be more likely than not required to sell, the securities in an unrealized loss position before recovery of their amortized cost bases. Furthermore, the Company has determined that there was no material change in the credit risk of these securities. As a result, the Company determined it did not hold any securities with any other-than-temporary impairment as of September 30, 2017. There were no realized gains or losses on available-for-sale securities during the nine months ended September 30, 2017 and 2016.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Measurements
Fair Value Measurements	4. Fair Value Measurements Assets measured at fair value on a recurring basis as of September 30, 2017 were as follows (in thousands): Quoted Prices Significant in Active Other Significant Markets for Observable Unobservable September 30, Identical Assets Inputs Inputs Financial Assets 2017 (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 66,797 $ 66,797 $ — $ — U.S. Treasuries 8,497 8,497 — — Government agency securities 8,498 8,498 — — Marketable securities: U.S. Treasuries 126,222 126,222 — — Government agency securities 82,927 82,927 — — Money market funds, included in restricted cash 1,619 1,619 — — Total financial assets $ 294,560 $ 294,560 $ — $ — Assets measured at fair value on a recurring basis as of December 31, 2016 were as follows (in thousands): Quoted Prices Significant in Active Other Significant Markets for Observable Unobservable December 31, Identical Assets Inputs Inputs Financial Assets 2016 (Level 1) (Level 2) (Level 3) Cash and cash equivalents $ 185,323 $ 185,323 $ — $ — Money market funds, included in restricted cash 1,619 1,619 — — Total financial assets $ 186,942 $ 186,942 $ — $ — There were no transfers between fair value measurement levels during the nine months ended September 30, 2017.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2017
Accrued Expenses
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): As of September 30, December 31, 2017 2016 Employee compensation costs $ 2,973 $ 2,480 Patent and license fees 3,851 13,251 Research and development 1,018 443 Professional services 499 729 Other 109 536 Total $ 8,450 $ 17,439

Property and Equipment, net

Property and Equipment, net	9 Months Ended
	Sep. 30, 2017
Property and Equipment, net
Property and Equipment, net	6. Property and Equipment, net Property and equipment, net consisted of the following (in thousands): As of September 30, December 31, 2017 2016 Building $ 35,167 $ 35,941 Laboratory equipment 6,352 5,130 Computer equipment 558 392 Leasehold improvements 177 200 Software 173 101 Furniture and office equipment 96 170 Total property and equipment 42,523 41,934 Less: accumulated depreciation (3,431) (1,556) Property and equipment, net $ 39,092 $ 40,378

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies
Commitments and Contingencies	7. Commitments and Contingencies Hurley Street Lease In February 2016, the Company entered into a lease agreement for approximately 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. 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 with cash held in a money market account, is recorded in restricted cash in the accompanying condensed consolidated financial statements as of September 30, 2017 and December 31, 2016. In connection with this lease, the landlord provided a tenant improvement allowance for costs associated with the design, engineering, and construction of tenant improvements for the leased facility. For accounting purposes, the Company was deemed the owner of the building during the construction period due to the fact that the Company was involved in the construction project, including having responsibilities for cost overruns for planned tenant improvements that did not qualify as “normal tenant improvements” under the lease accounting guidance. Throughout the construction period, the Company recorded the project construction costs incurred as an asset, along with a corresponding facility lease obligation, on its balance sheet for the total amount of the project costs incurred whether funded by the Company or the landlord. Construction was completed in October 2016, and the Company considered the requirements for sale-leaseback accounting treatment, which included an evaluation of whether all risks of ownership had transferred back to the landlord, as evidenced by a lack of continuing involvement in the leased property. The Company determined that the arrangement did not qualify for sale-leaseback accounting treatment, the building asset would remain on the Company’s balance sheet at its historical cost, and such asset would be depreciated over its estimated useful life of 30 years. The Company bifurcates its future lease payments pursuant to the Hurley Street lease into (i) a portion that is allocated to the building and (ii) a portion that is allocated to the land on which the building is located, which is recorded as rental expense. Although the Company did not begin making lease payments pursuant to the Hurley Street lease until November 2016, the portion of the lease obligation allocated to the land is treated for accounting purposes as an operating lease that commenced upon execution of the Hurley Street lease in February 2016. The lease will continue until October 2023. The Company has the option to extend the lease for an additional five year term at market-based rates. The Company began using this space as its headquarters in October 2016 and rental payments for this property began in November 2016. The base rent is subject to increases over the term of the lease. In February 2017, the Company subleased approximately 10 thousand square feet of the Hurley Street premises pursuant to a sublease (the “Sublease”). Under the terms of the Sublease, the total minimum rental revenue to be received in the future is $0.6 million as of September 30, 2017. The Sublease commenced in February 2017 and will expire on the eighteen month anniversary thereof, unless it is extended for an additional eighteen month term by the subtenant. If the subtenant elects to extend the term of the lease, the base rent is subject to a minimal increase for the subsequent eighteen month period. Licensor Expense Reimbursement The Company is obligated to reimburse The Broad Institute Inc. (“Broad”) and the President and Fellows of Harvard College (“Harvard”) for expenses incurred by each of them associated with the prosecution and maintenance of the patent rights that the Company licenses from them pursuant to the license agreement by and among the Company, Broad and Harvard, including the interference and opposition proceedings involving patents licensed to the Company under the license agreement. 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. During the three and nine months ended September 30, 2017, the Company recognized $5.1 million and $13.0 million in expense for such reimbursement, respectively. During the three and nine months ended September 30, 2016, the Company recognized $5.0 million and $16.0 million in expense for such reimbursement, respectively. Success Payments In 2016, the Company entered into patent license agreements with each of The General Hospital Corporation, d/b/a Massachusetts General Hospital (“MGH”) and Broad (collectively, the “2016 License Agreements”). Pursuant to the terms of the 2016 License Agreements, the Company is required to make certain success payments to MGH, Broad and Wageningen University (“Wageningen” and such payments, collectively, the “Success Payments”), payable in cash or, at the Company’s election, common stock in the case of MGH or, in the case of Broad and Wageningen, promissory notes payable in cash or, at the Company’s election subject to certain conditions, common stock of the Company. The Success Payments are payable, if and when, the Company’s market capitalization reaches specified thresholds for a specific period of time or upon a sale of the Company for consideration in excess of those thresholds, as discussed more fully in Note 8 (collectively, the “Payment Conditions”). The Success Payments were accounted for under the provisions of FASB ASC, Topic 505-50, Equity-Based Payments to Non-Employees. The Company has the right to terminate any of the 2016 License Agreements at will upon written notice. Absent any of the Payment Conditions being achieved prior to termination, the Company would not be obligated to pay any Success Payments. As such, the Company will recognize the expense and liability associated with each Success Payment upon achievement of the associated Payment Conditions, if ever. The Company triggered the first Success Payment under one of the 2016 License Agreements during the first quarter of 2017 when the Company’s market capitalization reached $750 million. On March 28, 2017, the Company issued promissory notes for an aggregate principal amount of $5.0 million to Broad and Wageningen, as discussed more fully within the Notes Payable section below, and the Company settled such notes in August 2017. Notes Payable In December 2016, in connection with the Company’s entry into the Cpf1 License Agreement with Broad (the “Cpf1 License Agreement”), one of the 2016 License Agreements, it issued promissory notes in an aggregate principal amount of $10.0 million to Broad and Wageningen (the “Initial Notes”). Outstanding principal and accrued interest on the Initial Notes were due and payable on the earlier of December 2017 or a specified period of time following a company sale or change of control event. The Initial Notes accrued interest at a rate of 4.8% per annum. The Company fully settled the outstanding principal and accrued interest on the Initial Notes by paying $0.2 million in cash to Wageningen in August 2017 and issuing 108,104 shares and 371,166 shares of common stock to Broad in August 2017 and September 2017, respectively, in connection with such settlement. In March 2017, a $5.0 million Success Payment under the Cpf1 License Agreement became due upon the market capitalization of the Company’s common stock reaching $750 million. The Company issued a promissory note to each of Broad and Wageningen in an aggregate original principal amount of $5.0 million (collectively, the “Success Payment Notes”). Outstanding principal and accrued interest on the Success Payment Notes were due and payable in August 2017. The Success Payment Notes were subject to the same interest and terms as the Initial Notes, other than the maturity date. The Company settled the outstanding principal and accrued interest on the Success Payment Notes in August 2017 by paying $0.4 million in cash to Wageningen and issuing 271,347 shares of common stock to Broad in August 2017 in connection with the settlement of the Success Payment Notes. Litigation The Company is not a party to any litigation and did not have contingency reserves established for any litigation liabilities as of September 30, 2017 or December 31, 2016.

Significant Agreements

Significant Agreements	9 Months Ended
	Sep. 30, 2017
Significant Agreements
Significant Agreements	8. Significant Agreements Juno Therapeutics Collaboration Agreement Summary of Agreement In May 2015, the Company entered into a Collaboration and License Agreement (the “Collaboration Agreement”) with Juno Therapeutics. The collaboration is focused on the research and development of engineered T cells with chimeric antigen receptors (“CARs”) and T cell receptors (“TCRs”) that have been genetically modified to recognize and kill other cells. The parties will pursue the research and development of CAR and TCR engineered T cell products utilizing the Company’s genome editing technologies with Juno Therapeutics’ CAR and TCR technologies across three research areas. The collaborative program of research to be undertaken by the parties pursuant to the Collaboration Agreement will be conducted in accordance with a mutually agreed upon research plan which outlines each party’s research and development responsibilities across the three research areas. The Company’s research and development responsibilities under the research plan are related to generating genome editing reagents that modify gene targets selected by Juno Therapeutics. Juno Therapeutics is responsible for evaluating and selecting for further research and development CAR and TCR engineered T cell products modified with the Company’s genome editing reagents. Except with respect to the Company’s obligations under the mutually agreed upon research plan, Juno Therapeutics has sole responsibility, at its own cost, for the worldwide research, development, manufacturing and commercialization of products within each of the three research areas for the diagnosis, treatment or prevention of any cancer in humans through the use of engineered T cells, excluding the diagnosis, treatment or prevention of medullary cystic kidney disease 1 (the “Exclusive Field”). The initial term of the research program commenced on May 26, 2015 and continues for five years ending on May 26, 2020 (the “Initial Research Program Term”). Juno Therapeutics may extend the Initial Research Program Term for up to two additional one year periods upon the payment of extension fees for each one year extension period, assuming the Company has agreed to the extension request(s) (together, the initial term and any extension period(s) are referred to as the “Research Program Term”). Under the terms of the Collaboration Agreement, the Company granted to Juno Therapeutics during the Research Program Term a nonexclusive, worldwide, royalty‑free, sublicensable (subject to certain conditions) license under certain of the intellectual property controlled by the Company solely for the purpose of conducting the following activities required under the specified research under the Collaboration Agreement: (i) conduct activities assigned to Juno Therapeutics under the research plan, (ii) conduct activities assigned to the Company under the research plan that the Company fails or refuses to conduct in a timely manner, (iii) use certain genome editing reagents generated under the research program to research, evaluate and conduct preclinical testing and development of certain engineered T cells and (iv) evaluate the data developed in the conduct of activities under the research plan (the “Research License”). Additionally, as it relates to two of the three research areas, the Company granted to Juno Therapeutics an exclusive, milestone and royalty‑bearing, sublicensable license under certain of the intellectual property controlled by the Company to research, develop, make and have made, use, offer for sale, sell, import and export selected CAR and TCR engineered T cell products in the Exclusive Field on a worldwide basis, specifically as it relates to certain targets selected by Juno Therapeutics pursuant to the research program. Furthermore, as it relates to the same two research areas, the Company granted to Juno Therapeutics a non‑exclusive, milestone and royalty‑bearing, sub licensable license under certain of the intellectual property controlled by the Company to use genome editing reagents generated under the research program that are used in the creation of certain CAR or TCR engineered T cell products on which Juno Therapeutics has filed an investigational new drug (“IND”) application in the Exclusive Field for the treatment or prevention of a cancer in humans to research, develop, make and have made, use, offer for sale, sell, import and export those CAR or TCR engineered T cell products in all fields outside of the Exclusive Field (the “Non‑Exclusive Field”) on a worldwide basis, specifically as it relates to certain targets selected by Juno Therapeutics pursuant to the research program (together, the license in the Exclusive Field and the license in the Non‑Exclusive Field are referred to as the “Development and Commercialization License” for each particular research area). Lastly, as it relates to the third research area, the Company granted to Juno Therapeutics a milestone and royalty‑bearing, sublicensable license under certain of the intellectual property controlled by the Company to use the genome editing reagents generated under the research program that are associated with certain CAR or TCR engineered T cell products to research, develop, make and have made, use, offer for sale, sell, import or export those CAR or TCR engineered T cell products in the Exclusive Field on a worldwide basis, specifically as it relates to certain products selected by Juno Therapeutics pursuant to the research program. The license associated with the third research area is exclusive as it relates to CAR or TCR engineered T cell products directed to certain targets as selected by Juno Therapeutics, but is otherwise non‑exclusive (referred to as the “Development and Commercialization License” for the third research area). The Collaboration Agreement will be managed on an overall basis by a project leader from each of the Company and Juno Therapeutics. The project leaders will serve as the contact point between the parties with respect to the research program and will be primarily responsible for facilitating the flow of information, interaction, and collaboration between the parties. In addition, the activities under the Collaboration Agreement during the Research Program Term will be governed by a joint research committee (“JRC”) formed by an equal number of representatives from the Company and Juno Therapeutics. The JRC will oversee, review and recommend direction of the research program. Among other responsibilities, the JRC will monitor and report research progress and ensure open and frequent exchange between the parties regarding research program activities. Under the terms of the Collaboration Agreement, the Company received a $25.0 million up‑front, non‑refundable, non‑creditable cash payment. In addition, Juno Therapeutics is obligated to pay to the Company an aggregate of up to $22.0 million in research and development funding over the Initial Research Program Term across the three research areas consisting primarily of funding for up to a specified maximum number of full time equivalents personnel each year over the Initial Research Program Term across three research areas. Under the terms of the Collaboration Agreement, there is no incremental compensation due to the Company with respect to the Development and Commercialization License granted to Juno Therapeutics associated with the first target or product, as applicable, designated by Juno Therapeutics within each of the three research areas. However, for two of the three research areas, Juno Therapeutics has the option to purchase up to three additional Development and Commercialization Licenses associated with other gene targets for an additional fee of approximately $2.5 million per target. In addition, Juno Therapeutics would be required to make certain milestone payments to the Company upon the achievement of specified development, regulatory and commercial events. More specifically, for the first product to achieve the associated event in each of the three research areas, the Company is eligible to receive up to a $77.5 million in development milestone payments and up to $80 million in regulatory milestone payments. In addition, the Company is eligible to receive additional development and regulatory milestone payments for subsequent products developed within each of the three research areas. Moreover, the Company is eligible for up to $75.0 million in commercial milestone payments associated with aggregate sales of all products within each of the three research areas. Development milestone payments are triggered upon the achievement of certain specified development criteria or upon initiation of a defined phase of clinical research for a product candidate. Regulatory milestone payments are triggered upon approval to market a product candidate by the United States Food and Drug Administration (“FDA”) or other global regulatory authorities. Commercial milestone payments are triggered when an approved pharmaceutical product reaches certain defined levels of net sales by the licensee. In addition, to the extent any of the product candidates covered by the licenses conveyed to Juno Therapeutics are commercialized, the Company would be entitled to receive tiered royalty payments of low double digits based on a percentage of net sales. Royalty payments are subject to certain reductions, including for any royalty payments required to be made by Juno Therapeutics related to a third‑party’s intellectual property rights, subject to an aggregate minimum floor. Royalties are due on a licensed product‑by‑licensed product and country‑by‑country basis from the date of the first commercial sale of each product in a country until the later of: (i) the tenth anniversary of the first commercial sale of such licensed product in such country and (ii) the expiration date in such country of the last to expire valid claim within the licensed intellectual property covering the manufacture, use or sale of such licensed product in such country. The Company achieved $2.5 million development milestones under the Collaboration Agreement resulting from technical progress in a research program in each of May 2016 (the “First Milestone”) and July 2017 (the “Second Milestone"). Due to the uncertainty of pharmaceutical development and the high historical failure rates generally associated with drug development, no additional milestone or royalty payments may ever be received from Juno Therapeutics. Unless earlier terminated, the Collaboration Agreement will continue in full force and effect, on a product‑by‑product and country‑by‑country basis until the date no further payments are due to the Company from Juno Therapeutics. Either party may terminate the Collaboration Agreement if the other party has materially breached or defaulted in the performance of any of its material obligations and such breach or default continues after the specified cure period. Either party may terminate the Collaboration Agreement in the event of the commencement of any proceeding in or for bankruptcy, insolvency, dissolution or winding up by or against the other party that is not dismissed or otherwise disposed of within a specified time period. Juno Therapeutics may terminate the Collaboration Agreement for convenience upon not less than six months prior written notice to the Company. The Company may terminate the Collaboration Agreement in the event that Juno Therapeutics brings, assumes, or participates in, or knowingly, willfully or recklessly assists in bringing a dispute or challenge against the Company related to its intellectual property. Termination of the Collaboration Agreement for any reason does not release either party from any liability which, at the time of such termination, has already accrued to the other party or which is attributable to a period prior to such termination nor preclude either party from pursuing any rights and remedies it may have under the agreement or at law or in equity with respect to any breach of the Collaboration Agreement. If Juno Therapeutics terminates the Collaboration Agreement as a result of the Company’s uncured material breach or default, then: (i) the licenses and rights conveyed to Juno Therapeutics will continue as set forth in the agreement, (ii) Juno Therapeutics’ obligations related to milestones and royalties will continue as set forth in the agreement and (iii) Juno Therapeutics’ rights to prosecute, maintain and enforce certain intellectual property rights will continue as set forth in the agreement. If Juno Therapeutics terminates the Collaboration Agreement for convenience or if the Company terminates the Collaboration Agreement as a result of Juno Therapeutics’ uncured material breach or default, then the licenses conveyed to Juno Therapeutics will terminate. Accounting Analysis The Company evaluated the Collaboration Agreement in accordance with the provisions of ASC Revenue Recognition—Multiple Element Arrangements (“ASC 605-25”). The Company’s arrangement with Juno Therapeutics contains the following deliverables: (i) research and development services during the Initial Research Program Term (the “R&D Services Deliverable”), (ii) the Research License, (iii) the Development and Commercialization Licenses related to each of the three research areas (each, the “Development and Commercialization License Deliverable” for the respective research area), (iv) significant and incremental discount related to the option to purchase up to three additional Development and Commercialization Licenses for two of the research areas (each, the “Discount Deliverable” for the associated option) and (v) JRC services during the Initial Research Program Term (the “JRC Deliverable”). The Company has determined that the options to purchase additional development and commercialization licenses within two of the research program areas related to other gene targets are substantive options. Juno Therapeutics is not contractually obligated to exercise the options. Moreover, as a result of the uncertain outcome of the discovery, research and development activities, there is significant uncertainty as to whether Juno Therapeutics will decide to exercise its option for any additional gene targets within either of the two applicable research areas. Consequently, the Company is at risk with regard to whether Juno Therapeutics will exercise the options. However, the Company has determined that the options to purchase additional development and commercialization licenses with respect to other gene targets within the two applicable research program areas are priced at a significant and incremental discount. As a result, the Company has concluded that the discounts to purchase development and commercialization licenses for up to three additional gene targets within both of the research areas represent separate elements in the arrangement at inception. Accordingly, the deliverables identified at inception of the arrangement include six separate deliverables related to the significant and incremental discount inherent in the pricing of the option to purchase up to three additional development and commercialization licenses for two of the research areas included within the research program. The Company has concluded that the Research License deliverable does not qualify for separation from the R&D Services Deliverable. As it relates to the assessment of standalone value, the Company has determined that Juno Therapeutics cannot fully exploit the value of the Research License deliverable without receipt of the R&D Services Deliverable. This is primarily due to the fact that Juno Therapeutics must rely upon the Company to provide the research and development services included in the research plan because the services incorporate technology that is proprietary to the Company. The services to be provided by the Company involve unique skills and specialized expertise, particularly as it relates to genome editing technology that is not available in the marketplace. Accordingly, Juno Therapeutics must obtain the research and development services from the Company which significantly limits the ability for Juno Therapeutics to utilize the Research License for its intended purpose on a standalone basis. Therefore, the Research License deliverable does not have standalone value from the R&D Services Deliverable. As a result, the Research License deliverable and the R&D Services Deliverable have been combined as a single unit of accounting (the “R&D Services Unit of Accounting”). Conversely, the Company has concluded that each of the other deliverables identified at the inception of the arrangement has standalone value from each of the other elements based on their nature. Factors considered in this determination included, among other things, the capabilities of the collaboration partner, whether any other vendor sells the item separately, whether the value of the deliverable is dependent on the other elements in the arrangement, whether there are other vendors that can provide the items and if the customer could use the item for its intended purpose without the other deliverables in the arrangement. Additionally, the Collaboration Agreement does not include a general right of return. Accordingly, each of the other deliverables included in the Juno Therapeutics arrangement qualifies as a separate unit of accounting. Therefore, the Company has identified eleven units of accounting in connection with its obligations under the collaboration arrangement with Juno Therapeutics as follows: (i) the R&D Services Unit of Accounting, (ii) three units of accounting related to the Development and Commercialization Licenses for each of the three research areas, (iii) six units of accounting related to each of the Discount Deliverables, and (iv) the JRC Deliverable. The Company has determined that neither Allocable arrangement consideration at inception is comprised of: (i) the up‑front payment of $25.0 million, (ii) the research support of $20.0 million and (iii) payments related to specialized materials costs of $2.0 million. The research support of $20.0 million and payments related to specialized materials costs of $2.0 million represent contingent revenue features because the Company’s retention of the associated arrangement consideration is dependent upon its future performance of research support services and development of specialized materials. The aggregate allocable arrangement consideration of $47.0 million was allocated among the separate units of accounting using the relative selling price method as follows: (i) R&D Services Unit of Accounting: $16.7 million, (ii) Development and Commercialization License for the first research area: $9.3 million, (iii) Development and Commercialization License for the second research area: $15.4 million, (iv) Development and Commercialization License for the third research area: $0.2 million, (v) the first Discount Deliverable for the first research area: $0.7 million, (vi) the second Discount Deliverable for the first research area: $0.4 million, (vii) the third Discount Deliverable for the first research area: $0.2 million, (viii) the first Discount Deliverable for the second research area: $2.0 million, (ix) the second Discount Deliverable for the second research area: $1.3 million, and (x) the third Discount Deliverable for the second research area: $0.8 million. No amounts were allocated to the JRC Deliverable because the associated BESP was determined to be de minimis. The amounts allocated to each of the development and commercialization licenses are based on the respective BESP calculations, which reflect the level of risk and expected probability of success inherent in the nature of the associated research area. The Company will recognize revenue related to amounts allocated to the R&D Services Unit of Accounting as the underlying services are performed. The Company will recognize revenue related to amounts allocated to each of the Development and Commercialization Licenses upon delivery of the associated license, assuming the research services are substantially complete at the time the license is delivered. The rights to be conveyed to Juno Therapeutics pursuant to each of the Development and Commercialization Licenses extend exclusively to an individual target or product, as applicable; therefore, delivery is deemed to occur upon the designation by Juno Therapeutics of the specific target or product, as applicable, whereupon the license becomes effective. The Company will recognize revenue related to amounts allocated to each of the Discount Deliverables upon the earlier of exercise of the associated option or upon lapsing of the underlying right, if the respective option expires unexercised. The Company has evaluated all of the milestones that may be received in connection with the Juno Therapeutics arrangement. In evaluating if a milestone is substantive, the Company assesses whether: (i) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the Company’s performance to achieve the milestone, (ii) the consideration relates solely to past performance, and (iii) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. All development and regulatory milestones are considered substantive on the basis of the contingent nature of the milestone, specifically reviewing factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the milestone as well as the level of effort and investment required. Accordingly, such amounts will be recognized as revenue in full in the period in which the associated milestone is achieved, assuming all other revenue recognition criteria are met. All commercial milestones will be accounted for in the same manner as royalties and recorded as revenue upon achievement of the milestone, assuming all other revenue recognition criteria are met. The Company will recognize royalty revenue in the period of sale of the related product(s), based on the underlying contract terms, provided that the reported sales are reliably measurable and the Company has no remaining performance obligations, assuming all other revenue recognition criteria are met. During the three and nine months ended September 30, 2017, the Company recognized revenue totaling approximately $3.1 million and $4.4 million, respectively, each inclusive of the Second Milestone payment. During the three and nine months ended September 30, 2016, the Company recognized revenue totaling approximately $0.8 million and $4.9 million, respectively, with $2.5 million of the revenue recognized in the nine month period relating to the First Milestone payment. The revenue is classified as collaboration and other research and development revenue in the accompanying condensed consolidated statement of operations. As of September 30, 2017 and December 31, 2016, there was approximately $26.3 million and $26.0 million of deferred revenue related to the Company’s collaboration with Juno Therapeutics, respectively, all of which is classified as long‑term in the accompanying condensed consolidated balance sheet. In addition, as of September 30, 2017, the Company has recorded accounts receivable of $0.7 million related to reimbursable research and development costs under the Collaboration Agreement for activities performed during the third quarter of 2017. There was no receivable balance as of December 31, 2016. During the three and nine months ended September 30, 2017, the Company paid $0.5 million in sublicense fees that were owed to certain of the Company’s licensors in connection with the Second Milestone, which the Company recorded as research and development expenses during such periods. During the nine months ended September 30, 2016, the Company paid $0.5 million in sublicense fees that were owed to certain of the Company’s licensors in connection with the First Milestone, which the Company recorded as research and development expenses during such period, and paid no such fees during the three months ended September 30, 2016. Allergan Pharmaceuticals Strategic Alliance and Option Agreement Summary of 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”). Over a seven-year research term, Allergan will have an exclusive option to exclusively license from the Company up to five collaboration development programs for the treatment of ocular disorders (each a “CDP”), including the Company’s Leber’s Congenital Amaurosis type 10 program (the “LCA10 Program”). Under the Allergan Agreement, the Company will use commercially reasonable efforts to develop at least five CDPs and deliver preclinical results and data meeting specified criteria with respect to each CDP (each, an “Option Package” and such criteria, the “Option Package Criteria”) to Allergan. The list of proposed targets that may be subject to a CDP may be amended from time to time by mutual agreement of the Company and Allergan. The Company is responsible for the preparation and delivery of a written development plan for each particular CDP setting forth the discovery and research activities to be conducted which is subject to the approval of the alliance steering committee that was formed under the Allergan Agreement, comprised of three members from each of the Company and Allergan (the “ASC”). The Company will maintain primary responsibility for the development efforts under each CDP. The Company is responsible for all research and development costs prior to the achievement of the Option Package Criteria. Upon achievement of the Option Package Criteria, as determined by the ASC, Allergan will have the ability, for a defined period of time (“Initial Option Period”) to exercise an option (each, an “Option”) to obtain a w orld-wide right and license to the Company’s background intellectual property and the Company’s interest in the CDP intellectual property to develop, commercialize, make, have made, use, offer for sale, sell, and import any gene editing therapy product that results from such CDP during the term of the Allergan Agreement (a “Licensed Product”) in any category of human diseases and conditions other than the diagnosis, treatment or prevention of any cancer in humans through the use of engineered T-cells and subject to specified other limitations . Allergan has the option to extend the Initial Option Period and require the Company to perform additional research and development services, subject to the payment of additional consideration. After exercise of an Option with respect to a CDP, with the exception of any CDP’s where the Company has exercised its profit-sharing option, Allergan will be responsible for all development, manufacturing, and commercialization activities in connection with licensed products arising from such CDP, other than with respect to the LCA10 Program, if LCA10 is designated as a CDP, for which the Company has retained the right to develop that program through the acceptance for filing of the first IND with respect to the LCA10 Program. Upon achievement of IND approval for LCA10, unless the Company has exercised its profit sharing option on LCA10, Allergan will be responsible for all development, manufacturing, and commercialization activities. The initial term of the Allergan Agreement commenced on March 14, 2017 (the “Effective Date”) and continues for seven years ending on March 14, 2024 (the “Research Term”). If the Company has not delivered an Option Package, which includes the results and data from the CDP, for five CDPs that satisfy the Option Package Criteria, then the Research Term will automatically extend by one-year increments until such obligation is satisfied, up to a maximum of ten years from the Effective Date. The activities under the Allergan Agreement during the Research Term will be governed by the ASC. The ASC will review and monitor the direction of the development plan, evaluate and determine which targets are selected to become CDP, establish the Option Package Criteria for each CDP and evaluate the achievement of such criteria as well as oversee the development and commercialization activities after Allergan has licensed a CDP. Under the terms of the Allergan Agreement, the Company received a $90.0 million up‑front, non‑refundable, non‑creditable cash payment (the “Allergan Upfront”) related to the Company’s research and development costs for Option Packages for at least five CDPs and for reimbursement of the Company’s past out of pocket costs with respect to the prosecution and defense of patents that it owns and in-licenses. Allergan has the option to purchase at least five development and commercialization licenses associated CDP that have satisfied the Option Package Criteria. The option exercise fee during the Initial Option Period is $15.0 million per CDP. If Allergan elects to extend the Initial Option Period, Allergan is required to pay an additional fee of $5.0 million to extend the option, at which point the Company is required to perform additional research services. If Allergan elects to exercise its option to a development and commercialization license after extending the Initial Option Period, Allergan must pay the Company the option exercise fee of $22.5 million, plus specified costs incurred by the Company in connection with the additional development work. Following the exercise by Allergan of an Option with respect to a CDP, Allergan would be required to make certain milestone payments to the Company upon the achievement of specified development, product approval and launch and commercial events, on a CDP by CDP basis. On a CDP by CDP basis, for the first product in the first field to achieve the associated event, the Company is eligible to receive up to an aggregate of $42 million for In addition, within 45 days of the acceptance by the applicable regulatory authority of the Company’s submission of an IND application with respect to the LCA10 Program, Allergan is required to pay the Company a one-time payment of $25.0 million (the “LCA10 IND Payment”), whether or not Allergan exercises its option under the Allergan Agreement to acquire an exclusive license with respect to the LCA10 Program. As of September 30, 2017, the next potential milestone payment that the Company may be entitled to receive under the Allergan Agreement is a substantive milestone payment of $8.0 million for the achievement of certain clinical criteria. With respect to the LCA10 Program and up to one other CDP of the Company’s choosing, following the exercise by Allergan of its Option to such programs, the Company will have the right to elect to participate in a profit-sharing arrangement with Allergan in the United States, on terms mutually agreed by the Company and Allergan and subject to a right of Allergan to reject such election under certain circumstances, under which the Company and Allergan would share equally in net profits and losses on specific terms to be agreed between the Company and Allergan, in lieu of Allergan paying royalties on net sales of any applicable Licensed Products in the United States, and in such event Allergan’s milestone payment obligations would be reduced, with the Company being eligible to receive development and product approval and launch milestone payments up to a low nine-digit amount in the aggregate and further sales milestone payments up to a high-eight digit amount in the aggregate, subject to reduction under certain circumstances. If the Company elects to participate in a profit-sharing arrangement, the Company is obligated to reimburse Allergan for half of the development costs incurred by Allergan with respect to the applicable CDP, and Allergan will retain control of all development and commercialization activities for the applicable Licensed Products. In addition, to the extent there is any Licensed Product, the Company would be entitled to receive tiered royalty payments of high single digits based on a percentage of net sales of such Licensed Product , subject to certain reductions under specified circumstances, and the Company will remain obligated to pay all license fees, milestone payments, and royalties due to its upstream licensors based on Allergan’s exercise of its license rights with respect to Licensed Products . However,

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2017
Stock-based Compensation
Stock-based Compensation	9 . Stock‑based Compensation Total compensation cost recognized for all stock‑based compensation awards in the condensed consolidated statements of operations was as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2017 2016 2017 2016 Research and development $ 2,431 $ 2,619 $ 9,130 $ 10,021 General and administrative 2,037 1,072 6,157 3,078 Total stock-compensation expense $ 4,468 $ 3,691 $ 15,287 $ 13,099 Restricted Stock From time to time, upon approval by the Company’s board of directors, certain employees and advisors have been granted restricted shares of common stock. These shares of restricted stock are subject to repurchase rights. Accordingly, the Company has recorded the proceeds from the issuance of restricted stock as a liability in the condensed consolidated balance sheets included as a component of accrued expenses or other long term liabilities based on the scheduled vesting dates. The restricted stock liability is reclassified into stockholders’ equity as the restricted stock vests. A summary of the status of and changes in unvested restricted stock as of September 30, 2017 is as follows: Weighted Average Grant Date Fair Value Shares Per Share Unvested Restricted Common Stock as of December 31, 2016 822,638 $ 0.0213 Issued — — Vested (556,560) $ 0.0172 Forfeited (5,294) 0.0300 Unvested Restricted Common Stock as of September 30, 2017 260,784 $ 0.0300 For the nine months ended September 30, 2017, the expense for restricted stock awards related to employees and non‑employees was $0.5 million and $4.0 million, respectively. As of September 30, 2017, the Company had no unrecognized stock‑based compensation expense related to its employee and non-employee unvested restricted stock awards. Stock Options Certain of the Company’s stock option agreements allow for the exercise of unvested awards. During 2014, options to purchase 75,304 shares of common stock for $0.03 per share were exercised prior to their vesting. The unvested shares are subject to repurchase by the Company if the employees cease to provide service to the Company, with or without cause. As such, the Company does not treat the exercise of unvested options as a substantive exercise. The Company has recorded the proceeds from the exercise of unvested stock options as a liability in the condensed consolidated balance sheets. The liability for unvested common stock subject to repurchase is reclassified into stockholders’ equity as the shares vest. The following is a summary of stock option activity for the three months ended September 30, 2017: Weighted Average Remaining Aggregate Intrinsic Shares Exercise Price Contractual Life (years) Value (in thousands) Outstanding at December 31, 2016 3,411,783 $ 13.71 8.8 $ 16,190 Granted 1,241,589 23.11 Exercised (114,814) 4.66 Cancelled (114,738) 13.16 Outstanding at September 30, 2017 4,423,820 $ 16.59 37,294 Vested and expected to vest at September 30, 2017 4,423,820 $ 16.59 37,294 Exercisable at September 30, 2017 1,397,719 $ 13.73 15,956 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. The Company had 8,916 and 21,955 shares of unvested restricted common stock outstanding at September 30, 2017 and December 31, 2016, respectively, resulting from the exercise of unvested stock options. Using the Black‑Scholes option pricing model, the weighted average fair value of options granted to employees and directors during the nine months ended September 30, 2017 and 2016 was $16.71 and $15.01, respectively. The expense related to options granted to employees and directors was $9.1 million and $4.0 million for the nine months ended September 30, 2017 and 2016, respectively. The fair value of each option issued to employees and directors was estimated at the date of grant using the Black‑Scholes option pricing model with the following weighted‑average assumptions: Three Months Ended Nine Months Ended September 30, September 30, 2017 2016 2017 2016 Risk free interest rate 1.9 % 1.3 % 2.1 % 1.4 % Expected dividend yield — — — — Expected term (in years) 6.25 6.25 6.25 6.25 Expected volatility 78.0 % 76.5 % 77.9 % 78.9 % There were no options issued to persons other than employees and directors during the nine months ended September 30, 2017 and 2016, respectively. As of September 30, 2017, the Company had unrecognized stock‑based compensation expense related to its employee stock options of $34.5 million which the Company expects to recognize over the remaining weighted average vesting period of 2.64 years.

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2017
Net Loss per Share
Net Loss per Share	10. 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 common shares 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 common shares and potentially dilutive securities outstanding for the period determined using the treasury stock and if converted methods. Contingently issuable shares are 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. Upon the closing of the March Offering, the Company sold 4,600,000 shares of common stock. The issuance of these shares resulted in a significant increase in the Company’s weighted-average shares outstanding for the nine months ended September 30, 2017 when compared to the comparable prior year period and is expected to continue to impact the year-over-year comparability of the Company’s net loss per share calculations for the next six months. 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 September 30, 2017 2016 Unvested restricted common stock 260,784 1,016,191 Outstanding stock options 4,423,820 3,090,810 Total 4,684,604 4,107,001 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.

Related-party Transactions

Related-party Transactions	9 Months Ended
	Sep. 30, 2017
Related-party Transactions
Related-party Transactions	11. Related‑party Transactions During the nine months ended September 30, 2016, the Company paid a related party $1.3 million in rent and facility-related fees. The Company did not make any payments to this related party in the nine months ended September 30, 2017. The Company received $0.6 million in rent and facility-related fees from a related party in the nine months ended September 30, 2017 in connection with the Sublease and no rent or facility-related payments were received from this related party in 2016.

Summary of Significant Accoun18

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Summary of Significant Accounting Policies
Unaudited Interim Financial Information	Unaudited Interim Financial Information The condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016 (the “Annual Report”). The unaudited condensed consolidated financial statements include the accounts of Editas Medicine, Inc. and its wholly owned subsidiary, Editas Securities Corporation. All intercompany transactions and balances of the subsidiary have been eliminated in consolidation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The three months ended September 30, 2017 and 2016 are referred to as the third quarter of 2017 and 2016, respectively. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with
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 with a remaining maturity date greater than one year are classified as non-current. The Company classifies all of its marketable securities as available-for-sale securities. Available-for-sale 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). If any adjustment to fair value reflects a decline in value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is “other-than-temporary.” To determine whether an impairment is other-than-temporary, the Company considers whether it has the ability and intent to hold the investment until a market price recovery and considers whether evidence indicating the cost of the investment is recoverable outweighs evidence to the contrary. The Company does not intend to sell the investments and it is not likely that the Company will be required to sell the investments before recovery of their amortized cost bases, which may be maturity.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), which supersedes the revenue recognition requirements in Accounts Standards Codification (“ASC”) 605, Revenue Recognition , and most industry-specific guidance. The new standard requires that an entity recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The update also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017 and should be applied retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying this update recognized at the date of initial application. Early adoption is permitted beginning after December 15, 2016, including interim reporting periods within those years. In April 2016, the FASB issued ASU No. 2016-10 , Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing (“ASU 2016-10”), which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”), related to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration and the presentation of sales and other similar taxes collected from customers. These standards have the same effective date and transition date as ASU 2014-09. The Company has three revenue arrangements, its license and collaboration with Juno Therapeutics, its award arrangement with the Cystic Fibrosis Foundation Therapeutics, Inc. (“CFFT”), and its strategic alliance with Allergan, pursuant to which it has recognized since inception a total of $11.8 million, $0.3 million, and $5.6 million, respectively, through September 30, 2017. The Company is analyzing the potential impact that ASU 2014-09, ASU 2016-10 and ASU 2016-12 may have on its historical revenue recognition under these three arrangements. This analysis includes, but is not limited to, reviewing variable consideration as it relates to its agreements, reviewing the method and timing of recognition of the upfront license payments, research funding and the two $2.5 million milestones received from Juno Therapeutics, assessing potential disclosures and evaluating the impact of each potential method of adoption on the Company’s consolidated financial statements. The Company will adopt the new standard effective January 1, 2018 and anticipates using the modified retrospective approach with a cumulative-effect adjustment to retained earnings in the period of initial application. The adoption of ASU 2014-09 may have a material impact on revenue recognition and notes to consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASU 2016-02”), which applies to all leases and will require lessees to record most leases on the balance sheet, but recognize expense in a manner similar to the current standard. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 and interim periods within those years. Entities are required to use a modified retrospective approach of adoption for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. Full retrospective application is prohibited. The Company is evaluating the potential impact that the adoption of ASU 2016-02 will have on the Company’s consolidated financial statements. In March 2016, the FASB, issued ASU No. 2016-09, Compensation - Stock Compensation (“ASU 2016-09”). ASU 2016-09 simplifies several aspects of the accounting for employee share-based payment transactions, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. Under this guidance, a company recognizes all excess tax benefits and tax deficiencies as income tax expense or benefit in the income statement as the awards vest or are settled. ASU 2016-09 is effective for public companies for annual reporting periods beginning after December 15, 2016, including interim periods within those annual reporting periods. Upon adoption of this standard on January 1, 2017, the Company recognized previously unrecognized excess tax benefits using the modified retrospective transition method, which resulted in a cumulative-effect increase of $179,000 to deferred tax assets which is offset by a corresponding decrease to the valuation allowance. The implementation of ASU 2016-09 does not have a material impact on stock-based compensation expense. As part of the adoption of ASU 2016-09, the Company elected to record forfeitures as they occur. In October 2016, the FASB issued ASU No. 2016-18, Restricted Cash (“ASU 2016-18”), which requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and restricted cash or restricted cash equivalents. Therefore, amounts described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 is effective for fiscal years beginning after December 15, 2017, and interim periods within those years. Early adoption is permitted. The Company is evaluating the potential impact that the adoption of ASU 2016-18 will have on the Company’s consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (“ASU 2017-01”), which clarified the definition of a business and provides a screen to determine when an integrated set of assets and activities is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. This new standard will be effective for fiscal years beginning after December 15, 2017, and interim periods within those years. Early adoption is permitted. The Company has adopted this new standard as of January 1, 2017, with prospective application to any business development transactions. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (“ASU 2017-09”), which provided guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The new guidance requires modification accounting if the vesting condition, fair value or award classification is not the same both before and after a change to the terms and conditions of the award. This new standard will be effective for fiscal years beginning after December 15, 2017, and interim periods within those years. Early adoption is permitted. The Company does not anticipate a material impact to its consolidated financial statements as a result of the adoption of this standard.

Cash Equivalents & Marketable19

Cash Equivalents & Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2017
Cash Equivalents & Marketable Securities
Schedule of cash equivalents and marketable securities	Cash equivalents and marketable securities consisted of the following at September 30, 2017 (in thousands): Gross Gross Amortized Unrealized Unrealized Fair September 30, 2017 Cost Gains Losses Value Cash equivalents: Money market funds $ 66,797 $ — $ — $ 66,797 U.S. Treasuries 8,497 — — 8,497 Government agency securities 8,498 — — 8,498 Marketable securities: U.S. Treasuries 126,222 — — 126,222 Government agency securities 82,950 — (23) 82,927 Total cash equivalents and marketable securities $ 292,964 $ — $ (23) $ 292,941 Cash equivalents and marketable securities consisted of the following at December 31, 2016 (in thousands): Gross Gross Amortized Unrealized Unrealized Fair December 31, 2016 Cost Gains Losses Value Cash equivalents: Money market funds $ 185,323 $ — $ — $ 185,323 Total cash equivalents and marketable securities $ 185,323 $ — $ — $ 185,323

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Measurements
Schedule of assets measured at fair value on a recurring basis	Assets measured at fair value on a recurring basis as of September 30, 2017 were as follows (in thousands): Quoted Prices Significant in Active Other Significant Markets for Observable Unobservable September 30, Identical Assets Inputs Inputs Financial Assets 2017 (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 66,797 $ 66,797 $ — $ — U.S. Treasuries 8,497 8,497 — — Government agency securities 8,498 8,498 — — Marketable securities: U.S. Treasuries 126,222 126,222 — — Government agency securities 82,927 82,927 — — Money market funds, included in restricted cash 1,619 1,619 — — Total financial assets $ 294,560 $ 294,560 $ — $ — Assets measured at fair value on a recurring basis as of December 31, 2016 were as follows (in thousands): Quoted Prices Significant in Active Other Significant Markets for Observable Unobservable December 31, Identical Assets Inputs Inputs Financial Assets 2016 (Level 1) (Level 2) (Level 3) Cash and cash equivalents $ 185,323 $ 185,323 $ — $ — Money market funds, included in restricted cash 1,619 1,619 — — Total financial assets $ 186,942 $ 186,942 $ — $ —

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2017
Accrued Expenses
Schedule of accrued expenses	Accrued expenses consisted of the following (in thousands): As of September 30, December 31, 2017 2016 Employee compensation costs $ 2,973 $ 2,480 Patent and license fees 3,851 13,251 Research and development 1,018 443 Professional services 499 729 Other 109 536 Total $ 8,450 $ 17,439

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	9 Months Ended
	Sep. 30, 2017
Property and Equipment, net
Schedule of property and equipment, net	Property and equipment, net consisted of the following (in thousands): As of September 30, December 31, 2017 2016 Building $ 35,167 $ 35,941 Laboratory equipment 6,352 5,130 Computer equipment 558 392 Leasehold improvements 177 200 Software 173 101 Furniture and office equipment 96 170 Total property and equipment 42,523 41,934 Less: accumulated depreciation (3,431) (1,556) Property and equipment, net $ 39,092 $ 40,378

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2017
Stock-based Compensation
Schedule of stock-based compensation expense	Total compensation cost recognized for all stock‑based compensation awards in the condensed consolidated statements of operations was as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2017 2016 2017 2016 Research and development $ 2,431 $ 2,619 $ 9,130 $ 10,021 General and administrative 2,037 1,072 6,157 3,078 Total stock-compensation expense $ 4,468 $ 3,691 $ 15,287 $ 13,099
Schedule of changes in unvested restricted stock	Weighted Average Grant Date Fair Value Shares Per Share Unvested Restricted Common Stock as of December 31, 2016 822,638 $ 0.0213 Issued — — Vested (556,560) $ 0.0172 Forfeited (5,294) 0.0300 Unvested Restricted Common Stock as of September 30, 2017 260,784 $ 0.0300
Schedule of stock option activity	Weighted Average Remaining Aggregate Intrinsic Shares Exercise Price Contractual Life (years) Value (in thousands) Outstanding at December 31, 2016 3,411,783 $ 13.71 8.8 $ 16,190 Granted 1,241,589 23.11 Exercised (114,814) 4.66 Cancelled (114,738) 13.16 Outstanding at September 30, 2017 4,423,820 $ 16.59 37,294 Vested and expected to vest at September 30, 2017 4,423,820 $ 16.59 37,294 Exercisable at September 30, 2017 1,397,719 $ 13.73 15,956
Schedule of assumptions used to value stock options	Three Months Ended Nine Months Ended September 30, September 30, 2017 2016 2017 2016 Risk free interest rate 1.9 % 1.3 % 2.1 % 1.4 % Expected dividend yield — — — — Expected term (in years) 6.25 6.25 6.25 6.25 Expected volatility 78.0 % 76.5 % 77.9 % 78.9 %

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Net Loss per Share
Schedule of anti-dilutive common stock equivalents	As of September 30, 2017 2016 Unvested restricted common stock 260,784 1,016,191 Outstanding stock options 4,423,820 3,090,810 Total 4,684,604 4,107,001

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 08, 2016	Feb. 03, 2016	Mar. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Liquidity
Common stock, shares outstanding				41,840,122	35,818,131
Accumulated deficit				$ (269,661)	$ (185,526)
Initial Public Offering
Liquidity
Shares sold	6,785,000		4,600,000
Price to the public	$ 16		$ 22.50
Aggregate net proceeds		$ 97,500	$ 96,700
Overallotment Option
Liquidity
Shares sold	885,000		600,000

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Details)	1 Months Ended	3 Months Ended		7 Months Ended	9 Months Ended		17 Months Ended	29 Months Ended
	May 31, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)item	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)
Revenue Recognition [Abstract]
Number of revenue agreements | item					3
Contracts Revenue		$ 6,282,000	$ 962,000		$ 10,061,000	$ 5,155,000
Accounting Standards Update 2016-16
Revenue Recognition [Abstract]
Adjustment to valuation allowance					179,000
Juno Therapeutics | Collaboration and License Agreement
Revenue Recognition [Abstract]
Contracts Revenue		3,100,000	$ 800,000		4,400,000	$ 4,900,000		$ 11,800,000
License Agreement Milestone Payment Received	$ 2,500,000
Cystic Fibrosis Foundation Therapeutics, Inc. | Development award agreement
Revenue Recognition [Abstract]
Contracts Revenue							$ 300,000
Allergan | Strategic Alliance
Revenue Recognition [Abstract]
Contracts Revenue		$ 3,200,000		$ 5,600,000	$ 5,600,000

Cash Equivalents & Marketable27

Cash Equivalents & Marketable Securities (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)item	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)
Cash equivalents and marketable securities
Amortized Cost	$ 292,964		$ 185,323
Gross Unrealized Losses	(23)
Fair Value	$ 292,941		185,323
Number of securities in an unrealized loss position | item	21
Securities held by the Company in an unrealized loss position for less than 12 months	$ 135,200
Number of securities in an unrealized loss position for more than 12 months | item	0
Realized gains (losses) on available-for-sale securities	$ 0	$ 0
U.S. Treasuries
Cash equivalents and marketable securities
Amortized Cost	126,222
Fair Value	126,222
Government agency securities
Cash equivalents and marketable securities
Amortized Cost	82,950
Gross Unrealized Losses	(23)
Fair Value	82,927
Money market funds
Cash equivalents and marketable securities
Amortized Cost	66,797		185,323
Fair Value	66,797		$ 185,323
U.S. Treasuries
Cash equivalents and marketable securities
Amortized Cost	8,497
Fair Value	8,497
Government agency securities
Cash equivalents and marketable securities
Amortized Cost	8,498
Fair Value	$ 8,498

Fair Value Measurements - Recur

Fair Value Measurements - Recurring Basis (Details) $ in Thousands, item in Millions	9 Months Ended
	Sep. 30, 2017USD ($)item	Dec. 31, 2016USD ($)
Financial Assets
Marketable securities	$ 292,941	$ 185,323
Transfers between levels | item	0
U.S. Treasuries
Financial Assets
Marketable securities	$ 126,222
Government agency securities
Financial Assets
Marketable securities	82,927
Money market funds
Financial Assets
Marketable securities	66,797	185,323
U.S. Treasuries
Financial Assets
Marketable securities	8,497
Government agency securities
Financial Assets
Marketable securities	8,498
Recurring
Financial Assets
Cash and cash equivalents		185,323
Total financial assets	294,560	186,942
Recurring | U.S. Treasuries
Financial Assets
Marketable securities	126,222
Recurring | Government agency securities
Financial Assets
Marketable securities	82,927
Recurring | Money market funds
Financial Assets
Cash and cash equivalents	66,797
Restricted cash	1,619	1,619
Recurring | U.S. Treasuries
Financial Assets
Cash and cash equivalents	8,497
Recurring | Government agency securities
Financial Assets
Cash and cash equivalents	8,498
Recurring | Level 1
Financial Assets
Cash and cash equivalents		185,323
Total financial assets	294,560	186,942
Recurring | Level 1 | U.S. Treasuries
Financial Assets
Marketable securities	126,222
Recurring | Level 1 | Government agency securities
Financial Assets
Marketable securities	82,927
Recurring | Level 1 | Money market funds
Financial Assets
Cash and cash equivalents	66,797
Restricted cash	1,619	$ 1,619
Recurring | Level 1 | U.S. Treasuries
Financial Assets
Cash and cash equivalents	8,497
Recurring | Level 1 | Government agency securities
Financial Assets
Cash and cash equivalents	$ 8,498

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accrued Expenses
Employee compensation costs	$ 2,973	$ 2,480
Patent and license fees	3,851	13,251
Research and development	1,018	443
Professional services	499	729
Other	109	536
Total	$ 8,450	$ 17,439

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property and equipment disclosures
Total property and equipment	$ 42,523	$ 41,934
Less: accumulated depreciation	(3,431)	(1,556)
Property and equipment, net	39,092	40,378
Building
Property and equipment disclosures
Total property and equipment	35,167	35,941
Laboratory equipment
Property and equipment disclosures
Total property and equipment	6,352	5,130
Computer equipment
Property and equipment disclosures
Total property and equipment	558	392
Leasehold improvements
Property and equipment disclosures
Total property and equipment	177	200
Software
Property and equipment disclosures
Total property and equipment	173	101
Furniture and office equipment
Property and equipment disclosures
Total property and equipment	$ 96	$ 170

Commitments and Contingencies -

Commitments and Contingencies - Operating Leases (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)	Feb. 28, 2017ft²	Feb. 29, 2016USD ($)ft²
Hurley Street Lease
Commitments and contingencies
Leased space ( in square feet) | ft²			59,783
Security deposit | $			$ 1.6
Estimated useful life	30 years
Extended lease option (in years)	5 years
Facility Sublease Arrangement
Commitments and contingencies
Leased space ( in square feet) | ft²		10,000
Future minimum rental revenue to be received | $	$ 0.6
Sublease term	18 months
Lease extension term	18 months

Commitments and Contingencies32

Commitments and Contingencies - Licensor Expense Reimbursement (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Licensor Expense Reimbursement
Commitments and contingencies
Payments for licensor expense reimbursement	$ 5.1	$ 5	$ 13	$ 16

Commitments and Contingencies33

Commitments and Contingencies - Notes Payable (Details) - USD ($) $ in Thousands	Mar. 28, 2017	Sep. 30, 2017	Aug. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Commitments and contingencies
Accrued expenses		$ 8,450			$ 17,439	$ 8,450
Notes Payable
Notes paid in cash						$ 600
2016 License Agreements
Commitments and contingencies
Market Capitalization				$ 750,000
Broad and Wageningen University | Cpf1 License Agreement
Commitments and contingencies
Market Capitalization				750,000
Notes Payable
Promissory notes issued	$ 5,000				$ 10,000
Interest rate (as a percentage)					4.80%
Notes paid in cash			$ 200
Common stock issued		371,166	108,104
Success Payments				5,000
Broad and Wageningen University | Cpf1 License Agreement | Success Payment Notes
Notes Payable
Promissory notes issued				$ 5,000
Notes paid in cash			$ 400
Common stock issued			271,347

Significant Agreements - Juno T

Significant Agreements - Juno Therapeutics Collaboration Agreement (Details) $ in Thousands	May 26, 2015item	Mar. 31, 2017USD ($)item	May 31, 2016USD ($)	May 31, 2015USD ($)item	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)item	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2016USD ($)
Collaboration and other research and development revenues					$ 6,282	$ 962		$ 10,061	$ 5,155
Research and development					20,396	10,832		56,735	30,144
Deferred revenue, long-term					97,851		$ 97,851	97,851		$ 97,851	$ 26,000
Accounts receivable					695		695	695		695	88
Juno Therapeutics
Deferred revenue, long-term					26,300		26,300	26,300		26,300	26,000
Accounts receivable					700		700	$ 700		700	$ 0
Allergan
Number of additional licenses | item								2
One time payment to acquire the license								$ 25,000
Potential development milestone payments					8,000		8,000	8,000		8,000
Number of days in which payment to be made		45 days
Allergan | Maximum
Potential Liability For Clinical Regulatory And Commercial Milestone Payments					90,000		90,000	90,000		90,000
Potential development milestone payments					42,000		42,000	42,000		42,000
Potential regulatory and commercial milestone payments					75,000		75,000	75,000		75,000
Collaboration and License Agreement | Juno Therapeutics
Number of research areas | item				3
Agreement term	5 years
Extensions | item	2
Extension period	1 year
Upfront fee received				$ 25,000
Potential research and development funding				$ 22,000
Number of additional licenses | item				3
Potential fee receivable for each gene target licensed				$ 2,500
Potential development milestone payments				77,500
Potential regulatory milestone payments				80,000
Potential commercial milestone payments				$ 75,000
Milestone payment received under license agreement			$ 2,500
Next possible milestone payment					2,500	2,500	2,500	2,500	2,500	2,500
Number of options to purchase Development and Commercialization License | item				3
Number of deliverables | item				6
Number of accounting units | item				11
Number of accounting units for Development and Commercialization License | item				3
Number of accounting units for discount deliverables | item				6
Allocable arrangement consideration - upfront payment				$ 25,000
Allocable arrangement consideration - research support				20,000
Allocable arrangement consideration - specialized material costs				2,000
Allocable arrangement consideration - aggregate arrangement consideration				47,000
Allocable arrangement consideration - R&D Services Unit of Accounting				16,700
Allocable arrangement consideration - Development and Commercialization License for the first research area				9,300
Allocable arrangement consideration - Development and Commercialization License for the second research area				15,400
Allocable arrangement consideration - Development and Commercialization License for the third research area				200
Allocable arrangement consideration - first Discount Deliverable for the first research area				700
Allocable arrangement consideration - second Discount Deliverable for the first research area				400
Allocable arrangement consideration - third Discount Deliverable for the first research area				200
Allocable arrangement consideration - first Discount Deliverable for the second research area				2,000
Allocable arrangement consideration - second Discount Deliverable for the second research area				1,300
Allocable arrangement consideration - third Discount Deliverable for the second research area				800
Allocable arrangement consideration -JRC Deliverable				$ 0
Collaboration and other research and development revenues					3,100	$ 800		4,400	4,900	11,800
Research and development					500			500	$ 500
Strategic Alliance | Allergan
Agreement term		7 years
Number of Collaboration Development Programs | item		5
Number of Committee Members | item		3
Extension period		1 year
Upfront fee received		$ 90,000
Option exercise price per CDP		15,000
Extension fee for Initial Option Period		5,000
Option exercise price for development and commercialization license		22,500
Allocable arrangement consideration - aggregate arrangement consideration		$ 90,000
Collaboration and other research and development revenues					3,200		5,600	5,600
Research and development					6,700			14,100
Deferred revenue					84,400		84,400	84,400		84,400
Deferred revenue, long-term					$ 71,500		$ 71,500	$ 71,500		$ 71,500
Contract termination notice		90 days
Strategic Alliance | Allergan | Maximum
Extension period		10 years

Significant Agreements - Other

Significant Agreements - Other Agreements (Details) $ in Thousands	1 Months Ended					3 Months Ended		9 Months Ended
	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Aug. 31, 2016USD ($)item	Oct. 31, 2014USD ($)shares	Aug. 31, 2014USD ($)shares	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)item	Sep. 30, 2016USD ($)
Notes payable		$ 10,000
Research and development						$ 20,396	$ 10,832	$ 56,735	$ 30,144
The General Hospital (MGH) | License Patent Rights
Upfront fee					$ 100
Stock issued to licensors | shares					66,848
Percentage of outstanding shares issued					0.50%
Research and development			$ 800
Potential liability for future clinical and regulatory milestone payments related to product approval			$ 4,900
Percentage of net sales threshold for potential milestone payments to be made			1.00%
Number of licensed products | item			4
The General Hospital (MGH) | Maximum | License Patent Rights
Potential liability for future clinical, regulatory and commercial milestone payments related to product approval					$ 3,700
Potential liability for future sales milestone payments					$ 1,800
Success Payments			$ 6,000
The General Hospital (MGH) | Minimum | License Patent Rights
Potential liability for future clinical, regulatory and commercial milestone payments related to product approval			$ 1,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | License Patent Rights
Upfront fee				$ 200
Stock issued to licensors | shares				561,531
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Cpf1 License Agreement
Royalties credit paid to third party (as a percent)								50.00%
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Cpf1 Market Cap Success Payments
Notes payable payment terms								150 days
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Cas9-II License Agreement
License Agreement Contract Termination Term								4 months
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Maximum | Cpf1 License Agreement
Upfront fee		$ 16,500
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Maximum | Cpf1 Success Payments
Success Payments								$ 125,000
Market capitalization threshold						10,000,000		10,000,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Maximum | Cas9-II License Agreement
Success Payments								30,000
Market capitalization threshold						9,000,000		9,000,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Minimum | Cpf1 Success Payments
Success Payments								750,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Rare disease | Maximum
Potential liability for future sales milestone payments				$ 36,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Rare disease | Maximum | Cpf1 License Agreement
Potential liability for future sales milestone payments						36,000		36,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | United States Europe And Japan | Maximum | License Patent Rights
Potential liability for future clinical and regulatory milestone payments related to product approval				14,800
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | United States Europe And Japan | Human disease | Maximum | Cpf1 License Agreement
Potential liability for future clinical and regulatory milestone payments related to product approval						20,000		20,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | United States Europe And Japan | Human disease | Maximum | Cas9-II License Agreement
Potential liability for future sales milestone payments						13,500		13,500
Potential liability for future clinical and regulatory milestone payments related to product approval						3,700		3,700
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | United States Europe And Japan | Rare disease | Maximum | Cpf1 License Agreement
Potential liability for future clinical and regulatory milestone payments related to product approval						6,000		6,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | United States Europe And Japan | Rare disease | Maximum | Cas9-II License Agreement
Potential liability for future sales milestone payments						9,000		9,000
Potential liability for future clinical and regulatory milestone payments related to product approval						1,100		$ 1,100
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | United States and one other | Human disease | Maximum | License Patent Rights
Potential liability for future clinical and regulatory milestone payments related to product approval				4,100
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | UNITED STATES | Human disease | Maximum | License Patent Rights
Potential liability for future sales milestone payments				$ 54,000
Allergan
Number of additional licenses | item								2
Allergan | Strategic Alliance
Upfront fee received	$ 90,000
Research and development						6,700		$ 14,100
License Agreement Contract Termination Term	90 days
Allergan | Maximum
Potential liability for future clinical, regulatory and commercial milestone payments related to product approval						$ 90,000		$ 90,000

Stock-based Compensation - Expe

Stock-based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock-based compensation disclosures
Compensation expense	$ 4,468	$ 3,691	$ 15,287	$ 13,099
Research and development.
Stock-based compensation disclosures
Compensation expense	2,431	2,619	9,130	10,021
General and administrative
Stock-based compensation disclosures
Compensation expense	$ 2,037	$ 1,072	$ 6,157	$ 3,078

Stock-based Compensation - Rest

Stock-based Compensation - Restricted Stock and Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2014
Changes in unvested restricted stock
Unvested restricted common stock, beginning of period (in shares)			822,638
Vested (in shares)			(556,560)
Forfeited (in shares)			(5,294)
Unvested restricted common stock, end of period(in shares)	260,784		260,784		822,638
Weighted Average Grant Date Fair Value
Balance, beginning of period			$ 0.0213
Vested (in dollars per share)			0.0172
Forfeited (in dollars per share)			0.0300
Balance, ending of period	$ 0.0300		$ 0.0300		$ 0.0213
Changes in unvested stock options
Compensation expense	$ 4,468	$ 3,691	$ 15,287	$ 13,099
Options exercised prior to vesting (in shares)						75,304
Options exercised prior to vesting , exercise price per share						$ 0.03
Outstanding, beginning of period (in shares)			3,411,783
Granted (in shares)			1,241,589
Exercised (in shares)			(114,814)
Cancelled (in shares)			(114,738)
Outstanding, end of period (in shares)	4,423,820		4,423,820		3,411,783
Vested and expected to vest (in shares)	4,423,820		4,423,820
Exercisable (in shares)	1,397,719		1,397,719
Outstanding, beginning of period (in dollars per share)			$ 13.71
Granted (in dollars per share)			23.11
Exercised (in dollars per share)			4.66
Cancelled (in dollars per share)			13.16
Outstanding, end of period (in dollars per share)	$ 16.59		16.59		$ 13.71
Vested and expected to vest outstanding, weighted average exercise price (in dollars per share)	16.59		16.59
Exercisable (in dollar per share)	$ 13.73		$ 13.73
Remaining contractual life			8 years 8 months 12 days		8 years 9 months 18 days
Vested and expected to vest, remaining contractual life			8 years 8 months 12 days
Exercisable, remaining contractual life			8 years 7 months 6 days
Aggregate intrinsic value	$ 37,294		$ 37,294		$ 16,190
Vesting and expected to vest, aggregate intrinsic value	37,294		37,294
Exercisable, aggregated intrinsic value	$ 15,956		$ 15,956
Unvested stock options (in shares)	8,916		8,916		21,955
Employees and directors
Changes in unvested stock options
Compensation expense			$ 9,100	$ 4,000
Weighted average fair value of options granted (per share)			$ 16.71	$ 15.01
Employees
Changes in unvested stock options
Unrecognized stock-based compensation expense	$ 34,500		$ 34,500
Period for recognition			2 years 7 months 21 days
Restricted Stock | Employees
Changes in unvested stock options
Compensation expense			$ 500
Unrecognized stock-based compensation expense	$ 0		0
Restricted Stock | Non-employees
Changes in unvested stock options
Compensation expense			$ 4,000
Employee and Consultant Options | Employees
Changes in unvested stock options
Granted (in shares)			0	0

Stock-based Compensation - Assu

Stock-based Compensation - Assumptions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Employees and directors
Assumptions
Risk free interest rate	1.90%	1.30%	2.10%	1.40%
Expected term (in years)	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months
Expected volatility	78.00%	76.50%	77.90%	78.90%
Employees
Assumptions
Unrecognized stock-based compensation expense	$ 34.5		$ 34.5
Period for recognition			2 years 7 months 21 days

Net Loss per Share (Details)

Net Loss per Share (Details) - shares	Feb. 08, 2016	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016
Potentially dilutive securities
Anti-dilutive common stock equivalent shares			4,684,604	4,107,001
Restricted Stock
Potentially dilutive securities
Anti-dilutive common stock equivalent shares			260,784	1,016,191
Outstanding stock options
Potentially dilutive securities
Anti-dilutive common stock equivalent shares			4,423,820	3,090,810
Initial Public Offering
Potentially dilutive securities
Shares sold	6,785,000	4,600,000

Related-party Transactions (Det

Related-party Transactions (Details) - Rent and facility related fees - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Fees paid to related party	$ 0	$ 1.3
Fees received from related party	$ 0.6	$ 0