Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2017	Aug. 07, 2017
Document and Entity Information
Entity Registrant Name	Editas Medicine, Inc.
Entity Central Index Key	0001650664
Document Type	10-Q
Document Period End Date	Jun. 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		41,627,446
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q2

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 144,096	$ 185,323
Marketable securities	180,699
Accounts receivable	820	88
Prepaid expenses and other current assets	2,257	1,772
Total current assets	327,872	187,183
Property and equipment, net	39,358	40,378
Restricted cash and other non-current assets	1,619	1,621
Total assets	368,849	229,182
Current liabilities:
Accounts payable	8,156	4,640
Accrued expenses	11,160	17,439
Notes payable	15,000	10,000
Deferred revenue, current	13,239	256
Other current liabilities	1,131	748
Total current liabilities	48,686	33,083
Deferred revenue, net of current portion	100,953	26,000
Construction financing lease obligation, net of current portion	33,878	35,096
Other non-current liabilities	328	396
Total liabilities	183,845	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; 41,354,833 and 36,662,724 shares issued, and 40,913,418 and 35,818,131 shares outstanding at June 30, 2017 and December 31, 2016, respectively	4	4
Additional paid-in capital	428,129	320,129
Accumulated other comprehensive loss	(67)
Accumulated deficit	(243,062)	(185,526)
Total stockholders’ equity	185,004	134,607
Total liabilities and stockholders’ equity	$ 368,849	$ 229,182

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 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	41,354,833	36,662,724
Common stock, shares outstanding	40,913,418	35,818,131

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Condensed Consolidated Statements of Operations
Collaboration and other research and development revenues	$ 3,097	$ 3,388	$ 3,779	$ 4,193
Operating expenses:
Research and development	17,318	10,430	36,339	19,312
General and administrative	11,894	12,158	24,182	21,920
Total operating expenses	29,212	22,588	60,521	41,232
Operating loss	(26,115)	(19,200)	(56,742)	(37,039)
Other income (expense), net:
Other income (expense), net	122	5	262	(25)
Interest income (expense), net	(446)	153	(1,056)	277
Total other income (expense), net	(324)	158	(794)	252
Net loss	(26,439)	(19,042)	(57,536)	(36,787)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(26,439)	(19,042)	(57,536)	(36,787)
Accretion of redeemable convertible preferred stock to redemption value				(47)
Net loss attributable to common stockholders	$ (26,439)	$ (19,042)	$ (57,536)	$ (36,834)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.65)	$ (0.54)	$ (1.49)	$ (1.28)
Weighted-average common shares outstanding, basic and diluted	40,830,161	35,286,719	38,669,793	28,783,758

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Condensed Consolidated Statements of Comprehensive Loss
Net loss	$ (26,439)	$ (19,042)	$ (57,536)	$ (36,787)
Other comprehensive loss:
Unrealized loss on available-for-sale securities	(67)		(67)
Comprehensive loss	$ (26,506)	$ (19,042)	$ (57,603)	$ (36,787)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flow from operating activities
Net loss	$ (57,536)	$ (36,787)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Stock-based compensation expense	10,820	9,409
Depreciation	1,282	433
Non-cash research and development expenses	5,000
Re-measurement of warrant to purchase redeemable securities		87
Other non-cash items, net	176	155
Changes in operating assets and liabilities:
Accounts receivable	(732)	(176)
Prepaid expenses and other current assets	(486)	(1,587)
Other non-current assets	2	2,224
Accounts payable	3,366	4,259
Accrued expenses	(6,200)	2,134
Deferred revenue	87,937	321
Net cash provided by (used in) operating activities	43,629	(19,528)
Cash flow from investing activities
Purchases of property and equipment	(1,018)	(2,104)
Purchases of marketable securities	(180,623)
Changes in restricted cash		(1,619)
Net cash used in investing activities	(181,641)	(3,723)
Cash flow from financing activities
Proceeds from public offering of common stock, net of issuance costs	96,685	97,684
Proceeds from exercise of stock options	490	37
Payments on construction financing lease obligation	(390)
Net cash provided by financing activities	96,785	97,721
Net (decrease) increase in cash and cash equivalents	(41,227)	74,470
Cash and cash equivalents, beginning of period	185,323	143,180
Cash and cash equivalents, end of period	144,096	217,650
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	91	264
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	$ 6	6
Offering costs incurred but unpaid at period end		$ 196

Nature of Business	6 Months Ended
Nature of Business	Jun. 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 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 nine months. As of June 30, 2017, there were 40,913,418 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 June 30, 2017, anticipated interest income, anticipated research support under the Company’s collaboration agreement with Juno Therapeutics and anticipated payments from the Cystic Fibrosis Foundation Therapeutics, Inc. (“CFFT”) 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 $243.1 million at June 30, 2017, and will require substantial additional capital to fund its operations. The Company has not generated any product revenues and has financed its operations primarily through public offerings, private placements of its equity securities, an equipment loan, and funding from its collaboration with Juno Therapeutics and its strategic alliance with Allergan. 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 Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 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 June 30, 2017 and 2016 are referred to as the second 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 United States generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, accrued expenses, stock‑based compensation expense, deferred tax valuation allowances and sub-license fees due to certain of our licensors. The Company bases its estimates on historical experience and other market‑specific or relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. 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” and, if so, mark the investment to market through a charge to the Company’s statement of operations. 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 CFFT, and its strategic alliance with Allergan, and pursuant to which it has recognized since inception a total of $8.7 million, $0.3 million, and $2.4 million, respectively, through June 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 license payment, research funding and the $2.5 million milestone 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. 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 does not expect this standard to have a material impact on the 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.

Cash Equivalents & Marketable Securities

6 Months Ended

Jun. 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 June 30, 2017 (in thousands):


			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
June 30, 2017	Cost		Gains		Losses		Value
Cash equivalents:
Money market funds	$	115,105	$	—	$	—	$	115,105
U.S. Treasuries		28,990		1		—		28,991
Marketable securities:
U.S. Treasuries		74,807		—		(21)		74,786
Government agency securities		105,960		—		(47)		105,913
Total cash equivalents and marketable securities	$	324,862	$	1	$	(68)	$	324,795

Cash equivalents and marketable securities consisted of the following at December 30, 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 June 30, 2017, the Company held 26 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 June 30, 2017 was $180.7 million, and there were no securities held by the Company in an unrealized loss position for more than 12 months. As of June 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 June 30, 2017.

There were no realized gains or losses on available-for-sale securities during the six months ended June 30, 2017 and 2016.

- Definition

The entire disclosure for cash and cash equivalent footnotes, which may include the types of deposits and money market instruments, applicable carrying amounts, restricted amounts and compensating balance arrangements. Cash and equivalents include: (1) currency on hand (2) demand deposits with banks or financial institutions (3) other kinds of accounts that have the general characteristics of demand deposits (4) short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments maturing within three months from the date of acquisition qualify.

+ References + Details

Fair Value Measurements

6 Months Ended

Jun. 30, 2017

Fair Value Measurements

Fair Value Measurements

4. Fair Value Measurements

Assets measured at fair value on a recurring basis as of June 30, 2017 were as follows (in thousands):


			Quoted Prices		Significant
			in Active		Other		Significant
			Markets for		Observable		Unobservable
	June 30,		Identical Assets		Inputs		Inputs
Financial Assets	2017		(Level 1)		(Level 2)		(Level 3)
Cash equivalents:
Money market funds	$	115,105	$	115,105	$	—	$	—
U.S. Treasuries		28,991		28,991		—		—
Marketable securities:
U.S. Treasuries		74,786		74,786		—		—
Government agency securities		105,913		105,913		—		—
Money market funds, included in restricted cash		1,619		—		—		—
Total financial assets	$	326,414	$	324,795	$	—	$	—

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 six months ended June 30, 2017.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Accrued Expenses

6 Months Ended

Jun. 30, 2017

Accrued Expenses

Accrued Expenses

5. Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	As of
	June 30,		December 31,
	2017		2016
Sublicense income fees	$	5,061	$	—
Employee compensation costs		2,356		2,480
Patent and license fees		2,211		13,251
Research and development		554		443
Professional services		927		729
Other		51		536
Total	$	11,160	$	17,439

Property and Equipment, net

6 Months Ended

Jun. 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
	June 30,		December 31,
	2017		2016
Building	$	35,167	$	35,941
Laboratory equipment		6,116		5,130
Computer equipment		435		392
Leasehold improvements		177		200
Software		136		101
Furniture and office equipment		96		170
Total property and equipment		42,127		41,934
Less: accumulated depreciation		(2,769)		(1,556)
Property and equipment, net	$	39,358	$	40,378

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Jun. 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 June 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. During the six months ended June 30, 2017, the Company has recorded $0.3 million in deferred rent attributable to the land. 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 $0.8 million as of June 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 six months ended June 30, 2017, the Company recognized $3.9 million and $7.9 million in expense for such reimbursement, respectively. During the three and six months ended June 30, 2016, the Company recognized $6.5 million and $10.9 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. 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”). Principal and accrued interest on the Initial Notes is 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 bear interest at a rate of 4.8% per annum. The Company may elect to make any payment of amounts outstanding under the Initial Notes either in the form of cash or, subject to certain conditions, in shares of the Company’s common stock of equal value, with such shares being valued for such purpose at the closing price of the Company’s common stock as reported the NASDAQ Stock Market for the trading day immediately preceding the date of such payment if the Company’s common stock is then listed on the NASDAQ Stock Market. In the event of a change of control of the Company or a sale of the Company, the Company will be required to pay all remaining principal and accrued interest on the Initial Notes in cash within a specified period following such event. Under the terms of the Cpf1 License Agreement, the Company may be required to issue additional promissory notes in connection with potential Success Payments. 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”). Principal and accrued interest on the Success Payment Notes are due and payable in August 2017, and the Company may prepay the Success Payment Notes at any time. The Success Payment Notes are subject to the same interest and terms as the Initial Notes, other than the maturity date. Under the terms of the Success Payment Notes and the Initial Notes, the entire unpaid principal and accrued interest of the Notes will become immediately due and payable upon a payment default or bankruptcy- and insolvency-related defaults. The Company believes that the carrying value of the Success Payments Notes and the Initial Notes approximates their fair value based on Level 3 inputs including a quoted rate. Other Contingencies The Company accrues a reserve for a contingent liability when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. In the first quarter of 2017, the Company recorded and paid $1.7 million related to sublicense income to certain licensors in connection with receiving an upfront payment from Allergan. In July 2017, the Company paid an additional $5.1 million to such licensors and remains in ongoing discussions with the licensors regarding the amount of payment due to such licensors under the sublicense income terms in the applicable license agreement. The $5.1 million is recorded as part of accrued expenses in the Company’s condensed consolidated financial statements. As of June 30, 2017, the Company estimates that it is reasonably possible that it may pay up to an additional $6.8 million to such licensors. If and when it becomes probable that the Company may need to pay such additional amount to such licensors, the Company will record an additional liability.

Significant Agreements	6 Months Ended
Significant Agreements	Jun. 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 will 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. In May 2016, the Company achieved a $2.5 million milestone under the Collaboration Agreement resulting from technical progress in a research program to create engineered T cells with CARs and TCRs to treat cancer. 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. As of June 30, 2017, the next potential milestone payment that the Company may be entitled to receive under the Collaboration Agreement is a substantive milestone payment of $2.5 million for the achievement of certain development criteria. The Company would recognize the milestone payment as revenue upon achievement. There are no cancellation, termination or refund provisions in the Collaboration Agreement that contain material financial consequences to the Company. 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, Topic 605-25, 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 vendor specific objective evidence of selling price nor third-party evidence of selling price is available for any of the units of accounting identified at inception of the arrangement with Juno Therapeutics. Accordingly, the selling price of each unit of accounting was determined based on the Company’s best estimate of selling price (“BESP”). The Company developed the BESP for all of the units of accounting included in the Collaboration Agreement with the objective of determining the price at which it would sell such an item if it were to be sold regularly on a standalone basis. The Company developed the BESP for the R&D Services Unit of Accounting and the JRC Deliverable primarily based on the nature of the services to be performed and estimates of the associated effort and cost of the services, adjusted for a reasonable profit margin that would be expected to be realized under similar contracts. The Company developed the BESP for each of the Development and Commercialization License units of accounting based on the probability‑weighted present value of expected future cash flows associated with each license related to each specific research area. In developing such estimate, the Company also considered applicable market conditions and relevant entity‑specific factors, including those factors contemplated in negotiating the agreement, probability of success and the time needed to commercialize a product candidate pursuant to the associated license. The Company developed the BESP for each of the Discount Deliverables based on the estimated value of the associated in‑the‑money options. In developing such estimate, the Company considered the period to exercise the option, an appropriate discount rate and the likelihood that a market participant who was entitled to the discount would exercise the option. 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 six months ended June 30, 2017, the Company recognized revenue totaling approximately $0.7 million and $1.4 million, respectively, with respect to the collaboration with Juno Therapeutics. During the three and six months ended June 30, 2016, the Company recognized revenue totaling approximately $3.3 million and $4.1 million, both including $2.5 million related to the first milestone payment with respect to the collaboration with Juno Therapeutics. The revenue is classified as collaboration and other research and development revenue in the accompanying condensed consolidated statement of operations. As of June 30, 2017, there was approximately $26.2 million of deferred revenue related to the Company’s collaboration with Juno Therapeutics, all of which is classified as long‑term in the accompanying condensed consolidated balance sheet. In addition, as of June 30, 2017, the Company has recorded accounts receivable of $0.8 million related to reimbursable research and development costs under the Collaboration Agreement for activities performed during the second quarter of 2017. Adverum Biotechnologies, Inc. Collaboration, Option, and License Agreement In August 2016, the Company entered into an agreement with Adverum Biotechnologies, Inc. (“Adverum”) to explore the delivery of genome editing medicines to treat up to five inherited retinal diseases. Under the terms of the agreement, the Company paid an upfront non-refundable fee of $1.0 million to evaluate Adverum’s next generation adeno-associated viral vectors (“AAVs”) for use in clinical development. The Company will support all preclinical activities related to this agreement, including research and development activities to be performed by Adverum, with $0.5 million of the upfront fee being creditable against this funding obligation. Accordingly, the Company has deferred and capitalized $0.5 million of the $1.0 million upfront fee as an advance payment for future research and development activities which the Company believes will be incurred in the future. The capitalized amount will be expensed as research and development expenses in the Company’s consolidated statements of operations as the related services are performed. The Company expensed the remaining $0.5 million as research and development expense during 2016. Additionally, the Company may pay, at its discretion, an additional fee of $1.0 million, per exercise, to exercise an option to receive an exclusive license to Adverum’s next generation AAVs for use in an indication chosen under the agreement. Adverum is also entitled to receive development and regulatory milestone payments up to a maximum of a mid-single digit millions of dollars per license based on the achievement of specific events for a product candidate that includes an Adverum vector (“Adverum Product”) and a low to mid-single digit millions of dollars based on the achievement of specific events for a product candidate that does not include an Adverum vector (“Non-Adverum Product”). Adverum is also entitled to receive certain commercial milestone payments for Adverum Products up to a maximum amount of a low double digit million dollar amount per product. The Company is also obligated to pay Adverum single digit to low double digit percentage royalties on net sales of Adverum Products and low single digit percentage royalties on sales of Non-Adverum Products sold in applicable territories during the royalty term. 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 world-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 application 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 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 development milestone payments and $75.0 million for product approval and launch milestone payments, in each case, for an indication in the field per CDP. In addition, the Company is eligible to receive additional development and product approval and launch milestone payments for subsequent products developed within two additional fields. The Company is also eligible for up to $90 million in sales milestone payments on a CDP by CDP basis, associated with aggregate worldwide sales. Certain product approval milestones are subject to certain reductions under specified circumstances, including for payments required to be made by Allergan to obtain certain third party intellectual property rights. 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 June 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, if a Licensed Product is subject to a profit sharing agreement the royalties will only be paid on ex-US net sales. 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 Licensed Product in a country until the later of: i) the tenth anniversary of the first commercial sale of such Licensed Product in such country 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 and iii) the expiration of an exclusive legal right granted by the regulatory authority in such country to market and sell such Licensed Product. Unless earlier terminated, the Allergan Agreement will terminate upon i) the expiration of the Research Term, if Allergan does not exercise an Option, ii) on a Licensed Product-by-Licensed Product and country-by-country basis, on the date of the expiration of all payment obligations under the Allergan Agreement with respect to such Licensed Product in such country or iii) in its entirety upon the expiration of all payment obligations with respect to the last Licensed Product in all countries, unless terminated earlier due to the early termination provisions. Either party may terminate the Allergan 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. During the Research Term, Allergan will have the right to terminate the Allergan Agreement on a CDP by CDP basis in the event of a change in control of the Company or for all CDPs, provided that Allergan will not have any right to exercise an Option for any CDPs following such termination. After the exercise of an Option, Allergan will have the right, at its sole discretion, to terminate the Allergan Agreement, on a CDP by CDP basis, upon 90 days’ written notice. The Company may terminate the Allergan Agreement in the event that Allergan 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. Lastly, Allergan may terminate the Allergan Agreement with respect to a CDP if a safety concern, as specified in the Allergan Agreement, arises. Termination of the Allergan Agreement for any reason will 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. In addition, termination of the Allergan Agreement will not 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 Allergan Agreement. If Allergan terminates the Allergan Agreement as a result of the Company’s uncured material breach or default, then: i) the licenses and rights conveyed to Allergan will continue as set forth in the agreement for any CDP Allergan has already licensed and ii) Allergan’s obligations related to milestones and royalties will continue as set forth in the agreement. If the Allergan Agreement is terminated for any other reason, then the options and licenses conveyed to Allergan under the agreement will terminate. Accounting Analysis The Company evaluated the Allergan Agreement in accordance with the provisions of ASC 605-25. The Company’s arrangement with Allergan contains the following deliverables: (i) research and development services during the Research Term (the “R&D Services Deliverable”), and (ii) ASC services during the Research Term (the “ASC Deliverable”). The Company has determined that the Options with respect to the CDP are substantive options. Allergan is not contractually obligated to exercise the Options and as a result of the uncertain outcome of the discovery, research and development activities as well as the significant option exercise fee payable upon exercise of an Option, there is significant uncertainty as to whether Allergan will decide to exercise its Option for any CDP. Consequently, the Company is at risk with regard to whether Allergan will exercise the Options. In addition, the option exercise fees are not priced at a significant and incremental discount. Accordingly, the substantive options are not considered deliverables at the inception of the arrangement and the associated option exercise payments are not included in allocable arrangement consideration. The Company has also determined that any obligations which are contingent upon the exercise of a substantive option are not considered deliverables at the outset of the arrangement. The Company has concluded that the services being provided as part of the ASC Deliverable does not qualify for separation from the R&D Services Deliverable. The ASC provides oversight and management of the overall Allergan Agreement, and the members of the ASC from the Company have specialized industry knowledge, particularly as it relates to genome editing technology. The Company has concluded that the ASC is a participatory obligation of the Company and is meant to facilitate the early stage research being performed and coordinate the activities of both the Company and Allergan. Further, the ASC services are critical to the selection of the CDP, the ongoing evaluation of the CDP and the development and evaluation of the Option Package Criteria. Accordingly, the Company’s participation on the ASC is essential to Allergan receiving value from the R&D Services Deliverable and as such, the ASC Deliverable along with the R&D Services Deliverable are considered one unit (the “CDP Services Unit”). As the Company concluded that the CDP Services Unit is the sole unit of accounting (the “CDP Services Unit of Accounting”), all of the initial arrangement consideration will be allocated to that unit and no allocation of arrangement consideration is necessary. Allocable arrangement consideration at inception is comprised solely of the up‑front payment of $90.0 million. The Company will recognize revenue related to the CDP Services Unit of Accounting as the underlying services are performed. In addition, as the LCA10 IND Payment is payable upon acceptance of the IND, it is contingent consideration related to the licensed technology. As such, if and when the LCA10 IND Payment is received, the Company will recognize revenue related to the LCA10 IND Payment in conjunction with the CDP Services Unit of Accounting as the underlying services are performed. The Company has evaluated all of the milestones that may be received in connection with the Allergan Agreement. 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 product approval and launch milestones are considered substantive on the basis of the contingent nature of the milestones, specifically reviewing factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the milestone. 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 sales 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 six month periods ended June 30, 2017, the Company recognized revenue totaling approximately $2.4 million with respect to the Allergan Agreement. As of June 30, 2017, there was $87.6 million of deferred revenue related to the Company’s strategic alliance with Allergan, of which $74.7 million is classified as long-term on the consolidated balance sheet. The Company will recognize revenue on a straight-line basis, as there is no discernible pattern or objective measure of performance of the services, over the estimated performance period. The estimated performance period is from the commencement of providing services related to the CDP Services Unit until the end of the Research Term. Other Agreements Licensing Agreements The Company is a party to a number of license agreements under which the Company licenses patents, patent applications and other intellectual property from third parties. The Company anticipates entering into these types of license agreements in the future. The Company believes the following agreements are significant to its business: Massachusetts General Hospital Agreements In August 2014, the Company entered into an agreement to license certain patent rights owned or co‑owned by MGH. Consideration for the granting of the license included the payment of an upfront license fee of $0.1 million, the issuance of 66,848 shares of the Company’s common stock, which was based on 0.5% of the Company’s outstanding stock on a fully diluted basis, and the right to receive future issuances of shares of common stock to maintain MGH’s ownership following the third tranche of the Company’s Series A redeemable convertible preferred stock financing (i.e. anti‑dilution protection liability), which was settled in June 2015. MGH is entitled to receive nominal annual license fees and future clinical, regulatory and commercial milestone payments in an aggregate maximum amount of $3.7 million and an aggregate amount of $1.8 million upon the occurrence of certain sales milestones. The Company is also obligated to pay MGH low single digit percentage royalties on net sales of products for the prevention or treatment of human disease and ranging from low single digit to low double digit percentage royalties on net sales of other products and services made by the Company, its affiliates or its sublicenses. The royalty percentage depends on the product and service, and whether such licensed product or licensed service is covered by a valid claim within the certain patent rights that the Company licenses from MGH. In August 2016, the Company entered into a license agreement with MGH (the “2016 MGH Agreement”) to license certain patent rights owned or co-owned by MGH (the “Additional MGH Patent Rights”). Consideration for granting the license included the payment of an upfront nonrefundable license fee of $0.8 million, which the Company recorded as research and development expense in 2016. Under the 2016 MGH Agreement, MGH is entitled to nominal annual license fees, clinical and regulatory milestone payments totaling less than $1.0 million in the aggregate per licensed product up to four licensed products or processes to achieve the specified clinical and regulatory milestones, and commercial sales milestone payments totaling up to $4.9 million in the aggregate, consisting of milestone payments due upon the first commercial sales for up to four licensed products or processes and milestone payments due upon annual net sales of products or processes meeting specified thresholds. The Company is also obligated to pay MGH royalties of less than 1% on net sales of products and processes for the prevention or treatment of human disease, and royalties of a low single-digit percentage on net sales of products and processes for the prevention or treatment of a non-human animal disease, made by the Company, its affiliates, or its sublicensees. The royalty percentages that the Company is obligated to pay are subject to reduction if at the time of sale the applicable product or process is not covered by a valid claim within the Additional MGH Patent Rights. Under the 2016 MGH Agreement, the Company is obligated to reimburse MGH for all patent costs and future reasonable costs associated with the prosecution, filing, and maintenance of the licensed patents. MGH is also entitled under the 2016 MGH Agreement to receive payments of up to $6.0 million in the event the Company’s market capitalization reaches specified thresholds exceeding a low ten-digit dollar amount, on or prior to the expiration or termination of the 2016 MGH Agreement (or if earlier, a Company sale) (“MGH Market Cap Success Payments”) or a Company sale for consideration in excess of those thresholds (“MGH Company Sale Success Payments”). Additional MGH Market Cap Success Payments become payable, and the amount of potential MGH Company Sale Success Payments would increase further, if the Company’s market capitalization reaches additional higher thresholds and the Company has at least one product candidate that is covered by a claim of an Additional MGH Patent Right and that (i) is the subject of a Phase 1 clinical trial of which the Company or an affiliate or sublicensee of the Company is the sponsor, (ii) was the subject of a Phase 1 clinical trial of which the Company or an affiliate or sublicensee of the Company was the sponsor with the Company having determined to conduct a subsequent clinical trial with respect to such product candidate, or (iii) has been approved for sale in either the United States or European Union. MGH Market Cap Success Payments are payable in cash or shares of Company common stock at the Company’s discretion, and MGH Company Sale Success Payments are payable solely in cash. The Broad Institute Agreements In October 2014, the Company entered into an agreement (the “Cas9-I License Agreement”) with Broad and Harvard to license certain patent rights owned or co‑owned by, or among, Broad, Massachusetts Institute of Technology (“MIT”), and Harvard (collectively, the “Institutions”). Consideration for the granting of the license included the payment of an upfront license issuance fee of $0.2 million and the issuance of 561,531 shares of the Company’s common stock. The Institutions are collectively entitled to receive clinical and regulatory milestone payments totaling up to $14.8 million in the aggregate per licensed product approved in the United States, European Union, and Japan for the treatment of a human disease that afflicts at least a specified number of patients in the aggregate in the United States. If the Company undergoes a change of control during the term of the license agreement, the clinical and regulatory milestone payments will be increased by a certain percentage in the mid‑double digits. The Company is also obligated to make additional payments to the Institutions, collectively, of up to an aggregate of $54.0 million upon the occurrence of certain sales milestones per licensed product for the treatment of a human disease that afflicts at least a specified number of patients in the aggregate in the United States. The Institutions are collectively entitled to receive clinical and regulatory milestone payments totaling up to $4.1 million in the aggregate per licensed product approved in the U.S. and at least one jurisdiction outside the U.S. for the treatment of a human disease based on certain criteria. The Company is also obligated to make additional payments to the Institutions, collectively, of up to an aggregate of $36.0 million upon the occurrence of certain sales milestones per licensed product for the treatment of a rare disease meeting certain criteria. The Institutions are entitled to receive from the Company nominal annual license fees and a mid‑single digit percentage royalties on net sales of products for the prevention or treatment of human disease and ranging from low single digit to high single digit percentage royalties on net sales of other products and services, made by the Company, its affiliates, or its sublicensees. The royalty percentage depends on the product and service, and whether such licensed product or licensed service is covered by a valid claim within the certain patent rights that the Company licenses from the Institutions. In December 2016, the Company entered into the Cpf1 License Agreement with Broad, for specified patent rights (the “Cpf1 Patent Rights”) related primarily to Cpf1 compositions of matter and their use for gene editing. Concurrently with entering into the Cpf1 License Agreement, the Company, Broad, and Harvard amended and restated the Cas9-I License Agreement as described below. Concurrently, the Company and Broad also entered into a license agreement (the “Cas9‑II License Agreement”) for specified patent rights (the “Cas9-II Patent Rights”) related primarily to certain Cas9 compositions of matter and their use for genome editing. The Company paid an upfront fee in aggregate of $16.5 million under these agreements, of which $10.0 million is in the form of notes payable, described further in Note 7. The upfront fee was recorded in research and development expenses during 2016. Cpf1 License Agreement Pursuant to the Cpf1 License Agreement, Broad, on behalf of itself, Harvard, MIT, Wageningen, and the University of Tokyo (“UTokyo” and, together with Broad, Harvard, MIT, and Wageningen, the “Cpf1 Institutions”) granted the Company an exclusive, worldwide, royalty‑bearing, sublicensable license to the Cpf1 Patent Rights, to make, have made, use, have used, sell, offer for sale, have sold, export and import products in the field of the prevention or treatment of human disease using gene therapy, editing of genetic material, or targeting of genetic material, subject to certain limitations and retained rights (collectively, the “Cpf1 Exclusive Field”), as well as a non‑exclusive, worldwide, royalty‑bearing sublicensable license to the Cpf1 Patent Rights for all other purposes, subject to certain limitations and retained rights. The Company is obligated to use commercially reasonable efforts to research, develop, and commercialize products in the Cpf1 Exclusive Field. The Company is also required to achieve certain development milestones within specified time periods for products covered by the Cpf1 Patent Rights, with Broad having the right to terminate the Cpf1 License Agreement if the Company fails to achieve these milestones within the required time periods. Broad and Wageningen are collectively entitled to receive clinical and regulatory milestone payments totaling up to $20.0 million in the aggregate per licensed product approved in the United States, European Union, and Japan for the prevention or treatment of a human disease that afflicts at least a specified number of patients in the aggregate in the United States. The Company is also obligated to make additional payments to Broad and Wageningen, collectively, of up to an aggregate of $54.0 million upon the occurrence of certain sales milestones per licensed product for the prevention or treatment of a human disease that afflicts at least a specified number of patients in the aggregate in the United States. Broad and Wageningen are collectively entitled to receive clinical and regulatory milestone payments totaling up to $6.0 million in the aggregate per licensed product approved in the United States, European Union and Japan for the prevention or treatment of a human disease that afflicts fewer than a specified number of patients in the aggregate in the United States or a specified number of patients per year in the United States (an “Ultra‑Orphan Disease”). The Company is also obligated to make additional payments to Broad and Wageningen, collectively, of up to an aggregate of $36.0 million upon the occurrence of certain sales milestones per licensed product for the prevention or treatment of an Ultra‑Orphan Disease. Broad and Wageningen, collectively, are entitled to receive, on a product‑by‑product and country‑by‑country basis, mid single‑digit percentage royalty on net sales of licensed products for the prevention or treatment of human disease, and royalties on net sales of other licensed products and licensed services, made by the Company, its affiliates, or its sublicensees. The royalty percentage depends on the product and service, and whether such licensed product or licensed service is covered by a valid claim within the Cpf1 Patent Rights. If the Company is legally required to pay royalties to a third party on net sales of the Company’s products because such third party holds patent rights that cover such licensed product, then the Company can credit up to a specified percentage of the amount paid to such third party against the royalties due to Broad and Wageningen in the same period. Such credit may not exceed 50% of the applicable royalties paid by the Company to the applicable third party. The Company’s obligation to pay royalties will expire on a product‑by‑product and country‑by‑country basis upon the later of the expiration of the last to expire valid claim of the Cpf1 Patent Rights that covers each licensed product or service in each country or the tenth anniversary of the date of the first commercial sale of the licensed product or licensed service. If the Company sublicenses any of the Cpf1 Patent Rights to a third party, Broad and Wageningen, collectively, have the right to receive sublicense income, depending on the stage of development of the products or services in question at the time of the sublicense. Under the Cpf1 License Agreement, Broad and Wageningen are also entitled, collectively, to receive success payments in the event the Company’s market capitalization reaches specified thresholds (the “Cpf1 Market Cap Success Payments”) or a Company sale for consideration in excess of those thresholds (the “Cpf1 Company Sale Success Payments” and, collectively with the Cpf1 Market Cap Success Payments, the “Cpf1 Success Payments”). The Cpf1 Success Payments payable to Broad and Wageningen range from $750 million to a mid eight digit dollar amount, and collectively will not exceed, in aggregate, $125.0 million, which maximum amount would be payable only if the Company reaches a market capitalization threshold of $10.0 billion and has at least one product candidate covered by a claim of a patent right licensed to the Company under either the Cpf1 License Agreement or the Cas9‑I License Agreement that is or was the subject of a clinical trial pursuant to development efforts by the Company or any Company affiliate or sublicensee. The Cpf1 Market Cap Success Payments are payable by the Company in cash or in the form of promissory notes on substantially the same terms and conditions as the Initial Notes, described further in Note 7, except that the maturity date of such notes will, subject to certain exceptions, be 150 days following issuance. Following a change in control of the Company, Cpf1 Market Cap Success Payments are required to be made in cash. Cpf1 Company Sale Success Payments are payable solely in cash. Unless terminated earlier, the term of the Cpf1 License Agreement will expire on a country‑by‑country basis, upon the expiration of the last to expire valid claim of the Cpf1 Patent Rights in such country. The Company has the right to terminate the Cpf1 License Agreement at will upon four months’ written notice to Broad. Either party may terminate the Cpf1 License Agreement upon a specified period of notice in the event of the other party’s uncured material breach of a material obligation, such notice period varying depending on the nature of the breach. Broad may terminate the Cpf1 License Agreement immediately if the Company challenges the enforceability, validity, or scope of any Cpf1 Patent Right or assist a third party to do so, or in the event of the Company’s bankruptcy or insolvency. Amendment and Restatement of Cas9-I License Agreement In December 2016, the Company amended and restated the Cas9‑I License Agreement to exclude additional fields from the scope of the exclusive license previously granted to the Company, to make the exclusive license to three targets become non‑exclusive, subject to the limitation that each of Broad and Harvard would only be permitted to grant a license to only one third party at a time with respect to each such target within the field of the exclusive license, and to revise certain provisions relating to the rights of Harvard and Broad to grant further licenses under specified circumstances to third parties that wish to develop and commercialize products that target a particular gene and that otherwise would fall within the scope of the exclusive license under this agreement, so that Harvard and Broad together would have rights substantially similar to the equivalent rights possessed by Broad under the Cpf1 License Agreement to designate gene targets for which the designating institution, whether alone or together with an affiliate or third party, has an interest in researching and developing products that would otherwise be covered by rights licensed by Harvard and/or Broad to the Company under this agreement, the Cpf1 License Agreement or the Cas9‑II Agreement (such agreement, as amended, the “Amended and Restated Cas9-I License Agreement”). In March 2017, the Company and Harvard and Broad further amended the Amended and Restated Cas9-I License Agreement to (i) grant an exclusive license from Broad to the Company with respect to certain patent rights that The Rockefeller University (“Rockefeller”) has or may have rights in and to and for which Rockefeller has, under a certain inter-institutional agreement that Broad and Rockefeller entered into in February 2017, appointed Broad as sole and exclusive agent for the purposes of licensing and (ii) provide to Rockefeller certain rights, including with respect to patent enforcement, indemnification, insurance, confidentiality, reservation of certain rights, and publicity, that are generally consistent with those granted to Broad, Harvard, MIT and the Howard Hughes Medical Institute under the Amended and Restated Cas9-I License Agreement. Cas9‑II License Agreement Pursuant to the Cas9‑II License Agreement, Broad, on behalf of itself, MIT, Harvard, and the University of Iowa Research Foundation, granted the Company an exclusive, worldwide, royalty bearing sublicensable license to certain of the Cas9‑II Patent Rights as well as a non‑exclusive, worldwide, royalty‑bearing sublicensable license to all of the Cas9‑II Patent Rights, in each case on terms substantially similar to the licenses granted to the Company under Cpf1 License Agreement except, among other things, for the following commitment amounts. Under the Cas9‑II License Agreement, the Company will pay an upfront license fee in a low seven digits amount as well as an annual license maintenance fee. The Company is obligated to pay clinical and regulatory milestone payments per licensed product approved in the United States, European Union and Japan for the prevention or treatment of a human disease that afflicts at least a specified number of patients in the aggregate in the United States totaling up to $3.7 million in the aggregate, and sales milestone payments for any such licensed product totaling up to $13.5 million in the aggregate. In addition, the Company is obligated to pay clinical and regulatory milestone payments totaling up to $1.1 million in the aggregate per licensed product approved in the United States and the European Union or Japan for the prevention or treatment of a human disease that afflicts fewer than a specified number of patients in the United States, plus sales milestone payments of up to $9.0 million for any such licensed product. Consistent with the Cpf1 License Agreement, the licensors are entitled to royalties on net sales of products for the prevention or treatment of human disease and other products and services made by the Company, its affiliates, or its sublicensees. Royalties due under other license agreements are creditable against these royalties up to a specified amount in the same period. Lastly, Broad is entitled to receive success payments if the Company’s market capitalization reaches specified thresholds ascending from a low ten-digit dollar amount to $9.0 billion or a Company sale. The potential success payments range from a low seven digit dollar amount to a low eight digit dollar amount and will not exceed, in aggregate, $30.0 million, which maximum amount would be owed only if the Company reaches a market capitalization threshold of $9.0 billion and has at least one product candidate covered by a claim of a patent right licensed to the Company under either the Cas9 II License Agreement or the Cas9-I License Agreement that is or was the subject of a clinical trial pursuant to development efforts by the Company or any Company affiliate or sublicensee.

Stock-based Compensation

6 Months Ended

Jun. 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				Six Months Ended
	June 30,				June 30,
	2017		2016		2017		2016
Research and development	$	3,086	$	3,943	$	6,699	$	7,402
General and administrative		1,930		1,254		4,120		2,007
Total stock-compensation expense	$	5,016	$	5,197	$	10,820	$	9,409

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 June 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	(394,485)	$	0.0164
Unvested Restricted Common Stock as of June 30, 2017	428,153	$	0.0258

For the six months ended June 30, 2017, the expense for restricted stock awards related to employees and non‑employees was $0.3 million and $3.5 million, respectively.

As of June 30, 2017, the Company had no unrecognized stock‑based compensation expense related to its employee unvested restricted stock awards. As of June 30, 2017, the Company had unrecognized stock‑based compensation expense related to its non‑employee unvested restricted stock awards of $0.5 million which is expected to be recognized in the third quarter of 2017 upon the expected vesting of such awards in August 2017.

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 June 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	1,224,965	$	23.16
Exercised	(100,802)	$	4.87
Cancelled	(91,238)	$	12.02
Outstanding at June 30, 2017	4,444,708	$	16.55	8.9	$	16,161
Vested and expected to vest at June 30, 2017	4,444,708	$	16.55	8.9	$	16,161
Exercisable at June 30, 2017	1,062,695	$	12.71	8.7	$	7,023

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 13,262 and 21,955 shares of unvested restricted common stock outstanding at June 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 six months ended June 30, 2017 and 2016 was $16.67 and $16.34, respectively. The expense related to options granted to employees and directors was $5.9 million and $2.4 million for the six months ended June 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				Six Months Ended
	June 30,				June 30,
	2017		2016		2017		2016
Risk free interest rate	2.0	%	1.4	%	2.1	%	1.5	%
Expected dividend yield	—		—		—		—
Expected term (in years)	6.25		6.25		6.25		6.25
Expected volatility	77.0	%	80.0	%	77.9	%	80.0	%

There were no options issued to persons other than employees and directors during the six months ended June 30, 2017 and 2016, respectively. As of June 30, 2017, the Company had unrecognized stock‑based compensation expense related to its employee stock options of $37.8 million which the Company expects to recognize over the remaining weighted average vesting period of 2.88 years.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Net Loss per Share

6 Months Ended

Jun. 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 included in the calculation of basic loss per share as of the beginning of the period in which all the necessary conditions have been satisfied. Contingently issuable shares are included in diluted loss per share based on the number of shares, if any, that would be issuable under the terms of the arrangement if the end of the reporting period was the end of the contingency period, if the results are dilutive.

For purposes of the diluted net loss per share calculation, stock options are considered to be common stock equivalents, but they were excluded from the Company’s calculation of diluted net loss per share allocable to common stockholders because their inclusion would have been anti-dilutive. Therefore, basic and diluted net loss per share applicable to common stockholders was the same for all periods presented. Contingently issuable shares of common stock pursuant to the 2016 License Agreements, as discussed more fully in Note 7, are excluded from the calculation of basic and diluted net loss per share calculation as the Payment Conditions have not been satisfied.

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 six months ended June 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 nine 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 June 30,
	2017	2016
Unvested restricted common stock	428,153	1,209,744
Outstanding stock options	4,444,708	2,596,228
Estimated number of shares issuable for convertible notes (1)	913,115	—
Total	5,785,976	3,805,972

(1)

Represents the number of shares that would have been issued if the Company had elected to pay the promissory notes, as discussed in Note 7, in shares of the Company’s common stock, based on the closing price of the common stock on June 30, 2017. The number of shares issued, for purposes of this presentation, is calculated by dividing the principal of the notes payable, including accrued interest, by the stock price per share.

The table above reflects restricted stock issued upon exercise of unvested stock options as exercised on the dates that the shares are no longer subject to repurchase.

Related-party Transactions	6 Months Ended
Related-party Transactions	Jun. 30, 2017
Related-party Transactions
Related-party Transactions	11. Related‑party Transactions During the six months ended June 30, 2016, the Company paid a related party $1.0 million in rent and facility-related fees. The Company did not make any payments to this related party in the six months ended June 30, 2017. The Company received $0.4 million in rent and facility-related fees from a related party in the six months ended June 30, 2017 in connection with the Sublease and no rent or facility-related payments were received from this related party in 2016.

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2017
Subsequent Events
Subsequent Events	12. Subsequent Events In July 2017, the Company achieved the next substantive milestone of $2.5 million resulting from technical progress in a research program under its collaboration with Juno Therapeutics. In August 2017, the Company issued an aggregate of 271,347 shares of its common stock to Broad and paid $0.4 million to Wageningen as payment of all outstanding principal and interest under the Success Payment Notes, as discussed in Note 7. Upon such issuance and payment, the Success Payment Notes were cancelled.

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 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 June 30, 2017 and 2016 are referred to as the second 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 United States generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, accrued expenses, stock‑based compensation expense, deferred tax valuation allowances and sub-license fees due to certain of our licensors. The Company bases its estimates on historical experience and other market‑specific or relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.
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” and, if so, mark the investment to market through a charge to the Company’s statement of operations.
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 CFFT, and its strategic alliance with Allergan, and pursuant to which it has recognized since inception a total of $8.7 million, $0.3 million, and $2.4 million, respectively, through June 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 license payment, research funding and the $2.5 million milestone 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. 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 does not expect this standard to have a material impact on the 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.

- Definition

Disclosure of accounting policy for investments in debt and equity securities that have readily determinable fair values (marketable securities). At a minimum, the disclosure might address accounting policies for investments classified as trading, available for sale, or held to maturity and may include how the entity determines whether impairments of available for sale or held to maturity investments are other than temporary, how the fair values of the entity's securities are determined, and the entity's accounting treatment for transfers between investment categories.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.M)
-URI http://asc.fasb.org/extlink&oid=65877573&loc=d3e87990-122713

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=68058157&loc=d3e18780-107790

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Readily Determinable Fair Value
-URI http://asc.fasb.org/extlink&oid=65888395

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section S50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6381980&loc=d3e87707-122711

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62652-112803

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(5))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Cash Equivalents & Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2017

Cash Equivalents & Marketable Securities

Schedule of cash equivalents and marketable securities

Cash equivalents and marketable securities consisted of the following at June 30, 2017 (in thousands):


			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
June 30, 2017	Cost		Gains		Losses		Value
Cash equivalents:
Money market funds	$	115,105	$	—	$	—	$	115,105
U.S. Treasuries		28,990		1		—		28,991
Marketable securities:
U.S. Treasuries		74,807		—		(21)		74,786
Government agency securities		105,960		—		(47)		105,913
Total cash equivalents and marketable securities	$	324,862	$	1	$	(68)	$	324,795

Cash equivalents and marketable securities consisted of the following at December 30, 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)

6 Months Ended

Jun. 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 June 30, 2017 were as follows (in thousands):


			Quoted Prices		Significant
			in Active		Other		Significant
			Markets for		Observable		Unobservable
	June 30,		Identical Assets		Inputs		Inputs
Financial Assets	2017		(Level 1)		(Level 2)		(Level 3)
Cash equivalents:
Money market funds	$	115,105	$	115,105	$	—	$	—
U.S. Treasuries		28,991		28,991		—		—
Marketable securities:
U.S. Treasuries		74,786		74,786		—		—
Government agency securities		105,913		105,913		—		—
Money market funds, included in restricted cash		1,619		—		—		—
Total financial assets	$	326,414	$	324,795	$	—	$	—

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)

6 Months Ended

Jun. 30, 2017

Accrued Expenses

Schedule of accrued expenses

Accrued expenses consisted of the following (in thousands):


	As of
	June 30,		December 31,
	2017		2016
Sublicense income fees	$	5,061	$	—
Employee compensation costs		2,356		2,480
Patent and license fees		2,211		13,251
Research and development		554		443
Professional services		927		729
Other		51		536
Total	$	11,160	$	17,439

Property and Equipment, net (Tables)

6 Months Ended

Jun. 30, 2017

Property and Equipment, net

Schedule of property and equipment, net

Property and equipment, net consisted of the following (in thousands):


	As of
	June 30,		December 31,
	2017		2016
Building	$	35,167	$	35,941
Laboratory equipment		6,116		5,130
Computer equipment		435		392
Leasehold improvements		177		200
Software		136		101
Furniture and office equipment		96		170
Total property and equipment		42,127		41,934
Less: accumulated depreciation		(2,769)		(1,556)
Property and equipment, net	$	39,358	$	40,378

Stock-based Compensation (Tables)

6 Months Ended

Jun. 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				Six Months Ended
	June 30,				June 30,
	2017		2016		2017		2016
Research and development	$	3,086	$	3,943	$	6,699	$	7,402
General and administrative		1,930		1,254		4,120		2,007
Total stock-compensation expense	$	5,016	$	5,197	$	10,820	$	9,409

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	(394,485)	$	0.0164
Unvested Restricted Common Stock as of June 30, 2017	428,153	$	0.0258

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	1,224,965	$	23.16
Exercised	(100,802)	$	4.87
Cancelled	(91,238)	$	12.02
Outstanding at June 30, 2017	4,444,708	$	16.55	8.9	$	16,161
Vested and expected to vest at June 30, 2017	4,444,708	$	16.55	8.9	$	16,161
Exercisable at June 30, 2017	1,062,695	$	12.71	8.7	$	7,023

Schedule of assumptions used to value stock options


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2017		2016		2017		2016
Risk free interest rate	2.0	%	1.4	%	2.1	%	1.5	%
Expected dividend yield	—		—		—		—
Expected term (in years)	6.25		6.25		6.25		6.25
Expected volatility	77.0	%	80.0	%	77.9	%	80.0	%

Net Loss per Share (Tables)

6 Months Ended

Jun. 30, 2017

Net Loss per Share

Schedule of anti-dilutive common stock equivalents

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 June 30,
	2017	2016
Unvested restricted common stock	428,153	1,209,744
Outstanding stock options	4,444,708	2,596,228
Estimated number of shares issuable for convertible notes (1)	913,115	—
Total	5,785,976	3,805,972

(1)

Nature of Business (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended
	Feb. 08, 2016	Feb. 03, 2016	Mar. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Liquidity
Common stock, shares outstanding				40,913,418	35,818,131
Accumulated deficit				$ (243,062)	$ (185,526)
Initial Public Offering
Liquidity
Shares sold	6,785,000		4,600,000
Price to the public	$ 16.00		$ 22.50
Aggregate net proceeds		$ 97,500	$ 96,700
Overallotment Option
Liquidity
Shares sold	885,000		600,000

Summary of Significant Accounting Policies (Details)	1 Months Ended	3 Months Ended		6 Months Ended		14 Months Ended	26 Months Ended
Summary of Significant Accounting Policies (Details)	May 31, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) item	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)
Revenue Recognition [Abstract]
Number of revenue agreements \| item				3
Contracts Revenue		$ 3,097,000	$ 3,388,000	$ 3,779,000	$ 4,193,000
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		$ 700,000	$ 3,300,000	1,400,000	$ 4,100,000		$ 8,700,000
License Agreement Milestone Payment Received	$ 2,500,000
Cystic Fibrosis Foundation Therapeutics, Inc. \| Development award agreement
Revenue Recognition [Abstract]
Contracts Revenue						$ 300,000
Allergen \| Strategic Alliance
Revenue Recognition [Abstract]
Contracts Revenue				$ 2,400,000

Cash Equivalents & Marketable Securities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($) item	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Cash equivalents and marketable securities
Amortized Cost	$ 324,862		$ 185,323
Gross Unrealized Gains	1
Gross Unrealized Losses	(68)
Fair Value	$ 324,795		185,323
Number of securities in an unrealized loss position \| item	26
Securities held by the Company in an unrealized loss position for less than 12 months	$ 180,700
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	74,807
Gross Unrealized Losses	(21)
Fair Value	74,786
Government agency securities
Cash equivalents and marketable securities
Amortized Cost	105,960
Gross Unrealized Losses	(47)
Fair Value	105,913
Money market funds
Cash equivalents and marketable securities
Amortized Cost	115,105		185,323
Fair Value	115,105		$ 185,323
U.S. Treasuries
Cash equivalents and marketable securities
Amortized Cost	28,990
Gross Unrealized Gains	1
Fair Value	$ 28,991

Fair Value Measurements - Recurring Basis (Details) $ in Thousands, item in Millions	6 Months Ended
	Jun. 30, 2017 USD ($) item	Dec. 31, 2016 USD ($)
Financial Assets
Marketable securities	$ 324,795	$ 185,323
Transfers between levels \| item	0.0
U.S. Treasuries
Financial Assets
Marketable securities	$ 74,786
Government agency securities
Financial Assets
Marketable securities	105,913
Money market funds
Financial Assets
Marketable securities	115,105	185,323
U.S. Treasuries
Financial Assets
Marketable securities	28,991
Recurring
Financial Assets
Cash and cash equivalents		185,323
Total financial assets	326,414	186,942
Recurring \| U.S. Treasuries
Financial Assets
Marketable securities	74,786
Recurring \| Government agency securities
Financial Assets
Marketable securities	105,913
Recurring \| Money market funds
Financial Assets
Cash and cash equivalents	115,105
Restricted cash	1,619	1,619
Recurring \| U.S. Treasuries
Financial Assets
Cash and cash equivalents	28,991
Recurring \| Level 1
Financial Assets
Cash and cash equivalents		185,323
Total financial assets	324,795	186,942
Recurring \| Level 1 \| U.S. Treasuries
Financial Assets
Marketable securities	74,786
Recurring \| Level 1 \| Government agency securities
Financial Assets
Marketable securities	105,913
Recurring \| Level 1 \| Money market funds
Financial Assets
Cash and cash equivalents	115,105
Restricted cash		$ 1,619
Recurring \| Level 1 \| U.S. Treasuries
Financial Assets
Cash and cash equivalents	$ 28,991

Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accrued Expenses
Sublicense income fees	$ 5,061
Employee compensation costs	2,356	$ 2,480
Patent and license fees	2,211	13,251
Research and development	554	443
Professional services	927	729
Other	51	536
Total	$ 11,160	$ 17,439

Property and Equipment, net (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Property and equipment disclosures
Total property and equipment	$ 42,127	$ 41,934
Less: accumulated depreciation	(2,769)	(1,556)
Property and equipment, net	39,358	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	6,116	5,130
Computer equipment
Property and equipment disclosures
Total property and equipment	435	392
Leasehold improvements
Property and equipment disclosures
Total property and equipment	177	200
Software
Property and equipment disclosures
Total property and equipment	136	101
Furniture and office equipment
Property and equipment disclosures
Total property and equipment	$ 96	$ 170

Commitments and Contingencies - Operating Leases (Details) - Hurley Street Lease $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($)	Feb. 29, 2016 USD ($) ft²
Commitments and contingencies
Leased space ( in square feet) \| ft²		59,783
Security deposit		$ 1.6
Estimated useful life	30 years
Deferred rent	$ 0.3
Extended lease option (in years)	5 years

Commitments and Contingencies - Notes Payable (Details) - USD ($) $ in Thousands		1 Months Ended
	Mar. 28, 2017	Aug. 31, 2017	Jul. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2017
Commitments and contingencies
Accrued expenses					$ 17,439	$ 11,160
2016 License Agreements
Commitments and contingencies
Market Capitalization				$ 750,000
Broad and Wageningen University \| Subsequent Event
Notes Payable
Success Payments		$ 400
Broad and Wageningen University \| Cpf1 License Agreement
Notes Payable
Promissory notes issued	$ 5,000			5,000	$ 10,000
Interest rate (as a percentage)					4.80%
Success Payments				5,000
Allergan \| Strategic Alliance
Commitments and contingencies
Contingent liability				$ 1,700
Accrued expenses						5,100
Allergan \| Strategic Alliance \| Maximum
Commitments and contingencies
Contingent liability						$ 6,800
Allergan \| Strategic Alliance \| Subsequent Event
Commitments and contingencies
Payments for licensor expense reimbursement			$ 5,100

Significant Agreements - Juno Therapeutics Collaboration Agreement (Details) $ in Thousands		1 Months Ended				3 Months Ended		6 Months Ended		12 Months Ended	26 Months Ended
	May 26, 2015 item	Mar. 31, 2017 USD ($) item	Aug. 31, 2016 USD ($) item	May 31, 2016 USD ($)	May 31, 2015 USD ($) item	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) item	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2017 USD ($)
Collaboration and other research and development revenues						$ 3,097	$ 3,388	$ 3,779	$ 4,193
Research and development						17,318	10,430	36,339	19,312
Deferred revenue, long-term						100,953		100,953		$ 26,000	$ 100,953
Accounts receivable						820		820		88	820
Juno Therapeutics
Deferred revenue, long-term						26,200		26,200			26,200
Accounts receivable						800		$ 800			800
Allergan
Number of additional licenses \| item								2
One time payment to acquire the license								$ 25,000
Potential development milestone payments		$ 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
Potential development milestone payments						42,000		42,000			42,000
Potential regulatory and commercial milestone payments						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
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						700	$ 3,300	1,400	$ 4,100		8,700
Collaboration and License Agreement \| Adverum Biotechnologies, Inc
Additional fees			$ 1,000
Maximum number of inherited retinal diseases, to be treated \| item			5
Up-front payment			$ 1,000
Adverum agreement consideration- preclinical activities			500
Advance payment on future research and development activities			$ 500
Research and development										$ 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						2,400		2,400
Deferred revenue						87,600		87,600			87,600
Deferred revenue, long-term						$ 74,700		$ 74,700			$ 74,700
Contract termination notice		90 days
Strategic Alliance \| Allergan \| Maximum
Extension period		10 years

Significant Agreements - Other Agreements (Details) $ in Thousands	1 Months Ended					3 Months Ended		6 Months Ended
	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Aug. 31, 2016 USD ($) item	Oct. 31, 2014 USD ($) shares	Aug. 31, 2014 USD ($) shares	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) item	Jun. 30, 2016 USD ($)
Notes payable		$ 10,000				$ 15,000		$ 15,000
Research and development						17,318	$ 10,430	$ 36,339	$ 19,312
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
Notes payable		10,000
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
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 - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Stock-based compensation disclosures
Compensation expense	$ 5,016	$ 5,197	$ 10,820	$ 9,409
Research and development.
Stock-based compensation disclosures
Compensation expense	3,086	3,943	6,699	7,402
General and administrative
Stock-based compensation disclosures
Compensation expense	$ 1,930	$ 1,254	$ 4,120	$ 2,007

Stock-based Compensation - Restricted Stock and Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 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)			(394,485)
Unvested restricted common stock, end of period(in shares)	428,153		428,153		822,638
Weighted Average Grant Date Fair Value
Balance, beginning of period			$ 0.0213
Vested (in dollars per share)			0.0164
Balance, ending of period	$ 0.0258		$ 0.0258		$ 0.0213
Changes in unvested stock options
Compensation expense	$ 5,016	$ 5,197	$ 10,820	$ 9,409
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)			1,224,965
Exercised (in shares)			(100,802)
Cancelled (in shares)			(91,238)
Outstanding, end of period (in shares)	4,444,708		4,444,708		3,411,783
Vested and expected to vest (in shares)	4,444,708		4,444,708
Exercisable (in shares)	1,062,695		1,062,695
Outstanding, beginning of period (in dollars per share)			$ 13.71
Granted (in dollars per share)			23.16
Exercised (in dollars per share)			4.87
Cancelled (in dollars per share)			12.02
Outstanding, end of period (in dollars per share)	$ 16.55		16.55		$ 13.71
Vested and expected to vest outstanding, weighted average exercise price (in dollars per share)	16.55		16.55
Exercisable (in dollar per share)	$ 12.71		$ 12.71
Remaining contractual life			8 years 10 months 24 days		8 years 9 months 18 days
Vested and expected to vest, remaining contractual life			8 years 10 months 24 days
Exercisable, remaining contractual life			8 years 8 months 12 days
Aggregate intrinsic value	$ 16,161		$ 16,161		$ 16,190
Vesting and expected to vest, aggregate intrinsic value	16,161		16,161
Exercisable, aggregated intrinsic value	$ 7,023		$ 7,023
Unvested stock options (in shares)	13,262		13,262		21,955
Employees and directors
Changes in unvested stock options
Compensation expense			$ 5,900	$ 2,400
Weighted average fair value of options granted (per share)			$ 16.67	$ 16.34
Employees
Changes in unvested stock options
Unrecognized stock-based compensation expense	$ 37,800		$ 37,800
Period for recognition			2 years 10 months 17 days
Restricted Stock \| Employees
Changes in unvested stock options
Compensation expense			$ 300
Unrecognized stock-based compensation expense	0		0
Restricted Stock \| Non-employees
Changes in unvested stock options
Compensation expense			3,500
Unrecognized stock-based compensation expense	$ 500		$ 500
Employee and Consultant Options \| Employees
Changes in unvested stock options
Granted (in shares)			0	0

Stock-based Compensation - Assumptions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Employees and directors
Assumptions
Risk free interest rate	2.00%	1.40%	2.10%	1.50%
Expected term (in years)	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months
Expected volatility	77.00%	80.00%	77.90%	80.00%
Employees
Assumptions
Unrecognized stock-based compensation expense	$ 37.8		$ 37.8
Period for recognition			2 years 10 months 17 days

Net Loss per Share (Details) - shares		1 Months Ended	6 Months Ended
Net Loss per Share (Details) - shares	Feb. 08, 2016	Mar. 31, 2017	Jun. 30, 2017	Jun. 30, 2016
Potentially dilutive securities
Anti-dilutive common stock equivalent shares			5,785,976	3,805,972
Restricted Stock
Potentially dilutive securities
Anti-dilutive common stock equivalent shares			428,153	1,209,744
Outstanding stock options
Potentially dilutive securities
Anti-dilutive common stock equivalent shares			4,444,708	2,596,228
Convertible notes
Potentially dilutive securities
Anti-dilutive common stock equivalent shares			913,115
Initial Public Offering
Potentially dilutive securities
Shares sold	6,785,000	4,600,000

Related-party Transactions (Details) - Rent and facility related fees - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Related Party Transaction [Line Items]
Fees paid to related party	$ 0.0	$ 1.0
Fees received from related party	$ 0.4	$ 0.0

Subsequent Events (Details) - USD ($) $ in Millions	1 Months Ended
Subsequent Events (Details) - USD ($) $ in Millions	Aug. 31, 2017	Jul. 31, 2017	Mar. 31, 2017
Cpf1 License Agreement \| Broad and Wageningen University
Subsequent Event [Line Items]
Success Payments			$ 5.0
Subsequent Event \| Juno Therapeutics
Subsequent Event [Line Items]
Milestone payment received under license agreement		$ 2.5
Subsequent Event \| Broad and Wageningen University
Subsequent Event [Line Items]
Stock Issued During Period, Shares, Issued for Services	271,347
Success Payments	$ 0.4