Editas Medicine (EDIT) 10-Q 4 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 27, 2018
Document and Entity Information
Entity Registrant Name	Editas Medicine, Inc.
Entity Central Index Key	1,650,664
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		47,204,376
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 217,671	$ 146,630
Marketable securities	141,150	182,509
Accounts receivable	931	679
Prepaid expenses and other current assets	3,060	2,381
Total current assets	362,812	332,199
Property and equipment, net	39,551	39,442
Restricted cash and other non-current assets	1,619	1,619
Total assets	403,982	373,260
Current liabilities:
Accounts payable	8,996	4,020
Accrued expenses	7,767	11,049
Notes payable		7,500
Deferred revenue, current	13,323	13,238
Other current liabilities	908	900
Total current liabilities	30,994	36,707
Deferred revenue, net of current portion	91,972	94,725
Construction financing lease obligation, net of current portion	33,190	33,431
Other non-current liabilities	311	317
Total liabilities	156,467	165,180
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; 47,119,176 and 45,025,448 shares issued, and 46,711,695 and 44,507,960 shares outstanding at March 31, 2018 and December 31, 2017, respectively	4	4
Additional paid-in capital	584,825	514,002
Accumulated other comprehensive loss	(52)	(76)
Accumulated deficit	(337,262)	(305,850)
Total stockholders’ equity	247,515	208,080
Total liabilities and stockholders’ equity	$ 403,982	$ 373,260

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Condensed Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	195,000,000	195,000,000
Common stock, shares issued	47,119,176	45,025,448
Common stock, shares outstanding	46,711,695	44,507,960

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Consolidated Statements of Operations
Collaboration and other research and development revenues	$ 3,927	$ 682
Operating expenses:
Research and development	21,300	19,021
General and administrative	14,186	12,288
Total operating expenses	35,486	31,309
Operating loss	(31,559)	(30,627)
Other income (expense), net:
Other income, net	182	140
Interest income (expense), net	438	(610)
Total other income (expense), net	620	(470)
Net loss	$ (30,939)	$ (31,097)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.67)	$ (0.85)
Weighted-average common shares outstanding, basic and diluted	45,992,008	36,485,421

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Consolidated Statements of Comprehensive Loss
Net loss	$ (30,939)	$ (31,097)
Other comprehensive loss:
Unrealized loss on marketable debt securities	(52)
Comprehensive loss	$ (30,991)	$ (31,097)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flow from operating activities
Net loss	$ (30,939)	$ (31,097)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Stock-based compensation expense	6,528	5,804
Depreciation	751	631
Non-cash research and development expense	1,942	5,000
Other non-cash items, net	(430)	69
Changes in operating assets and liabilities:
Accounts receivable	(252)	(857)
Prepaid expenses and other current assets	(761)	486
Other non-current assets		2
Accounts payable	5,095	10,078
Accrued expenses	(1,252)	(10,539)
Deferred revenue	(3,142)	90,214
Net cash (used in) provided by operating activities	(22,460)	69,791
Cash flow from investing activities
Purchases of property and equipment	(1,011)	(656)
Proceeds from the sale of equipment	5
Purchases of marketable securities	(52,674)
Proceeds from maturities of marketable securities	94,500
Net cash provided by (used in) investing activities	40,820	(656)
Cash flow from financing activities
Proceeds from offering of common stock, net of issuance costs	48,474	97,102
Proceeds from exercise of stock options	4,410	435
Payments on construction financing lease obligation	(203)	(443)
Net cash provided by financing activities	52,681	97,094
Net increase in cash and cash equivalents	71,041	166,229
Cash, cash equivalents and restricted cash, beginning of period	148,249	186,942
Cash, cash equivalents and restricted cash, end of period	219,290	353,171
Supplemental disclosure of cash and non-cash activities:
Fixed asset additions included in accounts payable and accrued expenses	129	7
Reclassification of liability for common stock subject to repurchase	3	3
Issuance of common stock for settlement of success payments	9,530
Adjustment to deferred revenue for revenue adoption	474
Offering costs included in accounts payable and accrued expenses	$ 19	$ 397

Nature of Business

Nature of Business	3 Months Ended
	Mar. 31, 2018
Nature of Business
Nature of Business	Editas Medicine, Inc. Notes to Condensed Consolidated Financial Statements (unaudited) 1. Nature of Business Editas Medicine, Inc. (the “Company”) is a research stage company dedicated to treating patients with genetically defined diseases by correcting their disease‑causing genes. The Company was incorporated in the state of Delaware in September 2013. Its principal offices are in Cambridge, Massachusetts. Since its inception, the Company has devoted substantially all of its efforts to business planning, research and development, recruiting management and technical staff, and raising capital. The Company has primarily financed its operations through various equity and debt financings, including the initial public offering of its common stock (the “IPO”), its follow-on public offerings of its common stock in March 2017 and December 2017, its at-the-market offering of its common stock in January 2018, and private placements of preferred stock, payments received under a research collaboration with Juno Therapeutics, Inc., a Celgene company that is a wholly-owned subsidiary of Celgene Corporation (“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 and received aggregate net proceeds of approximately $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 and received net proceeds of approximately $96.7 million (the “March Offering”), after deducting underwriting discounts and commissions and other offering expenses payable by the Company. In December 2017, the Company completed another follow-on offering and received net proceeds of approximately $57.2 million, after deducting underwriting discounts and other offering expenses payable by the Company. During January 2018, the Company completed at-the-market offerings and received net proceeds of approximately $48.5 million (the “January Offering”). 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 March 31, 2018, anticipated interest income, and anticipated research support under the Company’s collaboration agreement with Juno Therapeutics will enable it to fund its operating expenses and capital expenditure requirements for at least the next 24 months following the date of this Quarterly Report on Form 10-Q. The Company had an accumulated deficit of $337.3 million at March 31, 2018, and will require substantial additional capital to fund its operations. The Company has never generated any product revenue. There can be no assurance that the Company will be able to obtain additional debt or equity financing or generate product revenue or revenues from collaborative partners, on terms acceptable to the Company, on a timely basis or at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations, and financial condition.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
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 (“GAAP”) have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 (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 March 31, 2018 and 2017 are referred to as the first quarter of 2018 and 2017, 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 consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, accrued expenses, stock-based compensation expense and deferred tax valuation allowances. The Company bases its estimates on historical experience and other market-specific or relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. 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. Revenue Recognition Effective January 1, 2018, the Company adopted the provisions of Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”), using the modified retrospective transition method. Under this method, the Company recorded the cumulative effect of initially applying the new standard to all contracts as of the date of adoption. The Company enters into collaboration agreements and certain other agreements that are within the scope of ASC 606, under which the Company licenses, may license or grants an option to license rights to certain of the Company’s product candidates and performs research and development services in connection with such arrangements. The terms of these arrangements typically include payment of one or more of the following: non-refundable, up-front fees; reimbursement of research and development costs; development, clinical, regulatory and commercial sales milestone payments, and royalties on net sales of licensed products. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer. The promised good or services in the Company’s arrangements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. The Company provides options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised good or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract. The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. The Company’s contracts often include development and regulatory milestone payments that are as assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical milestones and any related constraint, and if necessary, adjust its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration and other research and development revenues in the period of adjustment. For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of the Company’s collaboration or strategic alliance arrangements. The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation. The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. Recent Accounting Pronouncements –Adopted In October 2016, the FASB issued Accounting Standards Update (“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 was effective for fiscal years beginning after December 15, 2017, and interim periods within those years. The guidance is effective on a retrospective basis. The Company adopted this guidance as of October 1, 2017. The Company reclassified restricted cash in the statements of cash flows to be included in the cash and cash equivalents balance. The reclassification was not material to the periods presented. The following table presents cash, cash equivalents and restricted cash as reported on the condensed consolidated balance sheets that equal the total amounts on the condensed consolidated statements of cash flows (in thousands): Three Months Ended March 31, 2018 2017 Cash and cash equivalents $ 217,671 $ 351,552 Restricted cash included in "Restricted cash and other non-current assets" 1,619 1,619 Total $ 219,290 $ 353,171 In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), which supersedes the revenue recognition requirements in FASB ASC Topic 605, Revenue Recognition (“ASC 605”), 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. Thereafter a series of clarifying ASU’s, narrow scope improvements and practical expedients were issued. This collective guidance resulted in the new revenue standards under ASC 606 and numerous updates have been issued subsequent to the initial guidance that provide clarification on a number of specific issues and require additional disclosures. ASC 606 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. The Company adopted the new standard effective January 1, 2018 using the modified retrospective approach. As part of the adoption, the Company reviewed all contracts that were not yet completed as of the date of initial application in determining the cumulative-effect impact related to the adoption of Topic 606. The adoption of ASC 606 resulted in the changes to (i) the allocation of arrangement consideration; including the determination of estimated selling price and the allocation of variable consideration to specific performance obligations for the Company’s collaboration agreement with Juno Therapeutics and (ii) the application of proportional performance as a measure of progress on service related deliverables for the Company’s strategic alliance with Allergan. Effective January 1, 2018, the Company’s adoption of ASC 606 resulted in increases of $0.5 million in deferred revenue and accumulated deficit, which was primarily due to an adjustment for two milestone payments previously earned that will now be recognized over time, partially offset by acceleration of proportional performance revenue. For the three months ended March 31, 2018, revenue increased by $0.1 million and net loss decreased by $0.1 million, which did not have a material impact on the Company’s basic and diluted earnings per share. The following table presents changes in the Company’s deferred revenue balance as of January 1, 2018 resulting from adoption of ASC 606 (in thousands): Balance at December 31, 2017 Adjustments Balance at January 1, 2018 Contract liabilities: Deferred revenue $ (107,963) $ (474) $ (108,437) During the three months ended March 31, 2018, the Company recognized the following revenue as a result of changes in its deferred revenue balance in the respective periods (in thousands): Revenue recognized in the period from: Amounts included in deferred revenue at the beginning of the period $ 2,895 In connection with its adoption of ASC 606, the Company has included the following financial statement line items for comparability purposes for the years ended March 31, 2018 (in thousands): Three Months Ended March 31, 2018 As reported under Topic 606 Balances without adoption of ASC 606 Effect of Change Collaboration and other research and development revenues $ 3,927 $ 3,853 $ 74 Operating loss (31,559) (31,633) 74 Net loss attributable to common stockholders (30,939) (31,013) 74 Net loss per share attributable to common stockholders, basic and diluted $ (0.67) $ (0.67) $ - Three Months Ended March 31, 2018 As reported under Topic 606 Balances without adoption of ASC 606 Effect of Change Deferred revenue, current $ (13,323) $ (13,238) $ (85) Deferred revenue, net of current portion (91,972) (91,637) (335) Accumulated deficit $ (337,262) $ (337,336) $ 74 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 was effective for fiscal years beginning after December 15, 2017, and interim periods within those years. Early adoption was permitted. The Company adopted this new standard as of January 1, 2017, with prospective application to any business development transactions In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (“ASU 2017-09”), which provided guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The new guidance requires modification accounting if the vesting condition, fair value or award classification is not the same both before and after a change to the terms and conditions of the award. This new standard was effective for fiscal years beginning after December 15, 2017, and interim periods within those years. The Company adopted this new standard as of January 1, 2018 and it did not have a material impact to its condensed consolidated financial statements. Recent Accounting Pronouncements – Issued In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASU 2016-02”), which applies to all leases and will require lessees to record most leases on the balance sheet, but recognize expense in a manner similar to the current standard. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 and interim periods within those years. Entities are required to use a modified retrospective approach of adoption for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. Full retrospective application is prohibited. The Company is evaluating the potential impact that the adoption of ASU 2016-02 will have on the Company’s consolidated financial statements.

Cash Equivalents & Marketable S

Cash Equivalents & Marketable Securities	3 Months Ended
	Mar. 31, 2018
Cash Equivalents & Marketable Securities
Cash Equivalents & Marketable Securities	3. Cash Equivalents & Marketable Securities Cash equivalents and marketable securities consisted of the following at March 31, 2018 (in thousands): Gross Gross Amortized Unrealized Unrealized Fair March 31, 2018 Cost Gains Losses Value Cash equivalents and marketable securities: Money market funds $ 164,950 $ — $ — $ 164,950 U.S. Treasuries 163,711 1 (30) 163,682 Government agency securities 29,963 — (23) 29,940 Total cash equivalents and marketable securities $ 358,624 $ 1 $ (53) $ 358,572 Cash equivalents and marketable securities consisted of the following at December 31, 2017 (in thousands): Gross Gross Amortized Unrealized Unrealized Fair December 31, 2017 Cost Gains Losses Value Cash equivalents and marketable securities: Money market funds $ 134,635 $ — $ — $ 134,635 U.S. Treasuries 135,601 — (47) 135,554 Government agency securities 58,979 — (29) 58,950 Total cash equivalents and marketable securities $ 329,215 $ — $ (76) $ 329,139 At March 31, 2018, the Company held 23 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 March 31, 2018 was $147.7 million, and there were no securities held by the Company in an unrealized loss position for more than 12 months. As of March 31, 2018, 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 March 31, 2018. There were no realized gains or losses on available-for-sale securities during the three months ended March 31, 2018 or 2017.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Measurements
Fair Value Measurements	4. Fair Value Measurements Assets measured at fair value on a recurring basis as of March 31, 2018 were as follows (in thousands): Quoted Prices Significant in Active Other Significant Markets for Observable Unobservable March 31, Identical Assets Inputs Inputs Financial Assets 2018 (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 164,950 $ 164,950 $ — $ — U.S. Treasuries 52,472 52,472 — — Marketable securities: U.S. Treasuries 111,210 111,210 — — Government agency securities 29,940 29,940 — — Money market funds, included in restricted cash 1,619 1,619 — — Total financial assets $ 360,191 $ 360,191 $ — $ — Assets measured at fair value on a recurring basis as of December 31, 2017 were as follows (in thousands): Quoted Prices Significant in Active Other Significant Markets for Observable Unobservable December 31, Identical Assets Inputs Inputs Financial Assets 2017 (Level 1) (Level 2) (Level 3) Cash and cash equivalents Money market funds $ 134,635 $ 134,635 $ — $ — U.S. Treasuries 11,995 11,995 — — Marketable securities: U.S. Treasuries 123,559 123,559 — — Government agency securities 58,950 58,950 — — Money market funds, included in restricted cash 1,619 1,619 — — Total financial assets $ 330,758 $ 330,758 $ — $ — There were no transfers between fair value measurement levels during the three months ended March 31, 2018.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2018
Accrued Expenses
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): As of March 31, December 31, 2018 2017 Employee related expenses $ 2,799 $ 3,708 Process and platform development expenses 2,179 2,301 Intellectual property and patent related fees 2,007 2,370 Professional service expenses 618 487 Other expenses 164 183 Success payment expenses — 2,000 Total $ 7,767 $ 11,049

Property and Equipment, net

Property and Equipment, net	3 Months Ended
	Mar. 31, 2018
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 March 31, December 31, 2018 2017 Building $ 35,167 $ 35,167 Laboratory equipment 8,169 7,415 Computer equipment 480 550 Leasehold improvements 177 177 Software 113 96 Furniture and office equipment 95 95 Total property and equipment 44,201 43,500 Less: accumulated depreciation (4,650) (4,058) Property and equipment, net $ 39,551 $ 39,442

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies
Commitments and Contingencies	7. Commitments and Contingencies Hurley Street Lease In February 2016, the Company entered into a lease agreement for 59,783 square feet of office and laboratory space located on Hurley Street in Cambridge, Massachusetts. The term of the lease began on October 1, 2016. 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 and other non-current assets in the accompanying condensed consolidated financial statements as of March 31, 2018 and December 31, 2017. In connection with this lease, the landlord provided a tenant improvement allowance for costs associated with the design, engineering, and construction of tenant improvements for the leased facility. For accounting purposes, the Company was deemed the owner of the building during the construction period due to the fact that the Company was involved in the construction project, including having responsibilities for cost overruns for planned tenant improvements that did not qualify as “normal tenant improvements” under the lease accounting guidance. Throughout the construction period, the Company recorded the project construction costs incurred as an asset, along with a corresponding facility lease obligation, on its balance sheet for the total amount of the project costs incurred whether funded by the Company or the landlord. Construction was completed in October 2016, and the Company considered the requirements for sale-leaseback accounting treatment, which included an evaluation of whether all risks of ownership had transferred back to the landlord, as evidenced by a lack of continuing involvement in the leased property. The Company determined that the arrangement did not qualify for sale-leaseback accounting treatment, the building asset would remain on the Company’s balance sheet at its historical cost, and such asset would be depreciated over its estimated useful life of 30 years. The Company bifurcates its future lease payments pursuant to the Hurley Street lease into (i) a portion that is allocated to the building and (ii) a portion that is allocated to the land on which the building is located, which is recorded as rental expense. Although the Company did not begin making lease payments pursuant to the Hurley Street lease until November 2016, the portion of the lease obligation allocated to the land is treated for accounting purposes as an operating lease that commenced upon execution of the Hurley Street lease in February 2016. The lease will continue until October 2023. The Company has the option to extend the lease for an additional five year term at market-based rates. The Company began using this space as its headquarters in October 2016 and rental payments for this property began in November 2016. The base rent is subject to increases over the term of the lease. In February 2017, the Company subleased approximately 10,000 square feet of the Hurley Street premises pursuant to a sublease (the “Sublease”). 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. The total minimum rental revenue to be received in the future is $0.3 million as of March 31, 2018. Licensor Expense Reimbursement The Company is obligated to reimburse The Broad Institute, Inc. (“Broad”) and the President and Fellows of Harvard College (“Harvard”) for expenses incurred by each of them associated with the prosecution and maintenance of the patent rights that the Company licenses from them pursuant to the license agreement by and among the Company, Broad and Harvard, including the interference and opposition proceedings involving patents licensed to the Company under the license agreement, and other license agreements between the Company and Broad. As such, the Company anticipates that it has a substantial commitment in connection with these proceedings until such time as these proceedings have been resolved, but the amount of such commitment is not determinable. The Company incurred an aggregate of $4.6 million and $4.0 million in expense for reimbursement under such license agreements during the three months ended March 31, 2018 and 2017, 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 records this expense as a research and development expense in its statements of operations. 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 and the Company settled such notes in August 2017.The Company triggered the second Success Payment under one of the 2016 License Agreements during the fourth quarter of 2017 when the Company’s market capitalization reached $1.0 billion. On December 6, 2017, the Company issued promissory notes for an aggregate principal amount of $7.5 million to Broad and the Company settled such notes in January 2018. The Company triggered the first Success Payment under the MGH license agreement during the fourth quarter of 2017 when the Company’s market capitalization reached $1.0 billion (the “First MGH Success Payment”). The Company accrued $2.0 million relating to the First MGH Success Payment owed to MGH which is included in accrued expense on the condensed consolidated balance sheet for the year ended December 31, 2017. The Company settled this liability in shares of common stock in January 2018. The Success Payments issued to the Broad and Wageningen are 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”). Outstanding principal and accrued interest on the Initial Notes were due and payable on the earlier of December 2017 or a specified period of time following a Company sale or change of control event. The Initial Notes accrued interest at a rate of 4.8% per annum. The Company fully settled the outstanding principal and accrued interest on the Initial Notes by paying $0.2 million in cash to Wageningen in August 2017 and issuing 108,104 shares and 371,166 shares of common stock to Broad in August 2017 and September 2017, respectively. In 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 “March Success Payment Notes”). Outstanding principal and accrued interest on the March Success Payment Notes were due and payable in August 2017. The March Success Payment Notes were subject to the same interest and terms as the Initial Notes, other than the maturity date. The Company settled the outstanding principal and accrued interest on the March Success Payment Notes in August 2017 by paying $0.4 million in cash to Wageningen and issuing 271,347 shares of common stock to Broad in August 2017. In September 2017, Wageningen designated Broad as the recipient of any future promissory notes that are owed to Wageningen pursuant to the Cpf1 License Agreement. In December 2017, $7.5 million in Success Payments under the Cpf1 License Agreement and the Cas9-II license agreement with Broad (the “Cas9-II License Agreement”), one of the 2016 License Agreements, became due upon the Company’s market capitalization reaching $1.0 billion. The Company issued promissory notes to Broad in an aggregate original principal amount of $7.5 million (collectively, the “December Success Payment Notes”). Outstanding principal and accrued interest on the December Success Payment Notes were due and payable in May 2018. The December Success Payment Notes were subject to the same interest and terms as the Initial Notes, other than the maturity date. The Company fully settled the outstanding principal and accrued interest on the December Success Payment Notes by issuing 225,909 shares of common stock to Broad in January 2018. Litigation The Company is not a party to any litigation and did not have contingency reserves established for any litigation liabilities as of March 31, 2018 or December 31, 2017.

Significant Agreements

Significant Agreements	3 Months Ended
	Mar. 31, 2018
Significant Agreements.
Significant Agreements	8. Significant Agreements Juno Therapeutics Collaboration Agreement Summary of Agreement In May 2015, the Company entered into a collaboration and license agreement (the “Collaboration Agreement”) with Juno Therapeutics. The collaboration is focused on the research and development of engineered T cells with chimeric antigen receptors (“CARs”) and T cell receptors (“TCRs”) that have been genetically modified to recognize and kill other cells. The parties will pursue the research and development of CAR and TCR engineered T cell products utilizing the Company’s genome editing technologies with Juno Therapeutics’ CAR and TCR technologies across three research areas. The collaborative program of research to be undertaken by the parties pursuant to the Collaboration Agreement will be conducted in accordance with a mutually agreed upon research plan which outlines each party’s research and development responsibilities across the three research areas. The Company’s research and development responsibilities under the research plan are related to generating genome editing reagents that modify gene targets selected by Juno Therapeutics. Juno Therapeutics is responsible for evaluating and selecting for further research and development CAR and TCR engineered T cell products modified with the Company’s genome editing reagents. Except with respect to the Company’s obligations under the mutually agreed upon research plan, Juno Therapeutics has sole responsibility, at its own cost, for the worldwide research, development, manufacturing and commercialization of products within each of the three research areas for the diagnosis, treatment or prevention of any cancer in humans through the use of engineered T cells, excluding the diagnosis, treatment or prevention of medullary cystic kidney disease 1 (the “Exclusive Field”). The initial term of the research program commenced on May 26, 2015 and continues for five years ending on May 26, 2020 (the “Initial Research Program Term”). Juno Therapeutics may extend the Initial Research Program Term for up to two additional one year periods upon the payment of extension fees for each one year extension period, assuming the Company has agreed to the extension request(s) (together, the initial term and any extension period(s) are referred to as the “Research Program Term”). Under the terms of the Collaboration Agreement, the Company granted to Juno Therapeutics during the Research Program Term a nonexclusive, worldwide, royalty‑free, sublicensable (subject to certain conditions) license under certain of the intellectual property controlled by the Company solely for the purpose of conducting the following activities required under the specified research under the Collaboration Agreement: (i) conduct activities assigned to Juno Therapeutics under the research plan, (ii) conduct activities assigned to the Company under the research plan that the Company fails or refuses to conduct in a timely manner, (iii) use certain genome editing reagents generated under the research program to research, evaluate and conduct preclinical testing and development of certain engineered T cells and (iv) evaluate the data developed in the conduct of activities under the research plan (the “Research License”). Additionally, as it relates to two of the three research areas, the Company granted to Juno Therapeutics an exclusive, milestone and royalty‑bearing, sublicensable license under certain of the intellectual property controlled by the Company to research, develop, make and have made, use, offer for sale, sell, import and export selected CAR and TCR engineered T cell products in the Exclusive Field on a worldwide basis, specifically as it relates to certain targets selected by Juno Therapeutics pursuant to the research program. Furthermore, as it relates to the same two research areas, the Company granted to Juno Therapeutics a non‑exclusive, milestone and royalty‑bearing, sub licensable license under certain of the intellectual property controlled by the Company to use genome editing reagents generated under the research program that are used in the creation of certain CAR or TCR engineered T cell products on which Juno Therapeutics has filed an investigational new drug (“IND”) application in the Exclusive Field for the treatment or prevention of a cancer in humans to research, develop, make and have made, use, offer for sale, sell, import and export those CAR or TCR engineered T cell products in all fields outside of the Exclusive Field (the “Non‑Exclusive Field”) on a worldwide basis, specifically as it relates to certain targets selected by Juno Therapeutics pursuant to the research program (together, the license in the Exclusive Field and the license in the Non‑Exclusive Field are referred to as the “Development and Commercialization License” for each particular research area). Lastly, as it relates to the third research area, the Company granted to Juno Therapeutics a milestone and royalty‑bearing, sublicensable license under certain of the intellectual property controlled by the Company to use the genome editing reagents generated under the research program that are associated with certain CAR or TCR engineered T cell products to research, develop, make and have made, use, offer for sale, sell, import or export those CAR or TCR engineered T cell products in the Exclusive Field on a worldwide basis, specifically as it relates to certain products selected by Juno Therapeutics pursuant to the research program. The license associated with the third research area is exclusive as it relates to CAR or TCR engineered T cell products directed to certain targets as selected by Juno Therapeutics, but is otherwise non‑exclusive (referred to as the “Development and Commercialization License” for the third research area). The Collaboration Agreement will be managed on an overall basis by a project leader from each of the Company and Juno Therapeutics. The project leaders will serve as the contact point between the parties with respect to the research program and will be primarily responsible for facilitating the flow of information, interaction, and collaboration between the parties. In addition, the activities under the Collaboration Agreement during the Research Program Term will be governed by a joint research committee (“JRC”) formed by an equal number of representatives from the Company and Juno Therapeutics. The JRC will oversee, review and recommend direction of the research program. Among other responsibilities, the JRC will monitor and report research progress and ensure open and frequent exchange between the parties regarding research program activities. Under the terms of the Collaboration Agreement, the Company received a $25.0 million up‑front, non‑refundable, non‑creditable cash payment. In addition, Juno Therapeutics is obligated to pay to the Company an aggregate of up to $22.0 million in research and development funding over the Initial Research Program Term across the three research areas consisting primarily of funding for up to a specified maximum number of full time equivalents personnel each year over the Initial Research Program Term across three research areas. Under the terms of the Collaboration Agreement, there is no incremental compensation due to the Company with respect to the Development and Commercialization License granted to Juno Therapeutics associated with the first target or product, as applicable, designated by Juno Therapeutics within each of the three research areas. However, for two of the three research areas, Juno Therapeutics has the option to purchase up to three additional Development and Commercialization Licenses associated with other gene targets for an additional fee of approximately $2.5 million per target. In addition, Juno Therapeutics would be required to make certain milestone payments to the Company upon the achievement of specified development, regulatory and commercial events. More specifically, for the first product to achieve the associated event in each of the three research areas, the Company is eligible to receive up to a $77.5 million in development milestone payments and up to $80 million in regulatory milestone payments. In addition, the Company is eligible to receive additional development and regulatory milestone payments for subsequent products developed within each of the three research areas. Moreover, the Company is eligible for up to $75.0 million in commercial milestone payments associated with aggregate sales of all products within each of the three research areas. Development milestone payments are triggered upon the achievement of certain specified development criteria or upon initiation of a defined phase of clinical research for a product candidate. Regulatory milestone payments are triggered upon approval to market a product candidate by the United States Food and Drug Administration (“FDA”) or other global regulatory authorities. Commercial milestone payments are triggered when an approved pharmaceutical product reaches certain defined levels of net sales by the licensee. In addition, to the extent any of the product candidates covered by the licenses conveyed to Juno Therapeutics are commercialized, the Company would be entitled to receive tiered royalty payments of low double digits based on a percentage of net sales. Royalty payments are subject to certain reductions, including for any royalty payments required to be made by Juno Therapeutics related to a third‑party’s intellectual property rights, subject to an aggregate minimum floor. Royalties are due on a licensed product‑by‑licensed product and country‑by‑country basis from the date of the first commercial sale of each product in a country until the later of: (i) the tenth anniversary of the first commercial sale of such licensed product in such country and (ii) the expiration date in such country of the last to expire valid claim within the licensed intellectual property covering the manufacture, use or sale of such licensed product in such country. The Company achieved $2.5 million development milestones under the Collaboration Agreement resulting from technical progress in a research program in each of May 2016 (the “First Milestone”) and July 2017 (the “Second Milestone”). Due to the uncertainty of pharmaceutical development and the high historical failure rates generally associated with drug development, no additional milestone or royalty payments may ever be received from Juno Therapeutics. Unless earlier terminated, the Collaboration Agreement will continue in full force and effect, on a product‑by‑product and country‑by‑country basis until the date no further payments are due to the Company from Juno Therapeutics. Either party may terminate the Collaboration Agreement if the other party has materially breached or defaulted in the performance of any of its material obligations and such breach or default continues after the specified cure period. Either party may terminate the Collaboration Agreement in the event of the commencement of any proceeding in or for bankruptcy, insolvency, dissolution or winding up by or against the other party that is not dismissed or otherwise disposed of within a specified time period. Juno Therapeutics may terminate the Collaboration Agreement for convenience upon not less than six months prior written notice to the Company. The Company may terminate the Collaboration Agreement in the event that Juno Therapeutics brings, assumes, or participates in, or knowingly, willfully or recklessly assists in bringing a dispute or challenge against the Company related to its intellectual property. Termination of the Collaboration Agreement for any reason does not release either party from any liability which, at the time of such termination, has already accrued to the other party or which is attributable to a period prior to such termination nor preclude either party from pursuing any rights and remedies it may have under the agreement or at law or in equity with respect to any breach of the Collaboration Agreement. If Juno Therapeutics terminates the Collaboration Agreement as a result of the Company’s uncured material breach or default, then: (i) the licenses and rights conveyed to Juno Therapeutics will continue as set forth in the agreement, (ii) Juno Therapeutics’ obligations related to milestones and royalties will continue as set forth in the agreement and (iii) Juno Therapeutics’ rights to prosecute, maintain and enforce certain intellectual property rights will continue as set forth in the agreement. If Juno Therapeutics terminates the Collaboration Agreement for convenience or if the Company terminates the Collaboration Agreement as a result of Juno Therapeutics’ uncured material breach or default, then the licenses conveyed to Juno Therapeutics will terminate. Accounting Analysis The Company has identified the following performance obligations: (i) Research License and the related research and development services during the Initial Research Program Term (the “Research License and Related Services”), (ii) three material rights related to the first Development and Commercialization Licenses related to each of the three research areas (each, a “First Development and Commercialization License Material Right”), (iii) six material rights related to the option to purchase up to three additional Development and Commercialization Licenses for two of the research areas (each, an “Additional License Material Right”) and (iv) JRC services during the Initial Research Program Term (the “JRC Services”). The Company has concluded that the Research License is not distinct from the research and development services during the Initial Research Program Term as Juno Therapeutics cannot obtain the benefit of the Research License without the Company performing the research and development services. The services incorporate proprietary technology and unique skills and specialized expertise, particularly as it relates to genome editing technology that is not available in the marketplace. As a result, the Research License has been combined with the research and development services into a combined performance obligation. The Company has concluded that the First Development and Commercialization License Material Rights for each respective research area and the Additional License Material Right with the two research areas to which it relate are a separate performance obligation under ASC 606 as Juno Therapeutics is provided incremental licenses for additional consideration that represents a significant discount from amounts that would otherwise would be offered outside the context of the contract. These material rights, of which there are nine in total, are distinct from the other performance obligations in the arrangement as they are options in the contract that are not required for Juno Therapeutics to obtain the benefit of the other promised goods or services in the arrangement. Similarly, the Company has concluded the JRC Services performance obligation is distinct from the other obligations in the arrangement as the other performance obligations are not dependent upon the JRC Services. As of January 1, 2018, the date of the initial application of ASC 606 by the Company, the total transaction price was determined to be $52.0 million, consisting of the $25.0 million upfront non-refundable, non-creditable cash payment, $22.0 million of research and development funding and $5.0 million of milestone payments received by the Company. The research and development funding is being provided based on the costs that are incurred to conduct the research and development services. The Company utilizes the most likely amount method to determine the amount of research and development funding to be received. The Company also utilized the most likely amount method to estimate any development and regulatory milestone payments to be received. As of January 1, 2018, there were no milestones that had not been received included in the transaction price. The Company considered the stage of development and the risks associated with the remaining development required to achieve the milestone, as well as whether the achievement of the milestone is outside the control of the Company or Juno Therapeutics. The outstanding milestone payments were fully constrained, as a result of the uncertainty whether any of the milestones would be achieved. The Company has determined that any commercial milestones and sales-based royalties will be recognized when the related sales occur as they were determined to relate predominantly to the license granted and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. There were no changes to the transaction price during the three months ended March 31, 2018. The transaction price was allocated to the performance obligations based on the relative estimated standalone selling prices of each performance obligation or, in the case of certain variable consideration, to one or more performance obligations. The estimated standalone selling prices for the Research License and Related Services is primarily based on the nature of the services to be performed and estimates of the associated effort and costs of the services, adjusted for a reasonable profit margin that would be expected to be realized under similar contracts. The Company developed the estimated standalone selling price for the materials rights based on the difference between the value of license granted and any additional consideration to be received upon exercise of the underlying option, adjusted for the probability of exercise. The value of the license granted was determined 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 transaction price allocated to each performance obligation was as follows: (i) Research License and Related Services: $27.0 million, (ii) Development and Commercialization License Material Right related to the first research area: $7.7 million, (iii) Development and Commercialization License Material Right related to the second research area: $12.8 million, (iv) Development and Commercialization License Material Right related to the third research area: $0.1 million, (v) the first Additional License Material Right for the first research area: $0.6 million, (vi) the second Additional License Material Right for the first research area: $0.3 million, (vii) the third Additional License Material Right for the first research area: $0.1 million, (viii) the first Additional License Material Right for the second research area: $1.7 million, (ix) the second Additional License Material Right for the second research area: $1.1 million, and (x) the third Additional License Material Right for the second research area: $0.6 million. No amounts were allocated to the JRC Services because the associated estimated standalone selling price was determined to be de minimis. The Company will recognize revenue related to amounts allocated to the Research License and Related Services as the underlying services are performed using a proportional performance model. The Company measures proportional performance based on the costs incurred relative to the total estimated costs of the research. Revenue related to the material rights will be recognized when the options are exercised and the Company transfers control of the related exclusive license or when the options lapse. 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, control is deemed to be transferred upon the designation by Juno Therapeutics of the specific target or product, as applicable, whereupon the license becomes effective. During the three months ended March 31, 2018 and 2017, the Company recognized revenue under the Collaboration Agreement totaling approximately $1.0 million and $0.7 million, respectively. The revenue is classified as collaboration and other research and development revenue in the accompanying condensed consolidated statement of operations. As of March 31, 2018 and December 31, 2017, there was approximately $27.1 million and $26.4 million of deferred revenue related to the Collaboration Agreement, respectively, all of which is classified as long term in the accompanying condensed consolidated balance sheet. In addition, as of March 31, 2018 and December 31, 2017, the Company has recorded accounts receivable of $0.8 million and $0.5 million related to reimbursable research and development costs under the Collaboration Agreement for activities performed during the first quarter of 2018 and fourth quarter of 2017, respectively. 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 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 “Steering Committee”). 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 Steering Committee, Allergan will have the ability, for a defined period of time (“Initial Option Period”) to exercise an option (each, an “Option”) to obtain a w orld-wide right and license to the Company’s background intellectual property and the Company’s interest in the CDP intellectual property to develop, commercialize, make, have made, use, offer for sale, sell, and import any gene editing therapy product that results from such CDP during the term of the Allergan Agreement (a “Licensed Product”) in any category of human diseases and conditions other than the diagnosis, treatment or prevention of any cancer in humans through the use of engineered T-cells and subject to specified other limitations . Allergan has the option to extend the Initial Option Period and require the Company to perform additional research and development services, subject to the payment of additional consideration. After exercise of an Option with respect to a CDP, with the exception of any CDP’s where the Company has exercised its profit-sharing option, Allergan will be responsible for all development, manufacturing, and commercialization activities in connection with licensed products arising from such CDP, other than with respect to the LCA10 Program, if LCA10 is designated as a CDP, for which the Company has retained the right to develop that program through the acceptance for filing of the first IND with respect to the LCA10 Program. Upon achievement of IND approval for LCA10, unless the Company has exercised its profit sharing option on LCA10, Allergan will be responsible for all development, manufacturing, and commercialization activities. The initial term of the Allergan Agreement commenced on March 14, 2017 (the “Effective Date”) and continues for seven years ending on March 14, 2024 (the “Research Term”). If the Company has not delivered an Option Package, which includes the results and data from the CDP, for five CDPs that satisfy the Option Package Criteria, then the Research Term will automatically extend by one-year increments until such obligation is satisfied, up to a maximum of ten years from the Effective Date. The activities under the Allergan Agreement during the Research Term will be governed by the Steering Committee. The Steering Committee will review and monitor the direction of the development plan, evaluate and determine which targets are selected to become CDP, establish the Option Package Criteria for each CDP and evaluate the achievement of such criteria as well as oversee the development and commercialization activities after Allergan has licensed a CDP. Under the terms of the Allergan Agreement, the Company received a $90.0 million up‑front, non‑refundable, non‑creditable cash payment (the “Allergan Upfront”) related to the Company’s research and development costs for Option Packages for at least five CDPs and for reimbursement of the Company’s past out of pocket costs with respect to the prosecution and defense of patents that it owns and in-licenses. Allergan has the option to purchase at least five development and commercialization licenses associated CDP that have satisfied the Option Package Criteria. The option exercise fee during the Initial Option Period is $15.0 million per CDP. If Allergan elects to extend the Initial Option Period, Allergan is required to pay an additional fee of $5.0 million to extend the option, at which point the Company is required to perform additional research services. If Allergan elects to exercise its option to a development and commercialization license after extending the Initial Option Period, Allergan must pay the Company the option exercise fee of $22.5 million, plus specified costs incurred by the Company in connection with the additional development work. Following the exercise by Allergan of an Option with respect to a CDP, Allergan would be required to make certain milestone payments to the Company upon the achievement of specified development, product approval and launch and commercial events, on a CDP by CDP basis. On a CDP by CDP basis, for the first product in the first field to achieve the associated event, the Company is eligible to receive up to an aggregate of $42 million for In addition, within 45 days of the acceptance by the applicable regulatory authority of the Company’s submission of an IND application with respect to the LCA10 Program, Allergan is required to pay the Company a one-time payment of $25.0 million (the “LCA10 IND Payment”), whether or not Allergan exercises its option under the Allergan Agreement to acquire an exclusive license with respect to the LCA10 Program. As of March 31, 2018, 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 development 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 defaul

Stock-based Compensation

Stock-based Compensation	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 2017 Research and development $ 3,910 $ 3,614 General and administrative 2,618 2,190 Total stock-compensation expense $ 6,528 $ 5,804 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 liability. 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 December 31, 2017 and March 31, 2018 is as follows: Weighted Average Grant Date Fair Value Shares Per Share Unvested Restricted Common Stock as of December 31, 2017 513,225 $ 18.70 Issued — — Vested (104,025) $ 4.88 Forfeited — — Unvested Restricted Common Stock as of March 31, 2018 409,200 $ 22.22 For the three months ended March 31, 2018, the expense for restricted stock awards related to non‑employees was $0.7 million. For the three months ended March 31, 2018, there was no expense for restricted stock awards related to employees. As of March 31, 2018, the Company had no unrecognized stock‑based compensation expense related to its employee unvested restricted stock awards and $10.5 million in unrecognized stock-based compensation expense related to its non-employee unvested restricted stock awards. Stock Options Certain of the Company’s stock option agreements allow for the exercise of unvested awards. During 2014, options to purchase 75,304 shares of common stock for $0.03 per share were exercised prior to their vesting. The unvested shares are subject to repurchase by the Company if the employees cease to provide service to the Company, with or without cause. As such, the Company does not treat the exercise of unvested options as a substantive exercise. The Company has recorded the proceeds from the exercise of unvested stock options as a liability in the condensed consolidated balance sheets. The liability for unvested common stock subject to repurchase is reclassified into stockholders’ equity as the shares vest. The following is a summary of stock option activity for the three months ended March 31, 2018: Weighted Average Remaining Aggregate Intrinsic Shares Exercise Price Contractual Life (years) Value (in thousands) Outstanding at December 31, 2017 4,372,136 $ 17.28 8.5 $ 60,591 Granted 1,469,881 $ 36.48 — — Exercised (308,497) $ 14.17 — — Cancelled (229,945) $ 21.54 — — Outstanding at March 31, 2018 5,303,575 $ 22.61 8.7 $ 61,944 Vested and expected to vest at March 31, 2018 5,303,575 $ 22.61 8.7 $ 61,944 Exercisable at March 31, 2018 1,553,297 $ 15.83 7.5 $ 27,662 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 281 and 4,572 shares of unvested restricted common stock outstanding at March 31, 2018 and December 31, 2017, 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 three months ended March 31, 2018 and 2017 was $25.82 and $16.73, respectively. The expense related to options granted to employees and directors was $4.6 million and $3.1 million for the three months ended March 31, 2018 and 2017, 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 March 31, 2018 2017 Risk free interest rate 2.6 % 2.1 % Expected dividend yield — — Expected term (in years) 6.25 6.25 Expected volatility 80.0 % 78.0 % There were no options issued to persons other than employees and directors during the three months ended March 31, 2018. As of March 31, 2018, the Company had unrecognized stock‑based compensation expense related to its employee stock options of $63.5 million which the Company expects to recognize over the remaining weighted average vesting period of 2.86 years.

Net Loss per Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2018
Net Loss per Share
Net Loss per Share	10. Net Loss per Share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted average number of common shares and potentially dilutive securities outstanding for the period determined using the treasury stock and if converted methods. Contingently issuable shares are For purposes of the diluted net loss per share calculation, stock options are considered to be common stock equivalents, but they were excluded from the Company’s calculation of diluted net loss per share allocable to common stockholders because their inclusion would have been anti-dilutive. Therefore, basic and diluted net loss per share applicable to common stockholders was the same for all periods presented. Upon the closing of the January Offering, the Company sold 1,429,205 shares of common stock. The issuance of these shares resulted in a significant increase in the Company’s weighted-average shares outstanding for the three months ended March 31, 2018 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 March 31, 2018 2017 Unvested restricted common stock 409,200 614,345 Outstanding stock options 5,303,575 4,309,750 Estimated number of shares issuable for convertible notes (1) — 678,349 Total 5,712,775 5,602,444 1) Represents the number of shares that would have been issued if the Company had elected to pay the Initial Notes and March Success Payment Notes, as discussed more fully in Note 7, in shares of the Company’s common stock, based on the closing price of the common stock on March 31, 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 such closing price. The table above reflects restricted stock issued upon exercise of unvested stock options as exercised on the dates that the shares are no longer subject to repurchase.

Related-party Transactions

Related-party Transactions	3 Months Ended
	Mar. 31, 2018
Related-party Transactions
Related-party Transactions	11. Related‑Party Transactions The Company received $0.2 million in rent and facility-related fees from a related party in the three months ended March 31, 2018 in connection with the Sublease and no rent or facility-related payments were received from this related party during the three months ended March 31, 2017.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events
Subsequent Events	12. Subsequent Events In May 2018, the Company entered into an amended and restated collaboration agreement with Juno Therapeutics. Such amended and restated collaboration agreement is more fully described in “Other Information” in Part II, Item 5 of this Quarterly Report on Form 10-Q.

Summary of Significant Accoun19

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
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 (“GAAP”) have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 (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 March 31, 2018 and 2017 are referred to as the first quarter of 2018 and 2017, 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 consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, accrued expenses, stock-based compensation expense and deferred tax valuation allowances. The Company bases its estimates on historical experience and other market-specific or relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.
Revenue Recognition	Revenue Recognition Effective January 1, 2018, the Company adopted the provisions of Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”), using the modified retrospective transition method. Under this method, the Company recorded the cumulative effect of initially applying the new standard to all contracts as of the date of adoption. The Company enters into collaboration agreements and certain other agreements that are within the scope of ASC 606, under which the Company licenses, may license or grants an option to license rights to certain of the Company’s product candidates and performs research and development services in connection with such arrangements. The terms of these arrangements typically include payment of one or more of the following: non-refundable, up-front fees; reimbursement of research and development costs; development, clinical, regulatory and commercial sales milestone payments, and royalties on net sales of licensed products. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer. The promised good or services in the Company’s arrangements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. The Company provides options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised good or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract. The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. The Company’s contracts often include development and regulatory milestone payments that are as assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical milestones and any related constraint, and if necessary, adjust its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration and other research and development revenues in the period of adjustment. For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of the Company’s collaboration or strategic alliance arrangements. The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation. The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional.
Recent Accounting Pronouncements	Recent Accounting Pronouncements –Adopted In October 2016, the FASB issued Accounting Standards Update (“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 was effective for fiscal years beginning after December 15, 2017, and interim periods within those years. The guidance is effective on a retrospective basis. The Company adopted this guidance as of October 1, 2017. The Company reclassified restricted cash in the statements of cash flows to be included in the cash and cash equivalents balance. The reclassification was not material to the periods presented. The following table presents cash, cash equivalents and restricted cash as reported on the condensed consolidated balance sheets that equal the total amounts on the condensed consolidated statements of cash flows (in thousands): Three Months Ended March 31, 2018 2017 Cash and cash equivalents $ 217,671 $ 351,552 Restricted cash included in "Restricted cash and other non-current assets" 1,619 1,619 Total $ 219,290 $ 353,171 In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), which supersedes the revenue recognition requirements in FASB ASC Topic 605, Revenue Recognition (“ASC 605”), 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. Thereafter a series of clarifying ASU’s, narrow scope improvements and practical expedients were issued. This collective guidance resulted in the new revenue standards under ASC 606 and numerous updates have been issued subsequent to the initial guidance that provide clarification on a number of specific issues and require additional disclosures. ASC 606 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. The Company adopted the new standard effective January 1, 2018 using the modified retrospective approach. As part of the adoption, the Company reviewed all contracts that were not yet completed as of the date of initial application in determining the cumulative-effect impact related to the adoption of Topic 606. The adoption of ASC 606 resulted in the changes to (i) the allocation of arrangement consideration; including the determination of estimated selling price and the allocation of variable consideration to specific performance obligations for the Company’s collaboration agreement with Juno Therapeutics and (ii) the application of proportional performance as a measure of progress on service related deliverables for the Company’s strategic alliance with Allergan. Effective January 1, 2018, the Company’s adoption of ASC 606 resulted in increases of $0.5 million in deferred revenue and accumulated deficit, which was primarily due to an adjustment for two milestone payments previously earned that will now be recognized over time, partially offset by acceleration of proportional performance revenue. For the three months ended March 31, 2018, revenue increased by $0.1 million and net loss decreased by $0.1 million, which did not have a material impact on the Company’s basic and diluted earnings per share. The following table presents changes in the Company’s deferred revenue balance as of January 1, 2018 resulting from adoption of ASC 606 (in thousands): Balance at December 31, 2017 Adjustments Balance at January 1, 2018 Contract liabilities: Deferred revenue $ (107,963) $ (474) $ (108,437) During the three months ended March 31, 2018, the Company recognized the following revenue as a result of changes in its deferred revenue balance in the respective periods (in thousands): Revenue recognized in the period from: Amounts included in deferred revenue at the beginning of the period $ 2,895 In connection with its adoption of ASC 606, the Company has included the following financial statement line items for comparability purposes for the years ended March 31, 2018 (in thousands): Three Months Ended March 31, 2018 As reported under Topic 606 Balances without adoption of ASC 606 Effect of Change Collaboration and other research and development revenues $ 3,927 $ 3,853 $ 74 Operating loss (31,559) (31,633) 74 Net loss attributable to common stockholders (30,939) (31,013) 74 Net loss per share attributable to common stockholders, basic and diluted $ (0.67) $ (0.67) $ - Three Months Ended March 31, 2018 As reported under Topic 606 Balances without adoption of ASC 606 Effect of Change Deferred revenue, current $ (13,323) $ (13,238) $ (85) Deferred revenue, net of current portion (91,972) (91,637) (335) Accumulated deficit $ (337,262) $ (337,336) $ 74 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 was effective for fiscal years beginning after December 15, 2017, and interim periods within those years. Early adoption was permitted. The Company adopted this new standard as of January 1, 2017, with prospective application to any business development transactions In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (“ASU 2017-09”), which provided guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The new guidance requires modification accounting if the vesting condition, fair value or award classification is not the same both before and after a change to the terms and conditions of the award. This new standard was effective for fiscal years beginning after December 15, 2017, and interim periods within those years. The Company adopted this new standard as of January 1, 2018 and it did not have a material impact to its condensed consolidated financial statements. Recent Accounting Pronouncements – Issued In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASU 2016-02”), which applies to all leases and will require lessees to record most leases on the balance sheet, but recognize expense in a manner similar to the current standard. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 and interim periods within those years. Entities are required to use a modified retrospective approach of adoption for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. Full retrospective application is prohibited. The Company is evaluating the potential impact that the adoption of ASU 2016-02 will have on the Company’s consolidated financial statements.

Summary of significant accoun20

Summary of significant accounting policies (Tables)	3 Months Ended
	Mar. 31, 2018
Summary of Significant Accounting Policies
Schedule of cash, cash equivalents, and restricted cash	Three Months Ended March 31, 2018 2017 Cash and cash equivalents $ 217,671 $ 351,552 Restricted cash included in "Restricted cash and other non-current assets" 1,619 1,619 Total $ 219,290 $ 353,171
Schedule of contract assets and liabilities	Balance at December 31, 2017 Adjustments Balance at January 1, 2018 Contract liabilities: Deferred revenue $ (107,963) $ (474) $ (108,437)
Schedule of change in contract assets and contract liabilities	Revenue recognized in the period from: Amounts included in deferred revenue at the beginning of the period $ 2,895
Schedule of financial statement line items for comparability purposes	Three Months Ended March 31, 2018 As reported under Topic 606 Balances without adoption of ASC 606 Effect of Change Collaboration and other research and development revenues $ 3,927 $ 3,853 $ 74 Operating loss (31,559) (31,633) 74 Net loss attributable to common stockholders (30,939) (31,013) 74 Net loss per share attributable to common stockholders, basic and diluted $ (0.67) $ (0.67) $ - Three Months Ended March 31, 2018 As reported under Topic 606 Balances without adoption of ASC 606 Effect of Change Deferred revenue, current $ (13,323) $ (13,238) $ (85) Deferred revenue, net of current portion (91,972) (91,637) (335) Accumulated deficit $ (337,262) $ (337,336) $ 74

Cash Equivalents & Marketable21

Cash Equivalents & Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2018
Cash Equivalents & Marketable Securities
Schedule of cash equivalents and marketable securities	Cash equivalents and marketable securities consisted of the following at March 31, 2018 (in thousands): Gross Gross Amortized Unrealized Unrealized Fair March 31, 2018 Cost Gains Losses Value Cash equivalents and marketable securities: Money market funds $ 164,950 $ — $ — $ 164,950 U.S. Treasuries 163,711 1 (30) 163,682 Government agency securities 29,963 — (23) 29,940 Total cash equivalents and marketable securities $ 358,624 $ 1 $ (53) $ 358,572 Cash equivalents and marketable securities consisted of the following at December 31, 2017 (in thousands): Gross Gross Amortized Unrealized Unrealized Fair December 31, 2017 Cost Gains Losses Value Cash equivalents and marketable securities: Money market funds $ 134,635 $ — $ — $ 134,635 U.S. Treasuries 135,601 — (47) 135,554 Government agency securities 58,979 — (29) 58,950 Total cash equivalents and marketable securities $ 329,215 $ — $ (76) $ 329,139

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 were as follows (in thousands): Quoted Prices Significant in Active Other Significant Markets for Observable Unobservable March 31, Identical Assets Inputs Inputs Financial Assets 2018 (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 164,950 $ 164,950 $ — $ — U.S. Treasuries 52,472 52,472 — — Marketable securities: U.S. Treasuries 111,210 111,210 — — Government agency securities 29,940 29,940 — — Money market funds, included in restricted cash 1,619 1,619 — — Total financial assets $ 360,191 $ 360,191 $ — $ — Assets measured at fair value on a recurring basis as of December 31, 2017 were as follows (in thousands): Quoted Prices Significant in Active Other Significant Markets for Observable Unobservable December 31, Identical Assets Inputs Inputs Financial Assets 2017 (Level 1) (Level 2) (Level 3) Cash and cash equivalents Money market funds $ 134,635 $ 134,635 $ — $ — U.S. Treasuries 11,995 11,995 — — Marketable securities: U.S. Treasuries 123,559 123,559 — — Government agency securities 58,950 58,950 — — Money market funds, included in restricted cash 1,619 1,619 — — Total financial assets $ 330,758 $ 330,758 $ — $ —

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2018
Accrued Expenses
Schedule of accrued expenses	Accrued expenses consisted of the following (in thousands): As of March 31, December 31, 2018 2017 Employee related expenses $ 2,799 $ 3,708 Process and platform development expenses 2,179 2,301 Intellectual property and patent related fees 2,007 2,370 Professional service expenses 618 487 Other expenses 164 183 Success payment expenses — 2,000 Total $ 7,767 $ 11,049

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	3 Months Ended
	Mar. 31, 2018
Property and Equipment, net
Schedule of property and equipment, net	Property and equipment, net consisted of the following (in thousands): As of March 31, December 31, 2018 2017 Building $ 35,167 $ 35,167 Laboratory equipment 8,169 7,415 Computer equipment 480 550 Leasehold improvements 177 177 Software 113 96 Furniture and office equipment 95 95 Total property and equipment 44,201 43,500 Less: accumulated depreciation (4,650) (4,058) Property and equipment, net $ 39,551 $ 39,442

Stock-based Compensation (Table

Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 2017 Research and development $ 3,910 $ 3,614 General and administrative 2,618 2,190 Total stock-compensation expense $ 6,528 $ 5,804
Schedule of changes in unvested restricted stock	Weighted Average Grant Date Fair Value Shares Per Share Unvested Restricted Common Stock as of December 31, 2017 513,225 $ 18.70 Issued — — Vested (104,025) $ 4.88 Forfeited — — Unvested Restricted Common Stock as of March 31, 2018 409,200 $ 22.22
Schedule of stock option activity	Weighted Average Remaining Aggregate Intrinsic Shares Exercise Price Contractual Life (years) Value (in thousands) Outstanding at December 31, 2017 4,372,136 $ 17.28 8.5 $ 60,591 Granted 1,469,881 $ 36.48 — — Exercised (308,497) $ 14.17 — — Cancelled (229,945) $ 21.54 — — Outstanding at March 31, 2018 5,303,575 $ 22.61 8.7 $ 61,944 Vested and expected to vest at March 31, 2018 5,303,575 $ 22.61 8.7 $ 61,944 Exercisable at March 31, 2018 1,553,297 $ 15.83 7.5 $ 27,662
Schedule of assumptions used to value stock options	Three Months Ended March 31, 2018 2017 Risk free interest rate 2.6 % 2.1 % Expected dividend yield — — Expected term (in years) 6.25 6.25 Expected volatility 80.0 % 78.0 %

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Net Loss per Share
Schedule of anti-dilutive common stock equivalents	As of March 31, 2018 2017 Unvested restricted common stock 409,200 614,345 Outstanding stock options 5,303,575 4,309,750 Estimated number of shares issuable for convertible notes (1) — 678,349 Total 5,712,775 5,602,444 1) Represents the number of shares that would have been issued if the Company had elected to pay the Initial Notes and March Success Payment Notes, as discussed more fully in Note 7, in shares of the Company’s common stock, based on the closing price of the common stock on March 31, 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 such closing price.

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ in Thousands	1 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Feb. 29, 2016	Mar. 31, 2018
Liquidity
Accumulated deficit		$ (305,850)			$ (337,262)
Initial Public Offering
Liquidity
Number of common stock issued	1,429,205
Aggregate net proceeds				$ 97,500
Follow-on Offering
Liquidity
Aggregate net proceeds		$ 57,200	$ 96,700
Public Offering
Liquidity
Aggregate net proceeds	$ 48,500

Summary Of Significant Accoun28

Summary Of Significant Accounting Policies - Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash, Cash Equivalents, and Restricted Cash
Cash and cash equivalents	$ 217,671	$ 146,630	$ 351,552
Restricted cash included in "Restricted cash and other non-current assets"	1,619		1,619
Total	$ 219,290	$ 148,249	$ 353,171	$ 186,942

Summary Of Significant Accoun29

Summary Of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017
Contract liabilities, deferred revenue:
Deferred revenue, Balance at Beginning of Period	$ (107,963)	$ (107,963)
Deferred revenue, Adjustments	(474)
Deferred revenue, Balance at End of Period	(108,437)
Accumulated deficit:
Accumulated deficit, Balance at Beginning of Period	$ (305,850)	(305,850)
Accumulated deficit, Balance at End of Period		(337,262)
Total revenue		3,927
Net loss		(30,939)	$ (31,097)
Effect of Change | ASU 2014-09
Contract liabilities, deferred revenue:
Deferred revenue, Balance at End of Period		(500)
Accumulated deficit:
Accumulated deficit, Balance at End of Period		74
Total revenue		74
Net loss		$ 74

Summary Of Significant Accoun30

Summary Of Significant Accounting Policies - Contract asset and liability (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Change in contract asset and contract liability balances
Amounts included in the contract liability at the beginning of the period	$ 2,895

Summary Of Significant Accoun31

Summary Of Significant Accounting Policies - Financial statements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Collaboration and other research and development revenues	$ 3,927
Operating loss	(31,559)	$ (30,627)
Net loss attributable to common stockholders	$ (30,939)	$ (31,097)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.67)	$ (0.85)
Deferred revenue, current	$ 13,323		$ 13,238
Deferred revenue, net of current portion	91,972		94,725
Accumulated deficit	(337,262)		$ (305,850)
As originally reported under Topic 606 | ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Collaboration and other research and development revenues	3,853
Operating loss	(31,633)
Net loss attributable to common stockholders	$ (31,013)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.67)
Deferred revenue, current	$ 13,238
Deferred revenue, net of current portion	91,637
Accumulated deficit	(337,336)
Effect of Change | ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Collaboration and other research and development revenues	74
Operating loss	74
Net loss attributable to common stockholders	74
Deferred revenue, current	85
Deferred revenue, net of current portion	335
Accumulated deficit	$ 74

Cash Equivalents & Marketable32

Cash Equivalents & Marketable Securities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)item	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Cash equivalents and marketable securities
Amortized Cost	$ 358,624		$ 329,215
Gross Unrealized Gains	1
Gross Unrealized Losses	(53)		(76)
Fair Value	$ 358,572		329,139
Number of securities in an unrealized loss position | item	23
Securities held by the Company in an unrealized loss position for less than 12 months	$ 147,700
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
Government agency securities
Cash equivalents and marketable securities
Amortized Cost	29,963		58,979
Gross Unrealized Losses	(23)		(29)
Fair Value	29,940		58,950
Money market funds
Cash equivalents and marketable securities
Amortized Cost	164,950		134,635
Fair Value	164,950		134,635
U.S. Treasuries
Cash equivalents and marketable securities
Amortized Cost	163,711		135,601
Gross Unrealized Gains	1
Gross Unrealized Losses	(30)		(47)
Fair Value	$ 163,682		$ 135,554

Fair Value Measurements - Recur

Fair Value Measurements - Recurring Basis (Details) $ in Thousands, item in Millions	3 Months Ended
	Mar. 31, 2018USD ($)item	Dec. 31, 2017USD ($)
Financial Assets
Marketable securities	$ 358,572	$ 329,139
Transfers between levels | item	0
Government agency securities
Financial Assets
Marketable securities	$ 29,940	58,950
Money market funds
Financial Assets
Marketable securities	164,950	134,635
U.S. Treasuries
Financial Assets
Marketable securities	163,682	135,554
Recurring
Financial Assets
Total financial assets	360,191	330,758
Recurring | U.S. Treasuries
Financial Assets
Marketable securities	111,210	123,559
Recurring | Government agency securities
Financial Assets
Marketable securities	29,940	58,950
Recurring | Money market funds
Financial Assets
Cash and cash equivalents	164,950	134,635
Restricted cash	1,619	1,619
Recurring | U.S. Treasuries
Financial Assets
Cash and cash equivalents	52,472	11,995
Recurring | Level 1
Financial Assets
Total financial assets	360,191	330,758
Recurring | Level 1 | U.S. Treasuries
Financial Assets
Marketable securities	111,210	123,559
Recurring | Level 1 | Government agency securities
Financial Assets
Marketable securities	29,940	58,950
Recurring | Level 1 | Money market funds
Financial Assets
Cash and cash equivalents	164,950	134,635
Restricted cash	1,619	1,619
Recurring | Level 1 | U.S. Treasuries
Financial Assets
Cash and cash equivalents	$ 52,472	$ 11,995

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued Expenses
Employee related expenses	$ 2,799	$ 3,708
Process and platform development expenses	2,179	2,301
Intellectual property and patent related fees	2,007	2,370
Professional service expenses	618	487
Other expenses	164	183
Success payment expenses		2,000
Total	$ 7,767	$ 11,049

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property and equipment disclosures
Total property and equipment	$ 44,201	$ 43,500
Less: accumulated depreciation	(4,650)	(4,058)
Property and equipment, net	39,551	39,442
Building
Property and equipment disclosures
Total property and equipment	35,167	35,167
Laboratory equipment
Property and equipment disclosures
Total property and equipment	8,169	7,415
Computer equipment
Property and equipment disclosures
Total property and equipment	480	550
Leasehold improvements
Property and equipment disclosures
Total property and equipment	177	177
Software
Property and equipment disclosures
Total property and equipment	113	96
Furniture and office equipment
Property and equipment disclosures
Total property and equipment	$ 95	$ 95

Commitments and Contingencies -

Commitments and Contingencies - Operating Leases (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)	Feb. 28, 2017ft²	Feb. 29, 2016USD ($)ft²
Hurley Street Lease
Commitments and contingencies
Leased space ( in square feet) | ft²			59,783
Security deposit | $			$ 1.6
Estimated useful life	30 years
Extended lease option (in years)	5 years
Facility Sublease Arrangement
Commitments and contingencies
Leased space ( in square feet) | ft²		10,000
Future minimum rental revenue to be received | $	$ 0.3

Commitments and Contingencies37

Commitments and Contingencies - Licensor Expense Reimbursement (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Licensor Expense Reimbursement
Commitments and contingencies
Expense for prosecution and maintenance of patent rights	$ 4.6	$ 4

Commitments and Contingencies38

Commitments and Contingencies - Notes Payable (Details) - USD ($) $ in Thousands	Dec. 06, 2017	Mar. 28, 2017	Jan. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Aug. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Mar. 31, 2018
Commitments and contingencies
Accrued expenses				$ 11,049					$ 11,049	$ 7,767
2016 License Agreements
Commitments and contingencies
Market Capitalization				1,000,000			$ 750,000		1,000,000
Broad and Wageningen University | 2016 License Agreements
Notes Payable
Promissory notes issued		$ 5,000
Broad and Wageningen University | Cpf1 License Agreement
Notes Payable
Promissory notes issued								$ 10,000
Interest rate (as a percentage)								4.80%
Success Payments							5,000
Broad and Wageningen University | Cpf1 License Agreement | Success Payment Notes
Notes Payable
Promissory notes issued							$ 5,000
The Broad Institute Inc | 2016 License Agreements
Notes Payable
Promissory notes issued	$ 7,500
The Broad Institute Inc | Cpf1 License Agreement
Notes Payable
Common stock issued					371,166	108,104
The Broad Institute Inc | Cpf1 License Agreement | Success Payment Notes
Notes Payable
Promissory notes issued				7,500
Common stock issued			225,909			271,347
Success Payments				$ 7,500
Wageningen University | Cpf1 License Agreement
Notes Payable
Notes paid in cash						$ 200
Wageningen University | Cpf1 License Agreement | Success Payment Notes
Notes Payable
Notes paid in cash						$ 400
The General Hospital (MGH) | 2016 License Agreements
Notes Payable
Success Payments									$ 2,000

Significant Agreements - Juno T

Significant Agreements - Juno Therapeutics Collaboration Agreement (Details) $ in Thousands	1 Months Ended				3 Months Ended
	Jul. 31, 2017USD ($)	Mar. 31, 2017USD ($)item	May 31, 2016USD ($)	May 31, 2015USD ($)item	Mar. 31, 2018USD ($)item	Mar. 31, 2017USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
Collaboration and other research and development revenues					$ 3,927
Research and development					21,300	$ 19,021
Deferred revenue							$ 108,437	$ 107,963
Deferred revenue, long-term					91,972			94,725
Accounts receivable					931			679
Juno Therapeutics
Allocable arrangement consideration - R&D Services Unit of Accounting					27,000
Allocable arrangement consideration - Development and Commercialization License for the first research area					7,700
Allocable arrangement consideration - Development and Commercialization License for the second research area					12,800
Allocable arrangement consideration - Development and Commercialization License for the third research area					100
Allocable arrangement consideration - first Discount Deliverable for the first research area					600
Allocable arrangement consideration - second Discount Deliverable for the first research area					300
Allocable arrangement consideration - third Discount Deliverable for the first research area					100
Allocable arrangement consideration - first Discount Deliverable for the second research area					1,700
Allocable arrangement consideration - second Discount Deliverable for the second research area					1,100
Allocable arrangement consideration - third Discount Deliverable for the second research area					600
Allocable arrangement consideration -JRC Deliverable					$ 0
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 development milestone payments					$ 42,000
Potential regulatory and commercial milestone payments					75,000
Potential commercial milestone payments					90,000
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
Potential fee receivable for each gene target licensed				$ 2,500
Number of additional licenses | item				3
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		$ 2,500
Next possible milestone payment					2,500
Collaboration and other research and development revenues					1,000	700
Deferred revenue					27,100			26,400
Accounts receivable					800			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				15,000
Extension fee for Initial Option Period		5,000				5,000
Option exercise price for development and commercialization license		$ 22,500				$ 22,500
Collaboration and other research and development revenues					2,900
Research and development					2,300
Deferred revenue					77,800			90,000
Deferred revenue, long-term					$ 64,900			$ 77,900
Contract termination notice					90 days
Strategic Alliance | Allergan | Maximum
Extension period		10 years

Significant Agreements - Accoun

Significant Agreements - Accounting Analysis (Details) $ in Millions	Jan. 01, 2018USD ($)
Significant Agreements.
Total transaction price	$ 52
Transaction price non refundable research and development funding	25
Transaction price milestone payment received	22
Milestone payments received	$ 5

Significant Agreements - Other

Significant Agreements - Other Agreements (Details) $ in Thousands	1 Months Ended			3 Months Ended		12 Months Ended
	Aug. 31, 2016USD ($)item	Oct. 31, 2014USD ($)shares	Aug. 31, 2014USD ($)shares	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)
Notes payable							$ 7,500
Research and development				$ 21,300	$ 19,021
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
Market capitalization threshold	1,000,000
Market capitalization							1,000,000
The General Hospital (MGH) | Maximum | License Patent Rights
Potential liability for future clinical, regulatory and commercial milestone payments related to product approval	1,000		$ 3,700
Potential liability for future sales milestone payments			$ 1,800
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
Success Payments	$ 6,000
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
Research and development						$ 16,500
License Agreement Contract Termination Term				4 months
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
Market capitalization							$ 1,000,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Maximum | Cpf1 License Agreement
Royalties credit paid to third party (as a percent)				50.00%
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Maximum | Cpf1 Success Payments
Success Payments				$ 10,000,000
Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) | Maximum | Cpf1 Market Cap Success Payments
Success Payments				125,000
Market capitalization threshold				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
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) | Minimum | Cas9-II License Agreement
Market capitalization threshold				1,000,000
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
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
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
Potential liability for future clinical and regulatory milestone payments related to product approval						$ 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
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
Potential liability for future clinical and regulatory milestone payments related to product approval				$ 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

Stock-based Compensation - Expe

Stock-based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock-based compensation disclosures
Compensation expense	$ 6,528	$ 5,804
Research and development.
Stock-based compensation disclosures
Compensation expense	3,910	3,614
General and administrative
Stock-based compensation disclosures
Compensation expense	$ 2,618	$ 2,190

Stock-based Compensation - Rest

Stock-based Compensation - Restricted Stock and Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2014
Changes in unvested restricted stock
Unvested restricted common stock, beginning of period (in shares)	513,225
Vested (in shares)	(104,025)
Unvested restricted common stock, end of period(in shares)	409,200		513,225
Weighted Average Grant Date Fair Value
Balance, beginning of period	$ 18.70
Vested (in dollars per share)	4.88
Balance, ending of period	$ 22.22		$ 18.70
Changes in unvested stock options
Compensation expense	$ 6,528	$ 5,804
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)	4,372,136
Granted (in shares)	1,469,881
Exercised (in shares)	(308,497)
Cancelled (in shares)	(229,945)
Outstanding, end of period (in shares)	5,303,575		4,372,136
Vested and expected to vest (in shares)	5,303,575
Exercisable (in shares)	1,553,297
Outstanding, beginning of period (in dollars per share)	$ 17.28
Granted (in dollars per share)	36.48
Exercised (in dollars per share)	14.17
Cancelled (in dollars per share)	21.54
Outstanding, end of period (in dollars per share)	22.61		$ 17.28
Vested and expected to vest outstanding, weighted average exercise price (in dollars per share)	22.61
Exercisable (in dollar per share)	$ 15.83
Remaining contractual life	8 years 8 months 12 days		8 years 6 months
Vested and expected to vest, remaining contractual life	8 years 8 months 12 days
Exercisable, remaining contractual life	7 years 6 months
Aggregate intrinsic value	$ 61,944		$ 60,591
Vesting and expected to vest, aggregate intrinsic value	61,944
Exercisable, aggregated intrinsic value	$ 27,662
Unvested stock options (in shares)	281		4,572
Employees and directors
Changes in unvested stock options
Compensation expense	$ 4,600	$ 3,100
Weighted average fair value of options granted (per share)	$ 25.82	$ 16.73
Employees
Changes in unvested stock options
Unrecognized stock-based compensation expense	$ 63,500
Restricted Stock | Employees
Changes in unvested stock options
Compensation expense	0
Unrecognized stock-based compensation expense	0
Restricted Stock | Non-employees
Changes in unvested stock options
Compensation expense	700
Unrecognized stock-based compensation expense	$ 10,500

Stock-based Compensation - Assu

Stock-based Compensation - Assumptions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Employees and directors
Assumptions
Risk free interest rate	2.60%	2.10%
Expected term (in years)	6 years 3 months	6 years 3 months
Expected volatility	80.00%	78.00%
Employees
Assumptions
Unrecognized stock-based compensation expense	$ 63.5
Period for recognition	2 years 10 months 10 days

Net Loss per Share (Details)

Net Loss per Share (Details) - shares	1 Months Ended	3 Months Ended
	Jan. 31, 2018	Mar. 31, 2018	Mar. 31, 2017
Potentially dilutive securities
Anti-dilutive common stock equivalent shares		5,712,775	5,602,444
Restricted Stock
Potentially dilutive securities
Anti-dilutive common stock equivalent shares		409,200	614,345
Outstanding stock options
Potentially dilutive securities
Anti-dilutive common stock equivalent shares		5,303,575	4,309,750
Convertible notes
Potentially dilutive securities
Anti-dilutive common stock equivalent shares			678,349
Initial Public Offering
Potentially dilutive securities
Number of common stock issued	1,429,205

Related-party Transactions (Det

Related-party Transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Rent and facility related fees
Related Party Transaction [Line Items]
Fees received from related party	$ 0.2	$ 0