CRISPR Therapeutics (CRSP) 10-K 10 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Mar. 01, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Trading Symbol	CRSP
Entity Registrant Name	CRISPR THERAPEUTICS AG
Entity Central Index Key	1,674,416
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		39,810,051
Entity Public Float		$ 605.6

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash	$ 315,520	$ 155,961
Accounts receivable, including related party amounts of $752 and $0 as of December 31, 2016 and 2015, respectively	3,157	339
Prepaid expenses and other current assets	1,511	540
Total current assets	320,188	156,840
Property and equipment, net	21,027	1,328
Intangible assets, net	399	454
Restricted cash	3,150	700
Other non-current assets	198	101
Total assets	344,962	159,423
Current liabilities:
Accounts payable	4,569	1,584
Accrued expenses, including related party amounts of $537 and $1,055 as of December 31, 2016 and 2015, respectively	16,320	8,430
Accrued tax liabilities	23	81
Deferred rent	1,027
Other current liabilities	59	60
Total current liabilities	21,998	10,155
Convertible loan, including accrued interest of $0 and $97 as of December 31, 2016 and 2015, respectively		38,336
Deferred revenue, including related party amounts of $527 and $0 as of December 31, 2016 and 2015, respectively	77,646	75,090
Deferred rent non-current	12,283	164
Other non-current liabilities	189	281
Total liabilities	112,116	124,026
Commitments and contingencies (Note 8)
Shareholders’ equity (deficit):
Common shares, CHF 0.03 par value, 40,253,674, and 5,528,079 shares authorized at December 31, 2016 and 2015, respectively, 40,164,307 and 5,528,079 shares issued at December 31, 2016 and 2015, respectively, 39,719,434, and 5,528,079 shares outstanding at December 31, 2016 and 2015, respectively, 15,325,607 and 2,444,364 shares in conditional capital at December 31, 2016 and 2015, respectively	1,216	181
Treasury shares, at cost, 444,873 shares and no shares at December 31, 2016 and 2015, respectively	0	0
Additional paid-in capital	288,739	4,636
Accumulated deficit	(57,083)	(33,906)
Accumulated other comprehensive loss	(26)	(8)
Total CRISPR Therapeutics AG shareholders’ equity (deficit)	232,846	(29,097)
Noncontrolling interest		(27)
Total shareholders’ equity (deficit)	232,846	(29,124)
Total liabilities, redeemable convertible preferred shares and shareholders’ equity (deficit)	$ 344,962	159,423
Series A-1 Redeemable Convertible Preferred Shares [Member]
Redeemable convertible preferred shares:
Redeemable convertible preferred shares		1,169
Series A-2 Redeemable Convertible Preferred Shares [Member]
Redeemable convertible preferred shares:
Redeemable convertible preferred shares		10,394
Series A-3 Redeemable Convertible Preferred Shares [Member]
Redeemable convertible preferred shares:
Redeemable convertible preferred shares		22,518
Series B Redeemable Convertible Preferred Shares [Member]
Redeemable convertible preferred shares:
Redeemable convertible preferred shares		$ 30,440

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) SFr in Thousands, $ in Thousands	Dec. 31, 2016USD ($)shares	Dec. 31, 2016CHF (SFr)SFr / sharesshares	Dec. 31, 2015USD ($)shares	Dec. 31, 2015CHF (SFr)SFr / sharesshares	Apr. 30, 2015shares	Dec. 31, 2014shares	Apr. 30, 2014SFr / sharesshares	Apr. 30, 2014$ / sharesshares	Dec. 31, 2013shares	Oct. 31, 2013SFr / sharesshares	Oct. 31, 2013$ / sharesshares
Accounts receivable, related party amount, current | $	$ 752		$ 0
Accrued expenses related party amount, current | $	537		1,055
Convertible loan, accrued interest | $	0		97
Deferred revenue related party amount | $	$ 527		$ 0
Redeemable convertible preferred stock, shares issued			18,837,024	18,837,024
Redeemable convertible preferred stock, shares outstanding			18,837,024	18,837,024
Common stock, par value | SFr / shares		SFr 0.03		SFr 0.03
Common stock, shares authorized	40,253,674	40,253,674	5,528,079	5,528,079
Common stock, shares issued	40,164,307	40,164,307	5,528,079	5,528,079
Common stock, shares outstanding	39,719,434	39,719,434	5,528,079	5,528,079
Common stock, conditional capital	15,325,607	15,325,607	2,444,364	2,444,364
Treasury stock, shares	444,873	444,873	0	0
Series A-1 Redeemable Convertible Preferred Shares [Member]
Redeemable convertible preferred stock, par value | (per share)		SFr 0.03		SFr 0.03						SFr 1.14	$ 1.28
Redeemable convertible preferred stock, shares authorized	0	0	440,001	440,001
Redeemable convertible preferred stock, shares issued	0	0	440,001	440,001						440,001	440,001
Redeemable convertible preferred stock, shares outstanding	0	0	440,001	440,001		440,001			440,001
Redeemable convertible preferred stock, aggregate liquidation preference | SFr		SFr 0		SFr 502
Common stock, shares issued										335,000	335,000
Series A-2 Redeemable Convertible Preferred Shares [Member]
Redeemable convertible preferred stock, par value | (per share)		SFr 0.03		SFr 0.03			SFr 3.05	$ 3.47
Redeemable convertible preferred stock, shares authorized	0	0	3,120,001	3,120,001
Redeemable convertible preferred stock, shares issued	0	0	3,120,001	3,120,001			3,120,001	3,120,001
Redeemable convertible preferred stock, shares outstanding	0	0	3,120,001	3,120,001		3,120,001
Redeemable convertible preferred stock, aggregate liquidation preference | SFr		SFr 0		SFr 9,512
Series A-3 Redeemable Convertible Preferred Shares [Member]
Redeemable convertible preferred stock, par value | SFr / shares		SFr 0.03		SFr 0.03
Redeemable convertible preferred stock, shares authorized	0	0	10,758,006	10,758,006
Redeemable convertible preferred stock, shares issued	0	0	10,758,006	10,758,006	10,758,006
Redeemable convertible preferred stock, shares outstanding	0	0	10,758,006	10,758,006
Redeemable convertible preferred stock, aggregate liquidation preference | $	$ 0		$ 22,850
Series B Redeemable Convertible Preferred Shares [Member]
Redeemable convertible preferred stock, par value | SFr / shares		SFr 0.03		SFr 0.03
Redeemable convertible preferred stock, shares authorized	0	0	4,519,016	4,519,016
Redeemable convertible preferred stock, shares issued	0	0	4,519,016	4,519,016
Redeemable convertible preferred stock, shares outstanding	0	0	4,519,016	4,519,016
Redeemable convertible preferred stock, aggregate liquidation preference | SFr		SFr 0		SFr 28,000

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Collaboration revenue	[1]	$ 5,164	$ 247
Operating expenses:
Research and development	[2]	42,238	12,573	$ 1,513
General and administrative		31,056	13,403	5,114
Total operating expenses		73,294	25,976	6,627
Loss from operations		(68,130)	(25,729)	(6,627)
Other income (expense):
Interest expense		(8,050)	(108)
Loss from equity method investment		(36,532)
Gain on extinguishment of convertible loan		11,482
Other income (expense), net		78,512	16	(236)
Total other income (expense), net		45,412	(92)	(236)
Net loss before (provision for) benefit from income taxes		(22,718)	(25,821)	(6,863)
(Provision for) benefit from income taxes		(484)	(7)	63
Net loss		(23,202)	(25,828)	(6,800)
Foreign currency translation adjustment		(18)	(6)	(2)
Comprehensive loss		(23,220)	(25,834)	(6,802)
Reconciliation of net loss to net loss attributable to common shareholders:
Net loss		(23,202)	(25,828)	(6,800)
Loss attributable to noncontrolling interest		25	325	536
Loss on extinguishment of redeemable convertible preferred shares				(745)
Net loss attributable to common shareholders		$ (23,177)	$ (25,503)	$ (7,009)
Net loss per share attributable to common shareholders—basic and diluted		$ (1.89)	$ (5.06)	$ 1.97
Weighted-average common shares outstanding used in net loss per share attributable to common shareholders—basic and diluted		12,257,483	5,037,404	3,559,985
[1]	Including the following amounts of revenue from a related party, see Note 16:
[2]	Including the following amounts of research and development from a related party, see Note 16:

Consolidated Statements of Ope5

Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue from related party	$ 1,190
Research and development from related party	$ 1,755	$ 1,055

Consolidated Statements of Rede

Consolidated Statements of Redeemable Convertible Preferred Shares and Shareholder's (Deficit) Equity - USD ($) $ in Thousands	Total	TRACR Hematology Limited [Member]	Series A-1 Redeemable Convertible Preferred Shares [Member]	Series A-2 Redeemable Convertible Preferred Shares [Member]	Series A-3 Redeemable Convertible Preferred Shares [Member]	Series B Redeemable Convertible Preferred Shares [Member]	Common Shares [Member]	Common Shares [Member]TRACR Hematology Limited [Member]	Treasury Shares [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]TRACR Hematology Limited [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total CRISPR Therapeutics AG Shareholders' (Deficit) Equity [Member]	Total CRISPR Therapeutics AG Shareholders' (Deficit) Equity [Member]TRACR Hematology Limited [Member]	Noncontrolling Interest [Member]	Noncontrolling Interest [Member]TRACR Hematology Limited [Member]
Beginning balance at Dec. 31, 2013			$ 424
Beginning balance (in shares) at Dec. 31, 2013			440,001
Beginning balance at Dec. 31, 2013	$ (581)						$ 98			$ 1,460		$ (2,139)		$ (581)
Beginning balance (in shares) at Dec. 31, 2013							3,559,985
Receipt of common shares subscription receivable	22						$ 22							22
Issuance of preferred shares net of issuance cost and subscription receivable				$ 5,101
Issuance of preferred shares net of issuance cost and subscription receivable (in shares)				3,120,001
Loss on extinguishment of preferred shares	(745)									(745)				(745)
Loss on extinguishment of preferred shares			$ 745
Equity-based compensation expense	695									453				453		$ 242
Other comprehensive income (loss)	(2)												$ (2)	(2)
Noncontrolling interest upon consolidation		$ 437															$ 437
Net loss	(6,800)											(6,264)		(6,264)		(536)
Ending balance at Dec. 31, 2014			$ 1,169	$ 5,101
Ending balance (in shares) at Dec. 31, 2014			440,001	3,120,001
Ending balance at Dec. 31, 2014	(6,974)						$ 120			1,168		(8,403)	(2)	(7,117)		143
Ending balance (in shares) at Dec. 31, 2014							3,559,985
Receipt of preferred shares subscription receivable				$ 5,293
Issuance of preferred shares net of issuance cost and subscription receivable					$ 22,518
Issuance of preferred shares net of issuance cost and subscription receivable (in shares)					10,758,006
Adjustment to noncontrolling interest upon share exchange transaction								$ 61			$ 1				$ 62		(62)
Adjustment to noncontrolling interest upon share exchange transaction (in shares)								1,968,094
Issuance of shares, net of issuance cost						$ 30,440
Issuance of shares, net of issuance cost (in shares)						4,519,016
Equity-based compensation expense	3,684									3,467				3,467		217
Other comprehensive income (loss)	(6)												(6)	(6)
Net loss	$ (25,828)											(25,503)		(25,503)		(325)
Ending balance at Dec. 31, 2015			$ 1,169	$ 10,394	$ 22,518	$ 30,440
Ending balance (in shares) at Dec. 31, 2015	18,837,024		440,001	3,120,001	10,758,006	4,519,016
Ending balance at Dec. 31, 2015	$ (29,124)						$ 181			4,636		(33,906)	(8)	(29,097)		(27)
Ending balance (in shares) at Dec. 31, 2015							5,528,079
Conversion of Convertible Loans						$ 61,929
Conversion of Convertible Loans (in shares)						5,464,608
Conversion of redeemable convertible preferred shares into common share, value	185,565		$ (1,169)	$ (10,394)	$ (45,368)	$ (128,634)	$ 823			184,742				185,565
Conversion of redeemable convertible preferred shares into common share (in shares)			(440,001)	(3,120,001)	(10,758,006)	(12,817,876)	27,135,884
Receipt of preferred shares net of issuance cost and subscription receivable					$ 22,850
Issuance of preferred shares net of issuance cost and subscription receivable						$ 36,265
Issuance of preferred shares net of issuance cost and subscription receivable (in shares)						2,834,252
Adjustment to noncontrolling interest upon share exchange transaction								$ 10			$ (62)				$ (52)		$ 52
Adjustment to noncontrolling interest upon share exchange transaction (in shares)								328,017
Issuance of shares, net of issuance cost	88,664						$ 213			88,451				88,664
Issuance of shares, net of issuance cost (in shares)							7,100,000
Repurchase of treasury shares, value							$ (13)			13
Repurchase of treasury shares (in shares)							(444,873)		444,873
Vesting of restricted shares, value	83						$ 2			81				83
Vesting of restricted shares (in shares)							53,427
Exercised of vested options, value	35						$ 1			34				35
Exercised of vested options(in shares)							18,900
Equity-based compensation expense	10,844									10,844				10,844
Other comprehensive income (loss)	(18)												(18)	(18)
Net loss	(23,202)											(23,177)		(23,177)		$ (25)
Ending balance (in shares) at Dec. 31, 2016			0	0	0	0
Ending balance at Dec. 31, 2016	$ 232,846						$ 1,216			$ 288,427		$ (56,771)	$ (26)	$ 232,846
Ending balance (in shares) at Dec. 31, 2016							39,719,434		444,873

Consolidated Statements of Red7

Consolidated Statements of Redeemable Convertible Preferred Shares and Shareholder's (Deficit) Equity (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common stock, issuance cost	$ 8,300
Series A-2 Redeemable Convertible Preferred Shares [Member]
Preferred shares, issuance cost			$ 36
Preferred shares, subscription receivable			$ 5,293
Series A-3 Redeemable Convertible Preferred Shares [Member]
Preferred shares, issuance cost		$ 332
Preferred shares, subscription receivable		22,850
Series B Redeemable Convertible Preferred Shares [Member]
Preferred shares, issuance cost	$ 1,800	$ 38

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Thousands, SFr in Millions	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Operating activities
Net loss	$ (23,202)	$ (25,828)	$ (6,800)
Reconciliation of net loss to net cash used in operating activities:
Depreciation and amortization expense	925	127	38
Equity-based compensation expense	10,844	3,684	695
Non-cash interest expense	8,050	97
Unrealized foreign currency remeasurement loss	2	(20)	(260)
Gain on extinguishment of convertible loan	(11,482)
Other income - formation of joint venture	(78,608)
Loss from equity method investment	36,380
Changes in:
Restricted cash	(2,450)	(650)	(16)
Accounts receivable	(2,818)	(339)
Prepaid expenses and other assets	(1,071)	(620)	(12)
Accounts payable and accrued expenses	3,860	7,708	1,583
Deferred revenue	1,917	75,090
Deferred rent	2,360	165
Other liabilities, net	(17)	14	(21)
Net cash (used in) provided by operating activities	(55,310)	59,428	(4,793)
Investing activities
Purchase of property and equipment	(3,016)	(1,154)
Proceeds from contribution of intellectual property to equity method investee	35,000
Cash investment in equity method investee	(100)
Net cash provided by (used in) investing activities	31,884	(1,154)
Financing activities
Proceeds from issuance of common shares in IPO, net of issuance costs	54,061
Proceeds from issuance of common shares in private placement	35,000
Proceeds from issuance of common shares			22
Proceeds from exercise of options	34
Proceeds from issuance of restricted shares		243
Issuance costs for preferred share financings	(1,810)	(370)	(36)
Proceeds from issuance of convertible loans	35,010	38,239
Net cash provided by financing activities	183,220	96,733	5,123
Effect of exchange rate changes on cash	(235)	9	254
Increase in cash	159,559	155,016	584
Cash, beginning of period	155,961	945	361
Cash, end of period	315,520	155,961	945
Supplemental disclosure of non-cash investing and financing activities
Property and equipment purchases in accounts payable and accrued expenses	7,014	246
Property and equipment related to lease incentives	10,785
Loss on extinguishment of redeemable convertible preferred shares			(745)
Conversion of preferred shares to common shares upon IPO	185,565
Conversion of Vertex and Bayer convertible loans and accrued interest	61,929
Issuance costs for public offering in accounts payable and accrued expenses	397
Contribution of intellectual property to Casebia	36,380
TRACR Hematology Limited [Member]
Supplemental disclosure of non-cash investing and financing activities
Noncontrolling interest upon consolidation of TRACR			547
Series A-2 Redeemable Convertible Preferred Shares [Member]
Financing activities
Proceeds from issuance of preferred shares		5,293	5,137
Series A-3 Redeemable Convertible Preferred Shares [Member]
Financing activities
Proceeds from issuance of preferred shares	22,850	22,850
Series B Redeemable Convertible Preferred Shares [Member]
Financing activities
Proceeds from issuance of preferred shares	$ 38,075	$ 30,478
Series A-1 Redeemable Convertible Preferred Shares [Member]
Supplemental disclosure of non-cash investing and financing activities
Loss on extinguishment of redeemable convertible preferred shares			$ 745

Organization and Operations

Organization and Operations	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Operations	1. Organization and Operations Nature of business CRISPR Therapeutics AG (“CRISPR” or the “Company”) was formed on October 28, 2013 in Basel, Switzerland. The Company was established to translate CRISPR/Cas9, a genome editing technology, into transformative gene-based medicines for the treatment of serious human diseases. The foundational intellectual property underlying the Company’s operations was licensed to the Company and its subsidiaries in April 2014. The Company devotes substantially all of its efforts to product research and development activities, initial market development and raising capital. The Company’s principal offices and operations are in Cambridge, Massachusetts. On January 23, 2014, the founders of the Company formed TRACR Hematology Limited (“TRACR”) in the United Kingdom, to further the development of the CRISPR/Cas9 technology into medicines for the treatment of blood-borne illnesses. As the Company was funding and managing TRACR’s operations in 2014, it has been consolidated by the Company from the date that the Company established a variable interest in TRACR in April 2014. In March 2015, the Company acquired 82.1% of the outstanding equity of TRACR in a share exchange transaction. Concurrent with its initial public offering (“IPO”) in October 2016, the Company acquired the outstanding non-controlling interest in TRACR as such, as of December 31, 2016 TRACR is a wholly-owned subsidiary of the Company. 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. The Company had an accumulated deficit of $57.1 million as of December 31, 2016 and has financed its operations to date from proceeds obtained from its initial public offering a series of preferred shares and convertible loan issuances and upfront fees received under its collaboration and joint venture arrangements. The Company will require substantial additional capital to fund its research and development and ongoing operating expenses. Liquidity In October 2016, the Company completed the IPO of its common shares (“Common Shares”), in which the Company sold 4,429,311 Common Shares, inclusive of 429,311 Common Shares sold by the Company pursuant to the partial exercise of an overallotment option granted to the underwriters in connection with the offering, at a price of $14.00 per share. The shares began trading on the NASDAQ Global Market on October 19, 2016. The aggregate net proceeds received by the Company from the offering were $53.7 million (see Note 2) after deducting underwriting discounts and commissions and other offering expenses payable by the Company. Concurrent with the IPO, the Company issued and sold 2,500,000 Common Shares to Bayer Global Investments B.V. (“Bayer BV”), in a private placement, at the IPO price of $14.00 per share, for aggregate net proceeds of $35.0 million. Common Shares totaling 170,689 of the overallotment option granted by the underwriters in connection with the initial public offering were reacquired by the Company and are reflected as treasury shares on the consolidated balance sheet as of December 31, 2016.

Summary of Significant Accounti

Summary of Significant Accounting Policies and Basis of Presentation	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies and Basis of Presentation	2. Summary of Significant Accounting Policies and basis of presentation Basis of Presentation and Use of Estimates The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”), and include the accounts of (i) the Company, (ii) its wholly-owned subsidiaries, CRISPR Ltd., CRISPR Inc., and TRACR, as of December 31, 2016. All intercompany accounts and transactions have been eliminated. Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) of the Financial Accounting Standards Board (“FASB”). Investments in partnerships where the Company has significant influence because it has a voting interest of 20% to 50%, are accounted for under the equity method. Results of associated companies are presented on a one-line basis. The Company accounts for its 50% investment share of Casebia Therapeutics LLP (“Casebia”) under the equity method of accounting. See Note 9 for further details. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, equity-based compensation expense, revenue recognition, equity method investments, and reported amounts of expenses during the reported period. Significant estimates in these consolidated financial statements have been made in connection with the calculation of revenues, research and development expenses, valuation of equity method of investment, equity-based compensation expense, fair value of Common Shares, fair value of intangible assets, and the provision for or benefit from income taxes. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. The Company utilizes significant estimates and assumptions in determining the fair value of its Common Shares. The Company utilized various valuation methodologies in accordance with the framework of the 2004 and 2013 American Institute of Certified Public Accountants Technical Practice Aids, Valuation of Privately- Held Company Equity Securities Issued as Compensation Reclassifications A change has been made to the presentation of deferred rent non-current as of December 31, 2015 to conform to the current year presentation. Stock Split In connection with preparing for its IPO, the Company’s board of directors and shareholders approved an amendment to the Company’s articles of association in July 2016. This amendment became effective upon registration in the Switzerland commercial register on July 27, 2016 and publication in the Swiss Official Gazette of Commerce on August 2, 2016. Pursuant to this amendment a 3 1 3 Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company and the Company’s chief operating decision maker, namely, the chief executive officer, view the Company’s operations and manage its business in one operating segment, which is the business of discovering, developing and commercializing therapies derived from or incorporating genome-editing technology. Foreign Currency Translation and Transactions The Company’s reporting currency is the U.S. Dollar. The Company‘s consolidated entities have the U.S. dollar as their functional currency with the exception of CRISPR Ltd. which has the British Pound Sterling (“GBP”) as its functional currency. CRISPR Ltd. has assets and liabilities translated into U.S. dollars at exchange rates in effect at the end of the year. Revenue and expenses are translated using the average exchange rates for the period. Net unrealized gains and losses resulting from foreign currency translation are included in accumulated other comprehensive income (loss), which is a separate component of shareholders’ (deficit) equity. Net foreign currency exchange transaction gains and losses resulting from the remeasurement of transactions denominated in currencies other than functional currency are included in other (expense) income, net in the consolidated statements of operations and comprehensive loss. Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of 90 days or less from the purchase date to be cash equivalents. As of December 31, 2016, and 2015, the Company had $315.5 million and $156.0 million in cash equivalents, respectively. All cash was held in depository accounts and is reported at fair value. Accounts Receivable Accounts receivable of $3.2 million at December 31, 2016 consist of receivables from Vertex Pharmaceuticals, Incorporated (“Vertex”) and Casebia. As of December 31, 2015, the Company had accounts receivable of $0.3 million consisting of receivables from Vertex. Accounts receivables are recorded at invoiced amounts due under both the Vertex and Casebia collaboration agreements (see Note 9). Vertex and Casebia are creditworthy entities that maintain an ongoing relationship with the Company, as such the Company did not have an allowance for estimated losses recorded related to these receivables. Concentrations of Credit Risk and Off-balance Sheet Risk Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash. The Company’s cash is held in accounts with financial institutions that management believes are creditworthy. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no financial instruments with off-balance sheet risk of loss. Deferred Public Offering Costs Deferred public offering costs, which primarily consist of direct, incremental legal and accounting fees relating to the IPO, were capitalized within other non-current assets prior to our IPO. The issuance costs of $8.3 million, including underwriter’s commissions, were offset against the IPO proceeds upon the consummation of the offering in October 2016. Fair Value of Financial Instruments The Company’s financial instruments consist of accounts payable, accrued expenses and other non-current liabilities. The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820, Fair Value Measurement and Disclosures The accounting standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, which are the following: Level 1 — Quoted prices in active markets that are accessible at the market date for identical unrestricted assets or liabilities. Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs for which all significant inputs are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amount of accounts receivable, accounts payable, and accrued expenses as reported on the consolidated balance sheets as of December 31, 2016 and 2015, approximate fair value, due to the short-term duration of these instruments. The fair value of the Company’s equity method investment in Casebia and convertible debt instruments were determined using level 3 inputs (See Note 9). Property and Equipment Property and equipment is stated at cost, less accumulated depreciation. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred. Upon disposal, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in the results of operations. Depreciation is recorded using the straight-line method over the estimated useful lives of the respective assets, which are as follows: Asset Estimated useful life Computer equipment and software 3 years Furniture, fixtures, and other 5 years Laboratory equipment 5 years Leasehold improvements Shorter of useful life or remaining lease term Impairment of Long-lived Assets The Company evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book value of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value. The Company has not recognized any impairment losses in the years ended December 31, 2016, 2015, and 2014. Revenue Recognition To date, the Company’s only source of revenue has been the collaboration and license agreement with Vertex as well as research and development services provided to Casebia under the joint venture with Bayer HealthCare LLC (“Bayer”) (see Note 9). The Company recognizes revenue in accordance with ASC Topic 605, Revenue Recognition • Persuasive evidence of an arrangement exists; • Delivery has occurred or services have been rendered; • The seller’s price to the buyer is fixed or determinable; and • Collectability is reasonably assured. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified in current liabilities. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue within non-current liabilities. The Company evaluates multiple-element arrangements based on the guidance in FASB ASC Topic 605-25, Revenue Recognition—Multiple-Element Arrangements The consideration received under the arrangement that is fixed or determinable is then allocated among the separate units of accounting based on the relative selling prices of the separate units of accounting. The Company determines the selling price of a unit of accounting within each arrangement following the hierarchy of evidence prescribed by ASC 605-25. Accordingly, the Company determines the estimated selling price for units of accounting within each arrangement using vendor-specific objective evidence (“VSOE”) of selling price, if available; third-party evidence (“TPE”) of selling price if VSOE is not available; or best estimate of selling price (“BESP”) if neither VSOE nor TPE is available. The Company typically uses BESP to estimate the selling price as it generally does not have VSOE or TPE of selling price for its units of accounting. Determining the BESP for a unit of accounting requires significant judgment. In developing the BESP for a unit of accounting, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. The Company periodically validates the BESP used for units of accounting by evaluating whether changes in the key assumptions used to determine the BESP will have a significant effect on the allocation of arrangement consideration between multiple units of accounting. The Company recognizes arrangement consideration allocated to each unit of accounting when all of the following criteria are met for that particular unit of accounting: persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the seller’s price to the buyer is fixed or determinable, and collectability is reasonably assured. In the event that a deliverable does not represent a separate unit of accounting, the Company recognizes revenue from the combined unit of accounting over the contractual or estimated performance period for the undelivered items, which is typically the term of the Company’s research and development obligations. If there is no discernible pattern of performance or objectively measurable performance measures do not exist, then the Company recognizes revenue under the arrangement on a straight-line basis over the period the Company is expected to complete its performance obligations. Conversely, if the pattern of performance over which the service is provided to the customer can be determined and objectively measurable performance measures exist, then the Company recognizes revenue under the arrangement using the proportional performance method. Revenue recognized is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the straight-line method or proportional performance method, as applicable, as of the period ending date. Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company expects to complete its performance obligations under an arrangement. Steering committee services that are not inconsequential or perfunctory and that are determined to be performance obligations are combined with other research services or performance obligations required under an arrangement, if any, in determining the level of effort required in an arrangement and the period over which the Company expects to complete its aggregate performance obligations. At the inception of an arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether: (i) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item as a result of a specific outcome resulting from the Company’s performance to achieve the milestone, (ii) the consideration relates solely to past performance, and (iii) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the particular milestone and the level of effort and investment required to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether a milestone satisfies all of the criteria required to conclude that a milestone is substantive. The Company will recognize revenue in its entirety upon successful accomplishment of any substantive milestones, assuming all other revenue recognition criteria are met. Milestones that are not considered substantive are recognized as earned if there are no remaining performance obligations or over the remaining period of performance, with a cumulative catch-up being recognized for the elapsed portion of the period of performance, assuming all other revenue recognition criteria are met. The Company will recognize royalty revenue in the period of sale of the related product(s), based on the underlying contract terms, provided that the reported sales are reliably measurable and the Company has no remaining performance obligations, assuming all other revenue recognition criteria are met. Research and Development Expenses Research and development costs, which include employee compensation costs, facilities, lab supplies and materials, overhead, preclinical development, and other related costs, are charged to expense as incurred. Research and development costs also include the costs the Company incurs in its performance of services or provision of materials in connection with the funded research undertaken as a part of the Company’s collaborative agreement with Vertex and Casebia. See Note 9 for further details. Operating Leases The Company leases office and laboratory facilities under a non-cancelable operating lease agreements. The lease agreements contain free or escalating rent payment provisions. The Company recognizes rent expense under such leases on a straight-line basis over the term of the lease with the difference between the expense and the payments recorded as deferred rent on the consolidated balance sheets. Lease renewal periods are considered on a lease-by-lease basis in determining the lease term. Funding of leasehold improvements by the Company’s landlord are accounted for as a tenant improvement allowance and are amortized as a reduction of rent expense over the term of the lease. Leasehold improvements are amortized straight-line over the shorter of the useful life or the remaining lease term. Equity Based Compensation Expense The Company recognizes equity-based compensation expense for awards of equity instruments to employees and non-employee directors based on the grant date fair value of those awards in accordance with FASB ASC Topic 718, Stock Compensation The Company accounts for stock options issued to non-employees under FASB ASC Topic 505-50, Equity Based Payments to Non-Employees The Black-Scholes option pricing model requires the input of certain subjective assumptions, including (i) the expected share price volatility, (ii) the calculation of expected term of the award, (iii) the risk-free interest rate and (iv) the expected dividend yield. Due to the lack of a public market for the trading of the Company’s Common Shares prior to its IPO and a lack of company-specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. The historical volatility is calculated based on a period of time commensurate with the expected term assumption. The group of representative companies have characteristics similar to the Company, including stage of product development and focus on the life science industry. The Company uses the simplified method, which is the average of the final vesting tranche date and the contractual term, to calculate the expected term for options granted to employees as it does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. For options granted to non-employees, the Company utilizes the contractual term of the arrangement as the basis for the expected term assumption. The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected term of the stock options. The Company uses an assumed dividend yield of zero as the Company has never paid dividends and has no current plans to pay any dividends on its Common Shares. The Company expenses the fair value of its equity-based compensation awards granted to employees on a straight-line basis over the associated service period, which is generally the period in which the related services are received. The Company measures equity-based compensation awards granted to non-employees at fair value as the awards vest and recognizes the resulting value as compensation expense at each financial reporting period. The Company records the expense for equity-based compensation awards subject to performance-based milestone vesting over the remaining service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions as of the reporting date. Patent Costs Costs to secure and prosecute patent application and other legal costs related to the protection of the Company’s intellectual property are expensed as incurred, and are classified as general and administrative expenses in the Company’s consolidated statements of operations. Income Taxes Income taxes are recorded in accordance with FASB ASC Topic 740, Income Taxes The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2016 and 2015, the Company does not have any significant uncertain tax positions. The Company’s practice is to recognize interest and/or penalties related to income tax matters in income tax expense. See Note 14 for further details. Comprehensive Loss Comprehensive loss consists of net income or loss and changes in equity during the period from transactions and other events and circumstances generated from non-owner sources. The Company’s net loss equals comprehensive loss, net of any changes in the foreign currency translation adjustment, for all periods presented. In addition, comprehensive loss attributable to the noncontrolling interest equals net loss for all periods presented. Variable Interest Entities The Company reviews each legal entity formed by parties related to the Company to determine whether or not the Company has a variable interest in the entity and whether or not the entity would meet the definition of a VIE in accordance with FASB ASC Topic 810, Consolidation If the Company determines it is the primary beneficiary of a VIE that meets the definition of a business, the Company measures the assets, liabilities and noncontrolling interests of the newly consolidated entity at fair value in accordance with FASB ASC Topic 805, Business Combinations In February 2016, Casebia Therapeutics LLP, a limited liability partnership, was formed in the United Kingdom. In March 2016 upon consummation of the JV, Bayer and the Company each received a 50% equity interest in the entity in exchange for their contributions to the entity. The Company determined that Casebia was considered a VIE and concluded that it is not the primary beneficiary of the VIE. As such, the Company did not consolidate Casebia’s results into the consolidated financial statements. See Note 4 for further details. As of December 31, 2016, TRACR is a wholly-owned subsidiary of the Company. See Note 4 for further details. For the year ended December 31, 2015, the Company consolidated the financial statements of TRACR into the Company’s consolidated financial statements as it was both a VIE and a majority owned subsidiary. For the year ended December 31, 2014, the Company consolidated TRACR as a VIE. Noncontrolling Interest Upon the IPO date of the Company, the non-controlling interest of TRACR was acquired, and as of the year ended December 31, 2016 TRACR is a wholly-owned subsidiary of the Company. See Note 4 for further details related to TRACR. The Company recorded non-controlling interest, which was related to TRACR during 2015 and 2016. The Company recorded net loss attributable to non-controlling interest on its consolidated statements of operations, reflecting the loss from non-controlling interest for the reporting period. Intangible Assets The Company’s intangible assets consist of acquired intellectual property rights and relate to the Company’s interest in TRACR. Intangible assets are recorded at fair value at the date of the business combination and are stated in the consolidated balance sheets net of accumulated amortization and impairments, if applicable. The Company evaluates the remaining useful life of intangible assets subject to amortization on a periodic basis to determine whether events and circumstances would indicate impairment or warrant a revision to the remaining useful life. If the estimate of an intangible asset’s remaining useful life is changed, the Company amortizes the remaining carrying value of the intangible asset prospectively over the revised remaining useful life. Intangible assets related to the acquired intellectual property rights are amortized over their estimated useful lives using the straight-line method as the pattern of revenues cannot be reasonably estimated. Amortization related to the acquired intellectual property rights is recorded in general and administrative expense in the consolidated statements of operations and comprehensive loss. Net Loss Per Share Attributable to Common Shareholders Basic net income (loss) per share is calculated by dividing net income (loss) attributable to common shareholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is calculated by dividing the net income attributable to common shareholders by the weighted-average number of common equivalent shares outstanding for the period, including any dilutive effect from outstanding stock options and warrants using the treasury stock method. The Company follows the two-class method when computing net income per share in periods when participating securities are outstanding. The two-class method determines net income per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common shareholders for the period to be allocated between common and participating securities based on their respective rights to receive dividends as if all income for the period had been distributed. Accordingly, in periods in which the Company reports a net loss attributable to common shareholders when participating securities are outstanding, losses are not allocated to the participating securities because they have no contractual obligation to share in the losses of the Company. For purposes of calculating diluted net income per share attributable to redeemable preferred shares, convertible loans, stock options, and unvested restricted common shares are considered common share equivalents. The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to do so would be anti-dilutive (in common stock equivalent shares): As of December 31, 2016 2015 2014 Convertible preferred shares — 18,837,024 3,560,002 Conversion of convertible loans — 4,110,987 — Dr. Emmanuelle Charpentier call option — 328,017 — Outstanding options 4,535,371 1,939,986 — Unvested unissued restricted shares 89,367 142,794 — Total 4,624,738 25,358,808 3,560,002 Subsequent Events The Company considered the events or transactions occurring after the balance sheet date, but prior to the issuance of the consolidated financial statements, for potential recognition or disclosure in its consolidated financial statements. All significant subsequent events have been properly disclosed in the consolidated financial statements. Recent Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers The Revenue ASUs provide an accounting standard for a single comprehensive model for use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance. The accounting standard is effective for interim and annual periods beginning after December 15, 2017, with an option to early adopt for interim and annual periods beginning after December 15, 2016. The guidance permits two methods of adoption: retrospectively to each prior reporting period presented (the full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). We currently anticipate adoption of the new standard effective January 1, 2018 under the full retrospective method. The Company is in the process of determining the impact of the Revenue ASUs on its financial statements. In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements—Going Concern In February 2016, the FASB issued ASU No. 2016-02, Leases In March 2016, the FASB issued ASU No. 2016-09, Compensation— Stock Compensation (Topic 718) In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Property and Equipment, net	3. Property and Equipment, net Property and equipment, net, consists of the following (in thousands): As of December 31, 2016 2015 Computer equipment and software $ 110 $ 118 Furniture, fixtures, and other 2,044 238 Laboratory equipment 2,970 861 Leasehold improvements 15,780 88 Construction work in process 1,065 95 21,969 1,400 Accumulated Depreciation (942 ) (72 ) Property and equipment, net $ 21,027 $ 1,328 Depreciation expense for the year ended December 31, 2016, 2015, and 2014 was $0.9 million, $0.1 million, and $0 million, respectively.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Variable Interest Entities	4. Variable Interest Entities TRACR Hematology Limited On January 23, 2014, the founders of the Company formed TRACR in the United Kingdom, to further the development of the CRISPR/Cas9 technology into medicines for the treatment of blood-borne illnesses. On April 14, 2014, TRACR licensed certain foundational intellectual property rights under joint ownership from Dr. Emmanuelle Charpentier to develop and commercialize products for the treatment or prevention of human diseases related to hemoglobinopathies. See Note 9 for further details of the technology license agreement with Dr. Charpentier. On April 14, 2014 the Company determined that it became the primary beneficiary of TRACR based on, among other factors, the Company’s power to direct the activities that significantly impacted the economic performance of TRACR and the Company’s financing of contractual obligations on behalf of TRACR, and the period in which the Company began to benefit from research and development of TRACR technology. Accordingly, the Company consolidated TRACR’s financial statements as a consolidated VIE beginning on April 14, 2014. On March 24, 2015, the Company acquired 4,600 ordinary shares of TRACR, representing 82.1% of the ordinary share capital, pursuant to a share exchange transaction with the shareholders of TRACR. In exchange for 4,600 ordinary shares of TRACR and the assignment of certain rights to subscribe ordinary shares of TRACR, the Company issued 852,846 Common Shares to two founders of TRACR, 656,031 restricted Common Shares to certain employees and non-employees, and 459,217 Common Shares to Fay Participation Corporation (“Fay Corp.”), an entity formed to hold Common Shares for future issuance to certain employees and non-employees. As of December 31, 2015, the Company held 4,600 ordinary shares of TRACR, representing 82.1% of the ordinary share capital of TRACR. Upon the share exchange on March 24, 2015, the Company recorded an adjustment of $0.1 million to decrease the carrying amount of the noncontrolling interest in TRACR and reflect the Company’s increased ownership interest in TRACR’s net assets. This adjustment was recognized directly in equity through additional paid-in capital and is attributable to the controlling interest. Pursuant to the share exchange transaction on March 24, 2015, the Company also entered into a freestanding call option agreement with Dr. Charpentier for 1,000 ordinary shares of TRACR, representing the remaining 17.9% of the ordinary share capital of TRACR. Under the terms of the call option agreement, the Company has the option to acquire the remaining 1,000 shares of TRACR held by Dr. Charpentier in exchange for 328,017 Common Shares of the Company. In the event the option is exercised by the Company prior to a liquidation event, the Company will indemnify Dr. Charpentier for all taxes owed as a result of the exchange. In addition, upon a bankruptcy, liquidation, closing of an IPO, winding up of the Company, a change in control or other deemed liquidation event, as defined in the call option agreement, the remaining 1,000 ordinary shares of TRACR held by Dr. Charpentier will automatically convert into 328,017 Common Shares of the Company. The call option was determined to have a fair value of $0.2 million at the time of the share exchange and was attributed to Dr. Charpentier’s for past services rendered to CRISPR and TRACR. Upon IPO, the call option was exercised and the remaining non-controlling interest of TRACR was acquired, resulting in a reduction of Noncontrolling interest of $0.1 million, stock based compensation of $0.2 million for original value of the call option, and additional paid-in capital of $0.1 million. Joint Venture with Bayer Healthcare LLC In December 2015, the Company entered into an agreement with Bayer to create a joint venture to discover, develop and commercialize new therapeutics for genetically linked diseases, including blood disorders, blindness and heart disease. On February 12, 2016, Casebia, a limited liability partnership, was formed in the United Kingdom. In March 2016 upon consummation of the JV, Bayer and the Company each received a 50% equity interest in the entity in exchange for their contributions to the entity. The Company determined that Casebia was considered a VIE and concluded that it is not the primary beneficiary of the VIE. As such, the Company did not consolidate Casebia’s results into the consolidated financial statements. See Note 9 for further details.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible Assets	5. Intangible Assets The Company’s intangible assets consist of acquired intellectual property rights related to the Company’s initial consolidation of TRACR in April 2014. Acquired intellectual property rights had an estimated life of 10 years. Intangible assets, net of accumulated amortization, are as follows (in thousands): Acquired intangible asset Cost Accumulated Amortization Net As of December 31, 2016 $ 547 $ (148 ) $ 399 As of December 31, 2015 $ 547 $ (93 ) $ 454 The Company recorded amortization expense of $0.1 million, $0.1 million, and $40 thousand for each of the years ended December 31, 2016, 2015, and 2014, respectively. As of December 31, 2016 and 2015, the remaining amortization period was 7.3 years and 8.3 years, respectively. The Company has not recorded any impairment charges for the years ended December 31, 2016, 2015 and 2014. The estimated future amortization of acquired intangible assets as of December 31, 2016 is expected to be as follows (in thousands): Year Ending December 31: Amount 2017 $ 55 2018 55 2019 55 2020 55 Thereafter 179 Total amortization $ 399

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued Expenses	6. Accrued Expenses Accrued expenses consist of the following (in thousands): As of December 31, 2016 2015 Payroll and employee-related costs $ 2,585 $ 773 Research costs 996 910 Licensing fees 492 1,055 Professional fees 2,715 2,412 Intellectual property costs 3,372 2,592 Accrued property and equipment 5,081 — Other 1,079 688 Total $ 16,320 $ 8,430

Convertible Loans

Convertible Loans	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Convertible Loans	7. Convertible Loans 2015 Convertible Loan Agreement with Vertex and certain existing shareholders On October 26, 2015, the Company entered into a convertible loan agreement with Vertex and certain existing shareholders (the “Vertex Convertible Loan”) under which the Company could borrow up to $40.0 million. The Vertex Convertible Loan accrues interest at 2.5% per annum and had an initial maturity date of April 26, 2016 subject to acceleration upon the occurrence of certain conditions stated in the loan agreement (the “Maturity Date”). On various dates between November 23 and December 7, 2015, the Company borrowed aggregate net proceeds of $38.2 million. The Vertex Convertible Loan included various embedded conversion, redemption and other features, as further described below, none of which required separate accounting from the host instrument under ASC 815. On January 29, 2016, all of the outstanding principal plus accrued interest of $0.2 million under the Vertex Convertible Loan was automatically converted into 2,859,278 Series B Preferred Shares in connection with a qualified financing described below. An event of default (“Event of Default”) is defined in the Vertex Convertible Loan Agreement and includes events of bankruptcy, insolvency or reorganization and, solely at the election of Vertex, a material breach that is not cured within the applicable notice and cure periods of the strategic collaboration, option and license agreement entered into by Vertex and the Company. See Note 9 for further details of the strategic, option and license agreement. Conversion Terms On the Maturity Date, the outstanding principal plus accrued interest automatically converts into Series B Preferred Shares at $9.33 per share. In the event the Company issues equity securities prior to the Maturity Date with aggregate proceeds of not less than $50.0 million, of which $5.0 million is raised from investors other than Vertex or existing shareholders, the outstanding principal plus accrued interest under the Vertex Convertible Loan automatically converts into the newly issued equity securities at the price per share paid by the investors in the financing. In the event of an underwritten public offering with shares of the Company listed on the New York Stock Exchange, the NASDAQ Global Market, or the NASDAQ Global Market, resulting in at least $50.0 million of proceeds to the Company closed prior to Maturity, the holders may elect, prior to the closing of the IPO, to convert the outstanding principal plus accrued interest into Series B Preferred Shares at $9.33 per share. Any Vertex Convertible Loan not converted prior to the closing of the IPO, shall automatically convert into Common Shares at a price paid by the investors for such shares in the IPO. Upon a liquidation event prior to the Maturity Date, the holders may elect to convert the outstanding principal plus accrued interest into either Common Shares at a price of $9.33 per share or Series B Preferred Shares at a price of $9.33 per share. Redemption Terms Upon an Event of Default, all outstanding principal plus accrued interest becomes immediately due and payable. Upon a liquidation event, if the holders do not exercise their conversion right, the outstanding principal plus accrued interest shall become due and payable in cash on the business day following the date on which the Company or its shareholders receive the proceeds from the liquidation event. Contingent Interest Upon an Event of Default, the outstanding amount of the Vertex Convertible Loan shall bear, in addition to the base interest of 2.5% per annum, default interest at a rate of 7.5% per annum. Convertible Loan with Bayer HealthCare LLC Concurrent with the execution of the Bayer Joint Venture agreement, the Company also entered into a Convertible Loan Agreement (“Bayer Convertible Loan”) with Bayer for $35.0 million. The Bayer Convertible Loan accrued interest at 2.0% per annum and matured on January 29, 2016 (the “Maturity Date”). On January 29, 2016, the Company issued the Bayer Convertible Loan in exchange for aggregate net proceeds of $35.0 million. The Bayer Convertible Loan included various embedded conversion, redemption and other features, none of which required separate accounting from the host instrument under ASC 815. Conversion of Convertible Loans to Series B Preferred Shares On January 29, 2016, concurrent with the issuance of the Bayer Convertible Loan, all of the outstanding principal under the $35.0 million Bayer Convertible Loan automatically converted into 2,605,330 Series B Preferred Shares at $13.43 per share. The Company determined the fair value of the Bayer Convertible Loan to be $24.5 million based on the fair value of the underlying Series B Preferred Shares that were exchanged as part of the immediate conversion. As the Bayer Convertible Loan was executed in contemplation of the joint venture agreement with Bayer, the Company evaluated the Bayer Convertible Loan as part of one multiple-element arrangement and using a relative fair value allocation allocated $27.0 million of aggregate arrangement consideration to the Bayer Convertible Loan upon issuance (See Note 9). Upon conversion, the Company accreted the Bayer Convertible Loan to its face value of $35.0 million through a charge to interest expense of $8.0 million and converted the $35.0 million to Series B Preferred Shares under the conversion model. The receipt of $35.0 million in proceeds under the Bayer Convertible Loan in exchange for equity securities, combined with the $38.2 million in proceeds from Vertex Convertible Loan, triggered an automatic conversion provision of the Vertex Convertible Loan Agreement. Accordingly, on January 29, 2016, the Vertex Convertible Loan, including loans from existing shareholders, plus accrued interest also converted into 2,859,278 of Series B Preferred Shares at $13.43 per share. The Company determined the fair value of the Vertex Convertible Loan to be $26.9 million based on the fair value of the underlying Series B Preferred Shares that were exchanged as part of the conversion. Upon extinguishment, the Company recorded a gain on extinguishment of $11.5 million for the difference between the carrying value of the debt and the fair value of the Series B Preferred Shares issued to settle the debt under the general extinguishment model.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Operating Leases As of December 31, 2016, the Company had five In April 2015, the Company entered into a lease for laboratory and office lease facilities in Cambridge, Massachusetts (the “200 Sidney Street Lease”). The 200 Sidney Street Lease lease expires in February 2022 with one additional five year extension period. The 200 Sidney Street Lease contains escalating rent clauses which require higher rent payments in future years. In June 2015, the Company entered into an agreement pursuant to which it has the right to use certain office facilities in London England. The current term expires in July 2017. The Company’s obligations under this right to use agreement are secured by a cash deposit in the approximate amount of GBP 9 thousand held by the office space provider. In October 2015, the Company entered into a lease for corporate housing in Cambridge, Massachusetts. The term of the original lease was renewed in November 2016 and the current term expires in November 2017 subject to additional one year renewals. The Company’s obligations under the terms of this lease are secured by a cash deposit in the approximate amount of $10 thousand held by the lessor. In April 2016, the Company entered into a sublease for office facilities in Cambridge Massachusetts. The Company’ obligations under the terms of this lease were secured by a cash deposit in the approximate amount of $26 thousand held by the lessor. This lease term expired in January 2017. In May 2016, the Company entered into a sublease pursuant to which it subleases in Cambridge, Massachusetts (the “610 Main Street Sublease”) the Company’s primary research and US office facility. The initial term of the 610 Main Street will expire on December 22, 2026. The Company has an option to extend the term of the 610 Main Street Sublease for an additional five year period if, at the time of expiration of the initial term, the sublessor does not intend to utilize the space for itself or its affiliates. The 610 Main Street Sublease contains escalating rent clauses which require higher rent payments in future years. The 610 Main Street Sublease included a $10.8 million tenant improvements allowance for normal tenant improvements, for which construction began in June 2016. The date of the construction coincided with the lease commencement date for accounting purposes under ASC 840, Leases In May 2016, the Company entered a $2.5 million letter of credit to secure the Company’s obligations under the 610 Main Street Sublease. The letter of credit is secured by cash held in a restricted depository account. The deposit is recorded in restricted cash in the accompanying consolidated balance sheet as of December 31, 2016. Future minimum payments required under the leases as of December 31, 2016, are as follows (in thousands): Year Ending December 31: Amount 2017 $ 6,685 2018 6,431 2019 6,624 2020 6,823 2021 7,027 Thereafter 30,335 Total minimum lease payments $ 63,925 Letters of Credit As of December 31, 2016 and 2015, the Company had restricted cash of $3.2 million and $0.7 million, respectively, representing letters of credit securing the Company’s obligations under certain leased facilities in Cambridge, Massachusetts at 200 Sidney Street and the 610 Main Street as well as certain credit card arrangements. The letters of credit are secured by cash held in a restricted depository account. The cash deposit is recorded in restricted cash in the accompanying consolidated balance sheet as of December 31, 2016 and 2015. Shareholder Settlement Under the terms of a shareholder agreement existing prior to the IPO, if a U.S. common shareholder elected to file a Qualified Electing Fund (“QEF”) and notified the Company of this election, the Company was required to make advance payments to the shareholder related to their individual tax liability. In September 2016, the Company formally offered an aggregate settlement of up to $2.0 million to certain U.S common shareholders in order to release the Company from any and all obligations or claims concerning and/or arising out of the Company’s status as a PFIC or a Controlled Foreign Corporation (a “CFC”) for any taxable year from 2013 through 2015, including for potential lack of timely notification of the Company’s PFIC status (an “Annual Information Statement”) for the year ended December 31, 2015. Following the formal settlement offer in September 2016, in the fourth quarter of 2016 the Company made payments to shareholders of $2.0 million, respectively, under the terms of the accepted settlements. The obligation to make advance payments under the shareholder agreement for tax years subsequent to 2015 terminated upon the closing of the IPO. The Company has made available a 2016 PFIC Annual Information Statement on its website for its shareholders. Sponsored Research Agreements The Company has engaged several research institutions to identify new delivery strategies and applications of the CRISPR/Cas9 technology. As a result of these efforts, the Company sponsored five research programs during 2016, with two of these programs continuing through 2018. In association with these agreements, the Company has committed to making payments for related research and development services of $0.7 million, and $0.1 million in 2017 and 2018, respectively. License Agreement with Anagenesis Biotechnologies SAS On June 7, 2016, the Company entered into a license agreement with Anagenesis Biotechnologies SAS (“Anagenesis”) pursuant to which the Company received an exclusive worldwide license to Anagenesis’ proprietary technology for all human based muscle diseases. Pursuant to the license agreement, the Company made a one-time upfront payment of $0.5 million to Anagenesis and is required to pay Anagenesis up to $89.0 million upon the achievement of future clinical, regulatory and sales milestones for each of the first allogeneic and autologous licensed products developed pursuant to the license agreement, as well as low single digit royalty payments on future sales of commercialized product candidates. The Company recorded the $0.5 million payment during the twelve months ended December 31, 2016 as research and development expense on the consolidated statement of operations. Licensing and Patent Assignment Agreements In April 2014, the Company and TRACR entered into technology license agreements with Dr. Emmanuelle Charpentier pursuant to which the Company licensed Dr. Charpentier’s interest to certain intellectual property rights jointly owned by Dr. Charpentier and others to develop and commercialize products for the treatment or prevention of human diseases. See Note 9 for further details. Litigation Under the Charpentier license agreement, the Company licenses a U.S. patent application that is currently subject to interference proceedings declared by the Patent Trial and Appeal Board (“PTAB”) of the U.S. Patent and Trademark Office. Following motions by the parties and other procedural matters, the PTAB concluded in February 2017 that the declared interference should be dismissed because the claim sets of the two parties were not directed to the same patentable invention in accordance with the PTAB’s two-way test for patent interferences. See Note 17 for further details. Under the Invention Management Agreement (“IMA”) signed on December 15, 2016, the Company is obligated to share costs related to patent maintenance, defense and prosecution. For the years ended December 31, 2016, 2015 and 2014, the Company incurred $3.0 million, $1.5 million and $1.1 million, respectively in shared costs. The Company recorded accrued legal costs from the cost sharing of $2.8 million and $2.6 million as of December 31, 2016 and 2015, respectively

Significant Contracts

Significant Contracts	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Significant Contracts	9. Significant Contracts Intellectual Property Agreements CRISPR Therapeutics AG—Charpentier License Agreement In April 2014, the Company entered into a technology license agreement with Dr. Emmanuelle Charpentier pursuant to which the Company licensed certain intellectual property rights under joint ownership from Dr. Charpentier to develop and commercialize products for the treatment or prevention of human diseases other than hemoglobinopathies (“CRISPR—Charpentier License Agreement”). In consideration for the granting of the license, the Company paid Dr. Charpentier an upfront fee of CHF 0.1 million ($0.1 million), and agreed to pay an immaterial annual license maintenance fee if Dr. Charpentier is not otherwise engaged in a service arrangement with the Company. During the years ended December 31, 2016, 2015 and 2014, Dr. Charpentier has been in a consulting arrangement with the Company, as such, no annual payments have been made under this provision. Dr. Charpentier is entitled to receive nominal clinical milestone payments. The Company is also obligated to pay Dr. Charpentier a low single digit percentage of sublicensing payments received under any sublicense agreement with a third party. In addition, the Company is also obligated to pay to Dr. Charpentier a low single-digit percentage royalty based on annual net sales of licensed products and licensed services by the Company and its affiliates and sublicensees. During the years ended December 31, 2016, 2015, and 2014 the Company recorded and accrued $0.5 million, $0.9 million, and $0 million, respectively, of sublicensing fees due to Dr. Emmanuelle Charpentier in research and development expense under the terms of the CRISPR—Charpentier License Agreement that was triggered by the execution of the Vertex collaboration agreement and the Bayer agreement. TRACR Hematology Limited—Charpentier License Agreement In April 2014, TRACR entered into a technology license agreement (“TRACR—Charpentier License Agreement”) with Dr. Emmanuelle Charpentier pursuant to which TRACR licensed certain intellectual property rights under joint ownership from Dr. Charpentier to develop and commercialize products for the treatment or prevention of human diseases related to hemoglobinopathies. In consideration for the granting of the license, Dr. Charpentier is entitled to receive nominal clinical milestone payments. TRACR is also obligated to pay Dr. Charpentier a low single digit percentage of sublicensing payments received under any sublicense agreement with a third party. In addition, TRACR is obligated to pay to Dr. Charpentier low single digit percentage royalties based on annual net sales of licensed products and licensed services by the Company and its affiliates and sublicensees. During the years ended December 31, 2016, 2015, and 2014 the Company recorded $0, $0.1 million, and $0, respectively, of sublicensing fees due to Dr. Emmanuelle Charpentier in research and development expense under the terms of the TRACR—Charpentier License Agreement that was triggered by the execution of the Vertex collaboration agreements. Invention Management Agreement On December 15, 2016, we entered into a an IMA, with the University of California (“California”), the University of Vienna (“Vienna”), Dr. Charpentier, Intellia therapeutics, Inc. (“Intellia”), Caribou Biosciences, Inc. (“Caribou”), ERS Genomics Ltd., or (“ERS”), and TRACR. Under the IMA, California and Vienna retroactively consent to Dr. Charpentier’s licensing of her rights to the CRISPR/Cas9 intellectual property, pursuant to the Charpentier License, to us, our wholly-owned subsidiary TRACR, and ERS, in the United States and globally. The IMA also provides retroactive consent of co-owners to sublicenses granted by us, TRACR and other licensees, prospective consent to sublicenses they may grant in future, retroactive approval of prior assignments by certain parties, and provides for, among other things, (i) good faith cooperation among the parties regarding patent maintenance, defense and prosecution, (ii) cost-sharing arrangements, and (iii) notice of and coordination in the event of third-party infringement of the subject patents and with respect to certain adverse claimants of the CRISPR/Cas9 intellectual property. Unless earlier terminated by the parties, the IMA will continue in effect until the later of the last expiration date of the patents underlying the CRISPR/Cas9 technology, or the date on which the last underlying patent application is abandoned. Patent Assignment Agreement In November 2014, the Company entered into a patent assignment agreement (“Patent Assignment Agreement”) with Dr. Emmanuelle Charpentier, Dr. Ines Fonfara, and Vienna (collectively, the “Assignors”), pursuant to which the Company was assigned all rights, title and interest in and to certain patent rights claimed in the U.S. Patent Application No.61/905,835. In consideration for the assignment of such rights, the Assignors are entitled to receive clinical milestone payments totaling up to €0.3 million (approximately $0.4 million) in the aggregate for the first human therapeutic product. The Company is also obligated to pay to the Assignors low single digit royalties based on annual net sales of licensed products and licensed services by the Company and its affiliates and sublicensees. During the years ended December 31, 2016, 2015, and 2014 the Company recorded $33 thousand, $0.1 million, $0, respectively, of sublicensing fees due to the Assignors in research and development expense under the terms of the Patent Assignment Agreement that was triggered by the execution of the Vertex collaboration agreement and the Bayer Agreement. Collaboration Agreement with Vertex Pharmaceuticals, Incorporated Summary of Agreement On October 26, 2015, the Company entered into a strategic collaboration, option, and license agreement (“Collaboration Agreement”) with Vertex, focused on the use of CRISPR’s gene editing technology, known as CRISPR/Cas9, to discover and develop potential new treatments aimed at the underlying genetic causes of human disease. The collaboration will evaluate the use of CRISPR-Cas9 across multiple diseases where targets have been validated through human genetics. Vertex and CRISPR will focus their initial gene editing research on discovering treatments to address the mutations and genes known to cause and contribute to sickle cell disease, beta-thalessemia and cystic fibrosis. Vertex and CRISPR will also evaluate a specified number of other genetic targets as part of the collaboration. For up to six targets, Vertex has an exclusive option to obtain: (1) an exclusive license to commercialize CRISPR technology (“Exclusive License”) or (2) a co-exclusive license with respect to hemoglobinopathy and beta-globin targets (“Co-exclusive License”). 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 (“R&D Services”) are related to generating genome editing reagents that modify gene targets selected by Vertex. Except with respect to the Company’s obligations under the mutually agreed upon research plan, Vertex has sole responsibility, at its own costs, for the worldwide research, development, manufacturing and commercialization of products resulting from the exclusive licenses obtained. The research collaboration will end on the earlier of the date on which Vertex has exercised six options to obtain exclusive/co-exclusive licenses with respect to a collaboration target, or the fourth anniversary of the effective date of the agreement. The research term may be extended as mutually agreed by the parties up to nine additional months to complete any research activities under the approved research plan that are incomplete on the fourth anniversary of the effective date. The Collaboration Agreement will be managed on an overall basis by a project leader from each of the Company and Vertex. In addition, the activities under the collaboration agreement during the research term will be governed by a joint research committee (“JRC”) formed by an equal number of representatives from the Company and Vertex. Decisions by the JRC will be made by consensus of the group, however, Vertex will have final decision-making authority in the event of disagreement, provided it is in good faith and not contrary to any explicit clause of the agreement. In connection with the agreement, Vertex made a nonrefundable upfront payment of $75.0 million. In addition, Vertex will fund all of the discovery activities conducted pursuant to the agreement. For potential hemoglobinopathy treatments, including treatments for sickle cell disease, the Company and Vertex will share equally all research and development costs and worldwide revenues. For other targets that Vertex elects to license, Vertex would lead all development and global commercialization activities. For each of up to six targets that Vertex elects to license, other than hemoglobinopathy and beta-globin targets, the Company has the potential to receive up to $420.0 million in development, regulatory and commercial milestones and royalties on net product sale. Vertex is entitled to terminate the Collaboration Agreement as a whole, or terminate the Collaboration Agreement in part with respect to a particular collaboration program, for convenience by providing the Company 90 days’ written notice of such termination; provided, however, that if any termination applies to a product for which Vertex has received marketing approval, Vertex will provide CRISPR no less than 270 days’ notice of such termination. If Vertex is in material breach of this Collaboration Agreement, the Company has the right to terminate the Collaboration Agreement in full at its discretion 90 days after delivery of written notice to Vertex. The Company evaluated the Collaboration Agreement in accordance with the provisions of ASC 605-25. The Company’s arrangement with Vertex contains the following initial deliverables: (i) a non-exclusive research license; (ii) the option to obtain an exclusive license for up to six Collaboration Targets; (iii) the option to obtain a co-exclusive license for hemoglobinopathy or beta-globin targets (which would be included within the maximum number of the aforementioned six collaboration targets); (iv) R&D Services; and (v) JRC participation. Management considered whether any of these deliverables could be considered separate units of accounting. Regarding the non-exclusive research license, the Company concluded that it does not have stand-alone value separate from the option to exercise the exclusive or co-exclusive license since Vertex would not benefit from acquiring a research license without the ability to obtain the license to commercialize the results of that research. As a result, the Company concluded that the research license should be combined with those options. Regarding the R&D Services, the Company concluded that there are other vendors in the market that could perform the related services. As such the Company concluded the R&D Services represent a separate unit of accounting. Regarding the JRC obligations, the Company concluded that the JRC obligations deliverable has standalone value from the option to license because the services could be performed by an outside party. As such the Company concluded the JRC obligations represent a separate unit of accounting. As a result, management concluded that there are four units of accounting at the inception of the agreement: (i) a combined unit of accounting representing the non-exclusive research license, and the option for up to six exclusive licenses to develop and commercialize the collaboration targets as these options do not have stand- alone value; (ii) a combined unit of accounting representing the non-exclusive research license, and the option for a co-exclusive license (subject to the aforementioned six license limit) to develop and commercialize the hemoglobinopathy or beta-globin targets as these options do not have stand-alone value; (iii) the performance of R&D Services; and (iv) the participation in the JRC. The Company has determined that neither VSOE of selling price nor TPE of selling price is available for any of the units of accounting identified at inception of the arrangement. Accordingly, the selling price of each unit of accounting was determined based on the Company’s BESP. The Company developed the BESP for all of the units of accounting included in the collaboration agreement with the objective of determining the price at which it would sell such an item if it were to be sold regularly on a standalone basis. The Company developed the BESP for the R&D Services and the JRC participation primarily based on the nature of the services to be performed and estimates of the associated effort and cost of the services, adjusted for a reasonable profit margin that would be expected to be realized under similar contracts. The Company’s BESP for the R&D Services was $26.7 million. The Company’s BESP for the JRC participation services was de minimis based on an estimate of time spent on preparation, participation, review and travel for the meetings. The Company’s BESP for each combined unit of the non-exclusive research license and the option for an exclusive license to develop and commercialize a single collaboration target is $37.7 million. As the Company expects Vertex to exercise five of these options, the total BESP is $188.5 million. BESP for this item was determined based on probability and present value adjusted cash flows from the royalties and milestones outlined in the Collaboration Agreement. BESP reflects the level of risk and expected probability of success inherent in the nature of the associated research area. The Company’s BESP for a non-exclusive research license and the option for a co-exclusive license to develop and commercialize a single hemoglobinopathy or beta-globin collaboration target is $12.5 million. As the Company expects Vertex to exercise one of these options, the total BESP is $12.5 million. BESP for this item was determined based on probability and present value adjusted cash flows from the equal sharing of project worldwide net profit or net loss. BESP reflects the level of risk and expected probability of success inherent in the nature of the associated research area. Allocable arrangement consideration at inception is comprised of: (i) the up-front payment of $75.0 million, (ii) the estimated R&D services of $26.7 million and (iii) payments related to the estimated exercise of options on future exclusive licenses for five targets of $50.0 million. The aggregate allocable arrangement consideration of $151.7 million was allocated among the separate units of accounting using the relative selling price method as follows: (i) R&D Services: $17.8 million, (ii) non-exclusive research license, and the option for an Exclusive License to develop and commercialize the five collaboration targets: $125.5 million, (iii) non-exclusive research license, and the option for one Co-exclusive License to develop and commercialize one hematology target: $8.4 million. The amount allocated to R&D Services will be recognized as the R&D Services are performed. The Company will recognize as license revenue an equal amount of the total arrangement consideration allocated to the exclusive licenses as each individual license is delivered to Vertex upon Vertex’s exercise of its options to such licenses. The Company will recognize $8.4 million as license revenue when the Co-exclusive License is delivered to Vertex upon Vertex’s exercise of its options to such license. The Company has evaluated all of the milestones that may be received in connection with the Collaboration Agreement. In evaluating if a milestone is substantive, the Company assesses whether: (i) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the Company’s performance to achieve the milestone, (ii) the consideration relates solely to past performance, and (iii) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company notes that the $10.0 million due upon the exercise of each option for an Exclusive License was determined to be part of the fixed and determinable consideration allocable at contract inception and is not subject to milestone method accounting. The first potential milestone the Company will be entitled to receive is the $10.0 million milestone due upon the filing of an Investigational New Drug Application (“IND”) for a selected Exclusive License. As the first developmental milestone of the agreement relates to the filing of an IND, the Company has considered it to be substantive. Accordingly, such amounts will be recognized as revenue in full in the period in which the associated milestone is achieved, assuming all other revenue recognition criteria are met. There are no other substantive milestones. As such the total amount of substantive milestones subject to milestone method accounting treatment is $10.0 million for each selected Exclusive License. The remaining milestones are predominately related to the development and commercialization of a product resulting from the arrangement and are payable with respect to each selected Exclusive License. Each milestone is payable only once per collaboration target, regardless of the number of products directed to such collaboration target that achieve the relevant milestone event. There are nine remaining clinical development and regulatory approval milestones which may trigger proceeds of up to $90.0 million and $235.0 million, respectively, for each selected Exclusive License, and two commercial milestones which may trigger proceeds of up to $75.0 million for each selected Exclusive License (which, when combined with the $10.0 million due upon exercise of the exclusive option and the $10.0 million development milestone associated with an IND, total $420.0 million for each selected Exclusive License), as follows: Developmental Milestone Events 1. Initiation of the first Clinical Trial of a Product 2. Establishment of POC for a Product 3. Initiation of the first Phase 3 Clinical Trial of a Product 4. Acceptance of Approval Application by the FDA for a Product 5. Acceptance of Approval Application by the EMA for a Product 6. Acceptance of Approval Application by a Regulatory Authority in Japan for a Product 7. Marketing Approval in the US for a Product 8. Marketing Approval in the EU for a Product 9. Marketing Approval in Japan for a Product Commercial Milestone Events 1. Annual Net Sales for Products with respect to a Collaboration Target exceed $500 million 2. Annual Net Sales for Products with respect to a Collaboration Target exceed $1.0 billion After Vertex has exercised an Exclusive License option, Vertex will be solely responsible for all research, development, manufacturing, and commercialization of licensed agents and products for the relevant target. As the Company’s involvement in this process is limited to observer status, management determined that milestones are not considered substantive because they do not relate solely to the past performance of the Company. Upon the achievement of a milestone, management will evaluate whether the triggering event occurs during or after the research term. If the triggering event occurs during the research term, management has elected to treat the milestone similar to an up-front payment. In these cases, if and when any of these milestones are received, the amount will be included in the overall arrangement consideration and allocated to the remaining identified deliverables. To the extent all deliverables have been satisfied, any additional consideration allocated to them could be immediately recognized. If the triggering event occurs after the research term, the Company will recognize the associated revenue in the period in which the event occurs. The Company will recognize royalty revenue in the period of sale of the related product(s), based on the underlying contract terms, provided that the reported sales are reliably measurable and the Company has no remaining performance obligations, assuming all other revenue recognition criteria are met. During the year ended December 31, 2016, 2015, and 2014, the Company recognized $4.0 million, $0.2 million, and $0 million of revenue with respect to the collaboration with Vertex. Research and development expense incurred by the Company in relation to its performance under the collaboration agreement for the years ended December 31, 2016 and 2015 was $7.0 million and $0.3 million, respectively. As of December 31, 2016 and 2015, there is $77.1 million and $75.1 million of non-current deferred revenue related to the Company’s collaboration with Vertex, respectively. Joint Venture with Bayer Healthcare LLC On December 19, 2015, the Company entered into an agreement to establish a joint venture (“Bayer Joint Venture”) to research the development of new therapeutics to cure blood disorders, blindness, and congenital heart disease. On February 12, 2016, the Company and Bayer completed the formation of the joint venture entity, Casebia, a limited liability partnership formed in the United Kingdom. Bayer and the Company each received a 50% equity interest in the entity in exchange for their contributions to the entity. The Company contributed $0.1 million in cash and licensed its proprietary CRISPR/Cas9 gene editing technology and intellectual property for selected disease indications. Bayer contributed its protein engineering expertise and relevant disease know-how. Bayer will provide up to $300.0 million in research and development funding to Casebia over the first five years, subject to certain conditions, of which the first $45.0 million was contributed upon formation in the first quarter of 2016. Under the joint venture agreement, the Company has no obligation to provide any additional funding and the Company’s ownership interest will not be diluted from future contributions from Bayer. The activities of Casebia are controlled by a management board under the joint control of the Company and Bayer. As Casebia is jointly controlled by the Company and Bayer, the Company accounts for its 50% interest using the equity method of accounting. Under the agreement, Casebia will pay the Company up to $35.0 million in exchange for a worldwide, exclusive license to commercialize the Company’s CRISPR/Cas9 technology specifically for the indications designated by Casebia. In March 2016, the Company received a non-refundable up-front payment of $20.0 million as a technology access fee. The remaining $15.0 million was paid on December 22, 2016 following delivery of the necessary consents from patent holders of the Company’s intellectual property. There are no milestone, royalties or other payments due to the Company under this aspect of the agreement. The Company determined that the contribution of the CRISRP/Cas9 technology by license to Casebia did not meet the definition of a business under ASC 805. The Company will also provide to Casebia compensated research and development services through a separate agreement. Concurrent with the execution of the Bayer Joint Venture agreement, the Company also entered into the Bayer Convertible Loan for $35.0 million. As the Bayer Joint Venture (including the CRISPR/Cas9 technology license and the research and development services) and the Bayer Convertible Loan were executed at the same time, the Company determined that they should be evaluated as one multiple-element arrangement. Additionally, the Company also determined that ASC 845, Nonmonetary Transactions The Company allocated the fair value of the consideration received using a relative fair value allocation. The allocable arrangement consideration included (i) the total cash payment by Casebia for the technology access fee, net of the Company’s $0.1 million contribution, of $34.9 million, (ii) the fair value of the equity interest in the Joint Venture of $36.4 million, (iii) the $35.0 million received from the issuance of the Convertible Debt, and (iv) $6.3 million of estimated cash consideration to be received under the research and development service arrangement, accumulating to $112.6 million. The Company identified the following elements under the transaction: (i) Combined element of an exclusive, worldwide, royalty free, license to the CRISPR/Cas9 technology specifically for the indications designated by Casebia, and delivery of the consents of the assignors of the underlying patents to the technology to develop, manufacture, and commercialize licensed products under that license (ii) Research and development services, and (iii) The issuance of the Bayer Convertible Loan. The Company determined the fair value of the license was $71.4 million based on the consideration paid and the fair value of the 50% interest in Casebia, which was determined utilizing discounted cash flows based on reasonable estimates and assumptions of cash flows expected from Casebia. The fair value of the separate research and development services was determined to be $6.3 million. The fair value of the Bayer Convertible Loan was determined to be $24.5 million, based on the fair value of the underlying preferred shares that were exchanged as part of the immediate conversion. Using a relative fair value allocation, the Company allocated the aggregate arrangement consideration paid as follows: (i) $63.6 million was allocated to the license and patent holder consent combined element (ii) $0.6 million was allocated to the future research and development services (iii) $27.0 million was allocated to the Bayer Convertible Loan The difference between combined above amounts of $91.2 million and the total allocable arrangement consideration of $112.6 million is due to allocable arrangement consideration associated with the $6.3 million of estimated cash consideration to be received under the research and development service arrangement and the remaining $15.0 million of the license fee paid upon the delivery of the consent from the patent holders of the Company’s intellectual property. Following delivery of the patent holders’ consent, which occurred on December 17, 2016, the combined amount attributed to the license and patent holder consent element and the remaining $15.0 million license fee, which amount to $78.6 million, was recognized as other income for the year ended December 31, 2016. The Company had determined that the license and patent holder consent combined element did not meet the definition of revenue because the licensing of its technology in connection with the formation of a joint venture is not part of the Company’s major ongoing or central operations. As the amount allocated to the Bayer Convertible Loan represents an $8.0 million discount to its $35.0 million face value, the Company recognized interest expense during the twelve months ended December 31, 2016 equal to the discount. The Convertible Loan automatically converted into Series B preferred shares on its January 29, 2016 maturity date. During 2016, the Company recorded an equity method investment of $36.5 million equal to the fair value of the Company’s interest in Casebia (which was included in the allocable arrangement consideration described above). Following delivery of the patent holders consent element and realization of the described gain allocated to the license and patent holder consent combined element, the Company recorded unrealized equity method losses up to the remaining amount of the $36.5 million investment. During the year ended December 31, 2016, the Company recognized $1.2 million, of revenue with respect to the collaboration with Casebia. Research and development expense incurred by the Company in relation to its performance under the agreement for the year ended December 31, 2016 was $1.2 million. As of December 31, 2016, there is $0.5 million of non-current deferred revenue related to the Company’s collaboration with Casebia, respectively. Unrecognized equity method losses in excess of the Company’s investment in Casebia totaled $4.0 million as of and for the year ended December 31, 2016. During 2016, the Company recorded $0.2 million of stock-based compensation expense related to Casebia employees. Total operating expenses, and net loss of Casebia for the twelve months ended December 31, 2016 was $80.8 million, which included research and development expenses equal to $77.4 million for the fair value of the CRISPR license acquired. Subscription Agreement with Bayer Global Investments B.V. On December 19, 2015, the Company entered into a subscription agreement, (“Subscription Agreement”), with Bayer BV. Pursuant to the Subscription Agreement, Bayer BV was given the option, at its election, to purchase $35.0 million of the Company’s Common Shares in a private placement concurrent with the Company’s IPO at a per share price equal to the public offering price, see Note 16 for further details.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Shares	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Redeemable Convertible Preferred Shares	10. Redeemable Convertible Preferred Shares Upon the closing of the Company’s IPO on October 24, 2016, all outstanding Preferred Shares of the Company were automatically converted into 27,135,884 Common Shares on a one-for-one basis. As of December 31, 2016, the Company had no Preferred Stock authorized, issued, or outstanding. As of December 31, 2015, the Company had 18,837,024 registered Preferred Shares issued and outstanding in share capital, which was comprised of (i) 440,001 Series A-1 Preferred Shares CHF 0.03 par value per share; (ii) 3,120,001 Series A-2 Preferred Shares, CHF 0.03 par value per share; (iii) 10,758,006 Series A-3 Preferred Shares, CHF 0.03 par value per share; and, (iv) 4,519,016 Series B Preferred Shares, CHF 0.03 par value per share, (collectively, the “Preferred Shares”) . The Company’s redeemable convertible preferred shares were classified as temporary or mezzanine equity on the accompanying consolidated balance sheets in accordance with authoritative guidance for the classification and measurement of redeemable securities as the Preferred Shares are contingently redeemable at the option of the holders. In October 2013, the Company issued 440,001 Series A-1 Preferred Shares for CHF 1.14 ($1.28) per share, resulting in gross proceeds of CHF 0.5 million ($0.6 million). Under the terms of the Series A-1 Preferred Shares Investment Agreement, the holders had the right to purchase an additional 1,315,790 Series A-1 Preferred Shares at CHF 1.14 ($1.28) per share (the “Series A-1 Tranche Rights”) contingent upon two or more shareholders holding Series A-1 Preferred Shares. These rights were not legally detachable. The Series A-1 Tranche Rights were evaluated under ASC 480 and ASC 815 and it was determined that they did not meet the requirements for separate accounting from the initial issuance of Series A-1 Preferred Shares. In connection with the issuance of the Series A-1 Preferred Shares, the Company also issued 335,000 Common Shares to the Series A Preferred Shares investors. The Company recorded the difference of $0.1 million between the fair value of the Common Shares issued and the price paid by the investors as an issuance cost discount to the Series A-1 Preferred Shares upon issuance. In April 2014, the Company issued 3,120,001 Series A-2 Preferred Shares in exchange for CHF 3.05 ($3.47) per share of such amount CHF 1.45 ($1.65) per share was received upon issuance resulting in gross proceeds of CHF 4.5 million ($5.1 million) and the balance of CHF 1.60 ($1.82) per share was called in February 2015 by the Board of Directors of the Company resulting in additional gross proceeds of CHF 5.0 million ($5.3 million). In connection with the issuance of the Series A-2 Preferred Shares, the Series A-1 Tranche Rights were terminated without exercise in April 2014. The Company’s policy requires the evaluation of amendments to preferred shares qualitatively to determine whether they are considered a modification or extinguishment. Based on this approach, the amendment to the terms of the Series A-1 Preferred Shares was considered an extinguishment due to the significance of the modifications to the substantive contractual terms of the Series A-1 Preferred Shares. Accordingly, the Company recorded a loss of $0.7 million on the Series A-1 Preferred Shares within additional paid-in capital equal to the difference between the fair value of the Series A-1 Preferred Shares of $1.2 million and the carrying amount of the Series A-1 Preferred Shares of $0.4 million upon extinguishment. The loss on extinguishment is reflected in the calculation of net loss available to common stockholders in accordance with FASB ASC Topic 260, Earnings per Share In April 2015, the Company issued 10,758,006 Series A-3 Preferred Shares in exchange for $4.24 per share whereby $2.12 per share was received upon issuance, resulting in gross proceeds of $22.8 million and the balance of $2.12 per share was due upon meeting certain milestones. As of December 31, 2015, none of the milestones had occurred and the Company had an outstanding subscription receivable of $22.8 million related to the Series A-3 Preferred Shares. In connection with the issuance of the Series A-3 Preferred Shares, the Company amended the dividend and conversion terms of the Series A-1 and Series A-2 Preferred Shares. The Company’s policy requires the evaluation of amendments to equity classified preferred shares qualitatively to determine whether they are considered a modification or extinguishment. Based on this approach, the amendment to the terms of the Series A-1 and A-2 Preferred Shares was considered a modification and as a result, there was no adjustment to the carrying value of the Series A-1 and A-2 Preferred Shares. The balance of the Series A-3 Preferred Share subscription receivable of $2.12 per share was called on May 5, 2016 by the Board of Directors and gross proceeds of $22.8 million were received by May 27, 2016. In May 2015, the Company issued 4,519,016 Series B Preferred Shares in exchange for CHF 6.20 ($6.74) per share resulting in gross proceeds of CHF 28.0 million ($30.5 million). In January 2016, the Company issued 5,464,608 Series B Preferred Shares upon conversion of $38.4 million of Vertex Convertible Loans plus accrued interest and $35.0 million of Bayer Convertible Loans at a conversion price of $13.43 per share. In June 2016, the Company issued 2,834,252 Series B Preferred Shares in exchange for $13.43 per share resulting in gross proceeds of $38.1 million.

Share Capital

Share Capital	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Share Capital	11. Share Capital The Company had 40,253,674 and 5,528,079 registered Common Shares as of December 31, 2016 and 2015, respectively, with a par value of CHF 0.03 per share. Conditional Capital Reserved for Future Issuance The Company had the following conditional capital reserved for future issuance: As of December 31, Type of Share Capital Conditional Capital 2016 2015 Common Shares Charpentier Call Option — 328,017 Common Shares Unvested unissued restricted stock 166,667 142,794 Common Shares Outstanding stock options 4,535,371 1,939,986 Common Shares Reserved for future issuance under stock option plans 5,290,643 33,567 Common Shares Shares available for bonds and similar debt instruments 4,919,700 — Common Shares Shares available for employee purchase plans 413,226 — Total 15,325,607 2,444,364 Common Share Issuances In October 2016, the Company completed an IPO whereby the Company sold 4,429,311 of its Common Shares, inclusive of 429,311 Common Shares sold by the Company pursuant to the partial exercise of an overallotment option granted to the underwriters in connection with the offering. Concurrent with the IPO, the Company issued and sold 2,500,000 Common Shares to Bayer BV, in a private placement. Additionally, the Company issued and subsequently reacquired the unexercised overallotment Common Shares of 170,689 at no cost, which are held in treasury. In March 2015, the Company entered into an agreement to acquire 82.1% of the ordinary share capital of TRACR in a share exchange transaction. In connection with this share exchange transaction, the Company issued 852,846 Common Shares to two founders of TRACR, 459,217 Common Shares to Fay Corp. and 656,031 restricted Common Shares to certain employee and non-employee advisors of TRACR. If the holders of any restricted common shares terminates the service relationship the unvested shares are subject to a right of repurchase at an escalating purchase price. If any of these holders of restricted Common Shares are terminated, in certain circumstances, the vested and unvested shares are subject to a right of repurchase at the shareholder’s original purchase price. The Company recorded equity-based compensation expense in April 2015 for the incremental value received by the holders in exchange for the vested TRACR shares as of the exchange date. The Company is also recognizing additional equity-based compensation expense for the exchange of TRACR restricted share awards which will continue to vest over a remaining term in the form of CRISPR restricted share awards. See Note 12 for further details of equity-based compensation related to this share exchange transaction. In April 2014, in conjunction with the sale of its Series A-2 Preferred Shares, the Company and its founders agreed to transfer 729,800 Founders’ Shares to several non-employees. The shares transferred were subject to service-based vesting conditions. If the holder of any restricted Common Shares terminates the service relationship, the unvested shares are subject to a right of repurchase at an escalating purchase price. Both vested and unvested shares are subject to a right of repurchase at the original purchase price upon certain triggering events such as termination for cause, material breach of agreement, and insolvency of the holder. In addition, the founders and an investor also agreed to transfer 1,192,585 fully vested Common Shares to Fay Corp. The Company recorded equity-based compensation expense for the Founders Shares and the Common Shares issued with vesting restrictions from the founders and Fay Corp. See Note 12 for further details of equity-based compensation related to these transfers. The Common Shares have the following characteristics: Voting Rights The holders of Common Shares are entitled to one vote for each Common Share held at all meetings of shareholders and written actions in lieu of meetings. Dividends The holders of Common Shares are entitled to receive dividends, if and when declared by the Board of Directors. As of December 31, 2016, no dividends have been declared or paid since the Company’s inception. Liquidation After payment to the holders of Preferred Shares of their liquidation preferences, the holders of the Common Shares are entitled to share ratably in the Company’s assets available for distribution to shareholders in the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or upon the occurrence of a deemed liquidation event.

Equity-based Compensation

Equity-based Compensation	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity-based Compensation	12. Equity-based Compensation Option and Grant Plans In July 2016, the shareholders approved the 2016 Share Option and Incentive Plan (the “2016 Plan”) and in April 2015, the shareholders approved the 2015 option and grant plan (the “2015 Plan” collectively the “Plans”). Subsequent to the IPO, no further options shall be granted under the 2015 Plan. The Plans provide for the issuance of equity awards in the form of restricted shares, options to purchase Common Shares which may constitute incentive stock options (“ISOs”) or non-statutory stock options (“NSOs”), unrestricted stock unit grants, and qualified performance-based awards to eligible employees, officers, directors, non-employee consultants, and other key personnel. Terms of the equity awards, including vesting requirements, are determined by the Board, subject to the provisions of the Plans. Options granted by the Company typically vest over four years and have a contractual life of ten years. During the years ended December 31, 2016, 2015 and 2014, the Company also issued outstanding Common Shares previously held by Founders and Fay Corp. to employees and non-employees as equity-based compensation (“Founder Awards”), which are subject to repurchase by the Company upon termination of the holder’s service relationship with the Company as well as upon certain triggering events such as termination for cause, material breach of agreement and insolvency of the holder that generally lapse over a requisite service period of four years. Equity-Based Compensation Expense The Company uses the straight-line attribution method to recognize stock-based compensation expense for stock options and restricted stock awards. Stock options and restricted stock generally vests over four years with 25% vesting on the first anniversary, and the remaining vesting monthly thereafter. The following table presents stock-based compensation expense in the Company’s Consolidated Statements of Operations: Year Ended December 31, 2016 2015 2014 Research and development $ 4,848 $ 1,924 $ 487 General and administrative 5,844 1,760 208 Loss from equity method investment 152 — — Total $ 10,844 $ 3,684 $ 695 Grant- Date Fair Value There were no stock options granted prior to 2015. The Company estimated the fair value of each employee and non-employee stock option award on the grant date using the Black-Scholes option-pricing model based on the following assumptions: Year Ended December 31 2016 2015 Employees: Options granted 2,411,240 1,913,319 Weighted - average exercise price $ 12.19 $ 2.32 Weighted-average grant date fair value $ 8.47 $ 3.11 Assumptions: Weighted-average expected volatility 81.0 % 76.4 % Expected term (in years) 6.0 6.0 Weighted-average risk free interest rate 1.4 % 1.7 % Expected dividend yield 0.0 % 0.0 % Non employees: Options granted 215,710 26,667 Weighted- average exercise price $ 19.54 $ 1.85 Weighted- average grant date fair value $ 17.38 $ 5.05 Assumptions: Weighted average expected volatility 88.2 % 84.1 % Expected term (in years) 10.0 10.0 Weighted-average risk free interest rate 2.4 % 2.2 % Expected dividend yield 0.0 % 0.0 % The fair value of the restricted stock awards was determined based on the fair value of Common Stock on the grant date. Non-employee stock options and restricted stock awards are marked-to-market at each reporting period. Share Based Payment Activity Stock Options The following table summarizes stock option activity for employees and non-employees during the year ended December 31, 2016 (intrinsic value in thousands): Stock Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2015 1,939,986 $ 2.31 9.7 $ 6,688 Granted 2,626,950 $ 12.79 Exercised (18,900 ) 1.81 $ 216 Cancelled or forfeited (12,665 ) 4.98 Outstanding at December 31, 2016 4,535,371 $ 8.38 9.1 $ 53,975 Exercisable at December 31, 2016 960,867 $ 3.24 8.8 $ 16,361 Vested or expected to vest at December 31, 2016 (1) 4,169,347 $ 8.23 9.1 $ 50,155 (1) This represents the number of vested stock options as of December 31, 2016 plus the unvested outstanding options at December 31, 2016 expected to vest in the future, adjusted for estimated forfeitures. The total unrecognized compensation cost for employee and non-employee stock options is adjusted for estimated forfeitures. As of December 31, 2016, the Company expects to recognize total unrecognized compensation cost related to stock options of $23.4 million over a remaining weighted-average period of 3.3 years. During 2016 and 2015, the Company granted options to purchase 123,333 and 261,389 Common Shares, respectively, subject to performance-based vesting conditions. As of December 31, 2016, options to purchase 262,538 Common Shares subject to performance-based vesting conditions were vested, as performance conditions were achieved, and options to purchase 12,500 Common Shares subject to performance-based vesting conditions were deemed probable of vesting. In addition, 686,665 options to purchase Common Shares, subject to service and performance-based vesting conditions, satisfied the performance conditions upon the Company’s IPO on October 18, 2016, and will continue to vest over their requisite service periods. Restricted Stock The following table summarizes restricted stock activity for employees and non-employees during the year ended December 31, 2016: Reflected as outstanding upon vesting Reflected as outstanding upon grant date Total Weighted- Average Grant Date Fair Value Unvested restricted Common Stock at December 31, 2015 142,794 1,485,244 1,628,038 $ 4.35 Vested (53,427 ) (834,388 ) (887,815 ) 4.78 Unvested restricted Common Stock at December 31, 2016 89,367 650,856 740,223 $ 3.84 During the years ended December 31, 2016 and 2015, the total fair value of restricted stock vested was $9.9 million, $2.3 million, respectively. At December 31, 2016, total unrecognized compensation expense related to unvested restricted stock was $7.2 million which the Company expects to recognize over a remaining weighted-average period of 1.4 years. During 2016 and 2015, the Company granted 0 and 50,000 restricted Common Shares, respectively, subject to performance-based vesting conditions. As of December 31, 2016 and 2015, 50,000 and 0 restricted Common Shares subject to performance-based vesting conditions were vested, respectively. As of December 31, 2015, there were 15,000 restricted Common Shares subject to performance-based vesting conditions deemed probable of vesting. During the year ended December 31, 2016, the Company and Fay Corp. transferred 290,400 Common Shares to a Founder, 268,093 of which are subject to vesting conditions with a weighted average grant date fair value of $12.65 per share. The unvested Common Shares are subject to repurchase by the Company upon termination of the holder’s service relationship with the Company as well as upon certain triggering events such as termination for cause, material breach of agreement and insolvency of the holder. The Company recognized expense related to the Common Shares transferred to the Founder of $2.6 million during the year ended December 31, 2016. As of December 31, 2016, Fay Corp. no longer held outstanding Common Shares of the Company.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
401(k) Savings Plan	13. 401(k) Savings Plan The Company established a defined‑contribution savings plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”) in November 2016. The 401(k) Plan covers all employees who meet defined minimum age and service requirements, and allows participants to defer a portion of their annual compensation on a pretax basis. The Company contributed $0.1 million to the 401(k) Plan for the year ended December 31, 2016.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes The Company is subject to U.S. federal and various state corporate income taxes as well as taxes in foreign jurisdictions for the foreign parent and where foreign subsidiaries have been established. For the years ended December 31, 2016, 2015 and 2014, the loss before provision for income taxes consist of the following (in thousands): Year ended December 31, 2016 2015 2014 Domestic $ 3,322 $ 593 $ — Foreign (26,040 ) (26,414 ) (6,863 ) Total $ (22,718 ) $ (25,821 ) $ (6,863 ) The provision for (benefit from) income taxes consist of the following (in thousands): Year ended December 31, 2016 2015 2014 Current income taxes: Federal $ (649 ) $ (23 ) $ — State 11 (12 ) — Foreign 17 (26 ) (11 ) Total current income taxes (621 ) (61 ) (11 ) Deferred income taxes: Federal 30 (37 ) — State 105 65 — Foreign 2 26 74 Total deferred income taxes 137 54 74 Total income tax (provision) benefit $ (484 ) $ (7 ) $ 63 A reconciliation of income tax expense computed at the statutory corporate income tax rate to the effective income tax rate for the years ended December 31, 2016, 2015 and 2014 is as follows: Year ended December 31, 2016 2015 2014 Income tax expense at statutory rate 10.3 % 10.3 % 10.3 % State income tax, net of federal benefit 1.3 % 0.1 % 0.0 % Nondeductible expenses 1.6 % 0.0 % 0.0 % Foreign rate differential (3.3 %) (1.4 %) 1.8 % Statutory to US GAAP permanent differences 6.6 % 0.0 % 0.0 % Stock-based compensation (4.9 %) (1.4 %) (1.1 %) Research credits 3.1 % 0.6 % 0.0 % Change in valuation allowance (16.8 %) (8.2 %) (10.1 %) Effective income tax rate (2.1 %) 0.0 % 0.9 % The federal statutory rate reflects the Switzerland mixed company service rate. Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. The significant components of the Company’s deferred tax assets are comprised of the following (in thousands): Year ended December 31, 2016 2015 Deferred tax assets: Net operating loss carryforwards $ 3,934 $ 2,600 Accruals and reserves 791 189 Deferred Rent 5,228 — Other deferred tax assets 7 72 Deferred revenue 2,525 406 Research credit 425 104 Total deferred tax assets 12,910 3,371 Less valuation allowance (6,770 ) (2,892 ) Net deferred tax assets 6,140 479 Deferred tax liabilities: Depreciation (5,909 ) (321 ) Intangible assets (68 ) (80 ) Other deferred tax liabilities — (53 ) Total deferred tax liabilities (5,977 ) (454 ) Long term deferred taxes $ 163 $ 25 The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets. Based on the Company’s history of operating losses in its non-U.S. jurisdictions, the Company has concluded that it is more-likely-than-not that the benefit of its non-U.S. deferred tax assets will not be realized. Accordingly, the Company has provided a full valuation allowance against its net deferred tax assets in Switzerland, and in the UK for its TRACR subsidiary, as of December 31, 2016 and 2015. The valuation allowance increased by $3.9 million during 2016, which is primarily attributable to losses in Switzerland. Additionally, the Company has established a valuation allowance for certain U.S. deferred tax assets. As of December 31, 2016, the Company had available non-U.S. net operating loss carryforwards of $41.7 million which begin to expire in 2020. As of December 31, 2016, the Company has U.S. domestic state research and development credit carryforwards of $0.2 million which begin to expire in 2031. As of December 31, 2016, the Company has U.S. domestic federal research and development credit carryforwards of $0.3 million which expire in 2036. ASC 740 clarifies the accounting for uncertainty in income taxes recognized in an enterprise’s financial statement by prescribing the minimum recognition threshold and measurement of a tax position taken or expected to be taken in a tax return. As of December 31, 2016 the Company had gross unrecognized tax benefits of $0.2 million of which $0.1 million would favorably impact the effective tax rate if recognized. The Company will recognize interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2016, 2015 and 2014, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s consolidated statements of operations and comprehensive loss. The aggregate changes in gross unrecognized tax benefits was as follows (in thousands): Year ended December 31, 2016 2015 2014 Balance at beginning of year $ 49 $ — $ — Increases for tax positions taken during current period 134 49 — Increases for tax positions taken in prior periods — — — Decreases for tax positions taken during current period — — — Decreases for tax positions taken in prior periods (20 ) — — Balance at end of year $ 163 $ 49 $ — The Company files income tax returns in the U.S. federal jurisdiction, Massachusetts, and certain non-U.S. jurisdictions. The Company is subject to U.S. federal, Massachusetts, and non-U.S. income tax examinations by authorities for all tax years.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	15. Selected Quarterly Financial Data (Unaudited) Prior to its IPO on October 18, 2016, the Company had outstanding participating Preferred Shares. During the fourth quarter of the year ended December 31, 2016, the Company had net income, although for the full year the Company had a net loss. Accordingly, the Company used the two-class method to calculate net income per share for the fourth quarter of 2016. For purposes of calculating basic net income per share for the fourth quarter of 2016, the Company excluded from the numerator $3.1 million of net income attributable to participating securities. The Company calculated diluted net income per share under both the if-converted method and the two-class method and concluded that the two-class method was more dilutive than the if-converted method. Accordingly, the two-class income allocations were reapplied after taking into account the dilutive effect of non-participating securities. This resulted in net income of $3.1 million being allocated to the participating securities and excluded from the numerator of the Common Stock dilutive net income per share calculation. 2016 First Quarter Second Quarter Third Quarter Fourth Quarter (1) Collaboration revenue $ 476 $ 795 $ 1,549 $ 2,344 Total operating expenses 12,128 17,353 16,159 27,654 Loss from operations (11,652 ) (16,558 ) (14,610 ) (25,310 ) Net (loss) income (8,442 ) (17,164 ) (14,694 ) 17,098 Net (loss) income attributable to common shareholders (8,439 ) (17,157 ) (14,680 ) 17,099 Net (loss) income per share attributable to common shareholders: Basic $ (1.53 ) $ (3.15 ) $ (2.77 ) $ 0.43 Diluted $ (1.53 ) $ (3.15 ) $ (2.77 ) $ 0.40 Weighted-average common shares outstanding used in net (loss) income per share attributable to common shareholders: Basic 5,528,079 5,448,855 5,292,348 32,987,335 Diluted 5,528,079 5,448,855 5,292,348 34,989,218 2015 First Quarter Second Quarter Third Quarter Fourth Quarter Collaboration revenue $ — $ — $ — $ 247 Total operating expenses 3,736 3,625 6,202 12,413 Loss from operations (3,736 ) (3,625 ) (6,202 ) (12,166 ) Net loss (3,522 ) (3,666 ) (6,354 ) (12,286 ) Net loss attributable to common shareholders $ (3,237 ) $ (3,643 ) $ (6,353 ) $ (12,270 ) Net loss per share applicable to common shareholders- basic and diluted $ (0.91 ) $ (0.80 ) $ (1.15 ) $ (2.22 ) Weighted-average common shares outstanding used in net loss per share attributable to common shareholders - basic and diluted 3,560,000 4,538,595 5,528,079 5,528,079 (1) During the fourth quarter the Company recorded an immaterial correction of an error of $1.2 million for rent expense related to the three months ended September 30, 2016. The Company determined that these errors are not material to the respective interim financial statements.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Related Party Transactions	16. Related Party Transactions We had the following transactions with related parties during the period: In connection with the Series A-3 Preferred Share financing, the Company paid $0.2 million on behalf of investors for legal and consulting costs incurred for the preparation and completion of the transaction. The Company is a party to intellectual property license agreements with Dr. Charpentier. In addition, Dr. Charpentier is a consultant to the Company. For the year ended December 31, 2016 and 2015, the Company paid Dr. Charpentier a total of $1.0 million and $34 thousand, respectively, in consulting, licensing and other fees. As of December 31, 2016 and 2015, the Company owed Dr. Charpentier approximately $0.5 million, and $1.0 million, respectively, of additional fees primarily related to the Vertex Collaboration Agreement and Bayer Joint Venture Agreement. During the year ended December 31, 2016, the Company formed a joint venture with Bayer. As a part of the agreement to form the joint venture, the Company also issued a $35.0 million convertible loan to Bayer, which converted into Series B preferred stock and ultimately common stock upon the IPO. Bayer also purchased 2,500,000 common shares through a private placement of $35 million during 2016. During the year ended December 31, 2016 and 2015, the Company recognized $1.2 million and $0 million, respectively, related to the performance of R&D services for Casebia, the Company’s joint venture with Bayer. See Note 9 for further detail.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	17. Subsequent Events Under the Charpentier license agreement, the Company licenses a U.S. patent application that is currently subject to interference proceedings declared by the PTAB of the U.S. Patent and Trademark Office. Following motions by the parties and other procedural matters, the PTAB concluded in February 2017 that the declared interference should be dismissed because the claim sets of the two parties were not directed to the same patentable invention in accordance with the PTAB’s two-way test for patent interferences.

Summary of Significant Accoun26

Summary of Significant Accounting Policies and Basis of Presentation (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”), and include the accounts of (i) the Company, (ii) its wholly-owned subsidiaries, CRISPR Ltd., CRISPR Inc., and TRACR, as of December 31, 2016. All intercompany accounts and transactions have been eliminated. Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) of the Financial Accounting Standards Board (“FASB”). Investments in partnerships where the Company has significant influence because it has a voting interest of 20% to 50%, are accounted for under the equity method. Results of associated companies are presented on a one-line basis. The Company accounts for its 50% investment share of Casebia Therapeutics LLP (“Casebia”) under the equity method of accounting. See Note 9 for further details. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, equity-based compensation expense, revenue recognition, equity method investments, and reported amounts of expenses during the reported period. Significant estimates in these consolidated financial statements have been made in connection with the calculation of revenues, research and development expenses, valuation of equity method of investment, equity-based compensation expense, fair value of Common Shares, fair value of intangible assets, and the provision for or benefit from income taxes. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. The Company utilizes significant estimates and assumptions in determining the fair value of its Common Shares. The Company utilized various valuation methodologies in accordance with the framework of the 2004 and 2013 American Institute of Certified Public Accountants Technical Practice Aids, Valuation of Privately- Held Company Equity Securities Issued as Compensation
Reclassifications	Reclassifications A change has been made to the presentation of deferred rent non-current as of December 31, 2015 to conform to the current year presentation.
Stock Split	Stock Split In connection with preparing for its IPO, the Company’s board of directors and shareholders approved an amendment to the Company’s articles of association in July 2016. This amendment became effective upon registration in the Switzerland commercial register on July 27, 2016 and publication in the Swiss Official Gazette of Commerce on August 2, 2016. Pursuant to this amendment a 3 1 3
Segment Information	Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company and the Company’s chief operating decision maker, namely, the chief executive officer, view the Company’s operations and manage its business in one operating segment, which is the business of discovering, developing and commercializing therapies derived from or incorporating genome-editing technology.
Foreign Currency Translation and Transactions	Foreign Currency Translation and Transactions The Company’s reporting currency is the U.S. Dollar. The Company‘s consolidated entities have the U.S. dollar as their functional currency with the exception of CRISPR Ltd. which has the British Pound Sterling (“GBP”) as its functional currency. CRISPR Ltd. has assets and liabilities translated into U.S. dollars at exchange rates in effect at the end of the year. Revenue and expenses are translated using the average exchange rates for the period. Net unrealized gains and losses resulting from foreign currency translation are included in accumulated other comprehensive income (loss), which is a separate component of shareholders’ (deficit) equity. Net foreign currency exchange transaction gains and losses resulting from the remeasurement of transactions denominated in currencies other than functional currency are included in other (expense) income, net in the consolidated statements of operations and comprehensive loss.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of 90 days or less from the purchase date to be cash equivalents. As of December 31, 2016, and 2015, the Company had $315.5 million and $156.0 million in cash equivalents, respectively. All cash was held in depository accounts and is reported at fair value.
Accounts Receivable	Accounts Receivable Accounts receivable of $3.2 million at December 31, 2016 consist of receivables from Vertex Pharmaceuticals, Incorporated (“Vertex”) and Casebia. As of December 31, 2015, the Company had accounts receivable of $0.3 million consisting of receivables from Vertex. Accounts receivables are recorded at invoiced amounts due under both the Vertex and Casebia collaboration agreements (see Note 9). Vertex and Casebia are creditworthy entities that maintain an ongoing relationship with the Company, as such the Company did not have an allowance for estimated losses recorded related to these receivables.
Concentrations of Credit Risk and Off-balance Sheet Risk	Concentrations of Credit Risk and Off-balance Sheet Risk Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash. The Company’s cash is held in accounts with financial institutions that management believes are creditworthy. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no financial instruments with off-balance sheet risk of loss.
Deferred Public Offering Costs	Deferred Public Offering Costs Deferred public offering costs, which primarily consist of direct, incremental legal and accounting fees relating to the IPO, were capitalized within other non-current assets prior to our IPO. The issuance costs of $8.3 million, including underwriter’s commissions, were offset against the IPO proceeds upon the consummation of the offering in October 2016.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial instruments consist of accounts payable, accrued expenses and other non-current liabilities. The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820, Fair Value Measurement and Disclosures The accounting standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, which are the following: Level 1 — Quoted prices in active markets that are accessible at the market date for identical unrestricted assets or liabilities. Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs for which all significant inputs are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amount of accounts receivable, accounts payable, and accrued expenses as reported on the consolidated balance sheets as of December 31, 2016 and 2015, approximate fair value, due to the short-term duration of these instruments. The fair value of the Company’s equity method investment in Casebia and convertible debt instruments were determined using level 3 inputs (See Note 9).
Property and Equipment	Property and Equipment Property and equipment is stated at cost, less accumulated depreciation. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred. Upon disposal, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in the results of operations. Depreciation is recorded using the straight-line method over the estimated useful lives of the respective assets, which are as follows: Asset Estimated useful life Computer equipment and software 3 years Furniture, fixtures, and other 5 years Laboratory equipment 5 years Leasehold improvements Shorter of useful life or remaining lease term
Impairment of Long-lived Assets	Impairment of Long-lived Assets The Company evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book value of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value. The Company has not recognized any impairment losses in the years ended December 31, 2016, 2015, and 2014.
Revenue Recognition	Revenue Recognition To date, the Company’s only source of revenue has been the collaboration and license agreement with Vertex as well as research and development services provided to Casebia under the joint venture with Bayer HealthCare LLC (“Bayer”) (see Note 9). The Company recognizes revenue in accordance with ASC Topic 605, Revenue Recognition • Persuasive evidence of an arrangement exists; • Delivery has occurred or services have been rendered; • The seller’s price to the buyer is fixed or determinable; and • Collectability is reasonably assured. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified in current liabilities. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue within non-current liabilities. The Company evaluates multiple-element arrangements based on the guidance in FASB ASC Topic 605-25, Revenue Recognition—Multiple-Element Arrangements The consideration received under the arrangement that is fixed or determinable is then allocated among the separate units of accounting based on the relative selling prices of the separate units of accounting. The Company determines the selling price of a unit of accounting within each arrangement following the hierarchy of evidence prescribed by ASC 605-25. Accordingly, the Company determines the estimated selling price for units of accounting within each arrangement using vendor-specific objective evidence (“VSOE”) of selling price, if available; third-party evidence (“TPE”) of selling price if VSOE is not available; or best estimate of selling price (“BESP”) if neither VSOE nor TPE is available. The Company typically uses BESP to estimate the selling price as it generally does not have VSOE or TPE of selling price for its units of accounting. Determining the BESP for a unit of accounting requires significant judgment. In developing the BESP for a unit of accounting, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. The Company periodically validates the BESP used for units of accounting by evaluating whether changes in the key assumptions used to determine the BESP will have a significant effect on the allocation of arrangement consideration between multiple units of accounting. The Company recognizes arrangement consideration allocated to each unit of accounting when all of the following criteria are met for that particular unit of accounting: persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the seller’s price to the buyer is fixed or determinable, and collectability is reasonably assured. In the event that a deliverable does not represent a separate unit of accounting, the Company recognizes revenue from the combined unit of accounting over the contractual or estimated performance period for the undelivered items, which is typically the term of the Company’s research and development obligations. If there is no discernible pattern of performance or objectively measurable performance measures do not exist, then the Company recognizes revenue under the arrangement on a straight-line basis over the period the Company is expected to complete its performance obligations. Conversely, if the pattern of performance over which the service is provided to the customer can be determined and objectively measurable performance measures exist, then the Company recognizes revenue under the arrangement using the proportional performance method. Revenue recognized is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the straight-line method or proportional performance method, as applicable, as of the period ending date. Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company expects to complete its performance obligations under an arrangement. Steering committee services that are not inconsequential or perfunctory and that are determined to be performance obligations are combined with other research services or performance obligations required under an arrangement, if any, in determining the level of effort required in an arrangement and the period over which the Company expects to complete its aggregate performance obligations. At the inception of an arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether: (i) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item as a result of a specific outcome resulting from the Company’s performance to achieve the milestone, (ii) the consideration relates solely to past performance, and (iii) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the particular milestone and the level of effort and investment required to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether a milestone satisfies all of the criteria required to conclude that a milestone is substantive. The Company will recognize revenue in its entirety upon successful accomplishment of any substantive milestones, assuming all other revenue recognition criteria are met. Milestones that are not considered substantive are recognized as earned if there are no remaining performance obligations or over the remaining period of performance, with a cumulative catch-up being recognized for the elapsed portion of the period of performance, assuming all other revenue recognition criteria are met. The Company will recognize royalty revenue in the period of sale of the related product(s), based on the underlying contract terms, provided that the reported sales are reliably measurable and the Company has no remaining performance obligations, assuming all other revenue recognition criteria are met.
Research and Development Expenses	Research and Development Expenses Research and development costs, which include employee compensation costs, facilities, lab supplies and materials, overhead, preclinical development, and other related costs, are charged to expense as incurred. Research and development costs also include the costs the Company incurs in its performance of services or provision of materials in connection with the funded research undertaken as a part of the Company’s collaborative agreement with Vertex and Casebia. See Note 9 for further details.
Operating Leases	Operating Leases The Company leases office and laboratory facilities under a non-cancelable operating lease agreements. The lease agreements contain free or escalating rent payment provisions. The Company recognizes rent expense under such leases on a straight-line basis over the term of the lease with the difference between the expense and the payments recorded as deferred rent on the consolidated balance sheets. Lease renewal periods are considered on a lease-by-lease basis in determining the lease term. Funding of leasehold improvements by the Company’s landlord are accounted for as a tenant improvement allowance and are amortized as a reduction of rent expense over the term of the lease. Leasehold improvements are amortized straight-line over the shorter of the useful life or the remaining lease term.
Equity-Based Compensation Expense	Equity Based Compensation Expense The Company recognizes equity-based compensation expense for awards of equity instruments to employees and non-employee directors based on the grant date fair value of those awards in accordance with FASB ASC Topic 718, Stock Compensation The Company accounts for stock options issued to non-employees under FASB ASC Topic 505-50, Equity Based Payments to Non-Employees The Black-Scholes option pricing model requires the input of certain subjective assumptions, including (i) the expected share price volatility, (ii) the calculation of expected term of the award, (iii) the risk-free interest rate and (iv) the expected dividend yield. Due to the lack of a public market for the trading of the Company’s Common Shares prior to its IPO and a lack of company-specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. The historical volatility is calculated based on a period of time commensurate with the expected term assumption. The group of representative companies have characteristics similar to the Company, including stage of product development and focus on the life science industry. The Company uses the simplified method, which is the average of the final vesting tranche date and the contractual term, to calculate the expected term for options granted to employees as it does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. For options granted to non-employees, the Company utilizes the contractual term of the arrangement as the basis for the expected term assumption. The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected term of the stock options. The Company uses an assumed dividend yield of zero as the Company has never paid dividends and has no current plans to pay any dividends on its Common Shares. The Company expenses the fair value of its equity-based compensation awards granted to employees on a straight-line basis over the associated service period, which is generally the period in which the related services are received. The Company measures equity-based compensation awards granted to non-employees at fair value as the awards vest and recognizes the resulting value as compensation expense at each financial reporting period. The Company records the expense for equity-based compensation awards subject to performance-based milestone vesting over the remaining service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions as of the reporting date.
Patent Costs	Patent Costs Costs to secure and prosecute patent application and other legal costs related to the protection of the Company’s intellectual property are expensed as incurred, and are classified as general and administrative expenses in the Company’s consolidated statements of operations.
Income Taxes	Income Taxes Income taxes are recorded in accordance with FASB ASC Topic 740, Income Taxes The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2016 and 2015, the Company does not have any significant uncertain tax positions. The Company’s practice is to recognize interest and/or penalties related to income tax matters in income tax expense. See Note 14 for further details.
Comprehensive Loss	Comprehensive Loss Comprehensive loss consists of net income or loss and changes in equity during the period from transactions and other events and circumstances generated from non-owner sources. The Company’s net loss equals comprehensive loss, net of any changes in the foreign currency translation adjustment, for all periods presented. In addition, comprehensive loss attributable to the noncontrolling interest equals net loss for all periods presented.
Variable Interest Entities	Variable Interest Entities The Company reviews each legal entity formed by parties related to the Company to determine whether or not the Company has a variable interest in the entity and whether or not the entity would meet the definition of a VIE in accordance with FASB ASC Topic 810, Consolidation If the Company determines it is the primary beneficiary of a VIE that meets the definition of a business, the Company measures the assets, liabilities and noncontrolling interests of the newly consolidated entity at fair value in accordance with FASB ASC Topic 805, Business Combinations In February 2016, Casebia Therapeutics LLP, a limited liability partnership, was formed in the United Kingdom. In March 2016 upon consummation of the JV, Bayer and the Company each received a 50% equity interest in the entity in exchange for their contributions to the entity. The Company determined that Casebia was considered a VIE and concluded that it is not the primary beneficiary of the VIE. As such, the Company did not consolidate Casebia’s results into the consolidated financial statements. See Note 4 for further details. As of December 31, 2016, TRACR is a wholly-owned subsidiary of the Company. See Note 4 for further details. For the year ended December 31, 2015, the Company consolidated the financial statements of TRACR into the Company’s consolidated financial statements as it was both a VIE and a majority owned subsidiary. For the year ended December 31, 2014, the Company consolidated TRACR as a VIE.
Noncontrolling Interest	Noncontrolling Interest Upon the IPO date of the Company, the non-controlling interest of TRACR was acquired, and as of the year ended December 31, 2016 TRACR is a wholly-owned subsidiary of the Company. See Note 4 for further details related to TRACR. The Company recorded non-controlling interest, which was related to TRACR during 2015 and 2016. The Company recorded net loss attributable to non-controlling interest on its consolidated statements of operations, reflecting the loss from non-controlling interest for the reporting period.
Intangible Assets	Intangible Assets The Company’s intangible assets consist of acquired intellectual property rights and relate to the Company’s interest in TRACR. Intangible assets are recorded at fair value at the date of the business combination and are stated in the consolidated balance sheets net of accumulated amortization and impairments, if applicable. The Company evaluates the remaining useful life of intangible assets subject to amortization on a periodic basis to determine whether events and circumstances would indicate impairment or warrant a revision to the remaining useful life. If the estimate of an intangible asset’s remaining useful life is changed, the Company amortizes the remaining carrying value of the intangible asset prospectively over the revised remaining useful life. Intangible assets related to the acquired intellectual property rights are amortized over their estimated useful lives using the straight-line method as the pattern of revenues cannot be reasonably estimated. Amortization related to the acquired intellectual property rights is recorded in general and administrative expense in the consolidated statements of operations and comprehensive loss.
Net Loss Per Share Attributable to Common Shareholders	Net Loss Per Share Attributable to Common Shareholders Basic net income (loss) per share is calculated by dividing net income (loss) attributable to common shareholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is calculated by dividing the net income attributable to common shareholders by the weighted-average number of common equivalent shares outstanding for the period, including any dilutive effect from outstanding stock options and warrants using the treasury stock method. The Company follows the two-class method when computing net income per share in periods when participating securities are outstanding. The two-class method determines net income per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common shareholders for the period to be allocated between common and participating securities based on their respective rights to receive dividends as if all income for the period had been distributed. Accordingly, in periods in which the Company reports a net loss attributable to common shareholders when participating securities are outstanding, losses are not allocated to the participating securities because they have no contractual obligation to share in the losses of the Company. For purposes of calculating diluted net income per share attributable to redeemable preferred shares, convertible loans, stock options, and unvested restricted common shares are considered common share equivalents. The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to do so would be anti-dilutive (in common stock equivalent shares): As of December 31, 2016 2015 2014 Convertible preferred shares — 18,837,024 3,560,002 Conversion of convertible loans — 4,110,987 — Dr. Emmanuelle Charpentier call option — 328,017 — Outstanding options 4,535,371 1,939,986 — Unvested unissued restricted shares 89,367 142,794 — Total 4,624,738 25,358,808 3,560,002
Subsequent Events	Subsequent Events The Company considered the events or transactions occurring after the balance sheet date, but prior to the issuance of the consolidated financial statements, for potential recognition or disclosure in its consolidated financial statements. All significant subsequent events have been properly disclosed in the consolidated financial statements.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers The Revenue ASUs provide an accounting standard for a single comprehensive model for use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance. The accounting standard is effective for interim and annual periods beginning after December 15, 2017, with an option to early adopt for interim and annual periods beginning after December 15, 2016. The guidance permits two methods of adoption: retrospectively to each prior reporting period presented (the full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). We currently anticipate adoption of the new standard effective January 1, 2018 under the full retrospective method. The Company is in the process of determining the impact of the Revenue ASUs on its financial statements. In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements—Going Concern In February 2016, the FASB issued ASU No. 2016-02, Leases In March 2016, the FASB issued ASU No. 2016-09, Compensation— Stock Compensation (Topic 718) In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash

Summary of Significant Accoun27

Summary of Significant Accounting Policies and Basis of Presentation (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Schedule of Estimated Useful Lives of Assets	Depreciation is recorded using the straight-line method over the estimated useful lives of the respective assets, which are as follows: Asset Estimated useful life Computer equipment and software 3 years Furniture, fixtures, and other 5 years Laboratory equipment 5 years Leasehold improvements Shorter of useful life or remaining lease term
Schedule of Antidilutive Securities Excluded from Calculation of Diluted Net Loss per Share	The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to do so would be anti-dilutive (in common stock equivalent shares): As of December 31, 2016 2015 2014 Convertible preferred shares — 18,837,024 3,560,002 Conversion of convertible loans — 4,110,987 — Dr. Emmanuelle Charpentier call option — 328,017 — Outstanding options 4,535,371 1,939,986 — Unvested unissued restricted shares 89,367 142,794 — Total 4,624,738 25,358,808 3,560,002

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Summary of Property and Equipment, net	Property and equipment, net, consists of the following (in thousands): As of December 31, 2016 2015 Computer equipment and software $ 110 $ 118 Furniture, fixtures, and other 2,044 238 Laboratory equipment 2,970 861 Leasehold improvements 15,780 88 Construction work in process 1,065 95 21,969 1,400 Accumulated Depreciation (942 ) (72 ) Property and equipment, net $ 21,027 $ 1,328

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets, Net of Accumulated Amortization	Intangible assets, net of accumulated amortization, are as follows (in thousands): Acquired intangible asset Cost Accumulated Amortization Net As of December 31, 2016 $ 547 $ (148 ) $ 399 As of December 31, 2015 $ 547 $ (93 ) $ 454
Schedule of Estimated Future Amortization of Acquired Intangible Assets	The estimated future amortization of acquired intangible assets as of December 31, 2016 is expected to be as follows (in thousands): Year Ending December 31: Amount 2017 $ 55 2018 55 2019 55 2020 55 Thereafter 179 Total amortization $ 399

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2016
Payables And Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued expenses consist of the following (in thousands): As of December 31, 2016 2015 Payroll and employee-related costs $ 2,585 $ 773 Research costs 996 910 Licensing fees 492 1,055 Professional fees 2,715 2,412 Intellectual property costs 3,372 2,592 Accrued property and equipment 5,081 — Other 1,079 688 Total $ 16,320 $ 8,430

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Summary of Future Minimum Payments Required under Leases	Future minimum payments required under the leases as of December 31, 2016, are as follows (in thousands): Year Ending December 31: Amount 2017 $ 6,685 2018 6,431 2019 6,624 2020 6,823 2021 7,027 Thereafter 30,335 Total minimum lease payments $ 63,925

Share Capital (Tables)

Share Capital (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Schedule of Conditional Capital Reserved for Future Issuance	The Company had the following conditional capital reserved for future issuance: As of December 31, Type of Share Capital Conditional Capital 2016 2015 Common Shares Charpentier Call Option — 328,017 Common Shares Unvested unissued restricted stock 166,667 142,794 Common Shares Outstanding stock options 4,535,371 1,939,986 Common Shares Reserved for future issuance under stock option plans 5,290,643 33,567 Common Shares Shares available for bonds and similar debt instruments 4,919,700 — Common Shares Shares available for employee purchase plans 413,226 — Total 15,325,607 2,444,364

Equity-based Compensation (Tabl

Equity-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Stock-Based Compensation Expense	The Company uses the straight-line attribution method to recognize stock-based compensation expense for stock options and restricted stock awards. Stock options and restricted stock generally vests over four years with 25% vesting on the first anniversary, and the remaining vesting monthly thereafter. The following table presents stock-based compensation expense in the Company’s Consolidated Statements of Operations: Year Ended December 31, 2016 2015 2014 Research and development $ 4,848 $ 1,924 $ 487 General and administrative 5,844 1,760 208 Loss from equity method investment 152 — — Total $ 10,844 $ 3,684 $ 695
Fair Value of Employee and Non-employee Stock Option Award on the Grant Date Using the Black-Scholes Option-Pricing Model	There were no stock options granted prior to 2015. The Company estimated the fair value of each employee and non-employee stock option award on the grant date using the Black-Scholes option-pricing model based on the following assumptions: Year Ended December 31 2016 2015 Employees: Options granted 2,411,240 1,913,319 Weighted - average exercise price $ 12.19 $ 2.32 Weighted-average grant date fair value $ 8.47 $ 3.11 Assumptions: Weighted-average expected volatility 81.0 % 76.4 % Expected term (in years) 6.0 6.0 Weighted-average risk free interest rate 1.4 % 1.7 % Expected dividend yield 0.0 % 0.0 % Non employees: Options granted 215,710 26,667 Weighted- average exercise price $ 19.54 $ 1.85 Weighted- average grant date fair value $ 17.38 $ 5.05 Assumptions: Weighted average expected volatility 88.2 % 84.1 % Expected term (in years) 10.0 10.0 Weighted-average risk free interest rate 2.4 % 2.2 % Expected dividend yield 0.0 % 0.0 %
Summary of Stock Option Activity for Employees and Non-employees	The following table summarizes stock option activity for employees and non-employees during the year ended December 31, 2016 (intrinsic value in thousands): Stock Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2015 1,939,986 $ 2.31 9.7 $ 6,688 Granted 2,626,950 $ 12.79 Exercised (18,900 ) 1.81 $ 216 Cancelled or forfeited (12,665 ) 4.98 Outstanding at December 31, 2016 4,535,371 $ 8.38 9.1 $ 53,975 Exercisable at December 31, 2016 960,867 $ 3.24 8.8 $ 16,361 Vested or expected to vest at December 31, 2016 (1) 4,169,347 $ 8.23 9.1 $ 50,155
Summary of the Company's Restricted Stock Activity	The following table summarizes restricted stock activity for employees and non-employees during the year ended December 31, 2016: Reflected as outstanding upon vesting Reflected as outstanding upon grant date Total Weighted- Average Grant Date Fair Value Unvested restricted Common Stock at December 31, 2015 142,794 1,485,244 1,628,038 $ 4.35 Vested (53,427 ) (834,388 ) (887,815 ) 4.78 Unvested restricted Common Stock at December 31, 2016 89,367 650,856 740,223 $ 3.84

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of Loss Before Provision for Income Taxes	The Company is subject to U.S. federal and various state corporate income taxes as well as taxes in foreign jurisdictions for the foreign parent and where foreign subsidiaries have been established. For the years ended December 31, 2016, 2015 and 2014, the loss before provision for income taxes consist of the following (in thousands): Year ended December 31, 2016 2015 2014 Domestic $ 3,322 $ 593 $ — Foreign (26,040 ) (26,414 ) (6,863 ) Total $ (22,718 ) $ (25,821 ) $ (6,863 )
Schedule of Provision for (Benefit from) Income Taxes	The provision for (benefit from) income taxes consist of the following (in thousands): Year ended December 31, 2016 2015 2014 Current income taxes: Federal $ (649 ) $ (23 ) $ — State 11 (12 ) — Foreign 17 (26 ) (11 ) Total current income taxes (621 ) (61 ) (11 ) Deferred income taxes: Federal 30 (37 ) — State 105 65 — Foreign 2 26 74 Total deferred income taxes 137 54 74 Total income tax (provision) benefit $ (484 ) $ (7 ) $ 63
Schedule of Reconciliation of Income Tax Expense Computed at Statutory Corporate Income Tax Rate to Effective Income Tax Rate	A reconciliation of income tax expense computed at the statutory corporate income tax rate to the effective income tax rate for the years ended December 31, 2016, 2015 and 2014 is as follows: Year ended December 31, 2016 2015 2014 Income tax expense at statutory rate 10.3 % 10.3 % 10.3 % State income tax, net of federal benefit 1.3 % 0.1 % 0.0 % Nondeductible expenses 1.6 % 0.0 % 0.0 % Foreign rate differential (3.3 %) (1.4 %) 1.8 % Statutory to US GAAP permanent differences 6.6 % 0.0 % 0.0 % Stock-based compensation (4.9 %) (1.4 %) (1.1 %) Research credits 3.1 % 0.6 % 0.0 % Change in valuation allowance (16.8 %) (8.2 %) (10.1 %) Effective income tax rate (2.1 %) 0.0 % 0.9 %
Schedule of Significant Components of the Company's Deferred Tax Assets	Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. The significant components of the Company’s deferred tax assets are comprised of the following (in thousands): Year ended December 31, 2016 2015 Deferred tax assets: Net operating loss carryforwards $ 3,934 $ 2,600 Accruals and reserves 791 189 Deferred Rent 5,228 — Other deferred tax assets 7 72 Deferred revenue 2,525 406 Research credit 425 104 Total deferred tax assets 12,910 3,371 Less valuation allowance (6,770 ) (2,892 ) Net deferred tax assets 6,140 479 Deferred tax liabilities: Depreciation (5,909 ) (321 ) Intangible assets (68 ) (80 ) Other deferred tax liabilities — (53 ) Total deferred tax liabilities (5,977 ) (454 ) Long term deferred taxes $ 163 $ 25
Schedule of Aggregate Changes in Gross Unrecognized Tax Benefits	The aggregate changes in gross unrecognized tax benefits was as follows (in thousands): Year ended December 31, 2016 2015 2014 Balance at beginning of year $ 49 $ — $ — Increases for tax positions taken during current period 134 49 — Increases for tax positions taken in prior periods — — — Decreases for tax positions taken during current period — — — Decreases for tax positions taken in prior periods (20 ) — — Balance at end of year $ 163 $ 49 $ —

Selected Quarterly Financial 35

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data	Prior to its IPO on October 18, 2016, the Company had outstanding participating Preferred Shares. During the fourth quarter of the year ended December 31, 2016, the Company had net income, although for the full year the Company had a net loss. Accordingly, the Company used the two-class method to calculate net income per share for the fourth quarter of 2016. For purposes of calculating basic net income per share for the fourth quarter of 2016, the Company excluded from the numerator $3.1 million of net income attributable to participating securities. The Company calculated diluted net income per share under both the if-converted method and the two-class method and concluded that the two-class method was more dilutive than the if-converted method. Accordingly, the two-class income allocations were reapplied after taking into account the dilutive effect of non-participating securities. This resulted in net income of $3.1 million being allocated to the participating securities and excluded from the numerator of the Common Stock dilutive net income per share calculation. 2016 First Quarter Second Quarter Third Quarter Fourth Quarter (1) Collaboration revenue $ 476 $ 795 $ 1,549 $ 2,344 Total operating expenses 12,128 17,353 16,159 27,654 Loss from operations (11,652 ) (16,558 ) (14,610 ) (25,310 ) Net (loss) income (8,442 ) (17,164 ) (14,694 ) 17,098 Net (loss) income attributable to common shareholders (8,439 ) (17,157 ) (14,680 ) 17,099 Net (loss) income per share attributable to common shareholders: Basic $ (1.53 ) $ (3.15 ) $ (2.77 ) $ 0.43 Diluted $ (1.53 ) $ (3.15 ) $ (2.77 ) $ 0.40 Weighted-average common shares outstanding used in net (loss) income per share attributable to common shareholders: Basic 5,528,079 5,448,855 5,292,348 32,987,335 Diluted 5,528,079 5,448,855 5,292,348 34,989,218 2015 First Quarter Second Quarter Third Quarter Fourth Quarter Collaboration revenue $ — $ — $ — $ 247 Total operating expenses 3,736 3,625 6,202 12,413 Loss from operations (3,736 ) (3,625 ) (6,202 ) (12,166 ) Net loss (3,522 ) (3,666 ) (6,354 ) (12,286 ) Net loss attributable to common shareholders $ (3,237 ) $ (3,643 ) $ (6,353 ) $ (12,270 ) Net loss per share applicable to common shareholders- basic and diluted $ (0.91 ) $ (0.80 ) $ (1.15 ) $ (2.22 ) Weighted-average common shares outstanding used in net loss per share attributable to common shareholders - basic and diluted 3,560,000 4,538,595 5,528,079 5,528,079 (1) During the fourth quarter the Company recorded an immaterial correction of an error of $1.2 million for rent expense related to the three months ended September 30, 2016. The Company determined that these errors are not material to the respective interim financial statements.

Organization and Operations - A

Organization and Operations - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Oct. 31, 2016	Oct. 31, 2016	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Mar. 31, 2015	Mar. 24, 2015
Organization and operations [Line Items]
Company formation date			Oct. 28, 2013
Company formation country name			Basel, Switzerland
Accumulated deficit			$ (57,083)		$ (33,906)
Proceeds from issuance of common shares			54,061
Proceeds from issuance of common shares in private placement			35,000
Common shares acquired	170,689
Cash	$ 315,500	$ 315,500	315,520		$ 155,961
Bayer Global Investments B.V [Member]
Organization and operations [Line Items]
Proceeds from issuance of common shares in private placement		$ 35,000	$ 35,000
IPO [Member]
Organization and operations [Line Items]
Issuance of shares, net of issuance cost (in shares)	4,429,311	4,429,311
Common shares price per share	$ 14	$ 14
Proceeds from issuance of common shares		$ 53,700
Common shares acquired		170,689
Overallotment Option [Member]
Organization and operations [Line Items]
Issuance of shares, net of issuance cost (in shares)	429,311	429,311
Common shares price per share	$ 14	$ 14
Common shares acquired		170,689
Concurrent Private Placement [Member] | Bayer Global Investments B.V [Member]
Organization and operations [Line Items]
Issuance of shares, net of issuance cost (in shares)	2,500,000	2,500,000	2,500,000
Common shares price per share	$ 14	$ 14
TRACR Hematology Limited [Member]
Organization and operations [Line Items]
Formation date, VIE			Jan. 23, 2014
Relationship nature and extent of involvement in VIE			On January 23, 2014, the founders of the Company formed TRACR Hematology Limited (“TRACR”) in the United Kingdom, to further the development of the CRISPR/Cas9 technology into medicines for the treatment of blood-borne illnesses. As the Company was funding and managing TRACR’s operations in 2014, it has been consolidated by the Company from the date that the Company established a variable interest in TRACR in April 2014. In March 2015, the Company acquired 82.1% of the outstanding equity of TRACR in a share exchange transaction. Concurrent with its initial public offering (“IPO”) in October 2016, the Company acquired the outstanding non-controlling interest in TRACR as such, as of December 31, 2016 TRACR is a wholly-owned subsidiary of the Company.
Purpose of VIE			To further the development of the CRISPR/Cas9 technology into medicines for the treatment of blood-borne illnesses.
Percentage of outstanding equity acquired			82.10%	82.10%		82.10%	82.10%

Summary of Significant Accoun37

Summary of Significant Accounting Policies and Basis of Presentation - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)SegmentAward	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Oct. 31, 2016USD ($)	Mar. 31, 2016	Feb. 12, 2016
Summary Of Significant Accounting Policies [Line Items]
Stock split, ratio	3.33
Stock split, description	3 1/3-for-one
Number of operating segments | Segment	1
Cash equivalents	$ 315,500,000	$ 156,000,000
Accounts receivable	3,157,000	339,000
Impairment loss	$ 0	0	$ 0
Assumed dividend yield, percent	0.00%
Number of equity-based compensation awards | Award	8
IPO [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred public offering costs				$ 8,300,000
Vertex and Casebia [Member] | Collaborative Arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable	$ 3,200,000
Allowance	$ 0
Vertex [Member] | Collaborative Arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable		$ 300,000
Casebia Therapeutics LLP [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	50.00%				50.00%	50.00%

Summary of Significant Accoun38

Summary of Significant Accounting Policies and Basis of Presentation - Schedule of Estimated Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2016
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	3 years
Furniture, Fixtures, and Other [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	5 years
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	5 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Leasehold improvements	Shorter of useful life or remaining lease term

Summary of Significant Accoun39

Summary of Significant Accounting Policies and Basis of Presentation - Schedule of Antidilutive Securities Excluded from Calculation of Diluted Net Loss per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	4,624,738	25,358,808	3,560,002
Outstanding Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	4,535,371	1,939,986
Unvested Unissued Restricted Shares [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	89,367	142,794
Dr. Emmanuelle Charpentier Call Option [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		328,017
Conversion of Convertible Loans [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		4,110,987
Convertible Preferred Shares [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		18,837,024	3,560,002

Property and Equipment, net - S

Property and Equipment, net - Summary of Property and Equipment, net (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 21,969	$ 1,400
Accumulated Depreciation	(942)	(72)
Property and equipment, net	21,027	1,328
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	110	118
Furniture, Fixtures, and Other [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,044	238
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,970	861
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	15,780	88
Construction Work in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 1,065	$ 95

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Abstract]
Depreciation expense	$ 0.9	$ 0.1	$ 0

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Detail) $ in Thousands	Sep. 30, 2016shares	Dec. 31, 2015shares	Mar. 24, 2015USD ($)Foundershares	Oct. 31, 2016shares	Mar. 31, 2015Foundershares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Mar. 31, 2016	Feb. 12, 2016
Casebia Therapeutics LLP [Member]
Variable Interest Entity [Line Items]
Date of formation of joint venture entity						Feb. 12, 2016
Equity method investment, ownership percentage						50.00%		50.00%	50.00%
Bayer Healthcare LLC [Member] | Casebia Therapeutics LLP [Member]
Variable Interest Entity [Line Items]
Equity method investment, ownership percentage								50.00%	50.00%
TRACR Hematology Limited [Member]
Variable Interest Entity [Line Items]
Number of shares acquired | shares	4,600	4,600	4,600
Percentage of shares acquired	82.10%		82.10%		82.10%	82.10%
Number of founders | Founder			2		2
TRACR Hematology Limited [Member] | Call Option [Member]
Variable Interest Entity [Line Items]
Shares held by subsidiary | shares			1,000
Remaining ownership percentage in VIE			17.90%
TRACR Hematology Limited [Member] | Common Stock [Member]
Variable Interest Entity [Line Items]
Reduction in noncontrolling interest						$ 10	$ 61
TRACR Hematology Limited [Member] | Additional Paid-in Capital [Member]
Variable Interest Entity [Line Items]
Decrease in noncontrolling interest			$ 100
Reduction in noncontrolling interest						$ (62)	$ 1
TRACR Hematology Limited [Member] | Founders' [Member] | Common Stock [Member]
Variable Interest Entity [Line Items]
Shares issued for acquisition | shares			852,846		852,846
TRACR Hematology Limited [Member] | Employees and Non-employees [Member] | Restricted Common Stock [Member]
Variable Interest Entity [Line Items]
Shares issued for acquisition | shares			656,031		656,031
TRACR Hematology Limited [Member] | Dr. Emmanuelle Charpentier [Member]
Variable Interest Entity [Line Items]
Conversion of ordinary shares into common shares | shares				328,017
TRACR Hematology Limited [Member] | Dr. Emmanuelle Charpentier [Member] | Call Option [Member]
Variable Interest Entity [Line Items]
Fair value of call option			$ 200
Reduction in noncontrolling interest			(100)
Reduction in stock based compensation			(200)
Reduction in additional paid-in capital			$ (100)
Fay Participation Corporation [Member] | Common Stock [Member]
Variable Interest Entity [Line Items]
Shares issued for acquisition | shares			459,217		459,217

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - Intellectual Property Rights [Member] - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite Lived Intangible Assets [Line Items]
Estimated useful life	10 years
Amortization expenses	$ 100,000	$ 100,000	$ 40,000
Remaining amortization period	7 years 3 months 18 days	8 years 3 months 18 days
Impairment charges	$ 0	$ 0	$ 0

Intangible Assets - Schedule of

Intangible Assets - Schedule of Intangible Assets, Net of Accumulated Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite Lived Intangible Assets [Line Items]
Acquired intangible asset, Net	$ 399	$ 454
Intellectual Property Rights [Member]
Finite Lived Intangible Assets [Line Items]
Acquired intangible asset, Cost	547	547
Acquired intangible asset, Accumulated Amortization	(148)	(93)
Acquired intangible asset, Net	$ 399	$ 454

Intangible Assets - Schedule 45

Intangible Assets - Schedule of Estimated Future Amortization of Acquired Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite Lived Intangible Assets [Line Items]
Acquired intangible asset, Net	$ 399	$ 454
Intellectual Property Rights [Member]
Finite Lived Intangible Assets [Line Items]
2,017	55
2,018	55
2,019	55
2,020	55
Thereafter	179
Acquired intangible asset, Net	$ 399	$ 454

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued Liabilities, Current [Abstract]
Payroll and employee-related costs	$ 2,585	$ 773
Research costs	996	910
Licensing fees	492	1,055
Professional fees	2,715	2,412
Intellectual property costs	3,372	2,592
Accrued property and equipment	5,081
Other	1,079	688
Total	$ 16,320	$ 8,430

Convertible Loans - Additional

Convertible Loans - Additional Information (Detail) - USD ($)	Jan. 29, 2016	Oct. 26, 2015	Jan. 31, 2016	Dec. 07, 2015	Dec. 31, 2016	Dec. 31, 2015	Apr. 26, 2016
Debt Conversion [Line Items]
Aggregate net proceeds borrowed					$ 35,010,000	$ 38,239,000
Conversion of convertible loans to Series B Preferred Shares					61,929,000
Proceeds raised from investors		$ 5,000,000
Gain on extinguishment of debt					$ 11,482,000
Common Shares [Member]
Debt Conversion [Line Items]
Preferred shares, conversion price per share		$ 9.33
IPO [Member]
Debt Conversion [Line Items]
Proceeds of public offering		$ 50,000,000
Minimum [Member]
Debt Conversion [Line Items]
Aggregate net proceeds borrowed		50,000,000
Vertex Convertible Loans [Member]
Debt Conversion [Line Items]
Borrowings under loan agreement		$ 40,000,000
Loan, accrued interest rate		2.50%			7.50%
Loan agreement maturity date					Apr. 26, 2016
Aggregate net proceeds borrowed				$ 38,200,000
Conversion of convertible loans to Series B Preferred Shares	$ 200,000
Vertex Convertible Loans [Member] | Base Interest Rate [Member]
Debt Conversion [Line Items]
Loan, accrued interest rate		2.50%
Bayer Convertible Loans [Member]
Debt Conversion [Line Items]
Loan agreement maturity date					Jan. 29, 2016
Aggregate net proceeds borrowed	$ 35,000,000
Borrowings under loan agreement					$ 35,000,000
Loan, accrued interest rate					2.00%
Fair value of convertible loan					$ 24,500,000
Series B Redeemable Convertible Preferred Shares [Member]
Debt Conversion [Line Items]
Preferred shares, shares issued upon conversion	2,859,278
Preferred shares, conversion price per share		$ 9.33	$ 13.43				$ 9.33
Series B Redeemable Convertible Preferred Shares [Member] | IPO [Member]
Debt Conversion [Line Items]
Preferred shares, conversion price per share		$ 9.33
Series B Redeemable Convertible Preferred Shares [Member] | Vertex Convertible Loans [Member]
Debt Conversion [Line Items]
Conversion of convertible loans to Series B Preferred Shares			$ 38,400,000
Preferred shares, shares issued upon conversion	2,859,278
Preferred shares, conversion price per share	$ 13.43
Fair value of convertible loan	$ 26,900,000
Gain on extinguishment of debt	11,500,000
Series B Redeemable Convertible Preferred Shares [Member] | Bayer Convertible Loans [Member]
Debt Conversion [Line Items]
Loan agreement maturity date					Jan. 29, 2016
Conversion of convertible loans to Series B Preferred Shares	$ 35,000,000		$ 35,000,000
Preferred shares, shares issued upon conversion	2,605,330
Preferred shares, conversion price per share	$ 13.43
Fair value of convertible loan	$ 24,500,000
Allocated to convertible loan	27,000,000
Interest expense	$ 8,000,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) £ in Thousands

Jun. 07, 2016USD ($)

Sep. 30, 2016USD ($)

May 31, 2016USD ($)

Apr. 30, 2016USD ($)

Nov. 30, 2015USD ($)

Jun. 30, 2015GBP (£)

Apr. 30, 2015

Dec. 31, 2016USD ($)Lease

Dec. 31, 2018USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)LeaseProgram

Dec. 31, 2015USD ($)

Dec. 31, 2014USD ($)

Contingencies And Commitments [Line Items]

Number of non-cancellable operating leases | Lease

5

Number of expired leases | Lease

3

3

Lease expiration year

2,017

Rental expense

$ 4,200,000

$ 1,300,000

$ 17,000

Deferred rent current

$ 1,027,000

1,027,000

Deferred rent non-current

12,283,000

12,283,000

164,000

Letters of credit secured by cash held in restricted depository account

3,150,000

3,150,000

700,000

Research and development expense

[1]

42,238,000

12,573,000

1,513,000

Cost sharing expensed relating to patent maintenance, defense and prosecution, incurred

3,000,000

1,500,000

$ 1,100,000

Cost sharing expensed relating to patent maintenance, defense and prosecution, accrued

2,800,000

2,600,000

Anagenesis Biotechnologies SAS [Member]

Contingencies And Commitments [Line Items]

Research and development expense

$ 500,000

Upfront payment

$ 500,000

Payment regarding achievement of future clinical, regulatory and sales milestones

$ 89,000,000

Sponsored Research Agreement [Member]

Contingencies And Commitments [Line Items]

Number of research programs | Program

5

Number of research programs continuing through 2018 | Program

2

Scenario Forecast [Member] | Sponsored Research Agreement [Member]

Contingencies And Commitments [Line Items]

Research and development expense

$ 100,000

$ 700,000

Formal Settlement Payment to US Common Shareholders [Member] | Maximum [Member]

Contingencies And Commitments [Line Items]

Aggregate settlement amount

$ 2,000,000

Formal Settlement Offer to US Common Shareholders [Member]

Contingencies And Commitments [Line Items]

Aggregate settlement amount

2,000,000

Letter of Credit [Member]

Contingencies And Commitments [Line Items]

Letters of credit secured by cash held in restricted depository account

3,200,000

$ 3,200,000

$ 700,000

Operating Lease, Research Facility Space [Member]

Contingencies And Commitments [Line Items]

Lease expiration date

Feb. 28, 2022

Extended term of lease expiration

5 years

Operating Lease, Primary Office and Research Facility Space [Member]

Contingencies And Commitments [Line Items]

Lease expiration date

Dec. 31, 2026

200 Sidney Street Lease [Member]

Contingencies And Commitments [Line Items]

Lease expiration date

Feb. 28, 2022

Extended term of lease expiration

5 years

Office Space Lease, London [Member]

Contingencies And Commitments [Line Items]

Lease expiration date

Jul. 31, 2017

Security cash deposit | £

£ 9

Corporate housing, Cambridge [Member]

Contingencies And Commitments [Line Items]

Lease expiration date

Nov. 30, 2017

Extended term of lease expiration

1 year

Security cash deposit

$ 10,000

610 Main Street Sublease [Member]

Contingencies And Commitments [Line Items]

Lease expiration date

Dec. 22, 2026

Jan. 31, 2017

Extended term of lease expiration

5 years

Rental expense

$ 2,300,000

Security cash deposit

$ 26,000

Tenant improvements allowance

10,800,000

Deferred rent liability

12,900,000

12,900,000

Tenant improvement allowance

10,200,000

10,200,000

Deferred rent current

1,000,000

1,000,000

Deferred rent non-current

$ 11,900,000

$ 11,900,000

610 Main Street Sublease [Member] | Letter of Credit [Member]

Contingencies And Commitments [Line Items]

Letters of credit secured by cash held in restricted depository account

$ 2,500,000

[1]

Including the following amounts of research and development from a related party, see Note 16:

Commitments and Contingencies49

Commitments and Contingencies - Summary of Future Minimum Payments Required under Leases (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,017	$ 6,685
2,018	6,431
2,019	6,624
2,020	6,823
2,021	7,027
Thereafter	30,335
Total minimum lease payments	$ 63,925

Significant Contracts - Additio

Significant Contracts - Additional Information (Detail) € in Millions, shares in Millions, SFr in Millions

Dec. 17, 2016USD ($)

Feb. 12, 2016USD ($)

Dec. 19, 2015shares

Oct. 26, 2015USD ($)Milestone

Mar. 31, 2016USD ($)

Apr. 30, 2014USD ($)

Apr. 30, 2014CHF (SFr)

Mar. 31, 2016USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Dec. 31, 2014USD ($)

Dec. 22, 2016USD ($)

Jan. 29, 2016USD ($)

Nov. 30, 2014USD ($)

Nov. 30, 2014EUR (€)

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Research and development expense

[1]

$ 42,238,000

$ 12,573,000

$ 1,513,000

Research and development arrangement, description

The research collaboration will end on the earlier of the date on which Vertex has exercised six options to obtain exclusive/co-exclusive licenses with respect to a collaboration target, or the fourth anniversary of the effective date of the agreement. The research term may be extended as mutually agreed by the parties up to nine additional months to complete any research activities under the approved research plan that are incomplete on the fourth anniversary of the effective date.

Non-current deferred revenue

$ 77,646,000

75,090,000

Date of joint venture agreement

Dec. 19, 2015

Cash contribution

$ 100,000

Fair value allocation of arrangement consideration paid

91,200,000

Remaining license fee

$ 15,000,000

Other income (expense), net

78,512,000

16,000

(236,000)

Equity method investment

36,500,000

Unrealized equity method losses

(36,532,000)

Stock-based compensation expense

10,844,000

3,684,000

695,000

Licensing Agreements [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Fair value

71,400,000

License and Patent Holder Consent [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Fair value allocation of arrangement consideration paid

63,600,000

Future Research and Development Services [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Fair value allocation of arrangement consideration paid

600,000

Bayer Convertible Loans [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Convertible Loan

35,000,000

Fair value of convertible loan

24,500,000

Fair value allocation of arrangement consideration paid

27,000,000

Debt instrument discount

8,000,000

Debt instrument face amount

$ 35,000,000

Loan agreement maturity date

Jan. 29, 2016

Bayer Convertible Loans [Member] | Series B Redeemable Convertible Preferred Shares [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Fair value of convertible loan

$ 24,500,000

Loan agreement maturity date

Jan. 29, 2016

Bayer Global Investments B.V [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Value of shares to be purchased via option through private placement | shares

35

Casebia Therapeutics LLP [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Research and development expense

$ 1,200,000

Nonrefundable upfront payment received

$ 20,000,000

Aggregate consideration receivable

112,600,000

Revenue from collaboration agreement

1,200,000

Non-current deferred revenue

$ 500,000

Date of formation of joint venture entity

Feb. 12, 2016

Equity method investment, ownership percentage

50.00%

50.00%

50.00%

50.00%

Cash contribution

$ 100,000

Remaining license fees to be received from joint venture entity

$ 15,000,000

Royalty payments due to company from joint venture entity

0

Other payments due to company from joint venture entity

$ 0

Convertible Loan

$ 35,000,000

Cash contribution

100,000

Technology fee

34,900,000

Equity interest in the Joint Venture

36,400,000

Estimated revenue related to research and development services

6,300,000

Unrecognized equity method losses in excess of Company's interest

4,000,000

Stock-based compensation expense

200,000

Net loss of joint venture

(80,800,000)

Casebia Therapeutics LLP [Member] | Fair Value of CRISPR License Acquired [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Research and development expense

77,400,000

Casebia Therapeutics LLP [Member] | Bayer Healthcare LLC [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Research and development expense

$ 45,000,000

Equity method investment, ownership percentage

50.00%

50.00%

50.00%

Research and development funding term

5 years

Maximum [Member] | Casebia Therapeutics LLP [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenue from collaboration agreement

$ 35,000,000

Maximum [Member] | Casebia Therapeutics LLP [Member] | Bayer Healthcare LLC [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Research and development expense

$ 300,000,000

Research and Development Services [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Fair value

6,300,000

Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Research and development expense

$ 7,000,000

300,000

Clinical milestone payment payable

$ 10,000,000

Nonrefundable upfront payment received

75,000,000

Potential milestone receivable

420,000,000

Number of days to terminate the collaboration agreement

90 days

Notice period in the event of material breach of collaboration agreement

90 days

Number of days to terminate the product

270 days

Best estimate selling price for research and development services

26,700,000

Best estimated selling price for single collaboration

37,700,000

Best estimated selling price for collaboration agreement

188,500,000

Estimated selling price for collaboration agreement

50,000,000

Aggregate consideration receivable

151,700,000

Revenue from collaboration agreement

$ 4,000,000

200,000

0

Non-current deferred revenue

77,100,000

75,090,000

Vertex Pharmaceuticals Inc [Member] | Research and Development Services [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Aggregate consideration receivable

17,800,000

Patent Assignment Agreement [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Research and development expense

33,000

100,000

0

Clinical milestone payment payable

$ 400,000

€ 0.3

Beta-Globin Collaboration [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Best estimated selling price for single collaboration

12,500,000

Non-Exclusive Research License and Exclusive License to Develop [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Aggregate consideration receivable

125,500,000

Non-Exclusive Research License and Co-Exclusive License to Develop [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Aggregate consideration receivable

8,400,000

Exclusive Option Agreement [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenue recognition, milestone method, revenue recognized

10,000,000

Investigational New Drug Application ("IND") [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenue recognition, milestone method, revenue recognized

10,000,000

Investigational New Drug Application ("IND") [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenue recognition, milestone method, revenue recognized

$ 10,000,000

Clinical Development And Regulatory Milestone [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Number of developmental milestone events | Milestone

9

Clinical Development Milestones [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenue recognition, milestone method, revenue recognized

$ 90,000,000

Regulatory Approval Milestone [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenue recognition, milestone method, revenue recognized

235,000,000

Commercial Milestones [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenue recognition, milestone method, revenue recognized

$ 75,000,000

Number of developmental milestone events | Milestone

2

Developmental Milestone Events [Member] | Vertex Pharmaceuticals Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenue recognition, milestone method, revenue recognized

$ 420,000,000

Commercial Milestone Event One [Member] | Vertex Pharmaceuticals Inc [Member] | Minimum [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Aggregate consideration receivable

500,000,000

Commercial Milestone Event Two [Member] | Vertex Pharmaceuticals Inc [Member] | Minimum [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Aggregate consideration receivable

$ 1,000,000,000

CRISPR-Charpentier License Agreement [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Upfront fees paid for license

$ 100,000

SFr 0.1

Annual payments for consulting agreement

0

0

0

Research and development expense

500,000

900,000

0

TRACR-Charpentier License Agreement [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Research and development expense

$ 0

$ 100,000

$ 0

[1]

Including the following amounts of research and development from a related party, see Note 16:

Redeemable Convertible Prefer51

Redeemable Convertible Preferred Shares - Additional Information (Detail) SFr / shares in Units, $ / shares in Units, $ in Thousands, SFr in Millions	Oct. 31, 2016shares	May 27, 2016USD ($)	Jan. 29, 2016USD ($)$ / shares	Oct. 31, 2016shares	Jun. 30, 2016USD ($)$ / sharesshares	Jan. 31, 2016USD ($)$ / sharesshares	May 31, 2015USD ($)$ / sharesshares	May 31, 2015CHF (SFr)SFr / sharesshares	Apr. 30, 2015USD ($)$ / sharesshares	Feb. 28, 2015USD ($)	Feb. 28, 2015CHF (SFr)SFr / shares	Apr. 30, 2014USD ($)$ / sharesshares	Apr. 30, 2014CHF (SFr)	Oct. 31, 2013USD ($)$ / sharesshares	Oct. 31, 2013CHF (SFr)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)shares	Dec. 31, 2016SFr / sharesshares	Oct. 19, 2016shares	Apr. 26, 2016$ / shares	Dec. 31, 2015SFr / shares	Oct. 26, 2015$ / shares	Feb. 28, 2015$ / shares	Apr. 30, 2014SFr / shares	Dec. 31, 2013shares	Oct. 31, 2013SFr / shares
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized																			0
Redeemable convertible preferred stock, shares issued																			0
Redeemable convertible preferred stock, shares outstanding																			0
Redeemable convertible preferred stock, shares issued																	18,837,024
Redeemable convertible preferred stock, shares outstanding																	18,837,024
Common stock, shares issued																	5,528,079		40,164,307
Loss on extinguishment of redeemable convertible preferred shares | $																		$ 745
Conversion of Vertex and Bayer convertible loans and accrued interest | $																$ 61,929
Vertex Convertible Loans [Member]
Temporary Equity [Line Items]
Conversion of Vertex and Bayer convertible loans and accrued interest | $			$ 200
Series A-1 Redeemable Convertible Preferred Shares [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued														440,001			440,001		0
Redeemable convertible preferred stock, shares outstanding																	440,001	440,001	0							440,001
Redeemable convertible preferred stock, par value | (per share)														$ 1.28					SFr 0.03			SFr 0.03					SFr 1.14
Proceeds from issuance of preferred shares														$ 600	SFr 0.5
Redeemable convertible preferred stock, right to purchase additional shares														1,315,790
Common stock, shares issued														335,000
Common stock, issuance cost discount | $														$ 100
Loss on extinguishment of redeemable convertible preferred shares | $												$ 700						$ (745)
Fair value of preferred shares | $												1,200
Carrying value of preferred shares | $												$ 400
Series A-2 Redeemable Convertible Preferred Shares [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued												3,120,001					3,120,001		0
Redeemable convertible preferred stock, shares outstanding																	3,120,001	3,120,001	0
Redeemable convertible preferred stock, par value | (per share)												$ 3.47							SFr 0.03			0.03			SFr 3.05
Proceeds from issuance of preferred shares												$ 5,100	SFr 4.5				$ 5,293	$ 5,137
Series A-2 Redeemable Convertible Preferred Shares [Member] | Preferred Stock Issuance [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value | (per share)												$ 1.65													SFr 1.45
Series A-2 Redeemable Convertible Preferred Shares [Member] | Board of Directors [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value | (per share)											SFr 1.60													$ 1.82
Proceeds from issuance of preferred shares										$ 5,300	SFr 5
Series A-3 Redeemable Convertible Preferred Shares [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued									10,758,006								10,758,006		0
Redeemable convertible preferred stock, shares outstanding																	10,758,006		0
Redeemable convertible preferred stock, par value | SFr / shares																			SFr 0.03			0.03
Proceeds from issuance of preferred shares | $		$ 22,800							$ 22,800							22,850	$ 22,850
Temporary equity, price per share | $ / shares									$ 4.24
Temporary equity share issued price per share | $ / shares									$ 2.12
Temporary equity, subscription receivable | $																	$ 22,800
Series B Redeemable Convertible Preferred Shares [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued																	4,519,016		0
Redeemable convertible preferred stock, shares outstanding																	4,519,016		0
Redeemable convertible preferred stock, par value | SFr / shares																			SFr 0.03			SFr 0.03
Proceeds from issuance of preferred shares					$ 38,075		$ 30,478	SFr 28								$ 38,075	$ 30,478
Temporary equity, price per share | (per share)					$ 13.43		$ 6.74	SFr 6.20
Common shares issued and sold					2,834,252	5,464,608	4,519,016	4,519,016									4,519,016
Preferred shares, conversion price per share | $ / shares						$ 13.43															$ 9.33		$ 9.33
Series B Redeemable Convertible Preferred Shares [Member] | Vertex Convertible Loans [Member]
Temporary Equity [Line Items]
Conversion of Vertex and Bayer convertible loans and accrued interest | $						$ 38,400
Preferred shares, conversion price per share | $ / shares			$ 13.43
Series B Redeemable Convertible Preferred Shares [Member] | Bayer Convertible Loans [Member]
Temporary Equity [Line Items]
Conversion of Vertex and Bayer convertible loans and accrued interest | $			$ 35,000			$ 35,000
Preferred shares, conversion price per share | $ / shares			$ 13.43
IPO [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized																				27,135,884
Redeemable convertible preferred stock, shares authorized																one-for-one
Common shares issued and sold	4,429,311			4,429,311
IPO [Member] | Series B Redeemable Convertible Preferred Shares [Member]
Temporary Equity [Line Items]
Preferred shares, conversion price per share | $ / shares																							$ 9.33

Share Capital - Additional Info

Share Capital - Additional Information (Detail)	Oct. 31, 2016USD ($)shares	Mar. 24, 2015Foundershares	Oct. 31, 2016shares	Mar. 31, 2015Foundershares	Apr. 30, 2014shares	Dec. 31, 2016USD ($)shares	Dec. 31, 2016SFr / sharesshares	Sep. 30, 2016	Dec. 31, 2015SFr / sharesshares
Class of Stock [Line Items]
Common stock, shares authorized							40,253,674		5,528,079
Common shares, par value | SFr / shares							SFr 0.03		SFr 0.03
Unvested restricted share award							89,367
Treasury stock, shares							444,873		0
Common shares sold	170,689
Repurchase of treasury shares, value | $	$ 0
Common Stock, Voting Rights						One vote for each common share
Dividends declared and paid | $						$ 0
Non Employees [Member] | Founders Shares Award | Series A-2 Preferred Shares [Member]
Class of Stock [Line Items]
Transfer of shares					729,800
IPO [Member]
Class of Stock [Line Items]
Issuance of shares, net of issuance cost (in shares)	4,429,311		4,429,311
Common shares sold			170,689
Overallotment Option [Member]
Class of Stock [Line Items]
Issuance of shares, net of issuance cost (in shares)	429,311		429,311
Common shares sold			170,689
Common Stock [Member]
Class of Stock [Line Items]
Issuance of shares, net of issuance cost (in shares)						7,100,000
Common shares sold						444,873
Repurchase of treasury shares, value | $						$ (13,000)
Common Stock [Member] | Fay Corp Awards [Member]
Class of Stock [Line Items]
Transfer of vested shares					1,192,585
Founders' [Member] | Fay Corp Awards [Member]
Class of Stock [Line Items]
Transfer of vested shares							268,093
Bayer Global Investments B.V [Member] | Private Placement [Member]
Class of Stock [Line Items]
Issuance of shares, net of issuance cost (in shares)	2,500,000		2,500,000			2,500,000
TRACR Hematology Limited [Member]
Class of Stock [Line Items]
Percentage of shares acquired		82.10%		82.10%			82.10%	82.10%
Number of founders | Founder		2		2
TRACR Hematology Limited [Member] | Founders' [Member] | Common Stock [Member]
Class of Stock [Line Items]
Shares issued for acquisition		852,846		852,846
TRACR Hematology Limited [Member] | Employees and Non-employees [Member] | Restricted Common Stock [Member]
Class of Stock [Line Items]
Shares issued for acquisition		656,031		656,031
Fay Corp [Corp] | Common Stock [Member]
Class of Stock [Line Items]
Shares issued for acquisition		459,217		459,217

Share Capital - Schedule of Con

Share Capital - Schedule of Conditional Capital Reserved for Future Issuance (Detail) - shares	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Conditional capital reserved for future issuance	15,325,607	2,444,364
Charpentier Call Option [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance		328,017
Unvested Unissued Restricted Stock [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	166,667	142,794
Outstanding Stock Options [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	4,535,371	1,939,986
Stock Option Plan [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	5,290,643	33,567
Bonds and Similar Debt Instruments[Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	4,919,700
Employee Purchase Plans [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	413,226

Equity-based Compensation - Opt

Equity-based Compensation - Option and Grant Plans - Additional Information (Detail) - Plans [Member]	12 Months Ended
	Dec. 31, 2016shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation, options, vesting period	4 years
Share-based Compensation, options, contractual life	10 years
IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment award, number of shares granted	0
Founder Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, requisite service period	4 years

Equity-based Compensation - Equ

Equity-based Compensation - Equity-Based Compensation Expense - Additional Information (Detail) - Stock Options and Restricted Stock Awards [Member]	12 Months Ended
	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation, options, vesting period	4 years
Share-based Compensation, options, vesting terms	vests over four years with 25% vesting on the first anniversary, and the remaining vesting monthly thereafter
Vesting Percentage on First Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation, options, vesting for first year percentage	25.00%

Equity-based Compensation - Sch

Equity-based Compensation - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-Based compensation expense	$ 10,844	$ 3,684	$ 695
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-Based compensation expense	4,848	1,924	487
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-Based compensation expense	5,844	$ 1,760	$ 208
Loss From Equity Method Investments [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-Based compensation expense	$ 152

Equity-based Compensation - Fai

Equity-based Compensation - Fair Value of Employee and Non-employee Stock Option Award on the Grant Date Using the Black-Scholes Option-Pricing Model (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%
Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	2,411,240	1,913,319
Weighted - average exercise price	$ 12.19	$ 2.32
Weighted-average grant date fair value	$ 8.47	$ 3.11
Weighted-average expected volatility	81.00%	76.40%
Expected term (in years)	6 years	6 years
Weighted-average risk free interest rate	1.40%	1.70%
Expected dividend yield	0.00%	0.00%
Non Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	215,710	26,667
Weighted - average exercise price	$ 19.54	$ 1.85
Weighted-average grant date fair value	$ 17.38	$ 5.05
Weighted-average expected volatility	88.20%	84.10%
Expected term (in years)	10 years	10 years
Weighted-average risk free interest rate	2.40%	2.20%
Expected dividend yield	0.00%	0.00%

Equity-based Compensation - Sum

Equity-based Compensation - Summary of Stock Option Activity for Employees and Non-employees (Detail) - Employees and Non-employees [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options, Outstanding, Beginning Balance	1,939,986
Stock Options, Granted	2,626,950
Stock Options, Exercised	(18,900)
Stock Options, Cancelled or forfeited	(12,665)
Stock Options, Outstanding, Ending Balance	4,535,371	1,939,986
Stock Options, Exercisable	960,867
Stock Options, Vested or expected to vest	4,169,347
Weighted-Average Exercise Price, Outstanding, Beginning Balance	$ 2.31
Weighted-Average Exercise Price, Granted	12.79
Weighted-Average Exercise Price, Exercised	1.81
Weighted-Average Exercise Price, Cancelled or forfeited	4.98
Weighted-Average Exercise Price, Outstanding, Ending Balance	8.38	$ 2.31
Weighted-Average Exercise Price, Exercisable	3.24
Weighted-Average Exercise Price, Vested or expected to vest	$ 8.23
Weighted-Average Remaining Contractual Term	9 years 1 month 6 days	9 years 8 months 12 days
Weighted-Average Remaining Contractual Term, Exercisable	8 years 9 months 18 days
Weighted-Average Remaining Contractual Term, Vested or expected to vest	9 years 1 month 6 days
Aggregate Intrinsic Value, Outstanding Balance	$ 6,688
Aggregate Intrinsic Value, Exercised	216
Aggregate Intrinsic Value, Outstanding Balance	53,975	$ 6,688
Aggregate Intrinsic Value, Exercisable	16,361
Aggregate Intrinsic Value, Vested or expected to vest	$ 50,155

Equity-based Compensation - Sha

Equity-based Compensation - Share Based Payment Activity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Oct. 18, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense		$ 23,400
Equity-based compensation expense not yet recognized, weighted-average service period for recognition		3 years 3 months 18 days
Stock-based compensation expense		$ 10,844	$ 3,684	$ 695
Common stock reserved for future issuance and held outstanding		15,325,607	2,444,364
Founders' [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Exercise Price, Vested or expected to vest		$ 12.65
Stock-based compensation expense		$ 2,600
Fay Corp Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation, number of shares issued		290,400
Common stock reserved for future issuance and held outstanding		0
Fay Corp Awards [Member] | Founders' [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Transfer of vested shares		268,093
Performance-Based [Member] | Vesting Percentage on First Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options, Granted		123,333	261,389
Share-based compensation, options, vested	686,665	262,538
Share-based compensation, options, deemed probable of vesting		12,500
Performance-Based [Member] | Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock, granted		0	50,000
Restricted stock, vested		50,000	0
Share-based compensation, restricted, deemed probable of vesting			15,000
Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense not yet recognized, weighted-average service period for recognition		1 year 4 months 24 days
Total fair value of restricted stock vested		$ 9,900	$ 2,300
Total unrecognized compensation expenses		$ 7,200
Restricted stock, vested		887,815

Equity-based Compensation - S60

Equity-based Compensation - Summary of the Company's Restricted Stock Activity (Detail) - Restricted Shares [Member]	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted Common Stock, Number of Shares, Beginning Balance	1,628,038
Unvested restricted Common Stock, Number of Shares, Vested	(887,815)
Unvested restricted Common Stock, Number of Shares, Ending Balance	740,223
Unvested restricted Common Stock, Weighted-Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 4.35
Unvested restricted Common Stock, Weighted-Average Grant Date Fair Value, Vested | $ / shares	4.78
Unvested restricted Common Stock, Weighted-Average Grant Date Fair Value, Ending Balance | $ / shares	$ 3.84
Reflected as Outstanding Upon Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted Common Stock, Number of Shares, Beginning Balance	142,794
Unvested restricted Common Stock, Number of Shares, Vested	(53,427)
Unvested restricted Common Stock, Number of Shares, Ending Balance	89,367
Reflected as Outstanding Upon Grant Date [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted Common Stock, Number of Shares, Beginning Balance	1,485,244
Unvested restricted Common Stock, Number of Shares, Vested	(834,388)
Unvested restricted Common Stock, Number of Shares, Ending Balance	650,856

401(k) Savings Plan - Additiona

401(k) Savings Plan - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Compensation And Retirement Disclosure [Abstract]
Company contributions toward the plan	$ 0.1

Income Taxes - Schedule of Loss

Income Taxes - Schedule of Loss Before Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Domestic	$ 3,322	$ 593
Foreign	(26,040)	(26,414)	$ (6,863)
Total	$ (22,718)	$ (25,821)	$ (6,863)

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for (Benefit from) Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current income taxes:
Federal	$ (649)	$ (23)
State	11	(12)
Foreign	17	(26)	$ (11)
Total current income taxes	(621)	(61)	(11)
Deferred income taxes:
Federal	30	(37)
State	105	65
Foreign	2	26	74
Total deferred income taxes	137	54	74
Total income tax (provision) benefit	$ (484)	$ (7)	$ 63

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Income Tax Expense Computed at Statutory Corporate Income Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Effective Income Tax Rate
Income tax expense at statutory rate	10.30%	10.30%	10.30%
State income tax, net of federal benefit	1.30%	0.10%	0.00%
Nondeductible expenses	1.60%	0.00%	0.00%
Foreign rate differential	(3.30%)	(1.40%)	1.80%
Statutory to US GAAP permanent differences	6.60%	0.00%	0.00%
Stock-based compensation	(4.90%)	(1.40%)	(1.10%)
Research credits	3.10%	0.60%	0.00%
Change in valuation allowance	(16.80%)	(8.20%)	(10.10%)
Effective income tax rate	(2.10%)	0.00%	0.90%

Income Taxes - Schedule of Sign

Income Taxes - Schedule of Significant Components of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss carryforwards	$ 3,934	$ 2,600
Accruals and reserves	791	189
Deferred Rent	5,228
Other deferred tax assets	7	72
Deferred revenue	2,525	406
Research credit	425	104
Total deferred tax assets	12,910	3,371
Less valuation allowance	(6,770)	(2,892)
Net deferred tax assets	6,140	479
Deferred tax liabilities:
Depreciation	(5,909)	(321)
Intangible assets	(68)	(80)
Other deferred tax liabilities		(53)
Total deferred tax liabilities	(5,977)	(454)
Long term deferred taxes	$ 163	$ 25

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation Allowance [Line Items]
Deferred tax assets, valuation allowance	$ 6,770,000	$ 2,892,000
Non-US Net operating loss carryforwards	$ 41,700,000
Operating loss carryforwards expiration period	2,020
Domestic state research and development credit carryforwards	$ 200,000
Research and development credit carryforwards expiration period	2,031
Unrecognized tax benefits, gross	$ 163,000	49,000
Unrecognized tax benefits would favorably impact the effective tax rate if recognized	100,000
Accrued interest or penalties related to uncertain tax positions	0	0	$ 0
Uncertain tax positions recognized	0	$ 0	$ 0
U.S. Domestic Federal [Member] | Research and Development [Member]
Valuation Allowance [Line Items]
Tax credit carryforward amount	$ 300,000
Tax credit carryforward, expiration year	2,036
Switzerland [Member]
Valuation Allowance [Line Items]
Increase in valuation allowance	$ 3,900,000
US [Member]
Valuation Allowance [Line Items]
Deferred tax assets, valuation allowance	$ 0

Income Taxes - Schedule of Aggr

Income Taxes - Schedule of Aggregate Changes in Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 49
Increases for tax positions taken during current period	134	$ 49
Decreases for tax positions taken in prior periods	(20)
Balance at end of year	$ 163	$ 49

Selected Quarterly Financial 68

Selected Quarterly Financial Data (Unaudited) - Additional Information (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2016USD ($)
Quarterly Financial Information Disclosure [Abstract]
Net Income attributable to Participating securities excluded from numerator for calculating basic net income per share	$ 3.1
Net Income attributable to participating securities excluded from numerator for calculating diluted net income per share	$ 3.1

Selected Quarterly Financial 69

Selected Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2016	[1]	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Collaboration revenue	$ 2,344		$ 1,549	$ 795	$ 476	$ 247				$ 5,164	[2]	$ 247	[2]
Total operating expenses	27,654		16,159	17,353	12,128	12,413	$ 6,202	$ 3,625	$ 3,736	73,294		25,976		$ 6,627
Loss from operations	(25,310)		(14,610)	(16,558)	(11,652)	(12,166)	(6,202)	(3,625)	(3,736)	(68,130)		(25,729)		(6,627)
Net loss	17,098		(14,694)	(17,164)	(8,442)	(12,286)	(6,354)	(3,666)	(3,522)	(23,202)		(25,828)		(6,800)
Net (loss) income attributable to common shareholders	$ 17,099		$ (14,680)	$ (17,157)	$ (8,439)	$ (12,270)	$ (6,353)	$ (3,643)	$ (3,237)	$ (23,177)		$ (25,503)		$ (7,009)
Net (loss) income per share attributable to common shareholders:
Basic	$ 0.43		$ (2.77)	$ (3.15)	$ (1.53)
Diluted	$ 0.40		$ (2.77)	$ (3.15)	$ (1.53)
Net loss per share attributable to common shareholders—basic and diluted						$ (2.22)	$ (1.15)	$ (0.80)	$ (0.91)	$ (1.89)		$ (5.06)		$ 1.97
Weighted-average common shares outstanding used in net (loss) income per share attributable to common shareholders:
Basic	32,987,335		5,292,348	5,448,855	5,528,079
Diluted	34,989,218		5,292,348	5,448,855	5,528,079
Weighted-average common shares outstanding used in net loss per share attributable to common shareholders—basic and diluted						5,528,079	5,528,079	4,538,595	3,560,000	12,257,483		5,037,404		3,559,985
[1]	During the fourth quarter the Company recorded an immaterial correction of an error of $1.2 million for rent expense related to the three months ended September 30, 2016. The Company determined that these errors are not material to the respective interim financial statements.
[2]	Including the following amounts of revenue from a related party, see Note 16:

Selected Quarterly Financial 70

Selected Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Information (Parenthetical) (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2016USD ($)
Rent Expense [Member]
Quarterly Financial Data [Line Items]
Immaterial correction of an error amount	$ 1.2

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	Oct. 31, 2016	Oct. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Issuance of convertible loans			$ 35,010	$ 38,239
Proceeds from issuance of common shares in private placement			35,000
Investors [Member] | Series A-3 Redeemable Convertible Preferred Shares [Member]
Related Party Transaction [Line Items]
Legal and consulting costs			200
Dr. Emmanuelle Charpentier [Member] | TRACR Hematology Limited [Member]
Related Party Transaction [Line Items]
Payment of consulting, licensing and other fees			1,000	34
Related party transaction additional fees			500	1,000
Bayer Healthcare LLC [Member]
Related Party Transaction [Line Items]
Issuance of convertible loans			35,000
Bayer Healthcare LLC [Member] | Casebia Therapeutics LLP [Member]
Related Party Transaction [Line Items]
Revenue related to research and development services			1,200	$ 0
Bayer Global Investments B.V [Member]
Related Party Transaction [Line Items]
Proceeds from issuance of common shares in private placement		$ 35,000	$ 35,000
Bayer Global Investments B.V [Member] | Private Placement [Member]
Related Party Transaction [Line Items]
Purchase of common shares	2,500,000	2,500,000	2,500,000