CRISPR Therapeutics (CRSP) 10-Q 28 Oct 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 24, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Title of 12(b) Security	Common Shares, CHF 0.03 par value
Trading Symbol	CRSP
Security Exchange Name	NASDAQ
Entity Registrant Name	CRISPR THERAPEUTICS AG
Entity Central Index Key	0001674416
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		55,204,242
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-37923
Entity Address, Address Line One	Baarerstrasse 14
Entity Address, City or Town	Zug
Entity Address, Country	CH
Entity Address, Postal Zip Code	6300
City Area Code	41 (0)41
Local Phone Number	561 32 77
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	V8
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 629,717	$ 456,649
Accounts receivable, including related party amounts of $39 and $88 as of September 30, 2019 and December 31, 2018, respectively	39	88
Prepaid expenses and other current assets, including related party amounts of $28,875 and $3,417 as of September 30, 2019 and December 31, 2018, respectively	34,309	9,658
Total current assets	664,065	466,395
Property and equipment, net	21,074	18,500
Intangible assets, net	249	289
Restricted cash	3,915	3,163
Operating lease assets	30,619
Other non-current assets	668	669
Total assets	720,590	489,016
Current liabilities:
Accounts payable	3,374	5,069
Accrued expenses, including related party amounts of $4,537 and $1,700 as of September 30, 2019 and December 31, 2018, respectively	22,397	20,852
Deferred revenue current, including related party amounts of $47,725 and $102 as of September 30, 2019 and December 31, 2018, respectively	47,725	102
Accrued tax liabilities	1,478	402
Deferred rent		1,202
Operating lease liabilities	4,805
Other current liabilities		119
Total current liabilities	79,779	27,746
Deferred revenue non-current, including related party amounts of $11,871 and $57,780 as of September 30, 2019 and December 31, 2018, respectively	11,871	57,780
Deferred rent non-current		11,052
Operating lease liabilities, net of current portion	36,827
Other non-current liabilities	235	243
Total liabilities	128,712	96,821
Commitments and contingencies, see Note 4
Shareholders’ equity:
Common shares, CHF 0.03 par value, 55,677,088 and 52,183,139 shares authorized at September 30, 2019 and December 31, 2018, respectively, 55,446,359 and 52,160,798 shares issued at September 30, 2019 and December 31, 2018, respectively, 55,189,370 and 51,852,862 shares outstanding at September 30, 2019 and December 31, 2018, respectively, 23,948,128 and 20,498,996 shares in conditional capital at September 30, 2019 and December 31, 2018, respectively.	1,684	1,584
Treasury shares, at cost, 256,989 and 307,936 shares at September 30, 2019 and December 31, 2018, respectively	(57)	(57)
Additional paid-in capital	845,526	682,245
Accumulated deficit	(255,253)	(291,569)
Accumulated other comprehensive loss	(22)	(8)
Total shareholders' equity	591,878	392,195
Total liabilities and shareholders’ equity	$ 720,590	$ 489,016

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) $ in Thousands	Sep. 30, 2019USD ($)shares	Dec. 31, 2018USD ($)shares
Statement Of Financial Position [Abstract]
Accounts receivable, related party amount, current | $	$ 39	$ 88
Prepaid expenses and other current assets, related party amount | $	28,875	3,417
Accrued expenses related party amount, current | $	4,537	1,700
Deferred revenue current related party amount | $	47,725	102
Deferred revenue non-current related party amount | $	$ 11,871	$ 57,780
Common stock, shares authorized | shares	55,677,088	52,183,139
Common stock, shares issued | shares	55,446,359	52,160,798
Common stock, shares outstanding | shares	55,189,370	51,852,862
Common stock, conditional capital | shares	23,948,128	20,498,996
Treasury stock, shares | shares	256,989	307,936

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Collaboration revenue	[1]	$ 211,928	$ 563	$ 212,574	$ 3,009
Operating expenses:
Research and development	[2]	57,246	39,820	130,601	84,972
General and administrative		15,519	10,175	46,216	31,752
Total operating expenses		72,765	49,995	176,817	116,724
Income (loss) from operations		139,163	(49,432)	35,757	(113,715)
Other income (expense):
Loss from equity method investment		(3,430)	(1,012)	(5,467)	(3,256)
Other income (expense), net		2,964	(130)	6,470	(101)
Total other income (expense), net		(466)	(1,142)	1,003	(3,357)
Net income (loss) before income taxes		138,697	(50,574)	36,760	(117,072)
Provision for income taxes		(274)	(137)	(444)	(319)
Net income (loss)		138,423	(50,711)	36,316	(117,391)
Foreign currency translation adjustment		(12)	(6)	(14)	(15)
Comprehensive income (loss)		138,411	(50,717)	36,302	(117,406)
Reconciliation of net income (loss) to net income (loss) attributable to common shareholders:
Net income (loss)		$ 138,423	$ (50,711)	$ 36,316	$ (117,391)
Net income (loss) per share attributable to common shareholders— basic		$ 2.52	$ (1.07)	$ 0.68	$ (2.51)
Weighted-average common shares outstanding used in net income (loss) per share attributable to common shareholders—basic		54,829,057	47,391,988	53,380,123	46,709,388
Net income (loss) per share attributable to common shareholders— diluted		$ 2.40	$ (1.07)	$ 0.65	$ (2.51)
Weighted-average common shares outstanding used in net income (loss) per share attributable to common shareholders—diluted		57,598,901	47,391,988	55,821,420	46,709,388
[1]	Including the following revenue from a related party, see Notes 6 & 11
[2]	Including the following research and development expense with a related party, see Notes 6 & 11

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue from related party	$ 211,928	$ 443	$ 212,574	$ 2,406
Research and development expense with a related party	$ 17,563	$ 418	$ 32,022	$ 2,770

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	ViaCyte [Member]	Common Shares [Member]	Common Shares [Member]ViaCyte [Member]	Treasury Shares [Member]	Treasury Shares [Member]ViaCyte [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]ViaCyte [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2017	$ 187,832		$ 1,240				$ 312,018		$ (125,440)	$ 14
Beginning balance (in shares) at Dec. 31, 2017			40,592,248		444,873
Cumulative effect of ASC 606 adoption | ASU 2014-09 [Member]	(1,148)								(1,148)
Issuance of common shares, net of issuance costs	122,597		$ 174				122,423
Issuance of common shares, net of issuance costs (in shares)			5,750,000
Vesting of restricted shares	13						13
Vesting of restricted shares (in shares)			10,042
Exercise of vested options	2,656		$ 9				2,647
Exercise of vested options (in shares)			328,525		(6,253)
Stock-based compensation expense	6,673						6,673
Other comprehensive loss	12									12
Net loss	(28,300)								(28,300)
Ending balance at Mar. 31, 2018	290,335		$ 1,423				443,774		(154,888)	26
Ending balance (in shares) at Mar. 31, 2018			46,680,815		438,620
Beginning balance at Dec. 31, 2017	187,832		$ 1,240				312,018		(125,440)	14
Beginning balance (in shares) at Dec. 31, 2017			40,592,248		444,873
Net loss	(117,391)
Ending balance at Sep. 30, 2018	417,314		$ 1,575		$ (57)		659,776		(243,979)	(1)
Ending balance (in shares) at Sep. 30, 2018			51,554,479		307,936
Beginning balance at Mar. 31, 2018	290,335		$ 1,423				443,774		(154,888)	26
Beginning balance (in shares) at Mar. 31, 2018			46,680,815		438,620
Vesting of restricted shares	14		$ 1				13
Vesting of restricted shares (in shares)			10,043
Exercise of vested options	3,729		$ 11		$ (50)		3,768
Exercise of vested options (in shares)			380,977		(29,259)
Stock-based compensation expense	9,477						9,477
Other comprehensive loss	(21)									(21)
Net loss	(38,380)								(38,380)
Ending balance at Jun. 30, 2018	265,154		$ 1,435		$ (50)		457,032		(193,268)	5
Ending balance (in shares) at Jun. 30, 2018			47,071,835		409,361
Issuance of common shares, net of issuance costs	184,456		$ 137				184,319
Issuance of common shares, net of issuance costs (in shares)			4,210,526
Vesting of restricted shares	21		$ 1				20
Vesting of restricted shares (in shares)			10,046
Exercise of vested options	1,841		$ 2				1,839
Exercise of vested options (in shares)			161,388		(741)
Repurchase of treasury shares	(7)				$ (7)
Repurchase of treasury shares (in shares)			(64,952)		64,952
Issuance of treasury shares to ViaCyte		$ 7,500						$ 7,500
Issuance of treasury shares to ViaCyte (in shares)				165,636		(165,636)
Stock-based compensation expense	9,066						9,066
Other comprehensive loss	(6)									(6)
Net loss	(50,711)								(50,711)
Ending balance at Sep. 30, 2018	417,314		$ 1,575		$ (57)		659,776		(243,979)	(1)
Ending balance (in shares) at Sep. 30, 2018			51,554,479		307,936
Beginning balance at Dec. 31, 2018	392,195		$ 1,584		$ (57)		682,245		(291,569)	(8)
Beginning balance (in shares) at Dec. 31, 2018			51,852,862		307,936
Issuance of common shares, net of issuance costs	23,472						23,472
Issuance of common shares, net of issuance costs (in shares)			631,580
Vesting of restricted shares	15						15
Vesting of restricted shares (in shares)			9,288
Exercise of vested options	1,832		$ 5				1,827
Exercise of vested options (in shares)			141,915
Stock-based compensation expense	10,696						10,696
Other comprehensive loss	8									8
Net loss	(48,408)								(48,408)
Ending balance at Mar. 31, 2019	379,810		$ 1,589		$ (57)		718,255		(339,977)
Ending balance (in shares) at Mar. 31, 2019			52,635,645		307,936
Beginning balance at Dec. 31, 2018	$ 392,195		$ 1,584		$ (57)		682,245		(291,569)	(8)
Beginning balance (in shares) at Dec. 31, 2018			51,852,862		307,936
Exercise of vested options (in shares)	475,062
Net loss	$ 36,316
Ending balance at Sep. 30, 2019	591,878		$ 1,684		$ (57)		845,526		(255,253)	(22)
Ending balance (in shares) at Sep. 30, 2019			55,189,370		256,989
Beginning balance at Mar. 31, 2019	379,810		$ 1,589		$ (57)		718,255		(339,977)
Beginning balance (in shares) at Mar. 31, 2019			52,635,645		307,936
Issuance of common shares, net of issuance costs	28,114		$ 40				28,074
Issuance of common shares, net of issuance costs (in shares)			732,108		(47,297)
Vesting of restricted shares	16		$ 1				15
Vesting of restricted shares (in shares)			12,317
Exercise of vested options	1,254						1,254
Exercise of vested options (in shares)			118,987		(3,650)
Stock-based compensation expense	12,198						12,198
Other comprehensive loss	(10)									(10)
Net loss	(53,699)								(53,699)
Ending balance at Jun. 30, 2019	367,683		$ 1,630		$ (57)		759,796		(393,676)	(10)
Ending balance (in shares) at Jun. 30, 2019			53,499,057		256,989
Issuance of common shares, net of issuance costs	68,661		$ 43				68,618
Issuance of common shares, net of issuance costs (in shares)			1,452,880
Vesting of restricted shares	12		$ 1				11
Vesting of restricted shares (in shares)			34,328
Exercise of vested options	2,338		$ 10				2,328
Exercise of vested options (in shares)			203,105
Stock-based compensation expense	14,773						14,773
Other comprehensive loss	(12)									(12)
Net loss	138,423								138,423
Ending balance at Sep. 30, 2019	$ 591,878		$ 1,684		$ (57)		$ 845,526		$ (255,253)	$ (22)
Ending balance (in shares) at Sep. 30, 2019			55,189,370		256,989

Consolidated Statements of Sh_2

Consolidated Statements of Shareholders' Equity (Parenthetical) $ in Millions

3 Months Ended

Sep. 30, 2019USD ($)

Jun. 30, 2019USD ($)

Mar. 31, 2019USD ($)

Sep. 30, 2018USD ($)

Jun. 30, 2018USD ($)

Mar. 31, 2018USD ($)

Sep. 30, 2019SFr / shares

Jun. 30, 2019SFr / shares

Mar. 31, 2019SFr / shares

Sep. 30, 2018SFr / shares

Jun. 30, 2018SFr / shares

Mar. 31, 2018SFr / shares

Common shares, par value

SFr 0.03

Common Shares [Member]

Issuance costs | $

$ 2.3

$ 1.3

$ 1.2

$ 15.5

$ 0

$ 8.2

Common shares, par value

SFr 0.03

SFr 0.03

SFr 0.03

SFr 0.03

SFr 0.03

SFr 0.03

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net income (loss)	$ 36,316	$ (117,391)
Reconciliation of net income (loss) to net cash used in operating activities:
Depreciation and amortization	3,293	2,574
Equity-based compensation	32,200	21,960
Loss from equity method investment	5,467	3,256
Expense related to ViaCyte transaction		15,109
Other income, non-cash		(169)
Changes in:
Accounts receivable	49	2,074
Prepaid expenses and other assets	(25,342)	(2,502)
Accounts payable and accrued expenses	420	7,982
Deferred revenue	1,714	(270)
Deferred rent		(528)
Operating lease assets and liabilities	(689)
Other liabilities, net	(127)	38
Net cash provided by (used in) operating activities	53,301	(67,867)
Investing activities:
Purchase of property and equipment	(5,732)	(1,773)
Net cash used in investing activities	(5,732)	(1,773)
Financing activities:
Proceeds from issuance of common shares, net of issuance costs	121,216	309,019
Proceeds from exercise of options	5,049	8,241
Repurchase of treasury shares		(57)
Net cash provided by financing activities	126,265	317,203
Effect of exchange rate changes on cash	(14)	(15)
Increase in cash	173,820	247,548
Cash, cash equivalents and restricted cash, beginning of period	459,812	242,912
Cash, cash equivalents and restricted cash, end of period	633,632	490,460
Supplemental disclosure of non-cash investing and financing activities
Property and equipment purchases in accounts payable and accrued expenses	428
Equity issuance costs in accounts payable and accrued expenses	$ 739	$ 1,980

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Reconciliation to amounts within the condensed consolidated balance sheets
Cash and cash equivalents	$ 629,717	$ 456,649	$ 487,295
Restricted cash	3,915	3,163	3,165
Cash, cash equivalents and restricted cash at end of period	$ 633,632	$ 459,812	$ 490,460	$ 242,912

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	1. Basis of Presentation and Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements are unaudited and have been prepared by the Company in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The Company views its operations and manages its business in one operating segment, which is the business of discovering, developing and commercializing therapies derived from or incorporating genome-editing technology. Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These interim financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the financial position and results of operations for the three and nine month interim periods ended September 30, 2019 and 2018. The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These interim financial statements should be read in conjunction with the audited financial statements for the year ended December 31, 2018, which are contained in the 2018 Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on February 25, 2019. Certain items in the prior year’s condensed consolidated financial statements have been reclassified to conform to the current presentation. As a result, no subtotals in the prior year condensed consolidated financial statements were impacted. Use of Estimates 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. Significant estimates in these consolidated financial statements have been made in connection with the calculation of revenues, research and development expenses and equity-based compensation expense. The Company bases its estimates on historical experience and various other assumptions, including, in certain circumstances, future projections that management believes to be reasonable. Actual results could differ from those estimates. Changes in estimates are reflected in reported results in the period in which they become known. Significant Accounting Policies The significant accounting policies used in preparation of these condensed consolidated financial statements for the three and nine months ended September 30, 2019 are consistent with those discussed in Note 2 to the consolidated financial statements in the Company’s 2018 Annual Report on Form 10-K filed with the SEC on February 25, 2019, except with respect to the Company’s lease accounting policy noted within the “Recently adopted accounting standards” section below. Recently Adopted Accounting Standards The Company adopted ASC 842, Leases Impact of Adopting ASC 842 on the Financial Statements January 1, 2019 Prior to ASC 842 Adoption ASC 842 Adjustment January 1, 2019 As Adjusted Consolidated Balance Sheet Data (in thousands): Prepaid expenses and other current assets (1) $ 9,658 $ (553 ) $ 9,105 Operating lease assets (2) $ — $ 26,087 $ 26,087 Deferred rent (3)(4) $ 1,026 $ (1,026 ) $ — Deferred rent non-current (3) $ 11,052 $ (11,052 ) $ — Operating lease liabilities (5) $ — $ 4,930 $ 4,930 Non-current operating lease liabilities (5) $ — $ 32,682 $ 32,682 (1) Represents reclassification of prepaid rent to operating lease assets. (2) Represents capitalization of operating lease assets and reclassification of equipment licenses from prepaid expenses to operating lease assets, offset by reclassification of deferred rent to operating lease assets. (3) Represents reclassification of deferred rent and tenant incentives to operating lease assets. (4) As of December 31, 2018, the deferred rent balance was $1,202, which included $176 of sublease income received prior to year-end but not due until January 1, 2019. (5) Represents recognition of operating lease liabilities.

Property and Equipment, net

Property and Equipment, net	9 Months Ended
	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Property and Equipment, net	2. Property and Equipment, net Property and equipment, net, consists of the following (in thousands): As of September 30, December 31, 2019 2018 Computer equipment $ 585 $ 443 Furniture, fixtures and other 2,640 2,453 Laboratory equipment 12,212 8,964 Leasehold improvements 16,210 13,776 Construction work in process 55 239 Total property and equipment, gross 31,702 25,875 Accumulated depreciation (10,628 ) (7,375 ) Total property and equipment, net $ 21,074 $ 18,500 Depreciation expense for the three and nine months ended September 30, 2019 was $1.3 million and $3.3 million, respectively. Depreciation expense for the three and nine months ended September 30, 2018 was $0.8 million and $2.6 million, respectively.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2019
Payables And Accruals [Abstract]
Accrued Expenses	3. Accrued Expenses Accrued expenses consist of the following (in thousands): As of September 30, December 31, 2019 2018 Payroll and employee-related costs $ 8,174 $ 7,321 Research costs 9,853 7,973 Licensing fees 26 625 Professional fees 2,537 1,848 Intellectual property costs 1,739 2,193 Accrued property and equipment 53 294 Other 15 598 Total $ 22,397 $ 20,852

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	4. Commitments and Contingencies Litigation In the ordinary course of business, the Company is from time to time involved in lawsuits, claims, investigations, proceedings, and threats of litigation relating to intellectual property, commercial arrangements, employment and other matters. While the outcome of those proceedings and claims cannot be predicted with certainty, the Company is not party to any legal or arbitration proceedings that may have significant effects on its financial position. It is not a party to any material proceedings in which any director, member of executive management or affiliate of the Company is either a party adverse to it or its subsidiaries or has a material interest adverse to it or its subsidiaries. As disclosed in its Current Report on Form 8-K filed with the SEC on June 26, 2019, on June 25, 2019, the Company received notification that the United States Patent and Trademark Office initiated an interference proceeding at the Patent Trial and Appeal Board (the “PTAB”) between certain pending U.S. patent applications co-owned by the University of California, the University of Vienna and Dr. Emmanuelle Charpentier (collectively, the “CVC Group”) and certain patents and a patent application currently owned by the Broad Institute and Massachusetts Institute of Technology and, in some instances, the President and Fellows of Harvard College (individually and collectively, the “Broad”), all of which are related to the single guide format of CRISPR/Cas9 genome editing technology in eukaryotic cells. The Company has an exclusive worldwide license in the field of human therapeutics to Dr. Charpentier’s rights as a co-owner of the CVC Group portfolio. Specifically, the PTAB has declared Patent Interference No. 106,115 between the CVC Group’s pending U.S. Patent Application Nos. 15/947,680; 15/947,700; 15/947,718; 15/981,807; 15/981,808; 15/981,809; 16/136,159; 16/136,165; 16/136,168; and 16/136,175, and the Broad’s U.S. Patent Nos. 8,697,359; 8,771,945; 8,795,965; 8,865,406; 8,871,445; 8,889,356; 8,895,308; 8,906,616; 8,932,814; 8,945,839; 8,993,233; 8,999,641; 9,840,713, and U.S. Patent Application No. 14/704,551. Letters of Credit As of September 30, 2019, the Company had restricted cash of $3.9 million representing letters of credit securing the Company’s obligations under certain leased facilities in Cambridge, Massachusetts, 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 September 30, 2019. Research Agreements The Company has engaged several research institutions and companies to identify new delivery strategies and applications of its gene-editing technology. The Company is also a party to a number of research license agreements which require significant upfront payments, future royalty payments and potential milestone payments from time to time, as well as intellectual property agreements, which require maintenance and milestone payments from time to time. In association with these agreements, the Company has committed to making payments of $1.4 million and $2.3 million in the fourth quarter of 2019 and for the year ended December 31, 2020, respectively. For the three and nine months ended September 30, 2019, the Company paid $0.2 million and $2.4 million, respectively, related to these research agreements. For the three and nine months ended September 30, 2018, the Company paid $0.3 million and $1.4 million, respectively, related to these research agreements. The Company is also a party to a number of manufacturing agreements that require upfront payments for the future performance of services. In connection with these agreements, the Company paid $2.2 million in upfront payments, which were recorded as prepaid expenses as of September 30, 2019. The Company will amortize the prepaid balance as services are performed.

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	5. Leases In June 2015, the Company entered into a lease agreement for the lease of research facility space with a commencement date of November 15, 2015 (the “2015 Lease”). The lease expires in February 2022. The 2015 Lease contains escalating rent clauses which require higher rent payments in future years. With the adoption of ASC 842, the Company has recorded a right-of-use asset and corresponding lease liability. In May 2016, the Company entered into a sublease agreement for its primary office and research facility in Cambridge, Massachusetts, with a commencement date of December 23, 2016 (the “2016 Sublease”). The sublease expires in December 2026, and the Company has an option to extend the term of 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 2016 Sublease contains escalating rent clauses which require higher rent payments in future years. With the adoption of ASC 842, the Company has recorded a right-of-use asset and corresponding lease liability. The right-of-use asset and corresponding lease liability does not include the additional five-year period under the option. In May 2019, the Company entered into a lease agreement for office facility space with a commencement date of June 1, 2019 (the “2019 Lease”). The lease expires in November 2026, and the Company has an option to extend the term of the lease for an additional five-year period based on certain conditions within the Company’s control. The 2019 Lease contains escalating rent clauses which require higher rent payments in future years. At lease commencement, the Company recorded a right-of-use asset and corresponding lease liability. The right-of-use asset and corresponding lease liability does not include the additional five-year period under the option. In addition, the Company rents certain office space in Zug, Switzerland, on a short-term basis for which a right-of-use asset and liability are not recorded, in accordance with the practical expedient elected. The Company has embedded leases in certain research and license agreements for which the Company has recorded a right of use asset and liability. These arrangements are not significant in comparison to the Company’s total operating lease assets and liabilities. In addition, the Company has identified certain short-term leases embedded within its manufacturing contracts which are not recorded on the Company’s balance sheet in accordance with the practical expedient elected. The Company identified and assessed the following estimates in recognizing the right-of-use asset and corresponding liability: • Expected lease term : The expected lease term for those leases commencing prior to January 1, 2019 did not change with the adoption of ASC 842. The expected lease term for leases commencing after the adoption of ASC 842 includes noncancelable lease periods and, when applicable, periods covered by an option to extend the lease if the Company is reasonably certain to exercise that option, as well as periods covered by an option to terminate the lease if the Company is reasonably certain not to exercise that option. • Incremental borrowing rate : As the discount rates in the Company’s lease are not implicit, the Company estimated the incremental borrowing rate based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term. The following table summarizes the lease assets and liabilities as of September 30, 2019 (in thousands): As of September 30, 2019 Assets Operating lease assets $ 30,619 Total lease assets 30,619 Liabilities Current Operating lease liabilities 4,805 Non-current Operating lease liabilities, net of current portion 36,827 Total lease liabilities $ 41,632 The following table summarizes operating lease costs included in research and development and general and administrative expense, as well as sublease income for the three and nine months ended September 30, 2019 (in thousands): Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 Operating lease costs $ 2,131 $ 5,857 Short-term lease costs 1,117 3,378 Variable lease costs 698 2,111 Sublease income — (525 ) Net lease cost $ 3,946 $ 10,821 The following table summarizes the maturity of undiscounted payments due under lease liabilities and the present value of those liabilities as of September 30, 2019 (in thousands): Total 2019 $ 1,997 2020 9,334 2021 8,816 2022 7,345 2023 7,363 Thereafter 23,254 Total $ 58,109 Present value adjustment (16,477 ) Present value of lease liabilities $ 41,632 The following table summarizes the lease term and discount rate as of September 30, 2019: As of September 30, 2019 Weighted-average remaining lease term (years) Operating leases 6.8 Weighted-average discount rate Operating leases 9.9 % The following table summarizes the cash paid for amounts included in the measurement of lease liabilities for the nine months ended September 30, 2019 (in thousands): Nine Months Ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities $ 6,362 Operating cash flows from operating leases $ 6,362

Significant Contracts

Significant Contracts	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Significant Contracts	6. Significant Contracts Agreements with Vertex Pharmaceuticals Incorporated and certain of its subsidiaries Summary On October 26, 2015, the Company entered into a strategic collaboration, option and license agreement (the “2015 Collaboration Agreement”) with Vertex Pharmaceuticals Incorporated and certain of its subsidiaries (“Vertex”). The 2015 Collaboration Agreement is focused on the use of the Company’s CRISPR/Cas9 gene editing technology to discover and develop potential new treatments aimed at the underlying genetic causes of human disease. On December 12, 2017, the Company and Vertex entered into Amendment No. 1 to the 2015 Collaboration Agreement (“Amendment No. 1”) and the Joint Development Agreement (the “JDA”). Amendment No. 1, among other things, modified certain definitions and provisions of the 2015 Collaboration Agreement to make them consistent with the JDA and clarified how many options are exercised (or deemed exercised) in connection with certain targets specified under the 2015 Collaboration Agreement. Amendment No. 1 also amended other provisions of the 2015 Collaboration Agreement, including the expiration terms. In connection with the 2015 Collaboration Agreement, Vertex made a nonrefundable upfront payment of $75.0 million. Under the 2015 Collaboration Agreement, Vertex agreed to fund the discovery activities conducted pursuant to the agreement while retaining options to co-exclusive and exclusive licenses. In December 2017, upon execution of the JDA and Amendment No. 1, Vertex exercised its option to obtain a co-exclusive license to develop and commercialize hemoglobinopathy and beta-globin targets. As such, 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. In connection with the JDA, the Company received a $7.0 million up-front payment from Vertex and subsequently received a one-time low seven-digit milestone payment upon the dosing of the second patient in a clinical trial with the initial product candidate. In addition, upon execution of the JDA and Amendment No. 1, it was clarified that Vertex may elect to license up to four remaining targets. For each of these targets, Vertex will lead development and global commercialization activities and the Company has the potential to receive up to $420.0 million in development, regulatory and commercial milestones and royalties on net product sales for each of the four targets (inclusive of $10 million due upon exercise of each exclusive option). In June 2019, the Company and Vertex entered into a series of agreements, which closed on July 23, 2019, including a strategic collaboration and license agreement (the “2019 Collaboration Agreement”) for the development and commercialization of products for the treatment of Duchenne Muscular Dystrophy (“DMD”) and Myotonic Dystrophy Type 1 (“DM1”). Under the terms of the 2019 Collaboration Agreement, the Company received an upfront, nonrefundable payment of $175 million. In addition, the Company is eligible to receive potential future payments of up to $825 million based upon the successful achievement of specified research, development, regulatory and commercial milestones for the DMD and DM1 programs. The Company is also eligible to receive tiered royalties on future net sales on any products that may result from this collaboration. For the DMD program, Vertex is responsible for all research, development, manufacturing and commercialization activities and all related costs. For the DM1 program, the Company will perform specified guide RNA research and Vertex is responsible for all other research, development, manufacturing and commercialization costs. Upon Investigational New Drug (“IND”) application filing, the Company has the option to forego the DM1 milestones and royalties and instead, co-develop and co-commercialize all DM1 products globally in exchange for payment of 50% of research and development costs incurred by Vertex from the effective date of the agreement through IND filing. In connection with the execution of the 2019 Collaboration Agreement, the Company and Vertex entered into a second amendment to the 2015 Collaboration Agreement (“Amendment No. 2”). Among other things, Amendment No. 2 modified certain definitions and provisions of the 2015 Collaboration Agreement to make them consistent with the 2019 Collaboration Agreement and set forth the number and identity of the collaboration targets under the 2015 Collaboration Agreement. The Company and Vertex agreed that one of the four remaining options under the 2015 Collaboration Agreement, as amended, would not be exercised; instead, the Company will reacquire the exclusive right and will conduct research and development activities for the specified target. Vertex will have the option to co-develop and co-commercialize the specified target upon IND filing in exchange for payment of 50% of research and development costs incurred by the Company from the effective date of the agreement through IND filing In October 2019, Vertex exercised options granted to it under the 2015 Collaboration Agreement to exclusively license three collaboration targets developed under the 2015 Collaboration Agreement. As a result, the Company is entitled to receive an aggregate of $30.0 million in option exercise payments from Vertex, which we expect to receive in the fourth quarter. Accounting for the Vertex Agreements The 2015 Collaboration Agreement, Amendment No. 1, Amendment No. 2, JDA and 2019 Collaboration Agreement are collectively the “Vertex Agreements.” The 2015 Collaboration Agreement, Amendment No. 1, and JDA are collectively the “2015 Agreements” and the 2019 Collaboration Agreement and Amendment No. 2. are collectively the “2019 Agreements.” The Vertex Agreements include components of a customer-vendor relationship as defined under ASC 606, Revenue from Contracts with Customers (“ ”) Collaborative Arrangements Research and Development Accounting Analysis Under ASC 606 Identification of the Contract(s) The 2019 Agreements represented a contract modification to the 2015 Agreements. As a result, the 2019 Agreements and the 2015 Agreements are combined for accounting purposes and treated as a single arrangement. Identification of Performance Obligations The Company concluded the following material promises were both capable of being distinct and distinct within the context of the Vertex Agreements and represented separate performance obligations: (i) an exclusive license for worldwide rights for DMD gene editing products (“DMD License”); (ii) an exclusive license for worldwide rights for DM1 gene editing products (“DM1 License”); (iii) the performance of specified guide RNA research for DM1 (“DM1 R&D Services”); (iv) a material right representing the option to obtain a co-exclusive development and commercialization license for a specified target (“Specified Target Option”); (v) three material rights representing the option for up to three exclusive licenses to develop and commercialize the collaboration targets (“Collaboration Target Options”), and (vi) the waiving of Vertex’s material right associated with its option to a fourth exclusive license in connection with the Company’s reacquisition of exclusive rights to the specified target. Determination of Transaction Price The overall transaction price was determined based on the remaining transaction price from the 2015 Agreements, as well as the transaction price from the 2019 Agreements. The transaction price includes variable consideration estimated using the most likely amount methodology. As such, the Company determined the transaction price totaling $268.6 million was comprised of: (i) $57.8 million of pre-existing deferred revenue from the 2015 Agreements; (ii) non-cash consideration of $10.0 million related to the waiving of Vertex’s material right associated with its option to a fourth exclusive license in connection with the Company’s reacquisition of exclusive rights to the specified target The Company determined that all other possible variable consideration resulting from milestones and royalties discussed above was fully constrained as of September 30, 2019. The Company will re-evaluate the transaction price in each reporting period. Allocation of Transaction Price to Performance Obligations The selling price of each performance obligation was determined based on the Company’s estimated standalone selling price (the “ESSP”). The Company developed the ESSP for all the performance obligations included in the Vertex Agreements 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 then allocated the transaction price to each performance obligation on a relative standalone selling price basis. The ESSP for the DMD License and DM1 License was determined to be $224.6 million and $76.2 million, respectively. The ESSP was determined based on probability and present value adjusted cash flows from projected worldwide net profit or net loss for each of the respective programs based on probability assessments, projections based on internal forecasts, industry data, and information from other guideline companies within the same industry and other relevant factors. The ESSP for the Specified Target Option material right was determined to be $17.5 million, which was based on the incremental discount between (i) the value of the probability and present value adjusted cash flows from the equal sharing of projected worldwide net profit or net loss increased by the value of the option provided to Vertex less (ii) the expected exercise price at the time of option exercise. The present value adjusted cash flows also considered projections based on internal forecasts, industry data, and information from other guideline companies within the same industry and other relevant factors. The ESSP for each of the three Collaboration Target Option material rights was determined to be $25.0 million, $22.2 million and $22.2 million, respectively, which was determined based the probability and present value adjusted cash flows from milestone payments owed for exclusive licenses, less the price paid to exercise each option. The aforementioned ESSP’s reflect the level of risk and expected probability of success inherent in the nature associated of the associated research area. The ESSP for the waiving of Vertex’s material right associated with its option to a fourth exclusive license under the 2015 Agreements was determined to be $10.0 million, or the contractual value of the option. The ESSP for the DM1 R&D Services was determined to be $1.7 million, which was based on 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. Recognition of Revenue The Company determined that the DMD License and DM1 License represent functional intellectual property, as the intellectual property provides Vertex with the ability to perform a function or task in the form of research and development. As such, the revenue related to the licenses was recognized at the point in time in which they were delivered during the third quarter of 2019. The Company concluded that the Specified Target Option and Collaboration Target Options are considered material rights under the Vertex Agreements. As a result, revenue related to these material rights will be recognized at a point in time, upon the exercise of the option by Vertex or expiration. The revenue allocated to the waiving of Vertex’s material right associated with its option to a fourth exclusive license was recognized at the point in time in which the option was waived, on the effective date of the 2019 Agreements. The Company will recognize revenue related to the DM1 R&D Services over time as the services are rendered, which is expected to be over an 18-month period from the effective date of the 2019 Agreements. The Company recognized $211.9 million and $212.1 million of revenue related to the Vertex Agreements for the three and nine months ended September 30, 2019, respectively. The Company recognized $0.1 million and $0.5 million of revenue related to the Vertex Agreements for the three and nine months ended September 30, 2018. As of September 30, 2019, there was $47.7 million of current deferred revenue and $11.9 million non-current deferred revenue related the Vertex Agreements. The amounts classified as current deferred revenue primarily relate to the Collaboration Target Options which expire less than one year from September 30, 2019. The amounts classified as non-current deferred revenue primarily relate to the Specified Target Option, which is not expected to occur within one year from September 30, 2019. The transaction price allocated to the remaining performance obligations was $59.6 million. Milestones under the Vertex Agreements The Company has evaluated the milestones that may be received in connection with the Vertex Agreements. In connection with the Collaboration Target Options, the Company is eligible to receive up to $420.0 million (inclusive of $10 million due upon exercise of each exclusive option) in development, regulatory and commercial milestones and royalties on net product sales for each of the three collaboration targets. 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. In connection with the JDA, the Company received a one-time low seven-digit milestone payment upon the dosing of the second patient in a clinical trial with the initial product candidate. Revenue was recognized for this milestone in the third quarter of 2019, the point in time in which the milestone was both probable and achieved. The Company is eligible to receive potential future payments of up to $825 million based upon the successful achievement of specified research, development, regulatory and commercial milestones for the DMD and DM1 programs. As discussed above, the first research milestone of $25.0 million was included in the transaction price. This amount is recorded as a contract asset within prepaid expenses and other current assets on the condensed consolidated balance sheet. The Company is also eligible to receive tiered royalties on future net sales on any products that may result from this collaboration; however, the Company has the option to forego the DM1 milestones and royalties to co-develop and co-commercialize all DM1 products globally. With the exception of the first research milestone of $25.0 million, each of the remaining milestones are fully constrained as of September 30, 2019. There is uncertainty that the events to obtain the research and developmental milestones will be achieved given the nature of clinical development and the stage of the CRISPR/Cas9 technology. The remaining research, development and regulatory milestones will be constrained until it is probable that a significant revenue reversal will not occur. Commercial milestones and royalties relate predominantly to a license of intellectual property and are determined by sales or usage-based thresholds. The commercial milestones and royalties are accounted for under the royalty recognition constraint and will be accounted for as constrained variable consideration. The Company applies the royalty recognition constraint for each commercial milestone and will not recognize revenue for each until the subsequent sale of a licensed product (achievement of each) occurs. As discussed above, in October 2019, Vertex exercised its three Collaboration Target Options. As a result, the Company will record revenue of $76.7 million during the fourth quarter of 2019, inclusive of $30 million in cash received related to the option exercises, as well as $46.7 million of previously deferred revenue allocated to the three Collaboration Target Options. Accounting Analysis under ASC 808 The Company did not identify any additional collaborative elements as a result of the 2019 Agreements. As such, the The Company recognized $7.5 million and $21.3 million of research and development expense related to the Vertex Agreements for the three and nine months ended September 30, 2019, respectively. The Company recognized $8.8 million and $25.4 million of research and development expense related to the collaboration with Vertex for the three and nine months ended September 30, 2018, respectively. Research and development expense for the three and nine months ended September 30, 2019 was net of $3.8 million and $11.8 million of reimbursements from Vertex, respectively. Research and development expense for the three and nine months ended September 30, 2018 was net of $3.7 million and $10.4 million of reimbursements from Vertex, respectively. Accounting Analysis under ASC 730 In connection with the 2019 Vertex Agreements, the Company and Vertex agreed that one of the four remaining options under the 2015 Agreements, as amended, would not be exercised; instead, the Company will conduct research and development activities for a specified target. Vertex will have the option to co-develop and co-commercialize the specified target in exchange for payment of 50% of research and development costs incurred by the Company from the effective date of the agreement through IND filing. If Vertex does not exercise its option to do so within a specified time period, Vertex is eligible to receive up to $395 million in potential specified research, development, regulatory and commercial milestones and tiered single-digit royalties on future net sales. In connection therewith, the Company determined that in order for the Company to obtain the right to conduct research and development activities on the specified target, it had waived its right to receive an option exercise payment of $10.0 million from Vertex, which was included as non-cash consideration in the transaction price described above. The Company then subsequently reacquired its rights to the specified target by waiving payment owed by Vertex of $10.0 million for a license that represents in-process research and development and therefore, $10.0 million of non-cash consideration was fully expensed upon the execution of the 2019 Agreements. The Company also determined that research and development services through IND for the specified target and any payment of future development and commercialization milestones, as well as sales-based milestones and royalties for the specified target, would be accounted for as research and development costs under ASC 730 and expensed as incurred. In addition, the Company also determined that should the Company elect its option to co-develop and co-commercialize all DM1 products globally, it will record the option fee as research and development expense upon exercise. Joint Venture with Bayer Healthcare LLC On December 19, 2015, the Company entered into an agreement with Bayer Healthcare LLC and certain of its affiliates (“Bayer”), to establish a joint venture to focus on the research and 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 Therapeutics LLP (“Casebia”). Bayer and the Company each received a 50% equity interest in the entity in exchange for their respective 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. Under the agreement, Casebia paid the Company $35.0 million in exchange for a worldwide, exclusive license to commercialize the Company’s gene-editing technology specifically for the indications covered by the license. There are no milestone, royalties or other payments due to the Company under this aspect of the agreement. The Company also entered into a separate services agreement with Casebia, under which the Company agreed to provide compensated research and development services. 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 and subsequently recorded unrealized equity method losses for the same amount. The Company has no further contractual obligations to provide cash financing to Casebia and accordingly, no additional losses have been recorded beyond the initial equity amount. Casebia’s net losses were $22.6 million and $54.9 million for the three and nine months ended September 30, 2019, respectively. Casebia’s net losses were $13.5 million and $25.8 million for the three and nine months ended September 30, 2018, respectively. Unrecognized equity method losses in excess of the Company’s equity investment in Casebia were $70.1 million and $45.3 million as of September 30, 2019 and December 31, 2018, respectively. The remaining performance obligations include research and development services, which are recorded as revenue under ASC 606 and cost sharing activities with Casebia related to shared research and technology licenses are accounted for as a cost/profit sharing arrangement under ASC 808, with the related impact of the cost sharing included as research and development expense. During the three and nine months ended September 30, 2019, the Company recognized $0.1 million and $0.5 million of revenue, respectively, related to the collaboration with Casebia. During the three and nine months ended September 30, 2018, the Company recognized $0.9 million and $2.0 million of revenue, respectively, related to the collaboration with Casebia. During the three and nine months ended September 30, 2019, the Company recognized $0.1 million and $0.7 million, respectively, of research and development expense related to the collaboration with Casebia. During the three and nine months ended September 30, 2018, the Company recognized $1.2 million and $2.4 million, respectively, of research and development expense related to the collaboration with Casebia. During the three and nine months ended September 30, 2019, the Company recognized a loss from equity method investment of $3.3 million and $5.5 million, respectively, related to stock-based compensation expense for Casebia employees. During the three and nine months ended September 30, 2018, the Company recognized a loss from equity method investment of $1.2 million and $2.2 million, respectively, related to stock-based compensation expense for Casebia employees.

Share Capital

Share Capital	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Share Capital	7. Share Capital The Company had 55,677,088 authorized common shares as of September 30, 2019, with a par value of CHF 0.03 per share. Included in the authorized common shares as of September 30, 2019 are 256,989 treasury shares which are legally outstanding but not considered outstanding for accounting purposes and 230,729 shares registered and reserved for future issuance. The Company had conditional capital reserved for future issuance of 19,028,428 common shares for employee benefit plans and 4,919,700 common shares for debt instruments as of September 30, 2019. Under Swiss law, authorized share capital consisted of 25,134,003 common shares as of September 30, 2019. At-the-Market Offering In August 2018, the Company entered into an Open Market Sale Agreement SM In August 2019, following the termination of the 2018 ATM by its terms, the Company entered into a new Open Market Sale Agreement SM

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	8. Stock-based Compensation During the three and nine months ended September 30, 2019 and 2018, the Company recognized the following stock-based compensation expense (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Research and development $ 6,262 $ 3,999 $ 17,137 $ 12,081 General and administrative 5,081 4,056 15,063 9,879 Loss from equity method investment 3,430 1,012 5,467 3,256 Total $ 14,773 $ 9,067 $ 37,667 $ 25,216 Stock option activity The following table summarizes stock option activity for the nine months ended September 30, 2019 (intrinsic value in thousands): Stock Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2018 6,689,311 $ 25.42 8.3 $ 68,572 Granted 2,136,873 $ 37.23 Exercised (475,062 ) $ 12.03 Cancelled or forfeited (337,020 ) $ 31.50 Outstanding at September 30, 2019 8,014,102 $ 29.10 8.0 $ 119,011 Exercisable at September 30, 2019 3,544,643 $ 21.65 7.1 $ 76,945 Vested and expected to vest at September 30, 2019 8,014,102 $ 29.10 8.0 $ 119,011 The Company estimated the fair value of each stock option award using the Black-Scholes option-pricing model based on the following assumptions: Nine Months Ended September 30, 2019 2018 Assumptions Weighted-average expected volatility 69.2 % 71.9 % Expected term (in years) 6.0 6.0 Risk-free interest rate 2.4 % 2.7 % Expected dividend yield 0.0 % 0.0 % As of September 30, 2019, total unrecognized compensation expense related to stock options was $93.3 million which the Company expects to recognize over a remaining weighted-average period of 2.8 years. In May 2018, the Company modified the terms of certain options held by a departing employee. The modification resulted in $2.2 million in stock-based compensation expense recorded during the period. In September 2019, the Company modified the terms of certain options held by non-employees. The modifications resulted in $2.9 million in stock-based compensation expense recorded during the period. Restricted stock activity The following table summarizes restricted stock activity for the nine months ended September 30, 2019: Restricted Stock Weighted- Average Grant Date Fair Value Unvested balance as of December 31, 2018 327,342 $ 36.72 Granted 145,000 43.61 Vested (69,091 ) 15.07 Cancelled or forfeited (23,000 ) 41.64 Unvested balance as of September 30, 2019 380,251 $ 42.98 As of September 30, 2019, total unrecognized compensation expense related to unvested restricted common shares was $10.5

Net Income (Loss) Per Share Att

Net Income (Loss) Per Share Attributable to Common Shareholders	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Income (Loss) Per Share Attributable to Common Shareholders	9. Basic net loss per share is calculated by dividing net 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 share equivalents outstanding for the period, including any dilutive effect from outstanding stock options and warrants using the treasury stock method. The following table sets forth the computation of basic and diluted net income (loss) per share for the periods ended (in thousands, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Basic net income (loss) per common share calculation: Net income (loss) attributable to common shareholders $ 138,423 $ (50,711 ) $ 36,316 $ (117,391 ) Net income (loss) attributable to common shareholders - basic $ 138,423 $ (50,711 ) $ 36,316 $ (117,391 ) Basic weighted-average common shares outstanding 54,829,057 47,391,988 53,380,123 46,709,388 Basic net income (loss) per common share $ 2.52 $ (1.07 ) $ 0.68 $ (2.51 ) Diluted net income (loss) per common share calculation: Net income (loss) attributable to common shareholders $ 138,423 $ (50,711 ) $ 36,316 $ (117,391 ) Net income (loss) attributable to common shareholders - diluted $ 138,423 $ (50,711 ) $ 36,316 $ (117,391 ) Weighted-average shares used to compute basic net income (loss) per common share 54,829,057 47,391,988 53,380,123 46,709,388 Effect of potentially dilutive securities: Outstanding options 2,612,354 — 2,326,824 — Unvested restricted common shares 157,490 — 114,473 — Weighted-average shares used to compute diluted net income (loss) per common share 57,598,901 47,391,988 55,821,420 46,709,388 Diluted net income (loss) per common share $ 2.40 $ (1.07 ) $ 0.65 $ (2.51 ) The Company did not include the securities in the following table in the computation of the net income (loss) per share calculations because the effect would have been anti-dilutive during each period : Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Outstanding options 2,612,354 6,698,579 2,326,824 6,698,579 Unvested restricted common shares 157,490 178,884 114,473 178,884 Total 2,769,844 6,877,463 2,441,297 6,877,463

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes During the three and nine months ended September 30, 2019, the Company recorded an income tax provision of $0.3 million and $0.4 million, respectively, representing an effective tax rate of 0.2% and 1.2%, respectively. During the three and nine months ended September 30, 2018, the Company recorded an income tax provision of $0.1 million and $0.3 million, respectively, representing an effective tax rate of -0.3% and -0.3%, respectively. The income tax provision is primarily attributable to the year-to-date pre-tax income earned by the Company’s U.S. subsidiary. The difference in the statutory tax rate and effective tax rate is primarily a result of the jurisdictional mix of earnings and losses that are not benefited. The Company maintains a valuation allowance against certain deferred tax assets that are not more-likely-than-not realizable. As a result, the Company has not recognized a tax benefit related to losses generated in Switzerland in the current periods.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	11. Related Party Transactions In the fourth quarter of 2018, upon becoming an owner of record of more than 10% of the voting interest of the Company, Vertex became a related party under ASC 850, Related party disclosures. Refer to Note 6 for discussion of transactions with Casebia and Vertex, related parties. The Company is a party to intellectual property license agreements with Dr. Emmanuelle Charpentier. For the three and nine months ended September 30, 2019, the Company paid Dr. Charpentier approximately $1.2 million of sublicense fees in research and development expense primarily related to the Vertex Agreements.

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements are unaudited and have been prepared by the Company in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The Company views its operations and manages its business in one operating segment, which is the business of discovering, developing and commercializing therapies derived from or incorporating genome-editing technology. Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These interim financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the financial position and results of operations for the three and nine month interim periods ended September 30, 2019 and 2018. The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These interim financial statements should be read in conjunction with the audited financial statements for the year ended December 31, 2018, which are contained in the 2018 Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on February 25, 2019. Certain items in the prior year’s condensed consolidated financial statements have been reclassified to conform to the current presentation. As a result, no subtotals in the prior year condensed consolidated financial statements were impacted.
Use of Estimates	Use of Estimates 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. Significant estimates in these consolidated financial statements have been made in connection with the calculation of revenues, research and development expenses and equity-based compensation expense. The Company bases its estimates on historical experience and various other assumptions, including, in certain circumstances, future projections that management believes to be reasonable. Actual results could differ from those estimates. Changes in estimates are reflected in reported results in the period in which they become known.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards The Company adopted ASC 842, Leases Impact of Adopting ASC 842 on the Financial Statements January 1, 2019 Prior to ASC 842 Adoption ASC 842 Adjustment January 1, 2019 As Adjusted Consolidated Balance Sheet Data (in thousands): Prepaid expenses and other current assets (1) $ 9,658 $ (553 ) $ 9,105 Operating lease assets (2) $ — $ 26,087 $ 26,087 Deferred rent (3)(4) $ 1,026 $ (1,026 ) $ — Deferred rent non-current (3) $ 11,052 $ (11,052 ) $ — Operating lease liabilities (5) $ — $ 4,930 $ 4,930 Non-current operating lease liabilities (5) $ — $ 32,682 $ 32,682 (1) Represents reclassification of prepaid rent to operating lease assets. (2) Represents capitalization of operating lease assets and reclassification of equipment licenses from prepaid expenses to operating lease assets, offset by reclassification of deferred rent to operating lease assets. (3) Represents reclassification of deferred rent and tenant incentives to operating lease assets. (4) As of December 31, 2018, the deferred rent balance was $1,202, which included $176 of sublease income received prior to year-end but not due until January 1, 2019. (5) Represents recognition of operating lease liabilities.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
ASC 842 [Member]
Impact of Adoption ASC 842 on the Financial Statements	Impact of Adopting ASC 842 on the Financial Statements January 1, 2019 Prior to ASC 842 Adoption ASC 842 Adjustment January 1, 2019 As Adjusted Consolidated Balance Sheet Data (in thousands): Prepaid expenses and other current assets (1) $ 9,658 $ (553 ) $ 9,105 Operating lease assets (2) $ — $ 26,087 $ 26,087 Deferred rent (3)(4) $ 1,026 $ (1,026 ) $ — Deferred rent non-current (3) $ 11,052 $ (11,052 ) $ — Operating lease liabilities (5) $ — $ 4,930 $ 4,930 Non-current operating lease liabilities (5) $ — $ 32,682 $ 32,682 (1) Represents reclassification of prepaid rent to operating lease assets. (2) Represents capitalization of operating lease assets and reclassification of equipment licenses from prepaid expenses to operating lease assets, offset by reclassification of deferred rent to operating lease assets. (3) Represents reclassification of deferred rent and tenant incentives to operating lease assets. (4) As of December 31, 2018, the deferred rent balance was $1,202, which included $176 of sublease income received prior to year-end but not due until January 1, 2019. (5) Represents recognition of operating lease liabilities.

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	9 Months Ended
	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net, consists of the following (in thousands): As of September 30, December 31, 2019 2018 Computer equipment $ 585 $ 443 Furniture, fixtures and other 2,640 2,453 Laboratory equipment 12,212 8,964 Leasehold improvements 16,210 13,776 Construction work in process 55 239 Total property and equipment, gross 31,702 25,875 Accumulated depreciation (10,628 ) (7,375 ) Total property and equipment, net $ 21,074 $ 18,500

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2019
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following (in thousands): As of September 30, December 31, 2019 2018 Payroll and employee-related costs $ 8,174 $ 7,321 Research costs 9,853 7,973 Licensing fees 26 625 Professional fees 2,537 1,848 Intellectual property costs 1,739 2,193 Accrued property and equipment 53 294 Other 15 598 Total $ 22,397 $ 20,852

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Summary of Lease Assets and Liabilities	The following table summarizes the lease assets and liabilities as of September 30, 2019 (in thousands): As of September 30, 2019 Assets Operating lease assets $ 30,619 Total lease assets 30,619 Liabilities Current Operating lease liabilities 4,805 Non-current Operating lease liabilities, net of current portion 36,827 Total lease liabilities $ 41,632
Summary of Operating Lease Costs Included in Research and Development and General and Administrative Expense, as well as Sublease Income	The following table summarizes operating lease costs included in research and development and general and administrative expense, as well as sublease income for the three and nine months ended September 30, 2019 (in thousands): Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 Operating lease costs $ 2,131 $ 5,857 Short-term lease costs 1,117 3,378 Variable lease costs 698 2,111 Sublease income — (525 ) Net lease cost $ 3,946 $ 10,821
Summary of Maturity of Undiscounted Payments Due under Lease Liabilities and Present Value of Those Liabilities	The following table summarizes the maturity of undiscounted payments due under lease liabilities and the present value of those liabilities as of September 30, 2019 (in thousands): Total 2019 $ 1,997 2020 9,334 2021 8,816 2022 7,345 2023 7,363 Thereafter 23,254 Total $ 58,109 Present value adjustment (16,477 ) Present value of lease liabilities $ 41,632
Summary of Lease Term and Discount Rate	The following table summarizes the lease term and discount rate as of September 30, 2019: As of September 30, 2019 Weighted-average remaining lease term (years) Operating leases 6.8 Weighted-average discount rate Operating leases 9.9 %
Summary of Cash Paid for Amounts Included in Measurement of Lease Liabilities	The following table summarizes the cash paid for amounts included in the measurement of lease liabilities for the nine months ended September 30, 2019 (in thousands): Nine Months Ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities $ 6,362 Operating cash flows from operating leases $ 6,362

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Stock-Based Compensation Expense	During the three and nine months ended September 30, 2019 and 2018, the Company recognized the following stock-based compensation expense (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Research and development $ 6,262 $ 3,999 $ 17,137 $ 12,081 General and administrative 5,081 4,056 15,063 9,879 Loss from equity method investment 3,430 1,012 5,467 3,256 Total $ 14,773 $ 9,067 $ 37,667 $ 25,216
Summary of Stock Option Activity	The following table summarizes stock option activity for the nine months ended September 30, 2019 (intrinsic value in thousands): Stock Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2018 6,689,311 $ 25.42 8.3 $ 68,572 Granted 2,136,873 $ 37.23 Exercised (475,062 ) $ 12.03 Cancelled or forfeited (337,020 ) $ 31.50 Outstanding at September 30, 2019 8,014,102 $ 29.10 8.0 $ 119,011 Exercisable at September 30, 2019 3,544,643 $ 21.65 7.1 $ 76,945 Vested and expected to vest at September 30, 2019 8,014,102 $ 29.10 8.0 $ 119,011
Assumptions to Estimate Fair Value of Stock Option Award Using the Black-Scholes Option-Pricing Model	The Company estimated the fair value of each stock option award using the Black-Scholes option-pricing model based on the following assumptions: Nine Months Ended September 30, 2019 2018 Assumptions Weighted-average expected volatility 69.2 % 71.9 % Expected term (in years) 6.0 6.0 Risk-free interest rate 2.4 % 2.7 % Expected dividend yield 0.0 % 0.0 %
Summary of Restricted Stock Activity	The following table summarizes restricted stock activity for the nine months ended September 30, 2019: Restricted Stock Weighted- Average Grant Date Fair Value Unvested balance as of December 31, 2018 327,342 $ 36.72 Granted 145,000 43.61 Vested (69,091 ) 15.07 Cancelled or forfeited (23,000 ) 41.64 Unvested balance as of September 30, 2019 380,251 $ 42.98

Net Income (Loss) Per Share A_2

Net Income (Loss) Per Share Attributable to Common Shareholders (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Income (Loss) per Share	The following table sets forth the computation of basic and diluted net income (loss) per share for the periods ended (in thousands, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Basic net income (loss) per common share calculation: Net income (loss) attributable to common shareholders $ 138,423 $ (50,711 ) $ 36,316 $ (117,391 ) Net income (loss) attributable to common shareholders - basic $ 138,423 $ (50,711 ) $ 36,316 $ (117,391 ) Basic weighted-average common shares outstanding 54,829,057 47,391,988 53,380,123 46,709,388 Basic net income (loss) per common share $ 2.52 $ (1.07 ) $ 0.68 $ (2.51 ) Diluted net income (loss) per common share calculation: Net income (loss) attributable to common shareholders $ 138,423 $ (50,711 ) $ 36,316 $ (117,391 ) Net income (loss) attributable to common shareholders - diluted $ 138,423 $ (50,711 ) $ 36,316 $ (117,391 ) Weighted-average shares used to compute basic net income (loss) per common share 54,829,057 47,391,988 53,380,123 46,709,388 Effect of potentially dilutive securities: Outstanding options 2,612,354 — 2,326,824 — Unvested restricted common shares 157,490 — 114,473 — Weighted-average shares used to compute diluted net income (loss) per common share 57,598,901 47,391,988 55,821,420 46,709,388 Diluted net income (loss) per common share $ 2.40 $ (1.07 ) $ 0.65 $ (2.51 )
Schedule of Antidilutive Securities not Include in Computation of Net Income (Loss) per Share	The Company did not include the securities in the following table in the computation of the net income (loss) per share calculations because the effect would have been anti-dilutive during each period : Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Outstanding options 2,612,354 6,698,579 2,326,824 6,698,579 Unvested restricted common shares 157,490 178,884 114,473 178,884 Total 2,769,844 6,877,463 2,441,297 6,877,463

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Net lease assets	$ 30,619
Net lease liabilities	$ 41,632
ASC 842 [Member]
Summary Of Significant Accounting Policies [Line Items]
Net lease assets		$ 26,087
Net lease liabilities		$ 37,600

Basis of Presentation and Sig_5

Basis of Presentation and Significant Accounting Policies - Impact of Adopting ASC 842 on Financial Statements (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Prepaid expenses and other current assets	$ 34,309		$ 9,658
Operating lease assets	30,619
Deferred rent			1,202
Deferred rent non-current			$ 11,052
Operating lease liabilities	4,805
Non-current operating lease liabilities	$ 36,827
ASC 842 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Prepaid expenses and other current assets		$ 9,105
Operating lease assets		26,087
Operating lease liabilities		4,930
Non-current operating lease liabilities		32,682
Prior [Member] | ASC 842 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Prepaid expenses and other current assets		9,658
Deferred rent		1,026
Deferred rent non-current		11,052
Adjustment [Member] | ASC 842 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Prepaid expenses and other current assets		(553)
Operating lease assets		26,087
Deferred rent		(1,026)
Deferred rent non-current		(11,052)
Operating lease liabilities		4,930
Non-current operating lease liabilities		$ 32,682

Basis of Presentation and Sig_6

Basis of Presentation and Significant Accounting Policies - Impact of Adopting ASC 842 on Financial Statements (Parenthetical) (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Deferred rent		$ 1,202
Sublease income	$ 525	$ 176

Property and Equipment, net - S

Property and Equipment, net - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 31,702	$ 25,875
Accumulated depreciation	(10,628)	(7,375)
Total property and equipment, net	21,074	18,500
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	585	443
Furniture, Fixtures and Other [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,640	2,453
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	12,212	8,964
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	16,210	13,776
Construction Work in Process [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 55	$ 239

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Depreciation expense	$ 1.3	$ 0.8	$ 3.3	$ 2.6

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accrued Liabilities Current [Abstract]
Payroll and employee-related costs	$ 8,174	$ 7,321
Research costs	9,853	7,973
Licensing fees	26	625
Professional fees	2,537	1,848
Intellectual property costs	1,739	2,193
Accrued property and equipment	53	294
Other	15	598
Total	$ 22,397	$ 20,852

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended		12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2020
Contingencies And Commitments [Line Items]
Research and development expense	[1]		$ 57,246	$ 39,820	$ 130,601	$ 84,972
Research Agreements [Member]
Contingencies And Commitments [Line Items]
Research and development expense			200	$ 300	2,400	$ 1,400
Research Agreements [Member] | Scenario Forecast [Member]
Contingencies And Commitments [Line Items]
Research and development expense		$ 1,400					$ 2,300
Manufacturing Agreements [Member] | Prepaid Expenses [Member]
Contingencies And Commitments [Line Items]
Upfront payment recorded as prepaid expense			2,200		2,200
Letter of Credit [Member]
Contingencies And Commitments [Line Items]
Letters of credit secured by cash held in restricted depository account			$ 3,900		$ 3,900
[1]	Including the following research and development expense with a related party, see Notes 6 & 11

Leases - Additional Information

Leases - Additional Information (Detail)	1 Months Ended			9 Months Ended
	May 31, 2019	May 31, 2016	Jun. 30, 2015	Sep. 30, 2019
2015 Lease [Member]
Lessee Lease Description [Line Items]
Lease commencement date			Nov. 15, 2015
Lease expiration date			Feb. 28, 2022
2016 Sublease [Member]
Lessee Lease Description [Line Items]
Lease commencement date		Dec. 23, 2016
Lease expiration date		Dec. 31, 2026
Lessee, operating sublease, option to extend				an option to extend the term of sublease for an additional five-year period if, at the time of expiration of the initial term
Lessee, operating sublease, existence of option to extend		true
Extended term of lease expiration		5 years
2019 Lease [Member]
Lessee Lease Description [Line Items]
Lease commencement date	Jun. 1, 2019
Lease expiration date	Nov. 30, 2026
Extended term of lease expiration	5 years
Lessee, operating lease, option to extend				an option to extend the term of the lease for an additional five-year period based on certain conditions within the Company’s control.
Lessee, operating lease, existence of option to extend	true

Leases - Summary of Lease Asset

Leases - Summary of Lease Assets and Liabilities (Detail) $ in Thousands	Sep. 30, 2019USD ($)
Assets
Operating lease assets	$ 30,619
Total lease assets	30,619
Liabilities
Operating lease liabilities, current	4,805
Operating lease liabilities, net of current portion	36,827
Total lease liabilities	$ 41,632

Leases - Summary of Operating L

Leases - Summary of Operating Lease Costs Included in Research and Development and General and Administrative Expense, as well as Sublease Income (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Operating lease costs	$ 2,131	$ 5,857
Short-term lease costs	1,117	3,378
Variable lease costs	698	2,111
Sublease income		(525)	$ (176)
Net lease cost	$ 3,946	$ 10,821

Leases - Summary of Maturity of

Leases - Summary of Maturity of Undiscounted Payments Due under Lease Liabilities and Present Value of Those Liabilities (Detail) $ in Thousands	Sep. 30, 2019USD ($)
Leases [Abstract]
2019	$ 1,997
2020	9,334
2021	8,816
2022	7,345
2023	7,363
Thereafter	23,254
Total	58,109
Present value adjustment	(16,477)
Present value of lease liabilities	$ 41,632

Leases - Summary of Lease Term

Leases - Summary of Lease Term and Discount Rate (Detail)	Sep. 30, 2019
Leases [Abstract]
Operating leases, weighted-average remaining lease term (years)	6 years 9 months 18 days
Operating leases, weighted-average discount rate	9.90%

Leases - Summary of Cash Paid f

Leases - Summary of Cash Paid for Amounts Included in Measurement of Lease Liabilities (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 6,362
Operating cash flows from operating leases	$ 6,362

Significant Contracts - Additio

Significant Contracts - Additional Information (Detail)		Feb. 12, 2016USD ($)	Oct. 26, 2015USD ($)	Oct. 31, 2019OptionLicense	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Sep. 30, 2019USD ($)Option	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2016USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-current deferred revenue						$ 11,871,000						$ 11,871,000		$ 57,780,000
Collaboration revenue	[1]					211,928,000			$ 563,000			212,574,000	$ 3,009,000
Current deferred revenue						47,725,000						47,725,000		102,000
Exercise of vested options						2,338,000	$ 1,254,000	$ 1,832,000	1,841,000	$ 3,729,000	$ 2,656,000
Research and development expense	[2]					57,246,000			39,820,000			$ 130,601,000	84,972,000
Date of joint venture agreement												Dec. 19, 2015
Equity method investment															$ 36,500,000
Unrealized equity method losses						3,430,000			1,012,000			$ 5,467,000	3,256,000		$ 36,500,000
Casebia Therapeutics LLP [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration revenue						100,000			900,000			500,000	2,000,000
Research and development expense						100,000			1,200,000			$ 700,000	2,400,000
Date of formation of joint venture entity												Feb. 12, 2016
Equity method investment, ownership percentage		50.00%
Cash contribution		$ 100,000
Other payments due to company from joint venture entity		0
Unrealized equity method losses						3,300,000			1,200,000			$ 5,500,000	2,200,000
Net loss of joint venture						22,600,000			13,500,000			54,900,000	25,800,000
Unrecognized equity method losses in excess of Company's interest												70,100,000		$ 45,300,000
Collaboration Target Options [Member] | Scenario Forecast [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue					$ 76,700,000
Exercise of vested options					30,000,000
Deferred revenue					46,700,000
Collaboration Target Options [Member] | Subsequent Event [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of collaboration target options | Option				3
License and Service [Member] | Casebia Therapeutics LLP [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration revenue		35,000,000
Royalty [Member] | Casebia Therapeutics LLP [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration revenue		$ 0
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Nonrefundable upfront payment received			$ 75,000,000									175,000,000
Transaction price												268,600,000
Non-current deferred revenue						11,900,000						11,900,000
Non-cash consideration received												10,000,000
Collaboration revenue						211,900,000			100,000			212,100,000	500,000
Current deferred revenue						47,700,000						47,700,000
Transaction price allocated to remaining performance obligations						59,600,000						59,600,000
Research and development expense						7,500,000			8,800,000			21,300,000	25,400,000
Reimbursements from research and license agreements						3,800,000			$ 3,700,000			11,800,000	$ 10,400,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Research and Development [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Variable consideration received												25,000,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Collaboration Target Options [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payment receivable						420,000,000						420,000,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | DM1 R&D Services [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration												1,700,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | DM1 R&D Services [Member] | Research and Development [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Variable consideration received												800,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | DMD License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration												224,600,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | DM1 License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration												76,200,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Specified Target Option Material Right [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration												17,500,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Collaboration Target Options Material Rights One [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration												25,000,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Collaboration Target Options Material Rights Two [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration												22,200,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Collaboration Target Options Material Rights Three [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration												22,200,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Joint Development Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Up-front payment received												$ 7,000,000
Agreement description												In connection with the JDA, the Company received a $7.0 million up-front payment from Vertex and subsequently received a one-time low seven-digit milestone payment upon the dosing of the second patient in a clinical trial with the initial product candidate.
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Exercise of Exclusive Option [Member] | Collaboration Target Options [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payment receivable						10,000,000						$ 10,000,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | 2019 Collaboration Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Nonrefundable upfront payment received												175,000,000
Maximum potential future payments												$ 825,000,000
Percentage of exchange payment of research and development costs												50.00%
Collaborative arrangement, license rights reacquired by waiving payment owed												$ 10,000,000
Non-cash consideration expensed upon execution of collaborative agreement												10,000,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | 2019 Collaboration Agreement [Member] | Prepaid Expenses and Other Current Assets [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract asset						25,000,000						25,000,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | 2015 Collaboration Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payment receivable						395,000,000						$ 395,000,000
Percentage of exchange payment of research and development costs												50.00%
Number of options would not be exercised under agreement | Option												1
Number of remaining options under agreement | Option												4
Non-current deferred revenue						$ 57,800,000						$ 57,800,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | 2015 Collaboration Agreement [Member] | Collaborative Arrangement Material Rights Fourth Exclusive License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration												$ 10,000,000
Vertex Pharmaceuticals Inc [Member] | 2015 Collaboration Agreement [Member] | Scenario Forecast [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate amount in option exercise payments to be received					$ 30,000,000
Vertex Pharmaceuticals Inc [Member] | 2015 Collaboration Agreement [Member] | Subsequent Event [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of exclusive license targets | License				3
[1]	Including the following revenue from a related party, see Notes 6 & 11
[2]	Including the following research and development expense with a related party, see Notes 6 & 11

Share Capital - Additional Info

Share Capital - Additional Information (Detail)	1 Months Ended		3 Months Ended	9 Months Ended
	Aug. 31, 2019USD ($)	Aug. 31, 2018USD ($)	Sep. 30, 2019USD ($)shares	Sep. 30, 2019USD ($)shares	Sep. 30, 2018USD ($)	Sep. 30, 2019SFr / shares	Dec. 31, 2018SFr / sharesshares
Class of Stock [Line Items]
Common stock, shares authorized			55,677,088	55,677,088			52,183,139
Common shares, par value | SFr / shares						SFr 0.03	SFr 0.03
Treasury stock, shares			256,989	256,989			307,936
Capital reserved for future issuance			230,729	230,729
Conditional capital reserved for future issuance			23,948,128	23,948,128			20,498,996
Net cash proceeds from sale of common stock | $				$ 121,216,000	$ 309,019,000
Sales Agreement With Jefferies LLC [Member] | 2018 ATM [Member]
Class of Stock [Line Items]
Common shares sold			1,452,880	2,816,568
Net cash proceeds from sale of common stock | $			$ 69,400,000	$ 121,900,000
Issuance costs | $			1,500,000	3,100,000
Payments of stamp taxes related to securities | $			500,000	700,000
Accrued stamp taxes | $			$ 700,000	$ 700,000
Sales Agreement With Jefferies LLC [Member] | Maximum [Member] | 2018 ATM [Member]
Class of Stock [Line Items]
Aggregate estimated gross proceeds | $		$ 125,000,000
Sales Agreement With Jefferies LLC [Member] | Maximum [Member] | 2019 ATM [Member]
Class of Stock [Line Items]
Aggregate estimated gross proceeds | $	$ 200,000,000
Swiss Law [Member]
Class of Stock [Line Items]
Common stock, shares authorized			25,134,003	25,134,003
Debt Instruments [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance			4,919,700	4,919,700
Employee Benefit Plans [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance			19,028,428	19,028,428

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 14,773	$ 9,067	$ 37,667	$ 25,216
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	6,262	3,999	17,137	12,081
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	5,081	4,056	15,063	9,879
Loss from Equity Method Investment [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,430	$ 1,012	$ 5,467	$ 3,256

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract]
Stock Options, Outstanding, Beginning Balance | shares	6,689,311
Stock Options, Granted | shares	2,136,873
Stock Options, Exercised | shares	(475,062)
Stock Options, Cancelled or forfeited | shares	(337,020)
Stock Options, Outstanding, Ending Balance | shares	8,014,102	6,689,311
Stock Options, Exercisable | shares	3,544,643
Stock Options, Vested or expected to vest | shares	8,014,102
Weighted-Average Exercise Price, Outstanding, Beginning Balance | $ / shares	$ 25.42
Weighted-Average Exercise Price, Granted | $ / shares	37.23
Weighted-Average Exercise Price, Exercised | $ / shares	12.03
Weighted-Average Exercise Price, Cancelled or forfeited | $ / shares	31.50
Weighted-Average Exercise Price, Outstanding, Ending Balance | $ / shares	29.10	$ 25.42
Weighted-Average Exercise Price, Exercisable | $ / shares	21.65
Weighted-Average Exercise Price, Vested or expected to vest | $ / shares	$ 29.10
Weighted-Average Remaining Contractual Term	8 years	8 years 3 months 18 days
Weighted-Average Remaining Contractual Term, Exercisable	7 years 1 month 6 days
Weighted-Average Remaining Contractual Term, Vested or expected to vest	8 years
Aggregate Intrinsic Value, Outstanding Balance | $	$ 119,011	$ 68,572
Aggregate Intrinsic Value, Exercisable | $	76,945
Aggregate Intrinsic Value, Vested or expected to vest | $	$ 119,011

Stock-based Compensation - Assu

Stock-based Compensation - Assumptions to Estimate Fair Value of Stock Option Award Using the Black-Scholes Option-Pricing Model (Detail)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-average expected volatility	69.20%	71.90%
Expected term (in years)	6 years	6 years
Risk-free interest rate	2.40%	2.70%
Expected dividend yield	0.00%	0.00%

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense related to stock options	$ 93,300		$ 93,300
Stock-based compensation expense	14,773	$ 9,067	37,667	$ 25,216
Departing Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			2,200
Non-Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 2,900
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, remaining weighted-average period for recognition			2 years 9 months 18 days
Restricted Common Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, remaining weighted-average period for recognition			1 year 5 months 1 day
Total unrecognized compensation expense	$ 10,500		$ 10,500

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Restricted Stock Activity (Detail) - Restricted Stock [Member]	9 Months Ended
	Sep. 30, 2019$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock, Unvested Beginning Balance | shares	327,342
Restricted Stock, Granted | shares	145,000
Restricted Stock, Vested | shares	(69,091)
Restricted Stock, Cancelled or forfeited | shares	(23,000)
Restricted Stock, Unvested Ending Balance | shares	380,251
Weighted-Average Grant Date Fair Value, Unvested Beginning Balance | $ / shares	$ 36.72
Weighted-Average Grant Date Fair Value, Granted | $ / shares	43.61
Weighted-Average Grant Date Fair Value, Vested | $ / shares	15.07
Weighted-Average Grant Date Fair Value, Cancelled or forfeited | $ / shares	41.64
Weighted-Average Grant Date Fair Value, Unvested Ending Balance | $ / shares	$ 42.98

Net Income (Loss) Per Share A_3

Net Income (Loss) Per Share Attributable to Common Shareholders - Schedule of Computation of Basic and Diluted Net Income (Loss) per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic net income (loss) per common share calculation:
Net income (loss) attributable to common shareholders	$ 138,423	$ (53,699)	$ (48,408)	$ (50,711)	$ (38,380)	$ (28,300)	$ 36,316	$ (117,391)
Net income (loss) attributable to common shareholders - basic	$ 138,423			$ (50,711)			$ 36,316	$ (117,391)
Basic weighted-average common shares outstanding	54,829,057			47,391,988			53,380,123	46,709,388
Basic net income (loss) per common share	$ 2.52			$ (1.07)			$ 0.68	$ (2.51)
Diluted net income (loss) per common share calculation:
Net income (loss) attributable to common shareholders	$ 138,423	$ (53,699)	$ (48,408)	$ (50,711)	$ (38,380)	$ (28,300)	$ 36,316	$ (117,391)
Net income (loss) attributable to common shareholders - diluted	$ 138,423			$ (50,711)			$ 36,316	$ (117,391)
Basic weighted-average common shares outstanding	54,829,057			47,391,988			53,380,123	46,709,388
Effect of potentially dilutive securities:
Weighted-average shares used to compute diluted net income (loss) per common share	57,598,901			47,391,988			55,821,420	46,709,388
Diluted net income (loss) per common share	$ 2.40			$ (1.07)			$ 0.65	$ (2.51)
Stock Options [Member]
Effect of potentially dilutive securities:
Effect of potentially dilutive securities	2,612,354						2,326,824
Unvested Restricted Common Shares [Member]
Effect of potentially dilutive securities:
Effect of potentially dilutive securities	157,490						114,473

Net Income (Loss) Per Share A_4

Net Income (Loss) Per Share Attributable to Common Shareholders - Schedule of Antidilutive Securities not Include in Computation of Net Income (Loss) per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not include in computation of net income (loss) per share	2,769,844	6,877,463	2,441,297	6,877,463
Outstanding Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not include in computation of net income (loss) per share	2,612,354	6,698,579	2,326,824	6,698,579
Unvested Restricted Common Shares [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not include in computation of net income (loss) per share	157,490	178,884	114,473	178,884

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income tax provision	$ 274	$ 137	$ 444	$ 319
Effective income tax rate	0.20%	(0.30%)	1.20%	(0.30%)

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2019
License [Member] | Research and Development [Member]
Related Party Transaction [Line Items]
Sublicense fees	$ 1.2		$ 1.2
Collaboration Agreement [Member] | Minimum [Member]
Related Party Transaction [Line Items]
Voting interest Percentage		10.00%