CRISPR Therapeutics (CRSP) 10-Q 28 Apr 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	Apr. 24, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
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
Entity Tax Identification Number	00-0000000
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		61,017,707
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	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 889,712	$ 943,771
Accounts receivable	25,117	99
Prepaid expenses and other current assets	14,453	43,677
Total current assets	929,282	987,547
Property and equipment, net	31,773	31,330
Intangible assets, net	221	235
Restricted cash	5,041	5,041
Operating lease assets	40,321	41,502
Other non-current assets	662	1,097
Total assets	1,007,300	1,066,752
Current liabilities:
Accounts payable	11,277	5,944
Accrued expenses	21,924	30,180
Deferred revenue, current	803	960
Accrued tax liabilities	284	583
Operating lease liabilities	9,005	8,489
Other current liabilities	11,793	10,950
Total current liabilities	55,086	57,106
Deferred revenue, non-current	11,776	11,776
Operating lease liabilities, net of current portion	42,390	44,050
Other non-current liabilities	11,951	14,395
Total liabilities	121,203	127,327
Commitments and contingencies, see Note 4
Shareholders’ equity:
Common shares, CHF 0.03 par value, 103,901,006 and 103,901,006 shares authorized at March 31, 2020 and December 31, 2019, respectively, 61,122,431 and 61,034,025 shares issued at March 31, 2020 and December 31, 2019, respectively 60,890,035 and 60,783,799 shares outstanding at March 31, 2020 and December 31, 2019, respectively.	1,850	1,847
Treasury shares, at cost, 232,396 and 250,226 shares at March 31, 2020 and December 31, 2019, respectively.	(63)	(63)
Additional paid-in capital	1,178,770	1,162,345
Accumulated deficit	(294,442)	(224,711)
Accumulated other comprehensive (loss) income	(18)	7
Total shareholders' equity	886,097	939,425
Total liabilities and shareholders’ equity	$ 1,007,300	$ 1,066,752

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - SFr / shares	Mar. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common stock, par value	SFr 0.03	SFr 0.03
Common stock, shares authorized	103,901,006	103,901,006
Common stock, shares issued	61,122,431	61,034,025
Common stock, shares outstanding	60,890,035	60,783,799
Treasury stock, shares	232,396	250,226

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Collaboration revenue	[1]	$ 157	$ 328
Operating expenses:
Research and development	[2]	54,193	33,822
General and administrative		19,550	14,929
Total operating expenses		73,743	48,751
Loss from operations		(73,586)	(48,423)
Other income (expense):
Loss from equity method investment			(1,025)
Other income, net		4,232	1,125
Total other income, net		4,232	100
Net loss before income taxes		(69,354)	(48,323)
Provision for income taxes		(377)	(85)
Net loss		(69,731)	(48,408)
Foreign currency translation adjustment		(25)	8
Comprehensive loss		$ (69,756)	$ (48,400)
Net loss per share attributable to common shareholders—basic and diluted		$ (1.15)	$ (0.93)
Weighted-average common shares outstanding used in net loss per share attributable to common shareholders—basic and diluted		60,847,683	52,093,208
[1]	Including the following revenue from a related party, see Notes 5 & 10:
[2]	Including the following research and development expense with a related party, see Notes 5 & 10:

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Income Statement [Abstract]
Revenue from related party	$ 328
Research and development expense with a related party	$ 7,587

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Shares [Member]	Treasury Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
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, value	1,832	$ 5		1,827
Exercise of vested options (in shares)		141,915
Stock-based compensation expense	10,696			10,696
Other comprehensive income (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
Ending balance at Dec. 31, 2019	939,425	$ 1,847	$ (63)	1,162,345	(224,711)	7
Ending balance (in shares) at Dec. 31, 2019		60,783,799	250,226
Vesting of restricted shares (in shares)		5,000
Exercise of vested options, value	$ 1,388	$ 3		1,385
Exercise of vested options (in shares)	88,466	83,406
Stock-based compensation expense	$ 14,151			14,151
Issuance of common shares related to license agreement	889			889
Issuance of common shares related to license agreement (in shares)		17,830	(17,830)
Other comprehensive income (loss)	(25)					(25)
Net loss	(69,731)				(69,731)
Ending balance at Mar. 31, 2020	$ 886,097	$ 1,850	$ (63)	$ 1,178,770	$ (294,442)	$ (18)
Ending balance (in shares) at Mar. 31, 2020		60,890,035	232,396

Consolidated Statements of Sh_2

Consolidated Statements of Shareholders' Equity (Parenthetical) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)	Mar. 31, 2020SFr / shares	Mar. 31, 2019SFr / shares
Common shares, par value		SFr 0.03
Common Shares [Member]
Issuance costs | $	$ 1.2
Common shares, par value		SFr 0.03	SFr 0.03

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities:
Net loss	$ (69,731)	$ (48,408)
Reconciliation of net loss to net cash used in operating activities:
Depreciation and amortization	2,091	812
Equity-based compensation	14,151	9,671
Loss from equity method investment		1,025
Other expense, non-cash	890
Changes in:
Accounts receivable	(25,018)	(243)
Prepaid expenses and other assets	29,659	(3,051)
Accounts payable and accrued expenses	(2,496)	(3,324)
Deferred revenue	(157)	(25)
Operating lease assets and liabilities	37
Other liabilities, net	(1,601)	(194)
Net cash used in operating activities	(52,175)	(43,737)
Investing activities:
Purchase of property and equipment	(2,991)	(1,097)
Net cash used in investing activities	(2,991)	(1,097)
Financing activities:
Proceeds from issuance of common shares, net of issuance costs		23,894
Proceeds from exercise of options, net of issuance costs	1,132	1,832
Net cash provided by financing activities	1,132	25,726
Effect of exchange rate changes on cash	(25)	8
Decrease in cash	(54,059)	(19,100)
Cash, cash equivalents and restricted cash, beginning of period	948,812	459,812
Cash, cash equivalents and restricted cash, end of period	894,753	440,712
Supplemental disclosure of non-cash investing and financing activities
Property and equipment purchases in accounts payable and accrued expenses	1,340	579
Equity issuance costs in accounts payable and accrued expenses	$ 39	$ 181

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Reconciliation to amounts within the condensed consolidated balance sheets
Cash and cash equivalents	$ 889,712	$ 943,771	$ 437,549
Restricted cash	5,041	5,041	3,163
Cash, cash equivalents and restricted cash at end of period	$ 894,753	$ 948,812	$ 440,712	$ 459,812

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
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, or GAAP. The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. Prior to December 13, 2019, the Company accounted for its 50% investment in Casebia Therapeutics Limited Liability Partnership, or Casebia, under the equity method. As described in Note 5, on December 13, 2019, Casebia became a fully-owned subsidiary and, as a result, the Company consolidated Casebia’s financial results from that date forward. 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, 2019, which are contained in the 2019 Annual Report on Form 10-K filed with the Securities and Exchange Commission, or the SEC, on February 12, 2020. 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. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, revenue recognition, equity-based compensation expense and reported amounts of expenses during the period. Significant estimates in these consolidated financial statements have been made in connection with revenue recognition and equity-based compensation expense. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. 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 months ended March 31, 2020 are consistent with those discussed in Note 2 to the consolidated financial statements in the Company’s 2019 Annual Report on Form 10-K filed with the SEC on February 12, 2020, except with respect to the Company’s policy on credit losses noted within the “Recently adopted accounting standards” section below. Recently Adopted Accounting Standards Credit Losses On January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements , Financial Instruments-Overall

Property and Equipment, net

Property and Equipment, net	3 Months Ended
	Mar. 31, 2020
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 March 31, December 31, 2020 2019 Computer equipment $ 727 $ 727 Furniture, fixtures and other 3,215 3,215 Laboratory equipment 18,555 16,640 Leasehold improvements 21,400 21,400 Construction work in process 1,999 1,394 Total property and equipment, gross 45,896 43,376 Accumulated depreciation (14,123 ) (12,046 ) Total property and equipment, net $ 31,773 $ 31,330 Depreciation expense for the three months ended March 31, 2020 and 2019 was $2.1 million and $1.0 million, respectively.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2020
Payables And Accruals [Abstract]
Accrued Expenses	3. Accrued Expenses Accrued expenses consist of the following (in thousands): As of March 31, December 31, 2020 2019 Payroll and employee-related costs $ 5,431 $ 15,229 Research costs 11,113 9,434 Licensing fees — 750 Professional fees 1,694 2,040 Intellectual property costs 2,780 2,311 Accrued property and equipment 148 407 Other 758 9 Total $ 21,924 $ 30,180

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	4. Commitments and Contingencies Future Lease Commitments The Company has entered into certain leasing commitments, for which, right of use assets and right of use liabilities are not reflected on the consolidated balance sheet as the leases have not yet commenced. In November 2019, the Company, together with one of its partners, committed to making payments to a clinical manufacturing organization under a lease arrangement. The lease arrangement is expected to commence in the second half of 2020, at which time an upfront payment of $2.6 million is due. In addition, the Company and its partner have committed to paying approximately $3.7 million in annual rental payments for a five-year 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. Letters of Credit As of March 31, 2020, the Company had restricted cash of $5.0 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 March 31, 2020. Research, License and Intellectual Property Agreements The Company has engaged several research institutions and companies to identify new delivery strategies and applications of the Company’s gene-editing technology. The Company is also a party to a number of research license agreements which require significant upfront payments and may be required to make future royalty payments and potential milestone payments from time to time. In addition, the Company is also a party to intellectual property agreements, which require maintenance and milestone payments from time to time. Further, the Company is a party to a number of manufacturing agreements that require upfront payments for the future performance of services. In association with these agreements, on a product-by-product basis, the counterparties are eligible to receive up to low eight-digit potential payments upon specified research, development and regulatory milestones. In addition, on a product-by-product basis, the counterparties are eligible to receive potential commercial milestone payments based on specified annual sales thresholds. The potential payments are low-single digit percentages of the specified annual sales thresholds. The counterparties are also eligible to receive low single-digit royalties on future net sales. Under certain circumstances and if certain contingent future events occur, Vertex Pharmaceuticals Incorporated and certain of its subsidiaries, or Vertex, is eligible to receive up to $395.0 million in potential specified research, development, regulatory and commercial milestones and tiered single-digit royalties on future net sales. Refer to Note 5 for further discussion on the Company’s arrangements with Vertex.

Significant Contracts

Significant Contracts	3 Months Ended
	Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Significant Contracts	5. 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, or the 2015 Collaboration Agreement, with 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, or Amendment No. 1, and the Joint Development Agreement, or 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 which it will lead global development and commercialization activities and the Company received the right to receive up to $420.0 million in development, regulatory and commercial milestones and royalties on net product sales for each of the 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, or the 2019 Collaboration Agreement, for the development and commercialization of products for the treatment of Duchenne muscular dystrophy, or DMD, and myotonic dystrophy type 1, or DM1. Under the terms of the 2019 Collaboration Agreement, the Company received an upfront, nonrefundable payment of $175.0 million. In addition, the Company is eligible to receive potential aggregate payments of up to $825.0 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, or 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, or 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 rights 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. If Vertex does not exercise its option to co-develop and co-commercialize the specified target, Vertex is eligible to receive up to $395.0 million in potential specified research, development, regulatory and commercial milestones and tiered single-digit royalties on future net sales. In October 2019, Vertex exercised the remaining three options granted to it under the 2015 Collaboration Agreement to exclusively license the collaboration targets developed under the 2015 Collaboration Agreement, resulting in a payment of $30.0 million to the Company in the fourth quarter of 2019. The Company achieved the first milestone under the 2019 Collaboration Agreement in the first quarter of 2020 and in connection therewith received a payment of $25.0 million in April 2020. Accounting for 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 2015 Collaboration Agreement, Amendment No. 1, Amendment No. 2, JDA and 2019 Collaboration Agreement are collectively the “Vertex Agreements.” The Vertex Agreements include components of a customer-vendor relationship as defined under ASC 606, Revenue from Contracts with Customers Collaborative Agreements Research and Development Accounting Analysis Under ASC 606 Accounting for the 2019 Agreements Identification of the Contract 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, or DMD License; (ii) an exclusive license for worldwide rights for DM1 gene editing products, or DM1 License; (iii) the performance of specified guide RNA research for DM1, or DM1 R&D Services; (iv) a material right representing the option to obtain a co-exclusive development and commercialization license for a specified target, or Specified Target Option; (v) three material rights representing the option for up to three exclusive licenses to develop and commercialize the collaboration targets, or 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; (iii) an upfront payment of $175.0 million; (iv) variable consideration of $25.0 million which represented the Company’s estimate related to a near-term research and development milestone for which the Company determined that it is not probable that a significant reversal of cumulative consideration will occur at the onset of the transaction; and (v) variable consideration of $0.8 million which represents the Company’s estimate of payments from Vertex for DM1 R&D Services. The Company determined that all other possible variable consideration resulting from milestones and royalties discussed above was fully constrained as of March 31, 2020. 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, or 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 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. On a relative basis, $151.1 million and $51.3 million of the transaction price was allocated to the DMD License and DM1 License, respectively. 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 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. On a relative basis, $11.8 million of the transaction price was allocated to the Specified Target Option material right. 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 on the probability and present value adjusted cash flows from milestone payments owed for exclusive licenses, less the price paid to exercise each option. On a relative basis, $46.7 million of the transaction price was allocated to the Collaboration Target Option material rights. The aforementioned ESSPs reflect the level of risk and expected probability of success inherent in the nature 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. On a relative basis, $6.7 million of the transaction price was allocated to the waiving of Vertex’s material right associated with its option to a fourth exclusive license under the 2015 Agreements. 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. On a relative basis, $1.1 million of the transaction price was allocated to the DM1 R&D Services. 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 revenue allocated to the waiving of Vertex’s material right associated with its option to a fourth exclusive license in connection with Company’s reacquisition of exclusive rights to the specified target was recognized at the point in time in which the option was waived, on the effective date of the 2019 Agreements. The Company concluded that the Specified Target Option and Collaboration Target Options were considered material rights under the Vertex Agreements. Revenue related to the three Collaboration Target Options material right was recognized at the point in time in which Vertex exercised the Collaboration Target Options, which occurred in the fourth quarter of 2019. Revenue related to the Specified Target Option will be recognized at the point in time in which the option is exercised. The Company recognizes 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. Accounting for the 2015 Agreements (prior to the execution of the 2019 Agreements) On January 1, 2018, the Company adopted ASC 606 using the modified retrospective approach. The Company applied the practical expedient in ASC 606-10-65-1 in identifying the satisfied and unsatisfied performance obligations, determining the transaction price and allocating the transaction price under the practical expedient in ASC 606 Identification of the Contract Amendment No. 1 and the JDA represented a contract modification to the 2015 Collaboration Agreement. As a result, 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 2015 Agreements and represented separate performance obligations: (i) the non-exclusive research license; (ii) four material rights representing the option for up to four exclusive licenses to develop and commercialize the collaboration targets; (iii) a combined performance obligation representing the co-exclusive research license, and a development and commercialization license to develop and commercialize hemoglobinopathies and beta-globin targets; and (iv) the performance of R&D Services. Determination of Transaction Price The overall transaction price was comprised of: (i) original upfront payment of $75.0 million, (ii) an upfront payment of $7.0 million under the JDA, and (iii) $19.3 million of variable consideration associated with the R&D services. The Company determined that all other possible variable consideration resulting from milestones and royalties discussed above was fully constrained at the time of the transaction. Allocation of Transaction Price to Performance Obligations The selling price of each performance obligation was determined based on the Company’s ESSP. The Company developed the ESSP for all the performance obligations included in the 2015 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 R&D Services was determined to be $19.3 million. The Company developed the ESSP for the R&D Services primarily based on the nature of the services to be performed and estimates of the associated effort and cost of the services, adjusted for a reasonable profit margin that would be expected to be realized under similar contracts. The Company allocated $19.3 million of the transaction price to R&D Services. The Company’s ESSP for each of the remaining material rights to obtain an exclusive license to develop and commercialize a single collaboration target are $45.6 million, $38.4 million, $17.3 million and $17.3 million for a total of $118.6 million. ESSPs for these items were determined based on the probability and present value adjusted cash flows from milestone payments owed for exclusive licenses, less the price paid to exercise each option. On a relative basis, $57.7 million of the transaction price was allocated to these material rights. The Company’s ESSP for the co-exclusive research license and the development and commercialization licenses for hemoglobinopathy and beta-globin targets is $48.9 million. The ESSP for this item was determined based on probability and present value adjusted cash flows from the equal sharing of projected worldwide net profit. ESSP reflects the level of risk and expected probability of success inherent in the nature of the associated research area. On a relative basis, $23.8 million of the transaction price was allocated to the co-exclusive research license and the development and commercialization licenses for hemoglobinopathy and beta-globin targets. The Company used a market-based approach to determine the ESSP of the non-exclusive research license of $1.0 million. The Company determined ESSP by use of comparative data, including in-licensed research agreements negotiated and executed within the Company. On a relative basis, $0.5 million of the transaction price was allocated to the non-exclusive research license. The aforementioned ESSPs reflect the level of risk and expected probability of success inherent in the nature of the associated research area. Recognition of Revenue The Company determined that the non-exclusive research license is symbolic intellectual property as Vertex receives value from the license through the Company’s ongoing activities, and, as such, the revenue related to the non-exclusive research license was recognized ratably over the term of the arrangement. Upon the execution of the JDA, a co-exclusive research, development and commercialization license was granted for hemoglobinopathy and beta-globin targets. The Company determined that the revenue related to these licenses was recognized at a point in time, in which they were delivered at inception of the JDA in December 2017. As Vertex has the material right in its option to obtain four additional exclusive licenses to develop and commercialize four additional collaboration targets, the Company determined that consideration allocated to these material rights would be included in the transaction price of the exclusive license and recognized at a point in time, upon the exercise of the option by Vertex or expiration. As the Company has a right to consideration from Vertex in an amount that corresponds directly with the value of the Company’s performance completed to date for the R&D services, the Company recognized revenue related to the R&D services as invoiced, in line with the practical expedient in ASC 606-10-55-18. Revenue recognized in connection with the Vertex Agreements Revenue recognized under the 2019 Agreements and revenue recognized under the 2015 Agreements for the three months ended March 31, 2020 and 2019, respectively, was not material. As of March 31, 2020, there was $0.8 million of current deferred revenue related to the collaboration with Vertex compared to $0.9 million as of December 31, 2019. As of March 31, 2020, there was $11.8 million of non-current deferred revenue related to the collaboration with Vertex, which is unchanged from December 31, 2019. The transaction price allocated to the remaining performance obligations was $12.6 million. Milestones under the Vertex Agreements The Company has evaluated the milestones that may be received in connection with the Vertex Agreements. As discussed above, the Company is eligible to receive up to $410.0 million in additional development, regulatory and commercial milestones and royalties on net product sales for each of the three collaboration targets that Vertex licensed in the fourth quarter of 2019. 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. The Company is eligible to receive potential future payments of up to $800.0 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. T his amount was recorded as a contract asset within prepaid expenses and other current assets on the condensed consolidated balance sheet at December 31, 2019. Each of the remaining milestones are fully constrained as of March 31, 2020. 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. Accounting Analysis under ASC 808 In connection with the 2019 Agreements, the Company identified the following collaborative elements, which were unchanged as those identified with the 2015 Agreements and are accounted for under ASC 808: (i) development and commercialization services for shared products; (ii) R&D Services for follow-on products; and (iii) committee participation. The related impact of the cost sharing associated with research and development is included in research and development expense. Expenses related to services performed by the Company are classified as research and development expense. Payments received from Vertex for partial reimbursement of expenses are recorded as a reduction of research and development expense. During the three months ended March 31, 2020 and 2019, the Company recognized $9.1 million and $7.1 million of research and development expense related to the Vertex Agreements. Research and development expense for the three months ended March 31, 2020 and 2019 was net of $5.5 million and $4.5 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 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. If Vertex does not exercise its option to do so within a specified time period, Vertex is eligible to receive up to $395.0 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, the Company 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 for the 2019 Agreements 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 Summary On December 19, 2015, the Company entered into an agreement with 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. Bayer and the Company each received a 50% equity interest in the entity in exchange for their respective contributions to the entity. At that time, the Company also entered into a separate service agreement with Casebia, under which the Company agreed to provide compensated research and development services. Collectively, these agreements are referred to as the “2015 Casebia Agreements.” On December 13, 2019, the Company, Bayer and Casebia entered into a series of transactions by which, among other things, the Company acquired 100% of the partnership interests in Casebia, or the Retirement Agreement, the Company and Bayer terminated their joint venture, or the Joint Venture Termination Agreement, and the Company and Bayer entered into a new option agreement, or the 2019 Option Agreement. Collectively, these agreements are referred to as the “2019 Casebia Agreements.” In connection with the Retirement Agreement, Casebia retired Bayer’s outstanding partnership interests in exchange for $22.0 million less certain estimated interim operating expenses of $6.0 million, and the Company acquired 100% of the partnership interests in Casebia. In connection with entering into the Retirement Agreement, the Company, Bayer and Casebia entered into the Joint Venture Termination Agreement. In connection therewith, the Company and Bayer agreed to terminate the Joint Venture Agreement from December 2015. Under the Joint Venture Termination Agreement, Casebia-owned patents are co-owned by the Company and Bayer, subject to certain exclusive licenses granted therein. Under the Joint Venture Termination Agreement, the Company and Bayer each retained rights to their respective contributed intellectual property. In connection with entering into the Retirement Agreement and the Joint Venture Termination Agreement, the Company and Bayer also entered into the 2019 Option Agreement, under which, among other things, the Company committed to invest amount in certain research and development activities as described under “Accounting Analysis – Accounting for 2019 Casebia Agreements”. In addition, Bayer has an option (exercisable during a specified exercise period defined by future events, but in no event longer than 5 years after the effective date of the 2019 Option Agreement) to co-develop and co-commercialize two products for the diagnosis, treatment or prevention of certain autoimmune disorders, eye disorders or hemophilia A disorders. In the event Bayer elects to co-develop and co-commercialize a product, the parties will negotiate and enter into a co-development and co-commercialization agreement, or the Co-Commercialization Agreement, for such product, and Bayer would be responsible for 50 % of the research and development costs incurred by the Company for such product going forward. Bayer would receive 50 % of all profits from sales of such product and would be responsible for 50 % of all losses. If Bayer elects to exercise its option to co-develop and co-commercialize a product, Bayer will make a one-time $20.0 million payment, or the Option Payment, to the Company that will become non-refundable once the parties execute a Co-Commercialization Agreement with respect to such optioned product. The Option Payment is payable In addition, following Bayer’s exercise of its option and/or the execution of the Co-Commercialization Agreement for an optioned product, for a period beginning on the effective date of such Co-Commercialization Agreement and ending on the earlier of the three month anniversary of such effective date or during the 90-day negotiation process of such Co-Commercialization Agreement, Bayer has a right to negotiate an exclusive license to develop and commercialize such optioned product. If Bayer exercises such right, the parties will enter into an exclusive license agreement for such optioned product on terms mutually agreeable to the parties. Further, the Option Payment paid for such optioned product would become credited against payments due under such exclusive license or any other exclusive license entered into in connection with the 2019 Option Agreement. Either party may terminate the 2019 Option Agreement upon the other party’s material breach, subject to specified notice and cure provisions. The Company may also terminate the 2019 Option Agreement in the event Bayer commences or participates in any action or proceeding challenging the validity or enforceability of any Company patent necessary or useful for the research, development, manufacture or commercialization of a product that is the subject of the 2019 Option Agreement. Bayer may also terminate the 2019 Option Agreement upon the Company’s bankruptcy or insolvency, or for convenience at any time, after giving written notice. Accounting Analysis Accounting for the 2015 Casebia Agreements 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 had no further contractual obligations to provide cash financing to Casebia and accordingly, no additional losses were recorded beyond the initial equity amount. Casebia’s net losses were $14.2 million for the three months ended March 31, 2019 and unrecognized equity method losses in excess of the Company’s equity method investment in Casebia were $51.9 million as of March 31, 2019. The remaining performance obligations prior to the 2019 Casebia Agreements included research and development services, which were recorded as revenue under ASC 606, and cost sharing activities with Casebia related to shared research and technology licenses, which were recorded as a cost/profit sharing arrangement under ASC 808, with the related impact of the cost sharing included as research and development expense. All performance obligations were terminated upon the execution of the 2019 Casebia Agreements. During the three months ended March 31, 2019, the Company recognized $0.2 million of revenue related to the collaboration with Casebia. During the three months ended March 31, 2019, the Company recognized $0.5 million of research and development expense related to the collaboration with Casebia. During the three months ended March 31, 2019, the Company recognized a loss from equity method investment of $1.0 million related to stock-based compensation expense for Casebia employees. Accounting for the 2019 Casebia Agreements The Company determined that the Retirement Agreement and Joint Venture Termination Agreement resulted in the Company obtaining a controlling interest in Casebia and should be accounted for as a separate component from the 2019 Option Agreement. In doing so, the Company allocated the consideration transferred of $41.0 million (consisting of $16.0 million of assets acquir

Share Capital

Share Capital	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Share Capital	6. Share Capital The Company had 103,901,006 authorized common shares as of March 31, 2020, with a par value of CHF 0.03 per share. Share Capital consisted of the following: As of Type of Share Capital Conditional Capital March 31, 2020 December 31, 2019 Common shares Registered share capital 61,036,566 61,036,566 Common shares Authorized share capital 19,246,503 19,246,503 Common shares Conditional share capital - Bonds or similar debt instruments 4,919,700 4,919,700 Common shares Conditional share capital - Employee benefit plans 18,698,237 18,698,237 Total 103,901,006 103,901,006 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 During the three months ended March 31, 2019, the Company sold 631,580 shares of common stock under the 2018 ATM for net cash proceeds of $23.9 million, after deducting commission fees of $0.7 million. For the year ended December 31, 2019, the Company issued and sold an aggregate of 2.8 million common shares under the 2018 ATM, at an average price of $44.38 per share, for aggregate proceeds of $120.6 million, which were net of equity issuance costs of $4.4 million. As of March 31, 2020, the Company has not yet issued or sold any securities under the 2019 ATM.

Stock-based Compensation

Stock-based Compensation	3 Months Ended
	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	7. Stock-based Compensation During the three months ended March 31, 2020 and 2019, the Company recognized the following stock-based compensation expense (in thousands): Three Months Ended March 31, 2020 2019 Research and development $ 7,362 $ 4,962 General and administrative 6,789 4,709 Loss from equity method investment - 1,025 Total $ 14,151 $ 10,696 Stock option activity The following table summarizes stock option activity for the three months ended March 31, 2020: Shares (in thousands) Weighted- average exercise price per share Outstanding at December 31, 2019 7,782,437 $ 31.30 Granted 887,458 $ 45.73 Exercised (88,466 ) $ 19.37 Cancelled or forfeited (86,114 ) $ 42.20 Outstanding at March 31, 2020 8,495,315 $ 32.82 Exercisable at March 31, 2020 3,697,079 $ 25.25 Vested and expected to vest at March 31, 2020 8,495,315 $ 32.82 As of March 31, 2020, total unrecognized compensation expense related to stock options was $107.3 million, which the Company expects to recognize over a remaining weighted-average period of 2.8 years. Restricted stock activity The following table summarizes restricted stock activity for the three months ended March 31, 2020: Restricted Stock Weighted- Average Grant Date Fair Value Unvested balance as of December 31, 2019 699,534 $ 56.53 Granted 277,970 45.78 Vested (5,000 ) 33.58 Cancelled or forfeited (5,444 ) 51.18 Unvested balance as of March 31, 2020 967,060 $ 53.59 As of March 31, 2020, total unrecognized compensation expense related to unvested restricted common shares was $39.9 million, which the Company expects to recognize over a remaining weighted-average vesting period of 2.4 years.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Shareholders	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Shareholders	8. The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands): Three Months Ended March 31, 2020 2019 Outstanding options 8,495,315 8,032,582 Unvested restricted common shares 967,060 345,296 Total 9,462,375 8,377,878

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes During the three months ended March 31, 2020 and 2019, the Company recorded an income tax provision of $0.4 million and $0.1 million, respectively, representing an effective tax rate of -0.5% and -0.2%, 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. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act, or the CARES Act, was enacted in the United States. The impact of the CARES Act on the Company for the period ending March 31, 2020 was not material.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	10. Related Party Transactions Casebia Prior to the termination of the joint venture in December 2019, Casebia was a related party under ASC 850, Related Party Disclosures . Joint Venture with Bayer Healthcare LLC. Vertex In the fourth quarter of 2018, upon becoming owners of record of more than 10% of the voting interest of the Company, Vertex became a related party under ASC 850 . Agreements with Vertex Pharmaceuticals Incorporated and certain of its subsidiaries

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
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, or GAAP. The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. Prior to December 13, 2019, the Company accounted for its 50% investment in Casebia Therapeutics Limited Liability Partnership, or Casebia, under the equity method. As described in Note 5, on December 13, 2019, Casebia became a fully-owned subsidiary and, as a result, the Company consolidated Casebia’s financial results from that date forward. 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, 2019, which are contained in the 2019 Annual Report on Form 10-K filed with the Securities and Exchange Commission, or the SEC, on February 12, 2020.
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. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, revenue recognition, equity-based compensation expense and reported amounts of expenses during the period. Significant estimates in these consolidated financial statements have been made in connection with revenue recognition and equity-based compensation expense. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. Changes in estimates are reflected in reported results in the period in which they become known.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards Credit Losses On January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements , Financial Instruments-Overall

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	3 Months Ended
	Mar. 31, 2020
Property Plant And Equipment [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net, consists of the following (in thousands): As of March 31, December 31, 2020 2019 Computer equipment $ 727 $ 727 Furniture, fixtures and other 3,215 3,215 Laboratory equipment 18,555 16,640 Leasehold improvements 21,400 21,400 Construction work in process 1,999 1,394 Total property and equipment, gross 45,896 43,376 Accumulated depreciation (14,123 ) (12,046 ) Total property and equipment, net $ 31,773 $ 31,330

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following (in thousands): As of March 31, December 31, 2020 2019 Payroll and employee-related costs $ 5,431 $ 15,229 Research costs 11,113 9,434 Licensing fees — 750 Professional fees 1,694 2,040 Intellectual property costs 2,780 2,311 Accrued property and equipment 148 407 Other 758 9 Total $ 21,924 $ 30,180

Significant Contracts (Tables)

Significant Contracts (Tables)	3 Months Ended
	Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Fair Value of Assets and Liabilities Received	As a result of the Retirement Agreement, the Company determined that it had obtained a controlling interest in a variable interest entity, for which it became the primary beneficiary. As such, under ASC 810, Consolidation Business Combinations Fair value Amount Cash and cash equivalents $ 6,784 Prepaid expenses and other current assets 2,565 Property, plant and equipment, net 9,340 Operating lease assets 11,003 Restricted cash 1,226 Accrued expenses and other current liabilities (3,915 ) Operating lease liabilities (11,003 ) Net assets $ 16,000

Share Capital (Tables)

Share Capital (Tables)	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Schedule of Share Capital	Share Capital consisted of the following: As of Type of Share Capital Conditional Capital March 31, 2020 December 31, 2019 Common shares Registered share capital 61,036,566 61,036,566 Common shares Authorized share capital 19,246,503 19,246,503 Common shares Conditional share capital - Bonds or similar debt instruments 4,919,700 4,919,700 Common shares Conditional share capital - Employee benefit plans 18,698,237 18,698,237 Total 103,901,006 103,901,006

Stock-based Compensation (Table

Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Stock-Based Compensation Expense	During the three months ended March 31, 2020 and 2019, the Company recognized the following stock-based compensation expense (in thousands): Three Months Ended March 31, 2020 2019 Research and development $ 7,362 $ 4,962 General and administrative 6,789 4,709 Loss from equity method investment - 1,025 Total $ 14,151 $ 10,696
Summary of Stock Option Activity	The following table summarizes stock option activity for the three months ended March 31, 2020: Shares (in thousands) Weighted- average exercise price per share Outstanding at December 31, 2019 7,782,437 $ 31.30 Granted 887,458 $ 45.73 Exercised (88,466 ) $ 19.37 Cancelled or forfeited (86,114 ) $ 42.20 Outstanding at March 31, 2020 8,495,315 $ 32.82 Exercisable at March 31, 2020 3,697,079 $ 25.25 Vested and expected to vest at March 31, 2020 8,495,315 $ 32.82
Summary of Restricted Stock Activity	The following table summarizes restricted stock activity for the three months ended March 31, 2020: Restricted Stock Weighted- Average Grant Date Fair Value Unvested balance as of December 31, 2019 699,534 $ 56.53 Granted 277,970 45.78 Vested (5,000 ) 33.58 Cancelled or forfeited (5,444 ) 51.18 Unvested balance as of March 31, 2020 967,060 $ 53.59

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Shareholders (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities not Include in Computation of Net Income (Loss) per Share	The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands): Three Months Ended March 31, 2020 2019 Outstanding options 8,495,315 8,032,582 Unvested restricted common shares 967,060 345,296 Total 9,462,375 8,377,878

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - Segment	3 Months Ended
	Mar. 31, 2020	Dec. 12, 2019
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments	1
Casebia Therapeutics Limited Liability Partnership [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage		50.00%

Property and Equipment, net - S

Property and Equipment, net - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 45,896	$ 43,376
Accumulated depreciation	(14,123)	(12,046)
Total property and equipment, net	31,773	31,330
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	727	727
Furniture, Fixtures and Other [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	3,215	3,215
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	18,555	16,640
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	21,400	21,400
Construction Work in Process [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 1,999	$ 1,394

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 2.1	$ 1

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accrued Liabilities Current [Abstract]
Payroll and employee-related costs	$ 5,431	$ 15,229
Research costs	11,113	9,434
Licensing fees		750
Professional fees	1,694	2,040
Intellectual property costs	2,780	2,311
Accrued property and equipment	148	407
Other	758	9
Total	$ 21,924	$ 30,180

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended
	Nov. 30, 2019	Mar. 31, 2020
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member]
Contingencies And Commitments [Line Items]
Milestone payment receivable		$ 410
Letter of Credit [Member]
Contingencies And Commitments [Line Items]
Letters of credit secured by cash held in restricted depository account		5
Lease Arrangement [Member]
Contingencies And Commitments [Line Items]
Upfront payment	$ 2.6
Annual rental payments	$ 3.7
Rental payments period	5 years
2015 Collaboration Agreement [Member] | Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member]
Contingencies And Commitments [Line Items]
Milestone payment receivable		$ 395

Significant Contracts - Additio

Significant Contracts - Additional Information (Detail)		Dec. 13, 2019USD ($)Product	Oct. 26, 2015USD ($)	Oct. 31, 2019License	Mar. 31, 2020USD ($)Option	Dec. 31, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2016USD ($)	Apr. 30, 2020USD ($)	Dec. 12, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-current deferred revenue					$ 11,776,000	$ 11,776,000
Current deferred revenue					803,000	960,000
Research and development expense	[1]				$ 54,193,000		$ 33,822,000
Date of joint venture agreement					Dec. 19, 2015
Operating expenses					$ 73,743,000		48,751,000
Equity method investment								$ 36,500,000
Unrealized equity method losses							1,025,000	$ 36,500,000
Collaboration revenue	[2]				157,000		328,000
Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense							500,000
Equity method investment, ownership percentage										50.00%
Unrealized equity method losses							1,000,000
Net loss of joint venture							14,200,000
Unrecognized equity method losses in excess of Company's interest							51,900,000
Business combination, consideration transferred					41,000,000
Net assets acquired					16,000,000
Fair value of controlling interest obtained					$ 32,000,000
Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Date of formation of joint venture entity					Feb. 12, 2016
Equity method investment, ownership percentage					50.00%
License and Service [Member] | Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration revenue							200,000
Non-Exclusive Research License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Transaction price allocated to remaining performance obligations			$ 500,000
Non-Exclusive Research License [Member] | Valuation, Market Approach
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for collaboration agreement			1,000,000
Retirement Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percentage of partnership interests		100.00%
Partnership outstanding exchange amount		$ 22,000,000
Operating expenses		$ 6,000,000
2019 Option Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense					$ 1,900,000
2019 Option Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of options exercised under agreement | Option					2
Equity method investment, ownership percentage					50.00%
Business combination, consideration transferred					$ 25,000,000
Payment to acquire business					16,000,000
2019 Option Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member] | Research And Development Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Fair value of obligations					20,200,000
2019 Option Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member] | Future Delivery of up to Two Options [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Fair value of obligations					4,800,000
2019 Option Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of products | Product		2
Non-refundable one-time option payment		$ 20,000,000
2019 Option Agreement [Member] | Research and Development [Member] | Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Business combination, consideration transferred					20,200,000
2019 Option Agreement [Member] | Certain Options [Member] | Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Business combination, consideration transferred					4,800,000
Co-commercialization Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percentage of research and development costs		50.00%
Percentage sharing of profit (loss) from sale of product		50.00%
2019 Casebia Agreement [Member] | Other Current Liabilities [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research obligation					11,800,000
2019 Casebia Agreement [Member] | Other Long-term Liabilities [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research obligation					11,300,000
2019 Casebia Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Equity method investment					0
Fair value of assets and liabilities					16,000,000
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
Milestone payment receivable					410,000,000
Transaction price					268,600,000
Non-current deferred revenue					11,800,000	11,800,000
Non-cash consideration received					10,000,000
Transaction price allocated to remaining performance obligations					12,600,000
Current deferred revenue					800,000	900,000
Maximum potential future payments					800,000,000
Contract asset					25,000,000
Research and development expense					9,100,000		7,100,000
Reimbursements from research and license agreements					5,500,000		$ 4,500,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Accounts Receivable [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract asset					25,000,000
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			19,300,000		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
Transaction price allocated to remaining performance obligations					46,700,000
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
Transaction price allocated to remaining performance obligations					1,100,000
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
Transaction price allocated to remaining performance obligations					151,100,000
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
Transaction price allocated to remaining performance obligations					51,300,000
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Specified Target Option Material Right
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration					17,500,000
Transaction price allocated to remaining performance obligations					11,800,000
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		$ 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
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 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] | 2015 Collaboration Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payment receivable					$ 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
Number of options exercised under agreement | Option					4
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | 2015 Collaboration Agreement [Member] | Collaborative Arrangement Material Rights Fourth Exclusive License
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration					$ 10,000,000
Transaction price allocated to remaining performance obligations					$ 6,700,000
Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration			19,300,000
Transaction price allocated to remaining performance obligations			19,300,000
Estimated standalone selling price for collaboration agreement			118,600,000
Vertex Pharmaceuticals Inc [Member] | Collaboration Target Options [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Transaction price allocated to remaining performance obligations			57,700,000
Vertex Pharmaceuticals Inc [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			45,600,000
Vertex Pharmaceuticals Inc [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			38,400,000
Vertex Pharmaceuticals Inc [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			17,300,000
Vertex Pharmaceuticals Inc [Member] | Rights Four [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration			17,300,000
Vertex Pharmaceuticals Inc [Member] | 2019 Collaboration Agreement [Member] | Scenario Forecast [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payment receivable									$ 25,000,000
Vertex Pharmaceuticals Inc [Member] | 2015 Collaboration Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate amount in option exercise payments received						$ 30,000,000
Number of exclusive license targets | License				3
Vertex Pharmaceuticals Inc [Member] | Beta Globin
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration			48,900,000
Transaction price allocated to remaining performance obligations			$ 23,800,000
[1]	Including the following research and development expense with a related party, see Notes 5 & 10:
[2]	Including the following revenue from a related party, see Notes 5 & 10:

Significant Contracts - Schedul

Significant Contracts - Schedule of Fair Value of Assets and Liabilities Received (Detail) $ in Thousands	Mar. 31, 2020USD ($)
Research And Development [Abstract]
Cash and cash equivalents	$ 6,784
Prepaid expenses and other current assets	2,565
Property, plant and equipment, net	9,340
Operating lease assets	11,003
Restricted cash	1,226
Accrued expenses and other current liabilities	(3,915)
Operating lease liabilities	(11,003)
Net assets	$ 16,000

Share Capital - Additional Info

Share Capital - Additional Information (Detail)	Mar. 31, 2020SFr / sharesshares	Aug. 31, 2019USD ($)	Aug. 31, 2018USD ($)	Mar. 31, 2019USD ($)shares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2019SFr / sharesshares
Class of Stock [Line Items]
Common stock, shares authorized | shares	103,901,006					103,901,006
Common shares, par value | SFr / shares	SFr 0.03					SFr 0.03
Net cash proceeds from sale of common stock				$ 23,894,000
Maximum [Member] | 2019 ATM [Member]
Class of Stock [Line Items]
Aggregate estimated gross proceeds		$ 200,000,000
Sales Agreement With Jefferies LLC [Member] | 2018 ATM [Member]
Class of Stock [Line Items]
Common shares sold | shares				631,580	2,800,000
Average issue price of common shares | $ / shares					$ 44.38
Net cash proceeds from sale of common stock				$ 23,900,000	$ 120,600,000
Issuance costs				$ 700,000
Equity issuance costs					$ 4,400,000
Sales Agreement With Jefferies LLC [Member] | 2019 ATM [Member]
Class of Stock [Line Items]
Common shares sold | shares	0
Sales Agreement With Jefferies LLC [Member] | Maximum [Member] | 2018 ATM [Member]
Class of Stock [Line Items]
Aggregate estimated gross proceeds			$ 125,000,000

Share Capital - Schedule of Sha

Share Capital - Schedule of Share Capital (Detail) - shares	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Registered share capital	61,036,566	61,036,566
Authorized share capital	103,901,006	103,901,006
Employee Benefit Plans [Member]
Class of Stock [Line Items]
Conditional share capital - Bonds or similar debt instruments	18,698,237	18,698,237
Bonds or Similar Debt Instruments [Member]
Class of Stock [Line Items]
Conditional share capital - Bonds or similar debt instruments	4,919,700	4,919,700
Swiss Law [Member]
Class of Stock [Line Items]
Authorized share capital	19,246,503	19,246,503

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 14,151	$ 10,696
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	7,362	4,962
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 6,789	4,709
Loss from Equity Method Investment [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense		$ 1,025

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Detail)	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract]
Shares, Outstanding, Beginning Balance | shares	7,782,437
Shares, Granted | shares	887,458
Shares, Exercised | shares	(88,466)
Shares, Cancelled or forfeited | shares	(86,114)
Shares, Outstanding, Ending Balance | shares	8,495,315
Shares, Exercisable | shares	3,697,079
Shares, Vested or expected to vest | shares	8,495,315
Weighted-Average Exercise Price, Outstanding, Beginning Balance | $ / shares	$ 31.30
Weighted-Average Exercise Price, Granted | $ / shares	45.73
Weighted-Average Exercise Price, Exercised | $ / shares	19.37
Weighted-Average Exercise Price, Cancelled or forfeited | $ / shares	42.20
Weighted-Average Exercise Price, Outstanding, Ending Balance | $ / shares	32.82
Weighted-Average Exercise Price, Exercisable | $ / shares	25.25
Weighted-Average Exercise Price, Vested or expected to vest | $ / shares	$ 32.82

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense related to stock options	$ 107.3
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	2 years 4 months 24 days
Total unrecognized compensation expense	$ 39.9

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Restricted Stock Activity (Detail) - Restricted Stock [Member]	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted common shares, Number of Shares, Beginning Balance | shares	699,534
Unvested restricted common shares, Number of Shares, Granted | shares	277,970
Unvested restricted common shares, Number of Shares, Vested | shares	(5,000)
Unvested restricted common shares, Number of Shares, Cancelled or forfeited | shares	(5,444)
Unvested restricted common shares, Number of Shares, Ending Balance | shares	967,060
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 56.53
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Granted | $ / shares	45.78
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Vested | $ / shares	33.58
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Cancelled or forfeited | $ / shares	51.18
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Ending Balance | $ / shares	$ 53.59

Net Loss Per Share Attributab_3

Net 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
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not include in computation of net income (loss) per share	9,462,375	8,377,878
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	8,495,315	8,032,582
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	967,060	345,296

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income tax provision	$ 377	$ 85
Effective income tax rate	(0.50%)	(0.20%)

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2018
Collaboration Agreement [Member] | Vertex Pharmaceuticals Inc [Member] | Minimum [Member]
Related Party Transaction [Line Items]
Voting interest Percentage	10.00%