CRISPR Therapeutics (CRSP) 10-Q 28 Oct 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Oct. 23, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
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
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		70,652,429
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, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 1,041,417	$ 943,771
Marketable securities	324,573
Accounts receivable	110	99
Prepaid expenses and other current assets	24,839	43,677
Total current assets	1,390,939	987,547
Property and equipment, net	37,924	31,330
Intangible assets, net	194	235
Restricted cash	16,845	5,041
Operating lease assets	38,454	41,502
Other non-current assets	662	1,097
Total assets	1,485,018	1,066,752
Current liabilities:
Accounts payable	19,020	5,944
Accrued expenses	35,445	30,180
Deferred revenue, current	610	960
Accrued tax liabilities	6,348	583
Operating lease liabilities	10,640	8,489
Other current liabilities	12,086	10,950
Total current liabilities	84,149	57,106
Deferred revenue, non-current	11,776	11,776
Operating lease liabilities, net of current portion	38,570	44,050
Other non-current liabilities	7,222	14,395
Total liabilities	141,717	127,327
Commitments and contingencies, see Note 6
Shareholders’ equity:
Common shares, CHF 0.03 par value, 115,172,786 and 103,901,006 shares authorized at September 30, 2020 and December 31, 2019, respectively, 70,799,178 and 61,034,025 shares issued at September 30, 2020 and December 31, 2019, respectively, 70,603,862 and 60,783,799 shares outstanding at September 30, 2020 and December 31, 2019, respectively.	2,157	1,847
Treasury shares, at cost, 195,316 and 250,226 shares at September 30, 2020 and December 31, 2019, respectively.	(63)	(63)
Additional paid-in capital	1,807,878	1,162,345
Accumulated deficit	(466,537)	(224,711)
Accumulated other comprehensive (loss) income	(134)	7
Total shareholders' equity	1,343,301	939,425
Total liabilities and shareholders’ equity	$ 1,485,018	$ 1,066,752

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - SFr / shares	Sep. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common stock, par value	SFr 0.03	SFr 0.03
Common stock, shares authorized	115,172,786	103,901,006
Common stock, shares issued	70,799,178	61,034,025
Common stock, shares outstanding	70,603,862	60,783,799
Treasury stock, shares	195,316	250,226

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Collaboration revenue	[1]	$ 148	$ 211,928	$ 349	$ 212,574
Operating expenses:
Research and development	[2]	71,008	57,246	184,581	130,601
General and administrative		21,539	15,519	62,442	46,216
Total operating expenses		92,547	72,765	247,023	176,817
Income (loss) from operations		(92,399)	139,163	(246,674)	35,757
Other income (expense):
Loss from equity method investment			(3,430)		(5,467)
Other income, net		160	2,964	5,804	6,470
Total other income (expense), net		160	(466)	5,804	1,003
Net income (loss) before income taxes		(92,239)	138,697	(240,870)	36,760
Provision for income taxes		(200)	(274)	(956)	(444)
Net income (loss)		(92,439)	138,423	(241,826)	36,316
Foreign currency translation adjustment		31	(12)	3	(14)
Unrealized loss on marketable securities		(144)		(144)
Comprehensive income (loss)		$ (92,552)	$ 138,411	$ (241,967)	$ 36,302
Net income (loss) per common share — basic		$ (1.32)	$ 2.52	$ (3.77)	$ 0.68
Basic weighted-average common shares outstanding		70,143,481	54,829,057	64,159,224	53,380,123
Net income (loss) per common share — diluted		$ (1.32)	$ 2.40	$ (3.77)	$ 0.65
Diluted weighted-average common shares outstanding		70,143,481	57,598,901	64,159,224	55,821,420
[1]	Including the following revenue from a related party, see Notes 7 & 12
[2]	Including the following research and development expense with a related party, see Notes 7 & 12

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, 2019
Income Statement [Abstract]
Revenue from related party	$ 31	$ 677
Research and development expense with a related party	$ 31	$ 14,490

Condensed Consolidated Statem_3

Condensed 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 income (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
Net income (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 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
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, value	1,254			1,254
Exercise of vested options (in shares)		118,987	(3,650)
Stock-based compensation expense	12,198			12,198
Other comprehensive income (loss)	(10)					(10)
Net income (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, value	2,338	$ 10		2,328
Exercise of vested options (in shares)		203,105
Stock-based compensation expense	14,773			14,773
Other comprehensive income (loss)	(12)					(12)
Net income (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
Beginning balance at Dec. 31, 2019	939,425	$ 1,847	$ (63)	1,162,345	(224,711)	7
Beginning 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)		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 income (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
Beginning balance at Dec. 31, 2019	$ 939,425	$ 1,847	$ (63)	1,162,345	(224,711)	7
Beginning balance (in shares) at Dec. 31, 2019		60,783,799	250,226
Exercise of vested options (in shares)	1,011,236
Net income (loss)	$ (241,826)
Ending balance at Sep. 30, 2020	1,343,301	$ 2,157	$ (63)	1,807,878	(466,537)	(134)
Ending balance (in shares) at Sep. 30, 2020		70,603,862	195,316
Beginning balance at Mar. 31, 2020	886,097	$ 1,850	$ (63)	1,178,770	(294,442)	(18)
Beginning balance (in shares) at Mar. 31, 2020		60,890,035	232,396
Issuance of common shares, net of issuance costs	82,189	$ 38		82,151
Issuance of common shares, net of issuance costs (in shares)		1,238,453
Vesting of restricted shares	1	$ 1
Vesting of restricted shares (in shares)		29,916
Exercise of vested options, value	6,345	$ 11		6,334
Exercise of vested options (in shares)		394,101	(37,080)
Stock-based compensation expense	15,697			15,697
Other comprehensive income (loss)	(3)					(3)
Net income (loss)	(79,656)				(79,656)
Ending balance at Jun. 30, 2020	910,670	$ 1,900	$ (63)	1,282,952	(374,098)	(21)
Ending balance (in shares) at Jun. 30, 2020		62,552,505	195,316
Issuance of common shares, net of issuance costs	494,589	$ 240		494,349
Issuance of common shares, net of issuance costs (in shares)		7,499,135
Vesting of restricted shares	1	$ 1
Vesting of restricted shares (in shares)		39,667
Exercise of vested options, value	12,659	$ 16		12,643
Exercise of vested options (in shares)		499,145
Purchase of common stock under ESPP	694			694
Purchase of common stock under ESPP (in shares)		13,410
Stock-based compensation expense	17,240			17,240
Other comprehensive income (loss)	(113)					(113)
Net income (loss)	(92,439)				(92,439)
Ending balance at Sep. 30, 2020	$ 1,343,301	$ 2,157	$ (63)	$ 1,807,878	$ (466,537)	$ (134)
Ending balance (in shares) at Sep. 30, 2020		70,603,862	195,316

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Shareholders' Equity (Parenthetical) $ in Millions	3 Months Ended
	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Sep. 30, 2020SFr / shares	Jun. 30, 2020SFr / shares	Mar. 31, 2020SFr / shares	Sep. 30, 2019SFr / shares	Jun. 30, 2019SFr / shares	Mar. 31, 2019SFr / shares
Common shares, par value						SFr 0.03
Common Shares [Member]
Issuance costs | $	$ 32.8	$ 3.1	$ 2.3	$ 1.3	$ 1.2
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_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities:
Net loss	$ (241,826)	$ 36,316
Reconciliation of net loss to net cash used in operating activities:
Depreciation and amortization	6,618	3,293
Equity-based compensation	47,088	32,200
Loss from equity method investment		5,467
Other expense, non-cash	979
Changes in:
Accounts receivable	(11)	49
Prepaid expenses and other assets	19,273	(25,342)
Accounts payable and accrued expenses	17,394	420
Deferred revenue	(350)	1,714
Operating lease assets and liabilities	(282)	(689)
Other liabilities, net	(6,037)	(127)
Net cash (used in) provided by operating activities	(157,154)	53,301
Investing activities:
Purchase of property, plant and equipment	(12,119)	(5,732)
Purchases of marketable securities	(325,316)
Maturities of marketable securities	509
Net cash used in investing activities	(336,926)	(5,732)
Financing activities:
Proceeds from issuance of common shares, net of issuance costs	582,225	121,216
Proceeds from exercise of options and ESPP contributions, net of issuance costs	21,300	5,049
Net cash provided by financing activities	603,525	126,265
Effect of exchange rate changes on cash	5	(14)
Increase in cash	109,450	173,820
Cash, cash equivalents and restricted cash, beginning of period	948,812	459,812
Cash, cash equivalents and restricted cash, end of period	1,058,262	633,632
Supplemental disclosure of non-cash investing and financing activities
Property and equipment purchases in accounts payable and accrued expenses	2,863	428
Equity issuance costs in accounts payable and accrued expenses	$ 5,955	$ 739

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Reconciliation to amounts within the condensed consolidated balance sheets
Cash and cash equivalents	$ 1,041,417	$ 943,771	$ 629,717
Restricted cash	16,845	5,041	3,915
Cash, cash equivalents and restricted cash at end of period	$ 1,058,262	$ 948,812	$ 633,632	$ 459,812

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 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 7, 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 and nine months ended September 30, 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 as noted immediately below and as noted within the “Recently Adopted Accounting Standards” section. Marketable Securities The Company’s investment strategy is focused on capital preservation. The Company invests in instruments that meet the credit quality standards outlined in the Company’s investment policy. The Company classifies marketable securities with a remaining maturity, when purchased, of greater than three months as available-for-sale. The Company classifies marketable securities available to fund current operations as current assets on its condensed consolidated balance sheets. Marketable securities are classified as long-term assets on the condensed consolidated balance sheets if (i) they have been in an unrealized loss position for longer than one year or (ii) the Company has the ability and intent to hold them (a) until the carrying value is recovered and (b) such holding period may be longer than one year. Marketable securities classified as Level 2 within the valuation hierarchy generally consist of U.S. treasury securities and government agency securities, corporate bonds, and commercial paper . Debt securities are carried at fair value with the unrealized gains and losses included in other comprehensive income (loss) as a component of stockholders’ equity until realized. Any premium arising at purchase is amortized to interest expense over the period of the earliest call date, and any discount arising at purchase is accreted to interest income over the life of the instrument. Realized gains and losses on debt s ecurities are determined using the specific identification method and are included in other income (expense), net. Effective January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements The Company assesses its available-for-sale debt securities under the available-for-sale debt security impairment model in ASC 326 as of each reporting date in order to determine if a portion of any decline in fair value below carrying value recognized on its available-for-sale debt securities is the result of a credit loss. The Company records credit losses in the condensed consolidated statements of operations and comprehensive loss as credit loss expense within other expense, net, which is limited to the difference between the fair value and the amortized cost of the security. To date, the Company has not recorded any credit losses on its available-for-sale debt securities. Recently Adopted Accounting Standards Credit Losses On January 1, 2020, the Company adopted ASC 326. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The targeted transition relief standard allows filers an option to irrevocably elect the fair value option of ASC 825-10 , Financial Instruments-Overall

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2020
Investments Debt And Equity Securities [Abstract]
Marketable Securities	2. Marketable Securities A summary of the Company’s cash equivalents and marketable securities, which are recorded at fair value (and do not include $125.7 million of cash at September 30, 2020) is shown below (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash equivalents: Money market funds $ 896,690 $ — $ — $ 896,690 Corporate debt securities 6,505 — (1 ) 6,504 Certificates of deposit 4,012 — — 4,012 Commercial paper 8,497 — — 8,497 Total cash equivalents 915,704 — (1 ) 915,703 Marketable securities: U.S. Treasury securities 39,978 2 — 39,980 Corporate debt securities 182,716 9 (154 ) 182,571 Certificates of deposit 9,153 — — 9,153 Government-sponsored enterprise securities 6,772 — — 6,772 Commercial paper 86,097 — — 86,097 Total marketable securities 324,716 11 (154 ) 324,573 Total cash equivalents and marketable securities $ 1,240,420 $ 11 $ (155 ) $ 1,240,276 The amortized cost of all cash equivalents as of December 31, 2019 approximated fair value and the Company did not hold any marketable securities as of December 31, 2019. As of September 30, 2020, the aggregate fair value of marketable securities that were in an unrealized loss position for less than twelve months was $107.9 million. As of September 30, 2020, no marketable securities were in an unrealized loss position for more than twelve months. The Company has recorded a net unrealized loss of $0.1 million during the three and nine months ended September 30, 2020 related to its debt securities, which is included in comprehensive income (loss) on the condensed consolidated statements of operations and comprehensive loss. The Company determined that there was no material change in the credit risk of the above investments. As such, an allowance for credit losses was not recognized. As of September 30, 2020, the Company does not intend to sell such securities and it is not more likely than not that the Company will be required to sell the securities before recovery of their amortized cost bases. No available-for-sale debt securities held as of September 30, 2020 had remaining maturities greater than two years.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the fair value hierarchy classification of such fair values as of September 30, 2020 and December 31, 2019 (in thousands): Fair Value Measurements at September 30, 2020 Total Level 1 Level 2 Level 3 Cash and cash equivalents: Cash $ 125,713 $ 125,713 $ — $ — Money market funds 896,690 896,690 — — Corporate debt securities 6,504 — 6,504 — Certificates of deposit 4,012 — 4,012 — Commercial paper 8,497 — 8,497 — Marketable securities: U.S. Treasury securities 39,980 — 39,980 — Corporate debt securities 182,572 — 182,572 — Certificates of deposit 9,153 — 9,153 — Government-sponsored enterprise securities 6,772 — 6,772 — Commercial paper 86,097 — 86,097 — Other non-current assets 600 — — 600 Total $ 1,366,590 $ 1,022,403 $ 343,587 $ 600 Fair Value Measurements at December 31, 2019 Total Level 1 Level 2 Level 3 Cash and cash equivalents: Cash $ 13,998 $ 13,998 — — Money market funds 929,773 929,773 — — Other non-current assets 600 — — 600 Total $ 944,371 $ 943,771 $ — $ 600 Marketable securities classified as Level 2 within the valuation hierarchy generally consist of U.S. treasury securities and government agency securities, corporate bonds, and commercial paper. The Company estimates the fair values of these marketable securities by taking into consideration valuations obtained from third-party pricing sources. The Company holds equity securities classified as Level 3 which are not material to the Company’s financial position.

Property and Equipment, net

Property and Equipment, net	9 Months Ended
	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Property and Equipment, net	4. Property and Equipment, net Property and equipment, net, consists of the following (in thousands): As of September 30, December 31, 2020 2019 Computer equipment $ 727 $ 727 Furniture, fixtures and other 3,416 3,215 Laboratory equipment 23,895 16,640 Leasehold improvements 25,473 21,400 Construction work in process 3,036 1,394 Total property and equipment, gross 56,547 43,376 Accumulated depreciation (18,623 ) (12,046 ) Total property and equipment, net $ 37,924 $ 31,330 Depreciation expense for the three and nine months ended September 30, 2020 was $2.3 million and $6.6 million, respectively.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2020
Payables And Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consist of the following (in thousands): As of September 30, December 31, 2020 2019 Payroll and employee-related costs $ 14,327 $ 15,229 Research costs 15,973 9,434 Licensing fees 915 750 Professional fees 1,762 2,040 Intellectual property costs 1,864 2,311 Accrued property and equipment 566 407 Other 38 9 Total $ 35,445 $ 30,180

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. 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 $3.7 million in annual rental payments to a clinical manufacturing organization under a lease arrangement for a five-year In May 2020, the Company entered into a lease agreement for a cell therapy manufacturing facility in Framingham, Massachusetts, or the Framingham Lease, for clinical and commercial production of the Company’s investigational cell therapy product candidates. The Framingham Lease is expected to commence in either the fourth quarter of 2020 or the first quarter of 2021. In connection therewith, the Company has committed to making at least $40.2 million in rental payments over the fifteen-year In July 2020, the Company entered into a lease agreement for an office and laboratory facility in Boston, Massachusetts, or the 2020 Boston Lease. The 2020 Boston Lease is expected to commence in the first half of 2022. In connection therewith, the Company has committed to making at least $292.5 million in rental payments over a lease term of 152 months. 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 September 30, 2020, the Company had restricted cash of $16.8 million, representing letters of credit securing the Company’s obligations under certain leased facilities, 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 condensed consolidated balance sheet as of September 30, 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 percentage royalties on future net sales. Refer to Note 7 for further discussion on the Company’s arrangements with Vertex.

Significant Contracts

Significant Contracts	9 Months Ended
	Sep. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Significant Contracts	7. 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 September 30, 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 Vertex Agreements for the three and nine months ended September 30, 2020, respectively, was not material. Revenue recognized under the Vertex Agreements for the three and nine months ended September 30, 2019 was $211.9 million and $212.1 million, respectively. As of September 30, 2020, there was $0.6 million of current deferred revenue related to the collaboration with Vertex compared to $0.9 million as of December 31, 2019. As of September 30, 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 $12.0 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 September 30, 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 and nine months ended September 30, 2020, the Company recognized $12.5 million and $31.5 million of research and development expense related to the Vertex Agreements, respectively. During the three and nine months ended September 30, 2019, the Company recognized $7.5 million and $21.3 million of research and development expense related to the Vertex Agreements, respectively. Research and development expense for the three and nine months ended September 30, 2020 was net of $6.8 million and $17.8 million of reimbursements from Vertex, 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. 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. Agreements 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 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 for the three and nine months ended September 30, 2019 were $22.6 million and $54.9 million, respectively. Unrecognized equity method losses in excess of the Company’s equity method investment in Casebia were $70.1 million as of September 30, 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 and nine months ended September 30, 2019, the Company recognized $0.1 million and $0.5 million, respectively, of revenue 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 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. 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 acquired net of the purchase price, as displayed in the table below, and $25.0 million of cash allocated to the 2019 Option Agreement) between the two components using a relative fair value approach. The Company determined the relative fair value related to obtaining a controlling interest

Share Capital

Share Capital	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Share Capital	8. Share Capital The Company had 115,172,786 authorized common shares as of September 30, 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 September 30, 2020 December 31, 2019 Common shares Registered share capital 71,633,951 61,036,566 Common shares Authorized share capital 21,125,426 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 17,493,709 18,698,237 Total 115,172,786 103,901,006 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 and nine months ended September 30, 2019, the Company sold 1.5 million and 2.8 million common shares, respectively, under the 2018 ATM for net cash proceeds of $69.4 million and $121.9 million, respectively, after deducting commission fees of $1.5 million and $3.1 million, respectively. In addition, the Company paid approximately $0.5 million and $0.7 million in stamp taxes during the three and nine months ended September 30, 2019, respectively, and accrued an additional $0.6 million for stamp taxes as of September 30, 2019 related to securities sold under the 2018 ATM. For the year ended December 31, 2019, the Company issued and sold an aggregate of 2.8 million common shares under the 2018 ATM, for aggregate proceeds of $120.6 million, which were net of equity issuance costs of $4.4 million. During the three and nine months ended September 30, 2020, the Company sold 0.1 million and 1.3 million common shares, respectively, under the 2019 ATM for net cash proceeds of $9.6 million and $91.9 million, respectively, after deducting commission fees $0.2 million and $2.4 million, respectively. In addition, the Company paid approximately $0.4 million in stamp taxes during the three and nine months ended September 30, 2020, respectively, and accrued an additional $0.6 million for stamp taxes as of September 30, 2020 related to securities sold under the 2019 ATM. July 2020 Offering In July 2020, the Company sold 7.4 million common shares through an underwritten public offering (inclusive of shares sold pursuant to the exercise of the underwriters’ option to purchase additional shares) at a public offering price of $70.00 per share for aggregate net proceeds of $484.8 million, which were net of equity issuance costs and stamp tax of $32.5 million, of which $4.9 million was accrued on the condensed consolidated balance sheet as of September 30, 2020.

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	9. Stock-based Compensation During the three and nine months ended September 30, 2020 and 2019, the Company recognized the following stock-based compensation expense (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 9,109 $ 6,262 $ 24,492 $ 17,137 General and administrative 8,131 5,081 22,596 15,063 Loss from equity method investment - 3,430 - 5,467 Total $ 17,240 $ 14,773 $ 47,088 $ 37,667 Stock option activity The following table summarizes stock option activity for the nine months ended September 30, 2020: Shares (in thousands) Weighted- average exercise price per share Outstanding at December 31, 2019 7,782,437 $ 31.30 Granted 1,468,758 $ 56.19 Exercised (1,011,236 ) $ 22.34 Cancelled or forfeited (307,053 ) $ 41.35 Outstanding at September 30, 2020 7,932,906 $ 36.66 Exercisable at September 30, 2020 3,741,338 $ 28.68 Vested and expected to vest at September 30, 2020 7,932,906 $ 36.66 As of September 30, 2020, total unrecognized compensation expense related to stock options was $105.5 million, which the Company expects to recognize over a remaining weighted-average period of 2.6 years. Restricted stock activity The following table summarizes restricted stock activity for the nine months ended September 30, 2020: Restricted Stock Weighted- Average Grant Date Fair Value Unvested balance as of December 31, 2019 699,534 $ 56.53 Granted 306,220 49.01 Vested (74,583 ) 50.60 Cancelled or forfeited (33,661 ) 46.23 Unvested balance as of September 30, 2020 897,510 $ 54.84 As of September 30, 2020, total unrecognized compensation expense related to unvested restricted common shares was $31.6 million, which the Company expects to recognize over a remaining weighted-average vesting period of 2.0 years.

Net Income (Loss) Per Share Att

Net Income (Loss) Per Share Attributable to Common Shareholders	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Net Income (Loss) Per Share Attributable to Common Shareholders	10. Basic net income (loss) per share is calculated by dividing net income (loss) attributable to common shareholders by the weighted-average number of common shares outstanding during the period. Diluted net income (loss) per share is calculated by dividing the net income (loss) 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 Company’s net income (loss) is net income (loss) attributable to common shareholders for all periods presented. 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, 2020 2019 2020 2019 Net income (loss) $ (92,439 ) $ 138,423 $ (241,826 ) $ 36,316 Basic weighted-average common shares outstanding 70,143,481 54,829,057 64,159,224 53,380,123 Effect of potentially dilutive securities: Outstanding options — 2,612,354 — 2,326,824 Unvested restricted common shares — 157,490 — 114,473 Employee stock purchase plan — — — — Diluted weighted-average common shares outstanding 70,143,481 57,598,901 64,159,224 55,821,420 Basic net income (loss) per common share (1.32 ) 2.52 (3.77 ) 0.68 Diluted net income (loss) per common share (1.32 ) 2.40 (3.77 ) 0.65 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 September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Outstanding options 7,932,906 3,791,475 7,932,906 3,911,071 Unvested restricted common shares 897,510 13,750 897,510 34,250 ESPP 11,808 — 11,808 — Total 8,842,224 3,805,225 8,842,224 3,945,321

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes During the three and nine months ended September 30, 2020, the Company recorded an income tax provision of $0.2 million and $1.0 million, respectively, representing an effective tax rate of -0.2% and -0.4%, respectively. 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. 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 which was not material.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2020
Related Party Transactions [Abstract]
Related Party Transactions	12. 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)	9 Months Ended
	Sep. 30, 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 7, 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.
Marketable Securities	Marketable Securities The Company’s investment strategy is focused on capital preservation. The Company invests in instruments that meet the credit quality standards outlined in the Company’s investment policy. The Company classifies marketable securities with a remaining maturity, when purchased, of greater than three months as available-for-sale. The Company classifies marketable securities available to fund current operations as current assets on its condensed consolidated balance sheets. Marketable securities are classified as long-term assets on the condensed consolidated balance sheets if (i) they have been in an unrealized loss position for longer than one year or (ii) the Company has the ability and intent to hold them (a) until the carrying value is recovered and (b) such holding period may be longer than one year. Marketable securities classified as Level 2 within the valuation hierarchy generally consist of U.S. treasury securities and government agency securities, corporate bonds, and commercial paper . Debt securities are carried at fair value with the unrealized gains and losses included in other comprehensive income (loss) as a component of stockholders’ equity until realized. Any premium arising at purchase is amortized to interest expense over the period of the earliest call date, and any discount arising at purchase is accreted to interest income over the life of the instrument. Realized gains and losses on debt s ecurities are determined using the specific identification method and are included in other income (expense), net. Effective January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements The Company assesses its available-for-sale debt securities under the available-for-sale debt security impairment model in ASC 326 as of each reporting date in order to determine if a portion of any decline in fair value below carrying value recognized on its available-for-sale debt securities is the result of a credit loss. The Company records credit losses in the condensed consolidated statements of operations and comprehensive loss as credit loss expense within other expense, net, which is limited to the difference between the fair value and the amortized cost of the security. To date, the Company has not recorded any credit losses on its available-for-sale debt securities.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards Credit Losses On January 1, 2020, the Company adopted ASC 326. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The targeted transition relief standard allows filers an option to irrevocably elect the fair value option of ASC 825-10 , Financial Instruments-Overall

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2020
Investments Debt And Equity Securities [Abstract]
Summary of Cash Equivalents and Marketable Securities Recorded at Fair Value	A summary of the Company’s cash equivalents and marketable securities, which are recorded at fair value (and do not include $125.7 million of cash at September 30, 2020) is shown below (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash equivalents: Money market funds $ 896,690 $ — $ — $ 896,690 Corporate debt securities 6,505 — (1 ) 6,504 Certificates of deposit 4,012 — — 4,012 Commercial paper 8,497 — — 8,497 Total cash equivalents 915,704 — (1 ) 915,703 Marketable securities: U.S. Treasury securities 39,978 2 — 39,980 Corporate debt securities 182,716 9 (154 ) 182,571 Certificates of deposit 9,153 — — 9,153 Government-sponsored enterprise securities 6,772 — — 6,772 Commercial paper 86,097 — — 86,097 Total marketable securities 324,716 11 (154 ) 324,573 Total cash equivalents and marketable securities $ 1,240,420 $ 11 $ (155 ) $ 1,240,276

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Financial Assets Measured at Fair Value on Recurring Basis	The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the fair value hierarchy classification of such fair values as of September 30, 2020 and December 31, 2019 (in thousands): Fair Value Measurements at September 30, 2020 Total Level 1 Level 2 Level 3 Cash and cash equivalents: Cash $ 125,713 $ 125,713 $ — $ — Money market funds 896,690 896,690 — — Corporate debt securities 6,504 — 6,504 — Certificates of deposit 4,012 — 4,012 — Commercial paper 8,497 — 8,497 — Marketable securities: U.S. Treasury securities 39,980 — 39,980 — Corporate debt securities 182,572 — 182,572 — Certificates of deposit 9,153 — 9,153 — Government-sponsored enterprise securities 6,772 — 6,772 — Commercial paper 86,097 — 86,097 — Other non-current assets 600 — — 600 Total $ 1,366,590 $ 1,022,403 $ 343,587 $ 600 Fair Value Measurements at December 31, 2019 Total Level 1 Level 2 Level 3 Cash and cash equivalents: Cash $ 13,998 $ 13,998 — — Money market funds 929,773 929,773 — — Other non-current assets 600 — — 600 Total $ 944,371 $ 943,771 $ — $ 600

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	9 Months Ended
	Sep. 30, 2020
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, 2020 2019 Computer equipment $ 727 $ 727 Furniture, fixtures and other 3,416 3,215 Laboratory equipment 23,895 16,640 Leasehold improvements 25,473 21,400 Construction work in process 3,036 1,394 Total property and equipment, gross 56,547 43,376 Accumulated depreciation (18,623 ) (12,046 ) Total property and equipment, net $ 37,924 $ 31,330

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following (in thousands): As of September 30, December 31, 2020 2019 Payroll and employee-related costs $ 14,327 $ 15,229 Research costs 15,973 9,434 Licensing fees 915 750 Professional fees 1,762 2,040 Intellectual property costs 1,864 2,311 Accrued property and equipment 566 407 Other 38 9 Total $ 35,445 $ 30,180

Significant Contracts (Tables)

Significant Contracts (Tables)	9 Months Ended
	Sep. 30, 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)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Schedule of Share Capital	Share Capital consisted of the following: As of Type of Share Capital Conditional Capital September 30, 2020 December 31, 2019 Common shares Registered share capital 71,633,951 61,036,566 Common shares Authorized share capital 21,125,426 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 17,493,709 18,698,237 Total 115,172,786 103,901,006

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Stock-Based Compensation Expense	During the three and nine months ended September 30, 2020 and 2019, the Company recognized the following stock-based compensation expense (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 9,109 $ 6,262 $ 24,492 $ 17,137 General and administrative 8,131 5,081 22,596 15,063 Loss from equity method investment - 3,430 - 5,467 Total $ 17,240 $ 14,773 $ 47,088 $ 37,667
Summary of Stock Option Activity	The following table summarizes stock option activity for the nine months ended September 30, 2020: Shares (in thousands) Weighted- average exercise price per share Outstanding at December 31, 2019 7,782,437 $ 31.30 Granted 1,468,758 $ 56.19 Exercised (1,011,236 ) $ 22.34 Cancelled or forfeited (307,053 ) $ 41.35 Outstanding at September 30, 2020 7,932,906 $ 36.66 Exercisable at September 30, 2020 3,741,338 $ 28.68 Vested and expected to vest at September 30, 2020 7,932,906 $ 36.66
Summary of Restricted Stock Activity	The following table summarizes restricted stock activity for the nine months ended September 30, 2020: Restricted Stock Weighted- Average Grant Date Fair Value Unvested balance as of December 31, 2019 699,534 $ 56.53 Granted 306,220 49.01 Vested (74,583 ) 50.60 Cancelled or forfeited (33,661 ) 46.23 Unvested balance as of September 30, 2020 897,510 $ 54.84

Net Income (Loss) Per Share A_2

Net Income (Loss) Per Share Attributable to Common Shareholders (Tables)	9 Months Ended
	Sep. 30, 2020
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, 2020 2019 2020 2019 Net income (loss) $ (92,439 ) $ 138,423 $ (241,826 ) $ 36,316 Basic weighted-average common shares outstanding 70,143,481 54,829,057 64,159,224 53,380,123 Effect of potentially dilutive securities: Outstanding options — 2,612,354 — 2,326,824 Unvested restricted common shares — 157,490 — 114,473 Employee stock purchase plan — — — — Diluted weighted-average common shares outstanding 70,143,481 57,598,901 64,159,224 55,821,420 Basic net income (loss) per common share (1.32 ) 2.52 (3.77 ) 0.68 Diluted net income (loss) per common share (1.32 ) 2.40 (3.77 ) 0.65
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 September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Outstanding options 7,932,906 3,791,475 7,932,906 3,911,071 Unvested restricted common shares 897,510 13,750 897,510 34,250 ESPP 11,808 — 11,808 — Total 8,842,224 3,805,225 8,842,224 3,945,321

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - Segment	9 Months Ended
	Sep. 30, 2020	Dec. 12, 2019
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments	1
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2020
Change in accounting principle, accounting standards update, immaterial effect	true
Change in accounting principle, type [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Casebia Therapeutics Limited Liability Partnership [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage		50.00%

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Marketable securities	$ 125,700,000	$ 125,700,000	$ 0
Marketable securities unrealized loss, Less than twelve months	107,900,000	107,900,000
Marketable securities unrealized loss, more than twelve months	0	0
Unrealized loss, net	100,000	100,000
Available-for-sale debt securities remaining maturities greater than two years	$ 0	$ 0

Marketable Securities - Summary

Marketable Securities - Summary of Cash Equivalents and Marketable Securities Recorded at Fair Value (Detail) $ in Thousands	Sep. 30, 2020USD ($)
Marketable Securities [Line Items]
Cash equivalents, amortized cost	$ 915,704
Cash equivalents, gross unrealized losses	(1)
Cash equivalents, fair value	915,703
Marketable securities, amortized cost	324,716
Marketable securities, gross unrealized gains	11
Marketable securities, gross unrealized losses	(154)
Marketable securities, fair value	324,573
Cash equivalents and marketable securities, amortized cost	1,240,420
Cash equivalents and marketable securities, gross unrealized gains	11
Cash equivalents and marketable securities, gross unrealized losses	(155)
Cash equivalents and marketable securities, fair value	1,240,276
Money Market Funds [Member]
Marketable Securities [Line Items]
Cash equivalents, amortized cost	896,690
Cash equivalents, fair value	896,690
Certificates of Deposit [Member]
Marketable Securities [Line Items]
Cash equivalents, amortized cost	4,012
Cash equivalents, fair value	4,012
Marketable securities, amortized cost	9,153
Marketable securities, fair value	9,153
Commercial Paper [Member]
Marketable Securities [Line Items]
Cash equivalents, amortized cost	8,497
Cash equivalents, fair value	8,497
Marketable securities, amortized cost	86,097
Marketable securities, fair value	86,097
US Treasury Securities [Member]
Marketable Securities [Line Items]
Marketable securities, amortized cost	39,978
Marketable securities, gross unrealized gains	2
Marketable securities, fair value	39,980
Corporate Debt Securities [Member]
Marketable Securities [Line Items]
Cash equivalents, amortized cost	6,505
Cash equivalents, gross unrealized losses	(1)
Cash equivalents, fair value	6,504
Marketable securities, amortized cost	182,716
Marketable securities, gross unrealized gains	9
Marketable securities, gross unrealized losses	(154)
Marketable securities, fair value	182,571
Government-sponsored Enterprise Securities [Member]
Marketable Securities [Line Items]
Marketable securities, amortized cost	6,772
Marketable securities, fair value	$ 6,772

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 6,784
Marketable securities, fair value	324,573
Recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other non-current assets	600	$ 600
Total	1,366,590	944,371
Recurring Basis [Member] | Cash [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	125,713	13,998
Recurring Basis [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	896,690	929,773
Recurring Basis [Member] | Corporate Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	6,504
Marketable securities, fair value	182,572
Recurring Basis [Member] | Certificates of Deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	4,012
Marketable securities, fair value	9,153
Recurring Basis [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	8,497
Marketable securities, fair value	86,097
Recurring Basis [Member] | US Treasury Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities, fair value	39,980
Recurring Basis [Member] | Government-sponsored Enterprise Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities, fair value	6,772
Recurring Basis [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	1,022,403	943,771
Recurring Basis [Member] | Level 1 [Member] | Cash [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	125,713	13,998
Recurring Basis [Member] | Level 1 [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	896,690	929,773
Recurring Basis [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	343,587
Recurring Basis [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	6,504
Marketable securities, fair value	182,572
Recurring Basis [Member] | Level 2 [Member] | Certificates of Deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	4,012
Marketable securities, fair value	9,153
Recurring Basis [Member] | Level 2 [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	8,497
Marketable securities, fair value	86,097
Recurring Basis [Member] | Level 2 [Member] | US Treasury Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities, fair value	39,980
Recurring Basis [Member] | Level 2 [Member] | Government-sponsored Enterprise Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities, fair value	6,772
Recurring Basis [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other non-current assets	600	600
Total	$ 600	$ 600

Property and Equipment, net - S

Property and Equipment, net - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 56,547	$ 43,376
Accumulated depreciation	(18,623)	(12,046)
Total property and equipment, net	37,924	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	3,416	3,215
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	23,895	16,640
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	25,473	21,400
Construction Work in Process [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 3,036	$ 1,394

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 2.3	$ 1.3	$ 6.6	$ 3.3

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Liabilities Current [Abstract]
Payroll and employee-related costs	$ 14,327	$ 15,229
Research costs	15,973	9,434
Licensing fees	915	750
Professional fees	1,762	2,040
Intellectual property costs	1,864	2,311
Accrued property and equipment	566	407
Other	38	9
Total	$ 35,445	$ 30,180

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended
	Jul. 31, 2020	May 31, 2020	Nov. 30, 2019	Sep. 30, 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				16.8
Lease Arrangement [Member]
Contingencies And Commitments [Line Items]
Annual rental payments			$ 3.7
Rental payments period	152 months	15 years	5 years
Lease Arrangement [Member] | Minimum [Member]
Contingencies And Commitments [Line Items]
Rental payments	$ 292.5	$ 40.2
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	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Sep. 30, 2020USD ($)Option	Sep. 30, 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				$ 11,776,000
Collaboration revenue	[1]				148,000				$ 211,928,000			349,000	$ 212,574,000
Current deferred revenue					610,000			960,000				610,000
Research and development expense	[2]				71,008,000				57,246,000			$ 184,581,000	130,601,000
Date of joint venture agreement												Dec. 19, 2015
Operating expenses					92,547,000				72,765,000			$ 247,023,000	176,817,000
Equity method investment														$ 36,500,000
Unrealized equity method losses									3,430,000				5,467,000	$ 36,500,000
Net loss of joint venture					(92,439,000)	$ (79,656,000)	$ (69,731,000)		138,423,000	$ (53,699,000)	$ (48,408,000)	(241,826,000)	36,316,000
Casebia Therapeutics Limited Liability Partnership [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense									100,000				700,000
Equity method investment, ownership percentage																50.00%
Unrealized equity method losses									3,300,000				5,500,000
Net loss of joint venture									22,600,000				54,900,000
Unrecognized equity method losses in excess of Company's interest													70,100,000
Business combination, consideration transferred												41,000,000
Net assets acquired					$ 16,000,000							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%							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									100,000				500,000
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					$ 4,400,000							$ 8,600,000
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%							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							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							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					11,600,000							11,600,000
2019 Casebia Agreement [Member] | Other Long-term Liabilities [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research obligation					4,800,000							4,800,000
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							0
Fair value of assets and liabilities					16,000,000							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							410,000,000
Transaction price												268,600,000
Non-current deferred revenue					11,800,000			11,800,000				11,800,000
Non-cash consideration received												10,000,000
Transaction price allocated to remaining performance obligations					12,000,000							12,000,000
Collaboration revenue					0				211,900,000			0	212,100,000
Current deferred revenue					600,000			900,000				600,000
Maximum potential future payments												800,000,000
Contract asset					25,000,000							25,000,000
Research and development expense					12,500,000				7,500,000			31,500,000	21,300,000
Reimbursements from research and license agreements					6,800,000				$ 3,800,000			17,800,000	$ 11,800,000
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							420,000,000
Transaction price allocated to remaining performance obligations					46,700,000							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							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							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							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							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							$ 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							$ 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							$ 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
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							$ 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]
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 revenue from a related party, see Notes 7 & 12
[2]	Including the following research and development expense with a related party, see Notes 7 & 12

Significant Contracts - Schedul

Significant Contracts - Schedule of Fair Value of Assets and Liabilities Received (Detail) $ in Thousands	Sep. 30, 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)	1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2020USD ($)$ / sharesshares	Aug. 31, 2019USD ($)	Aug. 31, 2018USD ($)	Sep. 30, 2020USD ($)shares	Sep. 30, 2019USD ($)shares	Sep. 30, 2020USD ($)shares	Sep. 30, 2019USD ($)shares	Dec. 31, 2019USD ($)shares	Sep. 30, 2020SFr / shares	Dec. 31, 2019SFr / sharesshares
Class of Stock [Line Items]
Common stock, shares authorized | shares				115,172,786		115,172,786				103,901,006
Common shares, par value | SFr / shares									SFr 0.03	SFr 0.03
Net cash proceeds from sale of common shares						$ 582,225,000	$ 121,216,000
July 2020 Offering [Member]
Class of Stock [Line Items]
Common shares sold | shares	7,400,000
Net cash proceeds from sale of common shares	$ 484,800,000
Common shares price per share | $ / shares	$ 70
Equity issuance costs and stamp tax	$ 32,500,000
Accrued equity issuance costs and stamp taxes				$ 4,900,000		$ 4,900,000
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					1,500,000		2,800,000	2,800,000
Net cash proceeds from sale of common shares					$ 69,400,000		$ 121,900,000	$ 120,600,000
Issuance costs					1,500,000		3,100,000
Equity issuance costs								$ 4,400,000
Payments of stamp taxes related to securities					500,000		700,000
Accrued stamp taxes					$ 600,000		$ 600,000
Sales Agreement With Jefferies LLC [Member] | 2019 ATM [Member]
Class of Stock [Line Items]
Common shares sold | shares				100,000		1,300,000
Net cash proceeds from sale of common shares				$ 9,600,000		$ 91,900,000
Issuance costs				200,000		2,400,000
Payments of stamp taxes related to securities				400,000		400,000
Accrued stamp taxes				$ 600,000		$ 600,000
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	Sep. 30, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Registered share capital	71,633,951	61,036,566
Authorized share capital	115,172,786	103,901,006
Employee Benefit Plans [Member]
Class of Stock [Line Items]
Conditional share capital - Bonds or similar debt instruments	17,493,709	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	21,125,426	19,246,503

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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 17,240	$ 14,773	$ 47,088	$ 37,667
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	9,109	6,262	24,492	17,137
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 8,131	5,081	$ 22,596	15,063
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		$ 5,467

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract]
Shares, Outstanding, Beginning Balance	7,782,437
Shares, Granted	1,468,758
Shares, Exercised	(1,011,236)
Shares, Cancelled or forfeited	(307,053)
Shares, Outstanding, Ending Balance	7,932,906
Shares, Exercisable	3,741,338
Shares, Vested or expected to vest	7,932,906
Weighted-Average Exercise Price, Outstanding, Beginning Balance	$ 31.30
Weighted-Average Exercise Price, Granted	56.19
Weighted-Average Exercise Price, Exercised	22.34
Weighted-Average Exercise Price, Cancelled or forfeited	41.35
Weighted-Average Exercise Price, Outstanding, Ending Balance	36.66
Weighted-Average Exercise Price, Exercisable	28.68
Weighted-Average Exercise Price, Vested or expected to vest	$ 36.66

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense related to stock options	$ 105.5
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 7 months 6 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
Total unrecognized compensation expense	$ 31.6

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Restricted Stock Activity (Detail) - Restricted Stock [Member]	9 Months Ended
	Sep. 30, 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	306,220
Unvested restricted common shares, Number of Shares, Vested | shares	(74,583)
Unvested restricted common shares, Number of Shares, Cancelled or forfeited | shares	(33,661)
Unvested restricted common shares, Number of Shares, Ending Balance | shares	897,510
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	49.01
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Vested | $ / shares	50.60
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Cancelled or forfeited | $ / shares	46.23
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Ending Balance | $ / shares	$ 54.84

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, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Net loss of joint venture	$ (92,439)	$ (79,656)	$ (69,731)	$ 138,423	$ (53,699)	$ (48,408)	$ (241,826)	$ 36,316
Basic weighted-average common shares outstanding	70,143,481			54,829,057			64,159,224	53,380,123
Effect of potentially dilutive securities:
Diluted weighted-average common shares outstanding	70,143,481			57,598,901			64,159,224	55,821,420
Basic net income (loss) per common share	$ (1.32)			$ 2.52			$ (3.77)	$ 0.68
Diluted net income (loss) per common share	$ (1.32)			$ 2.40			$ (3.77)	$ 0.65
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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 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	8,842,224	3,805,225	8,842,224	3,945,321
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	7,932,906	3,791,475	7,932,906	3,911,071
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	897,510	13,750	897,510	34,250
ESPP [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	11,808		11,808

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income tax provision	$ 200	$ 274	$ 956	$ 444
Effective income tax rate	(0.20%)	0.20%	(0.40%)	1.20%

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%