CRISPR Therapeutics (CRSP) 10-Q 8 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	CRSP
Entity Registrant Name	CRISPR THERAPEUTICS AG
Entity Central Index Key	1,674,416
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		47,186,829

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash	$ 341,767	$ 239,758
Accounts receivable, including related party amounts of $1,006 and $821 as of March 31, 2018 and December 31, 2017, respectively	1,260	2,626
Prepaid expenses and other current assets, including related party amounts of $605 and $1,871 as of March 31, 2018 and December 31, 2017, respectively	8,451	6,001
Total current assets	351,478	248,385
Property and equipment, net	18,907	18,857
Intangible assets, net	331	344
Restricted cash	3,165	3,154
Other non-current assets	571	606
Total assets	374,452	271,346
Current liabilities:
Accounts payable	2,546	1,639
Accrued expenses, including related party amounts of $78 and $0 as of March 31, 2018 and December 31, 2017, respectively	10,227	11,361
Accrued tax liabilities	433	347
Deferred rent	1,027	1,027
Other current liabilities	162	137
Total current liabilities	14,395	14,511
Deferred revenue non-current, including related party amounts of $0 and $91 as of March 31, 2018 and December 31, 2017, respectively	57,858	56,928
Deferred rent non-current	11,566	11,761
Other non-current liabilities	298	314
Total liabilities	84,117	83,514
Commitments and contingencies (Note 6)
Shareholders’ equity:
Common shares, CHF 0.03 par value, 47,166,907 and 41,092,969 shares authorized at March 31, 2018 and December 31, 2017, respectively, 47,119,435 and 41,037,121 shares issued at March 31, 2018 and December 31, 2017, respectively, 46,680,815 and 40,592,248 shares outstanding at March 31, 2018 and December 31, 2017, respectively, 16,114,039 and 16,419,632 shares in conditional capital at March 31, 2018 and December 31, 2017, respectively	1,423	1,240
Treasury shares, at cost, 438,620 and 444,873 shares at March 31, 2018 and December 31, 2017, respectively	0	0
Additional paid-in capital	443,774	312,018
Accumulated deficit	(154,888)	(125,440)
Accumulated other comprehensive income	26	14
Total shareholders' equity	290,335	187,832
Total liabilities and shareholders’ equity	$ 374,452	$ 271,346

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) $ in Thousands	Mar. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)shares
Statement Of Financial Position [Abstract]
Accounts receivable, related party amount, current | $	$ 1,006	$ 821
Prepaid expenses and other current assets, related party amount | $	605	1,871
Accrued expenses related party amount, current | $	78	0
Deferred revenue non-current related party amount | $	$ 0	$ 91
Common stock, shares authorized	47,166,907	41,092,969
Common stock, shares issued	47,119,435	41,037,121
Common stock, shares outstanding	46,680,815	40,592,248
Common stock, conditional capital	16,114,039	16,419,632
Treasury stock, shares	438,620	444,873

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Collaboration revenue	[1]	$ 1,358	$ 2,703
Operating expenses:
Research and development	[2]	19,519	14,805
General and administrative		8,836	8,642
Total operating expenses		28,355	23,447
Loss from operations		(26,997)	(20,744)
Other (expense) income:
Loss from equity method investment		(1,091)	(446)
Other expense, net		(126)	(6)
Total other (expense) income, net		(1,217)	(452)
Net loss before income taxes		(28,214)	(21,196)
Provision for income taxes		(86)	(279)
Net loss		(28,300)	(21,475)
Foreign currency translation adjustment		12	24
Comprehensive loss		(28,288)	(21,451)
Reconciliation of net loss to net loss attributable to common shareholders:
Net loss		$ (28,300)	$ (21,475)
Net loss per share attributable to common shareholders—basic and diluted		$ (0.62)	$ (0.54)
Weighted-average common shares outstanding used in net loss per share attributable to common shareholders—basic and diluted		45,877,428	39,725,947
[1]	Including the following revenue from a related party, see Note 10
[2]	Including the following research and development expense with a related party, See Note 10

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenue from related party	$ 1,082	$ 1,164
Research and development expense with a related party	$ 1,106	$ 1,136

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities:
Net loss	$ (28,300)	$ (21,475)
Reconciliation of net loss to net cash and restricted cash used in operating activities:
Depreciation and amortization	826	720
Equity-based compensation	5,582	3,300
Unrealized foreign currency remeasurement loss		1
Loss from equity method investment	1,091	446
Changes in:
Accounts receivable	1,366	(2,515)
Prepaid expenses and other assets	(2,426)	(394)
Accounts payable and accrued expenses	(439)	(3,648)
Deferred revenue	(218)	665
Deferred rent	(195)	(515)
Other liabilities, net	25	4
Net cash and restricted cash used in operating activities	(22,688)	(23,411)
Investing activities:
Purchase of property and equipment	(555)	(3,285)
Net cash and restricted cash (used in) provided by investing activities	(555)	(3,285)
Financing activities:
Proceeds from issuance of common shares in secondary offering, net of issuance	122,597
Proceeds from exercise of options	2,654	20
Net cash provided by financing activities	125,251	20
Effect of exchange rate changes on cash	12	29
(Decrease) increase in cash and restricted cash	102,020	(26,647)
Cash and restricted cash, beginning of period	242,912	318,670
Cash and restricted cash, end of period	344,932	292,023
Supplemental disclosure of non-cash investing and financing activities
Property and equipment purchases in accounts payable and accrued expenses	$ 307	$ 973

Organization and Operations

Organization and Operations	3 Months Ended
	Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Operations	1. Organization and Operations The Company CRISPR Therapeutics AG (“CRISPR” or the “Company”) was formed on October 28, 2013 in Basel, Switzerland. The Company was established to translate CRISPR/Cas9, a genome editing technology, into transformative gene-based medicines for the treatment of serious human diseases. The foundational intellectual property underlying the Company’s operations was licensed to the Company and its subsidiaries in April 2014. The Company devotes substantially all of its efforts to product research and development activities, initial market development and raising capital. The Company’s principal offices are headquartered in Zug, Switzerland and operations are in Cambridge, Massachusetts. The Company is subject to risks common to companies in the biotechnology industry, including but not limited to, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval for any drug product candidate that it may identify and develop, the need to successfully commercialize and gain market acceptance of its product candidates, dependence on key personnel, protection of proprietary technology, compliance with government regulations, development by competitors of technological innovations and ability to transition from pilot-scale manufacturing to large-scale production of products. The Company had an accumulated deficit of $154.9 million as of March 31, 2018 and has financed its operations to date from proceeds obtained from its IPO, a subsequent offering of its common shares in January 2018, a series of preferred shares and convertible loan issuances, and upfront fees received under its collaboration and joint venture arrangements. The Company will require substantial additional capital to fund its research and development and ongoing operating expenses. Liquidity In January 2018, the Company completed an offering of 5,750,000 shares of its common shares, which were sold at a price to the public of $22.75 per share. This offering resulted in $122.6 million of net proceeds to the Company. The Company expects its cash of $341.8 million at March 31, 2018 to be sufficient to fund its current operating plan through at least the next 24 months. Thereafter, the Company will be required to obtain additional funding. There can be no assurances, however, that the current operating plan will be achieved or that additional funding will be available on terms acceptable to the Company, or at all. Unaudited Interim Financial Information The condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with US GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Annual Report.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies The Company’s significant accounting policies are described in Note 2, “Summary of Significant Accounting Policies”, in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 (the “Annual Report”). Significant changes to the Company’s accounting policies as of a result of adopting ASC 606 are discussed below: Revenue Recognition In May 2014, the Financing Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers, which supersedes existing revenue recognition guidance. The Company adopted ASU 2014-09 and its related amendments (collectively known as “ASC 606”) on January 1, 2018 using the modified retrospective method, by recognizing the cumulative effect of initially applying ASC 606 as an adjustment to the opening balance of equity at January 1, 2018. The reported results for 2018 reflect the application of ASC 606 guidance while the reported results for 2017 were prepared under the guidance of ASC 605, Revenue Recognition (“ASC 605” or “legacy GAAP”). The Company has elected a practical expedient and applied ASC 606 only to contracts that are not completed at the date of initial application. ASC 606 applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. The Company’s revenue is from collaboration agreements. Within collaboration agreements, a counterparty may be a collaborator or partner that shares in the risks and benefits of developing a product to be marketed. These arrangements generally are in the scope of ASC 808, Collaborative Arrangements (“ASC 808”) yet may also contain vendor-customer aspects. Therefore, the Company considers all of the facts and circumstances to determine which transactions have a vendor-customer relationship that is subject to ASC 606. At the inception of each agreement the Company must determine which promised goods and services are under the scope of ASC 606 versus ASC 808 (discussed in the Collaborative Arrangements note below). In accordance with ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled to receive in exchange for these goods and services. To achieve this core principle, the Company applies the following five steps: 1) Identify the contract with the customer A contract with a customer exists when (i) the Company enters into an enforceable contract with a customer that defines each party’s rights regarding the goods or services to be transferred and identifies the related payment terms, (ii) the contract has commercial substance, and (iii) the Company determines that collection of substantially all consideration for goods and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration. 2) Identify the performance obligations in the contract Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct, whereby the customer can benefit from the good or service either on its own or together with other available resources, and are distinct in the context of the contract, whereby the transfer of the good or service is separately identifiable from other promises in the contract. To the extent a contract includes multiple promised goods and services, the Company must apply judgment to determine whether promised goods and services are capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. 3) Determine the transaction price The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in the Company’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment, which is discussed in further detail for each of the Company’s contracts with customers in Note 6. 4) Allocate the transaction price to performance obligations in the contract If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. 5) Recognize revenue when or as the Company satisfies a performance obligation The Company satisfies performance obligations either over time or at a point in time. Revenue is recognized over time if either 1) the customer simultaneously receives and consumes the benefits provided by the entity’s performance, 2) the entity’s performance creates or enhances an asset that the customer controls as the asset is created or enhanced, or 3) the entity’s performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. If the entity does not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring the control of a promised good or service to a customer. Examples of control are using the asset to produce goods or services, enhance the value of other assets, settle liabilities, and holding or selling the asset. ASC 606 requires the Company to select a single revenue recognition method for the performance obligation that faithfully depicts the Company’s performance in transferring control of the goods and services. The guidance allows entities to choose between two methods to measure progress toward complete satisfaction of a performance obligation: 1. Output methods - recognize revenue on the basis of direct measurements of the value to the customer of the goods or services transferred to date relative to the remaining goods or services promised under the contract (e.g. surveys of performance completed to date, appraisals of results achieved, milestones reached, time elapsed, and units of produced or units delivered); and 2. Input methods - recognize revenue on the basis of the entity’s efforts or inputs to the satisfaction of a performance obligation (e.g., resources consumed, labor hours expended, costs incurred, or time elapsed) relative to the total expected inputs to the satisfaction of that performance obligation. The Company has the right to consideration from a customer in an amount that corresponds directly with the value to the customer of the entity’s performance completed to date (i.e. R&D services), as such the Company has elected a practical expedient to recognize revenue in the amount to which the entity has a right to invoice for such services. The terms of the Company’s collaboration and license agreements contain multiple promised goods and services, which include options to license CRISPR/Cas9-based therapeutic products directed to specific targets, referred to as co-exclusive or exclusive licenses, joint steering committee participation, as well as research and development activities to be performed by the Company on behalf of the collaboration partner related to the licensed targets. Payments that the Company may receive under these agreements include nonrefundable upfront fees, payments for research activities, payments based upon the achievement of specified milestones and royalties on any resulting net product sales. To date, the Company’s only source of revenue has been the collaboration and license and joint development and commercialization agreement with Vertex Pharmaceuticals, Incorporated (“Vertex”) as well as research and development services provided to Casebia Therapeutics LLP (“Casebia”) under the joint venture with Bayer HealthCare LLC (“Bayer”). Please refer to Note 6 for the specific accounting treatment and revenue recognized during the period for each of these arrangements. Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company must consider the nature of the intellectual property to which the customer will have rights (i.e. access at a point in time or benefit of intellectual property enhancements over time). The Company recognizes revenue from non-refundable, up-front fees allocated to the license at a point in time/over the period the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement that includes development, regulatory or commercial milestone payments for promised goods and services, the Company evaluates the circumstances of whether the milestones will be reached and estimates the amount to be included in the transaction price that will not cause a significant revenue reversal. The Company will evaluate these types of payments for customer options once those options have been exercised. ASC 606 suggests two alternatives to use when estimating the amount of variable consideration: the expected value method and the most likely amount method. Under the expected value method, an entity considers the sum of probability-weighted amounts in a range of possible consideration amounts. Under the most likely amount method, an entity considers the single most likely amount in a range of possible consideration amounts. The Company will use the most likely amount method for development and regulatory milestone payments. Management believes the most likely amount method is the better predictor as the Company expects to be entitled to only one of two possible amounts. Additionally, management believes that the most likely amount of milestone consideration is its stated amount. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. The transaction price is then allocated to performance obligations on a specific basis or on a relative stand-alone selling price basis. The Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates whether it is probable that a significant revenue reversal will not occur in future periods, and if necessary, adjusts its estimates of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Up-front payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less. Contract Balances The Company recognizes a contract asset when the Company transfers goods or services to a customer before the customer pays consideration or before payment is due, excluding any amounts presented as a receivable (i.e. accounts receivable). A contract asset is an entity’s right to consideration in exchange for goods or services that the entity has transferred to a customer. The contract liabilities (i.e. deferred revenue) primarily relate to contracts where we have received payment but we have not yet satisfied the related performance obligations. The advance consideration received from customers for R&D services or licenses bundled with other promises is a contract liability, recorded as deferred revenue, until the underlying performance obligations are transferred to the customer. The change in deferred revenue is primarily related to the transition adjustment upon the adoption of ASC 606 for the three months ended March 31, 2018. Costs to Obtain and Fulfill a Contract with Customer The Company recognizes an asset related to incremental costs of obtaining a contract with a customer if the Company expects to recover those costs. The Company will recognize an asset from costs incurred to fulfill a contract only if such costs relate directly to a contract that the entity can specifically identify, the costs generate or enhance resources of the Company that will be used in satisfying performance obligations in the future, and the costs are expected to be recovered. Any assets recognized related to costs to obtain or fulfill a contract are amortized on a systematic basis that is consistent with the transfer to the customer of the goods or services to which the asset relates. Income Taxes The adoption of ASC 606 resulted in a reduction of revenue as of December 31, 2017, which in turn generated additional deferred tax assets. As the Company fully reserves its net deferred tax assets in the jurisdictions impacted by the adoption of ASC 606, this impact was offset by a corresponding change to the valuation allowance. Impact of Adopting ASC 606 on the Financial Statements The Company adopted ASC 606 using the modified retrospective method. The cumulative effect of applying the new guidance to all contracts with customers that were not completed as of January 1, 2018 was recorded as an adjustment to accumulated deficit as of the adoption date. The Company elected to apply a practical expedient to reflect the aggregate effect of all modifications that occur before the beginning of the earliest period presented when identifying the satisfied and unsatisfied performance obligations, determining the transaction price, and allocating the transaction price to the satisfied and unsatisfied performance obligations. As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made to the consolidated balance sheet as of January 1, 2018: As Reported December 31, 2017 ASC 606 Adjustment Adjusted January 1, 2018 Consolidated Balance Sheet Data (in thousands): Other current liabilities $ 137 $ 102 $ 239 Total current liabilities $ 14,511 $ 102 $ 14,613 Deferred revenue $ 56,928 $ 1,046 $ 57,974 Total liabilities $ 83,514 $ 1,148 $ 84,662 Accumulated deficit $ (125,440 ) $ (1,148 ) $ (126,588 ) Total shareholders' equity $ 187,832 $ (1,148 ) $ 186,684 Total liabilities and shareholders’ equity $ 271,346 $ - $ 271,346 Impact of New Revenue Guidance on Financial Statement Line Items The following table compares the reported condensed consolidated balance sheet, statement of operations and cash flows, as of and for the three months ended March 31, 2018, to the pro-forma amounts had the previous guidance been in effect: March 31, 2018 As Reported Under ASC 606 Adjustments Notes Adjusted Balance Under ASC 605 Consolidated Balance Sheet Data (in thousands): Other current liabilities $ 162 $ (102 ) (5) $ 60 Total current liabilities $ 14,395 $ (102 ) (5) $ 14,293 Deferred revenue $ 57,858 $ (945 ) (1)(2)(3)(5) $ 56,913 Total liabilities $ 84,117 $ (1,047 ) (1)(2)(3)(5) $ 83,070 Accumulated deficit $ (154,888 ) $ 1,047 (1)(2)(3) $ (153,841 ) Total shareholders' equity $ 290,335 $ 1,047 (1)(2)(3 $ 291,382 Total liabilities and shareholders’ equity $ 374,452 $ - (1)(2)(3) $ 374,452 Consolidated Statement of Operations Data (in thousands): Revenue $ 1,358 $ (101 ) (2)(3) $ 1,257 Operating loss $ (26,997 ) $ (101 ) (2)(3) $ (27,098 ) Loss before taxes $ (28,214 ) $ (101 ) (2)(3) $ (28,315 ) Net loss $ (28,300 ) $ (101 ) (2)(3) $ (28,401 ) Comprehensive loss $ (28,288 ) $ (101 ) (2)(3) $ (28,389 ) Consolidated Statement of Cash Flows (in thousands): Operating activities: Net loss $ (28,300 ) $ (101 ) (2)(3) $ (28,401 ) Reconciliation of net loss to net cash and restricted cash used in operating activities: Changes in: Deferred revenue $ (218 ) $ 203 (1)(2)(3)(4)(5) $ (15 ) Other liabilities, net $ 25 $ (102 ) (1)(2)(3)(4)(5) $ (77 ) Net cash used in operating activities $ (22,688 ) $ - (1)(2)(3)(4)(5) $ (22,668 ) (Decrease) increase in cash and restricted cash $ 102,020 $ - (1)(2)(3)(4)(5) $ 102,020 Cash and restricted cash, end of period $ 344,932 $ - (1)(2)(3)(4)(5) $ 344,932 (1) Adjustment of $1,148 to reverse the ASC 606 transition adjustment from retained earnings and deferred revenue. (2) Adjustment of $76 related to R&D services that would be deferred under ASC 605 versus recognized under ASC 606. (3) Adjustment of $25 related to non-exclusive research revenue that would be recognized upon option exercise under ASC 605 versus recognized overtime under ASC 606. (4) Adjustment to reverse the ASC 606 transition adjustment to retained earnings and deferred revenue netted to zero as the transaction did not impact cash. (5) Adjustment to reclass $102 from deferred revenue to current deferred revenue related to the change in revenue allocated to the non-exclusive research license recognized upon option exercise under ASC 605 versus ratably over time under ASC 606. Collaboration Arrangements The Company records the elements of its collaboration agreements that represent joint operating activities in accordance with ASC 808. Accordingly, the elements of the collaboration agreements that represent activities in which both parties are active participants and to which both parties are exposed to the significant risks and rewards that are dependent on the commercial success of the activities, are recorded as collaborative arrangements. The Company considers the guidance in ASC 606 in determining the appropriate treatment for the transactions between the Company and its collaborative partner and the transactions between the Company and third parties. Generally, the classification of transactions under the collaborative arrangements is determined based on the nature and contractual terms of the arrangement along with the nature of the operations of the participants. The Company evaluates the proper presentation of the commercial activities and the profit and loss sharing associated with the collaboration agreements. ASC 808 states that when payments between parties in a collaborative arrangement are not within the scope of other authoritative accounting literature, the income statement classification should be based on the nature of the arrangement, the nature of its business operations and the contractual terms of the arrangement. To the extent that these payments are not within the scope of other authoritative accounting literature, the income statement classification for the payments shall be based on an analogy to authoritative accounting literature or if there is no appropriate analogy, a reasonable, rational, and consistently applied accounting policy election. New Accounting Pronouncements - Recently Adopted From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that the Company adopts as of the specified effective date. Financial Instrument Accounting In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The new standard amends certain aspects of accounting and disclosure requirements of financial instruments, including the requirement that equity investments with readily determinable fair values be measured at fair value with changes in fair value recognized in the results of operations. The new standard was effective January 1, 2018. The Company adopted ASU No. 2016-01 in the first quarter of 2018. The adoption of this guidance did not have a material impact on the Company's financial position and results of operations. Income Taxes In October 2016, the FASB issued ASU No. 2016-16, Income Taxes Intra-Entity Transfers of Assets Other Than Inventory Statement of Cash Flows In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows Restricted Cash Business Combinations In January 2017, the FASB issued ASU No. 2017-01, Business Combinations In May 2017, the FASB issued ASU 2017-09, Compensation – Stock Compensation New Accounting Pronouncements - to be adopted in future periods In February 2016, the FASB issued ASU No. 2016-02, Leases Net Loss Per Share Attributable to Common Shareholders Basic net loss per share is calculated by dividing net loss attributable to common shareholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is calculated by dividing the net income attributable to common shareholders by the weighted-average number of common equivalent shares outstanding for the period, including any dilutive effect from outstanding stock options and warrants using the treasury stock method. The following common share equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect (in common stock equivalent shares): As of March 31, 2018 March 31, 2017 Outstanding options 6,638,120 4,829,891 Unvested unissued restricted common shares 47,472 80,987 Total 6,685,592 4,910,878 Basis of Presentation and Use of Estimates The accompanying condensed consolidated financial statements have been prepared in conformity with GAAP, and include the accounts of (i) the Company, and (ii) its wholly-owned subsidiaries, CRISPR Therapeutics Ltd., CRISPR Therapeutics Inc., and TRACR Hematology Inc. All intercompany accounts and transactions have been eliminated. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) of the FASB. The Company accounts for its 50% interest in Casebia under the equity method of accounting. See Note 6 for further details. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, equity-based compensation expense, revenue recognition, equity method investments, fair value of intangible assets, the provision for or benefit from income taxes and reported amounts of research and development expenses during the period. 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. The consolidated statements reflect all adjustments which are of a normal recurring nature necessary for presentation. Actual results may differ from those estimates or assumptions.

Property and Equipment, net

Property and Equipment, net	3 Months Ended
	Mar. 31, 2018
Property Plant And Equipment [Abstract]
Property and Equipment, net	3. Property and Equipment, net Property and equipment, net, consists of the following (in thousands): As of March 31, December 31, 2018 2017 Computer equipment $ 285 $ 285 Furniture, fixtures, and other 2,104 2,104 Laboratory equipment 7,144 6,603 Leasehold improvements 13,776 13,776 Construction work in process 321 - 23,630 22,768 Accumulated Depreciation (4,723 ) (3,911 ) Property and equipment, net $ 18,907 $ 18,857 Depreciation expense for the three month ended March 31, 2018 and 2017 was $0.8 million and $0.7 million respectively.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2018
Payables And Accruals [Abstract]
Accrued Expenses	4. Accrued Expenses Accrued expenses consist of the following (in thousands): As of March 31, December 31, 2018 2017 Payroll and employee-related costs $ 3,287 $ 5,550 Research costs 4,280 2,285 Licensing fees 778 609 Professional fees 989 2,176 Intellectual property costs 862 500 Other 31 241 Total $ 10,227 $ 11,361

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	5. Commitments and Contingencies Research Agreements The Company has engaged several research institutions and companies to identify new delivery strategies and applications of the CRISPR/Cas9 technology. As a result of these efforts, the Company sponsored research programs during the three months ended March 31, 2018. In association with these agreements, the Company has committed to making payments for related research and development services of $0.4 million and $0.1 in 2018 and 2019, respectively. The Company is also a party to a number of research license agreements which require upfront payments, future royalty payments and potential milestone payments from time to time which could be significant. In association with these agreements, the Company has committed to making payments for related research and development services of $0.5 million and $0.4 million in 2018 and 2019, respectively. In connection with these agreements, during the three months ended March 31, 2018 and 2017, the Company has made upfront payments of $0.2 million and milestone payments of $1.4 million, respectively. The Company is a party to a number of manufacturing agreements that require upfront payments for the future performance of services. In connection with these agreements, the Company has made upfront payments and recorded $2.5 million as prepaid expenses. Operating Leases In March 2017, the Company subleased a portion of one research and office facility to a third party effective April 1, 2017. The sublease term is less than the remaining term under the original lease, and as a result, the Company does not believe it has met a cease use date as it may re-enter the space following the sublease. Payments to be received from the sublessee are approximately $2.8 million and will offset scheduled rent payments due to the landlord under the original lease for the sublease term. Litigation The Company licenses a U.S. patent application that is currently subject to interference proceedings declared by the Patent Trial and Appeal Board (“PTAB”) of the U.S. Patent and Trademark Office. Following motions by the parties and other procedural matters, the PTAB concluded in February 2017 that the declared interference should be dismissed because the claim sets of the two parties were not directed to the same patentable invention in accordance with the PTAB’s two-way test for patent interferences. In April 2017, the regents of the University of California (“California”) appealed the PTAB decision to the U.S. Court of Appeals for the Federal Circuit. In the appeal, California is seeking review and reversal of the PTAB’s February 2017 decision, which terminated the interference without determining which inventors actually invented the use of the CRISPR/Cas9 genome editing technology in eukaryotic cells. On December 15, 2016, the Company entered into a Consent to Assignments, Licensing and Common Ownership and Invention Management Agreement (the “Invention Management Agreement”) with the University of California, University of Vienna, Dr. Emmanuelle Charpentier, Intellia Therapeutics, Inc. Caribou Biosciences, Inc., ERS Genomics Ltd. and TRACR Hematology Ltd. Under the Invention Management Agreement, the Company is obligated to share costs related to patent maintenance, defense and prosecution. During the three months ended March 31, 2018 and 2017, the Company incurred $0.5 million and $0.5 million, respectively, in shared costs. The Company recorded accrued legal costs from the cost sharing of $0.7 million and $0.9 million as of March 31, 2018 and 2017, respectively.

Significant Contracts

Significant Contracts	3 Months Ended
	Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Significant Contracts	6. Significant Contracts Collaboration Agreement with and Joint Development Agreement Vertex Pharmaceuticals, Incorporated Summary of Agreement On October 26, 2015, the Company entered into a strategic collaboration, option, and license agreement (“Collaboration Agreement”) with Vertex, focused on the use of CRISPR’s gene editing technology, known as CRISPR/Cas9, to discover and develop potential new treatments aimed at the underlying genetic causes of human disease. On December 12, 2017, the Company and Vertex entered into Amendment No. 1 to the Collaboration Agreement (the “Amendment”) and the Joint Development Agreement (the “JDA”). The Amendment, among other things, modified certain definitions and provisions of the 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 Collaboration Agreement. The Amendment also amended other provisions of the Collaboration Agreement, including the expiration terms of the Collaboration Agreement. In connection with the Collaboration Agreement, Vertex made a nonrefundable upfront payment of $75.0 million. Under the Collaboration Agreement, Vertex will fund all of 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, 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. For other targets that Vertex elects to license, Vertex would lead all development and global commercialization activities. For each of up to four remaining targets that Vertex elects to license, the Company has the potential to receive up to $420.0 million in development, regulatory and commercial milestones and royalties on net product sale. In connection with entering into the JDA, the Company received a $7.0 million up-front payment from Vertex and is eligible for a one-time low seven-digit milestone payment upon the dosing of the second patient in a clinical trial with the initial product candidate. The net profits and net losses, as applicable, incurred under the JDA will be shared equally between us and Vertex. Accounting for the Collaboration Agreement, Amendment and JDA As the overall arrangement was modified in December 2017, 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. The arrangement includes components of a customer-vendor relationship and a collaborative arrangement as defined under ASC 808. The Company will apply the guidance of ASC 606 by analogy to the vendor-customer performance obligations of the Collaboration Agreement and the performance obligations of the JDA subject to ASC 606 as outlined below. The Company will apply the guidance of ASC 808 to those elements in which there is a collaboration relationship in which both parties share equally in the risks and rewards of the research and development which include (i) development and commercialization services for currently identified shared products; (ii) R&D services for any follow-on products subject to the JDA; and (iii) committee participation. The Company evaluated the Collaboration Agreement, Amendment and JDA in accordance with the provisions of ASC 606. The Company identified the following 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. The selling price of each performance obligation was determined based on the Company’s estimated standalone selling price (the “ESSP”). The Company developed the ESSP for all the performance obligations included in the Collaboration Agreement and JDA 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 ESSP for material rights was determined based on the incremental discount given to Vertex based on the ESSP of the four remaining exclusive licenses and the exercise price paid at the time of exercise. 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’s ESSP for the satisfied and unsatisfied R&D Services was $19.3 million. 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 probability and present value adjusted cash flows from the milestones payments owed for exclusive licenses outlined in the Collaboration Agreement less the price paid to exercise the material right option. ESSP reflects the level of risk and expected probability of success inherent in the nature of the associated research area. The Company’s ESSP for the co-exclusive research license and the development and commercialization licenses for of the hemoglobinopathy and beta-globin targets is $48.9 million. ESSP for this item was determined based on probability and present value adjusted cash flows from the equal sharing of projected worldwide net profit or net loss. ESSP reflects the level of risk and expected probability of success inherent in the nature of the associated research area. The Company used a market-based approach to determine the ESSP of the non-exclusive research license of $1.0 million. The Company by used comparative data, including in-licensed research agreements negotiated and executed within the Company. 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, thus the Company will recognize revenue related to the R&D services as invoiced, in line with the practical expedient in ASC 606-10-55-18. The transaction price is 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 R&D services revenue will be recognized as invoiced and specifically allocated to the R&D services performance obligation. The remaining transaction price of $82.0 million was allocated among the performance obligations using the relative selling price method as follows: : (i) a non-exclusive research license: $0.5 million; (ii) a material right to discounts for exclusive licenses for up to four Collaboration Targets: $22.2 million, $18.7 million, $8.4 million and $8.4 million for a total of $57.7 million; and (iii) co-exclusive development and commercialization licenses for hemoglobinopathy and beta-globin targets identified in the JDA and co-exclusive research license for the follow-on products: $23.8 million. 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, as such, the revenue related to the non-exclusive research license will be 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 were recognized at a point in time, in which they were delivered at inception of the JDA in December 2017. As Vertex has 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. Milestones under the Collaboration Agreement The Company has evaluated all of the milestones that may be received in connection with the Collaboration Agreement and JDA. The first potential milestone the Company will be entitled to receive is the milestone in the JDA to receive a one-time low seven-digit milestone payment in any clinical trial in the initial shared product and is currently fully constrained. The remaining milestones are predominately related to the development and commercialization of a product resulting from the arrangement and are payable with respect to each selected exclusive license which have yet to be exercised and are not currently included in the determination of the transaction price. Each milestone is payable only once per collaboration target, regardless of the number of products directed to such collaboration target that achieve the relevant milestone event. There are nine remaining clinical development and regulatory approval milestones which may trigger proceeds of up to $90.0 million and $235.0 million, respectively, for each selected exclusive license, and two commercial milestones which may trigger proceeds of up to $75.0 million for each selected exclusive license (which, when combined with the $10.0 million due upon exercise of the exclusive option and the $10.0 million development milestone associated with an IND, total $420.0 million for each selected Exclusive License), as follows: Developmental Milestone Events 1. Initiation of the first Clinical Trial of a Product 2. Establishment of Proof of Concept for a Product 3. Initiation of the first Phase 3 Clinical Trial of a Product 4. Acceptance of Approval Application by the FDA for a Product 5. Acceptance of Approval Application by the EMA for a Product 6. Acceptance of Approval Application by a Regulatory Authority in Japan for a Product 7. Marketing Approval in the US for a Product 8. Marketing Approval in the EU for a Product 9. Marketing Approval in Japan for a Product Commercial Milestone Events 1. Annual Net Sales for Products with respect to a Collaboration Target exceed $500 million; and 2. Annual Net Sales for Products with respect to a Collaboration Target exceed $1.0 billion There is uncertainty that the events to obtain the developmental milestones will be achieved given the nature of clinical development and the stage of the CRISPR technology. Upon exercise of the exclusive license options, developmental milestones will be constrained until the Company is sure 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 will be accounted for under the royalty recognition constraint and will be accounted for as constrained variable consideration. The Company will apply 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. Collaborative elements The Company evaluated the Collaboration Agreement, Amendment and JDA in accordance with the provisions of ASC 808. The Company identified the following elements of ASC 808: (i) development and commercialization services for shared products; (ii) R&D services for follow-on products; and (iii) committee participation. The Company evaluated that the nature of the arrangement and determined the arrangement is a cost/profit sharing arrangement and not a revenue arrangement. Therefore, the related impact of the cost sharing associated with research and development will be included in R&D expense. Expenses related to services performed by the Company will be classified as R&D expense. Payments received from Vertex for partial reimbursement of expenses are recorded as a reduction of R&D expense. During the three months ended March 31, 2018 and 2017, the Company recognized $0.2 million and $1.5 million of revenue related to the collaboration with Vertex, respectively. Research and development expense incurred by the Company in relation to its performance under the Collaboration Agreement for the three months ended March 31, 2018 and 2017 was $0.2 million and $2.6 million, respectively. Research and development expense incurred by the Company in relation to its performance under the JDA for the three months ended March 31, 2018 and 2017 was $4.2 million and zero, respectively. As of March 31, 2018 and December 31, 2017, there was $57.9 million and $56.8 million of non-current deferred revenue related to the Collaboration Agreement, respectively. The transaction price allocated to the remaining performance obligations is $58.0 million. The remaining performance obligations will be recognized as follows: four material rights to obtain an exclusive commercialization and development license at a point in time, upon exercise; and the non-exclusive research license ratably over/within the remaining two-and-a-half-year research term. R&D services will be recognized as invoiced under the practical expedient and are not disclosed within the remaining performance obligation balance. Reported amounts for 2018 are reflective of accounting under ASC 606 and amounts for 2017 are reflective of accounting under ASC 605 and therefore may not be comparable. Joint Venture with Bayer Healthcare LLC On December 19, 2015, the Company entered into an agreement with Bayer Healthcare LLC, to establish a joint venture (“Bayer Joint Venture”) to focus on the research the development of new therapeutics to cure blood disorders, blindness, and congenital heart disease. On February 12, 2016, the Company and Bayer Healthcare completed the formation of the joint venture entity, Casebia Therapeutics LLP, a limited liability partnership formed in the United Kingdom. Bayer Healthcare and the Company each received a 50% equity interest in the entity in exchange for their contributions to the entity. The Company contributed $0.1 million in cash and licensed its proprietary CRISPR/Cas9 gene editing technology and intellectual property for selected disease indications. Bayer Healthcare contributed its protein engineering expertise and relevant disease know-how. Under the agreement, Casebia has paid the Company $35.0 million in exchange for a worldwide, exclusive license to commercialize the Company’s CRISPR/Cas9 technology specifically for the indications designated by Casebia. In March 2016, the Company received a non-refundable up-front payment of $20.0 million as a technology access fee. The remaining $15.0 million was paid on December 22, 2016 following delivery of the necessary consents from patent holders of the Company’s intellectual property. There are no milestone, royalties or other payments due to the Company under this aspect of the agreement. The Company determined that the contribution of the CRISRP/Cas9 technology by license to Casebia did not meet the definition of a business under ASC 805. The Company also entered into a separate services agreement with Casebia, under which the Company agreed to provide compensated research and development services. Concurrent with the execution of the Bayer Joint Venture agreement, the Company also entered into the Bayer Convertible Loan for $35.0 million. As the Bayer Joint Venture (including the CRISPR/Cas9 technology license and the research and development services) and the Bayer Convertible Loan were executed at the same time, the Company determined that the contracts should be combined and evaluated as a single arrangement. Additionally, the Company also determined that ASC 845, Nonmonetary Transactions (“ASC 845”) did not apply to this arrangement given the Company’s significant continuing involvement with Casebia and the amount of cash involved in the arrangement. As a result, the Company analogized to the guidance within ASC 606 regarding the allocation of arrangement consideration, however elements under transaction that were not in the scope of ASC 606 were accounted for by under accounting literature based on the allocated arrangement consideration. The Company determined the total consideration which would allocated to various elements of the transaction includes (i) the total cash payment by Casebia for the technology access fee, net of the Company’s $0.1 million contribution, of $34.9 million, (ii) the fair value of the equity interest in the Joint Venture of $36.4 million, (iii) the $35.0 million received from the issuance of the Convertible Debt, and (iv) $6.3 million of estimated cash consideration to be received under the research and development service arrangement, accumulating to $112.6 million. The Company identified the following performance obligations in the combined transaction: (i) Combined element of an exclusive, worldwide, royalty free, license to the CRISPR/Cas9 technology specifically for the indications designated by (ii) Research and development services, and The Company also identified the issuance of the Bayer Convertible Loan as another element to be accounted for under ASC 470. The Company allocated consideration to the performance obligations and other elements based on the relative proportion of their standalone selling prices. The Company determined the standalone selling price of the license was $71.4 million based on the consideration paid and the fair value of the 50% interest in Casebia, which was determined utilizing discounted cash flows based on reasonable estimates and assumptions of cash flows expected from Casebia. The standalone selling prices of the separate research and development services was determined to be $6.3 million and of the fair value of the Bayer Convertible Loan was determined to be $24.5 million, based on the fair value of the underlying preferred shares that were exchanged as part of the immediate conversion. Using a relative standalone selling price allocation, the Company allocated the aggregate arrangement consideration paid as follows: (i) $ (ii) $ The difference between combined above amounts of $106.3 million and the total transaction price of $112.6 million is due to variable consideration of $6.3 million associated with the research and development service arrangement. The amount of the transaction price related to the research and development services ($6.3 million) will be allocated specifically to the research and development performance obligation under the right to invoice practical expedient in ASC 606-10-55-18. The Company noted an immaterial difference due to this change at January 1, 2018. Following delivery of the patent holders’ consent, which occurred on December 17, 2016, the combined amount attributed to the license and patent holder consent element and the remaining $15.0 million license fee, which amount to $79.1 million, was recognized as other income for the year ended December 31, 2016. The Company had determined that the license and patent holder consent combined element did not meet the definition of revenue because the licensing of its technology in connection with the formation of a joint venture is not part of the Company’s major ongoing or central operations. As the amount allocated to the Bayer Convertible Loan represents an $8.0 million discount to its $35.0 million face value, the Company recognized interest expense during the twelve months ended December 31, 2017 equal to the discount. The Convertible Loan automatically converted into Series B preferred shares on its January 29, 2016 maturity date. During 2016, the Company recorded an equity method investment of $36.5 million equal to the fair value of the Company’s interest in Casebia (which was included in the allocable arrangement consideration described above). Following delivery of the patent holders consent element and realization of the described gain allocated to the license and patent holder consent combined element, the Company recorded unrealized equity method losses up to the remaining amount of the $36.5 million investment. The R&D services are the only remaining performance obligations as of March 31, 2018. At March 31, 2018 and December 31, 2017, the value of the Company’s equity method investment in Casebia was zero. Collaborative elements The Company also participates in cost sharing activities with Casebia with respective to shared research and technology licenses with other vendors. The Company evaluated that the nature of the activity and determined the arrangement is a cost/profit sharing arrangement and not a revenue arrangement. Therefore, the related impact of the cost sharing is included in R&D expense. Collaboration Revenue During the three months ended March 31, 2018 and 2017, the Company recognized $1.1 million and $1.2 million of revenue, respectively, related to the collaboration with Casebia. Amounts for 2018 are reflective of accounting under ASC 606 and amounts for 2017 are reflective of accounting under ASC 605 and therefore may not be comparable. During the three months ended March 31, 2018 and 2017, the Company recognized $1.1 million and $1.1 million of research and development expense, respectively, in relation to its performance under the agreement. During the three months ended March 31, 2018 and 2017, the Company recognized $1.1 million and $0.5 million respectively, of stock-based compensation expense related to Casebia employees. Deferred revenue related to the Company’s collaboration with Casebia was zero and $0.1 million as of March 31, 2018 and December 31, 2017, respectively. Unrecognized equity method losses in excess of the Company’s equity investment in Casebia was $26.8 million and $21.2 million as of March 31, 2018 and December 31, 2017, respectively. Total operating expenses and net loss of Casebia for the three months ended March 31, 2018 was $12.5 million and $12.3 million, respectively. Total operating expenses, and net loss of Casebia for the three months ended March 31, 2017 was $5.5 million.

Share Capital

Share Capital	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Share Capital	7. Share Capital The Company had 47,166,907 registered common shares as of March 31, 2018, with a par value of CHF 0.03 per share, which includes 147,473 shares of unvested unissued restricted common shares and 438,620 treasury shares which are legally outstanding but not considered outstanding for accounting purposes. Conditional Capital Reserved for Future Issuance The Company had the following conditional capital reserved for future issuance: As of Conditional Capital March 31, 2018 December 31, 2017 Unvested unissued restricted stock 166,667 166,667 Outstanding stock options 6,638,120 6,262,339 Reserved for future issuance under stock option plans (1) 3,976,326 4,657,700 Shares available for bonds and similar debt instruments 4,919,700 4,919,700 Shares available for employee purchase plans 413,226 413,226 Total 16,114,039 16,419,632 (1) The Company’s Board of Directors approved an increase to the option pool of 2,012,684 options in May 2017 and in March 2018, an increase to the option pool of an additional 4,000,000 options subject to shareholder approval.

Equity-based Compensation

Equity-based Compensation	3 Months Ended
	Mar. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity-based Compensation	8. Equity-based Compensation The Company uses the straight-line attribution method to recognize stock-based compensation expense for stock options and restricted stock awards. Stock options and restricted stock awards generally vest over four years with 25% vesting on the first anniversary of service commencement and the remaining 75% vesting monthly thereafter. The following table presents stock-based compensation expense included in the Company’s Condensed Consolidated Statements of Operations and Comprehensive Loss: Three Months Ended March 31, 2018 2017 Research and development $ 2,916 $ 1,730 General and administrative 2,666 1,570 Loss from equity method investment 1,091 446 Total $ 6,673 $ 3,746 Grant-Date Fair Value The Company estimated the fair value of each employee and non-employee stock option award using the Black-Scholes option-pricing model based on the following assumptions: Three Months Ended March 31, 2018 2017 Employees: Weighted average expected volatility 70.5 % 73.0 % Expected term (in years) 6.0 6.0 Risk free interest rate 2.7 % 2.2 % Expected dividend yield 0.0 % 0.0 % Non-employees: Weighted average expected volatility 81.1 % 81.0 % Expected term (in years) 9.1 10.0 Risk free interest rate 2.6 % 2.4 % Expected dividend yield 0.0 % 0.0 % The fair value of the restricted stock awards was determined based on the fair value of the common shares on the grant date. Non-employee stock options and restricted stock awards, including those granted to employees of Casebia, are marked-to-market at each reporting period. Share Based Payment Activity Stock Option Awards The following table summarizes stock option activity for employees and non-employees (intrinsic value in thousands): Stock Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2017 6,262,339 $ 13.24 8.8 $ 64,120 Granted 1,092,737 $ 50.33 Exercised (363,202 ) $ 10.77 Cancelled or forfeited (353,754 ) $ 11.92 Outstanding at March 31, 2018 6,638,120 $ 19.55 8.9 $ 179,644 Exercisable at March 31, 2018 1,687,503 $ 10.30 8.2 $ 59,746 Vested or expected to vest at March 31, 2018 (1) 6,638,120 $ 19.55 8.9 $ 179,644 (1) Represents the number of vested options at March 31, 2018 plus the number of unvested options expected to vest in the future. As of March 31, 2018, total unrecognized compensation expense related to stock options was $74.6 million which the Company expects to recognize over a remaining weighted-average period of 3.5 years During the three months ended March 31, 2018 and 2017, the Company granted options to purchase 0 and 15,000 common shares, respectively, subject to performance-based vesting conditions. During 2017, the Company also granted 150,000 stock options with market-based vesting conditions in which the recipient is eligible to receive between zero and 150,000 options to purchase common shares at the end of a four year service period based upon achieving a specified average stock price. As of March 31, 2018, no options to purchase common shares subject to market-based vesting conditions were vested; however 75,000 options were earned as the specified average stock price was achieved. Restricted Stock Awards The following table summarizes restricted stock activity for employees and non-employees during the three months ended March 31, 2018: Reflected as outstanding upon vesting Reflected as outstanding upon grant date Total Weighted- Average Grant Date Fair Value Unvested restricted common shares as of December 31, 2017 157,515 208,886 366,401 $ 8.49 Granted — — — — Vested (10,042 ) (102,963 ) (113,005 ) 6.59 Cancelled or forfeited — — — — Unvested restricted common shares as of March 31, 2018 147,473 105,923 253,396 $ 9.17 During the three months ended March 31, 2018, the total fair value of vested restricted common shares was $4.5 million. As of March 31, 2018, total unrecognized compensation expense related to unvested restricted common shares was $1.5 million which the Company expects to recognize over a remaining weighted-average period of two years.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes During the three months ended March 31, 2018 and 2017, the Company recorded an income tax provision of $0.1 million and $0.3 million, respectively, representing an effective tax rate of -0.3%, and -1.3%, respectively. The income tax provision is primarily attributable to the year-to-date pre-tax income earned by the Company’s U.S. subsidiary. The difference in the statutory tax rate and effective tax rate is primarily a result of the jurisdictional mix of earnings and losses that are not benefited. The Company maintains a valuation allowance against certain deferred tax assets that are not more-likely-than-not realizable. As a result, the Company has not recognized a tax benefit related to losses generated in Switzerland in the current periods. As disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017, the Company recorded provisional amounts in its 2017 financial statements to reflect the federal, state and foreign impacts of the Tax Cuts and Jobs Act (the “Act”). These amounts remain provisional and subject to Staff Accounting Bulletin No. 118, “Income Tax Accounting Implications of the Tax Cuts and Jobs Act,” (“SAB 118”) as of March 31, 2018. There have been no changes to the provisional amounts recorded in the 2017 financial statements during the three months ended March 31. 2018.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	10. Related Party Transactions The Company is a party to intellectual property license agreements with Dr. Charpentier. During the three months ended March 31, 2018 and 2017, the Company did not record any sublicensing fees due to Dr. Charpentier in research and development expense related to the Bayer Joint Venture Agreement. During the three months ended March 31, 2018 and 2017, the Company recognized revenue of $1.1 million, and $1.2 million, respectively, related to the collaboration with Casebia. During the three months ended March 31, 2018 and 2017, the Company recognized research and development expense of $1.1 million and $1.1 million, respectively, related to the performance of services for Casebia. The Company and Casebia have engaged several research institutions and companies to identify new delivery strategies and applications of the CRISPR/Cas9 technology. Additionally, the Company and Casebia are also a party to a number of research license agreements. The Company and Casebia will share costs associated with the research and license agreements. The Company received reimbursements of $0.4 million and $0.6 for both research and license agreements during the three months ended March 31, 2018 and 2017, respectively, which was recorded as a reduction of R&D expense in the income statement.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	11. Subsequent Events As of May 8, 2018, the Company is not aware of any events have occurred that have a material effect on the financial statements.

Summary of Significant Accoun18

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Revenue Recognition	Revenue Recognition In May 2014, the Financing Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers, which supersedes existing revenue recognition guidance. The Company adopted ASU 2014-09 and its related amendments (collectively known as “ASC 606”) on January 1, 2018 using the modified retrospective method, by recognizing the cumulative effect of initially applying ASC 606 as an adjustment to the opening balance of equity at January 1, 2018. The reported results for 2018 reflect the application of ASC 606 guidance while the reported results for 2017 were prepared under the guidance of ASC 605, Revenue Recognition (“ASC 605” or “legacy GAAP”). The Company has elected a practical expedient and applied ASC 606 only to contracts that are not completed at the date of initial application. ASC 606 applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. The Company’s revenue is from collaboration agreements. Within collaboration agreements, a counterparty may be a collaborator or partner that shares in the risks and benefits of developing a product to be marketed. These arrangements generally are in the scope of ASC 808, Collaborative Arrangements (“ASC 808”) yet may also contain vendor-customer aspects. Therefore, the Company considers all of the facts and circumstances to determine which transactions have a vendor-customer relationship that is subject to ASC 606. At the inception of each agreement the Company must determine which promised goods and services are under the scope of ASC 606 versus ASC 808 (discussed in the Collaborative Arrangements note below). In accordance with ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled to receive in exchange for these goods and services. To achieve this core principle, the Company applies the following five steps: 1) Identify the contract with the customer A contract with a customer exists when (i) the Company enters into an enforceable contract with a customer that defines each party’s rights regarding the goods or services to be transferred and identifies the related payment terms, (ii) the contract has commercial substance, and (iii) the Company determines that collection of substantially all consideration for goods and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration. 2) Identify the performance obligations in the contract Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct, whereby the customer can benefit from the good or service either on its own or together with other available resources, and are distinct in the context of the contract, whereby the transfer of the good or service is separately identifiable from other promises in the contract. To the extent a contract includes multiple promised goods and services, the Company must apply judgment to determine whether promised goods and services are capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. 3) Determine the transaction price The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in the Company’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment, which is discussed in further detail for each of the Company’s contracts with customers in Note 6. 4) Allocate the transaction price to performance obligations in the contract If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. 5) Recognize revenue when or as the Company satisfies a performance obligation The Company satisfies performance obligations either over time or at a point in time. Revenue is recognized over time if either 1) the customer simultaneously receives and consumes the benefits provided by the entity’s performance, 2) the entity’s performance creates or enhances an asset that the customer controls as the asset is created or enhanced, or 3) the entity’s performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. If the entity does not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring the control of a promised good or service to a customer. Examples of control are using the asset to produce goods or services, enhance the value of other assets, settle liabilities, and holding or selling the asset. ASC 606 requires the Company to select a single revenue recognition method for the performance obligation that faithfully depicts the Company’s performance in transferring control of the goods and services. The guidance allows entities to choose between two methods to measure progress toward complete satisfaction of a performance obligation: 1. Output methods - recognize revenue on the basis of direct measurements of the value to the customer of the goods or services transferred to date relative to the remaining goods or services promised under the contract (e.g. surveys of performance completed to date, appraisals of results achieved, milestones reached, time elapsed, and units of produced or units delivered); and 2. Input methods - recognize revenue on the basis of the entity’s efforts or inputs to the satisfaction of a performance obligation (e.g., resources consumed, labor hours expended, costs incurred, or time elapsed) relative to the total expected inputs to the satisfaction of that performance obligation. The Company has the right to consideration from a customer in an amount that corresponds directly with the value to the customer of the entity’s performance completed to date (i.e. R&D services), as such the Company has elected a practical expedient to recognize revenue in the amount to which the entity has a right to invoice for such services. The terms of the Company’s collaboration and license agreements contain multiple promised goods and services, which include options to license CRISPR/Cas9-based therapeutic products directed to specific targets, referred to as co-exclusive or exclusive licenses, joint steering committee participation, as well as research and development activities to be performed by the Company on behalf of the collaboration partner related to the licensed targets. Payments that the Company may receive under these agreements include nonrefundable upfront fees, payments for research activities, payments based upon the achievement of specified milestones and royalties on any resulting net product sales. To date, the Company’s only source of revenue has been the collaboration and license and joint development and commercialization agreement with Vertex Pharmaceuticals, Incorporated (“Vertex”) as well as research and development services provided to Casebia Therapeutics LLP (“Casebia”) under the joint venture with Bayer HealthCare LLC (“Bayer”). Please refer to Note 6 for the specific accounting treatment and revenue recognized during the period for each of these arrangements. Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company must consider the nature of the intellectual property to which the customer will have rights (i.e. access at a point in time or benefit of intellectual property enhancements over time). The Company recognizes revenue from non-refundable, up-front fees allocated to the license at a point in time/over the period the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement that includes development, regulatory or commercial milestone payments for promised goods and services, the Company evaluates the circumstances of whether the milestones will be reached and estimates the amount to be included in the transaction price that will not cause a significant revenue reversal. The Company will evaluate these types of payments for customer options once those options have been exercised. ASC 606 suggests two alternatives to use when estimating the amount of variable consideration: the expected value method and the most likely amount method. Under the expected value method, an entity considers the sum of probability-weighted amounts in a range of possible consideration amounts. Under the most likely amount method, an entity considers the single most likely amount in a range of possible consideration amounts. The Company will use the most likely amount method for development and regulatory milestone payments. Management believes the most likely amount method is the better predictor as the Company expects to be entitled to only one of two possible amounts. Additionally, management believes that the most likely amount of milestone consideration is its stated amount. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. The transaction price is then allocated to performance obligations on a specific basis or on a relative stand-alone selling price basis. The Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates whether it is probable that a significant revenue reversal will not occur in future periods, and if necessary, adjusts its estimates of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Up-front payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less. Contract Balances The Company recognizes a contract asset when the Company transfers goods or services to a customer before the customer pays consideration or before payment is due, excluding any amounts presented as a receivable (i.e. accounts receivable). A contract asset is an entity’s right to consideration in exchange for goods or services that the entity has transferred to a customer. The contract liabilities (i.e. deferred revenue) primarily relate to contracts where we have received payment but we have not yet satisfied the related performance obligations. The advance consideration received from customers for R&D services or licenses bundled with other promises is a contract liability, recorded as deferred revenue, until the underlying performance obligations are transferred to the customer. The change in deferred revenue is primarily related to the transition adjustment upon the adoption of ASC 606 for the three months ended March 31, 2018. Costs to Obtain and Fulfill a Contract with Customer The Company recognizes an asset related to incremental costs of obtaining a contract with a customer if the Company expects to recover those costs. The Company will recognize an asset from costs incurred to fulfill a contract only if such costs relate directly to a contract that the entity can specifically identify, the costs generate or enhance resources of the Company that will be used in satisfying performance obligations in the future, and the costs are expected to be recovered. Any assets recognized related to costs to obtain or fulfill a contract are amortized on a systematic basis that is consistent with the transfer to the customer of the goods or services to which the asset relates. Income Taxes The adoption of ASC 606 resulted in a reduction of revenue as of December 31, 2017, which in turn generated additional deferred tax assets. As the Company fully reserves its net deferred tax assets in the jurisdictions impacted by the adoption of ASC 606, this impact was offset by a corresponding change to the valuation allowance. Impact of Adopting ASC 606 on the Financial Statements The Company adopted ASC 606 using the modified retrospective method. The cumulative effect of applying the new guidance to all contracts with customers that were not completed as of January 1, 2018 was recorded as an adjustment to accumulated deficit as of the adoption date. The Company elected to apply a practical expedient to reflect the aggregate effect of all modifications that occur before the beginning of the earliest period presented when identifying the satisfied and unsatisfied performance obligations, determining the transaction price, and allocating the transaction price to the satisfied and unsatisfied performance obligations. As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made to the consolidated balance sheet as of January 1, 2018: As Reported December 31, 2017 ASC 606 Adjustment Adjusted January 1, 2018 Consolidated Balance Sheet Data (in thousands): Other current liabilities $ 137 $ 102 $ 239 Total current liabilities $ 14,511 $ 102 $ 14,613 Deferred revenue $ 56,928 $ 1,046 $ 57,974 Total liabilities $ 83,514 $ 1,148 $ 84,662 Accumulated deficit $ (125,440 ) $ (1,148 ) $ (126,588 ) Total shareholders' equity $ 187,832 $ (1,148 ) $ 186,684 Total liabilities and shareholders’ equity $ 271,346 $ - $ 271,346 Impact of New Revenue Guidance on Financial Statement Line Items The following table compares the reported condensed consolidated balance sheet, statement of operations and cash flows, as of and for the three months ended March 31, 2018, to the pro-forma amounts had the previous guidance been in effect: March 31, 2018 As Reported Under ASC 606 Adjustments Notes Adjusted Balance Under ASC 605 Consolidated Balance Sheet Data (in thousands): Other current liabilities $ 162 $ (102 ) (5) $ 60 Total current liabilities $ 14,395 $ (102 ) (5) $ 14,293 Deferred revenue $ 57,858 $ (945 ) (1)(2)(3)(5) $ 56,913 Total liabilities $ 84,117 $ (1,047 ) (1)(2)(3)(5) $ 83,070 Accumulated deficit $ (154,888 ) $ 1,047 (1)(2)(3) $ (153,841 ) Total shareholders' equity $ 290,335 $ 1,047 (1)(2)(3 $ 291,382 Total liabilities and shareholders’ equity $ 374,452 $ - (1)(2)(3) $ 374,452 Consolidated Statement of Operations Data (in thousands): Revenue $ 1,358 $ (101 ) (2)(3) $ 1,257 Operating loss $ (26,997 ) $ (101 ) (2)(3) $ (27,098 ) Loss before taxes $ (28,214 ) $ (101 ) (2)(3) $ (28,315 ) Net loss $ (28,300 ) $ (101 ) (2)(3) $ (28,401 ) Comprehensive loss $ (28,288 ) $ (101 ) (2)(3) $ (28,389 ) Consolidated Statement of Cash Flows (in thousands): Operating activities: Net loss $ (28,300 ) $ (101 ) (2)(3) $ (28,401 ) Reconciliation of net loss to net cash and restricted cash used in operating activities: Changes in: Deferred revenue $ (218 ) $ 203 (1)(2)(3)(4)(5) $ (15 ) Other liabilities, net $ 25 $ (102 ) (1)(2)(3)(4)(5) $ (77 ) Net cash used in operating activities $ (22,688 ) $ - (1)(2)(3)(4)(5) $ (22,668 ) (Decrease) increase in cash and restricted cash $ 102,020 $ - (1)(2)(3)(4)(5) $ 102,020 Cash and restricted cash, end of period $ 344,932 $ - (1)(2)(3)(4)(5) $ 344,932 (1) Adjustment of $1,148 to reverse the ASC 606 transition adjustment from retained earnings and deferred revenue. (2) Adjustment of $76 related to R&D services that would be deferred under ASC 605 versus recognized under ASC 606. (3) Adjustment of $25 related to non-exclusive research revenue that would be recognized upon option exercise under ASC 605 versus recognized overtime under ASC 606. (4) Adjustment to reverse the ASC 606 transition adjustment to retained earnings and deferred revenue netted to zero as the transaction did not impact cash. (5) Adjustment to reclass $102 from deferred revenue to current deferred revenue related to the change in revenue allocated to the non-exclusive research license recognized upon option exercise under ASC 605 versus ratably over time under ASC 606. Collaboration Arrangements The Company records the elements of its collaboration agreements that represent joint operating activities in accordance with ASC 808. Accordingly, the elements of the collaboration agreements that represent activities in which both parties are active participants and to which both parties are exposed to the significant risks and rewards that are dependent on the commercial success of the activities, are recorded as collaborative arrangements. The Company considers the guidance in ASC 606 in determining the appropriate treatment for the transactions between the Company and its collaborative partner and the transactions between the Company and third parties. Generally, the classification of transactions under the collaborative arrangements is determined based on the nature and contractual terms of the arrangement along with the nature of the operations of the participants. The Company evaluates the proper presentation of the commercial activities and the profit and loss sharing associated with the collaboration agreements. ASC 808 states that when payments between parties in a collaborative arrangement are not within the scope of other authoritative accounting literature, the income statement classification should be based on the nature of the arrangement, the nature of its business operations and the contractual terms of the arrangement. To the extent that these payments are not within the scope of other authoritative accounting literature, the income statement classification for the payments shall be based on an analogy to authoritative accounting literature or if there is no appropriate analogy, a reasonable, rational, and consistently applied accounting policy election.
New Accounting Pronouncements - Recently Adopted	New Accounting Pronouncements - Recently Adopted From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that the Company adopts as of the specified effective date. Financial Instrument Accounting In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The new standard amends certain aspects of accounting and disclosure requirements of financial instruments, including the requirement that equity investments with readily determinable fair values be measured at fair value with changes in fair value recognized in the results of operations. The new standard was effective January 1, 2018. The Company adopted ASU No. 2016-01 in the first quarter of 2018. The adoption of this guidance did not have a material impact on the Company's financial position and results of operations. Income Taxes In October 2016, the FASB issued ASU No. 2016-16, Income Taxes Intra-Entity Transfers of Assets Other Than Inventory Statement of Cash Flows In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows Restricted Cash Business Combinations In January 2017, the FASB issued ASU No. 2017-01, Business Combinations In May 2017, the FASB issued ASU 2017-09, Compensation – Stock Compensation
New Accounting Pronouncements - to be Adopted in Future Periods	New Accounting Pronouncements - to be adopted in future periods In February 2016, the FASB issued ASU No. 2016-02, Leases
Net Loss Per Share Attributable to Common Shareholders	Net Loss Per Share Attributable to Common Shareholders Basic net loss per share is calculated by dividing net loss attributable to common shareholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is calculated by dividing the net income attributable to common shareholders by the weighted-average number of common equivalent shares outstanding for the period, including any dilutive effect from outstanding stock options and warrants using the treasury stock method. The following common share equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect (in common stock equivalent shares): As of March 31, 2018 March 31, 2017 Outstanding options 6,638,120 4,829,891 Unvested unissued restricted common shares 47,472 80,987 Total 6,685,592 4,910,878
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying condensed consolidated financial statements have been prepared in conformity with GAAP, and include the accounts of (i) the Company, and (ii) its wholly-owned subsidiaries, CRISPR Therapeutics Ltd., CRISPR Therapeutics Inc., and TRACR Hematology Inc. All intercompany accounts and transactions have been eliminated. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) of the FASB. The Company accounts for its 50% interest in Casebia under the equity method of accounting. See Note 6 for further details. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, equity-based compensation expense, revenue recognition, equity method investments, fair value of intangible assets, the provision for or benefit from income taxes and reported amounts of research and development expenses during the period. 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. The consolidated statements reflect all adjustments which are of a normal recurring nature necessary for presentation. Actual results may differ from those estimates or assumptions.

Summary of Significant Accoun19

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Schedule of Antidilutive Securities Excluded from Computation of Net Loss per Share	The following common share equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect (in common stock equivalent shares): As of March 31, 2018 March 31, 2017 Outstanding options 6,638,120 4,829,891 Unvested unissued restricted common shares 47,472 80,987 Total 6,685,592 4,910,878
ASU 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Modified Retrospective Method to Adopt New Revenue Guidance and Adjustments to Consolidated Balance Sheet	As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made to the consolidated balance sheet as of January 1, 2018: As Reported December 31, 2017 ASC 606 Adjustment Adjusted January 1, 2018 Consolidated Balance Sheet Data (in thousands): Other current liabilities $ 137 $ 102 $ 239 Total current liabilities $ 14,511 $ 102 $ 14,613 Deferred revenue $ 56,928 $ 1,046 $ 57,974 Total liabilities $ 83,514 $ 1,148 $ 84,662 Accumulated deficit $ (125,440 ) $ (1,148 ) $ (126,588 ) Total shareholders' equity $ 187,832 $ (1,148 ) $ 186,684 Total liabilities and shareholders’ equity $ 271,346 $ - $ 271,346
Impact of New Revenue Guidance on Financial Statement Line Items	The following table compares the reported condensed consolidated balance sheet, statement of operations and cash flows, as of and for the three months ended March 31, 2018, to the pro-forma amounts had the previous guidance been in effect: March 31, 2018 As Reported Under ASC 606 Adjustments Notes Adjusted Balance Under ASC 605 Consolidated Balance Sheet Data (in thousands): Other current liabilities $ 162 $ (102 ) (5) $ 60 Total current liabilities $ 14,395 $ (102 ) (5) $ 14,293 Deferred revenue $ 57,858 $ (945 ) (1)(2)(3)(5) $ 56,913 Total liabilities $ 84,117 $ (1,047 ) (1)(2)(3)(5) $ 83,070 Accumulated deficit $ (154,888 ) $ 1,047 (1)(2)(3) $ (153,841 ) Total shareholders' equity $ 290,335 $ 1,047 (1)(2)(3 $ 291,382 Total liabilities and shareholders’ equity $ 374,452 $ - (1)(2)(3) $ 374,452 Consolidated Statement of Operations Data (in thousands): Revenue $ 1,358 $ (101 ) (2)(3) $ 1,257 Operating loss $ (26,997 ) $ (101 ) (2)(3) $ (27,098 ) Loss before taxes $ (28,214 ) $ (101 ) (2)(3) $ (28,315 ) Net loss $ (28,300 ) $ (101 ) (2)(3) $ (28,401 ) Comprehensive loss $ (28,288 ) $ (101 ) (2)(3) $ (28,389 ) Consolidated Statement of Cash Flows (in thousands): Operating activities: Net loss $ (28,300 ) $ (101 ) (2)(3) $ (28,401 ) Reconciliation of net loss to net cash and restricted cash used in operating activities: Changes in: Deferred revenue $ (218 ) $ 203 (1)(2)(3)(4)(5) $ (15 ) Other liabilities, net $ 25 $ (102 ) (1)(2)(3)(4)(5) $ (77 ) Net cash used in operating activities $ (22,688 ) $ - (1)(2)(3)(4)(5) $ (22,668 ) (Decrease) increase in cash and restricted cash $ 102,020 $ - (1)(2)(3)(4)(5) $ 102,020 Cash and restricted cash, end of period $ 344,932 $ - (1)(2)(3)(4)(5) $ 344,932 (1) Adjustment of $1,148 to reverse the ASC 606 transition adjustment from retained earnings and deferred revenue. (2) Adjustment of $76 related to R&D services that would be deferred under ASC 605 versus recognized under ASC 606. (3) Adjustment of $25 related to non-exclusive research revenue that would be recognized upon option exercise under ASC 605 versus recognized overtime under ASC 606. (4) Adjustment to reverse the ASC 606 transition adjustment to retained earnings and deferred revenue netted to zero as the transaction did not impact cash. (5) Adjustment to reclass $102 from deferred revenue to current deferred revenue related to the change in revenue allocated to the non-exclusive research license recognized upon option exercise under ASC 605 versus ratably over time under ASC 606.

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	3 Months Ended
	Mar. 31, 2018
Property Plant And Equipment [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net, consists of the following (in thousands): As of March 31, December 31, 2018 2017 Computer equipment $ 285 $ 285 Furniture, fixtures, and other 2,104 2,104 Laboratory equipment 7,144 6,603 Leasehold improvements 13,776 13,776 Construction work in process 321 - 23,630 22,768 Accumulated Depreciation (4,723 ) (3,911 ) Property and equipment, net $ 18,907 $ 18,857

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2018
Payables And Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued expenses consist of the following (in thousands): As of March 31, December 31, 2018 2017 Payroll and employee-related costs $ 3,287 $ 5,550 Research costs 4,280 2,285 Licensing fees 778 609 Professional fees 989 2,176 Intellectual property costs 862 500 Other 31 241 Total $ 10,227 $ 11,361

Share Capital (Tables)

Share Capital (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Schedule of Conditional Capital Reserved for Future Issuance	The Company had the following conditional capital reserved for future issuance: As of Conditional Capital March 31, 2018 December 31, 2017 Unvested unissued restricted stock 166,667 166,667 Outstanding stock options 6,638,120 6,262,339 Reserved for future issuance under stock option plans (1) 3,976,326 4,657,700 Shares available for bonds and similar debt instruments 4,919,700 4,919,700 Shares available for employee purchase plans 413,226 413,226 Total 16,114,039 16,419,632 (1) The Company’s Board of Directors approved an increase to the option pool of 2,012,684 options in May 2017 and in March 2018, an increase to the option pool of an additional 4,000,000 options subject to shareholder approval.

Equity-based Compensation (Tabl

Equity-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Stock-Based Compensation Expense	The Company uses the straight-line attribution method to recognize stock-based compensation expense for stock options and restricted stock awards. Stock options and restricted stock awards generally vest over four years with 25% vesting on the first anniversary of service commencement and the remaining 75% vesting monthly thereafter. The following table presents stock-based compensation expense included in the Company’s Condensed Consolidated Statements of Operations and Comprehensive Loss: Three Months Ended March 31, 2018 2017 Research and development $ 2,916 $ 1,730 General and administrative 2,666 1,570 Loss from equity method investment 1,091 446 Total $ 6,673 $ 3,746
Fair Value of Employee and Non-employee Stock Option Award Estimated Using the Black-Scholes Option-Pricing Model	The Company estimated the fair value of each employee and non-employee stock option award using the Black-Scholes option-pricing model based on the following assumptions: Three Months Ended March 31, 2018 2017 Employees: Weighted average expected volatility 70.5 % 73.0 % Expected term (in years) 6.0 6.0 Risk free interest rate 2.7 % 2.2 % Expected dividend yield 0.0 % 0.0 % Non-employees: Weighted average expected volatility 81.1 % 81.0 % Expected term (in years) 9.1 10.0 Risk free interest rate 2.6 % 2.4 % Expected dividend yield 0.0 % 0.0 %
Summary of Stock Option Activity for Employees and Non-employees	The following table summarizes stock option activity for employees and non-employees (intrinsic value in thousands): Stock Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2017 6,262,339 $ 13.24 8.8 $ 64,120 Granted 1,092,737 $ 50.33 Exercised (363,202 ) $ 10.77 Cancelled or forfeited (353,754 ) $ 11.92 Outstanding at March 31, 2018 6,638,120 $ 19.55 8.9 $ 179,644 Exercisable at March 31, 2018 1,687,503 $ 10.30 8.2 $ 59,746 Vested or expected to vest at March 31, 2018 (1) 6,638,120 $ 19.55 8.9 $ 179,644 (1) Represents the number of vested options at March 31, 2018 plus the number of unvested options expected to vest in the future.
Summary of the Company's Restricted Stock Activity	The following table summarizes restricted stock activity for employees and non-employees during the three months ended March 31, 2018: Reflected as outstanding upon vesting Reflected as outstanding upon grant date Total Weighted- Average Grant Date Fair Value Unvested restricted common shares as of December 31, 2017 157,515 208,886 366,401 $ 8.49 Granted — — — — Vested (10,042 ) (102,963 ) (113,005 ) 6.59 Cancelled or forfeited — — — — Unvested restricted common shares as of March 31, 2018 147,473 105,923 253,396 $ 9.17

Organization and Operations - A

Organization and Operations - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Organization and operations [Line Items]
Company formation date		Oct. 28, 2013
Company formation country name		Basel, Switzerland
Accumulated deficit		$ (154,888)	$ (125,440)
Proceeds from issuance of common shares		122,597
Cash		$ 341,767	$ 239,758
Equity Offering [Member]
Organization and operations [Line Items]
Issuance of shares, net of issuance cost (in shares)	5,750,000
Common shares price per share	$ 22.75
Proceeds from issuance of common shares	$ 122,600

Summary of Significant Accoun25

Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018	Feb. 12, 2016
Casebia Therapeutics LLP [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	50.00%	50.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Period between payment by the customer and the transfer of the promised goods or services	1 year

Summary of Significant Accoun26

Summary of Significant Accounting Policies - Modified Retrospective Method to Adopt New Revenue Guidance and Adjustments to Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other current liabilities	$ 162		$ 137
Total current liabilities	14,395		14,511
Deferred revenue	57,858		56,928
Total liabilities	84,117		83,514
Accumulated deficit	(154,888)		(125,440)
Total shareholders' equity	290,335		187,832
Total liabilities and shareholders’ equity	374,452		$ 271,346
ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other current liabilities		$ 239
Total current liabilities		14,613
Deferred revenue		57,974
Total liabilities		84,662
Accumulated deficit		(126,588)
Total shareholders' equity		186,684
Total liabilities and shareholders’ equity		271,346
ASC 606 Adjustment [Member] | ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other current liabilities	(102)	102
Total current liabilities	(102)	102
Deferred revenue	(945)	1,046
Total liabilities	(1,047)	1,148
Accumulated deficit	1,047	(1,148)
Total shareholders' equity	$ 1,047	$ (1,148)

Summary of Significant Accoun27

Summary of Significant Accounting Policies - Impact of New Revenue Guidance on Financial Statement Line Items (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other current liabilities		$ 162			$ 137
Total current liabilities		14,395			14,511
Deferred revenue		57,858			56,928
Total liabilities		84,117			83,514
Accumulated deficit		(154,888)			(125,440)
Total shareholders' equity		290,335			187,832
Total liabilities and shareholders’ equity		374,452			271,346
Revenue	[1]	1,358	$ 2,703
Operating loss		(26,997)	(20,744)
Loss before taxes		(28,214)	(21,196)
Net loss		(28,300)	(21,475)
Comprehensive loss		(28,288)	(21,451)
Operating activities:
Net loss		(28,300)	(21,475)
Changes in:
Deferred revenue		(218)	665
Other liabilities, net		25	4
Net cash used in operating activities		(22,688)	(23,411)
(Decrease) increase in cash and restricted cash		102,020	(26,647)
Cash and restricted cash, end of period		344,932	$ 292,023		$ 242,912	$ 318,670
ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other current liabilities				$ 239
Total current liabilities				14,613
Deferred revenue				57,974
Total liabilities				84,662
Accumulated deficit				(126,588)
Total shareholders' equity				186,684
Total liabilities and shareholders’ equity				271,346
Adjustments [Member] | ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other current liabilities		(102)		102
Total current liabilities		(102)		102
Deferred revenue		(945)		1,046
Total liabilities		(1,047)		1,148
Accumulated deficit		1,047		(1,148)
Total shareholders' equity		1,047		$ (1,148)
Revenue		(101)
Operating loss		(101)
Loss before taxes		(101)
Net loss		(101)
Comprehensive loss		(101)
Operating activities:
Net loss		(101)
Changes in:
Deferred revenue		203
Other liabilities, net		(102)
Adjusted Balance Under ASC 605 [Member] | ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other current liabilities		60
Total current liabilities		14,293
Deferred revenue		56,913
Total liabilities		83,070
Accumulated deficit		(153,841)
Total shareholders' equity		291,382
Total liabilities and shareholders’ equity		374,452
Revenue		1,257
Operating loss		(27,098)
Loss before taxes		(28,315)
Net loss		(28,401)
Comprehensive loss		(28,389)
Operating activities:
Net loss		(28,401)
Changes in:
Deferred revenue		(15)
Other liabilities, net		(77)
Net cash used in operating activities		(22,668)
(Decrease) increase in cash and restricted cash		102,020
Cash and restricted cash, end of period		$ 344,932
[1]	Including the following revenue from a related party, see Note 10

Summary of Significant Accoun28

Summary of Significant Accounting Policies - Impact of New Revenue Guidance on Financial Statement Line Items (Parenthetical) (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accumulated deficit		$ (154,888)			$ (125,440)
Research and development	[1]	19,519	$ 14,805
ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accumulated deficit				$ (126,588)
ASU 2014-09 [Member] | ASC 606 Adjustment [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Deferred revenue				1,148
Accumulated deficit		1,047		$ (1,148)
Research and development		76
Non-exclusive research revenue		25
Deferred revenue current		$ 102
[1]	Including the following research and development expense with a related party, See Note 10

Summary of Significant Accoun29

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Net Loss per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	6,685,592	4,910,878
Outstanding Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	6,638,120	4,829,891
Unvested Unissued Restricted Common Shares [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	47,472	80,987

Property and Equipment, net - S

Property and Equipment, net - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 23,630	$ 22,768
Accumulated Depreciation	(4,723)	(3,911)
Property and equipment, net	18,907	18,857
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	285	285
Furniture, Fixtures, and Other [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,104	2,104
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	7,144	6,603
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	13,776	$ 13,776
Construction Work in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 321

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property Plant And Equipment [Abstract]
Depreciation expense	$ 0.8	$ 0.7

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued Liabilities Current [Abstract]
Payroll and employee-related costs	$ 3,287	$ 5,550
Research costs	4,280	2,285
Licensing fees	778	609
Professional fees	989	2,176
Intellectual property costs	862	500
Other	31	241
Total	$ 10,227	$ 11,361

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)Sublease	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Contingencies And Commitments [Line Items]
Research and development expense	[1]	$ 19,519	$ 14,805
Cost sharing expensed relating to patent maintenance, defense and prosecution, incurred		500	500
Cost sharing expensed relating to patent maintenance, defense and prosecution, accrued		700	$ 900
Research and Office Facility [Member]
Contingencies And Commitments [Line Items]
Operating lease number of sublet portions | Sublease			1
Operating leases, sublease payments receivable		2,800
Research Institutions [Member] | Scenario Forecast [Member]
Contingencies And Commitments [Line Items]
Research and development expense				$ 100	$ 400
Research Agreements [Member]
Contingencies And Commitments [Line Items]
Upfront fees paid for license		200	$ 200
Milestone payments		1,400	$ 1,400
Research Agreements [Member] | Scenario Forecast [Member]
Contingencies And Commitments [Line Items]
Research and development expense				$ 400	$ 500
Manufacturing Agreements [Member] | Upfront Payments [Member]
Contingencies And Commitments [Line Items]
Upfront payment recorded as prepaid expense		$ 2,500
[1]	Including the following research and development expense with a related party, See Note 10

Significant Contracts - Additio

Significant Contracts - Additional Information (Detail)		Feb. 12, 2016USD ($)	Oct. 26, 2015USD ($)Milestone	Mar. 31, 2016USD ($)	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jan. 01, 2018USD ($)	Dec. 22, 2016USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense	[1]				$ 19,519,000	$ 14,805,000
Non-current deferred revenue					$ 57,858,000		$ 56,928,000
Date of joint venture agreement					Dec. 19, 2015
Standalone selling price allocation of arrangement consideration paid					$ 106,300,000
Remaining license fee								$ 15,000,000
Other income					(126,000)	(6,000)		79,100,000
Equity method investment								36,500,000
Unrealized equity method losses					(1,091,000)	(446,000)		$ (36,500,000)
Stock-based compensation expense					6,673,000	3,746,000
ASC 606 [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-current deferred revenue									$ 57,974,000
ASC 606 [Member] | ASC 605 [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-current deferred revenue					56,913,000
Licensing Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Standalone selling price					71,400,000
License and Patent Holder Consent [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Standalone selling price allocation of arrangement consideration paid					79,100,000
Research and Development Services [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Standalone selling price					6,300,000
Bayer Convertible Loans [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Fair value of convertible loan					24,500,000
Standalone selling price allocation of arrangement consideration paid					27,200,000
Debt instrument discount					8,000,000
Debt instrument face amount					$ 35,000,000
Bayer Convertible Loans [Member] | Series B Redeemable Convertible Preferred Shares [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Loan agreement maturity date					Jan. 29, 2016
Casebia Therapeutics LLP [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Nonrefundable upfront payment received				$ 20,000,000
Aggregate consideration receivable					$ 112,600,000
Revenue from collaboration agreement		$ 35,000,000
Research and development expense					1,100,000	1,100,000
Non-current deferred revenue					$ 0		100,000
Date of formation of joint venture entity					Feb. 12, 2016
Equity method investment, ownership percentage		50.00%			50.00%
Cash contribution		$ 100,000
Remaining license fees to be received from joint venture entity										$ 15,000,000
Royalty payments due to company from joint venture entity		0
Other payments due to company from joint venture entity		$ 0
Convertible Loan					$ 35,000,000
Cash contribution					100,000
Technology fee					34,900,000
Equity interest in the Joint Venture					36,400,000
Estimated revenue related to research and development services					6,300,000
Equity method investment					0		0
Stock-based compensation expense					1,100,000	500,000
Unrecognized equity method losses in excess of Company's interest					26,800,000		21,200,000
Operating expenses of joint venture					12,500,000	5,500,000
Net loss of joint venture					12,300,000	5,500,000
Casebia Therapeutics LLP [Member] | ASC 605 [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from collaboration agreement						1,200,000
Casebia Therapeutics LLP [Member] | ASC 606 [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from collaboration agreement					1,100,000
Research and Development Expenses [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Stock-based compensation expense					2,916,000	1,730,000
Non-Exclusive Research License [Member] | Market-based Approach [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for collaboration agreement			$ 1,000,000
Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Nonrefundable upfront payment received			75,000,000
Potential milestone receivable			420,000,000
Non-exclusive research revenue			19,300,000
Estimated standalone selling price for collaboration agreement			118,600,000
Revenue, Remaining Performance Obligation			82,000,000		58,000,000
Clinical milestone payment payable			10,000,000
Revenue from collaboration agreement					200,000	1,500,000
Research and development expense					200,000	2,600,000
Non-current deferred revenue					57,900,000		$ 56,800,000
Vertex Pharmaceuticals Inc [Member] | Research and Development Expenses [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Variable consideration received			19,300,000
Vertex Pharmaceuticals Inc [Member] | 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] | 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] | 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] | Joint Development Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Nonrefundable upfront payment received			7,000,000
Up-front payment received					$ 7,000,000
Agreement description					In connection with entering into the JDA, the Company received a $7.0 million up-front payment from Vertex and is eligible for a one-time low seven-digit milestone payment upon the dosing of the second patient in a clinical trial with the initial product candidate. The net profits and net losses, as applicable, incurred under the JDA will be shared equally between us and Vertex.
Research and development expense					$ 4,200,000	$ 0
Vertex Pharmaceuticals Inc [Member] | Beta-Globin [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated standalone selling price for single collaboration			48,900,000
Vertex Pharmaceuticals Inc [Member] | Non-Exclusive Research License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue, Remaining Performance Obligation			500,000
Vertex Pharmaceuticals Inc [Member] | Material Right to Discounts for Exclusive Licenses [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue, Remaining Performance Obligation			57,700,000
Vertex Pharmaceuticals Inc [Member] | Material Right to Discounts for Exclusive Licenses [Member] | Unit One [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue, Remaining Performance Obligation			22,200,000
Vertex Pharmaceuticals Inc [Member] | Material Right to Discounts for Exclusive Licenses [Member] | Unit Two [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue, Remaining Performance Obligation			18,700,000
Vertex Pharmaceuticals Inc [Member] | Material Right to Discounts for Exclusive Licenses [Member] | Unit Three [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue, Remaining Performance Obligation			8,400,000
Vertex Pharmaceuticals Inc [Member] | Material Right to Discounts for Exclusive Licenses [Member] | Unit Four [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue, Remaining Performance Obligation			8,400,000
Vertex Pharmaceuticals Inc [Member] | Coexclusive Development and Commercialization Licenses and Research License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue, Remaining Performance Obligation			$ 23,800,000
Vertex Pharmaceuticals Inc [Member] | Clinical Development And Regulatory Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of developmental milestone events | Milestone			9
Vertex Pharmaceuticals Inc [Member] | Clinical Development Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized			$ 90,000,000
Vertex Pharmaceuticals Inc [Member] | Regulatory Approval Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized			$ 235,000,000
Vertex Pharmaceuticals Inc [Member] | Commercial Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of developmental milestone events | Milestone			2
Revenue recognition, milestone method, revenue recognized			$ 75,000,000
Vertex Pharmaceuticals Inc [Member] | Investigational New Drug Application ("IND") [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized			10,000,000
Vertex Pharmaceuticals Inc [Member] | Developmental Milestone Events [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized			420,000,000
Vertex Pharmaceuticals Inc [Member] | Commercial Milestone Event One [Member] | Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate consideration receivable			500,000,000
Vertex Pharmaceuticals Inc [Member] | Commercial Milestone Event Two [Member] | Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate consideration receivable			$ 1,000,000,000
[1]	Including the following research and development expense with a related party, See Note 10

Share Capital - Additional Info

Share Capital - Additional Information (Detail) - SFr / shares	Mar. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common stock, shares authorized	47,166,907	41,092,969
Common shares, par value	SFr 0.03	SFr 0.03
Unvested unissued restricted common shares	253,396	366,401
Treasury stock, shares	438,620	444,873
Unvested Unissued Restricted Share Awards [Member]
Class of Stock [Line Items]
Unvested unissued restricted common shares	147,473

Share Capital - Schedule of Con

Share Capital - Schedule of Conditional Capital Reserved for Future Issuance (Detail) - shares	Mar. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Conditional capital reserved for future issuance	16,114,039	16,419,632
Unvested Unissued Restricted Stock [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	166,667	166,667
Outstanding Stock Options [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	6,638,120	6,262,339
Stock Option Plan [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	3,976,326	4,657,700
Bonds and Similar Debt Instruments [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	4,919,700	4,919,700
Employee Purchase Plans [Member]
Class of Stock [Line Items]
Conditional capital reserved for future issuance	413,226	413,226

Share Capital - Schedule of C37

Share Capital - Schedule of Conditional Capital Reserved for Future Issuance (Parenthetical) (Detail) - shares	1 Months Ended
	Mar. 31, 2018	May 31, 2017
Equity [Abstract]
Number of options approved		2,012,684
Number of additional options subject to shareholder approval	4,000,000

Equity-based Compensation - Equ

Equity-based Compensation - Equity-based Compensation Expense - Additional Information (Detail) - Stock Options and Restricted Stock Awards [Member]	3 Months Ended
	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation, options, vesting period	4 years
Share-based Compensation, options, vesting terms	vest over four years with 25% vesting on the first anniversary of service commencement and the remaining 75% vesting monthly thereafter.
Vesting Percentage on First Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation, options, vesting percentage	25.00%
Vesting Percentage after First Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation, options, vesting percentage	75.00%

Equity-based Compensation - Sch

Equity-based Compensation - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	$ 6,673	$ 3,746
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	2,916	1,730
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	2,666	1,570
Loss from Equity Method Investment [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	$ 1,091	$ 446

Equity-based Compensation - Fai

Equity-based Compensation - Fair Value of Employee and Non-employee Stock Option Award Estimated Using the Black-Scholes Option-Pricing Model (Detail)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average expected volatility	70.50%	73.00%
Expected term (in years)	6 years	6 years
Risk free interest rate	2.70%	2.20%
Expected dividend yield	0.00%	0.00%
Non Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average expected volatility	81.10%	81.00%
Expected term (in years)	9 years 1 month 6 days	10 years
Risk free interest rate	2.60%	2.40%
Expected dividend yield	0.00%	0.00%

Equity-based Compensation - Sum

Equity-based Compensation - Summary of Stock Option Activity for Employees and Non-employees (Detail) - Employees and Non-employees [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options, Outstanding, Beginning Balance	6,262,339
Stock Options, Granted	1,092,737
Stock Options, Exercised	(363,202)
Stock Options, Cancelled or forfeited	(353,754)
Stock Options, Outstanding, Ending Balance	6,638,120	6,262,339
Stock Options, Exercisable	1,687,503
Stock Options, Vested or expected to vest	6,638,120
Weighted-Average Exercise Price, Outstanding, Beginning Balance	$ 13.24
Weighted-Average Exercise Price, Granted	50.33
Weighted-Average Exercise Price, Exercised	10.77
Weighted-Average Exercise Price, Cancelled or forfeited	11.92
Weighted-Average Exercise Price, Outstanding, Ending Balance	19.55	$ 13.24
Weighted-Average Exercise Price, Exercisable	10.30
Weighted-Average Exercise Price, Vested or expected to vest	$ 19.55
Weighted-Average Remaining Contractual Term	8 years 10 months 24 days	8 years 9 months 18 days
Weighted-Average Remaining Contractual Term, Exercisable	8 years 2 months 12 days
Weighted-Average Remaining Contractual Term, Vested or expected to vest	8 years 10 months 24 days
Aggregate Intrinsic Value, Outstanding Balance	$ 179,644	$ 64,120
Aggregate Intrinsic Value, Exercisable	59,746
Aggregate Intrinsic Value, Vested or expected to vest	$ 179,644

Equity-based Compensation - Sha

Equity-based Compensation - Share Based Payment Activity - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense	$ 74.6
Equity-based compensation expense not yet recognized, weighted-average service period for recognition	3 years 6 months
Performance-Based [Member] | Vesting Percentage on First Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options, Granted	0	15,000
Market-Based [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options, Granted			150,000
Share-based compensation, requisite service period			4 years
Share-based compensation, options, vested	0
Share-based compensation, options, earned	75,000
Market-Based [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, options, eligible to receive			0
Market-Based [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, options, eligible to receive			150,000
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense not yet recognized, weighted-average service period for recognition	2 years
Total fair value of restricted stock vested	$ 4.5
Total unrecognized compensation expenses	$ 1.5

Equity-based Compensation - S43

Equity-based Compensation - Summary of the Company's Restricted Stock Activity (Detail)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted common shares, Number of Shares, Beginning Balance	366,401
Unvested restricted common shares, Number of Shares, Vested	(113,005)
Unvested restricted common shares, Number of Shares, Ending Balance	253,396
Restricted Stock Outstanding Upon Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted common shares, Number of Shares, Beginning Balance	157,515
Unvested restricted common shares, Number of Shares, Vested	(10,042)
Unvested restricted common shares, Number of Shares, Ending Balance	147,473
Restricted Stock Outstanding Upon Grant Date [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted common shares, Number of Shares, Beginning Balance	208,886
Unvested restricted common shares, Number of Shares, Vested	(102,963)
Unvested restricted common shares, Number of Shares, Ending Balance	105,923
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 8.49
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Vested | $ / shares	6.59
Unvested restricted common shares, Weighted-Average Grant Date Fair Value, Ending Balance | $ / shares	$ 9.17

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income tax provision	$ 86	$ 279
Effective income tax rate	(0.30%)	(1.30%)

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)		Feb. 12, 2016	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Research and development expense	[1]		$ 19,519,000	$ 14,805,000
Casebia Therapeutics LLP [Member]
Related Party Transaction [Line Items]
Revenue from collaboration agreement		$ 35,000,000
Research and development expense			1,100,000	1,100,000
Bayer Healthcare LLC [Member] | Casebia Therapeutics LLP [Member]
Related Party Transaction [Line Items]
Revenue from collaboration agreement			1,100,000	1,200,000
Research and development expense			1,100,000	1,100,000
Reimbursements from research and license agreements			400,000	600,000
Bayer Healthcare LLC [Member] | Research and Development [Member]
Related Party Transaction [Line Items]
Sublicense fees recorded			$ 0	$ 0
[1]	Including the following research and development expense with a related party, See Note 10