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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2016	Mar. 01, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Trading Symbol	WVE
Entity Registrant Name	WAVE LIFE SCIENCES LTD.
Entity Central Index Key	0001631574
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		23,542,569
Entity Public Float			$ 221,173,659

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 150,293	$ 161,220
Prepaid expenses and other current assets	1,483	146
Deferred tax assets	214	18
Total current assets	151,990	161,384
Property and equipment, net	8,607	2,789
Deferred tax assets	560	192
Restricted cash	3,601	1,055
Other assets	53	4
Total assets	164,811	165,424
Current liabilities:
Accounts payable	4,943	2,811
Accrued expenses and other current liabilities	4,445	945
Current portion of capital lease obligation	62	62
Current portion of deferred revenue	2,705
Total current liabilities	12,155	3,818
Long-term liabilities:
Capital lease obligation, net of current portion	16	78
Deferred revenue, net of current portion	8,311
Other liabilities	1,592	163
Total long-term liabilities	9,919	241
Total liabilities	22,074	4,059
Shareholders’ equity:
Ordinary shares, no par value; 23,502,169 and 21,551,423 shares issued and outstanding at December 31, 2016 and 2015, respectively	215,602	185,344
Additional paid-in capital	10,029	3,182
Accumulated other comprehensive income (loss)	(291)	41
Accumulated deficit	(90,477)	(35,076)
Total shareholders’ equity	134,863	153,491
Total liabilities, Series A preferred shares and shareholders’ equity	164,811	165,424
Series A Preferred Shares [Member]
Long-term liabilities:
Preferred stock value	$ 7,874	$ 7,874

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Common stock, par value
Common stock, shares issued	23,502,169	21,551,423
Common stock, shares outstanding	23,502,169	21,551,423
Series A Preferred Shares [Member]
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares issued	3,901,348	3,901,348
Preferred stock, shares outstanding	3,901,348	3,901,348

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenue	$ 1,485	$ 152
Operating expenses:
Research and development	40,818	9,057	$ 2,395
General and administrative	15,994	10,393	2,999
Total operating expenses	56,812	19,450	5,394
Loss from operations	(55,327)	(19,298)	(5,394)
Other income (expense), net:
Dividend income	255
Interest income (expense), net	337	86	(12)
Other income (expense), net	(50)	56	261
Total other income (expense), net	542	142	249
Loss before income tax provision	(54,785)	(19,156)	(5,145)
Income tax provision	(616)	(44)	(84)
Net loss	$ (55,401)	$ (19,200)	$ (5,229)
Net loss per share attributable to ordinary shareholders—basic and diluted	$ (2.43)	$ (1.83)	$ (1.34)
Weighted-average ordinary shares used in computing net loss per share attributable to ordinary shareholders—basic and diluted	22,800,628	10,501,455	3,911,556

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (55,401)	$ (19,200)	$ (5,229)
Other comprehensive loss:
Foreign currency translation	(332)	(15)	(169)
Comprehensive loss	$ (55,733)	$ (19,215)	$ (5,398)

Consolidated Statement of Series A Preferred Shares and Shareholders' Equity - USD ($) $ in Thousands	Total	IPO [Member]	Series A Preferred Shares [Member]	Series B Preferred Shares [Member]	Ordinary Shares [Member]	Ordinary Shares [Member] IPO [Member]	Additional Paid-In-Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2013	$ (7,762)		$ 2,022		$ 638			$ 225	$ (10,647)
Beginning balance, shares at Dec. 31, 2013			1,536,209		484,585
Conversion of related party notes payable to ordinary shares and Series A preferred shares	9,602		$ 5,852		$ 3,750
Conversion of related party notes payable to ordinary shares and Series A preferred shares, shares			2,365,139		1,515,596
Issuance of ordinary shares, net of offering costs	5,585				$ 5,585
Issuance of ordinary shares, net of offering costs, shares					2,263,291
Other comprehensive loss	(169)							(169)
Net loss	(5,229)								(5,229)
Ending balance at Dec. 31, 2014	2,027		$ 7,874		$ 9,973			56	(15,876)
Ending balance, shares at Dec. 31, 2014			3,901,348		4,263,472
Issuance of ordinary shares, net of offering costs	11,631	$ 100,366			$ 11,631	$ 100,366
Issuance of ordinary shares, net of offering costs, shares					4,769,077	6,993,126
Share-based compensation	4,024				$ 842		$ 3,182
Share-based compensation, shares					190,856
Temporary equity, Issuance of Series B preferred, net of issuance costs				$ 62,532
Temporary equity, Issuance of Series B preferred, net of issuance costs, shares				5,334,892
Temporary equity, Reclassification of Series A preferred shares			$ 7,874
Temporary equity, Reclassification of Series A preferred shares, shares			3,901,348
Reclassification of Series A preferred shares	(7,874)		$ (7,874)
Reclassification of Series A preferred shares, shares			(3,901,348)
Temporary equity, Conversion of Series B preferred shares into ordinary shares upon initial public offering				$ (62,532)
Temporary equity, Conversion of Series B preferred shares into ordinary shares upon initial public offering, shares				(5,334,892)
Conversion of Series B preferred shares into ordinary shares upon initial public offering	62,532				$ 62,532
Conversion of Series B preferred shares into ordinary shares upon initial public offering, shares					5,334,892
Other comprehensive loss	(15)							(15)
Net loss	(19,200)								(19,200)
Temporary equity, Ending balance at Dec. 31, 2015			$ 7,874
Temporary equity, Ending balance, shares at Dec. 31, 2015			3,901,348
Ending balance at Dec. 31, 2015	153,491				$ 185,344		3,182	41	(35,076)
Ending balance, shares at Dec. 31, 2015					21,551,423
Issuance of ordinary shares, net of offering costs	30,000				$ 30,000
Issuance of ordinary shares, net of offering costs, shares					1,875,000
Share-based compensation	6,847						6,847
Option exercises	258				$ 258
Option exercises, shares					75,746
Other comprehensive loss	(332)							(332)
Net loss	(55,401)								(55,401)
Temporary equity, Ending balance at Dec. 31, 2016			$ 7,874
Temporary equity, Ending balance, shares at Dec. 31, 2016			3,901,348
Ending balance at Dec. 31, 2016	$ 134,863				$ 215,602		$ 10,029	$ (291)	$ (90,477)
Ending balance, shares at Dec. 31, 2016					23,502,169

Consolidated Statement of Series A Preferred Shares and Shareholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Ordinary Shares [Member]
Issuance costs	$ 169	$ 15
Series B Preferred Shares [Member]
Issuance costs	3,468
IPO [Member] \| Ordinary Shares [Member]
Issuance costs	$ 3,702

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net loss	$ (55,401)	$ (19,200)	$ (5,229)
Adjustments to reconcile net loss to net cash flows used in operating activities:
Depreciation and amortization	784	594	281
Share-based compensation expense	6,847	4,024
Deferred rent	565	88	(6)
Loss on disposal of property and equipment			14
Deferred income taxes	(564)	36	84
Tax benefit related to share-based compensation	(310)
Changes in operating assets and liabilities:
Accounts receivable		193	(129)
Prepaid expenses and other current assets	(1,337)	(63)	(12)
Accounts payable	3,369	1,648	9
Accrued expenses and other current liabilities	2,296	267	410
Deferred revenue	11,015	(152)	152
Other non-current liabilities	864	38
Net cash used in operating activities	(31,872)	(12,527)	(4,426)
Cash flows from investing activities
Increase in restricted cash	(2,599)	(1,055)
Proceeds from government grant reimbursements for property and equipment		3	319
Proceeds from the sale of property and equipment	4		14
Purchases of property and equipment	(5,567)	(1,857)	(590)
Net cash used in investing activities	(8,162)	(2,909)	(257)
Cash flows from financing activities
Proceeds from initial public offering, net of offering costs and underwriter commissions		101,444
Costs associated with initial public offering	(1,075)
Proceeds from issuance of ordinary shares, net of offering costs	30,000	11,631	5,585
Proceeds from issuance of Series B preferred shares, net of offering costs		62,532
Proceeds from government grant		112	34
Payments on capital lease obligation	(62)	(126)
Proceeds from the exercise of share options	258
Net cash provided by financing activities	29,121	175,593	5,619
Effect of foreign exchange rates on cash	(14)	15	(327)
Net increase (decrease) in cash and cash equivalents	(10,927)	160,172	609
Cash and cash equivalents at beginning of period	161,220	1,048	439
Cash and cash equivalents at end of period	150,293	161,220	1,048
Supplemental disclosure of cash flow information:
Deferred offering costs in accounts payable and accrued expenses at period end		1,075	72
Cash paid for interest	29		86
Cash paid for taxes, net of refunds	554
Equipment acquired for capital lease obligation		268
Conversion of related party notes payable into ordinary and Series A preferred shares			9,602
Property and equipment purchases in accounts payable and accrued expenses at period end	$ 1,653	$ 306	$ 3

The Company	12 Months Ended
The Company	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
The Company	1. THE COMPANY Organization WAVE Life Sciences Ltd. (together with its subsidiaries, “WAVE,” “we” or the “Company”) is a genetic medicines company with an innovative and proprietary synthetic chemistry drug development platform that we are using to design, develop and commercialize a broad pipeline of first-in-class or best-in-class nucleic acid therapeutic candidates for genetically defined diseases. We are initially developing oligonucleotides that target genetic defects to either reduce the expression of disease-promoting proteins or transform the production of dysfunctional mutant proteins into the production of functional proteins. The Company was incorporated in Singapore on July 23, 2012 and has its principal U.S. office in Cambridge, Massachusetts. The Company was incorporated with the purpose of combining two commonly held companies, WAVE Life Sciences USA, Inc. (“WAVE USA”), a Delaware corporation (formerly Ontorii, Inc.), and WAVE Life Sciences Japan, Inc. (“WAVE Japan”), a company organized under the laws of Japan (formerly Chiralgen., Ltd.), which occurred on September 12, 2012. On May 31, 2016, WAVE Life Sciences Ireland Limited (“WAVE Ireland”) was formed as a wholly-owned subsidiary of WAVE Life Sciences Ltd. It was formed as a private company limited by shares and the company number is 583482. The Company’s primary activities since inception have been developing a synthetic chemistry drug development platform to design, develop and commercialize nucleic acid therapeutic programs, advancing the Company’s neurology franchise, expanding the Company’s research and development activities to enter the clinic, building the Company’s intellectual property, recruiting personnel and raising capital to support these activities. Risks and Uncertainties The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, developing internal manufacturing capabilities, dependence on key personnel, compliance with government regulations and the need to obtain additional financing. The Company’s therapeutic programs will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization of any product candidates. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance-reporting capabilities. The Company’s therapeutic programs are currently in the development or discovery stage. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees and consultants. Basis of Presentation The Company has prepared the accompanying consolidated financial statements in conformity with U.S. GAAP and in U.S. dollars.

Significant Accounting Policies

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Significant Accounting Policies

2. SIGNIFICANT ACCOUNTING POLICIES

Cash Equivalents

The Company considers all highly liquid securities with original final maturities of three months or less from the date of purchase to be cash equivalents. Cash equivalents are comprised of funds in money market accounts.

Principles of Consolidation

The Company’s consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include the valuation of its Series A preferred shares on conversion of the related party notes payable, the valuation of the Company’s ordinary shares prior to the initial public offering, the assumptions used to determine the fair value of share-based awards, the valuation allowance required for the Company’s deferred tax assets, and determining uncertain tax positions and the related liabilities. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.

Segment Data

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on developing its proprietary synthetic chemistry platform to develop and commercialize a broad pipeline of nucleic acid-based therapeutics.

Foreign Currency Translation

The functional currency of the Company’s Japanese subsidiary is the Japanese Yen and the functional currency for both the Company’s U.S. subsidiary and the Company’s Singapore entity is the U.S. dollar. Assets and liabilities of WAVE Japan are translated at period end exchange rates while revenues and expenses are translated at average exchange rates for the period. Intercompany loans that are not expected to be settled in the foreseeable future are translated at the historical rate for the date of each capital transaction. Net unrealized gains and losses from foreign currency translation are reflected as accumulated other comprehensive (loss) income within Series A preferred shares and shareholders’ equity and consolidated statements of comprehensive loss. Gains and losses on foreign currency transactions are included in the consolidated statements of operations within other income (expenses), net.

Fair Value of Financial Instruments

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy is a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the financial instrument based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the financial instrument and are developed based on the information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs:

Level 1—Unadjusted quoted prices in active markets that are accessible at the measurement date of identical, unrestricted assets.

Level 2—Quoted prices for similar assets, or inputs that are observable, either directly or indirectly, for substantially the full term through corroboration with observable market data. Level 2 includes investments valued at quoted prices adjusted for legal or contractual restrictions specific to the security.

Level 3—Pricing inputs are unobservable for the asset, that is, inputs that reflect the reporting entity’s own assumptions about the assumptions market participants would use in pricing the asset. Level 3 includes private investments that are supported by little or no market activity.

There were no financial instruments recorded at fair value as of December 31, 2016 and 2015. The carrying amounts of accounts receivable, accounts payable, and accrued expenses approximate their fair values due to their short-term maturities.

Concentration of Credit Risk

Cash and cash equivalents are financial instruments that potentially subject the Company to concentration of credit risk. The Company uses several financial institutions to maintain its cash and cash equivalents, all of which are high quality, accredited financial institutions and, accordingly, such funds are subject to minimal credit risk. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. The Company has no financial instruments with off-balance sheet risk of loss.

Restricted Cash

Restricted cash consists primarily of cash placed in separate restricted bank accounts as required under the terms of the Company’s lease agreements for its Cambridge, Massachusetts facility and the newly leased facility in Lexington, Massachusetts (refer to Note 8). As of December 31, 2016, the Company had $3.6 million of restricted cash, of which $2.6 million was related to the Lexington facility and the remaining $1.0 million was related to the Cambridge facility. As of December 31, 2015, the Company had $1.1 million of restricted cash, which was primarily related to the Cambridge facility.

Property and Equipment

Property and equipment, which consists of furniture and equipment and leasehold improvements are stated at cost less accumulated depreciation and amortization. Depreciation is calculated on a straight-line basis over the following estimated useful lives of the assets:

Equipment, Furniture and Software	3-7 years
Leasehold Improvements	Shorter of life of lease or useful life

Depreciation and amortization begins at the time the asset is placed in service. Maintenance and repairs are charged to operations as incurred. Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is reflected in the consolidated statements of operations.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. Long-lived assets are reviewed for impairment whenever events or other changes in circumstances indicate that the carrying amount may not be recoverable. Certain factors may exist or events may occur that indicate that impairment exists including, but not limited to, the following: significant underperformance relative to historical or projected future operating results; significant changes in the manner of use of the underlying assets; and significant adverse industry or market economic trends.

When performing the impairment assessment for long-lived assets, the Company compares the carrying value of such assets to the estimated undiscounted future net cash flows expected from the use of the assets and their eventual disposition. In the event that the carrying value of the assets is determined to be unrecoverable, the Company would estimate the fair value of the assets and record an impairment charge for the excess of the carrying value over the fair value.

Through December 31, 2016, the Company has not recognized any impairment charges.

Revenue Recognition

To date, the Company’s only significant source of revenue is derived from the Pfizer Collaboration Agreement (as defined in Note 5), pursuant to which the Company and Pfizer (as defined in Note 5) have agreed to collaborate on the discovery, development and commercialization of stereopure oligonucleotide therapeutics for the Pfizer Programs (as defined in Note 5), each directed at a genetically-defined hepatic target selected by Pfizer. The Company entered into the Pfizer Collaboration Agreement in May 2016.

The Company presents revenue from the Pfizer Collaboration Agreement under Financial Accounting Standards Board (“FASB”), Accounting Standards Codification (“ASC”) Topic 808, Collaborative Arrangements (“ASC 808”). In addition, the Company recognizes revenue in accordance with ASC Topic 605, Revenue Recognition (“ASC 605”). Accordingly, revenue is recognized for each unit of accounting when all of the following criteria are met:

•

persuasive evidence of an arrangement exists;

•

delivery has occurred or services have been rendered;

•

the seller’s price to the buyer is fixed or determinable; and

•

collectability is reasonably assured.

Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current portion of deferred revenue in the accompanying consolidated balance sheets. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion.

Pursuant to the accounting guidance in ASC 605‑25, the Company evaluates multiple‑element arrangements to determine (1) the deliverables included in the arrangement and (2) whether the individual deliverables represent separate units of accounting or whether they must be accounted for as a combined unit of accounting. This evaluation involves subjective determinations and requires the Company to make judgments about the individual deliverables and whether such deliverables are separable from the other aspects of the contractual relationship. Deliverables are considered separate units of accounting provided that the delivered item has value to the customer on a standalone basis and, if the arrangement includes a general right of return relative to the delivered item, delivery or performance of the undelivered item is considered probable and substantially in the Company’s control. In assessing whether an item has standalone value, the Company considers factors such as the research, development, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can use a deliverable for its intended purpose without the receipt of the remaining deliverable, whether the value of the deliverable is dependent on the undelivered item and whether there are other vendors that can provide the undelivered items.

Under the Pfizer Collaboration Agreement (as defined in Note 5), the Company and Pfizer agreed to collaborate on the discovery, development and commercialization of up to five Pfizer Programs, two of the five targets were declared upon initiation of the agreement. The Collaboration Agreement provides Pfizer with certain options to nominate up to three remaining programs and the Company is required to consider whether such options are substantive. Options are considered substantive if, at the inception of the arrangement, the Company is at risk as to whether the collaboration partner will choose to exercise the option. Factors that the Company considers in evaluating whether an option is substantive include whether the optional elements are essential to the functionality of other programs nominated, whether economic factors compel Pfizer to purchase the optional elements, the cost to exercise the option, the overall objective of the arrangement and, the benefit Pfizer might obtain from the arrangement without exercising the option. As December 31, 2016 Pfizer had declared three targets. Pfizer is entitled to nominate two additional targets by November 2017.

When an option is considered substantive and there is no significant incremental discount, the option is not considered a deliverable in the arrangement and no consideration is allocated to it. Conversely, when an option is not considered substantive or it is considered substantive but is priced at an incremental discount, it is analyzed to determine if it should be combined with other deliverables in the arrangement. Options that are substantive and priced at a significant and incremental discount are further assessed to determine whether a portion of the upfront payment should be allocated to the option and other deliverables in the arrangement.

At the inception of an arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether: (1) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from its performance to achieve the milestone, (2) the consideration relates solely to past performance and (3) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone and the level of effort and investment required to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether a milestone satisfies all of the criteria required to conclude that a milestone is substantive. Revenue from substantive milestones will be recognized in its entirety upon successful accomplishment of the milestone.

Aside from the program nomination payments, which relate to the options described above, the remaining milestone payments required under the Pfizer Collaboration Agreement are contingent upon the Company’s performance under the Pfizer Collaboration Agreement, including in certain instances, regulatory approval. The Company views these milestones as substantive and has excluded the amounts as allocable consideration at the outset of the arrangement. All commercial milestones will be accounted for in the same manner as royalties and recorded as revenue upon achievement of the milestone, assuming all other revenue recognition criteria are met.

The Company recognizes arrangement consideration allocated to each unit of accounting when all of the revenue recognition criteria in ASC 605 are satisfied for that particular unit of accounting. In the event that a deliverable does not represent a separate unit of accounting, the Company recognizes revenue from the combined unit of accounting over the Company’s contractual or estimated performance period for the undelivered elements, which is typically the term of the Company’s research and development obligations. If there is no discernible pattern of performance or objectively measurable performance measures do not exist, then the Company recognizes revenue under the arrangement on a straight‑line basis over the period the Company is expected to complete its performance obligations. Conversely, if the pattern of performance in which the service is provided to the customer can be determined and objectively measurable performance measures exist, then the Company recognizes revenue under the arrangement using the proportional performance method. Revenue recognized is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the straight‑line method or proportional performance method, as applicable, as of the period ending date.

The Company has concluded that the deliverables under the Pfizer Collaboration Agreement relate primarily to the research and development required by the Company for each of the programs nominated by Pfizer. The remaining deliverables, including sample supplies provided by each party to fulfill its obligation as a licensee, participation on a joint steering committee to oversee the research and development activities, and regulatory responsibilities related to filings and obtaining approvals related to the products that may result from each program do not represent separate units of accounting based on their dependence on the research and development efforts.

Because there is no discernible pattern of performance given the nature of the research and development efforts, the Company recognizes the allocated revenue for each deliverable under the Pfizer Collaboration Agreement on a straight‑line basis over the period the Company is expected to complete its performance obligations for each deliverable, or unit of accounting. For the first two Pfizer Programs, this period is expected to be from the initiation date of the Pfizer Collaboration Agreement, which was May 5, 2016, and for the other Pfizer Programs, the period is expected to be from the date that work commences on those programs through the earlier of (a) the termination of the research and development performance obligations under the Pfizer Collaboration Agreement, which is May 5, 2020 (the “Research Term”), or (b) the estimated date the Company expects to meet its research and development performance obligations under the Pfizer Collaboration Agreement. Given the uncertainty as to when the research and development performance obligations will be completed, the Company has used the Research Term for purposes of applying the straight-line method for revenue recognition for the year ended December 31, 2016.

Product Revenue

The Company has had no product revenue to date.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development costs include salaries, share-based compensation and other employee benefit expenses, third-party license fees and other operational costs related to the Company’s research and development activities, including allocated facility-related expenses and external costs of outside vendors engaged to conduct preclinical studies and other research and development activities. Costs associated with licenses of technology and patent costs are expensed as incurred and are generally included in research and development expense in the consolidated statement of operations.

Net Loss per Share

Basic net loss per share is computed using the weighted-average number of ordinary shares outstanding during the period. Diluted net loss per share is computed using the sum of the weighted-average number of ordinary shares outstanding during the period and, if dilutive, the weighted-average number of potential ordinary shares, including the assumed exercise of share options.

The Company applies the two-class method to calculate its basic and diluted net loss per share attributable to ordinary shareholders, as its Series A preferred shares are participating securities. The two-class method is an earnings allocation formula that treats a participating security as having rights to earnings that otherwise would have been available to ordinary shareholders. However, for the periods presented, the two-class method does not impact the net loss per ordinary share as the Company was in a net loss position for each of the periods presented and holders of Series A preferred shares do not participate in losses.

The Company’s Series A preferred shares contractually entitle the holders of such shares to participate in dividends but do not contractually require the holders of such shares to participate in losses of the Company. Accordingly, for periods in which the Company reports a net loss attributable to ordinary shareholders, diluted net loss per share attributable to ordinary shareholders is the same as basic net loss per share attributable to ordinary shareholders, since dilutive ordinary shares are not assumed to have been issued if their effect is anti-dilutive.

License Agreements and Patent Costs

Costs associated with licenses of technology and patent costs are expensed as incurred and are generally included in research and development expense in the consolidated statements of operations.

Share-Based Compensation

The Company measures and recognizes share-based compensation expense, for both employee and director option awards, based on the grant date fair value of the awards. The Company calculates the fair value of restricted share awards based on the grant date fair value of the underlying ordinary shares. The Company recognizes share-based compensation expense on a straight-line basis over the requisite service period of the awards, which is generally the vesting period.

The Company determines the fair value of share-based awards granted to non-employees as either the fair value of the consideration received or the fair value of the equity instruments issued, whichever is more reliably measurable. All issuances of equity instruments issued to non-employees as consideration for goods or services received by the Company are accounted for based on the fair value of the equity instruments issued. These awards are recorded in expense and additional paid-in capital in shareholders’ equity over the applicable service periods based on the fair value of the options at the end of each period.

The Company classifies share-based compensation expense in its consolidated statements of operations in the same manner in which the award recipient’s payroll costs are classified or in which the award recipients’ service payments are classified.

Prior to the Company’s initial public offering (“IPO”) in November 2015, the fair value of the ordinary shares underlying its share-based awards was estimated on each grant date by the board of directors. The board of directors determined the estimated per share fair value of the Company’s ordinary shares at various dates considering contemporaneous and retrospective valuations performed in accordance with the guidance outlined in the American Institute of Certified Public Accountants Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation (“the Practice Aid”). After the closing of our IPO, the board of directors determined that the fair value of the ordinary shares underlying our share-based awards be based on the closing price of the Company’s ordinary shares as reported by the NASDAQ Global Market on the date of grant.

The fair value of each share option grant was determined using the methods and assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment and estimation by management.

•

Fair Value of Ordinary Shares. As discussed above, prior to our IPO, the fair value of the Company’s ordinary shares underlying our share options was historically determined by the board of directors. Because prior to our IPO, there was no public market for our ordinary shares, the board of directors determined the fair value of our ordinary shares at the time of grant of the option by considering a number of objective and subjective factors, including valuations of comparable companies, sales of its shares to unrelated third parties, operating and financial performance and general and industry specific economic outlook. Following the completion of our IPO, the board of directors determined that the fair value of each ordinary share underlying our share-based awards would be based on the closing price of the Company’s ordinary shares as reported by the NASDAQ Global Market on the date of grant.

•

Expected Term. The expected term of share options represents the weighted-average period that the share options are expected to remain outstanding. The Company estimated the expected term using the simplified method, which is an average of the contractual term of the option and the vesting period.

•

Expected Volatility. Since there is limited historical data for the Company’s ordinary shares and limited company-specific historical volatility, it has determined the share price volatility for options granted based on an analysis of the volatility used by a peer group of publicly traded companies. In evaluating similarity, the Company considers factors such as industry, stage of life cycle and size.

•

Risk-free Interest Rate. The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of the grant for zero-coupon U.S. Treasury notes with remaining terms similar to the expected term of the options.

•

Dividend Rate. The expected dividend was assumed to be zero as the Company has never paid dividends and has no current plans to do so.

Income Taxes

The Company accounts for income taxes using an asset and liability approach, which requires recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements, but have not been reflected in taxable income. A valuation allowance is established to reduce deferred tax assets to their estimated realizable value. Therefore, the Company provides a valuation allowance to the extent that it is more likely than not that all or a portion of the deferred tax assets will not be realized in the future.

The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

The Company recognizes interest and penalties related to uncertain tax positions in the income tax provision on the consolidated statements of operations.

The Company has certain service arrangements in place between our U.S and Singapore entities, which include transfer pricing assumptions. The determination of the appropriate level of transfer pricing requires judgment based on transfer pricing analyses of comparable companies. The Company monitors the nature of their service arrangements for changes in our operations as well as economic conditions. The Company also periodically reviews the transfer pricing analyses for changes in the composition in the pool of comparable companies as well the related ongoing results of the comparable companies.

Early Adoption of Accounting Standards Update No. 2016-09

Effective for the quarter ended December 31, 2016, the Company adopted a change in accounting principle related to the early adoption of ASU 2016–09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). This revised standard affects forfeitures, cash flow presentation and income taxes. Additionally, this standard requires all excess tax benefits and deficiencies on share-based payment awards to be recognized as income tax expense or benefit in the statement of operations. In addition, the tax effects of exercised or vested awards should be treated as discrete items in the reporting period in which they occur and excess tax benefits should be classified with other income tax cash flows as an operating activity. The standard permits early adoption in any annual or interim period and will be applied by means of a cumulative-effect adjustment to the balance sheet as of the beginning of the fiscal year of adoption. The Company notes that it did not have any off-balance sheet attributes as of January 1, 2016 and therefore did not record a cumulative-effect adjustment to retained earnings. The standard permits the changes to the classification of the statement of cash flows to be applied either prospectively or retrospectively. The Company has elected to treat the change in classification of cash flows resulting from excess tax benefits or deficiencies on a retrospective basis and elected to recognize forfeitures as they occur on a modified-retrospective basis. There was an immaterial cumulative effect adjustment on forfeitures as a result of the adoption. The adoption of this standard also resulted in a current year tax benefit of $0.3 million which previously would have been recognized in the current period in additional paid-in capital.

Recently Issued Accounting Pronouncements

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The new standard will be effective on January 1, 2018 and earlier application is permitted only for annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. For the year ended December 31, 2016, revenue was generated exclusively from the Pfizer Collaboration Agreement. The Company is currently evaluating the potential impact that ASU 2014-09 may have on its financial position and results of operations as it relates to this single arrangement, and expects to elect the modified retrospective application as its transition method.

In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements – Going Concern (“ASU 2014-15”), which requires a company to evaluate the existence of conditions or events that raise substantial doubt about its ability to continue as a going concern within one year of the issuance date of its financial statements. The standard is effective for interim and annual periods ending after December 15, 2016 with early adoption permitted. The Company has evaluated the impact of ASU 2014-15 and has concluded that it does not have a material effect on the consolidated financial statements or footnote disclosures as of the December 31, 2016 adoption date, but may require additional disclosures in future periods.

In February 2015, the FASB issued ASU 2015-02, Consolidation (Topic 810) (“ASU 2015-02”), to address financial reporting considerations for the evaluation as to the requirement to consolidate certain legal entities. ASU 2015-02 is effective for fiscal years and for interim periods within those fiscal years beginning after December 15, 2015. The Company has evaluated the impact of ASU 2015-02 and has concluded that it has no effect on the consolidated financial statements.

In April 2015, the FASB issued ASU 2015-03, Interest—Imputation of Interest (Subtopic 835-30) (“ASU 2015-03”), as part of the initiative to reduce complexity in accounting standards. The update requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The Company has evaluated the impact of ASU 2015-03 and has concluded that it has no effect on the consolidated financial statements.

In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes (“ASU 2015-17”), which requires entities to present deferred tax assets and deferred tax liabilities as noncurrent in a classified balance sheet. The ASU simplifies the current guidance in ASC Topic 740, Income Taxes, which requires entities to separately present deferred tax assets and liabilities as current and noncurrent in a classified balance sheet. ASU 2015-17 is effective for fiscal years beginning after December 31, 2016, and interim periods within those annual periods. Early adoption is permitted for all entities as of the beginning of an interim or annual reporting period. The Company does not expect the impact of ASU 2015-17 to be material to its consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, Leases (“ASU 2016-02”), which requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. The update includes a short-term lease exception for leases with a term of 12 months or less, in which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases, using classification criteria that are substantially similar to the previous guidance. For lessees, the recognition, measurement, and presentation of expenses and cash flows arising from a lease have not significantly changed from previous U.S. GAAP. Lessees and lessors are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The modified retrospective approach includes a number of optional practical expedients that entities may elect to apply as well as transition guidance specific to nonstandard leasing transactions. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. The Company is currently evaluating the potential impact that the adoption of ASU 2016-02 may have on its consolidated financial statements.

In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). The ASU requires companies to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. Prior to the issuance of this ASU, existing guidance prohibited the recognition of current and deferred income taxes for an intra-entity asset transfer until the asset has been sold to an outside party. ASU 2016-16 will be effective for the Company in the first quarter of 2018 with early adoption permitted. The Company is currently evaluating the potential impact that the adoption of ASU 2016-16 may have on its consolidated financial statements.

In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASU 2016-18”). The ASU requires an entity to explain the changes in the total of cash, cash equivalents, restricted cash, and restricted cash equivalents on the statement of cash flows and to provide a reconciliation of the totals in that statement to the related captions in the balance sheet when the cash, cash equivalents, restricted cash, and restricted cash equivalents are presented in more than one line item on the balance sheet. This ASU is effective for annual and interim periods beginning after December 15, 2017, and is required to be adopted using a retrospective approach, with early adoption permitted. The Company is currently evaluating the potential impact that the adoption of ASU 2016-18 may have on its consolidated financial statements.

Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s consolidated financial statements upon adoption.

Property and Equipment, Net

12 Months Ended

Dec. 31, 2016

Property Plant And Equipment [Abstract]

Property and Equipment, Net

3. PROPERTY AND EQUIPMENT, NET

Property and equipment, net, consists of the following

	December 31,
	2016			2015
	(in thousands)
Furniture and equipment	$	7,231		$	3,936
Software		43			—
Leasehold improvements		1,964			267
Fixed assets in progress		1,863			198
Total		11,101			4,401
Less accumulated depreciation and amortization		(2,494	)		(1,612	)
Property and equipment, net	$	8,607		$	2,789

Leasehold improvements made during the year ended December 31, 2016 consisted of costs related to the Company’s leased facility in Cambridge, Massachusetts and the newly leased facility in Lexington, Massachusetts.

Leasehold improvements made during the year ended December 31, 2015 consisted primarily of costs related to the Company’s leased facility in Cambridge, Massachusetts.

Depreciation and amortization expense was $0.8 million, $0.6 million, and $0.3 million for the years ended December 31, 2016, 2015 and 2014, respectively.

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2016

Payables And Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

4. ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES

Accrued expenses and other current liabilities consist of the following:

	December 31,
	2016		2015
	(in thousands)
Accrued compensation	$	2,480	$	—
Accrued professional fees		417		401
Accrued vacation		589		191
Other		959		353
Total accrued expenses and other current liabilities	$	4,445	$	945

Pfizer Collaboration and Share Purchase Agreement	12 Months Ended
Pfizer Collaboration and Share Purchase Agreement	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Pfizer Collaboration and Share Purchase Agreement	5. PFIZER COLLABORATION AND SHARE PURCHASE AGREEMENT On May 5, 2016, the Company entered into a Research, License and Option Agreement (the “Pfizer Collaboration Agreement”) with Pfizer Inc. (“Pfizer”). Pursuant to the terms of the Pfizer Collaboration Agreement, the Company and Pfizer agreed to collaborate on the discovery, development and commercialization of stereopure oligonucleotide therapeutics for up to five programs (the “Pfizer Programs”), each directed at a genetically-defined hepatic target selected by Pfizer (the “Collaboration”). The Company received $10.0 million as an upfront license fee under the Pfizer Collaboration Agreement. Subject to option exercises by Pfizer, assuming five potential products are successfully developed and commercialized, the Company may earn up to $871.0 million in potential research, development and commercial milestone payments, plus royalties, tiered up to low double-digits, on sales of any products that may result from the Collaboration. None of the payments under the Pfizer Collaboration Agreement are refundable. Simultaneously with the entry into the Pfizer Collaboration Agreement, the Company entered into a Share Purchase Agreement (the “Pfizer Equity Agreement,” and together with the Pfizer Collaboration Agreement, the “Pfizer Agreements”) with C.P. Pharmaceuticals International C.V., an affiliate of Pfizer (the “Pfizer Affiliate”). Pursuant to the terms of the Pfizer Equity Agreement, the Pfizer Affiliate purchased 1,875,000 of the Company’s ordinary shares (the “Shares”) at a purchase price of $16.00 per share, for an aggregate purchase price of $30.0 million. The Company did not incur any material costs in connection with the issuance of the Shares. Under the Pfizer Collaboration Agreement, the parties agreed to collaborate during the four-year Research Term. During the Research Term, the Company is responsible to use its commercially reasonable efforts to advance up to five programs through to the selection of clinical candidates. At that stage, Pfizer may elect to license any of these Pfizer Programs exclusively and to have exclusive rights to undertake the clinical development of the resulting clinical candidates into products and the potential commercialization of any such products thereafter. In addition, the Company receives a non-exclusive, royalty-bearing sublicenseable license to use Pfizer’s hepatic targeting technology in any of the Company’s own hepatic programs that are outside the scope of the Collaboration (the “WAVE Programs”). If the Company uses this technology on the WAVE Programs, Pfizer is eligible to receive potential development and commercial milestone payments from the Company. Pfizer is also eligible to receive tiered royalties on sales of any products that include Pfizer’s hepatic targeting technology. Pfizer nominated two hepatic targets upon entry into the Collaboration in May 2016. In August 2016, Pfizer nominated the third hepatic target under the Collaboration and has the option to nominate two additional targets by November 5, 2017. The Company received a $2.5 million milestone payment related to the nomination of third target. The Company has determined that the options held by Pfizer under the Pfizer Collaboration Agreement are substantive and priced at a significant incremental discount. Accordingly, $3.0 million of the upfront payment has been allocated to the options to nominate the three remaining targets. The amount allocated to the three options will be recognized as the research and development are provided commencing from the date that Pfizer exercises each respective option, or immediately as each option expires unexercised. The portion of the upfront payment allocated to the initial two targets was $7.0 million and will be recognized as the research and development services are provided from the inception of the arrangement. Subsequently, in 2016, Pfizer exercised its option to nominate a third program. The Company will recognize $3.5 million of revenue (which is comprised of $1.0 million allocated to the option at inception of the arrangement and $2.5 million paid by Pfizer at the time of exercising the option) as the research and development services are provided. The Collaboration is managed by a joint steering committee in which both parties are represented equally, which will oversee the scientific progression of each Pfizer Program up to the clinical candidate stage. During the four-year Research Term and for a period of two years thereafter, the Company has agreed to work exclusively with Pfizer with respect to using any of the Company’s stereopure oligonucleotide technology that is specific for the applicable hepatic target which is the basis of any Pfizer Program. The stated term of the Pfizer Collaboration Agreement commenced on May 5, 2016 and terminates on the date of the last to expire payment obligation with respect to each Pfizer Program and with respect to each WAVE Program, expires on a program-by-program basis accordingly. Pfizer may terminate its rights related to a Pfizer Program under the Pfizer Collaboration Agreement at its own convenience upon 90 days’ notice to the Company. The Company may also terminate its rights related to a WAVE Program at its own convenience upon 90 days’ notice to Pfizer. The Pfizer Collaboration Agreement may also be terminated by either party in the event of an uncured material breach of the Collaboration Agreement by the other party. During the year ended December 31, 2016, the Company recognized revenue of $1.5 million under the Pfizer Collaboration Agreement. Deferred revenue amounted to $11.0 million as of December 31, 2016, of which $2.7 million is included in current liabilities.

Share Capital

12 Months Ended

Dec. 31, 2016

Equity [Abstract]

Share Capital

6. SHARE CAPITAL

Ordinary Shares

The following represents the historical ordinary share transactions of the Company from December 31, 2013 through December 31, 2016:

•

In February 2014, the Company issued 2,263,291 ordinary shares to a third-party investor at $2.47 per share for net proceeds of $5.6 million. In connection with this financing, holders of $9.6 million of related party notes payable agreed to convert such notes into 2,365,139 Series A preferred shares and 1,515,596 ordinary shares.

•

In January 2015, the Company issued 4,769,077 ordinary shares to a third-party investor and an existing investor at $2.47 per share for net proceeds of $11.6 million.

•

In March 2015, the Company granted 190,856 fully-vested ordinary shares to an executive of the Company.

•

In November 2015, the Company completed an initial public offering of its ordinary shares, in which the Company issued and sold 6,375,000 ordinary shares at a price to the public of $16.00 per share. In December 2015, the Company issued an additional 618,126 ordinary shares at a price of $16.00 per share pursuant to a partial exercise of the underwriters’ over-allotment option. The aggregate net proceeds to the Company from the initial public offering, inclusive of the over-allotment exercise, were $100.4 million after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company.

•

In May 2016, the Company granted 1,875,000 ordinary shares to Pfizer under the Pfizer Agreements (Note 5) at a purchase price of $16.00 per share, for an aggregate purchase price of $30.0 million.

Features of the Ordinary Shares

The ordinary shares have no par value and there is no authorized share capital under Singapore law. The rights, preferences, and privileges of ordinary shares are as follows:

New Share Offering

Prior to the closing of the Company’s initial public offering, any new ordinary shares or securities convertible into ordinary shares were required to be offered in the first instance to all the then holders of any class of shares, other than the Series A preferred shares, prior to issuance and each shareholder had the right of pre-emption with respect to any issuance of new ordinary shares or securities convertible into ordinary shares. This right of pre-emption did not apply to shares sold in the Company’s initial public offering and terminated immediately prior to the closing of the Company’s initial public offering.

Voting

The holders of ordinary shares are entitled to one vote for each ordinary share held at all meetings of shareholders and written actions in lieu of meetings provided, however, that except as otherwise required by law, holders of ordinary shares shall not be entitled to implement the following without the approval of more than 75% of the Company’s issued and outstanding ordinary shares:

(i)

effect a merger, split, corporate reorganization, liquidation, dissolution, or winding up of the Company or any member of the group;

(ii)

authorize or issue any additional shares, other equity interests in the Company or any convertible securities into such equity interests;

(iii)

effect any public offering or listing of the equity securities of the Company; or

(iv)

purchase, redeem, pay or declare any dividend on any shares or other equity interests in the Company.

Dividends

All dividends shall be declared and paid pro rata according to the number of shares held by each member entitled to receive dividends. The Company’s board of directors may deduct from any dividend all sums of money presently payable by the member to the Company on account of calls.

Liquidation

In the event of a liquidation, dissolution or winding up of, or a return of capital by the Company, the ordinary shares will rank equally with the Series A preferred shares after the payment of the liquidation preference of $10.00 for Series A preferred shares.

Series A Preferred Shares

The following represent the Series A preferred share transactions of the Company from December 31, 2013 through December 31, 2016:

•

In February 2014, holders of $9.6 million of related party notes payable agreed to convert such notes into 2,365,139 Series A preferred shares and 1,515,596 ordinary shares.

•

In connection with the private placement of Series B preferred shares on August 14, 2015, holders of the Company’s preference shares agreed to rename the existing “preference shares” as “Series A preferred shares.” In addition, as further described below, the terms of the Series A preferred shares were amended to remove their right of first refusal and to provide for their right to convert on a one-for-one basis into an aggregate of 3,901,348 ordinary shares at any time at the election of the holder. The rights of the Series A preferred shares are identical to the ordinary shares except that the Series A preferred shares have: (1) no voting rights other than in limited circumstances, (2) the right to a non-cumulative dividend if and when declared by the Company’s board of directors and (3) the right to convert the Series A preferred shares at any time on a one-for-one basis into ordinary shares at the discretion of the holder. The Company’s shareholders, including holders of Series A preferred shares, entered into an investors’ rights agreement and a voting agreement with the Company in connection with the private placement. Pursuant to the terms of the voting agreement, which terminated in connection with the Company’s IPO, investors who held at least 1,212,477 shares of registerable securities, including holders of Series A preferred shares and Series B preferred shares, had a right to purchase certain new securities offered by the Company. Additionally, in the event of the sale of 50% or more of the voting power of the Company or a deemed liquidation event, if the holders of at least a majority of the ordinary shares and the holders of 56% of the Series B preferred shares had voted for a sale of the Company, they had the right to force the other shareholders, including the holders of Series A preferred shares, to agree to such a sale.

•

In September 2015, the terms of the Series A preferred shares were further amended to provide that, upon the mandatory conversion of Series B preferred shares, which occurred on the completion of the initial public offering, the existing right of Series A preferred shares to a non-cumulative dividend if and when declared by our board of directors ceased and was replaced by a liquidation preference consisting of $0.0024743 per Series A preferred share, or an aggregate of $10.00 based on the number of Series A preferred shares outstanding at the date of the amendment.

The Company has accounted for the September 2015 amendment to the Series A preferred shares as a modification of the preferred shares based on upon a qualitative assessment of the amendment. The Company has not adjusted the carrying value of the Series A preferred shares since the fair value of the Series A preferred shares immediately prior and subsequent to the modification date resulted in an immaterial change in fair value.

The addition of the liquidation preference to the Series A preferred shares, however, resulted in the reclassification of the Series A preferred shares from permanent shareholders’ equity to temporary shareholders’ equity since the holders of the Series A preferred shares are entitled to a liquidation preference upon a deemed liquidation event, which is outside the control of the Company. In the event a deemed liquidation event were to occur, the Company would adjust the carrying value of the Series A preferred shares to their liquidation value, which amounts to $10.00 in the aggregate.

The Series A preferred shares have no par value and there is no authorized share capital under Singapore law. The Series A preferred shares are not redeemable.

Series B Preferred Shares Converted in Connection with Initial Public Offering

The following represents the historical Series B preferred share transactions of the Company from January 1, 2015 through the completion of our initial public offering:

•

On August 14, 2015, the Company issued an aggregate of 5,334,892 Series B preferred shares at a purchase price of $12.37 per share to certain third-party investors for $62.5 million of net proceeds.

•

Upon the completion of the initial public offering on November 16, 2015, all of the outstanding Series B preferred shares of the Company automatically converted into 5,334,892 of the Company’s ordinary shares.

Prior to the conversion of the Series B preferred shares into ordinary shares, the Series B preferred shares had a liquidation preference over the Series A preferred shareholders and ordinary shareholders equal to the original per share amount paid of $12.37 per share, plus any declared plus unpaid dividends, if any. Additionally, the holders of Series B preferred shares were entitled to voting rights, however, the Series B preferred shareholders were not entitled to any preferential dividends and their shares were not redeemable.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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Reference 13: http://www.xbrl.org/2003/role/presentationRef
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Share-Based Compensation

12 Months Ended

Dec. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-Based Compensation

7. SHARE-BASED COMPENSATION

In December 2014, the Company’s board of directors adopted the WAVE Life Sciences Ltd. 2014 Equity Incentive Plan (the “2014 Plan”), and reserved 1,763,714 ordinary shares for issuance under this plan, which, as approved, was increased to 5,064,544 in 2015.

The 2014 Plan authorizes the board of directors or a committee of the board to grant incentive share options, non-qualified share options, share appreciation rights and restricted share awards to eligible employees, outside directors and consultants of the Company. Options generally vest over a period of three or four years, and options that lapse or are forfeited are available to be granted again. The contractual life of all options is ten years from the date the option begins to vest.

During the years ended December 31, 2016 and 2015, the Company granted options to purchase 1,479,200 and 2,215,342 ordinary shares, respectively, to employees, directors and non-employees. During the year ended December 31, 2016, there were forfeitures of options to purchase 41,030 ordinary shares. There were no forfeitures of options during the year ended December 31, 2015. During the years ended December 31, 2016 and 2015 there were no cancellations of options. The Company did not grant any share options in 2014. In July 2016, the Company granted 22,750 restricted share units (“RSUs”) with a grant date fair value of $21.69 per unit. The RSUs fully vest upon the first anniversary of the grant date. Share-based compensation expense related to the RSUs is included in research and development expenses on the consolidated statements of operations. As of December 31, 2016, 1,197,426 ordinary shares remained available for future grant.

The Company recorded share-based compensation expense of $6.8 million and $4.0 million for the years ended December 31, 2016 and 2015, respectively, of which $2.7 million and $1.6 million respectively related to options granted to non-employees. The Company did not have any share-based compensation expense in 2014. The Company measures and records the value of options granted to non-employees over the period of time services are provided and, as such, unvested portions are subject to re-measurement at subsequent reporting periods.

Share option activity under the 2014 Plan is summarized as follows:

	Number of Shares			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)⁽¹⁾
Options outstanding as of January 1, 2016		2,215,342		$	3.88		9.30	$	26,740
Granted		1,479,200		20.79
Exercised		(75,746	)	3.42					1,887
Cancelled or forfeited		(41,030	)	10.23
Outstanding as of December 31, 2016		3,577,766		$	10.58		8.68	$	56,780
Options exercisable as of December 31, 2016		1,248,343		$	3.10		8.24	$	28,775
Options unvested as of December 31, 2016		2,329,423		$	14.58		8.92	$	28,006

(1)

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the share options and the fair value of the Company’s ordinary shares for those share options that had exercise prices lower than the fair value of the ordinary shares as of the end of the period.

RSU activity for the year ended December 31, 2016 is summarized as follows:

	RSUs		Average Grant Date Fair Value (in dollars per share)
RSUs Outstanding as of January 1, 2016		—	$	—
Granted		22,750		21.69
RSUs Outstanding at December 31, 2016		22,750	$	21.69

The assumptions used in the Black-Scholes option pricing model to determine the fair value of share options granted to employees during the period were as follows:

	For the Year Ended December 31,
	2016	2015
Risk-free interest rate	1.15% – 2.18%	1.56% - 1.89%
Expected term (in years)	3.00 – 6.25	5.52 - 6.12
Expected volatility	60.89% – 68.76%	62.14% - 71.02%
Expected dividend yield	0%	0%
Exercise price	$14.11 – 36.43	$2.47 - 13.08
Fair value of ordinary share	$14.11 – 36.43	$4.41 - 13.08

The assumptions used in the Black-Scholes option pricing model to determine the fair value of share options granted to non-employees during the period were as follows:

		Year Ended December 31, 2015
Risk-free interest rate		2.06% - 2.35%
Expected term (in years)		9.19 - 10.00
Expected volatility		62.65% - 69.80%
Expected dividend yield		0%
Exercise price		$2.47
Fair value of ordinary share		$4.41 - 15.95

There were no options granted to non-employees in 2016.

As of December 31, 2016, the unrecognized compensation cost related to outstanding options was $18.0 million for employees and $3.8 million for non-employees. The unrecognized compensation cost for employees and non-employees is expected to be recognized over a weighted-average period of approximately 2.23 years. The unrecognized compensation costs related to outstanding RSUs was $0.3 million as of December 31, 2016, and is expected to be recognized expense over a weighted-average period of approximately 0.53 years. For the years ended December 31, 2016 and 2015, the weighted-average grant date fair value per granted option was $30.23 and $6.64, respectively. For the year ended December 31, 2016, the weighted-average grant date fair value per granted RSU was $21.69. The aggregate fair value of options that vested during the year ended December 31, 2016 was $4.7 million.

In March 2015, the Company granted 190,856 fully-vested ordinary shares to an executive of the Company and the Company recorded compensation expense in the amount of $0.9 million.

Share-based compensation expense for the year ended December 31, 2016 and 2015 was classified in the consolidated statements of operations as follows:

	For the Year Ended December 31,
	2016		2015
	(in thousands)
Research and development expenses	$	4,936	$	2,268
General and administrative expenses		1,911		1,756
Total share-based compensation	$	6,847	$	4,024

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2016

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

8. COMMITMENTS AND CONTINGENCIES

Lease Arrangements

The Company enters into lease arrangements for its facilities as well as certain equipment. A summary of the arrangements are as follows:

Operating Leases

On September 26, 2016, and as amended on December 31, 2016 the Company entered into a 10 year and 9 month lease, which includes two successive five year renewal options, for its manufacturing function in Lexington, Massachusetts. Throughout the term of the Lease, the Company is responsible for paying certain costs and expenses, in addition to the rent, as specified in the Lease, including a proportionate share of applicable taxes, operating expenses and utilities. In connection with the lease agreement, the Company issued the lessor a letter of credit in the amount of $2.6 million, which is included in restricted cash at December 31, 2016.

In connection with the lease agreement, the Company is entitled to receive $11.5 million of tenant improvement allowances. The Company has received $0.1 million as of December 31, 2016, which is amortized over the period from the commencement of tenant improvement construction through to the end of the lease term.

As of December 31, 2016, property and equipment, net, includes $0.9 million related to construction costs for the facility in Lexington.

In April 2015, the Company entered into a lease agreement for an office and laboratory facility in Cambridge, Massachusetts, which commenced in October 2015 with a term of 7.5 years with a five-year renewal option to extend the lease. In connection with the lease, the Company issued the lessor a letter of credit in the amount of $1.0 million, which is recorded as restricted cash on the consolidated balance sheets at December 31, 2016 and 2015.

Previously, the Company leased its corporate office space in Boston, Massachusetts under a non-cancellable operating sublease with SNBL, a related party. On September 22, 2015, the Company terminated its sublease with SNBL and exited the premises on October 2, 2015. As a result of the termination of the sublease, the Company recorded approximately $0.2 million of additional depreciation and $0.1 million of exit costs during the year ended December 31, 2015. In connection with the termination, the Company agreed to guarantee SNBL certain obligations of an unrelated third party who entered into a sublease agreement with SNBL effective October 2, 2015. The guarantee provides that in the event the sub-lessee does not meet its lease obligations to SNBL, the Company will make the required payments. The guarantee agreement is effective through August 2019, when the final lease payments are due, and coincides with the original expiration of the lease. The Company simultaneously entered into an indemnification agreement with the sub-lessee to indemnify the Company for any costs incurred under the guaranty made by the Company to SNBL. The maximum amount of the guarantee over the three year and six month sub-lease period is $0.6 million, exclusive of any indemnification from the sub-lessee.

Future minimum lease payments under the Company’s non-cancelable operating leases as of December 31, 2016, are as follows:

For the Year Ended December 31,	Amount
	(in thousands)
2017		1,954
2018		4,660
2019		5,798
2020		5,972
2021		6,151
Thereafter		33,418
		57,953

The Company recorded rent expense of $1.5 million, $0.5 million and $0.3 million for the years ended December 31, 2016, 2015 and 2014, respectively.

Capital Lease

In April 2015, the Company entered in a three year lease to acquire laboratory equipment, which has been accounted for as a capital lease. The capital asset was valued at $0.3 million and is included in property and equipment, net, along with accumulated amortization of $0.1 million and less than $0.1 million as of December 31, 2016 and 2015, respectively.

Unasserted Claims

In the ordinary course of business, the Company may be subject to legal proceedings, claims and litigation as the Company operates in an industry susceptible to patent legal claims. The Company accounts for estimated losses with respect to legal proceedings and claims when such losses are probable and estimable. Legal costs associated with these matters are expensed when incurred. The Company is not currently a party to any material legal proceedings.

Net Loss Per Ordinary Share

12 Months Ended

Dec. 31, 2016

Earnings Per Share [Abstract]

Net Loss Per Ordinary Share

9. NET LOSS PER ORDINARY SHARE

Basic loss per share is computed by dividing net loss attributable to ordinary shareholders by the weighted-average number of ordinary shares outstanding:

	Year Ended December 31,
	2016			2015			2014
	(in thousands except share and per share data)
Numerator:
Net loss attributable to ordinary shareholders	$	(55,401	)	$	(19,200	)	$	(5,229	)
Denominator:
Weighted-average ordinary shares outstanding		22,800,628			10,501,455			3,911,556
Net loss per share, basic and diluted	$	(2.43	)	$	(1.83	)	$	(1.34	)

The Company’s potentially dilutive shares, which include outstanding share options to purchase ordinary shares, are considered to be ordinary share equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.

The following potential ordinary shares, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to ordinary shareholders for the periods indicated because including them would have had an anti-dilutive effect:

	As of December 31,
	2016		2015
Options to purchase ordinary shares		3,577,766		2,215,432
Restricted share units		22,750		—
Series A preferred shares		3,901,348		3,901,348

Income Taxes

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Income Taxes

10. INCOME TAXES

The components of loss before income taxes were as follows:

	Year Ended December 31,
	2016			2015			2014
	(in thousands)
Singapore	$	(53,387	)	$	(16,534	)	$	(4,542	)
Rest of world		(1,398	)		(2,622	)		(603	)
Loss before income taxes	$	(54,785	)	$	(19,156	)	$	(5,145	)

During the years ended December 31, 2016, 2015, and 2014, the Company recorded a tax provision of $0.6 million, less than $0.1 million, and $0.1 million, respectively, due to income taxed in the United States.

During the years ended December 31, 2016, 2015 and 2014, the Company recorded no income tax benefits for the net operating losses incurred in Japan and Singapore, due to its uncertainty of realizing a benefit from those items.

The deferred components of the benefit (provision) for income taxes were as follows:

	Year Ended December 31,
	2016			2015			2014
	(in thousands)
Current tax benefit (provision):
Singapore taxes	$	—		$	—		$	—
Rest of world taxes		(1,180	)		(8	)		—
Total current benefit (provision) income taxes	$	(1,180	)	$	(8	)	$	—
Deferred tax benefit (provision):
Singapore taxes	$	—		$	—		$	—
Rest of world taxes		564			(36	)		(84	)
Total deferred benefit (provision) income taxes	$	564		$	(36	)	$	(84	)
Total benefit (provision) income taxes	$	(616	)	$	(44	)	$	(84	)

A reconciliation of the Singapore statutory income tax rate to the Company’s effective income tax rate is as follows:

	Year Ended December 31,
	2016			2015			2014
Singapore statutory income tax rate		17.0	%		17.0	%		17.0	%
Research and development tax credits		3.1			2.3			2.2
Permanent differences		(0.9	)		5.5			—
Foreign exchange loss		—			—			2.0
Changes in reserves for uncertain tax positions		(3.6	)		(1.2	)		(2.2	)
Foreign rate differential		(0.1	)		1.2			4.5
Other		(0.9	)		0.2			—
Change in deferred tax asset valuation allowance		(15.7	)		(25.2	)		(25.1	)
Effective income tax rate		(1.1	)%		(0.2	)%		(1.6	)%

The components of the Company’s deferred tax assets as of December 31, 2016 and 2015 are as follows:

	December 31,
	2016			2015
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	16,046		$	7,037
Research and development credits		449			460
Accrued expenses		242			58
Share-based compensation		1,024			218
Other		102			149
Total deferred tax assets		17,863			7,922
Valuation allowance		(15,999	)		(7,466	)
Net deferred tax assets		1,864			456
Depreciation		(1,090	)		(246	)
Total deferred tax liability		(1,090	)		(246	)
Net deferred tax asset (liability)	$	774		$	210

A roll-forward of the valuation allowance for the years ended December 31, 2016 and 2015 is as follows:

	Year Ended December 31,
	2016			2015
	(in thousands)
Balance at beginning of year	$	7,466		$	2,658
Increase in valuation allowance		8,774			4,818
Reversal of valuation allowance		(282	)		—
Effect of foreign currency translation		41			(10	)
Balance at end of year	$	15,999		$	7,466

As of December 31, 2016 and 2015, the Company also has United States research and development credit carryforwards of approximately $0.2 million and $0.7 million, respectively, available to offset future U.S. federal income taxes and approximately $0.3 million and $0.4 million, respectively, available to offset future state income taxes. The U.S. federal and state research and development credits will begin to expire in 2031 and 2028, respectively.

As of December 31, 2016 and 2015, the Company has net operating loss carryforwards in Japan of $5.3 million and $4.3 million, respectively, which may be available to offset future income tax liabilities and begin to expire in 2017.

As of December 31, 2016 and 2015, the Company has net operating loss carryforwards in Singapore of $84.0 million and $31.8 million, respectively, which may be available to offset future income tax liabilities and can be carried forward indefinitely.

The Company has evaluated the positive and negative evidence bearing upon its ability to realize its deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products or generation of any revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets in Japan and Singapore. Accordingly, a full valuation allowance has been established against those deferred tax assets as of December 31, 2016 and 2015. Additionally, management has considered the Company’s expected utilization of research and development credit carryforwards and has concluded that it is more likely than not that the Company will not realize the benefits of the U.S. state research and development carryforward. The $0.3 million valuation allowance previously recorded against the federal research and development credit carryforward has been released in 2016 based on management’s assessment that the deferred tax asset is more-likely-than-not to be realized.

The valuation allowance increased by approximately $8.5 million in 2016, $4.8 million in 2015 and $1.3 million in 2014 primarily as a result of operating losses generated with no corresponding financial statement benefit. The Company may release this valuation allowance when management determines that it is more-likely-than-not that the deferred tax assets will be realized. Any release of valuation allowance will be recorded as a tax benefit increasing net income.

The Company’s reserves related to taxes and its accounting for uncertain tax positions are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more-likely-than-not to be realized following resolution of any potential contingencies present related to the tax benefit.

A summary of activity in the Company’s unrecognized tax benefits is as follows:

	2016			2015		2014
	(in thousands)
Unrecognized tax benefit during the year	$	1,280		$	1,025	$	901
Tax positions released related to prior years		(1,066	)		—		—
Tax positions related to the current year		2,129			255		124
Unrecognized tax benefit end of year	$	2,343		$	1,280	$	1,025

As of December 31, 2016, 2015 and 2014, the total amount of gross unrecognized tax benefits in the United States, which excludes interest and penalties, was $2.3 million, $1.3 million, and $1.0 million, respectively. At December 31, 2016, $1.7 million of the net unrecognized tax benefits, would affect the Company’s annual effective tax rate if recognized.

In 2015, the Company early adopted ASU 2013-11 and therefore unrecognized tax benefits related to net operating losses were netted against the related deferred tax asset. In 2016, the Company filed amended tax returns for tax years ended December 31, 2012 through December 31, 2014. As a result of the filing of the amended returns, the Company released $1.1 million of unrecognized tax benefits, which were previously netted with net operating loss deferred tax assets. As a result, the filing of the amended returns had no impact on the current year tax provision.

In 2016, the Company early adopted ASU 2016-09 which requires all excess tax benefits and deficiencies on share-based payment awards to be recognized as income tax expense or benefit in the statement of operations. The adoption of this standard resulted in a $0.3 million tax benefit that would have previously been recorded to additional paid-in capital.

The Company does not expect to record any material reductions in the measurement of its unrecognized tax benefits within the next twelve months.

The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision. As of December 31, 2016 and 2015, the Company had no accrued interest or penalties related to uncertain tax positions, and no amounts have been recognized in the Company’s statements of operations or comprehensive loss.

The Company files income tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by various taxing authorities in the United States, Japan, and Singapore. There are currently no pending income tax examinations. Tax years from 2012 to the present are still open to examination in the United States, from 2008 to the present in Japan, and from 2012 to the present in Singapore. To the extent that the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the tax authorities to the extent utilized in a future period.

As of December 31, 2016 and 2015, $1.7 million and less than $0.1 million, respectively, of cash was held by the subsidiaries outside of Singapore. The Company does not provide for Singapore income tax or foreign withholding taxes on foreign unrepatriated earnings, as the Company intends to permanently reinvest undistributed earnings in its foreign subsidiaries. If the Company decides to change this assertion in the future to repatriate any additional foreign earnings, the Company may be required to accrue and pay taxes. Because of the complexity of Singapore and foreign tax rules applicable to the distribution of earnings from foreign subsidiaries to Singapore, the determination of the unrecognized deferred tax liability on these earnings is not practicable.

Utilization of the net operating loss carryforwards and research and development tax credit carryforwards in the United States may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended (the “Code”), due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain shareholders or public groups in the shares of a corporation by more than 50% over a three-year period. In 2015, the Company completed a study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since its formation. The results of this study indicated that the Company experienced ownership changes as defined by Section 382 of the Code. Management has determined that the limitations will not have a material impact on the Company’s ability to utilize its research and development credit carryforwards to offset future tax liabilities.

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 31, 2016
Postemployment Benefits [Abstract]
Employee Benefit Plans	11. EMPLOYEE BENEFIT PLANS The Company has a 401(k) retirement and savings plan (the “401(k) Plan”) covering all U.S.-based employees. The 401(k) Plan allows employees to make pre-tax contributions up to the maximum allowable amount set by the IRS. Under the 401(k) Plan, the Company may make discretionary contributions as approved by the board of directors. The Company did not make contributions to the 401(k) Plan during the years ended December 2016, 2015, or 2014. The Company has a J401(k) defined contribution pension plan covering all Japan-based permanent employees that was adopted in 2010. The J401(k) defined contribution pension plan allows the Company to make pre-tax contributions up to the maximum allowable amount set by the chief officer of the Kyushu Regional Bureau of Health and Welfare’s approval and company’s wage regulation. Under the J401(k) defined contribution pension plan, the Company may make discretionary contributions as approved by the board of directors. The Company has made contributions of approximately $7 thousand, $7 thousand, and $5 thousand during the years ended December 31, 2016, 2015 and 2014, respectively.

Related Parties

12 Months Ended

Dec. 31, 2016

Related Parties

12. RELATED PARTIES

The Company had the following related party transactions for the periods presented in the accompanying consolidated financial statements, which have not otherwise been discussed in these notes to the consolidated financial statements:

•

The Company had cash of $118 thousand and $115 thousand at December 31, 2016 and 2015, respectively, in depository accounts with one of its investors, Kagoshima Bank, Ltd., an affiliate of one of its shareholders, Kagoshima Shinsangyo Sousei Investment Limited Partnership.

•

The Company made payments for lease rentals and other related expenses in the amount of $60 thousand and $178 thousand to Shin Nippon Biomedical Laboratories Ltd. (“SNBL”), a related party, for the years ended December 31, 2016 and 2015, respectively.

•

Pursuant to the terms of various service agreements with SNBL, which the Company paid SNBL $362 thousand for the year ended December 31, 2016 for contract research services provided to the Company and its affiliates. There were no payments made to SNBL related to these agreements for the year ended December 31, 2015.

•

In 2012, the Company entered into a consulting agreement with Dr. Gregory L. Verdine for services in the capacity as a scientific advisor. The consulting agreement does not have a specific term and may be terminated by either party upon 14 days’ prior written notice. Pursuant to the consulting agreement, the Company pays Dr. Verdine approximately $13 thousand per month, plus reimbursement for certain expenses.

•

The Company also has an informal consulting arrangement with Dr. Takeshi Wada for scientific advisory services in the amount of 250 thousand Japanese yen, or approximately $2 thousand, per month, plus reimbursement of certain expenses.

Geographic Data

12 Months Ended

Dec. 31, 2016

Text Block [Abstract]

Geographic Data

13. GEOGRAPHIC DATA

The Company’s long-lived assets consist of property and equipment, net, and are located in the following geographical areas:

	December 31, 2016		December 31, 2015
	(in thousands)
Asia	$	136	$	578
United States		8,471		2,211
Total long-lived assets	$	8,607	$	2,789

Selected Quarterly Financial Information (Unaudited)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Information (Unaudited)

14. SELECTED QUARTERLY FINANCIAL INFORMATION (UNAUDITED)

Selected quarterly results from operations for the years ended December 31, 2016 and 2015 are as follows:

	2016 Quarter Ended
	March 31			June 30			September 30			December 31
	(in thousands, except for per share data)
Revenues	$	-		$	417		$	392		$	676
Operating expenses		7,952			12,055			17,625			19,180
Loss from operations		(7,952	)		(11,638	)		(17,233	)		(18,504	)
Net loss		(7,847	)		(11,565	)		(17,535	)		(18,454	)
Basic and diluted net loss per ordinary share	$	(0.36	)	$	(0.51	)	$	(0.75	)	$	(0.79	)

	2015 Quarter Ended
	March 31			June 30			September 30			December 31
	(in thousands, except for per share data)
Revenues	$	26		$	126		$	—		$	—
Operating expenses		3,491			3,755			4,990			7,214
Loss from operations		(3,465	)		(3,629	)		(4,990	)		(7,214	)
Net loss		(3,465	)		(3,700	)		(4,936	)		(7,099	)
Basic and diluted net loss per ordinary share	$	(0.42	)	$	(0.40	)	$	(0.54	)	$	(0.46	)

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Cash Equivalents

Principles of Consolidation

Use of Estimates

Segment Data

Foreign Currency Translation

Fair Value of Financial Instruments

Level 1—Unadjusted quoted prices in active markets that are accessible at the measurement date of identical, unrestricted assets.

Concentration of Credit Risk

Restricted Cash

Property and Equipment

Equipment, Furniture and Software	3-7 years
Leasehold Improvements	Shorter of life of lease or useful life

Impairment of Long-Lived Assets

Revenue Recognition

•

persuasive evidence of an arrangement exists;

•

delivery has occurred or services have been rendered;

•

the seller’s price to the buyer is fixed or determinable; and

•

collectability is reasonably assured.

Product Revenue

The Company has had no product revenue to date.

Research and Development Costs

Net Loss per Share

License Agreements and Patent Costs

Costs associated with licenses of technology and patent costs are expensed as incurred and are generally included in research and development expense in the consolidated statements of operations.

Share-Based Compensation

•

Dividend Rate. The expected dividend was assumed to be zero as the Company has never paid dividends and has no current plans to do so.

Income Taxes

The Company recognizes interest and penalties related to uncertain tax positions in the income tax provision on the consolidated statements of operations.

Early Adoption of Accounting Standards Update No. 2016-09

Recently Issued Accounting Pronouncements

Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Schedule of Estimated Useful Life of Assets

Depreciation is calculated on a straight-line basis over the following estimated useful lives of the assets:

Equipment, Furniture and Software	3-7 years
Leasehold Improvements	Shorter of life of lease or useful life

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2016

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net, consists of the following

	December 31,
	2016			2015
	(in thousands)
Furniture and equipment	$	7,231		$	3,936
Software		43			—
Leasehold improvements		1,964			267
Fixed assets in progress		1,863			198
Total		11,101			4,401
Less accumulated depreciation and amortization		(2,494	)		(1,612	)
Property and equipment, net	$	8,607		$	2,789

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2016

Payables And Accruals [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:

	December 31,
	2016		2015
	(in thousands)
Accrued compensation	$	2,480	$	—
Accrued professional fees		417		401
Accrued vacation		589		191
Other		959		353
Total accrued expenses and other current liabilities	$	4,445	$	945

Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

Summary of Share Option Activity

Share option activity under the 2014 Plan is summarized as follows:

	Number of Shares			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)⁽¹⁾
Options outstanding as of January 1, 2016		2,215,342		$	3.88		9.30	$	26,740
Granted		1,479,200		20.79
Exercised		(75,746	)	3.42					1,887
Cancelled or forfeited		(41,030	)	10.23
Outstanding as of December 31, 2016		3,577,766		$	10.58		8.68	$	56,780
Options exercisable as of December 31, 2016		1,248,343		$	3.10		8.24	$	28,775
Options unvested as of December 31, 2016		2,329,423		$	14.58		8.92	$	28,006

(1)

Summary of RSU Activity

RSU activity for the year ended December 31, 2016 is summarized as follows:

	RSUs		Average Grant Date Fair Value (in dollars per share)
RSUs Outstanding as of January 1, 2016		—	$	—
Granted		22,750		21.69
RSUs Outstanding at December 31, 2016		22,750	$	21.69

Summary of Share-based Compensation Expense Classified in Consolidated Statements of Operations

Share-based compensation expense for the year ended December 31, 2016 and 2015 was classified in the consolidated statements of operations as follows:

	For the Year Ended December 31,
	2016		2015
	(in thousands)
Research and development expenses	$	4,936	$	2,268
General and administrative expenses		1,911		1,756
Total share-based compensation	$	6,847	$	4,024

Employee Stock Option [Member]

Summary of Fair Value of Share Options Granted

The assumptions used in the Black-Scholes option pricing model to determine the fair value of share options granted to employees during the period were as follows:

	For the Year Ended December 31,
	2016	2015
Risk-free interest rate	1.15% – 2.18%	1.56% - 1.89%
Expected term (in years)	3.00 – 6.25	5.52 - 6.12
Expected volatility	60.89% – 68.76%	62.14% - 71.02%
Expected dividend yield	0%	0%
Exercise price	$14.11 – 36.43	$2.47 - 13.08
Fair value of ordinary share	$14.11 – 36.43	$4.41 - 13.08

Non-Employees Stock Option [Member]

Summary of Fair Value of Share Options Granted

The assumptions used in the Black-Scholes option pricing model to determine the fair value of share options granted to non-employees during the period were as follows:

		Year Ended December 31, 2015
Risk-free interest rate		2.06% - 2.35%
Expected term (in years)		9.19 - 10.00
Expected volatility		62.65% - 69.80%
Expected dividend yield		0%
Exercise price		$2.47
Fair value of ordinary share		$4.41 - 15.95

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2016

Commitments And Contingencies Disclosure [Abstract]

Future Minimum Lease Payments Under Operating Leases

Future minimum lease payments under the Company’s non-cancelable operating leases as of December 31, 2016, are as follows:

For the Year Ended December 31,	Amount
	(in thousands)
2017		1,954
2018		4,660
2019		5,798
2020		5,972
2021		6,151
Thereafter		33,418
		57,953

Net Loss Per Ordinary Share (Tables)

12 Months Ended

Dec. 31, 2016

Earnings Per Share [Abstract]

Summary of Basic and Diluted Net Loss Per Ordinary Share Outstanding

Basic loss per share is computed by dividing net loss attributable to ordinary shareholders by the weighted-average number of ordinary shares outstanding:

	Year Ended December 31,
	2016			2015			2014
	(in thousands except share and per share data)
Numerator:
Net loss attributable to ordinary shareholders	$	(55,401	)	$	(19,200	)	$	(5,229	)
Denominator:
Weighted-average ordinary shares outstanding		22,800,628			10,501,455			3,911,556
Net loss per share, basic and diluted	$	(2.43	)	$	(1.83	)	$	(1.34	)

Anti-Dilutive Shares Excluded from Calculation of Diluted Net Loss Per Ordinary Share

	As of December 31,
	2016		2015
Options to purchase ordinary shares		3,577,766		2,215,432
Restricted share units		22,750		—
Series A preferred shares		3,901,348		3,901,348

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Components of Loss Before Income Taxes

The components of loss before income taxes were as follows:

	Year Ended December 31,
	2016			2015			2014
	(in thousands)
Singapore	$	(53,387	)	$	(16,534	)	$	(4,542	)
Rest of world		(1,398	)		(2,622	)		(603	)
Loss before income taxes	$	(54,785	)	$	(19,156	)	$	(5,145	)

Deferred Components of Benefit (Provision) for Income Taxes

The deferred components of the benefit (provision) for income taxes were as follows:

	Year Ended December 31,
	2016			2015			2014
	(in thousands)
Current tax benefit (provision):
Singapore taxes	$	—		$	—		$	—
Rest of world taxes		(1,180	)		(8	)		—
Total current benefit (provision) income taxes	$	(1,180	)	$	(8	)	$	—
Deferred tax benefit (provision):
Singapore taxes	$	—		$	—		$	—
Rest of world taxes		564			(36	)		(84	)
Total deferred benefit (provision) income taxes	$	564		$	(36	)	$	(84	)
Total benefit (provision) income taxes	$	(616	)	$	(44	)	$	(84	)

Components of Deferred Tax Assets

The components of the Company’s deferred tax assets as of December 31, 2016 and 2015 are as follows:

	December 31,
	2016			2015
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	16,046		$	7,037
Research and development credits		449			460
Accrued expenses		242			58
Share-based compensation		1,024			218
Other		102			149
Total deferred tax assets		17,863			7,922
Valuation allowance		(15,999	)		(7,466	)
Net deferred tax assets		1,864			456
Depreciation		(1,090	)		(246	)
Total deferred tax liability		(1,090	)		(246	)
Net deferred tax asset (liability)	$	774		$	210

Summary of Valuation Allowance

A roll-forward of the valuation allowance for the years ended December 31, 2016 and 2015 is as follows:

	Year Ended December 31,
	2016			2015
	(in thousands)
Balance at beginning of year	$	7,466		$	2,658
Increase in valuation allowance		8,774			4,818
Reversal of valuation allowance		(282	)		—
Effect of foreign currency translation		41			(10	)
Balance at end of year	$	15,999		$	7,466

Summary of Activity in Unrecognized Tax Benefits

A summary of activity in the Company’s unrecognized tax benefits is as follows:

	2016			2015		2014
	(in thousands)
Unrecognized tax benefit during the year	$	1,280		$	1,025	$	901
Tax positions released related to prior years		(1,066	)		—		—
Tax positions related to the current year		2,129			255		124
Unrecognized tax benefit end of year	$	2,343		$	1,280	$	1,025

Singapore [Member]

Reconciliation of Statutory Income Tax Rate

A reconciliation of the Singapore statutory income tax rate to the Company’s effective income tax rate is as follows:

	Year Ended December 31,
	2016			2015			2014
Singapore statutory income tax rate		17.0	%		17.0	%		17.0	%
Research and development tax credits		3.1			2.3			2.2
Permanent differences		(0.9	)		5.5			—
Foreign exchange loss		—			—			2.0
Changes in reserves for uncertain tax positions		(3.6	)		(1.2	)		(2.2	)
Foreign rate differential		(0.1	)		1.2			4.5
Other		(0.9	)		0.2			—
Change in deferred tax asset valuation allowance		(15.7	)		(25.2	)		(25.1	)
Effective income tax rate		(1.1	)%		(0.2	)%		(1.6	)%

Geographic Data (Tables)

12 Months Ended

Dec. 31, 2016

Text Block [Abstract]

Summary of Long-Lived Assets by Geographical Areas

The Company’s long-lived assets consist of property and equipment, net, and are located in the following geographical areas:

	December 31, 2016		December 31, 2015
	(in thousands)
Asia	$	136	$	578
United States		8,471		2,211
Total long-lived assets	$	8,607	$	2,789

Selected Quarterly Financial Information (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Schedule of Selected Quarterly Results from Operations

Selected quarterly results from operations for the years ended December 31, 2016 and 2015 are as follows:

	2016 Quarter Ended
	March 31			June 30			September 30			December 31
	(in thousands, except for per share data)
Revenues	$	-		$	417		$	392		$	676
Operating expenses		7,952			12,055			17,625			19,180
Loss from operations		(7,952	)		(11,638	)		(17,233	)		(18,504	)
Net loss		(7,847	)		(11,565	)		(17,535	)		(18,454	)
Basic and diluted net loss per ordinary share	$	(0.36	)	$	(0.51	)	$	(0.75	)	$	(0.79	)

	2015 Quarter Ended
	March 31			June 30			September 30			December 31
	(in thousands, except for per share data)
Revenues	$	26		$	126		$	—		$	—
Operating expenses		3,491			3,755			4,990			7,214
Loss from operations		(3,465	)		(3,629	)		(4,990	)		(7,214	)
Net loss		(3,465	)		(3,700	)		(4,936	)		(7,099	)
Basic and diluted net loss per ordinary share	$	(0.42	)	$	(0.40	)	$	(0.54	)	$	(0.46	)

Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	May 05, 2016 Program	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Significant Accounting Policies [Line Items]
Restricted cash		$ 3,601,000	$ 1,055,000
Impairment charges		$ 0
Expected dividend rate		0.00%
Description of Income tax benefit, likelihood of realized upon ultimate settlement		The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement.
Current year tax benefit		$ (1,180,000)	(8,000)
Accounting Standards Update 2016-09 [Member]
Significant Accounting Policies [Line Items]
Current year tax benefit		$ 300,000
Minimum [Member]
Significant Accounting Policies [Line Items]
Income tax examination, likelihood of settlement, percentage		50.00%
Pfizer Inc. [Member]
Significant Accounting Policies [Line Items]
Number of research programs, counterparty nomination \| Program	5
Lexington, MA [Member]
Significant Accounting Policies [Line Items]
Restricted cash		$ 2,600,000
Cambridge MA [Member]
Significant Accounting Policies [Line Items]
Restricted cash		$ 1,000,000	$ 1,100,000

Significant Accounting Policies - Schedule of Estimated Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2016
Equipment, Furniture and Software [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Property and equipment, estimated useful lives	3 years
Equipment, Furniture and Software [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Property and equipment, estimated useful lives	7 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, estimated useful lives	Shorter of life of lease or useful life

Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment gross	$ 11,101	$ 4,401
Less accumulated depreciation and amortization	(2,494)	(1,612)
Property and equipment, net	8,607	2,789
Furniture and Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment gross	7,231	3,936
Software [Member]
Property Plant And Equipment [Line Items]
Property and equipment gross	43
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment gross	1,964	267
Fixed Assets in Progress [Member]
Property Plant And Equipment [Line Items]
Property and equipment gross	$ 1,863	$ 198

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 784	$ 594	$ 281

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued compensation	$ 2,480
Accrued professional fees	417	$ 401
Accrued vacation	589	191
Other	959	353
Total accrued expenses and other current liabilities	$ 4,445	$ 945

Pfizer Collaboration and Share Purchase Agreement - Additional Information (Detail)			12 Months Ended
	Aug. 31, 2016 USD ($)	May 05, 2016 USD ($) Program Product $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Equity investment aggregate purchase price			$ 30,000,000	$ 11,631,000	$ 5,585,000
Current portion of deferred revenue			$ 2,705,000
Pfizer Inc. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of research programs, counterparty nomination \| Program		5
Research term, description			Under the Pfizer Collaboration Agreement, the parties agreed to collaborate during the four-year Research Term. During the Research Term, the Company is responsible to use its commercially reasonable efforts to advance up to five programs through to the selection of clinical candidates. At that stage, Pfizer may elect to license any of these Pfizer Programs exclusively and to have exclusive rights to undertake the clinical development of the resulting clinical candidates into products and the potential commercialization of any such products thereafter.
Deferred revenue			$ 11,000,000
Collaboration agreement, additional period after research program		2 years
Revenue recognized			1,500,000
Current portion of deferred revenue			$ 2,700,000
Maximum [Member] \| Pfizer Inc. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Expected earnings from milestone payments under research program		$ 871,000,000
Research, License and Option Agreement [Member] \| Pfizer Inc. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront amount related to research and development services		$ 10,000,000
Number of potential products are successfully developed and commercialized \| Product		5
Collaboration agreement refundable		$ 0
Shares issued under equity agreement \| shares		1,875,000
Equity investment aggregate purchase price		$ 30,000,000
Purchase price per share \| $ / shares		$ 16.00
Collaborative agreement research term		4 years
Milestone payment received	$ 2,500,000
Upfront payment allocated	3,000,000	$ 7,000,000
Deferred revenue	3,500,000
Collaboration agreement termination period		90 days
Research, License and Option Agreement [Member] \| Pfizer Inc. [Member] \| Option at Inception [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	1,000,000
Research, License and Option Agreement [Member] \| Pfizer Inc. [Member] \| Option at Exercising [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 2,500,000

Share Capital - Ordinary Shares - Additional Information (Detail)		1 Months Ended					12 Months Ended
	May 05, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Nov. 30, 2015 $ / shares shares	Mar. 31, 2015 shares	Jan. 31, 2015 USD ($) $ / shares shares	Feb. 28, 2014 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) Vote / shares $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) shares	Sep. 30, 2015 USD ($)
Class of Stock [Line Items]
Shares issued		21,551,423					23,502,169	21,551,423
Notes payable, related parties \| $						$ 9,600,000			$ 9,602,000
Notes payable convert to shares						1,515,596
Proceeds from sale of common stock \| $								$ 101,444,000
Equity investment aggregate purchase price \| $							$ 30,000,000	$ 11,631,000	$ 5,585,000
Common stock, par value \| $ / shares
Ordinary share holder, voting right							One vote for each ordinary share
Minimum percentage of issued and outstanding ordinary shares required for approval							75.00%
Voting rights, votes per share \| Vote / shares							1
Preferred stock, aggregate liquidation preference \| $							$ 10,000			$ 10,000
Singapore [Member]
Class of Stock [Line Items]
Common stock, par value \| $ / shares
Common stock, authorized							0
Research, License and Option Agreement [Member] \| Pfizer Inc. [Member]
Class of Stock [Line Items]
Shares issued under equity agreement	1,875,000
Purchase price per share \| $ / shares	$ 16.00
Equity investment aggregate purchase price \| $	$ 30,000,000
IPO [Member]
Class of Stock [Line Items]
Number of shares issued and sold			6,375,000
Shares issued, price per share \| $ / shares			$ 16.00
Equity investment aggregate purchase price \| $								$ 100,366,000
Underwriters Over-Allotment Option [Member]
Class of Stock [Line Items]
Number of shares issued and sold		618,126
Shares issued, price per share \| $ / shares		$ 16.00						$ 16.00
Proceeds from sale of common stock \| $		$ 100,400,000
Executive Officer [Member]
Class of Stock [Line Items]
Options to purchase common stock granted				190,856
Ordinary Shares [Member]
Class of Stock [Line Items]
Notes payable convert to shares						1,515,596
Shares issued under equity agreement							1,875,000	4,769,077	2,263,291
Equity investment aggregate purchase price \| $							$ 30,000,000	$ 11,631,000	$ 5,585,000
Ordinary Shares [Member] \| IPO [Member]
Class of Stock [Line Items]
Shares issued under equity agreement								6,993,126
Equity investment aggregate purchase price \| $								$ 100,366,000
Series A Preferred Shares [Member]
Class of Stock [Line Items]
Notes payable convert to shares						2,365,139
Third-Party Investor [Member]
Class of Stock [Line Items]
Shares issued					4,769,077	2,263,291
Shares issued, Per Share \| $ / shares					$ 2.47	$ 2.47
Proceeds from issuance of shares \| $					$ 11,600,000	$ 5,600,000

Share Capital - Series A Preferred Shares - Additional Information (Detail) - USD ($)		1 Months Ended	12 Months Ended
	Aug. 14, 2015	Feb. 28, 2014	Dec. 31, 2014	Dec. 31, 2016	Sep. 30, 2015
Class of Stock [Line Items]
Notes payable, related parties		$ 9,600,000	$ 9,602,000
Notes payable convert to shares		1,515,596
Minimum number of shares to be held to receive right to purchase new securities	1,212,477
Percentage of voting Right	50.00%
Preferred stock, aggregate liquidation preference				$ 10,000	$ 10,000
Series A Preferred Shares [Member]
Class of Stock [Line Items]
Notes payable convert to shares		2,365,139
Share issued for conversion	3,901,348
Preferred stock liquidation preference, per share					$ 0.0024743
Aggregate preferred stock liquidation preference, per share					$ 10.00
Series A Preferred Shares [Member] \| Singapore [Member]
Class of Stock [Line Items]
Preferred stock, par value
Preferred stock, shares authorized				0
Series B Preferred Shares [Member]
Class of Stock [Line Items]
Preferred stock, voting rights	56.00%
Preferred stock liquidation preference, per share				$ 12.37

Share Capital - Series B Preferred Shares - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Aug. 14, 2015	Dec. 31, 2016	Dec. 31, 2015	Nov. 16, 2015
Class of Stock [Line Items]
Proceeds from issuance of preferred shares			$ 62,532
IPO [Member]
Class of Stock [Line Items]
Convertible preferred stock converted into common stock				5,334,892
Sale of common stock, Date		Nov. 16, 2015
Series B Preferred Shares [Member]
Class of Stock [Line Items]
Preferred stock, shares issued	5,334,892
Preferred shares issued, Per Share	$ 12.37
Proceeds from issuance of preferred shares	$ 62,500
Preferred stock liquidation preference, per share		$ 12.37

Share-Based Compensation - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Jul. 31, 2016	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			$ 6,847,000	$ 4,024,000
Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase common stock granted		190,856
Restricted Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, granted	22,750		22,750
Average grant date fair value, granted	$ 21.69		$ 21.69
Unrecognized stock-based compensation weighted average recognition period			6 months 11 days
Unrecognized stock-based compensation expense			$ 300,000
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares reserved for issuance					1,763,714
Number of shares authorized (in shares)				5,064,544
Contractual life of options			10 years
Options to purchase common stock granted			1,479,200	2,215,342	0
Number of options forfeitures			41,030	0
Number of options cancelled			0	0
Ordinary shares available for future grant			1,197,426
Share-based compensation expense		$ 900,000	$ 6,800,000	$ 4,000,000	$ 0
Unrecognized stock-based compensation weighted average recognition period			2 years 2 months 23 days
Weighted average grant date fair value per granted option			$ 30.23	$ 6.64
Aggregate fair value of options vested			$ 4,700,000
2014 Plan [Member] \| Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase common stock granted		190,856
2014 Plan [Member] \| Non-Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase common stock granted			0
Share-based compensation expense			$ 2,700,000	$ 1,600,000
Unrecognized stock-based compensation expense			3,800,000
2014 Plan [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense			$ 18,000,000
2014 Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period			3 years
2014 Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period			4 years

Share-Based Compensation - Summary of Share Option Activity (Detail) - 2014 Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Number of Shares, Beginning Balance	2,215,342
Granted, Number of Shares	1,479,200	2,215,342	0
Exercised, Number of Shares	(75,746)
Cancelled or forfeited, Number of Shares	(41,030)	0
Options outstanding, Number of Shares, Ending Balance	3,577,766	2,215,342
Options exercisable, Number of Shares	1,248,343
Option unvested, Number of Shares	2,329,423
Options outstanding, Weighted Average Exercise Price, Beginning Balance	$ 3.88
Granted, Weighted Average Exercise Price	20.79
Exercised, Weighted Average Exercise Price	3.42
Cancelled or forfeited, Weighted Average Exercise Price	10.23
Option outstanding, Weighted Average Exercise Price, Ending Balance	10.58	$ 3.88
Options exercisable, Weighted Average Exercise Price	3.10
Options unvested, Weighted Average Exercise Price	$ 14.58
Options outstanding, Weighted Average Remaining Contractual Term	8 years 8 months 5 days	9 years 3 months 18 days
Options exercisable, Weighted Average Remaining Contractual Term	8 years 2 months 27 days
Options unvested, Weighted Average Remaining Contractual Term	8 years 11 months 1 day
Options outstanding, Aggregate Intrinsic Value	$ 56,780	$ 26,740
Options Exercised, Aggregate Intrinsic Value	1,887
Options exercisable, Aggregate Intrinsic Value	28,775
Options unvested, Aggregate Intrinsic Value	$ 28,006

Share-Based Compensation - Summary of RSU Activity (Detail) - Restricted Share Units [Member] - $ / shares	1 Months Ended	12 Months Ended
	Jul. 31, 2016	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of Shares	22,750	22,750
Outstanding, Number of Shares, Ending Balance		22,750
Granted, Average Grant Date Fair Value	$ 21.69	$ 21.69
Outstanding, Average Grant Date Fair Value, Ending Balance		$ 21.69

Share-Based Compensation - Summary of Fair Value of Share Options Granted to Employees (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.15%	1.56%
Risk-free interest rate, maximum	2.18%	1.89%
Expected volatility, minimum	60.89%	62.14%
Expected volatility, maximum	68.76%	71.02%
Expected dividend yield	0.00%	0.00%
Employee Stock Option [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	3 years	5 years 6 months 7 days
Exercise price	$ 14.11	$ 2.47
Fair value of ordinary share	$ 14.11	$ 4.41
Employee Stock Option [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 3 months	6 years 1 month 13 days
Exercise price	$ 36.43	$ 13.08
Fair value of ordinary share	$ 36.43	$ 13.08

Share-Based Compensation - Summary of Fair Value of Share Options Granted to Non-Employees (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%
Non-Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum		2.06%
Risk-free interest rate, maximum		2.35%
Expected volatility, minimum		62.65%
Expected volatility, maximum		69.80%
Expected dividend yield		0.00%
Exercise price		$ 2.47
Fair value of ordinary share, minimum		4.41
Fair value of ordinary share, maximum		$ 15.95
Non-Employees Stock Option [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)		9 years 2 months 9 days
Non-Employees Stock Option [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)		10 years

Share-Based Compensation - Summary of Share-based Compensation Expense Classified in Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	$ 6,847	$ 4,024
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	4,936	2,268
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	$ 1,911	$ 1,756

Commitments And Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments And Contingencies [Line Items]
Issuance of letter of credit recorded as restricted cash	$ 3,601,000	$ 1,055,000
Property and equipment, net	8,607,000	2,789,000
Lease rent expense	1,500,000	500,000	$ 300,000
Shin Nippon Biomedical Laboratories Ltd. (SNBL) [Member]
Commitments And Contingencies [Line Items]
Lease rent expense	$ 60,000	178,000
Laboratory Equipment [Member]
Commitments And Contingencies [Line Items]
Capital lease agreement period	3 years
Capital assets purchased	$ 300,000	300,000
Capital leases accumulated amortization	100,000
Laboratory Equipment [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Capital leases accumulated amortization		100,000
Lexington, MA [Member]
Commitments And Contingencies [Line Items]
Issuance of letter of credit recorded as restricted cash	2,600,000
Lexington, MA [Member] \| Construction Costs [Member]
Commitments And Contingencies [Line Items]
Property and equipment, net	$ 900,000
2016 Lexington, MA Lease [Member]
Commitments And Contingencies [Line Items]
Lease agreement term	10 years 9 months
Lease renewal term description	10 year and 9 month lease, which includes two successive five year renewal options
Lease extension period	5 years
Tenant improvement allowances	$ 11,500,000
Tenant improvement allowances received	100,000
2016 Lexington, MA Lease [Member] \| Letter of Credit [Member]
Commitments And Contingencies [Line Items]
Issuance of letter of credit recorded as restricted cash	$ 2,600,000
2015 Cambridge, MA Lease [Member]
Commitments And Contingencies [Line Items]
Lease agreement term	7 years 6 months
Lease extension period	5 years
2015 Cambridge, MA Lease [Member] \| Letter of Credit [Member]
Commitments And Contingencies [Line Items]
Issuance of letter of credit recorded as restricted cash	$ 1,000,000	1,000,000
2015 Boston, MA Lease Termination [Member]
Commitments And Contingencies [Line Items]
Guarantee agreement termination date	Aug. 31, 2019
2015 Boston, MA Lease Termination [Member] \| Shin Nippon Biomedical Laboratories Ltd. (SNBL) [Member]
Commitments And Contingencies [Line Items]
Lease agreement term	3 years 6 months
Accelerated depreciation		200,000
Additional exit costs related to termination of sublease agreement		$ 100,000
Maximum amount of guarantee for sublease	$ 600,000

Commitments And Contingencies - Future Minimum Lease Payments Under Operating Leases (Detail) $ in Thousands	Dec. 31, 2016 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2017	$ 1,954
2018	4,660
2019	5,798
2020	5,972
2021	6,151
Thereafter	33,418
Total	$ 57,953

Net Loss Per Ordinary Share - Summary of Basic and Diluted Net Loss Per Ordinary Share Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net loss attributable to ordinary shareholders									$ (55,401)	$ (19,200)	$ (5,229)
Denominator:
Weighted-average ordinary shares outstanding									22,800,628	10,501,455	3,911,556
Net loss per share, basic and diluted	$ (0.79)	$ (0.75)	$ (0.51)	$ (0.36)	$ (0.46)	$ (0.54)	$ (0.40)	$ (0.42)	$ (2.43)	$ (1.83)	$ (1.34)

Net Loss Per Ordinary Share - Anti-Dilutive Shares Excluded from Calculation of Diluted Net Loss Per Ordinary Share (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Series A Preferred Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from calculation of diluted net loss per share	3,901,348	3,901,348
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from calculation of diluted net loss per share	3,577,766	2,215,432
Restricted Share Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from calculation of diluted net loss per share	22,750

Income Taxes - Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Loss before income taxes	$ (54,785)	$ (19,156)	$ (5,145)
Singapore [Member]
Income Taxes [Line Items]
Loss before income taxes	(53,387)	(16,534)	(4,542)
Rest Of World [Member]
Income Taxes [Line Items]
Loss before income taxes	$ (1,398)	$ (2,622)	$ (603)

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Income tax benefit (provision)	$ (616,000)	$ (44,000)	$ (84,000)
Net operating loss carryovers	16,046,000	7,037,000
Reversal of valuation allowance	282,000
Increase in valuation allowance	8,500,000	4,800,000	1,300,000
Gross unrecognized tax benefit	2,343,000	1,280,000	1,025,000	$ 901,000
Unrecognized tax benefit that could affect annual effective tax rate if recognized	1,700,000
Accrued interest and penalties related to uncertain tax positions	0	0
Interest and penalties recognized in statement of operations	0	0
Subsidiaries Outside of Singapore [Member]
Income Taxes [Line Items]
Cash held by subsidiaries	1,700,000
Adjustments for New Accounting Principle, Early Adoption [Member]
Income Taxes [Line Items]
Income tax benefit (provision)	300,000
Gross unrecognized tax benefit	1,100,000
Federal [Member]
Income Taxes [Line Items]
Research and development tax credit carryforward	$ 200,000	700,000
Tax credit carryforward expiration year	2031
Federal [Member] \| Research and Development Credit Carryforwards [Member]
Income Taxes [Line Items]
Reversal of valuation allowance	$ 300,000
State [Member]
Income Taxes [Line Items]
Research and development tax credit carryforward	$ 300,000	400,000
Tax credit carryforward expiration year	2028
Maximum [Member] \| Subsidiaries Outside of Singapore [Member]
Income Taxes [Line Items]
Cash held by subsidiaries		100,000
United States [Member]
Income Taxes [Line Items]
Income tax benefit (provision)	$ (600,000)		(100,000)
Tax years open to examination	2012
United States [Member] \| Maximum [Member]
Income Taxes [Line Items]
Income tax benefit (provision)		(100,000)
Japan [Member]
Income Taxes [Line Items]
Income tax benefit (provision)	$ 0	0	0
Net operating loss carryovers	$ 5,300,000	4,300,000
Operating loss carryforwards expiration year	2017
Tax years open to examination	2008
Singapore [Member]
Income Taxes [Line Items]
Income tax benefit (provision)	$ 0	0	$ 0
Net operating loss carryovers	$ 84,000,000	$ 31,800,000
Tax years open to examination	2012

Income Taxes - Deferred Components of Benefit (Provision) for Income Taxes (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current tax benefit (provision):
Current year tax benefit	$ (1,180,000)	$ (8,000)
Deferred tax benefit (provision):
Total deferred benefit (provision) income taxes	564,000	(36,000)	$ (84,000)
Total benefit (provision) income taxes	(616,000)	(44,000)	(84,000)
Singapore [Member]
Deferred tax benefit (provision):
Total benefit (provision) income taxes	0	0	0
Rest Of World [Member]
Current tax benefit (provision):
Current year tax benefit	(1,180,000)	(8,000)
Deferred tax benefit (provision):
Total deferred benefit (provision) income taxes	$ 564,000	$ (36,000)	$ (84,000)

Income Taxes - Reconciliation of Statutory Income Tax Rate (Detail) - Singapore [Member]	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Singapore statutory income tax rate	17.00%	17.00%	17.00%
Research and development tax credits	3.10%	2.30%	2.20%
Permanent differences	(0.90%)	5.50%
Foreign exchange loss			2.00%
Changes in reserves for uncertain tax positions	(3.60%)	(1.20%)	(2.20%)
Foreign rate differential	(0.10%)	1.20%	4.50%
Other	(0.90%)	0.20%
Change in deferred tax asset valuation allowance	(15.70%)	(25.20%)	(25.10%)
Effective income tax rate	(1.10%)	(0.20%)	(1.60%)

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 16,046	$ 7,037
Research and development credits	449	460
Accrued expenses	242	58
Share-based compensation	1,024	218
Other	102	149
Total deferred tax assets	17,863	7,922
Valuation allowance	(15,999)	(7,466)	$ (2,658)
Net deferred tax assets	1,864	456
Depreciation	(1,090)	(246)
Total deferred tax liability	(1,090)	(246)
Net deferred tax asset (liability)	$ 774	$ 210

Income Taxes - Summary of Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets Net Of Valuation Allowance [Abstract]
Balance at beginning of year	$ 7,466	$ 2,658
Increase in valuation allowance	8,774	4,818
Reversal of valuation allowance	(282)
Effect of foreign currency translation	41	(10)
Balance at end of year	$ 15,999	$ 7,466

Income Taxes - Summary of Activity in Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Unrecognized tax benefit during the year	$ 1,280	$ 1,025	$ 901
Tax positions released related to prior years	(1,066)
Tax positions related to the current year	2,129	255	124
Unrecognized tax benefit end of year	$ 2,343	$ 1,280	$ 1,025

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
401(k) Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Discretionary contributions to defined contribution pension plan	$ 0	$ 0	$ 0
J401(k) [Member]
Defined Contribution Plan Disclosure [Line Items]
Discretionary contributions to defined contribution pension plan	$ 7	$ 7	$ 5

Related Parties - Additional Information (Detail) ¥ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 JPY (¥)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Related Party Transaction [Line Items]
Lease rentals and other related expenses	$ 1,500,000		$ 500,000	$ 300,000
Third-Party Investor [Member]
Related Party Transaction [Line Items]
Related party transaction amount	118,000		115,000
Shin Nippon Biomedical Laboratories Ltd. (SNBL) [Member]
Related Party Transaction [Line Items]
Lease rentals and other related expenses	60,000		178,000
Payment for contract research services	$ 362,000		$ 0
Scientific Advisor [Member] \| Consulting Agreement [Member]
Related Party Transaction [Line Items]
Consulting agreement termination notice period	14 days	14 days
Consulting service expenses	$ 13,000
Scientific Advisor [Member] \| Informal Consulting Arrangement [Member]
Related Party Transaction [Line Items]
Consulting service expenses	$ 2,000	¥ 250

Geographic Data - Summary of Long-Lived Assets by Geographical Areas (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Geographic Area Information [Line Items]
Property and equipment, net	$ 8,607	$ 2,789
Asia [Member]
Geographic Area Information [Line Items]
Property and equipment, net	136	578
United States [Member]
Geographic Area Information [Line Items]
Property and equipment, net	$ 8,471	$ 2,211

Selected Quarterly Financial Information (Unaudited) - Summary of Selected Quarterly Results from Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Information [Abstract]
Revenues	$ 676	$ 392	$ 417				$ 126	$ 26	$ 1,485	$ 152
Operating expenses	19,180	17,625	12,055	$ 7,952	$ 7,214	$ 4,990	3,755	3,491	56,812	19,450	$ 5,394
Loss from operations	(18,504)	(17,233)	(11,638)	(7,952)	(7,214)	(4,990)	(3,629)	(3,465)	(55,327)	(19,298)	(5,394)
Net loss	$ (18,454)	$ (17,535)	$ (11,565)	$ (7,847)	$ (7,099)	$ (4,936)	$ (3,700)	$ (3,465)	$ (55,401)	$ (19,200)	$ (5,229)
Basic and diluted net loss per ordinary share	$ (0.79)	$ (0.75)	$ (0.51)	$ (0.36)	$ (0.46)	$ (0.54)	$ (0.40)	$ (0.42)	$ (2.43)	$ (1.83)	$ (1.34)