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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2015	Dec. 17, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Trading Symbol	WVE
Entity Registrant Name	WAVE LIFE SCIENCES LTD.
Entity Central Index Key	0001631574
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		21,551,423

Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Current Assets:
Cash	$ 66,040,000	$ 1,048,000
Accounts receivable		200,000
Prepaid expenses and other current assets	147,000	103,000
Deferred tax assets	64,000	64,000
Deferred offering costs	1,736,000	72,000
Total current assets	67,987,000	1,487,000
Property and equipment, net	1,954,000	1,269,000
Deferred tax assets		182,000
Restricted cash	1,055,000	0
Total assets	70,996,000	2,938,000
Current Liabilities:
Accounts payable	2,875,000	125,000
Accrued expenses and other current liabilities	537,000	605,000
Deferred revenue		152,000
Current portion of capital lease obligation	62,000
Total current liabilities	3,474,000	882,000
Long-term liabilities:
Capital lease obligation, net of current portion	94,000
Other liabilities	31,000	29,000
Total long-term liabilities	125,000	29,000
Total liabilities	3,599,000	911,000
Shareholders' (deficit) equity:
Series A preferred shares, no par value; 3,901,348 shares issued and outstanding at December 31, 2014		7,874,000
Ordinary shares, no par value; 9,223,405 and 4,263,472 shares issued and outstanding at September 30, 2015 and December 31, 2014, respectively	22,446,000	9,973,000
Additional paid-in capital	2,368,000
Accumulated other comprehensive income	43,000	56,000
Accumulated deficit	(27,977,000)	(15,876,000)
Total shareholders' (deficit) equity	(3,120,000)	2,027,000
Total liabilities, Series A and B preferred shares, and shareholders' (deficit) equity	70,996,000	2,938,000
Series A Preferred Shares [Member]
Long-term liabilities:
Preferred stock value	7,874,000
Shareholders' (deficit) equity:
Total shareholders' (deficit) equity		$ 7,874,000
Series B Preferred Shares [Member]
Long-term liabilities:
Preferred stock value	$ 62,643,000

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2015	Dec. 31, 2014
Preferred stock, par value
Preferred stock, shares issued		3,901,348
Preferred stock, shares outstanding		3,901,348
Common stock, par value
Common stock, shares issued	9,223,405	4,263,472
Common stock, shares outstanding	9,223,405	4,263,472
Series A Preferred Shares [Member]
Preferred stock, par value	$ 0
Preferred stock, shares issued	3,901,348
Preferred stock, shares outstanding	3,901,348
Series B Preferred Shares [Member]
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares issued	5,334,892	0
Preferred stock, shares outstanding	5,334,892	0

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Revenue			$ 152
Operating expenses:
Research and development	$ 2,132	$ 585	5,589	$ 1,672
General and administrative	2,858	769	6,647	1,942
Total operating expenses	4,990	1,354	12,236	3,614
Loss from operations	(4,990)	(1,354)	(12,084)	(3,614)
Other income (expense):
Interest income (expense), net	25		10	(12)
Other, net	112	25	155	240
Total other income (expense), net	137	25	165	228
Loss before income tax provision	(4,853)	(1,329)	(11,919)	(3,386)
Income tax provision	(83)	(34)	(182)	(94)
Net loss	$ (4,936)	$ (1,363)	$ (12,101)	$ (3,480)
Net loss per share attributable to ordinary shareholders-basic and diluted	$ (0.54)	$ (0.32)	$ (1.36)	$ (0.92)
Weighted-average ordinary shares used in computing net loss per share attributable to ordinary shareholders-basic and diluted	9,223,405	4,263,472	8,895,660	3,792,841

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net loss	$ (4,936)	$ (1,363)	$ (12,101)	$ (3,480)
Other comprehensive income (loss)
Foreign currency translation	9	(50)	(13)	(136)
Comprehensive loss	$ (4,927)	$ (1,413)	$ (12,114)	$ (3,616)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Condensed Consolidated Statement of Series A and B Preferred Shares and Shareholders' (Deficit) Equity - 9 months ended Sep. 30, 2015 - USD ($) $ in Thousands	Total	Ordinary Shares [Member]	Additional Paid-In-Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Series A Preferred Shares [Member]	Series A Preferred Shares [Member] Temporary Equity [Member]	Series B Preferred Shares [Member] Temporary Equity [Member]
Beginning balance at Dec. 31, 2014	$ 2,027	$ 9,973		$ 56	$ (15,876)	$ 7,874
Beginning balance, shares at Dec. 31, 2014		4,263,472				3,901,348
Issuance of ordinary shares, net of issuance costs	11,631	$ 11,631
Issuance of ordinary shares, net of issuance costs, shares		4,769,077
Stock-based compensation	3,210	$ 842	$ 2,368
Stock-based compensation, shares		190,856
Issuance of Series B preferred, net of issuance costs								$ 62,643
Issuance of Series B preferred, net of issuance costs, shares								5,334,892
Reclassification of Series A preferred shares	(7,874)					$ (7,874)	$ 7,874
Reclassification of Series A preferred shares, shares						(3,901,348)	3,901,348
Other comprehensive income (loss)	(13)			(13)
Net loss	(12,101)				(12,101)
Ending balance at Sep. 30, 2015	$ (3,120)	$ 22,446	$ 2,368	$ 43	$ (27,977)		$ 7,874	$ 62,643
Ending balance, shares at Sep. 30, 2015		9,223,405					3,901,348	5,334,892

Condensed Consolidated Statement of Series A and B Preferred Shares and Shareholders' (Deficit) Equity (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($)
Ordinary Shares [Member]
Net of issuance costs	$ 169
Series B Preferred Shares [Member] \| Temporary Equity [Member]
Net of issuance costs	$ 3,357

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities
Net loss	$ (12,101)	$ (3,480)
Adjustments to reconcile net loss to net cash flows used in operating activities:
Depreciation and amortization	462	195
Share-based compensation expense	3,210
Deferred rent	(4)	(4)
Loss on disposal of property and equipment		7
Deferred income taxes	182	94
Changes in operating assets and liabilities:
Accounts receivable	193	68
Prepaid expenses and other current assets	(40)	5
Accounts payable	2,464	57
Accrued expenses and other current liabilities	(73)	(136)
Deferred revenue	(152)
Net cash used in operating activities	(5,859)	(3,194)
Cash flows from investing activities
Increase in restricted cash	(1,055)
Proceeds from government grant reimbursements for property and equipment	3	314
Purchase of property and equipment	(887)	(562)
Net cash used in investing activities	(1,939)	(248)
Cash flows from financing activities
Proceeds from issuance of ordinary shares, net of offering costs	11,631	5,585
Proceeds from issuance of Series B preferred shares, net of offering costs	62,643
Proceeds from government grant	112	34
Costs associated with initial public offering	(1,417)
Payments on capital lease obligation	(112)
Net cash provided by financing activities	72,857	5,619
Effect of foreign exchange rates on cash	(67)	(127)
Net increase in cash	64,992	2,050
Cash at beginning of period	1,048	439
Cash at end of period	66,040	2,489
Supplemental disclosure of cash flow information:
Conversion of related party notes payable into ordinary and Series A preferred shares		$ 9,602
Reclassification of Series A preferred shares from permanent equity to temporary equity	7,874
Equipment acquired for capital lease obligation	268
Increase in accounts payable for initial public offering costs	$ 319

The Company	9 Months Ended
The Company	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company	1. THE COMPANY *Organization* WAVE Life Sciences Ltd. (together with its subsidiaries, “WAVE” or the “Company”) is a preclinical biopharmaceutical company with an innovative and proprietary synthetic chemistry drug development platform that the Company is using to design, develop and commercialize a broad pipeline of first-in-class or best-in-class nucleic acid therapeutic candidates. The Company is initially developing nucleic acid therapeutics 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 office in Boston, 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) (“WAVE Japan”), a company organized under the laws of Japan (formerly Chiralgen., Ltd.), which occurred on September 12, 2012. The Company was created through the combination of entities that were under the common control of Shin Nippon Biomedical Laboratories Ltd. (“SNBL”) both prior to and immediately following the Company’s incorporation. Since the entities represent the combination of entities under common control, generally accepted accounting principles in the United States (“U.S. GAAP”) require the presentation of the combined companies as if they have always been combined entities. Therefore, on the date of incorporation, the Company recognized the assets and liabilities of WAVE USA and WAVE Japan at the carrying amounts of the assets and liabilities as recorded in the standalone financial statements of the respective companies on that date. The Company’s primary activities since inception have been conducting research and experimental development of biotechnology and chemicals, conducting preclinical testing, recruiting personnel, and raising capital to support development activities. *Initial Public Offering* On November 16, 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. On December 4, 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 approximately $100,458 after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company. Upon the listing of the Company’s ordinary shares on the NASDAQ Global Market on November 11, 2015, all of the outstanding Series B preferred shares of the Company automatically converted into 5,334,892 of the Company’s ordinary shares. *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, 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 pre-clinical 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	9 Months Ended
Significant Accounting Policies	Sep. 30, 2015
Accounting Policies [Abstract]
Significant Accounting Policies	2. SIGNIFICANT ACCOUNTING POLICIES The significant accounting policies described in the Company’s audited financial statements as of and for the year ended December 31, 2014, and the notes thereto, which are included in the Company’s final prospectus for the Company’s initial public offering filed pursuant to Rule 424(b) under the Securities Act with the Securities and Exchange Commission on November 12, 2015, have had no material changes during the nine months ended September 30, 2015, except as noted below. *Unaudited Interim Financial Data* The accompanying interim condensed consolidated balance sheet as of September 30, 2015, the related interim condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2015 and 2014, the related interim condensed consolidated statement of Series A and B preferred shares and shareholders’ (deficit) equity for the nine months ended September 30, 2015, the related interim condensed consolidated cash flows for the nine months ended September 30, 2015 and 2014 and the related interim information contained within the notes to the consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission for interim financial information. Accordingly, they do not include all of the information and the notes required by U.S. GAAP for complete financial statements. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2015 and 2014 are unaudited. In the opinion of management, the unaudited interim consolidated financial statements reflect all adjustments, consisting of normal and recurring adjustments, necessary for the fair presentation of the Company’s financial position at September 30, 2015 and the consolidated results of its operations, and comprehensive loss for the three and nine months ended September 30, 2015 and 2014 and the consolidated results of its cash flows for the nine months ended September 30, 2015 and 2014 are not necessarily indicative of the results to be expected for the year ending December 31, 2015 or any other interim period or future year or period. *Share Splits* The Company’s board of directors and shareholders approved a 50-for-1 forward share split of the Company’s outstanding ordinary and Series A preferred shares effective November 18, 2014. Additionally, on November 1, 2015, the Company’s board of directors and shareholders approved a 4.0415917-for-1 forward share split of the Company’s issued and outstanding ordinary shares, Series A preferred shares and Series B preferred shares. All share and per share amounts in the consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to the share splits. *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, but are not limited to the valuation of its Series A preferred shares on conversion of the related party notes payable, the valuation of the Company’s ordinary shares, the assumptions used to determine the fair value 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 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 income within shareholders’ (deficit) equity. Gains and losses on foreign currency transactions are included in the consolidated statements of operations within other, 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 September 30, 2015 and December 31, 2014. 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 is a financial instrument that potentially subjects the Company to concentration of credit risk. The Company uses eight financial institutions to maintain its cash, 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 a separate restricted bank account as required under the terms of the Company’s lease arrangement for its Cambridge, Massachusetts facility. There was no restricted cash as of December 31, 2014. *Deferred Offering Costs* The Company capitalizes certain legal, professional, accounting and other third party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in shareholders’ equity as a reduction to the carrying value of the shares issued. As of September 30, 2015 and December 31, 2014 the Company had recorded $1,736 and $72, respectively, of deferred offering costs in contemplation of the initial public offering. On November 16, 2015, the Company reclassified all of its deferred offering costs to additional paid in capital as a reduction of the proceeds from the initial public offering. *Revenue Recognition* Collaboration Agreement The Company had a collaboration agreement with a third party, which was entered into in late 2014 and terminated in May 2015. The Company was entitled to a non-refundable upfront amount of $152 related to research and development services performed under the agreement. The upfront fee was billed in 2014 and collected in early 2015. The Company recorded its right to the upfront payment as accounts receivable and deferred revenue at December 31, 2014. Upon receipt of the non-refundable payment, the Company began recognizing the upfront fee on a straight-line basis over the service period. Upon termination of the agreement, the Company recognized the remainder of the upfront fee. Revenue recognized under the agreement was $0 for the three months ended September 30, 2015 and 2014, and $152 and $0 for the nine months ended September 30, 2015 and 2014, respectively. There have been no other revenue generating activities from collaboration or license agreements entered into by the Company since its formation and through the three and nine months ended September 30, 2015 and the year ended December 31, 2014. 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 benefits of employees, 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. *Government Grants* The Company has applied for reimbursement of expenditures with the Japanese government for certain qualified operating or capital expenditures. The Company recognizes government grants when there is reasonable assurance that the Company will comply with the conditions attached to the grant arrangement and the grant will be received. Government grants for research and development efforts are recorded as grant income and classified in other, net in the consolidated statements of operations. Government grants related to reimbursements of capital expenditures are recognized as a reduction of the basis of the asset and recognized in the consolidated statements of operations over the estimated useful life of the depreciable asset as reduced depreciation expense. The Company recognized other income of $111 and $26 for the three months ended September 30, 2015 and 2014, respectively, and $155 and $134 for the nine months ended September 30, 2015 and 2014, respectively, which is included in the consolidated statements of operations. The Company recorded reimbursable capital expenditures of $0 for the three months ended September 30, 2014 and 2014, respectively, and $3 and $249 for the nine months ended September 30, 2015 and 2014 respectively, for which a reduction in the basis of the assets purchased was recorded in the consolidated balance sheets. *Recently Adopted Accounting Pronouncements* In July 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists (“ASU 2013-11”), which requires unrecognized tax benefits to be presented as a decrease in a net operating loss, similar tax loss or tax credit carryforward if certain criteria are met. The guidance was effective for fiscal years and interim periods within those years beginning after December 15, 2013 for public entities with early adoption permitted in 2013. The Company elected to early adopt ASU 2013-11 in 2013. In June 2014, the FASB issued ASU 2014-10, Development Stage Entities. The amendments in this update removed all incremental financial reporting requirements, including inception-to-date information and certain other disclosures currently required under U.S. GAAP, in the financial statements of development stage companies. The amendments are effective for annual reporting periods beginning after December 15, 2014 and interim reporting periods beginning after December 15, 2015. Early adoption is permitted for any annual reporting period or interim period for which the entity’s financial statements have not yet been issued (public business entities) or made available for issuance (other entities). The Company elected to early adopt this guidance in 2014 and, therefore, has not presented inception-to-date disclosures in its consolidated financial statements. *Recently Issued Accounting Pronouncements* In May 2014, the FASB issued ASU 2014-09—Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”). ASU 2014-09 supersedes most of the existing guidance on revenue recognition in ASC Topic 605, Revenue Recognition. The core principle of the revenue model is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. In applying the revenue model to contracts within its scope, an entity will need to (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract and (v) recognize revenue when (or as) the entity satisfies a performance obligation. On July 9, 2015, the FASB extended the effective date of adoption of the standard to interim reporting periods within annual reporting periods beginning after December 15, 2017 (that is, beginning in the first interim period within the year of adoption). Early adoption of the standard is permitted for all entities for interim and annual periods beginning after December 15, 2016. The Company has not yet determined the impact of ASU 2014-09 on expected revenues. In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements—Going Concern, on disclosure of uncertainties about an entity’s ability to continue as a going concern. This guidance addresses management’s responsibility in evaluating whether there is substantial doubt about a company’s ability to continue as a going concern and to provide related footnote disclosures. The guidance is effective for fiscal years beginning after December 15, 2016 and for interim periods within those fiscal years, with early adoption permitted. The Company does not expect the adoption of this guidance to have a material impact on the consolidated financial statements. 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 is evaluating the impact of ASU 2015-02 and if early adoption is appropriate in future reporting periods. 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. ASU 2015-03 is effective for annual periods beginning after December 15, 2015 and for interim periods within those fiscal years. The Company does not expect the impact of ASU 2015-03 to be material to its 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 15, 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. 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

9 Months Ended

Sep. 30, 2015

Property, Plant and Equipment [Abstract]

Property and Equipment

3. PROPERTY AND EQUIPMENT

Property and equipment, net, consists of the following:


	September 30, 2015			December 31, 2014
Furniture and equipment	$	2,862		$	2,331
Leasehold improvements		859			147

Total		3,721			2,478
Less accumulated depreciation and amortization		(1,767	)		(1,209	)

Property and equipment, net	$	1,954		$	1,269

Leasehold improvements made during the nine months ended September 30, 2015 consisted primarily of costs related to the Company’s newly leased office space in Cambridge, Massachusetts.

Depreciation and amortization expense was $284 and $91 for the three months ended September 30, 2015 and 2014, respectively, and $462 and $195 for the nine months ended September 30, 2015 and 2014, respectively.

Through September 30, 2015, the Company has not recognized any impairment charges.

Accrued Expenses

9 Months Ended

Sep. 30, 2015

Payables and Accruals [Abstract]

Accrued Expenses

4. ACCRUED EXPENSES

Accrued expenses and other current liabilities consist of the following:


	September 30, 2015		December 31, 2014
Accrued compensation	$	131	$	428
Other		406		177

Total accrued expenses and other current liabilities	$	537	$	605

Share Capital

9 Months Ended

Sep. 30, 2015

Equity [Abstract]

Share Capital

5. SHARE CAPITAL

Ordinary Shares

The following represent the historical ordinary share transactions of the Company from January 1, 2014 through September 30, 2015:

•

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 $5,585.

•

In February 2014, holders of $9,602 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 $11,631.

•

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

Series A Preferred Shares

The following represent the Series A preferred share transactions of the Company from January 1, 2014 through September 30, 2015:

•

In February 2014, holders of $9,602 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 other than: (1) no voting rights other than in limited circumstances, (2) the right to a non-cumulative dividend if and when declared by our 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, investors who hold at least 1,212,477 shares of registerable securities, including holders of Series A preferred shares and Series B preferred shares, have 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 vote to a sale of the Company, they have the right to force the other shareholders, including the holders of Series A preferred shares, to agree to such a sale.

•

On September 28, 2015, the terms of the Series A preferred shares were further amended to provide that, upon the mandatory conversion of Series B preferred shares, the existing right of Series A preferred shares to a non-cumulative dividend if and when declared by our board of directors shall cease and be replaced by a liquidation preference consisting of $0.0024743 per Series A preferred share, or an aggregate of $10 based on the number of Series A preferred shares outstanding at the date of the amendment.

The Company has accounted for the September 28, 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 in the aggregate.

Series B Preferred Shares

The following represents the historical Series B preferred share transactions of the Company from January 1, 2015 through September 30, 2015:

•

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 $62,643 of net proceeds.

Features of the Series B Preferred Shares

The Series B preferred shares have no par value and there is no authorized share capital under Singapore law. In the event of a liquidation, dissolution or winding up of, or a return of capital by the Company, the Series B preferred shares will rank above the holders of Series A preferred shares and ordinary shares and are therefore, entitled to a liquidation preference in the amount of the original per share amount paid of $12.37 per share, plus any declared plus unpaid dividends, if any. Since the redemption of the Series B preferred shares is outside the control of the Company, the Company has presented the Series B preferred shares as temporary equity. The rights, preferences, and privileges of the Series B preferred shares are as follows:

Dividends

Holders of Series B preferred shares are not entitled to any preferential dividends.

Liquidation

In the event of a liquidation, dissolution or winding up of, or a return of capital by the Company, the Series B preferred shares will rank above the holders of Series A preferred shares and ordinary shares and are therefore, entitled to a liquidation preference in the amount of the original per share amount paid of $12.37 per share, plus any declared plus unpaid dividends, if any.

Voting

Holders of the Series B preferred shares are entitled to vote at any general meeting.

Conversion

The Series B preferred shares are convertible on a one-for-one basis, subject to adjustment, into ordinary shares at the discretion of the holder and are mandatorily convertible upon the closing of the sale of Ordinary Shares to the public at a price per share of at least the Series B issue amount, in a firm-commitment underwritten public offering resulting in at least $50.0 million of gross proceeds to the Company or the date and time, or the occurrence of an event, specified by vote or written consent of the holders of at least 56% of the then issued Series B preferred shares. The Series B preferred shares were converted upon the closing of the Company’s initial public offering (Note 1).

Redemption

The Series B preferred shares are not redeemable.

Right of First Refusal

The Series B preferred shareholders are entitled to exercise a right of first refusal, a feature that dictates that in the case of a transfer by a specific shareholder (i) the Company, then (ii) the non-selling shareholder, and then (iii) any third party identified by the Company shall be entitled within a period of 60 days to serve a purchase notice to the selling shareholder requesting to sell to the Company or to the non-selling shareholder at the same price and terms as those offered by the prospective purchaser.

- 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Subparagraph (SAB TOPIC 4.E)
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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-Subparagraph (SX 210.3-04)
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Topic 505
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

+ Details

Share-Based Compensation

9 Months Ended

Sep. 30, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share-Based Compensation

6. SHARE-BASED COMPENSATION

Adoption of Equity Incentive Plan

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.

2014 Plan Activity

In March and August 2015, the Company’s board of directors approved an increase in the number of ordinary shares issuable under the 2014 Plan to 2,498,597 and 3,555,774 shares, respectively. The 2014 Plan authorizes the board of directors or a committee of the board to grant incentive share options, non-qualified share options, or NQSOs, share appreciation rights and restricted awards to eligible employees, outside directors and consultants of the Company. As of September 30, 2015, 1,421,537 ordinary shares remained available for future grant.

During the nine months ended September 30, 2015, the Company granted options to purchase 1,943,381 ordinary shares to employees, directors and non-employees. The Company did not grant any share options as of December 31, 2014. The Company recorded share-based compensation expense of $725 and $3,210, during the three and nine months ended September 30, 2015, respectively, of which $278 and $1,171 related to equity-classified options granted to non-employees. The Company did not have any share-based compensation expenses in 2014. 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. 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 ⁽¹⁾		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value ⁽²⁾
Outstanding as of January 1, 2015		—	$	—
Granted		1,943,381	$	2.65

Outstanding as of September 30, 2015		1,943,381	$	2.65		9.47	$	75,106

Options exercisable as of September 30, 2015		587,170	$	2.47		9.45	$	22,797

Options vested and expected to vest as of September 30, 2015		1,904,609	$	2.65		9.47	$	73,618

⁽¹⁾	Includes 547,502 options granted to non-employees during March 2015.

⁽²⁾	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.

As of September 30, 2015, the unrecognized compensation cost related to outstanding options was $3,396 for employees and $2,639 for non-employees and is expected to be recognized as expense over a weighted-average period of approximately 2.57 years. For the nine months ended September 30, 2015 and 2014, the weighted-average grant date fair value per granted option was $5.02 and $0.

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 $842.

Share-based compensation expense for the three and nine months ended September 30, 2015 was classified in the consolidated statements of operations as follows:


	Three Months Ended September 30, 2015		Nine Months Ended September 30, 2015
Research and development expenses	$	476	$	1,657
General and administrative expenses		242		1,553

Total share-based compensation	$	718	$	3,210

Operating Leases	9 Months Ended
Operating Leases	Sep. 30, 2015
Leases [Abstract]
Operating Leases	7. OPERATING LEASES 2015 Cambridge, MA Lease In April 2015, the Company entered into a lease agreement for an office and laboratory facility in Cambridge, Massachusetts. The lease term commenced in October 2015 and has a term of 7.5 years with a five year renewal option to extend the lease. In connection with signing the lease, the Company issued the lessor a letter of credit in the amount of $1,000, which is recorded as restricted cash on the consolidated balance sheets at September 30, 2015. Future minimum lease payments as of September 30, 2015 amounted to $200 in 2015, $834 in 2016, $1,030 in 2017, $1,321 in 2018, $1,360 in 2019 and $4,711 thereafter. 2015 Boston, MA Lease Termination On September 22, 2015, the Company terminated its sublease with SNBL for duplicate corporate office space, and exited the premises on October 2, 2015. In connection with the termination, the Company agreed to guarantee SNBL certain obligations of the unrelated third party (sub-lessee) 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, then the Company will make the required payments. The guarantee agreement is effective through August 2019, when the final lease payments are due. 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 sublease period would be $600, exclusive of any indemnification from the sub-lessee. The Company recorded approximately $190 of additional depreciation during the third quarter ended September 30, 2015 in connection with the termination of the agreement and expects to recognize approximately $91 of additional costs in connection with the exit from the premises in the fourth quarter of 2015.

Net Loss Per Ordinary Share

9 Months Ended

Sep. 30, 2015

Earnings Per Share [Abstract]

Net Loss Per Ordinary Share

8. NET LOSS PER ORDINARY SHARE

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 and Series B preferred shares do not participate in losses.

Basic loss per share is computed by dividing net loss attributable to ordinary shareholders by the weighted-average number of ordinary shares used in computing net loss per share attributable to ordinary shareholders.

The Company’s potentially dilutive shares, which include outstanding share options to purchase ordinary shares, Series A preferred shares, and Series B preferred 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 September 30,
	2015		2014
Options to purchase ordinary shares		1,943,381		—
Series A preferred shares		3,901,348		—
Series B preferred shares		5,334,892		—

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	9. INCOME TAXES The Company is a multi-national company subject to taxation in the United States, Japan and Singapore. During the three months ended September 30, 2015 and 2014, the Company recorded a tax provision of $83 and $34, respectively. During the nine months ended September 30, 2015 and 2014, the Company recorded a tax provision of $182, and $94, respectively, all of which are a result of income taxed in the United States for each respective period. During the three and nine months ended September 30, 2015 and 2014, the Company recorded no income tax benefits for the net operating losses incurred in Japan, due to its uncertainty of realizing a benefit from those items. 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. As discussed in Note 2, the Company early adopted ASU 2013-11 and therefore unrecognized tax benefits related to net operating losses are netted against the related deferred tax asset. The Company believes it is reasonably possible that approximately $700 of its unrecognized tax benefits may decrease by the end of 2015 as a result of the Company’s intention to amend its tax filings for transfer pricing in prior years. The impact of the reversal of the uncertain tax benefit will reduce the net operating loss carryforwards in the United States.

Related Parties

9 Months Ended

Sep. 30, 2015

Related Parties

10. 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 $100 and $17 at September 30, 2015 and December 31, 2014, respectively, in depository accounts with one of its investors, who became an investor in February 2014.

•

Pursuant to the terms of a service agreement previously held with SNBL, a related party, the Company paid SNBL $3 and $26 in the three months ended September 30, 2015 and 2014, respectively, and $12 and $71 in the nine months ended September 30, 2015 and 2014, respectively, for accounting and administrative services provided to the Company and its affiliates.

•

In February 2014 and in connection with the issuance of 2,263,291 ordinary shares to a third party investor, SNBL agreed to convert the outstanding principal and accrued interest due under the notes payable in the amount of $9,602 into 1,515,596 ordinary shares and 2,365,139 Series A preferred shares. No gain or loss was recognized on the transaction due to the related party nature of the transaction and because the fair value of the Series A preferred shares and ordinary shares was equal to the carrying value of the related party notes payable

•

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

•

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

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Geographic Data

9 Months Ended

Sep. 30, 2015

Text Block [Abstract]

Geographic Data

11. GEOGRAPHIC DATA

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


	September 30, 2015		December 31, 2014
Asia	$	620	$	745
United States		1,334		524

Total long-lived assets	$	1,954	$	1,269

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	12. SUBSEQUENT EVENTS In October 2015, the Company’s board of directors approved an increase in the number of ordinary shares issuable under the 2014 Equity Incentive Plan by 1,508,770 shares to 5,064,544. On November 5, 2015, the Company converted from a Singapore private limited company to a Singapore public limited company. In connection with this conversion, the Company changed its name from WAVE Life Sciences Pte. Ltd. to WAVE Life Sciences Ltd. All references to the Company have been changed to WAVE Sciences Ltd. in the accompanying consolidated financial statements and notes thereto.

Significant Accounting Policies (Policies)	9 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2015
Accounting Policies [Abstract]
Unaudited Interim Financial Data	*Unaudited Interim Financial Data* The accompanying interim condensed consolidated balance sheet as of September 30, 2015, the related interim condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2015 and 2014, the related interim condensed consolidated statement of Series A and B preferred shares and shareholders’ (deficit) equity for the nine months ended September 30, 2015, the related interim condensed consolidated cash flows for the nine months ended September 30, 2015 and 2014 and the related interim information contained within the notes to the consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission for interim financial information. Accordingly, they do not include all of the information and the notes required by U.S. GAAP for complete financial statements. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2015 and 2014 are unaudited. In the opinion of management, the unaudited interim consolidated financial statements reflect all adjustments, consisting of normal and recurring adjustments, necessary for the fair presentation of the Company’s financial position at September 30, 2015 and the consolidated results of its operations, and comprehensive loss for the three and nine months ended September 30, 2015 and 2014 and the consolidated results of its cash flows for the nine months ended September 30, 2015 and 2014 are not necessarily indicative of the results to be expected for the year ending December 31, 2015 or any other interim period or future year or period.
Share Splits	*Share Splits* The Company’s board of directors and shareholders approved a 50-for-1 forward share split of the Company’s outstanding ordinary and Series A preferred shares effective November 18, 2014. Additionally, on November 1, 2015, the Company’s board of directors and shareholders approved a 4.0415917-for-1 forward share split of the Company’s issued and outstanding ordinary shares, Series A preferred shares and Series B preferred shares. All share and per share amounts in the consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to the share splits.
Principles of Consolidation	*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	*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, but are not limited to the valuation of its Series A preferred shares on conversion of the related party notes payable, the valuation of the Company’s ordinary shares, the assumptions used to determine the fair value 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	*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	*Foreign Currency Translation* The functional currency of the Company’s Japanese subsidiary is the Japanese Yen 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 income within shareholders’ (deficit) equity. Gains and losses on foreign currency transactions are included in the consolidated statements of operations within other, net.
Fair Value of Financial Instruments	*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 September 30, 2015 and December 31, 2014. 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	*Concentration of Credit Risk* Cash is a financial instrument that potentially subjects the Company to concentration of credit risk. The Company uses eight financial institutions to maintain its cash, 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* Restricted cash consists primarily of cash placed in a separate restricted bank account as required under the terms of the Company’s lease arrangement for its Cambridge, Massachusetts facility. There was no restricted cash as of December 31, 2014.
Deferred Offering Costs	*Deferred Offering Costs* The Company capitalizes certain legal, professional, accounting and other third party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in shareholders’ equity as a reduction to the carrying value of the shares issued. As of September 30, 2015 and December 31, 2014 the Company had recorded $1,736 and $72, respectively, of deferred offering costs in contemplation of the initial public offering. On November 16, 2015, the Company reclassified all of its deferred offering costs to additional paid in capital as a reduction of the proceeds from the initial public offering.
Revenue Recognition	*Revenue Recognition* Collaboration Agreement The Company had a collaboration agreement with a third party, which was entered into in late 2014 and terminated in May 2015. The Company was entitled to a non-refundable upfront amount of $152 related to research and development services performed under the agreement. The upfront fee was billed in 2014 and collected in early 2015. The Company recorded its right to the upfront payment as accounts receivable and deferred revenue at December 31, 2014. Upon receipt of the non-refundable payment, the Company began recognizing the upfront fee on a straight-line basis over the service period. Upon termination of the agreement, the Company recognized the remainder of the upfront fee. Revenue recognized under the agreement was $0 for the three months ended September 30, 2015 and 2014, and $152 and $0 for the nine months ended September 30, 2015 and 2014, respectively. There have been no other revenue generating activities from collaboration or license agreements entered into by the Company since its formation and through the three and nine months ended September 30, 2015 and the year ended December 31, 2014. Product Revenue The Company has had no product revenue to date.
Research and Development Costs	*Research and Development Costs* Research and development costs are expensed as incurred. Research and development costs include salaries, share-based compensation and benefits of employees, 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.
Government Grants	*Government Grants* The Company has applied for reimbursement of expenditures with the Japanese government for certain qualified operating or capital expenditures. The Company recognizes government grants when there is reasonable assurance that the Company will comply with the conditions attached to the grant arrangement and the grant will be received. Government grants for research and development efforts are recorded as grant income and classified in other, net in the consolidated statements of operations. Government grants related to reimbursements of capital expenditures are recognized as a reduction of the basis of the asset and recognized in the consolidated statements of operations over the estimated useful life of the depreciable asset as reduced depreciation expense. The Company recognized other income of $111 and $26 for the three months ended September 30, 2015 and 2014, respectively, and $155 and $134 for the nine months ended September 30, 2015 and 2014, respectively, which is included in the consolidated statements of operations. The Company recorded reimbursable capital expenditures of $0 for the three months ended September 30, 2014 and 2014, respectively, and $3 and $249 for the nine months ended September 30, 2015 and 2014 respectively, for which a reduction in the basis of the assets purchased was recorded in the consolidated balance sheets.
Recently Adopted Accounting Pronouncements	*Recently Adopted Accounting Pronouncements* In July 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists (“ASU 2013-11”), which requires unrecognized tax benefits to be presented as a decrease in a net operating loss, similar tax loss or tax credit carryforward if certain criteria are met. The guidance was effective for fiscal years and interim periods within those years beginning after December 15, 2013 for public entities with early adoption permitted in 2013. The Company elected to early adopt ASU 2013-11 in 2013. In June 2014, the FASB issued ASU 2014-10, Development Stage Entities. The amendments in this update removed all incremental financial reporting requirements, including inception-to-date information and certain other disclosures currently required under U.S. GAAP, in the financial statements of development stage companies. The amendments are effective for annual reporting periods beginning after December 15, 2014 and interim reporting periods beginning after December 15, 2015. Early adoption is permitted for any annual reporting period or interim period for which the entity’s financial statements have not yet been issued (public business entities) or made available for issuance (other entities). The Company elected to early adopt this guidance in 2014 and, therefore, has not presented inception-to-date disclosures in its consolidated financial statements.
Recently Issued Accounting Pronouncements	*Recently Issued Accounting Pronouncements* In May 2014, the FASB issued ASU 2014-09—Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”). ASU 2014-09 supersedes most of the existing guidance on revenue recognition in ASC Topic 605, Revenue Recognition. The core principle of the revenue model is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. In applying the revenue model to contracts within its scope, an entity will need to (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract and (v) recognize revenue when (or as) the entity satisfies a performance obligation. On July 9, 2015, the FASB extended the effective date of adoption of the standard to interim reporting periods within annual reporting periods beginning after December 15, 2017 (that is, beginning in the first interim period within the year of adoption). Early adoption of the standard is permitted for all entities for interim and annual periods beginning after December 15, 2016. The Company has not yet determined the impact of ASU 2014-09 on expected revenues. In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements—Going Concern, on disclosure of uncertainties about an entity’s ability to continue as a going concern. This guidance addresses management’s responsibility in evaluating whether there is substantial doubt about a company’s ability to continue as a going concern and to provide related footnote disclosures. The guidance is effective for fiscal years beginning after December 15, 2016 and for interim periods within those fiscal years, with early adoption permitted. The Company does not expect the adoption of this guidance to have a material impact on the consolidated financial statements. 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 is evaluating the impact of ASU 2015-02 and if early adoption is appropriate in future reporting periods. 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. ASU 2015-03 is effective for annual periods beginning after December 15, 2015 and for interim periods within those fiscal years. The Company does not expect the impact of ASU 2015-03 to be material to its 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 15, 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. 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 (Tables)

9 Months Ended

Sep. 30, 2015

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net, consists of the following:


	September 30, 2015			December 31, 2014
Furniture and equipment	$	2,862		$	2,331
Leasehold improvements		859			147

Total		3,721			2,478
Less accumulated depreciation and amortization		(1,767	)		(1,209	)

Property and equipment, net	$	1,954		$	1,269

Accrued Expenses (Tables)

9 Months Ended

Sep. 30, 2015

Payables and Accruals [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:


	September 30, 2015		December 31, 2014
Accrued compensation	$	131	$	428
Other		406		177

Total accrued expenses and other current liabilities	$	537	$	605

Share-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Share Option Activity

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


	Number of Shares ⁽¹⁾		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value ⁽²⁾
Outstanding as of January 1, 2015		—	$	—
Granted		1,943,381	$	2.65

Outstanding as of September 30, 2015		1,943,381	$	2.65		9.47	$	75,106

Options exercisable as of September 30, 2015		587,170	$	2.47		9.45	$	22,797

Options vested and expected to vest as of September 30, 2015		1,904,609	$	2.65		9.47	$	73,618

⁽¹⁾	Includes 547,502 options granted to non-employees during March 2015.

⁽²⁾	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.

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

Share-based compensation expense for the three and nine months ended September 30, 2015 was classified in the consolidated statements of operations as follows:


	Three Months Ended September 30, 2015		Nine Months Ended September 30, 2015
Research and development expenses	$	476	$	1,657
General and administrative expenses		242		1,553

Total share-based compensation	$	718	$	3,210

Net Loss Per Ordinary Share (Tables)

9 Months Ended

Sep. 30, 2015

Earnings Per Share [Abstract]

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


	As of September 30,
	2015		2014
Options to purchase ordinary shares		1,943,381		—
Series A preferred shares		3,901,348		—
Series B preferred shares		5,334,892		—

Geographic Data (Tables)

9 Months Ended

Sep. 30, 2015

Text Block [Abstract]

Summary of Long-Lived Assets by Geographical Areas

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


	September 30, 2015		December 31, 2014
Asia	$	620	$	745
United States		1,334		524

Total long-lived assets	$	1,954	$	1,269

The Company - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			9 Months Ended
	Dec. 04, 2015	Nov. 16, 2015	Sep. 30, 2015
IPO [Member]
Subsidiary, Sale of Stock [Line Items]
Sale of common stock, Date			Nov. 10, 2015
Subsequent Event [Member] \| IPO [Member]
Subsidiary, Sale of Stock [Line Items]
Number of shares issued and sold		6,375,000
Shares issued, price per share		$ 16.00
Convertible preferred stock converted into common stock		5,334,892
Subsequent Event [Member] \| Underwriters Over-Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Number of shares issued and sold	618,126
Shares issued, price per share	$ 16.00
Proceeds from sale of common stock	$ 100,458

Significant Accounting Policies - Additional Information (Detail)			3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 01, 2015	Nov. 18, 2014	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Significant Accounting Policies [Line Items]
Stock split description					The Company's board of directors and shareholders approved a 50-for-1 forward share split of the Company's outstanding ordinary and Series A preferred shares effective November 18, 2014. Additionally, on November 1, 2015, the Company's board of directors and shareholders approved a 4.0415917-for-1 forward share split of the Company's issued and outstanding ordinary shares, Series A preferred shares and Series B preferred shares.
Restricted cash			$ 1,055,000		$ 1,055,000		$ 0
Deferred offering costs			1,736,000		1,736,000		72,000
Upfront amount related to research and development services							$ 152,000
Product revenue					0
Other income			111,000	$ 26,000	155,000	$ 134,000
Reimbursable capital expenditures			0	0	3,000	249,000
Ordinary Shares and Series A Preferred Shares [Member]
Significant Accounting Policies [Line Items]
Stock split ratio		50
Ordinary Shares, Series A Preferred Shares and Series B Preferred Shares [Member] \| Subsequent Event [Member]
Significant Accounting Policies [Line Items]
Stock split ratio	4.0415917
Collaboration Agreement [Member]
Significant Accounting Policies [Line Items]
Deferred revenue			$ 0	$ 0	$ 152,000	$ 0

Property and Equipment - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 3,721	$ 2,478
Less accumulated depreciation and amortization	(1,767)	(1,209)
Property and equipment, net	1,954	1,269
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	2,862	2,331
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 859	$ 147

Property and Equipment - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 284,000	$ 91,000	$ 462,000	$ 195,000
Impairment charges of long-lived asset			$ 0

Accrued Expenses - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued compensation	$ 131	$ 428
Other	406	177
Total accrued expenses and other current liabilities	$ 537	$ 605

Share Capital - Ordinary Shares - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			9 Months Ended
	Mar. 31, 2015	Jan. 31, 2015	Feb. 28, 2014	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Shares issued					9,223,405	4,263,472
Notes payable, related parties			$ 9,602	$ 9,602
Ordinary Shares [Member]
Class of Stock [Line Items]
Debt conversion, Converted instrument, Shares issued			1,515,596
Executive Officer [Member]
Class of Stock [Line Items]
Options to purchase common stock granted	190,856
Third-Party Investor [Member]
Class of Stock [Line Items]
Shares issued		4,769,077	2,263,291
Shares issued, Per Share		$ 2.47	$ 2.47
Proceeds from issuance of shares		$ 11,631	$ 5,585
Series A Preferred Shares [Member]
Class of Stock [Line Items]
Debt conversion, Converted instrument, Shares issued			2,365,139

Share Capital - Series A Preferred Shares - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Aug. 14, 2015	Sep. 30, 2015	Sep. 28, 2015
Class of Stock [Line Items]
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
Series A Preferred Shares [Member]
Class of Stock [Line Items]
Share issued for conversion	3,901,348
Preferred stock liquidation preference, per share			$ 0.0024743
Aggregate preferred stock liquidation preference, per share			$ 10
Series B Preferred Shares [Member]
Class of Stock [Line Items]
Preferred stock, voting rights	56.00%	56.00%
Preferred stock liquidation preference, per share		$ 12.37

Share Capital - Series B Preferred Shares - Additional Information (Detail) - USD ($)		9 Months Ended
	Aug. 14, 2015	Sep. 30, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Preferred stock, shares issued			3,901,348
Proceeds from issuance of preferred shares		$ 62,643,000
Preferred stock, par value
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	$ 62,643,000
Preferred stock liquidation preference, per share		$ 12.37
Preferred stock, conversion basis		The Series B preferred shares are convertible on a one-for-one basis, subject to adjustment, into ordinary shares at the discretion of the holder and are mandatorily convertible upon the closing of the sale of Ordinary Shares to the public at a price per share of at least the Series B issue amount, in a firm-commitment underwritten public offering resulting in at least $50.0 million of gross proceeds to the Company or the date and time, or the occurrence of an event, specified by vote or written consent of the holders of at least 56% of the then issued Series B preferred shares. The Series B preferred shares were converted upon the closing of the Company’s initial public offering.
Preferred stock, voting rights	56.00%	56.00%
Convertible preferred stock, conversion terms, common stock offering minimum gross proceeds		$ 50,000,000
Period required to serve purchase notice		60 days
Series B Preferred Shares [Member] \| Singapore [Member]
Class of Stock [Line Items]
Preferred stock, par value
Preferred stock, shares authorized		0

Share-Based Compensation - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended	9 Months Ended		12 Months Ended
	Dec. 31, 2014	Aug. 31, 2015	Mar. 31, 2015	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense				$ 718,000	$ 3,210,000
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]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares reserved for issuance	1,763,714						1,763,714
Ordinary shares issuable		3,555,774	2,498,597
Ordinary shares available for future grant				1,421,537	1,421,537
Options to purchase common stock granted	0				1,943,381
Share-based compensation expense			$ 842,000	$ 725,000	$ 3,210,000		$ 0
Contractual life of options					10 years
Unrecognized stock-based compensation weighted average recognition period					2 years 6 months 26 days
Weighted average grant date fair value per granted option					$ 5.02	$ 0.00
2014 Plan [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense				3,396,000	$ 3,396,000
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			547,502
Share-based compensation expense				278,000	1,171,000
Unrecognized stock-based compensation expense				$ 2,639,000	$ 2,639,000
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] \| 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		9 Months Ended
	Dec. 31, 2014	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of Shares	0	1,943,381
Outstanding, Number of Shares, Ending Balance		1,943,381
Options exercisable, Number of Shares		587,170
Options vested and expected to vest, Number of Shares		1,904,609
Granted, Weighted Average Exercise Price		$ 2.65
Outstanding, Weighted Average Exercise Price, Ending Balance		2.65
Options exercisable, Weighted Average Exercise Price		2.47
Options vested and expected to vest, Weighted Average Exercise Price		$ 2.65
Outstanding, Weighted Average Remaining Contractual Term		9 years 5 months 19 days
Options exercisable, Weighted Average Remaining Contractual Term		9 years 5 months 12 days
Options vested and expected to vest, Weighted Average Remaining Contractual Term		9 years 5 months 19 days
Outstanding, Aggregate Intrinsic Value, Ending Balance		$ 75,106
Options exercisable, Aggregate Intrinsic Value		22,797
Options vested and expected to vest, Aggregate Intrinsic Value		$ 73,618

Share-Based Compensation - Summary of Share Option Activity (Parenthetical) (Detail) - 2014 Plan [Member] - shares		1 Months Ended	9 Months Ended
	Dec. 31, 2014	Mar. 31, 2015	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase common stock granted	0		1,943,381
Non-Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase common stock granted		547,502

Share-Based Compensation - Summary of Share-based Compensation Expense Classified in Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	$ 718	$ 3,210
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	476	1,657
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	$ 242	$ 1,553

Operating Leases - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014
Leases, Operating [Abstract]
Issuance of letter of credit recorded as restricted cash		$ 1,055,000	$ 1,055,000	$ 0
2015 Cambridge, MA Lease [Member]
Leases, Operating [Abstract]
Lease agreement term			7 years 6 months
Lease extension period			5 years
Operating leases, future minimum payments due in remainder of fiscal year		200,000	$ 200,000
Operating leases, future minimum payments due in two years		834,000	834,000
Operating leases, future minimum payments due in three years		1,030,000	1,030,000
Operating leases, future minimum payments due in four years		1,321,000	1,321,000
Operating leases, future minimum payments due in five years		1,360,000	1,360,000
Operating leases, future minimum payments due thereafter		4,711,000	4,711,000
2015 Cambridge, MA Lease [Member] \| Letter of Credit [Member]
Leases, Operating [Abstract]
Issuance of letter of credit recorded as restricted cash		1,000,000	$ 1,000,000
2015 Boston, MA Lease Termination [Member]
Leases, Operating [Abstract]
Guarantee agreement termination date			Aug. 31, 2019
2015 Boston, MA Lease Termination [Member] \| Shin Nippon Biomedical Laboratories Ltd. (SNBL) [Member]
Leases, Operating [Abstract]
Lease agreement term			3 years 6 months
Maximum amount of guarantee for sublease		600,000	$ 600,000
Accelerated depreciation		$ 190,000
2015 Boston, MA Lease Termination [Member] \| Shin Nippon Biomedical Laboratories Ltd. (SNBL) [Member] \| Scenario, Forecast [Member]
Leases, Operating [Abstract]
Additional exit costs related to termination of sublease agreement	$ 91,000

Net Loss Per Ordinary Share - Anti-Dilutive Shares Excluded from Calculation of Diluted Net Loss Per Ordinary Share (Detail)	9 Months Ended
	Sep. 30, 2015 shares
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
Series B 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	5,334,892
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	1,943,381

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Taxes [Line Items]
Income tax provision	$ 83,000	$ 34,000	$ 182,000	$ 94,000
Unrecognized tax benefits related to net operating losses	700,000		700,000
United States [Member]
Income Taxes [Line Items]
Income tax provision	83,000	34,000	182,000	94,000
Japan [Member]
Income Taxes [Line Items]
Income tax provision	$ 0	$ 0	$ 0	$ 0

Related Parties - Additional Information (Detail) ¥ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended			12 Months Ended
	Feb. 28, 2014 USD ($) shares	Sep. 30, 2015 USD ($) shares	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) shares	Sep. 30, 2015 JPY (¥) shares	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) shares	Jan. 31, 2015 shares
Related Party Transaction [Line Items]
Issuance of ordinary shares		9,223,405		9,223,405	9,223,405		4,263,472
Notes payable, related parties \| $	$ 9,602,000					$ 9,602,000
Series A Preferred Shares [Member]
Related Party Transaction [Line Items]
Debt conversion, Converted instrument, Shares issued	2,365,139
Ordinary Shares [Member]
Related Party Transaction [Line Items]
Debt conversion, Converted instrument, Shares issued	1,515,596
Third-Party Investor [Member]
Related Party Transaction [Line Items]
Related party transaction amount \| $				$ 100,000			$ 17,000
Issuance of ordinary shares	2,263,291							4,769,077
Shin Nippon Biomedical Laboratories Ltd. (SNBL) [Member]
Related Party Transaction [Line Items]
Payment for accounting and administrative services \| $		$ 3,000	$ 26,000	$ 12,000		$ 71,000
Gain or loss recognized on transaction due to related party \| $	$ 0
Shin Nippon Biomedical Laboratories Ltd. (SNBL) [Member] \| Series A Preferred Shares [Member]
Related Party Transaction [Line Items]
Debt conversion, Converted instrument, Shares issued	2,365,139
Shin Nippon Biomedical Laboratories Ltd. (SNBL) [Member] \| Ordinary Shares [Member]
Related Party Transaction [Line Items]
Debt conversion, Converted instrument, Shares issued	1,515,596
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	Sep. 30, 2015	Dec. 31, 2014
Geographic Area Information [Line Items]
Property and equipment, net	$ 1,954	$ 1,269
Asia [Member]
Geographic Area Information [Line Items]
Property and equipment, net	620	745
United States [Member]
Geographic Area Information [Line Items]
Property and equipment, net	$ 1,334	$ 524

Subsequent Events - Additional Information (Detail) - 2014 Plan [Member] - shares	1 Months Ended
	Oct. 31, 2015	Aug. 31, 2015	Mar. 31, 2015
Subsequent Event [Line Items]
Ordinary shares issuable		3,555,774	2,498,597
Subsequent Event [Member]
Subsequent Event [Line Items]
Ordinary shares issuable	1,508,770
Number of shares authorized (in shares)	5,064,544