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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2016	Nov. 01, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2016
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		23,475,469

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 169,015	$ 161,220
Accounts receivable	2,500
Prepaid expenses and other current assets	625	146
Deferred tax assets		18
Total current assets	172,140	161,384
Property and equipment, net	6,693	2,789
Deferred tax assets	32	192
Restricted cash	1,055	1,055
Other assets	53	4
Total assets	179,973	165,424
Current liabilities:
Accounts payable	3,825	2,811
Accrued expenses and other current liabilities	4,833	945
Current portion of capital lease obligation	62	62
Current portion of deferred revenue	2,705
Total current liabilities	11,425	3,818
Long-term liabilities:
Capital lease obligation, net of current portion	31	78
Deferred revenue, net of current portion	8,987
Other liabilities	522	163
Total long-term liabilities	9,540	241
Total liabilities	20,965	4,059
Shareholders’ equity:
Ordinary shares, no par value; 23,474,369 and 21,551,423 shares issued and outstanding at September 30, 2016 and December 31, 2015, respectively	215,505	185,344
Additional paid-in capital	7,568	3,182
Accumulated other comprehensive income	84	41
Accumulated deficit	(72,023)	(35,076)
Total shareholders’ equity	151,134	153,491
Total liabilities, Series A preferred shares and shareholders’ equity	179,973	165,424
Series A Preferred Shares [Member]
Long-term liabilities:
Preferred stock value	$ 7,874	$ 7,874

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2016	Dec. 31, 2015
Common stock, par value
Common stock, shares issued	23,474,369	21,551,423
Common stock, shares outstanding	23,474,369	21,551,423
Series A Preferred Shares [Member]
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares issued	3,901,348	3,901,348
Preferred stock, shares outstanding	3,901,348	3,901,348

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Revenue	$ 392		$ 809	$ 152
Operating expenses:
Research and development	13,686	$ 2,132	26,823	5,589
General and administrative	3,939	2,858	10,809	6,647
Total operating expenses	17,625	4,990	37,632	12,236
Loss from operations	(17,233)	(4,990)	(36,823)	(12,084)
Other income (expense):
Interest income (expense), net	118	25	328	10
Other income (expense), net	(36)	112	(25)	155
Total other income (expense), net	82	137	303	165
Loss before income tax provision	(17,151)	(4,853)	(36,520)	(11,919)
Income tax provision	(384)	(83)	(427)	(182)
Net loss	$ (17,535)	$ (4,936)	$ (36,947)	$ (12,101)
Net loss per share attributable to ordinary shareholders-basic and diluted	$ (0.75)	$ (0.54)	$ (1.64)	$ (1.36)
Weighted-average ordinary shares used in computing net loss per share attributable to ordinary shareholders-basic and diluted	23,445,673	9,223,405	22,571,575	8,895,660

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (17,535)	$ (4,936)	$ (36,947)	$ (12,101)
Other comprehensive income (loss):
Foreign currency translation	8	9	43	(13)
Comprehensive loss	$ (17,527)	$ (4,927)	$ (36,904)	$ (12,114)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities
Net loss	$ (36,947)	$ (12,101)
Adjustments to reconcile net loss to net cash flows used in operating activities:
Depreciation and amortization	525	462
Share-based compensation expense	4,319	3,210
Deferred rent	371	(4)
Deferred income taxes	178	182
Tax benefit related to share-based compensation	(67)
Changes in operating assets and liabilities:
Accounts receivable	(2,500)	193
Prepaid expenses and other current assets	(466)	(40)
Other non-current assets	(53)
Accounts payable	1,899	2,464
Accrued expenses and other current liabilities	2,484	(73)
Deferred revenue	11,692	(152)
Other non-current liabilities	(13)
Net cash used in operating activities	(18,578)	(5,859)
Cash flows from investing activities
Increase in restricted cash		(1,055)
Proceeds from government grant reimbursements for property and equipment		3
Proceeds from the sale of property and equipment	4
Purchases of property and equipment	(2,838)	(887)
Net cash used in investing activities	(2,834)	(1,939)
Cash flows from financing activities
Proceeds from issuance of ordinary shares, net of offering costs	30,000	11,631
Proceeds from issuance of Series B preferred shares, net of offering costs		62,643
Proceeds from government grant		112
Costs associated with initial public offering	(1,075)	(1,417)
Payments on capital lease obligation	(47)	(112)
Proceeds from the exercise of share options	161
Tax benefit related to share-based compensation	67
Net cash provided by financing activities	29,106	72,857
Effect of foreign exchange rates on cash	101	(67)
Net increase in cash and cash equivalents	7,795	64,992
Cash and cash equivalents at beginning of period	161,220	1,048
Cash and cash equivalents at end of period	169,015	66,040
Supplemental disclosure of cash flow information:
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
Property and equipment purchases in accounts payable and accrued expenses at period end	$ 1,595

The Company	9 Months Ended
The Company	Sep. 30, 2016
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 biotechnology 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 Cambridge, Massachusetts. The Company was incorporated with the purpose of combining two commonly held companies, WAVE Life Sciences USA, Inc. (“WAVE USA”), a Delaware corporation (formerly Ontorii, Inc.), and WAVE Life Sciences Japan, Inc. (“WAVE Japan”), a company organized under the laws of Japan (formerly Chiralgen., Ltd.), which occurred on September 12, 2012. On May 31, 2016, WAVE Life Sciences Ireland Limited (“WAVE Ireland”) was formed as a wholly-owned subsidiary of WAVE Life Sciences Ltd. It was formed as a private company limited by shares and the company number is 583482. Its registered office is One Spencer Dock, North Wall Quay, Dublin 1, Ireland. The Company’s primary activities since inception have been developing a synthetic chemistry drug development platform to design, develop and commercialize nucleic acid therapeutic programs, advancing the Company’s neurology franchise, expanding the Company’s research and development activities to enter the clinic, building the Company’s intellectual property, recruiting personnel and raising capital to support these activities. Risks and Uncertainties The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, 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 condensed consolidated financial statements in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and in U.S. dollars.

Significant Accounting Policies

9 Months Ended

Sep. 30, 2016

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, 2015, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 30, 2016, have had no material changes during the three and nine months ended September 30, 2016, except for the two items discussed below.

Cash and Cash Equivalents

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

Revenue Recognition

To date, the Company’s only significant source of revenue is derived from the Pfizer Collaboration Agreement (as defined in Note 4), pursuant to which the Company and Pfizer (as defined in Note 4) have agreed to collaborate on the discovery, development and commercialization of stereopure oligonucleotide therapeutics for the Pfizer Programs (as defined in Note 4), each directed at a genetically-defined hepatic target selected by Pfizer. We entered into the Pfizer Collaboration Agreement in May 2016.

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

•

persuasive evidence of an arrangement exists;

•

delivery has occurred or services have been rendered;

•

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

•

collectability is reasonably assured.

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

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

The Pfizer Collaboration Agreement provides Pfizer with certain options and the Company is required to consider whether such options are substantive. Options are considered substantive if, at the inception of the arrangement, the Company is at risk as to whether the collaboration partner will choose to exercise the option. Factors that the Company considers in evaluating whether an option is substantive include the cost to exercise the option, the overall objective of the arrangement, the benefit the collaborator might obtain from the arrangement without exercising the option and the likelihood the option will be exercised.

When an option is considered substantive, the Company does not consider the option or item underlying the option to be a deliverable at the inception of the arrangement and the associated option fees are not included in allocable consideration, assuming the option is not priced at a significant and incremental discount. Conversely, when an option is not considered substantive, the Company would consider the option, including other deliverables contingent upon the exercise of the option, to be a deliverable at the inception of the arrangement and a corresponding amount would be included in allocable arrangement consideration. In addition, if the price of the option includes a significant incremental discount, the discount would be included as a deliverable at the inception of the arrangement.

The Company has determined that the options held by Pfizer under the Pfizer Collaboration Agreement are not substantive, mainly because they are deemed to be priced at a significant incremental discount as compared to the upfront license fee. Accordingly, the options are considered deliverables at the inception of the arrangement and, therefore, the Company has included any related amounts in the allocable consideration at the outset of the arrangement, which totals $17.5 million.

At the inception of an arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether: (1) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from its performance to achieve the milestone, (2) the consideration relates solely to past performance and (3) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone and the level of effort and investment required to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether a milestone satisfies all of the criteria required to conclude that a milestone is substantive. Milestones that are not considered substantive are recognized as earned if there are no remaining performance obligations over the remaining period of performance, assuming all other revenue recognition criteria are met.

Aside from the program nomination milestone payments, which relate to the options described above, the remaining milestone payments required under the Pfizer Collaboration Agreement are contingent upon the Company’s performance under the Pfizer Collaboration Agreement, including in certain instances, regulatory approval. The Company views the milestones as substantive and has excluded the amounts as allocable consideration at the outset of the arrangement.

During the nine months ended September 30, 2016, the Company received a non-refundable upfront payment of $40.0 million under the Pfizer Collaboration Agreement (as defined in Note 4), which included payment for 1,875,000 shares of the Company’s ordinary shares, which were valued at $30.0 million based on the purchase price of $16.00 per share. During the three months ended September 30, 2016, the Company recorded a receivable of $2.5 million related to a milestone payment that is due from Pfizer under the Pfizer Collaboration Agreement.

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

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

Because there is no discernible pattern of performance given the nature of the research and development efforts, the Company recognizes the allocated revenue for each deliverable under the Pfizer Collaboration Agreement on a straight‑line basis over the period the Company is expected to complete its performance obligations for each deliverable, or unit of accounting. For the first two Pfizer Programs, this period is expected to be from the initiation date of the Pfizer Collaboration Agreement, which was May 5, 2016, and for the other Pfizer Programs, the period is expected to be from the date that work commences on those programs through the earlier of (a) the termination of the research and development performance obligations under the Pfizer Collaboration Agreement, which is May 5, 2020 (the “Research Term”), or (b) the estimated date the Company expects to meet its research and development performance obligations under the Pfizer Collaboration Agreement. Given the uncertainty as to when the research and development performance obligations will be completed, the Company has used the Research Term, for purposes of applying the straight-line method for revenue recognition for the three and nine months ended September 30, 2016.

Unaudited Interim Financial Data

The accompanying interim condensed consolidated balance sheet as of September 30, 2016, the related interim condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2016 and 2015, and cash flows for the nine months ended September 30, 2016 and 2015, and the related interim information contained within the notes to the condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the SEC 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, 2016 and 2015 are unaudited. In the opinion of management, the unaudited interim condensed consolidated financial statements reflect all adjustments, consisting of normal and recurring adjustments, necessary for the fair presentation of the Company’s financial position and results of operations for the interim periods ended September 30, 2016 and 2015. The results of operations for the interim periods are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or any other interim period or future year or period.

Principles of Consolidation

The Company’s condensed 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.

Recently Issued Accounting Pronouncements

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The new standard will be effective on January 1, 2018 and earlier application is permitted only for annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. The Company is currently evaluating the potential impact that ASU 2014-09 may have on its 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 has evaluated the impact of ASU 2015-02 and has concluded that it has no effect on the consolidated financial statements.

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

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

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

In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), which simplifies share-based payment accounting through a variety of amendments. The standard will be effective for annual reporting periods and interim periods within those annual periods, beginning after December 31, 2016, and early adoption is permitted. The Company does not expect the impact of ASU 2016-09 to be material to its consolidated financial statements.

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

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.

Share-Based Compensation

9 Months Ended

Sep. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-Based Compensation

3. SHARE-BASED COMPENSATION

The WAVE Life Sciences Ltd. 2014 Equity Incentive Plan (the “2014 Plan”) authorizes the board of directors or a committee of the board to grant incentive share options (“ISOs”), non-qualified share options (“NQSOs”), share appreciation rights and restricted share awards to eligible employees, outside directors and consultants of the Company. Options generally vest over a period of three or four years, and options that lapse or are forfeited are available to be granted again. The contractual life of all options is ten years from the grant date.

As of September 30, 2016, 1,293,750 ordinary shares remained available for future grant under the 2014 Plan.

The Company measures and records the value of options granted to non-employees over the period of time that services are provided and, as such, unvested portions are subject to re-measurement at subsequent reporting periods.

Share Options

Share option activity under the 2014 Plan for the nine months ended September 30, 2016 is summarized as follows:

	Number of Shares			Weighted- Average Exercise Price
Options outstanding as of January 1, 2016		2,215,342		$	3.88
Granted		1,359,300		$	19.65
Exercised		(47,946	)	$	3.38
Cancelled or forfeited		(17,454	)	$	22.91
Outstanding as of September 30, 2016		3,509,242		$	9.98
Options exercisable as of September 30, 2016		1,077,232		$	2.54
Options vested and expected to vest as of September 30, 2016		3,387,639		$	9.87

The Company recorded share-based compensation expense related to options granted to non-employees in the amount of $0.9 million and $0.3 million for the three months ended September 30, 2016 and 2015, respectively. During the nine months ended September 30, 2016 and 2015, the Company recorded share-based compensation expense related to options granted to non-employees in the amount of $1.9 million and $1.2 million, respectively. Share-based compensation expense related to non-employees is recorded in research and development expenses.

Restricted Share Units

Restricted share unit activity for the nine months ended September 30, 2016 is summarized as follows:

	RSUs		Average Grant Date Fair Value (in dollars per share)
RSUs Outstanding as of January 1, 2016		—	$	—
Granted		22,750	$	21.69
Vested		—	$	—
Forfeited		—	$	—
RSUs Outstanding at September 30, 2016		22,750	$	21.69

In July 2016, the Company granted 22,750 restricted share units with a grant date fair value of $21.69 per unit. The restricted share units fully vest upon the first anniversary of the grant date. Share-based compensation expense related to the restricted share units is recorded in research and development expenses.

Share-based compensation expense for the three and nine months ended September 30, 2016 and 2015 was classified in the condensed consolidated statements of operations as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
	(in thousands)
Research and development expenses	$	1,695	$	476	$	3,207	$	1,657
General and administrative expenses		486		242		1,112		1,553
Total share-based compensation	$	2,181	$	718	$	4,319	$	3,210

- Definition

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

+ References + Details

Pfizer Collaboration and Share Purchase Agreement	9 Months Ended
Pfizer Collaboration and Share Purchase Agreement	Sep. 30, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Pfizer Collaboration and Share Purchase Agreement	4. PFIZER COLLABORATION AND SHARE PURCHASE AGREEMENT On May 5, 2016, the Company entered into a Research, License and Option Agreement (the “Pfizer Collaboration Agreement”) with Pfizer Inc. (“Pfizer”). Pursuant to the terms of the Pfizer Collaboration Agreement, the Company and Pfizer agreed to collaborate on the discovery, development and commercialization of stereopure oligonucleotide therapeutics for up to five programs (the “Pfizer Programs”), each directed at a genetically-defined hepatic target selected by Pfizer (the “Collaboration”). The Company received $10.0 million as an upfront license fee under the Pfizer Collaboration Agreement. Subject to option exercises by Pfizer, assuming five potential products are successfully developed and commercialized, the Company may earn up to $871.0 million in potential research, development and commercial milestone payments, plus royalties, tiered up to low double-digits, on sales of any products that may result from the Collaboration. None of the payments under the Pfizer Collaboration Agreement are refundable. Simultaneously with the entry into the Pfizer Collaboration Agreement, the Company entered into a Share Purchase Agreement (the “Pfizer Equity Agreement,” and together with the Pfizer Collaboration Agreement, the “Pfizer Agreements”) with C.P. Pharmaceuticals International C.V., an affiliate of Pfizer (the “Pfizer Affiliate”). Pursuant to the terms of the Pfizer Equity Agreement, the Pfizer Affiliate purchased 1,875,000 of the Company’s ordinary shares (the “Shares”) at a purchase price of $16.00 per share, for an aggregate purchase price of $30.0 million. The Company did not incur any material costs in connection with the issuance of the Shares. Under the Pfizer Collaboration Agreement, the parties agreed to collaborate during the four-year Research Term. During the Research Term, the Company is responsible to use its commercially reasonable efforts to advance up to five programs through to the selection of clinical candidates. At that stage, Pfizer may elect to license any of these Pfizer Programs exclusively and to have exclusive rights to undertake the clinical development of the resulting clinical candidates into products and the potential commercialization of any such products thereafter. In addition, the Company receives a non-exclusive, royalty-bearing sublicenseable license to use Pfizer’s hepatic targeting technology in any of the Company’s own hepatic programs that are outside the scope of the Collaboration (the “WAVE Programs”). If the Company uses this technology on the WAVE Programs, Pfizer is eligible to receive potential development and commercial milestone payments from the Company. Pfizer is also eligible to receive tiered royalties on sales of any products that include Pfizer’s hepatic targeting technology. Pfizer nominated two hepatic targets upon entry into the Collaboration in May 2016. In August 2016, Pfizer nominated the third hepatic target under the Collaboration and has the option to nominate two additional targets by November 5, 2017. The Collaboration is managed by a joint steering committee in which both parties are represented equally, which will oversee the scientific progression of each Pfizer Program up to the clinical candidate stage. During the four-year Research Term and for a period of two years thereafter, the Company has agreed to work exclusively with Pfizer with respect to using any of the Company’s stereopure oligonucleotide technology that is specific for the applicable hepatic target which is the basis of any Pfizer Program. The stated term of the Pfizer Collaboration Agreement commenced on May 5, 2016 and terminates on the date of the last to expire payment obligations with respect to each Pfizer Program and with respect to each WAVE Program, expires on a program-by-program basis accordingly. Pfizer may terminate its rights related to a Pfizer Program under the Pfizer Collaboration Agreement at its own convenience upon 90 days’ notice to the Company. The Company may also terminate its rights related to a WAVE Program at its own convenience upon 90 days’ notice to Pfizer. The Pfizer Collaboration Agreement may also be terminated by either party in the event of an uncured material breach of the Collaboration Agreement by the other party. During the three and nine months ended September 30, 2016, the Company recognized revenue of $0.4 million and $0.8 million, respectively, under the Pfizer Collaboration Agreement. Deferred revenue amounted to $11.7 million at September 30, 2016, of which $2.7 million is included in current liabilities.

Net Loss Per Ordinary Share

9 Months Ended

Sep. 30, 2016

Earnings Per Share [Abstract]

Net Loss Per Ordinary Share

5. 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 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 and Series A 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 ordinary share equivalents, 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,
	2016		2015
Options to purchase ordinary shares		3,509,242		1,943,381
Restricted share units		22,750		—
Series A preferred shares		3,901,348		3,901,348
Series B preferred shares		—		5,334,892

Leases	9 Months Ended
Leases	Sep. 30, 2016
Leases [Abstract]
Leases	6. LEASES On September 26, 2016, WAVE Life Sciences USA, Inc. (the “Subsidiary”), a wholly-owned subsidiary of WAVE Life Sciences Ltd. (and together with the Subsidiary for purposes of this Note 6, the “Company”) entered into a Lease Agreement (the “Lease”) with King 115 Hartwell LLC, an affiliate of King Street Properties Investments, LLC (the “Landlord”), primarily to build out and conduct certain of the Company’s Good Manufacturing Practice (“GMP”) manufacturing activities, as well as to provide additional laboratory and office space to support the Company’s growth (the “Manufacturing Facility”). The Manufacturing Facility will supplement the Company’s existing laboratory and office facility (the “Cambridge Facility”) at 733 Concord Avenue, Cambridge, Massachusetts, which serves as the Company’s U.S. headquarters. The Cambridge Facility is also leased to the Company by affiliates of the Landlord. The Manufacturing Facility is located at 115 Hartwell Avenue, Lexington, Massachusetts 02421, which is part of The Hartwell Innovation Campus. Under the terms of the Lease, the Company will lease 57,561 square feet (the “Initial Manufacturing Space”) for which the Company shall pay an average base rent of approximately $2.8 million per year during the initial term. The initial term of the Lease commences upon the Company’s occupancy of the Manufacturing Facility, which is anticipated under the Lease to be March 21, 2017, and continues for 10 years and nine months from the actual commencement date. The Lease provides the Company with options to renew for two successive terms of five years each, subject to the terms of the Lease. In addition to the Initial Manufacturing Space, the Company has the option, on or before December 31, 2016, to expand the Initial Manufacturing Space to include the remainder of the building, which is an additional 33,650 square feet (the “Expansion Option”). If the Company exercises the Expansion Option, the Company would be required to pay an additional average base rent of approximately $1.8 million per year during the initial term upon occupancy. Throughout the term of the Lease, the Company is responsible for paying certain costs and expenses, in addition to the rent, as specified in the Lease, including a proportionate share of applicable taxes, operating expenses, and utilities. The Lease includes various covenants, indemnities, defaults, termination rights, and other provisions customary for lease transactions of this nature, including the posting by the Company of an $2.6 million letter of credit as a security deposit which was not posted prior to September 30, 2016.

- Definition

The entire disclosure for lessor entity's leasing arrangements for operating, capital and leveraged leases.

+ References + Details

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	7. INCOME TAXES The Company is a multi-national company subject to taxation in the United States, Japan and Singapore. During the nine months ended September 30, 2016 and 2015, the Company recorded a tax provision of $0.4 million and $0.2 million, respectively, each of which are a result of income generated in the United States for each respective period. During the three and nine months ended September 30, 2016 and 2015, the Company recorded no income tax benefits for the net operating losses incurred in Japan and Singapore, due to its uncertainty of realizing a benefit from those items. In May 2016, the Company established a wholly-owned subsidiary in Ireland, however no income tax expense or benefit has been recorded. 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. During the nine months ended September 30, 2016, the Company amended its tax filings for transfer pricing adjustments in prior years, resulting in an approximately $1.0 million decrease in the U.S. net operating loss carryforwards and a corresponding decrease in the unrecognized tax benefits. This adjustment has no financial statement impact as historically the net operating losses were netted against the unrecognized tax benefits. The Company has $0.2 million of federal research and development credit carryforwards as a result of excess tax deductions related to share-based compensation. The Company will realize the benefit of these excess tax deductions through increases to shareholders’ equity in the periods in which these carryforward credits are utilized to reduce cash tax payments.

Related Parties

9 Months Ended

Sep. 30, 2016

Related Parties

8. RELATED PARTIES

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

•

The Company had cash of $128 thousand and $115 thousand at September 30, 2016 and December 31, 2015, respectively, in depository accounts with Kagoshima Bank, Ltd., an affiliate of one of our shareholders, Kagoshima Shinsangyo Sousei Investment Limited Partnership.

•

The Company made payments for lease rentals and other related expenses in the amount of $4 thousand and $55 thousand to Shin Nippon Biomedical Laboratories Ltd. (“SNBL”) for the three months ended September 30, 2016 and 2015, respectively. For the nine months ended September 30, 2016 and 2015 the Company paid SNBL $55 thousand, and $144 thousand, respectively, for lease rentals and other related expenses.

•

Pursuant to the terms of a service agreement held with SNBL, the Company paid SNBL $0 and $3 thousand for the three months ended September 30, 2016 and 2015, respectively, for accounting and administrative services provided to the Company and its affiliates. For the nine months ended September 30, 2016 and 2015 the Company paid SNBL $3 thousand and $12 thousand, respectively for accounting and administrative services provided to the Company and its affiliates.

•

Pursuant to the terms of a service agreement with SNBL, which the Company entered into in the third quarter 2015, the Company paid SNBL $4 thousand and $329 thousand for the three and nine months ended September 30, 2016, respectively, for contract research services provided to the Company and its affiliates. Although the agreement was entered into in the third quarter 2015, there were no payments made related to this agreement for the three and nine months ended September 30, 2015.

•

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

•

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

Geographic Data

9 Months Ended

Sep. 30, 2016

Text Block [Abstract]

Geographic Data

9. GEOGRAPHIC DATA

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

	September 30, 2016		December 31, 2015
	(in thousands)
Asia	$	476	$	578
United States		6,217		2,211
Total long-lived assets	$	6,693	$	2,789

Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2016

Accounting Policies [Abstract]

Cash and Cash Equivalents

Revenue Recognition

•

persuasive evidence of an arrangement exists;

•

delivery has occurred or services have been rendered;

•

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

•

collectability is reasonably assured.

Unaudited Interim Financial Data

Principles of Consolidation

Recently Issued Accounting Pronouncements

- Definition

Disclosure of accounting policy for cash and cash equivalents, including the policy for determining which items are treated as cash equivalents. Other information that may be disclosed includes (1) the nature of any restrictions on the entity's use of its cash and cash equivalents, (2) whether the entity's cash and cash equivalents are insured or expose the entity to credit risk, (3) the classification of any negative balance accounts (overdrafts), and (4) the carrying basis of cash equivalents (for example, at cost) and whether the carrying amount of cash equivalents approximates fair value.

+ References + Details

Share-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Share Option Activity

Share Options

Share option activity under the 2014 Plan for the nine months ended September 30, 2016 is summarized as follows:

	Number of Shares			Weighted- Average Exercise Price
Options outstanding as of January 1, 2016		2,215,342		$	3.88
Granted		1,359,300		$	19.65
Exercised		(47,946	)	$	3.38
Cancelled or forfeited		(17,454	)	$	22.91
Outstanding as of September 30, 2016		3,509,242		$	9.98
Options exercisable as of September 30, 2016		1,077,232		$	2.54
Options vested and expected to vest as of September 30, 2016		3,387,639		$	9.87

Summary of Restricted Share Units Activity

Restricted Share Units

Restricted share unit activity for the nine months ended September 30, 2016 is summarized as follows:

	RSUs		Average Grant Date Fair Value (in dollars per share)
RSUs Outstanding as of January 1, 2016		—	$	—
Granted		22,750	$	21.69
Vested		—	$	—
Forfeited		—	$	—
RSUs Outstanding at September 30, 2016		22,750	$	21.69

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

Share-based compensation expense for the three and nine months ended September 30, 2016 and 2015 was classified in the condensed consolidated statements of operations as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
	(in thousands)
Research and development expenses	$	1,695	$	476	$	3,207	$	1,657
General and administrative expenses		486		242		1,112		1,553
Total share-based compensation	$	2,181	$	718	$	4,319	$	3,210

Net Loss Per Ordinary Share (Tables)

9 Months Ended

Sep. 30, 2016

Earnings Per Share [Abstract]

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

	As of September 30,
	2016		2015
Options to purchase ordinary shares		3,509,242		1,943,381
Restricted share units		22,750		—
Series A preferred shares		3,901,348		3,901,348
Series B preferred shares		—		5,334,892

Geographic Data (Tables)

9 Months Ended

Sep. 30, 2016

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, 2016		December 31, 2015
	(in thousands)
Asia	$	476	$	578
United States		6,217		2,211
Total long-lived assets	$	6,693	$	2,789

Significant Accounting Policies - Additional Information (Detail) - Pfizer Inc. [Member] - Research, License and Option Agreement [Member] - USD ($) $ / shares in Units, $ in Millions		3 Months Ended	9 Months Ended
	May 05, 2016	Sep. 30, 2016	Sep. 30, 2016
Significant Accounting Policies [Line Items]
Program nomination milestone payments			$ 17.5
Non-refundable upfront amount related to research and development services			$ 40.0
Shares issued under equity agreement	1,875,000		1,875,000
Ordinary shares, value	$ 30.0		$ 30.0
Purchase price per share	$ 16.00	$ 16.00	$ 16.00
Milestone payment receivable		$ 2.5

Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 2,181	$ 718	$ 4,319	$ 3,210
Restricted Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, granted	22,750			22,750
Average grant date fair value, granted	$ 21.69			$ 21.69
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life of options				10 years
Ordinary shares available for future grant		1,293,750		1,293,750
2014 Plan [Member] \| Non-Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 900	$ 300	$ 1,900	$ 1,200
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]	9 Months Ended
	Sep. 30, 2016 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Number of Shares, Beginning Balance \| shares	2,215,342
Granted, Number of Shares \| shares	1,359,300
Exercised, Number of Shares \| shares	(47,946)
Cancelled or forfeited, Number of Shares \| shares	(17,454)
Options outstanding, Number of Shares, Ending Balance \| shares	3,509,242
Options exercisable, Number of Shares \| shares	1,077,232
Options vested and expected to vest, Number of Shares \| shares	3,387,639
Options outstanding, Weighted Average Exercise Price, Beginning Balance \| $ / shares	$ 3.88
Granted, Weighted Average Exercise Price \| $ / shares	19.65
Exercised, Weighted Average Exercise Price \| $ / shares	3.38
Cancelled or forfeited, Weighted Average Exercise Price \| $ / shares	22.91
Option outstanding, Weighted Average Exercise Price, Ending Balance \| $ / shares	9.98
Options exercisable, Weighted Average Exercise Price \| $ / shares	2.54
Options vested and expected to vest, Weighted Average Exercise Price \| $ / shares	$ 9.87

Share-Based Compensation - Summary of Restricted Stock Units Activity (Detail) - Restricted Share Units [Member] - $ / shares	1 Months Ended	9 Months Ended
	Jul. 31, 2016	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of Shares	22,750	22,750
Outstanding, Number of Shares, Ending Balance		22,750
Granted, Average Grant Date Fair Value	$ 21.69	$ 21.69
Outstanding, Average Grant Date Fair Value, Ending Balance		$ 21.69

Share-Based Compensation - Summary of Share-based Compensation Expense Classified in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	$ 2,181	$ 718	$ 4,319	$ 3,210
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	1,695	476	3,207	1,657
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	$ 486	$ 242	$ 1,112	$ 1,553

Pfizer Collaboration and Share Purchase Agreement - Additional Information (Detail)		3 Months Ended	9 Months Ended
	May 05, 2016 USD ($) Program Product $ / shares shares	Sep. 30, 2016 USD ($) $ / shares	Sep. 30, 2016 USD ($) $ / shares shares
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Current portion of deferred revenue		$ 2,705,000	$ 2,705,000
Pfizer Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of research programs, counterparty nomination \| Program	5
Research term, description			Under the Pfizer Collaboration Agreement, the parties agreed to collaborate during the four-year Research Term. During the Research Term, the Company is responsible to use its commercially reasonable efforts to advance up to five programs through to the selection of clinical candidates. At that stage, Pfizer may elect to license any of these Pfizer Programs exclusively and to have exclusive rights to undertake the clinical development of the resulting clinical candidates into products and the potential commercialization of any such products thereafter.
Collaboration agreement, additional period after research program	2 years
Revenue recognized		400,000	$ 800,000
Deferred revenue		11,700,000	11,700,000
Current portion of deferred revenue		$ 2,700,000	$ 2,700,000
Maximum [Member] \| Pfizer Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expected earnings from milestone payments under research program	$ 871,000,000
Research, License and Option Agreement [Member] \| Pfizer Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront amount related to research and development services	$ 10,000,000
Number of potential products are successfully developed and commercialized \| Product	5
Collaboration agreement refundable	$ 0
Shares issued under equity agreement \| shares	1,875,000		1,875,000
Equity investment aggregate purchase price	$ 30,000,000		$ 30,000,000
Purchase price per share \| $ / shares	$ 16.00	$ 16.00	$ 16.00
Collaborative agreement research term	4 years
Collaboration agreement termination period			90 days

Net Loss Per Ordinary Share - Anti-Dilutive Shares Excluded from Calculation of Diluted Net Loss Per Ordinary Share (Detail) - shares	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Series A Preferred Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from calculation of diluted net loss per share	3,901,348	3,901,348
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	3,509,242	1,943,381
Restricted Share Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from calculation of diluted net loss per share	22,750

Leases - Additional Information (Detail) $ in Millions		9 Months Ended
Leases - Additional Information (Detail) $ in Millions	Sep. 26, 2016 USD ($) ft² Term	Sep. 30, 2016 USD ($) ft²	Oct. 01, 2016 USD ($)
Initial Manufacturing Space [Member] \| Subsequent Event [Member] \| Letter of Credit [Member]
Operating Leased Assets [Line Items]
Security deposit			$ 2.6
WAVE Life Sciences USA, Inc. [Member] \| Initial Manufacturing Space [Member] \| King 115 Hartwell LLC [Member]
Operating Leased Assets [Line Items]
Area of lease \| ft²	57,561
Average base rent	$ 2.8
Lease agreement date of commencement	Mar. 21, 2017
Lease agreement, initial term	10 years 9 months
Lease renewal period	5 years
Number of successive lease renewal option \| Term	2
WAVE Life Sciences USA, Inc. [Member] \| Expansion Option [Member] \| King 115 Hartwell LLC [Member]
Operating Leased Assets [Line Items]
Area of lease \| ft²		33,650
Average base rent		$ 1.8

Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Taxes [Line Items]
Income tax benefit (provision)		$ 384,000	$ 83,000	$ 427,000	$ 182,000
Research and Development Credit Carryforwards [Member] \| Federal [Member]
Income Taxes [Line Items]
Research and development tax credit carryforward		200,000		200,000
United States [Member]
Income Taxes [Line Items]
Income tax benefit (provision)				400,000	200,000
Decrease in unrecognized tax benefits due to pricing adjustments in prior years				1,000,000
Japan [Member]
Income Taxes [Line Items]
Income tax benefit (provision)		0	0	0	0
Singapore [Member]
Income Taxes [Line Items]
Income tax benefit (provision)		$ 0	$ 0	$ 0	$ 0
Ireland [Member]
Income Taxes [Line Items]
Income tax benefit (provision)	$ 0

Related Parties - Additional Information (Detail) ¥ in Thousands	3 Months Ended		9 Months Ended			12 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 JPY (¥)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Third-Party Investor [Member]
Related Party Transaction [Line Items]
Related party transaction amount			$ 128,000			$ 115,000
Shin Nippon Biomedical Laboratories Ltd. (SNBL) [Member]
Related Party Transaction [Line Items]
Lease rentals and other related expenses	$ 4,000	$ 55,000	55,000		$ 144,000
Payment for accounting and administrative services	0	3,000	3,000		12,000
Payment for contract research services	$ 4,000	$ 0	$ 329,000		$ 0
Scientific Advisor [Member] \| Consulting Agreement [Member]
Related Party Transaction [Line Items]
Consulting agreement termination notice period			14 days	14 days
Consulting service expenses			$ 13,000
Scientific Advisor [Member] \| Informal Consulting Arrangement [Member]
Related Party Transaction [Line Items]
Consulting service expenses			$ 2,000	¥ 250

Geographic Data - Summary of Long-Lived Assets by Geographical Areas (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Geographic Area Information [Line Items]
Property and equipment, net	$ 6,693	$ 2,789
Asia [Member]
Geographic Area Information [Line Items]
Property and equipment, net	476	578
United States [Member]
Geographic Area Information [Line Items]
Property and equipment, net	$ 6,217	$ 2,211