Prothena (PRTA) 10-Q 7 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 20, 2017
Document Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	PRTA
Entity Registrant Name	Prothena Corp plc
Entity Central Index Key	1,559,053
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Ordinary Shares Outstanding		38,446,761

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 456,061	$ 386,923
Receivable from Roche	220	178
Prepaid expenses and other current assets	12,783	4,261
Total current assets	469,064	391,362
Non-current assets:
Property and equipment, net	55,384	56,452
Deferred tax assets, non-current	6,392	5,913
Restricted cash	4,056	4,056
Other non-current assets	2,784	2,193
Total non-current assets	68,616	68,614
Total assets	537,680	459,976
Current liabilities:
Accounts payable	11,062	13,069
Accrued research and development	18,482	19,073
Income taxes payable, current	53	378
Build-to-suit lease obligation, current	372	0
Other current liabilities	9,289	8,555
Total current liabilities	39,258	41,075
Non-current liabilities:
Income taxes payable, non-current	0	98
Deferred rent	266	2,080
Build-to-suit lease obligation, non-current	51,902	51,320
Total non-current liabilities	52,168	53,498
Total liabilities	91,426	94,573
Commitments and contingencies (Note 7)
Shareholders’ equity:
Euro deferred shares, €22 nominal value: Authorized shares - 10,000 at September 30, 2017 and December 31, 2016 Issued and outstanding shares - none at September 30, 2017 and December 31, 2016	0	0
Ordinary shares, $0.01 par value: Authorized shares - 100,000,000 at September 30, 2017 and December 31, 2016 Issued and outstanding shares - 38,443,261 and 34,752,116 at September 30, 2017 and December 31, 2016	384	348
Additional paid-in capital	840,462	654,266
Accumulated deficit	(394,592)	(289,211)
Total shareholders’ equity	446,254	365,403
Total liabilities and shareholders’ equity	$ 537,680	$ 459,976

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical)	Sep. 30, 2017$ / sharesshares	Sep. 30, 2017€ / sharesshares	Dec. 31, 2016$ / sharesshares	Dec. 31, 2016€ / sharesshares
Statement of Financial Position [Abstract]
Euro deferred shares, nominal value (in euros per share) | € / shares		€ 22		€ 22
Euro deferred shares, number of shares authorized (in shares)	10,000	10,000	10,000	10,000
Euro deferred shares, number of issued shares	0	0	0	0
Euro deferred shares, number of outstanding shares (in shares)	0	0	0	0
Ordinary shares, par value (in dollars per share) | $ / shares	$ 0.01		$ 0.01
Ordinary shares, number of authorized shares (in shares)	100,000,000	100,000,000	100,000,000	100,000,000
Ordinary shares, number of issued shares (in shares)	38,443,261	38,443,261	34,752,116	34,752,116
Ordinary shares, number of outstanding shares (in shares)	38,443,261	38,443,261	34,752,116	34,752,116

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Collaboration revenue	$ 219	$ 286	$ 27,290	$ 884
Total revenue	219	286	27,290	884
Operating expenses:
Research and development	41,315	26,838	101,045	79,690
General and administrative	12,438	16,136	34,182	31,452
Total operating expenses	53,753	42,974	135,227	111,142
Loss from operations	(53,534)	(42,688)	(107,937)	(110,258)
Other income (expense):
Interest income (expense), net	118	138	(228)	405
Other expense, net	(683)	(268)	(1,967)	(561)
Total other expense, net	(565)	(130)	(2,195)	(156)
Loss before income taxes	(54,099)	(42,818)	(110,132)	(110,414)
Provision for (benefit from) income taxes	(1,705)	421	(4,653)	791
Net loss	$ (52,394)	$ (43,239)	$ (105,479)	$ (111,205)
Basic and diluted net loss per share (in dollars per share)	$ (1.37)	$ (1.26)	$ (2.82)	$ (3.25)
Shares used to compute basic and diluted net loss per share (in shares)	38,292	34,413	37,384	34,266

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Operating activities
Net loss	$ (52,394)	$ (43,239)	$ (105,479)	$ (111,205)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization			2,285	1,509
Share-based compensation	7,102	11,448	19,357	19,718
Deferred income taxes			(479)	(3,156)
Interest expense under build-to-suit lease obligation			2,759	550
Gain from early lease retirement			(2,096)	0
Gain from disposal of fixed assets			(5)	0
Changes in operating assets and liabilities:
Receivable from Roche			(42)	100
Prepaid and other assets			(11,183)	(964)
Accounts payable, accruals and other liabilities			3,224	11,004
Net cash used in operating activities			(91,659)	(82,444)
Investing activities
Purchases of property and equipment			(3,250)	(9,497)
Proceeds from disposal of fixed assets			105	0
Net cash used in investing activities			(3,145)	(9,497)
Financing activities
Proceeds from issuance of ordinary shares in public offering, net			150,323	128,777
Proceeds from issuance of ordinary shares upon exercise of stock options			15,424	2,396
Reduction of build-to-suit lease obligation			(1,805)	0
Proceeds from tenant improvement allowance under build-to-suit transaction			0	2,812
Net cash provided by financing activities			163,942	133,985
Net increase in cash, cash equivalents and restricted cash			69,138	42,044
Cash, cash equivalents and restricted cash, beginning of the year			390,979	370,586	$ 370,586
Cash, cash equivalents and restricted cash, end of the period	$ 460,117	$ 412,630	460,117	412,630	$ 390,979
Supplemental disclosures of cash flow information
Cash paid for income taxes, net of refunds			294	1,557
Supplemental disclosures of non-cash investing and financing activities
Acquisition of property and equipment included in accounts payable and accrued liabilities			163	4,077
Stock option shortfall			0	(18)
Receivable from option exercises			1,128	76
Amounts capitalized under build-to-suit lease transaction			0	38,584
Interest capitalized during construction period for build-to-suit lease transaction			$ 0	$ 713

Organization

Organization	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Description of Business Prothena Corporation plc and its subsidiaries (“Prothena” or the “Company”) is a global, late-stage clinical biotechnology company establishing fully-integrated research, development and commercial capabilities. Fueled by its deep scientific understanding built over decades of research in protein misfolding and cell adhesion - the root causes of many serious or currently untreatable amyloid and inflammatory diseases - Prothena seeks to fundamentally change the course of progressive diseases associated with this biology. The Company's pipeline of antibody-based product candidates target a number of indications including AL amyloidosis (NEOD001), Parkinson’s disease and other related synucleinopathies (PRX002/RG7935) and ATTR amyloidosis (PRX004). The Company continues discovery of additional novel therapeutic candidates where its deep scientific understanding of disease pathology can be leveraged. The Company is a public limited company formed under the laws of Ireland. The Company separated from Elan Corporation, plc (“Elan”) on December 20, 2012. After the separation from Elan, and the related distribution of the Company's ordinary shares to Elan’s shareholders, the Company's ordinary shares commenced trading on The Nasdaq Global Market under the symbol “PRTA” on December 21, 2012 and currently trade on The Nasdaq Global Select Market. Liquidity and Business Risks As of September 30, 2017 , the Company had an accumulated deficit of $394.6 million and cash and cash equivalents of $456.1 million . In March 2017, the Company sold an aggregate of 2,700,000 ordinary shares for net proceeds of approximately $150.3 million , after deducting the underwriting discount and offering expenses, in an underwritten public offering. Based on the Company's business plans, management believes that the Company's cash and cash equivalents at September 30, 2017 are sufficient to meet its obligations for at least the next twelve months. To operate beyond such period, or if the Company elects to increase its spending on development programs significantly above current long-term plans or enters into potential licenses and or other acquisitions of complementary technologies, products or companies, the Company may need additional capital. The Company expects to continue to finance future cash needs that exceed its cash from operating activities primarily through its current cash and cash equivalents, its collaboration with Roche, and to the extent necessary, through proceeds from public or private equity or debt financings, loans and other collaborative agreements with corporate partners or other arrangements. The Company is subject to a number of risks, including but not limited to: the uncertainty of the Company's research and development (“R&D”) efforts resulting in future successful commercial products; obtaining regulatory approval for its product candidates; its ability to successfully commercialize its product candidates, if approved; significant competition from larger organizations; reliance on the proprietary technology of others; dependence on key personnel; uncertain patent protection; dependence on corporate partners and collaborators; and possible restrictions on reimbursement from governmental agencies and healthcare organizations, as well as other changes in the healthcare industry.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Preparation and Presentation of Financial Information These accompanying Unaudited Interim Condensed Consolidated Financial Statements have been prepared in accordance with the accounting principles generally accepted in the U.S. (“GAAP”) and with the instructions for Form 10-Q and Regulation S-X statements. Accordingly, they do not include all of the information and notes required for complete financial statements. These interim Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and Notes thereto contained in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on February 27, 2017 (the "2016 Form 10-K"). These Unaudited Interim Condensed Consolidated Financial Statements are presented in U.S. dollars, which is the functional currency of the Company and its consolidated subsidiaries. These Unaudited Interim Condensed Consolidated Financial Statements include the accounts of the Company and its consolidated subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Unaudited Interim Financial Information The accompanying Unaudited Interim Condensed Consolidated Financial Statements and related disclosures are unaudited, have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair presentation of the results of operations for the periods presented. The year-end condensed consolidated balance sheet data was derived from audited financial statements, however certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted. The condensed consolidated results of operations for any interim period are not necessarily indicative of the results to be expected for the full year or for any other future year or interim period. Certain amounts in the Condensed Consolidated Financial Statements have been reclassified to conform to the current year presentation. Use of Estimates The preparation of the Condensed Consolidated Financial Statements in conformity with GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosures. On an ongoing basis, management evaluates its estimates, including critical accounting policies or estimates related to revenue recognition, share-based compensation and research and development expenses. The Company bases its estimates on historical experience and on various other market specific and other relevant assumptions that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Because of the uncertainties inherent in such estimates, actual results may differ materially from these estimates. Significant Accounting Policies There were no significant changes to the accounting policies during the nine months ended September 30, 2017 , from the significant accounting policies described in Note 2 of the "Notes to Consolidated Financial Statements" in the 2016 Form 10-K, with the exception of those noted below. Share-based Compensation To determine the fair value of share-based payment awards, the Company uses the Black-Scholes option-pricing model. The determination of fair value using the Black-Scholes option-pricing model is affected by the Company’s share price as well as assumptions regarding a number of complex and subjective variables. Share-based compensation expense is recognized on a straight-line basis over the requisite service period for each award. Further, share-based compensation expense recognized in the Condensed Consolidated Statements of Operations is based on awards expected to vest and therefore the amount of expense has been reduced for estimated forfeitures. If actual forfeitures differ from estimates at the time of grant they will be revised in subsequent periods. The Company bases its assumptions on historical data when available or when not available, on a peer group of companies. If factors change and different assumptions are employed in determining the fair value of share-based awards, the share-based compensation expense recorded in future periods may differ significantly from what was recorded in the current period (see Note 10 for further information). The Company will record any excess tax benefits or deficiencies from its equity awards in its Condensed Consolidated Statements of Operations in the reporting periods in which stock options are exercised. Segment and Concentration of Risks The Company operates in one segment. The Company’s chief operating decision maker (the “CODM”), its Chief Executive Officer, manages the Company’s operations on a consolidated basis for purposes of allocating resources. When evaluating the Company’s financial performance, the CODM reviews all financial information on a consolidated basis. Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents and accounts receivable. The Company places its cash equivalents with high credit quality financial institutions and by policy, limits the amount of credit exposure with any one financial institution. Deposits held with banks may exceed the amount of insurance provided on such deposits. The Company has not experienced any losses on its deposits of cash and cash equivalents and its credit risk exposure is up to the extent recorded on the Company's Condensed Consolidated Balance Sheet. Receivable from Roche as of September 30, 2017 and December 31, 2016 are amounts due from Roche entities located in the U.S. and Switzerland under the License Agreement that became effective January 22, 2014. Revenue recorded in the Statements of Operations consists of reimbursement from Roche for research and development services. Credit risk exposure is up to the extent recorded on the Company's Condensed Consolidated Balance Sheet. As of September 30, 2017 , $54.7 million of the Company's long-lived assets were held in the U.S. and $0.7 million were in Ireland. As of December 31, 2016 , $55.7 million of the Company's long-lived assets were held in the U.S. and $0.8 million were in Ireland. The Company does not own or operate facilities for the manufacture, packaging, labeling, storage, testing or distribution of nonclinical or clinical supplies of any of its drug candidates, including for commercial supplies if the Company obtains regulatory approval to market any of its drug candidates. The Company instead contracts with and relies on third-parties to manufacture, package, label, store, test and distribute all pre-clinical development and clinical supplies of our drug candidates, and it plans to continue to do so for the foreseeable future, including for commercial supplies if the Company obtains regulatory approval to market any of its drug candidates. The Company also relies on third-party consultants to assist in managing these third-parties and assist with its manufacturing strategy. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update 2014-09 (ASU 2014-09), Revenue from Contracts with Customers, which is largely codified in Accounting Standards Codification 606 (ASC Topic 606). ASU 2014-09 supersedes the revenue recognition requirements in Revenue Recognition (Topic 605). ASC Topic 606 supersedes nearly all existing revenue recognition guidance under GAAP. To date, we have derived our revenues from a license and collaboration agreement and a service agreement. The consideration we are eligible to receive under these agreements includes upfront payments, research and development funding, milestone payments and royalties. The core principle of ASC Topic 606 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASC Topic 606 defines a five-step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP, including identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation, among others. ASC Topic 606 is effective for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period, which for the Company is January 1, 2018. Early adoption is permitted after January 1, 2017. The standard allows for two transition methods - retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying the standard recognized at the date of initial adoption. The Company expects to adopt the requirements of the new standard effective January 1, 2018 using the retrospective with the cumulative effect transition method. In March 2016, the FASB issued ASU No. 2016-08 Revenue from Contracts with Customers: Principal vs. Agent Considerations, to help provide interpretive clarifications on the new guidance for ASC Topic 606. In April 2016, the FASB issued ASU No. 2016-10 Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing to clarify the guidance for identifying performance obligations and accounting for licenses of intellectual property. In May 2016, the FASB issued ASU No. 2016-12 Revenue from Contracts with Customers: Narrow-Scope Improvements; and Practical Expedients, to improve the guidance on collectibility, noncash consideration, and completed contracts at transition. In December 2016, the FASB issued ASU No. 2016-20 Revenue from Contracts with Customers: Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers. ASC Topic 606 differs from the current accounting standard in many respects, such as in the accounting for variable consideration, including milestone payments and the measurement of progress toward completion of performance obligations. The Company does not expect the adoption of this standard to have a material impact on its consolidated financial statements in the period of adoption. Under its current accounting policy, the Company recognizes milestone revenue using the milestone method specified in ASC 605-28, which generally results in the recognition of the milestone payment as revenue in the period that the milestone is achieved. However, under the new accounting standard, it is possible to start to recognize milestone revenue before the milestone is achieved, subject to management’s assessment of whether it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. As such, the timing of revenue recognition for our license and collaboration agreements may change under the new revenue standard. In February 2016, the FASB issued Accounting Standards Update 2016-02 (ASU 2016-02), Leases (ASC Topic 842), which will require lessees to recognize assets and liabilities for leases with lease terms of more than 12 months. Consistent with current GAAP, the recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee primarily will depend on its classification as a finance or operating lease. However, unlike current GAAP, which requires only capital leases to be recognized on the balance sheet, the new guidance will require both types of leases to be recognized on the balance sheet. ASC Topic 842 is effective for annual periods beginning after December 15, 2018, and interim periods within those years. Early adoption is permitted for all entities. The standard requires that entities use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. Entities have the option to use certain relief. Full retrospective application is prohibited. Note 7, "Commitments and Contingencies" provides details on the Company's current lease arrangements. The Company continues to evaluate the provisions of ASC Topic 842 to determine the impact the adoption of ASU 2016-02 will have on its consolidated financial statements; however, the Company anticipates recognition of additional assets and corresponding liabilities related to leases on its consolidated balance sheets. Additionally, the Company expects to derecognize its build-to-suit asset and liabilities upon adoption pending its final evaluation. In March 2016, the FASB issued Accounting Standards Update 2016-09 (ASU 2016-09), Improvements to Employee Share-Based Payment Accounting, which modifies certain aspects of the accounting for share-based payment transactions, including income taxes, classification of awards and classification in the statement of cash flows. Through December 31, 2016, excess tax benefits or deficiencies from the Company's equity awards were recorded as additional paid-in capital in its Consolidated Balance Sheets. Upon adoption, the Company will record any excess tax benefits or deficiencies from its equity awards in its Condensed Consolidated Statements of Operations in the reporting periods in which stock options are exercised. This guidance also requires excess tax benefits and deficiencies to be presented as an operating activity on the statement of cash flows and allows an entity to make an accounting policy election to either estimate expected forfeitures or to account for them as they occur. The ASU is effective for reporting periods beginning after December 15, 2016, with early adoption permitted. The Company adopted this ASU on January 1, 2017. Pursuant to the adoption of ASU 2016-09, tax attributes previously tracked off balance sheet have been recorded as deferred tax assets, offset by a valuation allowance. In addition, the Company has reversed its non-current tax liability of $98,000 with the offsetting entry recorded to retained earnings pursuant to the adoption of this ASU. Further, the year-to-date excess benefits have been recorded as a discrete benefit to the tax provision. For the nine months ended September 30, 2017 , the Company recorded excess tax benefits of $5.4 million as part of its income tax provision in the Condensed Consolidated Statements of Operations. The Company's income tax expense will continue to be impacted by fluctuations in stock price between the grant dates and the exercise dates of its option awards. The presentation requirements for cash flows related to excess tax benefits will be applied retrospectively; as such, prior years have been restated. Lastly, the Company elected to continue to estimate the number of forfeitures related to share-based payments, rather than account for forfeitures as they occur. In August 2016, the FASB issued Accounting Standards Update 2016-15 (ASU 2016-15), Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payments, which clarifies existing guidance related to accounting for cash receipts and cash payments and classification of statement of cash flow. This guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, but early adoption is permitted. The Company does not expect the adoption of ASU 2016-15 to have an impact on its consolidated financial statements. In May 2017, the FASB issued Accounting Standards Update 2017-09 (ASU 2017-09), Compensation - Stock Compensation (Topic 718) - Scope of Modification Accounting, which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. Entities would apply the modification accounting guidance if the value, vesting requirements or classification of a share-based payment award changes. This pronouncement is effective for annual reporting periods beginning after December 15, 2017, but early adoption is permitted. The Company does not expect the adoption of ASU 2017-09 to have an impact on its consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures certain financial assets and liabilities at fair value on a recurring basis, including cash equivalents. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. A three-tier fair value hierarchy is established as a basis for considering such assumptions and for inputs used in the valuation methodologies in measuring fair value: Level 1 — Observable inputs such as quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 — Include other inputs that are based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant inputs are observable in the market or can be derived from observable market data. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs including interest rate curves, foreign exchange rates, and credit ratings. Level 3 — Unobservable inputs that are supported by little or no market activities, which would require the Company to develop its own assumptions. The fair value hierarchy also requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The carrying amounts of certain financial instruments, such as cash equivalents, accounts receivable, accounts payable and accrued liabilities, approximate fair value due to their relatively short maturities, and low market interest rates, if applicable. Based on the fair value hierarchy, the Company classifies its cash equivalents within Level 1. This is because the Company values its cash equivalents using quoted market prices. The Company’s Level 1 securities consist of $364.2 million and $307.3 million in money market funds included in cash and cash equivalents at September 30, 2017 and December 31, 2016 , respectively.

Composition of Certain Balance

Composition of Certain Balance Sheet Items	9 Months Ended
	Sep. 30, 2017
Composition of Certain Balance Sheet Items [Abstract]
Composition of Certain Balance Sheet Items	Composition of Certain Balance Sheet Items Property and Equipment, net Property and equipment, net consisted of the following (in thousands): September 30, 2017 December 31, 2016 Machinery and equipment $ 9,051 $ 9,629 Leasehold improvements 579 2,769 Purchased computer software 987 363 Build-to-suit property 51,760 51,359 62,377 64,120 Less: accumulated depreciation and amortization (6,993 ) (7,668 ) Property and equipment, net $ 55,384 $ 56,452 Depreciation expense was $0.8 million and $2.3 million for the three and nine months ended September 30, 2017 , respectively, compared to $0.8 million and $1.5 million for the three and nine months ended September 30, 2016 , respectively. Other Current Liabilities Other current liabilities consisted of the following (in thousands): September 30, 2017 December 31, 2016 Payroll and related expenses $ 7,509 $ 6,629 Professional services 384 435 Deferred rent 49 363 Other 1,347 1,128 Other current liabilities $ 9,289 $ 8,555

Net Loss Per Ordinary Share

Net Loss Per Ordinary Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Net Income (Loss) Per Ordinary Share	Net Loss Per Ordinary Share Basic net income (loss) per ordinary share is calculated by dividing net income (loss) by the weighted-average number of ordinary shares outstanding during the period. Shares used in diluted net income per ordinary share would include the dilutive effect of ordinary shares potentially issuable upon the exercise of stock options outstanding. However, potentially issuable ordinary shares are not used in computing diluted net loss per ordinary share as their effect would be anti-dilutive due to the loss recorded during the three and nine months ended September 30, 2017 and 2016 , and therefore diluted net loss per share is equal to basic net loss per share. Net loss per ordinary share was determined as follows (in thousands, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Numerator: Net loss $ (52,394 ) $ (43,239 ) $ (105,479 ) $ (111,205 ) Denominator: Weighted-average ordinary shares outstanding 38,292 34,413 37,384 34,266 Net loss per share: Basic and diluted net loss per share $ (1.37 ) $ (1.26 ) $ (2.82 ) $ (3.25 ) The equivalent ordinary shares not included in diluted net loss per share because their effect would be anti-dilutive are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Stock options to purchase ordinary shares 4,387 4,170 4,387 4,170

Build-to-Suit Lease

Build-to-Suit Lease	9 Months Ended
	Sep. 30, 2017
Leases [Abstract]
Build-to-Suit Lease	Build-to-Suit Lease In March 2016 , the Company entered into a noncancelable operating sublease (the "Lease") to lease 128,751 square feet of office and laboratory space in South San Francisco, California (the “Current SSF Facility”). Subsequently, in April 2016, the Company took possession of the Current SSF Facility. The Lease includes a free rent period and escalating rent payments and has a term that expires on December 31, 2023 , unless terminated earlier. The Company's obligation to pay rent commenced on August 1, 2016. The Company is obligated to make lease payments totaling approximately $39.2 million over the lease term. The Lease further provides that the Company is obligated to pay to the sublandlord and master landlord certain costs, including taxes and operating expenses. Expected future lease payments under the build-to-suit lease as of September 30, 2017 are included in Note 7, “Commitments and Contingencies.” In connection with this Lease, the Company received a tenant improvement allowance of $14.2 million from the sublandlord and the master landlord, for the costs associated with the design, development and construction of tenant improvements for the Current SSF Facility. The Company is obligated to fund all costs incurred in excess of the tenant improvement allowance. The scope of the tenant improvements did not qualify as “normal tenant improvements” under the lease accounting guidance. Accordingly, for accounting purposes, the Company is the deemed owner of the building during the construction period and the Company capitalized $36.5 million within property and equipment, net, including $1.2 million for capitalized interest and recognized a corresponding build-to-suit obligation in other non-current liabilities in the Condensed Consolidated Balance Sheets as of September 30, 2017 . The Company has also recognized structural and non-structural tenant improvements totaling $15.3 million as of September 30, 2017 as an addition to the build-to-suit lease property for amounts incurred by the Company during the construction period, of which $14.2 million were reimbursed by the landlord during the year ended December 31, 2016 through the tenant improvement allowance. The Company increased its financing obligation for the additional building costs reimbursements received from the landlord during the construction period. In addition, for the three and nine months ended September 30, 2017 , the Company recorded rent expense associated with the ground lease of $0.1 million and $0.4 million , respectively, in the Condensed Consolidated Statements of Operations. Total interest, which represents the cost of financing obligation under the Lease agreement, was $0.9 million and $2.8 million for the three and nine months ended September 30, 2017 , respectively, which was recognized within the Condensed Consolidated Statement of Operations. During the fourth quarter of 2016, construction on the build-to-suit lease property was substantially completed and the build-to-suit lease property was placed in service. As such, the Company evaluated the Lease to determine whether it had met the requirements for sale-leaseback accounting, including evaluating whether all risks of ownership have been transferred back to the landlord, as evidenced by a lack of continuing involvement in the build-to-suit lease property. The Company determined that the construction project did not qualify for sale-leaseback accounting and will instead be accounted for as a financing lease, given the Company’s expected continuing involvement after the conclusion of the construction period. The build-to-suit lease property remains on the Company’s Condensed Consolidated Balance Sheets as of September 30, 2017 at its historical cost of $51.8 million and is being depreciated over its estimated useful life. As of September 30, 2017 , the total amount of the build-to-suit lease obligation was $52.3 million , of which $0.4 million and $51.9 million were classified as current and non-current liability, respectively, on the Condensed Consolidated Balance Sheets. The Company expects to derecognize the build-to-suit lease property and financing lease obligation at the end of the lease term. The Company obtained a standby letter of credit in April 2016 in the initial amount of $4.1 million , which may be drawn down by the sublandlord in the event the Company fails to fully and faithfully perform all of its obligations under the Lease and to compensate the sublandlord for all losses and damages the sublandlord may suffer as a result of the occurrence of any default on the part of Company not cured within the applicable cure period. This standby letter of credit is collateralized by a certificate of deposit of the same amount which is classified as restricted cash. As of September 30, 2017 , none of the standby letter of credit amount has been used.

Commitment and Contingencies

Commitment and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitment and Contingencies	Commitments and Contingencies Lease Commitments The Company recognizes rent expense for its operating leases on a straight-line basis over the noncancelable lease term and records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. Where leases contain escalation clauses, rent abatements and/or concessions, such as rent holidays and landlord or tenant incentives or allowances, the Company applies them in the determination of straight-line rent expense over the lease term. The Company records the tenant improvement allowance for operating leases as deferred rent and associated expenditures as leasehold improvements that are being amortized over the shorter of their estimated useful life or the term of the lease. Rent expense was $0.2 million and $0.7 million for the three and nine months ended September 30, 2017 , respectively. Rent expense was $0.6 million and $1.6 million for the three and nine months ended September 30, 2016 , respectively. Dublin In August 2015 , the Company entered into an agreement to lease 6,258 square feet of office space in Dublin, Ireland. This lease has a term of 10 years from commencement and provides for an option to terminate the lease at the end of the fifth year of the term. It is also subject to a rent review every five years. As a result of this noncancelable operating lease, the Company is obligated to make lease payments totaling approximately €2.0 million , or $2.4 million as converted using an exchange rate as of September 30, 2017 , over the term of the lease, assuming current lease payments. Of this obligation, approximately $1.9 million remains outstanding as of September 30, 2017 . Switzerland In 2017, the Company entered into noncancelable operating subleases to lease office space in Zug, Switzerland. The lease terms expire in December 2017 and February 2018. The Company is obligated to make lease payments of approximately CHF 56,000 , or $58,000 as of September 30, 2017 , converted using an exchange rate as of September 30, 2017 . Future minimum payments under the above-described noncancelable operating lease as of September 30, 2017 are as follows (in thousands): Year Ended December 31, Operating Lease 2017 (3 months) $ 103 2018 260 2019 245 2020 245 2021 244 Thereafter 897 Total $ 1,994 Current SSF Facility In March 2016 , the Company entered into a noncancelable operating sublease of the Current SSF Facility which expires in December 31, 2023 . The Company is considered the "accounting owner" of the Current SSF Facility as a build-to-suit property and has recorded a build-to-suit lease obligation on its condensed consolidated balance sheet. Additional information regarding the build-to-suit lease is included in Note 6, "Build-To-Suit Lease." Future minimum payments under build-to-suit lease obligation as of September 30, 2017 are as follows (in thousands): Year Ended December 31, Expected Cash Payments Under Build-To-Suit Lease Obligation 2017 (3 months) $ 1,083 2018 4,915 2019 5,803 2020 5,979 2021 6,165 Thereafter 12,885 Total $ 36,830 Indemnity Obligations The Company has entered into indemnification agreements with its current and former directors and officers and certain key employees. These agreements contain provisions that may require the Company, among other things, to indemnify such persons against certain liabilities that may arise because of their status or service and advance their expenses incurred as a result of any indemnifiable proceedings brought against them. The obligations of the Company pursuant to the indemnification agreements continue during such time as the indemnified person serves the Company and continues thereafter until such time as a claim can be brought. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited; however, the Company has a director and officer liability insurance policy that limits its exposure and enables the Company to recover a portion of any future amounts paid. As a result of its insurance policy coverage, the Company believes the estimated fair value of these indemnification agreements is minimal. Accordingly, the Company had no liabilities recorded for these agreements as of September 30, 2017 and 2016 . Other Commitments In April 2017, the Company entered into a Letter Agreement with Boehringer Ingelheim Biopharmacuticals GmbH for supply of drug products. No product has been manufactured under this agreement. However, the commitment table below includes purchase obligations under this agreement. In the normal course of business, the Company enters into various firm purchase commitments primarily related to research and development activities. As of September 30, 2017 , the Company had non-cancelable purchase commitments to suppliers for $42.0 million of which $11.7 million is included in accrued current liabilities, and contractual obligations under license agreements of $1.8 million of which $0.3 million is included in accrued current liabilities. The following is a summary of the Company's non-cancelable purchase commitments and contractual obligations as of September 30, 2017 (in thousands): Total 2017 2018 2019 2020 2021 Thereafter Purchase Obligations $ 41,988 $ 18,835 $ 7,088 $ 16,065 $ — $ — $ — Contractual obligations under license agreements (1) 1,795 475 130 130 100 100 860 Total $ 43,783 $ 19,310 $ 7,218 $ 16,195 $ 100 $ 100 $ 860 (1) Excludes future obligations pursuant to the cost-sharing arrangement under the Company's License Agreement with Roche. Amounts of such obligations, if any, cannot be determined at this time.

Roche License Agreement

Roche License Agreement	9 Months Ended
	Sep. 30, 2017
Collaborative Agreement [Abstract]
Roche License Agreements	Roche License Agreement Overview In December 2013 , the Company entered into the License Agreement with Roche to develop and commercialize certain antibodies that target α- synuclein, including PRX002/RG7935. The License Agreement was evaluated under ASC 605-25, Multiple Element Arrangements. Under this License agreement, the Company recognizes research reimbursement as collaboration revenue as earned. The Company recognized $0.2 million and $0.7 million as collaboration revenue for research reimbursement from Roche for the three and nine months ended September 30, 2017 , respectively, as compared to $0.3 million and $0.9 million for the three and nine months ended September 30, 2016 , respectively. Cost sharing payments to Roche are recorded as R&D expenses. The Company recognized $1.6 million and $5.7 million in R&D expenses for payments made to Roche during the three and nine months ended September 30, 2017 , respectively, as compared to $1.0 million and $2.4 million for the three and nine months ended September 30, 2016 , respectively. Reimbursement for development costs from Roche during the three and nine months ended September 30, 2017 was $0.3 million and $1.4 million , respectively, as compared to $1.1 million and $3.0 million for the three and nine months ended September 30, 2016 , respectively, which was recognized as an offset to R&D expenses. Under the License Agreement, the Company is eligible to receive milestone payments upon the achievement of development, regulatory and various first commercial sales milestones. Milestone payments are evaluated under ASU No. 2010-17, Milestone Method of Revenue Recognition. Factors considered in this determination included scientific and regulatory risk that must be overcome to achieve each milestone, the level of effort and investment required to achieve the milestone, and the monetary value attributed to the milestone. Accordingly, the Company recognizes payments related to the achievement of this milestone when the milestone is achieved. The clinical and regulatory milestones under the License Agreement after the point at which the Company could opt-out are not considered to be substantive due to the fact that active participation in the development activities that generate the milestones is not required by the License Agreement, and the Company can opt-out of these activities. There are no refund or claw-back provisions and the milestones are uncertain of occurrence even after the Company has opted out. Based on this determination, these milestones will be recognized similar to the commercial milestone, which will be accounted for as contingent revenue payments with revenue recognized upon achievement of the milestone assuming all revenue recognition criteria are met. In June 2017, the Company achieved a $30.0 million clinical milestone under the License Agreement as a result of dosing of the first patient in the Phase 2 study for PRX002/RG7935. The milestone was allocated to the units of accounting based on the relative selling price method for income statement classification purposes. As such, the Company recognized $26.6 million of the $30.0 million milestone as collaboration revenue and $3.4 million as an offset to R&D expenses during the nine months ended September 30, 2017 . The Company did not achieve any clinical and regulatory milestones under the License Agreement during the three and nine months ended September 30, 2016 .

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Shareholders' Equity	Shareholders' Equity Ordinary Shares As of September 30, 2017 , the Company had 100,000,000 ordinary shares authorized for issuance with a par value of $0.01 per ordinary share and 38,443,261 ordinary shares issued and outstanding. Each ordinary share is entitled to one vote and, on a pro rata basis, to dividends when declared and the remaining assets of the Company in the event of a winding up. Euro Deferred Shares As of September 30, 2017 , the Company had 10,000 Euro Deferred Shares authorized for issuance with a nominal value of €22 per share. No Euro Deferred Shares are outstanding at September 30, 2017 . The rights and restrictions attaching to the Euro Deferred Shares rank pari passu with the ordinary shares and are treated as a single class in all respects. March 2017 Offering In March 2017, the Company completed an underwritten public offering of an aggregate of 2,700,000 of its ordinary shares at a public offering price of $57.50 per ordinary share. The Company received aggregate net proceeds of approximately $150.3 million , after deducting the underwriting discount and offering costs.

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation Amended and Restated 2012 Long Term Incentive Plan (“LTIP”) Employees and consultants of the Company, its subsidiaries and affiliates, as well as members of the Company's Board of Directors, are eligible to receive equity awards under the LTIP. The LTIP provides for the grant of stock options, including incentive stock options and nonqualified stock options, stock appreciation rights (“SARS”), restricted shares, restricted share units ("RSUs"), cash or stock-based performance awards and other share-based awards to eligible individuals. Options under the LTIP may be granted for periods up to ten years. All options issued to date have had a ten year life. The Company granted 162,500 and 1,447,300 share options during the three and nine months ended September 30, 2017 , respectively, and 132,500 and 1,252,975 share options during the three and nine months ended September 30, 2016 , respectively, under the LTIP. The Company's option awards generally vest over four years. In May 2017, the Company's shareholders approved an increase of 1,350,000 additional ordinary shares authorized for issuance under the LTIP. The aggregate number of ordinary shares authorized for issuance under the LTIP is 8,750,000 ordinary shares. As of September 30, 2017 , 2,321,248 ordinary shares remained available for grant, and options to purchase 4,386,752 ordinary shares under the LTIP were outstanding with a weighted-average exercise price of approximately $38.30 per share. Share-based Compensation Expense The Company estimates the fair value of share-based compensation on the date of grant using an option-pricing model. The Company uses the Black-Scholes model to value share-based compensation, excluding RSUs, which the Company values using the fair market value of its ordinary shares on the date of grant. The Black-Scholes option-pricing model determines the fair value of share-based payment awards based on the share price on the date of grant and is affected by assumptions regarding a number of complex and subjective variables. These variables include, but are not limited to, the Company’s share price, volatility over the expected life of the awards and actual and projected employee stock option exercise behaviors. Since the Company does not have sufficient historical employee share option exercise data, the simplified method has been used to estimate the expected life of all options. The expected volatility was based on a combination of historical volatility for the Company's stock and the historical volatilities of several of the Company's publicly traded comparable companies. Although the fair value of share options granted by the Company is estimated by the Black-Scholes model, the estimated fair value may not be indicative of the fair value observed in a willing buyer and seller market transaction. As share-based compensation expense recognized in the Condensed Consolidated Financial Statements is based on awards ultimately expected to vest, it has been reduced for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates. Forfeitures were estimated based on estimated future turnover and historical experience. Share-based compensation expense will continue to have an adverse impact on the Company’s results of operations, although it will have no impact on its overall financial position. The amount of unearned share-based compensation currently estimated to be expensed from now through the year 2020 related to unvested share-based payment awards at September 30, 2017 is $70.2 million . The weighted-average period over which the unearned share-based compensation is expected to be recognized is 2.83 years . If there are any modifications or cancellations of the underlying unvested securities, the Company may be required to accelerate and/or increase any remaining unearned share-based compensation expense. Future share-based compensation expense and unearned share-based compensation will increase to the extent that the Company grants additional equity awards. Share-based compensation expense recorded in these Condensed Consolidated Financial Statements for the three and nine months ended September 30, 2017 and 2016 was based on awards granted under the LTIP. The following table summarizes share-based compensation expense for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Research and development $ 2,820 $ 1,990 $ 7,863 $ 5,227 General and administrative (1) 4,282 9,458 11,494 14,491 Total share-based compensation expense $ 7,102 $ 11,448 $ 19,357 $ 19,718 (1) Includes $nil and $6.5 million for the three and nine months ended September 30, 2017 and 2016, respectively, of share-based compensation expense related to the accelerated vesting of stock options to the Company's former CEO upon his death. The Company recognized a tax benefit from share-based awards of $1.1 million and $3.0 million for the three and nine months ended September 30, 2017 , respectively, and $2.1 million and $3.5 million for the three and nine months ended September 30, 2016 , respectively. The fair value of the options granted to employees and non-employee directors during the three and nine months ended September 30, 2017 and 2016 was estimated as of the grant date using the Black-Scholes option-pricing model assuming the weighted-average assumptions listed in the following table: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Expected volatility 71.2% 75.2% 72.6% 74.9% Risk-free interest rate 2.0% 1.3% 2.0% 1.4% Expected dividend yield —% —% —% —% Expected life (in years) 6.0 6.0 6.0 6.0 Weighted average grant date fair value $38.06 $32.50 $35.63 $24.47 The fair value of employee stock options is being amortized on a straight-line basis over the requisite service period for each award. Each of the inputs discussed above is subjective and generally requires significant management judgment to determine. The following table summarizes the Company’s stock option activity during the nine months ended September 30, 2017 : Options Weighted Weighted Aggregate Outstanding at December 31, 2016 4,064,207 $ 27.19 6.79 $ 92,640 Granted 1,447,300 54.95 Exercised (991,145 ) 16.70 Canceled (133,610 ) 41.21 Outstanding at September 30, 2017 4,386,752 $ 38.30 7.96 $ 116,337 Vested and expected to vest at September 30, 2017 4,286,175 $ 38.01 7.94 $ 114,901 Vested at September 30, 2017 1,902,983 $ 24.97 6.67 $ 75,849 The total intrinsic value of options exercised was $13.6 million and $39.5 million during the three and nine months ended September 30, 2017 , respectively, and $2.7 million and $4.1 million during the three and nine months ended September 30, 2016 , respectively, determined as of the date of exercise.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The major taxing jurisdictions for the Company are Ireland and the U.S. The Company recorded an income tax benefit of $1.7 million and $4.7 million for three and nine months ended September 30, 2017 , respectively, as compared to an income tax expense of $421,000 and $791,000 for the three and nine months ended September 30, 2016 , respectively. The provision for income taxes differs from the statutory tax rate of 12.5% applicable to Ireland primarily due to Irish net operating losses for which a tax provision benefit is not recognized, U.S. income taxed at different rates, and excess tax benefits of stock options. The income tax provision reflects the estimate of the effective tax rate expected to be applicable for the full year and the Company re-evaluates this estimate each quarter based on its forecasted tax expense for the full year. Jurisdictions with a projected loss for the year where no tax benefit can be recognized are excluded from the estimated annual effective tax rate. The Company adopted ASU 2016-09 on January 1, 2017. Pursuant to the adoption of ASU 2016-09, tax attributes previously tracked off balance sheet have been recorded as deferred tax assets, offset by a valuation allowance. In addition, the Company has reversed its non-current tax liability of $98,000 , with the offsetting entry recorded to retained earnings pursuant to the adoption of this ASU. Further, the year-to-date excess benefits have been recorded as a discrete benefit to the tax provision. For the three and nine months ended September 30, 2017 , the Company recorded excess tax benefits of $2.0 million and $5.4 million , respectively, which were recorded as part of its income tax provision in the Condensed Consolidated Statements of Operations. The Company's income tax expense will continue to be impacted by fluctuations in stock price between the grant dates and the exercise dates of its option awards. The Company's deferred tax assets are composed primarily of its Irish subsidiaries' net operating loss carryovers, state net operating loss carryforwards available to reduce future taxable income of the Company's U.S. subsidiary, federal and California research and development credit carryforward, shared-based compensation and other temporary differences. The Company maintains a valuation allowance against its Irish and certain U.S. federal and state deferred tax assets. Each reporting period, the Company evaluates the need for a valuation allowance on its deferred tax assets by jurisdiction. No provision for income tax in Ireland has been recognized on undistributed earnings of the Company's U.S. subsidiary because the Company considers such earnings to be indefinitely reinvested.

Related Parties

Related Parties	9 Months Ended
	Sep. 30, 2016
Related Party Transactions [Abstract]
Related Parties	Related Parties Carol D. Karp commenced employment with the Company as its Chief Regulatory Officer on December 14, 2016. Prior to that, Ms. Karp provided consulting services to the Company under a written Consulting Agreement which was effective April 1, 2016. That Consulting Agreement terminated as of December 13, 2016, before Ms. Karp joined the Company. There were no consulting fees paid to Ms. Karp for the three and nine months ended September 30, 2017 . The Company paid a total of $123,900 and $192,500 (not including expense reimbursements) for the three and nine months ended September 30, 2016 , respectively, under the Consulting Agreement.

Summary of Significant Accoun18

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Preparation and Presentation of Financial Information	Basis of Preparation and Presentation of Financial Information These accompanying Unaudited Interim Condensed Consolidated Financial Statements have been prepared in accordance with the accounting principles generally accepted in the U.S. (“GAAP”) and with the instructions for Form 10-Q and Regulation S-X statements. Accordingly, they do not include all of the information and notes required for complete financial statements. These interim Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and Notes thereto contained in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on February 27, 2017 (the "2016 Form 10-K"). These Unaudited Interim Condensed Consolidated Financial Statements are presented in U.S. dollars, which is the functional currency of the Company and its consolidated subsidiaries. These Unaudited Interim Condensed Consolidated Financial Statements include the accounts of the Company and its consolidated subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Unaudited Interim Financial Information The accompanying Unaudited Interim Condensed Consolidated Financial Statements and related disclosures are unaudited, have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair presentation of the results of operations for the periods presented. The year-end condensed consolidated balance sheet data was derived from audited financial statements, however certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted. The condensed consolidated results of operations for any interim period are not necessarily indicative of the results to be expected for the full year or for any other future year or interim period. Certain amounts in the Condensed Consolidated Financial Statements have been reclassified to conform to the current year presentation.
Use of Estimates	Use of Estimates The preparation of the Condensed Consolidated Financial Statements in conformity with GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosures. On an ongoing basis, management evaluates its estimates, including critical accounting policies or estimates related to revenue recognition, share-based compensation and research and development expenses. The Company bases its estimates on historical experience and on various other market specific and other relevant assumptions that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Because of the uncertainties inherent in such estimates, actual results may differ materially from these estimates.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	Share-based Compensation To determine the fair value of share-based payment awards, the Company uses the Black-Scholes option-pricing model. The determination of fair value using the Black-Scholes option-pricing model is affected by the Company’s share price as well as assumptions regarding a number of complex and subjective variables. Share-based compensation expense is recognized on a straight-line basis over the requisite service period for each award. Further, share-based compensation expense recognized in the Condensed Consolidated Statements of Operations is based on awards expected to vest and therefore the amount of expense has been reduced for estimated forfeitures. If actual forfeitures differ from estimates at the time of grant they will be revised in subsequent periods. The Company bases its assumptions on historical data when available or when not available, on a peer group of companies. If factors change and different assumptions are employed in determining the fair value of share-based awards, the share-based compensation expense recorded in future periods may differ significantly from what was recorded in the current period (see Note 10 for further information). The Company will record any excess tax benefits or deficiencies from its equity awards in its Condensed Consolidated Statements of Operations in the reporting periods in which stock options are exercised.
Segment and Concentration of Risk	Segment and Concentration of Risks The Company operates in one segment. The Company’s chief operating decision maker (the “CODM”), its Chief Executive Officer, manages the Company’s operations on a consolidated basis for purposes of allocating resources. When evaluating the Company’s financial performance, the CODM reviews all financial information on a consolidated basis. Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents and accounts receivable. The Company places its cash equivalents with high credit quality financial institutions and by policy, limits the amount of credit exposure with any one financial institution. Deposits held with banks may exceed the amount of insurance provided on such deposits. The Company has not experienced any losses on its deposits of cash and cash equivalents and its credit risk exposure is up to the extent recorded on the Company's Condensed Consolidated Balance Sheet. Receivable from Roche as of September 30, 2017 and December 31, 2016 are amounts due from Roche entities located in the U.S. and Switzerland under the License Agreement that became effective January 22, 2014. Revenue recorded in the Statements of Operations consists of reimbursement from Roche for research and development services. Credit risk exposure is up to the extent recorded on the Company's Condensed Consolidated Balance Sheet. As of September 30, 2017 , $54.7 million of the Company's long-lived assets were held in the U.S. and $0.7 million were in Ireland. As of December 31, 2016 , $55.7 million of the Company's long-lived assets were held in the U.S. and $0.8 million were in Ireland. The Company does not own or operate facilities for the manufacture, packaging, labeling, storage, testing or distribution of nonclinical or clinical supplies of any of its drug candidates, including for commercial supplies if the Company obtains regulatory approval to market any of its drug candidates. The Company instead contracts with and relies on third-parties to manufacture, package, label, store, test and distribute all pre-clinical development and clinical supplies of our drug candidates, and it plans to continue to do so for the foreseeable future, including for commercial supplies if the Company obtains regulatory approval to market any of its drug candidates. The Company also relies on third-party consultants to assist in managing these third-parties and assist with its manufacturing strategy.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update 2014-09 (ASU 2014-09), Revenue from Contracts with Customers, which is largely codified in Accounting Standards Codification 606 (ASC Topic 606). ASU 2014-09 supersedes the revenue recognition requirements in Revenue Recognition (Topic 605). ASC Topic 606 supersedes nearly all existing revenue recognition guidance under GAAP. To date, we have derived our revenues from a license and collaboration agreement and a service agreement. The consideration we are eligible to receive under these agreements includes upfront payments, research and development funding, milestone payments and royalties. The core principle of ASC Topic 606 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASC Topic 606 defines a five-step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP, including identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation, among others. ASC Topic 606 is effective for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period, which for the Company is January 1, 2018. Early adoption is permitted after January 1, 2017. The standard allows for two transition methods - retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying the standard recognized at the date of initial adoption. The Company expects to adopt the requirements of the new standard effective January 1, 2018 using the retrospective with the cumulative effect transition method. In March 2016, the FASB issued ASU No. 2016-08 Revenue from Contracts with Customers: Principal vs. Agent Considerations, to help provide interpretive clarifications on the new guidance for ASC Topic 606. In April 2016, the FASB issued ASU No. 2016-10 Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing to clarify the guidance for identifying performance obligations and accounting for licenses of intellectual property. In May 2016, the FASB issued ASU No. 2016-12 Revenue from Contracts with Customers: Narrow-Scope Improvements; and Practical Expedients, to improve the guidance on collectibility, noncash consideration, and completed contracts at transition. In December 2016, the FASB issued ASU No. 2016-20 Revenue from Contracts with Customers: Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers. ASC Topic 606 differs from the current accounting standard in many respects, such as in the accounting for variable consideration, including milestone payments and the measurement of progress toward completion of performance obligations. The Company does not expect the adoption of this standard to have a material impact on its consolidated financial statements in the period of adoption. Under its current accounting policy, the Company recognizes milestone revenue using the milestone method specified in ASC 605-28, which generally results in the recognition of the milestone payment as revenue in the period that the milestone is achieved. However, under the new accounting standard, it is possible to start to recognize milestone revenue before the milestone is achieved, subject to management’s assessment of whether it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. As such, the timing of revenue recognition for our license and collaboration agreements may change under the new revenue standard. In February 2016, the FASB issued Accounting Standards Update 2016-02 (ASU 2016-02), Leases (ASC Topic 842), which will require lessees to recognize assets and liabilities for leases with lease terms of more than 12 months. Consistent with current GAAP, the recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee primarily will depend on its classification as a finance or operating lease. However, unlike current GAAP, which requires only capital leases to be recognized on the balance sheet, the new guidance will require both types of leases to be recognized on the balance sheet. ASC Topic 842 is effective for annual periods beginning after December 15, 2018, and interim periods within those years. Early adoption is permitted for all entities. The standard requires that entities use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. Entities have the option to use certain relief. Full retrospective application is prohibited. Note 7, "Commitments and Contingencies" provides details on the Company's current lease arrangements. The Company continues to evaluate the provisions of ASC Topic 842 to determine the impact the adoption of ASU 2016-02 will have on its consolidated financial statements; however, the Company anticipates recognition of additional assets and corresponding liabilities related to leases on its consolidated balance sheets. Additionally, the Company expects to derecognize its build-to-suit asset and liabilities upon adoption pending its final evaluation. In March 2016, the FASB issued Accounting Standards Update 2016-09 (ASU 2016-09), Improvements to Employee Share-Based Payment Accounting, which modifies certain aspects of the accounting for share-based payment transactions, including income taxes, classification of awards and classification in the statement of cash flows. Through December 31, 2016, excess tax benefits or deficiencies from the Company's equity awards were recorded as additional paid-in capital in its Consolidated Balance Sheets. Upon adoption, the Company will record any excess tax benefits or deficiencies from its equity awards in its Condensed Consolidated Statements of Operations in the reporting periods in which stock options are exercised. This guidance also requires excess tax benefits and deficiencies to be presented as an operating activity on the statement of cash flows and allows an entity to make an accounting policy election to either estimate expected forfeitures or to account for them as they occur. The ASU is effective for reporting periods beginning after December 15, 2016, with early adoption permitted. The Company adopted this ASU on January 1, 2017. Pursuant to the adoption of ASU 2016-09, tax attributes previously tracked off balance sheet have been recorded as deferred tax assets, offset by a valuation allowance. In addition, the Company has reversed its non-current tax liability of $98,000 with the offsetting entry recorded to retained earnings pursuant to the adoption of this ASU. Further, the year-to-date excess benefits have been recorded as a discrete benefit to the tax provision. For the nine months ended September 30, 2017 , the Company recorded excess tax benefits of $5.4 million as part of its income tax provision in the Condensed Consolidated Statements of Operations. The Company's income tax expense will continue to be impacted by fluctuations in stock price between the grant dates and the exercise dates of its option awards. The presentation requirements for cash flows related to excess tax benefits will be applied retrospectively; as such, prior years have been restated. Lastly, the Company elected to continue to estimate the number of forfeitures related to share-based payments, rather than account for forfeitures as they occur. In August 2016, the FASB issued Accounting Standards Update 2016-15 (ASU 2016-15), Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payments, which clarifies existing guidance related to accounting for cash receipts and cash payments and classification of statement of cash flow. This guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, but early adoption is permitted. The Company does not expect the adoption of ASU 2016-15 to have an impact on its consolidated financial statements. In May 2017, the FASB issued Accounting Standards Update 2017-09 (ASU 2017-09), Compensation - Stock Compensation (Topic 718) - Scope of Modification Accounting, which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. Entities would apply the modification accounting guidance if the value, vesting requirements or classification of a share-based payment award changes. This pronouncement is effective for annual reporting periods beginning after December 15, 2017, but early adoption is permitted. The Company does not expect the adoption of ASU 2017-09 to have an impact on its consolidated financial statements.

Composition of Certain Balanc19

Composition of Certain Balance Sheet Items (Tables)	9 Months Ended
	Sep. 30, 2017
Composition of Certain Balance Sheet Items [Abstract]
Schedule of Property and Equipment	Property and equipment, net consisted of the following (in thousands): September 30, 2017 December 31, 2016 Machinery and equipment $ 9,051 $ 9,629 Leasehold improvements 579 2,769 Purchased computer software 987 363 Build-to-suit property 51,760 51,359 62,377 64,120 Less: accumulated depreciation and amortization (6,993 ) (7,668 ) Property and equipment, net $ 55,384 $ 56,452
Schedule of Other Current Liabilities	Other current liabilities consisted of the following (in thousands): September 30, 2017 December 31, 2016 Payroll and related expenses $ 7,509 $ 6,629 Professional services 384 435 Deferred rent 49 363 Other 1,347 1,128 Other current liabilities $ 9,289 $ 8,555

Net Loss Per Ordinary Share (Ta

Net Loss Per Ordinary Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Calculation of Basic and Diluted Net Income or Loss Per Ordinary Share	Net loss per ordinary share was determined as follows (in thousands, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Numerator: Net loss $ (52,394 ) $ (43,239 ) $ (105,479 ) $ (111,205 ) Denominator: Weighted-average ordinary shares outstanding 38,292 34,413 37,384 34,266 Net loss per share: Basic and diluted net loss per share $ (1.37 ) $ (1.26 ) $ (2.82 ) $ (3.25 )
Ordinary Shares Equivalent Not Included in Diluted Net Loss Per Share	The equivalent ordinary shares not included in diluted net loss per share because their effect would be anti-dilutive are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Stock options to purchase ordinary shares 4,387 4,170 4,387 4,170

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Operating Lease Commitments	Future minimum payments under the above-described noncancelable operating lease as of September 30, 2017 are as follows (in thousands): Year Ended December 31, Operating Lease 2017 (3 months) $ 103 2018 260 2019 245 2020 245 2021 244 Thereafter 897 Total $ 1,994
Schedule of Future Minimum Payments Under Build-to-Suit Lease Obligations	Future minimum payments under build-to-suit lease obligation as of September 30, 2017 are as follows (in thousands): Year Ended December 31, Expected Cash Payments Under Build-To-Suit Lease Obligation 2017 (3 months) $ 1,083 2018 4,915 2019 5,803 2020 5,979 2021 6,165 Thereafter 12,885 Total $ 36,830
Contractual Obligation, Fiscal Year Maturity Schedule	The following is a summary of the Company's non-cancelable purchase commitments and contractual obligations as of September 30, 2017 (in thousands): Total 2017 2018 2019 2020 2021 Thereafter Purchase Obligations $ 41,988 $ 18,835 $ 7,088 $ 16,065 $ — $ — $ — Contractual obligations under license agreements (1) 1,795 475 130 130 100 100 860 Total $ 43,783 $ 19,310 $ 7,218 $ 16,195 $ 100 $ 100 $ 860 (1) Excludes future obligations pursuant to the cost-sharing arrangement under the Company's License Agreement with Roche. Amounts of such obligations, if any, cannot be determined at this time.

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2017
Summary of Share-Based Compensation Expense	The following table summarizes share-based compensation expense for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Research and development $ 2,820 $ 1,990 $ 7,863 $ 5,227 General and administrative (1) 4,282 9,458 11,494 14,491 Total share-based compensation expense $ 7,102 $ 11,448 $ 19,357 $ 19,718 (1) Includes $nil and $6.5 million for the three and nine months ended September 30, 2017 and 2016, respectively, of share-based compensation expense related to the accelerated vesting of stock options to the Company's former CEO upon his death.
Amended and Restated 2012 Long Term Incentive Plan [Member]
Fair Value of Options Granted	The fair value of the options granted to employees and non-employee directors during the three and nine months ended September 30, 2017 and 2016 was estimated as of the grant date using the Black-Scholes option-pricing model assuming the weighted-average assumptions listed in the following table: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Expected volatility 71.2% 75.2% 72.6% 74.9% Risk-free interest rate 2.0% 1.3% 2.0% 1.4% Expected dividend yield —% —% —% —% Expected life (in years) 6.0 6.0 6.0 6.0 Weighted average grant date fair value $38.06 $32.50 $35.63 $24.47
Summary of Company's Share Option Activity	The following table summarizes the Company’s stock option activity during the nine months ended September 30, 2017 : Options Weighted Weighted Aggregate Outstanding at December 31, 2016 4,064,207 $ 27.19 6.79 $ 92,640 Granted 1,447,300 54.95 Exercised (991,145 ) 16.70 Canceled (133,610 ) 41.21 Outstanding at September 30, 2017 4,386,752 $ 38.30 7.96 $ 116,337 Vested and expected to vest at September 30, 2017 4,286,175 $ 38.01 7.94 $ 114,901 Vested at September 30, 2017 1,902,983 $ 24.97 6.67 $ 75,849

Organization - Additional Infor

Organization - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended
	Mar. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit		$ 394,592	$ 289,211
Cash and cash equivalents		$ 456,061	$ 386,923
Underwritten Public And Over-Allotment Offering [Member]
Equity [Abstract]
Sale of Stock, Consideration Received on Transaction	$ 150,300
Underwritten Public And Over-Allotment Offering [Member] | Ordinary Share [Member]
Equity [Abstract]
Sale of Stock, Number of Shares Issued in Transaction	2,700,000

Summary of Significant Accoun24

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Jan. 01, 2017	Dec. 31, 2016
Significant accounting policies [line item]
Excess tax benefit booked to Income Tax Provision, Amount	$ (2,000)	$ (5,400)
Income taxes payable, non-current	0	0		$ (98)
Accounting Standards Update 2016-09
Significant accounting policies [line item]
Income taxes payable, non-current			$ 98
Retained Earnings | Accounting Standards Update 2016-09
Significant accounting policies [line item]
Cumulative effect of new accounting principle in period of adoption			$ 98
UNITED STATES
Significant accounting policies [line item]
Long-lived assets	54,700	54,700		55,700
IRELAND
Significant accounting policies [line item]
Long-lived assets	$ 700	$ 700		$ 800

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Money market funds at carrying value	$ 364.2	$ 307.3

Composition of Certain Balanc26

Composition of Certain Balance Sheet Items - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Composition of Certain Balance Sheet Items [Abstract]
Machinery and equipment	$ 9,051	$ 9,629
Leasehold improvements	579	2,769
Purchased computer software	987	363
Build-to-Suit Property	51,760	51,359
Property and equipment, gross	62,377	64,120
Less: accumulated depreciation and amortization	(6,993)	(7,668)
Property and equipment, net	$ 55,384	$ 56,452

Composition of Certain Balanc27

Composition of Certain Balance Sheet Items - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Composition of Certain Balance Sheet Items [Abstract]
Depreciation expense	$ 0.8	$ 0.8	$ 2.3	$ 1.5

Composition of Certain Balanc28

Composition of Certain Balance Sheet Items - Schedule of Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Composition of Certain Balance Sheet Items [Abstract]
Payroll and related expenses	$ 7,509	$ 6,629
Professional services	384	435
Deferred rent	49	363
Other	1,347	1,128
Other current liabilities	$ 9,289	$ 8,555

Net Loss Per Ordinary Share - C

Net Loss Per Ordinary Share - Calculation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net loss	$ (52,394)	$ (43,239)	$ (105,479)	$ (111,205)
Denominator
Weighted-average ordinary shares outstanding	38,292	34,413	37,384	34,266
Net loss per share
Basic and diluted net loss per share (in dollars per share)	$ (1.37)	$ (1.26)	$ (2.82)	$ (3.25)

Net Loss Per Ordinary Share - O

Net Loss Per Ordinary Share - Ordinary Shares Equivalent Not Included in Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Options to purchase ordinary shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock options to purchase ordinary shares not included in diluted net loss per share	4,387	4,170	4,387	4,170

Build-to-Suit Lease (Details)

Build-to-Suit Lease (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2016ft²	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)	Apr. 30, 2016USD ($)
Build-to-Suit Lease Obligations
Interest capitalized during construction period for build-to-suit lease transaction				$ 0	$ 713
Proceeds from tenant improvement allowance under build-to-suit lease transaction				0	2,812
Ground rent		$ 200	$ 600	700	$ 1,600
Built-to-suit leases, at cost		51,800		51,800
Build-to-suit lease obligation, current and noncurrent		52,300		52,300
Build-to-suit lease obligation, non-current		51,902		51,902		$ 51,320
Build-to-suit lease obligation, current		372		$ 372		0
Built-to-Suit Lease [Member]
Build-to-Suit Lease Obligations
Build-to-suit Area of real estate property (in sq ft) | ft²	128,751
Build-to-suit lease expiration date	Dec. 31, 2023
Build-to-suit lease, term of contract				7 years 9 months 30 days
Total lease payments due over lease term							$ 39,200
Tenant improvement allowance						14,200
Amount capitalized under Build-to-Suit Transaction				$ 36,500
Interest capitalized during construction period for build-to-suit lease transaction				1,200
Tenant improvements incurred		15,300		15,300
Proceeds from tenant improvement allowance under build-to-suit lease transaction						$ 14,200
Ground rent		100		400
Build-to-suit lease, interest expense		900		2,800
Line of credit facility							$ 4,100
Line of credit has been used		$ 0		$ 0

Commitment and Contingencies -

Commitment and Contingencies - Lease Narrative (Details) SFr in Thousands, $ in Thousands, € in Millions	1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2016	Aug. 31, 2015EUR (€)ft²	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017CHF (SFr)	Sep. 30, 2017USD ($)	Aug. 31, 2015USD ($)
Loss Contingencies [Line Items]
Operating Leases, Rent Expense			$ 200	$ 600	$ 700	$ 1,600
Future minimum payments due								$ 1,994
Dublin, Ireland [Member]
Loss Contingencies [Line Items]
Operating Leases, Area of office space (in sq ft) | ft²		6,258
Operating leases, term of contract (in years)		10 years
Operating Leases, Rent review term (in years)		5 years
Operating leases, Option to terminate, date		Aug. 31, 2020
Future minimum payments due		€ 2						1,900	$ 2,400
Zug, Switzerland [Member]
Loss Contingencies [Line Items]
Future minimum payments due							SFr 56	$ 58
Built-to-Suit Lease [Member]
Loss Contingencies [Line Items]
Operating Leases, Rent Expense			$ 100		$ 400
Build-to-suit lease expiration date	Dec. 31, 2023

Commitment and Contingencies Co

Commitment and Contingencies Commitment and Contingencies - Schedule of Future Lease Payments - Dublin (Details) $ in Thousands	Sep. 30, 2017USD ($)
Operating Lease
2017 (3 months)	$ 103
2,018	260
2,019	245
2,020	245
2,021	244
Thereafter	897
Total	$ 1,994

Commitment and Contingencies 34

Commitment and Contingencies - Current SSF Facility (Details) - Built-to-Suit Lease [Member] $ in Thousands	Sep. 30, 2017USD ($)
Build-to-suit Lease [Line Items]
2017 (3 months)	$ 1,083
2,018	4,915
2,019	5,803
2,020	5,979
2,021	6,165
Thereafter	12,885
Future payments due	$ 36,830

Commitment and Contingencies 35

Commitment and Contingencies Commitment and Contingencies - Commitment Narrative (Details) $ in Thousands	Sep. 30, 2017USD ($)
Loss Contingencies [Line Items]
Purchase obligation	$ 41,988
Accrued Liabilities [Member]
Loss Contingencies [Line Items]
Commitment to suppliers included in accrued liabilities	11,700
Contractual obligations under license agreements included in accrued current liabilities	300
Licensing Agreements [Member]
Loss Contingencies [Line Items]
Future payments due	$ 1,800

Commitment and Contingencies 36

Commitment and Contingencies - Contractual Obligations (Details) $ in Thousands	Sep. 30, 2017USD ($)
Purchase Obligations
Total	$ 41,988
2,017	18,835
2,018	7,088
2,019	16,065
2,020	0
2,021	0
Thereafter	0
Purchase and Contractual Obligations, Fiscal Year Maturity
Total	43,783
2,017	19,310
2,018	7,218
2,019	16,195
2,020	100
2,021	100
Thereafter	860
License Agreements [Member]
Contractual obligations under license agreements
Total	1,795
2,017	475
2,018	130
2,019	130
2,020	100
2,021	100
Thereafter	$ 860

Roche License Agreement (Detail

Roche License Agreement (Details) - Roche [Member] - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
License Agreement [Line Items]
Milestone Achievement, Clinical Milestone	$ 30
Collaboration Revenue, Clinical Milestone		$ 0		$ 26.6
Milestone Method, Portion of Milestone Amount used to Offset R&D Expense		0		3.4
Collaborative Arrangement [Member]
License Agreement [Line Items]
Cost sharing payments recognized as research and development expense		1.6	$ 1	5.7	$ 2.4
Research Reimbursement [Member]
License Agreement [Line Items]
Collaboration service revenue, research services		0.2	0.3	0.7	0.9
Development Costs Reimbursement [Member]
License Agreement [Line Items]
Development Reimbursement Recognized As Offset To Research And Development Expense		$ 0.3	$ 1.1	$ 1.4	$ 3

Shareholders' Equity (Details)

Shareholders' Equity (Details) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Mar. 31, 2017USD ($)$ / sharesshares	Sep. 30, 2017vote$ / sharesshares	Sep. 30, 2017€ / sharesshares	Dec. 31, 2016$ / sharesshares	Dec. 31, 2016€ / sharesshares
Equity [Abstract]
Ordinary shares, number of authorized shares (in shares)		100,000,000	100,000,000	100,000,000	100,000,000
Ordinary shares, par value (in dollars per share) | $ / shares		$ 0.01		$ 0.01
Ordinary shares, number of issued shares (in shares)		38,443,261	38,443,261	34,752,116	34,752,116
Ordinary shares, number of outstanding shares (in shares)		38,443,261	38,443,261	34,752,116	34,752,116
Votes per share | vote		1
Euro deferred shares, number of shares authorized (in shares)		10,000	10,000	10,000	10,000
Euro deferred shares, nominal value (in euros per share) | € / shares			€ 22		€ 22
Euro deferred shares, number of outstanding shares (in shares)		0	0	0	0
Underwritten Public And Over-Allotment Offering [Member]
Equity [Abstract]
Sale of Stock, Price Per Share | $ / shares	$ 57.50
Sale of Stock, Consideration Received on Transaction | $	$ 150.3
Ordinary Share [Member] | Underwritten Public And Over-Allotment Offering [Member]
Equity [Abstract]
Sale of Stock, Number of Shares Issued in Transaction	2,700,000

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Stock Option [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Tax Benefit from Compensation Expense		$ 1.1	$ 2.1	$ 3	$ 3.5
Intrinsic value of options exercised		$ 13.6	$ 2.7	$ 39.5	$ 4.1
Amended and Restated 2012 Long Term Incentive Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Grant period				10 years
Number of stock options granted to employees		162,500	132,500	1,447,300	1,252,975
Vesting period				4 years
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	1,350,000
Authorized shares for issuance		8,750,000		8,750,000
Number of shares available for grant		2,321,248		2,321,248
Options outstanding		4,386,752		4,386,752		4,064,207
Weighted average exercise price		$ 38.30		$ 38.30		$ 27.19
Non-Vested Awards, share-based compensation expected to be expensed through 2020, stock options		$ 70.2		$ 70.2
Expected recognition period of share-based compensation not yet recognized				2 years 9 months 29 days

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Share-Based Compensation Expense (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 7,102,000	$ 11,448,000	$ 19,357,000	$ 19,718,000
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	2,820,000	1,990,000	7,863,000	5,227,000
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	4,282,000	9,458,000	11,494,000	14,491,000
Former Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost	$ 0	$ 6,500,000	$ 0	$ 6,500,000

Share-Based Compensation - Fair

Share-Based Compensation - Fair Value of Options Granted (Detail) - Amended and Restated 2012 Long Term Incentive Plan [Member] - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	71.20%	75.20%	72.60%	74.90%
Risk-free interest rate	2.00%	1.30%	2.00%	1.40%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected life (in years)	6 years	6 years	6 years	6 years
Weighted average grant date fair value	$ 38.06	$ 32.50	$ 35.63	$ 24.47

Share-based Compensation - Shar

Share-based Compensation - Share-based Compensation Plan - Option Activity (Detail) - Amended and Restated 2012 Long Term Incentive Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Options
Options, outstanding beginning balance			4,064,207
Options, granted	162,500	132,500	1,447,300	1,252,975
Options, exercised			(991,145)
Options, canceled			(133,610)
Options, outstanding ending balance	4,386,752		4,386,752		4,064,207
Options, vested and expected to vest ending balance	4,286,175		4,286,175
Options, vested	1,902,983		1,902,983
Weighted Average Exercise Price
Weighted Average Exercise Price, outstanding beginning balance			$ 27.19
Weighted Average Exercise Price, granted			54.95
Weighted Average Exercise Price, exercised			16.70
Weighted Average Exercise Price, canceled			41.21
Weighted Average Exercise Price, outstanding ending balance	$ 38.30		38.30		$ 27.19
Weighted Average Exercise Price, vested and expected to vest, ending balance	38.01		38.01
Weighted Average Exercise Price, vested	$ 24.97		$ 24.97
Options, Additional Disclosures
Weighted Average Remaining Contractual Life, outstanding (in years)			7 years 11 months 16 days		6 years 9 months 15 days
Weighted Average Remaining Contractual Life, vested and expected to vest (in years)			7 years 11 months 9 days
Weighted Average Remaining Contractual Life, vested (in years)			6 years 8 months 1 day
Aggregate Intrinsic Value, outstanding	$ 116,337		$ 116,337		$ 92,640
Aggregate Intrinsic Value, vested and expected to vest, ending balance	114,901		114,901
Aggregate Intrinsic Value, vested	$ 75,849		$ 75,849

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jan. 01, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Income tax expense (benefit)	$ (1,705)	$ 421	$ (4,653)	$ 791
Excess tax benefit booked to Income Tax Provision, Amount	(2,000)		(5,400)
Income taxes payable, non-current	$ 0		$ 0			$ (98)
Accounting Standards Update 2016-09
Income Taxes [Line Items]
Income taxes payable, non-current					$ 98
Accounting Standards Update 2016-09 | Retained Earnings
Income Taxes [Line Items]
Cumulative effect of new accounting principle in period of adoption					$ 98
Revenue Commissioners, Ireland
Income Taxes [Line Items]
Ireland statutory tax rate, percent			12.50%	12.50%

Related Parties (Details)

Related Parties (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Chief Regulatory Officer [Member]
Related Party Transaction [Line Items]
Consulting payments	$ 0	$ 123,900	$ 0	$ 192,500