Aravive (ARAV) 10-K 10 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 28, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Trading Symbol	VSAR
Entity Registrant Name	Versartis, Inc.
Entity Central Index Key	1,513,818
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		35,046,325
Entity Public Float			$ 91,229,007

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets
Cash and cash equivalents	$ 201,153	$ 182,069
Prepaid expenses and other current assets	4,152	2,542
Total current assets	205,305	184,611
Other assets		327
Property and equipment, net	265	389
Total assets	205,570	185,327
Current liabilities
Accounts payable	1,357	1,671
Accrued liabilities	12,899	7,156
Income taxes payable	247
Upfront payment from collaboration partner (Note 6)	40,000
Total liabilities	54,503	8,827
Commitments and contingencies (Note 8)
Stockholders' equity
Preferred stock, $0.0001 par value, 5,000,000 shares authorized at December 31, 2016 and December 31, 2015; zero shares issued and outstanding at December 31, 2016 and December 31, 2015
Common stock, $0.0001 par value, 50,000,000 shares authorized at December 31, 2016 and December 31, 2015; 34,843,885 and 29,420,247 shares issued and outstanding at December 31, 2016 and December 31, 2015, respectively	3	3
Additional paid-in capital	440,667	369,933
Accumulated other comprehensive loss	(350)
Accumulated deficit	(289,253)	(193,436)
Total stockholders' equity	151,067	176,500
Total liabilities and stockholders’ equity	$ 205,570	$ 185,327

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	34,843,885	29,420,247
Common stock, shares outstanding	34,843,885	29,420,247

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating expenses
Research and development	$ 16,731	$ 20,664	$ 16,397	$ 18,192	$ 15,586	$ 15,400	$ 11,940	$ 17,100	$ 71,984	$ 60,025	$ 32,608
General and administrative	5,760	6,752	5,909	5,915	4,622	5,124	7,556	5,181	24,336	22,483	13,505
Total operating expenses	22,491	27,416	22,306	24,107	20,208	20,524	19,496	22,281	96,320	82,508	46,113
Loss from operations	(22,491)	(27,416)	(22,306)	(24,107)	(20,208)	(20,524)	(19,496)	(22,281)	(96,320)	(82,508)	(46,113)
Interest income	160	120	129	105	51	54	65	49	514	218	132
Other income (expense), net	446	(39)	59	(230)	32	91	(236)	226	236	113	(11,532)
Net loss before provision for income taxes	(21,885)	(27,335)	(22,118)	(24,232)					(95,570)	(82,177)	(57,513)
Provision for income taxes	247								247
Net loss	$ (22,132)	$ (27,335)	$ (22,118)	$ (24,232)	(20,125)	(20,379)	(19,667)	(22,006)	(95,817)	(82,177)	(57,513)
Deemed dividend related to beneficial conversion feature of convertible preferred stock											(25,559)
Net loss attributable to common stockholders					$ (20,125)	$ (20,379)	$ (19,667)	$ (22,006)	$ (95,817)	$ (82,177)	$ (83,072)
Net loss per share- basic and diluted	$ (0.64)	$ (0.92)	$ (0.75)	$ (0.82)	$ (0.69)	$ (0.69)	$ (0.67)	$ (0.79)	$ (3.11)	$ (2.84)	$ (4.39)
Weighted-average common shares used to compute basic and diluted net loss per share	34,609	29,574	29,489	29,422	29,379	29,354	29,293	27,810	30,784	28,964	18,922

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (95,817)	$ (82,177)	$ (83,072)
Other comprehensive loss:
Unrealized loss on cash flow hedge	(350)
Comprehensive loss	$ (96,167)	$ (82,177)	$ (83,072)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	IPO [Member]	Secondary Offering [Member]	Convertible preferred stock [Member]	Convertible preferred stock [Member]IPO [Member]	Convertible preferred stock [Member]Series D-2 Preferred [Member]	Convertible preferred stock [Member]Series E Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member]IPO [Member]	Common Stock [Member]Secondary Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]IPO [Member]	Additional Paid-in Capital [Member]Secondary Offering [Member]	Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning Balances at Dec. 31, 2013	$ (47,292)										$ 6,454				$ (53,746)
Beginning Balances at Dec. 31, 2013				$ 57,497
Beginning Balances, shares at Dec. 31, 2013								1,257,311
Beginning Balances, shares at Dec. 31, 2013				120,648,174
Issuance of convertible preferred stock						$ 9,977	$ 54,816
Issuance of convertible preferred stock, shares						13,168,291	48,758,857
Reclassification of warrant liability upon closing of IPO		$ 2,752										$ 2,752
Reclassification of call option liability upon closing of IPO		9,581										9,581
Conversion of convertible securities		122,290			$ (122,290)				$ 2			122,288
Conversion of convertible securities, shares					(182,575,322)				15,876,104
Issuance of common stock upon exercise of warrants	572										572
Issuance of common stock upon exercise of warrants, shares								158,179
Issuance of stock		$ 132,137										$ 132,137
Issuance of stock, shares									6,900,000
Issuance of common stock upon exercise of options	$ 59										59
Issuance of common stock upon exercise of options, shares	44,822							44,822
Issuance of common stock under employee benefit plans	$ 142										142
Issuance of common stock under employee benefit plans, shares								9,021
Beneficial conversion feature related to the issuance of Series E preferred stock	25,559			$ (25,559)							25,559
Deemed dividend related to beneficial conversion feature of convertible preferred stock	(25,559)			$ 25,559							(25,559)
Stock-based compensation	4,641										4,641
Net loss	(57,513)														(57,513)
Ending Balances at Dec. 31, 2014	167,369							$ 2			278,626				(111,259)
Ending Balances, shares at Dec. 31, 2014								24,245,437
Issuance of stock			$ 80,209							$ 1			$ 80,208
Issuance of stock, shares										4,999,999
Issuance of common stock upon exercise of options	$ 121										121
Issuance of common stock upon exercise of options, shares	90,851							90,851
Issuance of common stock under employee benefit plans	$ 279										279
Issuance of common stock under employee benefit plans, shares								83,960
Stock-based compensation	10,699										10,699
Net loss	(82,177)														(82,177)
Ending Balances at Dec. 31, 2015	176,500							$ 3			369,933				(193,436)
Ending Balances, shares at Dec. 31, 2015								29,420,247
Issuance of stock			$ 59,136										$ 59,136
Issuance of stock, shares										5,176,545
Issuance of common stock upon exercise of options	$ 140										140
Issuance of common stock upon exercise of options, shares	85,646							85,646
Issuance of common stock under employee benefit plans	$ 535										535
Issuance of common stock under employee benefit plans, shares								161,447
Stock-based compensation	10,923										10,923
Unrealized loss on cash flow hedge	(350)													$ (350)
Net loss	(95,817)														(95,817)
Ending Balances at Dec. 31, 2016	$ 151,067							$ 3			$ 440,667			$ (350)	$ (289,253)
Ending Balances, shares at Dec. 31, 2016								34,843,885

Consolidated Statements of Con7

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock [Member] | IPO [Member]
Stock issuance cost			$ 2,620
Common Stock [Member] | Secondary Offering [Member]
Stock issuance cost	$ 473	$ 866
Series D-2 Preferred [Member] | Issuance Date of February 2014 [Member]
Stock, issuance price per share			$ 0.76
Stock issuance cost			$ 23
Series E Preferred Stock [Member] | Issuance Date of February 2014 [Member]
Stock, issuance price per share			$ 1.13
Stock issuance cost			$ 184

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net loss	$ (95,817)	$ (82,177)	$ (57,513)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	215	194	107
Loss on disposition of assets			26
Stock-based compensation expense	10,923	10,699	4,641
Remeasurement of convertible preferred stock call option liability			9,560
Remeasurement of convertible preferred stock warrant liability			2,279
Changes in assets and liabilities
Prepaid expenses and other assets	(1,626)	317	(1,695)
Accounts payable	(315)	413	944
Accrued and other liabilities	5,742	1,490	1,998
Income taxes payable	247
Upfront payment from collaboration partner	40,000
Net cash used in operating activities	(40,631)	(69,064)	(39,653)
Cash flows from investing activities
Purchase of property and equipment	(90)		(827)
Security deposit for facility lease		(42)	55
Net cash used in investing activities	(90)	(42)	(772)
Cash flows from financing activities
Proceeds from issuance of common stock in initial public offering, net of issuance costs			132,137
Proceeds from issuance of common stock in follow-on offering, net of issuance costs	59,136	80,209
Proceeds from issuance of convertible preferred stock, net of issuance costs			64,793
Proceeds from exercise of convertible preferred stock warrants			572
Proceeds from issuance of common stock in connection with employee benefit plans	669	400	201
Net cash provided by financing activities	59,805	80,609	197,703
Net increase in cash and cash equivalents	19,084	11,503	157,278
Cash and cash equivalents at beginning of period	182,069	170,566	13,288
Cash and cash equivalents at end of period	$ 201,153	$ 182,069	170,566
Conversion of preferred stock call option liability [Member]
Supplemental disclosure of noncash items
Conversion of liability to additional paid in capital			9,581
Conversion of preferred stock warrant liability [Member]
Supplemental disclosure of noncash items
Conversion of liability to additional paid in capital			2,752
Conversion of preferred stock to common stock [Member]
Supplemental disclosure of noncash items
Conversion to common stock and additional paid in capital			$ 122,290

Formation and Business of the C

Formation and Business of the Company	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Formation and Business of the Company	1. Formation and Business of the Company Versartis, Inc., (the “Company”) was incorporated on December 10, 2008 in the State of Delaware. The Company is an endocrine-focused biopharmaceutical company initially developing long-acting recombinant human growth hormone for the treatment of growth hormone deficiency. The Company is developing drug candidates that it has licensed from Amunix Operating, Inc. (“Amunix”). The Company’s headquarters and operations are in Menlo Park, California. Since incorporation, the Company has been primarily performing research and development activities, including early and late stage clinical trials, filing patent applications, obtaining regulatory approvals, hiring personnel, and raising capital to support and expand these activities. Initial and Secondary Public Offerings In March 2014, the Company completed its initial public offering of shares of its common stock, or IPO, pursuant to which the Company issued 6,900,000 shares of common stock, which includes shares issued pursuant to the underwriters’ exercise of their over-allotment option, and received net proceeds of approximately $132.1 million, after underwriting discounts, commissions and offering expenses. In addition, in connection with the completion of the Company’s IPO, all convertible preferred stock converted into common stock. Effective with the closing of the IPO, the Company’s Amended and Restated Certificate of Incorporation authorizes the Company to issue 50.0 million shares of common stock and 5.0 million shares of preferred stock. In January 2015, the Company completed a secondary public offering of common stock, pursuant to which the Company issued 4,999,999 shares of common stock, which includes shares issued pursuant to the underwriters’ exercise of their over-allotment option, and received net proceeds of approximately $80.2 million, after underwriting discounts, commissions and estimated offering expenses. In October and November 2016, the Company completed a follow-on offering of common stock, pursuant to which the Company issued 5,176,545 shares of common stock, which includes shares issued pursuant to the underwriters’ partial exercise of their over-allotment option, and received net proceeds of approximately $59.1 million, after underwriting discounts, commissions and offering expenses.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The preparation of the accompanying consolidated financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates. The accompanying consolidated financial statements are consolidated for the year ended December 31, 2016 and December 31, 2015 and include the accounts of Versartis, Inc. and its wholly-owned subsidiaries, Versartis Cayman Holdings Company, incorporated in 2014, and Versartis GmbH, incorporated in 2015. All intercompany accounts and transactions have been eliminated. The U.S. dollar is the functional currency for all of the Company's subsidiaries and consolidated operations. Since inception, the Company has incurred net losses and negative cash flows from operations. At December 31, 2016, the Company had an accumulated deficit of $289.3 million and working capital of $150.8 million. The Company expects to continue to incur losses from costs related to the continuation of research and development and administrative activities for the foreseeable future. Although management has been successful in raising capital in the past, most recently $59.1 million in October and November 2016, there can be no assurance that the Company will be successful or that any needed financing will be available in the future at terms acceptable to the Company. Segments The Company operates in one segment. Management uses one measurement of profitability and does not segregate its business for internal reporting. All long-lived assets are maintained in the United States of America. Concentration of c r Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents. All of the Company’s cash and cash equivalents are held at several financial institutions that management believes are of high credit quality. Such deposits may, at times, exceed federally insured limits. The Company enters into forward foreign currency contracts that expose it to credit risk to the extent that the counterparties may be unable to meet the terms of the agreement. The Company does, however, seek to mitigate such risks by limiting its counterparties to major financial institutions. In addition, the potential risk of loss with any one counterparty resulting from this type of credit risk is monitored. Management does not expect material losses as a result of defaults by counterparties. Derivative Financial Instruments The Company engages in transactions denominated in foreign currencies and, as a result, is exposed to changes in foreign currency exchange rates. To manage the volatility resulting from fluctuating foreign currency exchange rates, the Company enters into option and forward foreign currency exchange contracts. The Company accounts for its derivative instruments as either assets or liabilities on the balance sheet and measures them at fair value. The Company assesses, both at inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting the changes in cash flows of the hedged items. If the Company determines that a forecasted transaction is no longer probable of occurring, it discontinues hedge accounting for the affected portion of the hedge instrument, and any related unrealized gain or loss on the contract is recognized in other comprehensive income (expense). Risk and Uncertainties The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s potential drug candidates, uncertainty of market acceptance of the Company’s products, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals and sole source suppliers. Products developed by the Company require clearances from the U.S. Food and Drug Administration (“FDA”), the Pharmaceuticals Medicines and Devices Agency (“PMDA”), or other international regulatory agencies prior to commercial sales. There can be no assurance that the products will receive the necessary clearances. If the Company was denied clearance, clearance was delayed or the Company was unable to maintain clearance, it could have a materially adverse impact on the Company. The Company expects to incur substantial operating losses for the next several years and will need to obtain additional financing in order to launch and commercialize any product candidates for which it receives regulatory approval. Even though the Company expects additional proceeds if certain clinical and regulatory milestones are met under the Teijin Agreement, there can be no assurance that such additional financing will be available at all, or will be at terms acceptable by the Company. Cash and c e The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. At December 31, 2016 and December 31, 2015 the Company’s cash and cash equivalents were held in multiple institutions with the United States and Europe and included deposits in money market funds which were unrestricted as to withdrawal or use. Property and e Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets, generally between three and five years. Leasehold improvements are amortized on a straight-line basis over the lesser of their useful life or the term of the lease. Maintenance and repairs are charged to expense as incurred, and improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the consolidated balance sheet and any resulting gain or loss is reflected in operations in the period realized. Impairment of Long-Lived Assets The Company reviews property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by the comparison of the carrying amount to the future net cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value (i.e. determined through estimating projected discounted future net cash flows or other acceptable methods of determining fair value) arising from the asset. There have been no such impairments of long-lived assets during the years ended December 31, 2016, 2015, and 2014. Fair Value of Financial Instruments The carrying value of the Company’s cash and cash equivalents, prepaid expenses, accounts payable and accrued liabilities approximate fair value due to the short-term nature of these items. Convertible preferred stock call option liability and convertible preferred stock warrant liability, which were outstanding through the completion of the Company’s initial public offering during the three months ended March 31, 2014, were carried at fair value. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows: Level I Unadjusted quoted prices in active markets for identical assets or liabilities; Level II Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level III Unobservable inputs that are supported by little or no market activity for the related assets or liabilities. The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s financial instruments consist of Level I assets as of December 31, 2016 and consist of Level I assets as of December 31, 2015. Level I securities are comprised of highly liquid money market funds. The Company’s foreign currency derivative contracts have maturities over a 12-month time horizon and is with a counterparty that has a minimum credit rating of A- or equivalent by Standard & Poor's, Moody's Investors Service, Inc. or Fitch, Inc. These contracts are reported as Level II assets, however there were none outstanding as of December 31, 2016 and December 31, 2015. Preclinical and Clinical Trial Accruals The Company’s clinical trial accruals are based on estimates of patient enrollment and related costs at clinical investigator sites as well as estimates for the services received and efforts expended pursuant to contracts with multiple research institutions and clinical research organizations (“CROs”) that conduct and manage clinical trials on the Company’s behalf. The Company estimates preclinical and clinical trial expenses based on the services performed, pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on its behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of patient enrollment and activity expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Payments made to third parties under these arrangements in advance of the receipt of the related services are recorded as prepaid expenses until the services are rendered. Convertible Preferred Stock Warrants The Company accounted for its convertible preferred stock warrants as liabilities based upon the characteristics and provisions of each instrument. Convertible preferred stock warrants classified as derivative liabilities were recorded on the Company’s consolidated balance sheet at their fair value on the date of issuance and revalued on each subsequent consolidated balance sheet, with fair value changes recognized as increases or reductions to other income (expense), net in the consolidated statements of operations. Prior to the IPO in March 2014, the Company had outstanding warrants which were classified as a liability and remeasured to fair value each reporting period. The Company had estimated the fair value of these liabilities using an option pricing model and assumptions that were based on the individual characteristics of the warrants on the valuation date, as well as assumptions for expected volatility, expected life, dividends, and risk-free interest rate. Immediately prior to the completion of the Company’s IPO in March 2014, all of the warrants were either exercised for cash or automatically net exercised for a total issuance of 158,179 shares of common stock, pursuant to the terms of the warrants. Just prior to the exercises, all outstanding warrants, covering 173,910 shares, were remeasured using the intrinsic value of the warrant computed as the difference between the $21.00 per share IPO price and the $5.17 per share exercise price of the warrant. The remeasurement of the fair value of these warrants from December 31, 2013 through the date of the conversion to a common stock warrant and following exercise resulted in a $2.3 million expense recorded to other income (expense), net in the consolidated statement of operations and comprehensive loss. The resulting fair value of approximately $2.8 million was reclassified to additional paid in capital upon completion of the IPO. Convertible Preferred Stock Call Option The Company determined that the Company’s obligation to issue, and the investors’ obligation to purchase, additional shares of the Company’s convertible preferred stock represented a freestanding financial instrument. The freestanding convertible preferred stock call option liability was initially recorded at fair value, with fair value changes recognized as increases or reductions to other income (expense), net in the consolidated statement of operations and comprehensive loss. At the time of the deemed exercise of the call option, the remaining value of the option was reclassified to additional paid in capital. Immediately prior to the Series D-2 financing completed in February 2014, the Company remeasured the fair value of the preferred stock call option liability associated with the Series D convertible preferred stock financing and recorded other expense of approximately $9.6 million in the consolidated statement of operations and comprehensive loss for the year ended December 31, 2014. Fair value was computed using a discount from the Company’s public offering price less the liquidation value of the underlying Series D convertible preferred stock. Convertible Preferred Stock The Company classified the convertible preferred stock as temporary equity on the balance sheets due to certain change in control events that are outside the Company’s control, including liquidation, sale or transfer of the Company, as holders of the convertible preferred stock can cause redemption of the shares. Upon the IPO in March 2014, all of the outstanding shares of convertible preferred stock automatically converted into 15,876,104 shares of common stock. Research and d Research and development costs are charged to operations as incurred. Research and development costs include, but are not limited to, payroll and personnel expenses, laboratory supplies, consulting costs, external research and development expenses and allocated overhead, including rent, equipment depreciation, and utilities. Costs to acquire technologies to be used in research and development that have not reached technological feasibility and have no alternative future use are expensed to research and development costs when incurred. Income t The Company accounts for income taxes under the asset and liability approach. Under this method, deferred tax assets and liabilities are determined based on the difference between the consolidated financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The provision for income taxes includes income taxes paid or payable for the current year plus the change in deferred taxes during the year. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position’s sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available. Stock-Based c For stock options granted to employees, the Company recognizes compensation expense for all stock-based awards based on the grant-date estimated fair value. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service period. The fair value of stock options is determined using the Black-Scholes option pricing model. The determination of fair value for stock-based awards on the date of grant using an option pricing model requires management to make certain assumptions regarding a number of complex and subjective variables. Stock-based compensation expense related to stock options granted to nonemployees is recognized based on the fair value of the stock options, determined using the Black-Scholes option pricing model, as they are earned. The awards generally vest over the time period the Company expects to receive services from the nonemployee. Consolidated Statement of Operations and Comprehensive Loss Comprehensive loss is defined as a change in equity of a business enterprise during a period, resulting from transactions from non-owner sources. Specifically, the Company includes cumulative foreign currency translation adjustments and net unrealized gains and losses on effective cash flow hedges. Net Loss per Share of Common Stock Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, convertible preferred stock, convertible notes payable, stock options and convertible preferred stock warrants are considered to be potentially dilutive securities. Because the Company has reported a net loss for the years ended December 31, 2016, 2015 and 2014, diluted net loss per common share is the same as basic net loss per common share for those periods. Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or FASB, or other standard setting bodies and adopted by us as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective is not expected to have a material impact on the Company’s financial position or results of operations upon adoption. In August 2016, the FASB issued guidance to simplify elements of cash flow classification. The guidance is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. The new guidance requires cash payments for debt prepayment or debt extinguishment costs to be classified as cash outflows for financing activities. It also requires cash payments made soon after an acquisition's consummation date (approximately three months or less) to be classified as cash outflows for investing activities. Payments made thereafter should be classified as cash outflows for financing activities up to the amount of the original contingent consideration liability. Payments made in excess of the amount of the original contingent consideration liability should be classified as cash outflows for operating activities. The guidance is required to be applied by the Company in the first quarter of 2018, but early adoption is permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements. In March 2016, the FASB issued Accounting Standards Update (“ASU”) No. 2016-09, Compensation – Stock Compensation (Topic 718) (“ASU 2016-09”), which simplified certain aspects of the accounting for share-based payment transactions, including income taxes, classification of awards and classification in the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. The Company will adopt ASU 2016-09 in the first quarter of 2017. The Company is currently evaluating the impact of the adoption of this guidance on its consolidated financial condition, results of operations and cash flows. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). In November 2015, the FASB issued ASU 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes, The Company is currently evaluating the impact of adoption and will apply the guidance and disclosure provisions of the new standard upon adoption. In August 2014, the FASB issued ASU 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern, which In May 2014, the FASB issued a new accounting standard that amends the guidance for the recognition of revenue from contracts with customers to transfer goods and services. The FASB has subsequently issued additional, clarifying standards to address issues arising from implementation of the new revenue recognition standard. The new revenue recognition standard and clarifying standards are effective for interim and annual periods beginning on January 1, 2018, and may be adopted earlier, but not before January 1, 2017. The revenue standards are required to be adopted by taking either a full retrospective approach or a modified retrospective approach. The Company is currently evaluating the impact that the revenue standards will have on our consolidated financial statements and determining the transition method that we will apply.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	3. Balance Sheet Components Prepaid expenses and other current assets (in thousands) December 31, 2016 2015 Preclinical and clinical $ 3,474 $ 1,770 Other 678 772 Total $ 4,152 $ 2,542 Property and equipment, net (in thousands) December 31, 2016 2015 Equipment and furniture $ 664 $ 575 Buildings, leasehold and building improvements 134 132 798 707 Less: Accumulated depreciation and amortization (533 ) (318 ) Property and equipment, net $ 265 $ 389 Accrued liabilities (in thousands) December 31, 2016 2015 Payroll and related $ 3,818 $ 2,296 Preclinical and clinical 8,803 4,376 Professional services 114 69 Other 164 415 Total $ 12,899 $ 7,156

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The Company’s financial instruments consist principally of cash and cash equivalents, prepaid expenses, foreign currency exchange contracts, accounts payable and accrued liabilities. The remaining financial instruments are reported on the Company’s Condensed Consolidated Balance Sheets at amounts that approximate current fair value. The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): Fair Value Measurements at December 31, 2016 Total Level 1 Level 2 Level 3 Assets Money market funds $ 85,911 $ 85,911 $ — $ — Fair Value Measurements at December 31, 2015 Total Level 1 Level 2 Level 3 Assets Money market funds $ 132,647 $ 132,647 $ — $ — The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy during the years ended December 31, 2016 or 2015. The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial instruments as follows: Convertible Convertible preferred stock preferred stock call option warrant liability liability Balance at January 1, 2014 $ 21 $ 474 Change in fair value recorded in other income (expense), net 9,560 2,278 Conversion of preferred stock into common stock and reclassification to permanent equity (9,581) (2,752) Balance at December 31, 2014 $ — $ —

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	5. Derivative Financial Instruments The Company’s relationships with vendors in foreign countries expose it to market risk associated with foreign currency exchange rate fluctuations between the U.S. dollar and various foreign currencies, the most significant of which is the Euro. In order to manage this risk, the Company hedges a portion of its foreign currency exposures related to certain forecasted operating expenses using foreign currency exchange forward or option contracts. In general, the market risk related to these contracts is offset by corresponding gains and losses on the hedged transactions. By working only with major financial institutions and closely monitoring current market conditions, the Company seeks to limit its counterparty risk to these contracts. Therefore, the Company’s overall risk of loss in the event of a counterparty default is exposed to the currency risk. The Company does not enter into derivative contracts for trading or speculative purposes. The Company hedges its exposure to foreign currency exchange rate fluctuations for forecasted operating expenses that are denominated in a non-functional currency. The derivative instruments the Company uses to hedge this exposure are designated as cash flow hedges and have maturity dates of 12 months or less. Upon executing a hedging contract and quarterly thereafter, the Company assesses both retrospective and prospective hedge effectiveness using regression analysis to assert the hedge is highly effective at offsetting changes in cash flow. The Company includes time value in its effectiveness assessment and recognizes any ineffectiveness in other income (expense). The effective component of the Company’s hedge is recorded in accumulated other comprehensive income (OCI) within stockholders' equity and subsequently reclassified into earnings when the hedged exposure affects earnings. Derivatives not designated as hedges are not speculative and are used to manage the Company’s economic exposure to foreign exchange rate movements but do not meet the strict hedge accounting requirements. Changes in the fair value of derivatives not designated in hedging relationships are recorded directly in earnings. Substantially all of the gains and losses related to the hedged forecasted transaction reported in accumulated other comprehensive income at December 31, 2016 are expected to be reclassified to research and development expenses within the next 12 months. The cash flow effects of the Company’s derivative contracts for the year ended December 31, 2016 are included within net cash provided by operating activities in the consolidated statements of cash flows. The Company had notional amounts on foreign currency exchange contracts of 9.1 million euros (a purchased call option on the Euro) that expired in December 2016 and none outstanding at December 31, 2016 and at December 31, 2015. While all of the Company’s derivative contracts allow it the right to offset assets or liabilities, the Company has presented amounts on a gross basis. Under the International Swap Dealers Association, Inc. master agreements with the respective counterparties of the foreign currency exchange contracts, subject to applicable requirements, the Company is allowed to net settle transactions of the same currency with a single net amount payable by one party to the other. The Company does not have any credit contingent features associated with its derivatives. The following table summarizes the effect of our foreign currency exchange contracts on the Company’s consolidated financial statements (in thousands): As of December 31, 2016 2015 Derivatives designated as hedges: Gains (losses) recognized in accumulated OCI (effective portion) $ (286 ) $ — Gains (losses) reclassified from accumulated OCI into operating expenses (effective portion) $ 64 $ — Gains (losses) recognized in other income (expense), net (ineffective portion and amounts excluded from effectiveness testing) $ — $ — Derivatives not designated as hedges: Gains (losses) recognized in other income (expense), net $ (80 ) $ — From time to time, the Company may discontinue cash flow hedges and as a result, record related amounts in other income (expense), net on its condensed consolidated statements of operations. The Company did not record any amounts in other income (expense), net at December 31, 2016 as a result of the discontinuance of cash flow hedges. As of December 31, 2016, the Company held no derivative contracts.

Teijin Agreement

Teijin Agreement	12 Months Ended
	Dec. 31, 2016
License And Supply Agreement [Abstract]
Teijin Agreement	6. Teijin Agreement In August 2016, the Company, entered into an Exclusive License and Supply Agreement (the “Agreement”) with Teijin Limited, or Teijin, a pharmaceutical company based in Japan, pursuant to which the Company granted to Teijin an exclusive license to develop, use, sell, offer for sale, import, and otherwise commercialize, in Japan, any pharmaceutical product incorporating somavaratan (VRS-317) , while Versartis retains exclusive rights to somavaratan in the rest of the world. Under the Agreement, the development and commercialization of somavaratan products in Japan will be overseen by a joint steering committee composed of representatives of Teijin and the Company. Versartis will be responsible for completing (at the Company’s expense) all ongoing clinical studies, including the current pediatric Growth Hormone Deficiency (GHD) Phase 2/3 trial, and its related long-term safety study, and the Company will also be responsible for a portion of the costs associated with any additional trials, if they are required by the Japanese authorities for approval of the Marketing Authorization Application, or MAA, in Japan in the pediatric indication, up to a cap on our share of such costs of $5.0 million. Following the MAA submission in Japan, Teijin will be responsible for conducting any additional Japanese studies for the pediatric or any other indications, at its own expense. The Company is required, under the Agreement, to supply Teijin with its clinical and commercial requirements for product for Japan. In exchange for delivering finished product for commercial use, the Company will receive a combination of a running royalty and transfer pricing based upon net sales of the product in Japan, in a percentage ranging from the high-20s to mid-30s. The Agreement continues until the earlier of (i) twelve years after the first commercial sale of a licensed product in Japan, or (ii) the expiration of certain Versartis patents, unless terminated earlier by mutual agreement of the parties. The initial term of the Agreement is subject to automatic extension for three three-year terms, unless otherwise mutually agreed. The Agreement may be earlier terminated by either party for the other party’s uncured material breach or insolvency. In addition, Teijin may terminate the Agreement without cause upon six months’ advance notice prior to the sale of a licensed product, and upon twelve months’ notice thereafter. The Company has recorded the $40.0 million upfront payment received from Teijin as a component of other current liabilities under the caption “Upfront payment from collaboration partner.” The Company concluded that the evidence of arrangement criteria pursuant to SEC Staff Accounting Bulletin No. 104 Revenue Recognition and applicable authoritative guidance has not been met as of December 31, 2016. The Company's analysis of the revenue recognition criteria will be completed upon the establishment and completion of the terms of a Commercial Supply Agreement with Teijin governing the supply of finished product to Teijin, as contemplated in the Agreement.

Convertible Preferred Stock War

Convertible Preferred Stock Warrants	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Convertible Preferred Stock Warrants	7. Convertible Preferred Stock Warrants In connection with the convertible note purchase agreements (“2012 Notes”), the Company issued convertible preferred stock warrants equal to 20% of the shares issuable on conversion of the 2012 Notes. The convertible preferred stock warrants were exercisable into shares of the same class of convertible preferred stock issued upon conversion of the related 2012 Notes. The convertible preferred stock warrants had a five-year term and an expiration date of October 12, 2017. The estimated fair value of these warrants of $433,000 at issuance was recorded as a debt discount on the 2012 Notes, and amortized to interest expense using the effective interest method through the original maturity date in 2013. The convertible preferred stock warrants were valued using an option pricing model with a risk-free interest rate of 0.21%, volatility of 90%, and an expected life equal to 1.5 years. As of December 31, 2013, the fair value of the warrants was estimated to be $474,000. The terms of the warrants provided that they would expire at the earlier of (i) the closing of an initial public offering, (ii) a sale of the company or (iii) October 12, 2017; provided that if a holder of the warrants does not notify us of the holder’s intent to exercise or not to exercise the warrant prior to the expiration date, and the fair market value of the underlying shares on the expiration date is greater than the exercise price, then the holder will be deemed to have net exercised the warrant immediately prior to the expiration date. Upon the closing of the Company’s IPO, the warrants were exercised for a total of 158,179 shares of common stock. Prior to the IPO in March 2014, the Company had outstanding warrants which were classified as a liability and remeasured to fair value each reporting period. The Company had estimated the fair value of these liabilities using an option pricing model and assumptions that were based on the individual characteristics of the warrants on the valuation date, as well as assumptions for expected volatility, expected life, dividends, and risk-free interest rate. Immediately prior to the completion of the Company’s IPO in March 2014, all of the warrants were either exercised for cash or automatically net exercised for a total issuance of 158,179 shares of common stock, pursuant to the terms of the warrants. Just prior to the exercises, all outstanding warrants, covering 173,910 shares, were remeasured using the intrinsic value of the warrant computed as the difference between the $21.00 per share IPO price and the $5.17 per share exercise price of the warrant. The remeasurement of the fair value of these warrants from December 31, 2013 through the date of the conversion to a common stock warrant and following exercise resulted in a $2.3 million expense recorded to other income (expense), net in the consolidated statement of operations and comprehensive loss. The resulting fair value of approximately $2.8 million was reclassified to additional paid in capital upon completion of the IPO.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Facility Leases In March 2014, the Company entered into an operating facility lease agreement to lease approximately 12,900 square feet in Menlo Park, California for its new headquarters building for a period of thirty-nine months. The total obligation for the Company under this lease is approximately $0.5 million as of December 31, 2016. In December 2015, the Company entered into an operating sublease agreement to lease additional office space in Menlo Park for a period of twenty-four months. The total obligation for the Company under this sublease is approximately $0.6 million as of December 31, 2016. Rent expense was $1,290,000, $763,000, and $520,000 for the years ended December 31, 2016, 2015, and 2014, respectively. As of December 31, 2016, the aggregate future minimum lease payments under the noncancellable operating lease arrangements are as follows (in thousands): Year Ended December 31, 2016 2017 $ 1,085 2018 — 2019 — 2020 — 2021 — Thereafter — $ 1,085 Boehringer Ingelheim Commercial Supply Agreement In December 2016, through the Company’s subsidiary, Versartis GmbH, entered into a Commercial Supply Agreement with Boehringer Ingelheim Biopharmaceuticals GmbH (“BI”), pursuant to which the Company engaged BI as a contract manufacturer to manufacture the bulk drug substance for our proprietary long-acting human growth hormone, somavaratan, fill it into the final container and closure and supply such drug product to us for commercial use. Under the agreement, each calendar year the Company is required to reserve minimum drug substance manufacturing capacity, order from BI a minimum number of batches of drug substance, and purchase and take possession of a minimum number of batches of drug product. If the Company does not order and purchase these minimum quantities, it will need to pay fees to BI based on the shortfalls in its product orders or purchases, unless there is a supply failure or supply interruption by BI. The agreement includes customary terms and conditions relating to, among other things, forecast, ordering, delivery, inspection, acceptance and product warranties. The initial term of the agreement continues for a period of eight years and, after the initial term, the agreement will automatically renew for periods of three years each. The agreement may be earlier terminated by either party for technical reasons if BI is unable to implement or consistently perform the manufacturing process on a commercial scale. The Company has the right to terminate this agreement if the Company is unable to achieve the clinical targets or target product profile for somavaratan or if it is unable to obtain regulatory approval of the product. The agreement may also be terminated by either party for the other party’s uncured material breach, insolvency, and certain change of control and force majeure events. In addition, either party may terminate the agreement without cause upon three years’ advance notice. Upon termination of the agreement or if the Company’s demand for the product exceeds the maximum capacity reservation at BI, the Company has the right to add an additional manufacturing site or transfer the entire manufacturing process to itself or it’s designee. Owen Mumford Manufacture and Supply Agreement In May 2016, the Company entered into a Manufacture and Supply Agreement with Owen Mumford Limited, a leading medical device manufacturer, pursuant to which the Company engaged Owen Mumford to: (1) manufacture a proprietary disposable autoinjector device and (2) assemble and supply a final combination product including the device and somavaratan, its proprietary long-acting form of human growth hormone. The Company will supply somavaratan in prefilled syringes to Owen Mumford for incorporation into the final combination product. Under the agreement, Owen Mumford agrees to manufacture the autoinjector device used in the product exclusively for the Company in the field of human growth hormone deficiency treatment, subject to a minimum purchase obligation. The Company is required to purchase its entire requirement of the final combination product from Owen Mumford, except that after a specified time period after regulatory approval in the European Union (“EU”), the Company may purchase from third parties a portion of its requirement for the European Economic Area. In addition, after a specified time period after regulatory approval in any major jurisdiction, the Company is required to purchase from Owen Mumford a minimum quantity of the product in each year. If the Company does not purchase such minimum quantity, it may pay a shortfall payment to Owen Mumford to maintain the scope of its exclusivity. If the Company fails to purchase the minimum and decline to pay the shortfall payment, the exclusivity will be limited to long-acting human growth hormone products. The agreement also includes customary terms and conditions relating to forecast, ordering, delivery, inspection and acceptance, among other matters. The initial term of the agreement continues until ten (10) years after the Company’s acceptance of the first shipment of the final combination product, and may be renewed for an additional time period by mutual agreement of the parties. The agreement may be earlier terminated by either party for the other party’s uncured material breach or insolvency. In addition, either party may terminate the agreement without cause upon twelve (12) months advance notice. If terminated by Owen Mumford without cause, Owen Mumford must continue to supply the autoinjector device and assemble the final combination product until the Company is able to identify, appoint, and qualify through all necessary regulatory approvals an alternate manufacturer. Purchase Commitments The Company conducts research and development programs through a combination of internal and collaborative programs that include, among others, arrangements with contract manufacturing organizations and contract research organizations. The Company had contractual arrangements with these organizations including license agreements with milestone obligations and service agreements with obligations largely based on services performed. In the normal course of business, the Company enters into various firm purchase commitments related to certain preclinical and clinical studies. At December 31, 2016 the noncancellable portion of these commitments, in aggregate, totaled approximately $7.1 million and is expected to be paid within the next fiscal year. Contingencies In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future, but have not yet been made. The Company accrues a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. As of December 31, 2016 the Company is contingently committed to make development and sales-related milestone payments of up to $30.0 million under certain circumstances, and other payments of $10.0 million, as well as royalties relating to potential future product sales under the License Agreement with Amunix. The amount, timing and likelihood of these payments are unknown as they are dependent on the occurrence of future events that may or may not occur, including approval by the FDA of potential drug candidates. Indemnification In accordance with the Company’s amended and restated Certificate of Incorporation and amended and restated bylaws, the Company has indemnification obligations to its officers and directors for certain events or occurrences, subject to certain limits, while they are serving at the Company’s request in such capacity. There have been no claims to date and the Company has a director and officer insurance policy that may enable it to recover a portion of any amounts paid for future claims. Litigation The Company may from time to time be involved in legal proceedings arising from the normal course of business. There are no pending or threatened legal proceedings as of December 31, 2016.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Common Stock	9. Common Stock The Certificate of Incorporation, as amended, authorizes the Company to issue 50,000,000 shares of common stock. Common stockholders are entitled to dividends as and when declared by the Board of Directors, subject to the rights of holders of all classes of stock outstanding having priority rights as to dividends. There have been no dividends declared to date. The holder of each share of common stock is entitled to one vote. The Company had reserved shares of common stock for future issuances as follows: December 31, 2016 2015 Issuance of equity based awards under stock plan 1,044,113 1,350,543 Issuance upon exercise of options under stock plan 4,452,700 3,240,969 Issuance of restricted stock units under stock plan 502,027 254,067 Total 5,998,840 4,845,579 In January 2015, the Company completed a secondary public offering of common stock, pursuant to which the Company issued 4,999,999 shares of common stock, which includes shares issued pursuant to the underwriters’ exercise of their over-allotment option, and received net proceeds of approximately $80.2 million, after underwriting discounts, commissions and estimated offering expenses. In October and November 2016, the Company completed a follow-on public offering of common stock to which the Company issued 5,176,545 shares of common stock, which includes shares issued pursuant to the underwriters’ exercise of their over-allotment option, and received net proceeds of approximately $59.1 million, after underwriting discounts, commissions and offering expenses.

Stock Based Awards

Stock Based Awards	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Based Awards	10. Stock Based Awards 2009 Equity Incentive Plan In February 2009, the Company adopted the Versartis, Inc. 2009 Stock Plan, which was amended in June 2011 (“2009 Plan”) for eligible employees, outside directors and consultants. The 2009 Plan provides for the granting of incentive stock options, non-statutory stock options, and stock purchase rights to acquire restricted stock. Terms of the stock option agreements, including vesting requirements, are determined by the board of directors, subject to the provisions in the 2009 Plan. Options granted by the Company generally vest over a period of four years and expire no later than ten years after the date of grant. Options may be exercised prior to vesting, subject to a right of repurchase by the Company. The board of directors determines the fair value of the underlying common stock at the time of the grant of each option. Upon the exercise of options, the Company issues new common stock from its authorized shares. Options under the 2009 Plan may be granted for periods of up to ten years. All options issued to date have had a ten year life. The exercise price of an ISO shall not be less than 100% of the estimated fair value of the shares on the date of grant, as determined by the Board of Directors. The exercise price of an ISO and NSO granted to a 10% shareholder shall not be less than 110% of the estimated fair value of the shares on the date of grant, respectively, as determined by the board of directors. The exercise price of a NSO shall not be less than the par value per share of common stock. To date, options granted generally vest over four years and vest at a rate of 25% upon the first anniversary of the issuance date and 1/36th per month thereafter. Upon adoption of the 2014 Equity Incentive Plan described below, no further grants will be made under the 2009 Plan. 2014 Equity Incentive Plan In March 2014, the Company’s board of directors adopted, and the Company’s stockholders approved, the 2014 Equity Incentive Plan, or the 2014 Plan. The 2014 Plan became effective at the time of the initial public offering and is the successor to the 2009 Plan. The 2014 Plan provides for the grant of ISOs to employees and for the grant of NSOs, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance-based stock awards, performance-based cash awards and other forms of equity compensation to employees, directors and consultants. Additionally, the 2014 Plan provides for the grant of performance cash awards to employees, directors and consultants. Initially, the aggregate number of shares of common stock that may be issued pursuant to stock awards under the 2014 Plan after the initial public offering is approximately 4.1 million, which includes options outstanding under the 2009 Plan. The number of shares of common stock reserved for issuance under the 2014 Plan will automatically increase on January 1 of each year, beginning on January 1, 2015 and ending on and including January 1, 2024, by 4.5% of the total number of shares of the Company’s capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by the board of directors. The maximum number of shares that may be issued upon the exercise of ISOs under the 2014 Plan is 12,000,000. The Company’s board of directors, or a duly authorized committee of the board of directors, will administer the 2014 Plan. The board of directors may also delegate to one or more of the Company’s officers the authority to (i) designate employees (other than officers) to receive specified stock awards, and (ii) determine the number of shares of our common stock to be subject to such stock awards. Subject to the terms of our 2014 Plan, the board of directors has the authority to determine the terms of awards, including recipients, the exercise, purchase or strike price of stock awards, if any, the number of shares subject to each stock award, the fair market value of a share of the Company’s common stock, the vesting schedule applicable to the awards, together with any vesting acceleration, and the form of consideration, if any, payable upon exercise or settlement of the award and the terms of the award agreements. Options granted under the 2014 Plan have a contractual life of ten years and generally vest over four years and vest at a rate of 25% upon the first anniversary of the issuance date and 1/36 th As of December 31, 2016, a total of 1,044,113 shares of common stock are available for future grant under the 2014 Plan. Activity under the Company’s stock option plans is set forth below: Weighted Average Weighted Remaining Aggregate Shares Average Contractual Intrinsic Available Number of Exercise Life Value for Grant Shares Price (in years) (in thousands) Balance at January 1, 2014 9,533 1,403,656 $ 1.90 Additional shares authorized 2,531,915 — — Options granted (1,471,142 ) 1,471,142 18.68 Restricted stock units granted (185,514 ) Options exercised — (44,822 ) 1.32 Options cancelled 106,609 (106,609 ) 18.43 Balances, December 31, 2014 991,401 2,723,367 $ 10.33 Additional shares authorized 1,091,045 — — Options granted (664,100 ) 664,100 15.34 Restricted stock units granted (123,450 ) — — Options exercised — (90,851 ) 1.34 Options cancelled 55,647 (55,647 ) 15.68 Balances, December 31, 2015 1,350,543 3,240,969 $ 11.51 Additional shares authorized 1,323,911 — — Options granted (1,399,522 ) 1,399,522 10.04 Restricted stock units granted (332,964 ) — — Options exercised — (85,646 ) 1.64 Options cancelled 102,145 (102,145 ) 14.90 Balances, December 31, 2016 1,044,113 4,452,700 $ 11.16 7.8 $ 25,162 Vested and expected to vest as of December 31, 2016 — 4,323,511 $ 11.14 7.8 $ 24,632 Exercisable as of December 31, 2016 — 2,246,742 $ 10.11 7.2 $ 15,498 The intrinsic values of outstanding, vested and exercisable options were determined by multiplying the number of shares by the difference in exercise price of the options and the fair value of the common stock. The intrinsic value of stock options exercised during the years ended December 31, 2016, 2015, and 2014, was $0.8 million, $1.4 million, and $0.8 million, respectively. The following table summarizes information with respect to stock options outstanding and currently exercisable and vested as of December 31, 2016: Options Exercisable Options Outstanding and Vested Weighted Average Weighted Average Remaining Remaining Range of Number Contractual Number Contractual Exercise Prices Outstanding Life (in Years) Outstanding Life (in Years) $1.27-$2.53 1,158,038 6.3 966,139 6.3 3.33-10.68 1,736,950 8.6 494,703 8.6 10.87-20.30 896,382 8.5 409,602 8.5 21.00-31.96 651,330 7.5 370,048 7.5 34.00 10,000 7.5 6,250 7.5 4,452,700 2,246,742 Stock Options Granted to Employees During the years ended December 31, 2016, 2015, and 2014 the Company granted stock options to employees to purchase shares of common stock with a weighted-average grant date fair value of $6.78, $10.62, and $16.90 per share, respectively. The fair value is being expensed over the vesting period of the options, which is usually 4 years on a straight line basis as the services are being provided. No tax benefits were realized from options and other share-based payment arrangements during the periods. As of December 31, 2016, total unrecognized employee stock-based compensation was $20.0 million, which is expected to be recognized over the weighted-average remaining vesting period of 2.3 years. The fair value of employee stock options was estimated using the Black-Scholes model with the following weighted-average assumptions Year Ended December 31, 2016 2015 2014 Expected volatility 77.9% 79.7% 84.9% Risk-free interest rate 1.5% 1.7% 1.9% Dividend yield 0.0% 0.0% 0.0% Expected life (in years) 6.0 6.0 6.1 Determining Fair Value of Stock Options The fair value of each grant of stock options was determined by the Company using the methods and assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment to determine. Expected Volatility – The expected stock price volatility assumption was determined by examining the historical volatilities of a group of industry peers, as the Company did not have any trading history for the Company’s common stock. The Company will continue to analyze the historical stock price volatility and expected term assumptions as more historical data for the Company’s common stock becomes available. Expected Term – The expected term of stock options represents the weighted average period the stock options are expected to be outstanding. For option grants that are considered to be “plain vanilla”, the Company has opted to use the simplified method for estimating the expected term as provided by the Securities and Exchange Commission. The simplified method calculates the expected term as the average time-to-vesting and the contractual life of the options. For other option grants, the expected term is derived from the Company’s historical data on employee exercises and post-vesting employment termination behavior taking into account the contractual life of the award. Risk-Free Interest Rate – The risk free rate assumption was based on the U.S. Treasury instruments with terms that were consistent with the expected term of the Company’s stock options. Expected Dividend – The expected dividend assumption was based on the Company’s history and expectation of dividend payouts. Forfeiture Rate – Forfeitures were estimated based on historical experience. Fair Value of Common Stock – The fair value of the shares of common stock underlying the stock options has historically been the responsibility of and determined by the Company’s board of directors. Because there had been no public market for the Company’s common stock prior to the initial public offering, the board of directors determined the fair value of common stock at the time of grant of the option by considering a number of objective and subjective factors including independent third-party valuations of the Company’s common stock, sales of convertible preferred stock to unrelated third parties, operating and financial performance, the lack of liquidity of capital stock and general and industry specific economic outlook, amongst other factors. Since the initial public offering in March 2014, the fair value of the underlying common stock is based upon quoted prices on the NASDAQ Global Select Market. Stock-based compensation expense, net of estimate forfeitures, is reflected in the statements of operations and comprehensive loss as follows (in thousands): Year Ended December 31, 2016 2015 2014 Operating Expenses Research and development $ 3,837 $ 3,032 $ 1,230 General and administrative 7,086 7,667 3,411 Total $ 10,923 $ 10,699 $ 4,641 In May 2015, the Company’s co-founder and then CEO, Jeff Cleland, resigned as President and CEO and as a member of the Company’s Board of Directors. As part of the Separation and Consulting Agreement entered into between the Company and Dr. Cleland, the Company incurred $2.4 million of additional separation related costs, of which $2.0 million was calculated as the full fair value of Dr. Cleland’s unexercised vested stock options as well as his unvested stock options expected to vest over the 12 month term of his consulting agreement. The remaining $0.4 million of incremental payroll costs incurred during the three months ended June 30, 2015 related to a one-time cash severance payment associated with the Company’s CEO transition. 2014 Employee Stock Purchase Plan The board of directors adopted, and the Company’s stockholders approved, the 2014 Employee Stock Purchase Plan, or the ESPP, in March 2014. The ESPP became effective on March 20, 2014. The maximum aggregate number of shares of common stock that may be issued under the ESPP is 150,000 shares (subject to adjustment to reflect any split of our common stock). Additionally, the number of shares of common stock reserved for issuance under the ESPP will increase automatically each year, beginning on January 1, 2015 and continuing through and including January 1, 2024, by the lesser of (i) 1% of the total number of shares of our common stock outstanding on December 31 of the preceding calendar year; and (ii) 300,000 shares of common stock (subject to adjustment to reflect any split of our common stock). The board of directors may act prior to the first day of any calendar year to provide that there will be no January 1 increase or that the increase will be for a lesser number of shares than would otherwise occur. Shares subject to purchase rights granted under the ESPP that terminate without having been exercised in full will not reduce the number of shares available for issuance under the ESPP. An employee may not be granted rights to purchase stock under the ESPP if such employee (i) immediately after the grant would own stock possessing 5% or more of the total combined voting power or value of the Company’s common stock, or (ii) holds rights to purchase stock under the ESPP that would accrue at a rate that exceeds $25,000 worth of our stock for each calendar year that the rights remain outstanding. The administrator may approve offerings with a duration of not more than 27 months, and may specify one or more shorter purchase periods within each offering. Each offering will have one or more purchase dates on which shares of common stock will be purchased for the employees who are participating in the offering. The administrator, in its discretion, will determine the terms of offerings under the ESPP. The ESPP permits participants to purchase shares of our common stock through payroll deductions with up to 15% of their earnings. The purchase price of the shares will be not less than 85% of the lower of the fair market value of our common stock on the first day of an offering or on the date of purchase. The Company estimated the fair value of our employees’ stock purchase rights under the ESPP using the Black-Scholes model with the following weighted-average assumptions: Year Ended December 31, 2016 2015 2014 Expected volatility 73.6% 72.1% 54.9% Risk-free interest rate 0.51% 0.26% 0.06% Dividend yield 0.0% 0.0% 0.0% Expected life (in years) 0.5 0.5 0.5 Restricted Stock Units Restricted stock units are shares of common stock which are forfeited if the employee leaves the Company prior to vesting. These stock units offer employees the opportunity to earn shares of the Company’s stock over time, rather than options that give the employee the right to purchase stock at a set price. As a result of these restricted stock units, the Company recognized $2.0 million, $1.4 million and $0.5 million in compensation expense during the years ended December 31, 2016, 2015 and 2014, respectively. As all of the restricted stock vests through 2016 and beyond, the Company will continue to recognize stock based compensation expense related to the grants of these restricted stock units. If all of the remaining restricted stock units that were granted in 2014 vest, the Company will recognize approximately $4.1 million in compensation expense over a weighted average remaining period of 2.5 years. However, no compensation expense will be recognized for restricted stock units that do not vest. A summary of the Company’s restricted stock activity is presented in the following tables: Weighted Average Number of Grant Date Shares Fair Value Restricted Stock Units Unvested at December 31, 2015 254,067 $ 21.11 Granted 332,964 10.63 Vested (79,756 ) 14.64 Forfeited/canceled (5,248 ) 21.71 Unvested at December 31, 2016 502,027 $ 14.43

Comprehensive Income

Comprehensive Income	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Comprehensive Income	11. Comprehensive Income The following table summarizes amounts reclassified out of Accumulated Other Comprehensive Income (AOCI) and their effect on the Company’s Consolidated Statements of Operations for the years ended December 31, 2016 and 2015. Foreign Currency Items Unrealized Gains and Losses on Cash Flow Hedges Total Balance at December 31, 2015 $ — $ — $ — Other comprehensive earnings (loss) before reclassifications — (286 ) (286 ) Amounts reclassified out of other comprehensive loss — (64 ) (64 ) Net current period other comprehensive loss — (350 ) (350 ) Balance at December 31, 2016 $ — $ (350 ) $ (350 )

Related Party

Related Party	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Related Party	12. Related Party Since inception the Company has entered into multiple agreements with Amunix which (i) with its affiliates, had owned approximately 10% of the Company’s preferred stock outstanding at December 31, 2013, and (ii) was represented on the Company’s Board of Directors prior to the Company’s initial public offering in March 2014. Since the initial public offering, Amunix has reduced its ownership percentage, which as of December 31, 2016, is less than 5% of the Company’s outstanding common stock. These agreements between the Company and Amunix include the following: • License Agreement effective December 29, 2008, as amended, (“License Agreement”), pursuant to which the Company has the right to develop three products, with the option to develop up to three additional products in exchange for certain additional financial considerations. Amunix granted the Company a worldwide, exclusive, revocable sub-licensable right and licensed its intellectual property for the Company to research, test and develop these products. The License Agreement obligates the Company to pay to Amunix certain future royalties related to these products. One of these products, and the option to develop one additional product, were sold to Diartis on December 30, 2010. The agreement was further amended at the close of the Company’s Series C preferred stock financing on January 7, 2013, to clarify the technology included in the License Agreement; The Company will pay Amunix additional consideration, in either cash or the Company’s stock, for additional targets selected by the Company. The Company will also pay up to $30.0 million of milestone payments to Amunix, under certain circumstances; • Joint Research Agreement effective November 13, 2009, as amended and combined with the License Agreement, establishing the process by which new targets will be identified and subsequently developed by the parties. In particular, the respective ownership of new inventions by the parties under various scenarios is contemplated. Overall, during the term of this agreement, the Company agreed to assign to Amunix its rights to all joint patents, and all the Company’s patents that are directed to compositions, processes and methods of use or recombinant PEGylation (“rPEG”) technology and/or targets comprising rPEG; • Service Agreement (“Service Agreement”) effective December 29, 2008, as amended, setting forth the terms under which Amunix has agreed to make covered products and marketed products for the Company as contemplated by the Licensing Agreement. Under the Service Agreement, Amunix agreed to undertake and complete the research, development and other services related to the covered products and marketed products as are reasonably requested by the Company from time to time. The specific milestones, deliverables, specifications and other terms with respect to any particular services project are to be detailed in mutually agreeable statements of work, which the parties are to negotiate (reasonably and in good faith) and execute promptly after the Company’s request for services; The aggregate amount of operating expenses (included both within research and development and general and administrative in the consolidated statements of operations) were $0.6 million, $0.8 million, and $0.8 million during the years ended December 31, 2016, 2015, and 2014, respectively. Amounts due to Amunix as of December 31, 2016 and December 31, 2015 were $0.1 million and $0.1 million, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes The provision for federal income taxes in 2016, 2015, and 2014 is as follows: December 31, 2016 2015 2014 Current Federal $ 247 $ — $ — State — — — 247 — — Deferred Federal $ — $ — $ — State — — — Total deferred tax expense — — — Total income tax expense $ 247 $ — $ — December 31, 2016 2015 2014 United States $ (10,421 ) $ (17,671 ) $ (49,850 ) Foreign (85,149 ) (64,506 ) (7,663 ) Net loss before provision for income taxes $ (95,570 ) $ (82,177 ) $ (57,513 ) Income tax expense in 2016, 2015, and 2014 differed from the amount expected by applying the statutory federal tax rate to the income or loss before taxes as summarized below: December 31, 2016 2015 2014 Federal tax benefit at statutory rate 34 % 34 % 34 % State tax benefit net of federal effect — — — Change in valuation allowance (3 )% (8 )% (23 )% Research and development credits 4 % 2 % 2 % Non-deductible warrant — — (7 )% Foreign loss not benefitted (30 )% (27 )% (5 )% Other Non-deductible expenses (5 )% (2 )% (1 )% Total 0 % 0 % 0 % Deferred income taxes reflect the net tax effects of net operating loss and tax credit carryforwards and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s net deferred tax assets at December 31, 2016 and 2015 are as follows (in thousands): December 31, 2016 2015 Net operating loss carry forwards $ 32,500 $ 33,684 Research and development tax credits 8,142 4,982 Stock based compensation and other 7,256 4,465 Depreciation and amortization 78 42 Total deferred tax assets 47,976 43,173 Less: Valuation allowance (47,976 ) (43,173 ) Net deferred tax assets $ — $ — The Company’s accounting for deferred taxes involves the evaluation of a number of factors concerning the realizability of its net deferred tax assets. The Company primarily considered such factors as its history of operating losses, the nature of the Company’s deferred tax assets, and the timing, likelihood and amount, if any, of future taxable income during the periods in which those temporary differences and carryforwards become deductible. At present, the Company does not believe that it is more likely than not that the deferred tax assets will be realized; accordingly, a full valuation allowance has been established and no deferred tax asset is shown in the accompanying balance sheets. The valuation allowance increased by approximately $4.8 million and $6.5 million in 2016 and 2015, respectively. At December 31, 2016, the Company has net operating loss carryforwards for federal income tax purposes of approximately $68.4 million and federal research and development tax credits of approximately $955,000, which begin to expire in 2029. The Company also has net operating loss carryforwards for state income tax purposes of approximately $55.1 million, which begin to expire in 2029, and state research and development tax credits of approximately $1,616,000 which have no expiration date. Additionally, the Company has an Orphan Drug Credit of approximately $20.9 million for federal income tax purposes, which begins to expire in 2033. The Company has foreign net operating loss carryforwards of $17.4 million, which begin to expire in 2023. The Company tracks a portion of its deferred tax assets attributable to stock option benefits in a separate memorandum account. Therefore, these amounts are not included in the Company’s gross or net deferred tax assets. The benefit of these stock options will not be recorded in equity unless it reduces taxes payable. As of December 31, 2016, the portion of the federal and state net operating losses related to stock option benefits was approximately $2.1 million. Utilization of net operating losses and tax credit carryforwards may be limited by the “ownership change” rules, as defined in Section 382 of the Internal Revenue Code (any such limitation, a “Section 382 limitation”). Similar rules may apply under state tax laws. The Company has performed an analysis to determine whether an “ownership change” occurred from inception to the Company’s initial public offering in March 2014. Based on this analysis, management determined that the Company did experience historical ownership changes of greater than 50% during this period. Therefore, the utilization of a portion of the Company’s net operating losses and credit carryforwards is currently limited. However, these Section 382 limitations are not expected to result in a permanent loss of the net operating losses and credit carryforwards. As such, a reduction to the Company’s gross deferred tax asset for its net operating loss and tax credit carryforwards is not necessary prior to considering the valuation allowance. The Company reviewed its stock ownership since the initial public offering through the year ended December 31, 2016 and concluded no ownership changes occurred which would result in a reduction of its net operating loss or in its research and development credits expiring unused. Although the Company concluded that it did not experience any further ownership change as of December 31, 2016, the Company may experience an ownership change, as defined under section 382, as a result of future offerings or other changes in the ownership of our stock. In the event the Company experiences any subsequent changes in ownership, the amount of net operating losses and research and development credit carryforwards useable in any taxable year could be limited and may expire unutilized. The Company follows the provisions of FASB Accounting Standards Codification 740-10 (ASC 740-10), Accounting for Uncertainty in Income Taxes. ASC 740-10 prescribes a comprehensive model for the recognition, measurement, presentation and disclosure in consolidated financial statements of uncertain tax positions that have been taken or expected to be taken on a tax return. No liability related to uncertain tax positions is recorded in the consolidated financial statements. At December 31, 2016, 2015, and 2014, the Company’s reserve for unrecognized tax benefits is approximately $10,116,000, $4,061,000, and $332,000, respectively. Due to the full valuation allowance at December 31, 2016, current adjustments to the unrecognized tax benefit will have no impact on the Company’s effective income tax rate; any adjustments made after the valuation allowance is released will have an impact on the tax rate. The Company does not anticipate any significant change in its uncertain tax positions within 12 months of this reporting date. The Company includes penalties and interest expense related to income taxes as a component of other expense and interest expense, respectively, as necessary. Because the statute of limitations does not expire until after the net operating loss and credit carryforwards are actually used, the statute is open for all tax years from inception, that is, for the period from December 10, 2008 (date of inception) to December 31, 2016 and forward for federal and state tax purposes. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Amount Balance at January 1, 2014 $ 287 Decreases based on tax positions taken during a prior period (102 ) Increases based on tax positions taken during a current period 147 Balance at December 31, 2014 $ 332 Increases based on tax positions taken during a prior period 3,562 Increases based on tax positions taken during a current period 167 Balance at December 31, 2015 $ 4,061 Gross increase related to prior year tax positions 4,628 Gross decrease related to prior year tax positions (3,559 ) Gross increase related to current year positions 4,986 Reductions to unrecognized tax benefits related to lapsing statute of limitations - Balance at December 31, 2016 $ 10,116 All tax years remain open for examination by federal and state tax authorities.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plan	14. Defined Contribution Plan The Company sponsors a 401(k) Plan, which stipulates that eligible employees can elect to contribute to the 401(k) Plan, subject to certain limitations of eligible compensation. The Company may match employee contributions in amounts to be determined at the Company’s sole discretion. To date, the Company has not made any matching contributions.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Net Loss per Share	15. Net loss per share The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands, except per share data): December 31, 2016 2015 2014 Net loss attributable to common stockholders - basic and diluted $ (95,817 ) $ (82,177 ) $ (83,072 ) Weighted-average shares used to compute basic and diluted net loss per share 30,784 28,964 18,922 Basic and diluted net loss per common share $ (3.11 ) $ (2.84 ) $ (4.39 ) Basic net loss attributable to common stockholders per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period. Diluted net loss attributable to common stockholders per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and dilutive common stock equivalents outstanding for the period, determined using the treasury-stock method and the as-if converted method, for convertible securities, if inclusion of these is dilutive. Because the Company has reported a net loss for the years ended December 31, 2016, 2015, and 2014, diluted net loss per common share is the same as basic net loss per common share for those years. The following potentially dilutive securities outstanding at the end of the years presented have been excluded from the computation of diluted shares outstanding: December 31, 2016 2015 2014 Options to purchase common stock 4,452,700 3,240,969 2,723,366 Restricted stock units 502,027 254,067 185,514

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Event	16. Subsequent Event In January 2017, the Company issued approximately 1,207,240 options to purchase common stock and restricted stock units in the aggregate in connection with its employee benefit plans.

Quarterly Results (Unaudited)

Quarterly Results (Unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results (Unaudited)	17. Quarterly Results (Unaudited) The following table is in thousands, except per share amounts: Quarters Ended March 31, June 30, September 30, December 31, 2016 2016 2016 2016 Consolidated Statement of operations data: Operating expenses Research and development $ 18,192 $ 16,397 $ 20,664 $ 16,731 General and administrative 5,915 5,909 6,752 5,760 Total operating expenses 24,107 22,306 27,416 22,491 Loss from operations (24,107 ) (22,306 ) (27,416 ) (22,491 ) Interest income 105 129 120 160 Other income (expense), net (230 ) 59 (39 ) 446 Net loss before provision for income taxes (24,232 ) (22,118 ) (27,335 ) (21,885 ) Provision for income taxes — — — 247 Net loss $ (24,232 ) $ (22,118 ) $ (27,335 ) $ (22,132 ) Net loss per share- basic and diluted $ (0.82 ) $ (0.75 ) $ (0.92 ) $ (0.64 ) Weighted-average common shares used to compute basic and diluted net loss per share 29,422 29,489 29,574 34,609 Quarters Ended March 31, June 30, September 30, December 31, 2015 2015 2015 2015 Consolidated Statement of operations data: Operating expenses Research and development $ 17,100 $ 11,940 $ 15,400 $ 15,586 General and administrative 5,181 7,556 5,124 4,622 Total operating expenses 22,281 19,496 20,524 20,208 Loss from operations (22,281 ) (19,496 ) (20,524 ) (20,208 ) Interest income 49 65 54 51 Other income (expense), net 226 (236 ) 91 32 Net loss and comprehensive loss (22,006 ) (19,667 ) (20,379 ) (20,125 ) Net loss attributable to common stockholders $ (22,006 ) $ (19,667 ) $ (20,379 ) $ (20,125 ) Net loss per basic and diluted share attributable to common stockholders $ (0.79 ) $ (0.67 ) $ (0.69 ) $ (0.69 ) Weighted-average common shares used to compute basic and diluted net loss per share 27,810 29,293 29,354 29,379

Schedule II Valuation and Quali

Schedule II Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2016
Valuation And Qualifying Accounts [Abstract]
Schedule II Valuation and Qualifying Accounts	VERSARTIS, INC. Schedule II: Valuation and Qualifying Accounts (in thousands) Balance at beginning of Additions/charged Balance at period to expense Deductions end of period Year ended December 31, 2016 Valuation allowances for deferred tax assets $ 43,173 $ 4,803 $ — $ 47,976 Year ended December 31, 2015 Valuation allowances for deferred tax assets $ 36,645 $ 6,528 $ — $ 43,173 Year ended December 31, 2014 Valuation allowances for deferred tax assets $ 23,964 $ 12,681 $ — $ 36,645

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The preparation of the accompanying consolidated financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates. The accompanying consolidated financial statements are consolidated for the year ended December 31, 2016 and December 31, 2015 and include the accounts of Versartis, Inc. and its wholly-owned subsidiaries, Versartis Cayman Holdings Company, incorporated in 2014, and Versartis GmbH, incorporated in 2015. All intercompany accounts and transactions have been eliminated. The U.S. dollar is the functional currency for all of the Company's subsidiaries and consolidated operations. Since inception, the Company has incurred net losses and negative cash flows from operations. At December 31, 2016, the Company had an accumulated deficit of $289.3 million and working capital of $150.8 million. The Company expects to continue to incur losses from costs related to the continuation of research and development and administrative activities for the foreseeable future. Although management has been successful in raising capital in the past, most recently $59.1 million in October and November 2016, there can be no assurance that the Company will be successful or that any needed financing will be available in the future at terms acceptable to the Company.
Segments	Segments The Company operates in one segment. Management uses one measurement of profitability and does not segregate its business for internal reporting. All long-lived assets are maintained in the United States of America.
Concentration of Credit Risk	Concentration of c r Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents. All of the Company’s cash and cash equivalents are held at several financial institutions that management believes are of high credit quality. Such deposits may, at times, exceed federally insured limits. The Company enters into forward foreign currency contracts that expose it to credit risk to the extent that the counterparties may be unable to meet the terms of the agreement. The Company does, however, seek to mitigate such risks by limiting its counterparties to major financial institutions. In addition, the potential risk of loss with any one counterparty resulting from this type of credit risk is monitored. Management does not expect material losses as a result of defaults by counterparties.
Derivative Financial Instruments	Derivative Financial Instruments The Company engages in transactions denominated in foreign currencies and, as a result, is exposed to changes in foreign currency exchange rates. To manage the volatility resulting from fluctuating foreign currency exchange rates, the Company enters into option and forward foreign currency exchange contracts. The Company accounts for its derivative instruments as either assets or liabilities on the balance sheet and measures them at fair value. The Company assesses, both at inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting the changes in cash flows of the hedged items. If the Company determines that a forecasted transaction is no longer probable of occurring, it discontinues hedge accounting for the affected portion of the hedge instrument, and any related unrealized gain or loss on the contract is recognized in other comprehensive income (expense).
Risk and Uncertainties	Risk and Uncertainties The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s potential drug candidates, uncertainty of market acceptance of the Company’s products, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals and sole source suppliers. Products developed by the Company require clearances from the U.S. Food and Drug Administration (“FDA”), the Pharmaceuticals Medicines and Devices Agency (“PMDA”), or other international regulatory agencies prior to commercial sales. There can be no assurance that the products will receive the necessary clearances. If the Company was denied clearance, clearance was delayed or the Company was unable to maintain clearance, it could have a materially adverse impact on the Company. The Company expects to incur substantial operating losses for the next several years and will need to obtain additional financing in order to launch and commercialize any product candidates for which it receives regulatory approval. Even though the Company expects additional proceeds if certain clinical and regulatory milestones are met under the Teijin Agreement, there can be no assurance that such additional financing will be available at all, or will be at terms acceptable by the Company.
Cash and Cash Equivalents	Cash and c e The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. At December 31, 2016 and December 31, 2015 the Company’s cash and cash equivalents were held in multiple institutions with the United States and Europe and included deposits in money market funds which were unrestricted as to withdrawal or use.
Property and Equipment, Net	Property and e Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets, generally between three and five years. Leasehold improvements are amortized on a straight-line basis over the lesser of their useful life or the term of the lease. Maintenance and repairs are charged to expense as incurred, and improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the consolidated balance sheet and any resulting gain or loss is reflected in operations in the period realized.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by the comparison of the carrying amount to the future net cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value (i.e. determined through estimating projected discounted future net cash flows or other acceptable methods of determining fair value) arising from the asset. There have been no such impairments of long-lived assets during the years ended December 31, 2016, 2015, and 2014.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying value of the Company’s cash and cash equivalents, prepaid expenses, accounts payable and accrued liabilities approximate fair value due to the short-term nature of these items. Convertible preferred stock call option liability and convertible preferred stock warrant liability, which were outstanding through the completion of the Company’s initial public offering during the three months ended March 31, 2014, were carried at fair value. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows: Level I Unadjusted quoted prices in active markets for identical assets or liabilities; Level II Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level III Unobservable inputs that are supported by little or no market activity for the related assets or liabilities. The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s financial instruments consist of Level I assets as of December 31, 2016 and consist of Level I assets as of December 31, 2015. Level I securities are comprised of highly liquid money market funds. The Company’s foreign currency derivative contracts have maturities over a 12-month time horizon and is with a counterparty that has a minimum credit rating of A- or equivalent by Standard & Poor's, Moody's Investors Service, Inc. or Fitch, Inc. These contracts are reported as Level II assets, however there were none outstanding as of December 31, 2016 and December 31, 2015.
Preclinical and Clinical Trial Accruals	Preclinical and Clinical Trial Accruals The Company’s clinical trial accruals are based on estimates of patient enrollment and related costs at clinical investigator sites as well as estimates for the services received and efforts expended pursuant to contracts with multiple research institutions and clinical research organizations (“CROs”) that conduct and manage clinical trials on the Company’s behalf. The Company estimates preclinical and clinical trial expenses based on the services performed, pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on its behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of patient enrollment and activity expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Payments made to third parties under these arrangements in advance of the receipt of the related services are recorded as prepaid expenses until the services are rendered.
Convertible Preferred Stock Warrants	Convertible Preferred Stock Warrants The Company accounted for its convertible preferred stock warrants as liabilities based upon the characteristics and provisions of each instrument. Convertible preferred stock warrants classified as derivative liabilities were recorded on the Company’s consolidated balance sheet at their fair value on the date of issuance and revalued on each subsequent consolidated balance sheet, with fair value changes recognized as increases or reductions to other income (expense), net in the consolidated statements of operations. Prior to the IPO in March 2014, the Company had outstanding warrants which were classified as a liability and remeasured to fair value each reporting period. The Company had estimated the fair value of these liabilities using an option pricing model and assumptions that were based on the individual characteristics of the warrants on the valuation date, as well as assumptions for expected volatility, expected life, dividends, and risk-free interest rate. Immediately prior to the completion of the Company’s IPO in March 2014, all of the warrants were either exercised for cash or automatically net exercised for a total issuance of 158,179 shares of common stock, pursuant to the terms of the warrants. Just prior to the exercises, all outstanding warrants, covering 173,910 shares, were remeasured using the intrinsic value of the warrant computed as the difference between the $21.00 per share IPO price and the $5.17 per share exercise price of the warrant. The remeasurement of the fair value of these warrants from December 31, 2013 through the date of the conversion to a common stock warrant and following exercise resulted in a $2.3 million expense recorded to other income (expense), net in the consolidated statement of operations and comprehensive loss. The resulting fair value of approximately $2.8 million was reclassified to additional paid in capital upon completion of the IPO.
Convertible Preferred Stock Call Option	Convertible Preferred Stock Call Option The Company determined that the Company’s obligation to issue, and the investors’ obligation to purchase, additional shares of the Company’s convertible preferred stock represented a freestanding financial instrument. The freestanding convertible preferred stock call option liability was initially recorded at fair value, with fair value changes recognized as increases or reductions to other income (expense), net in the consolidated statement of operations and comprehensive loss. At the time of the deemed exercise of the call option, the remaining value of the option was reclassified to additional paid in capital. Immediately prior to the Series D-2 financing completed in February 2014, the Company remeasured the fair value of the preferred stock call option liability associated with the Series D convertible preferred stock financing and recorded other expense of approximately $9.6 million in the consolidated statement of operations and comprehensive loss for the year ended December 31, 2014. Fair value was computed using a discount from the Company’s public offering price less the liquidation value of the underlying Series D convertible preferred stock.
Convertible Preferred Stock	Convertible Preferred Stock The Company classified the convertible preferred stock as temporary equity on the balance sheets due to certain change in control events that are outside the Company’s control, including liquidation, sale or transfer of the Company, as holders of the convertible preferred stock can cause redemption of the shares. Upon the IPO in March 2014, all of the outstanding shares of convertible preferred stock automatically converted into 15,876,104 shares of common stock.
Research and Development	Research and d Research and development costs are charged to operations as incurred. Research and development costs include, but are not limited to, payroll and personnel expenses, laboratory supplies, consulting costs, external research and development expenses and allocated overhead, including rent, equipment depreciation, and utilities. Costs to acquire technologies to be used in research and development that have not reached technological feasibility and have no alternative future use are expensed to research and development costs when incurred.
Income Taxes	Income t The Company accounts for income taxes under the asset and liability approach. Under this method, deferred tax assets and liabilities are determined based on the difference between the consolidated financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The provision for income taxes includes income taxes paid or payable for the current year plus the change in deferred taxes during the year. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position’s sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available.
Stock-Based Compensation	Stock-Based c For stock options granted to employees, the Company recognizes compensation expense for all stock-based awards based on the grant-date estimated fair value. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service period. The fair value of stock options is determined using the Black-Scholes option pricing model. The determination of fair value for stock-based awards on the date of grant using an option pricing model requires management to make certain assumptions regarding a number of complex and subjective variables. Stock-based compensation expense related to stock options granted to nonemployees is recognized based on the fair value of the stock options, determined using the Black-Scholes option pricing model, as they are earned. The awards generally vest over the time period the Company expects to receive services from the nonemployee.
Consolidated Statement of Operations and Comprehensive Loss	Consolidated Statement of Operations and Comprehensive Loss Comprehensive loss is defined as a change in equity of a business enterprise during a period, resulting from transactions from non-owner sources. Specifically, the Company includes cumulative foreign currency translation adjustments and net unrealized gains and losses on effective cash flow hedges.
Net Loss per Share of Common Stock	Net Loss per Share of Common Stock Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, convertible preferred stock, convertible notes payable, stock options and convertible preferred stock warrants are considered to be potentially dilutive securities. Because the Company has reported a net loss for the years ended December 31, 2016, 2015 and 2014, diluted net loss per common share is the same as basic net loss per common share for those periods.
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or FASB, or other standard setting bodies and adopted by us as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective is not expected to have a material impact on the Company’s financial position or results of operations upon adoption. In August 2016, the FASB issued guidance to simplify elements of cash flow classification. The guidance is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. The new guidance requires cash payments for debt prepayment or debt extinguishment costs to be classified as cash outflows for financing activities. It also requires cash payments made soon after an acquisition's consummation date (approximately three months or less) to be classified as cash outflows for investing activities. Payments made thereafter should be classified as cash outflows for financing activities up to the amount of the original contingent consideration liability. Payments made in excess of the amount of the original contingent consideration liability should be classified as cash outflows for operating activities. The guidance is required to be applied by the Company in the first quarter of 2018, but early adoption is permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements. In March 2016, the FASB issued Accounting Standards Update (“ASU”) No. 2016-09, Compensation – Stock Compensation (Topic 718) (“ASU 2016-09”), which simplified certain aspects of the accounting for share-based payment transactions, including income taxes, classification of awards and classification in the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. The Company will adopt ASU 2016-09 in the first quarter of 2017. The Company is currently evaluating the impact of the adoption of this guidance on its consolidated financial condition, results of operations and cash flows. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). In November 2015, the FASB issued ASU 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes, The Company is currently evaluating the impact of adoption and will apply the guidance and disclosure provisions of the new standard upon adoption. In August 2014, the FASB issued ASU 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern, which In May 2014, the FASB issued a new accounting standard that amends the guidance for the recognition of revenue from contracts with customers to transfer goods and services. The FASB has subsequently issued additional, clarifying standards to address issues arising from implementation of the new revenue recognition standard. The new revenue recognition standard and clarifying standards are effective for interim and annual periods beginning on January 1, 2018, and may be adopted earlier, but not before January 1, 2017. The revenue standards are required to be adopted by taking either a full retrospective approach or a modified retrospective approach. The Company is currently evaluating the impact that the revenue standards will have on our consolidated financial statements and determining the transition method that we will apply.

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets (in thousands) December 31, 2016 2015 Preclinical and clinical $ 3,474 $ 1,770 Other 678 772 Total $ 4,152 $ 2,542
Property and Equipment, Net	Property and equipment, net (in thousands) December 31, 2016 2015 Equipment and furniture $ 664 $ 575 Buildings, leasehold and building improvements 134 132 798 707 Less: Accumulated depreciation and amortization (533 ) (318 ) Property and equipment, net $ 265 $ 389
Accrued Liabilities	Accrued liabilities (in thousands) December 31, 2016 2015 Payroll and related $ 3,818 $ 2,296 Preclinical and clinical 8,803 4,376 Professional services 114 69 Other 164 415 Total $ 12,899 $ 7,156

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Financial Instruments Measured at Fair Value on Recurring Basis	The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): Fair Value Measurements at December 31, 2016 Total Level 1 Level 2 Level 3 Assets Money market funds $ 85,911 $ 85,911 $ — $ — Fair Value Measurements at December 31, 2015 Total Level 1 Level 2 Level 3 Assets Money market funds $ 132,647 $ 132,647 $ — $ —
Summary of Changes in Fair Value of Financial Instruments	The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial instruments as follows: Convertible Convertible preferred stock preferred stock call option warrant liability liability Balance at January 1, 2014 $ 21 $ 474 Change in fair value recorded in other income (expense), net 9,560 2,278 Conversion of preferred stock into common stock and reclassification to permanent equity (9,581) (2,752) Balance at December 31, 2014 $ — $ —

Derivative Financial Instrume30

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Summary of Effect of Foreign Currency Exchange Contracts on Consolidated Financial Statements	The following table summarizes the effect of our foreign currency exchange contracts on the Company’s consolidated financial statements (in thousands): As of December 31, 2016 2015 Derivatives designated as hedges: Gains (losses) recognized in accumulated OCI (effective portion) $ (286 ) $ — Gains (losses) reclassified from accumulated OCI into operating expenses (effective portion) $ 64 $ — Gains (losses) recognized in other income (expense), net (ineffective portion and amounts excluded from effectiveness testing) $ — $ — Derivatives not designated as hedges: Gains (losses) recognized in other income (expense), net $ (80 ) $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Summary of Future Minimum Lease Payments Required Under Non-Cancellable Operating Leases	As of December 31, 2016, the aggregate future minimum lease payments under the noncancellable operating lease arrangements are as follows (in thousands): Year Ended December 31, 2016 2017 $ 1,085 2018 — 2019 — 2020 — 2021 — Thereafter — $ 1,085

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Summary of Reserved Shares of Common Stock for Future Issuances	The Company had reserved shares of common stock for future issuances as follows: December 31, 2016 2015 Issuance of equity based awards under stock plan 1,044,113 1,350,543 Issuance upon exercise of options under stock plan 4,452,700 3,240,969 Issuance of restricted stock units under stock plan 502,027 254,067 Total 5,998,840 4,845,579

Stock Based Awards (Tables)

Stock Based Awards (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	Activity under the Company’s stock option plans is set forth below: Weighted Average Weighted Remaining Aggregate Shares Average Contractual Intrinsic Available Number of Exercise Life Value for Grant Shares Price (in years) (in thousands) Balance at January 1, 2014 9,533 1,403,656 $ 1.90 Additional shares authorized 2,531,915 — — Options granted (1,471,142 ) 1,471,142 18.68 Restricted stock units granted (185,514 ) Options exercised — (44,822 ) 1.32 Options cancelled 106,609 (106,609 ) 18.43 Balances, December 31, 2014 991,401 2,723,367 $ 10.33 Additional shares authorized 1,091,045 — — Options granted (664,100 ) 664,100 15.34 Restricted stock units granted (123,450 ) — — Options exercised — (90,851 ) 1.34 Options cancelled 55,647 (55,647 ) 15.68 Balances, December 31, 2015 1,350,543 3,240,969 $ 11.51 Additional shares authorized 1,323,911 — — Options granted (1,399,522 ) 1,399,522 10.04 Restricted stock units granted (332,964 ) — — Options exercised — (85,646 ) 1.64 Options cancelled 102,145 (102,145 ) 14.90 Balances, December 31, 2016 1,044,113 4,452,700 $ 11.16 7.8 $ 25,162 Vested and expected to vest as of December 31, 2016 — 4,323,511 $ 11.14 7.8 $ 24,632 Exercisable as of December 31, 2016 — 2,246,742 $ 10.11 7.2 $ 15,498
Stock Options Outstanding and Exercisable under Stock Option Plans	The following table summarizes information with respect to stock options outstanding and currently exercisable and vested as of December 31, 2016: Options Exercisable Options Outstanding and Vested Weighted Average Weighted Average Remaining Remaining Range of Number Contractual Number Contractual Exercise Prices Outstanding Life (in Years) Outstanding Life (in Years) $1.27-$2.53 1,158,038 6.3 966,139 6.3 3.33-10.68 1,736,950 8.6 494,703 8.6 10.87-20.30 896,382 8.5 409,602 8.5 21.00-31.96 651,330 7.5 370,048 7.5 34.00 10,000 7.5 6,250 7.5 4,452,700 2,246,742
Summary of Fair Value of Employee Stock Options	The fair value of employee stock options was estimated using the Black-Scholes model with the following weighted-average assumptions Year Ended December 31, 2016 2015 2014 Expected volatility 77.9% 79.7% 84.9% Risk-free interest rate 1.5% 1.7% 1.9% Dividend yield 0.0% 0.0% 0.0% Expected life (in years) 6.0 6.0 6.1
Schedule of Estimated Stock-Based Compensation Expense	Stock-based compensation expense, net of estimate forfeitures, is reflected in the statements of operations and comprehensive loss as follows (in thousands): Year Ended December 31, 2016 2015 2014 Operating Expenses Research and development $ 3,837 $ 3,032 $ 1,230 General and administrative 7,086 7,667 3,411 Total $ 10,923 $ 10,699 $ 4,641
Summary of Fair Value of Employees Stock Purchase Rights Under ESPP Using Black-Scholes Model with Following Weighted-Average Assumptions	The Company estimated the fair value of our employees’ stock purchase rights under the ESPP using the Black-Scholes model with the following weighted-average assumptions: Year Ended December 31, 2016 2015 2014 Expected volatility 73.6% 72.1% 54.9% Risk-free interest rate 0.51% 0.26% 0.06% Dividend yield 0.0% 0.0% 0.0% Expected life (in years) 0.5 0.5 0.5
Summary of Restricted Stock Activity	A summary of the Company’s restricted stock activity is presented in the following tables: Weighted Average Number of Grant Date Shares Fair Value Restricted Stock Units Unvested at December 31, 2015 254,067 $ 21.11 Granted 332,964 10.63 Vested (79,756 ) 14.64 Forfeited/canceled (5,248 ) 21.71 Unvested at December 31, 2016 502,027 $ 14.43

Comprehensive Income (Tables)

Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Summary of Amounts Reclassified out of Accumulated Other Comprehensive Income	The following table summarizes amounts reclassified out of Accumulated Other Comprehensive Income (AOCI) and their effect on the Company’s Consolidated Statements of Operations for the years ended December 31, 2016 and 2015. Foreign Currency Items Unrealized Gains and Losses on Cash Flow Hedges Total Balance at December 31, 2015 $ — $ — $ — Other comprehensive earnings (loss) before reclassifications — (286 ) (286 ) Amounts reclassified out of other comprehensive loss — (64 ) (64 ) Net current period other comprehensive loss — (350 ) (350 ) Balance at December 31, 2016 $ — $ (350 ) $ (350 )

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of Provision for Federal Income Taxes	The provision for federal income taxes in 2016, 2015, and 2014 is as follows: December 31, 2016 2015 2014 Current Federal $ 247 $ — $ — State — — — 247 — — Deferred Federal $ — $ — $ — State — — — Total deferred tax expense — — — Total income tax expense $ 247 $ — $ —
Schedule of Income (Loss) Before Income Taxes Attributed to Geographic Locations	December 31, 2016 2015 2014 United States $ (10,421 ) $ (17,671 ) $ (49,850 ) Foreign (85,149 ) (64,506 ) (7,663 ) Net loss before provision for income taxes $ (95,570 ) $ (82,177 ) $ (57,513 )
Summary of Statutory Federal Tax Rate to Income or Loss before Taxes	Income tax expense in 2016, 2015, and 2014 differed from the amount expected by applying the statutory federal tax rate to the income or loss before taxes as summarized below: December 31, 2016 2015 2014 Federal tax benefit at statutory rate 34 % 34 % 34 % State tax benefit net of federal effect — — — Change in valuation allowance (3 )% (8 )% (23 )% Research and development credits 4 % 2 % 2 % Non-deductible warrant — — (7 )% Foreign loss not benefitted (30 )% (27 )% (5 )% Other Non-deductible expenses (5 )% (2 )% (1 )% Total 0 % 0 % 0 %
Significant Components of Net Deferred Tax Assets	Significant components of the Company’s net deferred tax assets at December 31, 2016 and 2015 are as follows (in thousands): December 31, 2016 2015 Net operating loss carry forwards $ 32,500 $ 33,684 Research and development tax credits 8,142 4,982 Stock based compensation and other 7,256 4,465 Depreciation and amortization 78 42 Total deferred tax assets 47,976 43,173 Less: Valuation allowance (47,976 ) (43,173 ) Net deferred tax assets $ — $ —
Reconciliation of Amount of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Amount Balance at January 1, 2014 $ 287 Decreases based on tax positions taken during a prior period (102 ) Increases based on tax positions taken during a current period 147 Balance at December 31, 2014 $ 332 Increases based on tax positions taken during a prior period 3,562 Increases based on tax positions taken during a current period 167 Balance at December 31, 2015 $ 4,061 Gross increase related to prior year tax positions 4,628 Gross decrease related to prior year tax positions (3,559 ) Gross increase related to current year positions 4,986 Reductions to unrecognized tax benefits related to lapsing statute of limitations - Balance at December 31, 2016 $ 10,116

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Summary of Computation of Basic and Diluted Net Loss Per Share	The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands, except per share data): December 31, 2016 2015 2014 Net loss attributable to common stockholders - basic and diluted $ (95,817 ) $ (82,177 ) $ (83,072 ) Weighted-average shares used to compute basic and diluted net loss per share 30,784 28,964 18,922 Basic and diluted net loss per common share $ (3.11 ) $ (2.84 ) $ (4.39 )
Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Shares Outstanding	The following potentially dilutive securities outstanding at the end of the years presented have been excluded from the computation of diluted shares outstanding: December 31, 2016 2015 2014 Options to purchase common stock 4,452,700 3,240,969 2,723,366 Restricted stock units 502,027 254,067 185,514

Quarterly Results (Unaudited) (

Quarterly Results (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following table is in thousands, except per share amounts: Quarters Ended March 31, June 30, September 30, December 31, 2016 2016 2016 2016 Consolidated Statement of operations data: Operating expenses Research and development $ 18,192 $ 16,397 $ 20,664 $ 16,731 General and administrative 5,915 5,909 6,752 5,760 Total operating expenses 24,107 22,306 27,416 22,491 Loss from operations (24,107 ) (22,306 ) (27,416 ) (22,491 ) Interest income 105 129 120 160 Other income (expense), net (230 ) 59 (39 ) 446 Net loss before provision for income taxes (24,232 ) (22,118 ) (27,335 ) (21,885 ) Provision for income taxes — — — 247 Net loss $ (24,232 ) $ (22,118 ) $ (27,335 ) $ (22,132 ) Net loss per share- basic and diluted $ (0.82 ) $ (0.75 ) $ (0.92 ) $ (0.64 ) Weighted-average common shares used to compute basic and diluted net loss per share 29,422 29,489 29,574 34,609 Quarters Ended March 31, June 30, September 30, December 31, 2015 2015 2015 2015 Consolidated Statement of operations data: Operating expenses Research and development $ 17,100 $ 11,940 $ 15,400 $ 15,586 General and administrative 5,181 7,556 5,124 4,622 Total operating expenses 22,281 19,496 20,524 20,208 Loss from operations (22,281 ) (19,496 ) (20,524 ) (20,208 ) Interest income 49 65 54 51 Other income (expense), net 226 (236 ) 91 32 Net loss and comprehensive loss (22,006 ) (19,667 ) (20,379 ) (20,125 ) Net loss attributable to common stockholders $ (22,006 ) $ (19,667 ) $ (20,379 ) $ (20,125 ) Net loss per basic and diluted share attributable to common stockholders $ (0.79 ) $ (0.67 ) $ (0.69 ) $ (0.69 ) Weighted-average common shares used to compute basic and diluted net loss per share 27,810 29,293 29,354 29,379

Formation and Business of the38

Formation and Business of the Company - Additional Information (Detail) - USD ($) $ in Thousands	Nov. 04, 2016	Jan. 31, 2015	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Public Offering [Line Items]
Business incorporated date				Dec. 10, 2008
Proceeds from issuance of common stock in initial public offering, net of issuance costs			$ 132,100			$ 132,137
Common stock, shares authorized			50,000,000	50,000,000	50,000,000
Convertible preferred stock, shares authorized			5,000,000
Proceeds from issuance of common stock in follow-on offering, net of issuance costs	$ 59,100			$ 59,136	$ 80,209
IPO [Member]
Public Offering [Line Items]
Public offering shares of common stock issued			6,900,000
Secondary Offering [Member]
Public Offering [Line Items]
Public offering shares of common stock issued	5,176,545	4,999,999
Proceeds from issuance of common stock in follow-on offering, net of issuance costs	$ 59,100	$ 80,209

Summary of Significant Accoun39

Summary of Significant Accounting Policies - Additional Information (Detail)	Nov. 04, 2016USD ($)	Mar. 31, 2014USD ($)$ / sharesshares	Mar. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2016USD ($)SegmentDerivativeContract	Dec. 31, 2015USD ($)DerivativeContract	Dec. 31, 2014USD ($)
Significant Accounting Policies [Line Items]
Accumulated deficit				$ (289,253,000)	$ (193,436,000)
Working capital				150,800,000
Proceeds from issuance of common stock in follow-on offering, net of issuance costs	$ 59,100,000			$ 59,136,000	80,209,000
Number of operating segment | Segment				1
Cash and cash equivalents maturity period				Three months or less
Impairments of long-lived assets				$ 0	$ 0	$ 0
Number of securities issued upon exercise of warrants | shares		158,179	158,179
Remeasurement of outstanding warrants | shares		173,910
Warrants to purchase convertible preferred stock, exercise price | $ / shares		$ 5.17	$ 5.17
Reclassification of warrant liability			$ 2,300,000
Convertible preferred stock shares automatically converted into common stock | shares		15,876,104	15,876,104
Series D convertible preferred stock [Member]
Significant Accounting Policies [Line Items]
Remeasurement of preferred stock						9,600,000
IPO [Member]
Significant Accounting Policies [Line Items]
Warrants to purchase convertible preferred stock, exercise price | $ / shares		$ 21	$ 21
Reclassification of warrant liability						2,752,000
IPO [Member] | Additional Paid-in Capital [Member]
Significant Accounting Policies [Line Items]
Reclassification of warrant liability		$ 2,800,000				$ 2,752,000
Level II Assets [Member]
Significant Accounting Policies [Line Items]
Number of foreign currency derivative contracts outstanding | DerivativeContract				0	0
Minimum [Member]
Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives				3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives				5 years
Percentage for the amount of benefit realized upon ultimate settlement				50.00%

Balance Sheet Components - Prep

Balance Sheet Components - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Prepaid Expense And Other Assets [Abstract]
Preclinical and clinical	$ 3,474	$ 1,770
Other	678	772
Total	$ 4,152	$ 2,542

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, net (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 798	$ 707
Less: Accumulated depreciation and amortization	(533)	(318)
Property and equipment, net	265	389
Equipment and Furniture [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	664	575
Buildings, Leasehold and Building Improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 134	$ 132

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Payroll and related	$ 3,818	$ 2,296
Preclinical and clinical	8,803	4,376
Professional services	114	69
Other	164	415
Total	$ 12,899	$ 7,156

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments Measured at Fair Value on Recurring Basis (Detail) - Recurring [Member] - Money market funds [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, fair value	$ 85,911	$ 132,647
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, fair value	$ 85,911	$ 132,647

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Transfers within the hierarchy	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Fair Value of Financial Instruments (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2014USD ($)
Conversion of preferred stock call option liability [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 21
Change in fair value recorded in other income (expense), net	9,560
Conversion of preferred stock into common stock and reclassification to permanent equity	(9,581)
Conversion of preferred stock warrant liability [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	474
Change in fair value recorded in other income (expense), net	2,278
Conversion of preferred stock into common stock and reclassification to permanent equity	$ (2,752)

Derivative Financial Instrume46

Derivative Financial Instruments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2016EUR (€)	Dec. 30, 2016EUR (€)	Dec. 31, 2015EUR (€)
Foreign Currency Exchange Contracts [Member]
Derivatives Fair Value [Line Items]
Notional amounts on foreign currency exchange contracts | €		€ 0	€ 9,100,000	€ 0
Research and development [Member]
Derivatives Fair Value [Line Items]
Gain (loss) reclassification from accumulated other comprehensive income	12 months
Other Income (Expense) [Member]
Derivatives Fair Value [Line Items]
Gain (loss) on discontinuance of cash flow hedges | $	$ 0
Maximum [Member]
Derivatives Fair Value [Line Items]
Derivative instruments maturity term	12 months

Derivative Financial Instrume47

Derivative Financial Instruments - Summary of Effect of Foreign Currency Exchange Contracts on Consolidated Financial Statements (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Derivatives designated as hedges:
Gains (losses) recognized in accumulated OCI (effective portion)	$ (286)
Gains (losses) reclassified from accumulated OCI into operating expenses (effective portion)	64
Derivatives not designated as hedges:
Gains (losses) recognized in other income (expense), net	$ (80)

Teijin Agreement - Additional I

Teijin Agreement - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2016	Dec. 31, 2016
Revenue Recognition Milestone Method [Line Items]
Upfront payment from collaboration partner		$ 40,000,000
Teijin Limited [Member] | License and Supply Agreement [Member]
Revenue Recognition Milestone Method [Line Items]
Potential to receive development milestone	$ 35,000,000
Percentage of running royalty and transfer pricing receivable range, high	20.00%
Percentage of running royalty and transfer pricing receivable range, mid	30.00%
Agreement expiration terms		The Agreement continues until the earlier of (i) twelve years after the first commercial sale of a licensed product in Japan, or (ii) the expiration of certain Versartis patents, unless terminated earlier by mutual agreement of the parties. The initial term of the Agreement is subject to automatic extension for three three-year terms, unless otherwise mutually agreed. The Agreement may be earlier terminated by either party for the other party’s uncured material breach or insolvency. In addition, Teijin may terminate the Agreement without cause upon six months’ advance notice prior to the sale of a licensed product, and upon twelve months’ notice thereafter.
Agreement expiration period after commercialization		12 years
Agreement automatic extension term		3 years
Upfront payment from collaboration partner		$ 40,000,000
Teijin Limited [Member] | License and Supply Agreement [Member] | Upfront Payment Arrangement [Member]
Revenue Recognition Milestone Method [Line Items]
Payments received under license and supply agreement	$ 40,000,000
Maximum [Member] | License and Supply Agreement [Member]
Revenue Recognition Milestone Method [Line Items]
Costs associated with additional trials	5,000,000
Maximum [Member] | Teijin Limited [Member] | License and Supply Agreement [Member]
Revenue Recognition Milestone Method [Line Items]
Potential to receive regulatory milestone	55,000,000
Potential to receive sales milestone	$ 35,000,000

Convertible Preferred Stock W49

Convertible Preferred Stock Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2013
Class Of Stock [Line Items]
Number of securities issued upon exercise of warrants	158,179	158,179
Remeasurement of outstanding warrants	173,910
Warrants to purchase convertible preferred stock, exercise price	$ 5.17	$ 5.17
Reclassification of warrant liability		$ 2,300
IPO [Member]
Class Of Stock [Line Items]
Warrants to purchase convertible preferred stock, exercise price	$ 21	$ 21
Reclassification of warrant liability				$ 2,752
IPO [Member] | Additional Paid-in Capital [Member]
Class Of Stock [Line Items]
Reclassification of warrant liability	$ 2,800			$ 2,752
2012 Notes [Member]
Class Of Stock [Line Items]
Percentage of shares issuable on conversion of debt as warrants			20.00%
Warrants term			5 years
Warrants expiration date			Oct. 12, 2017
Fair value of warrants			$ 433		$ 474
Risk-free interest rate			0.21%
Expected volatility			90.00%
Expected term (in years)			1 year 6 months

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended		12 Months Ended
	Dec. 31, 2015	Mar. 31, 2014ft²	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Loss Contingencies [Line Items]
Rent expense			$ 1,290,000	$ 763,000	$ 520,000
Aggregate noncancelable purchase commitments			7,100,000
Other potential commitments			10,000,000
Pending or threatened legal proceedings			0
Maximum [Member]
Loss Contingencies [Line Items]
Commitment to make development and sales-related milestone payments			$ 30,000,000
Boehringer Ingelheim Commercial Supply Agreement [Member]
Loss Contingencies [Line Items]
Initial term of agreement period			8 years
Automatic renewal period of agreement			3 years
Termination period of agreement			3 years
Menlo Park, California [Member]
Loss Contingencies [Line Items]
Operating facility lease area | ft²		12,900
Operating facility lease term		39 months
Total obligation under lease			$ 500,000
Menlo Park, California [Member] | Sublease Agreement [Member]
Loss Contingencies [Line Items]
Operating facility lease term	24 months
Total obligation under lease			$ 600,000

Commitments and Contingencies51

Commitments and Contingencies - Summary of Future Minimum Lease Payments Required Under Non-Cancellable Operating Leases (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Leases [Abstract]
2,017	$ 1,085
Total, Future minimum lease payments	$ 1,085

Common Stock - Additional Infor

Common Stock - Additional Information (Detail) - USD ($)	Nov. 04, 2016	Jan. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2014
Class Of Stock [Line Items]
Common stock, shares authorized			50,000,000	50,000,000	50,000,000
Voting power per share			One
Common stock, dividends declared			$ 0
Proceeds from issuance of common stock in public offering, net of issuance costs	$ 59,100,000		$ 59,136,000	$ 80,209,000
Secondary Offering [Member]
Class Of Stock [Line Items]
Public offering shares of common stock issued	5,176,545	4,999,999
Proceeds from issuance of common stock in public offering, net of issuance costs	$ 59,100,000	$ 80,209,000

Common Stock - Summary of Reser

Common Stock - Summary of Reserved Shares of Common Stock for Future Issuances (Detail) - shares	Dec. 31, 2016	Dec. 31, 2015
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	5,998,840	4,845,579
Stock Compensation Plan [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	1,044,113	1,350,543
Options to purchase common stock [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	4,452,700	3,240,969
Restricted stock units [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	502,027	254,067

Stock Based Awards - Additional

Stock Based Awards - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended	12 Months Ended
	May 31, 2015	Feb. 28, 2009	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Mar. 20, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved				5,998,840	4,845,579
Common stock reserved for future issuance				1,044,113	1,350,543	991,401			9,533
Intrinsic value of stock option exercised				$ 800,000	$ 1,400,000	$ 800,000
Unrecognized employee stock-based compensation				$ 20,000,000
Weighted-average remaining vesting period				2 years 3 months 18 days
Unvested stock options expected to vest, term				7 years 9 months 18 days
Additional shares issued				1,323,911	1,091,045	2,531,915
Voting power per share				One
Recognized compensation expense				$ 10,923,000	$ 10,699,000	$ 4,641,000
Weighted Average Remaining Contractual Life, Options outstanding				7 years 9 months 18 days
Co-Founder And CEO [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Separation related costs	$ 2,400,000
Unexercised vested and expected to vest stock options	$ 2,000,000
Unvested stock options expected to vest, term	12 months
Incremental payroll costs			$ 400,000
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				4 years
Stock options, weighted-average grant date fair value				$ 6.78	$ 10.62	$ 16.90
Tax benefits realized from options and other share-based payment arrangements				$ 0	$ 0	$ 0
Restricted stock units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Recognized compensation expense				2,000,000	$ 1,400,000	$ 500,000
Approximate compensation expenses				$ 4,100,000
Weighted Average Remaining Contractual Life, Options outstanding				2 years 6 months
2009 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period		4 years
Options vested , description				Options granted generally vest over four years and vest at a rate of 25% upon the first anniversary of the issuance date and 1/36th?per month thereafter
2014 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				4 years
Options expiration period				10 years
Options vested , description				Options granted under the 2014 Plan have a contractual life of ten years and generally vest over four years and vest at a rate of 25% upon the first anniversary of the issuance date and 1/36th per month thereafter.
Number of shares reserved							4,100,000
Percentage of common stock issued and outstanding increase annually				4.50%
End date of automatic annual increase of shares reserved for issuance				Jan. 1, 2024
Common stock reserved for future issuance				1,044,113
2014 Plan [Member] | Incentive Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved				12,000,000
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved								150,000
Percentage of common stock issued and outstanding increase annually				1.00%
End date of automatic annual increase of shares reserved for issuance				Jan. 1, 2024
Additional shares issued				300,000
Voting power per share				Immediately after the grant would own stock possessing 5% or more of the total combined voting power or value of our common stock.
Percentage of stock possessing				5.00%
Rights to purchase stock that remains outstanding				$ 25,000
Offerings of purchase periods				27 months
Maximum employee subscription rate				15.00%
Maximum [Member] | 2009 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options expiration period		10 years
Minimum [Member] | 2009 Plan [Member] | Incentive Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of options granted, percentage				100.00%
Minimum [Member] | 2009 Plan [Member] | 10% Shareholders [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of options granted, percentage				110.00%
Minimum [Member] | 2014 Plan [Member] | Incentive Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of options granted, percentage				100.00%
Minimum [Member] | Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of options granted, percentage				85.00%

Stock Based Awards - Summary of

Stock Based Awards - Summary of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares Available for Grant
Shares Available for Grant, Beginning balance	1,350,543	991,401	9,533
Shares Available for Grant, Additional shares authorized	1,323,911	1,091,045	2,531,915
Shares Available for Grant, Options granted	(1,399,522)	(664,100)	(1,471,142)
Shares Available for Grant, Restricted stock units granted	(332,964)	(123,450)	(185,514)
Shares Available for Grant, Options cancelled	102,145	55,647	106,609
Shares Available for Grant, Ending balance	1,044,113	1,350,543	991,401
Number of shares
Number of Shares, Beginning balance	3,240,969	2,723,367	1,403,656
Number of Shares, Options granted	1,399,522	664,100	1,471,142
Number of Shares, Options exercised	(85,646)	(90,851)	(44,822)
Number of Shares, Options cancelled	(102,145)	(55,647)	(106,609)
Number of Shares, Ending balance	4,452,700	3,240,969	2,723,367
Number of Shares, Vested and expected to vest	4,323,511
Number of Shares, Exercisable	2,246,742
Weighted Average Exercise Price
Weighted Average Exercise Price, Beginning balance	$ 11.51	$ 10.33	$ 1.90
Weighted Average Exercise Price, Options granted	10.04	15.34	18.68
Weighted Average Exercise Price, Options exercised	1.64	1.34	1.32
Weighted Average Exercise Price, Options cancelled	14.90	15.68	18.43
Weighted Average Exercise Price, Ending balance	11.16	$ 11.51	$ 10.33
Weighted Average Exercise Price, Vested and expected to vest	11.14
Weighted Average Exercise Price, Exercisable	$ 10.11
Weighted Average Remaining Contractual Life (in years)
Weighted Average Remaining Contractual Life, Options outstanding	7 years 9 months 18 days
Weighted Average Remaining Contractual Life, Vested and expected to vest	7 years 9 months 18 days
Weighted Average Remaining Contractual Life, Exercisable	7 years 2 months 12 days
Aggregate Intrinsic Value, Options outstanding	$ 25,162
Aggregate Intrinsic Value, Vested and expected to vest	24,632
Aggregate Intrinsic Value, Exercisable	$ 15,498

Stock Based Awards - Stock Opti

Stock Based Awards - Stock Options Outstanding and Exercisable under Stock Option Plans (Detail)	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number	4,452,700
Options Exercisable and Vested, Outstanding Number	2,246,742
$1.27 - $2.53 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit | $ / shares	$ 1.27
Range of Exercise Price, Upper Limit | $ / shares	$ 2.53
Options Outstanding, Number	1,158,038
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	6 years 3 months 18 days
Options Exercisable and Vested, Outstanding Number	966,139
Options Exercisable and Vested, Weighted Average Remaining Contractual Life (Years)	6 years 3 months 18 days
$3.33 - $10.68 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit | $ / shares	$ 3.33
Range of Exercise Price, Upper Limit | $ / shares	$ 10.68
Options Outstanding, Number	1,736,950
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	8 years 7 months 6 days
Options Exercisable and Vested, Outstanding Number	494,703
Options Exercisable and Vested, Weighted Average Remaining Contractual Life (Years)	8 years 7 months 6 days
$10.87 - $20.30 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit | $ / shares	$ 10.87
Range of Exercise Price, Upper Limit | $ / shares	$ 20.30
Options Outstanding, Number	896,382
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	8 years 6 months
Options Exercisable and Vested, Outstanding Number	409,602
Options Exercisable and Vested, Weighted Average Remaining Contractual Life (Years)	8 years 6 months
$21.00 - $31.96 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit | $ / shares	$ 21
Range of Exercise Price, Upper Limit | $ / shares	$ 31.96
Options Outstanding, Number	651,330
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	7 years 6 months
Options Exercisable and Vested, Outstanding Number	370,048
Options Exercisable and Vested, Weighted Average Remaining Contractual Life (Years)	7 years 6 months
$34.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit | $ / shares	$ 34
Range of Exercise Price, Upper Limit | $ / shares	$ 34
Options Outstanding, Number	10,000
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	7 years 6 months
Options Exercisable and Vested, Outstanding Number	6,250
Options Exercisable and Vested, Weighted Average Remaining Contractual Life (Years)	7 years 6 months

Stock Based Awards - Summary 57

Stock Based Awards - Summary of Fair Value of Employee Stock Options (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected volatility	77.90%	79.70%	84.90%
Risk-free interest rate	1.50%	1.70%	1.90%
Dividend yield	0.00%	0.00%	0.00%
Expected life (in years)	6 years	6 years	6 years 1 month 6 days

Stock Based Awards - Schedule o

Stock Based Awards - Schedule of Estimated Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 10,923	$ 10,699	$ 4,641
Research and development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	3,837	3,032	1,230
General and administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 7,086	$ 7,667	$ 3,411

Stock Based Awards - Summary 59

Stock Based Awards - Summary of Fair Value of Employees Stock Purchase Rights Under ESPP Using Black-Scholes Model with Following Weighted-Average Assumptions (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	77.90%	79.70%	84.90%
Risk-free interest rate	1.50%	1.70%	1.90%
Dividend yield	0.00%	0.00%	0.00%
Expected life (in years)	6 years	6 years	6 years 1 month 6 days
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	73.60%	72.10%	54.90%
Risk-free interest rate	0.51%	0.26%	0.06%
Dividend yield	0.00%	0.00%	0.00%
Expected life (in years)	6 months	6 months	6 months

Stock Based Awards - Summary 60

Stock Based Awards - Summary of Restricted Stock Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Granted	332,964	123,450	185,514
Restricted stock units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Unvested beginning balance	254,067
Number of Shares, Granted	332,964
Number of Shares, Vested	(79,756)
Number of Shares, Forfeited/canceled	(5,248)
Number of Shares, Unvested ending balance	502,027	254,067
Weighted Average Grant-Date Fair Value, Unvested beginning balance	$ 21.11
Weighted Average Grant Date Fair Value, Granted	10.63
Weighted Average Grant Date Fair Value, Vested	14.64
Weighted Average Grant Date Fair Value, Forfeited/canceled	21.71
Weighted Average Grant Date Fair Value, Unvested ending balance	$ 14.43	$ 21.11

Comprehensive Income - Summary

Comprehensive Income - Summary of Amounts Reclassified out of Accumulated Other Comprehensive Income (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balances	$ 176,500
Other comprehensive earnings (loss) before reclassifications	(286)
Amounts reclassified out of other comprehensive loss	(64)
Net current period other comprehensive loss	(350)
Ending Balances	151,067
Unrealized Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive earnings (loss) before reclassifications	(286)
Amounts reclassified out of other comprehensive loss	(64)
Net current period other comprehensive loss	(350)
Ending Balances	(350)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Ending Balances	$ (350)

Related Party - Additional Info

Related Party - Additional Information (Detail) - Amunix Inc. [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Additional consideration, milestone payments				$ 30
Operating expenses from related party transaction	$ 0.6	$ 0.8	$ 0.8
Due to related party	$ 0.1	$ 0.1
Preferred stock [Member]
Related Party Transaction [Line Items]
Ownership percentage				10.00%
Common Stock [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Ownership percentage	5.00%

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for Federal Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016
Current
Federal		$ 247
Total current tax expense		247
Deferred
Total income tax expense	$ 247	$ 247

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income (Loss) Before Income Taxes Attributed to Geographic Locations (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
United States					$ (10,421)	$ (17,671)	$ (49,850)
Foreign					(85,149)	(64,506)	(7,663)
Net loss before provision for income taxes	$ (21,885)	$ (27,335)	$ (22,118)	$ (24,232)	$ (95,570)	$ (82,177)	$ (57,513)

Income Taxes - Summary of Statu

Income Taxes - Summary of Statutory Federal Tax Rate to Income or Loss before Taxes (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal tax benefit at statutory rate	34.00%	34.00%	34.00%
Change in valuation allowance	(3.00%)	(8.00%)	(23.00%)
Research and development credits	4.00%	2.00%	2.00%
Non-deductible warrant			(7.00%)
Foreign loss not benefitted	(30.00%)	(27.00%)	(5.00%)
Other Non-deductible expenses	(5.00%)	(2.00%)	(1.00%)
Total	0.00%	0.00%	0.00%

Income Taxes - Significant Comp

Income Taxes - Significant Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Net operating loss carry forwards	$ 32,500	$ 33,684
Research and development tax credits	8,142	4,982
Stock based compensation and other	7,256	4,465
Depreciation and amortization	78	42
Total deferred tax assets	47,976	43,173
Less: Valuation allowance	$ (47,976)	$ (43,173)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Increase in valuation allowance	$ 4,800	$ 6,500
Unrecognized tax benefits	10,116	$ 4,061	$ 332	$ 287
Employee Stock Option [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	2,100
Federal [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	68,400
Federal [Member] | Research and Development Tax Credits [Member]
Income Tax Contingency [Line Items]
Tax credits	$ 955
Tax credit, expiration	Begin to expire in 2029
Federal [Member] | Orphan Drug Credit [Member]
Income Tax Contingency [Line Items]
Tax credits	$ 20,900
Tax credit, expiration	Begins to expire in 2033
State [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 55,100
Operating loss carryforwards, expiration	Begin to expire in 2029
State [Member] | Research and Development Tax Credits [Member]
Income Tax Contingency [Line Items]
Tax credits	$ 1,616
Foreign [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 17,400
Operating loss carryforwards, expiration	Begin to expire in 2023

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Beginning Balance	$ 4,061	$ 332	$ 287
Decreases based on tax positions taken during a prior period	(3,559)		(102)
Increases based on tax positions taken during a prior period	4,628	3,562
Increases based on tax positions taken during a current period	4,986	167	147
Ending Balance	$ 10,116	$ 4,061	$ 332

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)
Compensation And Retirement Disclosure [Abstract]
Matching contributions made	$ 0

Net Loss per Share - Summary of

Net Loss per Share - Summary of Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net loss attributable to common stockholders - basic and diluted					$ (20,125)	$ (20,379)	$ (19,667)	$ (22,006)	$ (95,817)	$ (82,177)	$ (83,072)
Weighted-average shares used to compute basic and diluted net loss per share	34,609	29,574	29,489	29,422	29,379	29,354	29,293	27,810	30,784	28,964	18,922
Basic and diluted net loss per common share	$ (0.64)	$ (0.92)	$ (0.75)	$ (0.82)	$ (0.69)	$ (0.69)	$ (0.67)	$ (0.79)	$ (3.11)	$ (2.84)	$ (4.39)

Net Loss per Share - Summary 71

Net Loss per Share - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Options to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding	4,452,700	3,240,969	2,723,366
Restricted stock units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding	502,027	254,067	185,514

Subsequent Event - Additional I

Subsequent Event - Additional Information (Detail) - shares	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Subsequent Event [Line Items]
Number of Shares, Options granted		1,399,522	664,100	1,471,142
Subsequent event [Member]
Subsequent Event [Line Items]
Number of Shares, Options granted	1,207,240

Quarterly Results (Unaudited) -

Quarterly Results (Unaudited) - Schedule of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating expenses
Research and development	$ 16,731	$ 20,664	$ 16,397	$ 18,192	$ 15,586	$ 15,400	$ 11,940	$ 17,100	$ 71,984	$ 60,025	$ 32,608
General and administrative	5,760	6,752	5,909	5,915	4,622	5,124	7,556	5,181	24,336	22,483	13,505
Total operating expenses	22,491	27,416	22,306	24,107	20,208	20,524	19,496	22,281	96,320	82,508	46,113
Loss from operations	(22,491)	(27,416)	(22,306)	(24,107)	(20,208)	(20,524)	(19,496)	(22,281)	(96,320)	(82,508)	(46,113)
Interest income	160	120	129	105	51	54	65	49	514	218	132
Other income (expense), net	446	(39)	59	(230)	32	91	(236)	226	236	113	(11,532)
Net loss before provision for income taxes	(21,885)	(27,335)	(22,118)	(24,232)					(95,570)	(82,177)	(57,513)
Provision for income taxes	247								247
Net loss	$ (22,132)	$ (27,335)	$ (22,118)	$ (24,232)	(20,125)	(20,379)	(19,667)	(22,006)	(95,817)	(82,177)	(57,513)
Net loss attributable to common stockholders					$ (20,125)	$ (20,379)	$ (19,667)	$ (22,006)	$ (95,817)	$ (82,177)	$ (83,072)
Net loss per share- basic and diluted	$ (0.64)	$ (0.92)	$ (0.75)	$ (0.82)	$ (0.69)	$ (0.69)	$ (0.67)	$ (0.79)	$ (3.11)	$ (2.84)	$ (4.39)
Weighted-average common shares used to compute basic and diluted net loss per share	34,609	29,574	29,489	29,422	29,379	29,354	29,293	27,810	30,784	28,964	18,922

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts (Detail) - Valuation Allowances for Deferred Tax Assets [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 43,173	$ 36,645	$ 23,964
Additions/charged to expense	4,803	6,528	12,681
Balance at end of period	$ 47,976	$ 43,173	$ 36,645