Adverum Biotechnologies (ADVM) 10-K 4 Mar 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Feb. 29, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	AAVL
Entity Registrant Name	Avalanche Biotechnologies, Inc.
Entity Central Index Key	1,501,756
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		26,860,056
Entity Public Float			$ 328.5

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 221,348	$ 159,404
Marketable securities	37,732
Receivable from collaborative partner	449
Prepaid expenses and other current assets	1,463	874
Total current assets	260,992	160,278
Property and equipment, net	3,187	1,085
Deposit and other long-term assets	140	543
Total assets	264,319	161,906
Current liabilities:
Accounts payable	605	951
Restructuring liabilities	1,013
Accrued expenses and other current liabilities	4,007	3,707
Deferred rent, current portion	66
Deferred revenue, current portion	883	813
Total current liabilities	6,574	5,471
Long-term liabilities:
Deferred rent, net of current portion	447	306
Deferred revenue, net of current portion	4,706	6,646
Total liabilities	$ 11,727	$ 12,423
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 5,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.0001 par value, 300,000,000 shares authorized at December 31, 2015 and 2014; 25,858,722 and 22,754,037 shares issued and outstanding at December 31, 2015 and 2014, respectively	$ 3	$ 2
Additional paid-in capital	336,768	186,186
Accumulated other comprehensive (loss) income	(11)	10
Accumulated deficit	(84,168)	(36,715)
Total stockholders’ equity	252,592	149,483
Total liabilities and stockholders’ equity	$ 264,319	$ 161,906

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
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	300,000,000	300,000,000
Common stock, shares issued	25,858,722	22,754,037
Common stock, shares outstanding	25,858,722	22,754,037

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Collaboration revenue	$ 2,319	$ 572
Government grant revenue	0	0	$ 480
Total revenue	2,319	572	480
Operating expenses:
Research and development	25,462	16,976	2,151
General and administrative	22,107	7,998	1,783
Restructuring charges	2,573
Total operating expenses	50,142	24,974	3,934
Operating loss	(47,823)	(24,402)	(3,454)
Other income (expense)
Interest expense		(18)	(73)
Other income (expense), net	370	(21)	(4)
Change in fair value of embedded derivative			18
Change in fair value of warrant liabilities		(759)	(92)
Loss on extinguishment of related-party convertible notes		(204)	(1,671)
Total other income (expense), net	370	(1,002)	(1,822)
Net loss	(47,453)	(25,404)	(5,276)
Deemed dividend		(3,230)
Net loss attributable to common stockholders	(47,453)	(28,634)	(5,276)
Other comprehensive loss:
Net unrealized loss on marketable securities	(6)
Foreign currency translation adjustment	(15)	(17)	19
Comprehensive loss	$ (47,474)	$ (25,421)	$ (5,257)
Net loss per share attributable to common stockholders-basic and diluted	$ (1.86)	$ (2.46)	$ (1.44)
Weighted-average common shares outstanding-basic and diluted	25,479	11,651	3,673

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Convertible Preferred Stock Warrant [Member]	Convertible Preferred Stock Warrant [Member]Additional Paid-in Capital [Member]	Series A Preferred Stock [Member]	Series A Preferred Stock [Member]Common Stock [Member]	Series A Preferred Stock [Member]Additional Paid-in Capital [Member]	Series B Preferred Stock [Member]	Series B Preferred Stock [Member]Common Stock [Member]	Series B Preferred Stock [Member]Additional Paid-in Capital [Member]	Common Stock Warrant [Member]	Common Stock Warrant [Member]Common Stock [Member]	Common Stock Warrant [Member]Additional Paid-in Capital [Member]	IPO [Member]	IPO [Member]Common Stock [Member]	IPO [Member]Additional Paid-in Capital [Member]	Private Placement [Member]	Private Placement [Member]Common Stock [Member]	Private Placement [Member]Additional Paid-in Capital [Member]	Series A Convertible Preferred Stock [Member]	Series A Convertible Preferred Stock [Member]Related-party convertible notes [Member]	Series A Convertible Preferred Stock [Member]Convertible Preferred Stock Warrant [Member]	Series A Convertible Preferred Stock [Member]Series A Preferred Stock [Member]	Series B Convertible Preferred Stock [Member]	Series B Convertible Preferred Stock [Member]Related-party convertible notes [Member]	Series B Convertible Preferred Stock [Member]Series B Preferred Stock [Member]
BALANCE at Dec. 31, 2012	$ (3,468)		$ 117	$ 8	$ (3,593)
Temporary equity, Balance at Dec. 31, 2012																							$ 2,471
BALANCE, SHARES at Dec. 31, 2012		3,672,885
Temporary equity, Balance, shares at Dec. 31, 2012																							1,789,618
Conversion of the convertible securities																								$ 3,730
Conversion of the convertible securities, shares																								1,419,959
Issuance of convertible preferred stock for cash, net of issuance costs																							$ 1,791
Issuance of convertible preferred stock for cash, shares																							689,655
Stock-based compensation expense	$ 515		515
Common stock issued upon exercise of stock options, shares	0
Foreign currency translation adjustment	$ 19			19
Net loss	(5,276)				(5,276)
BALANCE at Dec. 31, 2013	(8,210)		632	27	(8,869)
Temporary equity, Balance at Dec. 31, 2013																							$ 7,992
BALANCE, shares at Dec. 31, 2013		3,672,885
Temporary equity, Balance, shares at Dec. 31, 2013																							3,899,232
Beneficial conversion feature in related-party convertible notes	2,000		2,000
Repurchase of beneficial conversion feature upon conversion of related-party convertible notes	(2,000)		(2,000)
Conversion of the convertible securities								$ 7,301		$ 7,301	$ 52,321	$ 1	$ 52,320													$ (7,301)		$ 2,222	$ (52,321)
Conversion of the convertible securities, shares									3,422,740			7,321,003														(3,422,740)		295,115	(7,321,003)
Issuance of convertible preferred stock for cash, net of issuance costs																											$ 50,099
Issuance of convertible preferred stock for cash, shares																											7,025,888
Repurchase of Series A convertible preferred stock for cash	(3,230)		(788)		(2,442)																		$ (770)
Repurchase of Series A convertible preferred stock for cash, shares																							(531,208)
Issuance of common stock warrants in consideration for services	307		307
Issuance of common stock upon exercise of warrants														$ 526		$ 526
Issuance of common stock upon exercise of warrants, shares															352,415
Issuance of common stock net of issuance costs						$ 851	$ 851										$ 92,224	$ 1	$ 92,223	$ 10,000		$ 10,000			$ 79
Issuance of common stock net of issuance costs, shares																		6,000,000			588,235				54,716
Issuance of common stock upon exercise of overallotment by underwriters, net of issuance costs	14,229		14,229
Issuance of common stock upon exercise of overallotment by underwriters, net of issuance costs, shares		900,000
Stock-based compensation expense	8,567		8,567
Common stock issued upon exercise of stock options	18		18
Common stock issued upon exercise of stock options, shares		496,759
Foreign currency translation adjustment	(17)			(17)
Net loss	(25,404)				(25,404)
BALANCE at Dec. 31, 2014	149,483	$ 2	186,186	10	(36,715)
BALANCE, shares at Dec. 31, 2014		22,754,037
Issuance of common stock warrants in consideration for services	218		218
Issuance of common stock net of issuance costs	138,954	$ 1	138,953
Issuance of common stock net of issuance costs, shares		2,599,375
Stock-based compensation expense	11,505		11,505
Common stock issued upon exercise of stock options	188		188
Common stock issued upon exercise of stock options, shares		399,434
Common stock issued under employee stock purchase plan	145		145
Common stock issued under employee stock purchase plan, shares		19,577
Restricted stock surrendered for taxes	(427)		(427)
Restricted stock surrendered for taxes, shares		(46,098)
Net unrealized loss on marketable securities	(6)			(6)
Foreign currency translation adjustment	(15)			(15)
Net loss	(47,453)				(47,453)
BALANCE at Dec. 31, 2015	$ 252,592	$ 3	$ 336,768	$ (11)	$ (84,168)
BALANCE, shares at Dec. 31, 2015		25,858,722
Common stock issued upon release of restricted stock units, shares		132,397

Consolidated Statements of Con6

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Issuance costs	$ 11,099	$ 2,806	$ 20
IPO [Member]
Issuance costs		9,776
Over-Allotment Option [Member]
Issuance costs		$ 1,071

Condensed Consolidated Statemen

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (47,453)	$ (25,404)	$ (5,276)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	812	162	26
Loss on disposal of property and equipment	21
Stock-based compensation expense	11,505	8,567	515
Non-cash research and development expense	218
Non-cash interest expense		18	53
Amortization of debt issuance costs			20
Change in fair value of embedded derivative liability			(18)
Amortization of premium on marketable securities	780
Change in fair value of warrant liabilities		759	92
Loss on extinguishment of related-party convertible notes		204	1,671
Non-cash collaboration acquisition costs associated with sale of Series A convertible preferred stock			812
Changes in operating assets and liabilities:
Accounts receivable, net	(6)	8	(7)
Prepaid expenses and other current assets	(531)	(624)	(293)
Deposit	(3)	7	(144)
Accounts payable	(312)	(6)	286
Accrued expenses and other current liabilities	724	2,904	80
Restructuring liabilities	1,013
Deferred revenue	(2,313)	7,459
Deferred rent	207	298	8
Net cash used in operating activities	(35,338)	(5,648)	(2,175)
Cash flows from investing activities:
Purchases of marketable securities	(88,427)
Maturities of marketable securities	49,850
Purchases of property and equipment	(2,992)	(943)	(91)
Net cash used in investing activities	(41,569)	(943)	(91)
Cash flows from financing activities:
Proceeds from public offering of common stock, net	138,954	106,453
Proceeds from issuance of related-party convertible notes		2,000	1,500
Repurchase of Series A convertible preferred stock		(4,000)
Proceeds from exercises of warrants		606
Proceeds from issuance of common stock pursuant to option exercises	188	18
Taxes paid related to net share settlement of restricted stock units	(427)
Proceeds from employee stock purchase plan	145
Net cash provided by financing activities	138,860	165,442	2,480
Effect of foreign currency exchange rate on cash and cash equivalents	(9)	(11)	(7)
Net increase in cash and cash equivalents	61,944	158,840	207
Cash and cash equivalents at beginning of period	159,404	564	357
Cash and cash equivalents at end of period	221,348	159,404	564
Supplemental schedule of noncash investing and financing information
Conversion of related-party convertible notes payable to convertible preferred stock		2,000	2,059
Warrants issued in connection with issuance of Series B convertible preferred stock		266
Warrants issued in connection with license agreements	218	42
Fixed assets in accounts payable and current liabilities	$ 178	235
Deferred stock issuance costs		379	50
Series A Preferred Stock [Member]
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock			1,000
Expenses related to issuance of convertible preferred stock			$ (20)
Series B Preferred Stock [Member]
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock		52,905
Expenses related to issuance of convertible preferred stock		(2,540)
Collaborative Partner [Member]
Cash flows from financing activities:
Proceeds from sales of common stock		$ 10,000

Description of the business

Description of the business	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Description of the business	1. Description of the business Nature of Business —Avalanche Biotechnologies, Inc. (the “Company”, “we” or “us”) was incorporated in Delaware on July 17, 2006, and is headquartered in Menlo Park, California. The Company is a gene therapy company committed to discovering and developing novel medicines that can offer life-changing therapeutic benefit to patients suffering from chronic or debilitating disease. Since the Company’s inception, it has devoted its efforts principally to performing research and development activities, including early clinical trials, filing patent applications, obtaining regulatory approvals, hiring personnel, and raising capital to support these activities. The Company has not generated any revenue from the sale of products since its inception. The Company has experienced net losses since its inception and has an accumulated deficit of $84.2 million as of December 31, 2015. The Company expects to incur losses and have negative net cash flows from operating activities as it expands its portfolio and engages in further research and development activities, particularly conducting preclinical studies and clinical trials. The Company believes that it has sufficient funds to continue operations for the foreseeable future. Initial Public and Follow-on Offerings —On August 5, 2014, the Company completed its initial public offering (IPO) of shares of its common stock. As a result, the following transactions were recorded in the Company’s consolidated financial statements on August 5, 2014 (the third quarter of 2014): · the sale of 6,900,000 shares of common stock, including 900,000 from the exercise by the underwriters of their option to purchase additional shares, at an offering price of $17.00 per share, for net proceeds of $106.5 million, after deducting the underwriters’ discounts, commissions and offering expenses; · concurrent with the IPO, the private placement of 588,235 shares of common stock to Regeneron Pharmaceuticals, Inc. (Regeneron), pursuant to the Regeneron agreement signed in May 2014, at the offering price of $17.00 per share for gross proceeds of $10.0 million and no underwriting discounts or commissions; · immediately prior to the completion of the IPO, all the outstanding shares of the Company’s convertible preferred stock were converted into 10,689,027 shares of common stock; and · immediately prior to the completion of the IPO, all then outstanding warrants for convertible preferred stock and common stock were exercised into 407,131 shares of common stock for proceeds of $0.6 million. Follow-on Offerings —In January 2015, the Company completed a public offering of 2,369,375 shares of its common stock (Follow-on Offering), which included 359,918 shares the Company issued pursuant to the underwriters’ exercise of their option to purchase additional shares, and the Company received net proceeds of approximately $130.6 million, after underwriting discounts, commissions and offering expenses. In March 2015, (i) the Company received net proceeds of approximately $8.3 million, after discounts and other issuance costs, which resulted from the sale of 230,000 common shares, and (ii) the Company issued 230,000 common shares to a stockholder that exercised warrants prior to the initial public offering.

Summary of significant accounti

Summary of significant accounting policies and basis of presentation	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of significant accounting policies and basis of presentation	2. Summary of significant accounting policies and basis of presentation Use of Estimates —The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (U.S. GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to clinical trial accruals, stock-based compensation, income taxes, fair value of common stock warrant and, prior to the IPO, fair value of embedded derivative liability, fair value of convertible preferred stock and fair values of common and convertible preferred stock warrants. The Company’s actual results may differ from these estimates under different assumptions or conditions. There have been no significant changes from the Company’s original estimates in any periods presented. Principles of Consolidation —The Company’s consolidated financial statements have been prepared in accordance with U.S. GAAP and include the accounts of the Company and its wholly-owned subsidiary in Australia. All intercompany transactions and balances have been eliminated in consolidation. Foreign Currency Translation —The Company’s consolidated financial statements are prepared in U.S. dollars. Its foreign subsidiary uses the Australian dollar as its functional currency and maintains its records in the local currency. Assets and liabilities are re-measured at exchange rates in effect at the end of the reporting period. Equity is measured at historical rates and income and expenses are re-measured at average exchange rates for the reporting period. The resulting foreign currency translation adjustment is recorded in accumulated other comprehensive (loss) income in the consolidated balance sheets and in the consolidated statements of operations and comprehensive loss. Transactions denominated in foreign currency are translated at exchange rates at the date of transaction with foreign currency gains (losses) recorded in other income (expense), net in the consolidated statements of operations and other comprehensive loss. Cash and Cash Equivalents —The Company considers all highly liquid investments purchased with original maturities of three months or less at the date of purchase to be cash equivalents. Cash and cash equivalents include cash held in banks and money market accounts. Cash equivalents are stated at fair value. Marketable Securities —All marketable securities, which consist of debt securities and certificates of deposit, have been classified as “available for sale” and are carried at fair value. Unrealized gains and losses, net of any related tax effects, are excluded from earnings and are included in other comprehensive loss and reported as a separate component of stockholders’ equity until realized. Realized gains and losses and declines in value judged to be other than temporary, if any, on available-for-sale securities are included in other income (expense), net. The cost of securities sold is based on the specific-identification method. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Interest on short-term investments is included in interest income. In accordance with the Company’s investment policy, management invests to diversify credit risk and only invests in securities with high credit quality, including U.S. government securities. The Company regularly evaluates whether declines in the fair value of its investments below their cost are other than temporary. The evaluation includes consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities, and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. If the Company determines that the decline in fair value of an investment is below its accounting basis and this decline is other than temporary, the Company would reduce the carrying value of the security it holds and records a loss for the amount of such decline. The Company has not recorded any realized losses or declines in value judged to be other than temporary on its investments. Deposit —Deposit in the amount of $0.1 million as of December 31, 2015 and 2014 represents amounts paid in connection with the Company’s facility lease agreement and recorded as a long-term asset. Segment Reporting —The Company operates and manages its business as one reporting and operating segment, which is the business of developing and commercializing gene therapeutics. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Concentrations of Credit Risk and Other Uncertainties —Financial instruments that potentially subject us to significant concentrations of credit risk consists primarily of cash and cash equivalents. As of December 31, 2015, substantially all of the Company’s cash and cash equivalents was deposited in accounts at four financial institutions, and amounts may exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of the depository institutions in which the financial instrument are held. The Company is subject to certain risks and uncertainties, including, but not limited to changes in any of the following areas that the Company believes could have a material adverse effect on future financial position or results of operations: ability to obtain future financing; regulatory approval and market acceptance of, and reimbursement for, the Company’s product candidates; performance of third-party clinical research organizations and manufacturers; development of sales channels; protection of the intellectual property; litigation or claims against the Company based on intellectual property, patent, product, regulatory or other factors; and the Company’s ability to attract and retain employees necessary to support the growth. Property and Equipment —Property and equipment are recorded at cost, net of accumulated depreciation and amortization. Depreciation is recorded using the straight-line method over the estimated useful lives of the assets, generally three to five years. Leasehold improvements are capitalized and amortized over the shorter period, expected life or lease term. Major replacements and improvements are capitalized, while general repairs and maintenance are expensed as incurred. Impairment of Long-Lived Assets —The Company evaluates the carrying amount of its long-lived assets whenever events or changes in circumstances indicate that the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition is less than the carrying amount of the asset. To date, there have been no such impairment losses. Deferred Offering Costs —The Company capitalizes deferred offering costs, which primarily consist of direct incremental legal and accounting fees relating to its public offerings. The Company offsets the deferred offering costs against its public offering proceeds upon the consummation of its public offerings. As of December 31, 2015 and 2014, $0 and $0.4 million of deferred offering costs were capitalized in deposit and other long-term assets on the Company’s consolidated balance sheets, respectively. Derivative Instruments —The Company had recorded convertible preferred stock warrants issued to investors and note holders as derivative liabilities. The convertible preferred stock warrants were initially recorded at fair value, with gains and losses arising from changes in fair value recognized in other income (expense) in the consolidated statements of operations and comprehensive loss at each period end while such instruments were outstanding and classified as long-term liabilities. In connection with the completion of the Company’s IPO in August 2014, all of the then outstanding warrants to purchase convertible preferred stock were exercised. As a result of the exercises, the Company recorded a $0.8 million loss related to the change in fair value in the Company’s consolidated statements of operations and comprehensive loss and reclassified the fair value of $0.9 million to additional paid-in capital. The Company had also recorded as a derivative liability the Company’s obligation to issue common stock warrants in connection with license agreements as the terms of the warrants were not fixed due to potential adjustments in the exercise price. The derivative liability associated with the common stock warrants was initially recorded at fair value, with gains and losses arising from changes in fair value recognized in the consolidated statements of operations and comprehensive loss at each period end while such instruments are classified as liabilities. In March 2014, the liability terminated upon the issuance of common stock warrant and was recorded to additional paid-in capital. Both the preferred stock and common stock warrant liabilities were valued using a Black-Scholes valuation model (refer to Note 11). Immediately prior to the completion of the IPO, all then outstanding warrants to purchase preferred stock and common stock were exercised, and the outstanding liability was reversed. Revenue Recognition —The Company has primarily generated contract revenue through a research and collaboration arrangement with a strategic partner for the development and commercialization of product candidates, and a license agreement related to the licensing of certain of the Company’s intellectual property. Additionally, the Company has historically generated grant revenue from research and development grant programs. The Company recognizes revenue in accordance with Accounting Standards Codification Topic 605, Revenue Recognition · Persuasive evidence of an arrangement exists; · Delivery has occurred or services have been rendered; · The seller’s price to the buyer is fixed or determinable; and · Collectability is reasonably assured. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, current portion. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. Collaboration and License Revenue In May 2014, the Company entered into a research collaboration and license agreement with Regeneron to discover, develop and commercialize novel gene therapy products for the treatment of ophthalmologic diseases. The collaboration covers up to eight distinct therapeutic targets (collaboration targets). The Company and Regeneron will collaborate during the initial research period of three years that can be extended by Regeneron for up to an additional five years. During the research period, Regeneron has the option to obtain an exclusive worldwide license for a collaboration target’s further development by giving written notice to the Company and paying $2.0 million per target. If Regeneron exercises its option, it will be responsible for all further development and commercialization of the target. The Company is then eligible to receive contingent payments of up to $80.0 million upon achievement of certain development and regulatory milestones for product candidates directed toward each collaboration target, for a combined total of up to $640.0 million in potential milestone payments for product candidates directed toward all eight collaboration targets, plus a royalty in the low- to mid-single-digits on worldwide net sales of collaboration products. For any two collaboration targets, the Company has an option to share up to 35% of the worldwide product candidate development costs and profits. If the Company exercises this option, the Company will not be eligible for milestone and royalty payments discussed above but rather the Company will share development costs and profits with Regeneron. The agreement will expire with respect to each collaboration target upon the earlier of the (a) expiration of the research term if the option right has not been triggered by the end of the research term or (b) expiration of the option right if the option right has not been exercised by Regeneron. If the option right has been exercised, the agreement in connection with each collaboration target will expire upon expiration of all payment obligations by Regeneron. In addition, the agreement, or Regeneron’s rights to any target development under the agreement, may terminate early under the following situations: · Regeneron may terminate the agreement for convenience at any time on a target by target basis or in totality upon a 30-day notice. · Each party can terminate the agreement if another party commits a material breach or material default in performance of its obligations and such breach or default is not cured within 60 days. · The agreement is automatically terminated upon initiation of any bankruptcy proceedings, reorganization or dissolution of either party. · The Company can terminate the agreement upon 30-day notice if Regeneron challenges the validity, scope or enforceability of any Company patent. In connection with the agreement, Regeneron also acquired a time-limited right of first negotiation for a potential license to develop and commercialize AVA-101, the Company’s gene therapy product currently under development and undergoing a Phase 2a clinical trial. If and when such negotiation is successful, the Company and Regeneron will enter into a separate agreement for AVA-101. Under the terms of the agreement, the Company received initial upfront non-refundable cash payments of $8.0 million that included payment for research license fees, prepaid collaboration research costs and the time-limited right of first negotiation for AVA-101. As the agreement provides for multiple deliverables, the Company accounts for this agreement as a multiple elements revenue arrangement. If deliverables did not appear to have a standalone value, they were combined with other deliverables into a unit of accounting with standalone value. The Company allocated the $8.0 million to the relative fair value of the two units of accounting identified in the arrangement. The Company expects to recognize $6.5 million for the research licenses and related research and development services ratably over the associated period of performance, which is the maximum research period of eight years. As there is no discernible pattern of performance and/or objectively measurable performance measures do not exist, the Company will recognize revenue on a straight-line basis over the eight year performance period. The remaining $1.5 million allocated to the second unit of accounting for the rights of first negotiation for AVA-101 was deferred. On November 2, 2015, Regeneron notified the Company that it is not exercising this right of first negotiation and the Company recognized the entire $1.5 million as revenue in 2015. As original research budget was fully used in the fourth quarter of 2015, the Company and Regeneron will agree on the reimbursement of additional research expenses annually. The Company will invoice for services performed quarterly. These additional research fees will be added to the research licenses and related research and development services unit of accounting, recorded as deferred revenue and recognized to revenue over the remaining research term. The Company recognized $0.8 million as revenue related to this unit of accounting during the year ended December 31, 2015, recorded $5.6 million of deferred revenue, including $0.9 million as current portion, and $0.4 million as receivable from collaboration partner as of December 31, 2015. The Company also recorded $30,000 license revenue in 2014 related to the licensing of certain of its intellectual property under a licensing agreement entered into during February 2014. Government Grants For the years ending December 31, 2013, the Company recognized $0.5 million of government grant revenue. No government grant revenue was recorded in 2015 and 2014 as we completed the work performed under the grant in 2013. We intend to continue to evaluate pursuing additional grant opportunities on a case-by-case basis. Research and Development Expenses —Research and development expenses are charged to expense as incurred. Research and development expenses include certain payroll, stock compensation and other personnel-related expenses, laboratory supplies, consulting costs, external contract research and development expenses, and allocated overhead, including rent, equipment depreciation and utilities. Advance payments for goods or services for future research and development activities are deferred and expensed as the goods are delivered or the related services are performed. The Company estimates preclinical studies 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 the Company’s behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third party service providers and the Company’s estimates of accrued expenses and on information available at each balance sheet date. 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. There have been no significant changes from the Company’s original estimates in any of the periods presented. The Company received tax credits from the Australian government in connection with certain research costs incurred in conducting research by the Company’s Australian subsidiary. These refunds do not depend on the taxable income or tax position of the Company and therefore the Company does not account for them under an income tax accounting model. The Company recognizes such tax credits in the period when qualified expenses are incurred as a reduction of research expenses. The Company has recorded the reimbursement of $0.1 million, $0.1 million and $0.8 million from the Australian tax authorities as a reduction of research and development expense in the consolidated statements of operations and comprehensive loss in the years ended December 31, 2015, 2014 and 2013, respectively. Fair Value Measurements —Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The carrying amounts of the Company’s financial instruments, including cash and cash equivalents, prepaid and other current assets, accounts payable, accrued expenses and other warrant liabilities approximate its fair value due to their short-term maturities. Refer to Note 5 for the methodologies and assumptions used in valuing financial instruments. Stock-Based Compensation Expense —Stock-based compensation expense related to awards to employees is measured at the grant date based on the fair value of the award. The fair value of the award that is ultimately expected to vest is recognized as expense on a straight-line basis over the requisite service period, which is generally the vesting period. The expense recognized for the portion of the award that is expected to vest has been reduced by an estimated forfeiture rate. The forfeiture rate is determined at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The Company uses the Black-Scholes valuation model as the method for determining the estimated fair value of stock-based awards. Expected Term —The expected term assumption represents the period that the Company’s stock-based awards are expected to be outstanding and is determined using the simplified method. Expected Volatility —Expected volatility is estimated using comparable public companies volatility for similar terms. Expected Dividend —The Black-Scholes valuation model calls for a single expected dividend yield as an input. The Company has never paid dividends and has no plans to pay dividends. Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury zero-coupon issues in effect at the time of grant for periods corresponding with the expected term of option. Stock-based compensation expense related to awards to non-employees is recognized based on the then-current fair value at each measurement date over the associated service period of the award, which is generally the vesting term, using the accelerated attribution method. The fair value of non-employee stock options is estimated using the Black-Scholes valuation model with assumptions generally consistent with those used for employee stock options, with the exception of the expected term, which is the remaining contractual life at each measurement date. Refer to Note 12 for more information on assumptions used in estimated stock-based compensation expense. Income Taxes —The Company accounts for income taxes using the asset and liability method. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. In evaluating the ability to recover its deferred income tax assets, the Company considers all available positive and negative evidence, including its operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. In the event the Company determines that it would be able to realize its deferred income tax assets in the future in excess of their net recorded amount, it would make an adjustment to the valuation allowance that would reduce the provision for income taxes. Conversely, in the event that all or part of the net deferred tax assets are determined not to be realizable in the future, an adjustment to the valuation allowance would be charged to earnings in the period when such determination is made. As of December 31, 2015 and 2014, the Company has recorded a full valuation allowance on its deferred tax assets. Tax benefits related to uncertain tax positions are recognized when it is more likely than not that a tax position will be sustained during an audit. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax. Comprehensive Loss —Comprehensive loss is comprised of net loss, deemed dividend to a preferred stockholder and other comprehensive income (loss). Other comprehensive income (loss) consists of foreign currency translation adjustments related to translation of the financial statements of the Australian subsidiary and unrealized gain (loss) on marketable securities. The Company did not have reclassifications from other comprehensive income (loss) to the income (loss) during 2015. Basic and Diluted Net Loss Per Share —Basic net loss per common share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net loss per common share is computed by dividing the net loss by the weighted-average number of common shares and dilutive common share equivalents outstanding during the period. Because the Company has reported a net loss attributable to common stockholders for all periods presented, diluted net loss per common share is the same as basic net loss attributable to common stockholders per common share for those periods. While shares of the convertible preferred stock were outstanding they were considered to be participating securities as they were entitled to participate in undistributed earnings with shares of common stock. Due to net losses in all periods presented, there is no impact on net loss per share calculation in applying the two-class method since the participating securities have no legal requirement to share in any losses. Recently Issued Accounting Pronouncements —In August 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern , requiring management to evaluate whether events or conditions could impact an entity’s ability to continue as a going concern and to provide disclosures if necessary. Management will be required to perform the evaluation within one year after the date that the financial statements are issued. Disclosures will be required if conditions give rise to substantial doubt and the type of disclosure will be determined based on whether management’s plans will be able to alleviate the substantial doubt. The accounting standards update will be effective for the first annual period ending after December 15, 2016, and for annual periods and interim periods thereafter with early application permitted. The adoption of this ASU is not expected to impact the Company’s financial position or results of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , Revenue Recognition to December 15, 2017 for interim and annual reporting periods beginning after that date and permitted early adoption of the standard, but not before the original effective date of December 15, 2016 In April 2015, the FASB issued ASU No. 2015-05, Customer’s Accounting of Fees Paid in Cloud Computing Arrangement to arrangements entered into or materially modified after the effective date. In November 2015, FASB issued ASU No. 2015-17, Balance Sheet Classification of Deferred Taxes On January 5, 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities

Restructuring Charges

Restructuring Charges	12 Months Ended
	Dec. 31, 2015
Restructuring And Related Activities [Abstract]
Restructuring Charges	3. Restructuring Charges On December 22, 2015, the Company implemented a restructuring plan to reduce operating costs and better align its workforce with the needs of its business following its decision to not initiate the Phase 2b clinical trial for AVA-101 in the second half of 2015. The plan resulted in a reduction of approximately 20% of the Company’s workforce, or 15 employees. Affected employees are eligible to receive severance payments. The plan will also trigger accelerated vesting of certain of the affected employees’ restricted stock unit awards (RSUs). In connection with the restructuring, the Company estimates aggregate restructuring charges of approximately $2.6 million in the fourth quarter of 2015 related to one-time termination severance payments and other employee-related benefits, including approximately $1.0 million of stock-based compensation expense related to the acceleration of RSUs. The Company recorded the $2.6 million as restructuring charges on the consolidated statements of operations and comprehensive loss for the year ended December 31, 2015. The following table summarizes the restructuring activities for the year ended December 31, 2015 (in thousands): One-Time Termination Benefits Non-Cash Charge Related to Acceleration of RSUs Total Restructuring liability as of December 31, 2014 $ — $ — $ — Costs incurred and recorded as restructuring charges 1,524 1,049 2,573 Cash payments (511 ) — (511 ) Non-cash settlements — (1,049 ) (1,049 ) Restructuring liability as of December 31, 2015 $ 1,013 $ — $ 1,013 The remaining liability related to the plan as of December 31, 2015 was $1.0 million and is expected to be paid out in the first half of 2016.

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 2015
Cash And Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	4. Cash Equivalents and Marketable Securities The following is a summary of the cash equivalents and marketable securities: December 31, 2015 Amortized Cost Basis Unrealized Gains Unrealized Loses Estimated Fair Value Money Market Funds $ 208,588 $ — $ — $ 208,588 Certificates of Deposit 1,680 — — 1,680 U.S. Treasury Securities 15,046 — (4 ) 15,042 U.S. Government Agency Securities 21,012 — (2 ) 21,010 246,326 — (6 ) 246,320 Less: Cash Equivalents (208,588 ) — — (208,588 ) Total Marketable Securities $ 37,738 $ — $ (6 ) $ 37,732 The Company did not hold any available-for-sale securities as of December 31, 2014. As of December 31, 2015, the contractual maturities of the Company’s marketable securities were less than one year. Management determined that the gross unrealized losses of $6,000 on the Company’s marketable securities as of December 31, 2015 were temporary in nature. The Company currently does not intend to sell these securities prior to maturity and does not consider these investments to be other-than-temporarily impaired at December 31, 2015. There were no sales of available-for-sale securities in any of the periods presented.

Fair Value Measurements and Fai

Fair Value Measurements and Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements and Fair Value of Financial Instruments	5. Fair Value Measurements and Fair Value of Financial Instruments The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, 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 assets or liabilities. Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The fair value of Level 1 securities are determined using quoted prices in active markets for identical assets. Level 1 securities consist of highly liquid money market funds. Financial assets and liabilities are considered Level 2 when their fair values are determined using inputs that are observable in the market or can be derived principally from or corroborated by observable market data such as pricing for similar securities, recently executed transactions, cash flow models with yield curves, and benchmark securities. In addition, Level 2 financial instruments are valued using comparisons to like-kind financial instruments and models that use readily observable market data as their basis. U.S. Treasury securities, U.S. government agency securities and certificate of deposit are valued primarily using market prices of comparable securities, bid/ask quotes, interest rate yields and prepayment spreads and are included in Level 2. In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy. Level 3 liabilities that were measured at estimated fair value on a recurring basis consist of common and preferred stock warrant liabilities. The estimated fair values of the outstanding common and preferred stock warrant liabilities were measured using the Black-Scholes valuation model (refer to Note 11). Due to the nature of valuation inputs, the valuation of the warrants is considered a Level 3 measurement. The convertible preferred stock and common stock warrants were exercised immediately prior to the IPO, in August 2014. During the periods presented, the Company has not changed the manner in which it values liabilities that are measured at estimated fair value using Level 3 inputs. There were no transfers within the hierarchy during the years ended December 31, 2015, 2014 and 2013. The following table summarizes, for assets and liabilities recorded at fair value, the respective fair value and the classification by level of input within the fair value hierarchy as described above (in thousands): Quoted Prices Significant Other Significant Total In Observable Inputs Unobservable Inputs Carrying (Level 1) (Level 2) (Level 3) December 31, 2015 Assets: Money Market Funds $ 208,588 $ 208,588 $ — $ — Certificates of Deposit 1,680 — 1,680 — U.S. Treasury Securities 15,042 — 15,042 — U.S. Government Agency Securities 21,010 — 21,010 — Total Cash Equivalents and Marketable Securities $ 246,320 $ 208,588 $ 37,732 $ — December 31, 2014 Assets: Money Market Funds $ 40,000 $ 40,000 $ — $ — Total Cash Equivalents $ 40,000 $ 40,000 $ — $ — The following table provides a summary of changes in the estimated fair value of the Company’s warrants liabilities and embedded derivative liability measured at estimated fair value using significant Level 3 inputs (in thousands): Convertible Preferred Stock Common Stock Warrant Liability (1) Warrant Liability (2) Balance as of January 1, 2014 $ 91 $ 42 Issuance of common stock warrant — (41 ) Change in fair value 760 (1 ) Exercises (851 ) — Balance as of December 31, 2014 $ — $ — (1) In July 2014, all of the then outstanding warrants to purchase convertible preferred stock and common stock were exercised immediately prior to the completion of the IPO. (2) In March 2014, the common stock warrant was issued and was recorded to additional paid-in capital.

Significant Agreements

Significant Agreements	12 Months Ended
	Dec. 31, 2015
Research And Development [Abstract]
Significant Agreements	6. Significant Agreements University of California —In May 2010, the Company entered into a license agreement, as amended, with the Regents of University of California (Regents) for exclusive rights in the United States to certain patents owned by the Regents. Under the terms of the agreement, the Company paid an up-front license fee of $100,000 and agreed to reimburse the Regents for patent-related expenses. The Company is obligated to pay the Regents royalties on net sales, if any, as well as an annual maintenance fee of $50,000 beginning in the calendar year after the first commercial sale of a licensed product and milestone payments related to the achievement of certain clinical and regulatory goals totaling up to $900,000 for the first indication and $500,000 for each additional indication for up to two additional indications. Through December 31, 2015, none of these goals had been achieved, and no milestones were payable.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Property and Equipment, Net	7. Property and Equipment, Net Property and equipment, net consists of the following (in thousands): December 31, 2015 December 31, 2014 Computer equipment and software $ 234 $ 142 Laboratory equipment 3,041 1,012 Furniture and fixtures 552 73 Leasehold improvements 351 48 Total property and equipment 4,178 1,275 Less accumulated depreciation and amortization (991 ) (190 ) Property and equipment, net $ 3,187 $ 1,085 Depreciation and amortization expense related to property and equipment was $812,000, $162,000 and $26,000 for the years ending December 31, 2015, 2014 and 2013, respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	8. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following (in thousands): December 31, 2015 December 31, 2014 Employees' compensation $ 2,047 $ 1,509 Accrued preclinical costs 642 1,005 Accrued professional fees 1,177 231 Accrued clinical and process development costs 101 942 Other 40 20 Total accrued expenses and other current liabilities $ 4,007 $ 3,707

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Facility Lease Agreement The Company leases its’ office building under a non-cancelable lease agreement, which expires on May 8, 2020. The Company may extend this lease for up to four years. The lease agreement provides for an escalation of rent payments each year. The Company records rent expense on a straight-line basis over the term of the lease. As of December 31, 2015, future minimum commitments under the Company’s facility operating lease were as follows (in thousands): YEARS ENDED DECEMBER 31, 2015 TOTAL LEASE COMMITMENTS 2016 $ 1,099 2017 1,129 2018 1,162 2019 1,197 2020 403 Total minimum lease payments $ 4,990 Rent expense recognized under the operating lease, including additional rent charges for utilities, parking, maintenance, and real estate taxes was $1,525,000, $662,000 and $53,000 for the years ended December 31, 2015, 2014 and 2013, respectively. Collaborations and License Agreements The Company is party to various agreements, principally relating to licensed technology that requires future payments relating to milestones or royalties on future sales of specified products. Through December 31, 2015, none of the goals had been achieved under the license agreements and no milestones were accrued or payable. Because the achievement of these milestones is not fixed and determinable, such commitments have not been included on the Company’s consolidated balance sheets. Aggregate annual maintenance fee’s payments were approximately $0.1 million for each of the years ended December 31, 2015 and 2014. Guarantees and Indemnifications In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for indemnification for certain liabilities. The 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. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. The Company also has indemnification obligations to its directors and executive officers for specified events or occurrences, subject to some limits, while they are serving at the Company’s request in such capacities. There have been no claims to date and the Company believes the fair value of these indemnification agreements is minimal. Accordingly, the Company has not recorded any liabilities for these agreements as of December 31, 2015. Legal Proceedings From time to time, the Company may become involved in litigation and other legal actions. The Company estimates the range of liability related to any pending litigation where the amount and range of loss can be estimated. The Company records its best estimate of a loss when the loss is considered probable. Where a liability is probable and there is a range of estimated loss with no best estimate in the range, the Company records a charge equal to at least the minimum estimated liability for a loss contingency when both of the following conditions are met: (i) information available prior to issuance of the financial statements indicates that it is probable that a liability had been incurred at the date of the financial statements and (ii) the range of loss can be reasonably estimated. In July 2015, three putative securities class action lawsuits were filed against the Company and certain of its officers in the United States District Court for the Northern District of California, each on behalf of a purported class of persons and entities who purchased or otherwise acquired the Company’s publicly traded securities between July 31, 2014 and June 15, 2015. The lawsuits assert claims under the Exchange Act and Securities Act and allege that the defendants made materially false and misleading statements and omitted allegedly material information related to, among other things, the Phase 2a clinical trial for AVA-101 and the prospects of AVA-101. The complaints seek unspecified damages, attorneys’ fees and other costs. In December 2015, a putative securities class action lawsuit was filed against the Company, the Company’s board of directors, underwriters of the Company’s January 13, 2015, follow-on public stock offering, and two of the Company’s institutional stockholders, in the Superior Court of the State of California for the County of San Mateo. The complaint alleges that, in connection with the Company’s follow-on stock offering, the defendants violated the Securities Act of 1933, as amended, by allegedly making materially false and misleading statements and by allegedly omitting material information related to the Phase 2a clinical trial for AVA-101 and the prospects of AVA-101. The complaint seeks unspecified compensatory and rescissory damages, attorneys’ fees and other costs. The Company believes that the claims in the asserted actions are without merit and intend to defend the lawsuits vigorously. The Company expects to incur costs associated with defending the actions. While the Company has various insurance policies related to the risks associated with its business, including directors’ and officers’ liability insurance policies, there is no assurance that the Company will be successful in its defense of the actions, that its insurance coverage, which contains a self-insured retention, will be sufficient, or that its insurance carriers will cover all claims or litigation costs. Due to the inherent uncertainties of litigation, the Company cannot reasonably predict at this time the timing or outcomes of these matters or estimate the amount of losses, or range of losses, if any, or their effect, if any, on its consolidated financial statements.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Convertible Preferred Stock	10. Convertible Preferred Stock In connection with the completion of the IPO in August 2014, all outstanding shares of Series A and Series B convertible preferred stock were converted into 10,689,027 shares of common stock on a one-for-one basis. In November 2013, the Company converted then outstanding convertible note into series A convertible preferred stock and recorded a $1.7 million loss on extinguishment of related-party convertible notes in the consolidated statement of operations and comprehensive loss. The Company also recorded a charge of $0.8 million associated with the intrinsic value of the convertible preferred Series A shares issued to a potential collaborator, which was recorded in general and administrative expense in the consolidated statements of operations and comprehensive loss for the year ended December 31, 2013. In April 2014, the Company completed a Series B convertible preferred stock financing, pursuant to which then outstanding convertible notes were converted into 295,115 shares of Series B convertible preferred stock at a conversion price of $6.78, which was equal to 90% of the original issuance price of $7.53 per share. At the time of the conversion, the Company recorded a $0.2 million loss on extinguishment of related-party convertible notes in the consolidated statements of operations and comprehensive loss and a repurchase of beneficial conversion feature of $2.0 million as credit to additional paid-in capital. In April 2014, the Company repurchased 531,208 shares of Series A convertible preferred stock for $4.0 million. The difference between the repurchase price of $7.53 and original issuance price of $1.45 was recorded as a deemed dividend of $3.2 million to a preferred stockholder and effected the calculation of net loss attributable to common stockholders and net loss per share for the year ended December 31, 2014.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Warrants	11. Warrants In connection with an amendment to the Lions Eye Institute (LEI) research agreement in August 2012 the Company agreed to issue to LEI a warrant to purchase 25,000 shares of common stock. The Company estimated the fair value of the obligation to issue this warrant to be approximately $5,000, which was recorded as research and development expense and common stock warrant liability. Until the Company issued the warrant, it classified it as a common stock warrant liability and re-measured the fair value at the end of each reporting period. In March 2014, the Company issued the common stock warrant to LEI with an exercise price of $2.75 per share, at which time the issued common stock warrant was reclassified to additional paid-in capital. In May 2014, the Company issued a warrant to purchase 63,415 shares of common stock with an exercise price of $6.83 to a financial services firm in connection with the Series B convertible preferred stock financing completed in April 2014. This warrant was exercisable immediately and expired on the earlier of the Company’s IPO or May 15, 2019. The Company estimated the fair value of this warrant to be approximately $0.3 million which was recorded as expenses related to issuance of Series B convertible preferred stock. The fair value of the warrant was calculated using the Black-Scholes valuation model, and was based on the common stock fair value of $6.83 per share, contractual term of the warrant of 5 years, a risk-free interest rate of 1.55%, an expected volatility of 75% and a 0% expected dividend yield. All of the above warrants to purchase common stock and preferred stock were exercised for cash of $0.6 million prior to the completion of the IPO in August 2014. As a result of the exercises of the warrants to purchase preferred stock, the Company recorded a $0.8 million loss related to the change in fair value in the Company’s consolidated statements of operations and comprehensive loss and reclassified the fair value of $0.9 million to permanent equity. The fair value of the warrants to purchase preferred stock was calculated using the Black-Scholes valuation model, and was based on the common stock fair value of $17.00 per share, contractual term of the warrants of 1.1 years, a risk-free interest rate of 0.1%, an expected volatility of 70% and a 0% expected dividend yield. On October 15, 2015, in connection with an amendment to the research agreement between the Company and the LEI, the Company issued to LEI a warrant to purchase 40,000 shares of common stock with an exercise price of $10.51 per share. This common stock warrant is exercisable immediately, and expires on October 15, 2020. The Company estimated the fair value of this warrant to be approximately $0.2 million which was recorded as debit to research and development expenses and credit to additional paid-in capital upon issuance. The fair value of the warrant was calculated using the Black-Scholes valuation model, and was based on the closing price of common stock on the issuance date of $8.35 per share, exercise price of $10.51, contractual term of the warrant of 5 years, a risk-free interest rate of 1.34%, an expected volatility of 75% and a 0% expected dividend yield. The amendment also provides for the issuance of an additional warrant to LEI to purchase up to 40,000 shares of the Company's common stock upon completion of the 36 month follow-up on the Phase 2a AVA-101 clinical study (Contingent Warrant). As of December 31, 2015, none of the shares subject to the Contingent Warrant were vested and exercisable. The Company is accounting for this warrant as a stock-based award issued for service and estimated the fair value of the costs associated with the service performed to be approximately $30,000 which was recorded as debit to research and development expenses and credit to additional paid-in capital in 2015. The fair value of the Contingent Warrant was calculated using the Black-Scholes valuation model, and was based on the closing price of common stock on December 31, 2015 of $9.52 per share, expected term of the warrants of 6.6 years, a risk-free interest rate of 1.1%, an expected volatility of 79% and a 0% expected dividend yield.

Stock Option Plans

Stock Option Plans	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option Plans	12. Stock Option Plans On December 26, 2006, the Company adopted the 2006 Equity Incentive Plan, which was amended by the board of directors on November 15, 2012 (2006 Plan). The 2006 Plan allowed for the granting of ISOs and NSOs to the employees, members of the board of directors and consultants of the Company. ISOs were granted only to the Company’s employees, including officers and directors who are also employees. NSOs were granted to the employees and consultants. In July 2014, the Company’s board of directors and its stockholders approved the establishment of the 2014 Equity Incentive Award Plan (2014 Plan), effective upon the date upon which the registration statement for the IPO was declared effective, which was July 30, 2014. As of the date of the IPO, the Company reserved for issuance under the 2014 Plan a total of 2,088,332 shares of its common stock, plus any additional shares that would otherwise return to the 2006 Plan as a result of forfeiture, termination or expiration of awards previously granted under the 2006 Plan. Options may no longer be issued under the 2006 Plan after July 30, 2014. In addition, the 2014 Plan provides for annual increases in the number of shares available for issuance thereunder on the first business day of each fiscal year, beginning with 2015, equal to four percent (4%) of the number of shares of the Company’s common stock outstanding as of such date or a lesser number of shares as determined by the Company’s board of directors. As of December 31, 2015, a total of 8,454,368 shares of common stock were authorized for issuance and 2,137,787 shares were available for future grants under the 2014 Plan. Options under the 2014 Plan may be granted for periods of up to 10 years and at prices no less than 100% of the estimated fair value of the shares on the date of grant as determined by the board of directors, provided, however, that the exercise price of an ISO and NSO granted to a 10% stockholder may not be less than 110% of the estimated fair value of the shares on the date of grant. Options granted to employees and non-employees generally vest ratably over four years. In July 2014, the Company’s board of directors and its stockholders approved the establishment of the 2014 Employee Stock Purchase Plan (2014 ESPP). The Company reserved for issuance 208,833 shares of its common stock and provided for annual increases in the number of shares available for issuance on the first business day of each fiscal year, beginning in 2015, equal to the lesser of one percent (1%) of the number of shares of the Company’s common stock outstanding as of such date or a number of shares as determined by the Company’s board of directors. During 2015, 19,577 shares were issued under the 2014 ESPP. A total of 416,796 shares of common stock have been reserved for issuance under the 2014 ESPP and were available for issuance under the 2014 ESPP as of December 31, 2015. As of December 31, 2015, there was $0.1 million of unrecognized compensation cost related to the ESPP, which is expected to be recognized over a weighted-average period of 0.4 years. The following table summarizes option activity under the Company’s stock plans and related information: WEIGHTED- NUMBER OF WEIGHTED- AVERAGE REMAINING AGGREGATE SHARE AVERAGE EXERCISE CONTRACTUAL LIFE INTRINSIC VALUE (a) (IN THOUSANDS) PRICE (IN YEARS) (IN THOUSANDS) Balance at January 1, 2015 4,932 $ 5.61 8.2 $ 238,653 Options granted 1,603 $ 21.91 Options exercised (400 ) $ 0.47 Options cancelled (641 ) $ 22.77 Balance at December 31, 2015 5,494 $ 8.75 7.8 28,618 Vested and expected to vest as of December 31, 2015 5,447 $ 8.64 7.8 28,524 Exercisable as of December 31, 2015 2,818 $ 3.45 6.9 21,978 (a) The aggregate intrinsic value is calculated as the difference between the options exercise price and the closing price of common stock of $9.52 per share as of December 31, 2015. In December 2015, the Company granted a stock option to purchase 910,000 shares of common stock shares to its new Chief Executive Officer. The option was granted as an inducement grant and outside of the 2014 Plan. The total intrinsic value of options exercised during the year ended December 31, 2015 and 2014 were $11.2 million and $15.7 million, respectively. There were no options exercised in 2013. The following table summarizes information with respect to stock options outstanding and currently exercisable and vested. As of December 31, 2015: OPTIONS OUTSTANDING OPTIONS EXERCISABLE AND VESTED WEIGHTED- WEIGHTED- NUMBER AVERAGE REMAINING NUMBER AVERAGE REMAINING RANGE OF OUTSTANDING CONTRACTUAL LIFE OUTSTANDING CONTRACTUAL LIFE EXERCISE PRICES (IN THOUSANDS) (IN YEARS) (IN THOUSANDS) (IN YEARS) $0.15-$0.27 2,644 6.5 2,156 6.4 $0.28-$2.95 429 8.1 190 8.1 $2.96-$11.50 1,284 9.5 193 8.4 $11.51-$35.00 707 8.8 243 8.7 $35.01-$58.92 430 9.2 36 9.0 The Company has recorded aggregate stock-based compensation expense related to the issuance of stock option awards to employees and nonemployees in the consolidated statement of operations and comprehensive loss as follows: (in thousands) YEARS ENDED DECEMBER 31 2015 2014 2013 Research and development $ 4,009 $ 7,331 $ 362 General and administrative 6,447 1,236 153 Restructuring charges 1,049 — — Total share-based compensation $ 11,505 $ 8,567 $ 515 Departure of Key Executive Officer Effective July 23, 2015, Thomas W. Chalberg, Jr., Ph.D., resigned as the Chief Executive Officer and President of the Company and as a member of the board of directors. In connection with Dr. Chalberg’s resignation and his engagement as a consultant and Scientific Advisor, Dr. Chalberg and the Company entered into a Separation Agreement and General Release, dated July 23, 2015 (the Separation Agreement). Under the Separation Agreement, Dr. Chalberg is providing consulting services to the Company and serving as a member of the Company’s Scientific Advisory Board until the first anniversary of July 23, 2015 (the consulting period). During the consulting period, subject to the terms and conditions of the Separation Agreement, Dr. Chalberg is paid a monthly fee at the same rate as his salary in effect prior to his resignation and is continuing to vest in outstanding equity awards held by him at the same rates in effect for such awards prior to his resignation. Shares of the Company’s common stock subject to his outstanding equity awards that were otherwise scheduled to vest following the expiration of the consulting period will not vest under any circumstances and were forfeited and cancelled on July 23, 2015. As a result, the Company recorded a one-time share-based payment charge of $2.4 million related to the cancellation of unvested stock options in July 2015. Restricted Stock Units (RSUs) RSUs are share awards that entitle the holder to receive freely tradable shares of the Company’s common stock upon vesting. The fair value of RSUs is based upon the closing sales price of the Company’s common stock on the grant date. RSUs granted to employees generally vest over a two-to-four year period. The following table summarizes the RSUs activity under the Company’s stock plans and related information: Weighted-Average Number of Grant-Date Shares (in thousands) Fair Value (in dollars) Outstanding at December 31, 2014 — $ — Granted 851 $ 13.85 Vested and released (132 ) $ 10.52 Forfeited (87 ) $ 24.21 Outstanding at December 31, 2015 632 $ 13.07 There were no RSUs granted prior to April 2015. The total fair value of RSUs that vested was $1.4 million for the year ended December 31, 2015. The number of restricted stock units vested includes shares of common stock that we withheld on behalf of employees to satisfy the minimum statutory tax withholding requirements. As of December 31, 2015, there was $6.2 million of unrecognized compensation cost related to unvested RSUs that we expect to recognize over a weighted-average period of 2.0 years. Stock Options Granted to Employees For the years ended December 31, 2015, 2014 and 2013, the Company recorded $11,764,000, $1,672,000 and $136,000, respectively, of stock-based compensation expense related to employees options. The fair value of each option issued to employees was estimated at the date of grant using the Black-Scholes valuation model with the following weighted-average assumptions: Options Employee Stock Purchase Plan YEARS ENDED DECEMBER 31 YEARS ENDED DECEMBER 31 2015 2014 2013 2015 2014 2013 Expected volatility 79 % 79 % 80 % 74 % — — Expected term (in years) 6.1 6.0 6.0 0.5 — — Expected dividend yield — — — — — — Risk-free interest rate 1.7 % 1.9 % 1.0 % 0.1 % — — The weighted-average fair values of options granted during fiscal years 2015, 2014 and 2013 were $15.91, $9.56 and $0.37, respectively. As of December 31, 2015, there was $14.2 million of unrecognized stock-based compensation expense related to employees’ awards that is expected to be recognized over a weighted-average period of 2.7 years. Stock Options Granted to Non-Employees Stock-based compensation expense related to stock options granted to nonemployees is recognized as the stock options are earned. The Company believes that the estimated fair value of the stock options is more readily measurable than the fair value of the services rendered. For the years ended December 31, 2015, 2014 and 2013, the Company recorded $(259,000), $6,895,000 and $379,000, respectively, of stock-based compensation expense related to non-employees options. We used the following weighted-average assumptions in estimating non-employees stock-based compensation expense: YEARS ENDED DECEMBER 31 2015 2014 2013 Option grants: Expected volatility 81 % 79 % 79 % Expected term (in years) 3.3 7.5 7.9 Expected dividend yield — — — Risk-free interest rate 1.0 % 2.2 % 1.8 % As of December 31, 2015, there was $1.1 million of unrecognized stock-based compensation expense related to non-employees’ awards that is expected to be recognized over a weighted-average period of 1.5 years. Fair Value of Common Stock In determining the exercise prices for options granted, the Company’s board of directors has considered the fair value of the common stock as of each grant date. Prior to the IPO, the fair value of the common stock underlying the stock options was determined by the board of directors at each award grant date based upon a variety of factors, including the results obtained from an independent third party valuation, the Company’s financial position and historical financial performance, the status of technological developments within the Company’s products, the composition and ability of the current management team, an evaluation or benchmark of the Company’s competition, the current business climate in the marketplace, the illiquid nature of the common stock, arm’s-length sales of the Company’s capital stock (including convertible preferred stock), the effect of the rights and preferences of the preferred stockholders and the prospects of a liquidity event, among others. After the completion of the Company’s IPO in August 2014, the fair value of the common stock is based on the closing price of the common stock on the date of grant.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2015
Postemployment Benefits [Abstract]
401(k) Savings Plan	13. 401(k) Savings Plan The Company established a defined-contribution savings plan under Section 401(k) of the Code. The 401(k) Plan covers all employees who meet defined minimum age and service requirements, and allows participants to defer a portion of their annual compensation on a pretax basis. The amount of contributions that the Company made to the 401(k) Plan during the year ended December 31, 2015 and 2014 was $0.1 million and $25,000, respectively

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes No income tax benefit or expense was recorded for the years ended December 31, 2015, 2014 and 2013. The following table presents domestic and foreign components of loss before provision for income taxes (in thousands): FOR THE YEARS ENDED DECEMBER 31, 2015 2014 2013 U.S. $ (47,235 ) $ (25,006 ) $ (5,031 ) Foreign (218 ) (398 ) (245 ) Loss before income taxes $ (47,453 ) $ (25,404 ) $ (5,276 ) A reconciliation of income tax expense computed at the statutory federal income tax rate of 34% to income taxes as reflected in the financial statements is as follows (in thousands): FOR THE YEARS ENDED DECEMBER 31, 2015 2014 2013 Federal income tax expense at statutory rate $ (16,134 ) $ (8,637 ) $ (1,794 ) Loss on extinguishment of related-party convertible notes — 69 568 Non-deductible foreign research expenses 45 85 26 Non-deductible stock compensation 1,418 161 46 Non-deductible expenses 295 285 28 Research and development tax credits (910 ) (304 ) (93 ) Change in valuation allowance 15,277 8,349 1,209 Foreign rate differential 9 (8 ) 10 Total tax expense (benefit) $ — $ — $ — Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The following table presents significant components of the Company’s deferred tax assets (in thousands): AS OF DECEMBER 31, 2015 2014 2013 Deferred tax assets: Net operating loss carryforwards $ 19,889 $ 8,526 $ 1,876 Accruals, reserve and other 2,681 222 109 Stock-based compensation 4,328 3,032 183 Tax credit carryforwards 1,945 659 145 Property and equipment — — 2 Intangibles 45 24 223 Other — 24 (1 ) Total deferred tax assets before valuation allowance 28,888 12,487 2,537 Valuation allowance (28,839 ) (12,457 ) (2,537 ) Total deferred tax assets 49 30 — Deferred tax liabilities: Property and equipment (49 ) (30 ) — Total deferred tax liabilities (49 ) (30 ) — Net deferred tax assets $ — $ — $ — The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets. Based on the Company’s history of operating losses, the Company has concluded that it is more likely than not that the benefit of its deferred tax assets will not be realized. Accordingly, the Company has provided a full valuation allowance for deferred tax assets as of December 31, 2015, 2014 and 2013. The valuation allowance increased approximately $16.4 million, $9.9 million and $1.4 million during the years ended December 31, 2015, 2014 and 2013, respectively, due to net operating losses. As of December 31, 2015, the Company had U.S. federal NOL carryforwards of approximately $79.4 million to offset future federal income. NOLs expire at various years beginning with 2026. As of December 31, 2015, the Company also had U.S. state NOL carryforwards of approximately $56.5 million to offset future state income. U.S. State NOLs expire at various years beginning with 2016. At December 31, 2015, the Company also had approximately $0.2 million of foreign net operating loss carryforwards which may be available to offset future foreign income; these carryforwards do not expire. As a result of certain realization requirements of Accounting Standard Codification Topic 718, Compensation – Stock Compensation As of December 31, 2015, the Company had federal research and development tax credit carryforwards of approximately $1.9 million available to reduce future tax liabilities which expire at various years beginning with 2032. As of December 31, 2015, the Company had state credit carryforwards of approximately $1.7 million available to reduce future tax liabilities which do not expire. Under Section 382 of the Internal Revenue Code of 1986, as amended (Code), the Company’s ability to utilize NOL carryforwards or other tax attributes, such as research tax credits, in any taxable year may be limited if we have experienced an “ownership change.” Generally, a Section 382 ownership change occurs if there is a cumulative increase of more than 50 percentage points in the stock ownership of one or more stockholders or groups of stockholders who owns at least 5% of a corporation’s stock within a specified testing period. Similar rules may apply under state tax laws. We believe that we have experienced at least two ownership changes under Section 382, which will result in limitations in the Company’s ability to utilize net operating losses and credits. In addition, we may experience ownership changes as a result of the Company’s initial public offering in August 2014, future offerings or other changes in the ownership of the Company’s stock. As a result, the amount of the NOLs and research and credit carryforwards presented in the Company’s financial statements could be limited and may expire unutilized. The Company files income tax returns in the United States, and state and foreign jurisdictions. The federal, state and foreign income tax returns are open under the statute of limitations subject to tax examinations for the tax years ended December 31, 2011 through December 31, 2015. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service, state or foreign tax authorities to the extent utilized in a future period. The Company has total unrecognized tax benefits as of December 31, 2015, 2014 and 2013 of approximately $1,568,000, $471,000 and $43,000 respectively. No amount of the unrecognized tax benefits, if recognized, would reduce the Company’s annual effective tax rate because the benefits are in the form of deferred tax assets for which a full valuation allowance has been recorded. The Company does not anticipate a significant change to its unrecognized tax benefits over the next twelve months. A reconciliation of the unrecognized tax benefits is as follows (in thousands): FOR THE YEARS ENDED DECEMBER 31, 2015 2014 2013 Unrecognized tax benefits as of the beginning of the year $ 471 $ 43 $ 5 Increase related to prior year tax provisions 172 272 7 Increase related to current year tax provisions 925 156 31 Unrecognized tax benefits as of the end of the year $ 1,568 $ 471 $ 43 The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2015 and 2014, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s consolidated statements of operations and comprehensive loss. There are no ongoing examinations by taxing authorities at this time.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Loss Per Share	15. Net Loss Per Share The following table sets forth the computation of the basic and diluted net loss per share for the years ended December 31, 2015, 2014 and 2013 (in thousands, except per share data): FOR THE YEARS ENDED DECEMBER 31, 2015 2014 2013 Net loss $ (47,453 ) $ (25,404 ) $ (5,276 ) Deemed dividend — (3,230 ) — Net loss attributable to common stockholders (47,453 ) (28,634 ) (5,276 ) Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share: Net shares outstanding 25,479 11,651 3,673 Basic and diluted net loss per share attributable to common stockholders $ (1.86 ) $ (2.46 ) $ (1.44 ) The following common stock equivalents outstanding at the end of the periods presented were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: AS OF DECEMBER 31, 2015 2014 2013 Options to purchase common stock 5,494 4,932 3,640 RSUs 632 — — Warrants to purchase common stock 40 — 264 Series A preferred stock — — 3,899 Warrants to purchase preferred stock — — 55 6,166 4,932 7,858

Selected Quarterly Financial In

Selected Quarterly Financial Information	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Information	16. Selected Quarterly Financial Information (Unaudited) The following amounts are in thousands, except per share amounts: Quarterly Results of Operations Quarter End March 31, 2015 June 30, 2015 September 30, 2015 December 31, 2015 (In thousands, except per share amounts) Revenue $ 203 $ 203 $ 953 $ 960 Total operating expenses (2)(3) $ (9,764 ) $ (10,085 ) $ (15,154 ) $ (15,139 ) Net loss $ (9,509 ) $ (9,766 ) $ (14,084 ) $ (14,094 ) Basic and diluted net loss per share $ (0.38 ) $ (0.38 ) $ (0.55 ) $ (0.55 ) Quarterly Results of Operations Quarter End March 31, 2014 June 30, 2014 September 2014 December 2014 (In thousands, except per share amounts) Revenue $ 30 $ 135 $ 204 $ 203 Total operating expenses $ (1,636 ) $ (4,588 ) $ (8,144 ) $ (10,606 ) Net loss $ (1,663 ) $ (5,094 ) $ (8,256 ) $ (10,391 ) Deemed dividend (1) $ — $ (3,230 ) $ — $ — Net loss attributable to common stockholders $ (1,663 ) $ (8,324 ) $ (8,256 ) $ (10,391 ) Basic and diluted net loss per share $ (0.45 ) $ (2.27 ) $ (0.50 ) $ (0.46 ) (1) In April 2014, we repurchased 531,208 shares of Series A convertible preferred stock for $4.0 million. The difference between the repurchase price of $7.53 per share and original issuance price of $1.45 per share was recorded as a deemed dividend of $3.2 million to a preferred stockholder and effected the calculation of net loss attributable to common stockholders and net loss per share for the year ended December 31, 2014. (2) In connection with the restructuring, the Company recorded estimated restructuring charges of approximately $2.6 million related to one-time termination severance payments and other employee-related benefits, including approximately $1.0 million of stock-based compensation expense related to the acceleration of RSUs in December 2015. (3) In July 2015, the Company’s then Chief Executive officer resigned and some of his stock-based awards were forfeited and cancelled, which that resulted in a $2.4 million of additional stock-based compensation expense recorded in general and administrative expenses in the Company’s consolidated financial statements. Basic and diluted net loss per share is computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted per share amounts may not equal annual basic and diluted net loss per share amounts.

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Event	17. Subsequent Event Proposed Transaction with Annapurna Therapeutics SAS On January 29, 2016, the Company entered into a definitive agreement (the Agreement) with Annapurna Therapeutics SAS (Annapurna), a privately-held biopharmaceutical company focused on advancing gene therapy for unmet medical needs, certain shareholders of Annapurna (the Contributors), and Shareholder Representative Services LLC, a Colorado limited liability company, acting as the representative of the Contributors. Upon the terms and subject to the conditions described in the Agreement, the Company will acquire all of the issued and outstanding capital stock of Annapurna in exchange for approximately 13.1 million newly issued shares of the Company’s common stock. The outstanding options or other rights to purchase capital stock of Annapurna (Annapurna Options) will be converted into options relating to approximately 4.7 million shares of the Company’s common stock (Company Options). Each Company Option will relate to the whole number of shares of Company’s common stock (rounded down to the nearest whole share) equal to the number of the shares of the common stock of Annapurna subject to such Annapurna Option multiplied by 9.5615 (as may be adjusted pursuant to the Agreement, the Exchange Ratio). Each Company Option will have substantially the same terms, including the same termination date and vesting schedule, as the Annapurna Option for which it is being exchanged, and the exercise price per share for such Company Option will be equal to the exercise price per share of such Annapurna Option divided by the Exchange Ratio. The transaction requires the Company’s stockholders’ vote and is expected to close in the second quarter of 2016. The Agreement may be terminated by either party under certain circumstances as defined in the Agreement, including, among others, if the closing of the acquisition has not occurred by the six-month anniversary of the execution of the Agreement, subject to certain exceptions, or if the Company’s stockholders fail to approve the issuance of the Company’s stock (Company Stock Issuance). The Agreement provides for the Company to pay to Annapurna a reverse termination fee of $4,000,000 if the Agreement is terminated by either party for the Company’s failure to obtain the required vote of the Company’s stockholders for the Company Stock Issuance or if the Agreement is terminated by Annapurna upon a certain defined triggering event. The Agreement also provides for the Company to pay to Annapurna termination fee of $6,000,000 (less the $4,000,000 termination fee described above, if paid) if the Agreement is terminated by either party for the failure to obtain the required vote of the Company’s stockholders or by Annapurna upon certain other triggering events, and either (x) the Company consummates within twelve months of such termination an alternative transaction that was publicly announced or communicated in writing to the Company’s board of directors prior to such termination or (y) the Company consummates within six months of such termination an alternative transaction that is first publicly announced or otherwise communicated in writing to the Company’s board of directors following the termination of the Agreement while an alternative transaction described in the foregoing clause (x) remains outstanding and not withdrawn.

Summary of significant accoun25

Summary of significant accounting policies and basis of presentation (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates —The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (U.S. GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to clinical trial accruals, stock-based compensation, income taxes, fair value of common stock warrant and, prior to the IPO, fair value of embedded derivative liability, fair value of convertible preferred stock and fair values of common and convertible preferred stock warrants. The Company’s actual results may differ from these estimates under different assumptions or conditions. There have been no significant changes from the Company’s original estimates in any periods presented.
Principles of Consolidation	Principles of Consolidation —The Company’s consolidated financial statements have been prepared in accordance with U.S. GAAP and include the accounts of the Company and its wholly-owned subsidiary in Australia. All intercompany transactions and balances have been eliminated in consolidation.
Foreign Currency Translation	Foreign Currency Translation —The Company’s consolidated financial statements are prepared in U.S. dollars. Its foreign subsidiary uses the Australian dollar as its functional currency and maintains its records in the local currency. Assets and liabilities are re-measured at exchange rates in effect at the end of the reporting period. Equity is measured at historical rates and income and expenses are re-measured at average exchange rates for the reporting period. The resulting foreign currency translation adjustment is recorded in accumulated other comprehensive (loss) income in the consolidated balance sheets and in the consolidated statements of operations and comprehensive loss. Transactions denominated in foreign currency are translated at exchange rates at the date of transaction with foreign currency gains (losses) recorded in other income (expense), net in the consolidated statements of operations and other comprehensive loss.
Cash and Cash Equivalents	Cash and Cash Equivalents —The Company considers all highly liquid investments purchased with original maturities of three months or less at the date of purchase to be cash equivalents. Cash and cash equivalents include cash held in banks and money market accounts. Cash equivalents are stated at fair value.
Marketable Securities	Marketable Securities —All marketable securities, which consist of debt securities and certificates of deposit, have been classified as “available for sale” and are carried at fair value. Unrealized gains and losses, net of any related tax effects, are excluded from earnings and are included in other comprehensive loss and reported as a separate component of stockholders’ equity until realized. Realized gains and losses and declines in value judged to be other than temporary, if any, on available-for-sale securities are included in other income (expense), net. The cost of securities sold is based on the specific-identification method. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Interest on short-term investments is included in interest income. In accordance with the Company’s investment policy, management invests to diversify credit risk and only invests in securities with high credit quality, including U.S. government securities. The Company regularly evaluates whether declines in the fair value of its investments below their cost are other than temporary. The evaluation includes consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities, and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. If the Company determines that the decline in fair value of an investment is below its accounting basis and this decline is other than temporary, the Company would reduce the carrying value of the security it holds and records a loss for the amount of such decline. The Company has not recorded any realized losses or declines in value judged to be other than temporary on its investments.
Deposit	Deposit —Deposit in the amount of $0.1 million as of December 31, 2015 and 2014 represents amounts paid in connection with the Company’s facility lease agreement and recorded as a long-term asset.
Segment Reporting	Segment Reporting —The Company operates and manages its business as one reporting and operating segment, which is the business of developing and commercializing gene therapeutics. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance.
Concentrations of Credit Risk and Other Uncertainties	Concentrations of Credit Risk and Other Uncertainties —Financial instruments that potentially subject us to significant concentrations of credit risk consists primarily of cash and cash equivalents. As of December 31, 2015, substantially all of the Company’s cash and cash equivalents was deposited in accounts at four financial institutions, and amounts may exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of the depository institutions in which the financial instrument are held. The Company is subject to certain risks and uncertainties, including, but not limited to changes in any of the following areas that the Company believes could have a material adverse effect on future financial position or results of operations: ability to obtain future financing; regulatory approval and market acceptance of, and reimbursement for, the Company’s product candidates; performance of third-party clinical research organizations and manufacturers; development of sales channels; protection of the intellectual property; litigation or claims against the Company based on intellectual property, patent, product, regulatory or other factors; and the Company’s ability to attract and retain employees necessary to support the growth.
Property and Equipment	Property and Equipment —Property and equipment are recorded at cost, net of accumulated depreciation and amortization. Depreciation is recorded using the straight-line method over the estimated useful lives of the assets, generally three to five years. Leasehold improvements are capitalized and amortized over the shorter period, expected life or lease term. Major replacements and improvements are capitalized, while general repairs and maintenance are expensed as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets —The Company evaluates the carrying amount of its long-lived assets whenever events or changes in circumstances indicate that the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition is less than the carrying amount of the asset. To date, there have been no such impairment losses.
Deferred Offering Costs	Deferred Offering Costs —The Company capitalizes deferred offering costs, which primarily consist of direct incremental legal and accounting fees relating to its public offerings. The Company offsets the deferred offering costs against its public offering proceeds upon the consummation of its public offerings. As of December 31, 2015 and 2014, $0 and $0.4 million of deferred offering costs were capitalized in deposit and other long-term assets on the Company’s consolidated balance sheets, respectively.
Derivative Instruments	Derivative Instruments —The Company had recorded convertible preferred stock warrants issued to investors and note holders as derivative liabilities. The convertible preferred stock warrants were initially recorded at fair value, with gains and losses arising from changes in fair value recognized in other income (expense) in the consolidated statements of operations and comprehensive loss at each period end while such instruments were outstanding and classified as long-term liabilities. In connection with the completion of the Company’s IPO in August 2014, all of the then outstanding warrants to purchase convertible preferred stock were exercised. As a result of the exercises, the Company recorded a $0.8 million loss related to the change in fair value in the Company’s consolidated statements of operations and comprehensive loss and reclassified the fair value of $0.9 million to additional paid-in capital. The Company had also recorded as a derivative liability the Company’s obligation to issue common stock warrants in connection with license agreements as the terms of the warrants were not fixed due to potential adjustments in the exercise price. The derivative liability associated with the common stock warrants was initially recorded at fair value, with gains and losses arising from changes in fair value recognized in the consolidated statements of operations and comprehensive loss at each period end while such instruments are classified as liabilities. In March 2014, the liability terminated upon the issuance of common stock warrant and was recorded to additional paid-in capital. Both the preferred stock and common stock warrant liabilities were valued using a Black-Scholes valuation model (refer to Note 11). Immediately prior to the completion of the IPO, all then outstanding warrants to purchase preferred stock and common stock were exercised, and the outstanding liability was reversed.
Revenue Recognition	Revenue Recognition —The Company has primarily generated contract revenue through a research and collaboration arrangement with a strategic partner for the development and commercialization of product candidates, and a license agreement related to the licensing of certain of the Company’s intellectual property. Additionally, the Company has historically generated grant revenue from research and development grant programs. The Company recognizes revenue in accordance with Accounting Standards Codification Topic 605, Revenue Recognition · Persuasive evidence of an arrangement exists; · Delivery has occurred or services have been rendered; · The seller’s price to the buyer is fixed or determinable; and · Collectability is reasonably assured. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, current portion. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. Collaboration and License Revenue In May 2014, the Company entered into a research collaboration and license agreement with Regeneron to discover, develop and commercialize novel gene therapy products for the treatment of ophthalmologic diseases. The collaboration covers up to eight distinct therapeutic targets (collaboration targets). The Company and Regeneron will collaborate during the initial research period of three years that can be extended by Regeneron for up to an additional five years. During the research period, Regeneron has the option to obtain an exclusive worldwide license for a collaboration target’s further development by giving written notice to the Company and paying $2.0 million per target. If Regeneron exercises its option, it will be responsible for all further development and commercialization of the target. The Company is then eligible to receive contingent payments of up to $80.0 million upon achievement of certain development and regulatory milestones for product candidates directed toward each collaboration target, for a combined total of up to $640.0 million in potential milestone payments for product candidates directed toward all eight collaboration targets, plus a royalty in the low- to mid-single-digits on worldwide net sales of collaboration products. For any two collaboration targets, the Company has an option to share up to 35% of the worldwide product candidate development costs and profits. If the Company exercises this option, the Company will not be eligible for milestone and royalty payments discussed above but rather the Company will share development costs and profits with Regeneron. The agreement will expire with respect to each collaboration target upon the earlier of the (a) expiration of the research term if the option right has not been triggered by the end of the research term or (b) expiration of the option right if the option right has not been exercised by Regeneron. If the option right has been exercised, the agreement in connection with each collaboration target will expire upon expiration of all payment obligations by Regeneron. In addition, the agreement, or Regeneron’s rights to any target development under the agreement, may terminate early under the following situations: · Regeneron may terminate the agreement for convenience at any time on a target by target basis or in totality upon a 30-day notice. · Each party can terminate the agreement if another party commits a material breach or material default in performance of its obligations and such breach or default is not cured within 60 days. · The agreement is automatically terminated upon initiation of any bankruptcy proceedings, reorganization or dissolution of either party. · The Company can terminate the agreement upon 30-day notice if Regeneron challenges the validity, scope or enforceability of any Company patent. In connection with the agreement, Regeneron also acquired a time-limited right of first negotiation for a potential license to develop and commercialize AVA-101, the Company’s gene therapy product currently under development and undergoing a Phase 2a clinical trial. If and when such negotiation is successful, the Company and Regeneron will enter into a separate agreement for AVA-101. Under the terms of the agreement, the Company received initial upfront non-refundable cash payments of $8.0 million that included payment for research license fees, prepaid collaboration research costs and the time-limited right of first negotiation for AVA-101. As the agreement provides for multiple deliverables, the Company accounts for this agreement as a multiple elements revenue arrangement. If deliverables did not appear to have a standalone value, they were combined with other deliverables into a unit of accounting with standalone value. The Company allocated the $8.0 million to the relative fair value of the two units of accounting identified in the arrangement. The Company expects to recognize $6.5 million for the research licenses and related research and development services ratably over the associated period of performance, which is the maximum research period of eight years. As there is no discernible pattern of performance and/or objectively measurable performance measures do not exist, the Company will recognize revenue on a straight-line basis over the eight year performance period. The remaining $1.5 million allocated to the second unit of accounting for the rights of first negotiation for AVA-101 was deferred. On November 2, 2015, Regeneron notified the Company that it is not exercising this right of first negotiation and the Company recognized the entire $1.5 million as revenue in 2015. As original research budget was fully used in the fourth quarter of 2015, the Company and Regeneron will agree on the reimbursement of additional research expenses annually. The Company will invoice for services performed quarterly. These additional research fees will be added to the research licenses and related research and development services unit of accounting, recorded as deferred revenue and recognized to revenue over the remaining research term. The Company recognized $0.8 million as revenue related to this unit of accounting during the year ended December 31, 2015, recorded $5.6 million of deferred revenue, including $0.9 million as current portion, and $0.4 million as receivable from collaboration partner as of December 31, 2015. The Company also recorded $30,000 license revenue in 2014 related to the licensing of certain of its intellectual property under a licensing agreement entered into during February 2014. Government Grants For the years ending December 31, 2013, the Company recognized $0.5 million of government grant revenue. No government grant revenue was recorded in 2015 and 2014 as we completed the work performed under the grant in 2013. We intend to continue to evaluate pursuing additional grant opportunities on a case-by-case basis.
Research and Development Expenses	Research and Development Expenses —Research and development expenses are charged to expense as incurred. Research and development expenses include certain payroll, stock compensation and other personnel-related expenses, laboratory supplies, consulting costs, external contract research and development expenses, and allocated overhead, including rent, equipment depreciation and utilities. Advance payments for goods or services for future research and development activities are deferred and expensed as the goods are delivered or the related services are performed. The Company estimates preclinical studies 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 the Company’s behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third party service providers and the Company’s estimates of accrued expenses and on information available at each balance sheet date. 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. There have been no significant changes from the Company’s original estimates in any of the periods presented. The Company received tax credits from the Australian government in connection with certain research costs incurred in conducting research by the Company’s Australian subsidiary. These refunds do not depend on the taxable income or tax position of the Company and therefore the Company does not account for them under an income tax accounting model. The Company recognizes such tax credits in the period when qualified expenses are incurred as a reduction of research expenses. The Company has recorded the reimbursement of $0.1 million, $0.1 million and $0.8 million from the Australian tax authorities as a reduction of research and development expense in the consolidated statements of operations and comprehensive loss in the years ended December 31, 2015, 2014 and 2013, respectively.
Fair Value Measurements	Fair Value Measurements —Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The carrying amounts of the Company’s financial instruments, including cash and cash equivalents, prepaid and other current assets, accounts payable, accrued expenses and other warrant liabilities approximate its fair value due to their short-term maturities. Refer to Note 5 for the methodologies and assumptions used in valuing financial instruments.
Stock-Based Compensation Expense	Stock-Based Compensation Expense —Stock-based compensation expense related to awards to employees is measured at the grant date based on the fair value of the award. The fair value of the award that is ultimately expected to vest is recognized as expense on a straight-line basis over the requisite service period, which is generally the vesting period. The expense recognized for the portion of the award that is expected to vest has been reduced by an estimated forfeiture rate. The forfeiture rate is determined at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The Company uses the Black-Scholes valuation model as the method for determining the estimated fair value of stock-based awards. Expected Term —The expected term assumption represents the period that the Company’s stock-based awards are expected to be outstanding and is determined using the simplified method. Expected Volatility —Expected volatility is estimated using comparable public companies volatility for similar terms. Expected Dividend —The Black-Scholes valuation model calls for a single expected dividend yield as an input. The Company has never paid dividends and has no plans to pay dividends. Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury zero-coupon issues in effect at the time of grant for periods corresponding with the expected term of option. Stock-based compensation expense related to awards to non-employees is recognized based on the then-current fair value at each measurement date over the associated service period of the award, which is generally the vesting term, using the accelerated attribution method. The fair value of non-employee stock options is estimated using the Black-Scholes valuation model with assumptions generally consistent with those used for employee stock options, with the exception of the expected term, which is the remaining contractual life at each measurement date. Refer to Note 12 for more information on assumptions used in estimated stock-based compensation expense.
Income Taxes	Income Taxes —The Company accounts for income taxes using the asset and liability method. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. In evaluating the ability to recover its deferred income tax assets, the Company considers all available positive and negative evidence, including its operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. In the event the Company determines that it would be able to realize its deferred income tax assets in the future in excess of their net recorded amount, it would make an adjustment to the valuation allowance that would reduce the provision for income taxes. Conversely, in the event that all or part of the net deferred tax assets are determined not to be realizable in the future, an adjustment to the valuation allowance would be charged to earnings in the period when such determination is made. As of December 31, 2015 and 2014, the Company has recorded a full valuation allowance on its deferred tax assets. Tax benefits related to uncertain tax positions are recognized when it is more likely than not that a tax position will be sustained during an audit. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax.
Comprehensive Loss	Comprehensive Loss —Comprehensive loss is comprised of net loss, deemed dividend to a preferred stockholder and other comprehensive income (loss). Other comprehensive income (loss) consists of foreign currency translation adjustments related to translation of the financial statements of the Australian subsidiary and unrealized gain (loss) on marketable securities. The Company did not have reclassifications from other comprehensive income (loss) to the income (loss) during 2015.
Basic and Diluted Net Loss Per Share	Basic and Diluted Net Loss Per Share —Basic net loss per common share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net loss per common share is computed by dividing the net loss by the weighted-average number of common shares and dilutive common share equivalents outstanding during the period. Because the Company has reported a net loss attributable to common stockholders for all periods presented, diluted net loss per common share is the same as basic net loss attributable to common stockholders per common share for those periods. While shares of the convertible preferred stock were outstanding they were considered to be participating securities as they were entitled to participate in undistributed earnings with shares of common stock. Due to net losses in all periods presented, there is no impact on net loss per share calculation in applying the two-class method since the participating securities have no legal requirement to share in any losses.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements —In August 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern , requiring management to evaluate whether events or conditions could impact an entity’s ability to continue as a going concern and to provide disclosures if necessary. Management will be required to perform the evaluation within one year after the date that the financial statements are issued. Disclosures will be required if conditions give rise to substantial doubt and the type of disclosure will be determined based on whether management’s plans will be able to alleviate the substantial doubt. The accounting standards update will be effective for the first annual period ending after December 15, 2016, and for annual periods and interim periods thereafter with early application permitted. The adoption of this ASU is not expected to impact the Company’s financial position or results of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , Revenue Recognition to December 15, 2017 for interim and annual reporting periods beginning after that date and permitted early adoption of the standard, but not before the original effective date of December 15, 2016 In April 2015, the FASB issued ASU No. 2015-05, Customer’s Accounting of Fees Paid in Cloud Computing Arrangement to arrangements entered into or materially modified after the effective date. In November 2015, FASB issued ASU No. 2015-17, Balance Sheet Classification of Deferred Taxes On January 5, 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities

Restructuring Charges (Tables)

Restructuring Charges (Tables)	12 Months Ended
	Dec. 31, 2015
Restructuring And Related Activities [Abstract]
Summary of Restructuring Activities	The following table summarizes the restructuring activities for the year ended December 31, 2015 (in thousands): One-Time Termination Benefits Non-Cash Charge Related to Acceleration of RSUs Total Restructuring liability as of December 31, 2014 $ — $ — $ — Costs incurred and recorded as restructuring charges 1,524 1,049 2,573 Cash payments (511 ) — (511 ) Non-cash settlements — (1,049 ) (1,049 ) Restructuring liability as of December 31, 2015 $ 1,013 $ — $ 1,013

Cash Equivalents and Marketab27

Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Cash And Cash Equivalents [Abstract]
Summary of Cash Equivalents and Marketable Securities	The following is a summary of the cash equivalents and marketable securities: December 31, 2015 Amortized Cost Basis Unrealized Gains Unrealized Loses Estimated Fair Value Money Market Funds $ 208,588 $ — $ — $ 208,588 Certificates of Deposit 1,680 — — 1,680 U.S. Treasury Securities 15,046 — (4 ) 15,042 U.S. Government Agency Securities 21,012 — (2 ) 21,010 246,326 — (6 ) 246,320 Less: Cash Equivalents (208,588 ) — — (208,588 ) Total Marketable Securities $ 37,738 $ — $ (6 ) $ 37,732

Fair Value Measurements and F28

Fair Value Measurements and Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Financial Assets Measured and Recognized at Fair Value on Recurring Basis	The following table summarizes, for assets and liabilities recorded at fair value, the respective fair value and the classification by level of input within the fair value hierarchy as described above (in thousands): Quoted Prices Significant Other Significant Total In Observable Inputs Unobservable Inputs Carrying (Level 1) (Level 2) (Level 3) December 31, 2015 Assets: Money Market Funds $ 208,588 $ 208,588 $ — $ — Certificates of Deposit 1,680 — 1,680 — U.S. Treasury Securities 15,042 — 15,042 — U.S. Government Agency Securities 21,010 — 21,010 — Total Cash Equivalents and Marketable Securities $ 246,320 $ 208,588 $ 37,732 $ — December 31, 2014 Assets: Money Market Funds $ 40,000 $ 40,000 $ — $ — Total Cash Equivalents $ 40,000 $ 40,000 $ — $ —
Summary of Changes in Estimated Fair Value of Warrants Liabilities and Embedded Derivative Liability	The following table provides a summary of changes in the estimated fair value of the Company’s warrants liabilities and embedded derivative liability measured at estimated fair value using significant Level 3 inputs (in thousands): Convertible Preferred Stock Common Stock Warrant Liability (1) Warrant Liability (2) Balance as of January 1, 2014 $ 91 $ 42 Issuance of common stock warrant — (41 ) Change in fair value 760 (1 ) Exercises (851 ) — Balance as of December 31, 2014 $ — $ — (1) In July 2014, all of the then outstanding warrants to purchase convertible preferred stock and common stock were exercised immediately prior to the completion of the IPO. (2) In March 2014, the common stock warrant was issued and was recorded to additional paid-in capital.

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following (in thousands): December 31, 2015 December 31, 2014 Computer equipment and software $ 234 $ 142 Laboratory equipment 3,041 1,012 Furniture and fixtures 552 73 Leasehold improvements 351 48 Total property and equipment 4,178 1,275 Less accumulated depreciation and amortization (991 ) (190 ) Property and equipment, net $ 3,187 $ 1,085

Accrued Expenses and Other Cu30

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): December 31, 2015 December 31, 2014 Employees' compensation $ 2,047 $ 1,509 Accrued preclinical costs 642 1,005 Accrued professional fees 1,177 231 Accrued clinical and process development costs 101 942 Other 40 20 Total accrued expenses and other current liabilities $ 4,007 $ 3,707

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Commitments under Facility Operating Lease	As of December 31, 2015, future minimum commitments under the Company’s facility operating lease were as follows (in thousands): YEARS ENDED DECEMBER 31, 2015 TOTAL LEASE COMMITMENTS 2016 $ 1,099 2017 1,129 2018 1,162 2019 1,197 2020 403 Total minimum lease payments $ 4,990

Stock Option Plans (Tables)

Stock Option Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Summary of Information with Respect to Stock Options Outstanding and Currently Exercisable and Vested	The following table summarizes information with respect to stock options outstanding and currently exercisable and vested. As of December 31, 2015: OPTIONS OUTSTANDING OPTIONS EXERCISABLE AND VESTED WEIGHTED- WEIGHTED- NUMBER AVERAGE REMAINING NUMBER AVERAGE REMAINING RANGE OF OUTSTANDING CONTRACTUAL LIFE OUTSTANDING CONTRACTUAL LIFE EXERCISE PRICES (IN THOUSANDS) (IN YEARS) (IN THOUSANDS) (IN YEARS) $0.15-$0.27 2,644 6.5 2,156 6.4 $0.28-$2.95 429 8.1 190 8.1 $2.96-$11.50 1,284 9.5 193 8.4 $11.51-$35.00 707 8.8 243 8.7 $35.01-$58.92 430 9.2 36 9.0
Stock-Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Nonemployees	The Company has recorded aggregate stock-based compensation expense related to the issuance of stock option awards to employees and nonemployees in the consolidated statement of operations and comprehensive loss as follows: (in thousands) YEARS ENDED DECEMBER 31 2015 2014 2013 Research and development $ 4,009 $ 7,331 $ 362 General and administrative 6,447 1,236 153 Restructuring charges 1,049 — — Total share-based compensation $ 11,505 $ 8,567 $ 515
Summary of Restricted Stock Units Activity	The following table summarizes the RSUs activity under the Company’s stock plans and related information: Weighted-Average Number of Grant-Date Shares (in thousands) Fair Value (in dollars) Outstanding at December 31, 2014 — $ — Granted 851 $ 13.85 Vested and released (132 ) $ 10.52 Forfeited (87 ) $ 24.21 Outstanding at December 31, 2015 632 $ 13.07
Schedule of Fair Value of Option Issued to Employees Valuation Assumptions	The fair value of each option issued to employees was estimated at the date of grant using the Black-Scholes valuation model with the following weighted-average assumptions: Options Employee Stock Purchase Plan YEARS ENDED DECEMBER 31 YEARS ENDED DECEMBER 31 2015 2014 2013 2015 2014 2013 Expected volatility 79 % 79 % 80 % 74 % — — Expected term (in years) 6.1 6.0 6.0 0.5 — — Expected dividend yield — — — — — — Risk-free interest rate 1.7 % 1.9 % 1.0 % 0.1 % — —
Non Employee Stock Option [Member]
Schedule of Non-Employees Stock Purchase Plan Valuation Assumptions	We used the following weighted-average assumptions in estimating non-employees stock-based compensation expense: YEARS ENDED DECEMBER 31 2015 2014 2013 Option grants: Expected volatility 81 % 79 % 79 % Expected term (in years) 3.3 7.5 7.9 Expected dividend yield — — — Risk-free interest rate 1.0 % 2.2 % 1.8 %
2006 and 2014 Equity Incentive Plan [Member]
Summary of Stock Options Activity	The following table summarizes option activity under the Company’s stock plans and related information: WEIGHTED- NUMBER OF WEIGHTED- AVERAGE REMAINING AGGREGATE SHARE AVERAGE EXERCISE CONTRACTUAL LIFE INTRINSIC VALUE (a) (IN THOUSANDS) PRICE (IN YEARS) (IN THOUSANDS) Balance at January 1, 2015 4,932 $ 5.61 8.2 $ 238,653 Options granted 1,603 $ 21.91 Options exercised (400 ) $ 0.47 Options cancelled (641 ) $ 22.77 Balance at December 31, 2015 5,494 $ 8.75 7.8 28,618 Vested and expected to vest as of December 31, 2015 5,447 $ 8.64 7.8 28,524 Exercisable as of December 31, 2015 2,818 $ 3.45 6.9 21,978 (a) The aggregate intrinsic value is calculated as the difference between the options exercise price and the closing price of common stock of $9.52 per share as of December 31, 2015.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Components of Loss Before Income Taxes	The following table presents domestic and foreign components of loss before provision for income taxes (in thousands): FOR THE YEARS ENDED DECEMBER 31, 2015 2014 2013 U.S. $ (47,235 ) $ (25,006 ) $ (5,031 ) Foreign (218 ) (398 ) (245 ) Loss before income taxes $ (47,453 ) $ (25,404 ) $ (5,276 )
Schedule of Reconciliation of Income Tax Expense Computed Statutory Federal Income Tax and Financial Statements	A reconciliation of income tax expense computed at the statutory federal income tax rate of 34% to income taxes as reflected in the financial statements is as follows (in thousands): FOR THE YEARS ENDED DECEMBER 31, 2015 2014 2013 Federal income tax expense at statutory rate $ (16,134 ) $ (8,637 ) $ (1,794 ) Loss on extinguishment of related-party convertible notes — 69 568 Non-deductible foreign research expenses 45 85 26 Non-deductible stock compensation 1,418 161 46 Non-deductible expenses 295 285 28 Research and development tax credits (910 ) (304 ) (93 ) Change in valuation allowance 15,277 8,349 1,209 Foreign rate differential 9 (8 ) 10 Total tax expense (benefit) $ — $ — $ —
Schedule of Deferred Tax Assets	The following table presents significant components of the Company’s deferred tax assets (in thousands): AS OF DECEMBER 31, 2015 2014 2013 Deferred tax assets: Net operating loss carryforwards $ 19,889 $ 8,526 $ 1,876 Accruals, reserve and other 2,681 222 109 Stock-based compensation 4,328 3,032 183 Tax credit carryforwards 1,945 659 145 Property and equipment — — 2 Intangibles 45 24 223 Other — 24 (1 ) Total deferred tax assets before valuation allowance 28,888 12,487 2,537 Valuation allowance (28,839 ) (12,457 ) (2,537 ) Total deferred tax assets 49 30 — Deferred tax liabilities: Property and equipment (49 ) (30 ) — Total deferred tax liabilities (49 ) (30 ) — Net deferred tax assets $ — $ — $ —
Schedule of Unrecognized Tax Benefits	A reconciliation of the unrecognized tax benefits is as follows (in thousands): FOR THE YEARS ENDED DECEMBER 31, 2015 2014 2013 Unrecognized tax benefits as of the beginning of the year $ 471 $ 43 $ 5 Increase related to prior year tax provisions 172 272 7 Increase related to current year tax provisions 925 156 31 Unrecognized tax benefits as of the end of the year $ 1,568 $ 471 $ 43

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders	The following table sets forth the computation of the basic and diluted net loss per share for the years ended December 31, 2015, 2014 and 2013 (in thousands, except per share data): FOR THE YEARS ENDED DECEMBER 31, 2015 2014 2013 Net loss $ (47,453 ) $ (25,404 ) $ (5,276 ) Deemed dividend — (3,230 ) — Net loss attributable to common stockholders (47,453 ) (28,634 ) (5,276 ) Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share: Net shares outstanding 25,479 11,651 3,673 Basic and diluted net loss per share attributable to common stockholders $ (1.86 ) $ (2.46 ) $ (1.44 )
Schedule of Antidilutive Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share	The following common stock equivalents outstanding at the end of the periods presented were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: AS OF DECEMBER 31, 2015 2014 2013 Options to purchase common stock 5,494 4,932 3,640 RSUs 632 — — Warrants to purchase common stock 40 — 264 Series A preferred stock — — 3,899 Warrants to purchase preferred stock — — 55 6,166 4,932 7,858

Selected Quarterly Financial 35

Selected Quarterly Financial Information (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following amounts are in thousands, except per share amounts: Quarterly Results of Operations Quarter End March 31, 2015 June 30, 2015 September 30, 2015 December 31, 2015 (In thousands, except per share amounts) Revenue $ 203 $ 203 $ 953 $ 960 Total operating expenses (2)(3) $ (9,764 ) $ (10,085 ) $ (15,154 ) $ (15,139 ) Net loss $ (9,509 ) $ (9,766 ) $ (14,084 ) $ (14,094 ) Basic and diluted net loss per share $ (0.38 ) $ (0.38 ) $ (0.55 ) $ (0.55 ) Quarterly Results of Operations Quarter End March 31, 2014 June 30, 2014 September 2014 December 2014 (In thousands, except per share amounts) Revenue $ 30 $ 135 $ 204 $ 203 Total operating expenses $ (1,636 ) $ (4,588 ) $ (8,144 ) $ (10,606 ) Net loss $ (1,663 ) $ (5,094 ) $ (8,256 ) $ (10,391 ) Deemed dividend (1) $ — $ (3,230 ) $ — $ — Net loss attributable to common stockholders $ (1,663 ) $ (8,324 ) $ (8,256 ) $ (10,391 ) Basic and diluted net loss per share $ (0.45 ) $ (2.27 ) $ (0.50 ) $ (0.46 ) (1) In April 2014, we repurchased 531,208 shares of Series A convertible preferred stock for $4.0 million. The difference between the repurchase price of $7.53 per share and original issuance price of $1.45 per share was recorded as a deemed dividend of $3.2 million to a preferred stockholder and effected the calculation of net loss attributable to common stockholders and net loss per share for the year ended December 31, 2014. (2) In connection with the restructuring, the Company recorded estimated restructuring charges of approximately $2.6 million related to one-time termination severance payments and other employee-related benefits, including approximately $1.0 million of stock-based compensation expense related to the acceleration of RSUs in December 2015. (3) In July 2015, the Company’s then Chief Executive officer resigned and some of his stock-based awards were forfeited and cancelled, which that resulted in a $2.4 million of additional stock-based compensation expense recorded in general and administrative expenses in the Company’s consolidated financial statements.

Description of Business - Addit

Description of Business - Additional Information (Detail) - USD ($)	Aug. 05, 2014	Mar. 31, 2015	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Date of incorporation				Jul. 17, 2006
Accumulated deficit				$ (84,168,000)	$ (36,715,000)
Issuance of common stock		230,000	2,369,375
Net proceeds from initial public offering				$ 138,954,000	$ 106,453,000
Net proceeds from issuance of common stock		$ 8,300,000	$ 130,600,000
Conversion of preferred stock, common stock issued upon conversion	10,689,027
Warrants [Member]
Class of Stock [Line Items]
Conversion of warrants into shares of common stock, shares	407,131
Conversion of warrants into shares of common stock, value	$ 600,000
IPO [Member]
Class of Stock [Line Items]
Issuance of common stock	6,900,000
Issuance of common stock upon exercise of overallotment by underwriters	900,000
Common stock, shares issued, price per share	$ 17
Net proceeds from initial public offering	$ 106,500,000
Private Placement [Member]
Class of Stock [Line Items]
Issuance of common stock	588,235
Common stock, shares issued, price per share	$ 17
Net proceeds from issuance of common stock	$ 10,000,000
Underwriting discount or commissions	$ 0
Over-Allotment Option [Member]
Class of Stock [Line Items]
Issuance of common stock			359,918

Summary of Significant Accoun37

Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	May. 31, 2014USD ($)Target	Dec. 31, 2015USD ($)Segment	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Summary Of Significant Accounting Policies [Line Items]
Deposits		$ 100,000	$ 100,000
Number of reportable segments | Segment		1
Number of operating segments | Segment		1
Impairment losses of long lived assets		$ 0
Deferred offering costs		$ 0	400,000
Collaboration fee for exclusive worldwide license per target	$ 2,000,000
Initial collaboration term	3 years
Additional collaboration term	5 years
Potential milestone earnings	$ 640,000,000
Potential target of collaborations | Target	8
Reimbursement of research and development expense		35.00%
Agreement termination scenario description		Regeneron may terminate the agreement for convenience at any time on a target by target basis or in totality upon a 30-day notice. Each party can terminate the agreement if another party commits a material breach or material default in performance of its obligations and such breach or default is not cured within 60 days. The agreement is automatically terminated upon initiation of any bankruptcy proceedings, reorganization or dissolution of either party. The Company can terminate the agreement upon 30-day notice if Regeneron challenges the validity, scope or enforceability of any Company patent.
Deferred revenue, current portion		$ 883,000	813,000
Revenue from licensing of intellectual property			30,000
Government grant revenue		0	0	$ 480,000
Tax credits due to reduction of research and development expense		910,000	304,000	93,000
Australian Tax Authorities [Member]
Summary Of Significant Accounting Policies [Line Items]
Tax credits due to reduction of research and development expense		100,000	$ 100,000	$ 800,000
Upfront Payment Arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Initial upfront non-refundable cash payments received		8,000,000
Regeneron Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Research collaboration and license agreement revenue		800,000
Regeneron Corporation [Member] | Research Collaboration And License Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue		5,600,000
Deferred revenue, current portion		900,000
Accounts receivable		400,000
Regeneron Corporation [Member] | Upfront Payment Arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized		6,500,000
Deferred revenue		$ 1,500,000
Performance period		8 years
Development and Regulatory Milestone [Member]
Summary Of Significant Accounting Policies [Line Items]
Potential milestone earnings	$ 80,000,000
Series A and B Convertible Preferred Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Gain (loss) on changes in fair value recorded in income statement		$ (800,000)
Reclassification of fair value to additional paid-in capital		$ 900,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets		3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets		5 years

Restructuring Charges - Additio

Restructuring Charges - Additional Information (Detail) $ in Thousands	Dec. 22, 2015Employee	Dec. 31, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Restructuring And Related Cost [Line Items]
Company workforce reduction percentage under restructuring plan	20.00%
Number of employees eliminated | Employee	15
Restructuring charges		$ 2,600	$ 2,573
Stock-based compensation expense			11,505	$ 8,567	$ 515
Restructuring liabilities		1,013	$ 1,013
RSUs | Restricted Stock Units [Member]
Restructuring And Related Cost [Line Items]
Stock-based compensation expense		$ 1,000

Restructuring Charges - Summary

Restructuring Charges - Summary of Restructuring Activities (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015
Restructuring Reserve [Line Items]
Restructuring liability beginning balance		$ 0
Costs incurred and recorded as restructuring charges	$ 2,600	2,573
Cash payments		(511)
Non-cash settlements		(1,049)
Restructuring liability ending balance	1,013	1,013
One-Time Termination Benefits [Member]
Restructuring Reserve [Line Items]
Restructuring liability beginning balance		0
Costs incurred and recorded as restructuring charges		1,524
Cash payments		(511)
Restructuring liability ending balance	1,013	1,013
Non-Cash Charge Related to Acceleration of RSUs [Member]
Restructuring Reserve [Line Items]
Restructuring liability beginning balance		0
Costs incurred and recorded as restructuring charges		1,049
Non-cash settlements		(1,049)
Restructuring liability ending balance	$ 0	$ 0

Cash Equivalents and Marketab40

Cash Equivalents and Marketable Securities - Summary of Cash Equivalents and Marketable Securities (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Cash and Cash Equivalents [Line Items]
Amortized Cost Basis	$ 37,738
Unrealized Loses	(6)
Estimated Fair Value	37,732
Less: Cash Equivalents, Amortized Cost Basis	(208,588)
Less: Cash Equivalents, Unrealized Gains	0
Less: Cash Equivalents, Unrealized Loses	0
Less: Cash Equivalents, Estimated Fair Value	(208,588)
Cash Equivalents And Marketable Securities [Member]
Cash and Cash Equivalents [Line Items]
Amortized Cost Basis	246,326
Unrealized Loses	(6)
Estimated Fair Value	246,320
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Amortized Cost Basis	208,588
Estimated Fair Value	208,588
Certificates of Deposit [Member]
Cash and Cash Equivalents [Line Items]
Amortized Cost Basis	1,680
Estimated Fair Value	1,680
U.S. Treasury Securities [Member]
Cash and Cash Equivalents [Line Items]
Amortized Cost Basis	15,046
Unrealized Loses	(4)
Estimated Fair Value	15,042
US Government Agency Securities [Member]
Cash and Cash Equivalents [Line Items]
Amortized Cost Basis	21,012
Unrealized Loses	(2)
Estimated Fair Value	$ 21,010

Cash Equivalents and Marketab41

Cash Equivalents and Marketable Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2014Security
Cash And Cash Equivalents [Abstract]
Marketable securities, gross unrealized losses	$ 6,000
Number of available-for-securities held | Security		0
Contractual maturities of marketable securities	Less than one year
Proceeds from sales of available-for-sale securities	$ 0

Fair Value Measurements and F42

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]
Liabilities transferred within Level 3	$ 0	$ 0	$ 0

Fair Value Measurements and F43

Fair Value Measurements and Fair Value of Financial Instruments - Financial Assets Measured and Recognized at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets:
Total assets	$ 246,320	$ 40,000
Money Market Funds [Member]
Assets:
Total assets	208,588	40,000
Certificates of Deposit [Member]
Assets:
Total assets	1,680
U.S. Treasury Securities [Member]
Assets:
Total assets	15,042
Quoted Prices in Active Markets (Level 1) [Member]
Assets:
Total assets	208,588	40,000
Quoted Prices in Active Markets (Level 1) [Member] | Money Market Funds [Member]
Assets:
Total assets	208,588	$ 40,000
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Total assets	37,732
Significant Other Observable Inputs (Level 2) [Member] | Certificates of Deposit [Member]
Assets:
Total assets	1,680
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Securities [Member]
Assets:
Total assets	15,042
U.S. Government Agency Securities [Member]
Assets:
Total assets	21,010
U.S. Government Agency Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Total assets	$ 21,010

Fair Value Measurements and F44

Fair Value Measurements and Fair Value of Financial Instruments - Summary of Changes in Estimated Fair Value of Warrants Liabilities and Embedded Derivative Liability (Detail) - Warrants [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2014USD ($)
Series A and B Convertible Preferred Stock [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 91
Change in fair value	760
Exercises	(851)
Common Stock [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	42
Issuance of common stock warrant	(41)
Change in fair value	$ (1)

Significant Agreements - Additi

Significant Agreements - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	May. 31, 2010	Dec. 31, 2015	Dec. 31, 2014
License Agreement [Line Items]
Annual maintenance fee payable		$ 100,000	$ 100,000
University of California [Member]
License Agreement [Line Items]
Upfront license fee paid	$ 100,000
Annual maintenance fee payable	50,000
Aggregate amount of milestone payments for first indication	900,000
Additional milestone payments for up to two additional indications	$ 500,000
Additional milestone payments recognized		$ 0

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 4,178	$ 1,275
Less accumulated depreciation and amortization	(991)	(190)
Property and equipment, net	3,187	1,085
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	234	142
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	3,041	1,012
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	552	73
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 351	$ 48

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 812	$ 162	$ 26

Accrued Expenses and Other Cu48

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued Expenses And Other Current Liabilities [Abstract]
Employees' compensation	$ 2,047	$ 1,509
Accrued preclinical costs	642	1,005
Accrued professional fees	1,177	231
Accrued clinical and process development costs	101	942
Other	40	20
Total accrued expenses and other current liabilities	$ 4,007	$ 3,707

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Jul. 31, 2015Claim	Dec. 31, 2015USD ($)Claim	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Commitments And Contingencies Disclosure [Abstract]
Lease renewal term		4 years
Lease expiration date		May 8, 2020
Rent expense		$ 1,525,000	$ 662,000	$ 53,000
Accrued royalties		0
Annual maintenance fee payable		100,000	$ 100,000
Claims paid to date related to indemnification issues		$ 0
Number of claims to date | Claim	3	0
Accruals or expenses related to indemnification issues		$ 0

Commitments and Contingencies50

Commitments and Contingencies - Schedule of Future Minimum Commitments (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,016	$ 1,099
2,017	1,129
2,018	1,162
2,019	1,197
2,020	403
Total minimum lease payments	$ 4,990

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Aug. 05, 2014	Apr. 30, 2014	Nov. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Conversion of preferred stock, shares converted	10,689,027
Loss on extinguishment of related-party convertible notes			$ 1,700		$ 204	$ 1,671
General and administrative				$ 22,107	7,998	$ 1,783
Fair value and repurchase of beneficial conversion feature				$ 2,000
Convertible preferred stock, value					$ 3,230
Outstanding Convertible Notes [Member]
Class of Stock [Line Items]
Loss on extinguishment of related-party convertible notes		$ 200
Series A Convertible Preferred Stock [Member]
Class of Stock [Line Items]
General and administrative			$ 800
Shares repurchased, number of shares		531,208			531,208
Convertible preferred stock, value		$ 4,000			$ 770
Share repurchased, price per share					$ 7.53
Common stock, shares issued, price per share			$ 1.45
Preferred stockholder, deemed dividend					$ 3,200
Series B Convertible Preferred Stock [Member] | Outstanding Convertible Notes [Member]
Class of Stock [Line Items]
Conversion of preferred stock, shares converted		295,115
Conversion price per share		$ 6.78
Percentage of conversion price to original issuance price		90.00%
Original issuance price per share		$ 7.53

Warrants - Additional Informati

Warrants - Additional Information (Detail) - USD ($)	Oct. 15, 2015	Aug. 05, 2014	May. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Aug. 31, 2012
Class of Warrant or Right [Line Items]
Fair value of common stock price per share				$ 17
Contractual term of warrant				1 year 1 month 6 days
Fair value of obligation risk free interest rate				0.10%
Fair value of obligation expected volatility rate				70.00%
Fair value of obligation expected dividend yield				0.00%
Common stock and preferred stock exercised for cash		$ 600,000			$ 606,000
Series A and B Convertible Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Gain (loss) on changes in fair value recorded in income statement				$ (800,000)
Reclassification of fair value to permanent equity				$ 900,000
LEI [Member]
Class of Warrant or Right [Line Items]
Warrant to purchase shares of common stock	40,000			40,000			25,000
Fair value of obligation to issue warrant	$ 200,000			$ 30,000			$ 5,000
Exercise price	$ 10.51					$ 2.75
Fair value of common stock price per share	$ 8.35			$ 9.52
Warrant expiration date	Oct. 15, 2020
Contractual term of warrant	5 years			6 years 7 months 6 days
Fair value of obligation risk free interest rate	1.34%			1.10%
Fair value of obligation expected volatility rate	75.00%			79.00%
Fair value of obligation expected dividend yield	0.00%			0.00%
LEI [Member] | Warrants [Member]
Class of Warrant or Right [Line Items]
Shares vested and exercisable				0
Financial Services Firm [Member]
Class of Warrant or Right [Line Items]
Warrant to purchase shares of common stock			63,415
Exercise price			$ 6.83
Fair value of common stock price per share			$ 6.83
Warrant expiration date			May 15, 2019
Contractual term of warrant			5 years
Financial Services Firm [Member] | Warrants [Member]
Class of Warrant or Right [Line Items]
Fair value of warrant liability			$ 300,000
Fair value of obligation risk free interest rate			1.55%
Fair value of obligation expected volatility rate			75.00%
Fair value of obligation expected dividend yield			0.00%

Stock Option Plans - Additional

Stock Option Plans - Additional Information (Detail) - USD ($)	1 Months Ended			12 Months Ended
	Dec. 31, 2015	Jul. 31, 2015	Jul. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation, weighted-average period				2 years 8 months 12 days
Total intrinsic value of options exercised				$ 11,200,000	$ 15,700,000
Common stock issued upon exercise of stock options, shares						0
One time share based payment charge related to cancellation of unvested stock option of CEO		$ 2,400,000		$ 11,764,000	$ 1,672,000	$ 136,000
Weighted-average fair values of options granted				$ 15.91	$ 9.56	$ 0.37
Unrecognized stock-based compensation expense related to employees' awards	$ 14,200,000			$ 14,200,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	6,200,000			$ 6,200,000
Unrecognized stock-based compensation, weighted-average period				2 years
RSU granted				851,000
Total fair values of RSUs vested				$ 1,400,000
Restricted Stock Units [Member] | Prior to April 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU granted				0
Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted period				3 years 3 months 18 days	7 years 6 months	7 years 10 months 24 days
Unrecognized stock-based compensation, weighted-average period				1 year 6 months
Unrecognized stock-based compensation expense related to employees' awards	$ 1,100,000			$ 1,100,000
Stock-based compensation expense				$ (259,000)	$ 6,895,000	$ 379,000
Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period, shares, employee stock purchase plan	910,000
Maximum [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted to employees vesting period				4 years
Minimum [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted to employees vesting period				2 years
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 100,000			$ 100,000
Unrecognized stock-based compensation, weighted-average period				4 months 24 days
2014 Equity Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of annual increase in number of shares available for future issuance			4.00%
Common stock shares authorized for issuance	8,454,368			8,454,368
Shares available for future grants	2,137,787			2,137,787
Stock options granted description				Options under the 2014 Plan may be granted for periods of up to 10 years and at prices no less than 100% of the estimated fair value of the shares on the date of grant as determined by the board of directors, provided, however, that the exercise price of an ISO and NSO granted to a 10% stockholder may not be less than 110% of the estimated fair value of the shares on the date of grant.
Stock options granted to employees and non-employees vesting period			4 years
2014 Equity Incentive Award Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted period			10 years
2014 Equity Incentive Award Plan [Member] | IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares available for future grant			2,088,332
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares available for future grant	416,796		208,833	416,796
Percentage increase in shares issued			1.00%
Common stock, shares issued				19,577

Stock Option Plans - Summary of

Stock Option Plans - Summary of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
NUMBER OF SHARES, Options exercised			0
2006 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
NUMBER OF SHARES, Beginning Balance	4,932,000
NUMBER OF SHARES, Options granted	1,603,000
NUMBER OF SHARES, Options exercised	(400,000)
NUMBER OF SHARES, Options cancelled	(641,000)
NUMBER OF SHARES, Ending Balance	5,494,000	4,932,000
NUMBER OF SHARES, Vested and expected to vest	5,447,000
NUMBER OF SHARES, Exercisable	2,818,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
WEIGHTED-AVERAGE EXERCISE PRICE, Beginning Balance	$ 5.61
WEIGHTED-AVERAGE EXERCISE PRICE, Options granted	21.91
WEIGHTED-AVERAGE EXERCISE PRICE, Options exercised	0.47
WEIGHTED-AVERAGE EXERCISE PRICE, Options cancelled	22.77
WEIGHTED-AVERAGE EXERCISE PRICE, Ending Balance	8.75	$ 5.61
WEIGHTED-AVERAGE EXERCISE PRICE, Vested and expected to vest	8.64
WEIGHTED-AVERAGE EXERCISE PRICE, Exercisable	$ 3.45
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	7 years 9 months 18 days	8 years 2 months 12 days
WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS), Vested and expected to vest	7 years 9 months 18 days
WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS), Exercisable	6 years 10 months 24 days
AGGREGATE INTRINSIC VALUE, Beginning Balance	$ 238,653
AGGREGATE INTRINSIC VALUE, Ending Balance	28,618	$ 238,653
AGGREGATE INTRINSIC VALUE, Vested and expected to vest	28,524
AGGREGATE INTRINSIC VALUE, Exercisable	$ 21,978

Stock Option Plans - Summary 55

Stock Option Plans - Summary of Stock Options Activity (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2015$ / shares
Equity [Abstract]
Aggregate intrinsic value of option per share	$ 9.52

Stock Option Plans - Summary 56

Stock Option Plans - Summary of Information with Respect to Stock Options Outstanding and Currently Exercisable and Vested (Detail)	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Range 1 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
RANGE OF EXERCISE PRICES, LOWER RANGE | $ / shares	$ 0.15
RANGE OF EXERCISE PRICES, UPPER PRICES | $ / shares	$ 0.27
OPTIONS OUTSTANDING, NUMBER OUTSTANDING | shares	2,644,000
OPTIONS OUTSTANDING, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	6 years 6 months
OPTIONS EXERCISABLE AND VESTED, NUMBER OUTSTANDING | shares	2,156,000
OPTIONS EXERCISABLE AND VESTED, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	6 years 4 months 24 days
Range 2 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
RANGE OF EXERCISE PRICES, LOWER RANGE | $ / shares	$ 0.28
RANGE OF EXERCISE PRICES, UPPER PRICES | $ / shares	$ 2.95
OPTIONS OUTSTANDING, NUMBER OUTSTANDING | shares	429,000
OPTIONS OUTSTANDING, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	8 years 1 month 6 days
OPTIONS EXERCISABLE AND VESTED, NUMBER OUTSTANDING | shares	190,000
OPTIONS EXERCISABLE AND VESTED, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	8 years 1 month 6 days
Range 3 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
RANGE OF EXERCISE PRICES, LOWER RANGE | $ / shares	$ 2.96
RANGE OF EXERCISE PRICES, UPPER PRICES | $ / shares	$ 11.50
OPTIONS OUTSTANDING, NUMBER OUTSTANDING | shares	1,284,000
OPTIONS OUTSTANDING, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	9 years 6 months
OPTIONS EXERCISABLE AND VESTED, NUMBER OUTSTANDING | shares	193,000
OPTIONS EXERCISABLE AND VESTED, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	8 years 4 months 24 days
Range 4 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
RANGE OF EXERCISE PRICES, LOWER RANGE | $ / shares	$ 11.51
RANGE OF EXERCISE PRICES, UPPER PRICES | $ / shares	$ 35
OPTIONS OUTSTANDING, NUMBER OUTSTANDING | shares	707,000
OPTIONS OUTSTANDING, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	8 years 9 months 18 days
OPTIONS EXERCISABLE AND VESTED, NUMBER OUTSTANDING | shares	243,000
OPTIONS EXERCISABLE AND VESTED, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	8 years 8 months 12 days
Range 5 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
RANGE OF EXERCISE PRICES, LOWER RANGE | $ / shares	$ 35.01
RANGE OF EXERCISE PRICES, UPPER PRICES | $ / shares	$ 58.92
OPTIONS OUTSTANDING, NUMBER OUTSTANDING | shares	430,000
OPTIONS OUTSTANDING, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	9 years 2 months 12 days
OPTIONS EXERCISABLE AND VESTED, NUMBER OUTSTANDING | shares	36,000
OPTIONS EXERCISABLE AND VESTED, WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (IN YEARS)	9 years

Stock Option Plans - Stock-Base

Stock Option Plans - Stock-Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Nonemployees (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation		$ 11,505	$ 8,567	$ 515
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation		4,009	7,331	362
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	$ 2,400	6,447	$ 1,236	$ 153
Restructuring Charges [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation		$ 1,049

Stock Option Plans - Summary 58

Stock Option Plans - Summary of Restricted Stock Units Activity (Detail) - Restricted Stock Units [Member]	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted | shares	851,000
Number of Shares, Vested and released | shares	(132,000)
Number of Shares, Forfeited | shares	(87,000)
Number of Shares, Ending Balance | shares	632,000
Weighted-Average Grant-Date Fair Value, Granted | $ / shares	$ 13.85
Weighted-Average Grant-Date Fair Value, Vested and released | $ / shares	10.52
Weighted-Average Grant-Date Fair Value, Forfeited | $ / shares	24.21
Weighted-Average Grant-Date Fair Value, Ending Balance | $ / shares	$ 13.07

Stock Option Plans - Schedule o

Stock Option Plans - Schedule of Employees Stock Purchase Plan Valuation Assumptions (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	79.00%	79.00%	80.00%
Expected term (in years)	6 years 1 month 6 days	6 years	6 years
Risk-free interest rate	1.70%	1.90%	1.00%
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	74.00%
Expected term (in years)	6 months	0 years	0 years
Risk-free interest rate	0.10%
Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	81.00%	79.00%	79.00%
Expected term (in years)	3 years 3 months 18 days	7 years 6 months	7 years 10 months 24 days
Risk-free interest rate	1.00%	2.20%	1.80%

401(k) Savings Plan - Additiona

401(k) Savings Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Compensation And Retirement Disclosure [Abstract]
Contribution by company	$ 100,000	$ 25,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Income tax benefit of expense	$ 0	$ 0	$ 0
Statutory federal income tax rate	34.00%
Increase in valuation allowance due to net operating loss	$ 16,400,000	9,900,000	1,400,000
Increase in equity	10,500,000
Unrecognized tax benefits	1,568,000	471,000	$ 43,000	$ 5,000
Unrecognized tax benefits, if recognized would effective annual tax rate	0
Accrued interest or penalties related to uncertain tax positions	0	0
Interest or penalties recognized	$ 0	$ 0
Minimum [Member]
Income Taxes [Line Items]
Tax examinations, year under examination	2,011
Maximum [Member]
Income Taxes [Line Items]
Tax examinations, year under examination	2,015
Domestic Tax Authority [Member]
Income Taxes [Line Items]
NOL carryforwards	$ 79,400,000
NOL carryforwards expiration	Expire at various years beginning with 2026
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforwards	$ 1,900,000
Tax credit carryforwards expiration	Expire at various years beginning with 2032
State credit carryforwards [Member]
Income Taxes [Line Items]
NOL carryforwards	$ 56,500,000
NOL carryforwards expiration	Expire at various years beginning with 2016
State credit carryforwards [Member] | Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforwards	$ 1,700,000
Foreign Tax Authority [Member]
Income Taxes [Line Items]
NOL carryforwards	$ 200,000

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
U.S.	$ (47,235)	$ (25,006)	$ (5,031)
Foreign	(218)	(398)	(245)
Loss before income taxes	$ (47,453)	$ (25,404)	$ (5,276)

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Income Tax Expense Computed Statutory Federal Income Tax and Financial Statements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal income tax expense at statutory rate	$ (16,134)	$ (8,637)	$ (1,794)
Loss on extinguishment of related-party convertible notes		69	568
Non-deductible foreign research expenses	45	85	26
Non-deductible stock compensation	1,418	161	46
Non-deductible expenses	295	285	28
Research and development tax credits	(910)	(304)	(93)
Change in valuation allowance	15,277	8,349	1,209
Foreign rate differential	9	(8)	10
Total tax expense (benefit)	$ 0	$ 0	$ 0

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets:
Net operating loss carryforwards	$ 19,889	$ 8,526	$ 1,876
Accruals, reserve and other	2,681	222	109
Stock-based compensation	4,328	3,032	183
Tax credit carryforwards	1,945	659	145
Property and equipment			2
Intangibles	45	24	223
Other		24	(1)
Total deferred tax assets before valuation allowance	28,888	12,487	2,537
Valuation allowance	(28,839)	(12,457)	(2,537)
Total deferred tax assets	49	30
Deferred tax liabilities:
Property and equipment	(49)	(30)
Total deferred tax liabilities	(49)	(30)
Net deferred tax assets	$ 0	$ 0	$ 0

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Unrecognized tax benefits as of the beginning of the year	$ 471,000	$ 43,000	$ 5,000
Increase related to prior year tax provisions	172,000	272,000	7,000
Increase related to current year tax provisions	925,000	156,000	31,000
Unrecognized tax benefits as of the end of the year	$ 1,568,000	$ 471,000	$ 43,000

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net loss	$ (14,094)	$ (14,084)	$ (9,766)	$ (9,509)	$ (10,391)	$ (8,256)	$ (5,094)	$ (1,663)	$ (47,453)	$ (25,404)	$ (5,276)
Deemed dividend							(3,230)			(3,230)
Net loss attributable to common stockholders					$ (10,391)	$ (8,256)	$ (8,324)	$ (1,663)	$ (47,453)	$ (28,634)	$ (5,276)
Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share:
Net shares outstanding									25,479	11,651	3,673
Basic and diluted net loss per share attributable to common stockholders	$ (0.55)	$ (0.55)	$ (0.38)	$ (0.38)	$ (0.46)	$ (0.50)	$ (2.27)	$ (0.45)	$ (1.86)	$ (2.46)	$ (1.44)

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Antidilutive Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	6,166	4,932	7,858
Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	632
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	5,494	4,932	3,640
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	40		264
Series A Preferred Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share			3,899
Warrants to Purchase Preferred Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share			55

Selected Quarterly Financial 68

Selected Quarterly Financial Information - Schedule of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 960	$ 953	$ 203	$ 203	$ 203	$ 204	$ 135	$ 30	$ 2,319	$ 572	$ 480
Total operating expenses	(15,139)	(15,154)	(10,085)	(9,764)	(10,606)	(8,144)	(4,588)	(1,636)	(50,142)	(24,974)	(3,934)
Net loss	$ (14,094)	$ (14,084)	$ (9,766)	$ (9,509)	(10,391)	(8,256)	(5,094)	(1,663)	(47,453)	(25,404)	(5,276)
Deemed dividend							(3,230)			(3,230)
Net loss attributable to common stockholders					$ (10,391)	$ (8,256)	$ (8,324)	$ (1,663)	$ (47,453)	$ (28,634)	$ (5,276)
Basic and diluted net loss per share	$ (0.55)	$ (0.55)	$ (0.38)	$ (0.38)	$ (0.46)	$ (0.50)	$ (2.27)	$ (0.45)	$ (1.86)	$ (2.46)	$ (1.44)

Selected Quarterly Financial 69

Selected Quarterly Financial Information - Schedule of Quarterly Financial Information (Parenthetical) (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Jul. 31, 2015	Apr. 30, 2014	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Quarterly Financial Information [Line Items]
Convertible preferred stock, value					$ 3,230
Restructuring charges			$ 2,600	$ 2,573
Stock-based compensation expense				11,505	$ 8,567	$ 515
Series A Convertible Preferred Stock [Member]
Schedule Of Quarterly Financial Information [Line Items]
Shares repurchased, number of shares		531,208			531,208
Convertible preferred stock, value		$ 4,000			$ 770
Share repurchased, price per share					$ 7.53
Preferred stockholder, deemed dividend					$ 3,200
Treasury stock original issuance price						$ 1.45
Restructuring Charges [Member]
Schedule Of Quarterly Financial Information [Line Items]
Stock-based compensation expense				1,049
Restructuring Charges [Member] | RSUs
Schedule Of Quarterly Financial Information [Line Items]
Stock-based compensation expense				1,000
General and Administrative Expenses [Member]
Schedule Of Quarterly Financial Information [Line Items]
Stock-based compensation expense	$ 2,400			$ 6,447	$ 1,236	$ 153

Subsequent Event - Additional I

Subsequent Event - Additional Information (Detail) - Subsequent Event [Member] - Annapurna Therapeutics SAS [Member]	Jan. 29, 2016USD ($)shares
Subsequent Event [Line Items]
Number of shares issued to acquired an entity | shares	13,100,000
Common stock exchange ratio	9.5615
Number of shares converted | shares	4,700,000
Termination fee lower | $	$ 4,000,000
Termination fee higher | $	$ 6,000,000