Adverum Biotechnologies (ADVM) 10-K 9 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Feb. 28, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Trading Symbol	ADVM
Entity Registrant Name	Adverum 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		42,063,237
Entity Public Float			$ 99.8

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 222,170	$ 221,348
Marketable securities		37,732
Receivable from collaborative partner	886	449
Prepaid expenses and other current assets	2,218	1,463
Total current assets	225,274	260,992
Property and equipment, net	4,169	3,187
Deposit and other long-term assets	140	140
Intangible assets	5,000
Total assets	234,583	264,319
Current liabilities:
Accounts payable	1,474	605
Restructuring liabilities	25	1,013
Accrued expenses and other current liabilities	6,451	4,007
Deferred rent, current portion	96	66
Deferred revenue, current portion	1,850	883
Total current liabilities	9,896	6,574
Long-term liabilities:
Deferred rent, net of current portion	352	447
Deferred revenue, net of current portion	7,099	4,706
Deferred tax liability, noncurrent	1,250	49
Other non-current liabilities	386
Total liabilities	18,983	11,727
Commitments and contingencies (Note 11)
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, 2016 and 2015; 41,805,009 and 25,858,722 shares issued and outstanding at December 31, 2016 and 2015, respectively	4	3
Additional paid-in capital	413,518	336,768
Accumulated other comprehensive loss	(7)	(11)
Accumulated deficit	(197,915)	(84,168)
Total stockholders’ equity	215,600	252,592
Total liabilities and stockholders’ equity	$ 234,583	$ 264,319

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	41,805,009	25,858,722
Common stock, shares outstanding	41,805,009	25,858,722

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Collaboration and license revenue	$ 1,455	$ 2,319	$ 572
Operating expenses:
Research and development	31,670	25,462	16,976
General and administrative	24,355	22,107	7,998
Impairment of goodwill and intangible assets	60,714
Restructuring charges		2,573
Total operating expenses	116,739	50,142	24,974
Operating loss	(115,284)	(47,823)	(24,402)
Other income (expense)
Interest expense			(18)
Other income (expense), net	762	370	(21)
Change in fair value of warrant liabilities			(759)
Loss on extinguishment of related-party convertible notes			(204)
Total other income (expense), net	762	370	(1,002)
Net loss before tax benefit	(114,522)	(47,453)	(25,404)
Income tax benefit	775	0	0
Net loss after tax benefit	(113,747)	(47,453)	(25,404)
Deemed dividend			(3,230)
Net loss attributable to common stockholders	(113,747)	(47,453)	(28,634)
Other comprehensive loss:
Net unrealized gain (loss) on marketable securities	6	(6)
Foreign currency translation adjustment	(2)	(15)	(17)
Comprehensive loss	$ (113,743)	$ (47,474)	$ (25,421)
Net loss per share attributable to common stockholders-basic and diluted	$ (3.14)	$ (1.86)	$ (2.46)
Weighted-average common shares outstanding-basic and diluted	36,246	25,479	11,651

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity - USD ($) $ in Thousands	Total	Convertible Preferred Stock Warrant [Member]	Series A Preferred Stock [Member]	Series B Preferred Stock [Member]	Common Stock Warrant [Member]	IPO [Member]	Private Placement [Member]	Common Stock [Member]	Common Stock [Member]Series A Preferred Stock [Member]	Common Stock [Member]Series B Preferred Stock [Member]	Common Stock [Member]Common Stock Warrant [Member]	Common Stock [Member]IPO [Member]	Common Stock [Member]Private Placement [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]Convertible Preferred Stock Warrant [Member]	Additional Paid-in Capital [Member]Series A Preferred Stock [Member]	Additional Paid-in Capital [Member]Series B Preferred Stock [Member]	Additional Paid-in Capital [Member]Common Stock Warrant [Member]	Additional Paid-in Capital [Member]IPO [Member]	Additional Paid-in Capital [Member]Private Placement [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Series A Convertible Preferred Stock [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, 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	$ 52,321						$ 1						$ 7,301	$ 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, net of issuance costs, shares																										7,025,888
Repurchase of Series A convertible preferred stock in April 2014	(3,230)													(788)								(2,442)	$ (770)
Repurchase of Series A convertible preferred stock in April 2014, shares																							(531,208)
Issuance of common stock warrants in consideration for services	307													307
Issuance of common stock net of issuance costs		$ 851				$ 92,224	$ 10,000					$ 1			$ 851				$ 92,223	$ 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 warrants					$ 526													$ 526
Issuance of common stock upon exercise of warrants, shares											352,415
Issuance of common stock upon exercise of option by underwriters, net of issuance costs of $1,071 in August 2014	14,229													14,229
Issuance of common stock upon exercise of option by underwriters, net of issuance costs of $1,071 in August 2014, 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
Common stock issued upon release of restricted stock units, shares								132,397
Restricted stock surrendered for taxes	(427)													(427)
Restricted stock surrendered for taxes, shares								(46,098)
Net unrealized gain (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
Issuance of common stock in consideration of acquisition	64,845							$ 1						64,844
Issuance of common stock in consideration of acquisition, shares								14,087,246
Remeasurement of contingent common stock warrant in consideration for services	8													8
Issuance of warrant in connection with financing arrangement	26													26
Stock-based compensation expense	11,416													11,416
Common stock issued upon exercise of stock options	763													763
Common stock issued upon exercise of stock options, shares								1,525,687
Common stock issued under employee stock purchase plan	186													186
Common stock issued under employee stock purchase plan, shares								56,696
Common stock issued upon release of restricted stock units, shares								385,524
Restricted stock surrendered for taxes	(493)													(493)
Restricted stock surrendered for taxes, shares								(108,866)
Net unrealized gain (loss) on marketable securities	6																				6
Foreign currency translation adjustment	(2)																				(2)
Net loss	(113,747)																					(113,747)
Balance at Dec. 31, 2016	$ 215,600							$ 4						$ 413,518							$ (7)	$ (197,915)
Balance, shares at Dec. 31, 2016								41,805,009

Consolidated Statements of Con6

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

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (113,747)	$ (47,453)	$ (25,404)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,603	812	162
Loss on disposal of property and equipment		21
Stock-based compensation expense	11,416	11,505	8,567
Non-cash research and development expense	8	218
Non-cash interest expense			18
Amortization of premium on marketable securities		780
Change in fair value of warrant liabilities			759
Loss on extinguishment of related-party convertible notes			204
Impairment of goodwill and intangible assets	60,714
Changes in operating assets and liabilities:
Accounts receivable, net	(437)	(6)	8
Prepaid expenses and other current assets	71	(531)	(624)
Deposit and other long-term assets		(3)	7
Accounts payable	(111)	(312)	(6)
Accrued expenses and other current liabilities	(190)	724	2,904
Restructuring liabilities	(988)	1,013
Deferred revenue	3,360	(2,313)	7,459
Deferred rent	(65)	207	298
Net cash used in operating activities	(38,366)	(35,338)	(5,648)
Cash flows from investing activities:
Purchases of marketable securities		(88,427)
Maturities of marketable securities	37,738	49,850
Purchases of property and equipment	(2,412)	(2,992)	(943)
Cash acquired in business acquisition	3,449
Net cash provided by (used in) investing activities	38,775	(41,569)	(943)
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
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	763	188	18
Taxes paid related to net share settlement of restricted stock units	(493)	(427)
Proceeds from employee stock purchase plan	186	145
Proceeds from a financing arrangement	100
Net cash provided by financing activities	556	138,860	165,442
Effect of foreign currency exchange rate on cash and cash equivalents	(143)	(9)	(11)
Net increase in cash and cash equivalents	822	61,944	158,840
Cash and cash equivalents at beginning of period	221,348	159,404	564
Cash and cash equivalents at end of period	222,170	221,348	159,404
Supplemental schedule of noncash investing and financing information
Issuance of common stock and exchange of stock options for business acquisition	64,845
Conversion of related-party convertible notes payable to convertible preferred stock			2,000
Warrants issued in connection with issuance of Series B convertible preferred stock			266
Warrants issued in connection with financing and license agreements	26	218	42
Fixed assets in accounts payable and current liabilities	$ 180	$ 178	235
Deferred stock issuance costs			379
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, 2016
Accounting Policies [Abstract]
Description of the business	1. Description of the business Nature of Business —Adverum Biotechnologies, Inc. (the “Company”, “we” or “us”) was incorporated in Delaware on July 17, 2006 as Avalanche Biotechnologies, Inc. and changed its name to Adverum Biotechnologies, Inc. on May 11, 2016. The Company is headquartered in Menlo Park, California. The Company is a gene therapy company committed to discovering and developing novel medicines that can offer potentially life-changing therapeutic benefit to patients living with rare diseases or diseases of the eye, who currently have limited or burdensome treatment options. We are leveraging our industry-leading adeno-associated virus (AAV)-based platform to generate gene therapy product candidates designed to provide durable efficacy by inducing sustained expression of a therapeutic protein. We have also acquired certain other gene therapy product candidates through our acquisition on May 11, 2016, of Annapurna Therapeutics SAS (Annapurna), a privately-held French gene therapy company. Our core capabilities include clinical development and in-house manufacturing expertise, specifically in process development, assay development, and novel vector development and we are led by a team with significant drug development and gene therapy expertise. Since the Company’s inception, it has devoted its efforts principally to performing research and development activities, including conducting preclinical studies, early clinical trials, filing patent applications, obtaining regulatory agreements, 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 $197.9 million as of December 31, 2016. The Company expects to incur losses and have negative net cash flows from operating activities as it engages in further research and development activities. The Company believes that it has sufficient funds to continue operations through the end of 2019. On May 11, 2016, the Company completed the acquisition of all the outstanding shares of Annapurna Therapeutics SAS, a French simplified joint stock company (“Annapurna”), in accordance with the terms of the acquisition agreement (the “Agreement”) dated as of January 29, 2016, as amended on April 6, 2016. As a result, Annapurna is now a wholly owned subsidiary of the Company. Pursuant to the terms of the Agreement, the Company issued 14,087,246 shares of the Company’s common stock, par value $0.0001 per share, for all of the issued and outstanding capital stock of Annapurna. All outstanding options and other rights to purchase capital stock of Annapurna were exchanged into the Company’s options for common stock. Refer to Note 3 for more details. Upon completion of the acquisition, the Company changed its name to “Adverum Biotechnologies, Inc.” The Company’s shares of common stock listed on The NASDAQ Global Market, previously trading through the close of business on Wednesday, May 11, 2016 under the ticker symbol “AAVL,” commenced trading on The NASDAQ Global Market under the ticker symbol “ADVM” on Thursday, May 12, 2016. Initial Public and Follow-on Offerings —In August 2014 and January 2015, the Company completed its initial public offering (IPO) and concurrent private placement and a follow on offering and raised a total of net proceeds of $237.1 million. 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 IPO.

Summary of significant accounti

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of significant accounting policies	2. Summary of significant accounting policies Basis of Presentation and Principles of Consolidation — The Company’s consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) and pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All inter-company transactions and balances have been eliminated in consolidation. Use of Estimates —The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, 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 research and development expense accruals, stock-based compensation expense, income taxes, and fair value of common 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. Foreign Currency Translation —The Company’s consolidated financial statements are prepared in U.S. dollars. Its foreign subsidiaries use the Euro and Australian dollar as their functional currency and maintains their records in the local currency, except our Ireland subsidiary that uses U.S. dollars as its’ functional currency. Assets and liabilities are re-measured at exchange rates in effect at the end of the reporting period at our France and Australia subsidiaries, and at historical exchange rates at our Irish subsidiary. 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 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. We did not have any marketable securities as of December 31, 2016. Deposit —Deposit in the amount of $0.1 million as of December 31, 2016 and 2015 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, 2016, substantially all of the Company’s cash and cash equivalents was deposited in accounts at five 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 instruments 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. Valuation of Long-Lived Assets and Purchased Intangible Assets —The Company evaluates the carrying value of amortizable long‑lived assets, whenever events, or changes in business circumstances or the planned use of long‑lived assets indicate that their carrying amounts may not be fully recoverable or that their useful lives are no longer appropriate. If these facts and circumstances exist, the Company assesses for recovery by comparing the carrying values of long‑lived assets with their future undiscounted net cash flows. If the comparison indicates that impairment exists, long‑lived assets are written down to their respective fair value based on discounted cash flows. Significant management judgment is required in the forecasting of future operating results that is used in the preparation of expected undiscounted cash flows. If management’s assumptions about future operating results were to change as a result of events or circumstances, the Company may be required to record an impairment loss on these assets. No impairment indicators were noted for the Company’s amortizable long-lived assets, fixed assets, in the periods presented. The Company also evaluates the carrying value of intangible assets (not subject to amortization) related to in‑process research and development (“IPR&D”) assets, which are considered to be indefinite‑lived until the completion or abandonment of the associated research and development efforts. Accordingly, amortization of the IPR&D assets will not occur until the product reaches commercialization. During the period the assets are considered indefinite‑lived, they will be tested for impairment on an annual basis, as well as between annual tests if the Company become aware of any events occurring or changes in circumstances that would indicate that the fair values of the IPR&D assets are less than their carrying amounts. If and when development is complete, which generally occurs when regulatory approval to market the product is obtained, the associated IPR&D assets would be deemed definite‑lived and would then be amortized based on their estimated useful lives at that point in time based on respective patent terms. If the related project is terminated or abandoned, the Company will have an impairment related to the IPR&D assets, calculated as the excess of its carrying value over fair value. The Company estimated fair value of IPR&D assets acquired in Annapurna transaction at the acquisition closing date, May 11, 2016, to be $16.2 million. As a result of management’s decision to change its manufacturing process for ADVM-043 and ADVM-053 by implementing its proprietary baculovirus-based production system during the fourth quarter of 2016 and based upon the Company’s analysis of the fair value of the IPR&D assets as of December 31, 2016, the Company recorded an impairment charge of $11.2 million. Refer to Note 3 for further details. Financial Liabilities —Prior to the Company’s IPO, the Company had recorded convertible preferred stock warrants issued to investors and note holders as derivative 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. During 2016, the Company entered into a sponsored research agreement with The Alpha-1 project, Inc. (TAP) with an embedded derivative, the Company determined to account for this financial liability at fair value. Refer to Note 13 for further details. Revenue Recognition —The Company has primarily generated revenue through license, research and collaboration arrangements with its strategic partners. The terms of these types of agreements may include (i) licenses to our technology, (ii) research In arrangements involving the delivery of more than one element, each required deliverable is The arrangement’s consideration that is fixed or determinable is allocated to each separate unit Payments or reimbursements for the Company’s research and development efforts for the arrangements where The Company’s collaboration and license agreements may include contingent payments related to Collaboration and License Revenue In August 2016, the Company entered into a collaboration, option and license agreement with Editas. Refer to Note 7 for details of the agreement. Under the terms of the agreement, the Company received initial payments of $1.0 million that included $0.5 million for research services. As the agreement provides for multiple deliverables, the Company accounts for this agreement as a multiple elements revenue arrangement. At the inception of the agreement, identified deliverables include research services, manufacturing of viral vectors for research, participation in joint research committee and exclusivity during the option period. These deliverables did not appear to have a standalone value and were combined into one unit of accounting. Options for each indication to license the Company’s AAV vector are considered substantive options and do not include significant incremental discounts. Therefore, they are not considered as deliverables under the agreement. The Company allocated the $1.0 million received to a single unit of accounting identified in the arrangement. The Company expects to recognize $1.0 million ratably over the associated period of performance, which is the maximum research period of three 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. During the year ended December 31, 2016, the Company recognized $139,000 as 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. Refer to Note 7 for details of the agreement. 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 license to develop and commercialize 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 a 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 recognizes $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 recognizes revenue on a straight-line basis over the eight years performance period. The remaining $1.5 million allocated to the second unit of accounting for the time-limited right of first negotiation for license to develop and commercialize AVA-101. 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 invoices for services performed quarterly. These additional research fees are 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 $1.4 million and $0.8 million during the year ended December 31, 2016 and 2015, respectively, related to the research licenses and research and development services unit of accounting in the Regeneron agreement. 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 and French governments in connection with certain research costs incurred in conducting research by the Company’s Australian and French subsidiaries. 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 $0.3 million, $0.1 million and $0.1 million from the 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, 2016, 2015 and 2014, 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, and accrued expenses approximate their fair values due to their short-term maturities. Refer to Note 6 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 granted 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 14 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, 2016 and 2015, 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 Company’s Australia, and France subsidiaries and unrealized gain (loss) on marketable securities. The Company did not have reclassifications from other comprehensive income (loss) to the income (loss) during 2016 and 2015 fiscal years. 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. Recent Accounting Standard Update Not Yet Effective —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 standard 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. This ASU will be effective for the Company in the first quarter of 2017. The adoption of this standard is not expected to impact the Company’s consolidated financial statements and related disclosures. 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 Revenue From Contracts With Customers: Principal vs. Agent Considerations Revenue From Contracts with Customers: Identifying Performance Obligations and Licensing Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients Technical Corrections and Improvement to Topic 606 – Revenue from Contracts with In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, which amends the current guidance on the classification and measurement of financial instruments. Although this ASU retains many current requirements, it significantly revises an entity’s accounting related to (i) the classification and measurement of investments in equity securities and (ii) the presentation of certain fair value changes for financial liabilities measured at fair value. This ASU also amends certain disclosure requirements associated with the fair value of financial instruments. The new standard is effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2017, with early adoption permitted for certain changes. This ASU will be effective for the Company in the first quarter of 2018 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted for certain provisions. The adoption of this standard is not expected to have a significant impact on the Company’s consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-2, Leases In March 2016, the FASB issued ASU No. 2016-9, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting, In June 2016, the FASB issued ASU No. 2016-13 Measurement of Credit Losses on Financial Instruments In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15) In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (ASU 2016-18) The Company has reviewed other recent accounting pronouncements and concluded they are either not applicable to the business or no material effect is expected on the consolidated financial statements as a result of future adoption. Accounting Standard Update Recently Adopted —In April 2015, the FASB issued ASU No. 2015-05, Customer’s Accounting of Fees Paid in Cloud Computing Arrangement , guidance on accounting for fees paid in cloud computing arrangements. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a services contract. All software licenses recognized under this guidance will be accounted for consistent with other licenses of intangible assets. The Company elected to adopt this ASU in the first quarter of fiscal 2016. The adoption of this standard did not have any impact on the Company's consolidated financial statements.

Acquisition of Annapurna

Acquisition of Annapurna	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Acquisition of Annapurna	3. Acquisition of Annapurna (a) Purchase Price Allocation On May 11, 2016, the Company completed the acquisition of all outstanding equity interests of Annapurna. Annapurna is a privately held French limited liability company and has two wholly-owned subsidiaries, Annapurna, Inc. in the U.S. and Annapurna Therapeutics Limited in Ireland. Annapurna is a biopharmaceutical company focused on discovering and developing novel gene therapy products for people living with severe rare diseases. The primary reasons for the acquisition were to expand the technology platforms within the Company’s research and development portfolio and to apply the Company’s resources and expertise in gene vectors development to advance Annapurna’s programs through development and clinical trials. Annapurna’s results of operations and fair value of assets acquired and liabilities assumed are included in the Company’s consolidated financial statements from the date of acquisition. The purchase price consideration was estimated to be $64.8 million, which was based on the Company’s common stock closing price on NASDAQ on the acquisition closing date of $4.14 per share. A total of 14,087,246 shares of the Company’s common stock were issued to shareholders of Annapurna in exchange for all common and preferred stock outstanding at the closing date. Annapurna stockholders did not receive any fractional shares of the Company’s common stock in connection with the acquisition. Instead of receiving any fractional shares, each Annapurna stockholder was paid an amount in cash (without interest) equal to such fraction amount multiplied by the average 10 business days sale price of the Company’s common stock on NASDAQ from the acquisition date. Annapurna Series O preferred shares issued to founders were canceled prior to the acquisition date and were not included in the purchase price consideration. Vesting of certain of Annapurna’s options and unvested common stock shares was accelerated at the closing date. The fair value of awards related to the accelerated vesting of options and shares of $0.9 million was excluded from the purchase price consideration and included in the Company’s operating expenses post acquisition. A portion of the purchase price has been attributed to the exchange of Annapurna’s options and other rights to purchase capital stock outstanding at the acquisition closing date for corresponding common stock options of the Company at an exchange ratio of 9.54655. The Company reserved 3,673,940 shares for the future exercise of the Company’s stock options. The total fair value of assumed Annapurna stock options and stock-based awards was estimated at $14.7 million on the acquisition date, using the Black-Scholes option pricing model, assuming no dividends, expected volatilities of 80% and 89%, risk-free interest rates of 1.4% and 1.1%, and expected lives of six and ten years for employees and non-employees awards, respectively. Of the total fair value, $7.4 million has been attributed as pre-combination service and included as part of the total purchase price consideration. The post-combination attribution amount of $7.2 million will be recognized as compensation expense over the remaining requisite service period. The Company has included $0.9 million in stock-based compensation expense related to the day-one post combination compensation expenses related to the accelerated vesting of options during the second quarter 2016. Total purchase price consideration was estimated as follows (in thousands): Fair value of common shares issued $ 58,321 Fair value of the Company's common share options exchanged for Annapurna options and other awards attributable to pre-combination services 7,422 Less: value of common stock and options accelerated vesting at close date (898 ) Total purchase price consideration $ 64,845 The transaction has been accounted for using the acquisition method based on ASC 805, Business Combinations, The allocation of total purchase price consideration is as follows (in thousands): Cash $ 3,449 Prepaid expenses and other assets 865 Property and equipment 185 Acquired intangible assets 16,200 Goodwill 49,514 Accounts payable (1,118 ) Accrued liabilities (1,848 ) Other noncurrent liabilities (377 ) Deferred tax liabilities (2,025 ) Total purchase price allocation $ 64,845 The identifiable intangible assets acquired consist of IPR&D assets related to products in development, as summarized in the table below (in thousands): IPR&D - Alpha-1 antitrypsin deficiency $ 11,700 IPR&D - Hereditary angioedema 4,500 Total acquired intangible assets $ 16,200 The fair value of each IPR&D asset is estimated using the income approach and calculated using cash flow projections adjusted for inherent risks regarding regulatory approval, promotion, and distribution, discounted at a rate of approximately 11.0%. The Company acquired two additional intangible assets relating to the Friedreich’s Ataxia (FA) and severe allergy programs, but the fair value of each of these assets was determined to be nominal and is not included in the total acquired intangible assets. All IPR&D intangible assets acquired are currently classified as indefinite-lived and are not currently being amortized. Acquired IPR&D assets were impaired in the fourth quarter 2016, refer to the discussion below. Goodwill, which represents the excess of the purchase price over the fair values assigned to the net assets acquired, was estimated in the amount of $49.5 million on the acquisition date. The full amount of the preliminary value of goodwill has been assigned to the entire Company, since management has determined that the Company has only one reporting unit. The goodwill is not deductible for tax purposes. During the second quarter of 2016, goodwill was impaired, refer to the discussion below. The amount of net loss of Annapurna included in the consolidated statements of operations and comprehensive loss from the acquisition date through the period ended December 31, 2016 was $16.6 million, including the $11.2 million impairment to IPR&D assets. Annapurna did not generate any revenues prior or post acquisition. The pro forma financial information combines the results of operations of Adverum and Annapurna as though the businesses had been combined as of the beginning of fiscal 2015. The pro forma financial information is presented for informational purposes only, and is not indicative of the results of operations that would have been achieved in the current or any future periods. The following table presents the unaudited pro forma results for the years ended December 31, 2016 and 2015 (in thousands, except per share data). Years ended December 31, 2016 2015 Pro forma information Collaboration and license revenue $ 1,455 $ 2,319 Net loss $ (117,551 ) $ (61,774 ) Basic and diluted loss per share $ (2.85 ) $ (1.56 ) Weighted-average common shares outstanding - basic and diluted 41,288 39,566 Pro-forma adjustments included the following: • Actual acquisition-related transaction costs of $2.5 million for year ended December 2016 were excluded from the 2016 pro forma results above. As these expenses were incurred prior to the closing of the acquisition, they were not included in the 2015 pro forma results. • Stock-based compensation expense related to the accelerated vesting associated with the acquisition of $0.9 million was excluded from the 2016 pro forma results and was recorded in the year ended December 31, 2015. • Stock-based compensation expense related to options granted to executives upon the acquisition closing of $0.2 million and $0.4 million was included in the 2016 and 2015 pro forma results above. • Interest expense related to convertible notes and changes in fair value of preferred stock warrants of $0.5 million for the year ended December 31, 2015 and $1.0 million for the year ended December 31, 2016, were excluded from 2015 and 2016 pro-forma results above, as the convertible notes and warrants were settled prior to the acquisition closing. • Bonuses paid in connection with closing of the acquisition in May 2016 of $0.4 million were excluded from the 2016 pro forma results and were recorded in the year ended December 31, 2015. The unaudited condensed pro forma information does not include any anticipated synergies that may be achievable subsequent to the date of acquisition. b) Impairment evaluation for goodwill and intangible assets As the Company recorded goodwill and IPR&D intangible assets upon the acquisition of Annapurna, the Company is required to test goodwill and indefinite lived intangible assets for impairment on an annual basis or more frequently if indicators of impairment exist. The Company operates as one reporting unit and goodwill was recorded to this reporting unit. During the second quarter of 2016, the Company noted a continuing decrease in its stock price that resulted in the market capitalization being less than the carrying value of the Company’s net assets as of June 30, 2016. As the operating losses are expected to increase significantly in the following years due to continuing pre-clinical and expected clinical trials, the Company concluded that it is more likely than not that the fair value of the Company’s one reporting unit is less than its carrying value and as a result performed a step one goodwill impairment analysis. In performing the step one analysis, the Company determined the fair value of the reporting unit using a market-based approach. The Company multiplied the stock price of $3.16 on June 30, 2016 by the 41.3 million common shares outstanding and applied a control premium to estimate the common equity value on a controlling basis. As the fair value was less than the carrying value of the Company’s net assets, the Company proceeded to step two of the impairment analysis. The second step of the analysis includes allocating the calculated fair value (determined in the step one analysis) of the reporting unit to its assets and liabilities to determine an implied fair value of goodwill. The implied fair value of goodwill was determined in the same manner as the amount of goodwill recognized in an acquisition. That is, the estimated fair value of the reporting unit was allocated to all of the assets and liabilities as if the Company had been acquired and the estimated fair value was the purchase price paid. As part of this assessment the Company considered the preliminary valuation of Annapurna net assets acquired, excluding goodwill, as their fair value from May 11, 2016, the acquisition closing date, to June 30, 2016 did not change. The Company also noted that the fair value of current assets and liabilities approximates their carrying value due to their short-term nature, the Company’s cash and cash equivalent balance is higher than the fair value estimated in the step one analysis, and the fair value of fixed assets approximates their recorded value as most of the Company’s fixed assets are acquired in the last couple of years. Based on this analysis, the implied fair value of the goodwill was zero. Accordingly, the total goodwill impairment charge was $49.5 million, which is included in impairment of goodwill and intangible assets on the consolidated statements of operations and comprehensive loss for the year ended December 31, 2016. In the fourth quarter of 2016, we performed our annual impairment assessment of our ADVM-043 and ADVM-053 IPR&D assets. Based on our decision in the fourth quarter to change our manufacturing process for ADVM-043 and ADVM-053 by implementing our proprietary baculovirus-based production system, we updated the related development and manufacturing costs. As a result, we revised our forecasts for manufacturing and related costs. In addition, we also reviewed and updated our expected timing of clinical trials, receipts of regulatory approvals and costs to complete. Based upon our analysis, we determined that the carrying value of $16.2 million for our ADVM-043 and ADVM-053 IPR&D assets was higher than their fair value of $5.0 million. Accordingly, we recorded an $11.2 million IPR&D impairment charge for the year ended December 31, 2016.

Restructuring Charges

Restructuring Charges	12 Months Ended
	Dec. 31, 2016
Restructuring And Related Activities [Abstract]
Restructuring Charges	4. 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 also triggered 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 years ended December 31, 2015 and 2016 (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 payments (988 ) — (988 ) Restructuring liability as of December 31, 2016 $ 25 $ — $ 25

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	5. Cash Equivalents and Marketable Securities The following is a summary of the cash equivalents and marketable securities (in thousands): December 31, 2016 Amortized Cost Basis Unrealized Gains Unrealized Loses Estimated Fair Value Money market funds - cash equivalent $ 215,916 $ — $ — $ 215,916 Total cash equivalents $ 215,916 $ — $ — $ 215,916 December 31, 2015 Money market funds - cash equivalent $ 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 During the year ended December 31, 2016, management sold the Company’s marketable securities at maturity and did not recognize any gains or losses on liquidation.

Fair Value Measurements and Fai

Fair Value Measurements and Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements and Fair Value of Financial Instruments	6. 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 a financing arrangement entered in 2016. 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, 2016 and 2015. 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, 2016 Assets: Money market funds - cash equivalent $ 215,916 $ 215,916 $ — $ — Total cash equivalents $ 215,916 $ 215,916 $ — $ — Other noncurrent liability: Financing arrangement $ 74 $ — $ — $ 74 December 31, 2015 Assets: Money market funds - cash equivalent $ 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 $ — In August 2016, the Company entered into a financing arrangement with an independent third party for a total amount of $0.3 million. Under the terms of the financing arrangement, the Company may be required to repay up to $1.4 million, depending on the achievement of certain development and commercialization milestones. The Company elected the fair value option to account for this financing arrangement. The fair value of the financing arrangement was determined based on the expected value approach and is classified as Level 3 within the fair value hierarchy. The Company received approximately $0.1 million and the changes in the fair value were insignificant during the year ended December 31, 2016. The key unobservable inputs in the valuation model include timing of milestones, probability of achievement of development and commercial milestones, and a discount factor. The following table presents quantitative information about the inputs and valuation methodologies used for the fair value measurements classified in Level 3 of the fair value hierarchy at December 31, 2016: Fair Value at December 31, 2016 (in thousands) Valuation Methodology Significant Unobservable Input Weighted-Average (range - if applicable) Financing arrangement $ 74 Expected value approach Milestone dates 2017 - 2023 Discount rate 5.5 % Percent probability of milestone achievements 18.2% to 80.0% Non-financial assets such as intangible assets, property, plant, and equipment are evaluated for impairment and adjusted to their fair value using Level 3 inputs, only when impairment is recognized. Fair values are considered Level 3 when management makes significant assumptions in developing a discounted cash flow model based upon a number of considerations including projections of revenues, earnings and a discount rate. In addition, in evaluating the fair value of goodwill impairment, further corroboration is obtained using our market capitalization.

Significant Agreements

Significant Agreements	12 Months Ended
	Dec. 31, 2016
Research And Development [Abstract]
Significant Agreements	7. Significant Agreements University of California — In May 2010, the Company entered into a license agreement with the Regents of University of California (Regents), as amended in September 2013. Under the license agreement, the Regents have granted to the Company an exclusive (even as to the Regents) license, with the right to grant sublicenses, under the Regents’ undivided interest in patent rights covering a method of using recombinant gene delivery vectors for treating or preventing diseases of the eye, to develop, make, have made, use offer for sale, import, export and sell products covered by such patent rights in all fields of use in the United States. The licensed patent rights are jointly owned by the Regents and Chiron Corporation, but the Company’s license extends only to the Regents’ interest in such patent rights. Under the license agreement, the Company is required to diligently proceed with the development, manufacture and sale of licensed products, which includes obligations to meet certain development-stage milestones within specified periods of time, and to market the resulting licensed products in sufficient quantity to meet market demand. The Company has the right and option to extend the date by which it must meet any milestone by six-months up to two times by paying an extension fee for each such extension. The Company has paid the Regents a license fee of $100,000. The Company is also obligated to make milestone payments totaling up to $900,000 upon reaching certain stages of development of the licensed products for one indication, and totaling up to $500,000 for each subsequent indication for which licensed products are developed, for up to a maximum of two additional indications. Through December 31, 2016, none of these goals had been achieved, and no milestones were payable. The Company must pay the Regents a low single-digit royalty on net sales of the licensed products by the Company or its sublicensees, subject to a minimum annual royalty payment of $50,000 beginning in the calendar year after the first commercial sale of a licensed product, until the patent rights upon which such royalties are based expire or are held invalid, which is currently expected to occur in 2020, subject to any potential patent term extensions. The Company is obligated to reimburse the Regents for expenses associated with the prosecution and maintenance of the licensed patents. Finally, the Company is obligated to pay the Regents a mid-teen percentage of non-royalty licensing revenue that the Company receives from sublicensees. The Company’s license agreement with the Regents continues in effect for the life of the last-to-expire patent. The Company may terminate this agreement without cause at any time upon 30 days’ prior written notice to the Regents. The Regents may terminate this agreement for a breach by the Company that remains uncured for 60 days, if the Company becomes insolvent, if the Company directly or through a third party files a claim that a licensed patent right is invalid or unenforceable or if the Company fails to meet or extend the date for meeting certain diligence milestones. Regeneron— 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. Editas— In August 2016, the Company entered into a collaboration, option and license agreement with Editas Medicine, Inc. (Editas) pursuant to which the Company and Editas will collaborate on certain studies using adeno-associated viral (AAV) vectors in connection with Editas’ genome editing technology and the Company will grant to Editas an exclusive option to obtain certain exclusive rights to use the Company’s proprietary vectors in up to five ophthalmic indications (Indications). The Company received a $1.0 million non-refundable upfront payment, with $0.5 million of such payment to be credited against Editas’ obligation to fund research and development costs. Under the terms of the agreement, both the Company and Editas will be subject to exclusivity obligations. Editas may exercise the option, with respect to a designated initial Indication, until the first anniversary of the effective date of the agreement. With respect to the four other Indications, Editas may exercise the option until the third anniversary of the effective date, provided that the option will expire on the second anniversary of the effective date if Editas has not exercised the option with respect to the initial Indication or any other Indication by such date. Upon each exercise of the option, Editas will pay the Company a $1.0 million fee per Indication. If Editas elects to develop a product using certain of the Company’s proprietary vectors, the Company will be eligible to receive up to a mid-teen million dollar amount in development and commercialization milestone payments for such product, and tiered royalties between the mid-single digits and low teens on net sales of such product, subject to certain adjustments. Unless earlier terminated, the agreement will be in effect until the later of the expiration of the option exercise period or the expiration of the royalty term of the last product. At any time after the option is first exercised, Editas may terminate the Agreement for convenience in its entirety or on an indication-by indication or country-by-country basis, upon prior written notice to the Company. The Company may also terminate the agreement if Editas challenges the Company’s patents relating to its proprietary vectors and does not withdraw such challenge within a defined period of time. In addition, either party may terminate the agreement with written notice upon a bankruptcy of the other party or upon an uncured material breach by the other party. Cornell University— In December 2016, the Company informed the appropriate persons at Cornell University (Cornell) that the Company decided to exercise its right to terminate the Company’s master service agreement (MSA), originally established in August 2014 and amended in December 2015. This MSA included gene therapy programs ADVM-043, ADVM-053 and severe allergy. The Company’s three licensing agreements with Cornell for these gene therapy programs remain unchanged. The decision to terminate the MSA is a result of Cornell’s failure to deliver therapeutic material of ADVM-043 suitable for use in human patients. As a result of this decision, the Company is in the final stages of contracting with a large-scale contract manufacturing organization that complies with current good manufacturing practice industry standards and can produce product quantities for both the Company’s planned clinical trials and potential commercial supply. This is part of the Company’s planned upgrade of the manufacturing process for ADVM-043, implementing its proprietary, highly-scalable baculovirus-based production system, in advance of the Company’s plans to initiate a Phase 1/2 clinical trial for ADVM-043 in the fourth quarter of 2017. Under the MSA, Cornell provided assistance in regulatory affairs, overall project management, and parameter development. The MSA, as amended, provided for Annapurna to pay Cornell $13.3 million ratably over 4 years for these services as services were performed. In December 2015, Annapurna Therapeutics Limited entered into three licensing agreements with Cornell, pursuant to which Annapurna will advance its gene therapy programs ADVM-043, ADVM-053, and severe allergy, which originally were initiated at the Department of Genetic Medicine at Weill Cornell. A1AT Deficiency License Agreement : Under this agreement, Annapurna Therapeutics Limited holds an exclusive license to certain technology related to alpha-1 antitrypsin (A1AT) deficiency and rights to an Investigational New Drug (IND) application to initiate clinical studies of gene therapy for A1AT. HAE License Agreement : Under this agreement, Annapurna Therapeutics Limited holds an exclusive license to certain technology related to hereditary angioedema (HAE) and a non-exclusive license to certain other intellectual property related to the HAE program. Allergy License Agreement : Under this agreement, Annapurna Therapeutics Limited holds an exclusive license to certain patents related to allergens and a non-exclusive license to certain other technology related to allergens. Across these three license agreements, Cornell is entitled to receive aggregate annual maintenance fees ranging from $30,000 to $300,000 per year, up to $16.0 million in aggregate milestone payments and royalties on sales in the low single-digits, subject to adjustments and minimum thresholds. The Company accrued $0.8 million as of December 31, 2016 and recorded total research and development expenses of $1.8 million (post Annapurna’s acquisition) for the period from May 11, 2016 through December 31, 2016, related to Cornell agreements. No milestone payments were probable to achieve and none were recorded as of December 31, 2016. Annapurna Therapeutics Limited may terminate any of these license agreements for convenience upon ninety days written notice. Cornell may terminate any of the license agreements for material breach if such breach is not cured within a specified number of days. Cornell may also terminate the HAE License Agreement and/or the Allergy License Agreement if Annapurna Therapeutics Limited commences any action and files a written claim asserting that any portion of the licensed patent rights invalid or unenforceable. Dr. Crystal, Chairman of Genetic Medicine, the Bruce Webster Professor of Internal Medicine and a Professor of Genetic Medicine and of Medicine at Weill Cornell, served as a consultant to Annapurna since inception and continues to provide services to the Company for the annual compensation of $0.3 million. Dr. Crystal also owns common shares of the Company and he does not have significant influence on the Company’s operations. REGENXBIO— A1AT Deficiency/Allergy License Agreement : In October 2015, Annapurna Therapeutics Limited entered into an exclusive worldwide license to certain intellectual property in order to make, have made, use, import, sell and offer for sale certain licensed products for the treatment of A1AT deficiency. Under this agreement, Annapurna Therapeutics Limited also has an option to be granted an exclusive worldwide license to certain intellectual property related to the treatment of severe allergies, which option expired in October 2016. Under this license agreement, REGENXBIO, Inc. (REGENXBIO) is eligible to receive annual maintenance fees, up to approximately $20.0 million in combined milestone payments and royalties in the mid-to-high single digits. Unless earlier terminated, this license agreement will be in effect on a country-by-country, licensed product-by-licensed product basis until the expiration, lapse, abandonment, or invalidation of the last claim of the licensed intellectual property to expire, lapse, or become abandoned or unenforceable for the applicable licensed product. Annapurna Therapeutics Limited may terminate this license agreement upon six months’ prior written notice. REGENXBIO may terminate this license agreement if Annapurna Therapeutics Limited is a specified number of days late in paying money due under the license agreement, or if Annapurna Therapeutics Limited, its affiliates, or any sublicensees become insolvent or, effective immediately, if they commence any action against REGENEXBIO or its licensors to declare or render any claim of the licensed patent rights invalid or unenforceable. Either party may terminate this license agreement for material breach if such breach is not cured within a specified number of days. Friedreich’s Ataxia License Agreement : In April 2014, Annapurna entered into an exclusive worldwide license to certain intellectual property related to the Friedreich’s Ataxia (FA) program to make, have made, use, import, sell and offer for sale licensed products using AAVrh10 for FA where the vector is administered by any route except directly to the central nervous system (FA Systemic). Under the terms of this license agreement, Annapurna also had an option to obtain a non-exclusive worldwide license to make, have made, use, import, sell and offer for sale licensed products using a single vector for each of FA where the vector is administered directly to the central nervous system (FA CNS) and FA Systemic. Under this license agreement, REGENXBIO is eligible to receive annual maintenance fees, up to $13.85 million in combined milestone fees and royalties in the mid-to-high single digits. The option to obtain a non-exclusive license to FA Systemic expired in April 2015 and the option to obtain a non-exclusive license for FA CNS expired in April 2016. Annapurna is obligated to achieve certain development milestones with respect to each licensed disease indication, including the filing of an IND for each licensed disease indication within a specified time period, which Annapurna may extend for additional time for a specified number of extensions upon the payment of a fee. The Company accrued $42,000 as of December 31, 2016 and recorded expenses of $62,000 (post Annapurna’s acquisition) for the period May 11, 2016 through December 31, 2016, related to REGENXBIO agreements. No milestone payments were probable to achieve and none were recorded as of December 31, 2016. Unless earlier terminated, this license agreement expires upon the expiration, lapse, abandonment, or invalidation of the last claim of the licensed intellectual property to expire, lapse, or become abandoned or unenforceable in all the countries of the world. Annapurna Therapeutics Limited may terminate this license agreement upon six months’ prior written notice. REGENXBIO may terminate this license agreement if Annapurna Therapeutics Limited is a specified number of days late in paying money due under the license agreement, or if Annapurna Therapeutics Limited, its affiliates, or any sublicensees become insolvent or, effective immediately, if they commence any action against REGENXBIO or its licensors to declare or render any claim of the licensed patent rights invalid or unenforceable. Either party may terminate this license agreement for material breach if such breach is not cured within a specified number of days. Inserm Transfert— In July 2014, Annapurna entered into an agreement with Inserm Transfert (Inserm) whereby Annapurna holds an exclusive license to certain patents to develop, make, have made, use, import, offer for sale and sell or otherwise distribute products for the treatment of Friedreich’s ataxia and a non-exclusive license to certain other intellectual property related to the FA program. The agreement was amended in October 2015 to increase the scope of the intellectual property under the licenses. Under this agreement, Inserm is entitled to receive certain de minimis license payments, certain development milestone payments of up to approximately €2.0 million in the aggregate and royalties on sales in the low single-digits, subject to adjustments. No milestone payments were probable to achieve and none were recorded as of December 31, 2016. Unless earlier terminated, this agreement will be in effect on a country-by-country, licensed product-by-licensed product basis the last claim of the licensed intellectual property Inserm may terminate this license agreement if Annapurna becomes the subject of a voluntary or involuntary petition in bankruptcy or fails to meet development milestones and such failure is not cured within a specified number of days. Inserm may also terminate the license granted to Annapurna in a given country if Annapurna (i) before regulatory approval of a product in any country, has ceased conducting any development of products in all countries for 12 consecutive months or (ii) after regulatory approval of a product in a given country, has ceased marketing such product in such country for 12 consecutive months. Pursuant to Section 4.7 of the agreement with Inserm, our acquisition of Annapurna triggered a one-time payment to Inserm of €250,000, which is recorded in accrued expenses and other current liabilities as of December 31, 2016.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Property and Equipment, Net	8. Property and Equipment, Net Property and equipment, net consists of the following (in thousands): December 31, 2016 December 31, 2015 Computer equipment and software $ 300 $ 234 Laboratory equipment 4,285 3,041 Furniture and fixtures 552 552 Leasehold improvements 1,522 351 Construction in progress 104 — Total property and equipment 6,763 4,178 Less accumulated depreciation and amortization (2,594 ) (991 ) Property and equipment, net $ 4,169 $ 3,187 Depreciation and amortization expense related to property and equipment was $1,603,000, $812,000 and $162,000 for the years ending December 31, 2016, 2015 and 2014, respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	9. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following (in thousands): December 31, 2016 December 31, 2015 Employees' compensation $ 2,570 $ 2,047 Accrued preclinical costs 1,683 642 Accrued professional fees 894 1,177 Accrued clinical and process development costs 1,142 101 Other 162 40 Total accrued expenses and other current liabilities $ 6,451 $ 4,007

Other Non-Current Liabilities

Other Non-Current Liabilities	12 Months Ended
	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Other Non-Current Liabilities	10. Other non-current liabilities Due to the innovative nature of Annapurna’s product candidate development programs, Annapurna has benefited from certain sources of financial assistance from Banque Publique d’Investissement (“BPI France”). BPI France provides financial assistance and support to emerging French enterprises to facilitate the development and commercialization of innovative technologies. The funds received by the Company are intended to finance its research and development efforts and the recruitment of specific personnel. The Company has received such funding in the form of conditional advances. In August 2015, BPI France granted Annapurna a €750,000 interest free conditional advance, of which €500,000 was drawn down as of December 31, 2015. The remaining €250,000 advance was not and is not expected to be drawn down on. Payments are scheduled in equal quarterly amounts of €25,000 from September 30, 2017 to June 30, 2022. This payment schedule will be modified if the Company will receive revenue from license or product sales before advances are paid in full. The Company calculated 7% imputed interest expense on these advances that was recorded as a discount at the issuance date. The discount is amortized as an interest expense over the life of the advances. As of December 31, 2016 the carrying value, which approximates the fair value, of the conditional advance was $365,000 of which $312,000 is recorded in other non-current liabilities and $53,000 is recorded in accrued expenses and other current liabilities. In addition, the Company recorded $16,000 interest expense from the acquisition closing date to December 31, 2016. In July 2016, the Company entered into a sponsored research agreement with The Alpha-1 Project, Inc. (TAP) in which TAP will fund the Company’s A1AT research activities of up to $300,000. The Company may repay up to 4.5 times the received amount if and when certain product approval and sales milestones are achieved. During the third quarter, the Company received $100,000 and issued the common stock warrant for 10,000 shares exercisable anytime during five years from the issuance date at an exercise price of $4.33 per share. Warrants were valued at $26,000 at the issuance date and recorded as equity. Financing arrangement was recorded at estimated fair value of $74,000 in other noncurrent liabilities as of December 31, 2016. Refer to Note 6 for valuation details of this financing arrangement.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. 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, 2016, future minimum commitments under the Company’s facility operating lease were as follows (in thousands): Years ended December 31, Future Commitments 2017 $ 1,129 2018 1,162 2019 1,197 2020 403 Total minimum lease payments $ 3,891 Rent expense recognized under the operating lease, including additional rent charges for utilities, parking, maintenance, and real estate taxes was $1,745,000, $1,525,000 and $662,000 for the years ended December 31, 2016, 2015 and 2014, respectively. Contractual Obligations We have a contractual obligation at December 31, 2016 to pay $10.0 million over the next 3 year under a Cornell MSA and $1.1 million for manufacturing in 2017. The MSA was cancelled on January 6, 2017 and as such the $10.0 commitments do not exist in the first quarter of 2017 but the commitment still exists at December 31, 2016. Collaborations and License Agreements The Company is a 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, 2016, 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 $0.6 and $0.1 million for each of the years ended December 31, 2016 and 2015. 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, 2016. 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. An amended consolidated complaint was filed in February 2016. On November 3, 2016, the Court granted the Company’s motion to dismiss the consolidated complaint. The plaintiffs filed an amended consolidated complaint on December 2, 2016. The Company’s motion to dismiss that amended complaint is pending. The Company also has filed a motion requesting that the Court order discovery in the related state court action (described below) stayed, and a motion requesting that the Court certify a class of investors who purchased the Company’s securities between July 31, 2014 and June 15, 2015. Both motions are pending. 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 plaintiff has dismissed the two institutional stockholder defendants. In August 2016, the Court denied the Company’s motion to stay without prejudice, denied the Company’s demurrer, and dismissed with leave to amend certain claims against the underwriter defendants. The plaintiff filed an amended complaint on November 2, 2016. The Company’s demurrer to that amended complaint and renewed motion to stay the action is pending. The Company believes that the claims in the asserted actions are without merit and intends to defend the lawsuits vigorously. Due to the inherent uncertainties of litigation, the Company cannot reasonably predict at this time the timing or outcomes of these matters. 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. Beginning in December 2016, the parties have been participating in private mediation, which to date has not progressed to a point where the Company is able to ascertain whether the mediation will be successful. Currently, there are no active mediation discussions between the parties. As a result of, among other things, the uncertain status of the mediation, the early stage of the proceedings, unresolved motions in the proceedings and the uncertainty of the potential outcomes of these and related issues, an estimate of a reasonably possible loss, or the range of losses, if any, or their effect, if any, on the Company’s consolidated financial statements, is not reasonably possible to estimate at this time.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Convertible Preferred Stock	12. 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 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, 2016
Equity [Abstract]
Warrants	13. 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 $8,000 which was recorded as debit to research and development expenses and credit to additional paid-in capital in 2016. 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, 2016 of $2.90 per share, expected term of the warrant of 5.6 years, a risk-free interest rate of 1.2%, an expected volatility of 72% and a 0% expected dividend yield. In July 2016, in connection with the TAP financing agreement the Company issued the common stock warrant for 10,000 shares exercisable anytime during five years from the issuance date at an exercise price of $4.33 per share. The warrant was valued at $26,000 at the issuance date using the Black-Scholes valuation model with the following assumptions: exercise price of $4.33 per share, expected term of the warrants of 5 years, a risk-free interest rate of 1.07%, an expected volatility of 72% and a 0% expected dividend. Issued warrant was recorded to the additional paid-in-capital.

Stock Option Plans

Stock Option Plans	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option Plans	14. 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, 2016, a total of 13,162,656 shares of common stock were authorized for issuance and 3,079,676 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 2016, 56,696 shares were issued under the 2014 ESPP. A total of 618,687 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, 2016. As of December 31, 2016, 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: (in thousands, except exercise prices and years) Options Outstanding Weighted-Average Exercise Price Weighted-Average Remaining Contract Life (in years) Aggregate Intrinsic Value (a) Balance at December 31, 2015 5,494 $ 8.75 7.8 $ 28,618 Options granted 5,098 1.30 Options exercised (1,526 ) 0.52 Options cancelled (1,617 ) 12.82 Balance at December 31, 2016 7,449 $ 4.46 8.4 $ 11,837 Vested and expected to vest as of December 31, 2016 7,337 $ 4.41 8.4 $ 11,836 Exercisable at December 31, 2016 3,995 $ 3.34 7.7 $ 8,674 (a) The aggregate intrinsic value is calculated as the difference between the options exercise price and the closing price of common stock of $2.90 per share as of December 31, 2016. The options granted during 2016, includes the Company’s stock options for 3,673,940 common stock shares issued in exchange for Annapurna stock options at $0.21 exercise price per share. In June 2016, the Company granted stock option to purchase 518,000 shares of common stock to its new Chief Executive Officer and Chief Financial Officer. In December 2015, the Company granted a stock option to purchase 910,000 shares of common stock shares to its new Principal Executive Officer. These options were granted outside of the 2014 Plan and not included in the table above. The total intrinsic value of options exercised during the years ended December 31, 2016, 2015 and 2014 were $7.1 million, $11.2 million and $15.7 million, respectively. 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, 2016 2015 2014 Research and development $ 6,616 $ 4,009 $ 7,331 General and administrative 4,800 6,447 1,236 Restructuring charges — 1,049 — Total share-based compensation $ 11,416 $ 11,505 $ 8,567 Departure of Key Executive Officers Stock-based compensation expense included additional charges of $1.5 million, recorded in general and administrative expense, and $1.4 million, recorded in research and development expense, related to stock modifications in connection with separation agreements for four Company’s executive officers for the year ended December 31, 2016. 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: (in thousands, except grant date fair value and years) Number of Units (in thousands) Weighted-Average Grant Date Fair Value (in dollars) Weighted-Average Remaining Contractual Term (in years) Outstanding units at December 31, 2015 632 $ 13.07 1.1 Granted 1,303 4.40 Vested and released (386 ) 12.20 Forfeited (500 ) 7.10 Outstanding units at December 31, 2016 1,049 $ 5.47 1.7 There were no RSUs granted prior to April 2015. The weighted-average grant date fair values of RSUs granted during fiscal years 2016 and 2015 were $4.40 and $13.85, respectively. The total fair value of RSUs that vested was $1.7 million and $1.4 million for the years ended December 31, 2016 and 2015, respectively. The number of restricted stock units vested includes shares of common stock that the Company withheld on behalf of employees to satisfy the minimum statutory tax withholding requirements. As of December 31, 2016, there was $3.8 million of unrecognized compensation cost related to unvested RSUs that the Company expects to recognize over a weighted-average period of 3.0 years. Stock Options Granted to Employees 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, 2016 2015 2014 2016 2015 2014 Expected volatility 81 % 79 % 79 % 70 % 74 % — Expected term (in years) 6.1 6.1 6.0 0.5 0.5 — Expected dividend yield — — — — — — Risk-free interest rate 1.8 % 1.7 % 1.9 % 0.6 % 0.1 % — The weighted-average fair values of options granted during fiscal years 2016, 2015 and 2014 were $3.35, $15.91 and $9.56, respectively. As of December 31, 2016, there was $11.3 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. The following table presents the weighted-average assumptions used to estimate non-employees stock-based compensation expense: Years Ended December 31, 2016 2015 2014 Option grants: Expected volatility 82 % 81 % 79 % Expected term (in years) 9.1 3.3 7.5 Expected dividend yield — — — Risk-free interest rate 2.1 % 1.0 % 2.2 % As of December 31, 2016, there was $2.6 million of unrecognized stock-based compensation expense related to non-employees’ awards that is expected to be recognized over a weighted-average period of 2.5 years.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2016
Postemployment Benefits [Abstract]
401(k) Savings Plan	15. 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, 2016 and 2015 was $0.3 million and $0.1 million, respectively

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	16. Income Taxes The Company recorded $0.8 million income tax benefit related to the change in the deferred tax liabilities balance due to intangible assets impairment recognized in the fourth quarter of 2016 and The following table presents domestic and foreign components of loss before provision for income taxes (in thousands): Years ended December 31, 2016 2015 2014 U.S. $ (96,498 ) $ (47,235 ) $ (25,006 ) Foreign (18,024 ) (218 ) (398 ) Loss before income taxes $ (114,522 ) $ (47,453 ) $ (25,404 ) 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): Years ended December 31, 2016 2015 2014 Federal income tax expense at statutory rate $ (38,938 ) $ (16,134 ) $ (8,637 ) Loss on extinguishment of related-party convertible notes — — 69 Non-deductible foreign research expenses 21 45 85 Non-deductible stock compensation 1,356 1,418 161 Non-deductible expenses 985 295 285 Goodwill impairment 16,834 Research and development tax credits (326 ) (910 ) (304 ) Change in valuation allowance 16,062 15,277 8,349 Foreign rate differential 3,231 9 (8 ) Total tax expense (benefit) $ (775 ) $ — $ — 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, 2016 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 15,785 $ 19,889 $ 8,526 Accruals, reserve and other 3,071 2,681 222 Stock-based compensation 3,848 4,328 3,032 Tax credit carryforwards 574 1,945 659 Property and equipment 54 — — Intangibles 68 45 24 Other — — 24 Total deferred tax assets before valuation allowance 23,400 28,888 12,487 Valuation allowance (23,400 ) (28,839 ) (12,457 ) Total deferred tax assets — 49 30 Deferred tax liabilities: Property and equipment — (49 ) (30 ) IPR&D (1,250 ) — — Total deferred tax liabilities $ (1,250 ) $ (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, 2016, 2015 and 2014. The valuation allowance decreased approximately $5.4 million, and increased $16.4 million and $9.9 million during the years ended December 31, 2016, 2015 and 2014, respectively, due to net operating losses. As of December 31, 2016, the Company had U.S. federal net operating losses (NOL) carryforwards of approximately $22.0 million to offset future federal income. NOLs expire at various years beginning with 2036. As of December 31, 2016, the Company also had U.S. state NOL carryforwards of approximately $6.7 million to offset future state income. U.S. State NOLs expire at various years beginning with 2036. At December 31, 2016, the Company also had approximately $25.6 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, 2016, the Company had federal research and development tax credit carryforwards of approximately $0.3 million available to reduce future tax liabilities which expire at various years beginning with 2036. As of December 31, 2016, the Company had state credit carryforwards of approximately $0.4 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 the Company experiences 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. The Company believes that it has experienced ownership changes under Section 382, which will result in limitations in the Company’s ability to utilize net operating losses and credits. In addition, the Company 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. Due to a May 11, 2016 ownership change, we determined that certain NOLs for both federal and state purposes are severely limited and therefore we removed a significant amount of NOLs from our deferred tax assets. 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, 2012 through December 31, 2016. 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, 2016, 2015 and 2014 of approximately $2.1 million, $1.6 million and $0.5 million, 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): Years ended December 31, 2016 2015 2014 Unrecognized tax benefits as of the beginning of the year $ 1,568 $ 471 $ 43 Increase (decrease) related to prior year tax provisions — 172 272 Increase related to current year tax provisions 589 925 156 Unrecognized tax benefits as of the end of the year $ 2,157 $ 1,568 $ 471 The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2016 and 2015, 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, 2016
Earnings Per Share [Abstract]
Net Loss per Share	17. 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, 2016, 2015 and 2014 (in thousands, except per share data): Years ended December 31, 2016 2015 2014 Net loss $ (113,747 ) $ (47,453 ) $ (25,404 ) Deemed dividend — — (3,230 ) Net loss attributable to common stockholders (113,747 ) (47,453 ) (28,634 ) Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share: Net shares outstanding 36,246 25,479 11,651 Basic and diluted net loss per share attributable to common stockholders $ (3.14 ) $ (1.86 ) $ (2.46 ) 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 (in thousands): As of December 31, 2016 2015 2014 Options to purchase common stock 7,449 5,494 4,932 Restricted stock units 1,049 632 — Warrants to purchase common stock 50 40 — 8,548 6,166 4,932

Selected Quarterly Financial In

Selected Quarterly Financial Information	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Information	18. Selected Quarterly Financial Information (Unaudited) The following amounts are in thousands, except per share amounts: Quarterly Results of Operations Quarters ended March 31, 2016 June 30, 2016 September 30, 2016 December 31, 2016 Revenue $ 265 $ 307 $ 395 $ 488 Total operating expenses (1)(2)(3) $ (15,773 ) $ (62,189 ) $ (14,902 ) $ (23,875 ) Net loss $ (15,392 ) $ (61,660 ) $ (14,301 ) $ (22,394 ) Basic and diluted net loss per share $ (0.57 ) $ (1.76 ) $ (0.35 ) $ (0.54 ) Quarterly Results of Operations Quarters ended March 31, 2015 June 30, 2015 September 2015 December 2015 Revenue $ 203 $ 203 $ 953 $ 960 Total operating expenses (4)(5) $ (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 ) ( 1 ) We performed a two-step goodwill impairment analysis and recorded a $49.1 million and a $0.4 million goodwill impairment charge in the second and third quarter of 2016, respectively, in our consolidated statements of operations and comprehensive loss. ( 2 ) In the fourth quarter of 2016, we performed our annual assessment of our ADVM-043 and ADVM-053 IPR&D assets. We recorded a $11.2 million IPR&D impairment charge. (3) In the first quarter of 2016, two officers of the company resigned and we recorded $2.2 million additional stock-based compensation expense related to acceleration of their stock-based awards due to modification of equity awards. ( 4 ) 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. ( 5 ) 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, 2016
Subsequent Events [Abstract]
Subsequent Event	19. Subsequent Event On February 23, 2017, Regeneron notified us that, pursuant to Section 2.3 of the collaboration agreement, it is extending the research term of the Collaboration Agreement for an additional three years, through May 1, 2020.

Summary of significant accoun27

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation — The Company’s consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) and pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All inter-company transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates —The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, 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 research and development expense accruals, stock-based compensation expense, income taxes, and fair value of common 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.
Foreign Currency Translation	Foreign Currency Translation —The Company’s consolidated financial statements are prepared in U.S. dollars. Its foreign subsidiaries use the Euro and Australian dollar as their functional currency and maintains their records in the local currency, except our Ireland subsidiary that uses U.S. dollars as its’ functional currency. Assets and liabilities are re-measured at exchange rates in effect at the end of the reporting period at our France and Australia subsidiaries, and at historical exchange rates at our Irish subsidiary. 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 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, 2016 and 2015 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, 2016, substantially all of the Company’s cash and cash equivalents was deposited in accounts at five 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 instruments 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.
Valuation of Long-Lived Assets and Purchased Intangible Assets	Valuation of Long-Lived Assets and Purchased Intangible Assets —The Company evaluates the carrying value of amortizable long‑lived assets, whenever events, or changes in business circumstances or the planned use of long‑lived assets indicate that their carrying amounts may not be fully recoverable or that their useful lives are no longer appropriate. If these facts and circumstances exist, the Company assesses for recovery by comparing the carrying values of long‑lived assets with their future undiscounted net cash flows. If the comparison indicates that impairment exists, long‑lived assets are written down to their respective fair value based on discounted cash flows. Significant management judgment is required in the forecasting of future operating results that is used in the preparation of expected undiscounted cash flows. If management’s assumptions about future operating results were to change as a result of events or circumstances, the Company may be required to record an impairment loss on these assets. No impairment indicators were noted for the Company’s amortizable long-lived assets, fixed assets, in the periods presented. The Company also evaluates the carrying value of intangible assets (not subject to amortization) related to in‑process research and development (“IPR&D”) assets, which are considered to be indefinite‑lived until the completion or abandonment of the associated research and development efforts. Accordingly, amortization of the IPR&D assets will not occur until the product reaches commercialization. During the period the assets are considered indefinite‑lived, they will be tested for impairment on an annual basis, as well as between annual tests if the Company become aware of any events occurring or changes in circumstances that would indicate that the fair values of the IPR&D assets are less than their carrying amounts. If and when development is complete, which generally occurs when regulatory approval to market the product is obtained, the associated IPR&D assets would be deemed definite‑lived and would then be amortized based on their estimated useful lives at that point in time based on respective patent terms. If the related project is terminated or abandoned, the Company will have an impairment related to the IPR&D assets, calculated as the excess of its carrying value over fair value. The Company estimated fair value of IPR&D assets acquired in Annapurna transaction at the acquisition closing date, May 11, 2016, to be $16.2 million. As a result of management’s decision to change its manufacturing process for ADVM-043 and ADVM-053 by implementing its proprietary baculovirus-based production system during the fourth quarter of 2016 and based upon the Company’s analysis of the fair value of the IPR&D assets as of December 31, 2016, the Company recorded an impairment charge of $11.2 million. Refer to Note 3 for further details.
Financial Liabilities	Financial Liabilities —Prior to the Company’s IPO, the Company had recorded convertible preferred stock warrants issued to investors and note holders as derivative 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. During 2016, the Company entered into a sponsored research agreement with The Alpha-1 project, Inc. (TAP) with an embedded derivative, the Company determined to account for this financial liability at fair value. Refer to Note 13 for further details.
Revenue Recognition	Revenue Recognition —The Company has primarily generated revenue through license, research and collaboration arrangements with its strategic partners. The terms of these types of agreements may include (i) licenses to our technology, (ii) research In arrangements involving the delivery of more than one element, each required deliverable is The arrangement’s consideration that is fixed or determinable is allocated to each separate unit Payments or reimbursements for the Company’s research and development efforts for the arrangements where The Company’s collaboration and license agreements may include contingent payments related to Collaboration and License Revenue In August 2016, the Company entered into a collaboration, option and license agreement with Editas. Refer to Note 7 for details of the agreement. Under the terms of the agreement, the Company received initial payments of $1.0 million that included $0.5 million for research services. As the agreement provides for multiple deliverables, the Company accounts for this agreement as a multiple elements revenue arrangement. At the inception of the agreement, identified deliverables include research services, manufacturing of viral vectors for research, participation in joint research committee and exclusivity during the option period. These deliverables did not appear to have a standalone value and were combined into one unit of accounting. Options for each indication to license the Company’s AAV vector are considered substantive options and do not include significant incremental discounts. Therefore, they are not considered as deliverables under the agreement. The Company allocated the $1.0 million received to a single unit of accounting identified in the arrangement. The Company expects to recognize $1.0 million ratably over the associated period of performance, which is the maximum research period of three 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. During the year ended December 31, 2016, the Company recognized $139,000 as 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. Refer to Note 7 for details of the agreement. 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 license to develop and commercialize 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 a 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 recognizes $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 recognizes revenue on a straight-line basis over the eight years performance period. The remaining $1.5 million allocated to the second unit of accounting for the time-limited right of first negotiation for license to develop and commercialize AVA-101. 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 invoices for services performed quarterly. These additional research fees are 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 $1.4 million and $0.8 million during the year ended December 31, 2016 and 2015, respectively, related to the research licenses and research and development services unit of accounting in the Regeneron agreement.
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 and French governments in connection with certain research costs incurred in conducting research by the Company’s Australian and French subsidiaries. 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 $0.3 million, $0.1 million and $0.1 million from the 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, 2016, 2015 and 2014, 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, and accrued expenses approximate their fair values due to their short-term maturities. Refer to Note 6 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 granted 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 14 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, 2016 and 2015, 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 Company’s Australia, and France subsidiaries and unrealized gain (loss) on marketable securities. The Company did not have reclassifications from other comprehensive income (loss) to the income (loss) during 2016 and 2015 fiscal years.
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.
Recent Accounting Standard Update Not Yet Effective	Recent Accounting Standard Update Not Yet Effective —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 standard 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. This ASU will be effective for the Company in the first quarter of 2017. The adoption of this standard is not expected to impact the Company’s consolidated financial statements and related disclosures. 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 Revenue From Contracts With Customers: Principal vs. Agent Considerations Revenue From Contracts with Customers: Identifying Performance Obligations and Licensing Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients Technical Corrections and Improvement to Topic 606 – Revenue from Contracts with In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, which amends the current guidance on the classification and measurement of financial instruments. Although this ASU retains many current requirements, it significantly revises an entity’s accounting related to (i) the classification and measurement of investments in equity securities and (ii) the presentation of certain fair value changes for financial liabilities measured at fair value. This ASU also amends certain disclosure requirements associated with the fair value of financial instruments. The new standard is effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2017, with early adoption permitted for certain changes. This ASU will be effective for the Company in the first quarter of 2018 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted for certain provisions. The adoption of this standard is not expected to have a significant impact on the Company’s consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-2, Leases In March 2016, the FASB issued ASU No. 2016-9, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting, In June 2016, the FASB issued ASU No. 2016-13 Measurement of Credit Losses on Financial Instruments In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15) In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (ASU 2016-18) The Company has reviewed other recent accounting pronouncements and concluded they are either not applicable to the business or no material effect is expected on the consolidated financial statements as a result of future adoption.
Accounting Standard Update Recently Adopted	Accounting Standard Update Recently Adopted —In April 2015, the FASB issued ASU No. 2015-05, Customer’s Accounting of Fees Paid in Cloud Computing Arrangement , guidance on accounting for fees paid in cloud computing arrangements. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a services contract. All software licenses recognized under this guidance will be accounted for consistent with other licenses of intangible assets. The Company elected to adopt this ASU in the first quarter of fiscal 2016. The adoption of this standard did not have any impact on the Company's consolidated financial statements.

Acquisition of Annapurna (Table

Acquisition of Annapurna (Tables)	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Summary of Total Purchase Price Consideration Estimated	Total purchase price consideration was estimated as follows (in thousands): Fair value of common shares issued $ 58,321 Fair value of the Company's common share options exchanged for Annapurna options and other awards attributable to pre-combination services 7,422 Less: value of common stock and options accelerated vesting at close date (898 ) Total purchase price consideration $ 64,845
Components of Allocation of Total Purchase Price Consideration	The allocation of total purchase price consideration is as follows (in thousands): Cash $ 3,449 Prepaid expenses and other assets 865 Property and equipment 185 Acquired intangible assets 16,200 Goodwill 49,514 Accounts payable (1,118 ) Accrued liabilities (1,848 ) Other noncurrent liabilities (377 ) Deferred tax liabilities (2,025 ) Total purchase price allocation $ 64,845
Summary of Identifiable Intangible Assets Acquired	The identifiable intangible assets acquired consist of IPR&D assets related to products in development, as summarized in the table below (in thousands): IPR&D - Alpha-1 antitrypsin deficiency $ 11,700 IPR&D - Hereditary angioedema 4,500 Total acquired intangible assets $ 16,200
Schedule of Pro Forma Financial Information	The following table presents the unaudited pro forma results for the years ended December 31, 2016 and 2015 (in thousands, except per share data). Years ended December 31, 2016 2015 Pro forma information Collaboration and license revenue $ 1,455 $ 2,319 Net loss $ (117,551 ) $ (61,774 ) Basic and diluted loss per share $ (2.85 ) $ (1.56 ) Weighted-average common shares outstanding - basic and diluted 41,288 39,566

Restructuring Charges (Tables)

Restructuring Charges (Tables)	12 Months Ended
	Dec. 31, 2016
Restructuring And Related Activities [Abstract]
Summary of Restructuring Activities	The following table summarizes the restructuring activities for the years ended December 31, 2015 and 2016 (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 payments (988 ) — (988 ) Restructuring liability as of December 31, 2016 $ 25 $ — $ 25

Cash Equivalents and Marketab30

Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Summary of Cash Equivalents and Marketable Securities	The following is a summary of the cash equivalents and marketable securities (in thousands): December 31, 2016 Amortized Cost Basis Unrealized Gains Unrealized Loses Estimated Fair Value Money market funds - cash equivalent $ 215,916 $ — $ — $ 215,916 Total cash equivalents $ 215,916 $ — $ — $ 215,916 December 31, 2015 Money market funds - cash equivalent $ 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 F31

Fair Value Measurements and Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured and Recognized at Fair Value	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, 2016 Assets: Money market funds - cash equivalent $ 215,916 $ 215,916 $ — $ — Total cash equivalents $ 215,916 $ 215,916 $ — $ — Other noncurrent liability: Financing arrangement $ 74 $ — $ — $ 74 December 31, 2015 Assets: Money market funds - cash equivalent $ 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 $ —
Quantitative Information About Inputs and Valuation Methodologies Used for Fair Value Measurements	The following table presents quantitative information about the inputs and valuation methodologies used for the fair value measurements classified in Level 3 of the fair value hierarchy at December 31, 2016: Fair Value at December 31, 2016 (in thousands) Valuation Methodology Significant Unobservable Input Weighted-Average (range - if applicable) Financing arrangement $ 74 Expected value approach Milestone dates 2017 - 2023 Discount rate 5.5 % Percent probability of milestone achievements 18.2% to 80.0%

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following (in thousands): December 31, 2016 December 31, 2015 Computer equipment and software $ 300 $ 234 Laboratory equipment 4,285 3,041 Furniture and fixtures 552 552 Leasehold improvements 1,522 351 Construction in progress 104 — Total property and equipment 6,763 4,178 Less accumulated depreciation and amortization (2,594 ) (991 ) Property and equipment, net $ 4,169 $ 3,187

Accrued Expenses and Other Cu33

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2016 December 31, 2015 Employees' compensation $ 2,570 $ 2,047 Accrued preclinical costs 1,683 642 Accrued professional fees 894 1,177 Accrued clinical and process development costs 1,142 101 Other 162 40 Total accrued expenses and other current liabilities $ 6,451 $ 4,007

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Commitments under Facility Operating Lease	As of December 31, 2016, future minimum commitments under the Company’s facility operating lease were as follows (in thousands): Years ended December 31, Future Commitments 2017 $ 1,129 2018 1,162 2019 1,197 2020 403 Total minimum lease payments $ 3,891

Stock Option Plans (Tables)

Stock Option Plans (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2016 2015 2014 Research and development $ 6,616 $ 4,009 $ 7,331 General and administrative 4,800 6,447 1,236 Restructuring charges — 1,049 — Total share-based compensation $ 11,416 $ 11,505 $ 8,567
Summary of Restricted Stock Units Activity	The following table summarizes the RSUs activity under the Company’s stock plans and related information: (in thousands, except grant date fair value and years) Number of Units (in thousands) Weighted-Average Grant Date Fair Value (in dollars) Weighted-Average Remaining Contractual Term (in years) Outstanding units at December 31, 2015 632 $ 13.07 1.1 Granted 1,303 4.40 Vested and released (386 ) 12.20 Forfeited (500 ) 7.10 Outstanding units at December 31, 2016 1,049 $ 5.47 1.7
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, 2016 2015 2014 2016 2015 2014 Expected volatility 81 % 79 % 79 % 70 % 74 % — Expected term (in years) 6.1 6.1 6.0 0.5 0.5 — Expected dividend yield — — — — — — Risk-free interest rate 1.8 % 1.7 % 1.9 % 0.6 % 0.1 % —
Non Employee Stock Option [Member]
Schedule of Non-Employees Stock Purchase Plan Valuation Assumptions	The following table presents the weighted-average assumptions used to estimate non-employees stock-based compensation expense: Years Ended December 31, 2016 2015 2014 Option grants: Expected volatility 82 % 81 % 79 % Expected term (in years) 9.1 3.3 7.5 Expected dividend yield — — — Risk-free interest rate 2.1 % 1.0 % 2.2 %
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: (in thousands, except exercise prices and years) Options Outstanding Weighted-Average Exercise Price Weighted-Average Remaining Contract Life (in years) Aggregate Intrinsic Value (a) Balance at December 31, 2015 5,494 $ 8.75 7.8 $ 28,618 Options granted 5,098 1.30 Options exercised (1,526 ) 0.52 Options cancelled (1,617 ) 12.82 Balance at December 31, 2016 7,449 $ 4.46 8.4 $ 11,837 Vested and expected to vest as of December 31, 2016 7,337 $ 4.41 8.4 $ 11,836 Exercisable at December 31, 2016 3,995 $ 3.34 7.7 $ 8,674 (a) The aggregate intrinsic value is calculated as the difference between the options exercise price and the closing price of common stock of $2.90 per share as of December 31, 2016.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
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): Years ended December 31, 2016 2015 2014 U.S. $ (96,498 ) $ (47,235 ) $ (25,006 ) Foreign (18,024 ) (218 ) (398 ) Loss before income taxes $ (114,522 ) $ (47,453 ) $ (25,404 )
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): Years ended December 31, 2016 2015 2014 Federal income tax expense at statutory rate $ (38,938 ) $ (16,134 ) $ (8,637 ) Loss on extinguishment of related-party convertible notes — — 69 Non-deductible foreign research expenses 21 45 85 Non-deductible stock compensation 1,356 1,418 161 Non-deductible expenses 985 295 285 Goodwill impairment 16,834 Research and development tax credits (326 ) (910 ) (304 ) Change in valuation allowance 16,062 15,277 8,349 Foreign rate differential 3,231 9 (8 ) Total tax expense (benefit) $ (775 ) $ — $ —
Schedule of Deferred Tax Assets	The following table presents significant components of the Company’s deferred tax assets (in thousands): As of December 31, 2016 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 15,785 $ 19,889 $ 8,526 Accruals, reserve and other 3,071 2,681 222 Stock-based compensation 3,848 4,328 3,032 Tax credit carryforwards 574 1,945 659 Property and equipment 54 — — Intangibles 68 45 24 Other — — 24 Total deferred tax assets before valuation allowance 23,400 28,888 12,487 Valuation allowance (23,400 ) (28,839 ) (12,457 ) Total deferred tax assets — 49 30 Deferred tax liabilities: Property and equipment — (49 ) (30 ) IPR&D (1,250 ) — — Total deferred tax liabilities $ (1,250 ) $ (49 ) $ (30 ) Net deferred tax assets $ — $ — $ —
Schedule of Unrecognized Tax Benefits	A reconciliation of the unrecognized tax benefits is as follows (in thousands): Years ended December 31, 2016 2015 2014 Unrecognized tax benefits as of the beginning of the year $ 1,568 $ 471 $ 43 Increase (decrease) related to prior year tax provisions — 172 272 Increase related to current year tax provisions 589 925 156 Unrecognized tax benefits as of the end of the year $ 2,157 $ 1,568 $ 471

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2016, 2015 and 2014 (in thousands, except per share data): Years ended December 31, 2016 2015 2014 Net loss $ (113,747 ) $ (47,453 ) $ (25,404 ) Deemed dividend — — (3,230 ) Net loss attributable to common stockholders (113,747 ) (47,453 ) (28,634 ) Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share: Net shares outstanding 36,246 25,479 11,651 Basic and diluted net loss per share attributable to common stockholders $ (3.14 ) $ (1.86 ) $ (2.46 )
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 (in thousands): As of December 31, 2016 2015 2014 Options to purchase common stock 7,449 5,494 4,932 Restricted stock units 1,049 632 — Warrants to purchase common stock 50 40 — 8,548 6,166 4,932

Selected Quarterly Financial 38

Selected Quarterly Financial Information (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following amounts are in thousands, except per share amounts: Quarterly Results of Operations Quarters ended March 31, 2016 June 30, 2016 September 30, 2016 December 31, 2016 Revenue $ 265 $ 307 $ 395 $ 488 Total operating expenses (1)(2)(3) $ (15,773 ) $ (62,189 ) $ (14,902 ) $ (23,875 ) Net loss $ (15,392 ) $ (61,660 ) $ (14,301 ) $ (22,394 ) Basic and diluted net loss per share $ (0.57 ) $ (1.76 ) $ (0.35 ) $ (0.54 ) Quarterly Results of Operations Quarters ended March 31, 2015 June 30, 2015 September 2015 December 2015 Revenue $ 203 $ 203 $ 953 $ 960 Total operating expenses (4)(5) $ (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 ) ( 1 ) We performed a two-step goodwill impairment analysis and recorded a $49.1 million and a $0.4 million goodwill impairment charge in the second and third quarter of 2016, respectively, in our consolidated statements of operations and comprehensive loss. ( 2 ) In the fourth quarter of 2016, we performed our annual assessment of our ADVM-043 and ADVM-053 IPR&D assets. We recorded a $11.2 million IPR&D impairment charge. (3) In the first quarter of 2016, two officers of the company resigned and we recorded $2.2 million additional stock-based compensation expense related to acceleration of their stock-based awards due to modification of equity awards. ( 4 ) 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. ( 5 ) 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 the Business - A

Description of the Business - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	May 11, 2016	Mar. 31, 2015	Jan. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Date of incorporation				Jul. 17, 2006
Change of entity name date				May 11, 2016
Accumulated deficit				$ (197,915)	$ (84,168)
Common stock, par value				$ 0.0001	$ 0.0001
Proceeds from sales of common stock		$ 8,300
Issuance of common stock		230,000
IPO and Private Placement and Follow On Offering [Member]
Class of Stock [Line Items]
Proceeds from sales of common stock			$ 237,100
Annapurna Therapeutics SAS [Member]
Class of Stock [Line Items]
Number of shares issued to acquired an entity	14,087,246
Common stock, par value	$ 0.0001

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended		3 Months Ended	8 Months Ended	12 Months Ended
	Aug. 31, 2016USD ($)	May 31, 2014USD ($)	Dec. 31, 2016USD ($)Security	Dec. 31, 2016USD ($)Security	Dec. 31, 2016USD ($)SecuritySegment	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	May 11, 2016USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of available-for-securities held | Security			0	0	0
Deposits			$ 100,000	$ 100,000	$ 100,000	$ 100,000
Number of reportable segments | Segment					1
Number of operating segments | Segment					1
Impairment losses of amortizable long-lived assets					$ 0	0
Collaboration and license revenue					1,455,000	2,319,000	$ 572,000
Tax credits due to reduction of research and development expense					326,000	910,000	304,000
Australian Tax Authorities [Member]
Summary Of Significant Accounting Policies [Line Items]
Tax credits due to reduction of research and development expense					300,000	100,000	$ 100,000
Upfront Payment Arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Initial payments received		$ 8,000,000
Editas Medicine Inc [Member]
Summary Of Significant Accounting Policies [Line Items]
Initial payments received	$ 1,000,000
Revenue recognized	$ 1,000,000
Performance period	3 years
Collaboration and license revenue					139,000
Regeneron Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Research collaboration and license agreement revenue					1,400,000	800,000
Regeneron Corporation [Member] | Upfront Payment Arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized		$ 6,500,000				$ 1,500,000
Performance period		8 years
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
IPR&D [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment of intangible assets			$ 11,200,000
Research Services [Member] | Editas Medicine Inc [Member]
Summary Of Significant Accounting Policies [Line Items]
Initial payments received	$ 500,000
Annapurna Therapeutics SAS [Member]
Summary Of Significant Accounting Policies [Line Items]
Acquisition closing date					May 11, 2016
Estimated fair value of identifiable intangible assets acquired								$ 16,200,000
Annapurna Therapeutics SAS [Member] | IPR&D [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated fair value of identifiable intangible assets acquired								$ 16,200,000
Impairment of intangible assets				$ 11,200,000	$ 11,200,000
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

Acquisition of Annapurna - Addi

Acquisition of Annapurna - Additional Information (Detail)	May 11, 2016USD ($)Segment$ / sharesshares	May 31, 2016USD ($)	Dec. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014
Business Acquisition [Line Items]
Total purchase price consideration						$ 64,845,000
IPR&D [Member]
Business Acquisition [Line Items]
Impairment of intangible assets			$ 11,200,000
Stock Options [Member]
Business Acquisition [Line Items]
Expected volatility						81.00%	79.00%	79.00%
Risk-free interest rate						1.80%	1.70%	1.90%
Expected term (in years)						6 years 1 month 6 days	6 years 1 month 6 days	6 years
Non Employee Stock Option [Member]
Business Acquisition [Line Items]
Expected volatility						82.00%	81.00%	79.00%
Risk-free interest rate						2.10%	1.00%	2.20%
Expected term (in years)						9 years 1 month 6 days	3 years 3 months 18 days	7 years 6 months
Annapurna Therapeutics SAS [Member]
Business Acquisition [Line Items]
Date of acquisition						May 11, 2016
Total purchase price consideration	$ 64,845,000
Number of shares issued to acquired an entity | shares	14,087,246
Fair value of awards related to accelerated vesting of options and shares	$ 900,000
Common stock exchange ratio			9.54655		9.54655	9.54655
Goodwill, description						Goodwill represented expected synergies of two combined companies.
Acquisition costs						$ 2,500,000
Fair value, discounted rate	11.00%
Goodwill	$ 49,514,000			$ 0
Number of reporting unit | Segment	1
Amount of net loss included in the consolidated statements of operations from acquisition date					$ 16,600,000
Revenues from the acquisition date					0
Interest expense related to convertible notes and changes in fair value of preferred stock warrants						1,000,000	$ 500,000
Bonuses paid		$ 400,000
Annapurna Therapeutics SAS [Member] | IPR&D [Member]
Business Acquisition [Line Items]
Impairment of intangible assets					$ 11,200,000	11,200,000
Annapurna Therapeutics SAS [Member] | Stock Options [Member]
Business Acquisition [Line Items]
Shares reserved for future exercise of stock options | shares	3,673,940
Fair value of estimated stock options and stock-based awards at acquisition	$ 14,700,000
Dividends	0.00%
Expected volatility	80.00%
Risk-free interest rate	1.40%
Expected term (in years)	6 years
Fair value of stock options attributed as pre-combination service and included as part of acquisition consideration	$ 7,400,000
Fair value of stock options post-combination attribution recognized as compensation expense	$ 7,200,000
Stock-based compensation expense related to vesting of options				$ 900,000
Annapurna Therapeutics SAS [Member] | Stock Options [Member] | Executives [Member]
Business Acquisition [Line Items]
Stock-based compensation expense related to vesting of stock options						$ 200,000	$ 400,000
Annapurna Therapeutics SAS [Member] | Non Employee Stock Option [Member]
Business Acquisition [Line Items]
Dividends	0.00%
Expected volatility	89.00%
Risk-free interest rate	1.10%
Expected term (in years)	10 years
Annapurna Therapeutics SAS [Member] | Common Shares [Member]
Business Acquisition [Line Items]
Number of shares issued to acquired an entity | shares	14,087,246
Share price of common stock on date of acquisition | $ / shares	$ 4.14

Acquisition of Annapurna - Summ

Acquisition of Annapurna - Summary of Total Purchase Price Consideration Estimated (Detail) - USD ($) $ in Thousands	May 11, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Total purchase price consideration		$ 64,845
Annapurna Therapeutics SAS [Member]
Business Acquisition [Line Items]
Less: value of common stock and options accelerated vesting at close date	$ (898)
Total purchase price consideration	64,845
Annapurna Therapeutics SAS [Member] | Common Shares [Member]
Business Acquisition [Line Items]
Fair value of common shares issued/common share options exchanged	58,321
Annapurna Therapeutics SAS [Member] | Common Shares [Member] | Stock Options [Member]
Business Acquisition [Line Items]
Fair value of common shares issued/common share options exchanged	$ 7,422

Acquisition of Annapurna - Comp

Acquisition of Annapurna - Components of Allocation of Total Purchase Price Consideration (Detail) - Annapurna Therapeutics SAS [Member] - USD ($) $ in Thousands	Jun. 30, 2016	May 11, 2016
Business Acquisition [Line Items]
Cash		$ 3,449
Prepaid expenses and other assets		865
Property and equipment		185
Acquired intangible assets		16,200
Goodwill	$ 0	49,514
Accounts payable		(1,118)
Accrued liabilities		(1,848)
Other noncurrent liabilities		(377)
Deferred tax liabilities		(2,025)
Total purchase price allocation		$ 64,845

Acquisition of Annapurna - Su44

Acquisition of Annapurna - Summary of Identifiable Intangible Assets Acquired (Detail) - Annapurna Therapeutics SAS [Member] $ in Thousands	May 11, 2016USD ($)
Acquired Indefinite Lived Intangible Assets [Line Items]
Acquired intangible assets	$ 16,200
IPR&D [Member]
Acquired Indefinite Lived Intangible Assets [Line Items]
Acquired intangible assets	16,200
IPR&D [Member] | Alpha-1 Antitrypsin Deficiency [Member]
Acquired Indefinite Lived Intangible Assets [Line Items]
Acquired intangible assets	11,700
IPR&D [Member] | Hereditary Angiodema [Member]
Acquired Indefinite Lived Intangible Assets [Line Items]
Acquired intangible assets	$ 4,500

Acquisition of Annapurna - Sche

Acquisition of Annapurna - Schedule of Pro Forma Financial Information (Detail) - Annapurna Therapeutics SAS [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Pro forma information
Collaboration and license revenue	$ 1,455	$ 2,319
Net loss	$ (117,551)	$ (61,774)
Basic and diluted loss per share	$ (2.85)	$ (1.56)
Weighted-average common shares outstanding - basic and diluted	41,288	39,566

Acquisition of Annapurna - Ad46

Acquisition of Annapurna - Additional Information1 (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2016	May 11, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Common shares outstanding			41,805,009		25,858,722
Goodwill impairment charge	$ 400	$ 49,100
Impairment of goodwill and intangible assets			$ 60,714
Annapurna Therapeutics SAS [Member]
Business Acquisition [Line Items]
Stock price		$ 3.16
Common shares outstanding		41,300,000
Goodwill		$ 0		$ 49,514
Annapurna Therapeutics SAS [Member] | Alpha-1 Antitrypsin Deficiency and Hereditary Angioedema [Member] | IPR&D [Member]
Business Acquisition [Line Items]
Carrying value of intangible assets			16,200
Fair value of intangible assets			5,000
Impairment of goodwill and intangible assets			11,200
Annapurna Therapeutics SAS [Member] | Impairment of Goodwill and Intangible Assets [Member]
Business Acquisition [Line Items]
Goodwill impairment charge			$ 49,500

Restructuring Charges - Additio

Restructuring Charges - Additional Information (Detail) $ in Thousands	Dec. 22, 2015Employee	Dec. 31, 2015USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
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			$ 11,416	$ 11,505	$ 8,567
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, 2016	Dec. 31, 2015
Restructuring Reserve [Line Items]
Restructuring liability beginning balance		$ 1,013	$ 0
Costs incurred and recorded as restructuring charges	$ 2,600		2,573
Cash payments		(988)	(511)
Non-cash settlements			(1,049)
Restructuring liability ending balance	1,013	25	1,013
One-Time Termination Benefits [Member]
Restructuring Reserve [Line Items]
Restructuring liability beginning balance		1,013	0
Costs incurred and recorded as restructuring charges			1,524
Cash payments		(988)	(511)
Restructuring liability ending balance	1,013	25	1,013
Non-Cash Charge Related to Acceleration of RSUs [Member]
Restructuring Reserve [Line Items]
Restructuring liability beginning balance		0	0
Costs incurred and recorded as restructuring charges			1,049
Non-cash settlements			(1,049)
Restructuring liability ending balance	$ 0	$ 0	$ 0

Cash Equivalents and Marketab49

Cash Equivalents and Marketable Securities - Summary of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
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)
Total Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Amortized Cost Basis	$ 215,916
Estimated Fair Value	215,916
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 - Cash Equivalent [Member]
Cash and Cash Equivalents [Line Items]
Amortized Cost Basis	215,916	208,588
Estimated Fair Value	$ 215,916	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 Marketab50

Cash Equivalents and Marketable Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)
Cash And Cash Equivalents [Abstract]
Recognized gains or losses on liquidation	$ 0

Fair Value Measurements and F51

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Aug. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities transferred within Level 3	$ 0	$ 0
Proceeds from financing arrangement	100,000
Financing Arrangement [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Proceeds from financing arrangement	$ 100,000
Financing Arrangement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amount borrowed under financing arrangement			$ 300,000
Future contingent milestone payments			$ 1,400,000

Fair Value Measurements and F52

Fair Value Measurements and Fair Value of Financial Instruments - Financial Assets and Liabilities Measured and Recognized at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets:
Assets	$ 215,916	$ 246,320
Financing Arrangement [Member]
Other noncurrent liability:
Other noncurrent liability	74
Money Market Funds - Cash Equivalent [Member]
Assets:
Assets	215,916	208,588
Certificates of Deposit [Member]
Assets:
Assets		1,680
U.S. Treasury Securities [Member]
Assets:
Assets		15,042
U.S. Government Agency Securities [Member]
Assets:
Assets		21,010
Quoted Prices in Active Markets (Level 1) [Member]
Assets:
Assets	215,916	208,588
Quoted Prices in Active Markets (Level 1) [Member] | Money Market Funds - Cash Equivalent [Member]
Assets:
Assets	215,916	208,588
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Assets		37,732
Significant Other Observable Inputs (Level 2) [Member] | Certificates of Deposit [Member]
Assets:
Assets		1,680
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Securities [Member]
Assets:
Assets		15,042
Significant Other Observable Inputs (Level 2) [Member] | U.S. Government Agency Securities [Member]
Assets:
Assets		$ 21,010
Significant Unobservable Inputs (Level 3) [Member] | Financing Arrangement [Member]
Other noncurrent liability:
Other noncurrent liability	$ 74

Fair Value Measurements and F53

Fair Value Measurements and Fair Value of Financial Instruments - Quantitative Information About Inputs and Valuation Methodologies Used for Fair Value Measurements (Detail) - Financing Arrangement [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other noncurrent liability	$ 74
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other noncurrent liability	$ 74
Valuation Methodology	Expected value approach
Discount rate	5.50%
Significant Unobservable Inputs (Level 3) [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Milestone dates	2,017
Percent probability of milestone achievements	18.20%
Significant Unobservable Inputs (Level 3) [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Milestone dates	2,023
Percent probability of milestone achievements	80.00%

Significant Agreements - Additi

Significant Agreements - Additional Information (Detail)

1 Months Ended

8 Months Ended

12 Months Ended

Dec. 31, 2016USD ($)Agreement

Aug. 31, 2016USD ($)

Dec. 31, 2015USD ($)Agreement

Oct. 31, 2015USD ($)

Oct. 31, 2015EUR (€)

May 31, 2014USD ($)Target

Apr. 30, 2014USD ($)

May 31, 2010USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Dec. 31, 2014USD ($)

Dec. 31, 2016EUR (€)

License Agreement [Line Items]

Annual maintenance fee payable

$ 600,000

$ 100,000

License agreement, recorded research and development expenses

$ 31,670,000

25,462,000

$ 16,976,000

Regeneron Corporation [Member]

License Agreement [Line Items]

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.

Potential target of collaborations | Target

8

Initial collaboration term

3 years

Additional collaboration term

5 years

Collaboration fee for exclusive worldwide license per target

$ 2,000,000

Potential milestone earnings

640,000,000

Reimbursement of research and development expense

35.00%

Regeneron Corporation [Member] | Development and Regulatory Milestone [Member]

License Agreement [Line Items]

Potential milestone earnings

$ 80,000,000

University of California [Member]

License Agreement [Line Items]

License fee paid

$ 100,000

Aggregate amount of milestone payments for one indication

$ 900,000

Additional milestone payments recognized

$ 0

Right and option to extend date to meet milestone, period

6 months

Right and option to extend date to meet milestone, description

The Company has the right and option to extend the date by which it must meet any milestone by six-months up to two times by paying an extension fee for each such extension.

Non-royalty licensing revenue, description

mid-teen percentage

Agreement termination scenario description

The Company may terminate this agreement without cause at any time upon 30 days’ prior written notice to the Regents. The Regents may terminate this agreement for a breach by the Company that remains uncured for 60 days, if the Company becomes insolvent, if the Company directly or through a third party files a claim that a licensed patent right is invalid or unenforceable or if the Company fails to meet or extend the date for meeting certain diligence milestones.

License agreement termination notice period

30 days

University of California [Member] | Maximum [Member]

License Agreement [Line Items]

Additional milestone payments for up to two additional indications

$ 500,000

University of California [Member] | Minimum [Member]

License Agreement [Line Items]

Annual royalty payment

$ 50,000

Editas Medicine Inc [Member]

License Agreement [Line Items]

Non-refundable upfront payment received

$ 1,000,000

Non-refundable upfront payment, obligation to fund research and development costs

500,000

Collaboration, option and license agreement fee receivable per indication

$ 1,000,000

Range of tiered royalties receivable on net sales

between the mid-single digits and low teens

Editas Medicine Inc [Member] | Maximum [Member]

License Agreement [Line Items]

Development and commercialization milestone payments receivable upon using proprietary vectors

mid-teen million dollar amount

Cornell University [Member]

License Agreement [Line Items]

Additional milestone payments recognized

$ 0

Agreement termination scenario description

Annapurna Therapeutics Limited may terminate any of these license agreements for convenience upon ninety days written notice. Cornell may terminate any of the license agreements for material breach if such breach is not cured within a specified number of days. Cornell may also terminate the HAE License Agreement and/or the Allergy License Agreement if Annapurna Therapeutics Limited commences any action and files a written claim asserting that any portion of the licensed patent rights invalid or unenforceable.

License agreement termination notice period

90 days

Number of license agreements | Agreement

3

3

Service fees payable

$ 13,300,000

$ 13,300,000

Service fees, payable period

4 years

Aggregate milestone payments and royalties on sales

$ 16,000,000

License agreement, accrued expenses

$ 800,000

$ 800,000

800,000

License agreement, recorded research and development expenses

1,800,000

Cornell University [Member] | Consultant [Member]

License Agreement [Line Items]

Annual compensation

300,000

Cornell University [Member] | Maximum [Member]

License Agreement [Line Items]

Annual maintenance fee payable

300,000

Cornell University [Member] | Minimum [Member]

License Agreement [Line Items]

Annual maintenance fee payable

30,000

REGENXBIO [Member]

License Agreement [Line Items]

Additional milestone payments recognized

$ 0

Agreement termination scenario description

Annapurna Therapeutics Limited may terminate this license agreement upon six months’ prior written notice. REGENXBIO may terminate this license agreement if Annapurna Therapeutics Limited is a specified number of days late in paying money due under the license agreement, or if Annapurna Therapeutics Limited, its affiliates, or any sublicensees become insolvent or, effective immediately, if they commence any action against REGENXBIO or its licensors to declare or render any claim of the licensed patent rights invalid or unenforceable. Either party may terminate this license agreement for material breach if such breach is not cured within a specified number of days.

License agreement termination notice period

6 months

License agreement, accrued expenses

$ 42,000

42,000

$ 42,000

License agreement, recorded expenses

$ 62,000

REGENXBIO [Member] | A1AT Deficiency/Allergy License Agreement [Member]

License Agreement [Line Items]

Agreement termination scenario description

Annapurna Therapeutics Limited may terminate this license agreement upon six months’ prior written notice. REGENXBIO may terminate this license agreement if Annapurna Therapeutics Limited is a specified number of days late in paying money due under the license agreement, or if Annapurna Therapeutics Limited, its affiliates, or any sublicensees become insolvent or, effective immediately, if they commence any action against REGENEXBIO or its licensors to declare or render any claim of the licensed patent rights invalid or unenforceable. Either party may terminate this license agreement for material breach if such breach is not cured within a specified number of days.

License agreement termination notice period

6 months

Aggregate milestone payments and royalties on sales

$ 20,000,000

REGENXBIO [Member] | Friedreich's Ataxia License Agreement [Member]

License Agreement [Line Items]

Aggregate milestone payments and royalties on sales

$ 13,850,000

Inserm Transfert [Member]

License Agreement [Line Items]

Additional milestone payments recognized

$ 0

Agreement termination scenario description

Annapurna may terminate this agreement upon 60 days’ prior written notice. Inserm may terminate this license agreement if Annapurna becomes the subject of a voluntary or involuntary petition in bankruptcy or fails to meet development milestones and such failure is not cured within a specified number of days. Inserm may also terminate the license granted to Annapurna in a given country if Annapurna (i) before regulatory approval of a product in any country, has ceased conducting any development of products in all countries for 12 consecutive months or (ii) after regulatory approval of a product in a given country, has ceased marketing such product in such country for 12 consecutive months.

License agreement termination notice period

60 days

Aggregate milestone payments and royalties on sales | €

€ 2,000,000

Inserm Transfert [Member] | Accrued Expenses and Other Current Liabilities [Member]

License Agreement [Line Items]

One-time payment due to termination of license agreement | €

€ 250,000

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 6,763	$ 4,178
Less accumulated depreciation and amortization	(2,594)	(991)
Property and equipment, net	4,169	3,187
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	300	234
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	4,285	3,041
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	552	552
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,522	$ 351
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 104

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 1,603	$ 812	$ 162

Accrued Expenses and Other Cu57

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued Expenses And Other Current Liabilities [Abstract]
Employees' compensation	$ 2,570	$ 2,047
Accrued preclinical costs	1,683	642
Accrued professional fees	894	1,177
Accrued clinical and process development costs	1,142	101
Other	162	40
Total accrued expenses and other current liabilities	$ 6,451	$ 4,007

Other Non-Current Liabilities -

Other Non-Current Liabilities - Additional Information (Detail)	1 Months Ended	3 Months Ended	8 Months Ended	12 Months Ended
	Jul. 31, 2016USD ($)$ / sharesshares	Sep. 30, 2016USD ($)$ / sharesshares	Dec. 31, 2016USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2016EUR (€)	Dec. 31, 2014USD ($)	Dec. 31, 2016EUR (€)	Dec. 31, 2015EUR (€)	Aug. 31, 2015EUR (€)
Line Of Credit Facility [Line Items]
Interest free conditional advance, interest expense						$ 18,000
Proceeds from financing arrangement				$ 100,000
Financing arrangement included in other noncurrent liabilities			$ 386,000	386,000
The Alpha-1 Project, Inc. [Member]
Line Of Credit Facility [Line Items]
Proceeds from financing arrangement		$ 100,000
Value of warrants	$ 26,000		26,000	26,000
Financing arrangement included in other noncurrent liabilities			74,000	$ 74,000
The Alpha-1 Project, Inc. [Member] | Common Shares [Member]
Line Of Credit Facility [Line Items]
Number of shares issued on exercise of warrants | shares	10,000	10,000
Exercise price | $ / shares	$ 4.33	$ 4.33
Expiration period	5 years	5 years
The Alpha-1 Project, Inc. [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Potential milestone earnings	$ 300,000
Expected percentage of milestone repayments	450.00%
BPI France [Member]
Line Of Credit Facility [Line Items]
Interest free conditional advance, conditions				The funds received by the Company are intended to finance its research and development efforts and the recruitment of specific personnel.	The funds received by the Company are intended to finance its research and development efforts and the recruitment of specific personnel.
Interest free conditional advance, maximum borrowing capacity | €									€ 750,000
Interest free conditional advance			$ 365,000	$ 365,000				€ 500,000
Interest free conditional advance, remaining borrowing capacity | €							€ 250,000
Interest free conditional advance, frequency of payments				Quarterly	Quarterly
Interest free conditional advance, periodic payment | €					€ 25,000
Interest free conditional advance, beginning date of periodic payment				Sep. 30, 2017	Sep. 30, 2017
Interest free conditional advance, ending date of periodic payment				Jun. 30, 2022	Jun. 30, 2022
Interest free conditional advance, imputed interest rate			7.00%	7.00%			7.00%
Interest free conditional advance, interest expense			$ 16,000
BPI France [Member] | Other Noncurrent Liabilities [Member]
Line Of Credit Facility [Line Items]
Interest free conditional advance			312,000	$ 312,000
BPI France [Member] | Accrued Expenses and Other Current Liabilities [Member]
Line Of Credit Facility [Line Items]
Interest free conditional advance			$ 53,000	$ 53,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Jan. 06, 2017	Dec. 31, 2015Claim	Jul. 31, 2015Claim	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)Claim	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Other Commitments [Line Items]
Lease renewal term					4 years
Lease expiration date					May 8, 2020
Rent expense					$ 1,745,000	$ 1,525,000	$ 662,000
Accrued royalties					0
Annual maintenance fee payable					600,000	$ 100,000
Claims paid to date related to indemnification issues					$ 0
Number of claims to date | Claim		1	3		0
Accruals or expenses related to indemnification issues					$ 0
Cornell University [Member] | MSA [Member]
Other Commitments [Line Items]
Contractual obligation payable over the next 3 year					$ 10,000,000
Contractual obligation payable period					3 years
Contractual obligation for manufacturing due in 2017					$ 1,100,000
Cornell University [Member] | MSA [Member] | Subsequent Event [Member]
Other Commitments [Line Items]
Agreement cancelled date	Jan. 6, 2017
Cornell University [Member] | MSA [Member] | Scenario, Forecast [Member]
Other Commitments [Line Items]
Commitment amount to be cancelled				$ 10,000,000

Commitments and Contingencies60

Commitments and Contingencies - Schedule of Future Minimum Commitments (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,017	$ 1,129
2,018	1,162
2,019	1,197
2,020	403
Total minimum lease payments	$ 3,891

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Aug. 05, 2014	Apr. 30, 2014	Dec. 31, 2016	Dec. 31, 2014	Nov. 30, 2013
Class of Stock [Line Items]
Conversion of preferred stock, shares converted	10,689,027
Loss on extinguishment of related-party convertible notes				$ 204
Fair value and repurchase of beneficial conversion feature			$ 2,000
Convertible preferred stock, value				$ 3,230
Series A Convertible Preferred Stock [Member]
Class of Stock [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
Common stock, shares issued, price per share					$ 1.45
Preferred stockholder, deemed dividend				$ 3,200
Outstanding Convertible Notes [Member]
Class of Stock [Line Items]
Loss on extinguishment of related-party convertible notes		$ 200
Outstanding Convertible Notes [Member] | Series B Convertible Preferred Stock [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	Jul. 31, 2016	May 31, 2014	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2015	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
The Alpha-1 Project, Inc. [Member]
Class of Warrant or Right [Line Items]
Fair value of common stock price per share			$ 4.33
Contractual term of warrant			5 years
Fair value of obligation risk free interest rate			1.07%
Fair value of obligation expected volatility rate			72.00%
Fair value of obligation expected dividend yield			0.00%
Value of warrants			$ 26,000			$ 26,000
The Alpha-1 Project, Inc. [Member] | Common Shares [Member]
Class of Warrant or Right [Line Items]
Warrant to purchase shares of common stock			10,000		10,000
Exercise price			$ 4.33		$ 4.33
Expiration period			5 years		5 years
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					$ 8,000				$ 5,000
Exercise price	$ 10.51								$ 2.75
Fair value of common stock price per share	$ 8.35					$ 2.90
Warrant expiration date	Oct. 15, 2020
Contractual term of warrant	5 years					5 years 7 months 6 days
Fair value of obligation risk free interest rate	1.34%					1.20%
Fair value of obligation expected volatility rate	75.00%					72.00%
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) $ / shares in Units, $ in Millions	May 11, 2016	Jun. 30, 2016shares	Dec. 31, 2015shares	Jul. 31, 2015USD ($)	Jul. 31, 2014shares	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)Executive$ / sharesshares	Dec. 31, 2015USD ($)$ / shares	Dec. 31, 2014USD ($)$ / shares
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 | $							$ 7.1	$ 11.2	$ 15.7
One time share based payment charge related to cancellation of unvested stock option of CEO | $				$ 2.4
Stock-based compensation expense for modifications | $						$ 2.2
Number of executive officers affected by modifications of stock-based compensation awards | Executive							4
Weighted-average fair values of options granted | $ / shares							$ 3.35	$ 15.91	$ 9.56
Unrecognized stock-based compensation expense related to employees' awards | $							$ 11.3
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost | $							$ 3.8
Unrecognized stock-based compensation, weighted-average period							3 years
RSU granted							1,303,000
Weighted-average grant date fair value of RSUs granted | $ / shares							$ 4.40	$ 13.85
Total fair values of RSUs vested | $							$ 1.7	$ 1.4
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							9 years 1 month 6 days	3 years 3 months 18 days	7 years 6 months
Unrecognized stock-based compensation, weighted-average period							2 years 6 months
Unrecognized stock-based compensation expense related to employees' awards | $							$ 2.6
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense for modifications | $							1.4
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense for modifications | $							$ 1.5
Annapurna Therapeutics SAS [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock options granted							3,673,940
Stock options exercise price granted | $ / shares							$ 0.21
Annapurna Therapeutics SAS [Member] | Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted period	10 years
Principal 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
Chief Executive Officer and Chief Financial Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period, shares, employee stock purchase plan		518,000
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 | $							$ 0.1
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							13,162,656
Shares available for future grants							3,079,676
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					208,833		618,687
Shares available for future grants							618,687
Percentage increase in shares issued					1.00%
Common stock, shares issued							56,696

Stock Option Plans - Summary of

Stock Option Plans - Summary of Stock Options Activity (Detail) - 2006 Equity Incentive Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Options Outstanding [Roll Forward]
Options Outstanding, Beginning Balance	5,494,000
Options Outstanding, granted	5,098,000
Options Outstanding, exercised	(1,526,000)
Options Outstanding, cancelled	(1,617,000)
Options Outstanding, Ending Balance	7,449,000	5,494,000
Options Outstanding, Vested and expected to vest	7,337,000
Options Outstanding, Exercisable	3,995,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price, Beginning Balance	$ 8.75
Weighted-Average Exercise Price, Options granted	1.30
Weighted-Average Exercise Price, Options exercised	0.52
Weighted-Average Exercise Price, Options cancelled	12.82
Weighted-Average Exercise Price, Ending Balance	4.46	$ 8.75
Weighted-Average Exercise Price, Vested and expected to vest	4.41
Weighted-Average Exercise Price, Exercisable	$ 3.34
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-Average Remaining Contractual Life (In years)	8 years 4 months 24 days	7 years 9 months 18 days
Weighted-Average Remaining Contractual Life (In years), Vested and expected to vest	8 years 4 months 24 days
Weighted-Average Remaining Contractual Life (In years), Exercisable	7 years 8 months 12 days
Aggregate Intrinsic Value, Options outstanding	$ 11,837	$ 28,618
Aggregate Intrinsic Value, Vested and expected to vest	11,836
Aggregate Intrinsic Value, Exercisable	$ 8,674

Stock Option Plans - Summary 65

Stock Option Plans - Summary of Stock Options Activity (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2016$ / shares
Equity [Abstract]
Aggregate intrinsic value of option per share	$ 2.90

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	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	$ 11,416	$ 11,505	$ 8,567
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	6,616	4,009	7,331
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation	$ 4,800	6,447	$ 1,236
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 67

Stock Option Plans - Summary of Restricted Stock Units Activity (Detail) - Restricted Stock Units [Member] - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Units, Beginning Balance	632,000
Number of Units, Granted	1,303,000
Number of Units, Vested and released	(386,000)
Number of Units, Forfeited	(500,000)
Number of Units, Ending Balance	1,049,000	632,000
Weighted-Average Grant-Date Fair Value, Beginning Balance	$ 13.07
Weighted-Average Grant-Date Fair Value, Granted	4.40	$ 13.85
Weighted-Average Grant-Date Fair Value, Vested and released	12.20
Weighted-Average Grant-Date Fair Value, Forfeited	7.10
Weighted-Average Grant-Date Fair Value, Ending Balance	$ 5.47	$ 13.07
Weighted-Average Remaining Contractual Term (In years)	1 year 8 months 12 days	1 year 1 month 6 days

Stock Option Plans - Schedule o

Stock Option Plans - Schedule of Employees Stock Purchase Plan Valuation Assumptions (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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)	6 years 1 month 6 days	6 years 1 month 6 days	6 years
Risk-free interest rate	1.80%	1.70%	1.90%
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	70.00%	74.00%
Expected term (in years)	6 months	6 months	0 years
Risk-free interest rate	0.60%	0.10%
Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	82.00%	81.00%	79.00%
Expected term (in years)	9 years 1 month 6 days	3 years 3 months 18 days	7 years 6 months
Risk-free interest rate	2.10%	1.00%	2.20%

401(k) Savings Plan - Additiona

401(k) Savings Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Contribution by company	$ 0.3	$ 0.1

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Income tax benefit of expense	$ 775,000	$ 0	$ 0
Statutory federal income tax rate	34.00%
Increase (decrease) in valuation allowance due to net operating loss	$ (5,400,000)	16,400,000	9,900,000
Unrecognized tax benefits	2,157,000	1,568,000	$ 471,000	$ 43,000
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	2,012
Maximum [Member]
Income Taxes [Line Items]
Tax examinations, year under examination	2,016
Domestic Tax Authority [Member]
Income Taxes [Line Items]
NOL carryforwards	$ 22,000,000
NOL carryforwards expiration	expire at various years beginning with 2036
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforwards	$ 300,000
Tax credit carryforwards expiration	expire at various years beginning with 2036
State credit carryforwards [Member]
Income Taxes [Line Items]
NOL carryforwards	$ 6,700,000
NOL carryforwards expiration	expire at various years beginning with 2036
State credit carryforwards [Member] | Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforwards	$ 400,000
Foreign Tax Authority [Member]
Income Taxes [Line Items]
NOL carryforwards	$ 25,600,000

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
U.S.	$ (96,498)	$ (47,235)	$ (25,006)
Foreign	(18,024)	(218)	(398)
Net loss before tax benefit	$ (114,522)	$ (47,453)	$ (25,404)

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, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal income tax expense at statutory rate	$ (38,938)	$ (16,134)	$ (8,637)
Loss on extinguishment of related-party convertible notes			69
Non-deductible foreign research expenses	21	45	85
Non-deductible stock compensation	1,356	1,418	161
Non-deductible expenses	985	295	285
Goodwill impairment	16,834
Research and development tax credits	(326)	(910)	(304)
Change in valuation allowance	16,062	15,277	8,349
Foreign rate differential	3,231	9	(8)
Total tax expense (benefit)	$ (775)	$ 0	$ 0

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 15,785	$ 19,889	$ 8,526
Accruals, reserve and other	3,071	2,681	222
Stock-based compensation	3,848	4,328	3,032
Tax credit carryforwards	574	1,945	659
Property and equipment	54
Intangibles	68	45	24
Other			24
Total deferred tax assets before valuation allowance	23,400	28,888	12,487
Valuation allowance	(23,400)	(28,839)	(12,457)
Total deferred tax assets		49	30
Deferred tax liabilities:
Property and equipment		(49)	(30)
IPR&D	(1,250)
Total deferred tax liabilities	(1,250)	(49)	(30)
Net deferred tax assets	$ 0	$ 0	$ 0

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Unrecognized tax benefits as of the beginning of the year	$ 1,568	$ 471	$ 43
Increase (decrease) related to prior year tax provisions		172	272
Increase related to current year tax provisions	589	925	156
Unrecognized tax benefits as of the end of the year	$ 2,157	$ 1,568	$ 471

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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net loss	$ (22,394)	$ (14,301)	$ (61,660)	$ (15,392)	$ (14,094)	$ (14,084)	$ (9,766)	$ (9,509)	$ (113,747)	$ (47,453)	$ (25,404)
Deemed dividend											(3,230)
Net loss attributable to common stockholders									$ (113,747)	$ (47,453)	$ (28,634)
Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share:
Net shares outstanding									36,246	25,479	11,651
Basic and diluted net loss per share attributable to common stockholders	$ (0.54)	$ (0.35)	$ (1.76)	$ (0.57)	$ (0.55)	$ (0.55)	$ (0.38)	$ (0.38)	$ (3.14)	$ (1.86)	$ (2.46)

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, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	8,548	6,166	4,932
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	1,049	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	7,449	5,494	4,932
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	50	40

Selected Quarterly Financial 77

Selected Quarterly Financial Information - Schedule of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 488	$ 395	$ 307	$ 265	$ 960	$ 953	$ 203	$ 203
Total operating expenses	(23,875)	(14,902)	(62,189)	(15,773)	(15,139)	(15,154)	(10,085)	(9,764)	$ (116,739)	$ (50,142)	$ (24,974)
Net loss	$ (22,394)	$ (14,301)	$ (61,660)	$ (15,392)	$ (14,094)	$ (14,084)	$ (9,766)	$ (9,509)	$ (113,747)	$ (47,453)	$ (25,404)
Basic and diluted net loss per share	$ (0.54)	$ (0.35)	$ (1.76)	$ (0.57)	$ (0.55)	$ (0.55)	$ (0.38)	$ (0.38)	$ (3.14)	$ (1.86)	$ (2.46)

Selected Quarterly Financial 78

Selected Quarterly Financial Information - Schedule of Quarterly Financial Information (Parenthetical) (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended					12 Months Ended
	Jul. 31, 2015	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Quarterly Financial Information [Line Items]
Goodwill impairment charge			$ 400	$ 49,100
Stock-based compensation expense due to modification of equity awards					$ 2,200
Restructuring charges						$ 2,600		$ 2,573
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 due to modification of equity awards							$ 1,500
Stock-based compensation expense	$ 2,400
IPR&D [Member]
Schedule Of Quarterly Financial Information [Line Items]
Impairment charge		$ 11,200

Subsequent Event - Additional I

Subsequent Event - Additional Information (Detail)	Feb. 23, 2017	May 31, 2014	Dec. 31, 2016
Subsequent Event [Line Items]
Collaboration agreement extension description			On February 23, 2017, Regeneron notified us that, pursuant to Section 2.3 of the collaboration agreement, it is extending the research term of the Collaboration Agreement for an additional three years, through May 1, 2020.
Regeneron Corporation [Member]
Subsequent Event [Line Items]
Collaboration agreement extension period		5 years
Subsequent Event [Member] | Regeneron Corporation [Member]
Subsequent Event [Line Items]
Collaboration agreement extension period	3 years