Genocea Biosciences (GNCAQ) 10-Q 9 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	5-May-14
Document and Entity Information	'	'
Entity Registrant Name	'GENOCEA BIOSCIENCES, INC.	'
Entity Central Index Key	'0001457612	'
Document Type	'10-Q	'
Document Period End Date	31-Mar-14	'
Amendment Flag	'false	'
Current Fiscal Year End Date	'--12-31	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Non-accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	17,324,429
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'

Condensed_Balance_Sheets

Condensed Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
Current assets:	'	'
Cash and cash equivalents	$65,839,000	$12,208,000
Restricted cash	157,000	157,000
Prepaid expenses and other current assets	944,000	510,000
Total current assets	66,940,000	12,875,000
Property and equipment, net	814,000	865,000
Restricted cash	316,000	158,000
Other assets	143,000	1,863,000
Total assets	68,213,000	15,761,000
Current liabilities:	'	'
Accounts payable	1,263,000	2,176,000
Accrued expenses and other current liabilities	1,483,000	1,418,000
Deferred revenue	12,000	12,000
Current portion of long-term debt	1,770,000	861,000
Current portion of deferred rent	17,000	26,000
Total current liabilities	4,545,000	4,493,000
Non-current liabilities:	'	'
Long-term debt, net of current portion	8,040,000	8,933,000
Accrued interest payable	25,000	11,000
Deferred rent, net of current portion	230,000	237,000
Warrants	'	656,000
Total liabilities	12,840,000	14,330,000
Commitments and contingencies (Note 6)	'	'
Stockholders' equity (deficit):	'	'
Common stock, $0.001 par value; Authorized - 191,690 shares; Issued - 17,322 and 327 shares at March 31, 2014 and December 31, 2013, respectively; outstanding - 17,299 and 303 at March 31, 2014 and December 31, 2013, respectively	17,000	'
Additional paid-in-capital	142,816,000	'
Deficit accumulated during the development stage	-87,460,000	-80,131,000
Total stockholders' equity (deficit)	55,373,000	-80,131,000
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	68,213,000	15,761,000
Seed convertible preferred stock	'	'
Redeemable convertible preferred stock:	'	'
Redeemable convertible preferred stock	'	3,000,000
Series A redeemable convertible preferred stock	'	'
Redeemable convertible preferred stock:	'	'
Redeemable convertible preferred stock	'	23,125,000
Series B redeemable convertible preferred stock	'	'
Redeemable convertible preferred stock:	'	'
Redeemable convertible preferred stock	'	24,937,000
Series C redeemable convertible preferred stock	'	'
Redeemable convertible preferred stock:	'	'
Redeemable convertible preferred stock	'	$30,500,000

Condensed_Balance_Sheets_Paren

Condensed Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Common stock, par value (in dollars per share)	$0.00	$0.00
Common stock, shares authorized	191,689,655	191,690,000
Common stock, shares issued	17,322,144	327,000
Common stock, shares outstanding	17,299,472	303,000
Seed convertible preferred stock	'	'
Redeemable convertible preferred stock, par value (in dollars per share)	$0.00	$0.00
Redeemable convertible preferred stock, shares authorized	0	4,615,000
Redeemable convertible preferred stock, shares issued	0	4,615,000
Redeemable convertible preferred stock, shares outstanding	0	4,615,000
Redeemable convertible preferred stock, liquidation preference (in dollars)	$0	$3,000
Series A redeemable convertible preferred stock	'	'
Redeemable convertible preferred stock, par value (in dollars per share)	$0.00	$0.00
Redeemable convertible preferred stock, shares authorized	0	36,662,000
Redeemable convertible preferred stock, shares issued	0	35,577,000
Redeemable convertible preferred stock, shares outstanding	0	35,577,000
Redeemable convertible preferred stock, liquidation preference (in dollars)	0	23,125
Series B redeemable convertible preferred stock	'	'
Redeemable convertible preferred stock, par value (in dollars per share)	$0.00	$0.00
Redeemable convertible preferred stock, shares authorized	0	35,099,000
Redeemable convertible preferred stock, shares issued	0	34,581,000
Redeemable convertible preferred stock, shares outstanding	0	34,581,000
Redeemable convertible preferred stock, liquidation preference (in dollars)	0	24,937
Series C redeemable convertible preferred stock	'	'
Redeemable convertible preferred stock, par value (in dollars per share)	$0.00	$0.00
Redeemable convertible preferred stock, shares authorized	0	53,276,000
Redeemable convertible preferred stock, shares issued	0	52,586,000
Redeemable convertible preferred stock, shares outstanding	0	52,586,000
Redeemable convertible preferred stock, liquidation preference (in dollars)	$0	$30,500

Condensed_Statements_of_Operat

Condensed Statements of Operations and Comprehensive Loss (USD $)	3 Months Ended		91 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Condensed Statements of Operations and Comprehensive Loss	'	'	'
Grant revenue	'	$259	$6,694
Operating expenses:	'	'	'
Research and development	4,407	3,980	64,529
General and administrative	1,966	810	22,918
Total operating expenses	6,373	4,790	87,447
Loss from operations	-6,373	-4,531	-80,753
Other (expense) income:	'	'	'
Change in fair value of warrant	-725	-6	-557
Loss on debt extinguishment	'	'	-200
Interest expense, net	-231	-127	-1,922
Other (expense) income	-956	-133	-2,679
Net loss	-7,329	-4,664	-83,432
Comprehensive loss	-7,329	-4,664	-83,432
Reconciliation of net loss to net loss attributable to common stockholders	'	'	'
Net loss	-7,329	-4,664	-83,432
Accretion of redeemable convertible preferred stock to redemption value	-180	-395	-6,094
Net loss attributable to common stockholders	($7,509)	($5,059)	($89,526)
Net loss per share attributable to common stockholders-basic and diluted (in dollars per share)	($0.76)	($17.09)	($153.56)
Weighted-average number of common shares used in net loss per share attributable to common stockholders - basic and diluted (in shares)	9,859	296	583

Condensed_Statements_of_Cash_F

Condensed Statements of Cash Flows (USD $)	3 Months Ended		91 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Operating activities	'	'	'
Net loss	($7,329)	($4,664)	($83,432)
Adjustments to reconcile net loss to net cash used in operating activities	'	'	'
Depreciation and amortization	78	86	1,686
Stock-based compensation	881	63	2,717
Stock issued for services	'	'	21
Stock issued for interest	'	'	2
Stock issued for license agreement	'	'	6
Non-cash interest expense for warrant issuance	'	'	509
Change in fair value of warrants liability	725	6	557
Non-cash interest expense	16	10	326
Loss on debt extinguishment	'	'	200
Changes in operating assets and liabilities:	'	'	'
Restricted cash	-158	'	-473
Prepaid expenses and other current assets	-435	88	-886
Other long-term assets	723	'	-1,053
Accounts payable	-1,095	-306	1,049
Deferred revenue	'	'	12
Accrued expenses	60	-338	1,447
Deferred rent	-15	-39	248
Accrued interest payable	15	36	25
Net cash used in operating activities	-6,534	-5,058	-77,039
Investing activities	'	'	'
Purchases of property and equipment	-27	-335	-2,501
Net cash used in investing activities	-27	-335	-2,501
Financing activities	'	'	'
Proceeds from IPO, net of issuance costs	60,133	'	60,133
Proceeds from issuance of notes payable and warrants to purchase redeemable preferred stock	'	'	4,075
Proceeds from issuance of preferred stock, net	'	'	71,348
Proceeds from issuance of long-term debt	'	'	15,547
Repayment of long-term debt	'	-417	-5,780
Proceeds from sale of restricted and unrestricted common stock	'	'	3
Proceeds from exercise of stock options	26	2	78
Proceeds form the exercise of warrants	33	'	33
Payments for debt issuance costs	'	'	-58
Net cash provided by (used in) financing activities	60,192	-415	145,379
Net increase (decrease) in cash and cash equivalents	53,631	-5,808	65,839
Cash and cash equivalents at beginning of period	12,208	11,516	'
Cash and cash equivalents at end of period	65,839	5,708	65,839
Supplemental cash flow information	'	'	'
Cash paid for interest	174	81	1,039
Supplemental disclosure of non-cash financing activities	'	'	'
Conversion of preferred stock to common stock upon closing of IPO	81,742	'	81,742
IPO closing costs included in accounts payable and accrued expenses	187	'	187
Reclassification of prepaid IPO closing costs from non-current assets to additional paid-in capital	998	'	998
Reclassification of warrants to additional paid-in capital	1,381	'	1,381
Accretion of redeemable convertible preferred stock to redemption value	180	395	6,094
Vesting of restricted stock	3	'	3
Leasehold improvements financed by landlord	'	'	237
Conversion of convertible debt and accrued interest to preferred stock	'	'	$4,298

Organization_and_operations

Organization and operations	3 Months Ended
	Mar. 31, 2014
Organization and operations	'
Organization and operations	'
	1. Organization and operations
	The Company
	Genocea Biosciences, Inc. (the “Company”) is a clinical stage biopharmaceutical company that was incorporated in Delaware on August 16, 2006 and has a principal place of business in Cambridge, Massachusetts. The Company has two products in clinical development: GEN-003, which is in a Phase 1/2a clinical trial to treat patients with herpes simplex virus type-2 (“HSV-2”), and GEN-004, which is being developed to prevent infections caused by pneumococcus and is in a Phase 1 clinical trial. The Company also has other product candidates that are currently in preclinical development. The Company developed GEN-003, GEN-004 and its preclinical product candidates using its proprietary platform technology called the AnTigen Lead Acquisition System (“ATLAS”). The ATLAS proprietary technology platform mimics the human immune response in the laboratory, potentially improving the effectiveness of vaccine discovery and drastically reducing the time needed to create promising vaccines.
	The Company is in the development stage and is devoting substantially all of its efforts to product research and development, initial market development, and raising capital. The Company has not generated any product revenue related to its primary business purpose to date and is subject to a number of risks similar to those of other development stage companies, including dependence on key individuals, competition from other companies, the need for development of commercially viable products, and the need to obtain adequate additional financing to fund the development of its product candidates. The Company is also subject to a number of risks similar to other companies in the life sciences industry, including regulatory approval of products, uncertainty of market acceptance of products, competition from substitute products and larger companies, the need to obtain additional financing, compliance with government regulations, protection of proprietary technology, dependence on third parties, product liability, and dependence on key individuals.
	As of March 31, 2014, the Company had a deficit accumulated during the development stage of approximately $87.5 million.  The Company had cash and cash equivalents of $65.8 million as of March 31, 2014. The Company believes that its existing cash and cash equivalents will be sufficient to fund operations and capital expenditures for at least the next twelve months.

Summary_of_significant_account

Summary of significant accounting policies	3 Months Ended
	Mar. 31, 2014
Summary of significant accounting policies	'
Summary of significant accounting policies	'
	2. Summary of significant accounting policies
	Initial Public Offering
	On February 10, 2014, the Company closed its initial public offering (“IPO”) of its common stock, $0.001 par value per share (“Common Stock”), pursuant to a registration statement on Form S-1, as amended. An aggregate of 5,500,000 shares of Common Stock registered under the registration statement were sold at a price of $12.00 per share. Net proceeds of the IPO were $61.4 million, excluding offering expenses of $2.4 million payable by the Company. In conjunction with this transaction, all shares of the Company’s redeemable convertible preferred stock were converted into 11,435,593 shares of common stock, and 96,988 employee and nonemployee performance-based options vested.
	Basis of presentation and use of estimates
	The accompanying condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These interim condensed financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended March 31, 2014 and 2013.
	The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full fiscal year. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2013 and the notes thereto which are included in the Company’s Annual Report on Form 10-K, as filed with the Securities and Exchange Commission on March 21, 2014.
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to clinical trial accruals, stock-based compensation expense, warrants to purchase redeemable securities, and reported amounts of revenues and expenses during the reported period. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.
	The Company utilized significant estimates and assumptions in determining the fair value of its common stock (“Common Stock”) prior to completion of the IPO. The Company utilized various valuation methodologies in accordance with the framework of the 2004 and 2013 American Institute of Certified Public Accountants Technical Practice Aids, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its Common Stock. Each valuation methodology includes estimates and assumptions that require the Company’s judgment. These estimates and assumptions include a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector, the prices at which the Company sold shares of preferred stock, the superior rights and preferences of securities senior to the Company’s Common Stock at the time and the likelihood of achieving a liquidity event, such as an initial public offering or a sale of the Company. Significant changes to the key assumptions used in the valuations could result in different fair values of Common Stock at each valuation date and materially affect the financial statements.
	Deferred initial public offering costs
	Deferred public offering costs, which primarily consist of direct, incremental legal and accounting fees related to the IPO, were capitalized within other assets as of December 31, 2013. The Company incurred $2.4 million in IPO costs and in February 2014, these public offering costs were offset against the proceeds upon completion of the IPO.
	Fair value of financial instruments
	The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820, Fair Value Measurement and Disclosures, established a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the financial instrument based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the financial instrument and are developed based on the best information available under the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported or disclosed fair value of the financial instruments and is not a measure of the investment credit quality. Fair value measurements are classified and disclosed in one of the following three categories:
	·                  Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.
	·                  Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.
	·                  Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.
	To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.
	Financial instruments measured at fair value on a recurring basis include cash equivalents (Note 3) and warrants to purchase redeemable securities (Note 5).
	An entity may elect to measure many financial instruments and certain other items at fair value at specified election dates. Subsequent unrealized gains and losses on items for which the fair value option has been elected will be reported in net loss. The Company did not elect to measure any additional financial instruments or other items at fair value. The Company is also required to disclose the fair value of financial instruments not carried at fair value. The fair value of the Company’s long-term debt is determined using current applicable rates for similar instruments as of the balance sheet dates and assessment of the credit rating of the Company. The carrying value of the Company’s long-term debt approximates fair value because the Company’s interest rate yield is near current market rates. The Company’s long-term debt is considered a Level 3 liability within the fair value hierarchy.
	Except for the valuation methodology utilized to value the warrants to purchase redeemable securities (Note 5), there have been no changes to the valuation methods utilized by the Company during the three months ended March 31, 2014 and 2013 or the period from August 16, 2006 (inception) through March 31, 2014. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of financial instruments between levels during the three months ended March 31, 2014 and 2013 or the period from August 16, 2006 (inception) through March 31, 2014.
	Reverse stock split
	On January 20, 2014, the Board of Directors and stockholders approved a 1-for-11.9 reverse stock split of the Company’s Common Stock, which was effected on January 21, 2014. Stockholders entitled to fractional shares as a result of the reverse stock split received a cash payment in lieu of receiving fractional shares upon the closing of the IPO. The Company’s historical share and per share information were retroactively adjusted to give effect to this reverse stock split. Shares of Common Stock underlying outstanding stock options were proportionately reduced and the respective exercise prices proportionately increased. Shares of Common Stock reserved for future issuance were presented on an as converted basis and the financial statements disclose the adjusted conversion ratios.

Cash_and_cash_equivalents

Cash and cash equivalents	3 Months Ended
	Mar. 31, 2014
Cash and cash equivalents	'
Cash and cash equivalents	'
	3. Cash and cash equivalents
	As of March 31, 2014 and December 31, 2013, cash and cash equivalents comprise funds in depository and money market accounts.
	The following table presents the cash and cash equivalents carried at fair value in accordance with the hierarchy defined in Note 2 (in thousands):
				Quoted prices		Significant		Significant
				in active		other		unobservable
				markets		observable		inputs
						inputs
		Total		(Level 1)		(Level 2)		(Level 3)
	March 31, 2014
	Cash	$	1,327	$	1,327	$	—	$	—
	Money Market funds, included in cash equivalents	64,512		64,512		—		—
	Total	$	65,839	$	65,839	$	—	$	—
	December 31, 2013
	Cash	$	249	$	249	$	—	$	—
	Money Market funds, included in cash equivalents	11,959		11,959		—		—
	Total	$	12,208	$	12,208	$	—	$	—
	Cash equivalents have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, utilizing third party pricing services or other market observable data. The pricing services utilize industry standard valuation models, including both income and market based approaches and observable market inputs to determine value. The Company validates the prices provided by its third party pricing services by reviewing their pricing methods and obtaining market values from other pricing sources. After completing its validation procedures, the Company did not adjust or override any fair value measurements provided by the pricing services as of March 31, 2014 and December 31, 2013.

LongTerm_Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2014
Long-Term Debt	'
Long-Term Debt	'
	4.  Long-Term Debt
	In October 2011, the Company entered into a Loan and Security Agreement with a financial institution, which provided for up to $5.0 million in debt financing (“Term Loan”). The Term Loan provided for a draw-down period on the facility through March 1, 2012. On March 1, 2012, the Company drew down the full $5.0 million available under the terms of this arrangement.
	From March 1, 2012 through May 1, 2012, the Company was obligated to make interest-only payments at the greater of the financial institution’s prime rate plus 5.00% or 8.00%. The Company began making 36 equal monthly payments of principal and accrued interest thereafter. During the 36-month period, the Term Loan bears interest at the greater of the financial institution’s prime rate plus 4.75% or 8.00%. The Company was also obligated to pay 6.50% of the advance on the final repayment date of the draw, which was April 1, 2015. This final payment was accrued over the term of the debt and was recorded in accrued interest payable.
	In connection with the Term Loan, the Company issued a fully-exercisable warrant to purchase 517,242 shares of Series B Preferred Stock. Upon closing of the IPO, these Series B Preferred Stock warrants automatically converted into warrants exercisable for 43,465 shares of Common Stock at an exercise price of $6.90 per share (Note 5). The Term Loan is collateralized by all the assets of the Company, except for those assets collateralized by an equipment term loan that was repaid as of December 31, 2013.
	On September 30, 2013, the Company entered into a new loan agreement which provided up to $10.0 million in debt financing (“New Term Loan”). Upon the closing of the New Term Loan, the Company drew down $3.5 million and paid off the remaining balance under the Term Loan. As part of the early repayment, the Company incurred a loss on debt extinguishment of $0.2 million. The New Term Loan provides for a draw-down period on the remaining facility of $6.5 million, which the Company drew down on December 19, 2013. The Company is obligated to make interest-only payments for the first 9 months and 33 equal payments of principal, together with accrued interest thereafter for each advance. The New Term Loan bears interest at a rate of 8% per annum. The Company is also obligated to pay 2% of the advance on the final repayment date of each draw. The final payment is being accrued over the term of the debt and recorded in accrued interest payable on the balance sheets. Should an event of default occur, including the occurrence of a material adverse change, the Company would be liable for immediate repayment of all amounts outstanding, including the 2% final payment associated with each draw. The New Term Loan is collateralized by all the assets of the Company.
	In connection with the New Term Loan, the Company issued a warrant to purchase 689,655 shares of Series C Preferred Stock at $0.58 per share. Upon the closing of the IPO, these Series C Preferred Stock warrants automatically converted into warrants exercisable for 57,954 shares of Common Stock at an exercise price of $6.90 per share (Note 5).
	Future principal payments on the New Term Loan are as follows (in thousands):
		March 31,
		2014
	2014	$	924
	2015	3,636
	2016	3,636
	2017	1,804
	Total	$	10,000

Warrants

Warrants	3 Months Ended
	Mar. 31, 2014
Warrants	'
Warrants	'
	5. Warrants
	As of December 31, 2013, the Company had outstanding warrants to purchase 2,291,512 shares of redeemable convertible preferred stock. On January 29, 2014, 21,695 warrants to purchase Series A Preferred stock were exercised for cash. On February 4, 2014, an additional 28,926 warrants to purchase Series A Preferred stock were exercised for cash. Prior to the closing of the IPO on February 10, 2014, warrants to purchase 987,840 shares of Series A preferred stock were exercised in a cashless exercise for 316,932 shares of Series A Preferred stock, which automatically converted into 26,633 shares of Common Stock upon the closing of the IPO. Also upon the closing of the IPO, warrants exercisable for 1,253,051 shares of redeemable convertible preferred stock were automatically converted into warrants exercisable for 105,297 shares of Common Stock. On February 12, 2014, 43,465 warrants were exercised in a cashless exercise for 16,593 shares of Common Stock.
	The warrants outstanding consist of the following (in thousands):
		March 31,		December 31,
		2014		2013
	Warrants to purchase Series A Preferred Stock	—		1,085
	Warrants to purchase Series B Preferred Stock	—		517
	Warrants to purchase Series C Preferred Stock	—		690
	Warrants to purchase Common Stock	62		—
	Total	62		2,292
	In connection with the closing of the IPO, all the warrants exercisable for redeemable convertible preferred stock were automatically converted into warrants exercisable for Common Stock, resulting in the reclassification of the related warrant to purchase redeemable securities liability to additional paid-in capital as the warrants to purchase shares of Common Stock are accounted for as equity instruments. The warrant to purchase redeemable securities liability was re-measured to fair value prior to reclassification to additional paid-in capital. As of March 31, 2014, the Company had no outstanding warrant to purchase redeemable securities liability.
	The warrant to purchase redeemable securities liability measured at fair value as of December 31, 2013 is as follows (in thousands):
					Quoted		Significant		Significant
					prices		other		unobservable
					in active		observable		inputs
					markets		inputs
		Total			(Level 1)		(Level 2)		(Level 3)
	December 31, 2013
	Warrants to purchase redeemable securities	$	656		$	—	$	—	$	656
	Total	$	656		$	—	$	—	$	656
	The following table sets forth a summary of changes in the fair value of the Company’s warrants to purchase redeemable securities, which represents a recurring measurement that is classified within Level 3 of the fair value hierarchy wherein fair value is estimated using significant unobservable inputs (in thousands):
		Three months ended
		March 31, 2014
	Beginning balance	$	656
	Change in fair value	725
	Warrants exercised	(323		)
	Reclassification to equity	(1,058		)
	Ending balance	$	—
	These warrants are considered Level 3 liabilities because their fair value measurements are based, in part, on significant inputs not observed in the market and reflect the Company’s assumptions as to the expected volatility of the Company’s Preferred stock. At December 31, 2013, the Company determined the fair value of the warrants to purchase redeemable securities based on input
	from management and the Board of Directors, which utilized an independent valuation of the Company’s enterprise value, determined utilizing an analytical valuation model. Any reasonable changes in the assumptions used in the valuation could materially affect the financial results of the Company. At December 31, 2013, the analytical valuation model used to calculate the fair value of warrants to purchase redeemable securities was a hybrid approach based on an OPM backsolve method and the PWERM. 35% of the value was attributed to the OPM backsolve method and 65% was attributed to the PWERM. After the enterprise value was determined, the total enterprise value was then allocated to the various outstanding equity instruments, including the warrants to purchase redeemable securities, utilizing the OPM.
	The fair value of warrants to purchase 21,695 shares of Series A Preferred stock prior to exercise on January 29, 2014 was estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:
		January 29,
		2014
	Fair value of underlying instrument	$	0.65
	Expected Volatility	55.57		%
	Expected term (in years)	0.04
	Risk-free interest rate	1.52		%
	Expected dividend yield	0		%
	These warrants were re-measured to a fair value of $7,783, which resulted in an increase in fair value of $2,142. The fair value of the warrants was reclassified to additional paid-in capital upon exercise on January 29, 2014.
	The fair value of warrants to purchase 28,926 shares of Series A Preferred stock prior to exercise on February 4, 2014 was estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:
		February 4,
		2014
	Fair value of underlying instrument	$	0.65
	Expected Volatility	55.03		%
	Expected term (in years)	0.02
	Risk-free interest rate	1.46		%
	Expected dividend yield	0		%
	These warrants were re-measured to a fair value of $10,357, which resulted in an increase in fair value of $2,839. The fair value of the warrants was reclassified to additional paid-in capital upon exercise on February 4, 2014.
	The fair value of warrants to purchase 987,840 shares of Series A Preferred stock prior to a cashless exercise for 316,932 shares of Series A Preferred stock on February 10, 2014, which automatically converted into 26,633 shares of Common Stock upon the closing of the IPO, was estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:
		February 10,
		2014
	Fair value of underlying instrument	$	7.74
	Expected Volatility	50.81		%
	Expected term (in years)	0.003
	Risk-free interest rate	1.48		%
	Expected dividend yield	0		%
	These warrants were re-measured to a fair value of $304,423, which resulted in an increase in fair value of $46,581. The fair value of the warrants was reclassified to additional paid-in capital upon exercise on February 10, 2014.
	The fair value of warrants exercisable for 1,253,051 shares of redeemable convertible preferred stock, which were automatically converted into warrants exercisable for 105,297 shares of Common Stock, was estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:
		February 10,
		2014
	Fair value of underlying instrument	$	6.96
	Expected Volatility	92.9		%
	Expected term (in years)	8.66
Risk-free interest rate	2.43		%
Expected dividend yield	0		%
The fair value of the remaining 105,297 warrants to purchase Common Stock were re-measured to a fair value of $1,058,269, which resulted in an increase in fair value of $673,040. The fair value of the warrants was reclassified to additional paid-in capital upon conversion.

Commitments_and_contingencies

Commitments and contingencies	3 Months Ended
	Mar. 31, 2014
Commitments and contingencies	'
Commitments and contingencies	'
	6. Commitments and contingencies
	Significant Contracts and Agreements
	In August 2006, the Company entered into an agreement to license certain intellectual property from The Regents of the University of California. The agreement required the Company to pay a non-refundable license fee of $25 thousand, and to issue 12,605 shares of Common Stock to the university. Such consideration was recorded in research and development expenses in 2006. The agreement calls for payments to be made by the Company upon the occurrence of a certain development milestone and a certain commercialization milestone for each distinct product covered by the licensed patents, in addition to certain royalties to be paid on marketed products or sublicense income. There were no other research and development expenses associated with this agreement in any of the other financial periods presented.
	In November 2007, the Company entered into an agreement to license certain intellectual property from Harvard University. The agreement required the Company to pay a non-refundable license fee of $75 thousand, and to issue 10,773 shares of common stock to the university. Such consideration, which totaled $93 thousand, was recorded in research and development expenses in 2007. The agreement also calls for payments to be made by the Company upon the occurrence of certain development and regulatory milestones, in addition to certain royalties on marketed products or sub-license income. In addition, the Company must make annual maintenance fee payments, which vary depending on the type of products under development. The Company incurred none, none and $266 thousand in annual maintenance fees and clinical milestones to Harvard University for the three months ended March 31, 2014 and 2013 and the period from August 16, 2006 (inception) to March 31, 2014, respectively.
	In August 2009, the Company entered into an agreement to license certain intellectual property from Isconova AB, now Novavax. The agreement required the Company to pay a non-refundable license fee of $750 thousand. The Company was also required to pay $200 thousand on the one-year anniversary in 2010. The agreement calls for payments to be made by the Company upon the occurrence of certain development and commercial milestones, in addition to certain royalties to be paid on marketed products or sublicense income. In addition, the Company has entered into a committed funding agreement whereby the Company is obligated to purchase a total of $1.6 million of services on a full-time equivalent basis. These services are expensed as incurred. The Company has expensed none, none and $1.7 million related to these services for the three months ended March 31, 2014 and 2013 and the period from August 16, 2006 (inception) to March 31, 2014, respectively.
	In January 2010, the Company entered into an agreement to license certain intellectual property from the University of Washington. The agreement required the Company to pay a non-refundable license fee of $20 thousand, and to issue 2,100 shares of common stock to the university. These amounts were recorded in research and development expenses in 2010. The agreement also calls for payments to be made by the Company upon the occurrence of certain development and commercial milestones, in addition to certain royalties on marketed products or sublicense income. In addition, the Company must make annual maintenance fee payments, which vary depending on the number of years from the effective date. The Company has expensed $20 thousand, $45 thousand and $110 thousand related to this agreement for the three months ended March 31, 2014 and 2013 and the period from August 16, 2006 (inception) to March 31, 2014, respectively.
	Supply agreements
	In August 2009, the Company entered into a supply agreement with a third party for the manufacture and supply of antigens used in the Company’s product candidates. The agreement calls for payments to be made by the Company upon the occurrence of certain manufacturing milestones, in addition to reimbursement of certain consumables. In June 2013, the Company entered into another supply agreement with the same vendor for the manufacture and supply of antigens to be used in the Company’s next clinical trials. The Company has expensed $613 thousand, $70 thousand and $8.1 million related to these agreements for the three months ended March 31, 2014, 2013 and the period from August 16, 2006 (inception) to March 31, 2014, respectively.
	In February 2014, the Company entered into a supply agreement with FUJIFILM Diosynth Biotechnologies U.S.A., Inc. (“Fujifilm”) for the manufacture and supply of antigens for the GEN-003 Phase 2 dose optimization clinical trial. Under the agreement, the Company is obligated to pay Fujifilm manufacturing milestones, in addition to reimbursement of certain material production related costs. Additionally, the Company is responsible for the payment of a reservation fee, which will equal a percentage of the expected production fees, to reserve manufacturing slots in the production timeframe. As of March 31, 2014, the Company has incurred $25 thousand in costs under this agreement.
	Restricted cash related to facilities leases
	Restricted cash related to facilities leases consisted of the following (in thousands):
		March 31,		December 31,
		2014		2013
	2012 Facilities Sublease	$	157	$		157
	2012 Master Facilities Lease	316		158
	Total	$	473	$	315
	At March 31, 2014, the Company has two outstanding letters of credit with a financial institution related to security deposits for the 2012 Facilities Sublease and the 2012 Master Facilities Lease, for a total of $473 thousand, which are secured by cash on deposit. The letter of credit related to the 2012 Facilities Sublease will expire on April 30, 2014.
	Litigation
	The Company does not believe it is a party to any litigation and does not have contingency reserves established for any litigation liabilities.

Redeemable_convertible_preferr

Redeemable convertible preferred stock	3 Months Ended
	Mar. 31, 2014
Redeemable convertible preferred stock	'
Redeemable convertible preferred stock	'
	7. Redeemable convertible preferred stock
	Upon the closing of the IPO on February 10, 2014, all of the outstanding shares of the Company’s redeemable convertible preferred stock were converted into 11,435,593 shares of its Common Stock. As of March 31, 2014, the Company does not have any redeemable convertible preferred stock issued or outstanding.

Common_stock

Common stock	3 Months Ended
	Mar. 31, 2014
Common stock	'
Common stock	'
	8. Common stock
	At March 31, 2014, the Company had authorized 191,689,655 shares of Common Stock, $0.001 par value per share, of which 17,322,144 shares were issued and 17,299,472 were outstanding.
	Restricted stock
	During 2006 and 2007, the Company’s founders and certain employees were issued shares and entered into Stock Restriction and Repurchase Agreements with the Company. During 2013, a director of the Company early exercised stock options and received 25,262 shares of common stock which were subject to a Stock Restriction and Repurchase Agreement with the Company. Under the terms of the agreements, shares of Common Stock issued are subject to a vesting schedule. Vesting occurs periodically at specified time intervals and specified percentages. All shares of Common Stock become fully vested within four years of the date of distribution. As of March 31, 2014, the Company has issued 31,135 shares of restricted common stock of which 7,463 shares have vested and 22,672 shares are subject to repurchase by the Company.
	Reserve for future issuance
	The Company has reserved for future issuances the following number of shares of Common Stock (in thousands):
		March 31,	December 31,
		2014	2013
	Conversion of Seed Preferred Stock	—	388
	Conversion of Series A Preferred Stock	—	2,990
	Conversion of Series B Preferred Stock	—	3,613
	Conversion of Series C Preferred Stock	—	4,419
	Options to purchase common stock	2,647	1,823
	Warrants to purchase Series A Preferred Stock	4	91
	Warrants to purchase Series B Preferred Stock	—	43
	Warrants to purchase Series C Preferred Stock	58	58
		2,709	13,425

Stockbased_compensation

Stock-based compensation	3 Months Ended
	Mar. 31, 2014
Stock-based compensation	'
Stock-based compensation	'
	9. Stock-based compensation
	The Company’s board of directors adopted the 2014 Equity Incentive Plan (the “2014 Equity Plan”), which was approved by its stockholders and became effective upon the closing of the IPO on February 10, 2014. The 2014 Equity Plan replaced the 2007 Equity Incentive Plan (the “2007 Equity Plan”).
	The 2014 Equity Plan provided for the grant of incentive stock options, non-qualified stock options and restricted stock awards to key employees and directors of, and consultants and advisors to, the Company. The maximum number of shares of Common Stock that may be delivered in satisfaction of awards under the 2014 Equity Plan is 903,494 shares, plus 219,765 shares that were available for grant under the 2007 Equity Plan on the date the 2014 Equity Plan was adopted. The 2014 Equity Plan provides that the number of shares available for issuance will automatically increase annually on each January 1st, from January 1st, 2015 through January 1, 2024, in amount equal to the lesser of 4% of the outstanding shares of the Company’s outstanding common stock as of the close of business on the immediately preceding December 31st or the number of shares determined the Company’s board of directors.
	Outstanding options awards granted from the 2007 Equity Plan, at the time of the adoption of the 2014 Equity Plan, remain outstanding and effective. The shares of Common Stock underlying awards that are cancelled, forfeited, repurchased, expire or are otherwise terminated under the 2007 Equity Plan are added to the shares of Common Stock available for issuance under the 2014 Equity Plan. As of March 31, 2014, the number of common shares that may be issued under both equity plans is 2,646,788 and 643,982 remain available for future grants.
	Stock Based Compensation Expense
	Total stock-based compensation expense is recognized for stock options granted to employees and non-employees and has been reported in the Company’s statements of operations as follows (in thousands):
		Three months ended March 31,
		2014			2013
	Research and development	$	477		$	18
	General and administrative	404			45
	Total	$	881		$	63
	Stock Options
	The following table summarizes stock option activity for employees and nonemployees (shares in thousands):
							Weighted-
				Weighted-			Average
				Average			Remaining	Aggregate
				Exercise			Contractual	Intrinsic
		Shares		Price			Term (years)	Value
	Outstanding at December 31, 2013	1,576		$	2.66		7.64	$	6,682
	Granted	479		$	12.09
	Exercised	(12	)	$	2.22
	Canceled	(40	)	$	2.27
	Outstanding at March 31, 2014	2,003		$	4.93		8	$	26,556
	Exercisable at March 31, 2014	1,036		$	2.54		6.92	$	16,219
	Vested or expected to vest at March 31, 2014	1,871		$	5.07		7.99	$	24,538
	Performance-Based Stock Options
	The Company granted stock options to certain employees, executive officers and consultants, which contain performance-based vesting criteria. Milestone events are specific to the Company’s corporate goals, which include, but are not limited to, certain clinical development milestones, business development agreements and capital fundraising events. Stock-based compensation expense associated with these performance-based stock options is recognized if the performance conditions are considered probable of being achieved, using management’s best estimates. During the three months ended March 31, 2014, the Company determined that 96,988 performance-based milestones were probable of achievement and accordingly, recorded $435 thousand in related stock-based compensation expense. There were no such milestones that were considered probable of achievement during the three months ended March 31, 2013, and accordingly, no stock-based compensation related to these milestones was recorded for this period. As of March 31, 2014, there are 56,336 performance-based common stock options outstanding for which the probability of achievement was not deemed probable.
	Employee Stock Purchase Plan
	In connection with the closing of the Company’s IPO on February 10, 2014, the Company’s board of directors adopted the 2014 Employee Stock Purchase Plan (the “2014 ESPP”). The 2014 ESPP authorizes the initial issuance of up to a total of 200,776 shares of Common Stock to participating eligible employees. The 2014 ESPP provides for six-month option periods commencing on January 1 and ending June 30 and commencing July 1 and ending December 31 of each calendar year. Unless otherwise determined by the administrator of the 2014 ESPP, the first offering will begin on July 1, 2014.

Income_taxes

Income taxes	3 Months Ended
	Mar. 31, 2014
Income taxes	'
Income taxes	'
	10. Income taxes
	Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. 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. There were no significant income tax provisions or benefits for the three months ended March 31, 2014 and 2013. Due to the uncertainty surrounding the realization of the favorable tax attributes in future tax returns, the Company has provided a full valuation allowance against its deferred tax assets.

Net_loss_per_share_attributabl

Net loss per share attributable to common stockholders	3 Months Ended
	Mar. 31, 2014
Net loss per share attributable to common stockholders	'
Net loss per share attributable to common stockholders	'
	11. Net loss per share attributable to common stockholders
	The Company computes basic and diluted earnings (loss) per share using a methodology that gives effect to the impact of outstanding participating securities (the “two-class method”). As the three month period ended March 31, 2014 and 2013 and the period from August 16, 2006 (inception) to March 31, 2014 resulted in net losses, there is no income allocation required under the two-class method or dilution attributed to weighted average shares outstanding in the calculation of diluted loss per share.
	The following common stock equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect (in thousands):
				The period from
				August 16, 2006
				(inception)
		March 31,	March 31,	March 31,
		2014	2013	2014
	Preferred stock	—	8,493	—
	Warrants	62	135	62
	Outstanding options	2,003	1,099	2,003
	Total	2,065	9,727	2,065

Subsequent_events

Subsequent events	3 Months Ended
	Mar. 31, 2014
Subsequent events	'
Subsequent events	'
	12. Subsequent events
	The Company has evaluated all events or transactions that occurred after March 31, 2014. In the judgment of management, there were no material events that impacted the unaudited condensed financial statements or disclosures.

Summary_of_significant_account1

Summary of significant accounting policies (Policies)	3 Months Ended
	Mar. 31, 2014
Summary of significant accounting policies	'
Initial Public Offering	'
	Initial Public Offering
	On February 10, 2014, the Company closed its initial public offering (“IPO”) of its common stock, $0.001 par value per share (“Common Stock”), pursuant to a registration statement on Form S-1, as amended. An aggregate of 5,500,000 shares of Common Stock registered under the registration statement were sold at a price of $12.00 per share. Net proceeds of the IPO were $61.4 million, excluding offering expenses of $2.4 million payable by the Company. In conjunction with this transaction, all shares of the Company’s redeemable convertible preferred stock were converted into 11,435,593 shares of common stock, and 96,988 employee and nonemployee performance-based options vested.
Basis of presentation and use of estimates	'
	Basis of presentation and use of estimates
	The accompanying condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These interim condensed financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended March 31, 2014 and 2013.
	The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full fiscal year. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2013 and the notes thereto which are included in the Company’s Annual Report on Form 10-K, as filed with the Securities and Exchange Commission on March 21, 2014.
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to clinical trial accruals, stock-based compensation expense, warrants to purchase redeemable securities, and reported amounts of revenues and expenses during the reported period. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.
	The Company utilized significant estimates and assumptions in determining the fair value of its common stock (“Common Stock”) prior to completion of the IPO. The Company utilized various valuation methodologies in accordance with the framework of the 2004 and 2013 American Institute of Certified Public Accountants Technical Practice Aids, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its Common Stock. Each valuation methodology includes estimates and assumptions that require the Company’s judgment. These estimates and assumptions include a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector, the prices at which the Company sold shares of preferred stock, the superior rights and preferences of securities senior to the Company’s Common Stock at the time and the likelihood of achieving a liquidity event, such as an initial public offering or a sale of the Company. Significant changes to the key assumptions used in the valuations could result in different fair values of Common Stock at each valuation date and materially affect the financial statements.
Deferred initial public offering costs	'
	Deferred initial public offering costs
	Deferred public offering costs, which primarily consist of direct, incremental legal and accounting fees related to the IPO, were capitalized within other assets as of December 31, 2013. The Company incurred $2.4 million in IPO costs and in February 2014, these public offering costs were offset against the proceeds upon completion of the IPO.
Fair value of financial instruments	'
	Fair value of financial instruments
	The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820, Fair Value Measurement and Disclosures, established a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the financial instrument based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the financial instrument and are developed based on the best information available under the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported or disclosed fair value of the financial instruments and is not a measure of the investment credit quality. Fair value measurements are classified and disclosed in one of the following three categories:
	·                  Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.
	·                  Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.
	·                  Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.
	To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.
	Financial instruments measured at fair value on a recurring basis include cash equivalents (Note 3) and warrants to purchase redeemable securities (Note 5).
	An entity may elect to measure many financial instruments and certain other items at fair value at specified election dates. Subsequent unrealized gains and losses on items for which the fair value option has been elected will be reported in net loss. The Company did not elect to measure any additional financial instruments or other items at fair value. The Company is also required to disclose the fair value of financial instruments not carried at fair value. The fair value of the Company’s long-term debt is determined using current applicable rates for similar instruments as of the balance sheet dates and assessment of the credit rating of the Company. The carrying value of the Company’s long-term debt approximates fair value because the Company’s interest rate yield is near current market rates. The Company’s long-term debt is considered a Level 3 liability within the fair value hierarchy.
	Except for the valuation methodology utilized to value the warrants to purchase redeemable securities (Note 5), there have been no changes to the valuation methods utilized by the Company during the three months ended March 31, 2014 and 2013 or the period from August 16, 2006 (inception) through March 31, 2014. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of financial instruments between levels during the three months ended March 31, 2014 and 2013 or the period from August 16, 2006 (inception) through March 31, 2014.
Reverse stock split	'
	Reverse stock split
	On January 20, 2014, the Board of Directors and stockholders approved a 1-for-11.9 reverse stock split of the Company’s Common Stock, which was effected on January 21, 2014. Stockholders entitled to fractional shares as a result of the reverse stock split received a cash payment in lieu of receiving fractional shares upon the closing of the IPO. The Company’s historical share and per share information were retroactively adjusted to give effect to this reverse stock split. Shares of Common Stock underlying outstanding stock options were proportionately reduced and the respective exercise prices proportionately increased. Shares of Common Stock reserved for future issuance were presented on an as converted basis and the financial statements disclose the adjusted conversion ratios.

Cash_and_cash_equivalents_Tabl

Cash and cash equivalents (Tables) (Cash and cash equivalents)	3 Months Ended
	Mar. 31, 2014
Cash and cash equivalents	'
Cash and cash equivalents	'
Schedule of cash and cash equivalents carried at fair value	'
	The following table presents the cash and cash equivalents carried at fair value in accordance with the hierarchy defined in Note 2 (in thousands):
				Quoted prices		Significant		Significant
				in active		other		unobservable
				markets		observable		inputs
						inputs
		Total		(Level 1)		(Level 2)		(Level 3)
	March 31, 2014
	Cash	$	1,327	$	1,327	$	—	$	—
	Money Market funds, included in cash equivalents	64,512		64,512		—		—
	Total	$	65,839	$	65,839	$	—	$	—
	December 31, 2013
	Cash	$	249	$	249	$	—	$	—
	Money Market funds, included in cash equivalents	11,959		11,959		—		—
	Total	$	12,208	$	12,208	$	—	$	—

LongTerm_Debt_Tables

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2014
Long-Term Debt	'
Schedule of future principal payments on the new term loan	'
	Future principal payments on the New Term Loan are as follows (in thousands):
		March 31,
		2014
	2014	$	924
	2015	3,636
	2016	3,636
	2017	1,804
	Total	$	10,000

Warrants_Tables

Warrants (Tables)	3 Months Ended
	Mar. 31, 2014
Warrants	'
Schedule of warrants outstanding	'
	The warrants outstanding consist of the following (in thousands):
		March 31,		December 31,
		2014		2013
	Warrants to purchase Series A Preferred Stock	—		1,085
	Warrants to purchase Series B Preferred Stock	—		517
	Warrants to purchase Series C Preferred Stock	—		690
	Warrants to purchase Common Stock	62		—
	Total	62		2,292
Schedule of changes in fair value of warrants to purchase redeemable securities measured on recurring basis	'
	The following table sets forth a summary of changes in the fair value of the Company’s warrants to purchase redeemable securities, which represents a recurring measurement that is classified within Level 3 of the fair value hierarchy wherein fair value is estimated using significant unobservable inputs (in thousands):
		Three months ended
		March 31, 2014
	Beginning balance	$	656
	Change in fair value	725
	Warrants exercised	(323		)
	Reclassification to equity	(1,058		)
	Ending balance	$	—
Warrants to purchase shares of series A preferred stock exercised, one	'
Warrants	'
Schedule of weighted average assumptions used to calculate the fair value of warrants	'
		January 29,
		2014
	Fair value of underlying instrument	$	0.65
	Expected Volatility	55.57		%
	Expected term (in years)	0.04
	Risk-free interest rate	1.52		%
	Expected dividend yield	0		%
Warrants to purchase shares of series A preferred stock exercised, two	'
Warrants	'
Schedule of weighted average assumptions used to calculate the fair value of warrants	'
		February 4,
		2014
	Fair value of underlying instrument	$	0.65
	Expected Volatility	55.03		%
	Expected term (in years)	0.02
	Risk-free interest rate	1.46		%
	Expected dividend yield	0		%
Warrants to purchase shares of series A preferred stock in cashless exercise	'
Warrants	'
Schedule of weighted average assumptions used to calculate the fair value of warrants	'
		February 10,
		2014
	Fair value of underlying instrument	$	7.74
	Expected Volatility	50.81		%
	Expected term (in years)	0.003
	Risk-free interest rate	1.48		%
	Expected dividend yield	0		%
Warrants to purchase redeemable convertible preferred stock automatically converted to warrants to purchase common stock	'
Warrants	'
Schedule of weighted average assumptions used to calculate the fair value of warrants	'
		February 10,
		2014
	Fair value of underlying instrument	$	6.96
	Expected Volatility	92.9		%
	Expected term (in years)	8.66
	Risk-free interest rate	2.43		%
	Expected dividend yield	0		%
Warrants to purchase redeemable securities	'
Warrants	'
Schedule of warrant to purchase redeemable securities liability measured at fair value	'
	The warrant to purchase redeemable securities liability measured at fair value as of December 31, 2013 is as follows (in thousands):
					Quoted		Significant		Significant
					prices		other		unobservable
					in active		observable		inputs
					markets		inputs
		Total			(Level 1)		(Level 2)		(Level 3)
	December 31, 2013
	Warrants to purchase redeemable securities	$	656		$	—	$	—	$	656
	Total	$	656		$	—	$	—	$	656

Commitments_and_contingencies_

Commitments and contingencies (Tables)	3 Months Ended
	Mar. 31, 2014
Commitments and contingencies	'
Schedule of restricted cash related to facilities leases	'
	Restricted cash related to facilities leases consisted of the following (in thousands):
		March 31,		December 31,
		2014		2013
	2012 Facilities Sublease	$	157	$		157
	2012 Master Facilities Lease	316		158
	Total	$	473	$	315

Common_stock_Tables

Common stock (Tables)	3 Months Ended
	Mar. 31, 2014
Common stock	'
Schedule of shares of common stock reserved for future issuance	'
	The Company has reserved for future issuances the following number of shares of Common Stock (in thousands):
		March 31,	December 31,
		2014	2013
	Conversion of Seed Preferred Stock	—	388
	Conversion of Series A Preferred Stock	—	2,990
	Conversion of Series B Preferred Stock	—	3,613
	Conversion of Series C Preferred Stock	—	4,419
	Options to purchase common stock	2,647	1,823
	Warrants to purchase Series A Preferred Stock	4	91
	Warrants to purchase Series B Preferred Stock	—	43
	Warrants to purchase Series C Preferred Stock	58	58
		2,709	13,425

Stockbased_compensation_Tables

Stock-based compensation (Tables)	3 Months Ended
	Mar. 31, 2014
Stock-based compensation	'
Schedule of stock-based compensation expense for stock options granted to employees and non-employees	'
	Total stock-based compensation expense is recognized for stock options granted to employees and non-employees and has been reported in the Company’s statements of operations as follows (in thousands):
		Three months ended March 31,
		2014			2013
	Research and development	$	477		$	18
	General and administrative	404			45
	Total	$	881		$	63
Schedule of stock option activity for employees and nonemployees	'
	The following table summarizes stock option activity for employees and nonemployees (shares in thousands):
							Weighted-
				Weighted-			Average
				Average			Remaining	Aggregate
				Exercise			Contractual	Intrinsic
		Shares		Price			Term (years)	Value
	Outstanding at December 31, 2013	1,576		$	2.66		7.64	$	6,682
	Granted	479		$	12.09
	Exercised	(12	)	$	2.22
	Canceled	(40	)	$	2.27
	Outstanding at March 31, 2014	2,003		$	4.93		8	$	26,556
	Exercisable at March 31, 2014	1,036		$	2.54		6.92	$	16,219
	Vested or expected to vest at March 31, 2014	1,871		$	5.07		7.99	$	24,538

Net_loss_per_share_attributabl1

Net loss per share attributable to common stockholders (Tables)	3 Months Ended
	Mar. 31, 2014
Net loss per share attributable to common stockholders	'
Schedule of common stock equivalents, presented on converted basis, were excluded from calculation of net loss per share due to anti-dilutive effect	'
	The following common stock equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect (in thousands):
				The period from
				August 16, 2006
				(inception)
		March 31,	March 31,	March 31,
		2014	2013	2014
	Preferred stock	—	8,493	—
	Warrants	62	135	62
	Outstanding options	2,003	1,099	2,003
	Total	2,065	9,727	2,065

Organization_and_operations_De

Organization and operations (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
	item
Organization and operations	'	'	'	'
Number of products in clinical development	2	'	'	'
Deficit accumulated during the development stage	$87,460	$80,131	'	'
Cash and cash equivalents	$65,839	$12,208	$5,708	$11,516
Minimum period for which existing cash and cash equivalents will be sufficient to fund operations and capital expenditures	'12 months	'	'	'

Summary_of_significant_account2

Summary of significant accounting policies (Details) (USD $)	0 Months Ended		3 Months Ended	91 Months Ended
	Feb. 10, 2014	Jan. 20, 2014	Mar. 31, 2014	Mar. 31, 2014	Feb. 28, 2014	Dec. 31, 2013	Mar. 31, 2013
Initial Public Offering	'	'	'	'	'	'	'
Common stock, par value (in dollars per share)	'	'	$0.00	$0.00	'	$0.00	'
Common stock issued in IPO (in shares)	5,500,000	'	'	'	'	'	'
Initial public offering price (in dollars per share)	$12	'	'	'	'	'	'
Net proceeds of IPO excluding offering expenses payable	$61,400,000	'	$60,133,000	$60,133,000	'	'	'
Offering expenses payable	2,400,000	'	'	'	'	'	'
Number of shares of common stock after conversion of redeemable convertible preferred stock to common stock	11,435,593	'	'	'	'	'	'
Employee and nonemployee performance based options vested (in shares)	96,988	'	'	'	'	'	'
Deferred initial public offering costs	'	'	'	'	'	'	'
Public offering costs incurred in IPO	'	'	'	'	2,400,000	'	'
Fair value of financial instruments	'	'	'	'	'	'	'
Transfers of financial assets between levels	'	'	0	0	'	'	0
Transfers of financial liabilities between levels	'	'	$0	$0	'	'	$0
Reverse stock split	'	'	'	'	'	'	'
Reverse stock split ratio	'	0.084034	'	'	'	'	'

Cash_and_cash_equivalents_Deta

Cash and cash equivalents (Details) (Recurring, USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Quoted prices in active markets (Level 1)	'	'
Cash and cash equivalents	'	'
Cash	$1,327	$249
Money Market funds, included in cash equivalents	64,512	11,959
Total	65,839	12,208
Total	'	'
Cash and cash equivalents	'	'
Cash	1,327	249
Money Market funds, included in cash equivalents	64,512	11,959
Total	$65,839	$12,208

LongTerm_Debt_Details

Long-Term Debt (Details) (USD $)

91 Months Ended

2 Months Ended

23 Months Ended

23 Months Ended

3 Months Ended

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Feb. 10, 2014

1-May-12

Mar. 31, 2014

Mar. 01, 2012

Oct. 31, 2011

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Sep. 30, 2013

Mar. 31, 2014

Sep. 30, 2013

Sep. 30, 2013

Warrants to purchase Series B Preferred Stock

Warrants to purchase Series C Preferred Stock

Warrants to purchase common stock

Warrants to purchase common stock

Term Loan

Term Loan

Term Loan

Term Loan

Term Loan

Term Loan

Term Loan

New Term Loan

New Term Loan

New Term Loan

New Term Loan

item

Warrants to purchase Series B Preferred Stock

Warrants to purchase common stock

Prime rate

item

Warrants to purchase Series C Preferred Stock

Warrants to purchase common stock

Long-Term Debt

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum debt financing under the agreement

'

'

'

'

'

'

'

'

$5,000,000

'

'

'

$10,000,000

'

'

'

Amount of drawings under the agreement

'

'

'

'

'

'

'

5,000,000

'

'

'

'

3,500,000

'

'

'

Variable rate basis

'

'

'

'

'

'Prime rate

'

'

'

'

'

'Prime rate

'

'

'

'

Spread on variable rate basis (as a percent)

'

'

'

'

'

5.00%

'

'

'

'

'

4.75%

'

'

'

'

Interest rate (as a percent)

'

'

'

'

'

8.00%

8.00%

'

'

'

'

'

8.00%

8.00%

'

'

Number of monthly payments of principal and accrued interest

'

'

'

'

'

'

36

'

'

'

'

'

'

'

'

'

Period of monthly payments of principal and accrued interest

'

'

'

'

'

'

'36 months

'

'

'

'

'

'

'

'

'

Percentage of advance payment on final repayment date

'

'

'

'

'

'

6.50%

'

'

'

'

'

2.00%

'

'

'

Number of shares of preferred stock that may be purchased by warrant

'

517,000

690,000

62,000

105,297

'

'

'

'

517,242

'

'

'

'

689,655

'

Loss on debt extinguishment

200,000

'

'

'

'

'

'

'

'

'

'

'

200,000

'

'

'

Remaining facility

'

'

'

'

'

'

'

'

'

'

'

'

6,500,000

'

'

'

Period of monthly payments of accrued interest

'

'

'

'

'

'

'

'

'

'

'

'

'9 months

'

'

'

Number of payments of principal

'

'

'

'

'

'

'

'

'

'

'

'

33

'

'

'

Exercise price of warrant (in dollars per share)

'

'

'

'

'

'

'

'

'

$6.90

'

'

'

'

$0.58

$6.90

Number of shares that may be purchased by warrant

'

'

'

'

'

'

'

'

'

'

43,465

'

'

'

'

57,954

Future principal payments

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2014

'

'

'

'

'

'

'

'

'

'

'

'

'

924,000

'

'

2015

'

'

'

'

'

'

'

'

'

'

'

'

'

3,636,000

'

'

2016

'

'

'

'

'

'

'

'

'

'

'

'

'

3,636,000

'

'

2017

'

'

'

'

'

'

'

'

'

'

'

'

'

1,804,000

'

'

Total

'

'

'

'

'

'

'

'

'

'

'

'

'

$10,000,000

'

'

Warrants_Details

Warrants (Details) (USD $)

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Jan. 29, 2014

Jan. 29, 2014

Feb. 04, 2014

Feb. 04, 2014

Feb. 12, 2014

Feb. 10, 2014

Feb. 10, 2014

Dec. 31, 2013

Dec. 31, 2013

Feb. 10, 2014

Mar. 31, 2014

Feb. 10, 2014

Feb. 10, 2014

Warrants to purchase redeemable convertible preferred stock

Warrants to purchase redeemable convertible preferred stock

Warrants to purchase redeemable convertible preferred stock

Warrants to purchase Series A Preferred Stock

Warrants to purchase shares of series A preferred stock exercised, one

Warrants to purchase shares of series A preferred stock exercised, one

Warrants to purchase shares of series A preferred stock exercised, two

Warrants to purchase shares of series A preferred stock exercised, two

Warrants to purchase shares of series A preferred stock in cashless exercise

Warrants to purchase shares of series A preferred stock in cashless exercise

Warrants to purchase shares of series A preferred stock in cashless exercise

Warrants to purchase Series B Preferred Stock

Warrants to purchase Series C Preferred Stock

Warrants to purchase redeemable convertible preferred stock automatically converted to warrants to purchase common stock

Warrants to purchase common stock

Warrants to purchase common stock

Warrants to purchase common stock

Recurring

Recurring

Total

Total

Total

Total

Significant unobservable inputs (Level 3)

Total

Warrants

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrants (in shares)

'

2,291,512

'

'

1,085,000

21,695

'

28,926

'

'

987,840

'

517,000

690,000

1,253,051

62,000

105,297

'

Series A Preferred stock resulting from the cashless exercise of warrants (in shares)

'

'

'

'

'

'

'

'

'

43,465

316,932

'

'

'

'

'

'

'

Common Stock resulting from the automatic conversion of Series A Preferred stock (in shares)

'

'

'

'

'

'

'

'

'

16,593

26,633

'

'

'

'

'

'

'

Warrants

$656,000

'

$656,000

$656,000

'

'

$7,783

'

$10,357

'

'

$304,423

'

'

'

'

'

$1,058,269

Warrants_Details_2

Warrants (Details 2) (USD $)	3 Months Ended		12 Months Ended	91 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014
Changes in the fair value of warrants to purchase redeemable securities, which represents a recurring measurement	'	'	'	'
Beginning balance	$656	'	'	'
Change in fair value	725	6	'	557
Warrants exercised	-323	'	'	'
Reclassification to equity	-1,058	'	'	'
Ending balance	'	'	$656	'
Percentage of fair value of warrants to purchase redeemable securities attributable to OPM backsolve method	'	'	35.00%	'
Percentage of fair value of warrants to purchase redeemable securities attributable to PWERM	'	'	65.00%	'

Warrants_Details_3

Warrants (Details 3) (USD $)

3 Months Ended

91 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Jan. 29, 2014

Jan. 29, 2014

Feb. 04, 2014

Feb. 04, 2014

Feb. 12, 2014

Feb. 10, 2014

Feb. 10, 2014

Feb. 10, 2014

Mar. 31, 2014

Feb. 10, 2014

Feb. 10, 2014

Warrants to purchase shares of series A preferred stock exercised, one

Warrants to purchase shares of series A preferred stock exercised, one

Warrants to purchase shares of series A preferred stock exercised, two

Warrants to purchase shares of series A preferred stock exercised, two

Warrants to purchase shares of series A preferred stock in cashless exercise

Warrants to purchase shares of series A preferred stock in cashless exercise

Warrants to purchase shares of series A preferred stock in cashless exercise

Warrants to purchase common stock

Warrants to purchase common stock

Warrants to purchase common stock

Warrants to purchase redeemable convertible preferred stock automatically converted to warrants to purchase common stock

Fair value

Fair value

Fair value

Fair value

Warrants

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrants (in shares)

'

'

'

'

21,695

'

28,926

'

'

987,840

'

105,297

62,000

'

1,253,051

Series A Preferred stock resulting from the cashless exercise of warrants (in shares)

'

'

'

'

'

'

'

'

43,465

316,932

'

'

'

'

'

Common Stock resulting from the automatic conversion of Series A Preferred stock (in shares)

'

'

'

'

'

'

'

'

16,593

26,633

'

'

'

'

'

Warrants

'

'

'

$656,000

'

$7,783

'

$10,357

'

'

$304,423

'

'

$1,058,269

'

Weighted average assumptions used to calculate the fair value of warrants

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair value of underlying instrument (in dollars per share)

'

'

'

'

0.65

'

0.65

'

'

7.74

'

'

'

'

6.96

Expected Volatility (as a percent)

'

'

'

'

55.57%

'

55.03%

'

'

50.81%

'

'

'

'

92.90%

Expected term

'

'

'

'

'14 days

'

'7 days

'

'

'1 day

'

'

'

'

'8 years 7 months 28 days

Risk-free interest rate (as a percent)

'

'

'

'

1.52%

'

1.46%

'

'

1.48%

'

'

'

'

2.43%

Expected dividend yield (as a percent)

'

'

'

'

0.00%

'

0.00%

'

'

0.00%

'

'

'

'

0.00%

Change in fair value

$725,000

$6,000

$557,000

'

$2,142

'

$2,839

'

'

$46,581

'

$673,040

'

'

'

Commitments_and_contingencies_1

Commitments and contingencies (Details) (Agreement to license certain intellectual property, USD $)

0 Months Ended

1 Months Ended

3 Months Ended

91 Months Ended

1 Months Ended

3 Months Ended

91 Months Ended

1 Months Ended

3 Months Ended

91 Months Ended

Aug. 31, 2006

Nov. 30, 2007

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Aug. 31, 2009

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Aug. 31, 2010

Jan. 31, 2010

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

The Regents of the University of California

Harvard University

Harvard University

Harvard University

Harvard University

Novavax

Novavax

Novavax

Novavax

Novavax

University of Washington

University of Washington

University of Washington

University of Washington

Significant Contracts and Agreements

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Non-refundable license fee payable

$25,000

$75,000

'

'

'

$750,000

'

'

'

$200,000

$20,000

'

'

'

Number of shares of common stock issuable

12,605

10,773

'

'

'

'

'

'

'

'

2,100

'

'

'

Total consideration

'

93,000

'

'

'

'

'

'

'

'

'

'

'

'

Annual maintenance fees and clinical milestones incurred

'

'

0

0

266,000

'

'

'

'

'

'

20,000

45,000

110,000

Period in which additional non-refundable license fee payable from date of licensing agreement

'

'

'

'

'

'1 year

'

'

'

'

'

'

'

'

Value of services obligated to be purchased by the entity under committed funding agreement

'

'

'

'

'

1,600,000

'

'

'

'

'

'

'

'

Value of services expensed as incurred by the entity related to committed funding agreement

'

'

'

'

'

'

$0

$0

$1,700,000

'

'

'

'

'

Commitments_and_contingencies_2

Commitments and contingencies (Details 2) (USD $)	3 Months Ended		91 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Supply agreements	'	'	'
Amount expensed related to supply agreements	$4,407	$3,980	$64,529
Supply agreement | Third party vendor	'	'	'
Supply agreements	'	'	'
Amount expensed related to supply agreements	613	70	8,100
Supply agreement | Fujifilm	'	'	'
Supply agreements	'	'	'
Amount expensed related to supply agreements	$25	'	'

Commitments_and_contingencies_3

Commitments and contingencies (Details 3) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	item
Restricted cash related to facilities leases	'	'
Restricted cash	$473	$315
Number of outstanding letters of credit	2	'
Letters of credit outstanding	473	'
2012 Facilities Sublease	'	'
Restricted cash related to facilities leases	'	'
Restricted cash	157	157
2012 Master Facilities Lease	'	'
Restricted cash related to facilities leases	'	'
Restricted cash	$316	$158

Redeemable_convertible_preferr1

Redeemable convertible preferred stock (Details)	0 Months Ended
	Feb. 10, 2014
Redeemable convertible preferred stock	'
Number of shares of common stock after conversion of redeemable convertible preferred stock to common stock	11,435,593

Common_stock_Details

Common stock (Details) (USD $)

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Warrants to purchase shares of series A preferred stock

Warrants to purchase shares of series A preferred stock

Warrants to purchase shares of series B preferred stock

Warrants to purchase shares of series C preferred stock

Warrants to purchase shares of series C preferred stock

Seed convertible preferred stock

Series A redeemable convertible preferred stock

Series B redeemable convertible preferred stock

Series C redeemable convertible preferred stock

Stock options

Stock options

Restricted common stock

Director

Stock options

Common stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares authorized

191,689,655

191,690,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, par value (in dollars per share)

$0.00

$0.00

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares issued

17,322,144

327,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares outstanding

17,299,472

303,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Options exercised (in shares)

'

'

'

'

'

'

'

'

'

'

'

12,000

'

'

25,262

Vesting period

'

'

'

'

'

'

'

'

'

'

'

'

'

'4 years

'

Number of shares issued

'

'

'

'

'

'

'

'

'

'

'

'

'

31,135

'

Number of shares vested

'

'

'

'

'

'

'

'

'

'

'

'

'

7,463

'

Number of shares subject to repurchase by entity

'

'

'

'

'

'

'

'

'

'

'

'

'

22,672

'

Shares of common stock reserved for future issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total common shares reserved for future issuance

2,709,000

13,425,000

4,000

91,000

43,000

58,000

58,000

388,000

2,990,000

3,613,000

4,419,000

2,647,000

1,823,000

'

'

Stockbased_compensation_Detail

Stock-based compensation (Details)	Mar. 31, 2014	Mar. 31, 2014	Feb. 10, 2014	Mar. 31, 2014
	2014 Equity Plan	2014 Equity Plan	2007 Equity Plan	2007 Equity Plan and 2014 Equity Plan
		Maximum
Stock-based compensation	'	'	'	'
Number of shares authorized	903,494	'	'	2,646,788
Number of shares available for grant	'	'	219,765	643,982
Percentage applied on total number of shares of common stock outstanding on previous calendar year for automatic inclusion in the plan	'	4.00%	'	'

Stockbased_compensation_Detail1

Stock-based compensation (Details 2) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Stock Based Compensation Expense	'	'
Stock-based compensation expense	$881	$63
Research and development	'	'
Stock Based Compensation Expense	'	'
Stock-based compensation expense	477	18
General and administrative	'	'
Stock Based Compensation Expense	'	'
Stock-based compensation expense	$404	$45

Stockbased_compensation_Detail2

Stock-based compensation (Details 3) (Stock options, USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Stock options	'	'
Shares	'	'
Outstanding at the beginning of the period (in shares)	1,576,000	'
Granted (in shares)	479,000	'
Exercised (in shares)	-12,000	'
Canceled (in shares)	-40,000	'
Outstanding at the end of the period (in shares)	2,003,000	1,576,000
Exercisable at the end of the period (in shares)	1,036,000	'
Vested or expected to vest at the end of the period (in shares)	1,871,000	'
Weighted - Average Exercise Price	'	'
Outstanding at the beginning of the period (in dollars per share)	$2.66	'
Granted (in dollars per share)	$12.09	'
Exercised (in dollars per share)	$2.22	'
Canceled (in dollars per share)	$2.27	'
Outstanding at the end of the period (in dollars per share)	$4.93	$2.66
Exercisable at the end of the period (in dollars per share)	$2.54	'
Vested or expected to vest at the end of the period (in dollars per share)	$5.07	'
Weighted- Average Remaining Contractual Term	'	'
Outstanding at the end of the period	'8 years	'7 years 7 months 20 days
Exercisable at the end of the period	'6 years 11 months 1 day	'
Vested or expected to vest at the end of the period	'7 years 11 months 26 days	'
Aggregate Intrinsic Value	'	'
Outstanding at the end of the period (in dollars )	$26,556	$6,682
Exercisable at the end of the period (in dollars )	16,219	'
Vested or expected to vest at the end of the period (in dollars )	$24,538	'

Stockbased_compensation_Detail3

Stock-based compensation (Details 4) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Additional disclosures	'	'
Stock-based compensation expense	$881	$63
Performance-based stock options	'	'
Additional disclosures	'	'
Number of options probable to achieve performance-based milestones	96,988	0
Stock-based compensation expense	$435	$0
Options outstanding (in shares)	56,336	'
Employee stock purchase plan | 2014 ESPP	'	'
Additional disclosures	'	'
Number of shares of common stock authorized under the plan	200,776	'
Option period	'6 months	'

Net_loss_per_share_attributabl2

Net loss per share attributable to common stockholders (Details)	3 Months Ended		91 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Common stock equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect	'	'	'
Common stock equivalents (in shares)	2,065	9,727	2,065
Preferred stock	'	'	'
Common stock equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect	'	'	'
Common stock equivalents (in shares)	'	8,493	'
Warrants	'	'	'
Common stock equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect	'	'	'
Common stock equivalents (in shares)	62	135	62
Outstanding options	'	'	'
Common stock equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect	'	'	'
Common stock equivalents (in shares)	2,003	1,099	2,003