Tetraphase Pharmaceuticals (TTPH) 10-Q 12 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	Apr. 30, 2013
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Entity Registrant Name	'TETRAPHASE PHARMACEUTICALS INC	'
Entity Central Index Key	'0001373707	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	25,832,982

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$89,011	$102,712
Accounts receivable	2,017	1,706
Prepaid expenses and other current assets	1,547	1,002
Total current assets	92,575	105,420
Property and equipment, net	238	235
Restricted cash	199	199
Other assets	31	32
Total assets	93,043	105,886
Current liabilities:	'	'
Accounts payable	3,925	1,881
Accrued expenses	4,083	5,290
Deferred revenue	'	92
Current portion of term loan payable	5,269	5,928
Total current liabilities	13,277	13,191
Accrued final interest payment on term loan	366	327
Term loan	3,737	4,560
Commitments and contingencies	'	'
Stockholders' equity:	'	'
Preferred stock, par value $0.001 per share; 5,000,000 shares authorized; no shares issued and outstanding	'	'
Common stock, par value $0.001 per share; 125,000,000 shares authorized; 25,812,982 and 25,629,281 shares issued and outstanding at March 31, 2014 and December 31, 2013, respectively	26	26
Additional paid-in capital	208,881	207,503
Deficit accumulated during the development stage	-133,244	-119,721
Total stockholders' equity	75,663	87,808
Total liabilities, convertible preferred stock and stockholders' equity	$93,043	$105,886

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Statement Of Financial Position [Abstract]	'	'
Preferred stock, par value	$0.00	$0.00
Preferred stock, authorized	5,000,000	5,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	25,812,982	25,629,281
Common stock, shares outstanding	25,812,982	25,629,281

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations and Comprehensive Loss (USD $)	3 Months Ended		93 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Income Statement [Abstract]	'	'	'
Revenues	$2,457	$2,700	$20,728
Operating expenses	'	'	'
Research and development	12,504	4,098	119,119
General and administrative	3,171	1,225	27,642
Total operating expenses	15,675	5,323	146,761
Loss from operations	-13,218	-2,623	-126,033
Other income (expense)	'	'	'
Interest income	5	'	623
Interest expense	-334	-431	-3,491
Other income	24	263	-4,343
Other expense, net	-305	-168	-7,211
Net loss	-13,523	-2,791	-133,244
Net loss per share applicable to common stockholders-basic and diluted	($0.53)	($1.51)	($42.06)
Weighted-average number of common shares used in net loss per share applicable to common stockholders-basic and diluted	25,734	1,848	3,168
Comprehensive loss	($13,523)	($2,791)	($133,244)

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended		93 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Operating activities	'	'	'
Net loss	($13,523)	($2,791)	($133,244)
Adjustments to reconcile net loss to net cash used in operating activities	'	'	'
Depreciation and amortization	25	36	2,533
Amortization of deferred financing costs and debt discount	70	84	711
Accretion of final interest payment on term loans	38	50	364
Fair value adjustment of warrants and investor right obligation	'	-263	5,099
Stock-based compensation expense	1,139	55	3,986
Loss from disposal of property and equipment	1	'	6
Changes in operating assets and liabilities:	'	'	'
Restricted cash	'	'	-199
Accounts receivable	-311	540	-2,017
Prepaid expenses and other current assets	-551	413	-1,547
Accounts payable	2,044	461	3,925
Accrued expenses	-1,207	-127	4,083
Deferred revenue	-92	-366	'
Net cash used in operating activities	-12,367	-1,908	-116,300
Investing activities	'	'	'
Purchases of property and equipment	-29	-10	-2,777
Net cash used in investing activities	-29	-10	-2,777
Financing activities	'	'	'
Proceeds from sale of common stock, net of issuance costs	'	68,688	118,793
Proceeds from sale of convertible preferred stock, net of issuance costs	'	'	79,841
Deferred financing fees	'	'	-275
Proceeds from issuance of term loan payable	'	3,000	18,750
Repayment of term loan payable	-1,545	-695	-9,524
Proceeds from sale of restricted common stock and common stock to founders	'	'	20
Proceeds from exercise of stock options	240	9	483
Net cash (used in) provided by financing activities	-1,305	71,002	208,088
Net (decrease) increase in cash and cash equivalents	-13,701	69,084	89,011
Cash and cash equivalents at beginning of period	102,712	9,079	'
Cash and cash equivalents at end of period	89,011	78,163	89,011
Supplemental cash flow and noncash financing activities	'	'	'
Cash paid for interest	237	233	2,391
Fair value of warrants issued in connection with issuance of term loan	'	115	684
Reclassification of investors rights/liability to stockholders' equity	'	'	5,321
Conversion of convertible preferred stock into common stock	'	79,832	79,832
Reclassification of warrant liability to additional paid-in-capital	'	462	462
Reclassification of deferred financing costs to additional paid-in-capital	'	'	$1,261

Organization_and_Operations

Organization and Operations	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Organization and Operations	'
	(1) Organization and Operations
	Tetraphase Pharmaceuticals, Inc. (the “Company”), is a clinical-stage biopharmaceutical company that was incorporated in Delaware on July 7, 2006 and has a principal place of business in Watertown, Massachusetts. The Company is using its proprietary chemistry technology to create novel antibiotics for serious and life-threatening multidrug-resistant infections. The Company’s lead product candidate, eravacycline, is being developed as a broad-spectrum intravenous and oral antibiotic for use as a first-line empiric monotherapy for the treatment of multidrug-resistant infections, including multidrug-resistant Gram-negative infections. The Company is conducting a Phase 3 clinical trial of eravacycline with intravenous administration for the treatment of complicated intra-abdominal infections (“cIAI”), and a second Phase 3 clinical trial of eravacycline for the treatment of complicated urinary tract infections (“cUTI”) with intravenous-to-oral step-down therapy. The Company expects to have data from the lead-in portion of the Phase 3 cUTI clinical trial in mid-2014, top-line data from the Phase 3 cIAI clinical trial in the first quarter of 2015, and top-line data from the Phase 3 cUTI clinical trial in mid-2015. The Company is also pursuing the discovery and development of additional antibiotics that target unmet medical needs, including multidrug-resistant Gram-negative bacteria.
	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 is subject to a number of risks similar to those of other development-stage life science companies, including dependence on key individuals, competition from other companies, the need for development of commercially viable products, and the need to obtain 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 industry, including rapid technological change, regulatory approval of products, uncertainty of market acceptance of products, competition, 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.
	The Company has incurred annual net operating losses in every year since its inception. As of March 31, 2014, the Company had incurred losses since inception of $133.2 million. The Company has not generated any product revenues related to its primary business purpose and has financed its operations primarily through public offerings of its common stock, private placements of its preferred stock, debt financings and funding from the United States government. The Company has not completed development of any product candidate and has devoted substantially all of its financial resources and efforts to research and development, including preclinical and clinical development. The Company expects to continue to incur significant expenses and increasing operating losses for at least the next several years. The Company expects to require additional financial resources to advance its product candidates to either commercial stage or liquidity events.
	There can be no assurance that the Company will be able to obtain additional debt or equity financing or generate revenues from collaborative partners, on terms acceptable to the Company, on a timely basis or at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations and financial condition.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	(2) Summary of Significant Accounting Policies
	Basis of Presentation
	The accompanying interim condensed consolidated financial statements are unaudited. These unaudited financial statements have been prepared in accordance with the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by United States generally accepted accounting principles (“GAAP”) for complete financial statements. These unaudited interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the accompanying notes for the year ended December 31, 2013 contained in the Company’s annual report on Form 10-K filed with the SEC on March 6, 2014 pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting of normal recurring adjustments) necessary to state fairly the Company’s financial position as of March 31, 2014, the results of operations and comprehensive loss and cash flows for the three months ended March 31, 2014 and 2013, and the period from July 7, 2006 (inception) to March 31, 2014. Interim operating results for the three months ended March 31, 2014 are not necessarily indicative of the results that may be expected for future interim periods or for the fiscal year ending December 31, 2014.
	The December 31, 2013 condensed consolidated balance sheet included herein was derived from audited consolidated financial statements, but does not include all disclosures including notes required by GAAP for complete financial statements.
	Segment Information
	Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment, which is the business of developing and commercializing its proprietary chemistry technology to create novel antibiotics for serious and life-threatening multidrug-resistant infections.
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses and related disclosures. On an ongoing basis, the Company’s management evaluates its estimates, including estimates related to clinical trial accruals, stock-based compensation expense, contract and grant revenues, and expenses. 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.
	Concentrations of Credit Risk and Off-Balance Sheet Risk
	Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash, cash equivalents and restricted cash. The Company maintains its cash and cash equivalent balances in the form of cash and money market accounts with financial institutions that management believes are creditworthy. The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimize its exposure to concentration of credit risk. The Company has no financial instruments with off-balance-sheet risk of loss.
	Principles of Consolidation
	The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Tetraphase Securities Corporation, a Massachusetts Securities Corporation. All significant intercompany balances and transactions have been eliminated in consolidation.
	Cash and Cash Equivalents
	The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. Cash and cash equivalents at March 31, 2014 and December 31, 2013 consisted of cash and money market funds.
	Fair Value Measurements
	The Company’s financial instruments consist principally of cash and cash equivalents, accounts receivable, accounts payable, accrued liabilities, and term loan payable. Fair value measurements are classified and disclosed in one of the following three categories:
			Level 1		—	Quoted prices in active markets for identical assets or liabilities.
			Level 2		—	Inputs other than Level 1 that are observable, either directly or indirectly, 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.
	Financial instruments measured at fair value as of March 31, 2014 and December 31, 2013 are classified below based on the three fair value hierarchy tiers described above (in thousands):
						Fair Value Measurements at
						Reporting Date Using
			Balance			Level 1		Level 2		Level 3
	March 31, 2014
	Cash		$	3,449		$	3,449	$	—	$	—
	Money market funds, included in cash equivalents		$	85,562		$	85,562	$	—	$	—
	December 31, 2013
	Cash		$	2,704		$	2,704	$	—	$	—
	Money market funds, included in cash equivalents		$	100,008		$	100,008	$	—	$	—
	The Company measures cash equivalents at fair value on a recurring basis. The fair value of cash equivalents is determined based on “Level 1” inputs, which consist of quoted prices in active markets for identical assets.
	The fair value of the Company’s term loan payable is determined using current applicable rates for similar instruments as of the balance sheet date. The Company’s term loan payable is a Level 3 liability within the fair value hierarchy. The fair value of the Company’s term loan payable at March 31, 2014, computed pursuant to a discounted cash flow technique using the effective interest rate under the loan, is $9.7 million. The effective interest rate considers the fair value of the warrant issued in connection with the loan, loan issuance costs and the deferred charge.
	The fair value of the preferred stock warrant liability as of March 25, 2013 was determined based on “Level 3” inputs utilizing the Black-Scholes option pricing model (Note 6). On March 25, 2013, upon completion of the Company’s initial public offering (“IPO”), the warrants to purchase preferred stock converted into warrants to purchase common stock and the Company reclassified the fair value of the warrants as of March 25, 2013 to additional paid-in capital. The following table presents activity in the preferred stock warrant liability during the three months ended March 31, 2013 (in thousands):
			Balance
	Fair value at December 31, 2012		$	610
	Value of warrants issued in 2013			115
	Decrease in fair value recognized in net loss			(263	)
	Reclassification of fair value to additional paid-in capital			(462	)
	Fair value at March 31, 2013		$	—
	Accounts Receivable
	In September 2011, the National Institutes of Health’s (“NIH”) National Institute of Allergy and Infectious Diseases (“NIAID”) division awarded a contract of up to $35.8 million over a five-year term for the development of TP-271, a preclinical compound, for respiratory disease caused by bacterial biothreat pathogens (“NIAID Contract”) (Note 3). The Company is collaborating with CUBRC Inc. (“CUBRC”), an independent, not for profit, research corporation that specializes in U.S. government-based contracts, on this NIAID Contract and has entered into a subcontract with CUBRC that could potentially provide funding to the Company of up to approximately $13.3 million over the five-year term, including committed funding of $7.6 million from the initial contract date through September 30, 2016, of which $5.1 million had been received by the Company through March 31, 2014. In addition during 2011, the Company was a subawardee under a separate grant from the NIAID (“NIAID Grant”) (Note 3).
	In January 2012 the Biomedical Advanced Research and Development Authority (“BARDA”), an agency of the U.S. Department of Health and Human Services, awarded a contract of up to $67.0 million for the development of eravacycline as a potential countermeasure for the treatment of disease caused by bacterial biothreat pathogens (“BARDA Contract”). The Company is also collaborating with CUBRC on the BARDA Contract and has entered into a subcontract with CUBRC that could potentially provide funding to the Company of up to approximately $39.8 million including committed funding of $15.7 million from the initial contract date through April 30, 2015, of which $13.0 million had been received by the Company through March 31, 2014 (Note 3).
	Accounts receivable at March 31, 2014 and December 31, 2013 represent amounts due from CUBRC under the Company’s subcontracts under the NIAID Contract and the BARDA Contract and under the Company’s subaward under the NIAID Grant. The Company’s practice is to bill the prime contractor, CUBRC, amounts for which the Company has been invoiced by third parties in the case of contract research or subcontractor costs or for internal costs incurred. Expenses directly associated with the Company’s NIAID and BARDA Contracts and NIAID Grant that have been accrued at the end of the reporting period are not billed to the prime contractor until third party invoices have been received or until internal costs have been paid. Unbilled accounts receivable was $0.1 million and $0.8 million at March 31, 2014 and December 31, 2013, respectively.
	Property and Equipment, Net
	Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization are provided using the straight-line method over the estimated useful lives of the respective assets, which is generally three to five years. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful economic lives of the related assets.
	Restricted Cash
	At March 31, 2014 and December 31, 2013 the Company had $199,000 in restricted cash deposits with a bank, of which $159,000 is collateral for a letter of credit issued to the landlord of the Company’s leased facility. If the Company defaults on its rental obligations, $159,000 will be payable to the lessor of the leased facility. In addition, the Company has $40,000 in restricted cash to secure the Company’s corporate credit card issued through the same bank.
	Revenue Recognition
	The Company’s revenue is derived from its subcontracts with CUBRC under the BARDA Contract and the NIAID Contract and its subaward under the NIAID Grant (Note 3). The Company recognizes revenue under these best-efforts, cost-reimbursable and cost-plus-fixed-fee subcontracts and subaward as the Company performs services under the subcontracts and subaward so long as a subcontract and subaward has been executed and the fees for these services are fixed or determinable, legally billable and reasonably assured of collection. Recognized amounts reflect the Company’s partial performance under the subcontracts and subaward and equal direct and indirect costs incurred plus fixed fees, where applicable. The Company does not recognize revenue under these arrangements for amounts related to contract periods where funding is not yet committed as amounts above committed funding thresholds would not be considered fixed or determinable or reasonably assured of collection. Revenues and expenses under these arrangements are presented gross on the condensed consolidated statements of operations and comprehensive loss as the Company has determined it is the primary obligor under these arrangements relative to the research and development services it performs as lead technical expert.
	Revenue under the Company’s subcontract with respect to the BARDA Contract is earned under a cost-reimbursable contract through which the Company is reimbursed for direct costs incurred plus allowable indirect costs. Billings under the Company’s subcontract under the BARDA Contract are based on approved provisional indirect billing rates that permit recovery of allowable fringe benefits, overhead and general and administrative expenses. During the three months ended March 31, 2014 and 2013, and the period from July 7, 2006 (inception) to March 31, 2014, the Company recognized revenue of $1.8 million, $1.8 million, and $14.4 million, respectively, from the Company’s subcontract under the BARDA Contract.
	Revenue under the Company’s subcontract with respect to the NIAID Contract is earned under a cost-plus-fixed-fee contract through which the Company is reimbursed for direct costs incurred plus allowable indirect costs and a fixed-fee earned. Billings under the Company’s subcontract under the NIAID Contract are based on approved provisional indirect billing rates that permit recovery of allowable fringe benefits, overhead and general and administrative expenses and a fixed fee. During the three months ended March 31, 2014 and 2013, and the period from July 7, 2006 (inception) to March 31, 2014, the Company recognized revenue of $0.6 million, $0.7 million, and $5.8 million, respectively, from the Company’s subcontract under the NIAID Contract.
	Revenue under the Company’s subaward with respect to the NIAID Grant is earned under a cost-reimbursable contract through which the Company is reimbursed for direct costs incurred plus allowable indirect costs. Billings under the Company’s subaward under the NIAID Grant are based on approved provisional indirect billing rates that permit recovery of allowable fringe benefits and general and administrative expenses. During the three months ended March 31, 2014 and 2013, and the period from July 7, 2006 (inception) to March 31, 2014, the Company recognized revenue of $57,000, $153,000 and $0.6 million, respectively, from the Company’s subaward under the NIAID Grant.
	Organizational Costs
	All organizational costs are expensed as incurred.
	Research and Development Expenses
	Research and development costs are charged to expense as incurred and include, but are not limited to:
		•		personnel-related expenses, including salaries, benefits, and stock-based compensation expense;
		•		expenses incurred under agreements with contract research organizations, contract manufacturing organizations and consultants that conduct clinical trials and preclinical studies;
		•		payments made under the Company’s license agreement with Harvard University;
		•		the cost of acquiring, developing and manufacturing clinical trial materials and lab supplies;
		•		facility, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, insurance and other supplies; and
		•		costs associated with preclinical activities and regulatory operations.
	Costs for certain development activities, such as clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the financial statements as prepaid or accrued research and development.
	Comprehensive Loss
Comprehensive loss consists of net income or loss and changes in equity during a period from transactions and other events and circumstances generated from non-owner sources. The Company’s net loss equals comprehensive loss for all periods presented.
Income Taxes
The Company uses the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial reporting and the tax reporting basis of assets and liabilities and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. The Company provides a valuation allowance against net deferred tax assets unless, based upon the available evidence, it is more likely than not that the deferred tax assets will be realized. The Company has evaluated available evidence and concluded that the Company may not realize the benefit of its deferred tax assets; therefore a valuation allowance has been established for the full amount of the deferred tax assets. The Company’s practice is to recognize interest and/or penalties related to income tax matters in income tax expense.
Stock-Based Compensation
The Company applies the provisions of ASC 718, Compensation-Stock Compensation to stock-based awards. Under ASC 718, the Company determines equity-based compensation at the grant date using the Black-Scholes option pricing model to estimate fair value. The Company recognizes the value of the award that is ultimately expected to vest as an expense on a straight-line basis over the requisite service period using the estimated fair market value of the stock. Any changes to the estimated forfeiture rates are accounted for prospectively.
Subsequent Events
The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.
Net Loss per Common Share
Basic net loss per share is calculated by dividing the net loss applicable to common stockholders by the weighted average number of shares of Common Stock outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing the net loss applicable to common stockholders by the weighted average number of common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, preferred stock, stock options and warrants are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.
On February 28, 2013, the Company’s board of directors approved an amendment to the Company’s certificate of incorporation to effect a 1-for-29 reverse split of its Common Stock. The Company effected this amendment to its certificate of incorporation on March 5, 2013. Following the Company’s reverse split, and effective as of the completion of the Company’s IPO on March 25, 2014, all of the Company’s preferred stock was converted to common stock at a 1-for-29 ratio. For purposes of calculating net loss per common share for the three months ended March 31, 2013 and the period from July 7, 2006 (inception) to March 31, 2014, the preferred stock that converted to common stock was included in the net loss per common share calculation on a post-conversion basis as of March 25, 2013, the effective date of conversion, and the corresponding converted shares were included on a pro-rata basis for each applicable reporting period. As a result, the weighted-average common shares outstanding during the three months ended March 31, 2013 and the period from July 7, 2006 (inception) to March 31, 2014, were 1.8 million and 3.2 million, respectively, as compared to 25.8 million and 19.9 million shares outstanding as of March 31, 2014 and 2013, respectively.
The amounts in the table below were excluded from the calculation of diluted weighted-average shares outstanding, prior to the use of the treasury stock method, due to their anti-dilutive effect:
		March 31,					The Period from
							July 7, 2006
							(inception) to
							March 31,
							2014
		2014			2013
Warrants			104,107			104,107		104,107
Outstanding stock options			3,544,365			1,535,948		3,554,365

Significant_Agreements_and_Con

Significant Agreements and Contracts	3 Months Ended
	Mar. 31, 2014
Research And Development [Abstract]	'
Significant Agreements and Contracts	'
	(3) Significant Agreements and Contracts
	License Agreement
	In August 2006, the Company entered into a license agreement for certain intellectual property with Harvard University (the “University”). Under the license agreement, the Company has paid the University an aggregate of $3.8 million in upfront license fees and development milestone payments, and has issued 31,379 shares of common stock to the University.
	The Company is obligated to make certain payments totaling up to approximately $15.1 million upon achievement of certain development and regulatory milestones and royalties on net sales of products covered by the agreement. In January 2007 and April 2010, the Company and the University amended the license agreement to include certain additional intellectual property. The Company paid an additional $25,000 to the University with each amendment. In February 2011, the license agreement was further amended to include additional intellectual property in the license granted by the University without the payment of any additional consideration. The Company also paid a $2.0 million milestone fee in October 2013 in connection with the dosing of the first patient in the Company’s Phase 3 clinical trial of eravacycline for the treatment of cIAI.
	Government Grant and Contracts
	BARDA Contract for Eravacycline
	The Company has received funding for its lead product candidate, eravacycline, under an award from BARDA. In January 2012, BARDA awarded a five-year contract that provides for up to a total of $67.0 million in funding for the development, manufacturing and clinical evaluation of eravacycline for the treatment of disease caused by bacterial biothreat pathogens.
	In connection with the BARDA Contract, in February 2012, the Company entered into a five-year cost-plus-fixed-fee subcontract with CUBRC under which it may receive funding of up to approximately $39.8 million, reflecting the portion of the BARDA funding that may be paid to the Company for its activities.
	Although the BARDA Contract and the Company’s subcontract with CUBRC under the BARDA Contract, have five-year terms, BARDA is entitled to terminate the project for convenience at any time, and is not obligated to provide continued funding beyond current-year amounts from Congressionally approved annual appropriations. To the extent that BARDA ceases to provide funding of the program to CUBRC, CUBRC has the right to cease providing funding to the Company. Committed funding from CUBRC under the Company’s BARDA subcontract is $15.7 million through April 30, 2015, the current contract end date, as a result of the exercise of several options by BARDA under the BARDA Contract. Total funds of $13.0 million had been received by the Company through March 31, 2014 under this contract.
	NIAID Grant and Contract for TP-271
	The Company has received funding for its preclinical compound TP-271 under two awards from NIAID for the development, manufacturing and clinical evaluation of TP-271 for respiratory diseases caused by biothreat and antibiotic-resistant public health pathogens, as well as bacterial pathogens associated with community-acquired bacterial pneumonia:
		•	the NIAID Grant awarded in July 2011 that provides up to a total of approximately $2.8 million over five years; and
		•	the NIAID Contract awarded in September 2011 that provides up to a total of approximately $35.8 million in funding over five years.
	In connection with the NIAID Grant, in November 2011, CUBRC awarded the Company a 55-month, no-fee subaward of approximately $980,000, reflecting the portion of the NIAID Grant funding that may be paid to the Company for its activities.
	In connection with the NIAID Contract, in October 2011, the Company entered into a five-year cost-plus-fixed-fee subcontract with CUBRC under which the Company may receive funding of up to approximately $13.3 million, reflecting the portion of the NIAID Contract funding that may be paid to the Company for its activities.
	Although the NIAID Contract, the NIAID Grant and the Company’s subcontract with CUBRC under the NIAID Contract have terms of five years, and the Company’s subaward under the NIAID Grant has a term of 55 months, NIAID is entitled to terminate the project for convenience at any time, and is not obligated to provide continued funding beyond September 30, 2016. To the extent NIAID ceases to provide funding of the programs to CUBRC, CUBRC has the right to cease providing funding to the Company. As of March 31, 2014, committed funding from CUBRC under the Company’s subcontract with respect to the NIAID Contract is $7.6 million through the current contract end date which has been extended to September 30, 2016. Total funds of $5.1 million had been received through March 31, 2014. Committed funding from CUBRC under the Company’s subaward with respect to the NIAID Grant is $0.7 million through the current contract end date, which has been extended to May 30, 2016. Total funds of $0.6 million had been received through March 31, 2014.

Prepaid_Expenses_and_Other_Cur

Prepaid Expenses and Other Current Assets	3 Months Ended
	Mar. 31, 2014
Text Block [Abstract]	'
Prepaid Expenses and Other Current Assets	'
	(4) Prepaid Expenses and Other Current Assets
	Prepaid expenses and other current assets at March 31, 2014 and December 31, 2013 consisted of the following (in thousands):
		March 31,		December 31,
		2014		2013
	Prepaid insurance	$	782	$	269
	Prepaid clinical costs		512		462
	Prepaid dues		95		30
	Prepaid rent		80		89
	Other		78		152
	Total	$	1,547	$	1,002

Accrued_Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2014
Payables And Accruals [Abstract]	'
Accrued Expenses	'
	(5) Accrued Expenses
	Accrued expenses at March 31, 2014 and December 31, 2013 consisted of the following (in thousands):
		March 31,		December 31,
		2014		2013
	Clinical trial related	$	1,369	$	1,849
	Drug supply and development		1,016		970
	Salaries and benefits		867		1,554
	Professional fees		355		246
	Other		476		671
	Total	$	4,083	$	5,290

LongTerm_Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Long-Term Debt	'
	(6) Long-Term Debt
	In May 2011, the Company executed a Loan and Security Agreement with Silicon Valley Bank and Oxford Finance (the “Term Loan”), which provided for up to $8.0 million funding, to be made available in two tranches. The Company borrowed the $8.0 million in two tranches during the year ended December 31, 2011. The Term Loan bears interest at 10% per annum and provides for a final payment of 2.75% of the original principal due at the maturity date of November 1, 2014. Under the terms of the Term Loan, the Company was only required to pay interest (and not principal) through February 28, 2012. Each tranche is being repaid in 33 monthly payments of equal principal, plus accrued interest, after the interest only period that ended on February 28, 2012. The final payment of 2.75% will be due at the same time as the last loan payment. The Term Loan matures on November 1, 2014. In connection with the entry into the Loan and Security Agreement, the Company issued to the lenders 10-year warrants to purchase an aggregate of 1,555,815 shares of Series C Preferred Stock, par value $0.001 per share (the “Series C Preferred Stock”) at a price of $0.2571 per share.
	In December 2012, the Company entered into an amendment to the Term Loan (the “2012 Term Loan”) to provide for up to an additional $9.2 million in funding, to be made available in two tranches. The Company borrowed the first tranche totaling $6.2 million under the 2012 Term Loan in December 2012 (“2012 Term A Loan”) and borrowed the remaining $3.0 million in February 2013 (“2012 Term B Loan”). Both the 2012 Term Loan A and the 2012 Term B Loan bear interest at 9% per annum.
	The Company was only required to pay interest (and not principal) for the first six months of each tranche of the 2012 Term Loan. Each tranche of the 2012 Term Loan is being repaid in 33 equal monthly payments of principal, plus accrued interest, after the interest only period. An additional payment of 2.90% of the original principal amount of each tranche will be due at the same time as the last loan payment for the tranche. The 2012 Term A Loan matures on March 1, 2016. In connection with the funding of the 2012 Term A Loan, the Company issued to the lenders 10-year warrants to purchase an aggregate of 964,605 shares of Series C Preferred Stock with an exercise price of $0.2571 per share. The 2012 Term B Loan matures on May 1, 2016. In connection with the funding of the 2012 Term B Loan, in February 2013, the warrant the Company issued to Silicon Valley Bank automatically became exercisable for an additional 233,372 shares of Series C Preferred Stock. In addition, the Company issued to Oxford Finance a 10-year warrant to purchase an additional 233,372 shares of Series C Preferred Stock with an exercise price of $0.2571 per share.
	The Term Loan and the 2012 Term Loan are collateralized by a blanket lien on all corporate assets, excluding intellectual property, and by a negative pledge of the Company’s intellectual property. The Term Loan and the 2012 Term Loan contain customary default provisions that include material adverse events, as defined therein. The Company has determined that the risk of subjective acceleration under the material adverse events clause is remote and therefore has classified the outstanding principal in current and long-term liabilities based on scheduled principal payments.
	Future principal payments on the Term Loan and the 2012 Term Loan are as follows (in thousands):
		March 31,
		2014
	2014 (9 months remaining)	$	4,582
	2015		3,513
	2016		1,132
	Total term loan payments		9,227
	Current term loan payable		5,430
	Less debt discount and issuance costs		(161	)
	Current term loan payable (net)		5,269
	Term loan payable, less current portion		3,797
	Less debt discount and issuance costs		(60	)
	Term loan payable, net	$	3,737

Stockbased_Compensation

Stock-based Compensation	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-based Compensation	'
	(7) Stock-based Compensation
	In August 2006, the Company adopted the Tetraphase Pharmaceuticals, Inc. Stock Incentive Plan (the “2006 Plan”) under which it was able to grant incentive stock options, nonqualified stock options, restricted stock, and stock grants to purchase up to 1,128,183 shares of Common Stock. In May 2010, the Company amended the plan to increase the number of shares of Common Stock issuable under the 2006 Plan to 1,853,288. The options expire ten years after the grant date. As of March 31, 2014, no shares were available for future issuance under the 2006 Plan.
	In February 2013, the Company’s board of directors and stockholders approved, effective upon the closing of the IPO, the 2013 Stock Incentive Plan (the “2013 Plan”). Under the 2013 Plan, the Company may grant incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards for the purchase of that number of shares of Common Stock equal to the sum of (i) 1,688,777 shares of Common Stock, (ii) 258,265 shares of Common Stock that were reserved for issuance under the 2006 Plan that remained available for issuance under the 2006 Plan upon the closing of the IPO, (iii) any shares of Common Stock subject to awards under the 2006 Plan which awards expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company without having been fully exercised or resulting in any Common Stock being issued. In addition, the number of shares of Common Stock that may be issued under the 2013 Plan is subject to automatic annual increases, to be added on January 1 of each year from January 1, 2014 through and including January 1, 2023, equal to the number of shares that is the lesser of (a) 3,000,000, (b) 4% of the then outstanding shares of Common Stock or (c) an amount determined by the Company’s board of directors. In January 2014, the number of shares authorized for issuance under the 2013 Plan increased by 1,025,171 shares. As of March 31, 2014, 620,147 shares were available for future issuance under the 2013 Plan.
	Terms of stock award agreements, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2013 Plan. Options granted by the Company typically vest over a four year period. Certain of the options are subject to acceleration of vesting in the event of certain change of control transactions. The options are exercisable from the date of grant for a period of ten years. For options granted prior to the Company’s IPO, the exercise price equaled the estimated fair value of the Common Stock as determined by the board of directors on the date of grant. For options granted subsequent to the Company’s IPO, the exercise price equaled the closing price of the Company’s stock on the NASDAQ Global Market on the date of grant.
	The following table summarizes stock option activity at March 31, 2014 and changes during the three months then ended is presented in the table and narrative below (in thousands except share and per share data):
			Shares			Weighted-			Weighted-		Aggregate
						Average			Average		Intrinsic
						Exercise			Remaining		Value
						Price			Contractual
									Term (years)
	Options outstanding at December 31, 2013			2,844,343		$	5.1			7.97	$	23,960
	Granted			1,013,650			14.66
	Exercised			(183,701	)		1.31
	Forfeited			(119,927	)		10.39
	Options outstanding at March 31, 2014			3,554,365		$	7.84			8.35	$	14,715
	Options vested or expected to vest at March 31, 2014 (1)			3,359,651		$	7.65			8.29	$	14,389
	Options exercisable at March 31, 2014			1,083,865		$	2.38			6.19	$	9,406
	-1	This represents the number of vested options as of March 31, 2014, plus the number of unvested options that the Company estimated as of March 31, 2014 would vest, based on the unvested options at March 31, 2014, as adjusted for the estimated forfeiture rate of 5.2%.
	The aggregate intrinsic value in the table above represents the value (the difference between the Company’s closing common stock price on the last trading day during the three months ended March 31, 2014 and the exercise price of the options, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on March 31, 2014. As of March 31, 2014, approximately $10.9 million of total unrecognized stock-based compensation expense related to unvested stock options is expected to be recognized over a weighted-average period of 3.2 years.
	Since the Company completed its IPO on March 25, 2013, it has not had sufficient historical data to support a calculation of volatility and expected life. As such, the Company has used a weighted-average volatility considering the Company’s own volatility, and the volatilities of a representative group of publicly traded companies. For purposes of identifying similar entities, the Company selected a group of publicly traded companies based on their disease focus, stage of clinical trials, number of compounds in clinical trials and number of years since incorporation for which historical information was available. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant, commensurate with the expected life assumption. The expected life of stock options granted represents the weighted-average period of time that stock options granted are expected to be outstanding determined using the simplified method for employee grants. For nonemployee grants, the expected life is equal to the remaining contractual term. The expected life is applied to the stock option grant group as a whole, as the Company does not expect substantially different exercise or post-vesting termination behavior among its employee population.
	During the three months ended March 31, 2014 and 2013, respectively, the assumptions used in the Black-Scholes pricing model for new grants were as follows:
			Three Months Ended March 31,
			2014			2013
	Volatility factor			53.50-53.96	%		54.5	%
	Expected term (in years)			5.81-6.11			5.82
	Risk-free interest rates			1.79-2.13	%		0.99	%
	Dividend yield			—			—
	Stock-based compensation expense recognized in the Company’s condensed consolidated statements of operations for stock options granted during the periods presented was as follows (in thousands):
			Three Months Ended						The Period
			March 31,						from July 7,
									2006
									(inception) to
									March 31,
			2014			2013			2014
	Research and development		$	366		$	12		$	2,052
	General and administrative			773			43			1,934
	Total		$	1,139		$	55		$	3,986

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying interim condensed consolidated financial statements are unaudited. These unaudited financial statements have been prepared in accordance with the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by United States generally accepted accounting principles (“GAAP”) for complete financial statements. These unaudited interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the accompanying notes for the year ended December 31, 2013 contained in the Company’s annual report on Form 10-K filed with the SEC on March 6, 2014 pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting of normal recurring adjustments) necessary to state fairly the Company’s financial position as of March 31, 2014, the results of operations and comprehensive loss and cash flows for the three months ended March 31, 2014 and 2013, and the period from July 7, 2006 (inception) to March 31, 2014. Interim operating results for the three months ended March 31, 2014 are not necessarily indicative of the results that may be expected for future interim periods or for the fiscal year ending December 31, 2014.
	The December 31, 2013 condensed consolidated balance sheet included herein was derived from audited consolidated financial statements, but does not include all disclosures including notes required by GAAP for complete financial statements.
Segment Information	'
	Segment Information
	Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment, which is the business of developing and commercializing its proprietary chemistry technology to create novel antibiotics for serious and life-threatening multidrug-resistant infections.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses and related disclosures. On an ongoing basis, the Company’s management evaluates its estimates, including estimates related to clinical trial accruals, stock-based compensation expense, contract and grant revenues, and expenses. 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.
Concentrations of Credit Risk and Off-Balance Sheet Risk	'
	Concentrations of Credit Risk and Off-Balance Sheet Risk
	Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash, cash equivalents and restricted cash. The Company maintains its cash and cash equivalent balances in the form of cash and money market accounts with financial institutions that management believes are creditworthy. The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimize its exposure to concentration of credit risk. The Company has no financial instruments with off-balance-sheet risk of loss.
Principles of Consolidation	'
	Principles of Consolidation
	The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Tetraphase Securities Corporation, a Massachusetts Securities Corporation. All significant intercompany balances and transactions have been eliminated in consolidation.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. Cash and cash equivalents at March 31, 2014 and December 31, 2013 consisted of cash and money market funds.
Fair Value Measurements	'
	Fair Value Measurements
	The Company’s financial instruments consist principally of cash and cash equivalents, accounts receivable, accounts payable, accrued liabilities, and term loan payable. Fair value measurements are classified and disclosed in one of the following three categories:
			Level 1		—	Quoted prices in active markets for identical assets or liabilities.
			Level 2		—	Inputs other than Level 1 that are observable, either directly or indirectly, 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.
	Financial instruments measured at fair value as of March 31, 2014 and December 31, 2013 are classified below based on the three fair value hierarchy tiers described above (in thousands):
						Fair Value Measurements at
						Reporting Date Using
			Balance			Level 1		Level 2		Level 3
	March 31, 2014
	Cash		$	3,449		$	3,449	$	—	$	—
	Money market funds, included in cash equivalents		$	85,562		$	85,562	$	—	$	—
	December 31, 2013
	Cash		$	2,704		$	2,704	$	—	$	—
	Money market funds, included in cash equivalents		$	100,008		$	100,008	$	—	$	—
	The Company measures cash equivalents at fair value on a recurring basis. The fair value of cash equivalents is determined based on “Level 1” inputs, which consist of quoted prices in active markets for identical assets.
	The fair value of the Company’s term loan payable is determined using current applicable rates for similar instruments as of the balance sheet date. The Company’s term loan payable is a Level 3 liability within the fair value hierarchy. The fair value of the Company’s term loan payable at March 31, 2014, computed pursuant to a discounted cash flow technique using the effective interest rate under the loan, is $9.7 million. The effective interest rate considers the fair value of the warrant issued in connection with the loan, loan issuance costs and the deferred charge.
	The fair value of the preferred stock warrant liability as of March 25, 2013 was determined based on “Level 3” inputs utilizing the Black-Scholes option pricing model (Note 6). On March 25, 2013, upon completion of the Company’s initial public offering (“IPO”), the warrants to purchase preferred stock converted into warrants to purchase common stock and the Company reclassified the fair value of the warrants as of March 25, 2013 to additional paid-in capital. The following table presents activity in the preferred stock warrant liability during the three months ended March 31, 2013 (in thousands):
			Balance
	Fair value at December 31, 2012		$	610
	Value of warrants issued in 2013			115
	Decrease in fair value recognized in net loss			(263	)
	Reclassification of fair value to additional paid-in capital			(462	)
	Fair value at March 31, 2013		$	—
Accounts Receivable	'
	Accounts Receivable
	In September 2011, the National Institutes of Health’s (“NIH”) National Institute of Allergy and Infectious Diseases (“NIAID”) division awarded a contract of up to $35.8 million over a five-year term for the development of TP-271, a preclinical compound, for respiratory disease caused by bacterial biothreat pathogens (“NIAID Contract”) (Note 3). The Company is collaborating with CUBRC Inc. (“CUBRC”), an independent, not for profit, research corporation that specializes in U.S. government-based contracts, on this NIAID Contract and has entered into a subcontract with CUBRC that could potentially provide funding to the Company of up to approximately $13.3 million over the five-year term, including committed funding of $7.6 million from the initial contract date through September 30, 2016, of which $5.1 million had been received by the Company through March 31, 2014. In addition during 2011, the Company was a subawardee under a separate grant from the NIAID (“NIAID Grant”) (Note 3).
	In January 2012 the Biomedical Advanced Research and Development Authority (“BARDA”), an agency of the U.S. Department of Health and Human Services, awarded a contract of up to $67.0 million for the development of eravacycline as a potential countermeasure for the treatment of disease caused by bacterial biothreat pathogens (“BARDA Contract”). The Company is also collaborating with CUBRC on the BARDA Contract and has entered into a subcontract with CUBRC that could potentially provide funding to the Company of up to approximately $39.8 million including committed funding of $15.7 million from the initial contract date through April 30, 2015, of which $13.0 million had been received by the Company through March 31, 2014 (Note 3).
	Accounts receivable at March 31, 2014 and December 31, 2013 represent amounts due from CUBRC under the Company’s subcontracts under the NIAID Contract and the BARDA Contract and under the Company’s subaward under the NIAID Grant. The Company’s practice is to bill the prime contractor, CUBRC, amounts for which the Company has been invoiced by third parties in the case of contract research or subcontractor costs or for internal costs incurred. Expenses directly associated with the Company’s NIAID and BARDA Contracts and NIAID Grant that have been accrued at the end of the reporting period are not billed to the prime contractor until third party invoices have been received or until internal costs have been paid. Unbilled accounts receivable was $0.1 million and $0.8 million at March 31, 2014 and December 31, 2013, respectively.
Property and Equipment, Net	'
	Property and Equipment, Net
	Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization are provided using the straight-line method over the estimated useful lives of the respective assets, which is generally three to five years. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful economic lives of the related assets.
Restricted Cash	'
	Restricted Cash
	At March 31, 2014 and December 31, 2013 the Company had $199,000 in restricted cash deposits with a bank, of which $159,000 is collateral for a letter of credit issued to the landlord of the Company’s leased facility. If the Company defaults on its rental obligations, $159,000 will be payable to the lessor of the leased facility. In addition, the Company has $40,000 in restricted cash to secure the Company’s corporate credit card issued through the same bank.
Revenue Recognition	'
	Revenue Recognition
	The Company’s revenue is derived from its subcontracts with CUBRC under the BARDA Contract and the NIAID Contract and its subaward under the NIAID Grant (Note 3). The Company recognizes revenue under these best-efforts, cost-reimbursable and cost-plus-fixed-fee subcontracts and subaward as the Company performs services under the subcontracts and subaward so long as a subcontract and subaward has been executed and the fees for these services are fixed or determinable, legally billable and reasonably assured of collection. Recognized amounts reflect the Company’s partial performance under the subcontracts and subaward and equal direct and indirect costs incurred plus fixed fees, where applicable. The Company does not recognize revenue under these arrangements for amounts related to contract periods where funding is not yet committed as amounts above committed funding thresholds would not be considered fixed or determinable or reasonably assured of collection. Revenues and expenses under these arrangements are presented gross on the condensed consolidated statements of operations and comprehensive loss as the Company has determined it is the primary obligor under these arrangements relative to the research and development services it performs as lead technical expert.
	Revenue under the Company’s subcontract with respect to the BARDA Contract is earned under a cost-reimbursable contract through which the Company is reimbursed for direct costs incurred plus allowable indirect costs. Billings under the Company’s subcontract under the BARDA Contract are based on approved provisional indirect billing rates that permit recovery of allowable fringe benefits, overhead and general and administrative expenses. During the three months ended March 31, 2014 and 2013, and the period from July 7, 2006 (inception) to March 31, 2014, the Company recognized revenue of $1.8 million, $1.8 million, and $14.4 million, respectively, from the Company’s subcontract under the BARDA Contract.
	Revenue under the Company’s subcontract with respect to the NIAID Contract is earned under a cost-plus-fixed-fee contract through which the Company is reimbursed for direct costs incurred plus allowable indirect costs and a fixed-fee earned. Billings under the Company’s subcontract under the NIAID Contract are based on approved provisional indirect billing rates that permit recovery of allowable fringe benefits, overhead and general and administrative expenses and a fixed fee. During the three months ended March 31, 2014 and 2013, and the period from July 7, 2006 (inception) to March 31, 2014, the Company recognized revenue of $0.6 million, $0.7 million, and $5.8 million, respectively, from the Company’s subcontract under the NIAID Contract.
	Revenue under the Company’s subaward with respect to the NIAID Grant is earned under a cost-reimbursable contract through which the Company is reimbursed for direct costs incurred plus allowable indirect costs. Billings under the Company’s subaward under the NIAID Grant are based on approved provisional indirect billing rates that permit recovery of allowable fringe benefits and general and administrative expenses. During the three months ended March 31, 2014 and 2013, and the period from July 7, 2006 (inception) to March 31, 2014, the Company recognized revenue of $57,000, $153,000 and $0.6 million, respectively, from the Company’s subaward under the NIAID Grant.
Organizational Costs	'
	Organizational Costs
	All organizational costs are expensed as incurred.
Research and Development Expenses	'
	Research and Development Expenses
	Research and development costs are charged to expense as incurred and include, but are not limited to:
		•		personnel-related expenses, including salaries, benefits, and stock-based compensation expense;
		•		expenses incurred under agreements with contract research organizations, contract manufacturing organizations and consultants that conduct clinical trials and preclinical studies;
		•		payments made under the Company’s license agreement with Harvard University;
		•		the cost of acquiring, developing and manufacturing clinical trial materials and lab supplies;
		•		facility, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, insurance and other supplies; and
		•		costs associated with preclinical activities and regulatory operations.
	Costs for certain development activities, such as clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the financial statements as prepaid or accrued research and development.
Comprehensive Loss	'
	Comprehensive Loss
	Comprehensive loss consists of net income or loss and changes in equity during a period from transactions and other events and circumstances generated from non-owner sources. The Company’s net loss equals comprehensive loss for all periods presented.
Income Taxes	'
	Income Taxes
	The Company uses the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial reporting and the tax reporting basis of assets and liabilities and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. The Company provides a valuation allowance against net deferred tax assets unless, based upon the available evidence, it is more likely than not that the deferred tax assets will be realized. The Company has evaluated available evidence and concluded that the Company may not realize the benefit of its deferred tax assets; therefore a valuation allowance has been established for the full amount of the deferred tax assets. The Company’s practice is to recognize interest and/or penalties related to income tax matters in income tax expense.
Stock-Based Compensation	'
	Stock-Based Compensation
	The Company applies the provisions of ASC 718, Compensation-Stock Compensation to stock-based awards. Under ASC 718, the Company determines equity-based compensation at the grant date using the Black-Scholes option pricing model to estimate fair value. The Company recognizes the value of the award that is ultimately expected to vest as an expense on a straight-line basis over the requisite service period using the estimated fair market value of the stock. Any changes to the estimated forfeiture rates are accounted for prospectively.
Subsequent Events	'
	Subsequent Events
	The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.
Net Loss per Common Share	'
	Net Loss per Common Share
	Basic net loss per share is calculated by dividing the net loss applicable to common stockholders by the weighted average number of shares of Common Stock outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing the net loss applicable to common stockholders by the weighted average number of common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, preferred stock, stock options and warrants are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.
	On February 28, 2013, the Company’s board of directors approved an amendment to the Company’s certificate of incorporation to effect a 1-for-29 reverse split of its Common Stock. The Company effected this amendment to its certificate of incorporation on March 5, 2013. Following the Company’s reverse split, and effective as of the completion of the Company’s IPO on March 25, 2014, all of the Company’s preferred stock was converted to common stock at a 1-for-29 ratio. For purposes of calculating net loss per common share for the three months ended March 31, 2013 and the period from July 7, 2006 (inception) to March 31, 2014, the preferred stock that converted to common stock was included in the net loss per common share calculation on a post-conversion basis as of March 25, 2013, the effective date of conversion, and the corresponding converted shares were included on a pro-rata basis for each applicable reporting period. As a result, the weighted-average common shares outstanding during the three months ended March 31, 2013 and the period from July 7, 2006 (inception) to March 31, 2014, were 1.8 million and 3.2 million, respectively, as compared to 25.8 million and 19.9 million shares outstanding as of March 31, 2014 and 2013, respectively.
	The amounts in the table below were excluded from the calculation of diluted weighted-average shares outstanding, prior to the use of the treasury stock method, due to their anti-dilutive effect:
			March 31,					The Period from
								July 7, 2006
								(inception) to
								March 31,
								2014
			2014			2013
	Warrants			104,107			104,107		104,107
	Outstanding stock options			3,544,365			1,535,948		3,554,365

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Financial Instruments Measured at Fair Value	'
	Financial instruments measured at fair value as of March 31, 2014 and December 31, 2013 are classified below based on the three fair value hierarchy tiers described above (in thousands):
					Fair Value Measurements at
					Reporting Date Using
		Balance			Level 1		Level 2		Level 3
	March 31, 2014
	Cash	$	3,449		$	3,449	$	—	$	—
	Money market funds, included in cash equivalents	$	85,562		$	85,562	$	—	$	—
	December 31, 2013
	Cash	$	2,704		$	2,704	$	—	$	—
	Money market funds, included in cash equivalents	$	100,008		$	100,008	$	—	$	—
Schedule of Preferred Stock Warrant Liability	'
	The following table presents activity in the preferred stock warrant liability during the three months ended March 31, 2013 (in thousands):
		Balance
	Fair value at December 31, 2012	$	610
	Value of warrants issued in 2013		115
	Decrease in fair value recognized in net loss		(263	)
	Reclassification of fair value to additional paid-in capital		(462	)
	Fair value at March 31, 2013	$	—
Amounts Excluded from Calculation of Diluted Weighted-Average Shares Outstanding	'
	The amounts in the table below were excluded from the calculation of diluted weighted-average shares outstanding, prior to the use of the treasury stock method, due to their anti-dilutive effect:
		March 31,					The Period from
							July 7, 2006
							(inception) to
							March 31,
							2014
		2014			2013
	Warrants		104,107			104,107		104,107
	Outstanding stock options		3,544,365			1,535,948		3,554,365

Prepaid_Expenses_and_Other_Cur1

Prepaid Expenses and Other Current Assets (Tables)	3 Months Ended
	Mar. 31, 2014
Text Block [Abstract]	'
Schedule of Prepaid Expenses and Other Current Assets	'
	Prepaid expenses and other current assets at March 31, 2014 and December 31, 2013 consisted of the following (in thousands):
		March 31,		December 31,
		2014		2013
	Prepaid insurance	$	782	$	269
	Prepaid clinical costs		512		462
	Prepaid dues		95		30
	Prepaid rent		80		89
	Other		78		152
	Total	$	1,547	$	1,002

Accrued_Expenses_Tables

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2014
Payables And Accruals [Abstract]	'
Accrued Expenses	'
	Accrued expenses at March 31, 2014 and December 31, 2013 consisted of the following (in thousands):
		March 31,		December 31,
		2014		2013
	Clinical trial related	$	1,369	$	1,849
	Drug supply and development		1,016		970
	Salaries and benefits		867		1,554
	Professional fees		355		246
	Other		476		671
	Total	$	4,083	$	5,290

LongTerm_Debt_Tables

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Future Principal Payments on Term Loan	'
	Future principal payments on the Term Loan and the 2012 Term Loan are as follows (in thousands):
		March 31,
		2014
	2014 (9 months remaining)	$	4,582
	2015		3,513
	2016		1,132
	Total term loan payments		9,227
	Current term loan payable		5,430
	Less debt discount and issuance costs		(161	)
	Current term loan payable (net)		5,269
	Term loan payable, less current portion		3,797
	Less debt discount and issuance costs		(60	)
	Term loan payable, net	$	3,737

Stockbased_Compensation_Tables

Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock Option Activity	'
	The following table summarizes stock option activity at March 31, 2014 and changes during the three months then ended is presented in the table and narrative below (in thousands except share and per share data):
			Shares			Weighted-		Weighted-		Aggregate
						Average		Average		Intrinsic
						Exercise		Remaining		Value
						Price		Contractual
								Term (years)
	Options outstanding at December 31, 2013			2,844,343		$	5.1	7.97		$	23,960
	Granted			1,013,650			14.66
	Exercised			(183,701	)		1.31
	Forfeited			(119,927	)		10.39
	Options outstanding at March 31, 2014			3,554,365		$	7.84	8.35		$	14,715
	Options vested or expected to vest at March 31, 2014 (1)			3,359,651		$	7.65	8.29		$	14,389
	Options exercisable at March 31, 2014			1,083,865		$	2.38	6.19		$	9,406
	-1	This represents the number of vested options as of March 31, 2014, plus the number of unvested options that the Company estimated as of March 31, 2014 would vest, based on the unvested options at March 31, 2014, as adjusted for the estimated forfeiture rate of 5.2%.
Assumptions Used in Black-Scholes Pricing Model for New Grants	'
	During the three months ended March 31, 2014 and 2013, respectively, the assumptions used in the Black-Scholes pricing model for new grants were as follows:
			Three Months Ended March 31,
			2014		2013
	Volatility factor		53.50-53.96%		54.50%
	Expected term (in years)		5.81-6.11		5.82
	Risk-free interest rates		1.79-2.13%		0.99%
	Dividend yield		—		—
Stock-based Compensation Expense Recognized for Stock Options Granted in the Condensed Consolidated Statements of Operations	'
	Stock-based compensation expense recognized in the Company’s condensed consolidated statements of operations for stock options granted during the periods presented was as follows (in thousands):
			Three Months Ended					The Period
			March 31,					from July 7,
								2006
								(inception) to
								March 31,
			2014			2013		2014
	Research and development		$	366		$	12	$	2,052
	General and administrative			773			43		1,934
	Total		$	1,139		$	55	$	3,986

Organization_and_Operations_Ad

Organization and Operations - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'	'
Company incorporation date	7-Jul-06	'
Losses incurred since inception	$133,244	$119,721

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)

3 Months Ended

12 Months Ended

93 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

93 Months Ended

3 Months Ended

93 Months Ended

1 Months Ended

1 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

93 Months Ended

1 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Jan. 31, 2012

Feb. 29, 2012

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Jan. 31, 2012

Feb. 29, 2012

Jan. 31, 2012

Sep. 30, 2011

Jul. 31, 2011

Oct. 31, 2011

Sep. 30, 2011

Mar. 31, 2014

Nov. 30, 2011

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Sep. 30, 2011

Jul. 31, 2011

Oct. 31, 2011

Sep. 30, 2011

Sep. 30, 2011

Jan. 31, 2012

Segment

Letter of Credit [Member]

Letter of Credit [Member]

Credit Card [Member]

Credit Card [Member]

Maximum [Member]

Minimum [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

September 1, 2011 through September 30, 2016 [Member]

January 1, 2012 through April 30, 2015 [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subaward Under the NIAID Grant [Member]

Subaward Under the NIAID Grant [Member]

Subaward Under the NIAID Grant [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subaward Under the NIAID Grant [Member]

Subaward Under the NIAID Grant [Member]

Subaward Under the NIAID Grant [Member]

Subaward Under the NIAID Grant [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Summary Of Significant Accounting Policies [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of operating segment

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maturity period of highly liquid investments

'Three months or less

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair value of loans payable

$9,700,000

'

'

$9,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Awarded contract for development, amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

67,000,000

'

'

'

'

'

'

'

'

'

'

'

35,800,000

2,800,000

'

'

'

'

Awarded contract for development, contract period

'

'

'

'

'

'

'

'

'

'

'5 years

'5 years

'

'

'

'

'

'

'

'

'

'5 years

'5 years

'5 years

'5 years

'

'55 months

'

'

'

'

'

'

'

'

'

Awarded contract for development, amount to be funded

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

39,800,000

39,800,000

'

'

'

'

5,100,000

980,000

'

'

'

'

'

13,300,000

13,300,000

7,600,000

15,700,000

Awarded contract for development, amount received

'

'

'

'

'

'

'

'

'

'

'

'

13,000,000

'

'

'

'

'

'

'

'

'

'

'

'

5,100,000

'

600,000

'

'

'

'

'

'

'

'

Unbilled accounts receivable

100,000

'

800,000

100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Useful lives of property and equipment

'

'

'

'

'

'

'

'

'5 years

'3 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Restricted cash

199,000

'

199,000

199,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Restricted cash, current

'

'

'

'

159,000

159,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Restricted cash, non-current

199,000

'

199,000

199,000

'

'

40,000

40,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount payable to lessors in respect of default on rental obligation

159,000

'

159,000

159,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenue from grants

'

'

'

'

'

'

'

'

'

'

'

'

$1,800,000

$1,800,000

$14,400,000

$600,000

$700,000

$5,800,000

'

'

'

'

'

'

'

'

'

$57,000

$153,000

$600,000

'

'

'

'

'

'

Initial public offering completion date

25-Mar-14

'

'

25-Mar-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reverse stock split ratio

'

'

0.034

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted-average number of common shares used in net loss per share applicable to common stockholders-basic and diluted

25,734,000

1,848,000

'

3,168,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares outstanding

25,812,982

19,900,000

25,629,281

25,812,982

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Financial Instruments Measured at Fair Value (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Cash [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents, fair value	$3,449	$2,704
Money Market Funds, Included in Cash Equivalents [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents, fair value	85,562	100,008
Level 1 [Member] | Cash [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents, fair value	3,449	2,704
Level 1 [Member] | Money Market Funds, Included in Cash Equivalents [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents, fair value	85,562	100,008
Level 2 [Member] | Cash [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents, fair value	'	'
Level 2 [Member] | Money Market Funds, Included in Cash Equivalents [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents, fair value	'	'
Level 3 [Member] | Cash [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents, fair value	'	'
Level 3 [Member] | Money Market Funds, Included in Cash Equivalents [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents, fair value	'	'

Summary_of_Significant_Account5

Summary of Significant Accounting Policies - Schedule of Preferred Stock Warrant Liability (Detail) (USD $)	3 Months Ended	93 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2014
Regulatory Assets [Abstract]	'	'
Fair value, Beginning Balance	$610	'
Value of warrants issued in 2013	115	684
Decrease in fair value recognized in net loss	-263	'
Reclassification of fair value to additional paid-in capital	($462)	($462)

Summary_of_Significant_Account6

Summary of Significant Accounting Policies - Amounts Excluded from Calculation of Diluted Weighted-Average Shares Outstanding (Detail)	3 Months Ended		93 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Warrants [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Antidilutive securities excluded from computation of earnings per share, amount	104,107	104,107	104,107
Outstanding Stock Options [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Antidilutive securities excluded from computation of earnings per share, amount	3,544,365	1,535,948	3,554,365

Significant_Agreements_and_Con1

Significant Agreements and Contracts - Additional Information (Detail) (USD $)

1 Months Ended

1 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

Jan. 31, 2012

Jan. 31, 2012

Sep. 30, 2011

Jul. 31, 2011

Sep. 30, 2011

Jul. 31, 2011

Apr. 30, 2010

Jan. 31, 2007

Aug. 31, 2006

Mar. 31, 2014

Oct. 31, 2013

Feb. 29, 2012

Mar. 31, 2014

Feb. 29, 2012

Jan. 31, 2012

Oct. 31, 2011

Sep. 30, 2011

Mar. 31, 2014

Oct. 31, 2011

Sep. 30, 2011

Nov. 30, 2011

Mar. 31, 2014

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

License Agreement with Harvard University (the University) [Member]

License Agreement with Harvard University (the University) [Member]

License Agreement with Harvard University (the University) [Member]

License Agreement with Harvard University (the University) [Member]

License Agreement with Harvard University (the University) [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subcontract with CUBRC [Member]

Subaward Under the NIAID Grant [Member]

Subaward Under the NIAID Grant [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Phase Three Clinical Trial [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

Biomedical Advanced Research and Development Authority (BARDA) [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Upfront and milestone payments

'

'

'

'

'

'

'

'

$3,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of common stock to be issued

'

'

'

'

'

'

'

'

31,379

'

'

'

'

'

'

'

'

'

'

'

'

'

Upfront and milestone payments

'

'

'

'

'

'

'

'

'

15,100,000

'

'

'

'

'

'

'

'

'

'

'

'

Payment for additional intellectual property

'

'

'

'

'

'

25,000

25,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Milestone payments

'

'

'

'

'

'

'

'

'

'

2,000,000

'

'

'

'

'

'

'

'

'

'

'

Awarded contract for development, amount

'

67,000,000

'

'

35,800,000

2,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Awarded contract for development, contract period

'5 years

'

'5 years

'5 years

'

'

'

'

'

'

'

'5 years

'

'

'

'5 years

'5 years

'

'

'

'55 months

'

Awarded contract for development, amount to be funded

'

'

'

'

'

'

'

'

'

'

'

'

'

39,800,000

39,800,000

'

'

5,100,000

13,300,000

13,300,000

980,000

'

Contractual amount during the twelve-month base period

'

'

'

'

'

'

'

'

'

'

'

'

15,700,000

'

'

'

'

7,600,000

'

'

'

'

Proceed from awarded contract for development

'

'

'

'

'

'

'

'

'

'

'

'

13,000,000

'

'

'

'

5,100,000

'

'

'

600,000

Contractual amount during the twelve-month base period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$700,000

Prepaid_Expenses_and_Other_Cur2

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]	'	'
Prepaid insurance	$782	$269
Prepaid clinical costs	512	462
Prepaid dues	95	30
Prepaid rent	80	89
Other	78	152
Total	$1,547	$1,002

Accrued_Expenses_Accrued_Expen

Accrued Expenses - Accrued Expenses (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Payables And Accruals [Abstract]	'	'
Clinical trial related	$1,369	$1,849
Drug supply and development	1,016	970
Salaries and benefits	867	1,554
Professional fees	355	246
Other	476	671
Total	$4,083	$5,290

LongTerm_Debt_Additional_Infor

Long-Term Debt - Additional Information (Detail) (USD $)

3 Months Ended

93 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

1 Months Ended

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Feb. 28, 2013

Dec. 31, 2012

Feb. 28, 2013

Dec. 31, 2012

Feb. 28, 2013

Dec. 31, 2012

31-May-11

Dec. 31, 2011

31-May-11

Feb. 28, 2013

Dec. 31, 2012

Dec. 31, 2012

2012 Term B Loan [Member]

2012 Term B Loan [Member]

2012 Term B Loan [Member]

2012 Term B Loan [Member]

2012 Term B Loan [Member]

Term Loan [Member]

Term Loan [Member]

Term Loan [Member]

Term Loan [Member]

2012 Term A Loan [Member]

2012 Term A Loan [Member]

2012 Term A Loan [Member]

Second Tranche [Member]

Second Tranche [Member]

Series C Convertible Preferred Shares [Member]

Tranches

Tranches

Series C Convertible Preferred Shares [Member]

First Tranche [Member]

Series C Convertible Preferred Shares [Member]

Installment

Second Tranche [Member]

Installment

Installment

First Tranche [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt, borrowing capacity

'

'

'

'

'

'

'

'

'

$8,000,000

'

'

'

'

'

Debt, number of tranches

'

'

'

'

'

'

'

'

2

2

'

'

'

'

'

Debt, borrowing

3,000,000

18,750,000

'

'

'

3,000,000

'

'

'

'

8,000,000

'

'

6,200,000

'

Debt, stated interest rate

'

'

'

9.00%

'

'

'

'

'

10.00%

'

'

9.00%

'

'

Debt, stated interest rate at maturity date

'

'

'

'

'

2.90%

2.90%

'

'

2.75%

'

'

'

2.90%

'

Debt, maturity date

'

'

'

'

'

'

1-May-16

'

'

1-Nov-14

'

'

'

1-Mar-16

'

Debt, number of installments

'

'

'

'

'

'

33

'

'

33

'

'

'

33

'

Warrants to purchase shares of stock, term

'

'

'

'

'

'

'

'10 years

'

'

'

'10 years

'

'

'10 years

Warrants to purchase shares of stock, shares

'

'

'

'

'

'

'

233,372

'

'

'

1,555,815

'

'

964,605

Warrants to purchase shares of stock, shares, exercise price per share

'

'

'

'

'

'

'

0.2571

'

'

'

0.2571

'

'

0.2571

Preferred stock, par value

'

$0.00

$0.00

'

'

'

'

'

'

'

'

$0.00

'

'

'

Debt, additional borrowing capacity

'

'

'

'

$9,200,000

'

'

'

'

'

'

'

'

'

'

Stock issued upon immediate exercise of warrant

'

'

'

'

'

'

'

233,372

'

'

'

'

'

'

'

Interest payment period

'

'

'

'

'

'

'

'

'6 months

'

'

'

'

'

'

LongTerm_Debt_Future_Principal

Long-Term Debt - Future Principal Payments on Term Loan (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Debt Disclosure [Abstract]	'	'
2014 (9 months remaining)	$4,582	'
2015	3,513	'
2016	1,132	'
Total term loan payments	9,227	'
Current term loan payable	5,430	'
Less debt discount and issuance costs	-161	'
Current term loan payable (net)	5,269	5,928
Term loan payable, less current portion	3,797	'
Less debt discount and issuance costs	-60	'
Term loan payable, net	$3,737	$4,560

Stockbased_Compensation_Additi

Stock-based Compensation - Additional Information (Detail) (USD $)	3 Months Ended	1 Months Ended		3 Months Ended		1 Months Ended			12 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Feb. 28, 2013	31-May-10	Mar. 31, 2014	Aug. 31, 2006	Jan. 31, 2014	Mar. 31, 2014	Feb. 28, 2013	Dec. 31, 2013
		Stock Incentive Plan 2006 [Member]	Stock Incentive Plan 2006 [Member]	Stock Incentive Plan 2006 [Member]	Stock Incentive Plan 2006 [Member]	Stock Incentive Plan 2013 [Member]	Stock Incentive Plan 2013 [Member]	Stock Incentive Plan 2013 [Member]	Stock Compensation Plan Agreements [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'	'	'
Shares authorized for issuance under stock incentive plan	'	'	'	'	1,128,183	'	'	1,688,777	'
Increase in number of shares of common stock issuable	'	'	1,853,288	'	'	1,025,171	'	'	'
Option vesting period	'	'	'	'10 years	'	'	'	'	'4 years
Outstanding shares available for future grants	'	258,265	'	0	'	'	620,147	'	'
Maximum threshold of shares outstanding for determining availability of grants	'	3,000,000	'	'	'	'	'	'	'
Percentage threshold of shares outstanding for determining availability of grants	'	4.00%	'	'	'	'	'	'	'
Share based compensation, contractual life	'	'	'	'	'	'	'	'	'10 years
Unrecognized stock-based compensation expense related to unvested stock options	$10.90	'	'	'	'	'	'	'	'
Weighted-average period of unrecognized stock-based compensation expense related to unvested stock options	'3 years 2 months 12 days	'	'	'	'	'	'	'	'

Stockbased_Compensation_Stock_

Stock-based Compensation - Stock Option Activity (Detail) (USD $)	3 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Number of Shares	'	'
Beginning balance	2,844,343	'
Granted	1,013,650	'
Exercised	-183,701	'
Forfeited	-119,927	'
Ending balance	3,554,365	2,844,343
Options vested or expected to vest at March 31, 2014	3,359,651	'
Options exercisable at March 31, 2014	1,083,865	'
Weighted Average Exercise Price	'	'
Beginning balance	$5.10	'
Granted	$14.66	'
Exercised	$1.31	'
Forfeited	$10.39	'
Ending balance	$7.84	$5.10
Options vested or expected to vest at March 31, 2014	$7.65	'
Options exercisable at March 31, 2014	$2.38	'
Weighted Average Remaining Contractual Term	'	'
Weighted-Average Remaining Contractual Term	'8 years 4 months 6 days	'7 years 11 months 19 days
Option vested or expected to vest at the end of the year	'8 years 3 months 15 days	'
Options exercisable at the end of the year	'6 years 2 months 9 days	'
Aggregate Intrinsic Value	'	'
Beginning balance	$23,960	'
Ending balance	14,715	23,960
Option vested or expected to vest at end of the year	14,389	'
Options exercisable at the end of year	$9,406	'

Stockbased_Compensation_Stock_1

Stock-based Compensation - Stock Option Activity (Parenthetical) (Detail)	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Estimated forfeiture rate	5.20%

Stockbased_Compensation_Assump

Stock-based Compensation - Assumptions Used in Black-Scholes Pricing Model for New Grants (Detail)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Volatility factor	'	54.50%
Volatility factor	53.50%	'
Volatility factor	53.96%	'
Expected term (in years)	'	'5 years 9 months 26 days
Risk-free interest rates	'	0.99%
Risk-free interest rates	1.79%	'
Risk-free interest rates	2.13%	'
Dividend yield	'	'
Minimum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Expected term (in years)	'5 years 9 months 22 days	'
Maximum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Expected term (in years)	'6 years 1 month 10 days	'

Stockbased_Compensation_Stockb

Stock-based Compensation - Stock-based Compensation Expense Recognized for Stock Options Granted in the Condensed Consolidated Statements of Operations (Detail) (USD $)	3 Months Ended		93 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Stock-based compensation expense	$1,139	$55	$3,986
Research and Development [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Stock-based compensation expense	366	12	2,052
General and Administrative [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Stock-based compensation expense	$773	$43	$1,934