Tetraphase Pharmaceuticals (TTPH) 10-K 6 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 28, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	TTPH
Entity Registrant Name	TETRAPHASE PHARMACEUTICALS INC
Entity Central Index Key	1373707
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		30,976,618
Entity Public Float			$294,692,854

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$121,042	$102,712
Accounts receivable	3,458	1,706
Prepaid expenses and other current assets	2,097	1,002
Total current assets	126,597	105,420
Property and equipment, net	300	235
Restricted cash	199	199
Other assets	108	32
Total assets	127,204	105,886
Current liabilities:
Accounts payable	4,105	1,881
Accrued expenses	9,477	5,290
Deferred revenue	258	92
Current portion of term loan payable	3,436	5,928
Total current liabilities	17,276	13,191
Accrued final interest payment on term loan	222	327
Deferred rent, net of current portion	16
Term loan payable	1,124	4,560
Commitments and contingencies
Preferred stock, par value $0.001 per share; 5,000 shares authorized; no shares issued and outstanding
Common stock, par value $0.001 per share; 125,000 shares authorized; 30,806 and 25,629 shares issued and outstanding at December 31, 2014 and 2013, respectively	31	26
Additional paid-in capital	294,998	207,503
Accumulated deficit	-186,463	-119,721
Total stockholders' equity	108,566	87,808
Total liabilities and stockholders' equity	$127,204	$105,886

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	30,806,000	25,629,000
Common stock, shares outstanding	30,806,000	25,629,000

Consolidated_Statements_of_Ope

Consolidated Statements of Operations and Comprehensive Loss (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Revenues	$9,098	$10,486	$7,600
Operating expenses:
Research and development	61,932	31,508	17,294
General and administrative	12,932	7,168	4,309
Total operating expenses	74,864	38,676	21,603
Loss from operations	-65,766	-28,190	-14,003
Other income (expense):
Interest income	17	10
Interest expense	-1,017	-1,719	-1,021
Other income (expense)	24	263	-63
Other expense, net	-976	-1,446	-1,084
Net loss	-66,742	-29,636	-15,087
Net loss per share-basic and diluted	($2.49)	($1.78)	($47.54)
Weighted-average number of common shares used in net loss per share-basic and diluted	26,807	16,665	317
Comprehensive loss	($66,742)	($29,636)	($15,087)

Consolidated_Statements_of_Con

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $)	Total	Series B Convertible Preferred Shares [Member]	Series C Convertible Preferred Shares [Member]	Series A-1 Convertible Preferred Shares [Member]	Series A-2 Convertible Preferred Shares [Member]	Common Shares [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
In Thousands, except Share data
Beginning Balance at Dec. 31, 2011	($68,603)	$9,946	$44,915	$9,925	$15,055		$6,395	($74,998)
Beginning Balance, shares at Dec. 31, 2011		57,471,000	175,418,000	10,040,000	13,096,000	306,000
Exercise of stock options	29						29
Exercise of stock options, shares						19,000
Stock-based compensation expense	612						612
Net loss	-15,087							-15,087
Ending Balance at Dec. 31, 2012	-83,049	9,946	44,915	9,925	15,055		7,036	-90,085
Ending Balance, shares at Dec. 31, 2012		57,471,000	175,418,000	10,040,000	13,096,000	325,000
Exercise of stock options	96						96
Exercise of stock options, shares						56,000
Issuance of common stock from initial public offering (net of underwriters discounts and issuance costs of $7,391)	73,194					12	73,182
Issuance of common stock from initial public offering, shares						11,512,000
Conversion of convertible preferred stock into common stock	79,841	-9,946	-44,915	-9,925	-15,055	9	79,832
Conversion of convertible preferred stock into common stock, shares		-57,471,000	-175,418,000	-10,040,000	-13,096,000	8,829,000
Reclassification of warrants for common stock	462						462
Issuance of common stock from follow-on public offering (net of underwriters discounts and issuance costs of $3,475)	45,599					5	45,594
Issuance of common stock from follow-on public offering, shares						4,907,000
Stock-based compensation expense	1,301						1,301
Net loss	-29,636							-29,636
Ending Balance at Dec. 31, 2013	87,808					26	207,503	-119,721
Ending Balance, shares at Dec. 31, 2013						25,629,000
Exercise of stock options	1,421						1,421
Exercise of stock options, shares	562,569					563,000
Issuance of common stock from follow-on public offering (net of underwriters discounts and issuance costs of $3,475)	80,766					5	80,761
Issuance of common stock from follow-on public offering, shares						4,543,000
Issuance of common stock under employee stock purchase plan	83						83
Issuance of common stock under employee stock purchase plan, shares						8,000
Issuance of common stock from warrant exercise, shares						63,000
Stock-based compensation expense	5,230						5,230
Net loss	-66,742							-66,742
Ending Balance at Dec. 31, 2014	$108,566					$31	$294,998	($186,463)
Ending Balance, shares at Dec. 31, 2014						30,806,000

Consolidated_Statements_of_Con1

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (Common Shares [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
IPO [Member]
Issuance of common stock from follow-on public offering, underwriters discounts and issuance costs		$7,391
Follow on Public Offering [Member]
Issuance of common stock from follow-on public offering, underwriters discounts and issuance costs	$5,542	$3,475

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net loss	($66,742)	($29,636)	($15,087)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	124	129	353
Amortization of deferred financing costs and debt discount	226	342	175
Accretion of final interest payment on term loans	115	199	128
Fair value adjustment of warrants and investor right obligation		-263	63
Stock-based compensation expense	5,230	1,301	612
Loss from disposal of property and equipment	2
Changes in operating assets and liabilities:
Restricted cash		-63
Accounts receivable	-1,752	746	-2,267
Prepaid expenses and other current assets	-1,199	-154	-227
Accounts payable	2,224	310	772
Accrued expenses and accrued final interest payment on term loan	3,983	3,190	-1,878
Deferred revenue	166	-607	699
Net cash used in operating activities	-57,623	-24,506	-16,657
Investing activities
Purchases of property and equipment	-191	-129	-54
Net cash used in investing activities	-191	-129	-54
Financing activities
Proceeds from sale of common stock, net of underwriter discounts and issuance costs	80,766	119,404	-611
Deferred financing fees			-85
Proceeds from issuance of term loan payable		3,000	6,200
Repayment of term loan payable	-6,126	-4,232	-2,197
Proceeds from issuance of stock under stock plans	1,504	96	29
Net cash provided by financing activities	76,144	118,268	3,336
Net increase (decrease) in cash and cash equivalents	18,330	93,633	-13,375
Cash and cash equivalents at beginning of period	102,712	9,079	22,454
Cash and cash equivalents at end of period	121,042	102,712	9,079
Supplemental cash flow information
Cash paid for interest	945	1,142	702
Fair value of warrants issued in connection with issuance of term loan		115	241
Conversion of convertible preferred stock into common stock		79,841
Reclassification of warrant liability to additional paid-in-capital		462
Reclassification of deferred financing costs to additional paid-in-capital		$1,261

Organization_and_Operations

Organization and Operations	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Organization and Operations	(1) Organization and Operations
	The Company
	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 is developing its lead product candidate eravacycline, a fully synthetic tetracycline derivative, as a broad-spectrum intravenous (“IV”) 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 global Phase 3 clinical program for eravacycline called IGNITE (Investigating Gram-Negative Infections Treated with Eravacycline) consisting of two Phase 3 clinical trials. IGNITE 1 is a Phase 3 clinical trial evaluating the safety and efficacy of eravacycline with IV administration for the treatment of complicated intra-abdominal infections (“cIAI”), for which the Company announced top-line data in December 2014. IGNITE 2, a second Phase 3 clinical trial of eravacycline for the treatment of complicated urinary tract infections (“cUTI”), with IV-to-oral transition therapy, is ongoing.
	Consistent with guidance issued by the United States Food and Drug Administration (“FDA”), with respect to the development of antibiotics for cIAI and the Company’s discussions with the FDA, the Company expects that positive results from these two Phase 3 clinical trials will be sufficient to support submission of a new drug application (“NDA”) for eravacycline in the treatment of cIAI and cUTI. In December 2014, the Company announced positive top-line data from IGNITE 1. In September 2014, the Company announced positive data from the lead-in portion of IGNITE 2, and in October 2014, the Company announced the selection of the oral dose for the IV-to-oral transition therapy (1.5 mg/kg IV followed by 200 mg oral dose) to be evaluated by the pivotal portion of IGNITE 2 and the initiation of patient enrollment. The Company expects to have top-line data from the pivotal portion of IGNITE 2 in mid-2015. If the Company completes the pivotal portion of IGNITE 2 when anticipated, and it is successful, the Company expects to submit an NDA to the FDA by the end of 2015 and a marketing authorization application (“MAA”), to the European Medicines Agency (“EMA”), in the first half of 2016. 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 devoting substantially all of its efforts to product research and development, market development, and raising capital. The Company is subject to a number of risks similar to those of other life science companies in a similar stage of development, including rapid technological change, dependence on key individuals, competition from other companies, compliance with government regulations, protection of proprietary technology, dependence on third parties, product liability, the need for development of commercially viable products, regulatory approval of products, uncertainty of market acceptance of products, and the need to obtain additional financing to fund the development of its product candidates. 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, and expects to require additional financial resources to advance its product candidates to either commercial stage or liquidity events.
	The Company has incurred annual net operating losses in every year since its inception. As of December 31, 2014, the Company had incurred losses since inception of $186.5 million. The Company has not generated any product revenues related to its primary business purpose and has financed its operations primarily through public offerings and private placements of its equity securities, debt financings and funding from the United States government. In March 2013, the Company completed the sale of 10,714,286 shares of common stock in the Company’s initial public offering (“IPO”) at a price to the public of $7.00 per share. In April 2013, the Company completed the sale of an additional 797,792 shares of common stock to the underwriters for the IPO upon the exercise of the underwriters’ option in the IPO to purchase additional shares of common stock at a price to the public of $7.00. In November 2013, the Company completed the sale of 4,907,403 shares of common stock in a follow-on public offering at a price to the public of $10.00 per share. In October 2014, the Company completed the sale of 4,542,500 shares of common stock in a follow-on public offering at a price to the public of $19.00 per share.
	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	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	(2) Summary of Significant Accounting Policies
	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 infections, including multidrug-resistant infections.
	Use of Estimates
	The preparation of financial statements in conformity with generally accepted accounting principles 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 consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Tetraphase Securities Corporation and Tetraphase Pharma Securities Inc., Massachusetts Securities Corporations, and Tetraphase Pharmaceuticals (Bermuda) Ltd. 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 December 31, 2014 and 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 December 31, 2014 and 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
	December 31, 2014
	Cash		$	2,919		$	2,919	$	—	$	—
	Money market funds, included in cash equivalents		$	118,123		$	118,123	$	—	$	—
	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 December 31, 2014, computed pursuant to a discounted cash flow technique using the effective interest rate based on the Company’s estimated borrowing rate at December 31, 2014, was $4.9 million.
	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 7). On March 25, 2013, upon completion of the Company’s 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 year ended December 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 December 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 $8.3 million from the initial contract date through September 30, 2016, of which $7.1 million had been received by the Company through December 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 funding under the BARDA Contract is also being used for certain activities in the development of eravacycline to treat certain infections caused by life-threatening multidrug-resistant bacteria. 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 $31.0 million from the initial contract date through September 9, 2016, of which $16.4 million had been received by the Company through December 31, 2014 (Note 3).
	Accounts receivable at December 31, 2014 and 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 $2.9 million and $0.8 million at December 31, 2014 and 2013, respectively.
	Property and Equipment, Net
	Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization are recognized 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 December 31, 2014 and 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 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 subcontracts with respect to the BARDA Contract and 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 subcontracts under the BARDA Contract and 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.
	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.
	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 provide preclinical, clinical, regulatory and manufacturing services;
		•		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, maintenance of the Company’s facilities, insurance and other supplies; and
		•		costs associated with preclinical and regulatory activities.
	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. In certain circumstances, the Company is required to make nonrefundable advance payments to vendors for goods or services that will be received in the future for use in research and development activities. In such circumstances, the nonrefundable advance payments are deferred and capitalized, even when there is no alternative future use for the research and development, until related goods or services are provided.
	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 Accounting Standards Codification (“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 for employee equity awards. 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. The Company records stock-based compensation expense for share-based payments issued to non-employees based on the fair value of the awards using the Black-Scholes option pricing model. Share-based payments issued to non-employees are revalued at each reporting period and as the equity instruments vest and are recognized as expense using the accelerated attribution method over the related service period.
	Recent Accounting Pronouncements Issued and Adopted
	In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The new standard will be effective for the Company on January 1, 2017. The Company is currently evaluating the potential impact that this update may have on the Company’s financial position and results of operations.
In June 2014, the FASB issued ASU 2014-10, which simplifies financial reporting for development stage entities by eliminating requirements specific to development stage entities. As a result, entities in a development stage will no longer need to present inception-to-date information about income statement line items, cash flows, and equity transactions. Instead, the new guidance clarifies how these entities should tailor existing disclosures to explain the risks and uncertainties related to their activities. This update is effective for annual periods beginning after December 15, 2014, and early application is permitted for any annual or interim period for which the entity’s financial statements have not yet been issued. The Company adopted this guidance prior to issuing the financial statements in the Company’s quarterly report on Form 10-Q for the period ended June 30, 2014. The adoption of ASU 2014-10 impacted disclosure only and did not have any impact on the Company’s financial position or results of operations.
In 2014, the FASB issued new guidance on management’s responsibility in evaluating whether or not there is substantial doubt about a company’s ability to continue as a going concern within one year from the date the financial statements are issued each reporting period. This new accounting guidance is effective for annual periods ending after December 15, 2016. Early adoption is permitted. The Company is in process of evaluating the new guidance and determining the expected effect on its financial statements.
Net Loss per Common Share
Basic net loss per share is calculated by dividing the net loss 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 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, 2013, 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 year ended December 31, 2013, 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 year ended December 31, 2013 was 16.7 million, as compared to 25.6 million shares outstanding as of December 31, 2013.
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:
		Year Ended December 31,
		2014			2013		2012
Preferred stock			—			—		8,828,438
Warrants			1,103			104,107		88,013
Outstanding stock options			3,409,497			2,844,343		1,442,810

Significant_Agreements_and_Con

Significant Agreements and Contracts	12 Months Ended
	Dec. 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, as of December 31, 2014, 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. This amount was recorded as research and development expense during the year ended December 31, 2013.
	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. The funding under the BARDA Contract is also being used for the development, manufacturing and clinical evaluation of eravacycline to treat certain infections caused by life-threatening multidrug-resistant bacteria.
	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 $31.0 million through September 9, 2016, the current contract end date, as a result of the exercise of several options by BARDA under the BARDA Contract. Total funds of $16.4 million had been received by the Company through December 31, 2014 under this contract. During the years ended December 31, 2014, 2013 and 2012, the Company recognized revenue of $6.9 million, $7.7 million and $4.9 million, respectively, from the Company’s subcontract under the BARDA 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 December 31, 2014, committed funding from CUBRC under the Company’s subcontract with respect to the NIAID Contract is $8.3 million through the current contract end date which has been extended to September 30, 2016, of which $7.1 million had been received through December 31, 2014. Committed funding from CUBRC under the Company’s subaward with respect to the NIAID Grant is $0.8 million through the current contract end date which has been extended to May 30, 2016, of which $0.7 million had been received through December 31, 2014.
	During the years ended December 31, 2014, 2013 and 2012, the Company recognized revenue of $2.1 million, $2.5 million, and $2.5 million, respectively, from the Company’s subcontract under the NIAID Contract. During the years ended December 31, 2014, 2013 and 2012, the Company recognized revenue of $135,000, $267,000 and $273,000, respectively, from the Company’s subaward under the NIAID Grant.

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property and Equipment	(4) Property and Equipment
	Property and equipment at December 31, 2014 and 2013 consisted of the following (in thousands):
		Estimated		December 31,
		Useful Life
		In Years		2014			2013
	Laboratory equipment		5	$	1,932		$	1,806
	Furniture and fixtures		5		178			170
	Office and computer equipment		3		163			176
	Leasehold improvements				527			527
					2,800			2,679
	Less accumulated depreciation and amortization				(2,500	)		(2,444	)
	Property and equipment, net			$	300		$	235
	Depreciation and amortization expense for the years ended December 31, 2014, 2013 and 2012 was $124,000, $129,000 and $353,000, respectively.

Accrued_Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued Expenses	(5) Accrued Expenses
	Accrued expenses at December 31, 2014 and 2013 consisted of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Drug supply and development	$	5,440	$	970
	Salaries and benefits		2,358		1,554
	Clinical trial related		724		1,849
	Preclinical		328		78
	Professional fees		346		246
	Other		281		593
	Total	$	9,477	$	5,290

LongTerm_Debt

Long-Term Debt	12 Months Ended
	Dec. 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 of funding, to be made available in two tranches. The Company borrowed the first $1.5 million in May 2011 and the second tranche for the remaining $6.5 million in December 2011. The Term Loan bore interest at 10% per annum and provided 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 was 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% was due at the same time as the last loan payment. The Term Loan matured on November 1, 2014, and has been paid in full.
	In December 2012, the Company amended 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 A Loan 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.
	The 2012 Term Loan is collateralized by a blanket lien on all corporate assets, excluding intellectual property, and by a negative pledge of the Company’s intellectual property. The 2012 Term Loan contains 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 2012 Term Loan are as follows (in thousands):
		December 31,
		2014
	2015		3,513
	2016		1,132
	Total term loan payments		4,645
	Current term loan payable		3,513
	Less debt discount and issuance costs		(77	)
	Current term loan payable, net		3,436
	Term loan payable, less current portion		1,132
	Less debt discount and issuance costs		(8	)
	Term loan payable, less current portion, net	$	1,124

Warrants

Warrants	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Warrants	(7) Warrants
	In May 2011, the Company issued warrants to purchase an aggregate of 1,555,815 shares of Series C Preferred Stock at an exercise price of $0.2571 per share in connection with the Term Loan (Note 6). The warrants are exercisable immediately and have a ten year life. The warrants were initially valued at $302,000 using the Black-Scholes pricing model with the following assumptions; risk free interest rate of 3.2%; dividend yield of zero; expected volatility of 67%; with an expected life of ten years, and were being expensed as additional interest over the term of the loan. In accordance with ASC 480, the characteristics of these warrants and the rights and privileges of the underlying Series C Preferred Stock resulted in the classification of these warrants as a liability and changes to the fair value of the warrants were recognized as a component of other income (expense) in the statement of operations and comprehensive loss.
	In December 2012, the Company issued warrants to purchase an aggregate of 964,605 shares of Series C Preferred Stock at an exercise price of $0.2571 per share in connection with the 2012 Term Loan (Note 6). The warrants are exercisable immediately and have a ten year life. The warrants were initially valued at $241,000 using the Black-Scholes pricing model with the following assumptions; risk free interest rate of 1.8%; dividend yield of zero; expected volatility of 61%; with an expected life of ten years, and are being expensed as additional interest over the term of the loan. In accordance with ASC 480, the characteristics of these warrants and the rights and privileges of the underlying Series C Preferred Stock resulted in the classification of these warrants as a liability and changes to the fair value of the warrants were recognized as a component of other income (expense) in the statement of operations and comprehensive loss.
	In connection with the February 2013 borrowing under the Term Loan, the warrant that the Company issued to Silicon Valley Bank in December 2012 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 warrants were initially valued at $115,000 using the Black-Scholes option pricing model with the following assumptions: risk-free interest rate of 1.89%, dividend yield of zero, expected volatility rate of 59% and an expected life of ten years, and are being expensed as additional interest over the term of the loan. The warrant was classified as a liability in accordance with ASC 480 and was subject to remeasurement at each balance sheet date and changes to the fair value were recognized as a component of other income (expense) in the statement of operations and comprehensive loss.
	The Company estimated the fair value of the preferred stock warrants using the Black-Scholes option pricing model based on the following assumptions:
		December 31,
		2012
	Expected volatility	60%
	Expected term (in years)	5.0-10.0
	Risk-free interest rate	0.72%-1.78%
	Expected dividend yield	0%
	Estimated fair value of Series A-1 Preferred Stock	$0.45
	Estimated fair value of Series C Preferred Stock	$0.34
	Upon completion of the IPO, the warrants related to the Term Loan became exercisable for 53,648 shares of the Company’s common stock at an exercise price of $7.46 per share, the warrants related to the 2012 Term A Loan became exercisable for 33,262 shares of the Company’s common stock at an exercise price of $7.46 per share and the warrants related to the 2012 Term B Loan became exercisable for 16,094 shares of the Company’s common stock at an exercise price of $7.46 per share. On the date of the conversion of the warrants, the Company revalued the outstanding warrants using the Black-Scholes option pricing model with the following assumptions: risk-free interest rate of 0.67% to 1.84%, dividend yield of zero, expected volatility rate of 59%, expected term of 5 to 10 years and stock price of $7.00. The fair value of the warrants at March 25, 2013 was $462,000. The Company recorded other income of $263,000 in the statement of operations and comprehensive loss during the year ended December 31, 2013 equal to the change in fair value of the warrants from December 31, 2012 to March 25, 2013. The Company reclassified the fair value of the warrants at March 25, 2013, of $462,000, to additional paid-in capital.
	On June 23, 2014, Silicon Valley Bank exercised its warrants under the Term Loan and 2012 Term Loan described above pursuant to the cashless exercise feature of the warrants. In connection with the exercise of the warrants under the Term Loan, the Company issued 12,354 shares of the Company’s common stock. Warrants to purchase 14,470 shares of common stock were cancelled as payment for the aggregate exercise price of the warrants. In connection with the exercise of the warrants under the 2012 Term Loan, the Company issued 11,366 shares of the Company’s common stock. Warrants to purchase 13,312 shares of common stock were cancelled as payment for the aggregate exercise price of the warrants.
	On December 13, 2014, Oxford Finance exercised its warrants under the Term Loan and 2012 Term Loan described above pursuant to the cashless exercise feature of the warrants. In connection with the exercise of the warrants under the Term Loan, the Company issued 20,488 shares of the Company’s common stock. Warrants to purchase 6,336 shares of common stock were cancelled as payment for the aggregate exercise price of the warrants. In connection with the exercise of the warrants under the 2012 Term Loan, the Company issued 18,849 shares of the Company’s common stock. Warrants to purchase 5,829 shares of common stock were cancelled as payment for the aggregate exercise price of the warrants.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Stockholders' Equity	(8) Stockholders’ Equity
	Initial Public Offering
	In March, 2013, the Company completed its IPO, issuing 10,714,286 shares of common stock at a price to the public of $7.00 per share, resulting in net proceeds to the Company of $68.0 million after deducting underwriting discounts of $4.4 million and offering costs of $2.5 million.
	In connection with the IPO, all of the Company’s outstanding preferred stock automatically converted into a total of 8,828,438 shares of its common stock.
	In April 2013, the Company completed the sale of an additional 797,792 shares to the underwriters upon the exercise of the underwriters’ option in the IPO to purchase additional shares of common stock at a price to the public of $7.00, resulting in net proceeds to the Company of $5.2 million after deducting underwriting discounts and commissions.
	2013 Follow-on Public Offering
	In November 2013, the Company completed a follow-on public offering, issuing 4,907,403 shares of common stock at a price to the public of $10.00 per share, resulting in net proceeds to the Company of $45.6 million after deducting underwriting discounts and commissions of $2.9 million and offering costs of $0.5 million.
	2014 Follow-on Public Offering
	In October 2014, the Company sold 4,542,500 shares of common stock in a follow-on public offering at a price to the public of $19.00 per share, resulting in net proceeds to the Company of $80.8 million after deducting underwriting discounts and commissions of $5.2 million and offering costs of $0.4 million.

Stockbased_Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based Compensation	(9) 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 December 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 December 31, 2014, 386,147 shares were available for future issuance under the 2013 Plan. In January 2015, the number of shares authorized for issuance under the 2013 Plan increased by 1,232,232 shares.
	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 Select Market on the date of grant.
	Stock option activity at December 31, 2014 and changes during the year then ended are 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			1,292,650			14.33
	Exercised			(562,569	)		2.53
	Canceled			(164,927	)		10.63
	Options outstanding at December 31, 2014			3,409,497		$	8.75		7.92	$	105,550
	Options vested or expected to vest at December 31, 2014 (1)			3,256,816		$	8.61		7.88	$	101,276
	Options exercisable at December 31, 2014			1,415,555		$	5.3		6.76	$	48,716
	-1	This represents the number of vested options as of December 31, 2014, plus the number of unvested options that the Company estimated as of December 31, 2014 would vest, based on the unvested options at December 31, 2014, as adjusted for the estimated forfeiture rate of 5.9%.
	The aggregate intrinsic value in the table above represents the difference between the Company’s closing common stock price on the last trading day during the year ended December 31, 2014 and the exercise price of the options, multiplied by the number of in-the-money options. The total intrinsic value of options exercised in the years ended December 31, 2014, 2013, and 2012 was $8.1 million, $0.5 million and $25,000, respectively. As of December 31, 2014, there was $11.7 million of total unrecognized stock-based compensation cost related to employee and non-employee unvested stock options granted under the 2006 Plan and the 2013 Plan. Total unrecognized compensation cost will be adjusted for future forfeitures. The Company expects to recognize that cost over a remaining weighted-average period of 2.6 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 life science/biotechnology companies based on their disease focus, stage of development, number of compounds in clinical trials and number of years as a publicly-traded company. 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 non-employee 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.
	The Company estimates the fair value of each employee and director stock option award on the grant date using the Black-Scholes option-pricing model based on the following assumptions:
			Year Ended December 31,
			2014		2013	2012
	Volatility factor		53.41-58.13%		54.50-60.54%	56.89-68.12%
	Expected life (in years)		5.31-6.11		5.8-7.1	6.0-6.1
	Risk-free interest rate		1.71%-2.13%		0.91%-2.01%	0.85% -1.21%
	Dividend yield		0%		0%	0%
	Compensation cost for stock options granted to employees is based on the estimated grant-date fair value and is recognized over the vesting period of the applicable option on a straight-line basis. Stock-based compensation expense related to stock options granted to employees was $4.0 million, $1.3 million, and $0.3 million during the years ended December 31, 2014, 2013, and 2012, respectively. The amount of stock-based compensation expense recognized during a period is based on the value of the portion of the awards that the Company determines are expected to vest. Forfeitures are required to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The term “forfeitures” is distinct from “cancellations” and represents only the unvested portion of the surrendered option. The Company re-evaluates this analysis quarterly, and adjusts the forfeiture rate as necessary. Ultimately, the actual expense recognized over the vesting period will only be for those options that vest.
	Using the Black-Scholes option-pricing model, the weighted-average grant date fair values of options granted to employees for the years ended December 31, 2014, 2013 and 2012 was $7.54, $4.52 and $2.32, respectively.
	Stock-based compensation expense recognized in the Company’s consolidated statements of operations for stock options granted during the periods presented was as follows (in thousands):
			Year Ended
			December 31,
			2014			2013		2012
	Research and development		$	1,845		$	690	$	463
	General and administrative			3,385			611		149
	Total		$	5,230		$	1,301	$	612
	Stock Option Grants to Non-employees
	During the year ended December 31, 2014, the Company granted nonqualified options to purchase 110,000 shares of common stock to non-employee consultants, with an average exercise price of $12.56 per share. There were no stock options granted to non-employee consultants during the years ended December 31, 2013 or 2012. The Company valued these options using the Black-Scholes option-pricing model and the options are revalued at each reporting period and as the equity instruments vest and are recognized as expense using the accelerated attribution method over the related service period. Stock-based compensation expense related to stock options granted to non-employees was $1.2 million, $39,000, and $0.3 million for the years ended December 31, 2014, 2013, and 2012, respectively. Stock-based compensation expense for the year ended December 31, 2014 was estimated using the Black-Scholes option pricing model with the following assumptions: risk-free interest rate of 2.11%; dividend rate of 0%; expected volatility of 56.69%; and an expected term of 9.3 years.

Employee_Stock_Purchase_Plan

Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Employee Stock Purchase Plan	(10) Employee Stock Purchase Plan
	On February 27, 2014, upon the recommendation of the Company’s compensation committee, the Company’s board of directors adopted, subject to stockholder approval, the 2014 Employee Stock Purchase Plan (the “ESPP”) pursuant to which the Company may sell up to an aggregate of 300,000 shares of Common Stock. The ESPP was approved by the Company’s stockholders on June 12, 2014. The ESPP allows eligible employees to purchase common stock at a price per share equal to 85% of the lower of the fair market value of the common stock at the beginning or end of each period during the term of the ESPP. The first offering period began on August 15, 2014, and concluded on November 14, 2014. The next offering period began on November 15, 2014, and will conclude on May 14, 2015. Pursuant to the ESPP, the Company sold a total of 8,394 shares of common stock during the year ended December 31, 2014 at a purchase price of $9.88, which represented 85% of the closing price of the Company’s common stock on August 15, 2014. The Company records stock-based compensation expense under the ESPP based on the fair value of the purchase rights using the Black-Scholes option pricing model. The total stock-based compensation expense recorded as a result of the ESPP was approximately $46,000 during the year ended December 31, 2014.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	(11) Income Taxes
	The Company accounts for income taxes under ASC 740. Deferred income tax assets and liabilities are determined based upon differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse.
	For the years ended December 31, 2014, 2013 and 2012, the Company did not have a current or deferred income tax expense or benefit.
	As of December 31, 2014 the Company had federal net operating loss carryforwards of approximately $170.4 million and state net operating loss carryforwards of $140.5 million, which are available to reduce future taxable income. The federal net operating loss carryforwards exclude approximately $5.5 million of deductions related to the exercise of stock options. This amount represents an excess tax benefit and has not been included in the gross deferred tax asset reflected for net operating losses. The Company also had federal tax credits of $4.1 million and state tax credits of $1.7 million, which may be used to offset future tax liabilities. The net operating loss (NOL) and tax credit carryforwards will expire at various dates through 2034. The NOL and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has not, as yet, conducted a study of research and development (“R&D”) credit carryforwards. This study may result in an adjustment to the Company’s R&D credit carryforwards; however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position.
	The Company has recorded no reserves or unrecognized tax benefits for tax positions taken. Since a full valuation allowance has been provided against the Company’s deferred tax assets, the effect of any unrecognized tax benefits would simply be to reduce the gross amount of the deferred tax asset and the corresponding valuation allowance. As of December 31, 2014 and 2013, the Company had no accrued interest or penalties related to uncertain tax positions.
	The principal components of the Company’s deferred tax assets are as follows (in thousands):
		Year ended
		December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss carry forwards	$	65,370		$	41,574
	Temporary differences		3,224			1,976
	Research and development credit and carry forwards		5,170			3,609
	Deferred tax assets		73,764			47,159
	Less valuation allowance		(73,764	)		(47,159	)
	Net deferred tax assets	$	—		$	—
	ASC 740 requires a valuation allowance to reduce the deferred tax assets reported, if based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a valuation allowance against its deferred tax assets at December 31, 2014 and 2013, respectively, because the Company’s management has determined that is it more likely than not that these assets will not be realized. The $26.6 million increase in the valuation allowance in 2014 primarily relates to the net loss incurred by the Company.
	The Company is currently open to examination under the statute of limitations by the Internal Revenue Service and state jurisdictions for the tax years ended 2010 through 2013. Carryforward tax attributes generated in years past may still be adjusted upon future examination if they have or will be used in a future period. The Company is currently not under examination by the Internal Revenue Service or any other jurisdictions for any tax years.
	A reconciliation of the Federal statutory tax rate of 34% to the Company’s effective income tax rate follows:
		Year ended
		December 31,
		2014			2013			2012
	Statutory tax rate		(34.00	)%		(34.00	)%		(34.00	)%
	State taxes, net of Federal benefits		(5.28	)%		(5.28	)%		(5.28	)%
	Permanent differences		0.61	%		0.93	%		1.01	%
	Credits		(2.34	)%		(4.33	)%		(0.09	)%
	Change in valuation allowance		39.87	%		39.92	%		38.92	%
	Other		1.14	%		2.76	%		(0.56	)%
	Effective tax rate		—	%		—	%		—	%

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	(12) Commitments and Contingencies
	Lease Commitments
	The Company leases its facilities under an operating lease for 15,899 square feet of office and laboratory space that was set to expire on July 31, 2015. In September 2014, the Company amended its operating lease to extend the lease term from July 31, 2015 through November 30, 2016 and also entered into a new sublease covering an additional 15,174 square feet of office and laboratory space, located next to the Company’s current headquarters, with a lease term from February 1, 2015 through November 30, 2016. The Company recognizes rent expense on a straight-line basis over the non-cancelable lease term.
	As of December 31, 2014, the aggregate minimum future rent payments under the lease and sublease agreements are as follows (in thousands):
		December 31,
		2014
	2015		1,431
	2016		1,238
	Total minimum lease payments	$	2,669
	The Company recorded $1.0 million, $0.6 million and $0.6 million in rent expense for the years ended December 31, 2014, 2013 and 2012, respectively.
	Litigation
	The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities.

Quarterly_Results_Unaudited

Quarterly Results (Unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results (Unaudited)	(13) Quarterly Results (Unaudited)
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2014			2014			2014			2014
		(in thousands, except per share data)
		(unaudited)
	Revenue	$	2,457		$	1,275		$	2,294		$	3,072
	Operating expenses		15,675			19,460			16,274			23,455
	Loss from operations		(13,218	)		(18,185	)		(13,980	)		(20,383	)
	Other expense, net		(305	)		(278	)		(226	)		(167	)
	Net loss	$	(13,523	)	$	(18,463	)	$	(14,206	)	$	(20,550	)
	Net loss per share—basic and diluted	$	(0.53	)	$	(0.71	)	$	(0.55	)	$	(0.69	)
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2013			2013			2013			2013
		(in thousands, except per share data)
		(unaudited)
	Revenue	$	2,700		$	3,722		$	2,166		$	1,898
	Operating expenses		5,323			8,680			11,852			12,821
	Loss from operations		(2,623	)		(4,958	)		(9,686	)		(10,923	)
	Other expense, net		(168	)		(468	)		(430	)		(380	)
	Net loss	$	(2,791	)	$	(5,426	)	$	(10,116	)	$	(11,303	)
	Net loss per share—basic and diluted	$	(1.51	)	$	(0.26	)	$	(0.49	)	$	(0.49	)

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
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 infections, including multidrug-resistant infections.
Use of Estimates	Use of Estimates
	The preparation of financial statements in conformity with generally accepted accounting principles 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 consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Tetraphase Securities Corporation and Tetraphase Pharma Securities Inc., Massachusetts Securities Corporations, and Tetraphase Pharmaceuticals (Bermuda) Ltd. 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 December 31, 2014 and 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 December 31, 2014 and 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
	December 31, 2014
	Cash		$	2,919		$	2,919	$	—	$	—
	Money market funds, included in cash equivalents		$	118,123		$	118,123	$	—	$	—
	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 December 31, 2014, computed pursuant to a discounted cash flow technique using the effective interest rate based on the Company’s estimated borrowing rate at December 31, 2014, was $4.9 million.
	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 7). On March 25, 2013, upon completion of the Company’s 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 year ended December 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 December 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 $8.3 million from the initial contract date through September 30, 2016, of which $7.1 million had been received by the Company through December 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 funding under the BARDA Contract is also being used for certain activities in the development of eravacycline to treat certain infections caused by life-threatening multidrug-resistant bacteria. 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 $31.0 million from the initial contract date through September 9, 2016, of which $16.4 million had been received by the Company through December 31, 2014 (Note 3).
	Accounts receivable at December 31, 2014 and 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 $2.9 million and $0.8 million at December 31, 2014 and 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 recognized 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 December 31, 2014 and 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 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 subcontracts with respect to the BARDA Contract and 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 subcontracts under the BARDA Contract and 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.
	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.
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 provide preclinical, clinical, regulatory and manufacturing services;
		•		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, maintenance of the Company’s facilities, insurance and other supplies; and
		•		costs associated with preclinical and regulatory activities.
	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. In certain circumstances, the Company is required to make nonrefundable advance payments to vendors for goods or services that will be received in the future for use in research and development activities. In such circumstances, the nonrefundable advance payments are deferred and capitalized, even when there is no alternative future use for the research and development, until related goods or services are provided.
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 Accounting Standards Codification (“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 for employee equity awards. 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. The Company records stock-based compensation expense for share-based payments issued to non-employees based on the fair value of the awards using the Black-Scholes option pricing model. Share-based payments issued to non-employees are revalued at each reporting period and as the equity instruments vest and are recognized as expense using the accelerated attribution method over the related service period.
Recent Accounting Pronouncements Issued and Adopted	Recent Accounting Pronouncements Issued and Adopted
	In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The new standard will be effective for the Company on January 1, 2017. The Company is currently evaluating the potential impact that this update may have on the Company’s financial position and results of operations.
	In June 2014, the FASB issued ASU 2014-10, which simplifies financial reporting for development stage entities by eliminating requirements specific to development stage entities. As a result, entities in a development stage will no longer need to present inception-to-date information about income statement line items, cash flows, and equity transactions. Instead, the new guidance clarifies how these entities should tailor existing disclosures to explain the risks and uncertainties related to their activities. This update is effective for annual periods beginning after December 15, 2014, and early application is permitted for any annual or interim period for which the entity’s financial statements have not yet been issued. The Company adopted this guidance prior to issuing the financial statements in the Company’s quarterly report on Form 10-Q for the period ended June 30, 2014. The adoption of ASU 2014-10 impacted disclosure only and did not have any impact on the Company’s financial position or results of operations.
	In 2014, the FASB issued new guidance on management’s responsibility in evaluating whether or not there is substantial doubt about a company’s ability to continue as a going concern within one year from the date the financial statements are issued each reporting period. This new accounting guidance is effective for annual periods ending after December 15, 2016. Early adoption is permitted. The Company is in process of evaluating the new guidance and determining the expected effect on its financial statements.
Net Loss per Common Share	Net Loss per Common Share
	Basic net loss per share is calculated by dividing the net loss 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 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, 2013, 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 year ended December 31, 2013, 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 year ended December 31, 2013 was 16.7 million, as compared to 25.6 million shares outstanding as of December 31, 2013.
	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:
			Year Ended December 31,
			2014			2013		2012
	Preferred stock			—			—		8,828,438
	Warrants			1,103			104,107		88,013
	Outstanding stock options			3,409,497			2,844,343		1,442,810

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Financial Instruments Measured at Fair Value	Financial instruments measured at fair value as of December 31, 2014 and 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
	December 31, 2014
	Cash	$	2,919		$	2,919	$	—	$	—
	Money market funds, included in cash equivalents	$	118,123		$	118,123	$	—	$	—
	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 year ended December 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 December 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:
		Year Ended December 31,
		2014			2013		2012
	Preferred stock		—			—		8,828,438
	Warrants		1,103			104,107		88,013
	Outstanding stock options		3,409,497			2,844,343		1,442,810

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and equipment at December 31, 2014 and 2013 consisted of the following (in thousands):
		Estimated		December 31,
		Useful Life
		In Years		2014			2013
	Laboratory equipment		5	$	1,932		$	1,806
	Furniture and fixtures		5		178			170
	Office and computer equipment		3		163			176
	Leasehold improvements				527			527
					2,800			2,679
	Less accumulated depreciation and amortization				(2,500	)		(2,444	)
	Property and equipment, net			$	300		$	235

Accrued_Expenses_Tables

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued Expenses	Accrued expenses at December 31, 2014 and 2013 consisted of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Drug supply and development	$	5,440	$	970
	Salaries and benefits		2,358		1,554
	Clinical trial related		724		1,849
	Preclinical		328		78
	Professional fees		346		246
	Other		281		593
	Total	$	9,477	$	5,290

LongTerm_Debt_Tables

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Future Principal Payments on Term Loan	Future principal payments on the 2012 Term Loan are as follows (in thousands):
		December 31,
		2014
	2015		3,513
	2016		1,132
	Total term loan payments		4,645
	Current term loan payable		3,513
	Less debt discount and issuance costs		(77	)
	Current term loan payable, net		3,436
	Term loan payable, less current portion		1,132
	Less debt discount and issuance costs		(8	)
	Term loan payable, less current portion, net	$	1,124

Warrants_Tables

Warrants (Tables)	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Estimated Fair Value of Preferred Stock Warrants Using Black-Scholes Option Pricing Model	The Company estimated the fair value of the preferred stock warrants using the Black-Scholes option pricing model based on the following assumptions:
		December 31,
		2012
	Expected volatility	60%
	Expected term (in years)	5.0-10.0
	Risk-free interest rate	0.72%-1.78%
	Expected dividend yield	0%
	Estimated fair value of Series A-1 Preferred Stock	$0.45
	Estimated fair value of Series C Preferred Stock	$0.34

Stockbased_Compensation_Tables

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Activity	Stock option activity at December 31, 2014 and changes during the year then ended are 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			1,292,650			14.33
	Exercised			(562,569	)		2.53
	Canceled			(164,927	)		10.63
	Options outstanding at December 31, 2014			3,409,497		$	8.75		7.92	$	105,550
	Options vested or expected to vest at December 31, 2014 (1)			3,256,816		$	8.61		7.88	$	101,276
	Options exercisable at December 31, 2014			1,415,555		$	5.3		6.76	$	48,716
	-1	This represents the number of vested options as of December 31, 2014, plus the number of unvested options that the Company estimated as of December 31, 2014 would vest, based on the unvested options at December 31, 2014, as adjusted for the estimated forfeiture rate of 5.9%.
Assumptions Used to Estimate Fair Value of Employee and Director Stock Option Award	The Company estimates the fair value of each employee and director stock option award on the grant date using the Black-Scholes option-pricing model based on the following assumptions:
			Year Ended December 31,
			2014		2013	2012
	Volatility factor		53.41-58.13%		54.50-60.54%	56.89-68.12%
	Expected life (in years)		5.31-6.11		5.8-7.1	6.0-6.1
	Risk-free interest rate		1.71%-2.13%		0.91%-2.01%	0.85% -1.21%
	Dividend yield		0%		0%	0%
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 consolidated statements of operations for stock options granted during the periods presented was as follows (in thousands):
			Year Ended
			December 31,
			2014			2013		2012
	Research and development		$	1,845		$	690	$	463
	General and administrative			3,385			611		149
	Total		$	5,230		$	1,301	$	612

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Components of Deferred Tax Assets	The principal components of the Company’s deferred tax assets are as follows (in thousands):
		Year ended
		December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss carry forwards	$	65,370		$	41,574
	Temporary differences		3,224			1,976
	Research and development credit and carry forwards		5,170			3,609
	Deferred tax assets		73,764			47,159
	Less valuation allowance		(73,764	)		(47,159	)
	Net deferred tax assets	$	—		$	—
Reconciliation of Federal Statutory Tax Rate to Effective Income Tax Rate	A reconciliation of the Federal statutory tax rate of 34% to the Company’s effective income tax rate follows:
		Year ended
		December 31,
		2014			2013			2012
	Statutory tax rate		(34.00	)%		(34.00	)%		(34.00	)%
	State taxes, net of Federal benefits		(5.28	)%		(5.28	)%		(5.28	)%
	Permanent differences		0.61	%		0.93	%		1.01	%
	Credits		(2.34	)%		(4.33	)%		(0.09	)%
	Change in valuation allowance		39.87	%		39.92	%		38.92	%
	Other		1.14	%		2.76	%		(0.56	)%
	Effective tax rate		—	%		—	%		—	%

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Minimum Future Rent Payments Under Lease and Sublease Agreements	As of December 31, 2014, the aggregate minimum future rent payments under the lease and sublease agreements are as follows (in thousands):
		December 31,
		2014
	2015		1,431
	2016		1,238
	Total minimum lease payments	$	2,669

Quarterly_Results_Unaudited_Ta

Quarterly Results (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Summary of Selected Quarterly Financial Information		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2014			2014			2014			2014
		(in thousands, except per share data)
		(unaudited)
	Revenue	$	2,457		$	1,275		$	2,294		$	3,072
	Operating expenses		15,675			19,460			16,274			23,455
	Loss from operations		(13,218	)		(18,185	)		(13,980	)		(20,383	)
	Other expense, net		(305	)		(278	)		(226	)		(167	)
	Net loss	$	(13,523	)	$	(18,463	)	$	(14,206	)	$	(20,550	)
	Net loss per share—basic and diluted	$	(0.53	)	$	(0.71	)	$	(0.55	)	$	(0.69	)
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2013			2013			2013			2013
		(in thousands, except per share data)
		(unaudited)
	Revenue	$	2,700		$	3,722		$	2,166		$	1,898
	Operating expenses		5,323			8,680			11,852			12,821
	Loss from operations		(2,623	)		(4,958	)		(9,686	)		(10,923	)
	Other expense, net		(168	)		(468	)		(430	)		(380	)
	Net loss	$	(2,791	)	$	(5,426	)	$	(10,116	)	$	(11,303	)
	Net loss per share—basic and diluted	$	(1.51	)	$	(0.26	)	$	(0.49	)	$	(0.49	)

Organization_and_Operations_Ad

Organization and Operations - Additional Information (Detail) (USD $)	12 Months Ended	1 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Oct. 31, 2014	Nov. 30, 2013	Apr. 30, 2013	Mar. 31, 2013	Dec. 31, 2013
Organization And Nature Of Operations [Line Items]
Company incorporation date	7-Jul-06
Losses incurred since inception	($186,463)					($119,721)
Common stock, shares issued	30,806,000					25,629,000
Common Shares [Member]
Organization And Nature Of Operations [Line Items]
Common stock, issue price		$19	$10
Common stock, shares issued		4,542,500	4,907,403
IPO [Member]
Organization And Nature Of Operations [Line Items]
Common stock, shares issued				797,792	10,714,286
Common stock, issue price				$7	$7
Common stock, shares issued				797,792	10,714,286
IPO [Member] | Common Shares [Member]
Organization And Nature Of Operations [Line Items]
Common stock, issue price				$7	$7

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
Share data in Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2012	Feb. 29, 2012	Sep. 30, 2011	Sep. 11, 2011	Jul. 31, 2011	Oct. 31, 2011
	Segment
Summary Of Significant Accounting Policies [Line Items]
Number of operating segment	1
Fair value of loans payable	$4,900,000
Unbilled accounts receivable	2,900,000	800,000
Restricted cash	199,000	199,000
Restricted cash, non-current	199,000	199,000
Amount payable to lessors in respect of default on rental obligation	159,000	159,000
New Accounting Pronouncement Effective	New guidance on management's responsibility in evaluating whether or not there is substantial doubt about a company's ability to continue as a going concern within one year from the date the financial statements are issued each reporting period. This new accounting guidance is effective for annual periods ending after December 15, 2016. Early adoption is permitted.
Initial public offering completion date	25-Mar-13
Weighted-average number of common shares used in net loss per share applicable to common stockholders-basic and diluted	26,807	16,665	317
Common stock, shares outstanding	30,806	25,629
Letter of Credit [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash, non-current	159,000	159,000
Credit Card [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash, non-current	40,000	40,000
Biomedical Advanced Research and Development Authority (BARDA) [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, contract period				5 years
Contract maturity date	9-Sep-16
Biomedical Advanced Research and Development Authority (BARDA) [Member] | Subcontract with CUBRC [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, contract period					5 years
Awarded contract for development, amount received	16,400,000
Biomedical Advanced Research and Development Authority (BARDA) [Member] | Subcontract with CUBRC [Member] | January 1, 2012 through April 30, 2015 [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, amount to be funded				31,000,000
National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, contract period						5 years	5 years	5 years
National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member] | Subcontract with CUBRC [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, contract period							5 years		5 years
Awarded contract for development, amount received	7,100,000
National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member] | Subcontract with CUBRC [Member] | September 1, 2011 through September 30, 2016 [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, amount to be funded							8,300,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of property and equipment	3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of property and equipment	5 years
Maximum [Member] | Biomedical Advanced Research and Development Authority (BARDA) [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, amount				67,000,000
Maximum [Member] | Biomedical Advanced Research and Development Authority (BARDA) [Member] | Subcontract with CUBRC [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, amount to be funded				39,800,000	39,800,000
Maximum [Member] | National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, amount						35,800,000	35,800,000	2,800,000
Maximum [Member] | National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member] | Subcontract with CUBRC [Member]
Summary Of Significant Accounting Policies [Line Items]
Awarded contract for development, amount to be funded							13,300,000		13,300,000

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Financial Instruments Measured at Fair Value (Detail) (USD $)	Dec. 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	$2,919	$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	118,123	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	2,919	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	$118,123	$100,008

Summary_of_Significant_Account5

Summary of Significant Accounting Policies - Schedule of Preferred Stock Warrant Liability (Detail) (USD $)	0 Months Ended	1 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Mar. 25, 2013	Feb. 28, 2013	Dec. 31, 2013	Dec. 31, 2012
Regulatory Assets [Abstract]
Fair value, Beginning Balance			$610
Value of warrants issued in 2013		115	115	241
Decrease in fair value recognized in net loss			-263
Reclassification of fair value to additional paid-in capital	-462		-462
Fair value, Ending Balance				$610

Summary_of_Significant_Account6

Summary of Significant Accounting Policies - Amounts Excluded from Calculation of Diluted Weighted-Average Shares Outstanding (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount			8,828,438
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1,103	104,107	88,013
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	3,409,497	2,844,343	1,442,810

Significant_Agreements_and_Con1

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

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

Jan. 31, 2012

Dec. 31, 2014

Sep. 30, 2011

Sep. 11, 2011

Jul. 31, 2011

Apr. 30, 2010

Jan. 31, 2007

Aug. 31, 2006

Oct. 31, 2013

Dec. 31, 2013

Feb. 29, 2012

Dec. 31, 2012

Oct. 31, 2011

Nov. 30, 2011

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

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

Awarded contract for development, contract period

5 years

Contract maturity date

9-Sep-16

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

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

Awarded contract for development, amount

67,000,000

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

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

Awarded contract for development, contract period

5 years

5 years

5 years

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

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

Awarded contract for development, amount

35,800,000

35,800,000

2,800,000

License Agreement Terms [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

License Agreement Terms [Member] | Phase Three Clinical Trial [Member]

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

Milestone payments

2,000,000

License Agreement Terms [Member] | Research and Development [Member] | Phase Three Clinical Trial [Member]

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

Milestone payments

2,000,000

Subcontract with CUBRC [Member] | Biomedical Advanced Research and Development Authority (BARDA) [Member]

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

Awarded contract for development, contract period

5 years

Committed funding for subcontracts

31,000,000

Proceed from awarded contract for development

16,400,000

Contracts Revenue

6,900,000

7,700,000

4,900,000

Subcontract with CUBRC [Member] | Biomedical Advanced Research and Development Authority (BARDA) [Member] | Maximum [Member]

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

Awarded contract for development, amount to be funded

39,800,000

39,800,000

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

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

Awarded contract for development, contract period

5 years

5 years

Committed funding for subcontracts

8,300,000

Proceed from awarded contract for development

7,100,000

Contracts Revenue

2,100,000

2,500,000

2,500,000

Subcontract with CUBRC [Member] | National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member] | Maximum [Member]

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

Awarded contract for development, amount to be funded

13,300,000

13,300,000

Subaward Under the NIAID Grant [Member] | National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]

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

Awarded contract for development, contract period

55 months

Awarded contract for development, amount to be funded

980,000

Committed funding for subcontracts

800,000

Proceed from awarded contract for development

700,000

Contracts Revenue

135,000

$267,000

$273,000

Property_and_Equipment_Propert

Property and Equipment - Property and Equipment (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$2,800	$2,679
Less accumulated depreciation and amortization	-2,500	-2,444
Property and equipment, net	300	235
Laboratory Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Property and equipment, gross	1,932	1,806
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Property and equipment, gross	178	170
Office and Computer Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Property and equipment, gross	163	176
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$527	$527

Property_and_Equipment_Additio

Property and Equipment - Additional Information (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property Plant and Equipment Useful Life and Values [Abstract]
Depreciation and amortization expense	$124	$129	$353

Accrued_Expenses_Accrued_Expen

Accrued Expenses - Accrued Expenses (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]
Drug supply and development	$5,440	$970
Salaries and benefits	2,358	1,554
Clinical trial related	724	1,849
Preclinical	328	78
Professional fees	346	246
Other	281	593
Total	$9,477	$5,290

LongTerm_Debt_Additional_Infor

Long-Term Debt - Additional Information (Detail) (USD $)	12 Months Ended		1 Months Ended			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012	Feb. 28, 2013	31-May-11	Dec. 31, 2011
			Installment		Tranches
					Installment
Debt Instrument [Line Items]
Debt, borrowing	$3,000,000	$6,200,000
2012 Term A Loan [Member]
Debt Instrument [Line Items]
Debt, stated interest rate				9.00%
2012 Term A Loan [Member] | First Tranche [Member]
Debt Instrument [Line Items]
Debt, borrowing			6,200,000
Debt, stated interest rate at maturity date			2.90%
Debt, maturity date			1-Mar-16
Debt, number of installments			33
2012 Term B Loan [Member]
Debt Instrument [Line Items]
Debt, stated interest rate				9.00%
Debt, additional borrowing capacity		9,200,000	9,200,000
2012 Term B Loan [Member] | Second Tranche [Member]
Debt Instrument [Line Items]
Debt, borrowing				3,000,000
Debt, stated interest rate at maturity date			2.90%	2.90%
Debt, number of installments			33
Term Loan [Member]
Debt Instrument [Line Items]
Debt, borrowing capacity					8,000,000
Debt, number of tranches			2		2
Debt, stated interest rate					10.00%
Debt, stated interest rate at maturity date					2.75%
Debt, maturity date					1-Nov-14
Debt, number of installments					33
Term Loan [Member] | First Tranche [Member]
Debt Instrument [Line Items]
Debt, borrowing					1,500,000
Term Loan [Member] | Second Tranche [Member]
Debt Instrument [Line Items]
Debt, borrowing						$6,500,000

LongTerm_Debt_Future_Principal

Long-Term Debt - Future Principal Payments on Term Loan (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Debt Disclosure [Abstract]
2015	$3,513
2016	1,132
Total term loan payments	4,645
Current term loan payable	3,513
Less debt discount and issuance costs	-77
Current term loan payable, net	3,436	5,928
Term loan payable, less current portion	1,132
Less debt discount and issuance costs	-8
Term loan payable, less current portion, net	$1,124	$4,560

Warrants_Additional_Informatio

Warrants - Additional Information (Detail) (USD $)

0 Months Ended

1 Months Ended

3 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

Mar. 25, 2013

Feb. 28, 2013

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Jun. 23, 2014

Dec. 31, 2012

31-May-11

Class of Warrant or Right [Line Items]

Fair value of Warrant

$610,000

$610,000

Risk-free interest rate

1.89%

Expected dividend yield

0.00%

0.00%

Expected volatility rate

59.00%

59.00%

Expected life of warrant

10 years

Fair value of Warrant

115,000

115,000

241,000

Stock price

$7

$7

Fair value of warrants

462,000

462,000

Other income

-167,000

-226,000

-278,000

-305,000

-380,000

-430,000

-468,000

-168,000

24,000

263,000

-63,000

Common stock, shares issued

30,806,000

25,629,000

30,806,000

25,629,000

May 2011 (Term Loan) [Member] | SVB Financial Group ("SVB") [Member]

Class of Warrant or Right [Line Items]

Common stock, shares issued

12,354

Number of warrants cancelled

14,470

May 2011 (Term Loan) [Member] | Oxford Finance [Member]

Class of Warrant or Right [Line Items]

Common stock, shares issued

20,488

20,488

Number of warrants cancelled

6,336

December 2012 (2012 Term A Loan) [Member] | SVB Financial Group ("SVB") [Member]

Class of Warrant or Right [Line Items]

Common stock, shares issued

11,366

Number of warrants cancelled

13,312

December 2012 (2012 Term A Loan) [Member] | Oxford Finance [Member]

Class of Warrant or Right [Line Items]

Common stock, shares issued

18,849

18,849

Number of warrants cancelled

5,829

Minimum [Member]

Class of Warrant or Right [Line Items]

Risk-free interest rate

0.67%

Expected life of warrant

5 years

Maximum [Member]

Class of Warrant or Right [Line Items]

Risk-free interest rate

1.84%

Expected life of warrant

10 years

Series C Convertible Preferred Shares [Member]

Class of Warrant or Right [Line Items]

Warrant to purchase shares of stock, exercise price per share

$0.26

Series C Convertible Preferred Shares [Member] | Silicon Valley Bank [Member]

Class of Warrant or Right [Line Items]

Stock issued upon immediate exercise of warrant

233,372

Series C Convertible Preferred Shares [Member] | Oxford Finance Corporation [Member]

Class of Warrant or Right [Line Items]

Warrant to purchase shares of stock, shares

233,372

Warrant to purchase shares of stock, term

10 years

2012 Term Loan [Member] | Series C Convertible Preferred Shares [Member]

Class of Warrant or Right [Line Items]

Warrant to purchase shares of stock, shares

964,605

964,605

Warrant to purchase shares of stock, exercise price per share

$0.26

$0.26

Warrant to purchase shares of stock, term

10 years

Fair value of Warrant

241,000

241,000

Risk-free interest rate

1.80%

Expected dividend yield

0.00%

Expected volatility rate

6100.00%

Expected life of warrant

10 years

Term Loan [Member]

Class of Warrant or Right [Line Items]

Warrants exercisable, shares

53,648

Warrants exercisable, exercise price

$7.46

$7.46

Term Loan [Member] | Series C Convertible Preferred Shares [Member]

Class of Warrant or Right [Line Items]

Warrant to purchase shares of stock, shares

1,555,815

Warrant to purchase shares of stock, exercise price per share

$0.26

Warrant to purchase shares of stock, term

10 years

Fair value of Warrant

$302,000

Risk-free interest rate

3.20%

Expected dividend yield

0.00%

Expected volatility rate

67.00%

Expected life of warrant

10 years

Term A Loan [Member]

Class of Warrant or Right [Line Items]

Warrants exercisable, shares

33,262

Warrants exercisable, exercise price

$7.46

$7.46

Term B Loan [Member]

Class of Warrant or Right [Line Items]

Warrants exercisable, shares

16,094

Warrants exercisable, exercise price

$7.46

$7.46

Warrants_Estimated_Fair_Value_

Warrants - Estimated Fair Value of Preferred Stock Warrants Using Black-Scholes Option Pricing Model (Detail) (USD $)	1 Months Ended	12 Months Ended
	Feb. 28, 2013	Dec. 31, 2014	Dec. 31, 2012
Estimated Fair Value Of Warrants [Line Items]
Expected volatility	59.00%	59.00%
Expected term (in years)	10 years
Risk-free interest rate	1.89%
Expected dividend yield	0.00%	0.00%
Estimated fair value of preferred Stock		$7
Warrants [Member]
Estimated Fair Value Of Warrants [Line Items]
Expected volatility			60.00%
Expected dividend yield			0.00%
Warrants [Member] | Series C Convertible Preferred Shares [Member]
Estimated Fair Value Of Warrants [Line Items]
Estimated fair value of preferred Stock			0.34
Series A-1 Convertible Preferred Shares [Member] | Warrants [Member]
Estimated Fair Value Of Warrants [Line Items]
Estimated fair value of preferred Stock			0.45
Minimum [Member]
Estimated Fair Value Of Warrants [Line Items]
Expected term (in years)		5 years
Risk-free interest rate		0.67%
Minimum [Member] | Warrants [Member]
Estimated Fair Value Of Warrants [Line Items]
Expected term (in years)			5 years
Risk-free interest rate			0.72%
Maximum [Member]
Estimated Fair Value Of Warrants [Line Items]
Expected term (in years)		10 years
Risk-free interest rate		1.84%
Maximum [Member] | Warrants [Member]
Estimated Fair Value Of Warrants [Line Items]
Expected term (in years)			10 years
Risk-free interest rate			1.78%

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 30, 2013	Mar. 31, 2013	Oct. 31, 2014	Nov. 30, 2013
Shareholders Equity [Line Items]
Proceeds from issuing of shares	$1,504,000	$96,000	$29,000
IPO [Member]
Shareholders Equity [Line Items]
Common stock, shares issued				797,792	10,714,286
Common stock, issue price				$7	$7
Proceeds from issuing of shares					68,000,000
Underwriting discounts					4,400,000
Offering costs					2,500,000
Conversion to common shares from preferred shares					8,828,438
Proceeds from issuing of shares				5,200,000
Follow on Public Offering [Member]
Shareholders Equity [Line Items]
Common stock, shares issued						4,542,500	4,907,403
Common stock, issue price						$19	$10
Offering costs						400,000	500,000
Proceeds from issuing of shares						80,800,000	45,600,000
Underwriting discounts and commissions						$5,200,000	$2,900,000

Stockbased_Compensation_Additi

Stock-based Compensation - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 28, 2013	31-May-10	Jan. 31, 2014	Jan. 31, 2015	Aug. 31, 2006
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total intrinsic value of options exercised	$8,100,000	$500,000	$25,000
Unrecognized stock-based compensation cost related to the unvested stock option	11,700,000
Weighted average period to recognize compensation cost unvested stock option	2 years 7 months 6 days
Stock-based compensation expense	5,230,000	1,301,000	612,000
Weighted average fair value of options granted	$7.54	$4.52	$2.32
Risk-free interest rate	2.11%
Dividend rate	0.00%	0.00%	0.00%
Expected volatility	56.69%
Expected term	9 years 3 months 18 days
Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,200,000	39,000	300,000
Options granted to purchase of common stock	110,000	0	0
Weighted average Exercise price of Options granted to non-employee	$12.56
Stock Incentive Plan 2006 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance under stock incentive plan								1,128,183
Increase in number of shares of common stock issuable					1,853,288
Option vesting period	10 years
Outstanding shares available for future grants	0			258,265
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%
Stock Incentive Plan 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance under stock incentive plan				1,688,777
Increase in number of shares of common stock issuable						1,025,171
Outstanding shares available for future grants	386,147
Stock Incentive Plan 2013 [Member] | Subsequent Events [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares of common stock issuable							1,232,232
Stock Compensation Plan Agreements [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period	4 years
Share based compensation, contractual life	10 years
Outstanding Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$4,000,000	$1,300,000	$300,000

Stockbased_Compensation_Stock_

Stock-based Compensation - Stock Option Activity (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Beginning balance	2,844,343
Granted	1,292,650
Exercised	-562,569
Canceled	-164,927
Ending balance	3,409,497	2,844,343
Options vested or expected to vest at December 31, 2014	3,256,816
Options exercisable at December 31, 2014	1,415,555
Weighted Average Exercise Price
Beginning balance	$5.10
Granted	$14.33
Exercised	$2.53
Canceled	$10.63
Ending balance	$8.75	$5.10
Options vested or expected to vest at December 31, 2014	$8.61
Options exercisable at December 31, 2014	$5.30
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term	7 years 11 months 1 day	7 years 11 months 19 days
Options vested or expected to vest at December 31, 2014	7 years 10 months 17 days
Options exercisable at December 31, 2014	6 years 9 months 4 days
Aggregate Intrinsic Value
Options outstanding	$105,550	$23,960
Options vested or expected to vest at December 31, 2014	101,276
Options exercisable at December 31, 2014	$48,716

Stockbased_Compensation_Stock_1

Stock-based Compensation - Stock Option Activity (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Estimated forfeiture rate	5.90%

Stockbased_Compensation_Assump

Stock-based Compensation - Assumptions Used to Estimate Fair Value of Employee and Director Stock Option Award (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility factor, Minimum	53.41%	54.50%	56.89%
Volatility factor, Maximum	58.13%	60.54%	68.12%
Expected term (in years)	9 years 3 months 18 days
Risk-free interest rates, Minimum	1.71%	0.91%	0.85%
Risk-free interest rates, Maximum	2.13%	2.01%	1.21%
Dividend yield	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 3 months 22 days	5 years 9 months 18 days	6 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 10 days	7 years 1 month 6 days	6 years 1 month 6 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 $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$5,230,000	$1,301,000	$612,000
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	1,845,000	690,000	463,000
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$3,385,000	$611,000	$149,000

Employee_Stock_Purchase_Plan_A

Employee Stock Purchase Plan - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 27, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price granted	$14.33
Stock-based compensation expense	$5,230,000	$1,301,000	$612,000
Employee [Member] | 2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, shares issued in period	8,394			300,000
Purchase price granted	$9.88
Exercise price for awards granted as percentage of market value on the date of grant	85.00%			85.00%
Stock-based compensation expense	$46,000
Stock options offering date	15-Nov-14			15-Aug-14
Stock options expiration date	14-May-15			14-Nov-14

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Income Taxes [Line Items]
Current income tax expense benefit	$0	$0	$0
Deferred income tax expense benefit	0	0	0
Deductions related to exercise of stock options	5,400,000
Minimum percentage of ownership interest of significant shareholders to limit the carryforward of losses	50.00%
Accrued interest and penalties related to uncertain tax position	0	0
Increase in valuation allowance	26,600,000
Statutory tax rate	-34.00%	-34.00%	-34.00%
Federal [Member]
Schedule Of Income Taxes [Line Items]
NOL carryforwards	170,400,000
NOL tax credit carryforward	5,500,000
State and Local Jurisdiction [Member]
Schedule Of Income Taxes [Line Items]
NOL carryforwards	140,500,000
NOL tax credit carryforward	$1,700,000

Income_Taxes_Components_of_Def

Income Taxes - Components of Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets:
Net operating loss carry forwards	$65,370	$41,574
Temporary differences	3,224	1,976
Research and development credit and carry forwards	5,170	3,609
Deferred tax assets	73,764	47,159
Less valuation allowance	-73,764	-47,159
Net deferred tax assets	$0	$0

Income_Taxes_Reconciliation_of

Income Taxes - Reconciliation of Federal Statutory Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Statutory tax rate	-34.00%	-34.00%	-34.00%
State taxes, net of Federal benefits	-5.28%	-5.28%	-5.28%
Permanent differences	0.61%	0.93%	1.01%
Credits	-2.34%	-4.33%	-0.09%
Change in valuation allowance	39.87%	39.92%	38.92%
Other	1.14%	2.76%	-0.56%
Effective tax rate	0.00%	0.00%	0.00%

Commitments_and_Contingencies_1

Commitments and Contingencies -Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended		90 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	sqft
Schedule Of Commitments And Contingencies [Line Items]
Operating lease expiration date	31-Jul-15
Amended operating lease expiration date	30-Nov-16
Office and laboratory space	15,174
Rent expense		$1	$0.60	$0.60
Property Subject to Operating Lease [Member]
Schedule Of Commitments And Contingencies [Line Items]
Area of office and laboratory	15,899

Commitments_and_Contingencies_2

Commitments and Contingencies - Minimum Future Rent Payments Under Lease and Sublease Agreements (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]
2015	$1,431
2016	1,238
Total minimum lease payments	$2,669

Quarterly_Results_Unaudited_Su

Quarterly Results (Unaudited) - Summary of Selected Quarterly Financial Information (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenue	$3,072	$2,294	$1,275	$2,457	$1,898	$2,166	$3,722	$2,700	$9,098	$10,486	$7,600
Operating expenses	23,455	16,274	19,460	15,675	12,821	11,852	8,680	5,323	74,864	38,676	21,603
Loss from operations	-20,383	-13,980	-18,185	-13,218	-10,923	-9,686	-4,958	-2,623	-65,766	-28,190	-14,003
Other expense, net	-167	-226	-278	-305	-380	-430	-468	-168	24	263	-63
Net loss	($20,550)	($14,206)	($18,463)	($13,523)	($11,303)	($10,116)	($5,426)	($2,791)	($66,742)	($29,636)	($15,087)
Net loss per share-basic and diluted	($0.69)	($0.55)	($0.71)	($0.53)	($0.49)	($0.49)	($0.26)	($1.51)	($2.49)	($1.78)	($47.54)