Tetraphase Pharmaceuticals (TTPH) 10-K 25 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 19, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	TTPH
Entity Registrant Name	TETRAPHASE PHARMACEUTICALS INC
Entity Central Index Key	1,373,707
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		36,599,227
Entity Public Float			$ 1,643,895,719

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 205,912	$ 121,042
Accounts receivable	4,151	3,458
Prepaid expenses and other current assets	3,705	2,097
Total current assets	213,768	126,597
Property and equipment, net	943	300
Restricted cash	199	199
Other assets	7	108
Total assets	214,917	127,204
Current liabilities:
Accounts payable	2,857	4,105
Accrued expenses	6,931	9,477
Deferred revenue	909	258
Current portion of term loan payable		3,436
Total current liabilities	10,697	17,276
Accrued final interest payment on term loan		222
Deferred rent, net of current portion	$ 165	16
Term loan payable		$ 1,124
Commitments and contingencies (Note 12)
Stockholders' equity:
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; 36,585 and 30,806 shares issued and outstanding at December 31, 2015 and 2014, respectively	$ 37	$ 31
Additional paid-in capital	473,670	294,998
Accumulated deficit	(269,652)	(186,463)
Total stockholders’ equity	204,055	108,566
Total liabilities and stockholders’ equity	$ 214,917	$ 127,204

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
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	$ 0.001	$ 0.001
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	36,585,000	30,806,000
Common stock, shares outstanding	36,585,000	30,806,000

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Revenues	$ 11,686	$ 9,098	$ 10,486
Operating expenses:
Research and development	73,768	61,932	31,508
General and administrative	20,916	12,932	7,168
Total operating expenses	94,684	74,864	38,676
Loss from operations	(82,998)	(65,766)	(28,190)
Other income (expense):
Interest income	42	17	10
Interest expense	(231)	(1,017)	(1,719)
Other income (expense)	(2)	24	263
Other expense, net	(191)	(976)	(1,446)
Net loss	$ (83,189)	$ (66,742)	$ (29,636)
Net loss per share-basic and diluted	$ (2.36)	$ (2.49)	$ (1.78)
Weighted-average number of common shares used in net loss per share-basic and diluted	35,261	26,807	16,665
Comprehensive loss	$ (83,189)	$ (66,742)	$ (29,636)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	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]
Beginning Balance at Dec. 31, 2012	$ (83,049)	$ 9,946	$ 44,915	$ 9,925	$ 15,055		$ 7,036	$ (90,085)
Beginning 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)	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)	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						563,000
Issuance of common stock from initial public offering (net of underwriters discounts and issuance costs)	80,766					$ 5	80,761
Issuance of common stock from initial public offering, shares						4,543,000
Reclassification of warrants for common stock	83						83
Reclassification of warrants for common stock, 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
Exercise of stock options	$ 4,672					$ 1	4,671
Exercise of stock options, shares	817,567					818,000
Issuance of common stock from follow-on public offering (net of underwriters discounts and issuance costs)	$ 162,151					$ 5	162,146
Issuance of common stock from follow-on public offering, shares						4,945,000
Issuance of common stock under employee stock purchase plan	239						239
Issuance of common stock under employee stock purchase plan, shares						16,000
Stock-based compensation expense	11,616						11,616
Net loss	(83,189)							(83,189)
Ending Balance at Dec. 31, 2015	$ 204,055					$ 37	$ 473,670	$ (269,652)
Ending Balance, shares at Dec. 31, 2015						36,585,000

Consolidated Statements of Con6

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - Common Shares [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
IPO [Member]
Issuance of common stock from follow-on public offering, underwriters discounts and issuance costs		$ 7,391	$ 7,391
Follow on Public Offering [Member]
Issuance of common stock from follow-on public offering, underwriters discounts and issuance costs	$ 10,924		$ 3,475

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (83,189)	$ (66,742)	$ (29,636)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	193	124	129
Amortization of deferred financing costs and debt discount	94	226	342
Accretion of final interest payment on term loans	45	115	199
Fair value adjustment of warrants and investor right obligation			(263)
Stock-based compensation expense	11,616	5,230	1,301
Loss from disposal of property and equipment	2	2
Changes in operating assets and liabilities:
Restricted cash			(63)
Accounts receivable	(693)	(1,752)	746
Prepaid expenses and other current assets	(1,514)	(1,199)	(154)
Accounts payable	(1,249)	2,224	310
Accrued expenses and accrued final interest payment on term loan	(2,663)	3,983	3,190
Deferred revenue	651	166	(607)
Net cash used in operating activities	(76,707)	(57,623)	(24,506)
Investing activities
Purchases of property and equipment	(838)	(191)	(129)
Net cash used in investing activities	(838)	(191)	(129)
Financing activities
Proceeds from sale of common stock, net of underwriter discounts and issuance costs	162,151	80,766	119,404
Proceeds from issuance of term loan payable			3,000
Repayment of term loan payable	(4,646)	(6,126)	(4,232)
Proceeds from issuance of stock under stock plans	4,910	1,504	96
Net cash provided by financing activities	162,415	76,144	118,268
Net increase in cash and cash equivalents	84,870	18,330	93,633
Cash and cash equivalents at beginning of period	121,042	102,712	9,079
Cash and cash equivalents at end of period	205,912	121,042	102,712
Supplemental cash flow information
Cash paid for interest	$ 363	$ 945	1,142
Fair value of warrants issued in connection with issuance of term loan			115
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, 2015
Organization Consolidation And Presentation Of Financial Statements [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 conducted a global phase 3 clinical program for eravacycline called IGNITE ( I G N I T E In December 2014, the Company announced that in IGNITE 1eravacycline met the primary endpoint of statistical non-inferiority compared to ertapenem, the control therapy for the trial, for the treatment of cIAI. In September 2015, the Company announced that eravacycline did not meet the primary endpoint of statistical non-inferiority in IGNITE 2 compared to levofloxacin, the control therapy for this trial. Consistent with guidance issued by the United States Food and Drug Administration (“FDA”) with respect to the development of antibiotics for cIAI and its the Company the Company has continues its The Company is 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. The Company has incurred annual net operating losses in every year since its inception. As of December 31, 2015, the Company had incurred losses since inception of $269.7 million. The Company has not generated any product revenues 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. There can be no assurance that the Company will be able to obtain additional debt or equity financing or generate product revenue or 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 Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
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 GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and related disclosures. On an ongoing basis, the Company’s management evaluates its estimates, including estimates related to clinical trial accruals, stock-based compensation expense, contract and grant revenues, and expenses. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. Concentrations of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash, cash equivalents and restricted cash. The Company maintains its cash and cash equivalent balances in the form of cash and money market accounts with financial institutions that management believes are creditworthy. The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimize its exposure to concentration of credit risk. The Company has no financial instruments with off-balance-sheet risk of loss. Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. 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, 2015 and 2014 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, 2015 and 2014 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, 2015 Cash $ 2,065 $ 2,065 $ — $ — Money market funds, included in cash equivalents $ 203,847 $ 203,847 $ — $ — December 31, 2014 Cash $ 2,919 $ 2,919 $ — $ — Money market funds, included in cash equivalents $ 118,123 $ 118,123 $ — $ — 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 was determined using current applicable rates for similar instruments as of the balance sheet date. The Company’s term loan payable was 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. 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 $10.8 million from the initial contract date through November 30, 2016, of which $7.7 million had been received by the Company through December 31, 2015. 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 $38.4 million from the initial contract date through February 17, 2017, of which $27.4 million had been received by the Company through December 31, 2015 (Note 3). Accounts receivable at December 31, 2015 and 2014 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, included in accounts receivable in the accompanying balance sheets, were $2.2 million and $2.9 million at December 31, 2015 and 2014, 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, 2015 and 2014 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 landlord. In addition, the Company has $40,000 in restricted cash to secure the Company’s corporate credit card issued through the same bank. Revenue Recognition The Company’s revenue is derived from its subcontracts with CUBRC under the BARDA Contract and the NIAID Contract and its subaward under the NIAID Grant (Note 3). The Company recognizes revenue under these best-efforts, cost-reimbursable and cost-plus-fixed-fee subcontracts and subaward as the Company performs services under the subcontracts and subaward so long as a subcontract and subaward has been executed and the fees for these services are fixed or determinable, legally billable and reasonably assured of collection. Recognized amounts reflect the Company’s partial performance under the subcontracts and subaward and equal direct and indirect costs incurred plus fixed fees, where applicable. The Company does not recognize revenue under these arrangements for amounts related to contract periods where funding is not yet committed as amounts above committed funding thresholds would not be considered fixed or determinable or reasonably assured of collection. Revenues and expenses under these arrangements are presented gross on the condensed consolidated statements of operations and comprehensive loss as the Company has determined it is the primary obligor under these arrangements relative to the research and development services it performs as lead technical expert. Revenue under the Company’s 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, regulatory and medical affair 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 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 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. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delayed the effective date of the new standard from January 1, 2017 to January 1, 2018. The FASB also agreed to allow entities to choose to adopt the standard as of the original effective date. In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements-Going Concern: Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern . Subsequent Events The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. Net Loss per Common Share Basic net loss per share is calculated by dividing the net loss 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, 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. 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, 2015 2014 2013 Warrants 1,103 1,103 104,107 Outstanding stock options 3,833,806 3,409,497 2,844,343

Significant Agreements and Cont

Significant Agreements and Contracts	12 Months Ended
	Dec. 31, 2015
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, 2015, the Company has paid the University an aggregate of $3.9 million in upfront license fees and development milestone payments, and has issued 31,379 shares of common stock to the University. For each product covered by the license agreement, the Company is obligated to make certain payments totaling up to approximately $15.1 million upon achievement of certain development and regulatory milestones and to pay additional royalties on net sales of such product. 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. 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 Contract 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 $38.4 million through February 17, 2017, the current contract end date, as a result of the exercise of several options by BARDA under the BARDA Contract. Total funds of $27.4 million had been received by the Company through December 31, 2015 under this contract. During the years ended December 31, 2015, 2014 and 2013, the Company recognized revenue of $10.8 million, $6.9 million and $7.7 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 November 30, 2016. To the extent that 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, 2015, committed funding from CUBRC under the Company’s subcontract with respect to the NIAID Contract is $10.8 million through the current contract end date which has been extended to November 30, 2016, of which $7.7 million had been received through December 31, 2015. Committed funding from CUBRC under the Company’s subaward with respect to the NIAID Grant is $0.9 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, 2015. During the years ended December 31, 2015, 2014 and 2013, the Company recognized revenue of $0.8 million, $2.1 million, and $2.5 million, respectively, from the Company’s subcontract under the NIAID Contract. During the years ended December 31, 2015, 2014 and 2013, the Company recognized revenue of $157,000, $135,000 and $267,000, respectively, from the Company’s subaward under the NIAID Grant.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Property and Equipment	(4) Property and Equipment Property and equipment at December 31, 2015 and 2014 consisted of the following (in thousands): Estimated December 31, Useful Life In Years 2015 2014 Laboratory equipment 5 $ 2,087 $ 1,932 Furniture and fixtures 5 484 178 Office and computer equipment 3 159 163 Leasehold improvements 891 527 3,621 2,800 Less accumulated depreciation and amortization (2,678 ) (2,500 ) Property and equipment, net $ 943 $ 300 Depreciation and amortization expense for the years ended December 31, 2015, 2014 and 2013 was $193,000, $124,000 and $129,000, respectively.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued Expenses	(5) Accrued Expenses Accrued expenses at December 31, 2015 and 2014 consisted of the following (in thousands): December 31, 2015 December 31, 2014 Drug supply and development $ 2,971 $ 5,440 Salaries and benefits 1,856 2,358 Clinical trial related 677 724 Preclinical 303 328 Professional fees 684 346 Other 440 281 Total $ 6,931 $ 9,477

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2015
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 originally provided for up to $8.0 million of funding, to be made available in two tranches. The Term Loan was paid in full on March 31, 2015. 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 “2012 Term A Loan” and the “2012 Term B Loan”). On March 31, 2015, the Company repaid the 2012 Term Loan. As a result, no indebtedness remains outstanding under either the Term Loan or the 2012 Term Loan. In connection with the funding of the 2012 Term A Loan, the Company issued to the lenders 10-year warrants to purchase an aggregate of 964,605 shares of Series C Preferred Stock with an exercise price of $0.2571 per share. In connection with the February 2013 borrowing under the 2012 Term B 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. Upon completion of the Company’s initial public offering (“IPO”), the warrants to purchase Series C Preferred Stock issued in connection with the Term Loan, the 2012 Term A Loan and the 2012 Term B Loan were converted into warrants to purchase common stock of the Company. 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.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2015
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 A 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 A 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 B 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 B 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, 2015
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. 2015 Follow-on Public Offering In March 2015, the Company sold 4,945,000 shares of common stock in a follow-on public offering at a price to the public of $35.00 per share, resulting in net proceeds to the Company of $162.2 million after deducting underwriting discounts and commissions of $10.4 million and offering costs of $0.5 million.

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased 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, 2015, 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. In January 2015, the number of shares authorized for issuance under the 2013 Plan increased by 1,232,232 shares. As of December 31, 2015, 337,628 shares were available for future issuance under the 2013 Plan. In January 2016, the number of shares authorized for issuance under the 2013 Plan increased by 1,463,391 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, 2015 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- Average Exercise Price Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value Options outstanding at December 31, 2014 3,409,497 $ 5.10 7.97 $ 23,960 Granted 1,834,500 40.90 Exercised (817,567 ) 5.71 Canceled (592,624 ) 22.08 Options outstanding at December 31, 2015 3,833,806 $ 22.72 7.80 $ 5,439 Options vested or expected to vest at December 31, 2015 (1) 3,367,031 $ 21.37 6.94 $ 5,309 Options exercisable at December 31, 2015 1,527,086 $ 12.35 6.54 $ 4,427 (1) This represents the number of vested options as of December 31, 2015, plus the number of unvested options that the Company estimated as of December 31, 2015 would vest, based on the unvested options at December 31, 2015, as adjusted for the estimated forfeiture rate of 18.2%. 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, 2015 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, 2015, 2014, and 2013 was $27.0 million, $8.1 million and $0.5 million, respectively. As of December 31, 2015, there was $24.8 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 2.5 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, 2015 2014 2013 Volatility factor 56.49-85.34% 53.41-58.13% 54.50-60.54% Expected life (in years) 5.31-6.11 5.31-6.11 5.8-7.1 Risk-free interest rate 1.35%-1.94% 1.71%-2.13% 0.91%-2.01% Dividend yield 0% 0% 0% Compensation cost for stock options and restricted stock units 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 and restricted stock units granted to employees was $12.6 million, $4.0 million, and $1.3 million during the years ended December 31, 2015, 2014, and 2013, 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, 2015, 2014 and 2013 was $22.78, $7.54 and $4.52, respectively. Stock-based compensation expense recognized in the Company’s consolidated statements of operations during the periods presented was as follows (in thousands): Year Ended December 31, 2015 2014 2013 Research and development $ 5,906 $ 1,845 $ 690 General and administrative 5,710 3,385 611 Total $ 11,616 $ 5,230 $ 1,301 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, 2015 or 2013. The Company initially valued these options using the Black-Scholes option-pricing model and revalues the options 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. The re-measurement of these non-employee options resulted in a reversal of expense of Restricted Stock Units In October 2015, the Company granted restricted stock units to employees. These restricted stock units vest in full after one year subject to continued employment with the company and had a grant price of $7.81 per share, which was the closing price of the Company’s common stock on the date of grant. The Company recorded stock based compensation expense of $0.6 million related to these restricted stock units for the year ended December 31, 2015. The restricted stock activity for the year ended December 31, 2015 is as follows: Number of Shares Weighted- Unvested at December 31, 2014 — — Granted 309,750 $7.81 Cancelled (875) 7.81 Expired — — Vested/Released — — Unvested at December 31, 2015 308,875 $7.81 As of December 31, 2015, there was $1.8 million of total unrecognized stock-based compensation expense related to restricted stock units granted under the Plan. The expense is expected to be recognized over a weighted-average period of 0.8 years.

Employee Stock Purchase Plan

Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Employee Stock Purchase Plan Text Block	(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 concluded on May 14, 2015. The next offering period began on May 15, 2015, and concluded on November 14, 2015. The next offering period began on November 15, 2015, and will conclude on May 14, 2016. Pursuant to the ESPP, the Company sold a total of 16,422 shares of common stock during the year ended December 31, 2015 under the ESPP at purchase prices of $19.29, and $9.30, respectively, which represented 85% of the closing price of the Company’s common stock on November 17, 2014, and November 13, 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 $156,000, and $46,000 during the years ended December 31, 2015, and 2014, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
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. Loss before income tax (benefit) provision consists of the following: Year ended December 31, 2015 2014 2013 United States $ (64,037 ) $ (66,742 ) $ (29,636 ) Foreign (19,152 ) — — Total loss before income taxes $ (83,189 ) $ (66,742 ) $ (29,636 ) For the years ended December 31, 2015, 2014 and 2013, the Company did not have a current or deferred income tax expense or benefit. A reconciliation of the Federal statutory tax rate of 34% to the Company’s effective income tax rate follows: Year ended December 31, 2015 2014 2013 Statutory tax rate (34.00 )% (34.00 )% (34.00 )% State taxes, net of Federal benefits (4.02 )% (5.28 )% (5.28 )% Permanent differences 0.71 % 0.61 % 0.93 % Credits (1.65 )% (2.34 )% (4.33 )% Change in valuation allowance 30.74 % 39.87 % 39.92 % Foreign rate differential 7.03 % — — Other 1.19 % 1.14 % 2.76 % Effective tax rate — % — % — % As of December 31, 2015 the Company had federal net operating loss carryforwards of approximately $225.6 million and state net operating loss carryforwards of $192.5 million, which are available to reduce future taxable income. The federal net operating loss carryforwards exclude approximately $26.9 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 $5.3 million and state tax credits of $1.9 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 2035. 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. The principal components of the Company’s deferred tax assets are as follows (in thousands): Year ended December 31, 2015 2014 Deferred tax assets: Net operating loss carry forwards $ 86,880 $ 65,370 Temporary differences 5,916 3,224 Research and development credit and carry forwards 6,543 5,170 Deferred tax assets 99,339 73,764 Less valuation allowance (99,339 ) (73,764 ) 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, 2015 and 2014, respectively, because the Company’s management has determined that is it more likely than not that these assets will not be realized. The $25.6 million increase in the valuation allowance in 2015 primarily relates to the net loss incurred by the Company. ASC 740, Accounting for Income Taxes, clarifies the accounting for uncertainty in income taxes recognized in an enterprise’s financial statement by prescribing the minimum recognition threshold and measurement of a tax position taken or expected to be taken in a tax return. At December 31, 2015, the Company had gross tax-effected unrecognized tax benefits of $0.8 million. At December 31, 2014, the Company had recorded no unrecognized tax benefits for tax positions taken. Unrecognized tax benefits represent tax positions for which reserves have been established. A full valuation allowance has been provided against the Company’s deferred tax assets, so that 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. The Company anticipates that the amount of unrecognized tax benefits recorded will not change in the next twelve months. As of December 31, 2015 and 2014, the Company had no accrued interest or penalties related to uncertain tax positions. The aggregate changes in gross unrecognized tax benefits during the years ended December 31, 2015, 2014, and 2013 were as follows (in thousands): Year ended December 31, 2015 2014 2013 Balance at beginning of year — — — Increases for tax positions taken during current period $ 249 — — Increases for tax positions taken in prior periods 573 — — Decreases for tax positions taken during current period — — — Decreases for tax positions taken in prior periods — — — Balance at end of year $ 822 — — 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 2012 through 2014. 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.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	(12) Commitments and Contingencies Lease Commitments On March 24, 2015, the Company amended its existing operating lease to expand its existing premises by an additional 13,711 square feet of office and laboratory space for a total of 29,610 square feet. The effective date of this amendment was April 1, 2015. On March 31, 2015, the Company canceled an existing sublease entered into in September 2014 covering 15,174 square feet of office and laboratory space. On June 18, 2015, the Company further amended its existing operating lease to expand its leased premises by an additional 7,828 square feet of office and laboratory space for a total of 37,438 square feet. The lease for the additional office and laboratory space was effective as of August 1, 2015. In connection with the amendment, the lease term was extended from November 30, 2016 to November 30, 2019. As of December 31, 2015, the aggregate minimum future rent payments under the lease and sublease agreements are as follows (in thousands): December 31, 2015 2016 1,645 2017 1,701 2018 1,752 2019 1,650 Total minimum lease payments $ 6,748 The Company recorded $1.7 million, $1.0 million and $0.6 million in rent expense for the years ended December 31, 2015, 2014 and 2013, respectively. Litigation During 2015, the Company was not a party to any litigation. The Company does not have contingency reserves established for any litigation liabilities. In January 2016, a securities class action lawsuit was filed against the Company, its chief executive officer, its former chief operating officer and its former chief financial officer, in the United States District Court for the District of Massachusetts. The complaint is brought on behalf of an alleged class of those who purchased common stock of the Company between March 5, 2015 and September 8, 2015, and alleges claims arising under Sections 10 and 20 of the Exchange Act of 1934, as amended. The complaint generally alleges that the defendants violated the federal securities laws by, among other things, making material misstatements or omissions concerning IGNITE2. The complaint seeks, among other relief, unspecified compensatory damages and attorneys’ fees, and costs. The Company believes it has valid defenses against these claims, and will engage in a vigorous defense of such litigation.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	(13) Employee Benefit Plan In 2007, the Company established the Tetraphase Pharmaceuticals, Inc. 401(k) Plan (the “401(k) Plan”) for its employees, which is designed to be qualified under Section 401(k) of the Internal Revenue Code. Eligible employees are permitted to contribute to the 401(k) Plan within statutory and 401(k) Plan limits. During 2014, the Company began to make matching contributions of 50% of the first 6% of employee contributions. The Company made matching contributions of $261,000, and $84,000 for the years ended December 31, 2015, and 2014, respectively .

Quarterly Results (Unaudited)

Quarterly Results (Unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results (Unaudited)	(14) Quarterly Results (Unaudited) Three Months Ended March 31, 2015 June 30, 2015 September 30, 2015 December 31, 2015 (in thousands, except per share data) (unaudited) Revenue $ 3,016 $ 3,343 $ 2,856 $ 2,471 Operating expenses 23,776 29,396 20,909 20,603 Loss from operations (20,760 ) (26,053 ) (18,053 ) (18,132 ) Other income (expense), net (226 ) 10 9 16 Net loss $ (20,986 ) $ (26,043 ) $ (18,044 ) $ (18,116 ) Net loss per share—basic and diluted $ (0.66 ) $ (0.72 ) $ (0.49 ) $ (0.50 ) Three Months Ended March 31, 2014 June 30, 2014 September 30, 2014 December 31, 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 )

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
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 GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and related disclosures. On an ongoing basis, the Company’s management evaluates its estimates, including estimates related to clinical trial accruals, stock-based compensation expense, contract and grant revenues, and expenses. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash, cash equivalents and restricted cash. The Company maintains its cash and cash equivalent balances in the form of cash and money market accounts with financial institutions that management believes are creditworthy. The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimize its exposure to concentration of credit risk. The Company has no financial instruments with off-balance-sheet risk of loss.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. 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, 2015 and 2014 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, 2015 and 2014 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, 2015 Cash $ 2,065 $ 2,065 $ — $ — Money market funds, included in cash equivalents $ 203,847 $ 203,847 $ — $ — December 31, 2014 Cash $ 2,919 $ 2,919 $ — $ — Money market funds, included in cash equivalents $ 118,123 $ 118,123 $ — $ — 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 was determined using current applicable rates for similar instruments as of the balance sheet date. The Company’s term loan payable was 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.
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 $10.8 million from the initial contract date through November 30, 2016, of which $7.7 million had been received by the Company through December 31, 2015. 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 $38.4 million from the initial contract date through February 17, 2017, of which $27.4 million had been received by the Company through December 31, 2015 (Note 3). Accounts receivable at December 31, 2015 and 2014 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, included in accounts receivable in the accompanying balance sheets, were $2.2 million and $2.9 million at December 31, 2015 and 2014, 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, 2015 and 2014 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 landlord. In addition, the Company has $40,000 in restricted cash to secure the Company’s corporate credit card issued through the same bank.
Revenue Recognition	Revenue Recognition The Company’s revenue is derived from its subcontracts with CUBRC under the BARDA Contract and the NIAID Contract and its subaward under the NIAID Grant (Note 3). The Company recognizes revenue under these best-efforts, cost-reimbursable and cost-plus-fixed-fee subcontracts and subaward as the Company performs services under the subcontracts and subaward so long as a subcontract and subaward has been executed and the fees for these services are fixed or determinable, legally billable and reasonably assured of collection. Recognized amounts reflect the Company’s partial performance under the subcontracts and subaward and equal direct and indirect costs incurred plus fixed fees, where applicable. The Company does not recognize revenue under these arrangements for amounts related to contract periods where funding is not yet committed as amounts above committed funding thresholds would not be considered fixed or determinable or reasonably assured of collection. Revenues and expenses under these arrangements are presented gross on the condensed consolidated statements of operations and comprehensive loss as the Company has determined it is the primary obligor under these arrangements relative to the research and development services it performs as lead technical expert. Revenue under the Company’s 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, regulatory and medical affair 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 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	Recent Accounting Pronouncements Issued 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. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delayed the effective date of the new standard from January 1, 2017 to January 1, 2018. The FASB also agreed to allow entities to choose to adopt the standard as of the original effective date. In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements-Going Concern: Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern .
Subsequent Events	Subsequent Events The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.
Net Loss per Common Share	Net Loss per Common Share Basic net loss per share is calculated by dividing the net loss 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, 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. 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, 2015 2014 2013 Warrants 1,103 1,103 104,107 Outstanding stock options 3,833,806 3,409,497 2,844,343

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Financial Instruments Measured at Fair Value	Financial instruments measured at fair value as of December 31, 2015 and 2014 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, 2015 Cash $ 2,065 $ 2,065 $ — $ — Money market funds, included in cash equivalents $ 203,847 $ 203,847 $ — $ — December 31, 2014 Cash $ 2,919 $ 2,919 $ — $ — Money market funds, included in cash equivalents $ 118,123 $ 118,123 $ — $ —
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, 2015 2014 2013 Warrants 1,103 1,103 104,107 Outstanding stock options 3,833,806 3,409,497 2,844,343

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Property and Equipment	Property and equipment at December 31, 2015 and 2014 consisted of the following (in thousands): Estimated December 31, Useful Life In Years 2015 2014 Laboratory equipment 5 $ 2,087 $ 1,932 Furniture and fixtures 5 484 178 Office and computer equipment 3 159 163 Leasehold improvements 891 527 3,621 2,800 Less accumulated depreciation and amortization (2,678 ) (2,500 ) Property and equipment, net $ 943 $ 300

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses at December 31, 2015 and 2014 consisted of the following (in thousands): December 31, 2015 December 31, 2014 Drug supply and development $ 2,971 $ 5,440 Salaries and benefits 1,856 2,358 Clinical trial related 677 724 Preclinical 303 328 Professional fees 684 346 Other 440 281 Total $ 6,931 $ 9,477

Warrants (Tables)

Warrants (Tables)	12 Months Ended
	Dec. 31, 2015
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

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option Activity	Stock option activity at December 31, 2015 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- Average Exercise Price Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value Options outstanding at December 31, 2014 3,409,497 $ 5.10 7.97 $ 23,960 Granted 1,834,500 40.90 Exercised (817,567 ) 5.71 Canceled (592,624 ) 22.08 Options outstanding at December 31, 2015 3,833,806 $ 22.72 7.80 $ 5,439 Options vested or expected to vest at December 31, 2015 (1) 3,367,031 $ 21.37 6.94 $ 5,309 Options exercisable at December 31, 2015 1,527,086 $ 12.35 6.54 $ 4,427 (1) This represents the number of vested options as of December 31, 2015, plus the number of unvested options that the Company estimated as of December 31, 2015 would vest, based on the unvested options at December 31, 2015, as adjusted for the estimated forfeiture rate of 18.2%.
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, 2015 2014 2013 Volatility factor 56.49-85.34% 53.41-58.13% 54.50-60.54% Expected life (in years) 5.31-6.11 5.31-6.11 5.8-7.1 Risk-free interest rate 1.35%-1.94% 1.71%-2.13% 0.91%-2.01% Dividend yield 0% 0% 0%
Stock-based Compensation Expense Recognized in the Condensed Consolidated Statements of Operations	Stock-based compensation expense recognized in the Company’s consolidated statements of operations during the periods presented was as follows (in thousands): Year Ended December 31, 2015 2014 2013 Research and development $ 5,906 $ 1,845 $ 690 General and administrative 5,710 3,385 611 Total $ 11,616 $ 5,230 $ 1,301
Summary of Restricted Stock Activity	The restricted stock activity for the year ended December 31, 2015 is as follows: Number of Shares Weighted- Unvested at December 31, 2014 — — Granted 309,750 $7.81 Cancelled (875) 7.81 Expired — — Vested/Released — — Unvested at December 31, 2015 308,875 $7.81

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Loss Before Income Tax (Benefit) Provision	Loss before income tax (benefit) provision consists of the following: Year ended December 31, 2015 2014 2013 United States $ (64,037 ) $ (66,742 ) $ (29,636 ) Foreign (19,152 ) — — Total loss before income taxes $ (83,189 ) $ (66,742 ) $ (29,636 )
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, 2015 2014 2013 Statutory tax rate (34.00 )% (34.00 )% (34.00 )% State taxes, net of Federal benefits (4.02 )% (5.28 )% (5.28 )% Permanent differences 0.71 % 0.61 % 0.93 % Credits (1.65 )% (2.34 )% (4.33 )% Change in valuation allowance 30.74 % 39.87 % 39.92 % Foreign rate differential 7.03 % — — Other 1.19 % 1.14 % 2.76 % Effective tax rate — % — % — %
Components of Deferred Tax Assets	The principal components of the Company’s deferred tax assets are as follows (in thousands): Year ended December 31, 2015 2014 Deferred tax assets: Net operating loss carry forwards $ 86,880 $ 65,370 Temporary differences 5,916 3,224 Research and development credit and carry forwards 6,543 5,170 Deferred tax assets 99,339 73,764 Less valuation allowance (99,339 ) (73,764 ) Net deferred tax assets $ — $ —
Aggregate Changes in Gross Unrecognized Tax Benefits	The aggregate changes in gross unrecognized tax benefits during the years ended December 31, 2015, 2014, and 2013 were as follows (in thousands): Year ended December 31, 2015 2014 2013 Balance at beginning of year — — — Increases for tax positions taken during current period $ 249 — — Increases for tax positions taken in prior periods 573 — — Decreases for tax positions taken during current period — — — Decreases for tax positions taken in prior periods — — — Balance at end of year $ 822 — —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Minimum Future Rent Payments Under Lease and Sublease Agreements	As of December 31, 2015, the aggregate minimum future rent payments under the lease and sublease agreements are as follows (in thousands): December 31, 2015 2016 1,645 2017 1,701 2018 1,752 2019 1,650 Total minimum lease payments $ 6,748

Quarterly Results (Unaudited) (

Quarterly Results (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Summary of Selected Quarterly Financial Information	(14) Quarterly Results (Unaudited) Three Months Ended March 31, 2015 June 30, 2015 September 30, 2015 December 31, 2015 (in thousands, except per share data) (unaudited) Revenue $ 3,016 $ 3,343 $ 2,856 $ 2,471 Operating expenses 23,776 29,396 20,909 20,603 Loss from operations (20,760 ) (26,053 ) (18,053 ) (18,132 ) Other income (expense), net (226 ) 10 9 16 Net loss $ (20,986 ) $ (26,043 ) $ (18,044 ) $ (18,116 ) Net loss per share—basic and diluted $ (0.66 ) $ (0.72 ) $ (0.49 ) $ (0.50 ) Three Months Ended March 31, 2014 June 30, 2014 September 30, 2014 December 31, 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 )

Organization and Operations - A

Organization and Operations - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Company incorporation date	Jul. 7, 2006
Accumulated deficit	$ (269,652)	$ (186,463)

Summary of Significant Accoun32

Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended						12 Months Ended
	Feb. 29, 2012USD ($)	Jan. 31, 2012USD ($)	Nov. 30, 2011USD ($)	Oct. 31, 2011USD ($)	Sep. 30, 2011USD ($)	Jul. 31, 2011	Dec. 31, 2015USD ($)Segment	Dec. 31, 2014USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segment | Segment							1
Fair value of loans payable								$ 4,900,000
Unbilled accounts receivable							$ 2,200,000	2,900,000
Restricted cash							199,000	199,000
Amount payable to landlord in respect of default on rental obligation							159,000	159,000
Letter of Credit [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash							159,000	159,000
Corporate Credit Card [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash							40,000	$ 40,000
NIAID Contract [Member] | National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]
Summary Of Significant Accounting Policies [Line Items]
Government contract for research and development, amount					$ 35,800,000
Contract receivable, term					5 years	5 years
NIAID Contract [Member] | CUBRC Inc [Member]
Summary Of Significant Accounting Policies [Line Items]
Contract receivable, term			55 months	5 years	5 years
Contract for research and development, amount			$ 980,000		$ 10,800,000
Funding proceeds							7,700,000
BARDA Contract [Member] | CUBRC Inc [Member]
Summary Of Significant Accounting Policies [Line Items]
Contract receivable, term	5 years
Contract for research and development, amount		$ 38,400,000
Funding proceeds							$ 27,400,000
Contract maturity date							Feb. 17, 2017
BARDA Contract [Member] | Biomedical Advanced Research and Development Authority (BARDA) [Member]
Summary Of Significant Accounting Policies [Line Items]
Government contract for research and development, amount		$ 67,000,000
Contract receivable, term		5 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of property and equipment							5 years
Maximum [Member] | NIAID Contract [Member] | National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member]
Summary Of Significant Accounting Policies [Line Items]
Government contract for research and development, amount					35,800,000
Maximum [Member] | NIAID Contract [Member] | CUBRC Inc [Member]
Summary Of Significant Accounting Policies [Line Items]
Contract for research and development, amount				$ 13,300,000	$ 13,300,000
Maximum [Member] | BARDA Contract [Member] | CUBRC Inc [Member]
Summary Of Significant Accounting Policies [Line Items]
Contract for research and development, amount	$ 39,800,000	$ 39,800,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of property and equipment							3 years

Summary of Significant Accoun33

Summary of Significant Accounting Policies - Financial Instruments Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	$ 2,065	$ 2,919
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	203,847	118,123
Level 1 [Member] | Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	2,065	2,919
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	$ 203,847	$ 118,123

Summary of Significant Accoun34

Summary of Significant Accounting Policies - Amounts Excluded from Calculation of Diluted Weighted-Average Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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	1,103	104,107
Outstanding Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	3,833,806	3,409,497	2,844,343

Significant Agreements and Co35

Significant Agreements and Contracts - Additional Information (Detail) - USD ($)	1 Months Ended								12 Months Ended
	Feb. 29, 2012	Jan. 31, 2012	Nov. 30, 2011	Oct. 31, 2011	Sep. 30, 2011	Jul. 31, 2011	Apr. 30, 2010	Jan. 31, 2007	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
BARDA Contract [Member] | Biomedical Advanced Research and Development Authority (BARDA) [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Government contract for research and development, amount		$ 67,000,000
Awarded contract for development, contract period		5 years
BARDA Contract [Member] | CUBRC Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Awarded contract for development, contract period	5 years
Committed funding for subcontracts		$ 38,400,000
Contract maturity date									Feb. 17, 2017
Proceed from awarded contract for development									$ 27,400,000
BARDA Contract [Member] | CUBRC Inc [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Committed funding for subcontracts	$ 39,800,000	$ 39,800,000
NIAID Contract [Member] | CUBRC Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Awarded contract for development, contract period			55 months	5 years	5 years
Committed funding for subcontracts			$ 980,000		$ 10,800,000
NIAID Contract [Member] | CUBRC Inc [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Committed funding for subcontracts				$ 13,300,000	13,300,000
NIAID Contract [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]
Government contract for research and development, amount					$ 35,800,000
Awarded contract for development, contract period					5 years	5 years
NIAID Contract [Member] | National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member] | Subcontract with CUBRC [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Committed funding for subcontracts									10,800,000
Proceed from awarded contract for development									7,700,000
Contracts Revenue									800,000	$ 2,100,000	$ 2,500,000
NIAID Contract [Member] | National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member] | Subaward Under the NIAID Grant [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Committed funding for subcontracts									900,000
Proceed from awarded contract for development									700,000
Contracts Revenue									157,000	135,000	267,000
NIAID Contract [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]
Government contract for research and development, amount					$ 35,800,000
Awarded contract for development, amount						$ 2,800,000
License Agreement Terms [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront and milestone payments									$ 3,900,000
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
Additional Funding Agreement Terms [Member] | BARDA Contract [Member] | CUBRC Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Committed funding for subcontracts									$ 38,400,000
Contract maturity date									Feb. 17, 2017
Proceed from awarded contract for development									$ 27,400,000
Contracts Revenue									$ 10,800,000	$ 6,900,000	$ 7,700,000

Property and Equipment - Proper

Property and Equipment - Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3,621	$ 2,800
Less accumulated depreciation and amortization	(2,678)	(2,500)
Property and equipment, net	$ 943	300
Laboratory Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	5 years
Property and equipment, gross	$ 2,087	1,932
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	5 years
Property and equipment, gross	$ 484	178
Office and Computer Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	3 years
Property and equipment, gross	$ 159	163
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 891	$ 527

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property Plant And Equipment Useful Life And Values [Abstract]
Depreciation and amortization expense	$ 193	$ 124	$ 129

Accrued Expenses - Accrued Expe

Accrued Expenses - Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Drug supply and development	$ 2,971	$ 5,440
Salaries and benefits	1,856	2,358
Clinical trial related	677	724
Preclinical	303	328
Professional fees	684	346
Other	440	281
Total	$ 6,931	$ 9,477

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Detail)	1 Months Ended			12 Months Ended
	Feb. 28, 2013$ / sharesshares	Dec. 31, 2012USD ($)Tranche$ / sharesshares	May. 31, 2011USD ($)Tranche$ / sharesshares	Dec. 31, 2015$ / sharesshares
Series C Convertible Preferred Shares [Member]
Debt Instrument [Line Items]
Warrant to purchase shares of stock, exercise price per share | $ / shares	$ 0.2571
Term Loan [Member]
Debt Instrument [Line Items]
Debt, borrowing capacity | $			$ 8,000,000
Warrants exercisable, shares | shares		53,648		53,648
Warrants exercisable, exercise price | $ / shares		$ 7.46		$ 7.46
Term Loan [Member] | Series C Convertible Preferred Shares [Member]
Debt Instrument [Line Items]
Warrants to purchase shares of stock, term			10 years
Warrants to purchase shares of stock, shares | shares			1,555,815
Warrant to purchase shares of stock, exercise price per share | $ / shares			$ 0.2571
2012 Term Loan [Member]
Debt Instrument [Line Items]
Debt, number of tranches | Tranche		2	2
Debt, additional borrowing capacity | $		$ 9,200,000
2012 Term Loan [Member] | Series C Convertible Preferred Shares [Member]
Debt Instrument [Line Items]
Warrants to purchase shares of stock, term		10 years
Warrants to purchase shares of stock, shares | shares		964,605
Warrant to purchase shares of stock, exercise price per share | $ / shares		$ 0.2571
2012 Term A Loan [Member]
Debt Instrument [Line Items]
Warrants exercisable, shares | shares		33,262
Warrants exercisable, exercise price | $ / shares		$ 7.46
2012 Term A Loan [Member] | Series C Convertible Preferred Shares [Member]
Debt Instrument [Line Items]
Warrants to purchase shares of stock, term		10 years
Warrants to purchase shares of stock, shares | shares		964,605
Warrant to purchase shares of stock, exercise price per share | $ / shares		$ 0.2571
2012 Term B Loan [Member]
Debt Instrument [Line Items]
Warrants exercisable, shares | shares		16,094
Warrants exercisable, exercise price | $ / shares		$ 7.46
2012 Term B Loan [Member] | Series C Convertible Preferred Shares [Member] | Silicon Valley Bank [Member]
Debt Instrument [Line Items]
Stock issued upon immediate exercise of warrant | shares	233,372
2012 Term B Loan [Member] | Series C Convertible Preferred Shares [Member] | Oxford Finance [Member]
Debt Instrument [Line Items]
Warrants to purchase shares of stock, term	10 years
Warrants to purchase shares of stock, shares | shares	233,372
Warrant to purchase shares of stock, exercise price per share | $ / shares	$ 0.2571

Warrants - Additional Informati

Warrants - Additional Information (Detail) - USD ($)

Dec. 13, 2014

Jun. 23, 2014

Mar. 25, 2013

Feb. 28, 2013

Dec. 31, 2012

May. 31, 2011

Dec. 31, 2015

Sep. 30, 2015

Jun. 30, 2015

Mar. 31, 2015

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2015

Dec. 31, 2014

Dec. 31, 2013

Class of Warrant or Right [Line Items]

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 warrants issued in connection with issuance of term loan

$ 115,000

$ 115,000

Stock price

$ 7

$ 7

Fair value of warrants

$ 462,000

462,000

Other income

$ 16,000

$ 9,000

$ 10,000

$ (226,000)

$ (167,000)

$ (226,000)

$ (278,000)

$ (305,000)

$ (2,000)

$ 24,000

$ 263,000

Common stock, shares issued

36,585,000

30,806,000

36,585,000

30,806,000

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

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 B Loan) [Member] | Oxford Finance [Member]

Class of Warrant or Right [Line Items]

Common stock, shares issued

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

$ 0.2571

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]

Warrants to purchase shares of stock, shares

233,372

Warrants to purchase shares of stock, term

10 years

Term Loan [Member]

Class of Warrant or Right [Line Items]

Warrants exercisable, shares

53,648

53,648

Warrants exercisable, exercise price

$ 7.46

$ 7.46

$ 7.46

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

Class of Warrant or Right [Line Items]

Warrants to purchase shares of stock, shares

1,555,815

Warrant to purchase shares of stock, exercise price per share

$ 0.2571

Warrants 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

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

Class of Warrant or Right [Line Items]

Warrants to purchase shares of stock, shares

964,605

Warrant to purchase shares of stock, exercise price per share

$ 0.2571

Warrants to purchase shares of stock, term

10 years

Fair value of Warrant

$ 241,000

Risk-free interest rate

1.80%

Expected dividend yield

0.00%

Expected volatility rate

61.00%

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) - $ / shares	1 Months Ended	12 Months Ended
	Feb. 28, 2013	Dec. 31, 2015	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 - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended					12 Months Ended
	Mar. 31, 2015	Oct. 31, 2014	Nov. 30, 2013	Apr. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Shareholders Equity [Line Items]
Proceeds from issuing of shares						$ 4,910	$ 1,504	$ 96
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
Underwriting discounts					4,400
Offering costs					$ 2,500
Conversion to common shares from preferred shares					8,828,438
Proceeds from issuing of shares				$ 5,200
Follow on Public Offering [Member]
Shareholders Equity [Line Items]
Common stock, shares issued	4,945,000	4,542,500	4,907,403
Common stock, issue price	$ 35	$ 19	$ 10
Offering costs	$ 500	$ 400	$ 500
Proceeds from issuing of shares	162,200	80,800	45,600
Underwriting discounts and commissions	$ 10,400	$ 5,200	$ 2,900

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) - USD ($)	Oct. 31, 2015	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014	Feb. 28, 2013	May. 31, 2010	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Aug. 31, 2006
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total intrinsic value of options exercised							$ 27,000,000	$ 8,100,000	$ 500,000
Unrecognized stock-based compensation cost related to the unvested stock option							$ 24,800,000
Weighted average period to recognize compensation cost unvested stock option							2 years 6 months
Stock-based compensation expense							$ 11,616,000	$ 5,230,000	$ 1,301,000
Weighted average fair value of options granted							$ 22.78	$ 7.54	$ 4.52
Dividend rate							0.00%	0.00%	0.00%
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
Stock-based compensation expense (reversal)							$ (1,000,000)
Options granted to purchase of common stock							0	110,000	0
Weighted average Exercise price of Options granted to non-employee								$ 12.56
Risk-free interest rate							2.17%	2.11%
Dividend rate							0.00%	0.00%
Expected volatility							86.02%	56.69%
Expected term							8 years 7 months 6 days	9 years 3 months 18 days
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
Stock Options and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense							$ 12,600,000	$ 4,000,000	$ 1,300,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period	1 year
Unrecognized stock-based compensation cost related to the unvested stock option							1,800,000
Stock-based compensation expense							$ 600,000
Share based compensation, grant price	$ 7.81						$ 7.81
Weighted-average period of cost expected to be recognized							9 months 18 days
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					258,265		0
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			1,232,232	1,025,171
Outstanding shares available for future grants							337,628
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		1,463,391

Stock-based Compensation - Stoc

Stock-based Compensation - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Number of Shares
Beginning balance	3,409,497
Granted	1,834,500
Exercised	(817,567)
Canceled	(592,624)
Ending balance	3,833,806	3,409,497
Options vested or expected to vest at December 31, 2015	3,367,031
Options exercisable at December 31, 2015	1,527,086
Weighted Average Exercise Price
Beginning balance	$ 5.10
Granted	40.90
Exercised	5.71
Canceled	22.08
Ending balance	22.72	$ 5.10
Options vested or expected to vest at December 31, 2015	21.37
Options exercisable at December 31, 2015	$ 12.35
Weighted Average Remaining Contractual Term
Weighted-Average Remaining Contractual Term	7 years 9 months 18 days	7 years 11 months 19 days
Options vested or expected to vest at December 31, 2015	6 years 11 months 9 days
Options exercisable at December 31, 2015	6 years 6 months 22 days
Aggregate Intrinsic Value
Options outstanding	$ 5,439	$ 23,960
Options vested or expected to vest at December 31, 2015	5,309
Options exercisable at December 31, 2015	$ 4,427

Stock-based Compensation - St45

Stock-based Compensation - Stock Option Activity (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Estimated forfeiture rate	18.20%

Stock-based Compensation - Assu

Stock-based Compensation - Assumptions Used to Estimate Fair Value of Employee and Director Stock Option Award (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility factor, Minimum	56.49%	53.41%	54.50%
Volatility factor, Maximum	85.34%	58.13%	60.54%
Risk-free interest rate, Minimum	1.35%	1.71%	0.91%
Risk-free interest rate, Maximum	1.94%	2.13%	2.01%
Dividend yield	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	5 years 3 months 22 days	5 years 3 months 22 days	5 years 9 months 18 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	6 years 1 month 10 days	6 years 1 month 10 days	7 years 1 month 6 days

Stock-based Compensation - St47

Stock-based Compensation - Stock-based Compensation Expense Recognized in the Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 11,616	$ 5,230	$ 1,301
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	5,906	1,845	690
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 5,710	$ 3,385	$ 611

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Restricted Stock Activity (Detail) - Restricted Stock Units [Member]	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Number of Shares
Granted | shares	309,750
Cancelled | shares	(875)
Ending balance | shares	308,875
Weighted-Average Exercise Price
Granted | $ / shares	$ 7.81
Cancelled | $ / shares	7.81
Ending balance | $ / shares	$ 7.81

Employee Stock Purchase Plan -

Employee Stock Purchase Plan - Additional Information (Detail) - USD ($)	Nov. 13, 2015	Nov. 17, 2014	Feb. 27, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price granted				$ 40.90
Stock-based compensation expense				$ 11,616,000	$ 5,230,000	$ 1,301,000
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			300,000	16,422	8,394
Purchase price granted	$ 9.30	$ 19.29			$ 9.88
Exercise price for awards granted as percentage of market value on the date of grant			85.00%	85.00%	85.00%
Stock-based compensation expense				$ 156,000	$ 46,000
Employee [Member] | First Offering Period [Member] | 2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options offering date			Aug. 15, 2014
Stock options expiration date			Nov. 14, 2014
Employee [Member] | Second Offering Period [Member] | 2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options offering date				Nov. 15, 2014
Stock options expiration date				May 14, 2015
Employee [Member] | Third Offering Period [Member] | 2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options offering date				May 15, 2015
Stock options expiration date				Nov. 14, 2015
Employee [Member] | Fourth Offering Period [Member] | 2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options offering date				Nov. 15, 2015
Stock options expiration date				May 14, 2016

Income Taxes - Schedule of Loss

Income Taxes - Schedule of Loss Before Income Tax (Benefit) Provision (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
United States	$ (64,037)	$ (66,742)	$ (29,636)
Foreign	(19,152)
Total loss before income taxes	$ (83,189)	$ (66,742)	$ (29,636)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Income Taxes [Line Items]
Current income tax expense benefit	$ 0	$ 0	$ 0
Deferred income tax expense benefit	$ 0	$ 0	$ 0
Statutory tax rate	(34.00%)	(34.00%)	(34.00%)
Deductions related to exercise of stock options	$ 26,900,000
Minimum percentage of ownership interest of significant shareholders to limit the carryforward of losses	50.00%
Increase in valuation allowance	$ 25,600,000
Unrecognized tax benefits	822,000	$ 0
Expected increase in unrecognized tax benefits	0
Expected decrease in unrecognized tax benefits	0
Accrued interest and penalties related to uncertain tax position	$ 0	$ 0
Earliest Tax Year
Schedule Of Income Taxes [Line Items]
Open Tax Year	2,012
Latest Tax Year
Schedule Of Income Taxes [Line Items]
Open Tax Year	2,014
Federal [Member]
Schedule Of Income Taxes [Line Items]
NOL carryforwards	$ 225,600,000
NOL tax credit carryforward	5,300,000
State and Local Jurisdiction [Member]
Schedule Of Income Taxes [Line Items]
NOL carryforwards	192,500,000
NOL tax credit carryforward	$ 1,900,000

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Federal Statutory Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Statutory tax rate	(34.00%)	(34.00%)	(34.00%)
State taxes, net of Federal benefits	(4.02%)	(5.28%)	(5.28%)
Permanent differences	0.71%	0.61%	0.93%
Credits	(1.65%)	(2.34%)	(4.33%)
Change in valuation allowance	30.74%	39.87%	39.92%
Foreign rate differential	7.03%
Other	1.19%	1.14%	2.76%
Effective tax rate	0.00%	0.00%	0.00%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carry forwards	$ 86,880	$ 65,370
Temporary differences	5,916	3,224
Research and development credit and carry forwards	6,543	5,170
Deferred tax assets	99,339	73,764
Less valuation allowance	(99,339)	(73,764)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Aggregate Change

Income Taxes - Aggregate Changes in Gross Unrecognized Tax Benefits (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 0
Increases for tax positions taken during current period	249,000
Increases for tax positions taken in prior periods	573,000
Balance at end of year	$ 822,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Aug. 01, 2015ft²	Apr. 01, 2015ft²	Mar. 31, 2015ft²
Schedule Of Commitments And Contingencies [Line Items]
Rent expense | $	$ 1.7	$ 1	$ 0.6
Existing Lease Amended on March 24, 2015 [Member]
Schedule Of Commitments And Contingencies [Line Items]
Area of office and laboratory					29,610
Additional area of office and laboratory					13,711
Canceled Lease Agreement [Member]
Schedule Of Commitments And Contingencies [Line Items]
Area of office and laboratory						15,174
Existing Lease Amended on June 18, 2015 [Member]
Schedule Of Commitments And Contingencies [Line Items]
Area of office and laboratory				37,438
Additional area of office and laboratory				7,828
Amended operating lease expiration date	Nov. 30, 2019

Commitments and Contingencies56

Commitments and Contingencies - Minimum Future Rent Payments Under Lease and Sublease Agreements (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,016	$ 1,645
2,017	1,701
2,018	1,752
2,019	1,650
Total minimum lease payments	$ 6,748

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Compensation And Retirement Disclosure [Abstract]
Percentage of matching contribution of employee contribution to the plan		50.00%
Matching contribution limit of employee's compensation		6.00%
Company's matching contribution to the plan	$ 261,000	$ 84,000

Quarterly Results (Unaudited) -

Quarterly Results (Unaudited) - Summary of Selected Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 2,471	$ 2,856	$ 3,343	$ 3,016	$ 3,072	$ 2,294	$ 1,275	$ 2,457	$ 11,686	$ 9,098	$ 10,486
Operating expenses	20,603	20,909	29,396	23,776	23,455	16,274	19,460	15,675	94,684	74,864	38,676
Loss from operations	(18,132)	(18,053)	(26,053)	(20,760)	(20,383)	(13,980)	(18,185)	(13,218)	(82,998)	(65,766)	(28,190)
Other income (expense)	16	9	10	(226)	(167)	(226)	(278)	(305)	(2)	24	263
Net loss	$ (18,116)	$ (18,044)	$ (26,043)	$ (20,986)	$ (20,550)	$ (14,206)	$ (18,463)	$ (13,523)	$ (83,189)	$ (66,742)	$ (29,636)
Net loss per share-basic and diluted	$ (0.50)	$ (0.49)	$ (0.72)	$ (0.66)	$ (0.69)	$ (0.55)	$ (0.71)	$ (0.53)	$ (2.36)	$ (2.49)	$ (1.78)