Trevena (TRVN) 10-K 7 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Mar. 02, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	TREVENA INC
Entity Central Index Key	1,429,560
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 94
Entity Common Stock, Shares Outstanding		64,785,659
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 16,557	$ 24,266
Marketable securities	49,543	86,335
Prepaid expenses and other current assets	1,393	1,788
Total current assets	67,493	112,389
Restricted cash	1,413	1,193
Property and equipment, net	3,805	1,059
Intangible asset, net	11	13
Total assets	72,722	114,654
Current liabilities:
Accounts payable	1,424	8,749
Accrued expenses and other current liabilities	4,303	8,208
Current portion of loans payable, net	12,425	5,039
Deferred rent	61	52
Total current liabilities	18,213	22,048
Loans payable, net	15,725	13,270
Capital leases, net of current portion	31	18
Deferred rent, net of current portion	3,006	187
Warrant liability	10	75
Other long term liabilities	1,104	475
Total liabilities	38,089	36,073
Commitments and contingencies (Note 8)
Stockholders’ equity:
Common stock—$0.001 par value; 100,000,000 shares authorized, 62,310,795 and 55,768,414 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively	62	56
Preferred stock—$0.001 par value; 5,000,000 shares authorized, none issued or outstanding at December 31, 2017 and December 31, 2016	0	0
Additional paid-in capital	392,103	364,148
Accumulated deficit	(357,490)	(285,625)
Accumulated other comprehensive income (loss)	(42)	2
Total stockholders’ equity	34,633	78,581
Total liabilities and stockholders’ equity	$ 72,722	$ 114,654

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock authorized (in shares)	100,000,000	100,000,000
Common stock issued (in shares)	62,310,795	55,768,414
Common stock outstanding (in shares)	62,310,795	55,768,414
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock authorized (in shares)	5,000,000	5,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Collaboration revenue	$ 0	$ 3,750	$ 6,250
Total revenue	0	3,750	6,250
Operating expenses:
General and administrative	19,639	16,077	12,797
Research and development	48,974	89,956	44,074
Restructuring charges	1,774	0	0
Total operating expenses	70,387	106,033	56,871
Loss from operations	(70,387)	(102,283)	(50,621)
Other income (expense):
Change in fair value of warrant liability	65	78	(70)
Miscellaneous income	614	222	174
Net (loss) gain on asset disposals	(56)	(16)	(8)
Interest income	679	743	331
Interest expense	(2,780)	(1,738)	(334)
Total other (expense) income	(1,478)	(711)	93
Net loss attributable to common stockholders	(71,865)	(102,994)	(50,528)
Other comprehensive income (loss), net:
Unrealized gain (loss) on marketable securities	(44)	208	(187)
Other comprehensive income (loss)	(44)	208	(187)
Comprehensive loss	$ (71,909)	$ (102,786)	$ (50,715)
Per share information:
Net loss per share of common stock—basic and diluted (in dollars per share)	$ (1.21)	$ (1.97)	$ (1.15)
Weighted average common shares outstanding, basic and diluted (in shares)	59,436,649	52,398,521	43,794,276

Statements of Stockholders' Equ

Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2014	$ 99,203	$ 39	$ 231,153	$ (131,970)	$ (19)
Balance (in shares) at Dec. 31, 2014		39,241,173
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense	3,427		3,427
Exercise of stock options	906	$ 1	905
Exercise of stock options (in shares)		384,033
Net exercise of common stock warrant	0
Net exercise of common stock warrant (in shares)		2,397
Issuance of common stock warrants	4		4
Issuance of common stock, net of issuance costs	90,306	$ 11	90,295
Issuance of common stock, net of issuance costs (in shares)		11,175,000
Unrealized gain (loss) on marketable securities	(187)				(187)
Net loss	(50,528)			(50,528)
Ending balance at Dec. 31, 2015	143,131	$ 51	325,784	(182,498)	(206)
Balance (in shares) at Dec. 31, 2015		50,802,603
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense	5,903		5,903
Exercise of stock options	256		256
Exercise of stock options (in shares)		149,622
Net exercise of common stock warrant	0
Net exercise of common stock warrant (in shares)		698
Issuance of common stock, net of issuance costs	32,077	$ 5	32,072
Issuance of common stock, net of issuance costs (in shares)		4,815,491
Unrealized gain (loss) on marketable securities	208				208
Adjustment to accumulated deficit as a result of adoption of ASU 2016-09	0		133	(133)
Net loss	(102,994)			(102,994)
Ending balance at Dec. 31, 2016	$ 78,581	$ 56	364,148	(285,625)	2
Balance (in shares) at Dec. 31, 2016	55,768,414	55,768,414
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense	$ 6,387		6,387
Exercise of stock options	361		361
Exercise of stock options (in shares)		293,809
Issuance of common stock warrants	501		501
Issuance of common stock, net of issuance costs	20,712	$ 6	20,706
Issuance of common stock, net of issuance costs (in shares)		6,248,572
Unrealized gain (loss) on marketable securities	(44)				(44)
Net loss	(71,865)			(71,865)
Ending balance at Dec. 31, 2017	$ 34,633	$ 62	$ 392,103	$ (357,490)	$ (42)
Balance (in shares) at Dec. 31, 2017	62,310,795	62,310,795

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net loss	$ (71,865)	$ (102,994)	$ (50,528)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	490	246	208
Stock-based compensation	6,387	5,903	3,427
Noncash interest expense on loans	1,050	534	180
Loss on disposal of assets	70	17	11
Revaluation of warrant liability	(65)	(78)	70
Amortization of bond premiums on marketable securities	474	1,334	1,210
Changes in operating assets and liabilities:
Prepaid expenses and other assets	612	104	(1,224)
Accounts payable and accrued expenses	(8,408)	7,130	2,821
Deferred revenue	0	(3,750)	3,750
Net cash used in operating activities	(71,255)	(91,554)	(40,075)
Investing activities:
Purchases of property and equipment	(3,495)	(605)	(361)
Purchase of intangible asset		0	(15)
Maturities of marketable securities	99,018	115,824	69,827
Purchases of marketable securities	(62,743)	(77,421)	(126,390)
Net cash provided by (used in) investing activities	32,780	37,798	(56,939)
Financing activities:
Proceeds from exercise of common stock options	361	256	906
Proceeds from loans payable, net	9,921	0	16,368
Proceeds from issuance of common stock, net	20,712	32,077	90,311
Capital lease payments	(8)	(4)	(3)
Net cash provided by financing activities	30,986	32,329	107,582
Net (decrease) increase in cash and cash equivalents	(7,489)	(21,427)	10,568
Cash, cash equivalents, and restricted cash—beginning of period	25,459	46,886	36,318
Cash, cash equivalents, and restricted cash—end of period	17,970	25,459	46,886
Supplemental disclosure of cash flow information:
Cash paid for interest	1,730	1,204	155
Capital lease additions	27	18	0
Common Stock
Supplemental disclosure of cash flow information:
Fair value of common stock warrants issued	$ 501	$ 0	$ 4

Organization and Description of

Organization and Description of the Business	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of the Business	Organization and Description of the Business Trevena, Inc., or the Company, was incorporated in Delaware as Parallax Therapeutics, Inc. on November 9, 2007. The Company began operations in December 2007, and its name was changed to Trevena, Inc. on January 3, 2008. The Company is a biopharmaceutical company developing innovative therapies based on breakthrough science to benefit patients and healthcare providers confronting serious medical conditions. The Company operates in one segment and has its principal office in Chesterbrook, Pennsylvania. Since commencing operations in 2007, the Company has devoted substantially all of its financial resources and efforts to research and development, including preclinical studies and clinical trials. The Company has never been profitable and has not yet commenced commercial operations. In January 2018, the United States Food and Drug Administration, or FDA, accepted the NDA submission for OLINVO, the Company's lead product candidate. The FDA also indicated that the Prescription Drug User Fee Act, or PDUFA, review date for the OLINVO NDA is November 2, 2018 and that it plans to hold an advisory committee meeting to discuss the NDA. If OLINVO ultimately receives regulatory approval, the Company plans to commercialize it in the United States, either on its own or with a commercial partner, for use in acute care settings such as hospitals and ambulatory surgery centers; outside the United States, the Company plans to commercialize OLINVO in certain countries with commercial partners. Since the Company's inception, the Company has incurred losses and negative cash flows from operations. At December 31, 2017 , the Company had an accumulated deficit of $357.5 million . The Company’s net loss was $71.9 million , $103.0 million and $50.5 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. The Company expects its cash and cash equivalents of $16.6 million and marketable securities of $49.5 million as of December 31, 2017 , together with interest thereon, to be sufficient to fund its operating expenses and capital expenditure requirements into the second quarter of 2019.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America, or U.S. GAAP. Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB. The Company’s functional currency is the U.S. dollar. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumption that affect the amounts reported in the financial statements and accompanying notes. Management used significant estimates in the following areas, among others: stock-based compensation expense, the determination of the fair value of stock-based awards, the fair value of liability-classified common stock warrants, the accounting for research and development costs, accrued expenses and the recoverability of the Company’s net deferred tax assets and related valuation allowance. The financial data and other information disclosed in these notes are not necessarily indicative of the results to be expected for any future year or period. The Company bases its estimates on historical experience and also on assumptions that it believes are reasonable, however, actual results could significantly differ from those results. Cash and Cash Equivalents and Marketable Securities The Company considers all highly liquid investments that have maturities of three months or less when acquired to be cash equivalents. Cash equivalents are valued at cost, which approximates their fair market value. The Company maintains a portion of its cash and cash equivalent balances in money market mutual funds that may invest substantially all of their assets in U.S. government agency securities, U.S. Treasury securities or reverse repurchase agreements, or RRAs. RRAs are collateralized by deposits in the form of ‘Government Securities and Obligations’ for an amount not less than 102% of their value. The Company does not hold any RRAs as of December 31, 2017 . The Company classifies its marketable securities as “available-for-sale”, pursuant to ASC Topic 320, Investments—Debt and Equity Securities , or ASC 320, carries them at fair market value and classifies them as current assets on its balance sheets. Unrealized gains and losses on marketable securities are recorded as a separate component of accumulated other comprehensive income/(loss) included in stockholders’ equity. As of December 31, 2017 and 2016 , the Company had $49.5 million and $86.3 million , respectively, in available-for-sale investments, all classified as current assets. See Note 3 for additional information. The fair value of the Company’s investments is determined based on observable market quotes or valuation models using assessments of counterparty credit worthiness, credit default risk of underlying security and overall capital market liquidity. The Company reviews unrealized losses associated with available-for-sale securities to determine the classification as “temporary” or “other-than-temporary” impairment. A temporary impairment results in an unrealized loss being recorded in other comprehensive income (loss). If a decline in the fair value is considered other-than-temporary, based on available evidence, the unrealized loss is transferred from other comprehensive income (loss) to the statement of operations. The Company considers various factors in determining the classification, including the length of time and extent to which the fair value has been less than the Company’s cost basis, the financial condition and near-term prospects of the issuer or investee, and the Company’s ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. Realized gains (losses) are included in interest income (expense) in the statement of operations and comprehensive income (loss) on a specific identification basis. Restricted Cash The Company maintains $1.3 million as collateral under a letter of credit for the Company’s facility lease obligations in Chesterbrook, Pennsylvania. The Company also maintains a letter of credit totaling $0.1 million as collateral for the Company’s facility lease obligations in King of Prussia, Pennsylvania. The Company has recorded these deposits and accumulated interest thereon as restricted cash on its balance sheet. Fair Value of Financial Instruments The carrying amount of the Company’s financial instruments, which include cash and cash equivalents, marketable securities, restricted cash, accounts payable and accrued expenses approximate their fair values, given their short-term nature. The carrying amount of the Company’s loans payable at December 31, 2017 and 2016 is the nominal value of the loan payable, which is the carrying value, net of debt discount and deferred charges. The nominal value approximates fair value because the interest rate is reflective of the rate the Company could obtain on debt with similar terms and conditions. Certain of the Company’s common stock warrants are carried at fair value, as disclosed in Note 3. The Company has evaluated the estimated fair value of financial instruments using available market information and management’s estimates. The use of different market assumptions and/or estimation methodologies could have a significant effect on the estimated fair value amounts. See Note 3 for additional information. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash, cash equivalents, marketable securities and restricted cash. The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimizes the exposure to concentration of credit risk. The Company has no off-balance sheet concentrations of credit risk such as foreign currency exchange contracts, option contracts or other hedging arrangements. Property and Equipment Property and equipment consists of computer and laboratory equipment, software, office equipment, furniture, manufacturing equipment and leasehold improvements and is recorded at cost. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred. Upon disposal, retirement or sale, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in the results of operations. Property and equipment are depreciated on a straight‑line basis over their estimated useful lives. The Company uses a life of three years for computer equipment and five years for laboratory equipment, office equipment, furniture, manufacturing equipment and software. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset. The Company reviews long‑lived assets when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparison of the book values of the assets to future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value, which is measured based on the projected discounted future net cash flows arising from the assets. No impairment losses have been recorded since inception. Intangible Asset The intangible asset recorded in the Company's financial statements is associated with the acquisition of the domain name for the Company's website. Identifiable intangible assets are initially recorded at fair market value at the time of acquisition, utilizing a cost approach and the initial value is amortized over the expected useful life of the asset. The Company also capitalizes costs incurred to renew or extend the term of recognized intangible assets. The determination of the value of intangible assets requires management to make estimates and assumptions that affect the Company’s consolidated financial statements. The Company assesses potential impairments to intangible assets when there is evidence of events or changes in circumstances that indicate the carrying amount of an asset may not be recovered. The Company’s judgements regarding the existence of impairment indicators and future cash flows related to intangible assets are based on operational performance of the Company, market conditions and other factors. If impairment is indicated, the Company will reduce the carrying value of the intangible assets to fair value. The Company believes the future cash flows to be received from its intangible asset will exceed the intangible asset carrying value, and accordingly, the Company has not recognized any impairment losses through December 31, 2017 . Common Stock Warrants Freestanding warrants that are related to the purchase of common stock are classified as liabilities and recorded at fair value regardless of the timing of the redemption feature or the redemption price or the likelihood of redemption. These warrants are subject to re-measurement at each balance sheet date and any change in fair value is recognized as a component of change in fair value of warrant liability in the statements of operations and comprehensive loss. The Company will continue to adjust the liability for changes in fair value until the earlier of the exercise or expiration of the warrants. The warrants are classified as Level 3 liabilities. See Note 3 for additional information. In addition, in connection with entering into loan agreements, the Company has issued warrants to purchase shares of the Company’s common stock. These detachable warrant instruments qualify for equity classification and have been allocated upon the relative fair value of the base instrument and the warrant. See Note 6 for additional information. Segment Information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the chief executive officer. The Company and the chief executive officer view the Company’s operations and manage its business as one operating segment. All long-lived assets of the Company reside in the United States. Revenue The Company recognizes collaboration revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price is fixed and determinable, and collectibility is reasonably assured. Research and Development Research and development cost are charged to expense as incurred. Research and development costs include, but are not limited to, personnel expenses, clinical trial supplies, fees for clinical trial services, manufacturing costs, consulting costs and allocated overhead, including rent, equipment, depreciation and utilities. 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 subject enrollment, clinical site activations or information provided to the Company by its vendors with respect to 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 expense, as the case may be. As part of the process of preparing its financial statements, the Company is required to estimate its expenses resulting from its obligations under contracts with vendors, clinical research organizations and consultants, and under clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. The Company’s objective is to reflect the appropriate trial expenses in its financial statements by matching those expenses with the period in which services are performed and efforts are expended. The Company may account for these expenses according to the progress of the trial as measured by subject progression and the timing of various aspects of the trial. The Company determines accrual estimates through financial models taking into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of trials, or the services completed. During the course of a clinical trial, the Company adjusts its clinical expense recognition if actual results differ from its estimates. The Company makes estimates of its accrued expenses as of each balance sheet date based on the facts and circumstances known to it at that time. The Company’s clinical trial accruals are dependent upon the timely and accurate reporting of contract research organizations and other third party vendors. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in it reporting amounts that are too high or too low for any particular period. For the years ended December 31, 2017 , 2016 and 2015 , there were no material adjustments to the Company’s prior period estimates of accrued expenses for clinical trials. Stock‑Based Compensation At December 31, 2017 , the Company had two stock‑based compensation plans, which are more fully described in Note 7. The Company has applied the fair value recognition provisions of Financial Accounting Standards Board Accounting Standards Codification Topic 718, Compensation — Stock Compensation , to account for stock-based compensation for employees. The Company recognizes compensation costs related to stock options granted to employees based on the estimated fair value of the awards on the date of grant. The Company has equity incentive plans under which various types of equity-based awards including, but not limited to, incentive stock options, non-qualified stock options, and restricted stock awards, may be granted to employees, non-employee directors, and non-employee consultants. The Company also has an inducement plan under which various types of equity-based awards, including non-qualified stock options and restricted stock awards, may be granted to new employees. For stock options granted to employees and directors, the Company recognizes compensation expense for all stock-based awards based on the estimated grant-date fair values. For restricted stock awards to employees, the fair value is based on the closing price of the Company's common stock on the date of grant. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service period. The fair value of stock options is determined using the Black-Scholes option pricing model. The Company utilizes a dividend yield of zero based on the fact that the Company has never paid cash dividends and has no current intention of paying cash dividends. As of fiscal year ended December 31, 2016 , the Company adopted the forfeiture rate methodology change in accordance with ASU 2016-9 to record forfeitures as they occur. See Note 7 for a discussion of the assumptions used by the Company in determining the grant date fair value of options granted under the Black‑Scholes option pricing model, as well as a summary of the stock option activity under the Company’s stock‑based compensation plan for all years presented. Income Taxes Income taxes are recorded in accordance with ASC Topic 740, Income Taxes , or ASC 740, which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position, as well as consideration of the available facts and circumstances. To date, the Company has not taken any uncertain tax position or recorded any reserves, interest or penalties. On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act, or the Tax Act. Additionally, the SEC staff issued SAB 118, which provides guidance on accounting for the effects of the Tax Act. See Note 13. Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive income (loss) relates to unrealized investment gains or losses on the Company’s marketable securities for all periods presented. Basic and Diluted Net Loss Per Share of Common Stock The Company’s 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. The diluted net loss per common share is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period. Because the impact of these items is anti‑dilutive during periods of net loss, there was no difference between basic and diluted net loss per share of common stock for all periods presented. Recently Adopted Accounting Standards In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, or ASU 2016-09, which amends ASC Topic 718, Compensation— Stock Compensation . ASU 2016-09 is designed to simplify several aspects of accounting for share-based payment award transactions that include the income tax consequences, classification of awards as either equity or liabilities, and classification of excess tax benefits on the statement of cash flows. This guidance also permits an accounting policy election to either estimate the number of awards that are expected to vest or account for forfeitures when they occur. The Company elected to early adopt the standard during the three months ended December 31, 2016 and has elected to recognize forfeitures as they occur. The adoption did not have a material effect on the Company's interim and annual 2016 financial statements. Recent Accounting Standards Not Yet Adopted In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income , which provides the option to reclassify stranded tax effects within accumulated other comprehensive income to retained earnings. This option would be available in each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Cuts and Jobs Act (or a portion thereof) is recorded. This is effective for the Company beginning after December 15, 2018, with early adoption permitted. These amendments should be applied in the period of adoption or retrospectively to each period in which the effect of the change in the U.S federal corporate income tax rate in the Tax Cuts and Jobs Act is recognized. The Company is evaluating the effect this standard will have on its financial statements and related disclosures. See Note 13. In May 2017, the FASB issued ASU No. 2017-09, Stock Compensation - Scope of Modification Accounting, which amends the scope of modification accounting for share-based payment arrangements. The amendment provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The new standard is effective for fiscal years beginning after December 15, 2017. The Company is currently evaluating the effect that this guidance may have on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230), to clarify how certain cash receipts and payments should be presented in the statement of cash flows. The standard is effective for annual periods beginning after December 15, 2017 and interim periods within that reporting period. Early adoption is permitted. The Company is evaluating the effect this standard will have on its financial statements and related disclosures. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842 ), which requires lessees to record most leases on their balance sheets and disclose key information about leasing arrangements in an effort to increase transparency and comparability among organizations. The standard is effective for annual periods beginning after December 15, 2018 and interim periods within that reporting period. Early adoption is permitted. The Company is evaluating the effect this standard will have on its financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers . ASU 2014-09 is a comprehensive new revenue recognition model requiring a company to recognize revenue to depict the transfer of goods or services to a customer in an amount reflecting the consideration it expects to receive in exchange for those goods or services. Additionally, in March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers, Principal versus Agent Considerations . ASU 2016-08 amends the principal versus agent guidance in ASU 2014-09 to clarify how an entity should identify the unit of accounting for the principal versus agent evaluation and how it should apply the control principal to certain types of arrangements. The effective date for both standards is January 1, 2018, with an option that permits companies to adopt the standard as early as the January 1, 2017 . Early application prior to the January 1, 2017 is not permitted. The Company has determined that they will elect the modified retrospective transition method, meaning the cumulative effect of applying the new guidance is recognized at the date of initial application as an adjustment to the opening accumulated deficit balance. Since the Company does not have any open contracts with customers as of December 31, 2017, the adoption of this standard is not expected to have a material impact on the Company's financial statements.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments ASC Topic 820, Fair Value Measurement, or ASC 820, establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes among the following: Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access. Level 2—Valuations based on quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active and models for which all significant inputs are observable, either directly or indirectly. Level 3—Valuations based on inputs that are unobservable and significant to the overall fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Cash, Cash Equivalents, Restricted Cash, and Marketable Securities The following table presents the Company’s cash, cash equivalents, restricted cash, and marketable securities as of December 31, 2017 and 2016 (in thousands): December 31, 2017 Adjusted Cost Unrealized Gains Unrealized Losses Fair Value Cash and Cash Equivalents Restricted Cash Marketable Securities Cash $ 6,783 $ — $ — $ 6,783 $ 5,370 $ 1,413 $ — Level 1 (1): Money market funds 11,187 — — 11,187 11,187 — — U.S. treasury securities 1,991 — — 1,991 — — 1,991 Subtotal 13,178 — — 13,178 11,187 — 1,991 Level 2 (2): U.S. government agency securities 47,594 — (42 ) 47,552 — — 47,552 Total $ 67,555 $ — $ (42 ) $ 67,513 $ 16,557 $ 1,413 $ 49,543 December 31, 2016 Adjusted Cost Unrealized Gains Unrealized Losses Fair Value Cash and Cash Equivalents Restricted Cash Marketable Securities Cash $ 13,756 $ — $ — $ 13,756 $ 12,563 $ 1,193 $ — Level 1 (1): Money market funds 10,043 — — 10,043 10,043 — — Level 2 (2): Repurchase agreements 1,660 1,660 1,660 U.S. government agency securities 86,333 19 (17 ) 86,335 — — 86,335 Subtotal 87,993 19 (17 ) 87,995 1,660 — 86,335 Total $ 111,792 $ 19 $ (17 ) $ 111,794 $ 24,266 $ 1,193 $ 86,335 (1) The fair value of Level 1 securities is estimated based on quoted prices in active markets for identical assets or liabilities. (2) The fair value of Level 2 securities is estimated based on observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term on the assets or liabilities. The Company classifies investments available to fund current operations as current assets on its balance sheets. As of December 31, 2017 , the Company did not hold any investment securities exceeding a one-year maturity. Unrealized gains and losses on marketable securities are recorded as a separate component of accumulated other comprehensive income (loss) included in stockholders’ equity. Realized gains (losses) are included in interest income (expense) in the statement of operations and comprehensive income (loss) on a specific identification basis. The Company did not record any realized gains or losses during the years ended December 31, 2017 and 2016 . To date, the Company has not recorded any impairment charges on marketable securities related to other-than-temporary declines in market value. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. We do not hold Level 3 securities, and therefore, there were no transfers in or out of Level 3 in the hierarchy during the years ended December 31, 2017 or 2016 . Warrant Liability At December 31, 2017 , there is an outstanding warrant to purchase up to 20,161 shares of the Company’s common stock with a fair value recorded as a liability as it contains a cash settlement feature upon certain strategic transactions. The following table sets forth a summary of changes in the fair value of this warrant liability, which represents a recurring measurement that is classified within Level 3 of the fair value hierarchy, wherein fair value is estimated using significant unobservable inputs (in thousands): Warrant Liability Balance as of January 1, 2016 $ 153 Amounts acquired or issued — Changes in estimated fair value (78 ) Balance as of December 31, 2016 75 Amounts acquired or issued — Changes in estimated fair value (65 ) Balance as of December 31, 2017 $ 10 On each re-measurement date, the fair value of the warrant classified as a liability is estimated using the Black-Scholes option pricing model. For this liability, the Company develops its own assumptions that do not have observable inputs or available market data to support the fair value. This method of valuation involves using inputs such as the fair value of the Company’s common stock, stock price volatility, the contractual term of the warrants, risk-free interest rates and dividend yields. Due to the nature of these inputs, the valuation of the warrants is considered a Level 3 measurement. The following assumptions were used at December 31, 2017 and 2016 to determine the warrant liability: December 31, 2017 2016 Estimated remaining term 4.3 years 5.3 years Risk-free interest rate 2.1 % 2.0 % Volatility 77.6 % 77.2 % Dividend yield — % — % Fair value of underlying instrument* $ 1.60 $ 5.88 *Trevena, Inc. closing stock price. The warrant liability is recorded on its own line item on the Company’s balance sheets and is marked-to-market at each reporting period with the change in fair value recorded on its own line in the statements of operations and comprehensive loss. In addition to the outstanding warrant to purchase 20,161 shares of common stock discussed above, the Company has outstanding warrants to purchase an aggregate of 102,930 shares of the Company’s common stock. These warrants qualify for equity classification and have been allocated upon the relative fair value of the base instrument and the warrant. See Note 6 for additional information.

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment, net	Property and Equipment, net Property and equipment consisted of the following (in thousands): Estimated Useful December 31, Life in Years 2017 2016 Laboratory equipment 5 $ — $ 1,935 Computers and software 3 - 5 749 521 Office equipment and furniture 5 872 314 Manufacturing equipment 5 242 242 Leasehold improvements 5 - 10 4,824 2,150 Leased assets 5 59 32 Total property and equipment 6,746 5,194 Less accumulated depreciation and amortization (2,941 ) (4,135 ) Property and equipment, net $ 3,805 $ 1,059 Depreciation and amortization expense was $0.5 million , $0.2 million , and $0.2 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, 2017 2016 Compensation and benefits $ 2,489 $ 2,680 Clinical trial expenses — 5,479 Restructuring (severance) 1,077 — Pharmaceutical development expenses 444 — Accrued interest 158 — Other accrued expenses and other current liabilities 135 49 Total accrued expenses and other current liabilities $ 4,303 $ 8,208

Loans Payable

Loans Payable	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Loans Payable	Loans Payable In September 2014, the Company entered into a loan and security agreement with Oxford Finance LLC and Pacific Western Bank (formerly Square 1Bank) (together, the lenders), pursuant to which the lenders agreed to lend the Company up to $35.0 million in a three -tranche series of term loans (Term Loans A, B, and C). Upon initially entering into the agreement, the Company borrowed $2.0 million under Term Loan A. In April 2015, the Company amended the agreement with the lenders to change the draw period for Term Loan B. In December 2015, the Company further amended the agreement with the lenders to, among other things, change the draw period for Term Loan C, modify the interest only period, and modify the maturity date of the loan. In December 2015, the Company borrowed the Term Loan B tranche of $16.5 million . The Company’s ability to draw an additional $16.5 million under Term Loan C was subject to the satisfaction of one or more specified triggers related to the results of the Company’s Phase 2b clinical trial of TRV027, which were announced in May 2016. Although those triggers were not attained, in December 2016, the Company and the lenders modified the terms and conditions under which the Company could exercise an option to draw $10.0 million of Term Loan C. In March 2017, the Company borrowed the Term Loan C tranche of $10.0 million . Borrowings under Term Loans A and B accrue interest at a fixed rate of 6.50% per annum. Borrowings under Term Loan C accrue interest at a fixed rate of 6.98% per annum. The Company is required to make payments of interest only on borrowings under the loan agreement on a monthly basis through and including January 1, 2018, after which payments of principal in equal monthly installments and accrued interest will be due until the loan matures on March 1, 2020. Upon the last payment date of the amounts borrowed under the agreement, the Company will be required to pay a final payment fee equal to 6.6% of the aggregate amounts borrowed, which is recorded as interest expense over the term of the loans payable. In addition, if the Company repays Term Loan A, Term Loan B, or Term Loan C prior to the applicable maturity date, it will pay the lenders a prepayment fee of 1.0% of Term Loans A and B respectively, and 3.0% of Term Loan C if the prepayment occurs on or before March 31, 2018, 2.0% of Term Loan C if the prepayment occurs on or between April 1, 2018 and March 31, 2019, and 1.0% of the Term Loan C if the prepayment occurs on or after April 1, 2019. The Company’s obligations under the loan and security agreement are secured by a first priority security interest in substantially all of the assets of the Company, including the Company's cash, cash equivalents, and marketable securities but excluding the Company's intellectual property (together, the collateral). The Company has agreed not to pledge or otherwise encumber its intellectual property, other than through grants of certain permitted non-exclusive or exclusive licenses or other conveyances of its intellectual property. The loan and security agreement includes affirmative and restrictive covenants, including: (a) financial reporting requirements; (b) limitations on the incurrence of indebtedness; (c) limitations on liens; (d) limitations on certain merger and acquisition transactions; (e) limitations on dispositions of certain assets; (f) limitations on fundamental corporate changes (including changes in control); (g) limitations on investments; (h) limitations on payments and distributions and (i) other covenants. The agreement also contains certain events of default, including for payment defaults, breaches of covenants, a material adverse change in the Company’s business, operations or condition (financial or otherwise), a material impairment in the value of the collateral or in the prospect of repayment of the Company's obligations to the lender, certain levies, attachments and other restraints on the Company’s business, insolvency, defaults under other agreements and misrepresentations. Upon an event of default, the lenders have the right to foreclose upon the available collateral, including the Company's existing cash and cash equivalents and marketable securities. In connection with entering into the agreement, the Company issued to the lenders and the placement agent warrants to purchase an aggregate of 7,678 shares of Trevena common stock, of which 5,728 shares remain outstanding as of December 31, 2017 . These detachable warrant instruments have qualified for equity classification and have been allocated upon the relative fair value of the base instrument and the warrants, according to the guidance of ASC 470-20-25-2. These warrants are exercisable immediately and have an exercise price of $5.8610 per share. The warrants may be exercised on a cashless basis and will terminate on the earlier of September 19, 2024 or the closing of a merger or consolidation transaction in which the Company is not the surviving entity. In connection with the draw of Term Loan B, the Company issued to the lenders and the placement agent additional warrants to purchase an aggregate of 34,961 shares of Trevena common stock. These warrants have substantially the same terms as those noted above, have an exercise price of $10.6190 per share and an expiration date of December 23, 2025. In connection with draw of Term Loan C, the Company issued to the lenders and placement agent additional warrants to purchase an aggregate of 62,241 shares of our common stock. These warrants have substantially the same terms as those noted above, and have an exercise price of $3.6150 per share and an expiration date of March 31, 2027. As of December 31, 2017 , borrowings of $28.5 million attributable to Term Loans A, B and C are outstanding. Interest expense of $1.7 million , $1.2 million and $0.2 million was recorded during the years ended December 31, 2017 , 2016 and 2015, respectively. The Company incurred lender and third party costs of $1.0 million , related to the issuance of our term loans. Per ASU 2015-3, Interest-Imputation of Interest , debt discount and debt issuance costs are to be presented as a contra-liability to the debt on the balance sheet. These costs will be amortized to interest expense over the life of the loans using the effective interest method. A total of $0.3 million , $0.1 million and $0.1 million of debt discount and debt issuance costs were amortized to interest expense during the years ended December 31, 2017 , 2016 , and 2015 , respectively. The following table summarizes how the issuance of Term Loans A, B, and C are reflected on the balance sheet at December 31, 2017 (in thousands): December 31, Gross proceeds $ 28,500 Debt discount and debt issuance costs (350 ) Carrying value 28,150 Current portion of loans payable, net 12,425 Loans payable, net $ 15,725 Aggregate maturities of long term debt as of December 31, 2017 are as follows (in thousands): 2018 $ 12,667 2019 12,667 2020 3,166 2021 — 2022 — $ 28,500 Debt Discount and deferred financing costs (350 ) $ 28,150

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Equity Offerings Under its certificate of incorporation, the Company was authorized to issue up to 100,000,000 shares of common stock as of December 31, 2017 and December 31, 2016 , respectively. The Company also was authorized to issue up to 5,000,000 shares of preferred stock as of December 31, 2017 and December 31, 2016 . The Company is required, at all times, to reserve and keep available out of its authorized but unissued shares of common stock sufficient shares to effect the conversion of the shares of the preferred stock and all outstanding stock options and warrants. On December 14, 2015, the Company entered into an at the market, or ATM, sales agreement with Cowen and Company, LLC, or Cowen, to offer and sell, from time to time at its sole discretion, shares of its common stock, par value $0.001 per share, having an aggregate offering price of up to $75.0 million through Cowen as its sales agent. Sales of the shares are deemed to be “at the market offerings”, as defined in Rule 415 under the Securities Act of 1933, as amended. The Company will pay Cowen a commission of up to three percent of the gross sales proceeds and provided Cowen with customary indemnification rights. In 2017, the Company issued and sold 6,248,572 shares of common stock under this ATM facility at a weighted average price per share of $3.41 resulting in gross proceeds of $21.3 million . The net offering proceeds to the Company were approximately $20.7 million after deducting related expenses, including commissions. In 2016, the Company issued and sold 4,815,491 shares of common stock under this ATM facility at a weighted average price per share of $6.865 resulting in gross proceeds of $33.1 million . The net offering proceeds to the Company were approximately $32.1 million after deducting related expenses, including commissions. On September 16, 2015, the Company issued and sold 7,475,000 shares of common stock in a public offering at a price of $9.75 per share, for gross proceeds of approximately $72.9 million . The net offering proceeds to the Company were approximately $68.3 million , after deducting underwriting discounts and commissions of approximately $4.4 million and offering costs of $0.2 million . On April 3, 2015, the Company entered into an ATM agreement with Cowen to offer and sell, from time to time at the Company’s sole discretion, shares of its common stock, par value $0.001 per share, having an aggregate offering price of up to $40.0 million through Cowen as its sales agent. The Company paid Cowen a commission of up to three percent of the gross sales proceeds and provided Cowen with customary indemnification rights. In 2015, the Company issued and sold an aggregate of 3,700,000 shares of common stock at a weighted average price per share of $6.0001 for aggregate gross proceeds of $22.9 million . The net offering proceeds to the Company were approximately $22.0 million after deducting related expenses, including commissions. This ATM agreement is no longer in effect. Equity Incentive Plans In 2008, the Company adopted the 2008 Equity Incentive Plan, as amended on February 29, 2008, January 7, 2010, July 8, 2010, December 10, 2010, June 23, 2011 and June 17, 2013, collectively, the 2008 Plan, that authorized the Company to grant restricted stock and stock options to eligible employees, directors and consultants to the Company. In 2013, the Company adopted the 2013 Equity Incentive Plan, as amended on May 14, 2014, collectively, 2013 Plan. The 2013 Plan became effective upon the Company’s entry into the underwriting agreement related to its IPO in January 2014 and, as of such date, no further grants were permitted under the 2008 Plan. The 2013 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance-based stock awards and other forms of equity compensation (collectively, stock awards), all of which may be granted to employees, including officers, non-employee directors and consultants of the Company. Additionally, the 2013 Plan provides for the grant of cash and stock based performance awards. The 2013 Plan contains an “evergreen” provision, pursuant to which the number of shares of common stock available for issuance under the plan automatically increases on January 1 of each year beginning in 2015. On December 15, 2016, the Company adopted the Trevena, Inc. Inducement Plan, or the Inducement Plan, effective January 1, 2017, pursuant to which the Company reserved 500,000 shares of the Company’s common stock for issuance under the Inducement Plan. The Plan provides for nonstatutory stock options and restricted stock unit awards. The only persons eligible to receive grants of awards under the Inducement Plan are individuals who satisfy the standards for inducement grants under Nasdaq Marketplace Rule 5635(c)(4) and the related guidance under Nasdaq IM 5635-1, including individuals who were not previously an employee or director of the Company or are following a bona fide period of non-employment, in each case as an inducement material to such individual’s agreement to enter into employment with the Company. Under all Plans, the amount, terms of grants and exercisability provisions are determined by the board of directors or its designee. The term of the options may be up to 10 years, and options are exercisable in cash or as otherwise determined by the board of directors or its designee. Vesting generally occurs over a period of not greater than four years. The estimated grant‑date fair value of the Company’s share‑based awards is amortized ratably over the awards’ service periods. Share‑based compensation expense recognized was as follows (in thousands): Year Ended December 31, 2017 2016 2015 Research and development $ 1,954 $ 3,511 $ 1,460 General and administrative 4,433 2,392 1,967 Total stock-based compensation $ 6,387 $ 5,903 $ 3,427 A summary of stock option activity and related information through December 31, 2017 follows: Options Outstanding Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Balance, December 31, 2015 4,630,073 $ 4.98 7.87 Granted 2,067,500 8.43 Exercised (149,622 ) 1.71 Forfeitures (177,373 ) (7.47 ) Balance, December 31, 2016 6,370,578 $ 6.10 7.60 Granted 4,187,344 3.96 Exercised (293,809 ) 1.23 Forfeited/canceled (1,639,890 ) (6.18 ) Balance, December 31, 2017 8,624,223 $ 5.22 7.17 Vested or expected to vest at December 31, 2017 8,624,223 $ 5.22 7.17 Exercisable at December 31, 2017 3,782,652 $ 5.18 5.04 The intrinsic value of the options exercisable as of December 31, 2017 was $0.4 million , based on the Company’s closing stock price of $1.60 per share and a weighted average exercise price of $5.18 per share. The Company uses the Black‑Scholes option‑pricing model to estimate the fair value of stock options at the grant date. The Black‑Scholes model requires the Company to make certain estimates and assumptions, including estimating the fair value of the Company’s common stock, assumptions related to the expected price volatility of the Company’s stock, the period during which the options will be outstanding, the rate of return on risk‑free investments and the expected dividend yield for the Company’s stock. The per-share weighted-average grant date fair value of the options granted to employees and directors during the year ended December 31, 2017 , 2016 and 2015 was estimated at $2.68 , $5.26 and $4.49 per share, respectively, on the date of grant using the Black-Scholes option-pricing model with the following weighted-average assumptions: Year Ended December 31, 2017 2016 2015 Expected term of options (in years) 6.2 6.2 6.2 Risk-free interest rate 2.0 % 1.5 % 1.7 % Expected volatility 75.6 % 68.6 % 68.5 % Dividend yield — % — % — % The weighted‑average valuation assumptions were determined as follows: • Risk‑free interest rate: The Company based the risk‑free interest rate on the interest rate payable on U.S. Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected option term. • Expected term of options: Due to its lack of sufficient historical data, the Company estimates the expected life of its employee stock options using the “simplified” method, as prescribed in Staff Accounting Bulletin No. 107, whereby the expected life equals the arithmetic average of the vesting term and the original contractual term of the option. • Expected stock price volatility: The Company estimated the expected volatility based on actual historical volatility of the stock price of similar companies with publicly‑traded equity securities. The Company calculated the historical volatility of the selected companies by using daily closing prices over a period of the expected term of the associated award. The companies were selected based on their enterprise value, risk profiles, position within the industry and with historical share price information sufficient to meet the expected term of the associated award. A decrease in the selected volatility would have decreased the fair value of the underlying instrument. • Expected annual dividend yield: The Company estimated the expected dividend yield based on consideration of its historical dividend experience and future dividend expectations. The Company has not historically declared or paid dividends to stockholders. Moreover, it does not intend to pay dividends in the future, but instead expects to retain any earnings to invest in the continued growth of the business. Accordingly, the Company assumed an expected dividend yield of 0.0% . • Estimated forfeiture rate: In 2016 , upon adoption of ASU 2016-9, the Company elected to record forfeitures upon occurrence, rather than utilizing an estimate. The fair value of the Company’s common stock, prior to the IPO, was determined by its board of directors with assistance from its management. The board of directors and management considered numerous objective and subjective factors in the assessment of fair value, including the price for the Company’s preferred stock that was sold to investors and the rights, preferences and privileges of the preferred stock and common stock, the Company’s financial condition and results of operations during the relevant periods and the status of strategic initiatives. These estimates involved a significant level of judgment. As of December 31, 2017 , there was $12.6 million of total unrecognized compensation expense related to unvested options that will be recognized over the weighted average remaining period of 2.64 years. Shares Available for Future Grant At December 31, 2017 , the Company has the following shares available to be granted: 2013 Plan Inducement Plan Available at December 31, 2016 1,101,331 500,000 Authorized 2,230,736 — Granted (3,966,844 ) (220,500 ) Forfeited/canceled 1,626,390 13,500 Available at December 31, 2017 991,613 293,000 Shares Reserved for Future Issuance At December 31, 2017 , the Company has reserved the following shares of common stock for issuance: Stock options outstanding under 2013 Plan 8,417,223 Shares available for future grant under 2013 Plan 991,613 Stock options outstanding under Inducement Plan 207,000 Shares available for future grant under Inducement Plan 293,000 Employee stock purchase plan 225,806 Warrants outstanding 123,091 Total shares of common stock reserved for future issuance 10,257,733

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Licenses On May 3, 2013, the Company entered into an agreement with Allergan plc (formerly Actavis plc and Forest Laboratories Holdings Limited) (“Allergan”), under which the Company granted to Allergan an exclusive option to license TRV027. Under the option agreement, the Company conducted, at its expense, a Phase 2b trial of TRV027 in acute heart failure. In March 2015, Allergan and the Company signed a letter agreement pursuant to which Allergan paid the Company $10.0 million to fund the expansion of the Phase 2b trial of TRV027 from 500 patients to 620 patients. Collaboration revenue was recognized on a straight-line basis over the study period and was fully recognized as of June 30, 2016. In August 2016, Allergan notified the Company of its decision not to exercise its option, and the Company therefore has retained all rights to TRV027. Operating Leases The Company leases office and laboratory space in Pennsylvania. The Company’s leases contain escalating rent clauses, which require higher rent payments in future years. The Company expenses rent on a straight‑line basis over the term of the lease, including any rent‑free periods. In December 2016, we entered into a 130 -month office lease for approximately 40,565 square feet of space in Chesterbrook, Pennsylvania for the Company’s principal executive office; the term for this lease is commenced in July 2017. In June 2017, the Company exercised the option to lease an additional 8,321 square feet of space in the same building. The term for this lease amendment commenced in November 2017. The Company's previous principal executive office was located in King of Prussia, Pennsylvania, pursuant to a lease that extends until September 2020. The Company had the option to terminate the lease after May 31, 2018 with a required termination payment of $0.15 million. In November 2017, in connection with our restructuring and reduction in force (see Note 10), the Company provided notice of its intent to terminate the facility lease of approximately 16,714 square feet of office and laboratory space in King of Prussia, Pennsylvania. The $0.15 million termination fee was paid to the landlord on the date the Company exercised the termination option. As a result, this lease will be deemed terminated on August 15, 2018. The Company historically leased vivarium space in Exton, Pennsylvania. The vivarium lease was able to be terminated at any time upon 90 days’ written notice by the Company. In October 2017, in connection with the restructuring and reduction in force, the vivarium lease was terminated. Early termination fees totaling less than $0.1 million were incurred. Rent expense under operating leases was $1.3 million , $0.6 million and $0.6 million in 2017 , 2016 and 2015 , respectively. Future minimum lease payments under noncancelable lease agreements as of December 31, 2017 , are as follows (in thousands): Operating Lease 2018 $ 970 2019 1,275 2020 1,352 2021 1,376 2022 and beyond 9,412 Total minimum lease payments $ 14,385 The Company had deferred rent of $3.1 million and $0.2 million at December 31, 2017 and 2016 , respectively, related to our facility leases. Legal Proceedings The Company is not involved in any legal proceeding that it expects to have a material effect on its business, financial condition, results of operations and cash flows.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2017
Revenue Recognition [Abstract]
Revenue	Revenue For arrangements with multiple elements, the Company recognizes revenue in accordance with the FASB’s Accounting Standards Update No. 2009-13, Multiple-Deliverable Revenue Arrangements, which provides guidance for separating and allocating consideration in a multiple element arrangement. Deliverables under the arrangement are separate units of accounting if the delivered item has value to the customer on a standalone basis and if the arrangement includes a general right of return relative to the delivery or performance of the undelivered item is considered probable and substantially within the Company’s control. The consideration that is fixed or determinable at the inception of the arrangement is allocated to the separate units of accounting based on their relative selling prices. Management exercises significant judgment in determining whether a deliverable is a separate unit of accounting. In determining the separate units of accounting, the Company evaluates whether the components have standalone value to the collaborator based on consideration of the relevant facts and circumstances for each arrangements. Whenever the Company determines that an element is delivered over a period of time, revenue is recognized using either a proportional performance model, if a pattern of performance can be determined, or a straight-line model over the period of performance, which is typically the research and development term. The Company entered into a letter agreement with Allergan in March 2015 under which the Company received a nonrefundable upfront fee of $10.0 million . The terms of this agreement contained multiple deliverables which included (i) research and development activities and (ii) testing and analysis related to a Phase 2b trial of TRV027. Collaboration revenue is recognized only when the price is fixed or determinable, persuasive evidence of an arrangement exists, delivery has occurred or the services have been rendered and the Company has fulfilled its performance obligations under the contract. The Allergan collaboration revenue was recorded on a straight-line basis and was fully recognized as of June 30, 2016.

Restructuring Charges

Restructuring Charges	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring Charges	Restructuring Charges On October 11, 2017, upon the approval of the Company's Board of Directors, the Company announced a restructuring and reduction in force of approximately 30% of the Company's workforce, or 21 employees. As part of this restructuring, the Company also halted its investment in early stage research. The Company incurred pre-tax restructuring charges of $1.8 million during the year ended December 31, 2017, primarily related to severance and personnel related costs in addition to lease termination payments, as detailed below. In October 2017, in connection with our restructuring and reduction in force, we terminated our lease related to vivarium space in Exton, Pennsylvania, under an agreement expiring on December 31, 2018. We incurred termination fees equivalent to three months rent, totaling less than $0.1 million , in relation to the early termination of this agreement. Additionally, in November 2017, we provided notice of our intent to terminate our facility lease of approximately 16,714 square feet of office and laboratory space in King of Prussia, Pennsylvania, under an agreement that expires in September 2020. We paid the landlord a $0.15 million termination fee on the date we exercised the termination option. As a result, this lease will be deemed terminated on August 15, 2018.

Net Loss Per Common Share

Net Loss Per Common Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Loss Per Common Share	Net Loss Per Common Share The following table sets forth the computation of basic and diluted net loss per share for the periods indicated (in thousands, except share and per share data): Year Ended December 31, 2017 2016 2015 Basic and diluted net loss per common share calculation: Net loss $ (71,865 ) $ (102,994 ) $ (50,528 ) Net loss attributable to common stockholders $ (71,865 ) $ (102,994 ) $ (50,528 ) Weighted average common shares outstanding 59,436,649 52,398,521 43,794,276 Net loss per share of common stock - basic and diluted $ (1.21 ) $ (1.97 ) $ (1.15 ) The following outstanding securities at December 31, 2017 , 2016 and 2015 have been excluded from the computation of diluted weighted shares outstanding, as they would have been anti‑dilutive: December 31, 2017 2016 2015 Options outstanding 8,624,223 6,370,578 4,630,073 Warrants 123,091 60,850 62,800 Total 8,747,314 6,431,428 4,692,873

Comprehensive Income (Loss)

Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Comprehensive Income (Loss)
Comprehensive Income (Loss)	Comprehensive Income (Loss) The following table presents changes in the components of accumulated other comprehensive income or loss, net of tax (in thousands): Balance, January 1, 2016 $ (206 ) Net unrealized loss arising during the period 208 Balance, December 31, 2016 $ 2 Net unrealized gains on marketable securities (44 ) Balance, December 31, 2017 $ (42 ) There were no reclassifications out of accumulated other comprehensive income or loss as well as no tax effect for all periods presented.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes As the Company has historically incurred net operating losses, the Company has not recorded a provision for income taxes. Deferred tax assets and liabilities reflect the net effects of net operating loss and tax credit carryovers and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The Company maintains a full valuation allowance against its net deferred tax assets because significant utilization of such amounts is not presently expected in the foreseeable future. On December 22, 2017, the U.S. government enacted comprehensive tax legislation , the Tax Act. The Tax Act makes broad and complex changes to the U.S. tax code that will affect 2017 including reducing the U.S. federal corporate tax rate to 21 percent. The following changes will affect 2018 (1) elimination of the corporate alternative minimum tax, or AMT, and changing how existing AMT credits can be realized; (2) a new limitation on deductible interest expense; (3) the repeal of the domestic production activity deduction; and (4) limitations on net operating losses , or NOLs, generated after December 31, 2017, to 80 percent of taxable income. The SEC staff issued SAB 118, which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. The Tax Act reduced the corporate tax rate to 21 percent, effective January 1, 2018. Consequently, Trevena has recorded a decrease related to deferred tax assets, or DTAs, and deferred tax liabilities, or DTLs, with a corresponding net adjustment to deferred income tax of expense of $42.0 million for the year ended December 31, 2017. This expense is offset fully by a change in the valuation allowance. The Company’s preliminary estimate of the Tax Act and the remeasurement of its deferred tax assets and liabilities is subject to the finalization of management’s analysis related to certain matters, such as developing interpretations of the provisions of the Tax Act, changes to certain estimates and the filing of the Company’s tax returns. U.S. Treasury regulations, administrative interpretations or court decisions interpreting the Tax Act may require further adjustments and changes in the Company’s estimates. The final determination of the Tax Act and the remeasurement of the Company’s deferred assets and liabilities will be completed as additional information becomes available, but no later than one year from the enactment of the Tax Act. Significant components of the Company’s net deferred tax assets as of December 31, are as follows (in thousands): December 31, 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 16,042 $ 15,748 Research and development credits 12,239 11,020 Research and development expenses capitalized for tax purposes 83,707 97,495 Deferred rent 365 97 Depreciation 427 553 Other temporary differences 3,203 1,895 Total deferred tax assets 115,983 126,808 Deferred tax liabilities: Prepaid expenses (65 ) (105 ) Total deferred tax liabilities (65 ) (105 ) Net deferred tax assets 115,918 126,703 Less valuation allowance (115,918 ) (126,703 ) Net deferred tax asset $ — $ — A reconciliation of income tax expense computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows: December 31, 2017 2016 2015 Percent of pre-tax income: U.S. federal statutory income tax rate 34.0 % 34.0 % 34.0 % Permanent Differences 0.1 % — % 0.1 % State taxes, net of federal benefit 6.7 % 6.6 % 6.6 % Research and development credit 1.7 % 4.0 % 3.9 % Rate change due to tax reform (58.5 )% — — Other 1.0 % — % 0.3 % Change in valuation allowance 15.0 % (44.6 )% (44.9 )% Effective income tax rate — % — % — % As of December 31, 2017 , the Company had federal and state net operating loss carryforwards of $55.7 million and $4.4 million that begin to expire at various dates starting in 2027. As of December 31, 2017 , the Company had federal research and development tax credit carryforwards of $ 12.2 million that begin to expire at various dates starting in 2027. The Company’s ability to utilize net operating loss carryforwards, or NOLs, or tax credit carryforwards may be subject to annual limitations under certain provisions of the Internal Revenue Code related to “changes in ownership.” The Company files income tax returns in the U.S. and the Commonwealth of Pennsylvania. Tax years for fiscal 2014 through 2016 are open and potentially subject to examination by the federal and state taxing authorities. The Company is currently not under examination by the Internal Revenue Service or any other jurisdictions for any tax years. To the extent the Company utilizes in the future any tax attribute NOL carryforwards from a tax period that may otherwise be closed to examination, the Internal Revenue Service, state tax authorities, or other governing parties may still adjust the NOL carryforwards upon their examination of the future period in which the attribute was utilized.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plan	Employee Benefit Plan The Company sponsors a 401(k) defined contribution plan for its employees. Employee contributions are voluntary. The Company matches employee contributions in an amount equal to 100% of the first 3% of eligible compensation and 50% of the next 2% of eligible compensation, and such employer contributions are immediately vested. During 2017 , 2016 and 2015 , the Company provided matching contributions of $0.4 million , $0.4 million and $0.3 million , respectively.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except share and per share amounts) 2017 Total revenue $ — $ — $ — $ — Loss from operations (20,975 ) (19,884 ) (15,413 ) (14,115 ) Net loss $ (20,714 ) $ (20,432 ) $ (15,999 ) $ (14,720 ) Net loss per share of common, basic and diluted $ (0.36 ) $ (0.35 ) $ (0.27 ) $ (0.24 ) Weighted average shares outstanding, basic and diluted 56,894,672 58,381,868 60,113,327 62,290,002 2016 Total revenue $ 1,875 $ 1,875 $ — $ — Loss from operations (17,749 ) (19,104 ) (29,713 ) (35,717 ) Net loss $ (17,732 ) $ (19,295 ) $ (29,985 ) $ (35,982 ) Net loss per share of common, basic and diluted $ (0.35 ) $ (0.37 ) $ (0.57 ) $ (0.67 ) Weighted average shares outstanding, basic and diluted 51,350,365 52,174,569 52,205,156 53,850,166 The quarters presented above for 2017 have been adjusted to reflect the adoption of ASU 2016-09 and related impact, that is deemed immaterial, of electing to recognize forfeitures of share-based payment awards as they occur rather than using an estimate.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Equity Offerings In 2018, the Company issued and sold 3,386,527 shares of common stock pursuant to the existing ATM facility with Cowen. The shares were sold at a weighted average price per share of $1.76 . The net offering proceeds to the Company were approximately $5.8 million after deducting related expenses, including commissions. Approximately $14.6 million remained available under the ATM sales facility as of the date of this filing.

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America, or U.S. GAAP. Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB. The Company’s functional currency is the U.S. dollar.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumption that affect the amounts reported in the financial statements and accompanying notes. Management used significant estimates in the following areas, among others: stock-based compensation expense, the determination of the fair value of stock-based awards, the fair value of liability-classified common stock warrants, the accounting for research and development costs, accrued expenses and the recoverability of the Company’s net deferred tax assets and related valuation allowance. The financial data and other information disclosed in these notes are not necessarily indicative of the results to be expected for any future year or period.
Cash and Cash Equivalents and Marketable Securities	Cash and Cash Equivalents and Marketable Securities The Company considers all highly liquid investments that have maturities of three months or less when acquired to be cash equivalents. Cash equivalents are valued at cost, which approximates their fair market value. The Company maintains a portion of its cash and cash equivalent balances in money market mutual funds that may invest substantially all of their assets in U.S. government agency securities, U.S. Treasury securities or reverse repurchase agreements, or RRAs. RRAs are collateralized by deposits in the form of ‘Government Securities and Obligations’ for an amount not less than 102% of their value. The Company does not hold any RRAs as of December 31, 2017 . The Company classifies its marketable securities as “available-for-sale”, pursuant to ASC Topic 320, Investments—Debt and Equity Securities , or ASC 320, carries them at fair market value and classifies them as current assets on its balance sheets. Unrealized gains and losses on marketable securities are recorded as a separate component of accumulated other comprehensive income/(loss) included in stockholders’ equity. As of December 31, 2017 and 2016 , the Company had $49.5 million and $86.3 million , respectively, in available-for-sale investments, all classified as current assets. See Note 3 for additional information. The fair value of the Company’s investments is determined based on observable market quotes or valuation models using assessments of counterparty credit worthiness, credit default risk of underlying security and overall capital market liquidity. The Company reviews unrealized losses associated with available-for-sale securities to determine the classification as “temporary” or “other-than-temporary” impairment. A temporary impairment results in an unrealized loss being recorded in other comprehensive income (loss). If a decline in the fair value is considered other-than-temporary, based on available evidence, the unrealized loss is transferred from other comprehensive income (loss) to the statement of operations. The Company considers various factors in determining the classification, including the length of time and extent to which the fair value has been less than the Company’s cost basis, the financial condition and near-term prospects of the issuer or investee, and the Company’s ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. Realized gains (losses) are included in interest income (expense) in the statement of operations and comprehensive income (loss) on a specific identification basis.
Restricted Cash	Restricted Cash The Company maintains $1.3 million as collateral under a letter of credit for the Company’s facility lease obligations in Chesterbrook, Pennsylvania. The Company also maintains a letter of credit totaling $0.1 million as collateral for the Company’s facility lease obligations in King of Prussia, Pennsylvania. The Company has recorded these deposits and accumulated interest thereon as restricted cash on its balance sheet.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amount of the Company’s financial instruments, which include cash and cash equivalents, marketable securities, restricted cash, accounts payable and accrued expenses approximate their fair values, given their short-term nature. The carrying amount of the Company’s loans payable at December 31, 2017 and 2016 is the nominal value of the loan payable, which is the carrying value, net of debt discount and deferred charges. The nominal value approximates fair value because the interest rate is reflective of the rate the Company could obtain on debt with similar terms and conditions. Certain of the Company’s common stock warrants are carried at fair value, as disclosed in Note 3. The Company has evaluated the estimated fair value of financial instruments using available market information and management’s estimates. The use of different market assumptions and/or estimation methodologies could have a significant effect on the estimated fair value amounts. See Note 3 for additional information.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash, cash equivalents, marketable securities and restricted cash. The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimizes the exposure to concentration of credit risk. The Company has no off-balance sheet concentrations of credit risk such as foreign currency exchange contracts, option contracts or other hedging arrangements.
Property and Equipment	Property and Equipment Property and equipment consists of computer and laboratory equipment, software, office equipment, furniture, manufacturing equipment and leasehold improvements and is recorded at cost. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred. Upon disposal, retirement or sale, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in the results of operations. Property and equipment are depreciated on a straight‑line basis over their estimated useful lives. The Company uses a life of three years for computer equipment and five years for laboratory equipment, office equipment, furniture, manufacturing equipment and software. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset. The Company reviews long‑lived assets when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparison of the book values of the assets to future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value, which is measured based on the projected discounted future net cash flows arising from the assets.
Intangible Asset	Intangible Asset The intangible asset recorded in the Company's financial statements is associated with the acquisition of the domain name for the Company's website. Identifiable intangible assets are initially recorded at fair market value at the time of acquisition, utilizing a cost approach and the initial value is amortized over the expected useful life of the asset. The Company also capitalizes costs incurred to renew or extend the term of recognized intangible assets. The determination of the value of intangible assets requires management to make estimates and assumptions that affect the Company’s consolidated financial statements. The Company assesses potential impairments to intangible assets when there is evidence of events or changes in circumstances that indicate the carrying amount of an asset may not be recovered. The Company’s judgements regarding the existence of impairment indicators and future cash flows related to intangible assets are based on operational performance of the Company, market conditions and other factors. If impairment is indicated, the Company will reduce the carrying value of the intangible assets to fair value.
Common Stock Warrants	Common Stock Warrants Freestanding warrants that are related to the purchase of common stock are classified as liabilities and recorded at fair value regardless of the timing of the redemption feature or the redemption price or the likelihood of redemption. These warrants are subject to re-measurement at each balance sheet date and any change in fair value is recognized as a component of change in fair value of warrant liability in the statements of operations and comprehensive loss. The Company will continue to adjust the liability for changes in fair value until the earlier of the exercise or expiration of the warrants. The warrants are classified as Level 3 liabilities. See Note 3 for additional information.
Segment Information	Segment Information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the chief executive officer. The Company and the chief executive officer view the Company’s operations and manage its business as one operating segment. All long-lived assets of the Company reside in the United States.
Revenue	Revenue The Company recognizes collaboration revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price is fixed and determinable, and collectibility is reasonably assured.
Research and Development	Research and Development Research and development cost are charged to expense as incurred. Research and development costs include, but are not limited to, personnel expenses, clinical trial supplies, fees for clinical trial services, manufacturing costs, consulting costs and allocated overhead, including rent, equipment, depreciation and utilities. 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 subject enrollment, clinical site activations or information provided to the Company by its vendors with respect to 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 expense, as the case may be. As part of the process of preparing its financial statements, the Company is required to estimate its expenses resulting from its obligations under contracts with vendors, clinical research organizations and consultants, and under clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. The Company’s objective is to reflect the appropriate trial expenses in its financial statements by matching those expenses with the period in which services are performed and efforts are expended. The Company may account for these expenses according to the progress of the trial as measured by subject progression and the timing of various aspects of the trial. The Company determines accrual estimates through financial models taking into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of trials, or the services completed. During the course of a clinical trial, the Company adjusts its clinical expense recognition if actual results differ from its estimates. The Company makes estimates of its accrued expenses as of each balance sheet date based on the facts and circumstances known to it at that time. The Company’s clinical trial accruals are dependent upon the timely and accurate reporting of contract research organizations and other third party vendors. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in it reporting amounts that are too high or too low for any particular period.
Stock-Based Compensation	Stock‑Based Compensation At December 31, 2017 , the Company had two stock‑based compensation plans, which are more fully described in Note 7. The Company has applied the fair value recognition provisions of Financial Accounting Standards Board Accounting Standards Codification Topic 718, Compensation — Stock Compensation , to account for stock-based compensation for employees. The Company recognizes compensation costs related to stock options granted to employees based on the estimated fair value of the awards on the date of grant. The Company has equity incentive plans under which various types of equity-based awards including, but not limited to, incentive stock options, non-qualified stock options, and restricted stock awards, may be granted to employees, non-employee directors, and non-employee consultants. The Company also has an inducement plan under which various types of equity-based awards, including non-qualified stock options and restricted stock awards, may be granted to new employees. For stock options granted to employees and directors, the Company recognizes compensation expense for all stock-based awards based on the estimated grant-date fair values. For restricted stock awards to employees, the fair value is based on the closing price of the Company's common stock on the date of grant. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service period. The fair value of stock options is determined using the Black-Scholes option pricing model. The Company utilizes a dividend yield of zero based on the fact that the Company has never paid cash dividends and has no current intention of paying cash dividends. As of fiscal year ended December 31, 2016 , the Company adopted the forfeiture rate methodology change in accordance with ASU 2016-9 to record forfeitures as they occur.
Income Taxes	Income Taxes Income taxes are recorded in accordance with ASC Topic 740, Income Taxes , or ASC 740, which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position, as well as consideration of the available facts and circumstances. To date, the Company has not taken any uncertain tax position or recorded any reserves, interest or penalties.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive income (loss) relates to unrealized investment gains or losses on the Company’s marketable securities for all periods presented.
Basic and Diluted Net Loss Per Share of Common Stock	Basic and Diluted Net Loss Per Share of Common Stock The Company’s 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. The diluted net loss per common share is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period. Because the impact of these items is anti‑dilutive during periods of net loss, there was no difference between basic and diluted net loss per share of common stock for all periods presented.
Recent Accounting Pronouncements	Recently Adopted Accounting Standards In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, or ASU 2016-09, which amends ASC Topic 718, Compensation— Stock Compensation . ASU 2016-09 is designed to simplify several aspects of accounting for share-based payment award transactions that include the income tax consequences, classification of awards as either equity or liabilities, and classification of excess tax benefits on the statement of cash flows. This guidance also permits an accounting policy election to either estimate the number of awards that are expected to vest or account for forfeitures when they occur. The Company elected to early adopt the standard during the three months ended December 31, 2016 and has elected to recognize forfeitures as they occur. The adoption did not have a material effect on the Company's interim and annual 2016 financial statements. Recent Accounting Standards Not Yet Adopted In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income , which provides the option to reclassify stranded tax effects within accumulated other comprehensive income to retained earnings. This option would be available in each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Cuts and Jobs Act (or a portion thereof) is recorded. This is effective for the Company beginning after December 15, 2018, with early adoption permitted. These amendments should be applied in the period of adoption or retrospectively to each period in which the effect of the change in the U.S federal corporate income tax rate in the Tax Cuts and Jobs Act is recognized. The Company is evaluating the effect this standard will have on its financial statements and related disclosures. See Note 13. In May 2017, the FASB issued ASU No. 2017-09, Stock Compensation - Scope of Modification Accounting, which amends the scope of modification accounting for share-based payment arrangements. The amendment provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The new standard is effective for fiscal years beginning after December 15, 2017. The Company is currently evaluating the effect that this guidance may have on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230), to clarify how certain cash receipts and payments should be presented in the statement of cash flows. The standard is effective for annual periods beginning after December 15, 2017 and interim periods within that reporting period. Early adoption is permitted. The Company is evaluating the effect this standard will have on its financial statements and related disclosures. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842 ), which requires lessees to record most leases on their balance sheets and disclose key information about leasing arrangements in an effort to increase transparency and comparability among organizations. The standard is effective for annual periods beginning after December 15, 2018 and interim periods within that reporting period. Early adoption is permitted. The Company is evaluating the effect this standard will have on its financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers . ASU 2014-09 is a comprehensive new revenue recognition model requiring a company to recognize revenue to depict the transfer of goods or services to a customer in an amount reflecting the consideration it expects to receive in exchange for those goods or services. Additionally, in March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers, Principal versus Agent Considerations . ASU 2016-08 amends the principal versus agent guidance in ASU 2014-09 to clarify how an entity should identify the unit of accounting for the principal versus agent evaluation and how it should apply the control principal to certain types of arrangements. The effective date for both standards is January 1, 2018, with an option that permits companies to adopt the standard as early as the January 1, 2017 . Early application prior to the January 1, 2017 is not permitted. The Company has determined that they will elect the modified retrospective transition method, meaning the cumulative effect of applying the new guidance is recognized at the date of initial application as an adjustment to the opening accumulated deficit balance. Since the Company does not have any open contracts with customers as of December 31, 2017, the adoption of this standard is not expected to have a material impact on the Company's financial statements.

Fair Value of Financial Instr24

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of cash and available-for-sale securities’ adjusted cost, gross unrealized gains, gross unrealized losses and fair values by significant investment category	The following table presents the Company’s cash, cash equivalents, restricted cash, and marketable securities as of December 31, 2017 and 2016 (in thousands): December 31, 2017 Adjusted Cost Unrealized Gains Unrealized Losses Fair Value Cash and Cash Equivalents Restricted Cash Marketable Securities Cash $ 6,783 $ — $ — $ 6,783 $ 5,370 $ 1,413 $ — Level 1 (1): Money market funds 11,187 — — 11,187 11,187 — — U.S. treasury securities 1,991 — — 1,991 — — 1,991 Subtotal 13,178 — — 13,178 11,187 — 1,991 Level 2 (2): U.S. government agency securities 47,594 — (42 ) 47,552 — — 47,552 Total $ 67,555 $ — $ (42 ) $ 67,513 $ 16,557 $ 1,413 $ 49,543 December 31, 2016 Adjusted Cost Unrealized Gains Unrealized Losses Fair Value Cash and Cash Equivalents Restricted Cash Marketable Securities Cash $ 13,756 $ — $ — $ 13,756 $ 12,563 $ 1,193 $ — Level 1 (1): Money market funds 10,043 — — 10,043 10,043 — — Level 2 (2): Repurchase agreements 1,660 1,660 1,660 U.S. government agency securities 86,333 19 (17 ) 86,335 — — 86,335 Subtotal 87,993 19 (17 ) 87,995 1,660 — 86,335 Total $ 111,792 $ 19 $ (17 ) $ 111,794 $ 24,266 $ 1,193 $ 86,335 (1) The fair value of Level 1 securities is estimated based on quoted prices in active markets for identical assets or liabilities. (2) The fair value of Level 2 securities is estimated based on observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term on the assets or liabilities.
Schedule of changes in the fair value of the Company's warrant liability representing a recurring measurement classified within Level 3, wherein fair value is estimated using significant unobservable inputs	The following table sets forth a summary of changes in the fair value of this warrant liability, which represents a recurring measurement that is classified within Level 3 of the fair value hierarchy, wherein fair value is estimated using significant unobservable inputs (in thousands): Warrant Liability Balance as of January 1, 2016 $ 153 Amounts acquired or issued — Changes in estimated fair value (78 ) Balance as of December 31, 2016 75 Amounts acquired or issued — Changes in estimated fair value (65 ) Balance as of December 31, 2017 $ 10
Schedule of assumptions used for valuation of warrants	The following assumptions were used at December 31, 2017 and 2016 to determine the warrant liability: December 31, 2017 2016 Estimated remaining term 4.3 years 5.3 years Risk-free interest rate 2.1 % 2.0 % Volatility 77.6 % 77.2 % Dividend yield — % — % Fair value of underlying instrument* $ 1.60 $ 5.88 *Trevena, Inc. closing stock price.

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of property and equipment	Property and equipment consisted of the following (in thousands): Estimated Useful December 31, Life in Years 2017 2016 Laboratory equipment 5 $ — $ 1,935 Computers and software 3 - 5 749 521 Office equipment and furniture 5 872 314 Manufacturing equipment 5 242 242 Leasehold improvements 5 - 10 4,824 2,150 Leased assets 5 59 32 Total property and equipment 6,746 5,194 Less accumulated depreciation and amortization (2,941 ) (4,135 ) Property and equipment, net $ 3,805 $ 1,059

Accrued Expenses and Other Cu26

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, 2017 2016 Compensation and benefits $ 2,489 $ 2,680 Clinical trial expenses — 5,479 Restructuring (severance) 1,077 — Pharmaceutical development expenses 444 — Accrued interest 158 — Other accrued expenses and other current liabilities 135 49 Total accrued expenses and other current liabilities $ 4,303 $ 8,208

Loans Payable (Tables)

Loans Payable (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt	The following table summarizes how the issuance of Term Loans A, B, and C are reflected on the balance sheet at December 31, 2017 (in thousands): December 31, Gross proceeds $ 28,500 Debt discount and debt issuance costs (350 ) Carrying value 28,150 Current portion of loans payable, net 12,425 Loans payable, net $ 15,725
Schedule of Maturities of Long-term Debt	Aggregate maturities of long term debt as of December 31, 2017 are as follows (in thousands): 2018 $ 12,667 2019 12,667 2020 3,166 2021 — 2022 — $ 28,500 Debt Discount and deferred financing costs (350 ) $ 28,150

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Schedule of share-based compensation expense recognized	The estimated grant‑date fair value of the Company’s share‑based awards is amortized ratably over the awards’ service periods. Share‑based compensation expense recognized was as follows (in thousands): Year Ended December 31, 2017 2016 2015 Research and development $ 1,954 $ 3,511 $ 1,460 General and administrative 4,433 2,392 1,967 Total stock-based compensation $ 6,387 $ 5,903 $ 3,427
Summary of stock option activity	A summary of stock option activity and related information through December 31, 2017 follows: Options Outstanding Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Balance, December 31, 2015 4,630,073 $ 4.98 7.87 Granted 2,067,500 8.43 Exercised (149,622 ) 1.71 Forfeitures (177,373 ) (7.47 ) Balance, December 31, 2016 6,370,578 $ 6.10 7.60 Granted 4,187,344 3.96 Exercised (293,809 ) 1.23 Forfeited/canceled (1,639,890 ) (6.18 ) Balance, December 31, 2017 8,624,223 $ 5.22 7.17 Vested or expected to vest at December 31, 2017 8,624,223 $ 5.22 7.17 Exercisable at December 31, 2017 3,782,652 $ 5.18 5.04
Schedule of weighted-average assumptions:	The per-share weighted-average grant date fair value of the options granted to employees and directors during the year ended December 31, 2017 , 2016 and 2015 was estimated at $2.68 , $5.26 and $4.49 per share, respectively, on the date of grant using the Black-Scholes option-pricing model with the following weighted-average assumptions: Year Ended December 31, 2017 2016 2015 Expected term of options (in years) 6.2 6.2 6.2 Risk-free interest rate 2.0 % 1.5 % 1.7 % Expected volatility 75.6 % 68.6 % 68.5 % Dividend yield — % — % — %
Schedule of shares of common stock reserved/available	At December 31, 2017 , the Company has reserved the following shares of common stock for issuance: Stock options outstanding under 2013 Plan 8,417,223 Shares available for future grant under 2013 Plan 991,613 Stock options outstanding under Inducement Plan 207,000 Shares available for future grant under Inducement Plan 293,000 Employee stock purchase plan 225,806 Warrants outstanding 123,091 Total shares of common stock reserved for future issuance 10,257,733 At December 31, 2017 , the Company has the following shares available to be granted: 2013 Plan Inducement Plan Available at December 31, 2016 1,101,331 500,000 Authorized 2,230,736 — Granted (3,966,844 ) (220,500 ) Forfeited/canceled 1,626,390 13,500 Available at December 31, 2017 991,613 293,000

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum lease payments, including termination fees, under non cancelable lease agreements	Future minimum lease payments under noncancelable lease agreements as of December 31, 2017 , are as follows (in thousands): Operating Lease 2018 $ 970 2019 1,275 2020 1,352 2021 1,376 2022 and beyond 9,412 Total minimum lease payments $ 14,385

Net Loss Per Common Share (Tabl

Net Loss Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of computation of basic and diluted net loss per share	The following table sets forth the computation of basic and diluted net loss per share for the periods indicated (in thousands, except share and per share data): Year Ended December 31, 2017 2016 2015 Basic and diluted net loss per common share calculation: Net loss $ (71,865 ) $ (102,994 ) $ (50,528 ) Net loss attributable to common stockholders $ (71,865 ) $ (102,994 ) $ (50,528 ) Weighted average common shares outstanding 59,436,649 52,398,521 43,794,276 Net loss per share of common stock - basic and diluted $ (1.21 ) $ (1.97 ) $ (1.15 )
Schedule of outstanding securities excluded from the computation of diluted weighted shares outstanding as they would have been anti-dilutive	The following outstanding securities at December 31, 2017 , 2016 and 2015 have been excluded from the computation of diluted weighted shares outstanding, as they would have been anti‑dilutive: December 31, 2017 2016 2015 Options outstanding 8,624,223 6,370,578 4,630,073 Warrants 123,091 60,850 62,800 Total 8,747,314 6,431,428 4,692,873

Comprehensive Income (Loss) (Ta

Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Comprehensive Income (Loss)
Schedule of components of accumulated other comprehensive income or loss, net of tax	The following table presents changes in the components of accumulated other comprehensive income or loss, net of tax (in thousands): Balance, January 1, 2016 $ (206 ) Net unrealized loss arising during the period 208 Balance, December 31, 2016 $ 2 Net unrealized gains on marketable securities (44 ) Balance, December 31, 2017 $ (42 )

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of significant components of the Company's deferred tax assets	Significant components of the Company’s net deferred tax assets as of December 31, are as follows (in thousands): December 31, 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 16,042 $ 15,748 Research and development credits 12,239 11,020 Research and development expenses capitalized for tax purposes 83,707 97,495 Deferred rent 365 97 Depreciation 427 553 Other temporary differences 3,203 1,895 Total deferred tax assets 115,983 126,808 Deferred tax liabilities: Prepaid expenses (65 ) (105 ) Total deferred tax liabilities (65 ) (105 ) Net deferred tax assets 115,918 126,703 Less valuation allowance (115,918 ) (126,703 ) Net deferred tax asset $ — $ —
Schedule of reconciliation of income tax expense computed at the statutory federal income tax rate to income taxes as reflected in the financial statements	A reconciliation of income tax expense computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows: December 31, 2017 2016 2015 Percent of pre-tax income: U.S. federal statutory income tax rate 34.0 % 34.0 % 34.0 % Permanent Differences 0.1 % — % 0.1 % State taxes, net of federal benefit 6.7 % 6.6 % 6.6 % Research and development credit 1.7 % 4.0 % 3.9 % Rate change due to tax reform (58.5 )% — — Other 1.0 % — % 0.3 % Change in valuation allowance 15.0 % (44.6 )% (44.9 )% Effective income tax rate — % — % — %

Selected Quarterly Financial 33

Selected Quarterly Financial Data (Unaudited) Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Condensed Income Statement	First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except share and per share amounts) 2017 Total revenue $ — $ — $ — $ — Loss from operations (20,975 ) (19,884 ) (15,413 ) (14,115 ) Net loss $ (20,714 ) $ (20,432 ) $ (15,999 ) $ (14,720 ) Net loss per share of common, basic and diluted $ (0.36 ) $ (0.35 ) $ (0.27 ) $ (0.24 ) Weighted average shares outstanding, basic and diluted 56,894,672 58,381,868 60,113,327 62,290,002 2016 Total revenue $ 1,875 $ 1,875 $ — $ — Loss from operations (17,749 ) (19,104 ) (29,713 ) (35,717 ) Net loss $ (17,732 ) $ (19,295 ) $ (29,985 ) $ (35,982 ) Net loss per share of common, basic and diluted $ (0.35 ) $ (0.37 ) $ (0.57 ) $ (0.67 ) Weighted average shares outstanding, basic and diluted 51,350,365 52,174,569 52,205,156 53,850,166

Organization and Description 34

Organization and Description of the Business (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments | segment									1
Liquidity
Accumulated deficit	$ 357,490				$ 285,625				$ 357,490	$ 285,625
Net loss	14,720	$ 15,999	$ 20,432	$ 20,714	35,982	$ 29,985	$ 19,295	$ 17,732	71,865	102,994	$ 50,528
Cash and cash equivalents	16,557				24,266				16,557	24,266
Marketable securities	$ 49,543				$ 86,335				$ 49,543	$ 86,335

Summary of Significant Accoun35

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017USD ($)segmentplan$ / shares	Dec. 31, 2016USD ($)$ / shares	Dec. 31, 2015$ / shares
Investments
Minimum percentage value of RRAs collateralized by deposits in the form of Government Securities and Obligations	102.00%
Marketable Securities	$ 49,543,000	$ 86,335,000
Restricted Cash
Letters of credit	1,300,000
Letter of credit collateral	100,000
Impairment losses	$ 0
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Number of operating segments | segment	1
Stock-Based Compensation
Number of stock-based compensation plans | plan	2
Dividend yield	0.00%
Basic and diluted net loss per common share calculation:
Difference between basic and diluted net loss per share of Common Stock (in dollars per share) | $ / shares	$ 0	$ 0	$ 0
Computer equipment
Restricted Cash
Estimated useful life	P3Y
Laboratory equipment, office equipment, furniture and software
Restricted Cash
Estimated useful life	P5Y

Fair Value of Financial Instr36

Fair Value of Financial Instruments - Hierarchy Table (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Total
Fair value
Adjusted Cost	$ 67,555	$ 111,792
Unrealized Gains	0	19
Unrealized Losses	(42)	(17)
Fair Value	67,513	111,794
Cash and Cash Equivalents | Total
Fair value
Fair Value	16,557	24,266
Restricted Cash | Total
Fair value
Fair Value	1,413	1,193
Marketable Securities | Total
Fair value
Fair Value	49,543	86,335
Cash
Fair value
Adjusted Cost	6,783	13,756
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	6,783	13,756
Cash | Cash and Cash Equivalents
Fair value
Fair Value	5,370	12,563
Cash | Restricted Cash
Fair value
Fair Value	1,413	1,193
Cash | Marketable Securities
Fair value
Fair Value	0	0
Level 1
Fair value
Adjusted Cost	13,178
Unrealized Gains	0
Unrealized Losses	0
Fair Value	13,178
Level 1 | Cash and Cash Equivalents
Fair value
Fair Value	11,187
Level 1 | Restricted Cash
Fair value
Fair Value	0
Level 1 | Marketable Securities
Fair value
Fair Value	1,991
Level 1 | Money market mutual funds
Fair value
Adjusted Cost	11,187	10,043
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	11,187	10,043
Level 1 | Money market mutual funds | Cash and Cash Equivalents
Fair value
Fair Value	11,187	10,043
Level 1 | Money market mutual funds | Restricted Cash
Fair value
Fair Value	0	0
Level 1 | Money market mutual funds | Marketable Securities
Fair value
Fair Value	0	0
Level 1 | U.S. treasury securities
Fair value
Adjusted Cost	1,991
Unrealized Gains	0
Unrealized Losses	0
Fair Value	1,991
Level 1 | U.S. treasury securities | Cash and Cash Equivalents
Fair value
Fair Value	0
Level 1 | U.S. treasury securities | Restricted Cash
Fair value
Fair Value	0
Level 1 | U.S. treasury securities | Marketable Securities
Fair value
Fair Value	1,991
Level 2
Fair value
Adjusted Cost		87,993
Unrealized Gains		19
Unrealized Losses		(17)
Fair Value		87,995
Level 2 | Cash and Cash Equivalents
Fair value
Fair Value		1,660
Level 2 | Restricted Cash
Fair value
Fair Value		0
Level 2 | Marketable Securities
Fair value
Fair Value		86,335
Level 2 | Repurchase agreements
Fair value
Adjusted Cost		1,660
Unrealized Gains
Unrealized Losses
Fair Value		1,660
Level 2 | Repurchase agreements | Cash and Cash Equivalents
Fair value
Fair Value		1,660
Level 2 | Repurchase agreements | Restricted Cash
Fair value
Fair Value
Level 2 | Repurchase agreements | Marketable Securities
Fair value
Fair Value
Level 2 | U.S. government agency securities
Fair value
Adjusted Cost	47,594	86,333
Unrealized Gains	0	19
Unrealized Losses	(42)	(17)
Fair Value	47,552	86,335
Level 2 | U.S. government agency securities | Cash and Cash Equivalents
Fair value
Fair Value	0	0
Level 2 | U.S. government agency securities | Restricted Cash
Fair value
Fair Value	0	0
Level 2 | U.S. government agency securities | Marketable Securities
Fair value
Fair Value	$ 47,552	$ 86,335

Fair Value of Financial Instr37

Fair Value of Financial Instruments - Additional Information (Details)	Dec. 31, 2017shares
Warrants
Warrants
Number of shares that can be purchased upon exercise of warrants (in shares)	20,161
Common Stock | Warrants
Warrants
Number of shares that can be purchased upon exercise of warrants (in shares)	102,930
Common Stock | Maximum | Warrants
Warrants
Number of shares that can be purchased upon exercise of warrants (in shares)	20,161

Fair Value of Financial Instr38

Fair Value of Financial Instruments - Summary of Changes in Warrant Liability (Details) - Warrants - Warrant Liability - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	$ 75	$ 153
Amounts acquired or issued	0	0
Changes in estimated fair value	(65)	(78)
Balance at the end of the period	$ 10	$ 75

Fair Value of Financial Instr39

Fair Value of Financial Instruments - Warrant Liability Assumptions (Details) - Level 3 - Warrants - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair value assumptions
Estimated remaining term	4 years 3 months 29 days	5 years 3 months 18 days
Common Stock
Fair value assumptions
Risk-free interest rate (as a percent)	2.10%	2.00%
Volatility (as a percent)	77.60%	77.20%
Dividend yield (as a percent)	0.00%	0.00%
Fair value of underlying instrument (in dollars per share)	$ 1.60	$ 5.88

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment
Total property and equipment	$ 6,746	$ 5,194
Less accumulated depreciation and amortization	(2,941)	(4,135)
Property and equipment, net	3,805	1,059
Depreciation and amortization expense	$ 490	246	$ 208
Laboratory equipment
Property and Equipment
Estimated useful life	P5Y
Total property and equipment	$ 0	1,935
Computers and software
Property and Equipment
Total property and equipment	$ 749	521
Computers and software | Minimum
Property and Equipment
Estimated useful life	P3Y
Computers and software | Maximum
Property and Equipment
Estimated useful life	P5Y
Office equipment and furniture
Property and Equipment
Estimated useful life	P5Y
Total property and equipment	$ 872	314
Manufacturing equipment
Property and Equipment
Estimated useful life	P5Y
Total property and equipment	$ 242	242
Leasehold improvements
Property and Equipment
Total property and equipment	$ 4,824	2,150
Leasehold improvements | Minimum
Property and Equipment
Estimated useful life	P5Y
Leasehold improvements | Maximum
Property and Equipment
Estimated useful life	P10Y
Leased Assets
Property and Equipment
Estimated useful life	P5Y
Total property and equipment	$ 59	$ 32

Accrued Expenses and Other Cu41

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Compensation and benefits	$ 2,489	$ 2,680
Clinical trial expenses	0	5,479
Restructuring (severance)	1,077	0
Pharmaceutical development expenses	444	0
Accrued interest	158	0
Other accrued expenses and other current liabilities	135	49
Total accrued expenses and other current liabilities	$ 4,303	$ 8,208

Loans Payable - Additional Info

Loans Payable - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2017$ / sharesshares	Mar. 31, 2017USD ($)	Apr. 30, 2015shares	Sep. 30, 2014USD ($)tranche$ / sharesshares
Long Term Debt
Gross proceeds	$ 28,500,000
Interest expense	2,780,000	$ 1,738,000	$ 334,000
Debt discount and debt issuance costs	350,000
Amortization of debt discount and issuance costs	$ 300,000	100,000	100,000
Warrants
Long Term Debt
Exercise price of warrants or rights (in dollars per share) | $ / shares	$ 10.6190						$ 5.8610
Lenders and Placement Agent | Common Stock | Warrants
Long Term Debt
Number of shares that can be purchased upon exercise of warrants (in shares) | shares	5,728						7,678
Loan and security agreement
Long Term Debt
Face amount							$ 35,000,000
Number of tranches | tranche							3
Term Loan A
Long Term Debt
Face amount							$ 2,000,000
Term Loan B
Long Term Debt
Face amount			16,500,000
Term Loan B | Common Stock | Warrants
Long Term Debt
Number of shares that can be purchased upon exercise of warrants (in shares) | shares						34,961
Term Loan C
Long Term Debt
Face amount		10,000,000			$ 10,000,000
Debt instrument borrowing capacity			16,500,000
Interest rate (as a percent)	6.98%
Term Loan C | Common Stock | Warrants
Long Term Debt
Number of shares that can be purchased upon exercise of warrants (in shares) | shares				62,241
Exercise price of warrants or rights (in dollars per share) | $ / shares				$ 3.6150
Term Loan C | Prepayment Date 1
Long Term Debt
Prepayment fee percent	3.00%
Term Loan C | Prepayment Date 2
Long Term Debt
Prepayment fee percent	2.00%
Term Loan C | Prepayment Date 3
Long Term Debt
Prepayment fee percent	1.00%
Term Loans A and B
Long Term Debt
Interest rate (as a percent)	6.50%
Prepayment fee percent	1.00%
Term Loans A, B, and C
Long Term Debt
Final payment fee	6.60%
Gross proceeds	$ 28,500,000
Debt discount and debt issuance costs	350,000
Term Loans A and B
Long Term Debt
Gross proceeds	28,500,000
Interest expense	$ 1,700,000	$ 1,200,000	$ 200,000
Term Loan A
Long Term Debt
Debt discount and debt issuance costs							$ 1,000,000

Loans Payable Loans Payable - I

Loans Payable Loans Payable - Issuance of Term Loans A and B (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Long Term Debt
Gross proceeds	$ 28,500
Debt Discount and deferred financing costs	(350)
Carrying value	28,150
Current portion of loans payable, net	12,425	$ 5,039
Loans payable, net	15,725	$ 13,270
Term Loans A, B, and C
Long Term Debt
Gross proceeds	28,500
Debt Discount and deferred financing costs	(350)
Carrying value	28,150
Current portion of loans payable, net	12,425
Loans payable, net	$ 15,725

Loans Payable - Maturities (Det

Loans Payable - Maturities (Details) $ in Thousands	Dec. 31, 2017USD ($)
Aggregate maturities of long term debt
2,018	$ 12,667
2,019	12,667
2,020	3,166
2,021	0
2,022	0
Loans payable, gross	28,500
Debt Discount and deferred financing costs	(350)
Carrying value	$ 28,150

Stockholders' Equity - Equity O

Stockholders' Equity - Equity Offerings (Details) - USD ($)	Sep. 16, 2015	Apr. 03, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 14, 2015
Class of Stock [Line Items]
Common stock authorized (in shares)			100,000,000	100,000,000
Preferred stock authorized (in shares)			5,000,000	5,000,000
Common stock, par value (in dollars per share)			$ 0.001	$ 0.001
Issuance of common stock, net of issuance costs			$ 20,712,000	$ 32,077,000	$ 90,306,000
Proceeds from issuance of common stock, net			$ 20,712,000	$ 32,077,000	$ 90,311,000
At-the-market sales facility
Class of Stock [Line Items]
Common stock, par value (in dollars per share)		$ 0.001				$ 0.001
Issuance of common stock, net of issuance costs (in shares)			6,248,572	4,815,491	3,700,000
Issuance of common stock, net of issuance costs			$ 21,300,000	$ 33,100,000	$ 22,900,000
Proceeds from issuance of common stock, net			$ 20,700,000	$ 32,100,000	$ 22,000,000
At-the-market sales facility | Maximum
Class of Stock [Line Items]
Offering price		$ 40,000,000				$ 75,000,000
Commission (as a percent)		3.00%	3.00%
At-the-market sales facility | Weighted-average
Class of Stock [Line Items]
Offering price (in dollars per share)			$ 3.41	$ 6.865	$ 6.0001
Public Offering
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs (in shares)	7,475,000
Offering price (in dollars per share)	$ 9.75
Issuance of common stock, net of issuance costs	$ 72,900,000
Proceeds from issuance of common stock, net	68,300,000
Payment of underwriting discounts and commissions	4,400,000
Offering expenses	$ 200,000

Stockholders' Equity - Equity I

Stockholders' Equity - Equity Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 15, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Incentive Plans
Dividend yield		0.00%
Options outstanding
Equity Incentive Plans
Intrinsic value of options exercisable		$ 0.4
Fair value of underlying instrument (in dollars per share)		$ 1.60
Exercisable at the end of the period (in dollars per share)		5.18
Per-share weighted-average grant date fair value of options granted (in dollars per share)		$ 2.68	$ 5.26	$ 4.49
Unrecognized compensation expense		$ 12.6
Weighted average remaining period for recognition of unrecognized compensation expense		2 years 7 months 22 days
2008 Plan and 2013 Plan
Equity Incentive Plans
Increase in number of shares authorized for issuance (in shares)	500,000
2008 Plan and 2013 Plan | Maximum
Equity Incentive Plans
Term of award		10 years
Vesting period		4 years

Stockholders' Equity Stockholde

Stockholders' Equity Stockholders' Equity - Share-based Compensation (Details) - Options outstanding - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Allocated share-based compensation expense	$ 6,387	$ 5,903	$ 3,427
Research and Development Expense
Class of Stock [Line Items]
Allocated share-based compensation expense	1,954	3,511	1,460
General and Administrative Expense
Class of Stock [Line Items]
Allocated share-based compensation expense	$ 4,433	$ 2,392	$ 1,967

Stockholder's Equity - Options

Stockholder's Equity - Options Outstanding (Details) - Options outstanding - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Balance at the beginning of the period (in shares)	6,370,578	4,630,073
Granted (in shares)	4,187,344	2,067,500
Exercised (in shares)	(293,809)	(149,622)
Forfeited/Cancelled (in shares)	(1,639,890)	(177,373)
Balance at the end of the period (in shares)	8,624,223	6,370,578	4,630,073
Vested or expected to vest at the end of the period (in shares)	8,624,223
Exercisable at the end of the period (in shares)	3,782,652
Weighted-Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 6.10	$ 4.98
Granted (in dollars per share)	3.96	8.43
Exercised (in dollars per share)	1.23	1.71
Forfeited/Cancelled (in dollars per share)	(6.18)	(7.47)
Balance at the end of the period (in dollars per share)	5.22	$ 6.10	$ 4.98
Vested or expected to vest at the end of the period (in dollars per share)	5.22
Exercisable at the end of the period (in dollars per share)	$ 5.18
Weighted Average Remaining Contractual Term
Options Outstanding at the end of the period	7 years 2 months 1 day	7 years 7 months 6 days	7 years 10 months 13 days
Vested or expected to vest at the end of the period	7 years 2 months 1 day
Exercisable at the end of the period	5 years 15 days

Stockholders' Equity Stockhol49

Stockholders' Equity Stockholders' Equity - Assumptions Used (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Dividend yield	0.00%
Weighted-average
Class of Stock [Line Items]
Expected term of options (in years)	6 years 2 months 12 days	6 years 2 months 12 days	6 years 2 months 12 days
Risk-free interest rate (as a percent)	2.00%	1.50%	1.70%
Expected volatility (as a percent)	75.60%	68.60%	68.50%
Dividend yield	0.00%	0.00%	0.00%

Stockholders' Equity Stockhol50

Stockholders' Equity Stockholders' Equity - Available for Grant (Details)	12 Months Ended
	Dec. 31, 2017shares
2013 plan
Class of Stock [Line Items]
Balance at the beginning of the period (in shares)	1,101,331
Authorized (in shares)	2,230,736
Granted (in shares)	(3,966,844)
Forfeitures/Expirations (in shares)	1,626,390
Balance at the end of the period (in shares)	991,613
Inducement Plan
Class of Stock [Line Items]
Balance at the beginning of the period (in shares)	500,000
Authorized (in shares)	0
Granted (in shares)	(220,500)
Forfeitures/Expirations (in shares)	13,500
Balance at the end of the period (in shares)	293,000

Stockholder's Equity - Shares A

Stockholder's Equity - Shares Available for Future Issuance (Details) - shares	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Employee stock purchase plan (in shares)	225,806
Warrants outstanding (in shares)	123,091
Total shares of common stock reserved for future issuance (in shares)	10,257,733
2013 plan
Class of Stock [Line Items]
Stock options outstanding (in shares)	8,417,223
Shares available for future grant (in shares)	991,613	1,101,331
Inducement Plan
Class of Stock [Line Items]
Stock options outstanding (in shares)	207,000
Shares available for future grant (in shares)	293,000	500,000

Commitments and Contingencies -

Commitments and Contingencies - Licenses (Details) - Allergan $ in Millions	1 Months Ended
	Mar. 31, 2015USD ($)patient
Collaboration Revenue.
Payment received to fund expansion of clinical trial | $	$ 10
Minimum
Collaboration Revenue.
Number of patients before expansion of the trial	500
Maximum
Collaboration Revenue.
Number of patients after expansion of the trial	620

Commitments and Contingencies53

Commitments and Contingencies - Operating Leases (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2016USD ($)ft²	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)ft²	Dec. 31, 2015USD ($)	Nov. 30, 2017ft²	Jun. 30, 2017ft²
Commitments and Contingencies
Notice period		90 days
Rent expense		$ 1,300	$ 600	$ 600
Future minimum payments under operating leases
2,018		970
2,019		1,275
2,020		1,352
2,021		1,376
2022 and beyond		9,412
Total minimum lease payments		14,385
Deferred rent	$ 200	3,100	$ 200
Chesterbrook, Pennsylvania
Commitments and Contingencies
Term lease	130 months
Area of real estate property (in sqft) | ft²	40,565		40,565			8,321
King of Prussia, Pennsylvania
Commitments and Contingencies
Area of real estate property (in sqft) | ft²					16,714
Lease termination payment (less than: $0.1 million)		150
Exton, Pennsylvania
Commitments and Contingencies
Lease termination payment (less than: $0.1 million)		$ 100

Revenue (Details)

Revenue (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue
Collaboration revenue		$ 0	$ 3,750	$ 6,250
Allergan
Revenue
Nonrefundable upfront fee	$ 10,000

Restructuring Charges (Details)

Restructuring Charges (Details) $ in Thousands	Oct. 11, 2017employee	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Nov. 30, 2017ft²
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated, percent	30.00%
Number of positions eliminated | employee	21
Restructuring charges		$ 1,774	$ 0	$ 0
Exton, Pennsylvania
Restructuring Cost and Reserve [Line Items]
Lease termination payment (less than: $0.1 million)		100
King of Prussia, Pennsylvania
Restructuring Cost and Reserve [Line Items]
Lease termination payment (less than: $0.1 million)		$ 150
Area of real estate property (in sqft) | ft²					16,714

Net Loss Per Common Share (Deta

Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic and diluted net loss per common share calculation:
Net loss	$ (14,720)	$ (15,999)	$ (20,432)	$ (20,714)	$ (35,982)	$ (29,985)	$ (19,295)	$ (17,732)	$ (71,865)	$ (102,994)	$ (50,528)
Net loss attributable to common stockholders									$ (71,865)	$ (102,994)	$ (50,528)
Weighted average common shares outstanding (in shares)	62,290,002	60,113,327	58,381,868	56,894,672	53,850,166	52,205,156	52,174,569	51,350,365	59,436,649	52,398,521	43,794,276
Net loss per share of common stock—basic and diluted (in dollars per share)	$ (0.24)	$ (0.27)	$ (0.35)	$ (0.36)	$ (0.67)	$ (0.57)	$ (0.37)	$ (0.35)	$ (1.21)	$ (1.97)	$ (1.15)
Outstanding securities excluded from computation of diluted weighted shares outstanding (in shares)									8,747,314	6,431,428	4,692,873
Options outstanding
Basic and diluted net loss per common share calculation:
Outstanding securities excluded from computation of diluted weighted shares outstanding (in shares)									8,624,223	6,370,578	4,630,073
Warrants
Basic and diluted net loss per common share calculation:
Outstanding securities excluded from computation of diluted weighted shares outstanding (in shares)									123,091	60,850	62,800

Comprehensive Income (Loss) (De

Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	$ 78,581	$ 143,131
Net unrealized gains (loss) on marketable securities	(44)	208
Ending balance	34,633	78,581
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	2	(206)
Ending balance	$ (42)	$ 2

Income Taxes - Deferred Taxes (

Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Provisional income tax expense (benefit)	$ 42,000
Deferred tax assets:
Net operating loss carryforwards	16,042	$ 15,748
Research and development credits	12,239	11,020
Research and development expenses capitalized for tax purposes	83,707	97,495
Deferred rent	365	97
Depreciation	427	553
Other temporary differences	3,203	1,895
Total deferred tax assets	115,983	126,808
Deferred tax liabilities:
Prepaid expenses	(65)	(105)
Total deferred tax liabilities	(65)	(105)
Net deferred tax assets	115,918	126,703
Less valuation allowance	(115,918)	(126,703)
Net deferred tax asset	$ 0	$ 0

Income Taxes - Effective Tax Ra

Income Taxes - Effective Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Percent of pre-tax income:
U.S. federal statutory income tax rate	34.00%	34.00%	34.00%
Permanent Differences	0.10%	0.00%	0.10%
State taxes, net of federal benefit	6.70%	6.60%	6.60%
Research and development credit	1.70%	4.00%	3.90%
Rate change due to tax reform	(58.50%)	0.00%	0.00%
Other	1.00%	0.00%	0.30%
Change in valuation allowance	15.00%	(44.60%)	(44.90%)
Effective income tax rate	0.00%	0.00%	0.00%
U.S. federal
Percent of pre-tax income:
Net operating loss carryforwards	$ 55.7
State Jurisdiction
Percent of pre-tax income:
Tax credit carryforwards	4.4
Research Tax Credit Carryforward | U.S. federal
Percent of pre-tax income:
Tax credit carryforwards	$ 12.2

Employee Benefit Plan (Details)

Employee Benefit Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Employer matching contribution for employee's contributions of the first 3% of eligible compensation	100.00%
Percentage of eligible compensation, matched 100% by employer	3.00%
Employer matching contribution for employee's contributions of the next 2% of eligible compensation	50.00%
Percentage of eligible compensation, matched 50% by employer	2.00%
Company's matching contributions to the plan	$ 0.4	$ 0.4	$ 0.3

Selected Quarterly Financial 61

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 1,875	$ 1,875	$ 0	$ 3,750	$ 6,250
Loss from operations	(14,115)	(15,413)	(19,884)	(20,975)	(35,717)	(29,713)	(19,104)	(17,749)	(70,387)	(102,283)	(50,621)
Net loss	$ (14,720)	$ (15,999)	$ (20,432)	$ (20,714)	$ (35,982)	$ (29,985)	$ (19,295)	$ (17,732)	$ (71,865)	$ (102,994)	$ (50,528)
Net loss per share of common stock—basic and diluted (in dollars per share)	$ (0.24)	$ (0.27)	$ (0.35)	$ (0.36)	$ (0.67)	$ (0.57)	$ (0.37)	$ (0.35)	$ (1.21)	$ (1.97)	$ (1.15)
Weighted average common shares outstanding, basic and diluted (in shares)	62,290,002	60,113,327	58,381,868	56,894,672	53,850,166	52,205,156	52,174,569	51,350,365	59,436,649	52,398,521	43,794,276

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 07, 2018	Mar. 07, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event.
Proceeds from issuance of common stock, net			$ 20,712	$ 32,077	$ 90,311
At-the-market sales facility
Subsequent Event.
Issuance of common stock, net of issuance costs (in shares)			6,248,572	4,815,491	3,700,000
Proceeds from issuance of common stock, net			$ 20,700	$ 32,100	$ 22,000
At-the-market sales facility | Weighted-average
Subsequent Event.
Offering price (in dollars per share)			$ 3.41	$ 6.865	$ 6.0001
Subsequent event | At-the-market sales facility
Subsequent Event.
Issuance of common stock, net of issuance costs (in shares)		3,386,527
Proceeds from issuance of common stock, net		$ 5,800
Remaining amount available under the ATM sales credit facility	$ 14,600
Subsequent event | At-the-market sales facility | Weighted-average
Subsequent Event.
Offering price (in dollars per share)	$ 1.76	$ 1.76