Agile Therapeutics (AGXRW) 10-K 15 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Mar. 10, 2017	Jun. 30, 2016
Document and Entity Information
Entity Registrant Name	AGILE THERAPEUTICS INC
Entity Central Index Key	1,261,249
Document Type	10-K
Document Period End Date	Dec. 31, 2016
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			$ 152.8
Entity Common Stock, Shares Outstanding		28,776,398
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 48,750	$ 34,395
Prepaid expenses	2,768	3,690
Total current assets	51,518	38,085
Property and equipment, net	12,330	12,318
Other assets	18	18
Total assets	63,866	50,421
Current liabilities:
Accounts payable	2,050	2,387
Accrued expenses	3,352	2,653
Loan payable, current portion	5,104	2,336
Warrant liability	172	406
Total current liabilities	10,678	7,782
Loan payable, long-term	10,899	12,896
Commitments and contingencies (Note 13)
Stockholders' equity:
Common stock, $.0001 par value, authorized 150,000,000 shares; 28,759,731 shares issued and outstanding as of December 31, 2016 and 22,315,612 shares issued and outstanding as of December 31, 2015;	3	2
Additional paid-in capital	235,754	194,468
Accumulated deficit	(193,468)	(164,727)
Total stockholders' equity	42,289	29,743
Total liabilities and stockholders' equity	$ 63,866	$ 50,421

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Balance Sheets
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized (in shares)	150,000,000	150,000,000
Common stock, issued (in shares)	28,759,731	22,315,612
Common stock, outstanding (in shares)	28,759,731	22,315,612

Statements of Operations

Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating expenses:
Research and development	$ 20,929	$ 25,622	$ 13,365
General and administrative	8,792	7,467	5,150
Total operating expenses	29,721	33,089	18,515
Loss from operations	(29,721)	(33,089)	(18,515)
Other income (expense)
Interest expense	(2,446)	(2,077)	(1,566)
Interest income	117	5	3
Change in fair value of warrants	234	(110)	348
Loss on extinguishment of debt		(1,036)
Loss before benefit from income taxes	(31,816)	(36,307)	(19,730)
Benefit from income taxes	3,075	5,972	3,653
Net loss	$ (28,741)	$ (30,335)	$ (16,077)
Net loss per share (basic and diluted) (in dollars per share)	$ (1.02)	$ (1.38)	$ (1.41)
Weighted-average shares outstanding (basic and diluted) (in shares)	28,273,331	22,017,229	11,394,971

Statements of Convertible Prefe

Statements of Convertible Preferred Stock and Changes in Stockholders' Equity (Deficit), Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Common StockRedeemable Convertible Preferred Stock	Common StockConvertible notesConvertible Promissory Notes, April 2014	Common StockPrivate Placement	Common StockInitial public offering	Common StockPublic Offering	Common Stock	Additional Paid-in CapitalRedeemable Convertible Preferred Stock	Additional Paid-in CapitalConvertible notesConvertible Promissory Notes, April 2014	Additional Paid-in CapitalPrivate Placement	Additional Paid-in CapitalInitial public offering	Additional Paid-in CapitalPublic Offering	Additional Paid-in Capital	Deficit Accumulated During the Development Stage	Redeemable Convertible Preferred Stock	Convertible notesConvertible Promissory Notes, April 2014	Private Placement	Initial public offering	Public Offering	Total
Balance at Dec. 31, 2013												$ 46,873	$ (118,315)						$ (71,442)
Balance (in shares) at Dec. 31, 2013						109,321
Increase (decrease) in stockholders' equity (deficit)
Share based compensation-stock options												1,381							1,381
Issuance of common stock for employee bonuses												80							80
Issuance of common stock for employee bonuses (in shares)						9,983
Conversion to common stock	$ 1						$ 69,232	$ 3,020						$ 69,233	$ 3,020
Conversion to common stock (in shares)	8,803,547	503,450
Common stock issued, net of expenses				$ 1						$ 49,743							$ 49,744
Common stock issued (in shares)				9,166,667
Exercise of stock options												67							67
Exercise of stock options (in shares)						41,904
Net loss													(16,077)						(16,077)
Balance at Dec. 31, 2014						$ 2						170,396	(134,392)						36,006
Balance (in shares) at Dec. 31, 2014						18,634,872
Increase (decrease) in stockholders' equity (deficit)
Share based compensation-stock options												2,965							2,965
Common stock issued, net of expenses									$ 19,330							$ 19,330
Common stock issued (in shares)			3,418,804
Fair value of common stock warrant issued with debt financing												1,184							1,184
Exercise of stock options												593							593
Exercise of stock options (in shares)						261,936
Net loss													(30,335)						(30,335)
Balance at Dec. 31, 2015						$ 2						194,468	(164,727)						29,743
Balance (in shares) at Dec. 31, 2015						22,315,612
Increase (decrease) in stockholders' equity (deficit)
Share-based compensation-stock options and RSUs												3,425							3,425
Vesting of RSUs (in shares)						16,666
Common stock issued, net of expenses					$ 1						$ 37,527							$ 37,528
Common stock issued (in shares)					6,338,583
Exercise of stock options												334							334
Exercise of stock options (in shares)						88,870
Net loss													(28,741)						(28,741)
Balance at Dec. 31, 2016						$ 3						$ 235,754	$ (193,468)						$ 42,289
Balance (in shares) at Dec. 31, 2016						28,759,731

Statements of Convertible Pref6

Statements of Convertible Preferred Stock and Changes in Stockholders' Equity (Deficit), Convertible Preferred Stock - 12 months ended Dec. 31, 2014 - USD ($) $ in Thousands	Series A-1 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series B Convertible Preferred Stock	Series C Convertible Preferred Stock
Balance at Dec. 31, 2013	$ 898	$ 544	$ 44,928	$ 22,862
Balance (in shares) at Dec. 31, 2013	137,787	66,116	4,510,066	1,578,400
Increase (decrease) in temporary equity
Conversion of preferred stock to common stock	$ (898)	$ (544)	$ (44,928)	$ (22,862)
Conversion of preferred stock to common stock	(137,787)	(66,116)	(4,510,066)	(1,578,400)
Balance at Dec. 31, 2014
Balance (in shares) at Dec. 31, 2014

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net loss	$ (28,741)	$ (30,335)	$ (16,077)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	19	18	12
Noncash stock bonus			80
Noncash stock based compensation	3,425	2,965	1,381
Loss on extinguishment of debt		1,036
Noncash interest	946	590	185
Change in fair value of warrants	(234)	110	(348)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	922	(1,209)	(2,335)
Accounts payable and accrued expenses	362	1,347	2,599
Net cash used in operating activities	(23,301)	(25,478)	(14,503)
Cash flows from investing activities
Acquisition of property and equipment	(31)	(290)	(96)
Net cash used in investing activities	(31)	(290)	(96)
Cash flows from financing activities
Proceeds from convertible bridge notes			3,000
Proceeds from issuance of term loan		16,265
Repayment of term loan		(15,784)
Principal payments of long-term debt	(985)
Return of principal payments of long-term debt	985
Proceeds from issuance of common stock, in public offering, net of offering costs	37,528		49,744
Proceeds from issuance of common stock in private placement, net of offering costs		19,330
Cash paid for financing costs	(175)	(423)	(150)
Proceeds from exercise of stock options	334	593	67
Net cash provided by financing activities	37,687	19,981	52,661
Net increase (decrease) in cash and cash equivalents	14,355	(5,787)	38,062
Cash and cash equivalents, beginning of year	34,395	40,182	2,120
Cash and cash equivalents, end of year	48,750	34,395	40,182
Supplemental cash flow information
Interest paid	$ 1,500	1,474	1,380
Supplemental disclosure of noncash financing activities
Fair value of common stock warrants issued		$ 1,184
Conversion of preferred stock into common stock			69,233
Conversion of notes payable and interest into common stock			$ 3,021

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2016
Organization and Description of Business
Organization and Description of Business	1. Organization and Description of Business Nature of Operations Agile Therapeutics, Inc. ("Agile" or the "Company") was incorporated in Delaware on December 22, 1997. Agile is a forward-thinking women's healthcare company dedicated to fulfilling the unmet health needs of today's women. The Company's activities since inception have consisted principally of raising capital and performing research and development. The Company is headquartered in Princeton, New Jersey. The Company's lead product candidate, Twirla®, also known as AG200-15, is a once-weekly prescription contraceptive patch that is at the end of Phase 3 clinical development. Substantially all of the Company's resources are currently dedicated to developing and seeking regulatory approval for Twirla. The Company has not generated product revenue to date and is subject to a number of risks similar to those of other early stage companies, including dependence on key individuals, the difficulties inherent in the development of commercially usable products, the potential need to obtain additional capital necessary to fund the development of its products, and competition from larger companies. The Company has incurred losses each year since inception. As of December 31, 2016, the Company had an accumulated deficit of approximately $193.5 million. The Company has financed its operations to date primarily through the issuance and sale of its common stock in both public and private offerings (see Note 9), private placements of its convertible preferred stock, venture loans, and non-dilutive grant funding. The Company expects to continue to incur net losses into the foreseeable future. As of December 31, 2016, the Company had cash and cash equivalents of $48.8 million. Although the Company has incurred recurring losses in each year since inception, the Company expects its cash and cash equivalents will be sufficient to fund operations for at least the next twelve months.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Polices Basis of Presentation The accompanying financial statements have been prepared in accordance with United States ("U.S.") generally accepted accounting principles ("GAAP") and include all adjustments necessary for the fair presentation of the Company's financial position for the periods presented. Use of Estimates The preparation of the Company's financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company bases its estimates and judgments on historical experience and various other assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company's balance sheets and the amounts of expenses reported for each of the periods presented are affected by estimates and assumptions, which are used for, but not limited to, the accounting for common stock warrants, stock-based compensation, income taxes, and accounting for research and development costs. Actual results could differ from those estimates. Risks and Uncertainties Product candidates developed by the Company typically will require approval from the FDA prior to commercial sales. There can be no assurance that the Company's product candidates will receive the required approval. If the Company was denied approval or such approval was delayed, or is unable to obtain the necessary financing to complete development and approval, there will be a material adverse impact on the Company's financial condition and results of operations. Stock Split On May 5, 2014, the Company effected a 1.4-for-1 stock split of the Company's common stock. All share and per share amounts of common stock contained in the Company's financial statements have been restated for all periods to give retroactive effect to the stock split. The shares of common stock retained a par value of $0.0001 per share. Accordingly, the stockholders' deficit reflects the stock split by reclassifying from "Additional paid-in Capital" to "Common Stock" in an amount equal to the par value of the increased shares resulting from the stock split. Cash and Cash Equivalents The Company considers all highly-liquid investments with an original maturity of three months or less when purchased to be cash equivalents. All cash and cash equivalents are held in United States financial institutions. Cash and cash equivalents include money market funds that invest primarily in commercial paper and U.S. government and U.S. government agency obligations. The Company maintains balances with financial institutions in excess of the FDIC limit. Fair Value of Financial Instruments In accordance with ASC 825, Financial Instruments , disclosures of fair value information about financial instruments are required, whether or not recognized in the balance sheet, for which it is practicable to estimate that value. Cash and cash equivalents are carried at fair value (see Note 3). Financial instruments, including accounts payable and accrued liabilities, are carried at cost, which approximates fair value given their short-term nature. Property and Equipment Property and equipment, consisting of manufacturing, office and computer equipment, is stated at cost, less accumulated depreciation. Depreciation is computed using the straight-line, method over the estimated useful lives of the assets. Expenditures incurred after the fixed assets have been put into operation, such as repairs and maintenance, are charged to earnings in the period in which costs are incurred. Improvements and additions are capitalized in accordance with Company policy. Long-Lived Assets In accordance with ASC 360, Property, Plant and Equipment , the Company's policy is to review long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Management does not believe that there has been any impairment of the carrying value of any long-lived assets as of December 31, 2016. Research and Development Expense Research and development costs are expensed as incurred. Research and development expense consists primarily of costs related to personnel, including salaries and other personnel-related expenses, expenses related to manufacturing, clinical trial expenses, consulting fees and support services used in drug development. All research and development costs are charged to operations as incurred in accordance with ASC 730, Research and Development . In certain circumstances, the Company is required to make advance payments to vendors for goods or services that will be received in the future for use in research and development activities. In such circumstances, the advance payments are deferred and are expensed when the activity has been performed or when the goods have been received. Deferred Financing Costs Costs directly attributable to the Company's term loan (see Note 8) are deferred and reported as a reduction of the related term loan. These costs represent legal fees and other costs related to the term loan and are being amortized over the term of the loan. Amortization of deferred financing costs charged to interest expense was $256, $211 and $59 for the years ended December 31, 2016, 2015 and 2014, respectively. Concentrations of Credit Risk Financial instruments which potentially subject the Company to credit risk consist principally of cash and cash equivalents. All cash and cash equivalents are held in business checking and money market accounts in United States financial institutions the balances of which exceed federally insured limits. The Company has not recognized any losses from credit risks on such accounts. The Company believes it is not exposed to significant credit risks on cash and cash equivalents. The Company has no financial instruments with off-balance sheet risk of accounting loss. Warrants The Company accounts for its warrants to purchase redeemable convertible stock in accordance with ASC 480, Distinguishing Liabilities from Equity . ASC 480 requires that a financial instrument, other than outstanding share, that, at inception, is indexed to an obligation to repurchase the issuer's equity shares, regardless of the timing or the probability of the redemption feature, and may require the issuer to settle the obligation by transferring assets be classified as a liability. The Company measures the fair value of its warrant liability using the Black-Scholes option pricing model with changes in fair value recognized as increases or reductions to other income (expense) in the statement of operations. In connection with the completion of the Company's initial public offering in May 2014, the warrants to purchase shares of Series A-1 and Series A-2 preferred stock expired unexercised and the warrants to purchase shares of Series C preferred stock automatically converted into warrants to purchase shares of common stock. Warrants with non-standard anti-dilution provisions (referred to as down round protection) are classified as liabilities and re-measured each reporting period. As of December 31, 2016, there were outstanding 62,505 warrants to purchase common stock at $6.00 per share. These warrants expire on December 14, 2019. The warrants issued in connection with the Company's debt financing completed in February 2015 (see Note 8) are classified as a component of stockholders' equity. The value of such warrants was determined using the Black-Scholes option-pricing model. Income Taxes The Company accounts for deferred taxes using the asset and liability method as specified by ASC 740, Income Taxes . Deferred income tax assets and liabilities are determined based on differences between the financial statement reporting and the tax basis of assets and liabilities, operating losses and tax credit carryforwards. Deferred income taxes are measured using the enacted tax rates and laws that are anticipated to be in effect when the differences are expected to reverse. The measurement of deferred income tax assets is reduced, if necessary, by a valuation allowance for any tax benefits which are not expected to be realized. The effect on deferred income tax assets and liabilities of a change in tax rates is recognized in the period that such tax rate changes are enacted. The Company has adopted the authoritative guidance on accounting for and disclosure of uncertainty in tax positions which prescribes a comprehensive model for the financial statement recognition, measurement, presentation and disclosure of uncertain tax positions taken or expected to be taken in income tax returns. The Company has no uncertain tax positions as of December 31, 2016 that qualifies for either recognition or disclosure in the financial statements under this guidance. Stock-Based Compensation The Company accounts for stock-based compensation in accordance with ASC 718, Compensation—Stock Compensation . The Company grants stock options for a fixed number of shares to employees and non-employees with an exercise price equal to the fair value of the shares at grant date. Compensation cost is recognized for all share-based payments granted and is based on the grant-date fair value estimated using the weighted-average assumption of the Black-Scholes option pricing model based on key assumptions such as stock price, expected volatility and expected term. The Company elects to account for forfeitures when they occur. The equity instrument is not considered to be issued until the instrument vests. As a result, compensation cost is recognized over the requisite service period with an offsetting credit to additional paid-in capital. The Company also awards restricted stock units ("RSUs") to employees. RSUs are generally subject to forfeiture if employment terminates prior to the completion of the vesting restrictions. The Company expenses the cost of the RSUs, which is determined to be the fair market value of the shares of common stock underlying the RSUs at the date of grant, ratably over the period during which the vesting restrictions lapse. Awards for consultants are accounted for under ASC 505-50, Equity Based Payments to Non-Employees . Any compensation expense related to consultants is marked-to-market over the applicable vesting period as they vest. Prior to May 22, 2014, the Company utilized various methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its stock. The methodologies included an option pricing method and a probability-weighted expected return methodology that determined an estimated value under an initial public offering (IPO) scenario and a sale scenario based upon an assessment of the probability of occurrence of each scenario. Each valuation methodology includes estimates and assumptions that require the Company's judgment. These estimates include assumptions regarding future performance, including the successful completion of clinical trials and the time to completing an IPO or sale of the Company. As with any valuation, significant changes to the key assumptions used in the valuations could result in different fair values of common stock at each valuation date. Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating and reporting segment, which is the business of developing its transdermal patch for use in contraception. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding plus the effect of dilutive potential common shares outstanding during the period determined using the treasury-stock and if-converted methods. For purposes of diluted net loss per share calculation, common stock warrants, unvested RSUs and stock options are considered to be potentially dilutive securities but are excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive and therefore, basic and diluted net loss per share were the same for all periods presented. The following table sets forth the outstanding potentially dilutive securities that have been excluded from the calculation of diluted net loss per share because to do so would be anti-dilutive (in common equivalent shares): Year Ended 2016 2015 2014 Convertible preferred stock — — — Convertible preferred stock warrants — — — Common stock warrants Unvested restricted stock units — — Common stock options ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Recent Accounting Pronouncements In August 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern, which defines management's responsibility to assess an entity's ability to continue as a going concern, and to provide related footnote disclosures if there is substantial doubt about its ability to continue as a going concern. The new standard is effective for the annual period ending after December 15, 2016, and for interim periods thereafter. The Company adopted ASU 2014-15 in the fourth quarter of 2016, which resulted in no change to the Company's financial statements. Additionally, the Company will perform quarterly evaluations to identify current conditions which may raise substantial doubt about the entity's ability to continue as a going concern within one year after the date that the financial statements are issued. In April 2015, the FASB issued an amendment to U.S. GAAP to simplify the balance sheet presentation of the costs for issuing debt. The changes were adopted in ASU No. 2015-03, Interest—Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issue Costs . ASU 2015-03 amends current presentation guidance by requiring that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. Prior to the issuance of ASU 2015-03, debt issuance costs were required to be presented as an asset in the balance sheet. The Company adopted the provisions of ASU 2015-03 on January 1, 2016 and prior period balances have been reclassified to conform to the current period presentation. As of December 31, 2015, $152 of debt issuance costs were reclassified in the balance sheet from "deferred financing costs, net" to "loan payable, current portion" and $139 was reclassified from "deferred financing costs, net" to "loan payable, long-term". The adoption of ASU 2015-03 did not have an impact on the Company's operations or cash flows. In February 2016, the FASB issued ASU No. 2016-02, Leases . The new standard establishes a right-of-use (ROU) model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the statement of operations. The new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. A modified retrospective transition approach is required for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company will be evaluating the impact of the pending adoption of the new standard on the Company's financial statements. In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting . This ASU requires all tax effects of share-based payment settlements to be recorded through the statement of operations. Currently, tax benefits in excess of compensation cost, or "windfalls", are recorded in equity, and tax deficiencies, or "shortfalls", are recorded to equity to the extent of previous windfalls, and then to the statement of operations. In addition, under the new guidance, companies will be permitted to make a policy election to recognize the impact of forfeitures either when they occur, or on an estimated basis. Finally, this update simplifies withholding requirements to allow companies to withhold up to an employee's maximum tax rate without resulting in liability classification for the award. ASU 2016-09 is effective for annual reporting periods beginning after December 15, 2016, and early adoption is permitted. The Company has adopted the provisions of this standard early and the impact on its financial statements was not material.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Measurements
Fair Value Measurements	3. Fair Value Measurements ASC 820, Fair Value Measurements and Disclosures, describes the fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Assets and liabilities that are measured at fair value are reported using a three-level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and minimizes the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: · Level 1—Quotes prices in active markets for identical assets and liabilities. The Company's Level 1 assets and liabilities consist of cash and cash equivalents. · Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted market prices for similar assets or liabilities in active markets or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets and liabilities. The Company has no Level 2 assets or liabilities. · Level 3—Unobservable inputs that are supported by little or no market data and which require internal development of assumptions about how market participant price the fair value of the assets or liabilities. The Company's Level 3 liabilities consist of the warrant liability. The Company is required to mark the value of its warrant liability to market and recognize the change in valuation in its statements of operations each reporting period. The following table sets forth the Company's financial instruments measured at fair value by level within the fair value hierarchy as of December 31, 2016 and 2015. Level 1 Level 2 Level 3 2016 Assets: Cash equivalents $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets at fair value $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Common stock warrants — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities at fair value $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The significant assumptions used in preparing the option pricing model for valuing the Company's warrants as of December 31, 2016 include (i) volatility (75.0%), (ii) risk free interest rate of 1.47% (estimated using treasury bonds with a 3 year life), (iii) strike price ($6.00) for the common stock warrants, (iv) fair value of common stock ($5.70) and (v) expected life (three years). The following is a roll forward of the fair value of Level 3 warrants: Beginning balance at December 31, 2013 $ Expiration of Series A-1 and Series A-2 warrants ) Change in fair value ​ ​ ​ ​ ​ Ending balance at December 31, 2014 Change in fair value ​ ​ ​ ​ ​ Ending balance at December 31, 2015 Change in fair value ) ​ ​ ​ ​ ​ Ending balance at December 31, 2016 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Level 1 Level 2 Level 3 2015 Assets: Cash equivalents $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets at fair value $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Common stock warrants — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities at fair value $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The significant assumptions used in preparing the option pricing model for valuing the Company's warrants as of December 31, 2015 include (i) volatility (75.0%), (ii) risk free interest rate of 1.54% (estimated using treasury bonds with a 4 year life), (iii) strike price ($6.00) for the common stock warrants, (iv) fair value of common stock ($9.76) and (v) expected life (four years). There were no transfers between Level 1, 2 or 3 during 2016 or 2015. If the Company's estimates regarding the fair value of its warrants are inaccurate, a future adjustment to these estimated fair values may be required. Additionally, these estimated fair values could change significantly.

Prepaid Expenses

Prepaid Expenses	12 Months Ended
	Dec. 31, 2016
Prepaid Expenses
Prepaid Expenses	4. Prepaid Expenses Prepaid expenses consist of the following: December 31 2016 2015 Prepaid clinical trial expense $ $ Prepaid insurance Other ​ ​ ​ ​ ​ ​ ​ ​ Total prepaid expenses $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2016
Property and Equipment
Property and Equipment	5. Property and Equipment Property and equipment, consisting of manufacturing, office and computer equipment, is stated at cost, less accumulated depreciation. Depreciation is computed using the straight-line, method over the estimated useful lives of the assets. Property and equipment consist of the following: December 31 Estimated 2016 2015 Office equipment $ $ 3 - 10 years Computer equipment 3 years Manufacturing equipment 5 years ​ ​ ​ ​ ​ ​ ​ ​ ​ Less: accumulated depreciation ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ Property and equipment, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As December 31, 2016 and 2015, manufacturing equipment includes approximately $12.4 million of equipment which is in the process of being constructed and qualified and is not currently being depreciated.

Accrued Liabilities

Accrued Liabilities	12 Months Ended
	Dec. 31, 2016
Accrued Liabilities
Accrued Liabilities	6. Accrued Liabilities Accrued liabilities consist of the following: December 31 2016 2015 Employee bonuses $ $ Accrued clinical trial costs Accrued professional fees and other ​ ​ ​ ​ ​ ​ ​ ​ Total accrued liabilities $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Convertible Note Financing

Convertible Note Financing	12 Months Ended
	Dec. 31, 2016
Convertible notes | Convertible Promissory Notes, April 2014
Convertible Note Financing
Convertible Note Financing	7. Convertible Note Financing On April 28, 2014, the Company and certain of the Company's existing preferred stockholders, all of whom qualify as accredited institutional investors, entered into a Convertible Subordinated Note Purchase Agreement pursuant to which such holders agreed to loan the Company an aggregate of $3.0 million. The Company issued Convertible Promissory Notes (the "Notes") to evidence its payment obligations with respect to the $3.0 million. The Notes had an interest rate of 8%, accruing daily and compounding annually. The Notes are convertible into unregistered equity securities of the Company upon the occurrence of events stated therein. The Notes and accrued interest automatically converted into 503,450 shares of common stock at $6.00 per share which was equal to the purchase price at which shares were sold to the public in an underwritten public offering (see Note 9). The Notes were subordinate to the Company's term loan with Oxford Finance LLC.

Loan and Security Agreements

Loan and Security Agreements	12 Months Ended
	Dec. 31, 2016
Secured debt
Loan and Security Agreements
Loan and Security Agreements	8. Loan and Security Agreements Oxford Finance LLC In December 2012, the Company entered into a Loan and Security Agreement (the "Oxford Loan") with Oxford Finance LLC ("Oxford") pursuant to which the Company borrowed a total of $15.0 million from Oxford. The Oxford Loan accrued interest at a fixed annual rate equal to 9.20% (Three-month U.S. Libor rate of 0.47% plus 8.73%). Interest on the Oxford Loan was payable monthly and principal was due in 30 equal consecutive monthly installments beginning on February 1, 2015 and ending on July 1, 2017. In addition, the Company was required to make a final payment of $675 on the maturity date of the Oxford Loan (July 1, 2017). In connection with the Oxford Loan, the Company issued Oxford warrants to purchase 62,505 shares of common stock at $6.00 per share. These warrants expire on December 14, 2019. In February 2015, the Company terminated and repaid all amounts outstanding under the Oxford Loan and recorded a loss on the extinguishment of the Oxford Loan (see further discussion below). Hercules Capital, Inc. In February 2015, the Company entered into a loan and security agreement (the "Hercules Loan") with Hercules Capital, Inc. ("Hercules") for a term loan of up to $25.0 million. In August 2016, the Company entered into the First Amendment to Loan and Security Agreement (the "First Amendment") with Hercules which amends certain terms of the Hercules Loan. A first tranche of $16.5 million was funded upon execution of the Hercules Loan, approximately $15.5 million of which was used to repay the Company's existing term loan with Oxford. The First Amendment extends the Company's option to draw down the second tranche of $8.5 million (the "Second Term Loan Advance") of the term loan facility provided under the Hercules Loan (the "Term Loan") until March 31, 2017, and makes the Second Term Loan Advance subject to the consent of Hercules, among other customary conditions. The Company is currently in discussions with Hercules to extend the period beyond March 31, 2017 during which the additional tranche of $8.5 million may be drawn. The First Amendment also extends the interest-only payments until January 31, 2017, in connection with the first tranche of $16.5 million (the "First Term Loan Advance" and together with the Second Term Loan Advance, the "Term Loan Advances"). The First Amendment also provides the Company the ability to extend further the interest-only payments for two successive periods as follows: (i) until April 30, 2017, subject to the Company successfully completing its SECURE clinical trial and the Company receiving data that supports the filing of a response to the U.S. Food and Drug Administration's complete response letter relating to the new drug application filed by the Company ("First Interest Only Period Extension") and (ii) until July 31, 2017, provided that (x) the Company has received the First Interest Only Period Extension and (y) the Company has received unrestricted gross cash proceeds in aggregate amount greater than or equal to $40.0 million from the issuance and sale by the Company of its equity securities ("Second Interest Only Period Extension"). The First Amendment provides the Term Loan will mature on December 1, 2018; provided, however, that if the First Interest Only Period Extension occurs on or prior to January 31, 2017, the Term Loan will mature on March 1, 2019; and provided further, however that if both (a) The First Interest Only Period Extension occurs on or prior to January 31, 2017, and (b) the Second Interest Only Period Extension occurs on or prior to April 30, 2017, the Term loan will mature on June 1, 2019. As a result of the First Amendment, and in connection with the extension of the interest-only period from the First Term Loan Advance, Hercules returned to the Company the principal payments paid by the Company in July and August 2016, which such returned payments will once again constitute outstanding Term Loan advances under the Hercules Loan. In connection with the execution of the First Amendment, the Company paid Hercules a facility fee of $165. The facility fee represents a debt issue cost which is being reflected as a reduction to the carrying amount of loan payable in accordance with ASU 2015-03. Such issue costs are being amortized to interest expense over the life of the loan using the effective interest method. The Hercules Loan accrues interest at a rate of the greater of 9.0% or 9.0% plus Prime minus 4.25% and is payable monthly. Principal is due in 23 equal consecutive monthly installments beginning on February 1, 2017 and ending on December 1, 2018. In addition, the Company is required to make a final payment of $610.5 on the maturity date of the Hercules Loan (December 1, 2018). The amount of the end of term final payment is being accrued over the loan term as interest expense. The Company may prepay all, but not less than all, of the Hercules Loan subject to a prepayment premium of 2.0% of the outstanding principal if prepaid during the second year (through February 24, 2017) and 1.0% of the outstanding principal if prepaid after February 24, 2017. The obligations of the Company under the Hercules Loan are secured by a perfected first position lien on all of the assets of the Company, excluding intellectual property assets. In connection with the Hercules Loan, the Company issued Hercules a warrant to purchase 180,274 shares of the Company's common stock at an exercise price of $5.89 per share which expires on February 24, 2020 and granted Hercules the right to participate in future equity financings in an amount up to $2.0 million while the loan and warrant are outstanding. The Company allocated the proceeds of $16.5 million in accordance with ASC 470 based on the relative fair values. The relative fair value of the warrants of approximately $1.2 million at the time of issuance, which was determined using the Black-Scholes option-pricing model, was recorded as additional paid-in capital and reduced the carrying value of the debt. The significant assumptions used in preparing the option pricing model for valuing the Company's warrant issued to Hercules include (i) volatility (75.0%), (ii) risk free interest rate of 1.22% (estimated using treasury bonds with a 4 year life), (iii) strike price ($5.89) for the common stock warrant, (iv) fair value of common stock ($9.82) and (v) expected life (four years). The discount on the debt is being amortized to interest expense over the term of the debt. As a result of the repayment of the Oxford Loan, the Company recorded a loss on the extinguishment of debt of approximately $1.0 million on the Company's statement of operations for the year ended December 31, 2015, representing a prepayment premium, the unamortized discount of the Oxford Loan and the write off of deferred financing costs. Interest expense on the Oxford Loan and the Hercules Loan including the accretion of the value of the related warrants, accrual of term loan back-end fee and amortization of the deferred financing costs was approximately $2,446, $2,077 and $1,545, for the years ended December 31, 2016, 2015 and 2014, respectively. The annual maturities of the Hercules Loan, as of December 31, 2016, are as follows: 2017 $ 2018 ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity
Stockholders' Equity	9. Stockholders' Equity Initial Public Offering and Related Transactions On May 29, 2014, the Company completed its initial public offering selling 9,166,667 shares of common stock at $6.00 per share. Proceeds from the Company's initial public offering, net of underwriting discounts and commissions and other offering costs, were $49.7 million. In addition, each of the following occurred in connection with the completion of the Company's IPO on May 29, 2014: · the conversion of all outstanding shares of convertible preferred stock into 8,809,325 shares of the Company's common stock; and · the conversion of the aggregate principal amount of $3.0 million and accrued interest under the Company's outstanding convertible subordinated promissory notes into 503,450 shares of the Company's common stock. On May 7, 2014, the Company filed an amendment to its amended and restated certificate of incorporation which, among other things, revised the automatic conversion provision relating to the Series C Preferred Stock, Series B Preferred Stock, Series A-1 Preferred Stock and Series A-2 Preferred Stock. Following such amendment, the Series C, the Series B, the Series A-1 and A-2 Preferred Stock automatically converted into shares of common stock at the then effective conversion price upon: (i) the closing of an underwritten public offering pursuant to an effective registration statement under the Securities Act of 1933, covering the offer and sale of common stock from which the Company receives gross proceeds of at least $45,000,000 or (ii) the affirmative vote of the holders of at least a majority of the voting power the Series C Preferred Stock, the Series B Preferred Stock and the Series A-1 Preferred Stock, respectively, after first giving effect, if in conjunction with a public offering which does not meet the standards set forth in clause (i) above, to any adjustment of the conversion price for each series of preferred stock to which it would otherwise be entitled by virtue of such public offering. On May 29, 2014, the Company filed an amended and restated certificate of incorporation (the "Restated Certificate") with the Secretary of State of the State of Delaware in connection with the closing of the Company's initial public offering of shares of its common stock. The Company's board of directors (the "Board") and stockholders previously approved the Restated Certificate effective as of and contingent upon the closing of the Company's initial public offering. The Restated Certificate amends and restates in its entirety the Company's second amended and restated certificate of incorporation, as amended. The Restated Certificate, among other things: (i) authorizes 150,000,000 shares of common stock; (ii) eliminates all references to the previously existing series of preferred stock; (iii) authorizes 10,000,000 shares of undesignated preferred stock that may be issued from time to time by the Board in one or more series; (iv) provides that the Board be divided into three classes with staggered three-year terms, with one class of directors to be elected at each annual meeting of the Company's stockholders; (v) provides that directors may only be removed with cause and only upon the affirmative vote of holders of at least 75% of the voting power of all then-outstanding shares of capital stock of the Company entitled to vote generally in the election of directors; (vi) provides that only the Board, the chairman of the Board, if one is appointed, or the chief executive officer may call a special meeting of stockholders; and (vii) requires that any action instituted against the Company's officers or directors in connection with their service to the Company be brought in the State of Delaware. 2015 Private Placement of Common Stock In January 2015, the Company completed a private placement of approximately 3.4 million shares of common stock at $5.85 per share. Proceeds from the Company's private placement, net of commissions and other offering costs, were approximately $19.3 million. Two of the Company's stockholders, who are also affiliated with members of the Company's Board of Directors, purchased a total of 1,623,932 shares of common stock for approximately $9.5 million in the private placement. Shelf Registration Statement On June 19, 2015, the Company filed a universal shelf registration statement with the SEC for the issuance of common stock, preferred stock, warrants, rights, debt securities and units up to an aggregate amount of $150.0 million (the "2015 Shelf Registration Statement"). On July 1, 2015, the 2015 Shelf Registration Statement was declared effective by the SEC. The Company completed an offering of common stock in January 2016 utilizing the 2015 Shelf Registration Statement (see Note 14). In the future, the Company may also periodically offer one or more of these securities in amounts, prices and terms to be announced when and if the securities are offered. At the time any of the securities covered by the 2015 Shelf Registration Statement are offered for sale, a prospectus supplement will be prepared and filed with the SEC containing specific information about the terms of any such offering. 2016 Public Offering of Common Stock In January 2016, the Company completed an underwritten public offering of 5,511,812 shares of its common stock at a public offering price of $6.35 per share. In February 2016, the underwriters of the public offering of common stock exercised in full their option to purchase an additional 826,771 shares of common stock at the public offering price of $6.35 per share, less underwriting discounts and commissions. A total of 6,338,583 shares of common stock were sold in the public offering resulting in total net proceeds of approximately $37.5 million. One of the Company's stockholders, who is also affiliated with a member of the Company's Board of Directors, purchased 393,700 shares of common stock for approximately $2.5 million in the public offering. Convertible Preferred Stock (Prior to IPO) Prior to its conversion in the IPO, the Company's convertible preferred stock was classified as temporary equity on its balance sheets instead of stockholders' (deficit) in accordance with authoritative guidance for the classification and measurement or redeemable securities. Upon certain change in control events that were outside of the Company's control, including liquidation, sale or transfer of control of the Company, holders of the convertible preferred stock could cause its redemption.

Equity Incentive Plans

Equity Incentive Plans	12 Months Ended
	Dec. 31, 2016
Equity Incentive Plans
Equity Incentive Plans	10. Equity Incentive Plans The Company had granted stock options under an amended and restated 1997 Equity Incentive Plan (the "1997 Plan") and a 2008 Equity Incentive Plan (the "2008 Plan"). The plans provided for the granting of incentive and non-statutory options and stock awards to consultants, directors, officers and employees. Such options are exercisable for a period of ten years and generally vest over a four-year period. In conjunction with the adoption of the 2008 Plan in April 2008, no additional grants were made from the 1997 Plan and issued options from the 1997 Plan remain outstanding. In 2014, the Company's Board of Directors approved the 2014 Equity Incentive Plan (the "2014 Plan"). The 2014 Plan is the successor to the Company's 2008 Plan and 1997 Plan. In conjunction with the adoption of the 2014 Plan in 2014, no additional grants were made from the 2008 Plan and options from the 1997 Plan and the 2008 Plan remain outstanding. As of December 31, 2016, there were 605,390 shares available for future grant under the 2014 Plan. Through December 31, 2016, the Company granted options to certain employees and nonemployees to purchase shares of common stock at exercise prices ranging from $0.71 to $285.71 per share. The Company recorded non cash stock based compensation expense of $3,425, $2,965 and $1,381 for the years ended December 31, 2016, 2015 and 2014, respectively, based on the fair market value of the options and shares granted at the grant date. Stock-based compensation expense was as follows: Year Ended December 31, 2016 2015 2014 Employee $ $ $ Non-employee ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock-based compensation expense was allocated as follows: Year Ended December 31, 2016 2015 2014 Research and development $ $ $ General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total stock-based compensation expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following assumptions were used to compute employee stock-based compensation under the Black-Scholes option pricing model: 2016 2015 2014 Risk-free interest rate % % % Expected volatility % % % Expected dividend yield % % % Expected life (in years) Risk-free interest rate. The Company bases the risk-free interest rate assumption on observed interest rates appropriate for the expected term of the stock option grants. Expected dividend yield. The Company bases the expected dividend yield assumption on the fact that it has never paid cash dividends and has no present intention to pay cash dividends. Expected volatility. The expected volatility assumption is based on volatilities of a peer group of similar companies whose share prices are publicly available. The peer group was developed based on comparable companies in the biotechnology and pharmaceutical industries. Expected term. The expected term represents the period of time that options are expected to be outstanding. Because the Company does not have historic exercise behavior, management determined the expected life assumption using the simplified method, which is an average of the contractual term of the option and its ordinary vesting period. Forfeitures. The Company has elected to record forfeitures as they occur. As of December 31, 2016, the unrecorded deferred stock-based compensation balance related to stock options was approximately $5.9 million and will be recognized over an estimated weighted-average amortization period of 1.71 years. The weighted average grant date fair value of options granted during the year ended December 31, 2016 was $4.21. The following table summarizes the options outstanding, options vested and the options exercisable as of December 31, 2016, 2015 and 2014: Options Weighted- Weighted- Aggregate Options outstanding at December 31, 2014 7.9 years Options granted Options exercised ) Options cancelled/forfeited ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options outstanding at December 31, 2015 7.8 years Options granted Options exercised ) Options cancelled/forfeited ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options outstanding at December 31, 2016 7.50 years $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options exercisable at December 31, 2016 6.45 years $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vested and expected to vest at December 31, 2016 7.50 years ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Intrinsic value in the above table was calculated as the difference between the Company's estimated stock price at December 31, 2016, of $5.70, and the exercise price, multiplied by the number of options. Intrinsic value for options exercised during 2016 amounts to $227. During the year ended December 31, 2016, there was one RSU grant of 50,000 shares of common stock (of which 16,666 shares vested at issuance). The grant date fair value was $5.93 per share and there was no intrinsic value at December 31, 2016. The remaining RSUs vest in February 2017 (16,667 shares) and February 2018 (16,667 shares) and the remaining expense to be recognized is $109.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Taxes
Income Taxes	11. Income Taxes As of December 31, 2016, the Company had available net operating loss carryforwards ("NOL") of approximately $177.4 million and $44.2 million for federal and state income tax reporting purposes, respectively, which are available to offset future federal and state taxable income, if any, through 2036. The Company also has research and development tax credit carryforwards of approximately $4.9 million and $0.4 million for federal and state income tax reporting purposes, respectively, which are available to reduce federal and state income taxes, if any, through 2036 and state income taxes, if any, through 2031. The Internal Revenue Code of 1986, as amended (the "Code") provides for a limitation on the annual use of NOL and other tax attributes (such as research and development tax credit carryforwards) following certain ownership changes, as defined by the Code that could significantly limit the Company's ability to utilize these carryforwards. At this time, the Company has not completed a study to assess whether an ownership change under Section 382 of the Code has occurred, or whether there have been multiple ownership changes since the Company's formation, due to the costs and complexities associated with such a study. The Company is likely to have experienced various ownership changes, as defined by the Code, as a result of past financings. Accordingly, the Company's ability to utilize the aforementioned carryforwards may be limited. Additionally, U.S. tax laws limit the time during which these carryforwards may be applied against future taxes. Therefore, the Company may not be able to take full advantage of these carryforwards for federal and state income tax purposes. The Company does not have any significant unrecognized tax benefits. As of December 31, 2016, the Company has not accrued interest or penalties related to uncertain tax positions. The Company's tax returns for the years ended December 31, 2013 through December 31, 2015 are still subject to examination by major tax jurisdictions. However, the Internal Revenue Service ("IRS") and state tax jurisdictions can audit the NOLs generated in prior years in the years that those NOLs are utilized. For all years through December 31, 2016, the Company generated research credit but has not conducted a study to document the qualified activities. This study may result in an adjustment to the Company's research and development credit carryforwards; however, until a study is completed and any adjustment in known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company's research and development credits and, if an adjustment is required, this adjustment would be offset by an adjustment to the deferred tax asset established for the research and development credit carryforwards and the valuation allowance. The tax effects of temporary differences that give rise to significant portions of the deferred tax assets are presented below: December 31 2016 2015 Deferred tax assets: Net operating loss carryforwards $ $ Research credit carryforward Stock options and other ​ ​ ​ ​ ​ ​ ​ ​ Total gross deferred tax assets Valuation allowance for deferred tax assets ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The gross deferred tax assets and the valuation allowance shown above represent the items which reduce the income tax benefit which would result from applying the federal statutory tax rate to the pretax loss and cause no income tax expense or benefit to be recorded for the years ended December 31, 2016 and 2015. The net change in the valuation allowance for the years ended December 31, 2016 and 2015 was an increase of $10.4 million and $8.9 million, respectively, related primarily to net operating losses incurred by the Company which are not currently deductible. A reconciliation of the U.S. statutory income tax rate to the Company's effective tax rate is as follows: December 31, 2016 2015 2014 Federal income tax at statutory rate % % % State income tax benefit, net of federal benefit % % % Research and development tax credits % % % Other % )% — % Increase to valuation allowance )% )% )% ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effective income tax rate % % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sale of New Jersey Net Operating Losses The Company received approval to sell a portion of the Company's New Jersey net operating losses (NOLs) as part of the Technology Business Tax Certificate Program sponsored by The New Jersey Economic Development Authority. Under the program, emerging biotechnology companies with unused NOLs and unused research and development credits are allowed to sell these benefits to other companies. In December 2016, the Company completed the sale of NOLs totaling approximately $28.2 million and research and development credits totaling approximately $0.8 million for net proceeds of approximately $3.0 million. Such proceeds are reflected as a tax benefit for the year ended December 31, 2016. On November 30, 2015, the Company completed the sale of NOLs totaling approximately $59.8 million and research and development credits totaling $1.1 million for net proceeds of approximately $6.0 million. Such proceeds are reflected as a tax benefit for the year ended December 31, 2015. On February 27, 2014, the Company completed the sale of NOLs totaling approximately $39.1 million and research and development credits totaling approximately $0.4 million for net proceeds of approximately $3.6 million. Such proceeds are reflected as a tax benefit for year ended December 31, 2014.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2016
Related Party Transactions
Related Party Transactions	12. Related Party Transactions Between March 17, 2014 and July 6, 2016, one of the Managing Partners of SmartPharma LLC, or SmartPharma, an entity which provides commercial and business development consulting services to the Company, served as Chief Commercial Officer of the Company. In connection with the appointment of this individual as Chief Commercial Officer, the Company amended its consulting agreement with SmartPharma to remove this individual from the list of persons providing service under the consulting agreement. SmartPharma invoiced the Company $3, $73 and $126 of fees for the years ended December 31, 2016 (through July 6, 2016), 2015 and 2014, respectively. In connection with the resignation of our Chief Commercial Officer who was affiliated with SmartPharma on July 6, 2016, the Company appointed a new Chief Commercial Officer.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies
Commitments and Contingencies	13. Commitments and Contingencies Operating Leases The Company leases approximately 8,200 square feet of office space in Princeton, NJ. The current term of the lease is for a five year period ending on November 30, 2020. The Company has the right to terminate the lease after November 30, 2018 under certain circumstances as defined in the lease. Rent expense was $195, $163 and $159 for the years ended December 31, 2016, 2015 and 2014, respectively. Future minimum annual lease commitments under the non-cancelable operating lease in effect as of December 31, 2016 are as follows: 2017 $ 2018 $ 2019 $ 2020 $ 2021 $ — Legal Proceedings Two complaints have been filed in federal court in the District of New Jersey on January 6, 2017 and January 20, 2017, titled Peng v. Agile Therapeutics, Inc., Alfred Altomari, and Elizabeth Garner, No. 17-cv-119 (D.N.J.), and Lichtenthal v. Agile Therapeutics, Inc., Alfred Altomari, and Elizabeth Garner, No. 17-cv-405 (D.N.J.), (collectively, the "Complaints") respectively, on behalf of a putative class of investors who purchased stock from March 9, 2016 through January 3, 2017. The complaints allege violations of the federal securities laws based on public statements made regarding the Company's Phase 3 "SECURE" clinical trial. Agile denies all allegations in the complaints and the Company plans to vigorously defend the complaints that have been filed. The Company records a provision for contingent losses when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. An unfavorable outcome to any legal matter, if material, could have an adverse effect on the Company's operations or its financial position. Based on its current knowledge, the Company does not believe that the amount of such possible loss or range of potential loss relating to the Complaints is reasonably estimable.

Quarterly Data (Unaudited)

Quarterly Data (Unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Data (Unaudited)
Quarterly Data (Unaudited)	14. Quarterly Data (Unaudited) The following tables summarize the quarterly results of operations for each of the quarters in 2016 and 2015. These quarterly results are unaudited, but in the opinion of management, have been prepared on the same basis as our audited financial information and include all adjustments (consisting only of normal recurring adjustments) necessary for a fair presentation of the information set forth herein. March 31, June 30, September 30, December 31, Total revenue $ — $ — $ — $ — Operating expenses $ $ $ $ ) Net loss $ ) $ ) $ ) $ ) Basic and diluted net loss per common share $ ) $ ) $ ) $ ) March 31, June 30, September 30, December 31, Total revenue $ — $ — $ — $ — Operating expenses $ $ $ $ Net income (loss) $ ) $ ) $ ) $ ) Basic and diluted net income loss per common share $ ) $ ) $ ) $ ) The net loss and basic and diluted net loss per share for the quarter ended December 31, 2016 includes a tax benefit of $3,075 from the sale of New Jersey state net operating losses. The net loss and basic and diluted net loss per share for the quarter ended December 31, 2015 includes a tax benefit of $5,972 from the sale of New Jersey state net operating losses (see Note 11).

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in accordance with United States ("U.S.") generally accepted accounting principles ("GAAP") and include all adjustments necessary for the fair presentation of the Company's financial position for the periods presented.
Use of Estimates	Use of Estimates The preparation of the Company's financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company bases its estimates and judgments on historical experience and various other assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company's balance sheets and the amounts of expenses reported for each of the periods presented are affected by estimates and assumptions, which are used for, but not limited to, the accounting for common stock warrants, stock-based compensation, income taxes, and accounting for research and development costs. Actual results could differ from those estimates.
Risks and Uncertainties	Risks and Uncertainties Product candidates developed by the Company typically will require approval from the FDA prior to commercial sales. There can be no assurance that the Company's product candidates will receive the required approval. If the Company was denied approval or such approval was delayed, or is unable to obtain the necessary financing to complete development and approval, there will be a material adverse impact on the Company's financial condition and results of operations.
Stock Split	Stock Split On May 5, 2014, the Company effected a 1.4-for-1 stock split of the Company's common stock. All share and per share amounts of common stock contained in the Company's financial statements have been restated for all periods to give retroactive effect to the stock split. The shares of common stock retained a par value of $0.0001 per share. Accordingly, the stockholders' deficit reflects the stock split by reclassifying from "Additional paid-in Capital" to "Common Stock" in an amount equal to the par value of the increased shares resulting from the stock split.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly-liquid investments with an original maturity of three months or less when purchased to be cash equivalents. All cash and cash equivalents are held in United States financial institutions. Cash and cash equivalents include money market funds that invest primarily in commercial paper and U.S. government and U.S. government agency obligations. The Company maintains balances with financial institutions in excess of the FDIC limit.
Fair Value of Financial Instruments	Fair Value of Financial Instruments In accordance with ASC 825, Financial Instruments , disclosures of fair value information about financial instruments are required, whether or not recognized in the balance sheet, for which it is practicable to estimate that value. Cash and cash equivalents are carried at fair value (see Note 3). Financial instruments, including accounts payable and accrued liabilities, are carried at cost, which approximates fair value given their short-term nature.
Property and Equipment	Property and Equipment Property and equipment, consisting of manufacturing, office and computer equipment, is stated at cost, less accumulated depreciation. Depreciation is computed using the straight-line, method over the estimated useful lives of the assets. Expenditures incurred after the fixed assets have been put into operation, such as repairs and maintenance, are charged to earnings in the period in which costs are incurred. Improvements and additions are capitalized in accordance with Company policy.
Long-Lived Assets	Long-Lived Assets In accordance with ASC 360, Property, Plant and Equipment , the Company's policy is to review long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Management does not believe that there has been any impairment of the carrying value of any long-lived assets as of December 31, 2016.
Research and Development Expense	Research and Development Expense Research and development costs are expensed as incurred. Research and development expense consists primarily of costs related to personnel, including salaries and other personnel-related expenses, expenses related to manufacturing, clinical trial expenses, consulting fees and support services used in drug development. All research and development costs are charged to operations as incurred in accordance with ASC 730, Research and Development . In certain circumstances, the Company is required to make advance payments to vendors for goods or services that will be received in the future for use in research and development activities. In such circumstances, the advance payments are deferred and are expensed when the activity has been performed or when the goods have been received.
Deferred Financing Costs	Deferred Financing Costs Costs directly attributable to the Company's term loan (see Note 8) are deferred and reported as a reduction of the related term loan. These costs represent legal fees and other costs related to the term loan and are being amortized over the term of the loan. Amortization of deferred financing costs charged to interest expense was $256, $211 and $59 for the years ended December 31, 2016, 2015 and 2014, respectively.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments which potentially subject the Company to credit risk consist principally of cash and cash equivalents. All cash and cash equivalents are held in business checking and money market accounts in United States financial institutions the balances of which exceed federally insured limits. The Company has not recognized any losses from credit risks on such accounts. The Company believes it is not exposed to significant credit risks on cash and cash equivalents. The Company has no financial instruments with off-balance sheet risk of accounting loss.
Warrants	Warrants The Company accounts for its warrants to purchase redeemable convertible stock in accordance with ASC 480, Distinguishing Liabilities from Equity . ASC 480 requires that a financial instrument, other than outstanding share, that, at inception, is indexed to an obligation to repurchase the issuer's equity shares, regardless of the timing or the probability of the redemption feature, and may require the issuer to settle the obligation by transferring assets be classified as a liability. The Company measures the fair value of its warrant liability using the Black-Scholes option pricing model with changes in fair value recognized as increases or reductions to other income (expense) in the statement of operations. In connection with the completion of the Company's initial public offering in May 2014, the warrants to purchase shares of Series A-1 and Series A-2 preferred stock expired unexercised and the warrants to purchase shares of Series C preferred stock automatically converted into warrants to purchase shares of common stock. Warrants with non-standard anti-dilution provisions (referred to as down round protection) are classified as liabilities and re-measured each reporting period. As of December 31, 2016, there were outstanding 62,505 warrants to purchase common stock at $6.00 per share. These warrants expire on December 14, 2019. The warrants issued in connection with the Company's debt financing completed in February 2015 (see Note 8) are classified as a component of stockholders' equity. The value of such warrants was determined using the Black-Scholes option-pricing model.
Income Taxes	Income Taxes The Company accounts for deferred taxes using the asset and liability method as specified by ASC 740, Income Taxes . Deferred income tax assets and liabilities are determined based on differences between the financial statement reporting and the tax basis of assets and liabilities, operating losses and tax credit carryforwards. Deferred income taxes are measured using the enacted tax rates and laws that are anticipated to be in effect when the differences are expected to reverse. The measurement of deferred income tax assets is reduced, if necessary, by a valuation allowance for any tax benefits which are not expected to be realized. The effect on deferred income tax assets and liabilities of a change in tax rates is recognized in the period that such tax rate changes are enacted. The Company has adopted the authoritative guidance on accounting for and disclosure of uncertainty in tax positions which prescribes a comprehensive model for the financial statement recognition, measurement, presentation and disclosure of uncertain tax positions taken or expected to be taken in income tax returns. The Company has no uncertain tax positions as of December 31, 2016 that qualifies for either recognition or disclosure in the financial statements under this guidance.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation in accordance with ASC 718, Compensation—Stock Compensation . The Company grants stock options for a fixed number of shares to employees and non-employees with an exercise price equal to the fair value of the shares at grant date. Compensation cost is recognized for all share-based payments granted and is based on the grant-date fair value estimated using the weighted-average assumption of the Black-Scholes option pricing model based on key assumptions such as stock price, expected volatility and expected term. The Company elects to account for forfeitures when they occur. The equity instrument is not considered to be issued until the instrument vests. As a result, compensation cost is recognized over the requisite service period with an offsetting credit to additional paid-in capital. The Company also awards restricted stock units ("RSUs") to employees. RSUs are generally subject to forfeiture if employment terminates prior to the completion of the vesting restrictions. The Company expenses the cost of the RSUs, which is determined to be the fair market value of the shares of common stock underlying the RSUs at the date of grant, ratably over the period during which the vesting restrictions lapse. Awards for consultants are accounted for under ASC 505-50, Equity Based Payments to Non-Employees . Any compensation expense related to consultants is marked-to-market over the applicable vesting period as they vest. Prior to May 22, 2014, the Company utilized various methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation , to estimate the fair value of its stock. The methodologies included an option pricing method and a probability-weighted expected return methodology that determined an estimated value under an initial public offering (IPO) scenario and a sale scenario based upon an assessment of the probability of occurrence of each scenario. Each valuation methodology includes estimates and assumptions that require the Company's judgment. These estimates include assumptions regarding future performance, including the successful completion of clinical trials and the time to completing an IPO or sale of the Company. As with any valuation, significant changes to the key assumptions used in the valuations could result in different fair values of common stock at each valuation date.
Segment Information	Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating and reporting segment, which is the business of developing its transdermal patch for use in contraception.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding plus the effect of dilutive potential common shares outstanding during the period determined using the treasury-stock and if-converted methods. For purposes of diluted net loss per share calculation, common stock warrants, unvested RSUs and stock options are considered to be potentially dilutive securities but are excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive and therefore, basic and diluted net loss per share were the same for all periods presented. The following table sets forth the outstanding potentially dilutive securities that have been excluded from the calculation of diluted net loss per share because to do so would be anti-dilutive (in common equivalent shares): Year Ended 2016 2015 2014 Convertible preferred stock — — — Convertible preferred stock warrants — — — Common stock warrants Unvested restricted stock units — — Common stock options ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Recent Accounting Pronouncements	Recent Accounting Pronouncements In August 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern , which defines management's responsibility to assess an entity's ability to continue as a going concern, and to provide related footnote disclosures if there is substantial doubt about its ability to continue as a going concern. The new standard is effective for the annual period ending after December 15, 2016, and for interim periods thereafter. The Company adopted ASU 2014-15 in the fourth quarter of 2016, which resulted in no change to the Company's financial statements. Additionally, the Company will perform quarterly evaluations to identify current conditions which may raise substantial doubt about the entity's ability to continue as a going concern within one year after the date that the financial statements are issued. In April 2015, the FASB issued an amendment to U.S. GAAP to simplify the balance sheet presentation of the costs for issuing debt. The changes were adopted in ASU No. 2015-03, Interest—Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issue Costs . ASU 2015-03 amends current presentation guidance by requiring that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. Prior to the issuance of ASU 2015-03, debt issuance costs were required to be presented as an asset in the balance sheet. The Company adopted the provisions of ASU 2015-03 on January 1, 2016 and prior period balances have been reclassified to conform to the current period presentation. As of December 31, 2015, $152 of debt issuance costs were reclassified in the balance sheet from "deferred financing costs, net" to "loan payable, current portion" and $139 was reclassified from "deferred financing costs, net" to "loan payable, long-term". The adoption of ASU 2015-03 did not have an impact on the Company's operations or cash flows. In February 2016, the FASB issued ASU No. 2016-02, Leases . The new standard establishes a right-of-use (ROU) model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the statement of operations. The new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. A modified retrospective transition approach is required for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company will be evaluating the impact of the pending adoption of the new standard on the Company's financial statements. In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting . This ASU requires all tax effects of share-based payment settlements to be recorded through the statement of operations. Currently, tax benefits in excess of compensation cost, or "windfalls", are recorded in equity, and tax deficiencies, or "shortfalls", are recorded to equity to the extent of previous windfalls, and then to the statement of operations. In addition, under the new guidance, companies will be permitted to make a policy election to recognize the impact of forfeitures either when they occur, or on an estimated basis. Finally, this update simplifies withholding requirements to allow companies to withhold up to an employee's maximum tax rate without resulting in liability classification for the award. ASU 2016-09 is effective for annual reporting periods beginning after December 15, 2016, and early adoption is permitted. The Company has adopted the provisions of this standard early and the impact on its financial statements was not material.

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Schedule of potentially dilutive securities excluded from calculation of diluted net loss per share	The following table sets forth the outstanding potentially dilutive securities that have been excluded from the calculation of diluted net loss per share because to do so would be anti-dilutive (in common equivalent shares): Year Ended 2016 2015 2014 Convertible preferred stock — — — Convertible preferred stock warrants — — — Common stock warrants Unvested restricted stock units — — Common stock options ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Measurements
Schedule of financial instruments measured at fair value by level within fair value hierarchy	Level 1 Level 2 Level 3 2016 Assets: Cash equivalents $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets at fair value $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Common stock warrants — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities at fair value $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Level 1 Level 2 Level 3 2015 Assets: Cash equivalents $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets at fair value $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Common stock warrants — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities at fair value $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of roll forward of fair value of Level 3 warrants	Beginning balance at December 31, 2013 $ Expiration of Series A-1 and Series A-2 warrants ) Change in fair value ​ ​ ​ ​ ​ Ending balance at December 31, 2014 Change in fair value ​ ​ ​ ​ ​ Ending balance at December 31, 2015 Change in fair value ) ​ ​ ​ ​ ​ Ending balance at December 31, 2016 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Prepaid Expenses (Tables)

Prepaid Expenses (Tables)	12 Months Ended
	Dec. 31, 2016
Prepaid Expenses
Schedule of components of prepaid expenses	December 31 2016 2015 Prepaid clinical trial expense $ $ Prepaid insurance Other ​ ​ ​ ​ ​ ​ ​ ​ Total prepaid expenses $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2016
Property and Equipment
Schedule of components of property and equipment	December 31 Estimated 2016 2015 Office equipment $ $ 3 - 10 years Computer equipment 3 years Manufacturing equipment 5 years ​ ​ ​ ​ ​ ​ ​ ​ ​ Less: accumulated depreciation ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ Property and equipment, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2016
Accrued Liabilities
Schedule of components of accrued liabilities	December 31 2016 2015 Employee bonuses $ $ Accrued clinical trial costs Accrued professional fees and other ​ ​ ​ ​ ​ ​ ​ ​ Total accrued liabilities $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Loan and Security Agreements (T

Loan and Security Agreements (Tables)	12 Months Ended
	Dec. 31, 2016
Loan and Security Agreements
Schedule of annual maturities of Hercules Loan	2017 $ 2018 ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Equity Incentive Plans
Schedule of stock-based compensation expense and allocation	Year Ended December 31, 2016 2015 2014 Employee $ $ $ Non-employee ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2016 2015 2014 Research and development $ $ $ General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total stock-based compensation expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of assumptions used to compute employee stock-based compensation	2016 2015 2014 Risk-free interest rate % % % Expected volatility % % % Expected dividend yield % % % Expected life (in years)
Summary of options outstanding, vested and exercisable	Options Weighted- Weighted- Aggregate Options outstanding at December 31, 2014 7.9 years Options granted Options exercised ) Options cancelled/forfeited ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options outstanding at December 31, 2015 7.8 years Options granted Options exercised ) Options cancelled/forfeited ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options outstanding at December 31, 2016 7.50 years $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options exercisable at December 31, 2016 6.45 years $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vested and expected to vest at December 31, 2016 7.50 years ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Taxes
Schedule of tax effects of temporary differences that give rise to significant portions of deferred tax assets	December 31 2016 2015 Deferred tax assets: Net operating loss carryforwards $ $ Research credit carryforward Stock options and other ​ ​ ​ ​ ​ ​ ​ ​ Total gross deferred tax assets Valuation allowance for deferred tax assets ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of reconciliation of U.S. statutory income tax rate to effective tax rate	December 31, 2016 2015 2014 Federal income tax at statutory rate % % % State income tax benefit, net of federal benefit % % % Research and development tax credits % % % Other % )% — % Increase to valuation allowance )% )% )% ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effective income tax rate % % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies
Schedule of future minimum annual lease commitments under non-cancelable operating lease	2017 $ 2018 $ 2019 $ 2020 $ 2021 $ —

Quarterly Data (Unaudited) (Tab

Quarterly Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Data (Unaudited)
Summary of quarterly results of operations	March 31, June 30, September 30, December 31, Total revenue $ — $ — $ — $ — Operating expenses $ $ $ $ ) Net loss $ ) $ ) $ ) $ ) Basic and diluted net loss per common share $ ) $ ) $ ) $ ) March 31, June 30, September 30, December 31, Total revenue $ — $ — $ — $ — Operating expenses $ $ $ $ Net income (loss) $ ) $ ) $ ) $ ) Basic and diluted net income loss per common share $ ) $ ) $ ) $ )

Organization and Description 33

Organization and Description of Business (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Organization and Description of Business
Product revenue	$ 0
Accumulated deficit	(193,468)	$ (164,727)
Cash and cash equivalents	$ 48,750	$ 34,395	$ 40,182	$ 2,120

Summary of Significant Accoun34

Summary of Significant Accounting Polices - Stock Split (Details)	May 05, 2014$ / shares	Dec. 31, 2016$ / shares	Dec. 31, 2015$ / shares
Stock split
Par value of common stock (in dollars per share)		$ 0.0001	$ 0.0001
Common Stock
Stock split
Stock split conversion ratio	1.4
Par value of common stock (in dollars per share)	$ 0.0001

Summary of Significant Accoun35

Summary of Significant Accounting Policies - Deferred Financing Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest expense
Deferred Financing Costs
Amortization of deferred financing costs	$ 256	$ 211	$ 59

Summary of Significant Accoun36

Summary of Significant Accounting Policies - Concentrations of Credit Risk (Details) $ in Thousands	Dec. 31, 2016USD ($)
Concentration of risk, financial assets
Financial instruments with off-balance sheet risk of accounting loss, assets	$ 0
Concentration risk, financial liabilities
Financial instruments with off-balance sheet risk of accounting loss, liabilities	$ 0

Summary of Significant Accoun37

Summary of Significant Accounting Policies - Warrants (Details) - Warrants - Common stock warrants	Dec. 31, 2016$ / sharesshares
Warrants
Common stock that can be purchased with warrants (in shares) | shares	62,505
Exercise price of warrants (in dollars per share) | $ / shares	$ 6

Summary of Significant Accoun38

Summary of Significant Accounting Policies - Uncertain Tax Positions and Segment Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)segment
Uncertainty in tax positions
Uncertain tax positions | $	$ 0
Segment Information
Number of operating segments	1
Number of reporting segments	1

Summary of Significant Accoun39

Summary of Significant Accounting Policies - Outstanding Potentially Dilutive Securities that are Anti-Dilutive (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	3,121,083	2,407,844	1,880,053
Common stock warrants
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	242,779	242,779	62,505
Unvested restricted stock units
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	33,334
Stock options
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	2,844,970	2,165,065	1,817,548

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Recent Accounting Pronouncements
Loan payable, current portion	$ 5,104	$ 2,336
Loan payable, long-term	$ 10,899	12,896
Accounting Standards Update 2015-03 | Adjustment
Recent Accounting Pronouncements
Deferred financing costs, net, reclassified to loan payable, current portion		(152)
Loan payable, current portion		152
Deferred financing costs, net, reclassified to loan payable, long-term		(139)
Loan payable, long-term		$ 139

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments Measured at Fair Value by Hierarchy Level and Significant Assumptions Used for Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Liabilities:
Common stock warrants	$ 172	$ 406
Significant assumptions used in preparing the option pricing model for valuing the Company's warrants
Fair value of common stock (in dollars per share)	$ 5.70
Recurring | Level 1
Assets:
Total assets at fair value	$ 48,659	34,324
Recurring | Level 1 | Cash equivalents
Assets:
Cash and cash equivalents	48,659	34,324
Recurring | Level 3
Liabilities:
Total liabilities at fair value	172	406
Recurring | Level 3 | Warrants | Common stock warrants
Liabilities:
Common stock warrants	$ 172	$ 406
Recurring | Level 3 | Warrants | Common stock warrants | Option pricing model
Significant assumptions used in preparing the option pricing model for valuing the Company's warrants
Volatility (as a percent)	75.00%	75.00%
Risk free interest rate (as a percent)	1.47%	1.54%
Life of treasury bonds	3 years	4 years
Strike price (in dollars per share)	$ 6	$ 6
Fair value of common stock (in dollars per share)	$ 5.70	$ 9.76
Expected life (in years)	3 years	4 years

Fair Value Measurements - Roll

Fair Value Measurements - Roll forward of Fair Value of Level 3 Warrants and Transfers Between Levels (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair value measurements
Asset transfers out of Level 1 into Level 2	$ 0	$ 0
Asset transfers out of Level 2 into Level 1	0	0
Asset transfers into (out of) Level 3	0	0
Liability transfers out of Level 1 into Level 2	0	0
Liability transfers out of Level 2 into Level 1	0	0
Liability transfers into (out of) Level 3	0	0
Liabilities | Warrants
Rollforward of the fair value of Level 3 warrants:
Beginning balance	406	296	$ 644
Expiration of Series A-1 and Series A-2 warrants			(493)
Change in fair value	(234)	110	145
Ending balance	$ 172	$ 406	$ 296

Prepaid Expenses (Details)

Prepaid Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Prepaid Expenses
Prepaid clinical trial expense	$ 2,005	$ 2,803
Prepaid insurance	665	780
Other	98	107
Total prepaid expenses	$ 2,768	$ 3,690

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment
Property and equipment, gross	$ 12,653	$ 12,622
Less: accumulated depreciation	(323)	(304)
Property and equipment, net	12,330	12,318
Office equipment
Property and Equipment
Property and equipment, gross	$ 55	$ 55
Office equipment | Minimum
Property and Equipment
Estimated Life (in years)	3 years	3 years
Office equipment | Maximum
Property and Equipment
Estimated Life (in years)	10 years	10 years
Computer equipment
Property and Equipment
Property and equipment, gross	$ 133	$ 106
Estimated Life (in years)	3 years	3 years
Manufacturing equipment
Property and Equipment
Property and equipment, gross	$ 12,465	$ 12,461
Estimated Life (in years)	5 years	5 years
Manufacturing equipment in process of being constructed and qualified
Property and Equipment
Property and equipment, gross	$ 12,400	$ 12,400

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued Liabilities
Employee bonuses	$ 1,041	$ 938
Accrued clinical trial costs	1,908	1,507
Accrued professional fees and other	403	208
Total accrued liabilities	$ 3,352	$ 2,653

Convertible Note Financing (Det

Convertible Note Financing (Details) - Convertible notes - Convertible Promissory Notes, April 2014 - USD ($) $ / shares in Units, $ in Millions	May 29, 2014	Dec. 31, 2014	Apr. 28, 2014
Convertible Note Financing
Aggregate amount of loan borrowed			$ 3
Interest rate (as a percent)			8.00%
Conversion price (in dollars per share)	$ 6
Common Stock
Convertible Note Financing
Conversion to common stock (in shares)	503,450	503,450

Loan and Security Agreements -

Loan and Security Agreements - Oxford Loan and Hercules Loan (Details)	1 Months Ended		12 Months Ended
	Feb. 28, 2015USD ($)$ / sharesshares	Dec. 31, 2012USD ($)installment$ / sharesshares	Dec. 31, 2016USD ($)installmentperiod$ / sharesshares	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Aug. 31, 2016USD ($)
Loan and Security Agreements
Fair value of common stock warrant issued with debt financing				$ 1,184,000
Loss on extinguishment of debt				1,036,000
Significant assumptions used in preparing the option pricing model for valuing the Company's warrants
Fair value of common stock (in dollars per share) | $ / shares			$ 5.70
Warrants | Common stock warrants | Hercules Capital, Inc.
Loan and Security Agreements
Common stock that can be purchased with warrants (in shares) | shares	180,274
Exercise price of warrants (in dollars per share) | $ / shares	$ 5.89
Significant assumptions used in preparing the option pricing model for valuing the Company's warrants
Volatility (as a percent)	75.00%
Risk free interest rate (as a percent)	1.22%
Life of treasury bonds	4 years
Strike price (in dollars per share) | $ / shares	$ 5.89
Fair value of common stock (in dollars per share) | $ / shares	$ 9.82
Expected life (in years)	4 years
Additional Paid-in Capital
Loan and Security Agreements
Fair value of common stock warrant issued with debt financing				1,184,000
Additional Paid-in Capital | Hercules Capital, Inc.
Loan and Security Agreements
Fair value of common stock warrant issued with debt financing	$ 1,200,000
Warrants | Common stock warrants
Loan and Security Agreements
Common stock that can be purchased with warrants (in shares) | shares			62,505
Exercise price of warrants (in dollars per share) | $ / shares			$ 6
Warrants | Common stock warrants | Oxford Finance LLC
Loan and Security Agreements
Common stock that can be purchased with warrants (in shares) | shares		62,505
Exercise price of warrants (in dollars per share) | $ / shares		$ 6
Secured debt
Loan and Security Agreements
Interest expense, including accretion of value of related warrants and amortization of deferred financing costs			$ 2,446,000	2,077,000	$ 1,545,000
Secured debt | Oxford Loan | Oxford Finance LLC
Loan and Security Agreements
Amount borrowed		$ 15,000,000
Repayment of existing debt	15,500,000
Number of consecutive monthly principal installments | installment		30
Final payment		$ 675,000
Secured debt | Hercules Loan | Hercules Capital, Inc.
Loan and Security Agreements
Maximum borrowing capacity	25,000,000
Fixed interest rate (as a percent)			9.00%
Number of consecutive monthly principal installments | installment			23
Final payment			$ 610,500
Discount on debt	1,200,000
Secured debt | Hercules Loan | Hercules Capital, Inc. | Minimum
Loan and Security Agreements
Proceeds From Issuance Of Common Stock, Minimum			40,000,000
Secured debt | Hercules Loan Tranche One | Hercules Capital, Inc.
Loan and Security Agreements
Amount borrowed	16,500,000
Secured debt | Hercules Loan Tranche Two | Hercules Capital, Inc.
Loan and Security Agreements
Additional amount available			$ 8,500,000
Secured debt | LIBOR | Oxford Loan | Oxford Finance LLC
Loan and Security Agreements
Interest rate (as a percent)		9.20%
Variable rate basis		Three-month U.S. Libor
Variable rate base (as a percent)		0.47%
Variable interest rate margin (as a percent)		8.73%
Secured debt | Prime | Hercules Loan | Hercules Capital, Inc.
Loan and Security Agreements
Variable rate basis			Prime minus 4.25%
Variable interest rate margin (as a percent)			9.00%
Variable rate adjustment (as a percent)			4.25%
Secured debt | Second year (through February 24, 2017) | Hercules Loan | Hercules Capital, Inc.
Loan and Security Agreements
Prepayment premium as percentage of outstanding principal			2.00%
Secured debt | After February 24, 2017 | Hercules Loan | Hercules Capital, Inc.
Loan and Security Agreements
Prepayment premium as percentage of outstanding principal			1.00%
Equity financings | Right to participate in future equity financings | Hercules Loan | Hercules Capital, Inc. | Maximum
Loan and Security Agreements
Equity financings amount	$ 2,000,000
Secured debt | Oxford Loan | Oxford Finance LLC
Loan and Security Agreements
Loss on extinguishment of debt				$ 1,000,000
Secured debt | Hercules Loan | Hercules Capital, Inc.
Loan and Security Agreements
Facility Fee						$ 165,000
Number of periods interest-only payment may be extended | period			2

Loan and Security Agreements 48

Loan and Security Agreements - Annual Maturities of Hercules Loan (Details) - Secured debt - Hercules Capital, Inc. - Hercules Loan $ in Thousands	Dec. 31, 2016USD ($)
Maturities of Loan
2,017	$ 5,612
2,018	10,888
Total	$ 16,500

Stockholders' Equity - Initial

Stockholders' Equity - Initial Public Offering and Related Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	May 29, 2014	Dec. 31, 2014
Convertible notes | Convertible Promissory Notes, April 2014
Stockholders' equity
Conversion to common stock	$ 3,000	$ 3,020
Redeemable Convertible Preferred Stock
Stockholders' equity
Conversion to common stock		$ 69,233
Common Stock | Convertible notes | Convertible Promissory Notes, April 2014
Stockholders' equity
Conversion to common stock (in shares)	503,450	503,450
Common Stock | Redeemable Convertible Preferred Stock
Stockholders' equity
Conversion to common stock		$ 1
Conversion to common stock (in shares)	8,809,325	8,803,547
Initial public offering
Stockholders' equity
Proceeds from the issuance of common stock, net	$ 49,700
Initial public offering | Common Stock
Stockholders' equity
Common stock issued (in shares)	9,166,667	9,166,667
Share price (in dollars per share)	$ 6

Stockholders' Equity - Amended

Stockholders' Equity - Amended and Restated Certificate of Incorporation (Details)	May 29, 2014seriesclassshares	May 29, 2014classshares	May 07, 2014USD ($)	Dec. 31, 2016shares	Dec. 31, 2015shares
Sale of stock
Number of shares of common stock authorized | shares	150,000,000	150,000,000		150,000,000	150,000,000
Authorized shares of preferred stock | shares	10,000,000	10,000,000
Board of Directors, number of classes | class		3
Term of Board member	3 years
Number of classes elected at each annual meeting | class	1
Minimum
Sale of stock
Number of series of preferred stock that may be issued | series	1
Affirmative vote of all then-outstanding shares of capital stock for removal of directors (as a percent)	75.00%
Series C Convertible Preferred Stock | Automatic conversion, underwritten public offering | Minimum
Sale of stock
Proceeds from Issuance of Common Stock | $			$ 45,000,000

Stockholders' Equity - Private

Stockholders' Equity - Private Placement (Details) - Private Placement $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2015USD ($)shareholder$ / sharesshares	Dec. 31, 2015shares
Sale of stock
Proceeds from the issuance of common stock, net | $	$ 19.3
Stockholders affiliated with members of Board of Directors
Sale of stock
Proceeds from the issuance of common stock, net | $	$ 9.5
Common Stock
Sale of stock
Common stock issued (in shares) | shares	3,400,000	3,418,804
Share price (in dollars per share) | $ / shares	$ 5.85
Common Stock | Stockholders affiliated with members of Board of Directors
Sale of stock
Number of stockholders affiliated with members of Board of Directors who purchased shares | shareholder	2
Common stock issued (in shares) | shares	1,623,932

Stockholders' Equity - Shelf Re

Stockholders' Equity - Shelf Registration Statement (Details) $ in Millions	Jun. 19, 2015USD ($)
2015 Shelf Registration
Sale of stock
Aggregate amount of securities issuable	$ 150

Stockholders' Equity - 2016 Pub

Stockholders' Equity - 2016 Public Offering of Common Stock (Details) $ / shares in Units, $ in Millions	1 Months Ended		2 Months Ended	12 Months Ended
	Feb. 29, 2016$ / sharesshares	Jan. 31, 2016USD ($)shareholder$ / sharesshares	Feb. 29, 2016USD ($)$ / sharesshares	Dec. 31, 2016shares
Public Offering
Sale of stock
Proceeds from the issuance of common stock, net | $			$ 37.5
Public Offering | Stockholders affiliated with members of Board of Directors
Sale of stock
Number of stockholders affiliated with members of Board of Directors who purchased shares | shareholder		1
Proceeds from the issuance of common stock, net | $		$ 2.5
Public Offering | Common Stock
Sale of stock
Common stock issued (in shares)		5,511,812	6,338,583	6,338,583
Share price (in dollars per share) | $ / shares		$ 6.35
Public Offering | Common Stock | Stockholders affiliated with members of Board of Directors
Sale of stock
Common stock issued (in shares)		393,700
Underwriter purchase option | Common Stock
Sale of stock
Common stock issued (in shares)	826,771
Share price (in dollars per share) | $ / shares	$ 6.35		$ 6.35

Equity Incentive Plans - Awards

Equity Incentive Plans - Awards Granted, Terms and Employee and Non-employee Stock-Based Compensation Expense (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2008	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity incentive plans
Total stock-based compensation expense		$ 3,425	$ 2,965	$ 1,381
1997 Plan
Equity incentive plans
Options granted (in shares)	0
2008 Plan
Equity incentive plans
Options granted (in shares)				0
2014 Equity Incentive Plan
Equity incentive plans
Shares available for grant		605,390
Stock options
Equity incentive plans
Options granted (in shares)		825,500	620,600
Total stock-based compensation expense		$ 3,425	$ 2,965	$ 1,381
Stock options | Minimum
Equity incentive plans
Exercise prices of options granted through the end of the year (in dollars per share)		$ 0.71
Stock options | Maximum
Equity incentive plans
Exercise prices of options granted through the end of the year (in dollars per share)		$ 285.71
Stock options | 1997 Plan and 2008 Plan
Equity incentive plans
Expiration period		10 years
Vesting period		4 years
Employee stock options
Equity incentive plans
Total stock-based compensation expense		$ 3,456	2,662	1,185
Non-employee stock options
Equity incentive plans
Total stock-based compensation expense		$ (31)	$ 303	$ 196

Equity Incentive Plans - Alloca

Equity Incentive Plans - Allocation of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 3,425	$ 2,965	$ 1,381
Stock options
Stock-Based Compensation Expense
Total stock-based compensation expense	3,425	2,965	1,381
Stock options | Research and development
Stock-Based Compensation Expense
Total stock-based compensation expense	1,063	1,161	617
Stock options | General and administrative
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 2,362	$ 1,804	$ 764

Equity Incentive Plans - Assump

Equity Incentive Plans - Assumptions Used to Compute Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock options
Equity incentive plans
Unrecorded deferred stock-based compensation balance related to stock options	$ 5.9
Weighted-average amortization period over which cost is expected to be recognized	1 year 8 months 16 days
Weighted average grant date fair value of options granted (in dollars per share)	$ 4.21
Employee stock options
Assumptions used to compute employee stock based compensation under the Black-Scholes option pricing model
Risk-free interest rate (as a percent)	1.48%	1.92%	1.84%
Expected volatility (as a percent)	75.00%	75.00%	104.80%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Expected life (in years)	6 years 3 months	6 years 3 months	6 years 3 months

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Activity for Options Outstanding, Options Exercisable and Intrinsic Value (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Aggregate Intrinsic Value
Estimated stock price (in dollars per share)	$ 5.70
Stock options
Options
Options outstanding at beginning of year (in shares)	2,165,065	1,817,548
Options granted (in shares)	825,500	620,600
Options exercised (in shares)	(88,870)	(261,936)
Options cancelled/forfeited (in shares)	(56,725)	(11,147)
Options outstanding at end of year (in shares)	2,844,970	2,165,065	1,817,548
Options exercisable at end of year (in shares)	1,482,812
Vested and expected to vest at end of year (in shares)	2,844,970
Weighted-Average Exercise Price
Options outstanding at beginning of year (in dollars per share)	$ 7.19	$ 5.56
Options granted (in dollars per share)		9.84
Options exercised (in dollars per share)		2.26
Options cancelled/forfeited (in dollars per share)		2.14
Options outstanding at end of year (in dollars per share)		$ 7.19	$ 5.56
Weighted-Average Remaining Contractual Life (Years)
Options outstanding at end of year	7 years 6 months	7 years 9 months 18 days	7 years 10 months 24 days
Options exercisable at end of year	6 years 5 months 12 days
Vested and expected to vest at end of year	7 years 6 months
Aggregate Intrinsic Value
Options outstanding at the end of the period (in dollars)	$ 1,772
Options exercisable at the end of the period (in dollars)	1,772
Options exercised during the year, intrinsic value	$ 227

Equity Incentive Plans - Summ58

Equity Incentive Plans - Summary of Restricted Stock Units (Details) - Unvested restricted stock units $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)item$ / sharesshares
Equity incentive plans
Number of RSU's granted | item	1
Granted (in shares)	50,000
Vested (in shares)	16,666
Weighted average grant date fair value of options granted (in dollars per share) | $ / shares	$ 5.93
Intrinsic value | $	$ 0
Unrecognized compensation expense | $	$ 109
February 2,017
Equity incentive plans
Vested (in shares)	16,667
February 2,018
Equity incentive plans
Vested (in shares)	16,667

Income Taxes - Net Operating Lo

Income Taxes - Net Operating Loss Carryforwards (Details) $ in Millions	Dec. 31, 2016USD ($)
Federal
Net operating loss carryforwards
Net operating loss carryforwards	$ 177.4
State
Net operating loss carryforwards
Net operating loss carryforwards	$ 44.2

Income Taxes - Research and Dev

Income Taxes - Research and Development Tax Credit Carryforwards (Details) - Research and Development $ in Millions	Dec. 31, 2016USD ($)
Federal
Tax credit carryforwards
Tax credit carryforwards	$ 4.9
State
Tax credit carryforwards
Tax credit carryforwards	$ 0.4

Income Taxes - Tax Effects of T

Income Taxes - Tax Effects of Temporary Differences that Give Rise to Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss carryforwards	$ 63,068	$ 54,197
Research credit carryforward	5,284	4,527
Stock options and other	2,250	1,474
Total gross deferred tax assets	70,602	60,198
Valuation allowance for deferred tax assets	(70,602)	(60,198)
Income taxes
Deferred income tax expense or benefit	0	0
Valuation allowance
Net change in the valuation allowance, related primarily to net operating losses	$ 10,400	$ 8,900

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of U.S. Statutory Income Tax Rate to Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of the U.S. statutory income tax rate to the Company's effective tax rate
Federal income tax at statutory rate (as a percent)	34.00%	34.00%	34.00%
State income tax benefit, net of federal benefit (as a percent)	6.00%	6.00%	6.00%
Research and development tax credits (as a percent)	2.00%	2.00%	3.00%
Other (as a percent)	1.00%	(2.00%)
Increase to valuation allowance (as a percent)	(33.00%)	(24.00%)	(24.00%)
Effective income tax rate (as a percent)	10.00%	16.00%	19.00%

Income Taxes - Sale of New Jers

Income Taxes - Sale of New Jersey Net Operating Losses (Details) - State - USD ($) $ in Millions	Nov. 30, 2015	Feb. 27, 2014	Dec. 31, 2016
Sale of New Jersey Net Operating Losses
NOLs			$ 44.2
Research and Development
Sale of New Jersey Net Operating Losses
Tax credits			0.4
New Jersey | Sale of unused NOLs and research and development credits
Sale of New Jersey Net Operating Losses
NOLs	$ 59.8	$ 39.1	28.2
Net proceeds from sale of NOL	6	3.6	3
New Jersey | Research and Development | Sale of unused NOLs and research and development credits
Sale of New Jersey Net Operating Losses
Tax credits	$ 1.1	$ 0.4	$ 0.8

Related Party Transactions (Det

Related Party Transactions (Details) - SmartPharma $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Jul. 06, 2016person
Related party transactions
Number of Managing Partners appointed to Chief Commercial Officer | person				1
Commercial and business development consulting services
Related party transactions
Fees invoiced by the related party | $	$ 3	$ 73	$ 126

Commitments and Contingencies65

Commitments and Contingencies (Details) $ in Thousands	Jan. 06, 2017complaint	Dec. 31, 2016USD ($)ft²	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Operating Leases
Area of office space leased (in square feet) | ft²		8,200
Lease term		5 years
Rent expense		$ 195	$ 163	$ 159
Future minimum annual lease commitments under the non-cancelable operating lease
2,017		192
2,018		200
2,019		200
2,020		$ 191
Legal Proceedings
Number of complaints filed in federal court | complaint	2

Quarterly Data (Unaudited) - Qu

Quarterly Data (Unaudited) - Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Data
Operating expenses	$ (7,810)	$ 7,091	$ 7,841	$ 6,980	$ 9,165	$ 8,965	$ 7,982	$ 6,977	$ 29,721	$ 33,089	$ 18,515
Net income (loss)	$ (5,201)	$ (7,804)	$ (8,418)	$ (7,318)	$ (3,899)	$ (9,411)	$ (8,486)	$ (8,538)	$ (28,741)	$ (30,335)	$ (16,077)
Basic and diluted net (loss) income per common share (in dollars per share)	$ (0.18)	$ (0.27)	$ (0.29)	$ (0.27)	$ (0.17)	$ (0.42)	$ (0.38)	$ (0.40)	$ (1.02)	$ (1.38)	$ (1.41)

Quarterly Data (Unaudited) - Ta

Quarterly Data (Unaudited) - Tax Benefit from Sale of New Jersey State Net Operating Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
New Jersey | Sale of unused NOLs and research and development credits
Sale of New Jersey Net Operating Losses
Tax benefit	$ 3,075	$ 5,972