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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2016	May 11, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q1
Trading Symbol	KMPH
Entity Registrant Name	KEMPHARM, INC
Entity Central Index Key	0001434647
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		14,642,037

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 77,333	$ 32,318
Marketable securities	33,668	19,002
Prepaid expenses and other current assets	386	2,758
Total current assets	111,387	54,078
Property and equipment, net	443	403
Other long-term assets	109	109
Total assets	111,939	54,590
Current liabilities:
Accounts payable and accrued expenses	4,178	4,906
Current portion of convertible notes	1,649	1,369
Current portion of term notes		2,041
Current portion of capital lease obligation	18	26
Total current liabilities	5,845	8,342
Convertible notes, net	90,086	7,412
Term notes, net		11,118
Derivative and warrant liability	27,479	37,839
Other long-term liabilities	11
Total liabilities	123,421	64,711
Commitments and contingencies (Note D)
Stockholders’ deficit:
Common stock, $0.0001 par value, 250,000,000 shares authorized, 14,498,930 shares issued and outstanding as of March 31, 2016 (unaudited); 14,490,954 shares issued and outstanding as of December 31, 2015	1	1
Additional paid-in capital	96,275	94,702
Preferred stock, $0.0001 par value, 10,000,000 shares authorized, no shares issued or outstanding as of March 31, 2016 (unaudited) or December 31, 2015
Accumulated deficit	(107,758)	(104,824)
Total stockholders' deficit	(11,482)	(10,121)
Total liabilities and stockholders' deficit	$ 111,939	$ 54,590

CONDENSED BALANCE SHEETS (PARENTHETICAL) - $ / shares	Mar. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	14,498,930	14,490,954
Common stock, shares outstanding	14,498,930	14,490,954
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

UNAUDITED CONDENSED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Revenue	$ 0	$ 0
Operating expenses:
Research and development	3,234	2,119
General and administrative	3,736	977
Total operating expenses	6,970	3,096
Loss from operations	(6,970)	(3,096)
Other (expense) income:
Loss on extinguishment of debt	(4,740)
Interest expense related to amortization of debt issuance costs and discount	(442)	(477)
Interest expense on principal	(1,150)	(632)
Fair value adjustment	10,278	(1,762)
Interest and other income	102
Total other income (expense)	4,048	(2,871)
Loss before income taxes	(2,922)	(5,967)
Income tax expense	(12)	(7)
Net loss	$ (2,934)	$ (5,974)
Net loss per share:
Basic and diluted	$ (0.20)	$ (2.50)
Weighted average common shares outstanding:
Basic and diluted	14,495,703	2,387,092

UNAUDITED CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net loss	$ (2,934)	$ (5,974)
Adjustments to reconcile net loss to net cash used in operating activities:
Loss on extinguishment of debt	4,740
Write-off of deferred offering costs	445
Stock-based compensation expense	1,022	91
Non-cash interest expense	968	632
Amortization of debt issuance costs and debt discount	442	477
Depreciation and amortization expense	26	20
Fair value adjustment	(10,278)	1,762
Change in assets and liabilities:
Prepaid expenses and other current assets	2,372	(30)
Accounts payable and accrued expenses	(679)	(977)
Other long-term liabilities	11
Net cash used in operating activities	(3,865)	(3,999)
Cash flows from investing activities:
Purchases of property and equipment	(66)	(21)
Purchases of marketable securities	(14,666)
Net cash used in investing activities	(14,732)	(21)
Cash flows from financing activities:
Proceeds from issuance of debt, net of discounts and commissions	82,800
Repayment of term notes and related accrued interest	(18,621)
Payment of debt and stock issuance costs	(583)
Repayment of obligations under capital lease	(8)	(8)
Proceeds from exercise of warrants	24	40
Net cash provided by financing activities	63,612	4,034
Net increase in cash and cash equivalents	45,015	14
Cash and equivalents, beginning of period	32,318	10,255
Cash and equivalents, end of period	77,333	10,269
Supplemental cash flow information:
Cash paid for interest	182
Deferred offering costs included in accounts payable and accrued expenses		442
Transfer of warrants to equity upon exercise	82
Fixed assets included in accounts payable and accrued expenses	12
Debt issuance costs included in accounts payable and accrued expenses	$ 309
Series D-1 Redeemable Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of Series D-1 redeemable convertible preferred stock		4,000
Series D Redeemable Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from exercise of warrants		$ 2

Description of Business and Basis of Presentation	3 Months Ended
Description of Business and Basis of Presentation	Mar. 31, 2016
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	A. Description of Business and Basis of Presentation Organization KemPharm, Inc. (the “Company”) is a clinical-stage specialty pharmaceutical company engaged in the discovery and development of proprietary prodrugs. Through the use of its Ligand Activated Therapy (“LAT”) platform technology, the Company is able to initiate and pursue the development of improved versions of widely prescribed, approved drugs. The Company was formed on October 30, 2006, and incorporated in Iowa, and reorganized in Delaware on May 30, 2014. The Company has experienced recurring losses from operations and negative operating cash flows due to its ongoing research and development of its potential product candidates. The Company also has a stockholders’ deficit at March 31, 2016. Various internal and external factors will affect whether and when the candidates become approved drugs and how significant their market share will be. The length of time and cost of developing and commercializing these candidates and/or failure of them at any stage of the drug approval process will materially affect the Company’s financial condition and future operations. Based upon our current operating plan, we believe that our existing cash and cash equivalents will enable us to fund our operating expenses and capital expenditure requirements through at least the next 21 months. The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information and with the instructions to Form 10-Q and Rule 8-03 of Regulation S-X. Accordingly, they do not include all of the information and related notes required by accounting principles generally accepted in the United States of America for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included in the accompanying financial statements. Operating results for the three months ended March 31, 2016, are not necessarily indicative of the results that may be expected for the full year ending December 31, 2016. This interim information should be read in conjunction with the audited financial statements included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2015, filed with the Securities and Exchange Commission (“SEC”) on March 15, 2016. Reverse Stock Split On April 2, 2015, the Company effected a 1-for-7.5 reverse stock split of its issued common stock. All applicable share data, per share amounts and related information in the unaudited condensed financial statements and notes thereto have been adjusted retroactively to give effect to the 1-for-7.5 reverse stock split. Initial Public Offering In April 2015, the Company completed an initial public offering (“IPO”) of its common stock. In connection with the initial closing of the IPO, the Company sold an aggregate of 5,090,909 shares of common stock at a price to the public of $11.00 per share. In May 2015, the underwriters in the IPO exercised their option to purchase additional shares pursuant to which the Company sold an additional 763,636 shares of common stock at a price equal to the public price of $11.00 per share. In the aggregate, net proceeds from the IPO including net proceeds from the underwriters’ exercise of their option to purchase additional shares, were $59.9 million, after deducting underwriting discounts and commissions of $4.5 million. In addition, offering expenses totaled $2.8 million. Upon completion of the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock were converted or reclassified into 5,980,564 shares of common stock and all outstanding warrants to acquire shares of the Company’s redeemable convertible preferred stock became warrants to acquire the Company’s common stock. In connection with the IPO, the Company amended and restated its Amended and Restated Certificate of Incorporation to change the authorized capital stock to 250,000,000 shares, designated as common stock, and 10,000,000 shares, designated as preferred stock, each with a par value of $0.0001 per share. Reclassifications During the quarter the Company adopted Accounting Standards Update (“ASU”) 2015-03, Interest – Imputation of Interest (Subtopic 835-30) (“ASU 2015-03”), which requires the debt issuance costs related to a recognized debt liability be presented in the balance sheet as direct deduction from the carrying amount of that debt liability, consistent with the presentation of debt discounts. The adoption of ASU 2015-03 reduced the Company’s assets and liabilities by the amount of the debt issuance costs, which were $4.2 million and $1.1 million at March 31, 2016 and December 31, 2015, respectively. This reclassification had no effect on previously reported net loss.

Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	B. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires the Company to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. On an ongoing basis, the Company evaluates its estimates, including those related to the useful lives of property and equipment, and assumptions used for purposes of determining stock-based compensation, income taxes, and the fair value of the derivative and warrant liability, among others. The Company bases its estimates on historical experience and on various other assumptions that it believes to be reasonable, the results of which form the basis for making judgements about the carrying value of assets and liabilities. Application of New or Revised Accounting Standards—Adopted From time to time, the Financial Accounting Standards Board (the “FASB”) or other standard-setting bodies issue accounting standards that are adopted by the Company as of the specified effective date. On April 5, 2012, President Obama signed the Jump-Start Our Business Startups Act (the “JOBS Act”) into law. The JOBS Act contains provisions that, among other things, reduce certain reporting requirements for an emerging growth company. As an emerging growth company, the Company may elect to adopt new or revised accounting standards when they become effective for non-public companies, which typically is later than public companies must adopt the standards. The Company has elected not to take advantage of the extended transition period afforded by the JOBS Act and, as a result, will comply with new or revised accounting standards on the relevant dates on which adoption of such standards is required for non-emerging growth companies. In June 2014, the FASB issued ASU 2014-12, Compensation–Stock Compensation (Topic 718): Accounting for Share-Based Payments when the Terms of an Award Provide that a Performance Target Could Be Achieved After the Requisite Service Period (“ASU 2014-12”). The amendments require that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. ASU 2014-12 is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Entities may apply ASU 2014-12 either (a) prospectively to all awards granted or modified after the effective date or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. If retrospective transition is adopted, the cumulative effect of applying this ASU as of the beginning of the earliest annual period presented in the financial statements should be recognized as an adjustment to the opening retained earnings balance at that date. Additionally, if retrospective transition is adopted, an entity may use hindsight in measuring and recognizing the compensation cost. The Company prospectively adopted ASU 2014-12 effective January 1, 2016. The adoption of ASU 2014-12 did not have a material impact on the financial statements as the Company does not have any performance-based awards that could be achieved after the requisite service period. In January 2015, the FASB issued ASU No. 2015-01, Income Statement - Extraordinary and Unusual Items (Subtopic 225-20); Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items (“ASU 2015-01”), which eliminates from GAAP the concept of extraordinary items, stating that the concept causes uncertainty because (1) it is unclear when an item should be considered both unusual and infrequent and (2) users do not find the classification and presentation necessary to identify those events and transactions. ASU 2015-01 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. The Company adopted ASU 2015-01 effective January 1, 2016. The adoption of ASU 2015-01 did not have a material impact on the Company’s financial statements as the Company had no extraordinary and/or unusual items recorded in prior periods. In April 2015, the FASB issued ASU 2015-03, which requires the debt issuance costs related to a recognized debt liability be presented in the balance sheet as direct deduction from the carrying amount of that debt liability, consistent with the presentation of debt discounts. The adoption of ASU 2015-03 reduced the Company’s assets and liabilities by the amount of the debt issuance costs, which were $4.2 million and $1.1 million at March 31, 2016 and December 31, 2015, respectively. This reclassification had no effect on previously reported net loss. Application of New or Revised Accounting Standards—Not Yet Adopted In May 2014, the FASB issued guidance codified in ASC Topic 606, Revenue Recognition—Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition, and becomes effective beginning January 1, 2018. The Company is currently evaluating the impact of the provisions of ASC 606 on its financial statements and disclosures. In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (“ASU 2014-15”), which amends ASC Subtopic 205-40 to provide guidance about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related disclosures. Specifically, the amendments (1) provide a definition of the term “substantial doubt,” (2) require an evaluation every reporting period, (3) provide principles for considering the mitigating effect of management’s plans, (4) require certain disclosures when substantial doubt is alleviated as a result of consideration of management’s plans, (5) require an express statement and other disclosures when substantial doubt is not alleviated and (6) require an assessment for a period of one year after the date that financial statements are issued. ASU 2014-15 is effective for fiscal years ending after December 15, 2016, and for annual periods and interim periods thereafter. The Company is currently evaluating the impact of the adoption of ASU 2014-15 on its financial statements and disclosures. In November 2015, the FASB issued ASU 2015-17, Income Taxes: Balance Sheet Classification of Deferred Taxes (Topic 740) (“ASU 2015-17”), which requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. This update applies to all entities that present a classified statement of financial position. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. The Company does not expect this standard to have a material impact on its financial statements upon adoption. In January 2016, the FASB issued ASU 2016-01, Financial Instruments Overall – Recognition and Measurement of Financial Assets and Liabilities (Topic 825-10) (“ASU 2016-01”), which provides several updates related to Topic 825-10. This update applies to all entities that hold financial assets or owe financial liabilities. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company does not expect this standard to have a material impact on its financial statements upon adoption. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires lessees to recognize assets and liabilities for operating leases with lease terms greater than twelve months in the balance sheet. The update also requires improved disclosures to help users of financial statements better understand the amount, timing and uncertainty of cash flows arising from leases. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-02 on its financial statements and disclosures. In March 2016, the FASB issued ASU 2016-06, Derivatives and Hedging (Topic 815); Contingent Put and Call Options in Debt Instruments (“ASU 2016-06”), which clarifies the requirements for assessing whether contingent call and put options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts. ASU 2016-06 is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-06 on its financial statements and disclosures. In March 2016, the FASB issued ASU 2016-09, Compensation–Stock Compensation (Topic 718); Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), which simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-09 on its financial statements and disclosures.

Debt Obligations

3 Months Ended

Mar. 31, 2016

Debt Disclosure [Abstract]

Debt Obligations

C. Debt Obligations

Deerfield Facility Agreement

On June 2, 2014, the Company entered into a $60 million facility agreement (the “Deerfield Facility Agreement”) with Deerfield Private Design Fund III, LP (“Deerfield”). The first payment to the Company under the terms of the Deerfield Facility Agreement consisted of a term loan of $15 million (the “Term Notes”) and a senior secured loan of $10 million (the “Deerfield Convertible Notes”). All loans issued under the Deerfield Facility Agreement bear interest at 9.75% per annum. Deerfield may convert any portion of the outstanding principal and any accrued but unpaid interest on the Deerfield Convertible Notes into shares of the Company’s common stock at an initial conversion price of $5.85 per share.

The Company also issued to Deerfield a warrant to purchase 14,423,076 shares of Series D redeemable convertible preferred stock (“Series D Preferred”) at an exercise price of $0.78 per share, which is exercisable until June 2, 2024 (the “Deerfield Warrant”). Upon completion of the IPO, the Deerfield Warrant automatically converted into a warrant to purchase 1,923,077 shares of the Company’s common stock at an exercise price of $5.85 per share. In the event that a Major Transaction occurs, as defined below, Deerfield may require the Company to redeem the Deerfield Warrant for a cash amount equal to the Black-Scholes value of the portion of the Deerfield Warrant to be redeemed (the “Put Option”). A Major Transaction is (i) a consolidation, merger, exchange of shares, recapitalization, reorganization, business combination or other similar event; (ii) the sale or transfer in one transaction or a series of related transactions of all or substantially all of the assets of the Company; (iii) a third-party purchase, tender or exchange offer made to the holders of outstanding shares, such that following such purchase, tender or exchange offer a change of control has occurred; (iv) the liquidation, bankruptcy, insolvency, dissolution or winding-up affecting the Company; (v) the shares of the Company’s common stock cease to be listed on any eligible market; and (vi) at any time, the shares of the Company’s common stock cease to be registered under Section 12 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”).

In addition, the Company issued to Deerfield 1,923,077 shares of Series D Preferred as consideration for the loans provided to the Company under the Deerfield Facility Agreement. Upon completion of the IPO, these shares automatically reclassified into 256,410 shares of the Company’s common stock. The Company recorded the fair value of the shares of Series D Preferred of $1.5 million, to debt issuance costs on the date of issuance. The Company recorded the fair value of the Deerfield Warrant and the embedded Put Option to debt discount on the date of issuance. The debt issuance costs and debt discount are amortized over the term of the related debt and the expense is recorded as interest expense in the statements of operations.

The Company must repay one-third of the outstanding principal amount of all debt issued under the Deerfield Facility Agreement on the fourth and fifth anniversaries of the Deerfield Facility Agreement. The Company is then obligated to repay the balance of the outstanding principal amount on February 14, 2020.

Interest accrued on outstanding debt under the Deerfield Facility Agreement is due quarterly in arrears. Upon notice to Deerfield, the Company may choose to have one or more of the first eight of such scheduled interest payments added to the outstanding principal amount of the debt issued under the Deerfield Facility Agreement, provided that all such interest will be due on July 1, 2016. The Company has elected this option on all seven of the scheduled interest payments to date. The accrued interest added to outstanding principal is reflected in the condensed balance sheets as current portion of convertible notes and current portion of term notes.

Deerfield is obligated to provide three additional tranches upon the Company’s request and after the satisfaction of specified conditions, including the FDA’s acceptance of a new drug application for our most advanced product candidate, Apadaz (formerly known as KP201/APAP), and, for the final two tranches, the subsequent approval for commercial sale thereof.

As of March 31, 2016, borrowings available to the Company under the Deerfield Facility Agreement were $35 million. Under the terms of the Deerfield Facility Agreement, future tranches to the Company are as follows:

•

The second tranche consists of a $10.0 million term loan that bears interest at 9.75% and a warrant to purchase 1,282,052 shares of the Company’s common stock at an exercise price of $5.85 per share.

•

The third and fourth tranches each consist of a $12.5 million term loan that bears interest at 9.75% and a warrant exercisable for the number of shares equal to 60% of the principal amount of such disbursement divided by 115% of the volume weighted average sales price of the Company’s common stock for the 20 consecutive trading days immediately prior to the date of such disbursement with an exercise price per share equal to 115% of such weighted average sales price.

Second Amendment to Senior Secured Convertible Note and Warrant

On January 6, 2016 the Company, entered into a Second Amendment (the “Second Amendment”) to the Deerfield Convertible Notes and Deerfield Warrant, by and between the Company and Deerfield. The Second Amendment, among other things, clarified the calculation of an anti-dilution adjustment of the conversion price and exercise price of the Deerfield Convertible Notes and Deerfield Warrant, respectively, in the event that the Company effects a firm commitment underwritten public offering of its securities. Except as modified by the Second Amendment and Third Amendment (as described below), all terms and conditions of the Deerfield Convertible Notes and Deerfield Warrant remain in full force and effect.

Issuance of 2021 Notes and Third Amendment to Senior Secured Convertible Note and Warrant

On February 9, 2016, the Company issued $86.25 million aggregate principal amount of its 5.50% Senior Convertible Notes due 2021 (the “2021 Notes”) to Cowen and Company, LLC and RBC Capital Markets, LLC. as representatives of the several initial purchasers (the “Initial Purchasers”), who subsequently resold the 2021 Notes to qualified institutional buyers (the “Note Offering”) in reliance on the exemption from registration provided by Rule 144A under the Securities Act of 1933, as amended (the “Securities Act”).

The net proceeds from the Note Offering were approximately $82.8 million, after deducting the Initial Purchasers’ discount and estimated offering expenses. Concurrent with the Note Offering, the Company used approximately $18.6 million of the net proceeds from the Note Offering to repay in full the Term Notes, plus all accrued but unpaid interest, a make whole interest payment and a prepayment premium on the Term Notes.

The 2021 Notes were issued pursuant to an Indenture, dated as of February 9, 2016 (the “Indenture”), between the Company and U.S. Bank National Association, as trustee. Interest on the 2021 Notes will be payable semi-annually in cash in arrears on February 1 and August 1 of each year, beginning on August 1, 2016, at a rate of 5.50% per year. The 2021 Notes mature on February 1, 2021 unless earlier converted or repurchased. The 2021 Notes are not redeemable prior to the maturity date, and no sinking fund is provided for the 2021 Notes.

The 2021 Notes are convertible at an initial conversion rate of 58.4454 shares of the Company’s common stock per $1,000 principal amount of the 2021 Notes, subject to adjustment under the Indenture, which is equal to an initial conversion price of approximately $17.11 per share of common stock. Upon conversion, the 2021 Notes will be settled in shares of the Company’s common stock, together with a cash payment in lieu of delivering any fractional share. The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, the Company will increase the conversion rate for a holder who elects to convert its 2021 Notes in connection with such a corporate event in certain circumstances.

If the Company undergoes a “fundamental change” (as defined in the indenture), holders may require that the Company repurchase for cash all or any portion of their 2021 Notes at a fundamental change repurchase price equal to 100% of the principal amount of the 2021 Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. In addition, holders who convert their 2021 notes on or after the date that is one year after the last date of original issuance of the 2021 Notes may also be entitled to receive, under certain circumstances, an interest make-whole payment payable in shares of the Company’s common stock. The Company is bifurcating the fundamental change and make-whole interest payment provisions as embedded derivatives and marking them to fair value each reporting period (Note H).

The Indenture includes customary terms and covenants, including certain events of default after which the 2021 Notes may be due and payable immediately.

In connection with the Note Offering, on February 3, 2016, the Company entered into a Third Amendment (the “Third Amendment”) to the Deerfield Facility Agreement, Deerfield Convertible Notes and Deerfield Warrant with Deerfield. The Third Amendment, among other things, eliminated the Company’s ability to require Deerfield to convert the Deerfield Convertible Notes into Company common stock. In addition, pursuant to the Third Amendment, Deerfield consented to the prepayment of the Term Notes and the issuance of the 2021 Notes. Except as modified by the Third Amendment, all terms and conditions of the Deerfield Facility Agreement remain in full force and effect.

Line of Credit

The Company has a $50,000 credit agreement with a financial institution (the “Line of Credit Agreement”). As of March 31, 2016 and December 31, 2015, the Company had $50,000 available under the Line of Credit Agreement. The Line of Credit Agreement is collateralized by all of the Company’s business assets. The Line of Credit Agreement contains no financial covenants. Borrowings under the Line of Credit Agreement carry interest at a rate equal to the prime rate plus 1.75% per annum. The Company is required to make interest only payments on any draws under the Line of Credit Agreement. The interest rate under the Line of Credit Agreement was 5% for the three months ended March 31, 2016 and 2015.

During the fourth quarter of 2015, the Company entered into an additional $100,000 credit agreement with the same financial institution (the “Second Line of Credit Agreement”). As of March 31, 2016, the Company had $62,000 available under the Second Line of Credit Agreement. The draws from this line of credit line are recorded in accounts payable and accrued expenses in the balance sheet. The Second Line of Credit Agreement is uncollateralized and contains no financial covenants. Borrowings under the Second Line of Credit Agreement carry interest at a rate equal to the prime rate plus 9.99% per annum. The Company is required to make interest only payments on any draws under the Second Line of Credit Agreement. The interest rate under the Second Line of Credit Agreement was 13.24% as of March 31, 2016.

Common Stock and Warrants

3 Months Ended

Mar. 31, 2016

Equity [Abstract]

Common Stock and Warrants

F. Common Stock and Warrants

Authorized, Issued, and Outstanding Common Shares

In April 2015, the Company amended and restated its Certificate of Incorporation to increase the number of its authorized shares of common stock to 250,000,000 shares. Of the authorized shares, 14,498,930 and 14,490,954 shares of common stock were issued and outstanding at March 31, 2016 and December 31, 2015, respectively.

At March 31, 2016 and December 31, 2015, the Company had reserved authorized shares of common stock for future issuance as follows:

	March 31, 2016		December 31, 2015
Conversion of Deerfield Convertible Notes		2,039,622		1,991,219
Conversion of 2021 Notes		5,040,914		—
Outstanding awards under equity incentive plans		1,956,586		1,397,511
Outstanding common stock warrants		2,316,996		2,325,383
Possible future issuances under equity incentive plans		1,426,611		1,410,848
Total common shares reserved for future issuance		12,780,729		7,124,961

Common Stock Activity

The following table summarizes common stock activity for the three months ended March 31, 2016:

	Shares of Common Stock
Balance at December 31, 2015		14,490,954
Common stock warrants exercised		7,976
Balance at March 31, 2016		14,498,930

The Company calculates the fair value of common stock warrants using a Monte Carlo simulation. There were warrants exercised for an aggregate of 7,976 and 10,161 shares of common stock during the three months ended March 31, 2016 and 2015, respectively. From 2008 through 2012, the Company issued warrants to purchase 595,920 shares of common stock in its private placement offerings of Series A redeemable convertible preferred stock, Series B redeemable convertible preferred stock and Series C redeemable convertible preferred stock (the “Underwriter Warrants”) and for leasing laboratory space. The Company accounted for the Underwriter Warrants as a derivative liability, which is adjusted to fair value at each reporting period, with the change in fair value recorded within other expenses in the statements of operations.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

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-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-SubTopic 10
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-Subparagraph (SX 210.3-04)
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 505
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-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

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-Name Accounting Standards Codification
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Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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-Name Accounting Standards Codification
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-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

+ Details

Stock-Based Compensation

3 Months Ended

Mar. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

G. Stock-Based Compensation

The Company maintains a stock-based compensation plan (the “Incentive Stock Plan”) that governs stock awards made to employees and directors prior to completion of the IPO.

In November 2014, the Board, and in April 2015, the Company’s stockholders, approved the Company’s 2014 Equity Incentive Plan (the “2014 Plan”) which became effective in April 2015. The 2014 Plan provides for the grant of stock options, other forms of equity compensation, and performance cash awards. The maximum number of shares of common stock that may be issued under the 2014 Plan is 2,846,304, as of March 31, 2016. The number of shares of common stock reserved for issuance under the 2014 Plan will automatically increase on January 1 of each year, beginning on January 1, 2016 and ending on and including January 1, 2024, by 4% of the total number of shares of the Company’s capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by the Board. Pursuant to the terms of the 2014 Plan, on January 1, 2016, the common stock reserved for issuance under the 2014 Plan automatically increased by 579,638 shares.

During the three months ended March 31, 2016 and 2015, no stock options were exercised.

Stock-based compensation expense recorded under the Incentive Stock Plan and the 2014 Plan is included in the following line items in the accompanying statements of operations (in thousands):

	Three Months Ended March 31,
	2016		2015
Research and development	$	187	$	41
General and administrative		835		50
	$	1,022	$	91

During the three months ended March 31, 2016, the Company recognized $29,000 of stock-based compensation expense related to performance-based incentive awards included in research and development expenses in connection with the vesting of stock options exercisable for an aggregate of 13,333 shares of common stock as a result of the acceptance of the new drug application for Apadaz for priority review in February 2016. During the three months ended March 31, 2015, the Company recognized $29,000 of stock-based compensation expense related to performance-based incentive awards included in general and administrative expenses in connection with the grant of fully vested stock options exercisable for an aggregate of 5,333 shares of common stock in connection with the Company issuing shares of Series D-1 Preferred.

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

H. Fair Value of Financial Instruments

The carrying amounts of certain financial instruments, including cash and cash equivalents and accounts payable, approximate their respective fair values due to the short-term nature of such instruments.

The fair value of the Deerfield Convertible Notes and the 2021 Notes was $30.8 million and $86.1 million, respectively, at March 31, 2016. Both the Deerfield Convertible Notes and the 2021 Notes fall within Level 3 of the fair value hierarchy as their value is based on the credit worthiness of the Company, which is an unobservable input.

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The Company evaluates its financial assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level in which to classify them for each reporting period. This determination requires significant judgements to be made. The following table summarizes the conclusions reached regarding fair value measurements as of March 31, 2016, and December 31, 2015 (in thousands):

	Balance at March 31, 2016		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Underwriter Warrant liability	$	2,421	$	—	$	—	$	2,421
Deerfield Warrant liability		24,173		—		—		24,173
Embedded Put Option		557		—		—		557
Fundamental change and make-whole interest provisions embedded in 2021 Notes		328		—		—		328
Total liabilities	$	27,479	$	—	$	—	$	27,479
Trading securities:
Certificates of deposit		12,111		12,111		—		—
Government bonds		21,557		21,557		—		—
Total assets	$	33,668	$	33,668	$	—	$	—

	Balance at December 31, 2015		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Underwriter Warrant liability	$	3,877	$	—	$	—	$	3,877
Deerfield Warrant liability		33,750		—		—		33,750
Embedded Put Option		212		—		—		212
Total liabilities	$	37,839	$	—	$	—	$	37,839
Trading securities:
Certificates of deposit		8,951		8,951		—		—
Government bonds		10,051		10,051		—		—
Total assets	$	19,002	$	19,002	$	—	$	—

The Company’s Underwriter Warrant liability, Deerfield Warrant liability, and the embedded Put Option on the Deerfield Warrant as well as the fundamental change and the make-whole interest provisions of the 2021 Notes are measured at fair value on a recurring basis. As of March 31, 2016 and December 31, 2015, the Underwriter Warrant liability, the Deerfield Warrant liability and the embedded Put Option are reported on the balance sheet in derivative and warrant liability. The 2021 Notes were issued during the first quarter of 2016 and the fundamental change and the make-whole interest provisions of the 2021 Notes are also reported on the balance sheet in derivative and warrant liability. The Company used a Monte Carlo simulation to value the Underwriter Warrant liability and the embedded Put Option at March 31, 2016 and December 31, 2015. A Monte Carlo simulation was also used to value the fundamental change and the make-whole interest provisions of the 2021 Notes as of the issuance date and March 31, 2016. Significant unobservable inputs used in measuring the fair value of these financial instruments included the Company’s estimated enterprise value, an estimate of the timing of a liquidity or fundamental change event, a present value discount rate and an estimate of the Company’s stock volatility using the volatilities of guideline peer companies. Changes in the fair value of the Underwriter Warrant liability, the Deerfield Warrant liability, the embedded Put Option and the fundamental change and the make-whole interest provisions of the 2021 Notes are reflected in the statements of operations as a fair value adjustment. A 10% increase in the enterprise value would result in an increase of $0.4 million in the estimated fair value of the Underwriter Warrant liability, an increase of $2.7 million in the estimated fair value of the Deerfield Warrant liability, no change in the estimated fair value of the embedded Put Option, and an increase of $0.1 million in the estimated fair value of the fundamental change and the make-whole interest provisions of the 2021 Notes at March 31, 2016.

A reconciliation of the beginning and ending balances for the derivative and warrant liability measured at fair value on a recurring basis using significant unobservable inputs (Level 3) is as follows (in thousands):

	Three Months Ended March 31,
	2016			2015
Balance at beginning of period	$	37,839		$	15,966
Exercise of warrants		(82	)		—
Adjustment to fair value		(10,278	)		1,762
Balance at end of period	$	27,479		$	17,728

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Net Loss Per Share

3 Months Ended

Mar. 31, 2016

Earnings Per Share [Abstract]

Net Loss Per Share

I. Net Loss Per Share

Under the two-class method, for periods with net income, basic net income per common share is computed by dividing the net income attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period. Net income attributable to common stockholders is computed by subtracting from net income the portion of current year earnings that participating securities would have been entitled to receive pursuant to their dividend rights had all of the year’s earnings been distributed. No such adjustment to earnings is made during periods with a net loss as the holders of the participating securities have no obligation to fund losses. Diluted net loss per common share is computed under the two-class method by using the weighted average number of shares of common stock outstanding plus, for periods with net income attributable to common stockholders, the potential dilutive effects of stock options and warrants. In addition, the Company analyzes the potential dilutive effect of the outstanding participating securities under the if-converted method when calculating diluted earnings per share in which it is assumed that the outstanding participating securities convert or are reclassified into common stock at the beginning of the period. The Company reports the more dilutive of the approaches (two-class or if-converted) as its diluted net income per share during the period. Due to the existence of net losses for the three month periods ended March 31, 2016 and 2015, basic and diluted loss per share were the same, as the effect of potentially dilutive securities would have been anti-dilutive.

The following securities, presented on a common stock equivalent basis, have been excluded from the calculation of weighted average common shares outstanding because their effect is anti-dilutive:

	Three Months Ended March 31,
	2016		2015
Redeemable convertible preferred stock:
Series A		—		1,293,838
Series B		—		829,234
Series C		—		2,474,122
Series D		—		967,786
Series D-1		—		426,667
Total redeemable convertible preferred stock		—		5,991,647
Warrants to purchase common stock		2,316,996		585,759
Warrants to purchase Series D preferred stock		—		2,066,543
Awards under equity incentive plans		1,956,586		549,824
Deerfield Convertible Notes		2,039,622		1,851,828
2021 Notes		5,040,914		—
Total		11,354,118		11,045,601

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2016
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires the Company to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. On an ongoing basis, the Company evaluates its estimates, including those related to the useful lives of property and equipment, and assumptions used for purposes of determining stock-based compensation, income taxes, and the fair value of the derivative and warrant liability, among others. The Company bases its estimates on historical experience and on various other assumptions that it believes to be reasonable, the results of which form the basis for making judgements about the carrying value of assets and liabilities.
Application of New or Revised Accounting Standards Adopted	Application of New or Revised Accounting Standards—Adopted From time to time, the Financial Accounting Standards Board (the “FASB”) or other standard-setting bodies issue accounting standards that are adopted by the Company as of the specified effective date. On April 5, 2012, President Obama signed the Jump-Start Our Business Startups Act (the “JOBS Act”) into law. The JOBS Act contains provisions that, among other things, reduce certain reporting requirements for an emerging growth company. As an emerging growth company, the Company may elect to adopt new or revised accounting standards when they become effective for non-public companies, which typically is later than public companies must adopt the standards. The Company has elected not to take advantage of the extended transition period afforded by the JOBS Act and, as a result, will comply with new or revised accounting standards on the relevant dates on which adoption of such standards is required for non-emerging growth companies. In June 2014, the FASB issued ASU 2014-12, Compensation–Stock Compensation (Topic 718): Accounting for Share-Based Payments when the Terms of an Award Provide that a Performance Target Could Be Achieved After the Requisite Service Period (“ASU 2014-12”). The amendments require that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. ASU 2014-12 is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Entities may apply ASU 2014-12 either (a) prospectively to all awards granted or modified after the effective date or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. If retrospective transition is adopted, the cumulative effect of applying this ASU as of the beginning of the earliest annual period presented in the financial statements should be recognized as an adjustment to the opening retained earnings balance at that date. Additionally, if retrospective transition is adopted, an entity may use hindsight in measuring and recognizing the compensation cost. The Company prospectively adopted ASU 2014-12 effective January 1, 2016. The adoption of ASU 2014-12 did not have a material impact on the financial statements as the Company does not have any performance-based awards that could be achieved after the requisite service period. In January 2015, the FASB issued ASU No. 2015-01, Income Statement - Extraordinary and Unusual Items (Subtopic 225-20); Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items (“ASU 2015-01”), which eliminates from GAAP the concept of extraordinary items, stating that the concept causes uncertainty because (1) it is unclear when an item should be considered both unusual and infrequent and (2) users do not find the classification and presentation necessary to identify those events and transactions. ASU 2015-01 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. The Company adopted ASU 2015-01 effective January 1, 2016. The adoption of ASU 2015-01 did not have a material impact on the Company’s financial statements as the Company had no extraordinary and/or unusual items recorded in prior periods. In April 2015, the FASB issued ASU 2015-03, which requires the debt issuance costs related to a recognized debt liability be presented in the balance sheet as direct deduction from the carrying amount of that debt liability, consistent with the presentation of debt discounts. The adoption of ASU 2015-03 reduced the Company’s assets and liabilities by the amount of the debt issuance costs, which were $4.2 million and $1.1 million at March 31, 2016 and December 31, 2015, respectively. This reclassification had no effect on previously reported net loss.
Application of New or Revised Accounting Standards Not Yet Adopted	Application of New or Revised Accounting Standards—Not Yet Adopted In May 2014, the FASB issued guidance codified in ASC Topic 606, Revenue Recognition—Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition, and becomes effective beginning January 1, 2018. The Company is currently evaluating the impact of the provisions of ASC 606 on its financial statements and disclosures. In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (“ASU 2014-15”), which amends ASC Subtopic 205-40 to provide guidance about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related disclosures. Specifically, the amendments (1) provide a definition of the term “substantial doubt,” (2) require an evaluation every reporting period, (3) provide principles for considering the mitigating effect of management’s plans, (4) require certain disclosures when substantial doubt is alleviated as a result of consideration of management’s plans, (5) require an express statement and other disclosures when substantial doubt is not alleviated and (6) require an assessment for a period of one year after the date that financial statements are issued. ASU 2014-15 is effective for fiscal years ending after December 15, 2016, and for annual periods and interim periods thereafter. The Company is currently evaluating the impact of the adoption of ASU 2014-15 on its financial statements and disclosures. In November 2015, the FASB issued ASU 2015-17, Income Taxes: Balance Sheet Classification of Deferred Taxes (Topic 740) (“ASU 2015-17”), which requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. This update applies to all entities that present a classified statement of financial position. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. The Company does not expect this standard to have a material impact on its financial statements upon adoption. In January 2016, the FASB issued ASU 2016-01, Financial Instruments Overall – Recognition and Measurement of Financial Assets and Liabilities (Topic 825-10) (“ASU 2016-01”), which provides several updates related to Topic 825-10. This update applies to all entities that hold financial assets or owe financial liabilities. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company does not expect this standard to have a material impact on its financial statements upon adoption. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires lessees to recognize assets and liabilities for operating leases with lease terms greater than twelve months in the balance sheet. The update also requires improved disclosures to help users of financial statements better understand the amount, timing and uncertainty of cash flows arising from leases. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-02 on its financial statements and disclosures. In March 2016, the FASB issued ASU 2016-06, Derivatives and Hedging (Topic 815); Contingent Put and Call Options in Debt Instruments (“ASU 2016-06”), which clarifies the requirements for assessing whether contingent call and put options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts. ASU 2016-06 is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-06 on its financial statements and disclosures. In March 2016, the FASB issued ASU 2016-09, Compensation–Stock Compensation (Topic 718); Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), which simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-09 on its financial statements and disclosures.

Common Stock and Warrants (Tables)

3 Months Ended

Mar. 31, 2016

Equity [Abstract]

Schedule of Authorized Shares of Common Stock Reserved for Future Issuance

At March 31, 2016 and December 31, 2015, the Company had reserved authorized shares of common stock for future issuance as follows:

	March 31, 2016		December 31, 2015
Conversion of Deerfield Convertible Notes		2,039,622		1,991,219
Conversion of 2021 Notes		5,040,914		—
Outstanding awards under equity incentive plans		1,956,586		1,397,511
Outstanding common stock warrants		2,316,996		2,325,383
Possible future issuances under equity incentive plans		1,426,611		1,410,848
Total common shares reserved for future issuance		12,780,729		7,124,961

Schedule of Common Stock Shares Activity

The following table summarizes common stock activity for the three months ended March 31, 2016:

	Shares of Common Stock
Balance at December 31, 2015		14,490,954
Common stock warrants exercised		7,976
Balance at March 31, 2016		14,498,930

Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2016

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table summarizes the conclusions reached regarding fair value measurements as of March 31, 2016, and December 31, 2015 (in thousands):

	Balance at March 31, 2016		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Underwriter Warrant liability	$	2,421	$	—	$	—	$	2,421
Deerfield Warrant liability		24,173		—		—		24,173
Embedded Put Option		557		—		—		557
Fundamental change and make-whole interest provisions embedded in 2021 Notes		328		—		—		328
Total liabilities	$	27,479	$	—	$	—	$	27,479
Trading securities:
Certificates of deposit		12,111		12,111		—		—
Government bonds		21,557		21,557		—		—
Total assets	$	33,668	$	33,668	$	—	$	—

	Balance at December 31, 2015		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Underwriter Warrant liability	$	3,877	$	—	$	—	$	3,877
Deerfield Warrant liability		33,750		—		—		33,750
Embedded Put Option		212		—		—		212
Total liabilities	$	37,839	$	—	$	—	$	37,839
Trading securities:
Certificates of deposit		8,951		8,951		—		—
Government bonds		10,051		10,051		—		—
Total assets	$	19,002	$	19,002	$	—	$	—

Reconciliation of Beginning and Ending Balances for Derivative and Warrant Liability Measured at Fair Value on Recurring Basis

	Three Months Ended March 31,
	2016			2015
Balance at beginning of period	$	37,839		$	15,966
Exercise of warrants		(82	)		—
Adjustment to fair value		(10,278	)		1,762
Balance at end of period	$	27,479		$	17,728

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2016

Earnings Per Share [Abstract]

Schedule of Anti-dilutive Securities Excluded from Calculation of Weighted Average Common Shares Outstanding

The following securities, presented on a common stock equivalent basis, have been excluded from the calculation of weighted average common shares outstanding because their effect is anti-dilutive:

	Three Months Ended March 31,
	2016		2015
Redeemable convertible preferred stock:
Series A		—		1,293,838
Series B		—		829,234
Series C		—		2,474,122
Series D		—		967,786
Series D-1		—		426,667
Total redeemable convertible preferred stock		—		5,991,647
Warrants to purchase common stock		2,316,996		585,759
Warrants to purchase Series D preferred stock		—		2,066,543
Awards under equity incentive plans		1,956,586		549,824
Deerfield Convertible Notes		2,039,622		1,851,828
2021 Notes		5,040,914		—
Total		11,354,118		11,045,601

Description of Business and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Millions		1 Months Ended		3 Months Ended
	Apr. 02, 2015	May 31, 2015 USD ($) $ / shares shares	Apr. 30, 2015 $ / shares shares	Mar. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Class Of Stock [Line Items]
Common stock, shares authorized		250,000,000	250,000,000	250,000,000	250,000,000
Preferred stock, shares authorized		10,000,000	10,000,000	10,000,000	10,000,000
Common stock, par value \| $ / shares		$ 0.0001		$ 0.0001	$ 0.0001
Preferred stock, par value \| $ / shares		0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Debt issuance costs, net \| $				$ 4.2	$ 1.1
Reverse stock split, description				1-for-7.5 reverse stock split
Reverse stock split	0.13
IPO
Class Of Stock [Line Items]
Number of shares of common stock sold			5,090,909
Common stock, price per share \| $ / shares		$ 11.00	$ 11.00
Additional number of common stock sold		763,636
Proceeds from initial public offering, net of underwriting discounts and commissions \| $		$ 59.9
Underwriting discounts and commissions \| $		4.5
IPO offering expenses \| $		$ 2.8
IPO \| Common stock
Class Of Stock [Line Items]
Number of preferred shares converted to common shares		5,980,564	5,980,564

Debt Obligations - Deerfield Facility Agreement - Additional Information (Detail) - USD ($)		3 Months Ended
	Jun. 02, 2014	Mar. 31, 2016	Apr. 30, 2015	Dec. 31, 2013
Series D Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Preferred stock called by warrants			15,499,324	1,079,453
Deerfield Warrant
Debt Instrument [Line Items]
Warrants expiration date	Jun. 02, 2024
Deerfield Facility Agreement
Debt Instrument [Line Items]
Line of credit agreement, maximum borrowing capacity	$ 60,000,000
Facility agreement, interest rate	9.75%
Facility agreement, repayment description		The Company must repay one-third of the outstanding principal amount of all debt issued under the Deerfield Facility Agreement on the fourth and fifth anniversaries of the Deerfield Facility Agreement. The Company is then obligated to repay the balance of the outstanding principal amount on February 14, 2020.
Facility agreement, repayment period		Feb. 14, 2020
Line of Credit Interest Payment, Due Date		Jul. 01, 2016
Line of credit agreement, available borrowing capacity		$ 35,000,000
Deerfield Facility Agreement \| First Tranche
Debt Instrument [Line Items]
Percentage of outstanding principal amount to be repaid		33.33%
Deerfield Facility Agreement \| Second Tranche
Debt Instrument [Line Items]
Facility agreement, interest rate		9.75%
Preferred stock called by warrants		1,282,052
Warrant, exercise price		$ 5.85
Line of credit agreement, available borrowing capacity		$ 10,000,000
Deerfield Facility Agreement \| Third Tranche
Debt Instrument [Line Items]
Facility agreement, interest rate		9.75%
Line of credit agreement, available borrowing capacity		$ 12,500,000
Warrants exercisable as percentage of principal amount of debt disbursed		60.00%
Weighted average sales price		115.00%
Consecutive trading days, threshold for warrant exercise		20 days
Deerfield Facility Agreement \| Fourth Tranche
Debt Instrument [Line Items]
Facility agreement, interest rate		9.75%
Line of credit agreement, available borrowing capacity		$ 12,500,000
Warrants exercisable as percentage of principal amount of debt disbursed		60.00%
Weighted average sales price		115.00%
Consecutive trading days, threshold for warrant exercise		20 days
Deerfield Facility Agreement \| Series D Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Preferred stock called by warrants	14,423,076
Shares issued as consideration for loans provided	1,923,077
Fair value of preferred shares	$ 1,500,000
Deerfield Facility Agreement \| Deerfield Warrant
Debt Instrument [Line Items]
Warrant, exercise price	$ 0.78
Warrants expiration date	Jun. 02, 2024
Deerfield Facility Agreement \| Term Notes
Debt Instrument [Line Items]
Facility agreement	$ 15,000,000
Deerfield Facility Agreement \| Deerfield Convertible Notes
Debt Instrument [Line Items]
Facility agreement	$ 10,000,000
Conversion price	$ 5.85
Deerfield Facility Agreement \| IPO
Debt Instrument [Line Items]
Reclassification of common stock shares	256,410
Deerfield Facility Agreement \| IPO \| Deerfield Warrant
Debt Instrument [Line Items]
Preferred stock called by warrants	1,923,077
Warrant, exercise price	$ 5.85

Debt Obligations - Issuance of 2021 Notes and Third Amendment to Senior Secured Convertible Note and Warrant - Additional Information (Detail) - 2021 Notes	Feb. 09, 2016 USD ($) $ / shares shares
Debt Instrument [Line Items]
Aggregate principal amount	$ 86,250,000
Interest rate of debt (as a percent)	5.50%
Net proceeds from issuance of debt	$ 82,800,000
Proceeds used for full repayment of long term debt	$ 18,600,000
Debt instrument, maturity date	Feb. 01, 2021
Debt instrument, sinking fund payment	$ 0
Shares issued on conversion of convertible notes \| shares	58.4454
Debt conversion principal amount	$ 1,000
Conversion price \| $ / shares	$ 17.11
Repurchase price as a percentage of principal amount of debt instrument	100.00%
Debt instrument conversion term	1 year

Stock-Based Compensation - Additional Information (Detail) - USD ($)		3 Months Ended
	Jan. 02, 2016	Mar. 31, 2016	Mar. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercised		0	0
Stock based compensation expense		$ 1,022,000	$ 91,000
Stock options fully vested and exercisable		13,333	5,333
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expense		$ 187,000	$ 41,000
Research and development \| Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expense		29,000
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expense		$ 835,000	50,000
General and administrative \| Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expense			$ 29,000
Two Thousand Fourteen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of outstanding capital stock		4.00%
Share-based compensation arrangement by share-based payment award, plan modification, description and terms		Number of shares of common stock reserved for issuance under the 2014 Plan will automatically increase on January 1 of each year, beginning on January 1, 2016 and ending on and including January 1, 2024,
Increase in number of common stock reserve for issuance	579,638
Two Thousand Fourteen Equity Incentive Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares issuable		2,846,304

Net Loss Per Share - Schedule of Anti-dilutive Securities Excluded from Calculation of Weighted Average Common Shares Outstanding (Detail) - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	11,354,118	11,045,601
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,316,996	585,759
Deerfield Warrant to Purchase Series D Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		2,066,543
Equity Incentive Plans
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,956,586	549,824
Convertible Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,039,622	1,851,828
Unsecured Convertible Promissory Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	5,040,914
Series A Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		1,293,838
Series B Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		829,234
Series C Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		2,474,122
Series D Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		967,786
Series D-1 Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		426,667
Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		5,991,647

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	D. Commitments and Contingencies From time to time, the Company is involved in various legal proceedings arising in the normal course of business. For some matters, a liability is not probable or the amount cannot be reasonably estimated and, therefore, an accrual has not been made. However, for such matters when it is probable that the Company has incurred a liability and can reasonably estimate the amount, the Company accrues and discloses such estimates. In 2014, a former financial advisor of the Company filed a request with the Iowa District Court to declare valid a purported right of first refusal to serve as the Company’s exclusive financial advisor for specified strategic transactions and to receive fees for the specified strategic transactions irrespective of whether any such specified transaction occurred during or after the term of the financial advisor’s service agreement. This filing by the former financial advisor was made in response to an action initiated by the Company in 2013 seeking a declaratory judgement finding that such purported right was invalid and unenforceable. Two former members of the Company’s board of directors (the “Board”) joined the lawsuit as intervenors based on the former financial advisor’s purported assignment of its rights, or a portion thereof, under the agreement to the intervenors. In September 2015, the court granted summary judgement in favor of the Company with respect to the Company’s declaratory judgement action and the former financial advisor’s counterclaims and the Company separately entered into settlement agreements with each of the intervenors. The settlements reached with the intervenors did not differ from the accrual previously recorded by the Company by a material amount. The former financial advisor subsequently filed a notice of appeal of the court’s ruling with the Supreme Court of Iowa. On January 6, 2016, the Company entered into a Settlement Agreement and Mutual Release (the “Settlement Agreement”) with the former financial advisor and Donald DeWaay, Jr. pursuant to which, among other things, the former financial advisor agreed, in exchange for the consideration described therein, to dismiss with prejudice its pending appeal. DFN’s appeal was subsequently dismissed by the Supreme Court of Iowa on January 7, 2016. The consideration in the settlement agreement did not differ from the accrual previously recorded by the Company by a material amount.

Preferred Stock and Warrants	3 Months Ended
Preferred Stock and Warrants	Mar. 31, 2016
Text Block [Abstract]
Preferred Stock and Warrants	E. Preferred Stock and Warrants Authorized, Issued, and Outstanding Preferred Stock In April 2015, the Company amended and restated its Certificate of Incorporation to decrease the number of its authorized shares of preferred stock to 10,000,000 shares with a par value of $0.0001 per share. As described in Note A, in April 2015, the Company completed an IPO of its common stock. Upon completion of the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock were automatically converted or reclassified into an aggregate of 5,980,564 shares of the Company’s common stock. As of March 31, 2016, the Company had 10,000,000 shares of authorized and undesignated preferred stock, and did not have any preferred stock outstanding. Series D-1 Redeemable Convertible Preferred Stock In February 2015, the Company entered into a stock purchase agreement with Cowen KP Investment, LLC in which Cowen KP Investment, LLC agreed to purchase and the Company agreed to sell 3,200,000 shares of the Company’s Series D-1 redeemable convertible preferred stock (“Series D-1 Preferred”) for $1.25 per share, or an aggregate of $4 million. Upon completion of the IPO, these shares automatically converted into 415,584 shares of the Company’s common stock. Warrants As described in Note A, in April 2015, the Company completed an IPO of its common stock. Upon completion of the IPO, and as of March 31, 2016, warrants to purchase 15,499,324 shares of Series D Preferred were reclassified into warrants to purchase 2,066,543 shares of the Company’s common stock. During 2013, the Company issued $3.8 million of convertible notes and the warrants (the “2013 Warrants”) to purchase 1,079,453 shares of equity securities in a future financing meeting specified criteria (a “Qualified Financing”). The 2013 Warrants allow the holders to purchase shares of the same class and series of equity securities issued in the Qualified Financing for an exercise price equal to the per share price paid by the purchasers of such equity securities in the Qualified Financing. When the Company entered into the Deerfield Facility Agreement, the 2013 Warrants became warrants to purchase 1,079,453 shares of Series D Preferred. Upon completion of the IPO, the 2013 Warrants automatically converted into warrants to purchase 143,466 shares of the Company’s common stock at an exercise price of $5.85 per share. The 2013 Warrants, if unexercised, expire on the earlier of June 2, 2019, or upon a liquidation event. On June 2, 2014, pursuant to the terms of the Deerfield Facility Agreement, the Company issued the Deerfield Warrant to purchase 14,423,076 shares of Series D Preferred. The Company recorded the fair value of the Deerfield Warrant as a debt discount and a warrant liability. The Deerfield Warrant, if unexercised, expires on the earlier of June 2, 2024, or upon a liquidation event. Upon completion of the IPO, the Deerfield Warrant automatically converted into a warrant to purchase 1,923,077 shares of the Company’s common stock at an exercise price of $5.85 per share. The Company is amortizing the debt discount to interest expense over the term of the Deerfield Convertible Notes. The Company determined that the 2013 Warrants and Deerfield Warrant should be recorded as a liability and stated at fair value at each reporting period upon inception. As stated above, upon completion of the IPO, the 2013 Warrants and the Deerfield Warrant automatically converted into warrants to purchase the Company’s common stock. The Company determined that the 2013 Warrants should be marked to fair value and reclassified to equity upon closing of the IPO. The Deerfield Warrant remains classified as a liability and is recorded at fair value at each reporting period since it can be settled in cash. Changes to the fair value of the warrant liability are recorded through the statements of operations as a fair value adjustment (Note H).

Preferred Stock and Warrants - Series D-1 Redeemable Convertible Preferred Stock - Additional Information (Detail) - Series D-1 Redeemable Convertible Preferred Stock - Cowen KP Investment LLC	1 Months Ended
	Feb. 28, 2015 USD ($) $ / shares shares
Temporary Equity [Line Items]
Redeemable convertible preferred stock, issuance of Series D-1 Preferred Stock	3,200,000
Redeemable convertible preferred stock, price per share \| $ / shares	$ 1.25
Redeemable convertible preferred stock, proceeds from issuance \| $	$ 4,000,000
Conversion of preferred stock into common stock upon IPO	415,584

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Increase in estimated fair value	$ (10,278,000)	$ 1,762,000
Changes in Fair Value Measurement
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Percentage of increase in enterprise value	10.00%
Underwriter Warrant Liability \| Changes in Fair Value Measurement
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Increase in estimated fair value	$ 400,000
Deerfield Warrant Liability \| Changes in Fair Value Measurement
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Increase in estimated fair value	2,700,000
Embedded Put Option \| Changes in Fair Value Measurement
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Increase in estimated fair value	0
Fundamental Change and Make-Whole Interest Provisions Embedded in 2021 Notes \| Changes in Fair Value Measurement
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Increase in estimated fair value	100,000
Fair Value Inputs Level3 \| Deerfield Facility Agreement \| Deerfield Convertible Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of long term debt instruments	30,800,000
Fair Value Inputs Level3 \| Deerfield Facility Agreement \| Term Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of long term debt instruments	$ 86,100,000

Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	$ 27,479	$ 37,839
Financial assets measured at fair value on recurring basis	33,668	19,002
Underwriter Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	2,421	3,877
Deerfield Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	24,173	33,750
Embedded Put Option
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	557	212
Fundamental Change and Make-Whole Interest Provisions Embedded in 2021 Notes
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	328
Certificates of Deposits
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial assets measured at fair value on recurring basis	12,111	8,951
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial assets measured at fair value on recurring basis	33,668	19,002
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Certificates of Deposits
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial assets measured at fair value on recurring basis	12,111	8,951
Fair Value Inputs Level3
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	27,479	37,839
Fair Value Inputs Level3 \| Underwriter Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	2,421	3,877
Fair Value Inputs Level3 \| Deerfield Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	24,173	33,750
Fair Value Inputs Level3 \| Embedded Put Option
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	557	212
Fair Value Inputs Level3 \| Fundamental Change and Make-Whole Interest Provisions Embedded in 2021 Notes
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	328
Government Bonds
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial assets measured at fair value on recurring basis	21,557	10,051
Government Bonds \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial assets measured at fair value on recurring basis	$ 21,557	$ 10,051

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Summary Of Accounting Policies Additional Textual [Abstract]
Debt issuance costs, net	$ 4.2	$ 1.1

Preferred Stock and Warrants - Authorized, Issued, and Outstanding Preferred Stock - Additional Information (Detail) - $ / shares	1 Months Ended
	May 31, 2015	Apr. 30, 2015	Mar. 31, 2016	Dec. 31, 2015
Temporary Equity [Line Items]
Preferred stock, shares authorized	10,000,000	10,000,000	10,000,000	10,000,000
Preferred stock, par value	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares outstanding			0	0
Common stock \| IPO
Temporary Equity [Line Items]
Number of preferred shares converted to common shares	5,980,564	5,980,564

Common Stocks and Warrants - Schedule of Reserved Authorized Shares of Common Stock for Future Issuance (Detail) - shares	Mar. 31, 2016	Dec. 31, 2015
Class Of Stock [Line Items]
Common shares reserved for future issuance	12,780,729	7,124,961
2021 Notes
Class Of Stock [Line Items]
Common shares reserved for future issuance	5,040,914
Convertible Notes
Class Of Stock [Line Items]
Common shares reserved for future issuance	2,039,622	1,991,219
Equity Incentive Plans
Class Of Stock [Line Items]
Common shares reserved for future issuance	1,956,586	1,397,511
Possible Future Issuances Under Equity Incentive Plans
Class Of Stock [Line Items]
Common shares reserved for future issuance	1,426,611	1,410,848
Common Stock Warrants
Class Of Stock [Line Items]
Common shares reserved for future issuance	2,316,996	2,325,383

Common Stock and Warrants - Summary of Common Stock Shares Activity (Detail) - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Common Stock Number Of Shares Par Value And Other Disclosures [Abstract]
Common stock, beginning balance	14,490,954
Common stock warrants exercised	7,976	10,161
Common stock, ending balance	14,498,930

Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	$ 1,022	$ 91
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	187	41
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	$ 835	$ 50