View Filing Data

Print Document View Excel Document

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2015	Mar. 11, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
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 Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Common Stock, Shares Outstanding		14,498,474
Entity Public Float			$ 206,967,240

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 32,318	$ 10,255
Marketable securities	19,002
Prepaid expenses and other current assets	2,758	23
Total current assets	54,078	10,278
Debt issuance costs, net	1,133	1,468
Property and equipment, net	403	352
Other long-term assets	109	1,616
Total assets	55,723	13,714
Current liabilities:
Accounts payable and accrued expenses	4,906	3,096
Current portion of convertible notes	1,369	325
Current portion of term notes	2,041	482
Current portion of capital lease obligation	26	32
Total current liabilities	8,342	3,935
Convertible notes, net	7,865	7,235
Term notes, net	11,798	10,853
Derivative and warrant liability	37,839	15,966
Capital lease obligation, net		26
Total liabilities	65,844	38,015
Commitments and contingencies (Note G)
Redeemable convertible preferred stock:
Total Redeemable Convertible Preferred Stock		24,207
Stockholders' deficit:
Common stock, $0.0001 par value, 250,000,000 shares authorized, 14,490,954 shares issued and outstanding as of December 31, 2015; 18,666,666 shares authorized, 2,381,041 shares issued and outstanding as of December 31, 2014	1
Additional paid-in capital	94,702	1,652
Preferred stock, $0.0001 par value, 10,000,000 shares authorized, no shares issued or outstanding as of December 31, 2015; no shares authorized, issued or outstanding as of December 31, 2014
Accumulated deficit	(104,824)	(50,160)
Total stockholders' deficit	(10,121)	(48,508)
Total liabilities, redeemable convertible preferred stock, and stockholders' deficit	$ 55,723	13,714
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Total Redeemable Convertible Preferred Stock		3,343
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Total Redeemable Convertible Preferred Stock		3,313
Series C Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Total Redeemable Convertible Preferred Stock		11,892
Series D Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Total Redeemable Convertible Preferred Stock		$ 5,659

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	250,000,000	18,666,666
Common stock, shares issued	14,490,954	2,381,041
Common stock, shares outstanding	14,490,954	2,381,041
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	0	1,294,000
Redeemable convertible preferred stock, shares issued	0	1,293,838
Redeemable convertible preferred stock, shares outstanding	0	1,293,838
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	0	829,234
Redeemable convertible preferred stock, shares issued	0	829,234
Redeemable convertible preferred stock, shares outstanding	0	829,234
Series C Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	0	2,474,400
Redeemable convertible preferred stock, shares issued	0	2,474,122
Redeemable convertible preferred stock, shares outstanding	0	2,474,122
Series D Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	0	10,000,000
Redeemable convertible preferred stock, shares issued	0	967,359
Redeemable convertible preferred stock, shares outstanding	0	967,359

STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Revenue	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	4,716	4,328	2,768	2,119	5,911	3,253	1,715	1,038	13,931	11,917	3,367
General and administrative	2,566	2,152	3,188	977	1,577	1,086	1,330	534	8,883	4,526	1,351
Total operating expenses	7,282	6,480	5,956	3,096	7,488	4,339	3,045	1,572	22,814	16,443	4,718
Loss from operations	(7,282)	(6,480)	(5,956)	(3,096)	(7,488)	(4,339)	(3,045)	(1,572)	(22,814)	(16,443)	(4,718)
Other (expense) income:
Gain on extinguishment of debt							1,900			1,900
Interest expense related to amortization of debt issuance costs and discount	(475)	(479)	(477)	(477)	(478)	(477)	(159)	0	(1,909)	(1,114)	(1,560)
Interest expense on principal	(698)	(687)	(654)	(632)	(631)	(173)	(704)	(96)	(2,671)	(1,605)	(157)
Fair value adjustment	(764)	(2,089)	(22,661)	(1,762)	(3,221)	(2,189)	(1,570)	(242)	(27,276)	(7,223)	1,137
Interest and other income	15	11	5		4	3			32	8	52
Total other expenses	(1,922)	(3,244)	(23,787)	(2,871)	(4,326)	(2,836)	(533)	(338)	(31,824)	(8,034)	(528)
Loss before income taxes	(9,204)	(9,724)	(29,743)	(5,967)	(11,814)	(7,175)	(3,578)	(1,910)	(54,638)	(24,477)	(5,246)
Income tax (expense) benefit	1	(20)		(7)	(27)	38	6	5	(26)	22	20
Net loss	$ (9,203)	$ (9,744)	$ (29,743)	$ (5,974)	$ (11,841)	$ (7,137)	$ (3,572)	$ (1,905)	$ (54,664)	$ (24,455)	$ (5,226)
Net loss per share:
Basic and diluted	$ (0.64)	$ (0.68)	$ (2.45)	$ (2.50)	$ (4.97)	$ (3.00)	$ (1.50)	$ (0.80)	$ (7.42)	$ (10.27)	$ (2.20)
Weighted average common shares outstanding:
Basic and diluted									7,368,681	2,381,041	2,381,041

STATEMENTS OF CHANGES IN REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT - USD ($) $ in Thousands	Total	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Series C Redeemable Convertible Preferred Stock	Series D Redeemable Convertible Preferred Stock	Series D-1 Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred Stock	Common stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance at Dec. 31, 2012	$ (19,175)							$ 1,304		$ (20,479)
Beginning balance at Dec. 31, 2012		$ 3,343	$ 3,313	$ 11,892			$ 18,548
Net loss	(5,226)									(5,226)
Stock-based compensation expense	134							134
Ending balance at Dec. 31, 2013	(24,267)							1,438		(25,705)
Ending balance at Dec. 31, 2013		3,343	3,313	11,892			18,548
Net loss	(24,455)									(24,455)
Stock-based compensation expense	214								$ 214
Change in par value								(1,438)	1,438
Conversion of 2013 Convertible notes into Series D Preferred stock					$ 4,159		4,159
Issuance of Series D Preferred stock as financing fee					1,500		1,500
Ending balance at Dec. 31, 2014	(48,508)								1,652	(50,160)
Ending balance at Dec. 31, 2014	24,207	3,343	3,313	11,892	5,659		24,207
Net loss	(54,664)									(54,664)
Stock-based compensation expense	2,369								2,369
Ending balance at Dec. 31, 2015	(10,121)							1	94,702	$ (104,824)
Exercise of stock options and warrants	4,749								4,749
Issuance of Series D-1 preferred stock						$ 4,000	4,000
Issuance of common stock in connection with IPO, net of discounts and commissions	59,892							$ 1	59,891
Conversion of 2013 warrants to equity classification	1,110								1,110
Conversion of preferred stock into common stock upon IPO	28,207	$ (3,343)	$ (3,313)	$ (11,892)	$ (5,659)	$ (4,000)	$ (28,207)		28,207
Offering expenses charged to equity	$ (3,276)								$ (3,276)

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (54,664)	$ (24,455)	$ (5,226)
Adjustments to reconcile net loss to net cash used in operating activities:
Gain on extinguishment of debt		(1,900)
Stock-based compensation expense	2,369	214	134
Non-cash interest expense	2,671	1,602	152
Amortization of debt issuance costs and debt discount	1,909	1,114	1,560
Depreciation and amortization expense	84	75	68
Fair value adjustment	27,276	7,223	(1,137)
Change in assets and liabilities:
Prepaid expenses and other current assets	(1,228)	523	(4)
Accounts payable and accrued expenses	1,315	933	126
Net cash used in operating activities	(20,268)	(14,671)	(4,327)
Cash flows from investing activities:
Proceeds from sale of assets		2	17
Purchases of property and equipment	(135)	(49)	(51)
Purchases of marketable securities	(19,002)
Net cash used in investing activities	(19,137)	(47)	(34)
Cash flows from financing activities:
Proceeds from initial public offering, net of discounts and commissions	59,892
Payment of deferred offering costs	(315)	(1,767)
Proceeds from issuance of debt		25,000	3,846
Repayment of line of credit		(35)	(5)
Payment of debt and stock issuance costs	(2,533)	(163)
Repayment of obligations under capital lease	(32)	(31)	(53)
Proceeds from exercise of warrants	413
Net cash provided by financing activities	61,468	23,004	3,788
Increase (decrease) in cash and cash equivalents	22,063	8,286	(573)
Cash and cash equivalents, beginning of year	10,255	1,969	2,542
Cash and cash equivalents, end of year	32,318	10,255	1,969
Supplemental cash flow information:
Cash paid for interest		3	5
Conversion feature on 2013 convertible notes and put option			1,150
Issuance of 2013 warrants and Deerfield warrant		7,610	410
Fixed assets financed by capital lease			$ 94
Embedded Deerfield put option on Deerfield warrant		220
Issuance of Series D preferred stock as transaction fee		1,500
Conversion of 2013 convertible notes and interest into Series D preferred stock		4,159
Deferred offering costs included in accounts payable and accrued expenses	428	$ 315
Conversion of preferred stock into common stock upon IPO	28,207
Offering expenses charged to equity	3,276
Reclassification of 2013 warrants to equity	1,110
Transfer of warrants to equity upon exercise	4,293
Series D-1 Redeemable Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of Series D-1 preferred stock	4,000
Series D Redeemable Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from exercise of warrants	$ 43

Description of Business and Basis of Presentation

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Description of Business and Basis of Presentation

A.	Description of Business and Basis of Presentation

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 December 31, 2015. 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.

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 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

Certain prior year amounts have been reclassified to conform to the current year presentation. These reclassifications had no effect on previously reported net loss.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2015

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, the fair value of the Company’s common stock 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 judgments about the carrying value of assets and liabilities.

Concentration of Credit Risk

Financial instruments that potentially expose the Company to concentrations of credit risk consist principally of cash on deposit with multiple financial institutions, the balances of which frequently exceed insured limits.

Cash and Cash Equivalents

The Company considers any highly liquid investments with an original maturity of three months or less to be cash and cash equivalents.

Marketable Securities

The Company maintains investment securities that are classified as trading securities. These securities are carried at fair value with unrealized gains and losses included in other income on the statement of operations. The securities primarily consist of certificates of deposit and government bonds.

Property and Equipment

The Company records property and equipment at cost less accumulated depreciation and amortization. Costs of renewals and improvements that extend the useful lives of the assets are capitalized. Maintenance and repairs are expensed as incurred. Depreciation is determined on a straight-line basis over the estimated useful lives of the assets, which generally range from three to fifteen years. Leasehold improvements are amortized over the shorter of the useful life of the asset or the term of the related lease. Upon retirement or disposition of assets, the costs and related accumulated depreciation and amortization are removed from the accounts with the resulting gains or losses, if any, reflected in results of operations.

Debt Issuance Costs

Debt issuance costs incurred in connection with financing arrangements are amortized over the life of the respective financing arrangement using the effective interest method.

Supply Arrangements

The Company enters into supply arrangements for the supply of components of its product candidates. These arrangements also may include a share of future revenue if related product candidates reach commercialization. Costs under these supply arrangements, if any, are expensed as incurred (Note H).

Impairment of Long-Lived Assets

Long-lived assets to be held and used are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable. When such events occur, the Company compares the carrying amounts of the assets to their undiscounted expected future cash flows. If the undiscounted cash flows are insufficient to recover the carrying values, an impairment loss is recorded for the difference between the carrying values and fair values of the asset. No such impairment occurred for the years ended December 31, 2015 and 2014.

Fair Value of Financial Instruments

The accounting standard for fair value measurements provides a framework for measuring fair value and requires disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date, based on the Company’s principal or, in absence of a principal, most advantageous market for the specific asset or liability.

The Company uses a three-tier fair value hierarchy to classify and disclose all assets and liabilities measured at fair value on a recurring basis, as well as assets and liabilities measured at fair value on a non-recurring basis, in periods subsequent to their initial measurement. The hierarchy requires the Company to use observable inputs when available, and to minimize the use of unobservable inputs, when determining fair value. The three tiers are defined as follows:

Level 1—Observable inputs that reflect quoted market prices (unadjusted) for identical assets or liabilities in active markets;

Level 2—Observable inputs other than quoted prices in active markets that are observable either directly or indirectly in the marketplace for identical or similar assets and liabilities; and

Level 3—Unobservable inputs that are supported by little or no market data, which require the Company to develop its own assumptions.

Research and Development

Major components of research and development costs include cash compensation, stock-based compensation, depreciation and amortization expense on research and development property and equipment, costs of preclinical studies, clinical trials and related clinical manufacturing, costs of drug development, costs of materials and supplies, facilities cost, overhead costs, regulatory and compliance costs, and fees paid to consultants and other entities that conduct certain research and development activities on the Company’s behalf. Costs incurred in research and development are expensed as incurred.

The Company records nonrefundable advance payments it makes for future research and development activities as prepaid expenses. Prepaid expenses are recognized as expense in the statements of operations as the Company receives the related goods or services.

Patent Costs

Patent costs, including related legal costs, are expensed as incurred and recorded within general and administrative expenses on the statements of operations.

Income Taxes

The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial reporting and tax basis of assets and liabilities, as well as for operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using the tax rates that are expected to apply to taxable income for the years in which those tax assets and liabilities are expected to be realized or settled. Valuation allowances are recorded to reduce deferred tax assets to the amount the Company believes is more likely than not to be realized.

Uncertain tax positions are recognized only when the Company believes it is more likely than not that the tax position will be upheld on examination by the taxing authorities based on the merits of the position. The Company recognizes interest and penalties, if any, related to unrecognized income tax uncertainties in income tax expense. The Company did not have any accrued interest or penalties associated with uncertain tax positions for the years ended December 31, 2015 and 2014.

The Company files income tax returns in the United States for federal and various state jurisdictions. With few exceptions, the Company is no longer subject to U.S. federal and state and local income tax examinations for years prior to 2010, although carryforward attributes that were generated prior to 2012 may still be adjusted upon examination by the Internal Revenue Service if used in a future period. No income tax returns are currently under examination by taxing authorities.

Stock-Based Compensation

The Company measures and recognizes compensation expense for all stock-based payment awards made to employees, officers and directors based on the estimated fair values of the awards as of the grant date. The Company records the value of the portion of the award that is ultimately expected to vest as expense over the requisite service period. The Company also accounts for equity instruments issued to non-employees using a fair value approach under Accounting Standards Codification (ASC) subtopic 505-50. The Company values equity instruments and stock options granted using the Black-Scholes option pricing model. The value of non-employee stock-based compensation is subject to periodic adjustments as the underlying equity instruments vest and is recognized as an expense over the term of the related financing or the period over which services are received.

Basic and Diluted Net Loss per Share of Common Stock

The Company uses the two-class method to compute net loss per common share because the Company has issued securities, other than common stock, that contractually entitle the holders to participate in dividends and earnings of the Company. The two-class method requires earnings for the period to be allocated between common stock and participating securities based upon their respective rights to receive distributed and undistributed earnings. Holders of each series of the Company’s redeemable convertible preferred stock are entitled to participate in distributions, when and if declared by the board of directors, that are made to common stockholders and, as a result, are considered participating securities.

Segment and Geographic Information

Operating segments are defined as components of an enterprise (business activity from which it earns revenue and incurs expenses) for which discrete financial information is available and regularly reviewed by the chief operating decision maker in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker (CODM) is its Chief Executive Officer. The Company views its operations and manages its business as a single operating and reporting segment. All assets of the Company were held in the United States for the years ended December 31, 2015 and 2014.

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 July 2013, the FASB issued Accounting Standard Update (“ASU”) No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exist (“ASU 2013-11”). ASU 2013-11 amends the presentation requirements of ASC Topic 740 Income Taxes and requires an unrecognized tax benefit to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, similar tax loss, or a tax credit carryforward. To the extent the tax benefit is not available at the reporting date under the governing tax law or if the entity does not intend to use the deferred tax asset for such purpose, the unrecognized tax benefit should be presented as a liability and not combined with deferred tax assets. ASU 2013-11 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. The amendments are to be applied to all unrecognized tax benefits that exist as of the effective date and may be applied retrospectively to each prior reporting period presented. The adoption of ASU 2013-11 in 2014 did not have a material impact on its financial statements as no uncertain tax positions existed for the years ended December 31, 2015 and 2014.

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 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. Earlier adoption is permitted. 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 expects this update to have a minimal impact on its financial statements upon adoption.

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 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, with early adoption permitted provided the guidance is applied from the beginning of the fiscal year of adoption. The Company does not expect this standard to have an impact on its financial statements upon adoption.

In April 2015, the FASB issued 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. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. Adoption of ASU 2015-03 will reduce assets and liabilities by the amount of the debt issuance costs, which are $1.1 million and $1.5 million at December 31, 2015 and 2014, respectively.

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.

Prepaid Expenses and Other Current Assets

12 Months Ended

Dec. 31, 2015

Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]

Prepaid Expenses and Other Current Assets

C.	Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	December 31,		December 31,
	2015		2014
Other receivables	$	2,375	$	—
Prepaid insurance		290		—
Other prepaid expenses and current assets		93		23
Total	$	2,758	$	23

Property and Equipment

12 Months Ended

Dec. 31, 2015

Property Plant And Equipment [Abstract]

Property and Equipment

D.	Property and Equipment

Property and equipment consists of the following (in thousands):

	December 31,			December 31,
	2015			2014
Laboratory equipment	$	530		$	530
Computers and hardware		176			73
Furniture and office equipment		169			137
Leasehold improvements		6			6
Total property and equipment		881			746
Less: accumulated depreciation and amortization		(478	)		(394	)
Property and equipment, net	$	403		$	352

The Company leases various equipment under capital lease agreements. The assets under capital leases are included in property and equipment as follows (in thousands):

		December 31,				December 31,
		2015				2014
Furniture and office equipment	$		94		$		94
Less: accumulated depreciation and amortization			(22	)			(12	)
	$		72		$		82

The estimated useful lives of property and equipment are as follows:

	Useful Life
Asset Category	(in years)
Laboratory equipment		10
Computers and hardware	3-7
Furniture and office equipment	5-10
Leasehold improvements	15

Depreciation and amortization expense, including amounts pertaining to assets held under capital leases, was approximately $84,000, $75,000 and $68,000 for the years ended December 31, 2015, 2014 and 2013, respectively.

Accounts Payable and Accrued Expenses

12 Months Ended

Dec. 31, 2015

Payables And Accruals [Abstract]

Accounts Payable and Accrued Expenses

E.	Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses consist of the following (in thousands):

	December 31,		December 31,
	2015		2014
Accounts payable	$	1,252	$	1,582
Accrued interest		698		631
Accrued banking fees		700		700
Accrued payroll		947		183
Other accrued expenses		1,309		-
Total	$	4,906	$	3,096

Debt Obligations

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Debt Obligations

F.	Debt Obligations

Deerfield Facility Agreement

On June 2, 2014, the Company entered into a $60.0 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 $15.0 million (the “Term Notes”) and a senior secured loan of $10.0 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 stock”) 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 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 stock 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 stock of $1.5 million, to debt issuance costs on the date of issuance. The Company recorded the fair value of the Deerfield Warrant of $7.6 million and the fair value of the embedded Put Option of $0.2 million 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 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 six of the scheduled interest payments to date. The accrued interest added to outstanding principal is reflected in the 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 (“NDA”) for KP201/APAP and, for the final two tranches, the subsequent approval for commercial sale thereof.

As of December 31, 2015, borrowings available to the Company under the Deerfield Facility Agreement were $35.0 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 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 5.50% Senior Convertible 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 on the Term Notes, a make whole interest payment on the term note and a prepayment premium on the term note.

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.

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.

Conversion of 2013 Convertible Notes into Series D Preferred Stock

From June 2013 through October 2013, the Company issued 10.0% unsecured convertible promissory notes (the “2013 Convertible Notes”) for gross proceeds of $3.8 million. The 2013 Convertible Notes accrued interest from the date of issuance through the maturity date, with such interest payable in cash upon maturity. The 2013 Convertible Notes did not have a stated maturity date and instead matured under various scenarios, such as the sale of substantially all of the assets of the Company, dissolution of the Company, failure to observe covenants, and voluntary or involuntary bankruptcy. In accordance with the terms of the 2013 Convertible Notes, and effected by the written consent of the holders of a majority of the outstanding principal of such notes, on June 2, 2014, the principal amount of the 2013 Convertible Notes of $3.8 million and all accrued interest of $0.3 million converted into 5,332,348 shares of Series D preferred stock at $0.78 per share. Upon the conversion of the 2013 Convertible Notes, the embedded conversion feature of the 2013 Convertible Notes and Put Option was marked to fair value and the balance of $1.9 million was recorded as a gain on extinguishment of debt.

Line of Credit

The Company has a $50,000 credit agreement with a financial institution (the “Line of Credit Agreement”). As of December 31, 2015 and 2014, 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% as of December 31, 2015 and 2014.

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 December 31, 2015, the Company had $100,000 available under the Second Line of Credit Agreement. 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 December 31, 2015.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2015

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

G.	Commitments and Contingencies

Legal Matters

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 settlement amount was commiserate with the contingency recorded in the books and records of the Company. The consideration in the settlement agreement did not differ from the accrual previously recorded by the Company by a material amount.

Lease Agreements

Iowa

The Company leases office and laboratory facilities in Iowa under a long-term non-cancelable operating lease. The Company’s lease for its Iowa facilities expires in September 2016 and includes a renewal option that could extend the lease for an additional three years.

Florida

The Company leases office space in Florida under a long-term non-cancelable operating lease. In April 2015, the Company signed a first amendment to the lease to expand the amount of office space in the current facility. In December 2015, the Company signed a second amendment to the lease to move from one facility to an adjacent facility with more office space. The adjacent facility requires build out and is anticipated to be ready by mid-2016. The expiration date on the Company’s lease for its Florida facility is dependent on the adjacent facility’s build out completion date. Currently the lease is expected to expire in mid-2025 and includes renewal options that could extend the lease for two additional five year terms.

Virginia

The Company leases office and laboratory facilities in Virginia under a short-term non-cancelable operating lease. The Company’s lease for its Virginia facilities expires in August 2016. The Company anticipates, based on historical experience, extending the lease term for a period of 12 months upon expiration.

North Carolina

The Company leases office space in North Carolina under a long-term non-cancelable operating lease. The expiration date of the Company’s lease is May 2020 and includes renewal options that could extend the lease for an additional three years.

Capital Lease

The Company leases various laboratory, computer and other office equipment that are accounted for as capital leases and that require ongoing payments including interest expense. The capital leases are financed through various financial institutions and are collateralized by the underlying assets. As of December 31, 2015, the interest rate for assets under remaining capital leases was 0.67%.

Rent expense for non-cancelable operating leases was $0.3 million, $0.2 million and $0.1 million for the years ended December 31, 2015, 2014 and 2013, respectively.

Future minimum lease payments under capital leases and non-cancelable operating leases as of December 31, 2015 were as follows (in thousands):

	Capital			Operating
Year Ending December 31,	Leases			Leases
2016	$	27		$	440
2017		—			487
2018		—			497
2019		—			485
2020		—			428
Thereafter		—			5,354
Total minimum lease payments		27		$	7,691
Less: amounts representing interest		(1	)
Total	$	26

Supply Arrangement

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Supply Arrangement

H.	Supply Arrangement

As of December 31, 2015, the Company has one manufacturing arrangement that involves potential future expenditures related to research and development.

In November 2009, the Company entered into a supply agreement (the “Supply Agreement”) with Johnson Matthey Inc. (“JMI”) whereby JMI has agreed to supply the Company with all of the KP201 necessary for clinical trials and commercial sale for a price equal to JMI’s manufacturing cost and to provide process optimization and development services for KP201. The Company’s most advanced product candidate, KP201/APAP, is a combination of KP201 and acetaminophen (“APAP”) and is under development to treat acute moderate to moderately severe pain. The Company submitted an NDA for KP201/APAP in the second half of 2015 under Section 505(b)(2) of the Federal Food, Drug and Cosmetic Act. No expense was recorded under this agreement for the years ended December 31, 2015 and 2014. The Company must purchase all of its U.S. KP201 needs from JMI and JMI cannot supply KP201 to other companies. The term of the Supply Agreement extends as long as the Company holds a valid and enforceable patent for KP201 or until the tenth anniversary of KP201’s commercial launch, whichever date is later. Upon the expiration of such term, the agreement will automatically renew for a period of two years unless either party provides 12 months prior notice of its intent not to renew. Under the agreement, JMI will receive a tiered-based royalty share on the net sales on the commercial sale of a FDA approved drug incorporating KP201. No reliable estimate of the future payments can be made at this time.

Preferred Stock and Warrants

12 Months Ended

Dec. 31, 2015

Text Block [Abstract]

Preferred Stock and Warrants

I.	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 December 31, 2015, the Company had 10,000,000 shares of authorized and undesignated preferred stock, and did not have any preferred stock outstanding.

Preferred Stock Activity

The following table summarizes redeemable convertible preferred stock activity for the years ended December 31, 2015 and 2014:

	Shares of
	Series A			Series B			Series C			Series D			Series D-1
	Preferred			Preferred			Preferred			Preferred			Preferred			Total
Balance, January 1, 2013		9,704,215			6,220,000			18,557,408			—			—			34,481,623
Balance, December 31, 2013		9,704,215			6,220,000			18,557,408			—			—			34,481,623
Shares issued upon conversion of 2013 Convertible Notes		—			—			—			5,332,348			—			5,332,348
Shares issued for financing fee to Deerfield		—			—			—			1,923,077			—			1,923,077
Balance, December 31, 2014		9,704,215			6,220,000			18,557,408			7,255,425			—			41,737,048
Issuance of Series D-1 preferred stock		—			—			—			—			3,200,000			3,200,000
Exercise of Series D preferred warrants		—			—			—			3,205			—			3,205
Effect of reverse stock-split		(8,410,377	)		(5,390,766	)		(16,083,286	)		(6,290,844	)		(2,784,416	)		(38,959,689	)
Less: Conversion of preferred stock into common stock upon IPO		(1,293,838	)		(829,234	)		(2,474,122	)		(967,786	)		(415,584	)		(5,980,564	)
Balance, December 31, 2015		—			—			—			—			—			—

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 for $1.25 per share, or an aggregate of $4.0 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 December 31, 2015, warrants to purchase 15,499,324 shares of Series D preferred stock were reclassified into warrants to purchase 2,066,543 shares of the Company’s common stock. As of December 31, 2014, the Company had pre-split outstanding warrants to purchase 15,502,529 shares of Series D preferred stock at an exercise price of $0.78 per share. During the year ended December 31, 2015, warrants to purchase 3,205 shares of Series D preferred stock were exercised.

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”) (Note F). 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 stock. 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 stock (Note F). 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 Term Notes and 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 marked the 2013 Warrants to fair value and reclassified them 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 L).

Common Stock and Warrants

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Common Stock and Warrants

J.	Common Stock and Warrants

Authorized, Issued, and Outstanding Common Shares

In April 2015, the Company amended its Certificate of Incorporation to increase the number of its authorized shares of common stock to 250,000,000 shares. Of the authorized shares, 14,490,954 and 2,381,041 shares of common stock were issued and outstanding at December 31, 2015 and 2014, respectively.

At December 31, 2015 and 2014, the Company had reserved authorized shares of common stock for future issuance as follows:

	December 31,		December 31,
	2015		2014
Conversion of Series A redeemable convertible preferred stock		—		1,293,838
Conversion of Series B redeemable convertible preferred stock		—		829,234
Conversion of Series C redeemable convertible preferred stock		—		2,474,122
Conversion of Series D redeemable convertible preferred stock		—		967,359
Conversion of Series D-1 redeemable convertible preferred stock		—		—
Conversion of Deerfield Convertible Notes		1,991,219		1,808,353
Outstanding awards under equity incentive plans		1,397,511		395,185
Outstanding common stock warrants		2,325,383		595,920
Outstanding Series D redeemable convertible preferred stock warrants		—		2,066,970
Possible future issuances under equity incentive plans		1,410,848		365,706
Total common shares reserved for future issuance		7,124,961		10,796,687

Common Stock Activity

The following table summarizes common stock activity during the year ended December 31, 2015 (there was no common stock activity during the years ended December 31, 2014 and 2013):

	Shares of
	Common Stock
Balance at December 31, 2014		2,381,041
Issuance of common stock in connection with the IPO		5,854,545
Conversion of preferred stock to common stock in connection with the IPO		5,980,564
Common stock warrants exercised		270,038
Common stock options exercised		4,766
Balance at December 31, 2015		14,490,954

The Company calculates the fair value of common stock warrants using a Monte Carlo simulation. There were warrants exercised for an aggregate of 270,038 shares of common stock during the year ended December 31, 2015 and there were no warrants exercised during the year ended December 31, 2014. 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 accounts 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

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-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

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-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

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

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
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-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

12 Months Ended

Dec. 31, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

K.	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 2,266,666, as of December 31, 2015. In addition, 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 year ended December 31, 2015, stock options to acquire 4,766 shares of common stock were exercised with an intrinsic value of $54,000. No stock options were exercised during the years ended December 31, 2014 and 2013.

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):

	Year ended December 31,
	2015		2014		2013
Research and development	$	610	$	62	$	29
General and administrative		1,759		152		105
	$	2,369	$	214	$	134

Stock Option Awards

The Company estimates the fair value of stock options using the Black-Scholes option-pricing model, which requires the use of subjective assumptions, including the expected term of the option, the expected stock price volatility, expected dividend yield and the risk-free interest rate for the expected term of the option. The expected term represents the period of time the stock options are expected to be outstanding. Due to the lack of sufficient historical exercise data to provide a reasonable basis upon which to otherwise estimate the expected term of the stock options, the Company uses the simplified method to estimate the expected term for its “plain vanilla” stock options. Under the simplified method, the expected term of an option is presumed to be the mid-point between the vesting date and the end of the contractual term. Some options, for example those that have exercise prices in excess of the fair value of the underlying stock, are not considered “plain vanilla” stock options. For these options, the Company uses an expected term equal to the contractual term of the option. Expected volatility is based on historical volatilities for publicly traded stock of comparable companies over the estimated expected term of the stock options. The Company assumes no dividend yield because dividends are not expected to be paid in the near future, which is consistent with the Company’s history of not paying dividends.

The Company recognizes compensation expense related to stock-based payment transactions upon satisfaction of the requisite service or vesting requirements. Forfeitures are estimated at the time of grant and revised based on actual forfeitures, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

Using the Black-Scholes option-pricing model, the weighted-average fair value of awards granted during the years ended December 31, 2015, 2014 and 2013 fair value was $10.63, $4.50 and $3.00 per share, respectively. The assumptions used to estimate fair value are as follows:

	December 31,	December 31,	December 31,
	2015	2014	2013
Risk-free interest rate	1.40% - 1.99%	0.91% - 2.70%	0.52% - 2.80%
Expected term (in years)	4.33 - 6.25	7.00 - 10.00	4.04 - 10.00
Expected volatility	68.79% - 86.84%	86.00% - 95.00%	58.55% - 92.00%
Expected dividend yield	0%	0%	0%

The activity under the Incentive Stock Plan and the 2014 Plan for the year ended December 31, 2015 is summarized as follows:

							Weighted
							Average
					Weighted		Remaining
					Average		Contractual		Aggregate
	Number of				Exercise		Term		Intrinsic
	Options				Price		(in years)		Value
Outstanding balance at January 1, 2015		395,185		$		5.40		7.24	$	1,275,980
Granted		1,010,457		$		16.30
Exercised		(4,766	)	$		5.85
Forfeited		(3,365	)	$		5.85
Outstanding balance at December 31, 2015		1,397,511		$		13.28		8.58	$	9,204,403
Exercisable at December 31, 2015		384,087		$		6.71		6.55	$	5,057,062
Vested and expected to vest at December 31, 2015		1,254,325		$		13.00		8.49	$	8,614,743

Information regarding currently outstanding and exercisable options as of December 31, 2015 is as follows:

		Options Outstanding				Options Exercisable
				Weighted				Weighted
				Average				Average
				Remaining				Remaining
				Contractual				Contractual
		Number of		Term		Number of		Term
Exercise Price		Shares		(in years)		Shares		(in years)
$0.75			12,000		1.50		12,000		1.50
$3.00			20,666		2.54		20,666		2.54
$4.65			49,327		2.61		49,327		2.61
$5.85			305,061		7.23		207,428		6.91
$	8.63		154,639		9.03		6,666		8.57
$	11.00		21,333		9.30		—		—
$	11.41		170,035		9.41		88,000		9.41
$	16.61		11,250		9.94		—		—
$	18.29		205,000		9.49		—		—
$	18.61		38,400		9.65		—		—
$	19.02		62,000		9.65		—		—
$	20.45		335,000		9.68		—		—
$	21.37		6,400		9.70		—		—
$	22.12		6,400		9.71		—		—
			1,397,511		8.58		384,087		6.55

The total fair value of stock options vested during the years ended December 31, 2015, 2014 and 2013, was $1.1 million, $0.2 million and $0.2 million, respectively.

Unvested stock options as of December 31, 2015 and 2014 were as follows:

		Number of Unvested Shares
		December 31,		December 31,
Exercise Price		2015		2014
$5.85			97,633		225,018
$	8.63		147,973		—
$	11.00		21,333		—
$	11.41		82,035		—
$	16.61		11,250		—
$	18.29		205,000		—
$	18.61		38,400		—
$	19.02		62,000		—
$	20.45		335,000		—
$	21.37		6,400		—
$	22.12		6,400		—
			1,013,424		225,018

As of December 31, 2015, there was $9.0 million of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the 2014 Plan and the Company’s 2007 stock incentive plan. That compensation cost is expected to be recognized over a weighted-average period of 2.77 years.

During the year ended December 31, 2015, the Company recognized $0.7 million of stock-based compensation expense related to performance-based awards included in general and administrative expenses and $0.2 million of stock-based compensation expense related to performance-based awards included in research and development expenses. These awards were in connection with the grant of fully vested stock options exercisable for an aggregate of 163,998 shares of common stock during the year ended December 31, 2015. The Company did not recognize any stock-based compensation expense related to performance-based incentive awards during the years ended December 31, 2014 or 2013, since the strategic initiatives set for the awards were not achieved or probable of achievement.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

L.	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 Term Notes was $42.0 million and $14.1 million, respectively, at December 31, 2015. Both the Deerfield Convertible Notes and Term 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 judgments to be made. The following table summarizes the conclusions reached regarding fair value measurements as of December 31, 2015 and 2014 (in thousands):

			Quoted Prices		Significant
			in Active		Other		Significant
	Balance at		Markets for		Observable		Unobservable
	December 31,		Identical Assets		Inputs		Inputs
	2015		(Level 1)		(Level 2)		(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	$	—	$	—

			Quoted Prices		Significant
			in Active		Other		Significant
	Balance at		Markets for		Observable		Unobservable
	December 31,		Identical Assets		Inputs		Inputs
	2014		(Level 1)		(Level 2)		(Level 3)
Underwriter warrant liability	$	2,746	$	—	$	—	$	2,746
2013 warrant liability		520		—		—		520
Deerfield warrant liability		12,560		—		—		12,560
Embedded put option		140		—		—		140
Total liabilities	$	15,966	$	—	$	—	$	15,966

The Company’s Underwriter Warrant liability, Deerfield Warrant liability and the embedded Put Option on the Deerfield Warrant are measured at fair value on a recurring basis. The 2013 Warrant liability was recorded at fair value on a recurring basis through the completion of the IPO. As of December 31, 2015 and 2014, the Underwriter Warrant liability, the Deerfield Warrant liability and the embedded Put Option are reported on the balance sheet in derivative and warrant liability. Upon closing of the IPO in April 2015, the 2013 Warrant liability was marked to fair value and then reclassified to equity. The Company used a Monte Carlo simulation to value the Underwriter Warrant liability and the embedded Put Option at December 31, 2015 and 2014. The Company used a Monte Carlo simulation to value the 2013 Warrant liability as of December 31, 2014, and the closing date of the IPO. 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 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 2013 Warrant liability, the Deerfield Warrant liability and the embedded Put Option 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 $1.9 million in the estimated fair value of the Deerfield Warrant liability, and no change in the estimated fair value of the embedded Put Option at December 31, 2015.

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):

	2015			2014
Balance at beginning of period	$	15,966		$	2,813
Issuance of Deerfield warrant		—			7,610
Embedded put option		—			220
Conversion of 2013 Convertible Notes		—			(1,900	)
Reclassification of 2013 warrants to equity		(1,110	)		—
Exercise of warrants		(4,293	)		—
Adjustment to fair value		27,276			7,223
Balance at end of period	$	37,839		$	15,966

- 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

Income Taxes

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Income Taxes

M.	Income Taxes

The Company’s financial statements include a total state tax benefit of $15,000, $22,000 and $20,000 on a loss before income taxes of $54.6 million, $24.5 million and $5.2 million for the years ended December 31, 2015, 2014 and 2013, respectively. A reconciliation of the difference between the benefit for income taxes and income taxes at the statutory U.S. federal income tax rate is as follows (in thousands):

	Year ended December 31,
	2015				2014				2013
Federal statutory rate		34.00		%		34.00		%		34.00		%
Effect of:
Change in valuation allowance		(19.25	)			(32.88	)			(38.38	)
State tax benefit (net of federal)		4.06				5.96				7.53
Warrant liability		(15.28	)			(9.39	)			6.08
State research and development credit		0.03				0.09				0.37
Federal research and development credit		0.84				3.29				2.53
Conversion feature and put option on 2013 convertible notes		(1.68	)			(1.26	)			(8.81	)
Interest expense		—				0.21				(0.99	)
Stock-based compensation		(1.28	)			—				—
Other		(1.42	)			0.07				(1.95	)
Federal income tax provision effective rate		0.02		%		0.09		%		0.38		%

The components of deferred tax assets and liabilities are as follows (in thousands):

	December 31,			December 31,			December 31,
	2015			2014			2013
Deferred tax assets relating to:
Net operating loss carryforwards	$	26,617		$	16,390		$	9,606
Research and development tax carryforward		2,254			1,793			899
Compensation		232			83			76
Total gross deferred tax assets		29,103			18,266			10,581
Deferred tax liabilities relating to:
Property and equipment		80			170			176
Total gross deferred tax liabilities		80			170			176
Deferred tax assets less liabilities		29,023			18,096			10,405
Valuation allowance		(29,023	)		(18,096	)		(10,405	)
Net deferred tax asset (liability)	$	—		$	—		$	—

In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment. Based upon the level of historical taxable income and projections for future taxable income over the periods in which the deferred tax assets are deductible, management believes it is more likely than not that the Company will not realize the benefits of these deductible differences in the future.

The Company had the following federal net operating loss carryforward and research activities credits as of December 31, 2015 (in thousands):

			Research
	Net Operating		Activities
Year Incurred	Loss Carryforwards		Credit		Expiration
2007	$	454	$	30		2027
2008		1,178		65		2028
2009		3,060		176		2029
2010		3,423		149		2030
2011		9,929		176		2031
2012		—		170		2032
2013		4,353		133		2033
2014		15,819		894		2034
2015		24,189		461		2035
	$	62,405	$	2,254

The Company also has certain state net operating loss carryforwards totaling $59.7 million that expire between 2027 and 2035. Due to potential ownership changes that may have occurred or would occur in the future, IRC Section 382 may place additional limitations on the Company’s ability to utilize the net operating loss carryforward.

Financial Interpretation No. 48 (“FIN 48”), Accounting for Uncertainty in Income Taxes, uses the term “more likely than not” to evaluate whether or not a tax position will be sustained upon examination. The Company has not identified any tax positions that do not meet the more likely than not threshold.

Net Loss Per Share

12 Months Ended

Dec. 31, 2015

Earnings Per Share [Abstract]

Net Loss Per Share

N.	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 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.

The following table summarizes the computation of basic and diluted net loss and net loss per share of the Company (in thousands, except share and per share amounts):

	Year ended December 31,
	2015			2014			2013
Net loss - basic and diluted	$	(54,664	)	$	(24,455	)	$	(5,226	)
Weighted-average number of common shares - basic and diluted		7,368,681			2,381,041			2,381,041
Net loss per share - basic and diluted	$	(7.42	)	$	(10.27	)	$	(2.20	)

Diluted net loss per share is the same as basic net loss per share for all periods presented because the effects of potentially dilutive items were anti-dilutive given the Company’s net loss. 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:

	December 31,		December 31,		December 31,
	2015		2014		2013
Redeemable convertible preferred stock:
Series A		—		1,293,838		1,293,838
Series B		—		829,234		829,234
Series C		—		2,474,122		2,474,122
Series D		—		967,359		—
Total redeemable convertible preferred stock		—		5,564,553		4,597,194
Warrants to purchase common stock		2,325,383		595,920		595,920
Warrants to purchase Series D preferred stock		—		2,066,970		143,893
Awards under equity incentive plans		1,397,511		395,185		296,255
2013 Convertible Notes		—		—		683,417
Deerfield Convertible Notes		1,991,219		1,808,353		—

Employee Benefit Plan

12 Months Ended

Dec. 31, 2015

Postemployment Benefits [Abstract]

Employee Benefit Plan

O.	Employee Benefit Plan

The Company has a 401(k) retirement plan (the “401(k) Plan”) that covers all employees. The Company may provide a discretionary match with a maximum amount of 4% of the participant’s compensation, which vests immediately. The Company made matching contributions under the 401(k) Plan of $113,000, $69,000 and $50,000 for the years ended December 31, 2015, 2014 and 2013, respectively.

The Company has a discretionary profit sharing plan (the “Profit Sharing Plan”) that covers all employees. Employees become eligible participants in the Profit Sharing Plan once they have provided three years of service to the Company. The Company made no contributions to the Profit Sharing Plan in 2015, 2014 or 2013.

Subsequent Events

12 Months Ended

Dec. 31, 2015

Subsequent Events [Abstract]

Subsequent Events

P.	Subsequent Events (unaudited)

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 the 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.

Withdrawal of Registration Statement on Form S-1

On February 3, 2016, the Company requested that the Securities and Exchange Commission (the “Commission”) consent to the withdrawal of the Company’s Registration Statement on Form S-1 filed with the Commission on December 18, 2015.

Issuance of 5.50% Senior Convertible 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 the 2021 Notes to Initial Purchasers, who subsequently resold the 2021 Notes to qualified institutional buyers in reliance on the exemption from registration provided by Rule 144A under the Securities Act.

The 2021 Notes were issued pursuant to the Indenture. 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.

In connection with the Note Offering, on February 3, 2016, the Company entered into 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.

Quarterly Results of Operations (unaudited)

12 Months Ended

Dec. 31, 2015

Quarterly Financial Information Disclosure [Abstract]

Quarterly Results of Operations

Q.Quarterly Results of Operations (unaudited)

The following tables set forth unaudited quarterly statements of operations data for each of the quarters indicated. The financial statements for each of these quarters have been prepared on the same basis as the audited financial statements included herein and, in the opinion of management, include all adjustments, consisting only of normal recurring adjustments, necessary for the fair statement of the results of operations for these periods. You should read this information together with our financial statements and related notes included herein. These quarterly operating results are not necessarily indicative of the results for any future period.

	Three-Months Ended
	Dec 31,	Sep 30,	Jun 30,	Mar 31,	Dec 31,	Sep 30,	Jun 30,	Mar 31,
	2015	2015	2015	2015	2014	2014	2014	2014
Revenue	$ —	$ —	$ —	$ —	$ —	$ —	$ —	$ —
Operating expenses:
Research and development	4,716	4,328	2,768	2,119	5,911	3,253	1,715	1,038
General and administrative	2,566	2,152	3,188	977	1,577	1,086	1,330	534
Total operating expenses	7,282	6,480	5,956	3,096	7,488	4,339	3,045	1,572
Loss from operations	(7,282)	(6,480)	(5,956)	(3,096)	(7,488)	(4,339)	(3,045)	(1,572)
Other income (expenses):
Gain on extinguishment of debt	—	—	—	—	—	—	1,900	—
Amortization of debt discount	(475)	(479)	(477)	(477)	(478)	(477)	(159)	—
Interest expense	(698)	(687)	(654)	(632)	(631)	(173)	(704)	(96)
Fair value adjustment	(764)	(2,089)	(22,661)	(1,762)	(3,221)	(2,189)	(1,570)	(242)
Interest and other income	15	11	5	—	4	3	—	—
Total other expenses	(1,922)	(3,244)	(23,787)	(2,871)	(4,326)	(2,836)	(533)	(338)
Loss before income taxes	(9,204)	(9,724)	(29,743)	(5,967)	(11,814)	(7,175)	(3,578)	(1,910)
Income tax (expense) benefit	1	(20)	—	(7)	(27)	38	6	5
Net loss	$(9,203)	$(9,744)	$(29,743)	$(5,974)	$(11,841)	$(7,137)	$(3,572)	$(1,905)
Net loss per share:
Basic and diluted	$ (0.64)	$ (0.68)	$ (2.45)	$ (2.50)	$ (4.97)	$ (3.00)	$ (1.50)	$ (0.80)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Use of Estimates

Concentration of Credit Risk

Cash and Cash Equivalents

The Company considers any highly liquid investments with an original maturity of three months or less to be cash and cash equivalents.

Marketable Securities

Property and Equipment

Debt Issuance Costs

Debt issuance costs incurred in connection with financing arrangements are amortized over the life of the respective financing arrangement using the effective interest method.

Supply Arrangements

Impairment of Long-Lived Assets

Fair Value of Financial Instruments

Level 1—Observable inputs that reflect quoted market prices (unadjusted) for identical assets or liabilities in active markets;

Level 2—Observable inputs other than quoted prices in active markets that are observable either directly or indirectly in the marketplace for identical or similar assets and liabilities; and

Level 3—Unobservable inputs that are supported by little or no market data, which require the Company to develop its own assumptions.

Research and Development

Patent Costs

Patent costs, including related legal costs, are expensed as incurred and recorded within general and administrative expenses on the statements of operations.

Income Taxes

Stock-Based Compensation

Basic and Diluted Net Loss per Share of Common Stock

Segment and Geographic Information

Application of New or Revised Accounting Standards Adopted

Application of New or Revised Accounting Standards—Adopted

Application of New or Revised Accounting Standards Not Yet Adopted

Application of New or Revised Accounting Standards—Not Yet Adopted

Prepaid Expenses and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2015

Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]

Components of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	December 31,		December 31,
	2015		2014
Other receivables	$	2,375	$	—
Prepaid insurance		290		—
Other prepaid expenses and current assets		93		23
Total	$	2,758	$	23

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2015

Property Plant And Equipment [Abstract]

Components of Property and Equipment

Property and equipment consists of the following (in thousands):

	December 31,			December 31,
	2015			2014
Laboratory equipment	$	530		$	530
Computers and hardware		176			73
Furniture and office equipment		169			137
Leasehold improvements		6			6
Total property and equipment		881			746
Less: accumulated depreciation and amortization		(478	)		(394	)
Property and equipment, net	$	403		$	352

Assets under Capital Leases Included in Property and Equipment

The Company leases various equipment under capital lease agreements. The assets under capital leases are included in property and equipment as follows (in thousands):

		December 31,				December 31,
		2015				2014
Furniture and office equipment	$		94		$		94
Less: accumulated depreciation and amortization			(22	)			(12	)
	$		72		$		82

Estimated Useful Lives of Property and Equipment

The estimated useful lives of property and equipment are as follows:

	Useful Life
Asset Category	(in years)
Laboratory equipment		10
Computers and hardware	3-7
Furniture and office equipment	5-10
Leasehold improvements	15

Accounts Payable and Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2015

Payables And Accruals [Abstract]

Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses consist of the following (in thousands):

	December 31,		December 31,
	2015		2014
Accounts payable	$	1,252	$	1,582
Accrued interest		698		631
Accrued banking fees		700		700
Accrued payroll		947		183
Other accrued expenses		1,309		-
Total	$	4,906	$	3,096

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2015

Commitments And Contingencies Disclosure [Abstract]

Future Minimum Lease Payments under Capital Leases and Non-Cancelable Operating Leases

Future minimum lease payments under capital leases and non-cancelable operating leases as of December 31, 2015 were as follows (in thousands):

	Capital			Operating
Year Ending December 31,	Leases			Leases
2016	$	27		$	440
2017		—			487
2018		—			497
2019		—			485
2020		—			428
Thereafter		—			5,354
Total minimum lease payments		27		$	7,691
Less: amounts representing interest		(1	)
Total	$	26

Preferred Stock and Warrants (Tables)

12 Months Ended

Dec. 31, 2015

Text Block [Abstract]

Summary of Redeemable Convertible Preferred Stock Activity

The following table summarizes redeemable convertible preferred stock activity for the years ended December 31, 2015 and 2014:

	Shares of
	Series A			Series B			Series C			Series D			Series D-1
	Preferred			Preferred			Preferred			Preferred			Preferred			Total
Balance, January 1, 2013		9,704,215			6,220,000			18,557,408			—			—			34,481,623
Balance, December 31, 2013		9,704,215			6,220,000			18,557,408			—			—			34,481,623
Shares issued upon conversion of 2013 Convertible Notes		—			—			—			5,332,348			—			5,332,348
Shares issued for financing fee to Deerfield		—			—			—			1,923,077			—			1,923,077
Balance, December 31, 2014		9,704,215			6,220,000			18,557,408			7,255,425			—			41,737,048
Issuance of Series D-1 preferred stock		—			—			—			—			3,200,000			3,200,000
Exercise of Series D preferred warrants		—			—			—			3,205			—			3,205
Effect of reverse stock-split		(8,410,377	)		(5,390,766	)		(16,083,286	)		(6,290,844	)		(2,784,416	)		(38,959,689	)
Less: Conversion of preferred stock into common stock upon IPO		(1,293,838	)		(829,234	)		(2,474,122	)		(967,786	)		(415,584	)		(5,980,564	)
Balance, December 31, 2015		—			—			—			—			—			—

Common Stock and Warrants (Tables)

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Schedule of Authorized Shares of Common Stock Reserved for Future Issuance

At December 31, 2015 and 2014, the Company had reserved authorized shares of common stock for future issuance as follows:

	December 31,		December 31,
	2015		2014
Conversion of Series A redeemable convertible preferred stock		—		1,293,838
Conversion of Series B redeemable convertible preferred stock		—		829,234
Conversion of Series C redeemable convertible preferred stock		—		2,474,122
Conversion of Series D redeemable convertible preferred stock		—		967,359
Conversion of Series D-1 redeemable convertible preferred stock		—		—
Conversion of Deerfield Convertible Notes		1,991,219		1,808,353
Outstanding awards under equity incentive plans		1,397,511		395,185
Outstanding common stock warrants		2,325,383		595,920
Outstanding Series D redeemable convertible preferred stock warrants		—		2,066,970
Possible future issuances under equity incentive plans		1,410,848		365,706
Total common shares reserved for future issuance		7,124,961		10,796,687

Schedule of Common Stock Shares Activity

The following table summarizes common stock activity during the year ended December 31, 2015 (there was no common stock activity during the years ended December 31, 2014 and 2013):

	Shares of
	Common Stock
Balance at December 31, 2014		2,381,041
Issuance of common stock in connection with the IPO		5,854,545
Conversion of preferred stock to common stock in connection with the IPO		5,980,564
Common stock warrants exercised		270,038
Common stock options exercised		4,766
Balance at December 31, 2015		14,490,954

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock-Based Compensation Expense

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):

	Year ended December 31,
	2015		2014		2013
Research and development	$	610	$	62	$	29
General and administrative		1,759		152		105
	$	2,369	$	214	$	134

Black-Scholes-Merton Option Pricing Model

The assumptions used to estimate fair value are as follows:

	December 31,	December 31,	December 31,
	2015	2014	2013
Risk-free interest rate	1.40% - 1.99%	0.91% - 2.70%	0.52% - 2.80%
Expected term (in years)	4.33 - 6.25	7.00 - 10.00	4.04 - 10.00
Expected volatility	68.79% - 86.84%	86.00% - 95.00%	58.55% - 92.00%
Expected dividend yield	0%	0%	0%

Schedule of Stock Option Activity

The activity under the Incentive Stock Plan and the 2014 Plan for the year ended December 31, 2015 is summarized as follows:

							Weighted
							Average
					Weighted		Remaining
					Average		Contractual		Aggregate
	Number of				Exercise		Term		Intrinsic
	Options				Price		(in years)		Value
Outstanding balance at January 1, 2015		395,185		$		5.40		7.24	$	1,275,980
Granted		1,010,457		$		16.30
Exercised		(4,766	)	$		5.85
Forfeited		(3,365	)	$		5.85
Outstanding balance at December 31, 2015		1,397,511		$		13.28		8.58	$	9,204,403
Exercisable at December 31, 2015		384,087		$		6.71		6.55	$	5,057,062
Vested and expected to vest at December 31, 2015		1,254,325		$		13.00		8.49	$	8,614,743

Information Regarding Currently Outstanding and Exercisable Options

Information regarding currently outstanding and exercisable options as of December 31, 2015 is as follows:

		Options Outstanding				Options Exercisable
				Weighted				Weighted
				Average				Average
				Remaining				Remaining
				Contractual				Contractual
		Number of		Term		Number of		Term
Exercise Price		Shares		(in years)		Shares		(in years)
$0.75			12,000		1.50		12,000		1.50
$3.00			20,666		2.54		20,666		2.54
$4.65			49,327		2.61		49,327		2.61
$5.85			305,061		7.23		207,428		6.91
$	8.63		154,639		9.03		6,666		8.57
$	11.00		21,333		9.30		—		—
$	11.41		170,035		9.41		88,000		9.41
$	16.61		11,250		9.94		—		—
$	18.29		205,000		9.49		—		—
$	18.61		38,400		9.65		—		—
$	19.02		62,000		9.65		—		—
$	20.45		335,000		9.68		—		—
$	21.37		6,400		9.70		—		—
$	22.12		6,400		9.71		—		—
			1,397,511		8.58		384,087		6.55

Unvested Stock Options

Unvested stock options as of December 31, 2015 and 2014 were as follows:

		Number of Unvested Shares
		December 31,		December 31,
Exercise Price		2015		2014
$5.85			97,633		225,018
$	8.63		147,973		—
$	11.00		21,333		—
$	11.41		82,035		—
$	16.61		11,250		—
$	18.29		205,000		—
$	18.61		38,400		—
$	19.02		62,000		—
$	20.45		335,000		—
$	21.37		6,400		—
$	22.12		6,400		—
			1,013,424		225,018

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2015

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 December 31, 2015 and 2014 (in thousands):

			Quoted Prices		Significant
			in Active		Other		Significant
	Balance at		Markets for		Observable		Unobservable
	December 31,		Identical Assets		Inputs		Inputs
	2015		(Level 1)		(Level 2)		(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	$	—	$	—

			Quoted Prices		Significant
			in Active		Other		Significant
	Balance at		Markets for		Observable		Unobservable
	December 31,		Identical Assets		Inputs		Inputs
	2014		(Level 1)		(Level 2)		(Level 3)
Underwriter warrant liability	$	2,746	$	—	$	—	$	2,746
2013 warrant liability		520		—		—		520
Deerfield warrant liability		12,560		—		—		12,560
Embedded put option		140		—		—		140
Total liabilities	$	15,966	$	—	$	—	$	15,966

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

	2015			2014
Balance at beginning of period	$	15,966		$	2,813
Issuance of Deerfield warrant		—			7,610
Embedded put option		—			220
Conversion of 2013 Convertible Notes		—			(1,900	)
Reclassification of 2013 warrants to equity		(1,110	)		—
Exercise of warrants		(4,293	)		—
Adjustment to fair value		27,276			7,223
Balance at end of period	$	37,839		$	15,966

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of Difference Between Benefit for Income Taxes and Income Taxes at Statutory U.S Federal Income Tax Rate

A reconciliation of the difference between the benefit for income taxes and income taxes at the statutory U.S. federal income tax rate is as follows (in thousands):

	Year ended December 31,
	2015				2014				2013
Federal statutory rate		34.00		%		34.00		%		34.00		%
Effect of:
Change in valuation allowance		(19.25	)			(32.88	)			(38.38	)
State tax benefit (net of federal)		4.06				5.96				7.53
Warrant liability		(15.28	)			(9.39	)			6.08
State research and development credit		0.03				0.09				0.37
Federal research and development credit		0.84				3.29				2.53
Conversion feature and put option on 2013 convertible notes		(1.68	)			(1.26	)			(8.81	)
Interest expense		—				0.21				(0.99	)
Stock-based compensation		(1.28	)			—				—
Other		(1.42	)			0.07				(1.95	)
Federal income tax provision effective rate		0.02		%		0.09		%		0.38		%

Components of Net Deferred Tax Assets and Liabilities

The components of deferred tax assets and liabilities are as follows (in thousands):

	December 31,			December 31,			December 31,
	2015			2014			2013
Deferred tax assets relating to:
Net operating loss carryforwards	$	26,617		$	16,390		$	9,606
Research and development tax carryforward		2,254			1,793			899
Compensation		232			83			76
Total gross deferred tax assets		29,103			18,266			10,581
Deferred tax liabilities relating to:
Property and equipment		80			170			176
Total gross deferred tax liabilities		80			170			176
Deferred tax assets less liabilities		29,023			18,096			10,405
Valuation allowance		(29,023	)		(18,096	)		(10,405	)
Net deferred tax asset (liability)	$	—		$	—		$	—

Federal Net Operating Loss Carryforward And Research Activities Credits

The Company had the following federal net operating loss carryforward and research activities credits as of December 31, 2015 (in thousands):

			Research
	Net Operating		Activities
Year Incurred	Loss Carryforwards		Credit		Expiration
2007	$	454	$	30		2027
2008		1,178		65		2028
2009		3,060		176		2029
2010		3,423		149		2030
2011		9,929		176		2031
2012		—		170		2032
2013		4,353		133		2033
2014		15,819		894		2034
2015		24,189		461		2035
	$	62,405	$	2,254

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2015

Earnings Per Share [Abstract]

Computation of Basic and Diluted Net Loss and Net Loss Per Share

The following table summarizes the computation of basic and diluted net loss and net loss per share of the Company (in thousands, except share and per share amounts):

	Year ended December 31,
	2015			2014			2013
Net loss - basic and diluted	$	(54,664	)	$	(24,455	)	$	(5,226	)
Weighted-average number of common shares - basic and diluted		7,368,681			2,381,041			2,381,041
Net loss per share - basic and diluted	$	(7.42	)	$	(10.27	)	$	(2.20	)

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:

	December 31,		December 31,		December 31,
	2015		2014		2013
Redeemable convertible preferred stock:
Series A		—		1,293,838		1,293,838
Series B		—		829,234		829,234
Series C		—		2,474,122		2,474,122
Series D		—		967,359		—
Total redeemable convertible preferred stock		—		5,564,553		4,597,194
Warrants to purchase common stock		2,325,383		595,920		595,920
Warrants to purchase Series D preferred stock		—		2,066,970		143,893
Awards under equity incentive plans		1,397,511		395,185		296,255
2013 Convertible Notes		—		—		683,417
Deerfield Convertible Notes		1,991,219		1,808,353		—

Quarterly Results of Operations (unaudited) (Tables)

12 Months Ended

Dec. 31, 2015

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Operating Results

	Three-Months Ended
	Dec 31,	Sep 30,	Jun 30,	Mar 31,	Dec 31,	Sep 30,	Jun 30,	Mar 31,
	2015	2015	2015	2015	2014	2014	2014	2014
Revenue	$ —	$ —	$ —	$ —	$ —	$ —	$ —	$ —
Operating expenses:
Research and development	4,716	4,328	2,768	2,119	5,911	3,253	1,715	1,038
General and administrative	2,566	2,152	3,188	977	1,577	1,086	1,330	534
Total operating expenses	7,282	6,480	5,956	3,096	7,488	4,339	3,045	1,572
Loss from operations	(7,282)	(6,480)	(5,956)	(3,096)	(7,488)	(4,339)	(3,045)	(1,572)
Other income (expenses):
Gain on extinguishment of debt	—	—	—	—	—	—	1,900	—
Amortization of debt discount	(475)	(479)	(477)	(477)	(478)	(477)	(159)	—
Interest expense	(698)	(687)	(654)	(632)	(631)	(173)	(704)	(96)
Fair value adjustment	(764)	(2,089)	(22,661)	(1,762)	(3,221)	(2,189)	(1,570)	(242)
Interest and other income	15	11	5	—	4	3	—	—
Total other expenses	(1,922)	(3,244)	(23,787)	(2,871)	(4,326)	(2,836)	(533)	(338)
Loss before income taxes	(9,204)	(9,724)	(29,743)	(5,967)	(11,814)	(7,175)	(3,578)	(1,910)
Income tax (expense) benefit	1	(20)	—	(7)	(27)	38	6	5
Net loss	$(9,203)	$(9,744)	$(29,743)	$(5,974)	$(11,841)	$(7,137)	$(3,572)	$(1,905)
Net loss per share:
Basic and diluted	$ (0.64)	$ (0.68)	$ (2.45)	$ (2.50)	$ (4.97)	$ (3.00)	$ (1.50)	$ (0.80)

Description of Business and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands		1 Months Ended		12 Months Ended
	Apr. 02, 2015	May 31, 2015 USD ($) $ / shares shares	Apr. 30, 2015 $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 $ / shares shares
Class Of Stock [Line Items]
Reverse stock split, description				1-for-7.5 reverse stock split
Reverse stock split	0.13
Proceeds from initial public offering, net of underwriting discounts and commissions \| $				$ 59,892
Common stock, shares authorized		250,000,000	250,000,000	250,000,000	18,666,666
Preferred stock, shares authorized		10,000,000	10,000,000	10,000,000	0
Common stock, par value \| $ / shares		$ 0.0001		$ 0.0001	$ 0.0001
Preferred stock, par value \| $ / shares		0.0001	$ 0.0001	$ 0.0001	$ 0.0001
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 \| $		$ 59,900
Underwriting discounts and commissions \| $		4,500
IPO offering expenses \| $		$ 2,800
IPO \| Common stock
Class Of Stock [Line Items]
Number of shares of common stock sold				5,854,545
Number of preferred shares converted to common shares		5,980,564	5,980,564	5,980,564

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Asset impairment charges	$ 0	$ 0
Uncertain tax positions	0	0
Debt issuance costs, net	$ 1,133,000	$ 1,468,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, useful lives	3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, useful lives	15 years

Prepaid Expenses and Other Current Assets - Components of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Prepaid Expense And Other Assets Current [Abstract]
Other receivables	$ 2,375
Prepaid insurance	290
Other prepaid expenses and current assets	93	$ 23
Total	$ 2,758	$ 23

Property and Equipment - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 881	$ 746
Less: accumulated depreciation and amortization	(478)	(394)
Property and equipment, net	403	352
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	530	530
Computers and Hardware
Property Plant And Equipment [Line Items]
Property and equipment, gross	176	73
Furniture and Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	169	137
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 6	$ 6

Property and Equipment - Assets under Capital Leases Included in Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Capital Leases Balance Sheet Assets By Major Class Net Lessee Balance Sheet [Abstract]
Furniture and office equipment	$ 94	$ 94
Less: accumulated depreciation and amortization	(22)	(12)
Capital Leases, Balance Sheet, Assets by Major Class, Net, Total	$ 72	$ 82

Property and Equipment - Estimated Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2015
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, useful lives	10 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, useful lives	15 years
Minimum
Property Plant And Equipment [Line Items]
Property and equipment, useful lives	3 years
Minimum \| Computers and Hardware
Property Plant And Equipment [Line Items]
Property and equipment, useful lives	3 years
Minimum \| Furniture and Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, useful lives	5 years
Maximum
Property Plant And Equipment [Line Items]
Property and equipment, useful lives	15 years
Maximum \| Computers and Hardware
Property Plant And Equipment [Line Items]
Property and equipment, useful lives	7 years
Maximum \| Furniture and Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, useful lives	10 years

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 84	$ 75	$ 68

Accounts Payable and Accrued Expenses - Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Accounts payable	$ 1,252	$ 1,582
Accrued interest	698	631
Accrued banking fees	700	700
Accrued payroll	947	183
Other accrued expenses	1,309
Total	$ 4,906	$ 3,096

Debt Obligations - Deerfield Facility Agreement - Additional Information (Detail) - USD ($)		12 Months Ended
	Jun. 02, 2014	Dec. 31, 2015	Apr. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Deerfield Warrant
Debt Instrument [Line Items]
Warrants expiration date	Jun. 02, 2024
Series D Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Preferred stock called by warrants			15,499,324	15,502,529	1,079,453
Warrant, exercise price				$ 0.78
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 \| 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 \| Put Option
Debt Instrument [Line Items]
Fair value of embedded put option	$ 200,000
Deerfield Facility Agreement \| Deerfield Warrant
Debt Instrument [Line Items]
Warrant, exercise price	$ 0.78
Warrants expiration date	Jun. 02, 2024
Fair value of warrants	$ 7,600,000
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 \| 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 5.50% Senior Convertible Notes and Third Amendment to Senior Secured Convertible Note and Warrant - Additional Information (Detail) - Subsequent Event - 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

Debt Obligations - Conversion of 2013 Convertible Notes into Series D Preferred Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	5 Months Ended	12 Months Ended
	Jun. 02, 2014	Jun. 30, 2014	Oct. 31, 2013	Dec. 31, 2014	Dec. 31, 2015
Debt Instrument [Line Items]
Accrued interest				$ 631	$ 698
Gain on extinguishment of debt		$ 1,900		$ 1,900
Unsecured Convertible Promissory Notes
Debt Instrument [Line Items]
Convertible notes, interest rate			10.00%
Gross proceeds from issuance of convertible notes			$ 3,800
Outstanding principal balance of convertible notes	$ 3,800
Accrued interest	300
Gain on extinguishment of debt	$ 1,900
Unsecured Convertible Promissory Notes \| Series D Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Conversion price	$ 0.78
Shares issued on conversion of convertible notes	5,332,348

Debt Obligations - Line of Credit - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
First Line of Credit Agreement
Debt Instrument [Line Items]
Line of credit	$ 50,000	$ 50,000	$ 50,000
Line of credit, description of variable rate basis		prime rate plus 1.75% per annum
Line of credit, basis spread on variable rate		1.75%
Convertible notes, interest rate	5.00%	5.00%	5.00%
Second Line of Credit Agreement
Debt Instrument [Line Items]
Line of credit	$ 100,000	$ 100,000
Line of credit, description of variable rate basis		prime rate plus 9.99% per annum
Line of credit, basis spread on variable rate	9.99%
Convertible notes, interest rate	13.24%	13.24%

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References + Details

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Interest rate for assets under remaining capital leases	0.67%
Rent expense for non-cancelable operating leases	$ 0.3	$ 0.2	$ 0.1
IOWA
Loss Contingencies [Line Items]
Lease facilities expires date	Sep. 30, 2016
Renewal option extend lease an additional year	3 years
FLORIDA
Loss Contingencies [Line Items]
Renewal option extend lease an additional year	5 years
Lease facilities expires date	mid-2025
Description of extend lease renewal options	Renewal options that could extend the lease for two additional five year terms.
VIRGINIA
Loss Contingencies [Line Items]
Lease facilities expires date	Aug. 31, 2016
Renewal option extend lease an additional year	12 months
NORTH CAROLINA
Loss Contingencies [Line Items]
Lease facilities expires date	May 31, 2020
Renewal option extend lease an additional year	3 years

Commitments and Contingencies - Future Minimum Lease Payments under Capital Leases and Non-Cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2015 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2016	$ 27
2017	0
2018	0
2019	0
2020	0
Thereafter	0
Total minimum lease payments	27
Less: amounts representing interest	(1)
Total	26
2016	440
2017	487
2018	497
2019	485
2020	428
Thereafter	5,354
Total minimum lease payments	$ 7,691

Supply Arrangement - Additional Information (Detail)	12 Months Ended
Supply Arrangement - Additional Information (Detail)	Dec. 31, 2015 USD ($) Agreement	Dec. 31, 2014 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Number of manufacturing arrangement \| Agreement	1
Supply arrangement expense \| $	$ 0	$ 0
Supply arrangement, automatic renewal period	2 years
Supply arrangement, period of prior notice	12 months

Preferred Stock and Warrants - Authorized, Issued, and Outstanding Preferred Stock - Additional Information (Detail) - $ / shares	1 Months Ended		12 Months Ended
	May 31, 2015	Apr. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Temporary Equity [Line Items]
Preferred stock, shares authorized	10,000,000	10,000,000	10,000,000	0
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	5,980,564

Preferred Stock and Warrants - Summary of Redeemable Convertible Preferred Stock Activity (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Temporary Equity [Line Items]
Less: Conversion of preferred stock into common stock upon IPO	(5,980,564)
Pre-split Retroactive Adjustment
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding, beginning balance	41,737,048	34,481,623	34,481,623
Shares issued upon conversion of 2013 Convertible notes		5,332,348
Shares issued for financing fee to Deerfield		1,923,077
Redeemable convertible preferred stock, issuance of Series D-1 Preferred Stock	3,200,000
Redeemable convertible preferred stock, exercise of Series D Preferred warrants	3,205
Effect of reverse stock-split
Less: Conversion of preferred stock into common stock upon IPO
Redeemable convertible preferred stock, shares outstanding, ending balance		41,737,048	34,481,623
Post-split Retroactive Adjustment
Temporary Equity [Line Items]
Effect of reverse stock-split	(38,959,689)
Series A Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding, beginning balance	1,293,838
Less: Conversion of preferred stock into common stock upon IPO	(1,293,838)
Redeemable convertible preferred stock, shares outstanding, ending balance	0	1,293,838
Series A Redeemable Convertible Preferred Stock \| Pre-split Retroactive Adjustment
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding, beginning balance	9,704,215	9,704,215	9,704,215
Redeemable convertible preferred stock, shares outstanding, ending balance		9,704,215	9,704,215
Series A Redeemable Convertible Preferred Stock \| Post-split Retroactive Adjustment
Temporary Equity [Line Items]
Effect of reverse stock-split	(8,410,377)
Series B Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding, beginning balance	829,234
Less: Conversion of preferred stock into common stock upon IPO	(829,234)
Redeemable convertible preferred stock, shares outstanding, ending balance	0	829,234
Series B Redeemable Convertible Preferred Stock \| Pre-split Retroactive Adjustment
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding, beginning balance	6,220,000	6,220,000	6,220,000
Redeemable convertible preferred stock, shares outstanding, ending balance		6,220,000	6,220,000
Series B Redeemable Convertible Preferred Stock \| Post-split Retroactive Adjustment
Temporary Equity [Line Items]
Effect of reverse stock-split	(5,390,766)
Series C Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding, beginning balance	2,474,122
Less: Conversion of preferred stock into common stock upon IPO	(2,474,122)
Redeemable convertible preferred stock, shares outstanding, ending balance	0	2,474,122
Series C Redeemable Convertible Preferred Stock \| Pre-split Retroactive Adjustment
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding, beginning balance	18,557,408	18,557,408	18,557,408
Redeemable convertible preferred stock, shares outstanding, ending balance		18,557,408	18,557,408
Series C Redeemable Convertible Preferred Stock \| Post-split Retroactive Adjustment
Temporary Equity [Line Items]
Effect of reverse stock-split	(16,083,286)
Series D Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding, beginning balance	967,359
Redeemable convertible preferred stock, exercise of Series D Preferred warrants	3,205
Less: Conversion of preferred stock into common stock upon IPO	(967,786)
Redeemable convertible preferred stock, shares outstanding, ending balance	0	967,359
Series D Redeemable Convertible Preferred Stock \| Pre-split Retroactive Adjustment
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding, beginning balance	7,255,425
Shares issued upon conversion of 2013 Convertible notes		5,332,348
Shares issued for financing fee to Deerfield		1,923,077
Redeemable convertible preferred stock, exercise of Series D Preferred warrants	3,205
Redeemable convertible preferred stock, shares outstanding, ending balance		7,255,425
Series D Redeemable Convertible Preferred Stock \| Post-split Retroactive Adjustment
Temporary Equity [Line Items]
Effect of reverse stock-split	(6,290,844)
Series D-1 Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Less: Conversion of preferred stock into common stock upon IPO	(415,584)
Series D-1 Redeemable Convertible Preferred Stock \| Pre-split Retroactive Adjustment
Temporary Equity [Line Items]
Redeemable convertible preferred stock, issuance of Series D-1 Preferred Stock	3,200,000
Series D-1 Redeemable Convertible Preferred Stock \| Post-split Retroactive Adjustment
Temporary Equity [Line Items]
Effect of reverse stock-split	(2,784,416)

Preferred Stock and Warrants - Series D-1 Redeemable Convertible Preferred Stock - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Feb. 28, 2015	Dec. 31, 2015
Temporary Equity [Line Items]
Conversion of preferred stock into common stock upon IPO		5,980,564
Series D-1 Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Conversion of preferred stock into common stock upon IPO		415,584
Series D-1 Redeemable Convertible Preferred Stock \| Cowen KP Investment LLC
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	$ 1.25
Redeemable convertible preferred stock, proceeds from issuance	$ 4,000,000
Conversion of preferred stock into common stock upon IPO	415,584

Preferred Stock and Warrants - Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Jun. 02, 2014	Dec. 31, 2015	Dec. 31, 2013	Apr. 30, 2015	Dec. 31, 2014
2013 Warrants
Temporary Equity [Line Items]
Warrants issued			1,079,453
Warrants expiration date		Jun. 02, 2019
Deerfield Warrant
Temporary Equity [Line Items]
Warrants issued	14,423,076
Warrants expiration date	Jun. 02, 2024
Convertible Notes
Temporary Equity [Line Items]
Debt instrument issued			$ 3.8
Series D Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred stock called by warrants			1,079,453	15,499,324	15,502,529
Warrant, exercise price					$ 0.78
Redeemable convertible preferred stock, exercise of Series D Preferred warrants		3,205
Common stock
Temporary Equity [Line Items]
Preferred stock called by warrants			143,466	2,066,543
Warrant, exercise price			$ 5.85
Common stock \| Deerfield Warrant
Temporary Equity [Line Items]
Preferred stock called by warrants	1,923,077
Warrant, exercise price	$ 5.85

Common Stock and Warrants - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	May 31, 2015	Apr. 30, 2015	Dec. 31, 2012
Class Of Stock [Line Items]
Common stock, shares authorized	250,000,000	18,666,666	250,000,000	250,000,000
Common stock, shares issued	14,490,954	2,381,041
Common stock, shares outstanding	14,490,954	2,381,041
Common stock warrants exercised	270,038	0
Private Placement
Class Of Stock [Line Items]
Common stock called by warrants					595,920

Common Stocks and Warrants - Schedule of Reserved Authorized Shares of Common Stock for Future Issuance (Detail) - shares	Dec. 31, 2015	Dec. 31, 2014
Class Of Stock [Line Items]
Common shares reserved for future issuance	7,124,961	10,796,687
Series A Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Common shares reserved for future issuance		1,293,838
Series B Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Common shares reserved for future issuance		829,234
Series C Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Common shares reserved for future issuance		2,474,122
Series D Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Common shares reserved for future issuance		967,359
Convertible Notes
Class Of Stock [Line Items]
Common shares reserved for future issuance	1,991,219	1,808,353
Series D redeemable convertible preferred stock warrants
Class Of Stock [Line Items]
Common shares reserved for future issuance		2,066,970
Equity Incentive Plans
Class Of Stock [Line Items]
Common shares reserved for future issuance	1,397,511	395,185
Possible Future Issuances Under Equity Incentive Plans
Class Of Stock [Line Items]
Common shares reserved for future issuance	1,410,848	365,706
Common Stock Warrants
Class Of Stock [Line Items]
Common shares reserved for future issuance	2,325,383	595,920

Common Stock and Warrants - Summary of Common Stock Shares Activity (Detail) - shares	1 Months Ended		12 Months Ended
	May 31, 2015	Apr. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Class Of Stock [Line Items]
Common stock, beginning balance			2,381,041
Common stock warrants exercised			270,038	0
Common stock options exercised			4,766
Common stock, ending balance			14,490,954	2,381,041
IPO
Class Of Stock [Line Items]
Number of shares of common stock sold		5,090,909
Common stock \| IPO
Class Of Stock [Line Items]
Number of shares of common stock sold			5,854,545
Shares conversion of common stock	5,980,564	5,980,564	5,980,564

Stock-Based Compensation - Additional Information (Detail) - USD ($)		12 Months Ended
	Jan. 01, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercised		4,766	0	0
Intrinsic value of stock options exercised		$ 54,000
Weighted-average fair value of awards granted		$ 10.63	$ 4.50	$ 3.00
Total fair value of stock options vested		$ 1,100,000	$ 200,000	$ 200,000
Stock based compensation expense		$ 2,369,000	214,000	134,000
Stock options fully vested and exercisable		163,998
Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expense			0	0
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expense		$ 1,759,000	152,000	105,000
General and administrative \| Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expense		700,000
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expense		610,000	$ 62,000	$ 29,000
Research and development \| Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expense		$ 200,000
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,
Two Thousand Fourteen Equity Incentive Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares issuable		2,266,666
Two Thousand Fourteen Equity Incentive Plan \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of common stock reserve for issuance	579,638
2014 Plan and 2007 stock incentive plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation cost		$ 9,000,000
Compensation cost recognition weighted-average period		2 years 9 months 7 days

Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	$ 2,369	$ 214	$ 134
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	610	62	29
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	$ 1,759	$ 152	$ 105

Stock-Based Compensation - Black-Scholes-Merton Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions and Methodology [Line Items]
Risk-free interest rate, minimum	1.40%	0.91%	0.52%
Risk-free interest rate, maximum	1.99%	2.70%	2.80%
Expected volatility, minimum	68.79%	86.00%	58.55%
Expected volatility, maximum	86.84%	95.00%	92.00%
Expected dividend yield	0.00%	0.00%	0.00%
Minimum
Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions and Methodology [Line Items]
Expected term (in years)	4 years 3 months 29 days	7 years	4 years 15 days
Maximum
Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions and Methodology [Line Items]
Expected term (in years)	6 years 3 months	10 years	10 years

Stock-Based Compensation - Schedule of Stock Option Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Shares Under Option
Granted	1,010,457
Exercised	(4,766)	0	0
Forfeited	(3,365)
Outstanding balance at December 31, 2015	1,397,511
Exercisable at December 31, 2015	384,087
Vested and expected to vest at December 31, 2015	1,254,325
Weighted Average Exercise Price
Outstanding balance at January 1, 2015	$ 5.40
Granted	16.30
Exercised	5.85
Forfeited	5.85
Outstanding balance at December 31, 2015	13.28	$ 5.40
Exercisable at December 31, 2015	6.71
Vested and expected to vest at December 31, 2015	$ 13.00
Weighted Average Remaining Contractual Term (years)
Outstanding balance	8 years 6 months 29 days	7 years 2 months 27 days
Exercisable at December 31, 2015	6 years 6 months 18 days
Vested and expected to vest at December 31, 2015	8 years 5 months 27 days
Aggregate Intrinsic Value
Options outstanding, Aggregate intrinsic value	$ 9,204,403	$ 1,275,980
Options exercisable, Aggregate intrinsic value	5,057,062
Options vested and expected to vest, Aggregate intrinsic value	$ 8,614,743

Stock-Based Compensation - Information Regarding Currently Outstanding and Exercisable Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2015
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 5.85
Options Outstanding, Number of Shares	1,397,511		395,185
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	8 years 6 months 29 days	7 years 2 months 27 days
Options Exercisable Number of Shares	384,087
Options Exercisable Weighted- Average Remaining Contractual Term (in years)	6 years 6 months 18 days
0.75
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 0.75
Options Outstanding, Number of Shares	12,000
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	1 year 6 months
Options Exercisable Number of Shares	12,000
Options Exercisable Weighted- Average Remaining Contractual Term (in years)	1 year 6 months
3.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 3.00
Options Outstanding, Number of Shares	20,666
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	2 years 6 months 15 days
Options Exercisable Number of Shares	20,666
Options Exercisable Weighted- Average Remaining Contractual Term (in years)	2 years 6 months 15 days
4.65
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 4.65
Options Outstanding, Number of Shares	49,327
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	2 years 7 months 10 days
Options Exercisable Number of Shares	49,327
Options Exercisable Weighted- Average Remaining Contractual Term (in years)	2 years 7 months 10 days
5.85
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 5.85
Options Outstanding, Number of Shares	305,061
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	7 years 2 months 23 days
Options Exercisable Number of Shares	207,428
Options Exercisable Weighted- Average Remaining Contractual Term (in years)	6 years 10 months 28 days
8.63
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 8.63
Options Outstanding, Number of Shares	154,639
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 11 days
Options Exercisable Number of Shares	6,666
Options Exercisable Weighted- Average Remaining Contractual Term (in years)	8 years 6 months 26 days
11.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 11.00
Options Outstanding, Number of Shares	21,333
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 3 months 18 days
11.41
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 11.41
Options Outstanding, Number of Shares	170,035
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 4 months 28 days
Options Exercisable Number of Shares	88,000
Options Exercisable Weighted- Average Remaining Contractual Term (in years)	9 years 4 months 28 days
16.61
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 16.61
Options Outstanding, Number of Shares	11,250
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 11 months 9 days
18.29
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 18.29
Options Outstanding, Number of Shares	205,000
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 5 months 27 days
18.61
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 18.61
Options Outstanding, Number of Shares	38,400
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 7 months 24 days
19.02
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 19.02
Options Outstanding, Number of Shares	62,000
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 7 months 24 days
20.45
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 20.45
Options Outstanding, Number of Shares	335,000
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 8 months 5 days
21.37
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 21.37
Options Outstanding, Number of Shares	6,400
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 8 months 12 days
22.12
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 22.12
Options Outstanding, Number of Shares	6,400
Options Outstanding Weighted- Average Remaining Contractual Term (in years)	9 years 8 months 16 days

Stock-Based Compensation - Nonvested Stock Option Awards (Detail) - shares	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	1,013,424	225,018
5.85
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	97,633	225,018
8.63
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	147,973
11.00
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	21,333
11.41
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	82,035
16.61
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	11,250
18.29
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	205,000
18.61
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	38,400
19.02
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	62,000
20.45
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	335,000
21.37
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	6,400
22.12
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares	6,400

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Increase in estimated fair value	$ 764,000	$ 2,089,000	$ 22,661,000	$ 1,762,000	$ 3,221,000	$ 2,189,000	$ 1,570,000	$ 242,000	$ 27,276,000	$ 7,223,000	$ (1,137,000)
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
Preferred Stock 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									1,900,000
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
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	42,000,000								42,000,000
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	$ 14,100,000								$ 14,100,000

Fair Value of Financial Instruments - Reconciliation of Beginning and Ending Balances for Derivative and Warrant Liability Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Balance at beginning of period	$ 15,966	$ 2,813
Issuance of Deerfield Warrant		7,610
Embedded put option		220
Conversion of 2013 Convertible Notes		(1,900)
Reclassification of 2013 warrants to equity	(1,110)
Exercise of warrants	(4,293)
Adjustment to fair value	27,276	7,223
Balance at end of period	$ 37,839	$ 15,966

Income Tax - Additional information (Detail) - USD ($)	3 Months Ended								12 Months Ended
Income Tax - Additional information (Detail) - USD ($)	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax [Line Items]
State tax benefit									$ 15,000	$ 22,000	$ 20,000
Loss before income taxes	$ (9,204,000)	$ (9,724,000)	$ (29,743,000)	$ (5,967,000)	$ (11,814,000)	$ (7,175,000)	$ (3,578,000)	$ (1,910,000)	(54,638,000)	$ (24,477,000)	$ (5,246,000)
Net operating loss carry forwards	62,405,000								$ 62,405,000
Net operating loss carry forwards expiration year, beginning year									2027
Net operating loss carry forwards expiration year, ending year									2035
State [Member]
Income Tax [Line Items]
Net operating loss carry forwards	$ 59,700,000								$ 59,700,000

Income Taxes - Schedule of Reconciliation of Difference Between Benefit for Income Taxes and Income Taxes at Statutory U.S Federal Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation Of Effective Income Tax Rate [Line Items]
Federal statutory rate	34.00%	34.00%	34.00%
Change in valuation allowance	(19.25%)	(32.88%)	(38.38%)
State tax benefit (net of federal)	4.06%	5.96%	7.53%
Warrant liability	(15.28%)	(9.39%)	6.08%
Conversion feature and put option on 2013 convertible notes	(1.68%)	(1.26%)	(8.81%)
Interest expense		0.21%	(0.99%)
Stock-based compensation	(1.28%)
Other	(1.42%)	0.07%	(1.95%)
Federal income tax provision effective rate	0.02%	0.09%	0.38%
State [Member]
Reconciliation Of Effective Income Tax Rate [Line Items]
Research and development credit	0.03%	0.09%	0.37%
Federal
Reconciliation Of Effective Income Tax Rate [Line Items]
Research and development credit	0.84%	3.29%	2.53%

Income Taxes - Components of Net Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets relating to:
Net operating loss carryforwards	$ 26,617	$ 16,390	$ 9,606
Research and development tax carryforward	2,254	1,793	899
Compensation	232	83	76
Total gross deferred tax assets	29,103	18,266	10,581
Deferred tax liabilities relating to:
Property and equipment	80	170	176
Total gross deferred tax liabilities	80	170	176
Deferred tax assets less liabilities	29,023	18,096	10,405
Valuation allowance	(29,023)	(18,096)	(10,405)
Net deferred tax asset (liability)	$ 0	$ 0	$ 0

Income Taxes - Federal Net Operating Loss Carryforward And Research Activities Credits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]
Net Operating Loss Carryforwards	$ 62,405
Research Activities Credit	2,254	$ 1,793	$ 899
Tax Year 2007
Operating Loss Carryforwards [Line Items]
Net Operating Loss Carryforwards	454
Research Activities Credit	$ 30
Expiration	2027
Tax Year 2008
Operating Loss Carryforwards [Line Items]
Net Operating Loss Carryforwards	$ 1,178
Research Activities Credit	$ 65
Expiration	2028
Tax Year 2009
Operating Loss Carryforwards [Line Items]
Net Operating Loss Carryforwards	$ 3,060
Research Activities Credit	$ 176
Expiration	2029
Tax Year 2010
Operating Loss Carryforwards [Line Items]
Net Operating Loss Carryforwards	$ 3,423
Research Activities Credit	$ 149
Expiration	2030
Tax Year 2011
Operating Loss Carryforwards [Line Items]
Net Operating Loss Carryforwards	$ 9,929
Research Activities Credit	$ 176
Expiration	2031
Tax Year 2012
Operating Loss Carryforwards [Line Items]
Research Activities Credit	$ 170
Expiration	2032
Tax Year 2013
Operating Loss Carryforwards [Line Items]
Net Operating Loss Carryforwards	$ 4,353
Research Activities Credit	$ 133
Expiration	2033
Tax Year 2014
Operating Loss Carryforwards [Line Items]
Net Operating Loss Carryforwards	$ 15,819
Research Activities Credit	$ 894
Expiration	2034
Tax Year 2015
Operating Loss Carryforwards [Line Items]
Net Operating Loss Carryforwards	$ 24,189
Research Activities Credit	$ 461
Expiration	2035

Net Loss Per Share - Summary of Computation of Basic and Diluted Net Loss and Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net loss - basic and diluted	$ (9,203)	$ (9,744)	$ (29,743)	$ (5,974)	$ (11,841)	$ (7,137)	$ (3,572)	$ (1,905)	$ (54,664)	$ (24,455)	$ (5,226)
Weighted-average number of common shares - basic and diluted									7,368,681	2,381,041	2,381,041
Net loss per share - basic and diluted	$ (0.64)	$ (0.68)	$ (2.45)	$ (2.50)	$ (4.97)	$ (3.00)	$ (1.50)	$ (0.80)	$ (7.42)	$ (10.27)	$ (2.20)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss Per Share - Schedule of Anti-dilutive Securities Excluded from Calculation of Weighted Average Common Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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	2,325,383	595,920	595,920
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		2,066,970	143,893
Equity Incentive Plans
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,397,511	395,185	296,255
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			683,417
Convertible Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,991,219	1,808,353
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	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	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	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		967,359
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		5,564,553	4,597,194

Employee Benefit Plan - Additional information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
401K Retirement Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contribution to Savings Plan	4.00%
Employer matching contribution	$ 113	$ 69	$ 50
Profit Sharing Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contribution to Savings Plan	0.00%	0.00%	0.00%

Subsequent Events - Additional Information (Detail) - Subsequent Event - 2021 Notes	Feb. 09, 2016 USD ($) $ / shares shares
Subsequent Event [Line Items]
Debt instrument issued	$ 86,250,000
Net proceeds from issuance of debt	82,800,000
Debt issuance costs	$ 18,600,000
Debt instrument, maturity date	Feb. 01, 2021
Debt instrument, sinking fund payment	$ 0
Convertible notes, interest rate	5.50%
Shares issued on conversion of convertible notes \| shares	58.4454
Debt conversion principal amount	$ 1,000
Conversion price \| $ / shares	$ 17.11

Quarterly Results of Operations (unaudited) - Schedule of Quarterly Operating Results (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	4,716	4,328	2,768	2,119	5,911	3,253	1,715	1,038	13,931	11,917	3,367
General and administrative	2,566	2,152	3,188	977	1,577	1,086	1,330	534	8,883	4,526	1,351
Total operating expenses	7,282	6,480	5,956	3,096	7,488	4,339	3,045	1,572	22,814	16,443	4,718
Loss from operations	(7,282)	(6,480)	(5,956)	(3,096)	(7,488)	(4,339)	(3,045)	(1,572)	(22,814)	(16,443)	(4,718)
Other (expense) income:
Gain on extinguishment of debt							1,900			1,900
Amortization of debt discount	(475)	(479)	(477)	(477)	(478)	(477)	(159)	0	(1,909)	(1,114)	(1,560)
Interest expense	(698)	(687)	(654)	(632)	(631)	(173)	(704)	(96)	(2,671)	(1,605)	(157)
Fair value adjustment	(764)	(2,089)	(22,661)	(1,762)	(3,221)	(2,189)	(1,570)	(242)	(27,276)	(7,223)	1,137
Interest and other income	15	11	5		4	3			32	8	52
Total other expenses	(1,922)	(3,244)	(23,787)	(2,871)	(4,326)	(2,836)	(533)	(338)	(31,824)	(8,034)	(528)
Loss before income taxes	(9,204)	(9,724)	(29,743)	(5,967)	(11,814)	(7,175)	(3,578)	(1,910)	(54,638)	(24,477)	(5,246)
Income tax (expense) benefit	1	(20)		(7)	(27)	38	6	5	(26)	22	20
Net loss	$ (9,203)	$ (9,744)	$ (29,743)	$ (5,974)	$ (11,841)	$ (7,137)	$ (3,572)	$ (1,905)	$ (54,664)	$ (24,455)	$ (5,226)
Net loss per share:
Basic and diluted	$ (0.64)	$ (0.68)	$ (2.45)	$ (2.50)	$ (4.97)	$ (3.00)	$ (1.50)	$ (0.80)	$ (7.42)	$ (10.27)	$ (2.20)

Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	$ 37,839	$ 15,966
Financial assets measured at fair value on recurring basis	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	3,877	2,746
Deerfield Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	33,750	12,560
Embedded Put Option
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis	212	140
2013 Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis		520
Certificates of Deposits
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial assets measured at fair value on recurring basis	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	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	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	37,839	15,966
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	3,877	2,746
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	33,750	12,560
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	212	140
Fair Value Inputs Level3 \| 2013 Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis		$ 520
Government Bonds
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial assets measured at fair value on recurring basis	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	$ 10,051