Alpine Immune Sciences (ALPN) 10-K 8 Mar 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 29, 2016	Jun. 30, 2015
Document and Entity Information
Entity Registrant Name	Nivalis Therapeutics, Inc.
Entity Central Index Key	1,626,199
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 177,549,046
Entity Common Stock, Shares Outstanding		15,462,030
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 24,991	$ 27,812
Marketable securities	62,263
Prepaid expenses and other current assets	432	630
Total current assets	87,686	28,442
Property and equipment and other assets, net	223	101
Total assets	87,909	28,543
Current liabilities:
Accounts payable	994	929
Accrued direct program expenses	1,555	1,244
Accrued employee benefits	1,675	210
Accrued other liabilities	195	32
Total current liabilities	$ 4,419	$ 2,415
Commitments and contingencies
Convertible preferred stock with liquidation preference; $0.001 par value; zero and 23,228,986 shares authorized, respectively; zero and 19,978,986 shares issued and outstanding, respectively		$ 41,880
Preferred stock, $0.001 par value; 10,000,000 and zero shares authorized, respectively; no shares issued and outstanding
Common stock, $0.001 par value; 200,000,000 and 35,000,000 shares authorized, respectively; 15,462,030 and 2,211,158 shares issued and outstanding, respectively	$ 15	$ 2
Additional paid-in capital	232,309	110,265
Accumulated other comprehensive income	3
Accumulated deficit	(148,837)	(126,019)
Total stockholders' equity (deficit)	83,490	(15,752)
Total liabilities and stockholders' equity (deficit)	$ 87,909	$ 28,543

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Balance Sheets
Convertible preferred stock with liquidation preference, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock with liquidation preference, shares authorized	0	23,228,986
Convertible preferred stock with liquidation preference, shares issued	0	19,978,986
Convertible preferred stock with liquidation preference, shares outstanding	0	19,978,986
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	35,000,000
Common stock, shares issued	15,462,030	2,211,158
Common stock, shares outstanding	15,462,030	2,211,158

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ 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
Statements of Operations and Comprehensive Loss
Revenue									$ 0
Operating expenses:
Research and development	$ 4,293	$ 4,279	$ 4,465	$ 3,017	$ 2,822	$ 2,164	$ 3,363	$ 3,851	16,054	$ 12,200	$ 13,136
General and administrative	2,337	1,822	1,387	1,298	664	490	594	539	6,844	2,287	2,141
Loss from operations	(6,630)	(6,101)	(5,852)	(4,315)	(3,486)	(2,654)	(3,957)	(4,390)	(22,898)	(14,487)	(15,277)
Interest and other income, net	67	12		1		35	9	252	80	296	10
Interest expense						(392)	(241)	(212)		(845)	(931)
Net loss	(6,563)	(6,089)	(5,852)	(4,314)	(3,486)	(3,011)	(4,189)	(4,350)	(22,818)	(15,036)	(16,198)
Gain on extinguishment of convertible debt as a capital transaction						378				378
Net loss attributable to common stockholders	$ (6,563)	$ (6,089)	$ (5,852)	$ (4,314)	$ (3,486)	$ (2,633)	$ (4,189)	$ (4,350)	(22,818)	(14,658)	(16,198)
Change in unrealized gains on marketable securities, net									3
Comprehensive loss									$ (22,815)	$ (14,658)	$ (16,198)
Weighted average shares outstanding - basic and diluted (in shares)	15,452	15,451	4,159	2,209	2,207	343	163	161	9,371	723	155
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (0.42)	$ (0.39)	$ (1.41)	$ (1.95)	$ (1.58)	$ (7.68)	$ (25.70)	$ (27.02)	$ (2.43)	$ (20.27)	$ (104.50)

Statement of Convertible Prefer

Statement of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	2013 NotesSeries E Convertible Preferred Stock	2014 NotesSeries 1 Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Series 1 Convertible Preferred Stock	Series 2 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series C-1 Convertible Preferred Stock	Series C-2 Convertible Preferred Stock	Series D Convertible Preferred Stock	Series E Convertible Preferred Stock	Series A-1 Convertible Preferred Stock	Total
Balance, beginning at Dec. 31, 2012				$ 19,595		$ (94,785)			$ 9,000	$ 18,155	$ 19,980	$ 15,675	$ 14,983	$ 2	$ (75,188)
Balance, beginning (in shares) at Dec. 31, 2012			171						1,393	2,811	2,379	7,203	4,266	1,992
Conversion of notes payable, net of issuance costs															12,365
Employee stock-based compensation expense				98			$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0		98
Net loss			$ 0	0	$ 0	(16,198)								$ 0	(16,198)
Balance, ending at Dec. 31, 2013				19,693		(110,983)			$ 9,000	$ 18,155	$ 19,980	$ 15,675	$ 14,983	$ 2	(91,288)
Balance, ending (in shares) at Dec. 31, 2013			171						1,393	2,811	2,379	7,203	4,266	1,992
Conversion of convertible preferred stock to common stock								$ 29,935
Conversion of convertible preferred stock to common stock (in shares)								11,166
Conversion of notes payable, net of issuance costs	$ 12,326	$ 12,329													24,655
Conversion of notes payable, net of issuance costs (in shares)	3,528	8,813
Recapitalization			$ 2	90,120					$ (9,000)	$ (18,155)	$ (19,980)	$ (15,675)	$ (27,309)	$ (2)	90,120
Recapitalization (in shares)			2,040						(1,393)	(2,811)	(2,379)	(7,203)	(7,794)	(1,992)
Gain on extinguishment of convertible debt				378			(384)								378
Restricted stock units forfeited (in shares)			(1)
Exercise of incentive stock options				2											2
Exercise of incentive stock options (in shares)			1
Reclass of preferred stock warrant liabilities to equity				2											2
Employee stock-based compensation expense				70											70
Net loss						(15,036)									(15,036)
Balance, ending at Dec. 31, 2014			$ 2	110,265		(126,019)	$ 11,945	$ 29,935							(15,752)
Balance, ending (in shares) at Dec. 31, 2014			2,211				8,813	11,166
Conversion of convertible preferred stock to common stock			$ 7	41,873			$ (11,945)	$ (29,935)							41,880
Conversion of convertible preferred stock to common stock (in shares)			6,916				(8,813)	(11,166)
Issuance of common stock, net of offering costs			$ 6	78,765											78,771
Issuance of common stock, net of offering costs (in shares)			6,325
Issuance of common stock under the employee stock purchase plan				59											59
Issuance of common stock under the employee stock purchase plan (in shares)			9
Exercise of incentive stock options				4											4
Exercise of incentive stock options (in shares)			1
Employee stock-based compensation expense				1,343											1,343
Change in unrealized gains on marketable securities, net					3										3
Net loss						(22,818)									(22,818)
Balance, ending at Dec. 31, 2015			$ 15	$ 232,309	$ 3	$ (148,837)									$ 83,490
Balance, ending (in shares) at Dec. 31, 2015			15,462

Statement of Convertible Prefe6

Statement of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Millions	Jun. 22, 2015	Dec. 31, 2015
Statement of Convertible Preferred Stock and Stockholders' Equity (Deficit)
Issuance of common stock, offering costs	$ 3.6	$ 9.8

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (22,818)	$ (15,036)	$ (16,198)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and loss on disposal of assets	66	88	219
Stock-based compensation expense	1,343	70	98
Change in value of preferred stock warrant liabilities and derivative		(296)	(9)
Amortization of deferred financing costs and noncash interest		708	521
Changes in operating assets and liabilities:
Prepaid expenses and other	198	(380)	107
Accounts payable	65	258	400
Accrued direct program expenses	311	355	540
Accrued employee benefits	1,465	(183)	55
Accrued other liabilities	163	(32)	(26)
Net cash used in operating activities	(19,207)	(14,448)	(14,293)
Investing activities
Purchases of property and equipment	(188)	(4)	(125)
Purchases of marketable securities	(76,260)
Proceeds from sales and maturities of marketable securities	14,000
Net cash used in investing activities	(62,448)	(4)	(125)
Financing activities
Proceeds from issuance of common stock, net of offering costs	78,771
Proceeds from employee stock purchases and stock options exercised	63	2
Proceeds from issuance of convertible preferred stock, net		29,935
Decrease in restricted cash		2,500
Proceeds from notes payable, net		11,868	12,000
Principal payment on debt		(3,139)	(1,189)
Net cash provided by financing activities	78,834	41,166	10,811
Net increase (decrease) in cash and cash equivalents	(2,821)	26,714	(3,607)
Cash and cash equivalents, beginning of period	27,812	1,098	4,705
Cash and cash equivalents, end of period	24,991	27,812	1,098
Supplemental disclosures of cash flow information
Cash paid for interest		165	124
Conversion of convertible preferred stock to common stock	$ 41,880
Conversion of convertible debt and accrued interest to convertible preferred stock, net		$ 24,655	$ 12,365

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2015
Organization and Description of Business
Organization and Description of Business	1. Organization and Description of Business Nivalis Therapeutics, Inc. (the “ Company ” or “ Nivalis ” ) is a clinical stage pharmaceutical company committed to the discovery, development and commercialization of therapeutics for people with cystic fibrosis. In addition to developing innovative solutions intended to extend and improve the lives of people with cystic fibrosis, Nivalis plans to utilize its proprietary S-nitrosoglutathione reductase (GSNOR) inhibitor portfolio to develop therapeutics for other diseases. The Company was incorporated on August 1, 2012, under the laws of the State of Delaware, upon the conversion of its predecessor entity N30 Pharmaceuticals, LLC from a Delaware limited l iability company to a Delaware c orporation (the “ Company Conversion ” ). On February 11, 2015, the Company changed its name from N30 Pharmaceuticals, Inc. to Nivalis Therapeutics, Inc.

Liquidity Risks

Liquidity Risks	12 Months Ended
	Dec. 31, 2015
Liquidity Risks
Liquidity Risks	2. Liquidity Risks The Company has incurred operating losses and has an accumulated deficit as a result of ongoing research and development spending. As of December 31, 2015, the Company had an accumulated deficit of $148.8 million. Net losses and net cash used in operating activities for the year ended December 31, 2015 were $22.8 million and $19.2 million, respectively. The Company anticipates that operating losses and net cash used in operating activities will continue and substantially increase over the next several years as it expands development activities for its N91115 product candidate. The Company has historically financed its operations primarily through the sale of its equity securities and debt offerings. The Company will continue to be dependent upon such sources of funds until it is able to generate positive cash flows from its operations. Management has determined that the Company’s existing cash, cash equivalents and marketable securities as of December 31, 2015 will be sufficient to fund operations at least through the next twelve months. The Company expects to fund future operations through the sale of its equity securities, incurring debt, entering into partnerships, or obtaining grants or other nondilutive sources of financing. There can be no assurance that sufficient funds from these sources will be available to the Company when needed or at all or on terms that are favorable to the Company. If the Company is unable to obtain additional funding from these or other sources when needed, or to the extent needed, it would have a negative impact on the Company’s financial condition and its ability to pursue its business strategy. It could force the Company to delay, limit, reduce or terminate research and development programs and commercialization efforts or cause the Company to cease operations in full.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include all adjustments necessary for the presentation of the Company’s financial position, results of operations and cash flows for the periods presented. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts and disclosures reported in the financial statements and accompanying notes, including accrued liabilities and the fair value-based measurement of equity instruments. Actual results could differ materially from those estimates. The Company evaluates its estimates and assumptions as facts and circumstances dictate. 2014 Stock Conversion and Reverse Stock Split Effective September 23, 2014, all outstanding shares of the Company’s preferred stock were converted on an 11.556 -for-1 basis into shares of common stock (the “Stock Conversion”). Concurrent with this Stock Conversion, the Company effected a reverse stock split of its common stock, par value $0.001 per share. Every four shares of common stock were reclassified and combined into one share of common stock. Fractional shares were issued as a result of the reverse stock split. The total number of authorized shares of common stock was also proportionally decreased on a 4-for-1 basis and the par value per share of the common stock continued to be $0.001 . 2015 Stock Conversion and Reverse Stock Split On May 26, 2015, the Company’s Board of Directors approved a 1-for- 2.889 reverse stock split of its common stock, which became effective on June 1, 2015. Upon the effectiveness of the reverse stock split, (i) every 2.889 shares of outstanding common stock were decreased to one share of common stock, (ii) the number of shares of common stock into which each outstanding option, right and warrant to purchase common stock is exercisable was proportionally decreased on a 1-for-2.889 basis and the exercise price of each outstanding option, right and warrant to purchase common stock was proportionately increased on a 1-for-2.889 basis, and (iii) the conversion ratio for each share of the Company’s convertible preferred stock which was convertible into common stock was proportionally decreased on a corresponding basis in connection with the 1-for-2.889 reverse split. No fractional shares were issued as a result of the reverse stock split. The total number of authorized shares of common stock and the par value per share of common stock did not change as a result of the reverse stock split. Effective June 22, 2015, all outstanding shares of convertible preferred stock were converted on a 2.889-for-1 basis into shares of common stock in connection with the closing of our initial public offering. All of the share numbers, share prices, exercise prices and other per share information throughout these financial statements for all periods presented have been adjusted, on a retroactive basis, to reflect the 1-for-4 reverse stock split and the 1-for-2.889 reverse stock split and the conversion of all convertible preferred stock on the closing of our initial public offering. Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of deposits with commercial banks in checking, interest- bearing and demand money market accounts. Marketable Securities The Company has designated marketable securities as available-for-sale securities and accounts for them at their respective fair values. Marketable securities are classified as short-term or long-term based on the nature of the securities and their availability to meet current operating requirements. Securities that are classified as available-for-sale are carried at fair value, including accrued interest, with temporary unrealized gains and losses reported as a component of stockholders' equity (deficit) until their disposition. The Company reviews all available-for-sale securities at each period end to determine if they remain available-for-sale based on the Company’s then current intent and ability to sell the security if it is required to do so. The cost of securities sold is based on the specific identification method. All marketable securities are subject to a periodic impairment review. The Company will recognize an impairment charge when a decline in the fair value of the investments below the cost basis is judged to be other-than-temporary. Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company has established guidelines to limit its exposure to credit risk by placing investments with high credit quality financial institutions, diversifying its investment portfolio and making investments with maturities that maintain safety and liquidity. At December 31, 2015 and 2014, the Company’s cash equivalents were with money market funds that invest in securities issued by the U.S. Treasury. At December 31, 2015, the Company’s marketable securities were in U.S. Treasury securities, obligations of U.S. government agencies and high-grade corporate debt securities. Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Lab equipment, computer equipment and software are depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are depreciated over the shorter of the estimated useful lives of the assets or the lease term. Maintenance and repairs are expensed as incurred. Impairment of Long-Lived Assets Long-lived assets, such as property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized for an amount by which the carrying amount of the asset exceeds the fair value of the asset. The Company has not yet generated consistent positive cash flows on an annual basis, and such positive cash flows may not materialize for a significant period in the future. As a result, it is reasonably possible that future evaluations of long-lived assets may result in a conclusion that such assets have been impaired. Accrued Direct Program Expenses Substantial portions of the Company’s preclinical studies and clinical trials are performed by third-party laboratories, medical centers, contract research organizations and other vendors (collectively CROs). These CROs generally bill monthly or quarterly for services performed or upon achieving certain milestones. For preclinical studies, the Company accrues expenses based upon estimated percentage of work completed and the contract milestones remaining. For clinical studies, expenses are accrued based upon the number of patients enrolled and the duration of the study. The Company monitors patient enrollment, the progress of clinical studies and related activities to the extent possible through internal reviews of data reported to the Company by the CROs or within software tracking systems, correspondence with the CROs and clinical site visits. Company estimates depend on the timeliness and accuracy of the data provided by the CROs regarding the status of each program and total program spending. The Company periodically evaluates these estimates to determine if adjustments are necessary or appropriate based on information received. No vendor comprised more than 10% of all external costs in 2015, 2014, and 2013. Research and Development The Company expenses costs associated with research and development as incurred. These costs include direct program expenses, which are payments made to third parties that specifically relate to the Company’s research and development, such as payments to clinical research organizations, clinical investigators, manufacturing of clinical material, pre-clinical testing and consultants. In addition, employee costs (salaries, payroll taxes, benefits and travel) for employees contributing to research and development activities are classified as research and development costs. Stock-Based Compensation The Company measures employee and director stock-based compensation expense for all stock and purchase awards at the grant date based on the fair value measurement of the award. The expense is recorded over the related service period, generally the vesting period, net of estimated forfeitures. Any changes to the estimated forfeiture rates are accounted for prospectively. The Company calculates the fair value measurement of stock options using the Black-Scholes valuation model and the single-option method and recognizes expense using the straight-line attribution approach. Income Taxes The Company accounts for income taxes under an asset and liability approach. Deferred income taxes reflect the impact of temporary differences between assets and liabilities recognized for tax and financial reporting purposes measured by applying enacted tax rates and laws that will be in effect when the differences are expected to reverse, net operating loss and tax credit carryforwards. Tax benefits are recorded when the benefit is more likely than not to be sustained upon audit. The Company accrues interest and penalties related to uncertain tax positions in income tax expense. Valuation allowances are provided when necessary to reduce net deferred tax assets to an amount that is more likely than not to be realized. Segment Information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on discovering and developing potential drugs. No revenue has been generated since inception, and all tangible assets are held in the United States. Comprehensive Loss Comprehensive loss is comprised of net loss and adjustments for the change in unrealized gains and losses on the Company’s investments in available-for-sale marketable securities. The Company presents comprehensive loss and its components in the statements of operations and comprehensive loss for the year ended December 31, 2015. Net Loss per Share The Company reports net loss per share in accordance with the standard codification of ASC “Earnings per Share” (“ASC 260”). Under ASC 260, basic earnings per share, which excludes dilution, is computed by dividing net loss available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted earnings per share reflects the potential dilution of securities that could be exercised or converted into common shares, and is computed by dividing net loss available to common stockholders by the weighted average of common shares outstanding plus the dilutive potential common shares. Diluted earnings per share excludes the impact of convertible preferred stock, employee stock options, restricted stock and stock purchase rights, as the effect would be anti-dilutive. During a loss period, the assumed exercise of in-the-money stock options and other potentially diluted instruments has an anti-dilutive effect and therefore, these instruments are excluded from the computation of dilutive earnings per share. Recent Accounting Pronouncements In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements – Going Concern Disclosure of Uncertainties About an Entity’s Ability to Continue as a Going Concern, which requires management to evaluate whether there are conditions or events that raise substantial doubt about an entity’s ability to continue as a going concern and to provide disclosures when certain criteria are met. The guidance is effective for annual periods beginning in 2016 and interim reporting periods starting in the first quarter of 2017. Early application is permitted. The Company does not expect the standard will have a material impact on its disclosures. In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes. The new standard requires that deferred tax assets and liabilities be classified as noncurrent in a classified statement of financial position. The guidance is effective for financial statements issued for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Earlier application is permitted for all entities as of the beginning of an interim or annual report period. The amendments in this standard may be applied either prospectively to all deferred tax assets and liabilities or retrospectively to all periods presented. The Company adopted this standard as of December 31, 2015 with prospective application. As a result, the Company reclassified its deferred tax assets classified as current to noncurrent and its deferred tax liabilities classified as current to noncurrent as of December 31, 2015. Prior year balances were not retrospectively adjusted. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The new guidance requires organizations that lease assets to recognize assets and liabilities on the balance sheet related to the rights and obligations created by those leases, regardless of whether they are classified as finance or operating leases. Consistent with current guidance, the recognition, measurement, and presentation of expenses and cash flows arising from a lease primarily will depend on its classification as a finance or operating lease. The guidance also requires new disclosures to help financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, with early application permitted. The new standard is to be applied using a modified retrospective approach. The Company is currently evaluating the impact of the new pronouncement on its financial statements. Fair Value of Financial Instruments The carrying amounts of cash equivalents and marketable securities approximate their fair value based upon quoted market prices. Certain financial instruments are not measured at fair value on a recurring basis, but are recorded at amounts that approximate their fair value due to their liquid or short-term nature, such as cash, accounts payable, accrued direct program expenses, and accrued employee benefits , and other financial instruments included within current assets or current liabilities. The Company accounted for warrants to purchase its redeemable preferred stock pursuant to ASC Topic 480, Distinguishing Liabilities from Equity , and classified them as liabilities. The fair value of the outstanding preferred stock warrant liabilities at December 31, 2013 was $267,750 . Subsequent to the completion of the Stock Conversion on September 23, 2014, whereby all outstanding shares of preferred stock were converted into shares of common stock, and the warrants became exercisable for shares of common stock pursuant to the adjustment provisions of the warrants, the fair value of the preferred stock warrant liabilities was remeasured and reclassified into equity. During the year ended December 31, 2014 a remeasurement gain of $265,750 was recognized in interest and other income, net in the statement of operations and comprehensive loss. Upon the Stock Conversion, the remaining balance of $2,000 was reclassified from liabilities to equity. Fair Value Measurements In general, asset and liability fair values are determined using the following categories: Level 1 – inputs utilize quoted prices in active markets for identical assets or liabilities. Level 2 – inputs include quoted prices for similar assets or liabilities in active markets, and inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly. Level 3 – inputs are unobservable inputs and include situations where there is little, if any, market activity for the balance sheet items at period end. Pricing inputs are unobservable for the terms and are based on the Company’s own estimates about the assumptions that a market participant would use in pricing as asset. The Company’s financial instruments, including money market investments, corporate debt securities, U.S. Treasury securities and obligations of U.S. government agencies, are measured at fair value on a recurring basis. There were no transfers between levels for the year ended December 31, 2015. Assets and liabilities measured at fair value on a recurring basis consisted of the following types of instruments as of December 31, 2015 and 2014 (in thousands): Quoted prices Quoted prices Quoted prices in active for similar assets in active markets for observable in the markets for December 31, identical assets marketplace December 31, identical assets Description 2015 (Level 1) (Level 2) 2014 (Level 1) Assets measured at fair value: Money market investments $ $ $ — $ $ U.S. Treasury securities, obligations of U.S. government agencies, corporate debt securities and reverse repurchase agreements — — —

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 2015
Cash, Cash Equivalents and Marketable Securities
Cash, Cash Equivalents and Marketable Securities	4. Cash, Cash Equivalents and Marketable Securities The following is a summary of cash, cash equivalents and marketable securities as of December 31, 2015 and 2014 (in thousands): Gross unrealized Gross unrealized Fair market Amortized Cost gains losses value December 31, 2015 Cash $ $ – $ – $ Money market funds – – Reverse repurchase agreements – – U.S. Treasury securities and obligations of U.S. government agencies Corporate debt securities Total for December 31, 2015 $ $ $ $ December 31, 2014 Cash $ $ – $ – $ Money market funds – – Total for December 31, 2014 $ $ – $ – $

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2015
Property and Equipment
Property and Equipment	5. Property and Equipment Property and equipment consist of the following as of December 31, 2015 and 2014 (in thousands): Estimated Useful Life December 31, (in years) 2015 2014 Lab equipment 5 $ $ Computer equipment and software 3 Leasehold improvements 2 Total Less accumulated depreciation Property and equipment, net $ $ Depreciation expenses were approximately $ 66,000 , $ 86,000 and $ 219,000 for the years ended December 31, 2015, 2014 and 2013, respectively.

Notes Payable

Notes Payable	12 Months Ended
	Dec. 31, 2015
Notes Payable
Notes Payable	6. Notes Payable As of December 31, 2015, the Company had no debt outstanding. Loan and Security Agreement During February 2011, the Company entered into a $5.0 million loan and security agreement (“Loan Agreement”) with Horizon Technology Finance (“Horizon”). The interest rate for these loans was 11.25% . The Loan Agreement required that the Company maintain $2.5 million in an account that was subject to an Account Control Agreement and restricted the Company from withdrawing the funds from this account without Horizon’s prior written consent. During July 2014, the entire outstanding balance under the Loan Agreement was paid in full and the remaining restricted cash held by the Company was fully released. The payment also released all previously pledged assets held as collateral under the loan. Convertible Debt During February 2014 through September 2014 , the Company issued subordinated secured convertible promissory notes (the “2014 Notes”), to two related party investors totaling $12.0 million at an interest rate of 8.0% per annum. The outstanding principal and accrued and unpaid interest was convertible at the option of the investor into preferred shares in the Company. The 2014 Notes included a change in control redemption which was deemed an embedded derivative. This redemption right and the right to convert at 75% of the price at which a new series of preferred stock was issued required the Company to bifurcate and separately account for the embedded derivatives, however the amount recorded and the impact on net loss was not material. As part of the Stock Conversion on September 23, 2014, the holders of the 2014 Notes agreed to the issuance of shares of a newly created Series 1 convertible preferred stock in settlement of the 2014 Notes. The Company issued 8,813,203 Series 1 convertible preferred shares at a price of $1.40 per share through the settlement of $12,373,741 of convertible debt and related interest held by two separate investors. This transaction resulted in a gain on extinguishment of $378,251 , which was recognized through equity during the year ended December 31, 2014, as this was a transaction with stockholders.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies
Commitments and Contingencies	7. Commitments and Contingencies Operating Lease The Company has a lease obligation for office and laboratory space , which will expire on March 31, 2018. The Company has the option to renew the lease for an additional three -year term and has the option to terminate the lease at any time after March 31, 2017, for a termination fee of $25,000 . The approximate future minimum payments under these lease arrangements as of December 31, 2015, are as follows (in thousands): 2016 $ 2017 2018 Total $ During 2015, 2014 and 2013, the Company incurred approximately $267,000 , $225,000 and $257,000 for rent expense, respectively. Purchase Commitments The Company has entered into contracts with external parties to provide the Company future services, which include research and development, clinical development support and testing services. As of December 31, 2015, the Company’s obligation for future services under these contracts approximated $9,194,000 with approximately $8,642,000 payable within one year. These purchase obligations include both cancellable and non-cancellable amounts.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity
Stockholders' Equity	8. Stockholders’ Equity During February 2014, the Company increased its authorized number of shares of convertible preferred stock to 30,233,694 shares. During March 2014, the Company increased its authorized number of shares of convertible preferred stock to 60,503,445 shares and increased its authorized number of shares of common stock to 25,000,000 shares. Immediately following the Stock Conversion and the one-for- four reverse stock split effected in September 2014, the Company reestablished its authorized number of shares of convertible preferred stock to 8,866,753 shares and its authorized number of shares of common stock to 15,742,382 shares. During November 2014, the Company increased its authorized number of shares of convertible preferred stock to 23,228,986 shares and increased its authorized number of shares of common stock to 35,000,000 shares. Concurrent with the Company’s initial public offering completed in June 2015 (the “IPO”), the Company increased its authorized number of shares of common stock to 2 00 , 000 , 000 shares , eliminated its authorized shares of convertible preferred s tock and authorized 10 ,000,000 shares of preferred stock for future issuance . Convertible Preferred Stock Immediately prior to the Stock Conversion, the Company had six series of outstanding convertible preferred stock: Series A-1 convertible preferred stock, Series A-2 convertible preferred stock, Series C-1 convertible preferred stock, Series C-2 convertible preferred stock, Series D convertible preferred stock and Series E convertible preferred stock. The convertible preferred stock was initially recorded at the issuance price on the date of issuance, net of issuance costs. As a result of the Stock Conversion o n September 23, 2014 , all outstanding preferred stock was converted into shares of common stock on an 11.556 -for-1 basis. Concurrent with the Stock Conversion, a newly created Series 1 convertible preferred stock was issued in the settlement of the 2014 Notes. In November and December 2014, the Company raised $31.0 million gross proceeds in a private placement of Series 2 convertible preferred stock . On June 22, 2015, prior to the closing of the Company’s IPO, all outstanding shares of convertible preferred stock, amounting to 19,978,986 shares, were automatically converted into 6,915,525 shares of common stock in accordance with the terms of the Company’s amended and restated certificate of incorporation then in existence. As of December 31, 2015, the Company had no preferred stock or convertible preferred stock outstanding . Common Stock On June 22, 2015, the Company completed its IPO of 6,325,000 shares of its common stock, including 875,000 shares from the exercise of the underwriters’ over-allotment option , at a price to the public of $14.00 per share for aggregate gross proceeds of $88.6 million. The Company received proceeds of $78.8 million from its IPO, net of $3.6 million in expenses and $6.2 million in underwriters’ discounts and commissions relating to the issuance and distribution of the securities. At December 31, 2015, shares of common stock have been reserved for issuance as follows: Options to purchase common stock - issued Options to purchase common stock - unissued Employee stock purchase plan Common stock warrants - issued Total Stock-Based Compensation Restricted Stock Prior to the Company Conversion on August 1, 2012, the Company issued Class B units to employees, which were considered profits interest. The fair value of these units was recorded as stock-based compensation expense on a straight-line basis over the requisite service period of each award, generally four years. As a result of the Company Conversion on August 1, 2012, the Company converted the vested and unvested Class B units into 171,415 shares of common stock subject to stock restriction agreements. These shares vest over the same vesting period of the original Class B unit grants and any unvested shares would be forfeited upon the termination of the employee. Stock Options In August 2012, the Company adopted the 2012 Stock Incentive Plan (the “2012 Plan”). A total of 147,109 shares of common stock were originally reserved for issuance under the 2012 Plan. On November 17, 2014, and December 12, 2014, the Company’s Board of Directors approved an increase of 623,052 and 519,210 shares, respectively, to the total number of shares that may be issued under the 2012 Plan, which after these increases totaled 1,289,371 shares. As of December 31, 2015, 1,288,174 accumulated shares had been granted under the 2012 Plan to employees and directors , while 685 shares had been exercised and 512 shares were terminated upon the termination of the 2012 Plan effective with the closing of the Company’s IPO. In May 2015, the Company’s Board of Directors and its s tockholders approved the 2015 Equity Incentive Plan (the “2015 Plan”). Effective with the Company’s IPO closing, a total of 1,081,700 shares of common stock were originally reserved for issuance under the 2015 Plan. The 2015 Plan provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2015 Plan on January 1 of each calendar year, from January 1, 2016 through January 1, 2025. The number of shares added each year will be equal to: (a) 5% of the total number of shares of Common Stock issued and outstanding on December 31 of the preceding calendar year; or (b) such lesser number of shares of Common Stock approved by the Board of Directors on or prior to such immediately preceding December 31. The 2015 Plan provides for the granting of incentive and nonqualified stock options, stock appreciation rights, restricted stock, restricted stock units, performance-based awards and other share-based awards to its employees, directors and consultants. Stock options granted vest over either a one -year period or three -year period for Board of Director grants or over a four -year period for employee grants and expire 10 years from the date of grant. The fair value of each option grant for the year ended December 31, 2015, 2014 and 2013, was estimated at the date of grant using the Black-Scholes option-pricing model with the following assumptions: 2015 2014 2013 Estimated dividend yield – * – Weighted-average expected stock price volatility % * % Weighted-average risk-free interest rate % * % Weighted-average expected life of option (in years) * Weighted-average fair value per option $ * $ * There were no options granted during 2014 Due to limited historical data, the Company estimates stock price volatility based on the actual volatility of comparable publicly traded companies over the expected life of the option. The expected term represents the average time that options that vest are expected to be outstanding. The Company does not have sufficient history of exercise of stock options to estimate the expected term for employee stock options and, thus, continues to calculate expected life based on the midpoint between the average vesting date and the contractual term, which is in accordance with the simplified method. The risk-free rate is based on the United States Treasury yield curve for the expected life of the option. The fair value of the common stock utilized in the fair value estimation of option and restricted stock arrangements prior to the Company’s IPO of June 2015 has been determined utilizing contemporaneous valuations primarily based on an option pricing methodology. The tables below summarize the stock option activity for the year ended December 31, 2015: Weighted Available for Options Average Grant Outstanding Exercise Price Balance as of January 1, 2015 $ Additional authorized – Granted Exercised – Cancelled Shares terminated from the 2012 Plan – Balance as of December 31, 2015 $ Weighted- Average Remaining Weighted- Contractual Aggregate Number of Average Life Intrinsic Options Exercise Price (In Years) Value As of December 31, 2015: Options outstanding $ $ Options expected to vest, net of estimated forfeitures $ $ Options exercisable $ $ During 2015, 2014 and 2013, the Company recorded approximately $1.3 million, $66,000 and $91,000 , respectively, in employee stock-based compensation expense for the vesting of stock options. No stock options have been granted to consultants. As of December 31, 2015, there was approximately $7.1 million of total unrecognized stock-based compensation expense related to nonvested stock options, which is expected to be recognized over a weighted-average period of 3.3 years. The Company did not recognize a tax benefit related to share-based compensation expense during the years ended December 31, 2015, 2014 and 2013 as the Company maintains net operating loss carryforwards and has established a valuation allowance against the entire net deferred tax asset as of December 31, 2015. Employee Stock Purchase Plan In May 2015, the Company’s Board of Directors and its s tockholders approved the Nivalis Therapeutics, Inc. Employee Stock Purchase Plan (the “Purchase Plan”). Effective on the closing of the Company’s IPO, a total of 231,800 shares of common stock were made available for sale under the Purchase Plan. The Purchase Plan may be amended, suspended or terminated at any time by the Board of Directors, however s tockholder approval is required to increase the number of common stock available under the Purchase Plan or to change the employees eligible to participate in the Purchase Plan. The Purchase Plan provides for a series of successive six -month offering periods, from January to June and July to December of each calendar year during which participating employees may elect to have up to 15% of their compensation withheld and applied to the purchase of common stock at the end of each offering period. The purchase price of the common stock is 85% of the lower of the fair value of a share of common stock on the first trading date of each offering period or the fair value of a share of common stock on the last trading day of the offering period. The Company sold 8,924 shares to employees on December 31, 2015. There were 222,876 shares available for sale under the Purchase Plan as of December 31, 2015. The weighted-average estimated grant date fair value of purchase awards under the Purchase Plan during the year ended December 31, 2015 was $5.18 . The total share-based compensation expense recorded as a result of the Purchase Plan was approximately $22,000 during the year ended December 31, 2015. The fair value of purchase awards granted to our employees during the year ended December 31, 2015 was estimated using the Black-Scholes option pricing model using the weighted-average assumptions provided in the following table: Estimated dividend yield – Expected stock price volatility % Risk-free interest rate % Expected life of option (in years) Due to limited historical data, the Company estimates stock price volatility based on the actual volatility of comparable publicly traded companies over the expected life of the purchase right. The risk-free rate is based on the U.S. Treasury yield in effect at the time of grant with terms similar to the contractual term of the purchase right. The expected term represents the six-month offering period for the Purchase Plan.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Taxes
Income Taxes	9 . Income Taxes No provision for federal or state income tax expense has been recorded for the years ended December 31, 2015, 2014 and 2013, since the Company generated net operating losses in all years. Deferred income taxes reflect the net tax effect of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets and liabilities at December 31, 2015 and 2014 are as follows (in thousands): 2015 2014 Deferred tax assets: Net operating loss carryforwards $ $ Research credit carryforwards Accrued benefits and other Intangible assets Valuation allowance Net deferred tax assets Deferred tax liabilities: Property and equipment $ – $ – The Company records a full valuation allowance against its net deferred tax assets since the Company cannot conclude that it was more likely than not that its deferred tax assets would be realized. At December 31, 2015, the Company had federal and state income loss carryforwards of $54.7 million that begin to expire in 2032 for both federal and state purposes. Additionally, The Company has research and development credits of approximately $1.8 million available for federal purposes, which begin to expire in 2032. The utilization of the federal net operating loss and credit carryforwards to reduce future income taxes will depend on the Company’s ability to generate sufficient taxable income prior to the expiration of the carryforwards. In addition, the utilization of the federal net operating loss and credit carryforwards may be subject to limitations under the rules regarding a change in stock ownership as determined by the Internal Revenue Code and state laws. Section 382 of the Internal Revenue Code of 1986, as amended, imposes annual limitations on the utilization of net operating loss (“NOL”) carryforwards, other tax carryforwards and certain built-in losses upon an ownership change as defined by that section. In general terms, an ownership change may result from transactions that increase the aggregate ownership of certain stockholders in the Company stock by more than 50 percentage points over a three year testing period (“Section 382 Ownership Change”). If the Company has undergone a Section 382 Ownership change, an annual limitation would be imposed on certain tax attributes of the Company, including NOL and capital loss carryforwards and certain other losses and credits. As of December 31, 2015, the Company has not performed a formal study to determine whether there are Section 382 limitations that apply and such limitations could be significant. The difference between actual income tax rate for the years ended December 31, 2015, 2014 and 2013, and the statutory federal income tax rate are as follows: 2015 2014 2013 % of Pretax % of Pretax % of Pretax Earnings Earnings Earnings Income tax benefit at statutory rate % % % State income taxes, net of federal tax benefit % % % Research and development credits % % % Nondeductible expenses % % % Change in valuation allowance % % % Income tax expense (benefit) % % % As of December 31, 2015 and 2014, the Company had no unrecognized tax benefits. The Company has analyzed its filing positions in all significant federal and state jurisdictions where it is required to file income tax returns, as well as open tax years in these jurisdictions. With few exceptions, the Company is no longer subject to U.S. federal, state and local tax examinations by taxing authorities for years before 2012. No income tax returns are currently under examination by taxing authorities .

Employment Benefit Plan

Employment Benefit Plan	12 Months Ended
	Dec. 31, 2015
Employment Benefit Plan
Employment Benefit Plan	10. Employment Benefit Plan The Company outsources its payroll, benefits and human resource administration functions to a Professional Employer Organization (PEO). The Company’s employees are eligible to participate in the PEO’s Multiple Employer Retirement Savings Plan (401(k) plan). The 401(k) plan allows immediate participation by U.S. employees that are 20 years of age or older. Participants may defer up to 75% of their gross pay, up to a maximum limit determined by U.S. federal law. The Company provides all active employees with a safe harbor contribution equal to 3% of compensation (regardless of participation in the 401(k) plan) up to maximum U.S. federal law limits. These safe harbor contributions vest immediately. During 2015, 2014 and 2013, the Company paid approximately $115,000 , $129,000 and $142,000 , respectively, for employer contributions and plan expenses.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2015
Net Loss per Share
Net Loss per Share	11. Net Loss per Share The Company excluded the following common stock equivalents, outstanding as of the years ended December 31, 2015, 2014 and 2013, from the computation of diluted net loss per share for these same periods because they had an anti-dilutive impact on the computation: December 31, 2015 2014 2013 Options to purchase common stock - issued Unvested restricted common stock Convertible preferred stock — Warrants to purchase convertible preferred and common stock Total

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data
Quarterly Financial Data	12. Quarterly Financial Data (Unaudited) The results of operations on a quarterly basis for the years ended December 31, 2015 and 2014 were as follows (in thousands , except per share data ): March 31, June 30, September 30, December 31, March 31, June 30, September 30, December 31, 2015 2015 2015 2015 2014 2014 2014 2014 Revenue $ — $ — $ — $ — $ — $ — $ — $ — Operating expenses: Research and development General and administrative Loss from operations Interest and other income, net — — Interest expense — — — — — Net loss Gain on extinguishment of convertible debt as a capital transaction — — — — — — — Net loss attributable to common stockholders $ $ $ $ $ $ $ $ Weighted average shares outstanding - basic and diluted Net loss per share attributable to common stockholders - basic and diluted $ $ $ $ $ $ $ $

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events
Subsequent Events	13. Subsequent Events The Company evaluated events after the balance sheet date of December 31, 2015 and up to the date the Company filed this Annual Report and determined that no subsequent activity required disclosure.

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Summary of Significant Accounting Policies
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include all adjustments necessary for the presentation of the Company’s financial position, results of operations and cash flows for the periods presented. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts and disclosures reported in the financial statements and accompanying notes, including accrued liabilities and the fair value-based measurement of equity instruments. Actual results could differ materially from those estimates. The Company evaluates its estimates and assumptions as facts and circumstances dictate.
Stock Conversion and Reverse Stock Split	2014 Stock Conversion and Reverse Stock Split Effective September 23, 2014, all outstanding shares of the Company’s preferred stock were converted on an 11.556 -for-1 basis into shares of common stock (the “Stock Conversion”). Concurrent with this Stock Conversion, the Company effected a reverse stock split of its common stock, par value $0.001 per share. Every four shares of common stock were reclassified and combined into one share of common stock. Fractional shares were issued as a result of the reverse stock split. The total number of authorized shares of common stock was also proportionally decreased on a 4-for-1 basis and the par value per share of the common stock continued to be $0.001 . 2015 Stock Conversion and Reverse Stock Split On May 26, 2015, the Company’s Board of Directors approved a 1-for- 2.889 reverse stock split of its common stock, which became effective on June 1, 2015. Upon the effectiveness of the reverse stock split, (i) every 2.889 shares of outstanding common stock were decreased to one share of common stock, (ii) the number of shares of common stock into which each outstanding option, right and warrant to purchase common stock is exercisable was proportionally decreased on a 1-for-2.889 basis and the exercise price of each outstanding option, right and warrant to purchase common stock was proportionately increased on a 1-for-2.889 basis, and (iii) the conversion ratio for each share of the Company’s convertible preferred stock which was convertible into common stock was proportionally decreased on a corresponding basis in connection with the 1-for-2.889 reverse split. No fractional shares were issued as a result of the reverse stock split. The total number of authorized shares of common stock and the par value per share of common stock did not change as a result of the reverse stock split. Effective June 22, 2015, all outstanding shares of convertible preferred stock were converted on a 2.889-for-1 basis into shares of common stock in connection with the closing of our initial public offering. All of the share numbers, share prices, exercise prices and other per share information throughout these financial statements for all periods presented have been adjusted, on a retroactive basis, to reflect the 1-for-4 reverse stock split and the 1-for-2.889 reverse stock split and the conversion of all convertible preferred stock on the closing of our initial public offering.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of deposits with commercial banks in checking, interest- bearing and demand money market accounts.
Marketable Securities	Marketable Securities The Company has designated marketable securities as available-for-sale securities and accounts for them at their respective fair values. Marketable securities are classified as short-term or long-term based on the nature of the securities and their availability to meet current operating requirements. Securities that are classified as available-for-sale are carried at fair value, including accrued interest, with temporary unrealized gains and losses reported as a component of stockholders' equity (deficit) until their disposition. The Company reviews all available-for-sale securities at each period end to determine if they remain available-for-sale based on the Company’s then current intent and ability to sell the security if it is required to do so. The cost of securities sold is based on the specific identification method. All marketable securities are subject to a periodic impairment review. The Company will recognize an impairment charge when a decline in the fair value of the investments below the cost basis is judged to be other-than-temporary.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company has established guidelines to limit its exposure to credit risk by placing investments with high credit quality financial institutions, diversifying its investment portfolio and making investments with maturities that maintain safety and liquidity. At December 31, 2015 and 2014, the Company’s cash equivalents were with money market funds that invest in securities issued by the U.S. Treasury. At December 31, 2015, the Company’s marketable securities were in U.S. Treasury securities, obligations of U.S. government agencies and high-grade corporate debt securities.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Lab equipment, computer equipment and software are depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are depreciated over the shorter of the estimated useful lives of the assets or the lease term. Maintenance and repairs are expensed as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets, such as property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized for an amount by which the carrying amount of the asset exceeds the fair value of the asset. The Company has not yet generated consistent positive cash flows on an annual basis, and such positive cash flows may not materialize for a significant period in the future. As a result, it is reasonably possible that future evaluations of long-lived assets may result in a conclusion that such assets have been impaired.
Accrued Direct Program Expenses	Accrued Direct Program Expenses Substantial portions of the Company’s preclinical studies and clinical trials are performed by third-party laboratories, medical centers, contract research organizations and other vendors (collectively CROs). These CROs generally bill monthly or quarterly for services performed or upon achieving certain milestones. For preclinical studies, the Company accrues expenses based upon estimated percentage of work completed and the contract milestones remaining. For clinical studies, expenses are accrued based upon the number of patients enrolled and the duration of the study. The Company monitors patient enrollment, the progress of clinical studies and related activities to the extent possible through internal reviews of data reported to the Company by the CROs or within software tracking systems, correspondence with the CROs and clinical site visits. Company estimates depend on the timeliness and accuracy of the data provided by the CROs regarding the status of each program and total program spending. The Company periodically evaluates these estimates to determine if adjustments are necessary or appropriate based on information received. No vendor comprised more than 10% of all external costs in 2015, 2014, and 2013.
Research and Development	Research and Development The Company expenses costs associated with research and development as incurred. These costs include direct program expenses, which are payments made to third parties that specifically relate to the Company’s research and development, such as payments to clinical research organizations, clinical investigators, manufacturing of clinical material, pre-clinical testing and consultants. In addition, employee costs (salaries, payroll taxes, benefits and travel) for employees contributing to research and development activities are classified as research and development costs.
Stock-Based Compensation	Stock-Based Compensation The Company measures employee and director stock-based compensation expense for all stock and purchase awards at the grant date based on the fair value measurement of the award. The expense is recorded over the related service period, generally the vesting period, net of estimated forfeitures. Any changes to the estimated forfeiture rates are accounted for prospectively. The Company calculates the fair value measurement of stock options using the Black-Scholes valuation model and the single-option method and recognizes expense using the straight-line attribution approach.
Income Taxes	Income Taxes The Company accounts for income taxes under an asset and liability approach. Deferred income taxes reflect the impact of temporary differences between assets and liabilities recognized for tax and financial reporting purposes measured by applying enacted tax rates and laws that will be in effect when the differences are expected to reverse, net operating loss and tax credit carryforwards. Tax benefits are recorded when the benefit is more likely than not to be sustained upon audit. The Company accrues interest and penalties related to uncertain tax positions in income tax expense. Valuation allowances are provided when necessary to reduce net deferred tax assets to an amount that is more likely than not to be realized.
Segment Information	Segment Information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on discovering and developing potential drugs. No revenue has been generated since inception, and all tangible assets are held in the United States.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is comprised of net loss and adjustments for the change in unrealized gains and losses on the Company’s investments in available-for-sale marketable securities. The Company presents comprehensive loss and its components in the statements of operations and comprehensive loss for the year ended December 31, 2015.
Net Loss per Share	Net Loss per Share The Company reports net loss per share in accordance with the standard codification of ASC “Earnings per Share” (“ASC 260”). Under ASC 260, basic earnings per share, which excludes dilution, is computed by dividing net loss available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted earnings per share reflects the potential dilution of securities that could be exercised or converted into common shares, and is computed by dividing net loss available to common stockholders by the weighted average of common shares outstanding plus the dilutive potential common shares. Diluted earnings per share excludes the impact of convertible preferred stock, employee stock options, restricted stock and stock purchase rights, as the effect would be anti-dilutive. During a loss period, the assumed exercise of in-the-money stock options and other potentially diluted instruments has an anti-dilutive effect and therefore, these instruments are excluded from the computation of dilutive earnings per share.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements – Going Concern Disclosure of Uncertainties About an Entity’s Ability to Continue as a Going Concern, which requires management to evaluate whether there are conditions or events that raise substantial doubt about an entity’s ability to continue as a going concern and to provide disclosures when certain criteria are met. The guidance is effective for annual periods beginning in 2016 and interim reporting periods starting in the first quarter of 2017. Early application is permitted. The Company does not expect the standard will have a material impact on its disclosures. In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes. The new standard requires that deferred tax assets and liabilities be classified as noncurrent in a classified statement of financial position. The guidance is effective for financial statements issued for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Earlier application is permitted for all entities as of the beginning of an interim or annual report period. The amendments in this standard may be applied either prospectively to all deferred tax assets and liabilities or retrospectively to all periods presented. The Company adopted this standard as of December 31, 2015 with prospective application. As a result, the Company reclassified its deferred tax assets classified as current to noncurrent and its deferred tax liabilities classified as current to noncurrent as of December 31, 2015. Prior year balances were not retrospectively adjusted. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The new guidance requires organizations that lease assets to recognize assets and liabilities on the balance sheet related to the rights and obligations created by those leases, regardless of whether they are classified as finance or operating leases. Consistent with current guidance, the recognition, measurement, and presentation of expenses and cash flows arising from a lease primarily will depend on its classification as a finance or operating lease. The guidance also requires new disclosures to help financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, with early application permitted. The new standard is to be applied using a modified retrospective approach. The Company is currently evaluating the impact of the new pronouncement on its financial statements.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of cash equivalents and marketable securities approximate their fair value based upon quoted market prices. Certain financial instruments are not measured at fair value on a recurring basis, but are recorded at amounts that approximate their fair value due to their liquid or short-term nature, such as cash, accounts payable, accrued direct program expenses, and accrued employee benefits , and other financial instruments included within current assets or current liabilities. The Company accounted for warrants to purchase its redeemable preferred stock pursuant to ASC Topic 480, Distinguishing Liabilities from Equity , and classified them as liabilities. The fair value of the outstanding preferred stock warrant liabilities at December 31, 2013 was $267,750 . Subsequent to the completion of the Stock Conversion on September 23, 2014, whereby all outstanding shares of preferred stock were converted into shares of common stock, and the warrants became exercisable for shares of common stock pursuant to the adjustment provisions of the warrants, the fair value of the preferred stock warrant liabilities was remeasured and reclassified into equity. During the year ended December 31, 2014 a remeasurement gain of $265,750 was recognized in interest and other income, net in the statement of operations and comprehensive loss. Upon the Stock Conversion, the remaining balance of $2,000 was reclassified from liabilities to equity.
Fair Value Measurements	Fair Value Measurements In general, asset and liability fair values are determined using the following categories: Level 1 – inputs utilize quoted prices in active markets for identical assets or liabilities. Level 2 – inputs include quoted prices for similar assets or liabilities in active markets, and inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly. Level 3 – inputs are unobservable inputs and include situations where there is little, if any, market activity for the balance sheet items at period end. Pricing inputs are unobservable for the terms and are based on the Company’s own estimates about the assumptions that a market participant would use in pricing as asset. The Company’s financial instruments, including money market investments, corporate debt securities, U.S. Treasury securities and obligations of U.S. government agencies, are measured at fair value on a recurring basis. There were no transfers between levels for the year ended December 31, 2015. Assets and liabilities measured at fair value on a recurring basis consisted of the following types of instruments as of December 31, 2015 and 2014 (in thousands): Quoted prices Quoted prices Quoted prices in active for similar assets in active markets for observable in the markets for December 31, identical assets marketplace December 31, identical assets Description 2015 (Level 1) (Level 2) 2014 (Level 1) Assets measured at fair value: Money market investments $ $ $ — $ $ U.S. Treasury securities, obligations of U.S. government agencies, corporate debt securities and reverse repurchase agreements — — —

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Summary of Significant Accounting Policies
Schedule of assets measured at fair value on a recurring basis (in thousands)	Quoted prices Quoted prices Quoted prices in active for similar assets in active markets for observable in the markets for December 31, identical assets marketplace December 31, identical assets Description 2015 (Level 1) (Level 2) 2014 (Level 1) Assets measured at fair value: Money market investments $ $ $ — $ $ U.S. Treasury securities, obligations of U.S. government agencies, corporate debt securities and reverse repurchase agreements — — —

Cash, Cash Equivalents and Ma23

Cash, Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Cash, Cash Equivalents and Marketable Securities
Schedule of cash, cash equivalents and marketable securities (in thousands)	Gross unrealized Gross unrealized Fair market Amortized Cost gains losses value December 31, 2015 Cash $ $ – $ – $ Money market funds – – Reverse repurchase agreements – – U.S. Treasury securities and obligations of U.S. government agencies Corporate debt securities Total for December 31, 2015 $ $ $ $ December 31, 2014 Cash $ $ – $ – $ Money market funds – – Total for December 31, 2014 $ $ – $ – $

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property and Equipment
Schedule of property and equipment (in thousands)	Estimated Useful Life December 31, (in years) 2015 2014 Lab equipment 5 $ $ Computer equipment and software 3 Leasehold improvements 2 Total Less accumulated depreciation Property and equipment, net $ $

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies
Schedule of future minimum payments under lease arrangements (in thousands)	The approximate future minimum payments under these lease arrangements as of December 31, 2015, are as follows (in thousands): 2016 $ 2017 2018 Total $

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity
Schedule of common stock reserved for issuance	Options to purchase common stock - issued Options to purchase common stock - unissued Employee stock purchase plan Common stock warrants - issued Total
Schedule of options valuation assumptions	2015 2014 2013 Estimated dividend yield – * – Weighted-average expected stock price volatility % * % Weighted-average risk-free interest rate % * % Weighted-average expected life of option (in years) * Weighted-average fair value per option $ * $ * There were no options granted during 2014
Schedule of stock option activity	The tables below summarize the stock option activity for the year ended December 31, 2015: Weighted Available for Options Average Grant Outstanding Exercise Price Balance as of January 1, 2015 $ Additional authorized – Granted Exercised – Cancelled Shares terminated from the 2012 Plan – Balance as of December 31, 2015 $ Weighted- Average Remaining Weighted- Contractual Aggregate Number of Average Life Intrinsic Options Exercise Price (In Years) Value As of December 31, 2015: Options outstanding $ $ Options expected to vest, net of estimated forfeitures $ $ Options exercisable $ $
Schedule of Purchase Plan valuation assumptions	Estimated dividend yield – Expected stock price volatility % Risk-free interest rate % Expected life of option (in years)

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Taxes
Schedule of significant components of deferred tax assets and liabilities (in thousands)	2015 2014 Deferred tax assets: Net operating loss carryforwards $ $ Research credit carryforwards Accrued benefits and other Intangible assets Valuation allowance Net deferred tax assets Deferred tax liabilities: Property and equipment $ – $ –
Schedule of difference between actual income tax rates and the statutory federal income tax rate	2015 2014 2013 % of Pretax % of Pretax % of Pretax Earnings Earnings Earnings Income tax benefit at statutory rate % % % State income taxes, net of federal tax benefit % % % Research and development credits % % % Nondeductible expenses % % % Change in valuation allowance % % % Income tax expense (benefit) % % %

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Net Loss per Share
Schedule of anti-dilutive common stock equivalents	December 31, 2015 2014 2013 Options to purchase common stock - issued Unvested restricted common stock Convertible preferred stock — Warrants to purchase convertible preferred and common stock Total

Quarterly Financial Data (Una29

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data
Schedule of results of operations on a quarterly basis (in thousands, except share and per share amounts)	The results of operations on a quarterly basis for the years ended December 31, 2015 and 2014 were as follows (in thousands , except per share data ): March 31, June 30, September 30, December 31, March 31, June 30, September 30, December 31, 2015 2015 2015 2015 2014 2014 2014 2014 Revenue $ — $ — $ — $ — $ — $ — $ — $ — Operating expenses: Research and development General and administrative Loss from operations Interest and other income, net — — Interest expense — — — — — Net loss Gain on extinguishment of convertible debt as a capital transaction — — — — — — — Net loss attributable to common stockholders $ $ $ $ $ $ $ $ Weighted average shares outstanding - basic and diluted Net loss per share attributable to common stockholders - basic and diluted $ $ $ $ $ $ $ $

Liquidity Risks (Details)

Liquidity Risks (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liquidity Risks
Accumulated deficit	$ 148,837	$ 126,019
Net loss	22,815	14,658	$ 16,198
Cash used in operating activities	19,207	$ 14,448	$ 14,293
Revenues	$ 0

Summary of Significant Accoun31

Summary of Significant Accounting Policies (Details)	May. 26, 2015	Sep. 23, 2014$ / shares	Dec. 31, 2015$ / shares	Dec. 31, 2014$ / shares
Significant Accounting Policies
Preferred stock conversion ratio		11.556
Common stock, par value (in dollars per share)		$ 0.001	$ 0.001	$ 0.001
Stock split conversion ratio	0.3461	0.25
Maximum | Vendor concentration risk
Significant Accounting Policies
Concentration risk (as a percent)			10.00%

Summary of Significant Accoun32

Summary of Significant Accounting Policies (FV) (Details) - USD ($)	Sep. 23, 2014	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2013
Assets measured at fair value:
Fair market value		$ 27,812,000	$ 87,254,000
Preferred stock warrant liabilities
Fair Value Measurements
Warrant fair value				$ 267,750
Remeasurement gain		265,750
Reclass from liability to equity	$ 2,000
Money market funds
Assets measured at fair value:
Fair market value		26,926,000	12,131,000
Money market funds | Recurring
Assets measured at fair value:
Fair market value		26,926,000	12,131,000
Money market funds | Recurring | Level 1
Assets measured at fair value:
Fair market value		$ 26,926,000	12,131,000
U.S. Treasury securities, obligations of U.S. government agencies, corporate debt securities and reverse repurchase agreements | Recurring
Assets measured at fair value:
Fair market value			73,261,000
U.S. Treasury securities, obligations of U.S. government agencies, corporate debt securities and reverse repurchase agreements | Recurring | Level 2
Assets measured at fair value:
Fair market value			$ 73,261,000

Cash, Cash Equivalents and Ma33

Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of cash, cash equivalents and marketable securities
Amortized Cost	$ 87,251	$ 27,812
Gross unrealized gains	26
Gross unrealized losses	(23)
Fair market value	87,254	27,812
Cash
Summary of cash, cash equivalents and marketable securities
Amortized Cost	1,862	886
Fair market value	1,862	886
Money market funds
Summary of cash, cash equivalents and marketable securities
Amortized Cost	12,131	26,926
Fair market value	12,131	$ 26,926
Reverse repurchase agreements
Summary of cash, cash equivalents and marketable securities
Amortized Cost	6,000
Fair market value	6,000
U.S. Treasury securities and obligations of U.S. government agencies
Summary of cash, cash equivalents and marketable securities
Amortized Cost	28,982
Gross unrealized gains	4
Gross unrealized losses	(7)
Fair market value	28,979
Corporate debt securities
Summary of cash, cash equivalents and marketable securities
Amortized Cost	38,276
Gross unrealized gains	22
Gross unrealized losses	(16)
Fair market value	$ 38,282

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property and Equipment
Property and equipment, gross	$ 1,669	$ 1,492
Less accumulated depreciation	(1,456)	(1,401)
Property and equipment, net	213	91
Depreciation expense	$ 66	88	$ 219
Lab equipment
Property and Equipment
Estimated Useful Life (in years)	5 years
Property and equipment, gross	$ 1,146	1,099
Computer equipment and software
Property and Equipment
Estimated Useful Life (in years)	3 years
Property and equipment, gross	$ 421	291
Leasehold improvements
Property and Equipment
Estimated Useful Life (in years)	2 years
Property and equipment, gross	$ 102	$ 102

Notes Payable (Details)

Notes Payable (Details)	May. 26, 2015	Sep. 23, 2014USD ($)security$ / shares	Sep. 30, 2014USD ($)item	Dec. 31, 2014USD ($)	Dec. 31, 2015USD ($)	Feb. 28, 2011USD ($)
Notes Payable
Debt outstanding					$ 0
Access to restricted cash				$ 2,500,000
Stock split conversion ratio	0.3461	0.25
Security Agreement
Notes Payable
Debt issued						$ 5,000,000
Interest rate (as a percent)						11.25%
Restricted proceeds						$ 2,500,000
2014 Notes
Notes Payable
Debt issued			$ 12,000,000
Interest rate (as a percent)			8.00%
Number of investors | item			2
Percentage of new series conversion price			75.00%
Debt and related interest		$ 12,373,741
Gain on extinguishment recognized through equity		$ 378,251
2014 Notes | Preferred Stock | Series 1 Convertible Preferred Stock
Notes Payable
Conversion price (in dollars per share) | $ / shares		$ 1.40
Conversion of debt to preferred stock (in shares) | security		8,813,203

Commitments and Contingencies36

Commitments and Contingencies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating lease
2,016	$ 292,000
2,017	293,000
2,018	79,000
Total	664,000
Rent expense	267,000	$ 225,000	$ 257,000
Purchase commitment obligation	9,194,000
Purchase commitment obligation payable within one year	$ 8,642,000
Office and laboratory space
Operating lease
Operating lease renewal term (in years)	3 years
Termination fees	$ 25,000

Stockholders' Equity (Details)

Stockholders' Equity (Details) $ / shares in Units, $ in Thousands	Jun. 22, 2015USD ($)$ / sharesshares	May. 26, 2015	Sep. 23, 2014shares	Dec. 31, 2014USD ($)shares	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)shares	Dec. 31, 2013item	Jun. 30, 2015shares	Nov. 30, 2014shares	Mar. 31, 2014shares	Feb. 28, 2014shares
Stockholders' Equity
Authorized convertible preferred stock (in shares)				23,228,986	0	23,228,986
Common stock, shares authorized			15,742,382	35,000,000	200,000,000	35,000,000		200,000,000	35,000,000	25,000,000
Stock split conversion ratio		0.3461	0.25
Authorized preferred stock (in shares)				0	10,000,000	0		10,000,000
Preferred stock conversion ratio			11.556
Proceeds from issuance of convertible preferred stock | $						$ 29,935
Convertible preferred stock outstanding (in shares)				19,978,986	0	19,978,986
Stock issued upon conversion (in shares)	6,915,525
Preferred stock outstanding (in shares)				0	0	0
Aggregate gross proceeds from issuance of common stock, net of offering costs | $	$ 88,600
Proceeds from issuance of common stock, net of offering costs | $	78,800
Issuance of common stock, offering costs | $	3,600				$ 9,800
Underwriters’ discounts and commissions | $	$ 6,200
IPO
Stockholders' Equity
Issuance of common stock, net of offering costs (in shares)	6,325,000
Price per share (in dollars per share) | $ / shares	$ 14
Underwriters' Over-Allotment Option
Stockholders' Equity
Issuance of common stock, net of offering costs (in shares)	875,000
Convertible preferred stock
Stockholders' Equity
Authorized convertible preferred stock (in shares)			8,866,753						23,228,986	60,503,445	30,233,694
Stock split conversion ratio			0.25
Number of series of outstanding stock | item							6
Preferred stock conversion ratio			11.556
Convertible preferred stock outstanding (in shares)	19,978,986
Series 2 Convertible Preferred Stock
Stockholders' Equity
Proceeds from issuance of convertible preferred stock | $				$ 31,000

Stockholders' Equity (Reserved)

Stockholders' Equity (Reserved) (Details)	Dec. 31, 2015shares
Stockholders' Equity
Common stock reserved for issuance	2,632,290
Options to purchase common stock - issued
Stockholders' Equity
Common stock reserved for issuance	1,810,155
Options to purchase common stock - unissued
Stockholders' Equity
Common stock reserved for issuance	580,725
Employee stock purchase plan
Stockholders' Equity
Common stock reserved for issuance	222,876
Common stock warrants - issued
Stockholders' Equity
Common stock reserved for issuance	18,534

Stockholders' Equity (Options a

Stockholders' Equity (Options and ESPP) (Details) - USD ($)	Dec. 12, 2014	Nov. 17, 2014	Aug. 01, 2012	May. 31, 2015	Jul. 31, 2012	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Aug. 31, 2012
Share-based compensation
Recognized tax benefit						$ 0	$ 0	$ 0
2012 Plan
Share-based compensation
Number of shares authorized (in shares)	1,289,371								147,109
Additional number of shares authorized (in shares)	519,210	623,052
2015 Plan
Share-based compensation
Number of shares authorized (in shares)				1,081,700
Annual percentage increase, authorized shares (as a percent)				5.00%
The Purchase Plan
Share-based compensation
Number of shares authorized (in shares)				231,800		222,876
Employee stock-based compensation expense						$ 22,000
Offering period				6 months
Highest percentage of compensation employees may utilize for purchase of common stock (as a percent)				15.00%
Purchase price relative to fair value (as a percent)				85.00%
Shares sold to employees (in shares)						8,924
Weighted-average grant date fair value (in dollars per share)						$ 5.18
Share-based compensation expense						$ 22,000
Options to purchase common stock
Share-based compensation
Additional number of shares authorized (in shares)						1,081,700
Options granted (in shares)						1,723,824	0
Options exercised (in shares)						1,285
Shares terminated (in shares)						512
Employee stock-based compensation expense						$ 1,300,000	$ 66,000	91,000
Unrecognized compensation cost related to nonvested stock options						$ 7,100,000
Weighted-average period of recognition (in years)						3 years 3 months 18 days
Share-based compensation expense						$ 1,300,000	$ 66,000	$ 91,000
Options to purchase common stock | 2012 Plan
Share-based compensation
Options granted (in shares)						1,288,174
Options exercised (in shares)						685
Shares terminated (in shares)						512
Options to purchase common stock | 2015 Plan
Share-based compensation
Term (in years)						10 years
Options to purchase common stock | 2015 Plan | Director | Minimum
Share-based compensation
Vesting period (in years)						1 year
Options to purchase common stock | 2015 Plan | Director | Maximum
Share-based compensation
Vesting period (in years)						3 years
Options to purchase common stock | 2015 Plan | Employee
Share-based compensation
Vesting period (in years)						4 years
Common Stock
Share-based compensation
Options exercised (in shares)						1,000	1,000
Common Stock | Restricted stock
Share-based compensation
Units converted to shares, stock issued (in shares)			171,415
Class B units
Share-based compensation
Requisite service period (in years)					4 years

Stockholders' Equity (Assumptio

Stockholders' Equity (Assumptions) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Options to purchase common stock
Fair value assumptions
Weighted-average expected stock price volatility (as a percent)	75.70%		120.80%
Weighted-average risk-free interest rate (as a percent)	1.80%		1.20%
Weighted-average expected life of option	6 years 2 months 19 days		6 years 3 months
Weighted-average fair value per option (in dollars per share)	$ 5.09		$ 2.95
Options granted (in shares)	1,723,824	0
The Purchase Plan
Fair value assumptions
Estimated dividend yield (as a percent)	0.00%
Weighted-average expected stock price volatility (as a percent)	62.50%
Weighted-average risk-free interest rate (as a percent)	0.10%
Weighted-average expected life of option	6 months

Stockholders' Equity (OptionAct

Stockholders' Equity (OptionActivity) (Details) - Options to purchase common stock - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Available for Grant
Balance (in shares)	1,222,631
Additional authorized (in shares)	1,081,700
Granted (in shares)	(1,723,824)	0
Cancelled (in shares)	730
Shares terminated from the 2012 Plan (in shares)	(512)
Balance (in shares)	580,725	1,222,631
Options Outstanding
Balance (in shares)	66,055
Granted (in shares)	1,723,824	0
Exercised (in shares)	(1,285)
Cancelled (in shares)	(730)
Balance (in shares)	1,787,864	66,055
Expected to vest, net of estimated forfeitures (in shares)	1,696,002
Exercisable (in shares)	72,609
Weighted Average Exercise Price
Balance (in dollars per share)	$ 3.36
Granted (in dollars per share)	7.69
Exercised (in dollars per share)	3.36
Cancelled (in dollars per share)	3.36
Balance (in dollars per share)	7.54	$ 3.36
Expected to vest, net of estimated forfeitures (in dollars per share)	7.51
Exercisable (in dollars per share)	$ 6.28
Weighted-Average Remaining Contractual Life (In Years)
Outstanding (in years)	9 years 2 months 12 days
Expected to vest, net of estimated forfeitures (in years)	9 years 2 months 12 days
Exercisable (in years)	7 years 8 months 12 days
Aggregate Intrinsic Value
Outstanding	$ 4,168,473
Expected to vest, net of estimated forfeitures	3,968,169
Exercisable	$ 240,175

Income Taxes (DTA and DTL) (Det

Income Taxes (DTA and DTL) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets:
Net operating loss carryforwards	$ 20,280	$ 12,822
Research credit carryforwards	1,813	1,215
Accrued benefits and other	643	71
Intangible assets	125	144
Valuation allowance	(22,858)	(14,242)
Net deferred tax assets	3	10
Deferred tax liabilities:
Property and equipment	(3)	(10)
Federal
Deferred tax assets:
Provision for income tax	0	0	$ 0
State
Deferred tax assets:
Provision for income tax	$ 0	$ 0	$ 0

Income Taxes (NOL) (Details)

Income Taxes (NOL) (Details) $ in Millions	Dec. 31, 2015USD ($)
Income Taxes
Operating loss carryforwards	$ 54.7

Income Taxes (Credit) (Details)

Income Taxes (Credit) (Details) $ in Millions	Dec. 31, 2015USD ($)
Federal | Research and development credits
Tax credit carryforward
Tax credit carryforwards	$ 1.8

Income Taxes (Rates) (Details)

Income Taxes (Rates) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
% of Pretax Earnings
Income tax benefit at statutory rate (as a percent)	34.00%	34.00%	34.00%
State income taxes, net of federal tax benefit (as a percent)	3.10%	3.10%	3.10%
Research and development credits (as a percent)	2.60%	3.50%	4.30%
Nondeductible expenses (as a percent)	(1.90%)	(1.00%)	(1.30%)
Change in valuation allowance (as a percent)	(37.80%)	(39.60%)	(40.10%)
Income tax expense (benefit) (as a percent)	0.00%	0.00%	0.00%
Unrecognized tax benefits	$ 0	$ 0

Employment Benefit Plan (Detail

Employment Benefit Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employment Benefit Plan
Gross pay contribution maximum (as a percent)	75.00%
Company contributions during the period	$ 115,000	$ 129,000	$ 142,000

Net Loss per Share (Details)

Net Loss per Share (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Loss per Share
Antidilutive common stock equivalents	1,829,007	7,025,747	1,909,291
Options to purchase common stock
Net Loss per Share
Antidilutive common stock equivalents	1,810,155	88,346	144,290
Restricted stock
Net Loss per Share
Antidilutive common stock equivalents	318	3,342	11,950
Convertible preferred stock
Net Loss per Share
Antidilutive common stock equivalents		6,915,525	1,734,517
Common stock warrants - issued
Net Loss per Share
Antidilutive common stock equivalents	18,534	18,534	18,534

Quarterly Financial Data (Una48

Quarterly Financial Data (Unaudited) (Details) - 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 Data
Revenue									$ 0
Operating expenses:
Research and development	$ 4,293	$ 4,279	$ 4,465	$ 3,017	$ 2,822	$ 2,164	$ 3,363	$ 3,851	16,054	$ 12,200	$ 13,136
General and administrative	2,337	1,822	1,387	1,298	664	490	594	539	6,844	2,287	2,141
Loss from operations	(6,630)	(6,101)	(5,852)	(4,315)	(3,486)	(2,654)	(3,957)	(4,390)	(22,898)	(14,487)	(15,277)
Interest and other income, net	67	12		1		35	9	252	80	296	10
Interest expense						(392)	(241)	(212)		(845)	(931)
Net loss	(6,563)	(6,089)	(5,852)	(4,314)	(3,486)	(3,011)	(4,189)	(4,350)	(22,818)	(15,036)	(16,198)
Gain on extinguishment of convertible debt as a capital transaction						378				378
Net loss attributable to common stockholders	$ (6,563)	$ (6,089)	$ (5,852)	$ (4,314)	$ (3,486)	$ (2,633)	$ (4,189)	$ (4,350)	$ (22,818)	$ (14,658)	$ (16,198)
Weighted average shares outstanding - basic and diluted (in shares)	15,452	15,451	4,159	2,209	2,207	343	163	161	9,371	723	155
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (0.42)	$ (0.39)	$ (1.41)	$ (1.95)	$ (1.58)	$ (7.68)	$ (25.70)	$ (27.02)	$ (2.43)	$ (20.27)	$ (104.50)