Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2016	Apr. 30, 2016
Document and Entity Information [Abstract]
Entity Registrant Name	Onconova Therapeutics, Inc.
Entity Central Index Key	0001130598
Document Type	10-Q
Document Period End Date	Mar. 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		27,401,035
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q1

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 16,835	$ 19,799
Receivables	1,368	1,504
Prepaid expenses and other current assets	1,153	1,832
Restricted cash	50	50
Total current assets	19,406	23,185
Property and equipment, net	224	248
Other non-current assets	12	12
Total assets	19,642	23,445
Current liabilities:
Accounts payable	3,296	3,421
Accrued expenses and other current liabilities	3,891	3,729
Deferred revenue	455	455
Total current liabilities	7,642	7,605
Warranty liability	295
Deferred revenue, non-current	4,886	5,000
Total liabilities	$ 12,823	$ 12,605
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.01 par value, 5,000,000 authorized at December 31, 2015 and 2014, none issued and outstanding at December 31, 2015 and 2014
Common stock, $0.01 par value, 75,000,000 authorized at March 31, 2016 and December 31, 2015, 27,401,035 and 25,464,193 shares issued and outstanding at March 31, 2016 and December 31, 2015	$ 274	$ 255
Additional paid in capital	331,528	328,334
Accumulated other comprehensive income	(16)	(22)
Accumulated deficit	(325,797)	(318,557)
Total Onconova Therapeutics, Inc. stockholders' equity	5,989	10,010
Non-controlling interest	830	830
Total stockholders' equity	6,819	10,840
Total liabilities and stockholders' equity	$ 19,642	$ 23,445

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2016	Dec. 31, 2015
Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	27,401,035	25,464,193
Common stock, shares outstanding	27,401,035	25,464,193

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Consolidated Statements of Operations
Revenue	$ 1,474	$ 114
Operating expenses:
General and administrative	3,172	2,965
Research and development	5,822	9,498
Total operating expenses	8,994	12,463
Loss from operations	(7,520)	(12,349)
Change in fair value of warrant liability	271
Other income, net	9	(18)
Net loss	(7,240)	(12,367)
Net loss attributable to non-controlling interest		24
Net loss attributable to Onconova Therapeutics, Inc.	$ (7,240)	$ (12,343)
Net loss per share of common stock, basic and diluted (in dollars per shares)	$ (0.27)	$ (0.57)
Basic and diluted weighted average shares outstanding (in shares)	27,315,899	21,703,173

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Consolidated Statements of Comprehensive Loss
Net loss	$ (7,240)	$ (12,367)
Other comprehensive income, before tax:
Foreign currency translation adjustments, net	6	(30)
Other comprehensive income (loss), net of tax	6	(30)
Comprehensive income	(7,234)	(12,397)
Comprehensive income attributable to non-controlling interest		24
Comprehensive income attributable to Onconova Therapeutics, Inc.	$ (7,234)	$ (12,373)

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid in Capital	Accumulated deficit	Accumulated other comprehensive income (loss)	Non-controlling interest	Total
Increase (Decrease) in Stockholders' Equity (Deficit)
Shares, Outstanding	25,464,193
Balance at Dec. 31, 2015	$ 255	$ 328,334	$ (318,557)	$ (22)	$ 830	$ 10,840
Balance (in shares) at Dec. 31, 2015						25,464,193
Increase (Decrease) in Stockholders' Equity (Deficit)
Net loss			(7,240)			$ (7,240)
Other comprehensive loss				6		6
Stock-based compensation		2,170				2,170
Issuance of common stock, net	$ 19	1,024				1,043
Issuance of common stock, net (in shares)	1,936,842
Balance at Mar. 31, 2016	$ 274	$ 331,528	$ (325,797)	$ (16)	$ 830	$ 6,819
Balance (in shares) at Mar. 31, 2016						27,401,035
Increase (Decrease) in Stockholders' Equity (Deficit)
Shares, Outstanding	27,401,035

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities:
Net loss	$ (7,240)	$ (12,367)
Adjustment to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	24	72
Change in fair value of warrant liabilities	(271)
Stock compensation expense	2,170	1,383
Changes in assets and liabilities:
Receivables	136	98
Prepaid expenses and other current assets	679	495
Restricted cash		75
Accounts payable	(125)	(170)
Accrued expenses	162	675
Other liabilities		(1)
Deferred revenue	(114)	(114)
Net cash used in provided by operating activities	(4,579)	(9,854)
Financing activities:
Proceeds from the sale of common stock and warrants, net of costs	1,609
Net cash provided by financing activities	1,609
Effect of foreign currency translation on cash	6	(30)
Net decrease increase in cash and cash equivalents	(2,964)	(9,884)
Cash and cash equivalents at beginning of period	19,799	43,582
Cash and cash equivalents at end of period	$ 16,835	$ 33,698

Nature of Business	3 Months Ended
Nature of Business	Mar. 31, 2016
Nature of Business
Nature of Business	1. Nature of Business The Company Onconova Therapeutics, Inc. (the “Company”) was incorporated in the State of Delaware on December 22, 1998 and commenced operations on January 1, 1999. The Company’s headquarters are located in Newtown, Pennsylvania. The Company is a clinical-stage biopharmaceutical company focused on discovering and developing novel small molecule drug candidates to treat cancer. Using its proprietary chemistry platform, the Company has created an extensive library of targeted anti-cancer agents designed to work against specific cellular pathways that are important to cancer cells. The Company believes that the drug candidates in its pipeline have the potential to be efficacious in a variety of cancers. The Company has three clinical-stage product candidates and several preclinical programs. In 2012, the Company entered into a development and license agreement with Baxter Healthcare SA, the predecessor in interest to Baxalta GmbH (together with its affiliates, “Baxalta”), pursuant to which the Company granted an exclusive, royalty-bearing license for the research, development, commercialization and manufacture (in specified instances) of rigosertib in all therapeutic indications in Europe. On March 3, 2016, the Company received a notification of Baxalta’s election to terminate the development and license agreement based on a strategic reprioritization review, effective August 30, 2016, at which time the rights the Company licensed to Baxalta will revert to the Company at no cost. In 2011, the Company entered into a license agreement, as subsequently amended, with SymBio Pharmaceuticals Limited (“SymBio”), which grants SymBio certain rights to commercialize rigosertib in Japan and Korea. The Company has retained development and commercialization rights to rigosertib in the rest of the world, including the United States. During 2012, Onconova Europe GmbH was established as a wholly owned subsidiary of the Company for the purpose of further developing business in Europe. In April 2013, GBO, LLC, a Delaware limited liability company, (“GBO”) was formed pursuant to an agreement with GVK Biosciences Private Limited, a private limited company located in India, (“GVK”) to collaborate and develop two programs using the Company’s technology platform. The two preclinical programs sublicensed to GBO have not been developed to clinical stage as initially hoped, and the Company is in discussions with GVK regarding the future of GBO. Liquidity The Company has incurred recurring operating losses since inception. For the three months ended March 31, 2016, the Company incurred a net loss of $7,240,000 and as of March 31, 2016 the Company had generated an accumulated deficit of $325,797,000. The Company anticipates operating losses to continue for the foreseeable future due to, among other things, costs related to research, development of its product candidates and its preclinical programs, strategic alliances and its administrative organization. At March 31, 2016, the Company had cash and cash equivalents of $16,835,000. The Company will require substantial additional financing to fund its ongoing clinical trials and operations, and to continue to execute its strategy. From its inception through July 2013, the Company raised significant capital through the issuance of redeemable convertible preferred stock, par value $0.01 per share, in ten series denominated as Series A through Series J (collectively, the “Preferred Stock”). On July 30, 2013, the Company completed its initial public offering (the “IPO”) of 5,941,667 shares of the Company’s common stock, par value $0.01 per share (“Common Stock”), at a price of $15.00 per share, including 775,000 shares of Common Stock issued upon the exercise in full by the underwriters of their option to purchase additional shares at the same price to cover over-allotments. The Company received net proceeds of $79,811,000 from the sale, net of underwriting discounts and commissions and other estimated offering expenses. Immediately prior to the consummation of the IPO, all outstanding shares of Preferred Stock automatically converted into shares of Common Stock at the applicable conversion ratio then in effect. In October 2014, the Company entered into a sales agreement with Cantor Fitzgerald & Co. (“Cantor”) to create an at-the-market equity program under which the Company had the ability to offer and sell shares of its Common Stock having an aggregate offering price of up to $20,000,000 through Cantor (see Note 12). Net proceeds from sales of Common Stock under this program were $6,018,000 during the year ended December 31, 2015. The sales agreement with Cantor was terminated on January 5, 2016, and there were no sales of Common Stock under this program during the three months ended March 31, 2016. In October 2015 the Company entered into a purchase agreement with Lincoln Park Capital Fund, LLC (“Lincoln Park”). Upon execution of this purchase agreement, Lincoln Park purchased 846,755 shares of the Company’s Common Stock for $1,500,000. Subject to the terms and conditions of the purchase agreement, including the effectiveness of a registration statement covering the resale of the shares, the Company may sell additional shares of its Common Stock, having an aggregate offering price of up to $15,000,000 to Lincoln Park from time to time until December 1, 2018. On January 5, 2016, the Company entered into a securities purchase agreement with an institutional investor providing for the issuance and sale by the Company of 1,936,842 shares of the Company’s Common Stock and warrants to purchase 968,421 shares of the Company’s Common Stock for aggregate net proceeds of $1,609,000. (See Note 12) The Company has and may continue to delay, scale-back, or eliminate certain of its research and development activities and other aspects of its operations until such time as the Company is successful in securing adequate additional funding. The Company is exploring various dilutive and non-dilutive sources of funding, including equity financings, strategic alliances, business development and other sources. The future success of the Company is dependent upon its ability to obtain additional funding. There can be no assurance, however, that the Company will be successful in obtaining such funding in sufficient amounts, on terms acceptable to the Company, or at all. These factors raise substantial doubt about the Company’s ability to continue as a going concern.

Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2016
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The condensed consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States (“GAAP”) for interim financial information. Certain information and footnotes normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The financial statements include the consolidated accounts of the Company, its wholly-owned subsidiary, Onconova Europe GmbH, and GBO. All significant intercompany transactions have been eliminated. Unaudited Interim Financial Information The accompanying condensed consolidated balance sheet as of March 31, 2016, the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2016 and 2015, the consolidated statement of stockholders’ equity for the three months ended March 31, 2016 and the condensed consolidated statements of cash flows for the three months ended March 31, 2016 and 2015 are unaudited. The interim unaudited condensed consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of March 31, 2016 and the results of its operations, and its cash flows for the three months ended March 31, 2016 and 2015. The financial data and other information disclosed in these notes related to the three months ended March 31, 2016 and 2015 are unaudited. The results for the three months ended March 31, 2016 are not necessarily indicative of results to be expected for the year ending December 31, 2016, any other interim periods, or any future year or period. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto for the year ended December 31, 2015 included in the Company’s annual report on Form 10-K filed with the SEC on March 28, 2016. Certain prior year amounts have been reclassified to conform to current period presentation. Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one segment, which is the identification and development of oncology therapeutics. Significant Accounting Policies The Company’s significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2015 included in the Company’s annual report on Form 10-K filed with the SEC on March 28, 2016. Since the date of such financial statements, there have been no changes to the Company’s significant accounting policies. Fair Value Measurements The carrying amounts reported in the accompanying consolidated financial statements for cash and cash equivalents, marketable securities, accounts payable, and accrued liabilities approximate their respective fair values because of the short-term nature of these accounts. The fair value of the warrant liability is discussed in Note 6, “Fair Value Measurements.” Warrant Accounting Common stock warrants are accounted for in accordance with applicable accounting guidance provided in ASC Topic 815, Derivatives and Hedging — Contracts in Entity’s Own Equity (ASC Topic 815), as either derivative liabilities or as equity instruments depending on the specific terms of the warrant agreement. The Company’s warrants (see Note 12) are considered to be derivative warrants and are classified as liabilities and recorded at fair value. The warrants are subject to re-measurement at each balance sheet date and any change in fair value is recognized as a component of change in fair value of warrant liability in the consolidated statements of operations. The Company uses the Black-Scholes pricing model to value the related derivative warrant liability. The warrants are classified as Level 3 liabilities (see Note 6 for a discussion of the fair value hierarchy). Recent Accounting Pronouncements In May 2014, the FASB issued guidance on revenue from contracts with customers that will supersede most current revenue recognition guidance. The underlying principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance permits the use of either a retrospective or cumulative effect transition method. In July 2015, the FASB approved a one-year deferral of the effective date of the guidance to interim and annual periods beginning on or after December 15, 2017. Early adoption is permitted but not before the original effective date of December 15, 2016. The Company has not yet selected a transition method and is currently evaluating the impact of the amended guidance on the Company’s consolidated financial position, results of operations and related disclosures. In August 2014, the FASB issued guidance on determining when and how to disclose going-concern uncertainties in the financial statements. The new standard requires management to perform interim and annual assessments of an entity’s ability to continue as a going concern within one year of the date the financial statements are issued. An entity must provide certain disclosures if conditions or events raise substantial doubt about the entity’s ability to continue as a going concern. The guidance applies to all entities and is effective for annual periods ending after December 15, 2016, and interim periods thereafter, with early adoption permitted. The Company is evaluating the potential impact of the new guidance on its consolidated financial statements. In March 2016, the FASB issued guidance which clarifies the implementation guidance on principal versus agent considerations in the revenue recognition standard issued in May 2014. The new standard clarifies how an entity should identify the unit of accounting (i.e. the specified good or service) for the principal versus agent evaluation and how it should apply the control principle to certain types of arrangements. The effective date and transition requirements are the same as the effective date and transition requirements in the May 2014 revenue standard (Accounting Standards Codification 606). The Company is currently assessing the adoption methodology and the impact the adoption of these ASUs will have on its consolidated financial position, results of operations and related disclosures.

Revenue

3 Months Ended

Mar. 31, 2016

Revenue

Revenue

3. Revenue

The Company recognized revenue under its license and collaboration agreements with Baxalta and SymBio as follows:

	Three Months Ended March 31,
	2016		2015

Baxalta	$	1,221,000	$	—
Symbio	253,000		114,000

	$	1,474,000	$	114,000

See Note 8, “License and Collaboration Agreements,” for a further discussion of the agreements with Baxalta and SymBio.

Net Loss Per Share of Common Stock

3 Months Ended

Mar. 31, 2016

Net Loss Per Share of Common Stock

Net Loss Per Share of Common Stock

4. Net Loss Per Share of Common Stock

The following potentially dilutive securities outstanding at March 31, 2016 and 2015 have been excluded from the computation of diluted weighted average shares outstanding, as they would be antidilutive:

	March 31,
	2016	2015
Warrants	968,421	4,597
Stock options	5,671,213	4,570,386

	6,639,634	4,574,983

Balance Sheet Detail

3 Months Ended

Mar. 31, 2016

Balance Sheet Detail

Balance Sheet Detail

5. Balance Sheet Detail

Receivables:

	March 31,		December 31,
	2016		2015

Amounts due from Baxalta	$	1,221,000	$	1,384,000
Other	147,000		120,000

	$	1,368,000	$	1,504,000

Prepaid expenses and other current assets:

	March 31,		December 31,
	2016		2015

Research and development	$	514,000	$	1,018,000
Manufacturing	126,000		168,000
Insurance	307,000		451,000
Other	206,000		195,000

	$	1,153,000	$	1,832,000

Property and equipment:

	March 31,			December 31,
	2016			2015

Property and equipment	$	2,228,000		$	2,228,000
Accumulated depreciation	(2,004,000		)	(1,980,000		)

	$	224,000		$	248,000

Accrued expenses and other current liabilities:

	March 31,		December 31,
	2016		2015

Research and development	$	2,133,000	$	2,979,000
Employee compensation	1,566,000		438,000
Professional fees	192,000		306,000
Other	—		6,000

	$	3,891,000	$	3,729,000

Fair Value Measurements

3 Months Ended

Mar. 31, 2016

Fair Value Measurements

Fair Value Measurements

6. Fair Value Measurements

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date.

During the year ended December 31, 2015 the Company had no assets or liabilities requiring fair value measurements. On January 5, 2016, the Company entered into a securities purchase agreement (“Securities Purchase Agreement”) with an institutional investor providing for the issuance and sale by the Company of 1,936,842 shares of the Company’s Common Stock, at a purchase price of $0.95 per share and warrants to purchase up to 968,421 shares of the Company’s Common Stock (the “Warrants”) for aggregate gross proceeds of $1,840,000 (see Note 12).

The Company utilizes a valuation hierarchy for disclosure of the inputs to the valuations used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. Level 3 inputs are unobservable inputs based on the Company’s own assumptions used to measure assets and liabilities at fair value. A financial asset or liability’s classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement.

The Company had no assets or liabilities classified as Level 1 or Level 2. The warrant liability (see Note 12) is classified as Level 3.

The Company has classified the warrants as a liability and has re-measured the liability to estimated fair value at March 31, 2016, using the Black-Scholes option pricing model with the following assumptions:

		March 31, 2016
Risk-free interest rate		1.38%
Expected volatility		79.76%
Expected term		5.28 years
Expected dividend yield		0%

Expected volatility is based on the historical volatility of the Company’s common stock since its IPO in July 2013.

The following fair value hierarchy table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of March 31, 2016:

	Fair Value Measurement as of March 31, 2016
	Level 1		Level 2		Level 3		Balance

Warrant liability	$	—	$	—	$	295,000	$	295,000

Total	$	—	$	—	$	295,000	$	295,000

The following table presents a reconciliation of the Company’s liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the three months ended March 31, 2016:

	Warrant Liability
Balance at December 31, 2015	$	—
Issuance of warrants	566,000

Change in fair value upon re-measurement	(271,000		)

Balance at March 31, 2016	$	295,000

There were no transfers between Level 1 and Level 2 in any of the periods reported.

- Definition

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

+ References + Details

Stock-Based Compensation

3 Months Ended

Mar. 31, 2016

Stock-Based Compensation

Stock-Based Compensation

7. Stock-Based Compensation

In January 2008, the board of directors approved the 2007 Equity Compensation Plan (the “2007 Plan”), which amended, restated and renamed the Company’s 1999 Stock Based Compensation Plan (the “1999 Plan”), which provided for the granting of incentive and nonqualified stock options and restricted stock to its employees, directors and consultants at the discretion of the board of directors.

Further, in July 2013, the Company’s board of directors and stockholders approved the 2013 Equity Compensation Plan (the ‘‘2013 Plan’’), which amended, restated and renamed the 2007 Plan. Under the 2013 Plan, the Company may grant incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units, deferred share awards, performance awards and other equity-based awards to employees, directors and consultants. The Company initially reserved 6,107,831 shares of Common Stock for issuance, subject to adjustment as set forth in the 2013 Plan. The 2013 Plan includes an evergreen provision, pursuant to which the maximum aggregate number of shares that may be issued under the 2013 Plan is increased on the first day of each fiscal year by the lesser of (a) a number of shares equal to four percent (4%) of the issued and outstanding Common Stock of the Company, without duplication, (b) 2,000,000 shares and (c) such lesser number as determined by the Company’s board of directors, subject to specified limitations. At March 31, 2016, there were 1,859,089 shares available for future issuance.

Stock-based compensation expense includes stock options granted to employees and non-employees and has been reported in the Company’s statements of operations and comprehensive loss in either research and development expenses or general and administrative expenses depending on the function performed by the optionee. No net tax benefits related to the stock-based compensation costs have been recognized since the Company’s inception. The Company recognized stock-based compensation expense as follows for the three months ended March 31, 2016 and 2015:

	Three months ended March 31,
	2016		2015
General and Administrative	$	970,000	$	760,000
Research and development	1,200,000		623,000

	$	2,170,000	$	1,383,000

A summary of stock option activity for the three months ended March 31, 2016 is as follows:

	Options Outstanding
	Shares Available for Grant		Number of Shares		Weighted- Average Exercise Price	Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Balance, December 31, 2015	1,354,133		5,157,602		8.56	7.46	—
Authorized	1,018,567		—
Granted	(929,567	)	929,567		0.65
Exercised	—		—
Forfeited	415,956		(415,956	)	8.57

Balance, March 31, 2016	1,859,089		5,671,213		7.26	7.70	—
Vested or expected to vest, March 31, 2016			5,593,994		7.26	7.70	—
Exercisable, March 31, 2016			3,806,024		8.81	7.07	—

Information with respect to stock options outstanding and exercisable at March 31, 2016 is as follows:

Exercise Price	Shares	Exercisable
$ 0.65	920,588	363,298
$ 1.48 - $2.69	879,182	318,767
$ 3.98 - $4.52	866,691	460,476
$ 5.76 - $7.53	920,913	878,872
$ 13.28 - $13.32	860,810	797,985
$ 13.48 - $14.75	558,931	398,466
$ 15.00 - $29.14	664,098	588,160

	5,671,213	3,806,024

Options granted after April 23, 2013

The Company accounts for all stock-based payments made after April 23, 2013 to employees and directors using an option pricing model for estimating fair value. Accordingly, stock-based compensation expense is measured based on the estimated fair value of the awards on the date of grant, net of forfeitures. Compensation expense is recognized for the portion that is ultimately expected to vest over the period during which the recipient renders the required services to the Company using the straight-line single option method. In accordance with authoritative guidance, the fair value of non-employee stock based awards is re-measured as the awards vest, and the resulting increase in fair value, if any, is recognized as expense in the period the related services are rendered.

The Company uses the Black-Scholes option-pricing model to estimate the fair value of stock options at the grant date. The Black-Scholes model requires the Company to make certain estimates and assumptions, including estimating the fair value of the Company’s common stock, assumptions related to the expected price volatility of the Company’s stock, the period during which the options will be outstanding, the rate of return on risk-free investments and the expected dividend yield for the Company’s stock.

As of March 31, 2016, there was $4,199,000 of unrecognized compensation expense related to the unvested stock options issued from April 24, 2013 through March 31, 2016, which is expected to be recognized over a weighted-average period of approximately 2.16 years.

The weighted-average assumptions underlying the Black-Scholes calculation of grant date fair value include the following:

		Three months ended March 31, 2016
Risk-free interest rate		1.45%
Expected volatility		78.34%
Expected term		5.38 years
Expected dividend yield		0%
Weighted average grant date fair value		$ 0.41

The weighted-average valuation assumptions were determined as follows:

Risk-free interest rate: The Company based the risk-free interest rate on the interest rate payable on U.S. Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected option term.

Expected term of options: Due to its lack of sufficient historical data, the Company estimates the expected life of its employee stock options using the “simplified” method, as prescribed in Staff Accounting Bulletin (SAB) No. 107, whereby the expected life equals the arithmetic average of the vesting term and the original contractual term of the option.

Expected stock price volatility: Expected volatility is based on the historical volatility of the Company’s common stock since its IPO in July 2013.

Expected annual dividend yield: The Company has never paid, and does not expect to pay in the foreseeable future, dividends. Accordingly, the Company assumed an expected dividend yield of 0.0%.

Estimated forfeiture rate: The Company’s estimated annual forfeiture rate on stock option grants was 4.14% in 2016, 2015 and 2014, based on the historical forfeiture experience.

Options granted through April 23, 2013

At certain times throughout the Company’s history, the chairman of the Company’s board of directors, who is also a significant stockholder of the Company (the “Significant Holder”), has afforded option holders the opportunity for liquidity in transactions in which options were exercised and the shares of Common Stock issued in connection therewith were simultaneously purchased by the Significant Holder (each, a “Purchase Transaction”). Because the Company had established a pattern of providing cash settlement alternatives for option holders, the Company has accounted for its stock-based compensation awards as liability awards, the fair value of which is then re-measured at each balance sheet date.

On April 23, 2013, the Company distributed a notification letter to all equity award holders under the Company’s 2007 Equity Compensation Plan (the “2007 Plan”) advising them that Purchase Transactions would no longer occur, unless, at the time of a Purchase Transaction, the option holder has held the Common Stock issued upon exercise of options for a period of greater than six months prior to selling such Common Stock to the Significant Holder and that any such sale to the Significant Holder would be at the fair value of the Common Stock on the date of such sale. Based on these new criteria for Purchase Transactions, the Company remeasured options outstanding under the 2007 Plan as of April 23, 2013 to their intrinsic value and reclassified such options from liabilities to stockholders’ deficit within the Company’s consolidated balance sheets, which amounted to $14,482,000. As of March 31, 2016, there was $88,000 of unrecognized compensation expense related to these unvested awards, which is expected to be recognized over a weighted-average period of approximately 0.70 years.

Research Agreements	3 Months Ended
Research Agreements	Mar. 31, 2016
Research Agreements
Research Agreements	8. Research Agreements The Company has entered into various licensing and right-to-sublicense agreements with educational institutions for the exclusive use of patents and patent applications, as well as any patents that may develop from research being conducted by such educational institutions in the field of anticancer therapy, genes and proteins. Results from this research have been licensed to the Company pursuant to these agreements. Under one of these agreements with Temple University (“Temple”), the Company is required to make annual maintenance payments to Temple and royalty payments based upon a percentage of sales generated from any products covered by the licensed patents, with minimum specified royalty payments. As no sales had been generated through March 31, 2016 under the licensed patents, the Company has not incurred any royalty expenses related to this agreement. In addition, the Company is required to pay Temple 25% of any sublicensing fees received by the Company. The Company signed a funding agreement with the Leukemia and Lymphoma Society (“LLS”) in May 2010, which was amended in January 2013, to fund the development of rigosertib (the “LLS-funded Research Program”). Under the LLS-funded Research Program, the Company was entitled to receive milestone payments of up to $8,000,000 through 2013 in connection with the proposed clinical trial to be conducted, ONTIME, after which LLS was not obligated to fund any further amounts. Under the terms of the funding agreement, if the LLS-funded Research Program lead to approval of rigosertib by the regulatory authorities, the Company would have been required to proceed with commercialization of the licensed product or repay the amount funded. LLS was entitled to receive regulatory and commercial milestone payments and royalties from the Company based on the Company’s net sales of the licensed product after regulatory approval, with the amount of such milestone payments and royalties not to exceed three times the amount funded. During the year ended December 31, 2012, in connection with the execution of the Baxter agreement, the Company paid $1,000,000 to LLS. This payment reduced the maximum potential milestone and royalty payment obligation under this agreement to $23,000,000. No further payments would be due to LLS if the LLS-funded Research Program did not meet its clinical endpoints for safety and efficacy. As a result of the potential obligation to repay the funds under this arrangement, the $8,000,000 of milestone payments received was initially recorded as deferred revenue. The Company received guidance from regulatory authorities during 2015 that the LLS-funded Research Program was not sufficient to support a regulatory submission. Based on the guidance and the commencement of the INSPIRE trial during the fourth quarter of 2015, the company determined that the research program covered by the LLS funding agreement was unsuccessful and, as a result, the funding received non-repayable. Accordingly, the Company recognized the $8.0 million of deferred revenue during the quarter ended December 31, 2015.

License and Collaboration Agreements	3 Months Ended
License and Collaboration Agreements	Mar. 31, 2016
License and Collaboration Agreements
License and Collaboration Agreements	9. License and Collaboration Agreements Baxalta Agreement In September 2012, the Company entered into a development and license agreement with Baxter Healthcare SA, the predecessor in interest to Baxalta GmbH (together with its affiliates, “Baxalta”), pursuant to which the Company granted an exclusive, royalty-bearing license for the research, development, commercialization and manufacture (in specified instances) of rigosertib in all therapeutic indications in Europe. In accordance with this agreement, the Company received an upfront cash payment of $50,000,000 in 2012. On March 3, 2016, the Company received a notification of Baxalta’s election to terminate the development and license agreement based on a strategic reprioritization review, effective August 30, 2016. The agreement with Baxalta remains in effect pending the effectiveness of such termination. In accordance with the terms of the Baxalta agreement, upon termination, the rights licensed to Baxalta will revert to the Company at no cost. Additionally, any rights the Company had to funding, pre-commercial milestone payments and royalties from Baxalta will terminate in accordance with the agreement. Among other things, the Baxalta agreement contemplated development of rigosertib IV in higher-risk MDS patients, through the Company’s ONTIME trial and, potentially, additional Phase 3 clinical trials. The ONTIME trial did not achieve its primary endpoint and the Company is continuing the development of rigosertib IV in higher-risk MDS patients through its INSPIRE trial. In accordance with the agreement, the Company elected to have Baxalta fund fifty percent of the costs of the INSPIRE trial, up to $15.0 million. The Company recorded revenue of $1,221,000 during the three months ended March 31, 2016 related to Baxalta’s funding of the INSPIRE trial. The Company has overall responsibility for the trial, including determination of the trial specifications, selection of third party service providers and payment for all services and materials. Baxalta terminated the development and license agreement after commencement of the INSPIRE trial and after the Company had elected to have Baxalta reimburse the Company for costs incurred in running this trial, per contract. The Company will attempt to maximize Baxalta’s financial support for the INSPIRE trial, but there can be no assurances regarding the amount of funds which the Company will receive from Baxalta. As of February 29, 2016, Baxalta beneficially owned 2,603,295 shares of the Company’s Common Stock. SymBio Agreement In July 2011, the Company entered into a license agreement with SymBio, as subsequently amended, granting SymBio an exclusive, royalty-bearing license for the development and commercialization of rigosertib in Japan and Korea. Under the SymBio license agreement, SymBio is obligated to use commercially reasonable efforts to develop and obtain market approval for rigosertib inside the licensed territory and the Company has similar obligations outside of the licensed territory. The Company has also entered into an agreement with SymBio providing for it to supply SymBio with development-stage product. Under the SymBio license agreement, the Company also agreed to supply commercial product to SymBio under specified terms that will be included in a commercial supply agreement to be negotiated prior to the first commercial sale of rigosertib. The supply of development-stage product and the supply of commercial product will be at the Company’s cost plus a defined profit margin. Sales of development-stage product have been de minimis. The Company has additionally granted SymBio a right of first negotiation to license or obtain the rights to develop and commercialize compounds having a chemical structure similar to rigosertib in the licensed territory. Under the terms of the SymBio license agreement, the Company received an upfront payment of $7,500,000. The Company is eligible to receive milestone payments of up to an aggregate of $22,000,000 from SymBio upon the achievement of specified development and regulatory milestones for specified indications. Of the regulatory milestones, $5,000,000 is due upon receipt of marketing approval in the United States for rigosertib IV in higher-risk MDS patients, $3,000,000 is due upon receipt of marketing approval in Japan for rigosertib IV in higher-risk MDS patients, $5,000,000 is due upon receipt of marketing approval in the United States for rigosertib oral in lower-risk MDS patients, and $5,000,000 is due upon receipt of marketing approval in Japan for rigosertib oral in lower-risk MDS patients. Furthermore, upon receipt of marketing approval in the United States and Japan for an additional specified indication of rigosertib, which the Company is currently not pursuing, an aggregate of $4,000,000 would be due. In addition to these pre-commercial milestones, the Company is eligible to receive tiered milestone payments based upon annual net sales of rigosertib by SymBio of up to an aggregate of $30,000,000. Further, under the terms of the SymBio license agreement, SymBio will make royalty payments to the Company at percentage rates ranging from the mid-teens to 20% based on net sales of rigosertib by SymBio. Royalties will be payable under the SymBio agreement on a country-by-country basis in the licensed territory, until the later of the expiration of marketing exclusivity in those countries, a specified period of time after first commercial sale of rigosertib in such country, or the expiration of all valid claims of the licensed patents covering rigosertib or the manufacture or use of rigosertib in such country. If no valid claim exists covering the composition of matter of rigosertib or the use of or treatment with rigosertib in a particular country before the expiration of the royalty term, and specified competing products achieve a specified market share percentage in such country, SymBio’s obligation to pay the Company royalties will continue at a reduced royalty rate until the end of the royalty term. In addition, the applicable royalties payable to the Company may be reduced if SymBio is required to pay royalties to third-parties for licenses to intellectual property rights necessary to develop, use, manufacture or commercialize rigosertib in the licensed territory. The license agreement with SymBio will remain in effect until the expiration of the royalty term. However, the SymBio license agreement may be terminated earlier due to the uncured material breach or bankruptcy of a party, or force majeure. If SymBio terminates the license agreement in these circumstances, its licenses to rigosertib will survive, subject to SymBio’s milestone and royalty obligations, which SymBio may elect to defer and offset against any damages that may be determined to be due from the Company. In addition, the Company may terminate the license agreement in the event that SymBio brings a challenge against it in relation to the licensed patents, and SymBio may terminate the license agreement without cause by providing the Company with written notice within a specified period of time in advance of termination. The Company determined that the deliverables under the SymBio agreement include the exclusive, royalty-bearing, sublicensable license to rigosertib, the research and development services to be provided by the Company and its obligation to serve on a joint committee. The Company concluded that the license did not have standalone value to SymBio and was not separable from the research and development services, because of the uncertainty of SymBio’s ability to develop rigosertib in the SymBio territory on its own and the uncertainty of SymBio’s ability to sublicense rigosertib and recover a substantial portion of the original upfront payment of $7,500,000 paid by SymBio to the Company. The supply of rigosertib for SymBio’s commercial requirements is contingent upon the receipt of regulatory approvals to commercialize rigosertib in Japan and Korea. Because the Company’s commercial supply obligation was contingent upon the receipt of future regulatory approvals, and there were no binding commitments or firm purchase orders pending for commercial supply at or near the execution of the agreement, the commercial supply obligation is deemed to be contingent and is not valued as a deliverable under the SymBio agreement. If SymBio orders the supplies from the Company, the Company expects the pricing for this supply to equal its third-party manufacturing cost plus a pre-negotiated percentage, which will not result in a significant incremental discount to market rates. Due to the lack of standalone value for the license, research and development services, and joint committee obligation, the upfront payment is being recognized ratably using the straight line method through December 2027, the expected term of the agreement.

Preclinical Collaboration	3 Months Ended
Preclinical Collaboration	Mar. 31, 2016
Preclinical Collaboration
Preclinical Collaboration	10. Preclinical Collaboration In December 2012, the Company agreed to form GBO, an entity owned by the Company and GVK. The purpose of GBO is to collaborate on and develop two programs through filing of an investigational new drug application and/or conducting proof of concept studies using the Company’s technology platform. If a program failure occurs for one or both programs, the Company may contribute additional assets to GBO to establish a replacement program or programs. During 2013, GVK made an initial capital contribution of $500,000 in exchange for a 10% interest in GBO, and the Company made an initial capital contribution of a sublicense to all the intellectual property controlled by the Company related to the two specified programs in exchange for a 90% interest. Under the terms of the agreement, GVK may make additional capital contributions. The GVK percentage interest in GBO may change from the initial 10% to up to 50%, depending on the amount of its total capital contributions. During November 2014, GVK made an additional capital contribution of $500,000 which increased its interest in GBO to 17.5%. The Company evaluates its variable interests in GBO on a quarterly basis and has determined that it is the primary beneficiary. For thirty days following the 15-month anniversary of the commencement of either of the two programs, the Company will have an option to (i) cancel the license and (ii) purchase all rights in and to that program. There are three of these buy-back scenarios depending on the stage of development of the underlying assets. In addition, upon the occurrence of certain events, namely termination of the Company’s participation in the programs either with or without a change in control, GVK will be entitled to purchase or obtain the Company’s interest in GBO. GVK will have operational control of GBO and the Company will have strategic and scientific control. The two preclinical programs sublicensed to GBO have not been developed to clinical stage as initially hoped, and the Company is in discussions with GVK regarding the future of GBO.

Related-Party Transactions	3 Months Ended
Related-Party Transactions	Mar. 31, 2016
Related-Party Transactions
Related-Party Transactions	11. Related-Party Transactions The Company is party to a research agreement, as amended, with Mount Sinai School of Medicine (“Mount Sinai”), with which a member of the Company’s board of directors and a significant stockholder is associated. Mount Sinai is undertaking research on behalf of the Company on the terms set forth in the agreements. Mount Sinai, in connection with the Company, will prepare applications for patents generated from the research. Results from all projects will belong exclusively to Mount Sinai, but the Company will have an exclusive option to license any inventions. Payments to Mount Sinai under this research agreement for the three months ended March 31, 2016 and 2015 were $0 and $357,000, respectively. At March 31, 2016 and December 31, 2015, the Company had $187,000 and $0, respectively, payable to Mount Sinai under this agreement. The Company has entered into a consulting agreement with a member of its board of directors, who is also a significant stockholder. The board member provides consulting services to the Company on the terms set forth in the agreement. Payments to this board member for the three months ended March 31, 2016 and 2015 were $33,000 and $49,000, respectively. At March 31, 2016 and December 31, 2015, the Company had no outstanding amounts payable under this agreement.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Securities Registrations and Sales Agreements	3 Months Ended
Securities Registrations and Sales Agreements	Mar. 31, 2016
Securities Registrations and Sales Agreements
Securities Registrations and Sales Agreements	12. Securities Registrations and Sales Agreements In October 2014, the Company entered into a sales agreement with Cantor Fitzgerald & Co. (“Cantor”) to create an at-the-market equity program under which the Company from time to time was able to offer and sell shares of its Common Stock through Cantor. A registration statement (Form S-3 No. 333-199219) covering the shares offered through the Cantor program and other securities was filed with the SEC on October 8, 2014 and became effective on November 20, 2014. During the year ended December 31, 2015, 2,715,165 shares were sold under the Cantor sales agreement for net proceeds of $6,018,000. The Cantor sales agreement was terminated on January 5, 2016, and there were no sales of Common Stock under this program during the three months ended March 31, 2016. On October 8, 2015, the Company entered into a purchase agreement and a registration rights agreement with Lincoln Park. A registration statement (Form S-1 No. 333-207533) covering the offer and resale by Lincoln Park of shares of Common Stock sold by the Company to Lincoln Park was filed with the SEC on October 20, 2015 and became effective on November 3, 2015. Subject to the terms and conditions of the purchase agreement, including the effectiveness of a registration statement covering the resale of the shares, the Company may sell additional shares of its Common Stock, having an aggregate offering price of up to $15,000,000 to Lincoln Park from time to time until December 1, 2018. Upon execution of the Lincoln Park purchase agreement, Lincoln Park made an initial purchase of 846,755 shares of the Company’s Common Stock for $1,500,000. Subject to the terms and conditions of the purchase agreement, including the effectiveness of a registration statement covering the resale of the shares, the Company has the right to sell to and Lincoln Park is obligated to purchase up to an additional $15,000,000 of shares of Common Stock, subject to certain limitations, from time to time until December 1, 2018. The Company may direct Lincoln Park, at its sole discretion and subject to certain conditions, to purchase up to 100,000 shares of Common Stock on any business day, increasing to up to 250,000 shares depending upon the closing sale price of the Common Stock (such purchases, “Regular Purchases”). However, in no event shall a Regular Purchase be more than $1,000,000. The purchase price of shares of Common Stock related to the future funding will be based on the prevailing market prices of such shares at the time of sales. In addition, the Company may direct Lincoln Park to purchase additional amounts as accelerated purchases if on the date of a Regular Purchase the closing sale price of the Common Stock is not below the threshold price as set forth in the Purchase Agreement. The Company’s sales of shares of Common Stock to Lincoln Park under the Purchase Agreement are limited to no more than the number of shares that would result in the beneficial ownership by Lincoln Park and its affiliates, at any single point in time, of more than 4.99% of the then-outstanding shares of the Common Stock, which limit will increase to 9.99% on May 1, 2016. Pursuant to the terms of the Lincoln Park purchase agreement and to comply with the listing rules of the NASDAQ Stock Market, the number of shares issued to Lincoln Park thereunder shall not exceed 19.99% of the Company’s shares outstanding on October 8, 2015 unless the approval of the Company’s stockholders is obtained. This limitation shall not apply if the average price paid for all shares issued and sold under the purchase agreement is equal to or greater than $1.556. The Company is not required or permitted to issue any shares of Common Stock under the Lincoln Park purchase agreement if such issuance would breach the Company’s obligations under the listing rules of the NASDAQ Stock Market. As consideration for entering into the purchase agreement, the Company issued to Lincoln Park 200,000 shares of Common Stock. Lincoln Park represented to the Company, among other things, that it was an “accredited investor” (as such term is defined in Rule 501(a) of Regulation D under the Securities Act of 1933, as amended (the “Securities Act”), and the Company sold the securities in reliance upon an exemption from registration contained in Section 4(2) under the Securities Act. The securities sold may not be offered or sold in the United States absent registration or an applicable exemption from registration requirements. The net proceeds to the Company under the Lincoln Park purchase agreement will depend on the frequency and prices at which the Company may sell shares of Common Stock to Lincoln Park. The Company expects that the proceeds received from the initial purchase and any additional proceeds from future sales to Lincoln Park will be used to fund the development of the Company’s clinical and preclinical programs, for other research and development activities and for general corporate purposes. On January 5, 2016, the Company entered into a securities purchase agreement (“Securities Purchase Agreement”) with an institutional investor providing for the issuance and sale by the Company of 1,936,842 shares of the Company’s Common Stock, at a purchase price of $0.95 per share and warrants to purchase up to 968,421 shares of the Company’s Common Stock (the “Warrants”) for aggregate gross proceeds of $1,840,000. The Warrants will be exercisable from July 11, 2016 through July 11, 2021 at an exercise price of $1.15 per share of Common Stock, subject to customary adjustments. Net proceeds from the sale of the Common Stock and Warrants (not including any future proceeds from the exercise of the Warrants) were approximately $1,609,000 after deducting certain fees due to the placement agent and the Company’s estimated transaction expenses. The net proceeds received by the Company from the transactions will be used to fund the development of the Company’s clinical and preclinical programs, for other research and development activities and for general corporate purposes. The shares of Common Stock sold by the Company pursuant to the Securities Purchase Agreement were sold pursuant to an effective shelf registration statement on Form S-3, which was initially filed with the SEC on October 8, 2014 and subsequently declared effective on November 20, 2014 (File No. 333- 199219). The Warrants were issued and sold without registration under the Securities Act in reliance on the exemptions provided by Section 4(a)(2) of the Securities Act and/or Regulation D promulgated thereunder and in reliance on similar exemptions under applicable state laws. Accordingly, the Warrants and the shares of Common Stock underlying the Warrants may not be offered or sold except pursuant to an effective registration statement under the Securities Act or pursuant to an available exemption from, or in a transaction not subject to, the registration requirements of the Securities Act and in accordance with applicable state securities laws.

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2016
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States (“GAAP”) for interim financial information. Certain information and footnotes normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The financial statements include the consolidated accounts of the Company, its wholly-owned subsidiary, Onconova Europe GmbH, and GBO. All significant intercompany transactions have been eliminated.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying condensed consolidated balance sheet as of March 31, 2016, the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2016 and 2015, the consolidated statement of stockholders’ equity for the three months ended March 31, 2016 and the condensed consolidated statements of cash flows for the three months ended March 31, 2016 and 2015 are unaudited. The interim unaudited condensed consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of March 31, 2016 and the results of its operations, and its cash flows for the three months ended March 31, 2016 and 2015. The financial data and other information disclosed in these notes related to the three months ended March 31, 2016 and 2015 are unaudited. The results for the three months ended March 31, 2016 are not necessarily indicative of results to be expected for the year ending December 31, 2016, any other interim periods, or any future year or period. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto for the year ended December 31, 2015 included in the Company’s annual report on Form 10-K filed with the SEC on March 28, 2016. Certain prior year amounts have been reclassified to conform to current period presentation.
Segment Information	Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one segment, which is the identification and development of oncology therapeutics.
Significant Accounting Policies	Significant Accounting Policies The Company’s significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2015 included in the Company’s annual report on Form 10-K filed with the SEC on March 28, 2016. Since the date of such financial statements, there have been no changes to the Company’s significant accounting policies.
Fair Value Measurements	Fair Value Measurements The carrying amounts reported in the accompanying consolidated financial statements for cash and cash equivalents, marketable securities, accounts payable, and accrued liabilities approximate their respective fair values because of the short-term nature of these accounts. The fair value of the warrant liability is discussed in Note 6, “Fair Value Measurements.”
Stock Warrants	Warrant Accounting Common stock warrants are accounted for in accordance with applicable accounting guidance provided in ASC Topic 815, Derivatives and Hedging — Contracts in Entity’s Own Equity (ASC Topic 815), as either derivative liabilities or as equity instruments depending on the specific terms of the warrant agreement. The Company’s warrants (see Note 12) are considered to be derivative warrants and are classified as liabilities and recorded at fair value. The warrants are subject to re-measurement at each balance sheet date and any change in fair value is recognized as a component of change in fair value of warrant liability in the consolidated statements of operations. The Company uses the Black-Scholes pricing model to value the related derivative warrant liability. The warrants are classified as Level 3 liabilities (see Note 6 for a discussion of the fair value hierarchy).
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued guidance on revenue from contracts with customers that will supersede most current revenue recognition guidance. The underlying principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance permits the use of either a retrospective or cumulative effect transition method. In July 2015, the FASB approved a one-year deferral of the effective date of the guidance to interim and annual periods beginning on or after December 15, 2017. Early adoption is permitted but not before the original effective date of December 15, 2016. The Company has not yet selected a transition method and is currently evaluating the impact of the amended guidance on the Company’s consolidated financial position, results of operations and related disclosures. In August 2014, the FASB issued guidance on determining when and how to disclose going-concern uncertainties in the financial statements. The new standard requires management to perform interim and annual assessments of an entity’s ability to continue as a going concern within one year of the date the financial statements are issued. An entity must provide certain disclosures if conditions or events raise substantial doubt about the entity’s ability to continue as a going concern. The guidance applies to all entities and is effective for annual periods ending after December 15, 2016, and interim periods thereafter, with early adoption permitted. The Company is evaluating the potential impact of the new guidance on its consolidated financial statements. In March 2016, the FASB issued guidance which clarifies the implementation guidance on principal versus agent considerations in the revenue recognition standard issued in May 2014. The new standard clarifies how an entity should identify the unit of accounting (i.e. the specified good or service) for the principal versus agent evaluation and how it should apply the control principle to certain types of arrangements. The effective date and transition requirements are the same as the effective date and transition requirements in the May 2014 revenue standard (Accounting Standards Codification 606). The Company is currently assessing the adoption methodology and the impact the adoption of these ASUs will have on its consolidated financial position, results of operations and related disclosures.

Revenue (Tables)

3 Months Ended

Mar. 31, 2016

Revenue

Recognized revenue under license and collaboration agreements

	Three Months Ended March 31,
	2016		2015

Baxalta	$	1,221,000	$	—
Symbio	253,000		114,000

	$	1,474,000	$	114,000

Net Loss Per Share of Common Stock (Tables)

3 Months Ended

Mar. 31, 2016

Net Loss Per Share of Common Stock

Schedule of antidilutive securities which have been excluded from the computation of diluted weighted average shares outstanding

	March 31,
	2016	2015
Warrants	968,421	4,597
Stock options	5,671,213	4,570,386

	6,639,634	4,574,983

Balance Sheet Detail (Tables)

3 Months Ended

Mar. 31, 2016

Balance Sheet Detail

Schedule of receivables

	March 31,		December 31,
	2016		2015

Amounts due from Baxalta	$	1,221,000	$	1,384,000
Other	147,000		120,000

	$	1,368,000	$	1,504,000

Schedule of prepaid expenses and other current assets

	March 31,		December 31,
	2016		2015

Research and development	$	514,000	$	1,018,000
Manufacturing	126,000		168,000
Insurance	307,000		451,000
Other	206,000		195,000

	$	1,153,000	$	1,832,000

Schedule of property and equipment

	March 31,			December 31,
	2016			2015

Property and equipment	$	2,228,000		$	2,228,000
Accumulated depreciation	(2,004,000		)	(1,980,000		)

	$	224,000		$	248,000

Schedule of accrued expenses and other current liabilities

	March 31,		December 31,
	2016		2015

Research and development	$	2,133,000	$	2,979,000
Employee compensation	1,566,000		438,000
Professional fees	192,000		306,000
Other	—		6,000

	$	3,891,000	$	3,729,000

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2016

Fair Value Measurements

Schedule of Black-Scholes option pricing model assumptions

		March 31, 2016
Risk-free interest rate		1.38%
Expected volatility		79.76%
Expected term		5.28 years
Expected dividend yield		0%

Schedule of financial assets and liabilities measured at fair value on a recurring basis

	Fair Value Measurement as of March 31, 2016
	Level 1		Level 2		Level 3		Balance

Warrant liability	$	—	$	—	$	295,000	$	295,000

Total	$	—	$	—	$	295,000	$	295,000

Schedule of reconciliation of liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3)

	Warrant Liability
Balance at December 31, 2015	$	—
Issuance of warrants	566,000

Change in fair value upon re-measurement	(271,000		)

Balance at March 31, 2016	$	295,000

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

Stock-Based Compensation

Schedule of stock-based compensation expense

	Three months ended March 31,
	2016		2015
General and Administrative	$	970,000	$	760,000
Research and development	1,200,000		623,000

	$	2,170,000	$	1,383,000

Schedule of stock option activity

A summary of stock option activity for the three months ended March 31, 2016 is as follows:

	Options Outstanding
	Shares Available for Grant		Number of Shares		Weighted- Average Exercise Price	Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Balance, December 31, 2015	1,354,133		5,157,602		8.56	7.46	—
Authorized	1,018,567		—
Granted	(929,567	)	929,567		0.65
Exercised	—		—
Forfeited	415,956		(415,956	)	8.57

Balance, March 31, 2016	1,859,089		5,671,213		7.26	7.70	—
Vested or expected to vest, March 31, 2016			5,593,994		7.26	7.70	—
Exercisable, March 31, 2016			3,806,024		8.81	7.07	—

Schedule of information with respect to stock options outstanding and exercisable

Information with respect to stock options outstanding and exercisable at March 31, 2016 is as follows:

Exercise Price	Shares	Exercisable
$ 0.65	920,588	363,298
$ 1.48 - $2.69	879,182	318,767
$ 3.98 - $4.52	866,691	460,476
$ 5.76 - $7.53	920,913	878,872
$ 13.28 - $13.32	860,810	797,985
$ 13.48 - $14.75	558,931	398,466
$ 15.00 - $29.14	664,098	588,160

	5,671,213	3,806,024

Schedule of weighted-average assumptions used for estimating the fair value of the stock compensation granted

		Three months ended March 31, 2016
Risk-free interest rate		1.45%
Expected volatility		78.34%
Expected term		5.38 years
Expected dividend yield		0%
Weighted average grant date fair value		$ 0.41

Nature of Business - Liquidity - Financial Statement Items (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Nature of Business
Net loss	$ (7,240)	$ (12,367)
Accumulated deficit	(325,797)		$ (318,557)
Cash and cash equivalents	$ 16,835	$ 33,698	$ 19,799	$ 43,582

Nature of Business - Liquidity - Sale of Stock (Details) $ / shares in Units, $ in Thousands		3 Months Ended
	Jul. 30, 2013 USD ($) $ / shares shares	Mar. 31, 2016 class $ / shares	Dec. 31, 2015 $ / shares
Sale of Securities
Preferred stock, par value per share (in dollars per share)		$ 0.01
Number of series denominated as Series A through Series J preferred stock \| class		10
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
IPO
Sale of Securities
Issuance of stock (in shares) \| shares	5,941,667
Common stock, par value (in dollars per share)	$ 0.01
Price per share (in dollars per share)	$ 15.00
Proceeds from initial public offering of common stock, net of issuance costs \| $	$ 79,811
Over-allotment option
Sale of Securities
Issuance of stock (in shares) \| shares	775,000

Nature of Business - Liquidity - Sales and Purchase Agreements (Details) - USD ($)		1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 08, 2015	Oct. 31, 2014	Mar. 31, 2016	Dec. 31, 2015
Sale of Securities
Net proceeds from sales of common stock			$ 1,609,000
At-the-market equity program
Sale of Securities
Issuance of stock (in shares)				2,715,165
Aggregate offering price		$ 20,000,000
Net proceeds from sales of common stock			$ 0	$ 6,018,000
Purchase agreement \| Lincoln Park
Sale of Securities
Issuance of stock (in shares)	846,755
Aggregate offering price	$ 15,000,000
Net proceeds from sales of common stock	$ 1,500,000

Nature of Business - Liquidity - Securities Purchase Agreement (Details) - Securities Purchase Agreement $ in Thousands	Jan. 05, 2016 USD ($) shares
Sale of Securities
Issuance of stock (in shares)	1,936,842
Aggregate net proceeds \| $	$ 1,609
Common Stock Warrants
Sale of Securities
Share of common stock warrants will purchase (in shares)	968,421

Summary of Significant Accounting Policies (Details)	3 Months Ended
Summary of Significant Accounting Policies (Details)	Mar. 31, 2016 segment
Segment Information
Number of operating segments	1

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Mar. 31, 2015
Revenue
Revenues	$ 1,474	$ 114
License and collaboration
Revenue
Revenues	1,474	114
Baxalta \| License and collaboration
Revenue
Revenues	1,221
SymBio \| License and collaboration
Revenue
Revenues	$ 253	$ 114

Net Loss Per Share of Common Stock (Details) - shares	3 Months Ended
Net Loss Per Share of Common Stock (Details) - shares	Mar. 31, 2016	Mar. 31, 2015
Potentially dilutive securities outstanding excluded from the computation of diluted weighted average shares as they would be antidilutive
Potentially dilutive securities outstanding excluded from the computation of diluted weighted average shares	6,639,634	4,574,983
Warrant
Potentially dilutive securities outstanding excluded from the computation of diluted weighted average shares as they would be antidilutive
Potentially dilutive securities outstanding excluded from the computation of diluted weighted average shares	968,421	4,597
Stock options
Potentially dilutive securities outstanding excluded from the computation of diluted weighted average shares as they would be antidilutive
Potentially dilutive securities outstanding excluded from the computation of diluted weighted average shares	5,671,213	4,570,386

Balance Sheet Detail - Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Receivables:
Amounts due from Baxalta	$ 1,221	$ 1,384
Other	147	120
Receivables, Net, Current, Total	$ 1,368	$ 1,504

Balance Sheet Detail - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Prepaid expenses and other current assets:
Research and development	$ 514	$ 1,018
Manufacturing	126	168
Insurance	307	451
Other	206	195
Total	$ 1,153	$ 1,832

Balance Sheet Detail - Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Property and equipment:
Property and equipment	$ 2,228	$ 2,228
Accumulated depreciation	(2,004)	(1,980)
Property and equipment, net	$ 224	$ 248

Balance Sheet Detail - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Accrued expenses
Research and development	$ 2,133	$ 2,979
Employee compensation	1,566	438
Professional fees	192	306
Other		6
Total	$ 3,891	$ 3,729

Fair Value Measurements - Securities Purchase Agreement (Details) - Securities Purchase Agreement $ / shares in Units, $ in Thousands	Jan. 05, 2016 USD ($) $ / shares shares
Sale of Securities
Issuance of stock (in shares)	1,936,842
Share price (in dollars per share) \| $ / shares	$ 0.95
Aggregate gross proceeds \| $	$ 1,840
Common Stock Warrants
Sale of Securities
Share of common stock warrants will purchase (in shares)	968,421

Fair Value Measurements - Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Level 1
Fair Value Measurements
Assets	$ 0	$ 0
Liabilities	0	0
Level 2
Fair Value Measurements
Assets	0	0
Liabilities	$ 0	$ 0

Fair Value Measurements - Fair Value Assumptions (Details)	3 Months Ended
	Mar. 31, 2016
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option pricing model
Risk-free interest rate (as a percent)	1.38%
Expected volatility (as a percent)	79.76%
Expected term	5 years 3 months 11 days
Expected dividend yield (as a percent)	0.00%

Fair Value Measurements - Fair Value Hierarchy Table (Details) - Recurring basis $ in Thousands	Mar. 31, 2016 USD ($)
Liabilities measured at fair value
Warrant liability	$ 295
Total	295
Level 3
Liabilities measured at fair value
Warrant liability	295
Total	$ 295

Fair Value Measurements - Reconciliation of Level 3 Liabilities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Reconciliation of the warrant liability measured at fair value
Issuance of warrants	$ 566
Change in fair value upon re-measurement	(271)
Balance at the end of the period	$ 295

Fair Value Measurements - Transfers (Details) $ in Thousands	Mar. 31, 2016 USD ($)
Fair Value Measurements
Amount of transfers of assets out of Level 1 into Level 2	$ 0
Amount of transfers of assets out of Level 2 into Level 1	0
Amount of transfers of liabilities out of Level 1 into Level 2	0
Amount of transfers of liabilities out of Level 2 into Level 1	$ 0

Stock-Based Compensation - Common Stock Reserved for Issuance and Shares Available for Future Issuance (Details) - Stock options - shares	Mar. 31, 2016	Dec. 31, 2015	Jul. 31, 2013
Stock-Based Compensation
Common Stock reserved for issuance (in shares)			6,107,831
Evergreen provision, percentage of issued and outstanding common stock (as a percent)	4.00%
Evergreen provision, shares (in shares)	2,000,000
Common Stock available for future issuance (in shares)	1,859,089	1,354,133

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Stock-Based Compensation
Net tax benefits related to the stock-based compensation costs	$ 0
Total stock-based compensation	2,170	$ 1,383
General and administrative
Stock-Based Compensation
Total stock-based compensation	970	760
Research and development
Stock-Based Compensation
Total stock-based compensation	$ 1,200	$ 623

Stock-Based Compensation - Summary of Stock Option Activity (Details) - Stock options - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Shares Available for Grant
Balance at the beginning of the period (in shares)	1,354,133
Authorized (in shares)	1,018,567
Granted (in shares)	(929,567)
Forfeited (in shares)	(415,956)
Balance at the end of the period (in shares)	1,859,089	1,354,133
Number of Shares
Balance at the beginning of the period (in shares)	5,157,602
Granted (in shares)	(929,567)
Forfeited (in shares)	(415,956)
Balance at the end of the period (in shares)	5,671,213	5,157,602
Vested or expected to vest at the end of the period (in shares)	5,593,994
Exercisable at the end of the period (in shares)	3,806,024
Weighted-Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 8.56
Granted (in dollars per share)	0.65
Forfeited (in dollars per share)	8.57
Balance at the end of the period (in dollars per share)	7.26	$ 8.56
Vested or expected to vest at the end of the period (in dollars per share)	7.26
Exercisable at the end of the period (in dollars per share)	$ 8.81
Additional Disclosures
Weighted average remaining contractual term	7 years 8 months 12 days	7 years 5 months 16 days
Weighted average remaining contractual term of options vested or expected to vest	7 years 8 months 12 days
Weighted average remaining contractual term of options exercisable	7 years 26 days

Stock-Based Compensation - Stock Options Outstanding and Exercisable (Details) - Stock options	3 Months Ended
	Mar. 31, 2016 $ / shares shares
Share-Based Compensation
Shares (in shares)	5,671,213
Exercisable (in shares)	3,806,024
Exercise Price Range $0.65
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) \| $ / shares	$ 0.65
Exercise price, upper range limit (in dollars per share) \| $ / shares	$ 0.65
Shares (in shares)	920,588
Exercisable (in shares)	363,298
Exercise Price Range $1.48 - $2.69
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) \| $ / shares	$ 1.48
Exercise price, upper range limit (in dollars per share) \| $ / shares	$ 2.69
Shares (in shares)	879,182
Exercisable (in shares)	318,767
Exercise Price Range $3.98 - $4.52
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) \| $ / shares	$ 3.98
Exercise price, upper range limit (in dollars per share) \| $ / shares	$ 4.52
Shares (in shares)	866,691
Exercisable (in shares)	460,476
Exercise Price Range $5.76 - $7.53
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) \| $ / shares	$ 5.76
Exercise price, upper range limit (in dollars per share) \| $ / shares	$ 7.53
Shares (in shares)	920,913
Exercisable (in shares)	878,872
Exercise Price Range $13.28 - $13.32
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) \| $ / shares	$ 13.28
Exercise price, upper range limit (in dollars per share) \| $ / shares	$ 13.32
Shares (in shares)	860,810
Exercisable (in shares)	797,985
Exercise Price Range $13.48 - $14.75
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) \| $ / shares	$ 13.48
Exercise price, upper range limit (in dollars per share) \| $ / shares	$ 14.75
Shares (in shares)	558,931
Exercisable (in shares)	398,466
Exercise Price Range $15.00 - $29.14
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) \| $ / shares	$ 15.00
Exercise price, upper range limit (in dollars per share) \| $ / shares	$ 29.14
Shares (in shares)	664,098
Exercisable (in shares)	588,160

Stock-Based Compensation - Options Granted after April 23, 2013 - Unrecognized Compensation Expense (Details) - Options granted after April 23, 2013 - Stock options $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Stock-Based Compensation
Unrecognized compensation expense related to unvested stock options	$ 4,199
Weighted-average period for recognizing unrecognized compensation expense related to unvested stock options (in years)	2 years 1 month 28 days

Stock-Based Compensation - Options Granted after April 23, 2013 - Fair Value Assumptions (Details) - Options granted after April 23, 2013 - Stock options	3 Months Ended
	Mar. 31, 2016 $ / shares
Assumptions used
Risk-free interest rates (as a percent)	1.45%
Expected volatility (as a percent)	78.34%
Expected term	5 years 4 months 17 days
Expected dividend yield (as a percent)	0.00%
Weighted-average grant fair value (in dollars per share)	$ 0.41
Annualized forfeiture rate (as a percent)	4.14%

Stock-Based Compensation - Options Granted through April 23, 2013 (Details) - Stock options - 2007 Plan - Options granted through April 23, 2013 - USD ($) $ in Thousands		3 Months Ended
	Apr. 23, 2013	Mar. 31, 2016
Stock-Based Compensation
Reclassification to stockholders' deficit	$ 14,482
Unrecognized compensation expense related to unvested stock options		$ 88
Weighted-average period for recognizing unrecognized compensation expense related to unvested stock options (in years)		8 months 12 days

Research Agreements (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Research Agreements (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2012	Dec. 31, 2015	May. 31, 2010
Research Agreements
Deferred revenue, non-current	$ 4,886		$ 5,000
Temple
Research Agreements
Sales generated from products covered by the licensed patents	$ 0
Percentage of sublicensing fees received to be paid by the entity	25.00%
LLS \| Rigosertib
Research Agreements
Payments made in connection with the collaboration agreement		$ 1,000
Potential milestone payments				$ 8,000
Potential milestone and royalty payment obligation	$ 23,000		23,000
Deferred revenue, non-current			$ 8,000
Deferred revenue recognized	$ 8,000

License and Collaboration Agreements - Baxalta Agreement (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
	Feb. 28, 2014	Sep. 30, 2012	Mar. 31, 2016	Mar. 31, 2015	Feb. 29, 2016	Dec. 31, 2015
License and collaboration agreements
Revenue			$ 1,474	$ 114
Common stock issued (in shares)			27,401,035			25,464,193
Beneficial owner \| Baxalta
License and collaboration agreements
Common stock issued (in shares)					2,603,295
License agreement \| Rigosertib \| Baxalta
License and collaboration agreements
Revenue			$ 1,221
Upfront payment		$ 50,000
License agreement \| Rigosertib \| Baxalta \| Rigosertib IV in higher risk MDS patients
License and collaboration agreements
Funding percentage to the entity (as a percent)	50.00%
Cost funded to the entity	$ 15,000

License and Collaboration Agreements - SymBio Agreement (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Jul. 31, 2011	Mar. 31, 2016	Mar. 31, 2015
License and collaboration agreements
Revenue		$ 1,474	$ 114
License agreement \| Rigosertib \| SymBio
License and collaboration agreements
Upfront payment	$ 7,500
Aggregate milestone payments	22,000
Aggregate potential milestone payments based on annual net sales of rigosertib	$ 30,000
Percentage of royalty payments based on net sales of rigosertib (as a percent)	20.00%
Supply commitment agreement \| Rigosertib \| SymBio
License and collaboration agreements
Binding commitments	$ 0
United States and Japan \| License agreement \| Rigosertib \| SymBio
License and collaboration agreements
Aggregate milestone payments due upon receipt of marketing approval for an additional indication	4,000
United States \| License agreement \| Rigosertib \| SymBio \| MDS IV indication
License and collaboration agreements
Regulatory milestones payments due upon receipt of marketing approval for indication	5,000
United States \| License agreement \| Rigosertib \| SymBio \| Rigosertib oral in lower risk MDS patients
License and collaboration agreements
Regulatory milestones payments due upon receipt of marketing approval for indication	5,000
Japan \| License agreement \| Rigosertib \| SymBio \| MDS IV indication
License and collaboration agreements
Regulatory milestones payments due upon receipt of marketing approval for indication	3,000
Japan \| License agreement \| Rigosertib \| SymBio \| Rigosertib oral in lower risk MDS patients
License and collaboration agreements
Regulatory milestones payments due upon receipt of marketing approval for indication	$ 5,000

Preclinical Collaboration (Details) - GBO $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
Preclinical Collaboration (Details) - GBO $ in Thousands	Nov. 30, 2014 USD ($)	Mar. 31, 2016 item	Dec. 31, 2013 USD ($)	Dec. 31, 2012 Program
Preclinical Collaboration
Number of new programs to be collaborated and developed \| Program				2
Ownership interest in the joint venture (as a percent)			90.00%
Period for which option available to cancel the license and purchase all rights following 15-month anniversary of commencement of program		30 days
Period of anniversary following which option available to cancel the license and purchase all rights for thirty days		15 months
Number of buy-back scenarios \| item		3
GVK BIO
Preclinical Collaboration
Initial capital contribution			$ 500
Ownership interest in the joint venture (as a percent)	17.50%		10.00%
Additional capital contributions	$ 500
GVK BIO \| Minimum
Preclinical Collaboration
Ownership interest in the joint venture (as a percent)			10.00%
GVK BIO \| Maximum
Preclinical Collaboration
Ownership interest in the joint venture (as a percent)			50.00%

Related-Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Mount Sinai
Related-party transactions
Payments to related party	$ 0	$ 357
Amounts due to related party	187		$ 0
Member of board of directors
Related-party transactions
Payments to related party	33	$ 49
Amounts due to related party	$ 0		$ 0

Securities Registrations and Sales Agreements - Sales and Purchase Agreements (Details) - USD ($)			1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 05, 2016	Oct. 08, 2015	Oct. 31, 2014	Mar. 31, 2016	Dec. 31, 2015
Securities Registrations and Sales Agreement
Net proceeds from sales of common stock				$ 1,609,000
At-the-market equity program
Securities Registrations and Sales Agreement
Aggregate offering price			$ 20,000,000
Issuance of stock (in shares)					2,715,165
Net proceeds from sales of common stock				$ 0	$ 6,018,000
Securities Purchase Agreement
Securities Registrations and Sales Agreement
Issuance of stock (in shares)	1,936,842
Price per share (in dollars per share)	$ 0.95
Lincoln Park \| Purchase agreement
Securities Registrations and Sales Agreement
Aggregate offering price		$ 15,000,000
Issuance of stock (in shares)		846,755
Net proceeds from sales of common stock		$ 1,500,000
Business day limit (in shares)		100,000
Business day limit contingent upon the closing price of the stock (in shares)		250,000
Regular purchase, one day limit		$ 1,000,000
Beneficial ownership percentage (as a percent)		4.99%
Beneficial ownership percentage after 180 days (as a percent)		9.99%
Maximum shares issued as a percentage of shares outstanding (as a percent)		19.99%
Minimum average price per share (in dollars per share)		$ 1.556
Stock issued as consideration (in shares)		200,000

Securities Registrations and Sales Agreements - Securities Purchase Agreement (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Jan. 05, 2016	Mar. 31, 2016
Sale of Securities
Value of stock issued		$ 1,043
Net proceeds from sales of common stock		$ 1,609
Securities Purchase Agreement
Sale of Securities
Issuance of stock (in shares)	1,936,842
Share price (in dollars per share)	$ 0.95
Value of stock issued	$ 1,840
Aggregate net proceeds	$ 1,609
Securities Purchase Agreement \| Common Stock Warrants
Sale of Securities
Share of common stock warrants will purchase (in shares)	968,421
Exercise price (in dollars per share)	$ 1.15

Nature of Business - The Company - Clinical-stage Product Candidates (Details)	Mar. 31, 2016 item
Nature of Business
Number of clinical-stage product candidates	3