Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2015	Mar. 15, 2016	Jun. 30, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	Onconova Therapeutics, Inc.
Entity Central Index Key	0001130598
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Smaller Reporting Company
Entity Public Float			$ 30.1
Entity Common Stock, Shares Outstanding		27,401,035
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 19,799	$ 43,582
Receivables	1,504	132
Prepaid expenses and other current assets	1,832	3,066
Restricted cash	50	125
Total current assets	23,185	46,905
Property and equipment, net	248	420
Other non-current assets	12	12
Total assets	23,445	47,337
Current liabilities:
Accounts payable	3,421	4,027
Accrued expenses and other current liabilities	3,729	5,777
Deferred revenue	455	455
Total current liabilities	7,605	10,259
Deferred revenue, non-current	5,000	13,455
Other		1
Total liabilities	$ 12,605	$ 23,715
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 December 31, 2015 and 2014, 25,464,193 and 21,703,173 shares issued and outstanding at December 31, 2015 and 2014	$ 255	$ 217
Additional paid in capital	328,334	317,122
Accumulated other comprehensive income	(22)	(13)
Accumulated deficit	(318,557)	(294,578)
Total Onconova Therapeutics, Inc. stockholders' equity	10,010	22,748
Non-controlling interest	830	874
Total stockholders' equity	10,840	23,622
Total liabilities and stockholders' equity	$ 23,445	$ 47,337

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
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	25,464,193	21,703,173
Common stock, shares outstanding	25,464,193	21,703,173

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Consolidated Statements of Operations
Revenue	$ 11,456	$ 800
Operating expenses:
General and administrative	9,533	15,119
Research and development	25,895	49,425
Total operating expenses	35,428	64,544
Loss from operations	(23,972)	(63,744)
Change in fair value of warrant liability		20
Other income, net	(35)	(52)
Net loss before income taxes	(24,007)	(63,776)
Income taxes	16	19
Net loss	(24,023)	(63,795)
Net loss attributable to non-controlling interest	44	113
Net loss attributable to Onconova Therapeutics, Inc.	$ (23,979)	$ (63,682)
Net loss per share of common stock, basic and diluted (in dollars per shares)	$ (1.05)	$ (2.94)
Basic and diluted weighted average shares outstanding (in shares)	22,739,760	21,653,536

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Consolidated Statements of Comprehensive Loss
Net loss	$ (24,023)	$ (63,795)
Other comprehensive income, before tax:
Foreign currency translation adjustments, net	(9)	(14)
Other comprehensive income (loss), net of tax	(9)	(14)
Comprehensive income (loss)	(24,032)	(63,809)
Comprehensive income (loss) attributable to non-controlling interest	44	113
Comprehensive income (loss) attributable to Onconova Therapeutics, Inc.	$ (23,988)	$ (63,696)

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
Balance at Dec. 31, 2013	$ 215	$ 311,093	$ (230,896)	$ 1	$ 487	$ 80,900
Balance (in shares) at Dec. 31, 2013	21,467,482
Increase (Decrease) in Stockholders' Equity (Deficit)
Net loss			(63,682)		(113)	(63,795)
Contribution from non-controlling interest					500	500
Other comprehensive loss				(14)		(14)
Exercise of stock options	$ 2	961				963
Exercise of stock options (in shares)	235,691
Stock-based compensation		5,068				5,068
Balance at Dec. 31, 2014	$ 217	317,122	(294,578)	(13)	874	$ 23,622
Balance (in shares) at Dec. 31, 2014	21,703,173					21,703,173
Increase (Decrease) in Stockholders' Equity (Deficit)
Net loss			(23,979)		(44)	$ (24,023)
Other comprehensive loss				(9)		(9)
Stock-based compensation		3,786				3,786
Issuance of common stock, net	$ 38	7,426				7,464
Issuance of common stock, net (in shares)	3,761,920
Common stock surrendered (in shares)	(900)
Balance at Dec. 31, 2015	$ 255	$ 328,334	$ (318,557)	$ (22)	$ 830	$ 10,840
Balance (in shares) at Dec. 31, 2015	25,464,193					25,464,193

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net loss	$ (24,023)	$ (63,795)
Adjustment to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	150	434
Loss on asset disposal	22
Change in fair value of warrant liabilities		(20)
Treasury note discount amortization		(6)
Stock compensation expense	3,786	5,068
Changes in assets and liabilities:
Receivables	(1,372)	(31)
Prepaid expenses and other current assets	1,234	1,220
Restricted cash	(75)
Accounts payable	(606)	317
Accrued expenses and other current liabilities	(2,048)	(43)
Other liabilities	(1)	(5)
Deferred revenue	(8,455)	(787)
Net cash used in provided by operating activities	(31,238)	(57,648)
Investing activities:
Payments for purchase of property and equipment		(228)
Maturities of marketable securities		40,000
Net cash provided by investing activities		39,772
Financing activities:
Proceeds from the sale of common stock, net of costs	7,464
Proceeds from the exercise of stock options		963
Contribution from non-controlling interest		500
Net cash provided by financing activities	7,464	1,463
Effect of foreign currency translation on cash	(9)	(14)
Net decrease increase in cash and cash equivalents	(23,783)	(16,427)
Cash and cash equivalents at beginning of period	43,582	60,009
Cash and cash equivalents at end of period	$ 19,799	$ 43,582

Nature of Business	12 Months Ended
Nature of Business	Dec. 31, 2015
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. To accelerate and broaden the development of rigosertib, the Company's most advanced product candidate, the Company entered into a development and license agreement in 2012 with Baxter Healthcare SA ("BHSA"). Subsequently, Baxter International Inc.("Baxter") assigned the development and license agreement from BHSA to Baxalta GmbH ("Baxalta"), in preparation for the anticipated spin-off by Baxter of Baxalta Incorporated. The spin-off was effective on July 1, 2015. The Company understands that Baxalta is an indirect wholly-owned subsidiary of Baxalta Incorporated. The development and license agreement granted Baxalta an exclusive, royalty-bearing license for the research, development, commercialization and manufacture (in specified instances) of rigosertib in all therapeutic indications in Europe (the "Baxalta Territory"). 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. 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 year ended December 31, 2015, the Company incurred a net loss of $24,023,000 and as of December 31, 2015 the Company had generated an accumulated deficit of $318,557,000. 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. The Company will require substantial additional financing to fund its 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 ("Series A Preferred Stock" through "Series J Preferred Stock," respectively, and 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 (the "Sales Agreement") with Cantor Fitzgerald & Co. ("Cantor") to create an at-the-market equity program under which the Company from time to time may offer and sell shares of its Common Stock, having an aggregate offering price of up to $20,000,000 through Cantor (see Note 15). Net proceeds from sales of Common Stock under this program were $6,018,000 during the year ended December 31, 2015. The Cantor Sales Agreement was terminated on January 5, 2016. In October 2015 the Company entered into a purchase agreement (the "Purchase Agreement") with Lincoln Park Capital Fund, LLC ("Lincoln Park"). Upon signing of the Purchase Agreement, Lincoln Park purchased 846,755 shares of the Company's Common Stock for $1,500,000. Under the Purchase Agreement, the Company may from time to time, after the effectiveness of a registration statement covering such shares, offer and sell additional shares of its Common Stock, having an aggregate offering price of up to $15,000,000 to Lincoln Park. On January 5, 2016, the Company entered into a Securities Purchase Agreement with an institutional investor (the "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 $1,646,000. (See Note 16) During 2015, the Company implemented cost-reduction programs to reduce its operating losses. These programs may delay, scale-back, or eliminate certain of the Company's 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 also exploring various dilutive and non-dilutive sources of funding, including equity and debt financings, strategic alliances, business development and other sources. Such financings would be used to fund future research and development programs, including clinical trials for which the Company does not currently have the resources to fund, and the future success of the Company is dependent upon its ability to obtain additional financing. There can be no assurance, however, that the Company will be successful in obtaining such financing at the level needed to complete its research and development programs, on terms acceptable to the Company, or at all, or that the Company will obtain approvals necessary to market its products or achieve profitability or sustainable, positive cash flow. These factors raise substantial doubt about the Company's ability to continue as a going concern.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2015

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States ("GAAP"). 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.

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.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses, other comprehensive income and related disclosures. On an ongoing basis, management evaluates its estimates, including estimates related to clinical trial accruals, warrant liability, and allocation of consideration to multiple element collaborative arrangements. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.

Concentrations of Credit Risk and Off-Balance Sheet Risk

Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash, cash equivalents, restricted cash and marketable securities. The Company maintains a portion of its cash and cash equivalent balances in the form of money market accounts with financial institutions that management believes are creditworthy. Marketable securities are invested in U.S. Treasury obligations. The Company has no financial instruments with off-balance sheet risk of loss.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original or remaining maturity from the date of purchase of three months or less to be cash equivalents. Cash and cash equivalents include bank demand deposits, marketable securities with maturities of three months or less at purchase, and money market funds that invest primarily in certificates of deposit, commercial paper and U.S. government and U.S. government agency obligations. Cash equivalents are reported at fair value.

Fair Value of Financial Instruments

The carrying amounts reported in the accompanying consolidated financial statements for cash and cash equivalents, accounts payable and accrued liabilities approximate their respective fair values because of the short-term nature of these accounts.

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation. Property and equipment are depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized over the useful life of the asset or the lease term, whichever is shorter. Maintenance and repairs are expensed as incurred. The following estimated useful lives were used to depreciate the Company's assets:

		Estimated Useful Life
Lab equipment		5 - 6 years
Software		3 years
Computer and office equipment		5 - 6 years
Leasehold improvements		Shorter of the lease term or estimated useful life

Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized.

The Company reviews long-lived assets for impairment when events or changes in circumstances indicate that the carrying value of the assets may not be recoverable. Recoverability is measured by comparison of the assets' book value to future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceeds their fair value, which is measured based on the projected discounted future net cash flows generated from the assets. No impairment losses have been recorded through December 31, 2015.

Restricted Cash

Under one of the Company's office leases, the Company is required to provide the landlord a $125,000 letter of credit, which is secured by cash collateral recorded as restricted cash on the consolidated balance sheet as of December 31, 2014. The letter of credit expired in March 2015 and the restriction on cash was discontinued. In February 2015, the Company was required to provide a $50,000 letter of credit to a surety company related to the Company's international shipments, which is secured by cash collateral recorded as restricted cash on the consolidated balance sheet as of December 31, 2015.

Foreign Currency Translation

The reporting currency of the Company and its U.S. subsidiaries is the U.S. dollar. The functional currency of the Company's non-U.S. subsidiary is the local currency. Assets and liabilities of the foreign subsidiary are translated into U.S. dollars based on exchange rates at the end of the period. Revenues and expenses are translated at average exchange rates during the reporting period. Gains and losses arising from the translation of assets and liabilities are included as a component of accumulated other comprehensive income. Gains and losses resulting from foreign currency transactions are reflected within the Company's results of operations. The Company has not utilized any foreign currency hedging strategies to mitigate the effect of its foreign currency exposure.

Revenue Recognition

The Company's revenue is generated primarily through collaborative research and license agreements. The terms of these agreements contain multiple deliverables which may include (i) licenses, (ii) research and development activities, (iii) participation in joint steering committees and (iv) product supply. The terms of these agreements may include nonrefundable upfront license fees, payments for research and development activities, payments based upon the achievement of certain milestones, royalty payments based on product sales derived from the collaboration, and payments for supplying product. In all instances, revenue is recognized only when the price is fixed or determinable, persuasive evidence of an arrangement exists, delivery has occurred or the services have been rendered, collectability of the resulting receivable is reasonably assured, and the Company has fulfilled its performance obligations under the contract.

For arrangements with multiple elements, the Company recognizes revenue in accordance with the Financial Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") No. 2009-13, Multiple-Deliverable Revenue Arrangements ("ASU 2009-13"), which provides guidance for separating and allocating consideration in a multiple element arrangement. The selling prices of deliverables under an arrangement may be derived using third-party evidence ("TPE"), or a best estimate of selling price ("BESP"), if vendor-specific objective evidence of selling price ("VSOE") is not available. The objective of BESP is to determine the price at which the Company would transact a sale if the element within the license agreement was sold on a standalone basis. Establishing BESP involves management's judgment and considers multiple factors, including market conditions and company-specific factors, including those factors contemplated in negotiating the agreements, as well as internally developed models that include assumptions related to market opportunity, discounted cash flows, estimated development costs, probability of success and the time needed to commercialize a product candidate pursuant to the license. In validating the BESP, management considers whether changes in key assumptions used to determine the BESP will have a significant effect on the allocation of the arrangement consideration between the multiple deliverables. The Company may use third-party valuation specialists to assist it in determining BESP. Deliverables under the arrangement are separate units of accounting if (i) the delivered item has value to the customer on a standalone basis and (ii) if the arrangement includes a general right of return relative to the delivered item, delivery or performance of the undelivered item is considered probable and substantially within the Company's control. The arrangement consideration that is fixed or determinable at the inception of the arrangement is allocated to the separate units of accounting based on their relative selling prices. The appropriate revenue recognition model is applied to each element and revenue is accordingly recognized as each element is delivered. Management exercises significant judgment in determining whether a deliverable is a separate unit of accounting.

In determining the separate units of accounting, the Company evaluates whether the license has standalone value to the collaborator based on consideration of the relevant facts and circumstances for each arrangement. Factors considered in this determination include the research and development capabilities of the collaborator and the availability of relevant research expertise in the marketplace. In addition, the Company considers whether or not (i) the collaborator could use the license for its intended purpose without the receipt of the remaining deliverables, (ii) the value of the license was dependent on the undelivered items and (iii) the collaborator or other vendors could provide the undelivered items.

Under a collaborative research and license agreement, a steering committee is typically responsible for overseeing the general working relationships, determining the protocols to be followed in the research and development performed and evaluating the results from the continued development of the product. The Company evaluates whether its participation in joint steering committees is a substantive obligation or whether the services are considered inconsequential or perfunctory. The factors the Company considers in determining if its participation in a joint steering committee is a substantive obligation include: (i) which party negotiated or requested the steering committee, (ii) how frequently the steering committee meets, (iii) whether or not there are any penalties or other recourse if the Company does not attend the steering committee meetings, (iv) which party has decision making authority on the steering committee and (v) whether or not the collaborator has the requisite experience and expertise associated with the research and development of the licensed intellectual property.

Whenever the Company determines that an element is delivered over a period of time, revenue is recognized using either a proportional performance model, if a pattern of performance can be determined or a straight-line model over the period of performance, which is typically the research and development term. Progress achieved under the Company's various clinical research organization contracts are typically used as the measure of performance when applying the proportional performance method. At the end of each reporting period, the Company reassesses its cumulative measure of performance and makes appropriate adjustments, if necessary. The Company recognizes revenue using the proportional performance model whenever the Company is able to make reasonably reliable estimates of the level of effort required to complete its performance obligations under an arrangement. Revenue recognized under the proportional performance model at each reporting period is determined by multiplying the total expected payments under the contract (excluding royalties and payments contingent upon achievement of milestones) by the ratio of the level of effort incurred to date to the estimated total level of effort required to complete the performance obligations under the arrangement. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the proportional performance model as of each reporting period. Alternatively, if the Company is not able to make reasonably reliable estimates of the level of effort required to complete its performance obligations under an arrangement, then revenue under the arrangement is recognized on a straight-line basis over the period expected to be required to complete the Company's performance obligations.

Incentive milestone payments may be triggered either by the results of the Company's research efforts or by events external to it, such as regulatory approval to market a product or attaining agreed-upon sales levels. Consideration that is contingent upon achievement of a milestone is recognized in its entirety as revenue in the period in which the milestone is achieved, but only if the consideration earned from the achievement of a milestone meets all the criteria for the milestone to be considered substantive at the inception of the arrangement. For a milestone to be considered substantive, the consideration earned by achieving the milestone must (i) be commensurate with either the Company's performance to achieve the milestone or the enhancement of the value of the item delivered as a result of a specific outcome resulting from the Company's performance to achieve the milestone, (ii) relate solely to past performance and (iii) be reasonable relative to all deliverables and payment terms in the collaboration agreement.

For events for which the occurrences are contingent solely upon the passage of time or are the result of performance by a third party, the contingent payments will be recognized as revenue when payments are earned, the amounts are fixed and determinable and collectability is reasonably assured.

Royalties are recorded as earned in accordance with the contract terms when third party sales can be reliably measured and collectability is reasonably assured.

Research and Development Expenses

Research and development costs are charged to expense as incurred. These costs include, but are not limited to, license fees related to the acquisition of in-licensed products; employee-related expenses, including salaries, benefits and travel; expenses incurred under agreements with contract research organizations and investigative sites that conduct clinical trials and preclinical studies; the cost of acquiring, developing and manufacturing clinical trial materials; facilities, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, insurance and other supplies; and costs associated with preclinical activities and regulatory operations.

Costs for certain development activities, such as clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to the Company by its vendors with respect to their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid or accrued research and development expense, as the case may be.

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources.

Income Taxes

The Company accounts for income taxes under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. The deferred tax asset primarily includes net operating loss and tax credit carry forwards, accrued expenses not currently deductible and the cumulative temporary differences related to certain research and patent costs, which have been charged to expense in the accompanying statements of operations but have been recorded as assets for income tax purposes. The portion of any deferred tax asset for which it is more likely than not that a tax benefit will not be realized must then be offset by recording a valuation allowance. A full valuation allowance has been established against all of the deferred tax assets (see Note 7, "Income Taxes"), as it is more likely than not that these assets will not be realized given the Company's history of operating losses. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not to be sustained upon examination based on the technical merits of the position. The amount for which an exposure exists is measured as the largest amount of benefit determined on a cumulative probability basis that the Company believes is more likely than not to be realized upon ultimate settlement of the position.

Stock-Based Compensation Expense

The Company applies the provisions of FASB Accounting Standards Codification ("ASC") Topic 718, Compensation—Stock Compensation ("ASC 718"), which requires the measurement and recognition of compensation expense for all stock-based awards made to employees and non-employees, including employee stock options.

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"), 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") (See Note 8). Because the Company had established a pattern of providing cash settlement alternatives for option holders, the Company accounted for its stock-based compensation awards as liability awards. The Company measured liability awards based on the award's intrinsic value on the grant date and then re-measured them at each reporting date until the date of settlement. Compensation expense was recognized on a straight-line basis over the requisite service period for each separately vesting portion of the award. Compensation expense for each period until settlement was based on the change in intrinsic value (or a portion of the change in intrinsic value, depending on the percentage of the requisite service that has been rendered at the reporting date). Changes in the intrinsic value of a liability that occur after the end of the requisite service period were considered compensation expense in the period in which the changes occur. On April 23, 2013, the Company distributed a notification letter to all equity award holders under 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. The remaining expense for these options is being recognized on a straight-line basis over the remaining requisite service period.

Share-based payment transactions with employees, including grants of employee stock options, are recognized as compensation expense over the requisite service period based on their estimated fair values. ASC 718 also requires significant judgment and the use of estimates, particularly surrounding Black-Scholes assumptions such as stock price volatility over the option term and expected option lives, as well as expected option forfeiture rates, to estimate the grant date fair value of equity-based compensation and requires the recognition of the fair value of stock compensation in the statement of operations.

Clinical Trial Expense Accruals

As part of the process of preparing its financial statements, the Company is required to estimate its expenses resulting from its obligations under contracts with vendors, clinical research organizations and consultants and under clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. The Company's objective is to reflect the appropriate trial expenses in its financial statements by matching those expenses with the period in which services are performed and efforts are expended. The Company accounts for these expenses according to the progress of the trial as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates through financial models taking into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of trials, or the services completed. During the course of a clinical trial, the Company adjusts its clinical expense recognition if actual results differ from its estimates. The Company makes estimates of its accrued expenses as of each balance sheet date based on the facts and circumstances known to it at that time. The Company's clinical trial accruals are dependent upon the timely and accurate reporting of contract research organizations and other third-party vendors. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in it reporting amounts that are too high or too low for any particular period. For the years ended December 31, 2015 and 2014, there were no material adjustments to the Company's prior period estimates of accrued expenses for clinical trials.

Collaboration Arrangements

A collaboration arrangement is defined as a contractual arrangement that has or may have significant financial milestones associated with success-based development, which include certain arrangements the Company has entered into regarding the research and development, manufacture and/or commercialization of products and product candidates. These collaborations generally provide for non-refundable, upfront license fees, research and development and commercial performance milestone payments, cost sharing and royalty payments. The collaboration agreements with third-parties are performed on a "best efforts" basis with no guarantee of either technological or commercial success. The Company evaluates whether an arrangement is a collaboration arrangement at its inception based on the facts and circumstances specific to the arrangement. The Company reevaluates whether an arrangement qualifies or continues to qualify as a collaboration arrangement whenever there is a change in the anticipated or actual ultimate commercial success of the endeavor. See Note 12, "License and Collaboration Agreements," for a discussion of the Company's current collaborations with Baxalta and SymBio.

Basic and Diluted Net Loss Per Share of Common Stock

Basic net loss per share of common stock is computed by dividing net loss applicable to common stockholders by the weighted-average number of shares of Common Stock outstanding during the period, excluding the dilutive effects of stock options and warrants. Diluted net loss per share of common stock is computed by dividing the net loss applicable to common stockholders by the sum of the weighted-average number of shares of Common Stock outstanding during the period plus the potential dilutive effects of stock options and warrants outstanding during the period calculated in accordance with the treasury stock method, but are excluded if their effect is anti-dilutive. Because the impact of these items is anti-dilutive during periods of net loss, there was no difference between basic and diluted net loss per share of Common Stock for the years ended December 31, 2015 and 2014.

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 financial reporting process and its consolidated financial position, results of operations and related disclosures.

Property and Equipment

12 Months Ended

Dec. 31, 2015

Property and Equipment

Property and Equipment

3. Property and Equipment

Property and equipment and related accumulated depreciation are as follows:

	December 31,
	2015			2014
Laboratory equipment	$	1,037,000		$	1,037,000
Software		92,000			92,000
Computer and office equipment		354,000			433,000
Leasehold improvements		745,000			1,063,000

		2,228,000			2,625,000
Less accumulated depreciation		(1,980,000	)		(2,205,000	)

	$	248,000		$	420,000

Depreciation and amortization expense was $150,000 and $434,000 for the years ended December 31, 2015 and 2014, respectively.

Net Loss Per Share of Common Stock

12 Months Ended

Dec. 31, 2015

Net Loss Per Share of Common Stock

Net Loss Per Share of Common Stock

4. Net Loss Per Share of Common Stock

The following table sets forth the computation of basic and diluted earnings per share for the years ended December 31, 2015 and 2014:

	Year ended December 31,
	2015			2014
Basic and diluted net loss per share of common stock:
Net loss attributable to Onconova Therapeutics, Inc	$	(23,979,000	)	$	(63,682,000	)


Weighted average shares of common stock outstanding		22,739,760			21,653,536


Net loss per share of common stock—basic and diluted	$	(1.05	)	$	(2.94	)

The following potentially dilutive securities outstanding at December 31, 2015 and 2014 have been excluded from the computation of diluted weighted average shares outstanding, as they would be antidilutive:

	December 31,
	2015		2014
Warrants		4,597		4,597
Stock options		5,157,602		4,631,299

		5,162,199		4,635,896

Revenue

12 Months Ended

Dec. 31, 2015

Revenue

Revenue

5. Revenue

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

	Year ended December 31,
	2015		2014
LLS	$	8,000,000	$	—
Baxalta		2,893,000		334,000
SymBio		563,000		466,000

	$	11,456,000	$	800,000

See Note 11, "Research Agreements," and Note 12, "License and Collaboration Agreements," for a further discussion of the agreements with LLS, Baxalta and SymBio.

Balance Sheet Detail

12 Months Ended

Dec. 31, 2015

Balance Sheet Detail

Balance Sheet Detail

6. Balance Sheet Detail

Receivables:

	December 31,
	2015		2014
Amounts due from Baxalta	$	1,384,000	$	—
Other		120,000		132,000

	$	1,504,000	$	132,000

Prepaid expenses and other current assets are as follows:

	December 31,
	2015		2014
Research and development	$	1,018,000	$	1,782,000
Manufacturing		168,000		451,000
Insurance		451,000		578,000
Other		195,000		255,000

	$	1,832,000	$	3,066,000

Accrued expenses and other current liabilities are as follows:

	December 31,
	2015		2014
Research and development	$	2,979,000	$	4,482,000
Employee compensation		438,000		854,000
Professional fees		306,000		418,000
Other		6,000		23,000

	$	3,729,000	$	5,777,000

Income Taxes

12 Months Ended

Dec. 31, 2015

Income Taxes

Income Taxes

7. Income Taxes

The Company accounts for income taxes under FASB ASC 740 ("ASC 740"). Deferred income tax assets and liabilities are determined based upon differences between financial reporting and tax bases of assets and liabilities, which are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse.

Income taxes have been based on the following income (loss) before income tax expense:

	December 31,
	2015			2014
Domestic	$	(24,057,000	)	$	(63,910,000	)
Foreign		50,000			134,000

	$	(24,007,000	)	$	(63,776,000	)

The provision for income taxes consists of the following:

	December 31,
	2015		2014
Current
US Federal	$	—	$	—
State and Local		—		—
Foreign		16,000		19,000

Total Current	$	16,000	$	19,000

Deferred
US Federal	$	—	$	—
State and Local		—		—
Foreign		—		—

Total Deferred	$	—	$	—

Total Expense (Benefit)	$	16,000	$	19,000

As of December 31, 2015, the Company had federal net operating loss ("NOL") carry forwards of $178,911,000, state NOL carry forwards of $201,464,000 and research and development tax credit carry forwards of $66,237,000, which are available to reduce future taxable income. The federal NOL and tax credit carry forwards will begin to expire at various dates starting in 2022. The state NOL carry forwards will begin to expire at various dates starting in 2016. The NOL carry forwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. NOL and tax credit carry forwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, as well as similar state tax provisions. This could limit the amount of NOLs that the Company can utilize annually to offset future taxable income or tax liabilities. The amount of the annual limitation, if any, will be determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years.

The Company's reserves related to taxes are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized. The Company recognized no material adjustment for unrecognized income tax benefits. Through December 31, 2015, the Company had no unrecognized tax benefits or related interest and penalties accrued.

The principal components of the Company's deferred tax assets are as follows:

	December 31,
	2015			2014
Deferred tax assets:
Net operating loss carryovers	$	73,648,000		$	63,776,000
R&D tax credits		66,374,000			56,750,000
Non-qualified stock options		6,079,000			4,916,000
Deferred revenue		2,198,000			5,648,000
Charitable contributions		6,000			6,000
Accrued expenses		617,000			691,000
Fixed assets		149,000			164,000

Deferred tax assets		149,071,000			131,951,000
Less valuation allowance		(149,071,000	)		(131,951,000	)

Net deferred tax assets	$	—		$	—

ASC 740 requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a full valuation allowance against its deferred tax assets at December 31, 2015 and 2014, respectively, because the Company's management has determined that is it more likely than not that these assets will not be fully realized. The Company experienced a net change in valuation allowance of $17,120,000 and $38,647,000 for the years ended December 31, 2015 and 2014, respectively.

A reconciliation of income tax (expense) benefit at the statutory federal income tax rate and income taxes as reflected in the financial statements is as follows:

	December 31,
	2015			2014
Federal income tax expense at statutory rate		34.0	%		34.0	%
Permanent items		(13.6	)		(8.9	)
State income tax, net of federal benefit		12.9			4.2
Tax credits		40.2			33.8
Provision to return		(2.1	)		(2.4	)
Change in valuation allowance		(71.4	)		(60.7	)
Other		—			—

Effective income tax rate		(0.0	)%		(0.0	)%

Stock-Based Compensation

12 Months Ended

Dec. 31, 2015

Stock-Based Compensation

Stock-Based Compensation

8. 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 December 31, 2015, there were 1,354,133 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 years ended December 31, 2015 and 2014:

	Year ended December 31,
	2015		2014
General and administrative	$	1,936,000	$	2,082,000
Research and development		1,850,000		2,986,000

	$	3,786,000	$	5,068,000

A summary of stock option activity for the year ended December 31, 2015 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, 2014		1,012,310			4,631,299		$	10.04		7.89	$	42,923
Authorized		868,126			—
Granted		(1,018,100	)		1,018,100		$	2.27
Exercised		—			—
Forfeitures		491,797			(491,797	)	$	9.49

Balance, December 31, 2015		1,354,133			5,157,602		$	8.56		7.46	$	0

Vested or expected to vest, December 31, 2015					5,077,680		$	8.56		7.46	$	0

Exercisable at December 31, 2015					3,227,121		$	10.05		6.66	$	0

The intrinsic value of options exercised during the years ended December 31, 2015 and 2014 was $0 and $1,842,000, respectively. The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the quoted price of the Company's common stock for those awards that have an exercise price currently below the closing price.

Information with respect to stock options outstanding and exercisable at December 31, 2015 is as follows:

Exercise Price	Shares		Exercisable
$1.48 - $2.69		908,725		141,483
$3.98 - $4.52		918,388		347,524
$5.76 - $7.53		1,079,786		1,025,289
$13.28 - $13.48		1,518,704		1,078,982
$14.68 - $15.12		668,499		585,632
$21.79 - $29.14		63,500		48,211

		5,157,602		3,227,121

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 December 31, 2015, there was $6,040,000 of unrecognized compensation expense related to the unvested stock options issued from April 24, 2013 through December 31, 2015, which is expected to be recognized over a weighted-average period of approximately 2.85 years.

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

	Year ended December 31,
	2015	2014
Risk-free interest rate	1.60%	1.84%
Expected volatility	75.8%	78.6%
Expected term	6.17 years	6.15 years
Expected dividend yield	0%	0%
Weighted-average grant date fair value	$1.50	$3.10

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: Due to the Company's limited operating history and a lack of company specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. When selecting these public companies on which it has based its expected stock price volatility, the Company selected companies with comparable characteristics to it, including enterprise value, risk profiles, position within the industry, and with historical share price information sufficient to meet the expected life of the stock-based awards. The historical volatility data was computed using the daily closing prices for the selected companies' shares during the equivalent period of the calculated expected term of the stock-based awards. Due to its lack of sufficient historical data, the Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available.
	•	Expected annual dividend yield: The Company has never paid, and does not expect to pay dividends in the foreseeable future. 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 2015 and 4.14% in 2014, based on the historical forfeiture experience.

Options granted on or prior to April 23, 2013

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 December 31, 2015, there was $249,000 of unrecognized compensation expense related to these unvested awards, which is expected to be recognized over a weighted-average period of approximately 1.04 years.

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2015
Employee Benefit Plan
Employee Benefit Plan	9. Employee Benefit Plan In October 2007, the Company established a 401(k) Retirement Savings Plan. Employees are eligible to participate in the plan as soon as they join the Company if they are at least 21 years of age and work a minimum of 1,000 hours per year. The Company matches $0.60 for every dollar of the first 6% of payroll that employees invest, up to the legal limit. Employer contributions vest over four years at the rate of 25% per year. For the years ended December 31, 2015 and 2014, the Company contributed $146,000 and $276,000, respectively.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2015

Commitments and Contingencies

Commitments and Contingencies

10. Commitments and Contingencies

Operating leases

In January 2007, the Company entered into a lease for 8,100 square feet of office and lab space in Newtown, Pennsylvania, and in October 2009, the Company and the landlord amended the lease to add three additional one-year options to extend the lease term. In November 2013 the Company renewed the lease for the period April 1, 2014 to March 31, 2015, for rent of $11,000 per month. In December 2014 the Company renewed the lease for the period April 1, 2015 to March 31, 2016, for rent of $11,500 per month. In November 2015 the Company renewed the lease for the period April 1, 2016 to March 31, 2017, for rent of $11,900 per month In September 2012, the Company sub-leased an additional 1,356 square feet of office space. The lease has been renewed through February 28, 2017 for rent of $1,600 per month.

The Company rents office space in Munich, Germany under one year leases that run from January 1 to December 31. For the period January 1, 2015 to December 31, 2015 the rent was €5,700 per month. For the period January 1, 2016 to December 31, 2016 the rent is €3,500 per month.

Future minimum lease payments under these non-cancellable leases having terms in excess of one year as of December 31, 2015 are as follows:

	December 31, 2015
2016	$	161,000
2017		39,000

Total minimum lease payments	$	200,000

Rent expense was $288,000 and $389,000 for the years ended December 31, 2015 and 2014, respectively.

Employment agreements

The Company has entered into employment agreements with certain of its executives. The agreements provide for, among other things, salary, bonus and severance payments.

Research Agreements	12 Months Ended
Research Agreements	Dec. 31, 2015
Research Agreements
Research Agreements	11. 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 December 31, 2015 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. In 2011, the Company recorded $1,875,000 of expense related to the Temple agreement in connection with the collaboration agreement the Company executed with SymBio. In 2012, the company recorded $12,500,000 of expense related to the Temple agreement in connection with the collaboration agreement the Company executed with Baxter. 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, ON TIME, 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	12 Months Ended
License and Collaboration Agreements	Dec. 31, 2015
License and Collaboration Agreements
License and Collaboration Agreements	12. License and Collaboration Agreements Baxalta Agreement In September 2012, the Company entered into a development and license agreement with Baxter Healthcare SA. Subsequently, Baxter International Inc.("Baxter") assigned the development and license agreement from Baxter Healthcare SA ("BHSA") to Baxalta GmbH ("Baxalta"), in preparation for the anticipated spin-off by Baxter of Baxalta Incorporated. The spin-off was effective on July 1, 2015 and Baxalta Incorporated, became a standalone, publicly traded company traded on the New York Stock Exchange. The Company understands that Baxalta is an indirect wholly-owned subsidiary of Baxalta Incorporated. The development and license agreement granted Baxalta an exclusive, royalty-bearing license for the research, development, commercialization and manufacture (in specified instances) of rigosertib in all therapeutic indications in Europe (the "Baxalta Territory"). In accordance with this agreement, BHSA made a $50,000,000 upfront payment to the Company. In July 2012, BHSA purchased $50,000,000 of the Company's Series J Preferred Stock, which automatically converted to shares of Common Stock immediately prior to the consummation of the IPO. BHSA also invested $4,950,000 in the Company's IPO. The securities of the Company owned by BHSA have also been transferred to Baxalta as part of the spin-off of Baxalta Incorporated. On March 3, 2016, the Company received a notice from Baxalta notifying the Company of Baxalta's election to terminate the development and license agreement based on a strategic reprioritization review, effective August 30, 2016. In accordance with the terms of the Baxalta agreement, upon termination, the rights that the Company had licensed to Baxalta would revert to the Comapny at no cost. Additionally, any rights the Company had to funding, pre-commercial milestone payments and royalties from Baxalta would terminate in accordance with the agreement. Under the terms of the agreement, the Company was initially required to perform research and development to advance three initial rigosertib indications, rigosertib intravenous ("IV") in higher-risk myelodysplastic syndrome ("MDS") patients, rigosertib IV in pancreatic cancer patients and rigosertib oral in lower-risk MDS patients, through Phase 3, Phase 3 and Phase 2 clinical trials, respectively. 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. As the Company's ONTIME trial did not achieve its primary endpoint, 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 $2,893,000 during the year ended December 31, 2015 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 following termination. In December 2013, a pre-planned interim futility and safety analysis of the pancreatic cancer trial was performed and the trial was discontinued. As a result, the Company is not pursuing a pancreatic cancer indication at this time. On January 27, 2015, Onconova was notified that BHSA had elected not to pursue additional clinical trials, or the submission of a drug approval application, for rigosertib oral in lower-risk MDS patients. Onconova would have received a milestone payment under its agreement with BHSA if the parties had mutually agreed to progress the development of oral rigosertib in lower-risk MDS patients. The Company would have been eligible to receive pre-commercial milestone payments if specified development and regulatory milestones were achieved during the term of the agreement. The potential pre-commercial development milestone payments to the Company included $25,000,000 for each drug approval application filed for indications specified in the agreement and up to $100,000,000 for marketing approval for each of the specified MDS indications. In addition to these pre-commercial milestones, the Company would have been eligible to receive up to an aggregate of $250,000,000 in milestone payments based on Baxalta's achievement of pre-specified threshold levels of annual net sales of rigosertib. The Company would also have been entitled to receive royalties at percentage rates ranging from the low-teens to the low-twenties on net sales of rigosertib by Baxalta in the Baxalta Territory. On March 3, 2016, the Company received notification from Baxalta of its 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. The Company determined that the deliverables under the original Baxter agreement included the exclusive, royalty-bearing, sublicensable license to rigosertib and the research and development services to be performed by the Company. The Company concluded that the license had standalone value to Baxter and was separable from the research and development services because the license was sublicensable, there were no restrictions as to Baxter's use of the license and Baxter had significant research capabilities in this field. In determining the separate units of accounting, the Company considered applicable accounting guidance and noted that in an arrangement with multiple deliverables, the delivered item or items shall be considered a separate unit of accounting if the delivered item or items have value to the customer on a stand-alone basis. The item or items have value on a stand-alone basis if they are sold separately by any vendor or the customer could resell the delivered item(s) on a stand-alone basis. In the context of a customer's ability to resell the delivered item(s), this criterion does not require the existence of an observable market for the deliverable(s). The Baxter agreement allowed Baxter to sublicense rigosertib and its ability to sublicense was not contingent on the approval or right of first refusal by the Company. The Company determined that Baxter's ability to sublicense the intellectual property to others demonstrates that the license had stand-alone value. In addition, at the time of entering into the Baxter agreement in September 2012, the rigosertib program was in a Phase 3 clinical trial for higher-risk MDS, a Phase 3 clinical trial for pancreatic cancer and a Phase 2 trial for lower-risk MDS. The protocols for the clinical trials had been written and provided to Baxter and a Special Protocol Assessment had already been granted to the Company by the U.S. Food and Drug Administration (the "FDA") for higher-risk MDS. These later stage clinical trials, where protocols had been prepared and trials were in process, could have been completed more easily by entities other than the Company, as compared to earlier stage clinical trials. The remaining services to be performed by the Company were not proprietary and could have been performed by other qualified parties. For example, the Company relied on clinical research organizations ("CROs") to complete the clinical trials, and Baxter could have engaged the same or similar CROs to complete the trials on its behalf. Although Baxter was not performing development activities related to rigosertib, Baxter possessed the internal expertise (or a vendor could have been hired) to complete the efforts under the rigosertib programs without further assistance from the Company. Baxter had the rights and full access to past and future intellectual information in order to obtain regulatory approval of rigosertib in Europe. In connection with the Baxter agreement, the Company licensed to Baxter all information and all patents controlled by the Company necessary for the development, manufacture, use and sale of rigosertib and all present and future formulations and dosages in all present and future therapeutic indications in the licensed territory. Accordingly, given Baxter's ability to sublicense under the agreement and its ability internally or with outside help to conduct the ongoing development efforts, the Company concluded that the license had stand-alone value. In order to determine if the license can be treated as a separate unit of accounting, the Company also considered whether there was a general right of return associated with the license. The $50,000,000 upfront payment received by the Company was non-refundable; therefore, there was no right of return for the license. As a result, the Company concluded that the license was a separate unit of accounting. The Company was not able to establish vendor-specific objective evidence of selling price or third-party evidence for either the license or the research and development services and instead allocated the arrangement consideration between the license and research and development services based on their relative selling prices using best estimate of selling price ("BESP"). Management developed the BESP of the license using a discounted cash flow model, taking into consideration assumptions including the development and commercialization timeline, discount rate and probability of success. Management utilized a third party valuation specialist to assist with the determination of BESP of the license. Management estimated the selling price of the research and development services using third party costs and a discounted cash flow model. The estimated selling prices utilized assumptions including internal estimates of research and development personnel needed to perform the research and development services; and estimates of expected cash outflows to third parties for services and supplies over the expected period that the services will be performed. The key assumptions in these models included the following market conditions and entity-specific factors: (a) the specific rights provided under the license, (b) the stage of development of rigosertib and estimated remaining development and commercialization timelines, (c) the probability of successfully developing and commercializing rigosertib, (d) the market size including the associated sales figures which generate royalty revenue, (e) cost of goods sold, which was assumed to be a specified percentage of revenues based on estimated cost of goods sold of a typical oncology product, (f) sales and marketing costs, which were based on the costs required to field an oncology sales force and marketing group, including external costs required to promote an oncology product, (g) the expected product life of rigosertib assuming commercialization and (h) the competitive environment. The Company utilized a discount rate of 16%, representing the cost of capital derived from returns on equity for comparable companies. Based on management's analyses, it was determined that the BESP of the license was $120,000,000 and the BESP of the research and development services was $20,600,000. As noted above, the Company received an up-front payment of $50,000,000 under the Baxter agreement, which represented the allocable agreement consideration. Based on the respective BESPs, this payment was allocated $42,400,000 to the license and $7,600,000 to the research and development services. Since the delivery of the license occurred upon the execution of the Baxter agreement and there was no general right of return, $42,400,000 of the $50,000,000 upfront payment was recognized upon the execution of the Baxter agreement. The portion allocated to research and development services was recognized over the period of performance on a proportional performance basis through March 31, 2014. Management estimated the period of performance to be the period necessary for completion of the non-contingent obligations to perform research and development services required to advance the three formulations of rigosertib described above. As of March 31, 2014, all of the deferred revenue related to such research and development services was recognized. The amount of this revenue recognized during the year ended December 31, 2014 was $333,000. The Company and Baxter agreed to establish a joint committee to facilitate the governance and oversight of the parties' activities under the agreements. Management considered whether participation on the joint committee was a deliverable and determined that it was not a deliverable. Had management considered participation on the joint committee as a deliverable, it would not have had a material impact on the accounting for the arrangement based on the analysis of the estimated selling price of such participation. As noted above, in July 2012, Baxter purchased Series J Preferred Stock. Because the Series J Preferred Stock was acquired within several months of the Baxter development and license agreement, management considered whether the Series J Preferred Stock was issued at fair value and if not, whether the consideration received for the Series J Preferred Stock ($50,000,000) or for the collaboration and license agreement ($50,000,000) should be allocated in the financial statements in a manner differently than the prices stated in the agreements. Management, with the assistance of an outside valuation specialist, determined that the price paid by Baxter for the Series J Preferred Stock approximated its fair value, and therefore the consideration received under the agreements was allocated in accordance with terms of the individual agreements. 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. The Company recognized revenues under this agreement of $455,000 and $455,000, for the years ended December 31, 2015 and 2014, respectively. In addition, the Company recognized revenues related to the supply agreement with Symbio in the amounts of $108,000 and $11,000 for the years ended December 31, 2015 and 2014, respectively.

Preclinical Collaboration	12 Months Ended
Preclinical Collaboration	Dec. 31, 2015
Preclinical Collaboration
Preclinical Collaboration	13. 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	12 Months Ended
Related-Party Transactions	Dec. 31, 2015
Related-Party Transactions
Related-Party Transactions	14. Related-Party Transactions The Company has entered into a research agreement, as subsequently amended, with the Mount Sinai School of Medicine ("Mount Sinai"), with which a member of its board of directors and a significant stockholder is affiliated. 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 years ended December 31, 2015 and 2014 were $1,089,000 and $1,215,000, respectively. At December 31, 2015 and 2014, the Company had no outstanding amounts payable to Mount Sinai. The Company purchases chemical compounds and sources development services from corporations owned by a former member of its board of directors. The Company's aggregate payments to these suppliers for the years ended December 31, 2015 and 2014 were $8,000 and $446,000, respectively. At December 31, 2015 and 2014, the Company owed this supplier $0 and $8,000, respectively, which is included in accounts payable on the consolidated balance sheets. Presently, the Company has consolidated its operations to its Newtown, Pennsylvania headquarters. Previously the Company also occupied office space in Pennington, New Jersey pursuant to a lease which ran through May 2015, from a corporation related to this supplier and affiliated with the former member of its board of directors. 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 years ended December 31, 2015 and 2014 were $197,000 and $194,000, respectively. At December 31, 2015 and December 31, 2014, 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	12 Months Ended
Securities Registrations and Sales Agreements	Dec. 31, 2015
Securities Registrations and Sales Agreements
Securities Registrations and Sales Agreements	15. 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), relating to the shares, which was filed with the SEC 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. On October 8, 2015, the Company entered into a Purchase Agreement, and a registration rights agreement (the "Registration Rights Agreement") with Lincoln Park. A registration statement (Form S-1 No. 333-207533), relating to the shares, which was filed with the SEC became effective on November 3, 2015. Upon signing of the Purchase Agreement, Lincoln Park made an initial purchase of 846,755 shares of the Company's Common Stock for $1,500,000. Under the terms and subject to the conditions of the Purchase Agreement, the Company has the right to sell to and Lincoln Park is obligated to purchase up to an additional $15,000,000 in amounts of shares of Common Stock, subject to certain limitations, from time to time, over the 36-month period commencing on November 3, 2015, the effective date of the registration statement filed with the SEC (the "Commencement Date"). 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% 180 days after the Commencement Date. Pursuant to the terms of the 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 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 under the Purchase Agreement to the Company will depend on the frequency and prices at which the Company sells shares of its stock to Lincoln Park. The Company expects that the proceeds received by the Company and any additional proceeds from future sales to Lincoln Park under the Purchase Agreement will be used for general corporate purposes and working capital requirements.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2015
Subsequent Events
Subsequent Events	16. Subsequent Events Sale of Securities On January 5, 2016, the Company entered into a Securities Purchase Agreement (the "Securities Purchase Agreement") with an institutional investor (the "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 (the "Common Shares") and warrants to purchase 968,421 shares of the Company's common stock (the "Warrants") for aggregate gross proceeds of $1,840,000. Each Warrant is initially exercisable on the six (6) month anniversary of the issuance date at an exercise price equal to $1.15 per share of common stock, subject to customary adjustments, and has a term of exercise of five (5) years from the initial exercise date. Net proceeds from the transactions were approximately $1,646,000 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 Common Shares were offered by the Company 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 "Registration Statement"). 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 Investor may exercise the Warrants and sell the underlying shares only pursuant to an effective registration statement under the Securities Act covering the resale of those shares, an exemption under Rule 144 under the Securities Act or another applicable exemption under the Securities Act. Workforce Reduction In February 2016, the Company, as part of its ongoing commitment to reduce costs and conserve cash implemented a workforce reduction of 6 employees, which represented approximately 17 percent of its workforce. Affected employees were offered severance pay in accordance with Company policy or, if applicable, their employment agreements. As part of the workforce reduction, Ajay Bansal, the Company's Chief Financial Officer, and Thomas McKearn, M.D., Ph.D., the Company's President, Research & Development, were notified that their employment with the Company was terminated. Mr. Bansal and Dr. McKearn each depart in good standing with the Company. Each of Mr. Bansal and Dr. McKearn will receive severance benefits consistent with a termination "without cause" pursuant to his employment agreement and the Company has agreed to extend the post-termination exercise period of their outstanding option awards until February 12, 2018, in consideration for a customary general release. As a result of the workforce reduction, the Company estimates that it will record in the first quarter of 2016, a one-time severance-related charge totaling approximately $2.8 million, which includes a non-cash charge of approximately $1.6 million related to the accelerated vesting of the outstanding stock options for certain of the affected employees. Baxalta Development and License Agreement On March 3, 2016, the Company received a notice from Baxalta notifying the Company of Baxalta's election to terminate the development and license agreement between the Company and Baxalta (as successor to Baxter Healthcare SA) based on a strategic reprioritization review, effective August 30, 2016. This termination notice was received after commencement of the INSPIRE trial, which was designed in consultation with Baxalta. Under the terms of the development and license agreement, Baxalta is making cost-sharing payments to the Company equal to fifty percent of the costs of the Company's INSPIRE trial, up to $15.0 million. The development and license agreement granted Baxalta an exclusive, royalty-bearing license for the research, development and commercialization of the Company's lead product candidate, rigosertib, in all therapeutic indications in specified countries comprising most of Europe. In accordance with the terms of the development and license agreement, upon termination, the rights that the Company had licensed to Baxalta will revert to the Company at no cost to the Company. Additionally, prior to the effective date of the termination, Baxalta will transition material to the Company and will continue to fund its share of the costs of the INSPIRE trial.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2015

Summary of Significant Accounting Policies

Basis of Presentation

Segment Information

Use of Estimates

Concentrations of Credit Risk and Off-Balance Sheet Risk

Cash and Cash Equivalents

Fair Value of Financial Instruments

Property and Equipment

		Estimated Useful Life
Lab equipment		5 - 6 years
Software		3 years
Computer and office equipment		5 - 6 years
Leasehold improvements		Shorter of the lease term or estimated useful life

Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized.

Restricted Cash

Foreign Currency Translation

Revenue Recognition

Royalties are recorded as earned in accordance with the contract terms when third party sales can be reliably measured and collectability is reasonably assured.

Research and Development Expenses

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources.

Income Taxes

Stock-Based Compensation Expense

Clinical Trial Expense Accruals

Collaboration Arrangements

Basic and Diluted Net Loss Per Share of Common Stock

Recent Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Summary of Significant Accounting Policies

Schedule of estimated useful lives used to depreciate the Company's assets

		Estimated Useful Life
Lab equipment		5 - 6 years
Software		3 years
Computer and office equipment		5 - 6 years
Leasehold improvements		Shorter of the lease term or estimated useful life

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2015

Property and Equipment

Schedule of property and equipment and related accumulated depreciation

	December 31,
	2015			2014
Laboratory equipment	$	1,037,000		$	1,037,000
Software		92,000			92,000
Computer and office equipment		354,000			433,000
Leasehold improvements		745,000			1,063,000

		2,228,000			2,625,000
Less accumulated depreciation		(1,980,000	)		(2,205,000	)

	$	248,000		$	420,000

Net Loss Per Share of Common Stock (Tables)

12 Months Ended

Dec. 31, 2015

Net Loss Per Share of Common Stock

Schedule of computation of basic and diluted earnings per share

	Year ended December 31,
	2015			2014
Basic and diluted net loss per share of common stock:
Net loss attributable to Onconova Therapeutics, Inc	$	(23,979,000	)	$	(63,682,000	)


Weighted average shares of common stock outstanding		22,739,760			21,653,536


Net loss per share of common stock—basic and diluted	$	(1.05	)	$	(2.94	)

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

	December 31,
	2015		2014
Warrants		4,597		4,597
Stock options		5,157,602		4,631,299

		5,162,199		4,635,896

Revenue (Tables)

12 Months Ended

Dec. 31, 2015

Revenue

Recognized revenue under license and collaboration agreements

	Year ended December 31,
	2015		2014
LLS	$	8,000,000	$	—
Baxalta		2,893,000		334,000
SymBio		563,000		466,000

	$	11,456,000	$	800,000

Balance Sheet Detail (Tables)

12 Months Ended

Dec. 31, 2015

Balance Sheet Detail

Schedule of receivables

	December 31,
	2015		2014
Amounts due from Baxalta	$	1,384,000	$	—
Other		120,000		132,000

	$	1,504,000	$	132,000

Schedule of prepaid expenses and other current assets

	December 31,
	2015		2014
Research and development	$	1,018,000	$	1,782,000
Manufacturing		168,000		451,000
Insurance		451,000		578,000
Other		195,000		255,000

	$	1,832,000	$	3,066,000

Schedule of accrued expenses and other current liabilities

	December 31,
	2015		2014
Research and development	$	2,979,000	$	4,482,000
Employee compensation		438,000		854,000
Professional fees		306,000		418,000
Other		6,000		23,000

	$	3,729,000	$	5,777,000

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Taxes

Schedule of income taxes based on income (loss) before income tax expense

	December 31,
	2015			2014
Domestic	$	(24,057,000	)	$	(63,910,000	)
Foreign		50,000			134,000

	$	(24,007,000	)	$	(63,776,000	)

Schedule of provision for income taxes

	December 31,
	2015		2014
Current
US Federal	$	—	$	—
State and Local		—		—
Foreign		16,000		19,000

Total Current	$	16,000	$	19,000

Deferred
US Federal	$	—	$	—
State and Local		—		—
Foreign		—		—

Total Deferred	$	—	$	—

Total Expense (Benefit)	$	16,000	$	19,000

Schedule of principal components of the Company's deferred tax assets

	December 31,
	2015			2014
Deferred tax assets:
Net operating loss carryovers	$	73,648,000		$	63,776,000
R&D tax credits		66,374,000			56,750,000
Non-qualified stock options		6,079,000			4,916,000
Deferred revenue		2,198,000			5,648,000
Charitable contributions		6,000			6,000
Accrued expenses		617,000			691,000
Fixed assets		149,000			164,000

Deferred tax assets		149,071,000			131,951,000
Less valuation allowance		(149,071,000	)		(131,951,000	)

Net deferred tax assets	$	—		$	—

Schedule of reconciliation of income tax (expense) benefit at the statutory federal income tax rate and income taxes as reflected in the financial statements

	December 31,
	2015			2014
Federal income tax expense at statutory rate		34.0	%		34.0	%
Permanent items		(13.6	)		(8.9	)
State income tax, net of federal benefit		12.9			4.2
Tax credits		40.2			33.8
Provision to return		(2.1	)		(2.4	)
Change in valuation allowance		(71.4	)		(60.7	)
Other		—			—

Effective income tax rate		(0.0	)%		(0.0	)%

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Stock-Based Compensation

Schedule of stock-based compensation expense

	Year ended December 31,
	2015		2014
General and administrative	$	1,936,000	$	2,082,000
Research and development		1,850,000		2,986,000

	$	3,786,000	$	5,068,000

Schedule of stock option activity

				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, 2014		1,012,310			4,631,299		$	10.04		7.89	$	42,923
Authorized		868,126			—
Granted		(1,018,100	)		1,018,100		$	2.27
Exercised		—			—
Forfeitures		491,797			(491,797	)	$	9.49

Balance, December 31, 2015		1,354,133			5,157,602		$	8.56		7.46	$	0

Vested or expected to vest, December 31, 2015					5,077,680		$	8.56		7.46	$	0

Exercisable at December 31, 2015					3,227,121		$	10.05		6.66	$	0

Schedule of information with respect to stock options outstanding and exercisable

Information with respect to stock options outstanding and exercisable at December 31, 2015 is as follows:

Exercise Price	Shares		Exercisable
$1.48 - $2.69		908,725		141,483
$3.98 - $4.52		918,388		347,524
$5.76 - $7.53		1,079,786		1,025,289
$13.28 - $13.48		1,518,704		1,078,982
$14.68 - $15.12		668,499		585,632
$21.79 - $29.14		63,500		48,211

		5,157,602		3,227,121

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

	Year ended December 31,
	2015	2014
Risk-free interest rate	1.60%	1.84%
Expected volatility	75.8%	78.6%
Expected term	6.17 years	6.15 years
Expected dividend yield	0%	0%
Weighted-average grant date fair value	$1.50	$3.10

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2015

Commitments and Contingencies

Schedule of future minimum lease payments under non-cancellable leases

	December 31, 2015
2016	$	161,000
2017		39,000

Total minimum lease payments	$	200,000

Nature of Business - Net Loss and Accumulated Deficit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Nature of Business
Net loss	$ (24,023)	$ (63,795)
Accumulated deficit	$ (318,557)	$ (294,578)

Nature of Business - Sale of Stock (Details) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Oct. 08, 2015 USD ($) shares	Jul. 30, 2013 USD ($) class $ / shares shares	Oct. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 $ / shares
Sale of Securities
Preferred stock, par value per share (in dollars per share) \| $ / shares		$ 0.01
Number of series denominated as Series A through Series J preferred stock \| class		10
Common stock, par value (in dollars per share) \| $ / shares				$ 0.01	$ 0.01
Net proceeds from sales of common stock				$ 7,464
IPO
Sale of Securities
Issuance of stock (in shares) \| shares		5,941,667
Common stock, par value (in dollars per share) \| $ / shares		$ 0.01
Price per share (in dollars per share) \| $ / shares		$ 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
At-the-market equity program
Sale of Securities
Issuance of stock (in shares) \| shares				2,715,165
Aggregate offering price			$ 20,000
Net proceeds from sales of common stock				$ 6,018
Purchase agreement \| Lincoln Park
Sale of Securities
Issuance of stock (in shares) \| shares	846,755
Aggregate offering price	$ 15,000
Net proceeds from sales of common stock	$ 1,500

Nature of Business - Sale of Securities (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 05, 2016	Dec. 31, 2015
Sale of Securities
Net proceeds from sales of common stock		$ 7,464
Subsequent event \| Securities Purchase Agreement
Sale of Securities
Issuance of stock (in shares)	1,936,842
Net proceeds from sales of common stock	$ 1,646
Common Stock Warrants \| Subsequent event \| Securities Purchase Agreement
Sale of Securities
Share of common stock warrants will purchase (in shares)	968,421

Summary of Significant Accounting Policies - Concentrations of Credit Risk and Off-Balance Sheet Risk (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Concentrations of Credit Risk and Off-Balance Sheet Risk
Off-balance sheet risk, asset	$ 0
Off-balance sheet risk, liability	$ 0

Summary of Significant Accounting Policies - Property and Equipment (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Property and Equipment
Impairment losses	$ 0
Laboratory equipment \| Minimum
Property and Equipment
Estimated useful lives	P5Y
Laboratory equipment \| Maximum
Property and Equipment
Estimated useful lives	P6Y
Software
Property and Equipment
Estimated useful lives	P3Y
Computer and office equipment \| Minimum
Property and Equipment
Estimated useful lives	P5Y
Computer and office equipment \| Maximum
Property and Equipment
Estimated useful lives	P6Y

Summary of Significant Accounting Policies - Restricted Cash (Details) - Letter of credit - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Letter of credit provided to landlord
Restricted Cash
Letter of credit amount		$ 125
Letter of credit provided to surety company
Restricted Cash
Letter of credit amount	$ 50

Property and Equipment - Property and Equipment and Related Accumulated Depreciation (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property and Equipment
Property and equipment, gross	$ 2,228	$ 2,625
Less accumulated depreciation	(1,980)	(2,205)
Property and equipment, net	248	420
Laboratory equipment
Property and Equipment
Property and equipment, gross	1,037	1,037
Software
Property and Equipment
Property and equipment, gross	92	92
Computer and office equipment
Property and Equipment
Property and equipment, gross	354	433
Leasehold improvements
Property and Equipment
Property and equipment, gross	$ 745	$ 1,063

Net Loss Per Share of Common Stock - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Basic and diluted net loss per share of common stock:
Net loss attributable to Onconova Therapeutics, Inc.	$ (23,979)	$ (63,682)
Weighted average shares of common stock outstanding (in shares)	22,739,760	21,653,536
Net loss per share of common stock, basic and diluted (in dollars per shares)	$ (1.05)	$ (2.94)

- Definition

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

+ References + Details

Net Loss Per Share of Common Stock - Potentially Dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
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	5,162,199	4,635,896
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	4,597	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	5,157,602	4,631,299

Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Revenue
Revenues	$ 11,456	$ 800
LLS
Revenue
Revenues	8,000
Baxalta \| License and collaboration
Revenue
Revenues	2,893	334
SymBio \| License and collaboration
Revenue
Revenues	$ 563	$ 466

Balance Sheet Detail - Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Receivables:
Amounts due from Baxalta	$ 1,384
Other	120	$ 132
Receivables, Net, Current, Total	$ 1,504	$ 132

Balance Sheet Detail - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Prepaid expenses and other current assets:
Research and development	$ 1,018	$ 1,782
Manufacturing	168	451
Insurance	451	578
Other	195	255
Total	$ 1,832	$ 3,066

Balance Sheet Detail - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued expenses
Research and development	$ 2,979	$ 4,482
Employee compensation	438	854
Professional fees	306	418
Other	6	23
Total	$ 3,729	$ 5,777

Income Taxes - Income (Loss) before Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income taxes based on income (loss) before income tax expense
Domestic	$ (24,057)	$ (63,910)
Foreign	50	134
Net loss before income taxes	$ (24,007)	$ (63,776)

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Current
Foreign	$ 16	$ 19
Total Current	16	19
Deferred
Total Deferred	0	0
Total Expense (Benefit)	$ 16	$ 19

Income Taxes - Tax Credit Carry Forwards (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Research and Development Tax Credit Carry Forwards \| IRS
Income Taxes
Tax credit carry forwards	$ 66,237

Income Taxes - Unrecognized Tax Benefits (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Unrecognized tax benefits
Unrecognized tax benefits	$ 0
Interest and penalties accrued	$ 0

Income Taxes - Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryovers	$ 73,648	$ 63,776
R&D tax credits	66,374	56,750
Non-qualified stock options	6,079	4,916
Deferred revenue	2,198	5,648
Charitable contributions	6	6
Accrued expenses	617	691
Fixed assets	149	164
Deferred tax assets	149,071	131,951
Less valuation allowance	(149,071)	(131,951)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Reconciliation of Income Tax (Expense) Benefit at the Statutory Federal Income Tax Rate and Income Taxes (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of income tax (expense) benefit at the statutory federal income tax rate and income taxes
Federal income tax expense at statutory rate (as a percent)	34.00%	34.00%
Permanent items (as a percent)	(13.60%)	(8.90%)
State income tax, net of federal benefit (as a percent)	12.90%	4.20%
Tax credits (as a percent)	40.20%	33.80%
Provision to return (as a percent)	(2.10%)	(2.40%)
Change in valuation allowance (as a percent)	(71.40%)	(60.70%)
Effective income tax rate (as a percent)	0.00%	0.00%

Stock-Based Compensation - Common Stock Reserved for Issuance and Shares Available for Future Issuance (Details) - Stock options - shares	Dec. 31, 2015	Dec. 31, 2014	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)	1,354,133	1,012,310

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Stock-Based Compensation
Net tax benefits related to the stock-based compensation costs	$ 0
Total stock-based compensation	3,786	$ 5,068
General and administrative
Stock-Based Compensation
Total stock-based compensation	1,936	2,082
Research and development
Stock-Based Compensation
Total stock-based compensation	$ 1,850	$ 2,986

Stock-Based Compensation - Summary of Stock Option Activity (Details) - Stock options - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Shares Available for Grant
Balance at the beginning of the period (in shares)	1,012,310
Authorized (in shares)	868,126
Granted (in shares)	(1,018,100)
Forfeited (in shares)	(491,797)
Balance at the end of the period (in shares)	1,354,133	1,012,310
Number of Shares
Balance at the beginning of the period (in shares)	4,631,299
Granted (in shares)	(1,018,100)
Forfeited (in shares)	(491,797)
Balance at the end of the period (in shares)	5,157,602	4,631,299
Vested or expected to vest at the end of the period (in shares)	5,077,680
Exercisable at the end of the period (in shares)	3,227,121
Weighted-Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 10.04
Granted (in dollars per share)	2.27
Forfeited (in dollars per share)	9.49
Balance at the end of the period (in dollars per share)	8.56	$ 10.04
Vested or expected to vest at the end of the period (in dollars per share)	8.56
Exercisable at the end of the period (in dollars per share)	$ 10.05
Additional Disclosures
Weighted average remaining contractual term	7 years 5 months 16 days	7 years 10 months 21 days
Weighted average remaining contractual term of options vested or expected to vest	7 years 5 months 16 days
Weighted average remaining contractual term of options exercisable	6 years 7 months 28 days
Aggregate intrinsic value of options outstanding	$ 0	$ 42,923
Aggregate intrinsic value of options vested or expected to vest	0
Aggregate intrinsic value of options exercisable	$ 0

Stock-Based Compensation - Stock Options Outstanding and Exercisable (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Share-Based Compensation
Shares (in shares)	5,157,602
Exercisable (in shares)	3,227,121
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)	908,725
Exercisable (in shares)	141,483
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)	918,388
Exercisable (in shares)	347,524
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)	1,079,786
Exercisable (in shares)	1,025,289
Exercise Price Range $13.28 - $13.48
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	$ 13.48
Shares (in shares)	1,518,704
Exercisable (in shares)	1,078,982
Exercise Price Range $14.86 - $15.12
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) \| $ / shares	$ 14.68
Exercise price, upper range limit (in dollars per share) \| $ / shares	$ 15.12
Shares (in shares)	668,499
Exercisable (in shares)	585,632
Exercise Price Range $21.79 - $29.14
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) \| $ / shares	$ 21.79
Exercise price, upper range limit (in dollars per share) \| $ / shares	$ 29.14
Shares (in shares)	63,500
Exercisable (in shares)	48,211

Stock-Based Compensation - Unrecognized Compensation Expense (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Stock-Based Compensation
Unrecognized compensation cost of options granted but not yet vested	$ 6,040
Weighted-average period for recognizing unrecognized compensation expense related to unvested stock options	2 years 10 months 6 days

Stock-Based Compensation - Fair Value Assumptions (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Assumptions used
Risk-free interest rates (as a percent)	1.60%	1.84%
Expected volatility (as a percent)	75.80%	78.60%
Expected term	6 years 2 months 1 day	6 years 1 month 24 days
Expected dividend yield (as a percent)	0.00%	0.00%
Weighted-average grant fair value (in dollars per share)	$ 1.50	$ 3.10
Annualized forfeiture rate (as a percent)	4.14%	4.14%

Stock-Based Compensation - Additional Disclosures (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Stock-Based Compensation
Reclassification to stockholders' deficit	$ 14,482
Unrecognized compensation expense of unvested liability awards	$ 249
Weighted-average period for recognizing unrecognized compensation expense of unvested liability awards	1 year 15 days

Employee Benefits Plan (Details) - USD ($)	12 Months Ended
Employee Benefits Plan (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Employee Benefit Plan
Minimum age of employees required to be eligible for participation	21 years
Minimum working hours per year required to be eligible for participation	1000 hours
Employer's match for every dollar of the first specified percentage of payroll that employees invest	$ 0.60
Employer's matching contribution percentage	6.00%
Employer's contribution, vesting period	4 years
Employer contribution annual vesting percentage	25.00%
Contributions	$ 146,000	$ 276,000

Commitments and Contingencies - Office and Lab Space in Newton, Pennsylvania (Details)	1 Months Ended	12 Months Ended			19 Months Ended
	Oct. 31, 2009 Option	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Feb. 28, 2017 USD ($)	Sep. 30, 2012 ft²	Jan. 31, 2007 ft²
Office and lab space of 8,100 square feet area in Newtown, Pennsylvania
Operating leases
Area of space leased (in square feet) \| ft²							8,100
Number of options available for lease extensions \| Option	3
Additional lease term under option	1 year
Lease rent per month \| $		$ 11,900	$ 11,500	$ 11,000
Additional office space of 1,356 square feet area in Newtown, Pennsylvania
Operating leases
Area of space leased (in square feet) \| ft²						1,356
Sub-lease rent per month \| $					$ 1,600

Commitments and Contingencies - Office Space in Munich, Germany (Details) - Office Space in Munich, Germany - EUR (€)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Operating leases
Lease term	1 year
Lease rent per month	€ 3,500	€ 5,700

Commitments and Contingencies - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Future minimum lease payments under non-cancellable leases
2016	$ 161
2017	39
Total minimum lease payments	$ 200

Research Agreements (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended			24 Months Ended
Research Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2015	Jan. 31, 2013
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%
Payments made in connection with the collaboration agreement				$ 1,875
Expense in connection with the collaboration agreement			$ 12,500
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			$ 23,000
Milestone payments received recorded as deferred revenue					$ 8,000
Deferred revenue recognized	$ 8,000

License and Collaboration Agreements (Details) $ in Thousands	1 Months Ended				12 Months Ended
	Jul. 31, 2013 USD ($)	Sep. 30, 2012 USD ($) item	Jul. 31, 2012 USD ($)	Jul. 31, 2011 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
License and collaboration agreements
Revenue					$ 11,456	$ 800
License agreement \| Baxalta
License and collaboration agreements
Consideration received for the Preferred Stock	$ 4,950
License agreement \| Baxter
License and collaboration agreements
Consideration received for the Preferred Stock		$ 50,000
Discount rate (as a percent)		16.00%
BESP of the license		$ 120,000
BESP of the research and development services		20,600
Up-front payment allocated to license		42,400
Up-front payment allocated to research and development services		7,600
Allocated up-front payment of license recognized upon execution of agreement		$ 42,400
Research and development revenue						333
License agreement \| Rigosertib \| Baxalta
License and collaboration agreements
Number of initial rigosertib indications \| item		3
Revenue					$ 2,893
Upfront payment		$ 50,000
Aggregate potential milestone payments based on annual net sales of rigosertib		250,000
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 agreement \| Rigosertib \| Baxalta \| Rigosertib IV in pancreatic cancer patients
License and collaboration agreements
Potential pre-commercial milestone payments for joint decision to proceed with the development of rigosertib for certain indications		25,000
License agreement \| Rigosertib \| Baxalta \| Maximum \| Rigosertib IV in pancreatic cancer patients
License and collaboration agreements
Potential pre-commercial payments that could be received for each drug approval application filed for indications specified in the agreement		100,000
License agreement \| Rigosertib \| Baxter
License and collaboration agreements
Upfront payment		$ 50,000
License agreement \| Rigosertib \| SymBio
License and collaboration agreements
Revenue					455	455
Upfront payment				$ 7,500
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%
License agreement \| Rigosertib \| SymBio \| Maximum
License and collaboration agreements
Aggregate milestone payments				$ 22,000
Supply commitment agreement \| Rigosertib \| SymBio
License and collaboration agreements
Revenue					$ 108	$ 11
Binding commitments				0
Series J Preferred Stock \| License agreement \| Baxalta
License and collaboration agreements
Consideration received for the Preferred Stock			$ 50,000
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
United States \| License agreement \| Rigosertib \| SymBio \| Rigosertib IV in combination with gemcitabine for pancreatic cancer patients
License and collaboration agreements
Regulatory milestones payments due upon receipt of marketing approval for indication				5,000
Potential development milestones payments due after enrollment of the first patient in event of decision made to start phase 3 clinical trial of indication				3,000
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
Japan \| License agreement \| Rigosertib \| SymBio \| Rigosertib IV in combination with gemcitabine for pancreatic cancer patients
License and collaboration agreements
Regulatory milestones payments due upon receipt of marketing approval for indication				$ 3,000

Preclinical Collaboration (Details) - GBO $ in Thousands	1 Months Ended	12 Months Ended
Preclinical Collaboration (Details) - GBO $ in Thousands	Nov. 30, 2014 USD ($)	Dec. 31, 2015 item	Dec. 31, 2013 USD ($)	Dec. 31, 2014 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	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Corporations owned by former board members
Related-party transactions
Payments to related party	$ 8	$ 446
Amounts due to related party	0	8
Member of board of directors
Related-party transactions
Payments to related party	197	194
Amounts due to related party	0	0
Mount Sinai \| Member of board of directors and significant stockholder are affiliated
Related-party transactions
Payments to related party	1,089	1,215
Amounts due to related party	$ 0	$ 0

Securities Registrations and Sales Agreements (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Nov. 03, 2015	Oct. 08, 2015	Oct. 31, 2014	Dec. 31, 2015
Securities Registrations and Sales Agreement
Net proceeds from sales of common stock				$ 7,464
At-the-market equity program
Securities Registrations and Sales Agreement
Aggregate offering price			$ 20,000
Issuance of stock (in shares)				2,715,165
Net proceeds from sales of common stock				$ 6,018
Lincoln Park \| Purchase agreement
Securities Registrations and Sales Agreement
Aggregate offering price		$ 15,000
Issuance of stock (in shares)		846,755
Net proceeds from sales of common stock		$ 1,500
Purchase period	36 months
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
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

Subsequent Events - Sale of Securities (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Jan. 05, 2016	Dec. 31, 2015
Sale of Securities
Value of stock issued		$ 7,464
Net proceeds from sales of common stock		$ 7,464
Subsequent event \| 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
Net proceeds from sales of common stock	$ 1,646
Common Stock Warrants \| Subsequent event \| Securities Purchase Agreement
Sale of Securities
Share of common stock warrants will purchase (in shares)	968,421
Exercisable, term (in months)	6 months
Exercise price (in dollars per share)	$ 1.15
Exercise, term (in years)	5 years

Subsequent Events - Workforce Reduction (Details) - Subsequent event - Employee severance $ in Millions	1 Months Ended	3 Months Ended
	Feb. 29, 2016 employee	Mar. 31, 2016 USD ($)
Workforce Reduction
Workforce reduction, number of employees \| employee	6
Workforce reduction, number of employees as a percentage of workforce (as a percent)	17.00%
Forecast
Workforce Reduction
Severance-related charge		$ 2.8
Accelerated vesting of the outstanding stock options for certain of the affected employees		$ 1.6

Subsequent Events - Baxalta Development and License Agreement (Details) - Rigosertib IV in higher risk MDS patients - License agreement - Rigosertib - Baxalta $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Baxalta Development and License Agreement
Funding percentage to the entity (as a percent)	50.00%
Cost funded to the entity	$ 15.0

Nature of Business - The Company (Details)	Dec. 31, 2015 product Program
Nature of Business
Number of clinical-stage product candidates \| product	3
Number of programs \| Program	2

Summary of Significant Accounting Policies - Segment Information (Details)	12 Months Ended
	Dec. 31, 2015 segment
Segment Information
Number of operating segments	1

Summary of Significant Accounting Policies - Stock Based Compensation Expense (Details) $ in Thousands	Apr. 23, 2013 USD ($)
Stock-Based Compensation Expense
Reclassification of options from liabilities to stockholders' deficit	$ 14,482

Income Taxes - Net Operating Loss Carryforwards (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Federal
Income Taxes
Net operating loss (NOL) carry forwards	$ 178,911
State
Income Taxes
Net operating loss (NOL) carry forwards	$ 201,464