Traws Pharma (TRAW) 10-K20 Mar 142013 FY Annual reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Feb. 28, 2014	Jun. 28, 2013
Document and Entity Information	'	'	'
Entity Registrant Name	'Onconova Therapeutics, Inc.	'	'
Entity Central Index Key	'0001130598	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
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	'Non-accelerated Filer	'	'
Entity Public Float	'	'	$107.30
Entity Common Stock, Shares Outstanding	'	21,638,029	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
Current assets:	'	'
Cash and cash equivalents	$60,009,000	$81,527,000
Marketable securities	39,994,000	'
Prepaid expenses and other current assets	4,387,000	1,725,000
Total current assets	104,390,000	83,252,000
Property and equipment, net	626,000	463,000
Restricted cash	125,000	125,000
Other non-current assets	12,000	12,000
Total assets	105,153,000	83,852,000
Current liabilities:	'	'
Accounts payable	3,710,000	5,517,000
Accrued expenses and other current liabilities	5,820,000	3,925,000
Warrant liability	20,000	62,000
Option liability	0	11,967,000
Deferred revenue	788,000	3,907,000
Total current liabilities	10,338,000	25,378,000
Deferred revenue, non-current	13,909,000	15,421,000
Other	6,000	44,000
Total liabilities	24,253,000	40,843,000
Commitments and contingencies	'	'
Redeemable convertible preferred stock, $0.01 par value per share, none and 18,548,253 shares authorized at December 31, 2013 and 2012, none and 16,912,199 issued and outstanding at December 31, 2013 and 2012	'	201,315,000
Stockholders' equity (deficit):	'	'
Preferred stock, $0.01 par value, 5,000,000 and none authorized at December 31, 2013 and 2012, none issued and outstanding at December 31, 2013 and 2012	'	'
Common stock, $0.01 par value, 75,000,000 and 30,145,155 authorized at December 31, 2013 and 2012, 21,467,482 and 2,606,484 shares issued and outstanding at December 31, 2013 and 2012	215,000	26,000
Additional paid in capital	311,093,000	10,021,000
Accumulated other comprehensive income	1,000	'
Accumulated deficit	-230,896,000	-168,353,000
Total Onconova Therapeutics, Inc stockholders' equity (deficit)	80,413,000	-158,306,000
Non-controlling interest	487,000	'
Total stockholders' equity (deficit)	80,900,000	-158,306,000
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	$105,153,000	$83,852,000

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Consolidated Balance Sheets	'	'
Redeemable convertible preferred stock, par value per share (in dollars per share)	$0.01	$0.01
Redeemable convertible preferred stock, shares authorized	0	18,548,253
Redeemable convertible preferred stock, shares issued	0	16,912,199
Redeemable convertible preferred stock, shares outstanding	0	16,912,199
Preferred stock, par value (in dollars per share)	$0.01	$0.01
Preferred stock, shares authorized	5,000,000	0
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	30,145,155
Common stock, shares issued	21,467,482	2,606,484
Common stock, shares outstanding	21,467,482	2,606,484

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended								12 Months Ended
Consolidated Statements of Operations (USD $)	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements of Operations	'	'	'	'	'	'	'	'	'	'	'
Revenue	$1,930,000	$1,116,000	$591,000	$1,116,000	$2,969,000	$42,803,000	$220,000	$198,000	$4,753,000	$46,190,000	$1,487,000
Operating expenses:	'	'	'	'	'	'	'	'	'	'	'
General and administrative	4,403,000	5,927,000	3,117,000	3,346,000	2,698,000	8,922,000	1,627,000	2,460,000	16,793,000	15,707,000	6,436,000
Research and development	12,086,000	15,293,000	10,047,000	12,756,000	10,576,000	26,962,000	6,776,000	8,448,000	50,182,000	52,762,000	22,624,000
Total operating expenses	16,489,000	21,220,000	13,164,000	16,102,000	13,274,000	35,884,000	8,403,000	10,908,000	66,975,000	68,469,000	29,060,000
Loss from operations	-14,559,000	-20,104,000	-12,573,000	-14,986,000	-10,305,000	6,919,000	-8,183,000	-10,710,000	-62,222,000	-22,279,000	-27,573,000
Change in fair value of warrant liability	61,000	-31,000	-2,000	14,000	2,000	-25,000	999,000	-609,000	42,000	367,000	1,287,000
Interest expense	-1,000	-1,000	-2,000	'	'	-8,357,000	-230,000	-21,000	-4,000	-8,608,000	-19,000
Other income, net	-126,000	47,000	15,000	127,000	41,000	28,000	-2,000	541,000	63,000	608,000	11,000
Net loss before income taxes	-14,625,000	-20,089,000	-12,562,000	-14,845,000	-10,262,000	-1,435,000	-7,416,000	-10,799,000	-62,121,000	-29,912,000	-26,294,000
Income taxes	3,000	432,000	'	'	'	'	'	'	435,000	'	'
Net loss	-14,628,000	-20,521,000	-12,562,000	-14,845,000	-10,262,000	-1,435,000	-7,416,000	-10,799,000	-62,556,000	-29,912,000	-26,294,000
Net loss attributable to non-controlling interest	13,000	'	'	'	'	'	'	'	13,000	'	'
Net loss attributable to Onconova Therapeutics, Inc.	-14,615,000	-20,521,000	-12,562,000	-14,845,000	-10,262,000	-1,435,000	-7,416,000	-10,799,000	-62,543,000	-29,912,000	-26,294,000
Accretion of redeemable convertible preferred stock	'	-269,000	-1,032,000	-1,019,000	-1,010,000	-785,000	-927,000	-1,231,000	-2,320,000	-3,953,000	-4,020,000
Net loss applicable to common stockholders	($14,615,000)	($20,790,000)	($13,594,000)	($15,864,000)	($11,272,000)	($2,220,000)	($8,343,000)	($12,030,000)	($64,863,000)	($33,865,000)	($30,314,000)
Net loss per share of common stock, basic and diluted (in dollars per share)	($0.68)	($1.34)	($5.21)	($6.08)	($4.89)	($1.02)	($3.84)	($5.53)	($6.12)	($15.35)	($14.18)
Basic and diluted weighted average shares outstanding (in shares)	21,419,208	15,480,416	2,609,495	2,607,406	2,305,315	2,174,392	2,173,549	2,173,553	10,594,227	2,206,888	2,137,403

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (USD $)	12 Months Ended
Consolidated Statements of Comprehensive Loss (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements of Comprehensive Loss	'	'	'
Net loss	($62,556,000)	($29,912,000)	($26,294,000)
Other comprehensive income, before tax:	'	'	'
Foreign currency translation adjustments, net	1,000	'	'
Other comprehensive income, net of tax	1,000	'	'
Comprehensive loss	-62,555,000	-29,912,000	-26,294,000
Comprehensive loss attributable to non-controlling interest	13,000	'	'
Comprehensive loss attributable to Onconova Therapeutics, Inc.	($62,542,000)	($29,912,000)	($26,294,000)

Consolidated_Statements_of_Red

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (USD $)	Total	Redeemable Convertible Preferred Stock	Preferred Stock	Common Stock	Additional Paid in Capital	Accumulated deficit	Accumulated other comprehensive income	Non-controlling interest
Balance at Dec. 31, 2010	($108,717,000)	$105,734,000	$300,000	$21,000	$7,000	($108,745,000)	'	'
Balance (in shares) at Dec. 31, 2010	'	10,211,835	'	2,068,032	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'
Net loss	-26,294,000	'	'	'	'	-26,294,000	'	'
Net loss	-26,294,000	'	'	'	'	'	'	'
Issuance of preferred stock, net of issuance costs	'	7,917,000	-300,000	'	'	'	'	'
Issuance of preferred stock, net of issuance costs (in shares)	'	819,329	'	'	'	'	'	'
Exercise of stock options	612,000	'	'	1,000	611,000	'	'	'
Exercise of stock options (in shares)	'	'	'	99,896	'	'	'	'
Issuance of preferred stock upon exercise of warrants	'	2,326,000	'	'	'	'	'	'
Issuance of preferred stock upon exercise of warrants (in shares)	'	196,005	'	'	'	'	'	'
Accretion of preferred stock to redemption value	-4,020,000	4,020,000	'	'	-618,000	-3,402,000	'	'
Balance at Dec. 31, 2011	-138,419,000	119,997,000	'	22,000	'	-138,441,000	'	'
Balance (in shares) at Dec. 31, 2011	'	11,227,169	'	2,167,928	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'
Net loss	-29,912,000	'	'	'	'	-29,912,000	'	'
Net loss	-29,912,000	'	'	'	'	'	'	'
Issuance of preferred stock, net of issuance costs	'	47,796,000	'	'	'	'	'	'
Issuance of preferred stock, net of issuance costs (in shares)	'	3,030,303	'	'	'	'	'	'
Exercise of stock options	4,694,000	'	'	4,000	4,690,000	'	'	'
Exercise of stock options (in shares)	'	'	'	438,556	'	'	'	'
Proceeds from stockholder in connection with settlement of stock option exercises	3,943,000	'	'	'	3,943,000	'	'	'
Settlement of stock option liabilities	-2,835,000	'	'	'	-2,835,000	'	'	'
Issuance of preferred stock upon exercise of warrants	'	2,802,000	'	'	'	'	'	'
Issuance of preferred stock upon exercise of warrants (in shares)	'	221,399	'	'	'	'	'	'
Exchange of convertible debt and preferred stock	'	26,767,000	'	'	'	'	'	'
Exchange of convertible debt and preferred stock (in shares)	'	2,433,328	'	'	'	'	'	'
Beneficial conversion feature on convertible debt	8,176,000	'	'	'	8,176,000	'	'	'
Accretion of preferred stock to redemption value	-3,953,000	3,953,000	'	'	-3,953,000	'	'	'
Balance at Dec. 31, 2012	-158,306,000	201,315,000	'	26,000	10,021,000	-168,353,000	'	'
Balance (in shares) at Dec. 31, 2012	'	16,912,199	'	2,606,484	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'
Net loss	-62,543,000	'	'	'	'	-62,543,000	'	'
Net loss	-62,556,000	'	'	'	'	'	'	-13,000
Contribution from non-controlling interest	500,000	'	'	'	'	'	'	500,000
Other comprehensive income	1,000	'	'	'	'	'	1,000	'
Exercise of stock options	195,000	'	'	1,000	194,000	'	'	'
Exercise of stock options (in shares)	'	'	'	81,204	'	'	'	'
Stock-based compensation	5,462,000	'	'	'	5,462,000	'	'	'
Reclassification of stock option liability	14,482,000	'	'	'	14,482,000	'	'	'
Conversion convertible preferred stock into common stock	203,631,000	-203,635,000	'	129,000	203,502,000	'	'	'
Conversion convertible preferred stock into common stock (in shares)	'	-16,912,199	'	12,838,127	'	'	'	'
Issuance of common stock, net of issuance costs	79,811,000	'	'	59,000	79,752,000	'	'	'
Issuance of common stock, net of issuance costs (in shares)	'	'	'	5,941,667	'	'	'	'
Accretion of preferred stock to redemption value	-2,320,000	2,320,000	'	'	-2,320,000	'	'	'
Balance at Dec. 31, 2013	$80,900,000	'	'	$215,000	$311,093,000	($230,896,000)	$1,000	$487,000
Balance (in shares) at Dec. 31, 2013	'	'	'	21,467,482	'	'	'	'

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
Consolidated Statements of Cash Flows (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities:	'	'	'
Net loss	($62,556,000)	($29,912,000)	($26,294,000)
Adjustment to reconcile net loss to net cash (used in) provided by operating activities:	'	'	'
Depreciation and amortization	446,000	319,000	316,000
Loss on asset disposal	'	3,000	'
Amortization of deferred financing fees	'	15,000	21,000
Amortization of debt discount	'	8,176,000	'
Change in fair value of warrant liabilities	-42,000	-367,000	-1,287,000
Treasury note discount amortization	-4,000	'	'
Stock compensation expense	8,015,000	13,844,000	6,000
Changes in assets and liabilities:	'	'	'
Grants receivable	'	78,000	1,730,000
Prepaid expenses and other current assets	-2,662,000	-1,098,000	253,000
Other assets	'	-15,000	'
Accounts payable	-1,807,000	-97,000	2,230,000
Accrued expenses	1,894,000	2,573,000	1,123,000
Other liabilities	-37,000	-41,000	58,000
Deferred revenue	-4,631,000	8,155,000	7,673,000
Net cash (used in) provided by operating activities	-61,384,000	1,633,000	-14,171,000
Investing activities:	'	'	'
Payments for purchase of property and equipment	-609,000	-279,000	-256,000
Security deposits	'	'	15,000
Purchases of marketable securities	-39,990,000	'	'
Net cash used in investing activities	-40,599,000	-279,000	-241,000
Financing activities:	'	'	'
Proceeds from initial public offering of common stock, net of issuance costs	79,811,000	'	'
Proceeds from the exercise of stock options	157,000	165,000	154,000
Contribution from non-controlling interest	500,000	'	'
Reverse stock split cash paid in lieu of fractional shares	-4,000	'	'
Proceeds from stockholder in connection with settlement of stock option exercises	'	3,943,000	'
Settlement of stock options	'	-2,835,000	'
Proceeds from the exercise of warrants	'	2,167,000	1,918,000
Repayments of long-term debt	'	'	-917,000
Release of cash restricted for debt repayment	'	'	792,000
Proceeds from stockholder loan and convertible debt	'	25,824,000	620,000
Net cash provided by financing activities	80,464,000	77,460,000	9,785,000
Effect of foreign currency translation on cash	1,000	'	'
Net (decrease) increase in cash and cash equivalents	-21,518,000	78,814,000	-4,627,000
Cash and cash equivalents at beginning of period	81,527,000	2,713,000	7,340,000
Cash and cash equivalents at end of period	60,009,000	81,527,000	2,713,000
Supplemental disclosure of cash flow information:	'	'	'
Income taxes paid	435,000	'	'
Series H Preferred Stock	'	'	'
Financing activities:	'	'	'
Proceeds from the sale of preferred stock	'	400,000	7,218,000
Series J Preferred Stock	'	'	'
Financing activities:	'	'	'
Proceeds from the sale of preferred stock	'	$47,796,000	'

Nature_of_Business

Nature of Business	12 Months Ended
Nature of Business	Dec. 31, 2013
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 wide variety of cancers without causing harm to normal cells. The Company has three clinical-stage product candidates and six preclinical programs. To accelerate and broaden the development of rigosertib, the Company's most advanced product candidate, the Company entered into a collaboration and license agreement in 2012 with Baxter Healthcare SA ("Baxter"), a subsidiary of Baxter International Inc., to commercialize rigosertib in Europe. In 2011, the Company entered into a collaboration and license agreement with SymBio Pharmaceuticals Limited ("SymBio") 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 a collaboration agreement with GVK Biosciences Private Limited, a private limited company located in India, ("GVK BIO") to collaborate and develop two new clinical programs using the Company's technology platform.

	Liquidity

	The Company has incurred recurring operating losses since inception. For the year ended December 31, 2013, the Company incurred a net loss of $62,556,000 and as of December 31, 2013, the Company had generated an accumulated deficit of $230,896,000. The Company anticipates operating losses to continue for the foreseeable future due to, among other things, costs related to research funding, development of its product candidates and its preclinical programs, strategic alliances and the development of its administrative organization. The Company will require substantial additional financing to fund its operations and to continue to execute its strategy.

	The Company raised significant capital through the issuance of its 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"). See Note 10.

	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. As a result of the conversion, as of July 30, 2013, the Company had no shares of Preferred Stock outstanding. See Note 10.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
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.

	Prior to completion of its IPO on July 30, 2013, the Company utilized estimates and assumptions in determining the fair value of its Common Stock. The Company granted stock options at exercise prices not less than the fair value of its Common Stock as determined by the board of directors, with input from management. Management used the assistance of a third-party valuation firm in estimating the fair value of the Common Stock. The board of directors determined the estimated fair value of the Common Stock based on a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector and the historic prices at which the Company sold shares of Preferred Stock.

	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.

	Marketable Securities

	Marketable securities with original maturities longer than three months but which mature in less than one year from the balance sheet date are classified as current assets. Marketable securities that mature more than one year from the balance sheet date are classified as noncurrent assets. Marketable securities that the Company has the intent and ability to hold to maturity are classified as investments held-to-maturity and are reported at amortized cost. The difference between the acquisition cost and face values of held-to-maturity investments is amortized over the remaining term of the investments and added to or subtracted from the acquisition cost and interest income. As of December 31, 2013, all of the Company's investments were classified as held-to-maturity.

	Fair Value of Financial Instruments

	The carrying amounts reported in the accompanying consolidated financial statements for cash and cash equivalents, marketable securities, accounts payable and accrued liabilities approximate their respective fair values because of the short-term nature of these accounts. The fair value of the warrant liability is discussed in Note 4, "Fair Value Measurements."

	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, 2013.

	Restricted Cash

	Under the Company's office lease, the Company is required to provide the landlord a $125,000 letter of credit, which is recorded as restricted cash on the consolidated balance sheets as of December 31, 2013 and 2012.

	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

	Currently, 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.

The Company recognized revenue of $4,176,000 and $45,490,000 during the years ended December 31, 2013 and 2012, respectively, as a result of its license and collaboration agreement with Baxter. The Company recognized revenue of $577,000, $503,000 and $227,000 during the years ended December 31, 2013, 2012 and 2011, respectively, as a result of its license and collaboration agreement with SymBio. The remaining revenue recognized during the years ended December 31, 2012 and 2011 of $197,000 and $1,260,000, respectively, pertained to research and development services provided by the Company under certain research grants. The Baxter and SymBio agreements are the only agreements that are being accounted for under ASU 2009-13. See Note 15, "License and Collaboration Agreements," for a further discussion of the agreements with Baxter and SymBio.

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 8, "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.

Preferred Stock

The Company accounted for the redemption premium and issuance costs on its Preferred Stock using the effective interest method, accreting such amounts to its Preferred Stock from the date of issuance to the earliest date of redemption. 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. As a result of the conversion, as of July 30, 2013, the Company had no shares of Preferred Stock outstanding. See Note 10.

Stock Warrants

Freestanding warrants that are related to the purchase of Stock are classified as liabilities and recorded at fair value. The warrants are subject to re-measurement at each balance sheet date and any change in fair value is recognized as a component of change in fair value of warrant liability in the consolidated statements of operations. See Note 10. The warrants are classified as Level 3 liabilities (see Note 4 for a discussion of the fair value hierarchy).

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 11) 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, 2013, 2012 and 2011, 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 15, "License and Collaboration Agreements," for a discussion of the Company's current collaborations with Baxter 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 Preferred Stock, warrants to purchase Preferred Stock and stock options. 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 Preferred Stock and warrants to purchase Preferred Stock, and stock options 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, 2013, 2012 and 2011.

Recent Accounting Pronouncements

In February 2013, the Financial Accounting Standards Board (the "FASB") amended its guidance to require an entity to present the effect of certain significant reclassifications out of accumulated other comprehensive income on the respective line items in net income. The new accounting guidance does not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income. The guidance is effective prospectively for fiscal years beginning after December 15, 2012. The Company adopted these new provisions for the quarter beginning January 1, 2013. As the guidance requires additional presentation only, there was no impact to the Company's consolidated financial position, results of operations or cash flows.

In July 2013, the FASB issued guidance clarifying that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax benefit is disallowed. In situations where a net operating loss carryforward, a similar tax loss, or a tax credit carryforward is not available at the reporting date under the tax law of the applicable jurisdiction or the tax law of the jurisdiction does not require, and the entity does not intend to use, the deferred tax asset for such purpose, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be netted with the deferred tax asset. The guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. Early adoption is permitted. The guidance is to be applied prospectively to all unrecognized tax benefits that exist at the effective date. Retrospective application is permitted. The Company is currently evaluating the impact that adoption will have on the determination or reporting of its financial results.

Property_and_Equipment

Property and Equipment	12 Months Ended
Property and Equipment	Dec. 31, 2013
Property and Equipment	'
Property and Equipment	'

	3. Property and Equipment

	Property and equipment and related accumulated depreciation are as follows:


		December 31,
		2013			2012
	Laboratory equipment	$	866,000		$	764,000
	Software		92,000			91,000
	Computer and office equipment		433,000			323,000
	Leasehold improvements		1,011,000			633,000


			2,402,000			1,811,000
	Less accumulated depreciation		(1,776,000	)		(1,348,000	)


	Property and equipment, net	$	626,000		$	463,000





	Depreciation and amortization expense was $449,000, $319,000 and $316,000 for the years ended December 31, 2013, 2012 and 2011, respectively.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2013
Fair Value Measurements	'
Fair Value Measurements	'

	4. Fair Value Measurements

	The Company applies various valuation approaches in determining the fair value of its financial assets and liabilities within a hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company's assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available under the circumstances. The fair value hierarchy is broken down into three levels based on the source of inputs as follows:

	Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access.

	Level 2—Valuations based on quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active and models for which all significant inputs are observable, either directly or indirectly.

	Level 3—Valuations based on inputs that are unobservable and significant to the overall fair value measurement.

	The availability of observable inputs can vary among the various types of financial assets and liabilities. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, for financial statement disclosure purposes, the level in the fair value hierarchy within which the fair value measurement is classified is based on the lowest level input that is significant to the overall fair value measurement.

	The Company had no assets or liabilities classified as Level 1 or Level 2. The Series G Preferred Stock warrants (see Note 10) are classified as Level 3. The fair values of these instruments are determined using models based on market observable inputs and management judgment. There were no material re-measurements of fair value during the years ended December 31, 2013 and 2012 with respect to financial assets and liabilities, other than those assets and liabilities that are measured at fair value on a recurring basis.

	The Company has classified the Series G Preferred Stock warrants as a liability and has re-measured the liability to estimated fair value at December 31, 2013 and 2012, using the Black-Scholes option pricing model using the following assumptions: contractual life according to the remaining terms of the warrants, no dividend yield, weighted average risk-free interest rate of 0.34% and 0.31% at December 31, 2013 and 2012, respectively, and weighted average volatility of 74.40% and 64.87% at December 31, 2013 and 2012, respectively

	The following fair value hierarchy table presents information about the Company's financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2013 and 2012.


		Fair Value Measurement as of									Fair Value Measurement as of
		December 31, 2013									December 31, 2012
		Level 1			Level 2		Level 3		Balance		Level 1		Level 2		Level 3		Balance
	Warrant liability	$	—		$	—	$	20,000	$	20,000	$	—	$	—	$	62,000	$	62,000


	Total	$	—		$	—	$	20,000	$	20,000	$	—	$	—	$	62,000	$	62,000





	The following table presents a reconciliation of the Company's liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the years ended December 31, 2013 and 2012:


		Warrant
		Liability
	Balance at December 31, 2011	$	1,064,000
	Settlements of warrant liability awards		(635,000	)
	Expiration of warrant liability awards		(975,000	)
	Change in fair value upon re-measurement		608,000


	Balance at December 31, 2012		62,000
	Change in fair value upon re-measurement		(42,000	)


	Balance at December 31, 2013	$	20,000





	The fair values of cash equivalents, marketable securities, accounts payable and accrued liabilities approximate their respective carrying values due to the short-term nature of these accounts.

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

Net_Loss_Per_Share_of_Common_S

Net Loss Per Share of Common Stock	12 Months Ended
Net Loss Per Share of Common Stock	Dec. 31, 2013
Net Loss Per Share of Common Stock	'
Net Loss Per Share of Common Stock	'

	5. 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, 2013, 2012 and 2011:


		Year ended December 31,
		2013			2012			2011
	Basic and diluted net loss per share of common stock:
	Net loss	$	(62,543,000	)	$	(29,912,000	)	$	(26,294,000	)
	Accretion to redemption value of preferred stock		(2,320,000	)		(3,953,000	)		(4,020,000	)


	Net loss applicable to common stockholders	$	(64,863,000	)	$	(33,865,000	)	$	(30,314,000	)




	Weighted average shares of common stock outstanding		10,594,227			2,206,888			2,137,403




	Net loss per share of common stock—basic and diluted	$	(6.12	)	$	(15.35	)	$	(14.18	)





	The following potentially dilutive securities outstanding at December 31, 2013, 2012 and 2011 have been excluded from the computation of diluted weighted average shares outstanding, as they would be antidilutive:


		December 31,
		2013			2012			2011
	Preferred Stock		—			12,838,127			8,575,918
	Warrants		4,597			4,597			426,539
	Stock options		4,344,365			2,564,147			2,026,396


			4,348,962			15,406,871			11,028,853

Balance_Sheet_Detail

Balance Sheet Detail	12 Months Ended
Balance Sheet Detail	Dec. 31, 2013
Balance Sheet Detail	'
Balance Sheet Detail	'

	6. Balance Sheet Detail

	Prepaid expenses and other current assets are as follows:


		December 31,
		2013		2012
	Research and development	$	2,242,000	$	1,429,000
	Manufacturing		1,051,000		—
	Insurance		645,000		101,000
	Other		449,000		195,000


		$	4,387,000	$	1,725,000





	Accrued expenses and other current liabilities are as follows:


		December 31,
		2013		2012
	Research and development	$	4,625,000	$	3,521,000
	Employee compensation		509,000		247,000
	Taxes		302,000		—
	Other		384,000		157,000


		$	5,820,000	$	3,925,000

Debt

Debt	12 Months Ended
Debt	Dec. 31, 2013
Debt	'
Debt	'

	7. Debt

	In December 2011, the chairman of the Company's board of directors, who is also a significant stockholder of the Company, advanced $620,000 to the Company to fund operations. Interest accrued at 10% per annum. The stockholder loan was exchanged for convertible promissory notes in April 2012 (see Note 9).

Income_Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2013
Income Taxes	'
Income Taxes	'

	8. 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:


			Year Ended December 31,
			2013			2012			2011
	Domestic		$	(62,154,000	)	$	(29,912,000	)	$	(26,294,000	)
	Foreign			33,000			—			—


	Total		$	(62,121,000	)	$	(29,912,000	)	$	(26,294,000	)





	The provision for income taxes consists of the following:


			Year Ended December 31,
			2013			2012			2011
	Current
	US Federal		$	140,000		$	—		$	—
	State and Local			285,000			—			—
	Foreign			10,000			—			—


	Total Current		$	435,000		$	—		$	—


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


	Total Deferred		$	—		$	—		$	—


	Total Expense (Benefit)		$	435,000		$	—		$	—





	As of December 31, 2013, the Company had federal net operating loss ("NOL") carry forwards of $119,165,000, state NOL carry forwards of $99,165,000 and research and development tax credit carry forwards of $35,085,000, 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 shareholders 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, 2013, 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:


			Year Ended December 31,
			2013			2012
	Deferred tax assets:
	Net operating loss carryovers		$	47,364,000		$	35,921,000
	R&D tax credits			35,223,000			13,868,000
	Non-qualified stock options			3.988,000			1,057,000
	Deferred revenue			5,938,000			4,246,000
Charitable contributions			6,000			6,000
Accrued expenses			586,000			40,000
Fixed assets			199,000			159,000


Deferred tax assets			93,304,000			55,297,000
Less valuation allowance			(93,304,000	)		(55,297,000	)


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, 2013 and 2012, 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 $38,007,000and $8,718,000 for the years ended December 31, 2013 and 2012, 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:


		Year Ended
		December 31,
		2013			2012			2011
Federal income tax expense at statutory rate			34	%		34	%		34	%
Permanent items			(8.3	)		(25.1	)		(5.6	)
State income tax, net of federal benefit			4.5			1.8			6.2
Tax credits			34.4			18.5			22.1
Provision to return			(3.8	)		0			(5.1	)
Change in valuation allowance			(61.2	)		(29.1	)		(51.6	)
Other			(0.2	)		(0.1	)		0


Effective income tax rate			(0.6	)%		0	%		0	%

Convertible_Promissory_Notes

Convertible Promissory Notes	12 Months Ended
Convertible Promissory Notes	Dec. 31, 2013
Convertible Promissory Notes	'
Convertible Promissory Notes	'

	9. Convertible Promissory Notes

	In March 2012, the Company offered to its stockholders the opportunity to participate in a $30,000,000 private placement of convertible promissory notes (the "Convertible Debt Offering"). From April through July 2012, the Company had aggregate closings of the Convertible Debt Offering of $26,444,000, including $620,000 from the principal that remained outstanding on a stockholder loan at December 31, 2011.

	The convertible promissory notes issued in the Convertible Debt Offering carried a 10% interest rate calculated on the basis of a 360-day year and were scheduled to mature on June 29, 2013. The convertible promissory notes provided the holder the right to convert any portion of the outstanding principal and interest in exchange for equity instruments upon the completion of an initial public offering that generated aggregate proceeds in excess of $25,000,000 (the "IPO Scenario") or upon the completion of an equity offering that generated aggregate proceeds in excess of $15,000,000 (the "Equity Scenario"). In the event of a conversion under the IPO Scenario, the holder would have received shares of Common Stock equal to the offering price that was initially offered to the public. In the event of a conversion under the Equity Scenario, the holder would have received equity instruments equivalent to those issued in the Equity Scenario at a conversion price equal to the lower of $11.00 per share or the original issuance price of the underlying equity instrument. If the Company merged with another company while the convertible promissory notes were still outstanding, immediately after which the Company's stockholders owned less than 50% of the voting stock of the surviving company, then each convertible promissory note would have been required to be redeemed for an amount equal to two times the outstanding principal amount together with any unpaid and accrued interest.

	In July 2012, the Company amended and restated its certificate of incorporation and designated Series I Preferred Stock. The Company and the holders of the convertible promissory notes amended the Equity Scenario provision of the notes to permit the holders to convert the convertible promissory notes into shares of Series I Preferred Stock at a conversion price of $11.00 per share.

	In connection with the amendment of the convertible promissory notes, the notes were also analyzed to determine the existence of a beneficial conversion feature. The Company concluded that an $8,176,000 contingent beneficial conversion feature existed related to the Equity Scenario as of July 2012. The fair value of the Series I Preferred Stock used to calculate the value of the beneficial conversion feature was determined by management with the assistance of a third-party valuation firm.

	On July 27, 2012, the holders of the convertible promissory notes exercised their right to convert the outstanding principal and interest into Series I Preferred Stock. Upon conversion, the holders received 2,443,328 shares of Series I Preferred Stock, and the Company recorded interest expense of $8,176,000, which was equal to the amount of the unamortized contingent beneficial conversion feature.

Preferred_Stock_and_Stockholde

Preferred Stock and Stockholders' Equity (Deficit)	12 Months Ended
Preferred Stock and Stockholders' Equity (Deficit)	Dec. 31, 2013
Preferred Stock and Stockholders' Equity (Deficit)	'
Preferred Stock and Stockholders' Equity (Deficit)	'

	10. Preferred Stock and Stockholders' Equity (Deficit)

	Capitalization

	The following is the composition of share capital as of December 31, 2013 and 2012:


			Authorized						Issued and Outstanding
			December 31,			December 31,			December 31,			December 31,
			2013			2012			2013			2012
	Shares of $0.01 par value per share:
	Common stock			75,000,000			30,145,155			21,467,482			2,606,484




	Shares of $0.01 par value per share:
	Preferred Stock			5,000,000			—			—			—




	Redeemable Preferred Stock:
	Series A Preferred Stock			—			400,000			—			107,000
	Series B Preferred Stock			—			1,200,000			—			1,107,189
	Series C Preferred Stock			—			1,200,000			—			1,069,946
	Series D Preferred Stock			—			1,625,000			—			1,583,568
	Series E Preferred Stock			—			1,650,000			—			1,633,082
	Series F Preferred Stock			—			2,000,000			—			2,000,000
	Series G Preferred Stock			—			2,700,000			—			1,934,359
	Series H Preferred Stock			—			2,042,950			—			2,013,424
	Series I Preferred Stock			—			2,700,000			—			2,433,328
	Series J Preferred Stock			—			3,030,303			—			3,030,303


	Total Redeemable Preferred Stock			—			18,548,253			—			16,912,199





	In preparation for the IPO, the Company's board of directors and stockholders approved a one-for-1.333 reverse stock split of the Company's Common Stock. The reverse stock split became effective on July 17, 2013. All Common Stock share and per share amounts in the condensed consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. The reverse stock split did not result in a retroactive adjustment of share amounts for the Preferred Stock.

	In July 2012, the Company issued 2,433,328 shares of Series I Preferred Stock in exchange for the conversion of the convertible promissory notes and accrued interest in the amount of $26,444,000 and $323,000, respectively. The effective conversion price was $11.00 per share. Additionally, in July 2012, the Company issued 3,030,303 shares of Series J Preferred Stock at $16.50 per share for gross proceeds of $50,000,000. Issuance costs associated with this offering were $2,204,000.

	Series A Preferred Stock was issued at $5.00 per share; Series B Preferred Stock was issued at $5.75 per share; Series C Preferred Stock was issued at $3.56 per share; Series D Preferred Stock was issued at $4.67 per share; Series E Preferred Stock was issued at $9.76 per share; Series F Preferred Stock was issued at $11.00 per share; Series G and Series H Preferred Stock were issued at $9.79 per share; Series I Preferred Stock was issued at $11.00 per share; and Series J Preferred Stock was issued at $16.50 per share.

	The following is the activity of the Preferred Stock for the year ended December 31, 2013 and 2012:


			December 31,			Issuance of			Exercise of			Accretion of			Conversion of			December 31,
			2012			Preferred			warrants			redemption			Preferred Stock			2013
						Stock						premium and			into Common
												issuance costs			Stock
												on Preferred
												Stock
	Series A
	Shares			107,000			—			—			—			(107,000	)		—
	Amount		$	535,000		$	—		$	—		$	—		$	(535,000	)	$	—
	Series B
	Shares			1,107,189			—			—			—			(1,107,189	)		—
	Amount		$	12,733,000		$	—		$	—		$	—		$	(12,733,000	)	$	—
Series C
Shares			1,069,946			—			—			—			(1,069,946	)		—
Amount		$	7,618,000		$	—		$	—		$	—		$	(7,618,000	)	$	—
Series D
Shares			1,583,568			—			—			—			(1,583,568	)		—
Amount		$	18,211,000		$	—		$	—		$	—		$	(18,211,000	)	$	—
Series E
Shares			1,633,082			—			—			—			(1,633,082	)		—
Amount		$	18,780,000		$	—		$	—		$	—		$	(18,780,000	)	$	—
Series F
Shares			2,000,000			—			—			—			(2,000,000	)		—
Amount		$	23,000,000		$	—		$	—		$	—		$	(23,000,000	)	$	—
Series G
Shares			1,934,359			—			—			—			(1,934,359	)		—
Amount		$	22,819,000		$	—		$	—		$	—		$	(22,819,000	)	$	—
Series H
Shares			2,013,424			—			—			—			(2,013,424	)		—
Amount		$	22,005,000		$	—		$	—		$	868,000		$	(22,873,000	)	$	—
Series I
Shares			2,433,328			—			—			—			(2,433,328	)		—
Amount		$	26,933,000		$	—		$	—		$	226,000		$	(27,159,000	)	$	—
Series J
Shares			3,030,303			—			—			—			(3,030,303	)		—
Amount		$	48,681,000		$	—		$	—		$	1,226,000		$	(49,907,000	)	$	—


Total
Shares			16,912,199			—			—			—			(16,912,199	)		—


Amount		$	201,315,000		$	—		$	—		$	2,320,000		$	(203,635,000	)	$	—









		January 1,			Issuance of			Exercise of			Accretion of			December 31,
		2012			Preferred			warrants			redemption			2012
					Stock						premium and
											issuance costs on
											Preferred Stock
Series A
Shares			107,000			—			—			—			107,000
Amount		$	535,000		$	—		$	—		$	—		$	535,000
Series B
Shares			1,107,189			—			—			—			1,107,189
Amount		$	12,733,000		$	—		$	—		$	—		$	12,733,000
Series C
Shares			1,069,946			—			—			—			1,069,946
Amount		$	7,618,000		$	—		$	—		$	—		$	7,618,000
Series D
Shares			1,583,568			—			—			—			1,583,568
Amount		$	18,211,000		$	—		$	—		$	—		$	18,211,000
Series E
Shares			1,633,082			—			—			—			1,633,082
Amount		$	18,780,000		$	—		$	—		$	—		$	18,780,000
Series F
Shares			2,000,000			—			—			—			2,000,000
Amount		$	23,000,000		$	—		$	—		$	—		$	23,000,000
Series G
Shares			1,712,960			—			221,399			—			1,934,359
Amount		$	18,574,000		$	—		$	2,802,000		$	1,443,000		$	22,819,000
Series H
Shares			2,013,424			—			—			—			2,013,424
Amount		$	20,546,000		$	—		$	—		$	1,459,000		$	22,005,000
Series I
Shares			—			2,433,328			—			—			2,433,328
Amount		$	—		$	26,767,000		$	—		$	166,000		$	26,933,000
Series J
Shares			—			3,030,303			—			—			3,030,303
Amount		$	—		$	47,796,000		$	—		$	885,000		$	48,681,000


Total
Shares			11,227,169			5,463,631			221,399			—			16,912,199


Amount		$	119,997,000		$	74,563,000		$	2,802,000		$	3,953,000		$	201,315,000





Voting

Prior to the consummation of the IPO, each holder of outstanding shares of Preferred Stock had the right to one vote for each share of Common Stock into which such Preferred Stock could then be converted. The holders of shares of Preferred Stock had full voting rights and powers equal to the voting rights and powers of shares of Common Stock and were entitled to notice of any stockholders' meeting and voted together with the holders of Common Stock, with respect to any question upon which holders of shares of Common Stock have the right to vote, as a single class, including without limitation, actions to increase or decrease the aggregate number of authorized shares of Common Stock and/or Preferred Stock.

Dividends

Prior to the consummation of the IPO, the holders of each share of Series A, Series B, Series C, Series D, Series E, Series F, Series G, Series H, Series I and Series J Preferred Stock were entitled to receive dividends when, as, and if declared by the Company's board of directors in the following order of preference: (i) the Series D, Series E, Series F, Series G, Series H, Series I and Series J Preferred Stock, which ranked pari passu; (ii) the Series B and Series C Preferred Stock, which ranked pari passu; (iii) the Series A Preferred Stock; and then (iv) Common Stock.

Liquidation

Prior to the consummation of the IPO, the assets of the Company legally available for distribution to stockholders were distributable in the following order of priority: (i) the holders of the shares of Series D, Series E, Series F, Series G, Series H, Series I and Series J Preferred Stock, which ranked pari passu; (ii) the holders of the shares of Series B and Series C Preferred Stock, which ranked pari passu; (iii) the holders of the shares of Series A Preferred Stock; and (iv) the holders of the shares of Common Stock. Each series of Preferred Stock was entitled to receive an amount per share equal to the greater of (1) the original issuance price for such series, plus all declared but unpaid dividends thereon, or (2) the amount that the holders of such series would receive per share of Common Stock if all shares of such series of Preferred Stock were converted to Common Stock immediately prior to such liquidation. If, upon a deemed liquidation event, the assets of the Company were insufficient to make payment in full to all holders of a series of Preferred Stock, then such assets would be distributed among the holders of such series of Preferred Stock at the time outstanding ratably in proportion to the full amount to which they would otherwise be respectively entitled. The holders of Common Stock were entitled to receive, after the payment of the liquidation preference of all Preferred Stock outstanding, the remaining assets of the Company on a pro rata basis.

Conversion

Prior to the consummation of the IPO, each issued and outstanding share of Preferred Stock was convertible into Common Stock at the holder's option at any time after the date of issuance or automatically upon the occurrence of certain events as defined in the Company's ninth amended and restated certificate of incorporation, at a defined conversion rate. Prior to the consummation of the IPO, the number of shares of Common Stock into which one share of each series of Preferred Stock was convertible was as follows, after giving effect to the reverse stock split discussed in Note 18: the Series A Preferred Stock, 0.80; the Series B Preferred Stock, 0.85; the Series C Preferred Stock, 0.75; the Series D Preferred Stock, 0.75; the Series E Preferred Stock, 0.75; the Series F Preferred Stock, 0.77; the Series G Preferred Stock, 0.75; the Series H Preferred Stock, 0.75; the Series I Preferred Stock, 0.75; and the Series J Preferred Stock, 0.75.

The conversion price for each share of Preferred Stock was subject to adjustment upon the occurrence of certain events. The conversion price of each share of a series of Preferred Stock was adjusted if the Company issued additional shares, subject to specified exceptions, at a price lower than the then current conversion price for such series, which is measured and recognized if the contingency occurs.

On July 30, 2013, 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. See Note 10.

Redemption

To the extent it was then lawfully able to do so, the Company was required at any time, upon written request of the holders of at least 66.67% of the then outstanding Series A, Series B and Series C Preferred Stock collectively, or upon written request of the holders of at least a majority of the then outstanding shares of Series D, Series E and Series F Preferred Stock collectively, in each case as determined on an as-converted to Common Stock basis, to redeem the requested number of outstanding shares of Series A Preferred Stock at $5.00 per share, Series B Preferred Stock at $11.50 per share, and Series C Preferred Stock at $7.12 per share, and/or Series D, E and F Preferred Stock at $11.50 per share, as the case may be.

In addition, to the extent it was lawfully able to do so, the Company was required at any time, upon written request of the holders of at least a majority of the then outstanding shares of Series G Preferred Stock, to redeem, from the holders requesting such redemption, the requested number of outstanding shares of Series G Preferred Stock at $11.50 per share.

To the extent it would have been lawfully able to do so, the Company would have been required at any time on or after September 21, 2013, upon written request of the holders of at least a majority of the then outstanding shares of Series H Preferred Stock, to redeem, from the holders requesting such redemption, the requested number of outstanding shares of Series H Preferred Stock at $11.50 per share.

To the extent it would have been lawfully able to do so, the Company would have been required at any time on or after July 25, 2015, upon written request of the holders of at least a majority of the then outstanding shares of Series I Preferred Stock, to redeem, from the holders requesting such redemption, the requested number of outstanding shares of Series I Preferred Stock at $11.50 per share.

To the extent it would have been lawfully able to do so, the Company would have been required at any time on or after July 27, 2015, upon written request of the holders of at least a majority of the then outstanding shares of Series J Preferred Stock, to redeem, from the holders requesting such redemption, the requested number of outstanding shares of Series J Preferred Stock at $18.00 per share.

If, upon any applicable redemption date, defined as 60 days after the Company receives the written request for redemption, the funds of the Company legally available for redemption of Preferred Stock would have been insufficient to redeem the total number of shares to be redeemed on that date, those funds that were legally available would have been used to redeem the maximum possible number of shares, ratably among the holders of such shares to be redeemed. All remaining shares not redeemed would have remained outstanding until such time as additional funds became legally available for redemption.

If more than one series of Preferred Stock had been contemporaneously subject to redemption, the redemption rights of the Preferred Stock would have followed the liquidation order of priority. As of December 31, 2012, Preferred Stock with an aggregate redemption value of $103,122,000 was currently redeemable.

Warrant Transactions

The Company issued 6,128 Series G Preferred Stock warrants in connection with a loan and security agreement. Additionally, the Company issued one Series G Preferred Stock warrant for every two shares of Series G Preferred Stock purchased in 2009 and 2010. The warrants were initially recorded at their fair value calculated using the Black-Scholes model, with the following weighted average assumptions: exercise price of $9.79, share price of $9.79, expected term of three years, risk-free rate of 1.52% and volatility of 85.46%. The warrants are classified as liabilities because they are exercisable for Preferred Stock, and the value of the warrants is adjusted to current fair value at each reporting period end. For the years ended December 31, 2013, 2012 and 2011, the Company recorded $42,000, $367,000 and $1,287,000, respectively, in the consolidated statements of operations related to the change in the fair value of the outstanding warrants.

Immediately prior to the consummation of the IPO, the 6,128 Series G Preferred Stock warrants outstanding were automatically converted into 4,597 Common Stock warrants (after giving effect to the one-for-1.333 reverse stock split).

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
Stock-Based Compensation	Dec. 31, 2013
Stock-Based Compensation	'
Stock-Based Compensation	'

	11. 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. Under the 2007 Plan, the Company increased the number of shares reserved for issuance under the 2007 Plan such that the number of reserved shares is equal to 17% of the fully diluted shares calculated annually on December 10th.

	Further, in July 2013, the Company's board of directors and stockholders approved, effective immediately prior to the listing of the Common Stock on the NASDAQ Global Market, 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, of which 676,236 shares of Common Stock will be available for future issuance.


			2013			2012
	Shares of Common Stock reserved for issuance under the 2013 Plan			6,107,831			4,107,831





	Stock options may be granted with exercise prices of not less than the estimated fair value of the Common Stock on the date of grant and generally vest over a period of up to four years. Stock options granted under the 2013 Plan generally expire no later than ten years from the date of grant. A summary of stock option activity for the years ended December 31, 2013 and 2012 is as follows:


			Number of			Weighted-			Weighted-
			Options			Average			Average
						Exercise			Remaining
						Price			Contractual
									Term
									(in years)
	Outstanding at December 31, 2010			1,823,266		$	4.41			6.09
	Granted			344,479			6.13
	Exercised			(99,896	)		1.53
	Forfeited			(41,453	)		5.43


	Outstanding at December 31, 2011			2,026,396		$	4.81			6.39
	Granted			977,807			12.51
	Exercised			(438,556	)		2.9
	Forfeited			(1,500	)		1.53


	Outstanding at December 31, 2012			2,564,147			8.1			7.52
	Granted			1,967,940			14.6
	Exercised			(81,204	)		1.93
	Forfeited			(106,518	)		12.23


	Outstanding at December 31, 2013			4,344,365		$	11.05			7.91




	Vested or expected to vest at December 31, 2013			4,344,365		$	11.05			7.91
	Exercisable at December 31, 2013			2,347,744		$	8.72			6.63

	At December 31, 2013 and 2012, the aggregate intrinsic value of the option liability recorded was $0 and $11,967,000, respectively. During the years ended December 31, 2013 and 2012, the Company granted 1,967,940 and 977,807 options at an intrinsic value of $0 at the grant date.

	At certain times throughout the Company's history, the Significant Holder has afforded option holders the opportunity for liquidity in transactions in which options were exercised and the shares of Common Stock issued in connection therewith were simultaneously purchased by the Significant Holder. Because the Company has established a pattern of providing cash settlement alternatives for option holders, the Company has accounted for its stock-based compensation awards as liability awards, the fair value of which is then re-measured at each balance sheet date. Upon the exercise of stock options from January 1, 2013 through April 23, 2013, stock option liabilities of $38,000 were reclassified to stockholders' deficit.

	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.

	A roll forward of the stock option liability balance for the years ended December 31, 2013 and 2012 is as follows:


	Balance at December 31, 2011		$	2,648,000
	Change in intrinsic value upon re-measurement			13,844,000
	Settlements of option liability awards			(4,525,000	)


Balance at December 31, 2012			11,967,000
Change in intrinsic value upon re-measurement			2,553,000
Settlements of option liability awards			(38,000	)
Reclassification to stockholders' equity (deficit)			(14,482,000	)


Balance at December 31, 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 estimates the fair value of its share-based awards to employees and directors using the Black-Scholes option pricing model. The Black-Scholes model requires the input of highly complex and subjective assumptions, including (a) the expected stock price volatility, (b) the calculation of the expected term of the award, (c) the risk free interest rate and (d) expected dividends. 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. The Company has estimated the expected life of its employee stock options using the "simplified" method, whereby, the expected life equals the arithmetic average of the vesting term and the original contractual term of the option. The risk-free interest rates for periods within the expected life of the option are based on the U.S. Treasury yield curve in effect during the period the options were granted. The Company has never paid, and does not expect to pay dividends in the foreseeable future.

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.

During the period from April 23, 2013 through December 31, 2013, the Company granted options to purchase shares of its Common Stock as follows:


Shares			Exercise Price
	310,540		$	13.28
	4,800		$	14.75
	763,000		$	15
	17,500		$	21.79
	57,500		$	28.81
	500		$	27.71
	16,000		$	14.67
	32,500		$	14.68
	765,600		$	13.48

The Company recorded $4,733,000 of compensation expense related to these options. The fair value of these options was estimated using the Black-Scholes option pricing model with the following weighted-average assumptions: no dividend yield, volatility of 77.00%, maximum contractual life of 5.87 years, and a risk-free interest rate of 1.73%.

The weighted-average grant-date fair value of stock options granted during the period from April 23, 2013 through December 31, 2013 and the years ended December 31, 2012 and 2011 was $9.72, $0.00, and $0.00, respectively. The fair value of shares vested during the years ended December 31, 2013, 2012, and 2011 was $9,875,000, $5,554,000, and $1,712,000, respectively.

The Company recognized stock-based compensation expense as follows for the years ended December 31, 2013 and 2012:


		Year ended December 31,
		2013			2012			2011
General and administrative		$	4,845,000		$	7,199,000		$	3,000
Research and development			3,170,000			6,645,000			3,000


		$	8,015,000		$	13,844,000		$	6,000

As of December 31, 2013, there was $1,875,000 of unrecognized compensation expense related to the unvested liability awards, which is expected to be recognized over a weighted-average period of approximately 2.32 years.

As of December 31, 2013, there was $3,597,000 of unrecognized compensation expense related to the unvested stock options issued from April 23, 2013 through December 31, 2013, which is expected to be recognized over a weighted-average period of approximately 3.65 years. The Company accounts for stock options issued to nonemployees using a fair value approach.

Information with respect to stock options outstanding and exercisable at December 31, 2013 is as follows:


Exercise		Shares			Weighted			Exercisable
Price					Average
					Remaining
					Contractual
					Life (years)
$1.33 - $2.67			154,117			1.41			154,117
$5.76 - 6.00			801,208			4.92			792,730
$6.13 - $7.53			639,888			6.41			553,790
$13.28 - $13.48			1,870,852			9.97			418,644
$14.67 - $15.00			805,300			9.59			421,244
$21.79 - $28.81			73,000			9.72			7,219


			4,344,365			7.91			2,347,744





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. The intrinsic value of options exercised during the years ended December 31, 2013, 2012, and 2011 was $1,076,000, $4,510,000, and $459,000, respectively. At December 31, 2013 the aggregate intrinsic value of options outstanding and vested options were $10,212,000 and $9,742,000, respectively.

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2013
Employee Benefit Plan	'
Employee Benefit Plan	'

	12. 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 $0.50 ($0.60 beginning January 1, 2014) 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, 2013, 2012 and 2011, the Company contributed $289,000, $159,000 and $131,000, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies	'
Commitments and Contingencies	'

	13. Commitments and Contingencies

	Operating leases

	In November 2010, the Company entered into a lease for 3,117 square feet of office space in Pennington, New Jersey. The lease had an original term of two years, with an option for two additional years. For the first two years of the lease, the Company was obligated to pay $4,400 per month, or $53,000 annually, beginning when possession of the facility was taken on February 1, 2011. The Company was required to provide the landlord a $125,000 letter of credit, the collateral for which is recorded as restricted cash on the consolidated balance sheets. This lease was renewed on February 1, 2012 with a 3.5% increase in the rent, to $5,000 per month. On October 2, 2012, the Company leased an additional 2,130 square feet of office space for $3,100 per month, or $38,000 annually.

	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. The Company exercised the first option for the period from April 1, 2012 to March 31, 2013 and the second option for the period from April 1, 2013 to March 31, 2014 for rent of $11,000 per month. In September 2012, the Company sub-leased an additional 1,356 square feet of office space for one year for $1,600 per month, or $19,000 annually.

	Future minimum lease payments under these non-cancellable leases having terms in excess of one year as of December 31, 2013 are as follows:


		December 31, 2013
	2014	$	245,000
	2015		39,000


	Total minimum lease payments	$	284,000





	Rent expense was $309,000, $233,000 and $186,000 for the years ended December 31, 2013, 2012 and 2011, 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

Research Agreements	12 Months Ended
Research Agreements	Dec. 31, 2013
Research Agreements	'
Research Agreements	'

	14. 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, 2013 under the licensed patents, the Company did not incur any royalty expenses for the years ended December 31, 2013, 2012 and 2011. In addition, the Company is required to pay Temple 25% of any sublicensing fees received by the Company. In September 2011, the Company made a payment to Temple in the amount of $1,875,000 in connection with the collaboration agreement the Company executed in July 2011 with SymBio. Such payment was recorded in the consolidated statement of operations as research and development expenses. In 2012, the Company became obligated to pay Temple $12,500,000 in connection with the collaboration agreement the Company executed in 2012 with Baxter. Such expense was recorded in the consolidated statement of operations as research and development expenses. As of December 31, 2012, $1,405,000 of this amount was not yet paid and was included in accrued expenses and other current liabilities in the consolidated balance sheets. This amount was paid during 2013.

	In May 2010, the Company signed a funding agreement with the Leukemia and Lymphoma Society ("LLS") to fund the development of rigosertib. Under this agreement, the Company was entitled to receive milestone payments of up to $10,000,000 through 2013 in connection with clinical trials to be conducted. The aggregate milestone payment amount was subsequently reduced to $8,000,000 pursuant to an amendment signed in January 2013, after which LLS was not obligated to fund any further amounts. In the event that the research is successful, the Company must proceed with commercialization of the licensed product or repay the amount funded. In addition, LLS is entitled to receive regulatory and commercial milestone payments and royalties from the Company based on the Company's net sales of the licensed product, with the amount of such milestone payments and royalties not to exceed three times the amount funded ($24,000,000). During the year ended December 31, 2012, in connection with the execution of the Baxter agreement (Note 15), the Company paid $1,000,000 to LLS and recorded this amount in research and development expenses. This payment reduced the maximum milestone and royalty payment obligation under this agreement to $23,000,000 at December 31, 2013 and 2012. As a result of the potential obligation to repay the funds under this arrangement, the milestone payments received through December 31, 2012 amounting to $8,000,000 have been recorded as deferred revenue at December 31, 2013 and 2012 and will be recognized as revenue commencing with the resolution of the repayment contingency.

License_and_Collaboration_Agre

License and Collaboration Agreements	12 Months Ended
License and Collaboration Agreements	Dec. 31, 2013
License and Collaboration Agreements	'
License and Collaboration Agreements	'

	15. License and Collaboration Agreements

	Baxter Agreement

	In September 2012, the Company entered into a development and license agreement with Baxter granting Baxter an exclusive, royalty-bearing license for the research, development, commercialization and manufacture (in specified instances) of rigosertib in all therapeutic indications in Europe (the "Baxter Territory"). In July 2012, Baxter purchased $50.0 million of the Company's Series J convertible preferred stock, which converted to shares of Common Stock immediately prior to the consummation of the IPO. Baxter also invested $5.0 million in the Company's initial public offering in July 2013.

	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. In December 2013, a pre-planned interim futility and safety analysis of the pancreatic cancer trial was performed and the trial was discontinued. In February 2014, the Company announced top-line analysis of a Phase 3 trial of rigosertib IV in higher risk MDS patients. Although the results of this study showed numerical improvement in median overall survival in the rigosertib treated patients, the observed improvement of 2.4 months did not meet the required level of statistical significance. However, a statistically significant improvement in median overall survival was evident in the subset of patients who had progressed on or failed to respond to previous treatment with hypomethylating agents (HMAs).

	If an additional Phase 3 clinical trial beyond the current Phase 3 clinical trial in process for rigosertib IV in higher risk MDS patients is required to obtain marketing approval in the Baxter Territory, the Company could require Baxter to fund a percentage of the costs of such additional trial up to a specified maximum. At the completion of the current Phase 2 trial for rigosertib oral in lower risk MDS patients and the review of the resulting data and findings, the Company and Baxter will decide whether or not to pursue further development of rigosertib for this indication. If the Company and Baxter mutually agree to progress the development of rigosertib oral in lower risk MDS patients, then certain milestone payments will be payable to the Company, and the Company will be required to use its commercially reasonable efforts to progress the development of rigosertib for this indication to a drug approval application in the Baxter Territory. The Company and Baxter will work together for potential future rigosertib indications, beyond the initial indications noted above. Generally, if Baxter chooses to participate in the development of additional indications, Baxter will be responsible for a percentage of all research and development costs and expenses and the Company could earn additional milestone payments. Baxter has full responsibility for all commercialization activities for the product in the Baxter Territory, at Baxter's sole cost and expense.

	The Company and Baxter have agreed to negotiate a supply agreement under terms satisfactory to both parties whereby the Company will supply Baxter with Baxter's required levels of product to support commercialization efforts in the Baxter Territory. Baxter also has the right to engage third parties for the manufacture and supply of its requirements for the licensed product.

	Under the terms of the agreement, Baxter made an upfront payment of $50,000,000. The Company is eligible to receive pre-commercial milestone payments of up to an aggregate of $337,500,000 if specified development and regulatory milestones are achieved. The potential pre-commercial development milestone payments to the Company include the following:



	•
	$50,000,000 for achievement of the primary endpoint of a Phase 3 clinical trial for rigosertib IV in higher risk MDS patients (the "MDS IV indication") or mutual agreement of the Parties to file for any marketing approval in either the European Union as a whole or in all of the Big Five EU Countries;

	•
	$25,000,000 for the joint decision to proceed with the development of rigosertib for lower risk MDS; and

	•
	$25,000,000 for each drug approval application filed for indications specified in the arrangement with Baxter.

	The Company may also receive up to $212,500,000 in milestone payments for regulatory approvals of the rigosertib MDS indications specified in the arrangement with Baxter, each of which may be up to and in excess of $100,000,000. The Company is also potentially eligible to receive an additional $20,000,000 pre-commercial milestone payment related to the timing of regulatory approval of the MDS IV indication in Europe. In addition to these pre-commercial milestones, the Company is eligible to receive up to an aggregate of $250,000,000 in milestone payments based on Baxter's achievement of pre-specified threshold levels of annual net sales of rigosertib. The Company will also be entitled to receive royalties at percentage rates ranging from the low-teens to the low-twenties on net sales of rigosertib by Baxter in the Baxter Territory.

	The agreement with Baxter will remain in effect until the expiration of all applicable royalty terms and satisfaction of all payment obligations in each licensed country, unless terminated earlier due to the uncured material breach or bankruptcy of a party, force majeure, or in the event of a specified commercial failure. The Company may terminate the agreement in the event that Baxter brings a challenge against it in relation to the licensed patents. Baxter may terminate the agreement without cause commencing after a specified period of time from the execution of the agreement.

	The Company determined that the deliverables under the Baxter agreement include 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 is sublicensable, there are no restrictions as to Baxter's use of the license and Baxter has 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 allows Baxter to sublicense rigosertib and its ability to sublicense is 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 has 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 FDA for higher risk MDS. These later stage clinical trials, where protocols have been prepared and trials are in process, can be 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 are not proprietary and could be performed by other qualified parties. For example, the Company relies on clinical research organizations ("CROs") to complete the clinical trials, and Baxter could engage the same or similar CROs to complete the trials on its behalf. Although Baxter is not performing development activities related to rigosertib, Baxter possesses the internal expertise (or a vendor could be hired) to complete the efforts under the rigosertib programs without further assistance from the Company.

	Baxter develops, manufactures and markets products that save and sustain the lives of people with hemophilia, immune disorders, infectious diseases, kidney disease, trauma, and other chronic and acute medical conditions. As a global, diversified healthcare company, Baxter applies a unique combination of expertise in medical devices, pharmaceuticals and biotechnology to create products that advance patient care worldwide. Baxter employs over 50,000 people, with significant revenues and expenditures for research and development. Baxter has expertise in completing clinical trials, assessing clinical trial results and preparing regulatory filings and has also developed and obtained regulatory and marketing approval in Europe for numerous products used to treat hematologic conditions. Baxter has expertise in rare hematologic conditions, and rigosertib is a natural complement to Baxter's existing treatments for patients with these conditions.

	Baxter has 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 has 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 is a general right of return associated with the license. The $50,000,000 upfront payment received by the Company is non-refundable; therefore, there is no right of return for the license. As a result, the Company concluded that the license is a separate unit of accounting.

	The Company was not able to establish VSOE or TPE 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 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 represents 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 is being 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. For the years ended December 31, 2013 and 2012, the Company recognized $4,176,000 and $3,100,000, respectively, of research and development revenue under the Baxter agreement.

	The Company and Baxter have 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 may be 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 Preferred Stock was issued at fair value and if not, whether the consideration received for the 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, $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 we are 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. For the years ended December 31, 2013, 2012 and 2011, the Company recognized revenues of $455,000, $455,000 and $227,000, respectively, under this agreement. In addition, the Company recognized revenues of $122,000 and $48,000 for the years ended December 31, 2013 and 2012, respectively, related to the supply agreement with SymBio.

Preclinical_Collaboration

Preclinical Collaboration	12 Months Ended
Preclinical Collaboration	Dec. 31, 2013
Preclinical Collaboration	'
Preclinical Collaboration	'

	16. Preclinical Collaboration

	In December 2012, we formed GBO, LLC, or GBO, an entity jointly-owned by both us and GVK Biosciences Private Limited, or GVK. The purpose of GBO is to collaborate on and develop two programs through filing of an investigational new drug application ("IND") and/or conducting proof of concept studies using the Company's technology platform.

	During the year ended December 31, 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 sub-license 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 joint venture agreement, GVK will make additional capital contributions (with a minimum of $500,000) necessary to complete the major studies plus the exercise of the proof on concept study option leading to deliverables under the programs including an IND approval for one product and completion of IND studies for the other product. The GVK percentage interest in GBO accordingly may change from the initial 10% to up to 50%, depending on the amount of its total capital contributions. 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. GVK will have operational control of GBO and the Company will have strategic and scientific control.

RelatedParty_Transactions

Related-Party Transactions	12 Months Ended
Related-Party Transactions	Dec. 31, 2013
Related-Party Transactions	'
Related-Party Transactions	'

	17. 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 for the years ended December 31, 2013, 2012 and 2011 were $1,235,000, $1,230,000 and $554,000, respectively. At December 31, 2013 and 2012, the Company had no outstanding amounts payable to Mount Sinai.

	The Company outsources the synthesis of some of its chemical compounds to vendors in the United States and in foreign countries. A supplier, of which a member of the Company's board of directors and a significant stockholder is an owner, produces one of these compounds under contract. The Company's aggregate payments for these services for the years ended December 31, 2013, 2012 and 2011 were $0, $157,000 and $6,000, respectively. At December 31, 2013 and 2012, the Company owed this supplier $0 and $107,000, respectively, which is included in accounts payable on the consolidated balance sheets.

	The Company purchases chemical compounds 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, 2013, 2012 and 2011 were $804,000, $410,000 and $970,000, respectively. At December 31, 2013 and 2012, the Company owed this supplier $50,000 and $0, respectively, which is included in accounts payable on the consolidated balance sheets. The Company also rents office space in Pennington, New Jersey from a corporation related to these suppliers and affiliated with the former member of the Company's 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, 2013, 2012 and 2011 were $182,000, $165,000 and $158,000, respectively.

Initial_Public_Offering

Initial Public Offering	12 Months Ended
Initial Public Offering	Dec. 31, 2013
Initial Public Offering	'
Initial Public Offering	'

	18. Initial Public Offering

	On July 24, 2013, the Company's Registration Statement was declared effective by the SEC, and on July 25, 2013, the Company's Common Stock began trading on the NASDAQ Global Market under the symbol ONTX.

	On July 30, 2013, 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. As a result of the conversion, as of September 30, 2013, the Company had no shares of Preferred Stock outstanding.

	On July 30, 2013, the Company completed the IPO. The Company received net proceeds of $79,811,000 from the IPO, net of underwriting discounts and commissions and other estimated offering expenses.

	In preparation for the IPO, the Company's board of directors and stockholders approved a one-for-1.333 reverse stock split of the Company's Common Stock. The reverse stock split became effective on July 17, 2013. All Common Stock share and per share amounts in the consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. The reverse stock split did not result in a retroactive adjustment of share amounts for the Preferred Stock. In addition, in July 2013, the Company's board of directors and stockholders approved an amendment of the Company's certificate of incorporation to, among other things, change the definition of a designated public offering to remove the per share price requirement and to set the threshold at gross proceeds to the Company of at least $25.0 million.

Quarterly_Data

Quarterly Data	12 Months Ended
Quarterly Data	Dec. 31, 2013
Quarterly Data (unaudited)	'
Quarterly Data (unaudited)`	'

	19. Quarterly Data (unaudited)


			2013
			First			Second			Third			Fourth
			Quarter			Quarter			Quarter			Quarter
	Revenue		$	1,116,000		$	591,000		$	1,116,000		$	1,930,000
	Operating expenses:
	General and administrative			3,346,000			3,117,000			5,927,000			4,403,000
	Research and development			12,756,000			10,047,000			15,293,000			12,086,000


	Total operating expenses			16,102,000			13,164,000			21,220,000			16,489,000


	Loss from operations			(14,986,000	)		(12,573,000	)		(20,104,000	)		(14,559,000	)
	Change in fair value of warrant liability			14,000			(2,000	)		(31,000	)		61,000
	Interest expense			—			(2,000	)		(1,000	)		(1,000	)
	Other income, net			127,000			15,000			47,000			(126,000	)


	Net loss before income taxes			(14,845,000	)		(12,562,000	)		(20,089,000	)		(14,625,000	)
	Income taxes			—			—			432,000			3,000


	Net loss			(14,845,000	)		(12,562,000	)		(20,521,000	)		(14,628,000	)
	Net loss attributable to non-controlling interest			—			—			—			13,000


	Net loss attributable to Onconova Therapeutics, Inc			(14,845,000	)		(12,562,000	)		(20,521,000	)		(14,615,000	)
	Accretion of redeemable convertible preferred stock			(1,019,000	)		(1,032,000	)		(269,000	)		—


	Net loss applicable to common stockholders		$	(15,864,000	)	$	(13,594,000	)	$	(20,790,000	)	$	(14,615,000	)




	Net loss per share of common stock, basic and diluted*		$	(6.08	)	$	(5.21	)	$	(1.34	)	$	(0.68	)




	Basic and diluted weighted average shares outstanding			2,607,406			2,609,495			15,480,416			21,419,208









			2012
			First			Second			Third			Fourth
			Quarter			Quarter			Quarter			Quarter
	Revenue		$	198,000		$	220,000		$	42,803,000		$	2,969,000
	Operating expenses:
	General and administrative			2,460,000			1,627,000			8,922,000			2,698,000
	Research and development			8,448,000			6,776,000			26,962,000			10,576,000


Total operating expenses			10,908,000			8,403,000			35,884,000			13,274,000


Loss from operations			(10,710,000	)		(8,183,000	)		6,919,000			(10,305,000	)
Change in fair value of warrant liability			(609,000	)		999,000			(25,000	)		2,000
Change in fair value option liability			—			—			—			—
Interest expense			(21,000	)		(230,000	)		(8,357,000	)		—
Other income, net			541,000			(2,000	)		28,000			41,000


Net loss before income taxes			(10,799,000	)		(7,416,000	)		(1,435,000	)		(10,262,000	)
Income taxes			—			—			—			—


Net loss			(10,799,000	)		(7,416,000	)		(1,435,000	)		(10,262,000	)
Net loss attributable to non-controlling interest			—			—			—			—


Net loss attributable to Onconova Therapeutics, Inc			(10,799,000	)		(7,416,000	)		(1,435,000	)		(10,262,000	)
Accretion of redeemable convertible preferred stock			(1,231,000	)		(927,000	)		(785,000	)		(1,010,000	)


Net loss applicable to common stockholders		$	(12,030,000	)	$	(8,343,000	)	$	(2,220,000	)	$	(11,272,000	)




Net loss per share of common stock, basic and diluted*		$	(5.53	)	$	(3.84	)	$	(1.02	)	$	(4.89	)




Basic and diluted weighted average shares outstanding			2,173,553			2,173,549			2,174,392			2,305,315






*
Earnings Per Share (EPS) in each quarter is computed using the weighted-average number of shares outstanding during that quarter while EPS for the full year is computed using the weighted-average number of shares outstanding during the year. Thus, the sum of the four quarters' EPS does not equal the full-year EPS.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Basis of Presentation	'

	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	'

	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	'

	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.

	Prior to completion of its IPO on July 30, 2013, the Company utilized estimates and assumptions in determining the fair value of its Common Stock. The Company granted stock options at exercise prices not less than the fair value of its Common Stock as determined by the board of directors, with input from management. Management used the assistance of a third-party valuation firm in estimating the fair value of the Common Stock. The board of directors determined the estimated fair value of the Common Stock based on a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector and the historic prices at which the Company sold shares of Preferred Stock.

Concentrations of Credit Risk and Off-Balance Sheet Risk	'

	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	'

	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.

Marketable Securities	'

	Marketable Securities

	Marketable securities with original maturities longer than three months but which mature in less than one year from the balance sheet date are classified as current assets. Marketable securities that mature more than one year from the balance sheet date are classified as noncurrent assets. Marketable securities that the Company has the intent and ability to hold to maturity are classified as investments held-to-maturity and are reported at amortized cost. The difference between the acquisition cost and face values of held-to-maturity investments is amortized over the remaining term of the investments and added to or subtracted from the acquisition cost and interest income. As of December 31, 2013, all of the Company's investments were classified as held-to-maturity.

Fair Value of Financial Instruments	'

	Fair Value of Financial Instruments

	The carrying amounts reported in the accompanying consolidated financial statements for cash and cash equivalents, marketable securities, accounts payable and accrued liabilities approximate their respective fair values because of the short-term nature of these accounts. The fair value of the warrant liability is discussed in Note 4, "Fair Value Measurements."

Property and Equipment	'

	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, 2013.

Restricted Cash	'

	Restricted Cash

	Under the Company's office lease, the Company is required to provide the landlord a $125,000 letter of credit, which is recorded as restricted cash on the consolidated balance sheets as of December 31, 2013 and 2012.

Foreign Currency Translation	'

	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	'

	Revenue Recognition

	Currently, 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.

	The Company recognized revenue of $4,176,000 and $45,490,000 during the years ended December 31, 2013 and 2012, respectively, as a result of its license and collaboration agreement with Baxter. The Company recognized revenue of $577,000, $503,000 and $227,000 during the years ended December 31, 2013, 2012 and 2011, respectively, as a result of its license and collaboration agreement with SymBio. The remaining revenue recognized during the years ended December 31, 2012 and 2011 of $197,000 and $1,260,000, respectively, pertained to research and development services provided by the Company under certain research grants. The Baxter and SymBio agreements are the only agreements that are being accounted for under ASU 2009-13. See Note 15, "License and Collaboration Agreements," for a further discussion of the agreements with Baxter and SymBio.

Research and Development Expenses	'

	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

	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	'

	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 8, "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.

Preferred Stock	'

	Preferred Stock

	The Company accounted for the redemption premium and issuance costs on its Preferred Stock using the effective interest method, accreting such amounts to its Preferred Stock from the date of issuance to the earliest date of redemption. 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. As a result of the conversion, as of July 30, 2013, the Company had no shares of Preferred Stock outstanding. See Note 10.

Stock Warrants	'

	Stock Warrants

	Freestanding warrants that are related to the purchase of Stock are classified as liabilities and recorded at fair value. The warrants are subject to re-measurement at each balance sheet date and any change in fair value is recognized as a component of change in fair value of warrant liability in the consolidated statements of operations. See Note 10. The warrants are classified as Level 3 liabilities (see Note 4 for a discussion of the fair value hierarchy).

Stock-Based Compensation Expense	'

	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 11) 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	'

	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, 2013, 2012 and 2011, there were no material adjustments to the Company's prior period estimates of accrued expenses for clinical trials.

Collaboration Arrangements	'

	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 15, "License and Collaboration Agreements," for a discussion of the Company's current collaborations with Baxter and SymBio.

Basic and Diluted Net Loss Per Share of Common Stock	'

	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 Preferred Stock, warrants to purchase Preferred Stock and stock options. 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 Preferred Stock and warrants to purchase Preferred Stock, and stock options 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, 2013, 2012 and 2011.

Recent Accounting Pronouncements	'

	Recent Accounting Pronouncements

	In February 2013, the Financial Accounting Standards Board (the "FASB") amended its guidance to require an entity to present the effect of certain significant reclassifications out of accumulated other comprehensive income on the respective line items in net income. The new accounting guidance does not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income. The guidance is effective prospectively for fiscal years beginning after December 15, 2012. The Company adopted these new provisions for the quarter beginning January 1, 2013. As the guidance requires additional presentation only, there was no impact to the Company's consolidated financial position, results of operations or cash flows.

	In July 2013, the FASB issued guidance clarifying that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax benefit is disallowed. In situations where a net operating loss carryforward, a similar tax loss, or a tax credit carryforward is not available at the reporting date under the tax law of the applicable jurisdiction or the tax law of the jurisdiction does not require, and the entity does not intend to use, the deferred tax asset for such purpose, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be netted with the deferred tax asset. The guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. Early adoption is permitted. The guidance is to be applied prospectively to all unrecognized tax benefits that exist at the effective date. Retrospective application is permitted. The Company is currently evaluating the impact that adoption will have on the determination or reporting of its financial results.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
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

Property and Equipment (Tables)	12 Months Ended
Property and Equipment (Tables)	Dec. 31, 2013
Property and Equipment	'
Schedule of property and equipment and related accumulated depreciation	'




		December 31,
		2013			2012
	Laboratory equipment	$	866,000		$	764,000
	Software		92,000			91,000
	Computer and office equipment		433,000			323,000
	Leasehold improvements		1,011,000			633,000


			2,402,000			1,811,000
	Less accumulated depreciation		(1,776,000	)		(1,348,000	)


	Property and equipment, net	$	626,000		$	463,000

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2013
Fair Value Measurements	'
Schedule of financial assets and liabilities measured at fair value on a recurring basis	'




		Fair Value Measurement as of									Fair Value Measurement as of
		December 31, 2013									December 31, 2012
		Level 1			Level 2		Level 3		Balance		Level 1		Level 2		Level 3		Balance
	Warrant liability	$	—		$	—	$	20,000	$	20,000	$	—	$	—	$	62,000	$	62,000


	Total	$	—		$	—	$	20,000	$	20,000	$	—	$	—	$	62,000	$	62,000




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






		Warrant
		Liability
	Balance at December 31, 2011	$	1,064,000
	Settlements of warrant liability awards		(635,000	)
	Expiration of warrant liability awards		(975,000	)
	Change in fair value upon re-measurement		608,000


	Balance at December 31, 2012		62,000
	Change in fair value upon re-measurement		(42,000	)


	Balance at December 31, 2013	$	20,000

Net_Loss_Per_Share_of_Common_S1

Net Loss Per Share of Common Stock (Tables)	12 Months Ended
Net Loss Per Share of Common Stock (Tables)	Dec. 31, 2013
Net Loss Per Share of Common Stock	'
Schedule of computation of basic and diluted earnings per share	'




		Year ended December 31,
		2013			2012			2011
	Basic and diluted net loss per share of common stock:
	Net loss	$	(62,543,000	)	$	(29,912,000	)	$	(26,294,000	)
	Accretion to redemption value of preferred stock		(2,320,000	)		(3,953,000	)		(4,020,000	)


	Net loss applicable to common stockholders	$	(64,863,000	)	$	(33,865,000	)	$	(30,314,000	)




	Weighted average shares of common stock outstanding		10,594,227			2,206,888			2,137,403




	Net loss per share of common stock—basic and diluted	$	(6.12	)	$	(15.35	)	$	(14.18	)




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




		December 31,
		2013			2012			2011
	Preferred Stock		—			12,838,127			8,575,918
	Warrants		4,597			4,597			426,539
	Stock options		4,344,365			2,564,147			2,026,396


			4,348,962			15,406,871			11,028,853

Balance_Sheet_Detail_Tables

Balance Sheet Detail (Tables)	12 Months Ended
Balance Sheet Detail (Tables)	Dec. 31, 2013
Balance Sheet Detail	'
Schedule of prepaid expenses and other current assets	'




		December 31,
		2013		2012
	Research and development	$	2,242,000	$	1,429,000
	Manufacturing		1,051,000		—
	Insurance		645,000		101,000
	Other		449,000		195,000


		$	4,387,000	$	1,725,000




Schedule of accrued expenses and other current liabilities	'




		December 31,
		2013		2012
	Research and development	$	4,625,000	$	3,521,000
	Employee compensation		509,000		247,000
	Taxes		302,000		—
	Other		384,000		157,000


		$	5,820,000	$	3,925,000

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2013
Income Taxes	'
Schedule of income taxes based on income (loss) before income tax expense	'




		Year Ended December 31,
		2013			2012			2011
	Domestic	$	(62,154,000	)	$	(29,912,000	)	$	(26,294,000	)
	Foreign		33,000			—			—


	Total	$	(62,121,000	)	$	(29,912,000	)	$	(26,294,000	)




Schedule of provision for income taxes	'




		Year Ended December 31,
		2013			2012			2011
	Current
	US Federal	$	140,000		$	—		$	—
	State and Local		285,000			—			—
	Foreign		10,000			—			—


	Total Current	$	435,000		$	—		$	—


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


	Total Deferred	$	—		$	—		$	—


	Total Expense (Benefit)	$	435,000		$	—		$	—




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






		Year Ended December 31,
		2013			2012
	Deferred tax assets:
	Net operating loss carryovers	$	47,364,000		$	35,921,000
	R&D tax credits		35,223,000			13,868,000
	Non-qualified stock options		3.988,000			1,057,000
	Deferred revenue		5,938,000			4,246,000
	Charitable contributions		6,000			6,000
	Accrued expenses		586,000			40,000
	Fixed assets		199,000			159,000


	Deferred tax assets		93,304,000			55,297,000
	Less valuation allowance		(93,304,000	)		(55,297,000	)


	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	'






		Year Ended
		December 31,
		2013			2012			2011
	Federal income tax expense at statutory rate		34	%		34	%		34	%
	Permanent items		(8.3	)		(25.1	)		(5.6	)
	State income tax, net of federal benefit		4.5			1.8			6.2
	Tax credits		34.4			18.5			22.1
	Provision to return		(3.8	)		0			(5.1	)
	Change in valuation allowance		(61.2	)		(29.1	)		(51.6	)
	Other		(0.2	)		(0.1	)		0


	Effective income tax rate		(0.6	)%		0	%		0	%

Preferred_Stock_and_Stockholde1

Preferred Stock and Stockholders' Equity (Deficit) (Tables)	12 Months Ended
Preferred Stock and Stockholders' Equity (Deficit) (Tables)	Dec. 31, 2013
Preferred Stock and Stockholders' Equity (Deficit)	'
Schedule of composition of share capital	'






			Authorized						Issued and Outstanding
			December 31,			December 31,			December 31,			December 31,
			2013			2012			2013			2012
	Shares of $0.01 par value per share:
	Common stock			75,000,000			30,145,155			21,467,482			2,606,484




	Shares of $0.01 par value per share:
	Preferred Stock			5,000,000			—			—			—




	Redeemable Preferred Stock:
	Series A Preferred Stock			—			400,000			—			107,000
	Series B Preferred Stock			—			1,200,000			—			1,107,189
	Series C Preferred Stock			—			1,200,000			—			1,069,946
	Series D Preferred Stock			—			1,625,000			—			1,583,568
	Series E Preferred Stock			—			1,650,000			—			1,633,082
	Series F Preferred Stock			—			2,000,000			—			2,000,000
	Series G Preferred Stock			—			2,700,000			—			1,934,359
	Series H Preferred Stock			—			2,042,950			—			2,013,424
	Series I Preferred Stock			—			2,700,000			—			2,433,328
	Series J Preferred Stock			—			3,030,303			—			3,030,303


	Total Redeemable Preferred Stock			—			18,548,253			—			16,912,199




Schedule of activity of the Preferred Stock	'






			December 31,			Issuance of			Exercise of			Accretion of			Conversion of			December 31,
			2012			Preferred			warrants			redemption			Preferred Stock			2013
						Stock						premium and			into Common
												issuance costs			Stock
												on Preferred
												Stock
	Series A
	Shares			107,000			—			—			—			(107,000	)		—
	Amount		$	535,000		$	—		$	—		$	—		$	(535,000	)	$	—
	Series B
	Shares			1,107,189			—			—			—			(1,107,189	)		—
	Amount		$	12,733,000		$	—		$	—		$	—		$	(12,733,000	)	$	—
	Series C
	Shares			1,069,946			—			—			—			(1,069,946	)		—
	Amount		$	7,618,000		$	—		$	—		$	—		$	(7,618,000	)	$	—
	Series D
	Shares			1,583,568			—			—			—			(1,583,568	)		—
	Amount		$	18,211,000		$	—		$	—		$	—		$	(18,211,000	)	$	—
	Series E
	Shares			1,633,082			—			—			—			(1,633,082	)		—
	Amount		$	18,780,000		$	—		$	—		$	—		$	(18,780,000	)	$	—
	Series F
	Shares			2,000,000			—			—			—			(2,000,000	)		—
	Amount		$	23,000,000		$	—		$	—		$	—		$	(23,000,000	)	$	—
	Series G
	Shares			1,934,359			—			—			—			(1,934,359	)		—
	Amount		$	22,819,000		$	—		$	—		$	—		$	(22,819,000	)	$	—
	Series H
	Shares			2,013,424			—			—			—			(2,013,424	)		—
	Amount		$	22,005,000		$	—		$	—		$	868,000		$	(22,873,000	)	$	—
	Series I
	Shares			2,433,328			—			—			—			(2,433,328	)		—
	Amount		$	26,933,000		$	—		$	—		$	226,000		$	(27,159,000	)	$	—
	Series J
	Shares			3,030,303			—			—			—			(3,030,303	)		—
	Amount		$	48,681,000		$	—		$	—		$	1,226,000		$	(49,907,000	)	$	—


	Total
	Shares			16,912,199			—			—			—			(16,912,199	)		—


	Amount		$	201,315,000		$	—		$	—		$	2,320,000		$	(203,635,000	)	$	—









			January 1,			Issuance of			Exercise of			Accretion of			December 31,
			2012			Preferred			warrants			redemption			2012
						Stock						premium and
												issuance costs on
												Preferred Stock
Series A
Shares			107,000			—			—			—			107,000
Amount		$	535,000		$	—		$	—		$	—		$	535,000
Series B
Shares			1,107,189			—			—			—			1,107,189
Amount		$	12,733,000		$	—		$	—		$	—		$	12,733,000
Series C
Shares			1,069,946			—			—			—			1,069,946
Amount		$	7,618,000		$	—		$	—		$	—		$	7,618,000
Series D
Shares			1,583,568			—			—			—			1,583,568
Amount		$	18,211,000		$	—		$	—		$	—		$	18,211,000
Series E
Shares			1,633,082			—			—			—			1,633,082
Amount		$	18,780,000		$	—		$	—		$	—		$	18,780,000
Series F
Shares			2,000,000			—			—			—			2,000,000
Amount		$	23,000,000		$	—		$	—		$	—		$	23,000,000
Series G
Shares			1,712,960			—			221,399			—			1,934,359
Amount		$	18,574,000		$	—		$	2,802,000		$	1,443,000		$	22,819,000
Series H
Shares			2,013,424			—			—			—			2,013,424
Amount		$	20,546,000		$	—		$	—		$	1,459,000		$	22,005,000
Series I
Shares			—			2,433,328			—			—			2,433,328
Amount		$	—		$	26,767,000		$	—		$	166,000		$	26,933,000
Series J
Shares			—			3,030,303			—			—			3,030,303
Amount		$	—		$	47,796,000		$	—		$	885,000		$	48,681,000


Total
Shares			11,227,169			5,463,631			221,399			—			16,912,199


Amount		$	119,997,000		$	74,563,000		$	2,802,000		$	3,953,000		$	201,315,000

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
Stock-Based Compensation (Tables)	Dec. 31, 2013
Stock-Based Compensation	'
Schedule of shares reserved for issuance under the 2013 Plan	'






			2013			2012
	Shares of Common Stock reserved for issuance under the 2013 Plan			6,107,831			4,107,831




Schedule of stock option activity	'






			Number of			Weighted-		Weighted-
			Options			Average		Average
						Exercise		Remaining
						Price		Contractual
								Term
								(in years)
	Outstanding at December 31, 2010			1,823,266		$	4.41		6.09
	Granted			344,479			6.13
	Exercised			(99,896	)		1.53
	Forfeited			(41,453	)		5.43


	Outstanding at December 31, 2011			2,026,396		$	4.81		6.39
	Granted			977,807			12.51
	Exercised			(438,556	)		2.9
	Forfeited			(1,500	)		1.53


	Outstanding at December 31, 2012			2,564,147			8.1		7.52
	Granted			1,967,940			14.6
	Exercised			(81,204	)		1.93
	Forfeited			(106,518	)		12.23


	Outstanding at December 31, 2013			4,344,365		$	11.05		7.91




	Vested or expected to vest at December 31, 2013			4,344,365		$	11.05		7.91
	Exercisable at December 31, 2013			2,347,744		$	8.72		6.63
Schedule of roll forward of the stock option liability	'






	Balance at December 31, 2011		$	2,648,000
	Change in intrinsic value upon re-measurement			13,844,000
	Settlements of option liability awards			(4,525,000	)


	Balance at December 31, 2012			11,967,000
	Change in intrinsic value upon re-measurement			2,553,000
	Settlements of option liability awards			(38,000	)
	Reclassification to stockholders' equity (deficit)			(14,482,000	)


	Balance at December 31, 2013		$	—




Schedule of options granted to purchase shares of Common Stock	'




	Shares			Exercise Price
		310,540		$	13.28
		4,800		$	14.75
		763,000		$	15
		17,500		$	21.79
		57,500		$	28.81
		500		$	27.71
		16,000		$	14.67
		32,500		$	14.68
		765,600		$	13.48



Schedule of stock-based compensation expense	'






			Year ended December 31,
			2013			2012		2011
	General and administrative		$	4,845,000		$	7,199,000	$	3,000
	Research and development			3,170,000			6,645,000		3,000


			$	8,015,000		$	13,844,000	$	6,000
Schedule of information with respect to stock options outstanding and exercisable	'






	Exercise		Shares			Weighted		Exercisable
	Price					Average
						Remaining
						Contractual
						Life (years)
	$1.33 - $2.67			154,117			1.41		154,117
	$5.76 - 6.00			801,208			4.92		792,730
	$6.13 - $7.53			639,888			6.41		553,790
	$13.28 - $13.48			1,870,852			9.97		418,644
	$14.67 - $15.00			805,300			9.59		421,244
	$21.79 - $28.81			73,000			9.72		7,219


				4,344,365			7.91		2,347,744

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
Commitments and Contingencies (Tables)	Dec. 31, 2013
Commitments and Contingencies	'
Schedule of future minimum lease payments under non-cancellable leases	'






		December 31, 2013
	2014	$	245,000
	2015		39,000


	Total minimum lease payments	$	284,000

Quarterly_Data_Tables

Quarterly Data (Tables)	12 Months Ended
Quarterly Data (Tables)	Dec. 31, 2013
Quarterly Data (unaudited)	'
Schedule of quarterly data	'






			2013
			First			Second			Third			Fourth
			Quarter			Quarter			Quarter			Quarter
	Revenue		$	1,116,000		$	591,000		$	1,116,000		$	1,930,000
	Operating expenses:
	General and administrative			3,346,000			3,117,000			5,927,000			4,403,000
	Research and development			12,756,000			10,047,000			15,293,000			12,086,000


	Total operating expenses			16,102,000			13,164,000			21,220,000			16,489,000


	Loss from operations			(14,986,000	)		(12,573,000	)		(20,104,000	)		(14,559,000	)
	Change in fair value of warrant liability			14,000			(2,000	)		(31,000	)		61,000
	Interest expense			—			(2,000	)		(1,000	)		(1,000	)
	Other income, net			127,000			15,000			47,000			(126,000	)


	Net loss before income taxes			(14,845,000	)		(12,562,000	)		(20,089,000	)		(14,625,000	)
	Income taxes			—			—			432,000			3,000


	Net loss			(14,845,000	)		(12,562,000	)		(20,521,000	)		(14,628,000	)
	Net loss attributable to non-controlling interest			—			—			—			13,000


	Net loss attributable to Onconova Therapeutics, Inc			(14,845,000	)		(12,562,000	)		(20,521,000	)		(14,615,000	)
	Accretion of redeemable convertible preferred stock			(1,019,000	)		(1,032,000	)		(269,000	)		—


	Net loss applicable to common stockholders		$	(15,864,000	)	$	(13,594,000	)	$	(20,790,000	)	$	(14,615,000	)




	Net loss per share of common stock, basic and diluted*		$	(6.08	)	$	(5.21	)	$	(1.34	)	$	(0.68	)




	Basic and diluted weighted average shares outstanding			2,607,406			2,609,495			15,480,416			21,419,208









			2012
			First			Second			Third			Fourth
			Quarter			Quarter			Quarter			Quarter
	Revenue		$	198,000		$	220,000		$	42,803,000		$	2,969,000
	Operating expenses:
	General and administrative			2,460,000			1,627,000			8,922,000			2,698,000
	Research and development			8,448,000			6,776,000			26,962,000			10,576,000


Total operating expenses			10,908,000			8,403,000			35,884,000			13,274,000


Loss from operations			(10,710,000	)		(8,183,000	)		6,919,000			(10,305,000	)
Change in fair value of warrant liability			(609,000	)		999,000			(25,000	)		2,000
Change in fair value option liability			—			—			—			—
Interest expense			(21,000	)		(230,000	)		(8,357,000	)		—
Other income, net			541,000			(2,000	)		28,000			41,000


Net loss before income taxes			(10,799,000	)		(7,416,000	)		(1,435,000	)		(10,262,000	)
Income taxes			—			—			—			—


Net loss			(10,799,000	)		(7,416,000	)		(1,435,000	)		(10,262,000	)
Net loss attributable to non-controlling interest			—			—			—			—


Net loss attributable to Onconova Therapeutics, Inc			(10,799,000	)		(7,416,000	)		(1,435,000	)		(10,262,000	)
Accretion of redeemable convertible preferred stock			(1,231,000	)		(927,000	)		(785,000	)		(1,010,000	)


Net loss applicable to common stockholders		$	(12,030,000	)	$	(8,343,000	)	$	(2,220,000	)	$	(11,272,000	)




Net loss per share of common stock, basic and diluted*		$	(5.53	)	$	(3.84	)	$	(1.02	)	$	(4.89	)




Basic and diluted weighted average shares outstanding			2,173,553			2,173,549			2,174,392			2,305,315






*
Earnings Per Share (EPS) in each quarter is computed using the weighted-average number of shares outstanding during that quarter while EPS for the full year is computed using the weighted-average number of shares outstanding during the year. Thus, the sum of the four quarters' EPS does not equal the full-year EPS.

Nature_of_Business_Details

Nature of Business (Details) (USD $)

0 Months Ended

3 Months Ended

12 Months Ended

Jul. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Apr. 30, 2013

item

Nature of Business

Number of clinical-stage product candidates

Number of preclinical programs

Number of clinical programs developed by GBO, LLC

Net loss

($14,615,000)

($20,521,000)

($12,562,000)

($14,845,000)

($10,262,000)

($1,435,000)

($7,416,000)

($10,799,000)

($62,543,000)

($29,912,000)

($26,294,000)

Accumulated deficit

-230,896,000

-168,353,000

-230,896,000

-168,353,000

Preferred stock, par value per share (in dollars per share)

$0.01

Number of series denominated as Series A through Series J preferred stock

Initial Public Offering

Common stock, par value (in dollars per share)

$0.01

Net proceeds received from the sale, net of underwriting discounts and commissions and other estimated offering expenses

79,811,000

Preferred stock outstanding (in shares)

16,912,199

IPO

Initial Public Offering

Number of shares issued in initial public offering

5,941,667

Common stock, par value (in dollars per share)

$0.01

Price per share (in dollars per share)

$15

Number of shares issued pursuant to an option granted to the underwriters to cover over-allotments

775,000

Net proceeds received from the sale, net of underwriting discounts and commissions and other estimated offering expenses

$79,811,000

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
	item	Dec. 31, 2012
Segment Information	'	'
Number of operating segments	1	'
Concentrations of Credit Risk and Off-Balance Sheet Risk	'	'
Off-balance sheet risk, asset	$0	'
Off-balance sheet risk, liability	0	'
Property and Equipment	'	'
Impairment losses	0	'
Restricted Cash	'	'
Restricted cash	$125,000	$125,000
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_Account4

Summary of Significant Accounting Policies (Details 2) (USD $)

0 Months Ended

3 Months Ended

12 Months Ended

Apr. 24, 2013

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jul. 30, 2013

Revenue Recognition

Recognized revenues

$1,930,000

$1,116,000

$591,000

$1,116,000

$2,969,000

$42,803,000

$220,000

$198,000

$4,753,000

$46,190,000

$1,487,000

Research and development revenue

197,000

1,260,000

Preferred Stock

Preferred stock outstanding (in shares)

16,912,199

Stock-Based Compensation Expense

Reclassification of options from liabilities to stockholders' deficit

14,482,000

Collaboration arrangement | Baxter

Revenue Recognition

Recognized revenues

4,176,000

45,490,000

Research and development revenue

4,176,000

3,100,000

Collaboration arrangement | SymBio

Revenue Recognition

Recognized revenues

$577,000

$503,000

$227,000

Property_and_Equipment_Details

Property and Equipment (Details) (USD $)	12 Months Ended
Property and Equipment (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property and Equipment	'	'	'
Property and equipment, gross	$2,402,000	$1,811,000	'
Less accumulated depreciation	-1,776,000	-1,348,000	'
Property and equipment, net	626,000	463,000	'
Depreciation and amortization expense	446,000	319,000	316,000
Laboratory equipment	'	'	'
Property and Equipment	'	'	'
Property and equipment, gross	866,000	764,000	'
Software	'	'	'
Property and Equipment	'	'	'
Property and equipment, gross	92,000	91,000	'
Computer and office equipment	'	'	'
Property and Equipment	'	'	'
Property and equipment, gross	433,000	323,000	'
Leasehold improvements	'	'	'
Property and Equipment	'	'	'
Property and equipment, gross	$1,011,000	$633,000	'

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	12 Months Ended
Fair Value Measurements (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Series G Preferred Stock Warrant	'	'
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option pricing model	'	'
Risk-free interest rate (as a percent)	1.52%	'
Warrants \| Series G Preferred Stock Warrant	'	'
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option pricing model	'	'
Dividend yield (as a percent)	0.00%	0.00%
Weighted average volatility (as a percent)	74.40%	64.87%
Warrants \| Series G Preferred Stock Warrant \| Weighted average	'	'
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option pricing model	'	'
Risk-free interest rate (as a percent)	0.34%	0.31%
Recurring basis	'	'
Financial assets and liabilities measured at fair value	'	'
Warrant liability	20,000	62,000
Total	20,000	62,000
Recurring basis \| Level 3	'	'
Financial assets and liabilities measured at fair value	'	'
Warrant liability	20,000	62,000
Total	20,000	62,000

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 2) (USD $)	12 Months Ended
Fair Value Measurements (Details 2) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Additional disclosures	'	'
Amount of transfers of assets out of Level 1 into Level 2	$0	$0
Amount of transfers of assets out of Level 2 into Level 1	0	0
Amount of transfers of liabilities out of Level 1 into Level 2	0	0
Amount of transfers of liabilities out of Level 2 into Level 1	0	0
Warrants	'	'
Reconciliation of the warrant liability measured at fair value	'	'
Balance at the beginning of the period	62,000	1,064,000
Settlements of warrant liability awards	'	-635,000
Expiration of warrant liability awards	'	-975,000
Change in fair value upon re-measurement	-42,000	608,000
Balance at the end of the period	$20,000	$62,000

Net_Loss_Per_Share_of_Common_S2

Net Loss Per Share of Common Stock (Details) (USD $)	3 Months Ended								12 Months Ended
Net Loss Per Share of Common Stock (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Basic and diluted net loss per share of common stock:	'	'	'	'	'	'	'	'	'	'	'
Net loss	($14,615,000)	($20,521,000)	($12,562,000)	($14,845,000)	($10,262,000)	($1,435,000)	($7,416,000)	($10,799,000)	($62,543,000)	($29,912,000)	($26,294,000)
Accretion to redemption value of preferred stock	'	-269,000	-1,032,000	-1,019,000	-1,010,000	-785,000	-927,000	-1,231,000	-2,320,000	-3,953,000	-4,020,000
Net loss applicable to common stockholders	($14,615,000)	($20,790,000)	($13,594,000)	($15,864,000)	($11,272,000)	($2,220,000)	($8,343,000)	($12,030,000)	($64,863,000)	($33,865,000)	($30,314,000)
Weighted average shares of common stock outstanding (in shares)	21,419,208	15,480,416	2,609,495	2,607,406	2,305,315	2,174,392	2,173,549	2,173,553	10,594,227	2,206,888	2,137,403
Net loss per share of common stock-basic and diluted (in dollars per shares)	($0.68)	($1.34)	($5.21)	($6.08)	($4.89)	($1.02)	($3.84)	($5.53)	($6.12)	($15.35)	($14.18)
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	'	'	'	'	'	'	'	'	4,348,962	15,406,871	11,028,853
Preferred Stock	'	'	'	'	'	'	'	'	'	'	'
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	'	'	'	'	'	'	'	'	'	12,838,127	8,575,918
Warrants	'	'	'	'	'	'	'	'	'	'	'
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	426,539
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	'	'	'	'	'	'	'	'	4,344,365	2,564,147	2,026,396

Balance_Sheet_Detail_Details

Balance Sheet Detail (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Prepaid expenses	'	'
Research and development	$2,242,000	$1,429,000
Manufacturing	1,051,000	'
Insurance	645,000	101,000
Other	449,000	195,000
Total	4,387,000	1,725,000
Accrued expenses	'	'
Research and development	4,625,000	3,521,000
Employee compensation	509,000	247,000
Income taxes	302,000	'
Other	384,000	157,000
Total	$5,820,000	$3,925,000

Debt_Details

Debt (Details) (USD $)	12 Months Ended		1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011
	Dec. 31, 2012	Dec. 31, 2011	Stockholder loan
Debt	'	'	'
Amount advanced	$25,824,000	$620,000	$620,000
Interest rate (as a percent)	'	'	10.00%

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended								12 Months Ended
Income Taxes (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income taxes based on income (loss) before income tax expense	'	'	'	'	'	'	'	'	'	'	'
Domestic	'	'	'	'	'	'	'	'	($62,154,000)	($29,912,000)	($26,294,000)
Foreign	'	'	'	'	'	'	'	'	33,000	'	'
Net loss before income taxes	-14,625,000	-20,089,000	-12,562,000	-14,845,000	-10,262,000	-1,435,000	-7,416,000	-10,799,000	-62,121,000	-29,912,000	-26,294,000
Current	'	'	'	'	'	'	'	'	'	'	'
US Federal	'	'	'	'	'	'	'	'	140,000	'	'
State and Local	'	'	'	'	'	'	'	'	285,000	'	'
Foreign	'	'	'	'	'	'	'	'	10,000	'	'
Total Current	'	'	'	'	'	'	'	'	435,000	'	'
Total Expense (Benefit)	3,000	432,000	'	'	'	'	'	'	435,000	'	'
Income Taxes	'	'	'	'	'	'	'	'	'	'	'
Research and development tax credit carry forwards	35,085,000	'	'	'	'	'	'	'	35,085,000	'	'
Unrecognized tax benefits	'	'	'	'	'	'	'	'	'	'	'
Unrecognized tax benefits	0	'	'	'	'	'	'	'	0	'	'
Interest and penalties accrued	0	'	'	'	'	'	'	'	0	'	'
Deferred tax assets:	'	'	'	'	'	'	'	'	'	'	'
Net operating loss carryovers	47,364,000	'	'	'	35,921,000	'	'	'	47,364,000	35,921,000	'
R&D tax credits	35,223,000	'	'	'	13,868,000	'	'	'	35,223,000	13,868,000	'
Non-qualified stock options	3,988,000	'	'	'	1,057,000	'	'	'	3,988,000	1,057,000	'
Deferred revenue	5,938,000	'	'	'	4,246,000	'	'	'	5,938,000	4,246,000	'
Charitable contributions	6,000	'	'	'	6,000	'	'	'	6,000	6,000	'
Accrued expenses	586,000	'	'	'	40,000	'	'	'	586,000	40,000	'
Fixed assets	199,000	'	'	'	159,000	'	'	'	199,000	159,000	'
Deferred tax assets	93,304,000	'	'	'	55,297,000	'	'	'	93,304,000	55,297,000	'
Less valuation allowance	-93,304,000	'	'	'	-55,297,000	'	'	'	-93,304,000	-55,297,000	'
Net change in valuation allowance	'	'	'	'	'	'	'	'	38,007,000	8,718,000	'
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%	34.00%
Permanent items (as a percent)	'	'	'	'	'	'	'	'	-8.30%	-25.10%	-5.60%
State income tax, net of federal benefit (as a percent)	'	'	'	'	'	'	'	'	4.50%	1.80%	6.20%
Tax credits (as a percent)	'	'	'	'	'	'	'	'	34.40%	18.50%	22.10%
Provision to return (as a percent)	'	'	'	'	'	'	'	'	-3.80%	0.00%	-5.10%
Change in valuation allowance (as a percent)	'	'	'	'	'	'	'	'	-61.20%	-29.10%	-51.60%
Other (as a percent)	'	'	'	'	'	'	'	'	-0.20%	-0.10%	0.00%
Effective income tax rate (as a percent)	'	'	'	'	'	'	'	'	-0.60%	0.00%	0.00%
Federal	'	'	'	'	'	'	'	'	'	'	'
Income Taxes	'	'	'	'	'	'	'	'	'	'	'
Net operating loss (NOL) carry forwards	119,165,000	'	'	'	'	'	'	'	119,165,000	'	'
State	'	'	'	'	'	'	'	'	'	'	'
Income Taxes	'	'	'	'	'	'	'	'	'	'	'
Net operating loss (NOL) carry forwards	$99,165,000	'	'	'	'	'	'	'	$99,165,000	'	'

Convertible_Promissory_Notes_D

Convertible Promissory Notes (Details) (USD $)	Dec. 31, 2011	Jul. 31, 2012	Mar. 31, 2012	Jul. 31, 2012	Jul. 27, 2012	Jul. 31, 2012
	Stockholder loan	Convertible Debt Offering	Convertible Debt Offering	Convertible Debt Offering	Convertible Debt Offering	Convertible Debt Offering
					Series I Preferred Stock	Series I Preferred Stock
Convertible promissory notes	'	'	'	'	'	'
Amount of notes offered in private placement	'	'	$30,000,000	'	'	'
Aggregate closings	'	'	'	26,444,000	'	'
Principal outstanding	620,000	'	'	'	'	'
Interest rate (as a percent)	10.00%	'	10.00%	'	'	'
Period on the basis of which interest rate is calculated	'	'	'360 days	'	'	'
Minimum aggregate proceeds required for debt conversion, IPO scenario	'	'	25,000,000	'	'	'
Minimum aggregate proceeds required for debt conversion, equity scenario	'	'	15,000,000	'	'	'
Conversion price (in dollars per share)	'	'	$11	'	'	$11
Maximum ownership percentage of voting stock of surviving entity below which debt will be redeemed at amount equal to specified times the outstanding principal amount together with any unpaid and accrued interest	'	'	50.00%	'	'	'
Redemption amount as multiplier of outstanding principal amount together with any unpaid and accrued interest when ownership percentage of voting stock of surviving entity falls below specified percentage	'	'	2	'	'	'
Contingent beneficial conversion feature	'	8,176,000	'	'	'	'
Number of shares of preferred stock issued upon conversion	'	'	'	'	2,443,328	2,433,328
Interest expense	'	'	'	'	$8,176,000	'

Preferred_Stock_and_Stockholde2

Preferred Stock and Stockholders' Equity (Deficit) (Details) (USD $)

0 Months Ended

3 Months Ended

12 Months Ended

4 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

12 Months Ended

Jul. 30, 2013

Jul. 17, 2013

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jul. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Jul. 27, 2012

Jul. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

item

Series G Preferred Stock Warrant

Convertible Debt Offering

Preferred stock

Series A Preferred Stock

Series B Preferred Stock

Series C Preferred Stock

Series D Preferred Stock

Series E Preferred Stock

Series F Preferred Stock

Series G Preferred Stock

Series H Preferred Stock

Series I Preferred Stock

Series J Preferred Stock

Minimum

Convertible Debt Offering

item

Preferred stock and stockholders' deficit

Gross proceeds from issuance of shares of preferred stock

$50,000,000

Shares of preferred stock issued

16,912,199

107,000

1,107,189

1,069,946

1,583,568

1,633,082

2,000,000

1,934,359

2,013,424

2,433,328

3,030,303

Reverse stock split of common stock

0.75

Number of shares of preferred stock issued upon conversion of note

2,443,328

2,433,328

Principal amount of the notes converted

26,444,000

Accrued interest

323,000

Issue price (in dollars per share)

$5.75

$3.56

$4.67

$9.76

$11

$9.79

$11

$16.50

Number of shares of preferred stock issued

5,463,631

2,433,328

3,030,303

Issuance costs associated with offering

2,204,000

Composition of share capital

Common stock, par value per share (in dollars per share)

$0.01

Preferred stock, par value per share (in dollars per share)

$0.01

Common stock authorized (in shares)

75,000,000

30,145,155

75,000,000

30,145,155

Common stock issued (in shares)

21,467,482

2,606,484

21,467,482

2,606,484

Common stock outstanding (in shares)

21,467,482

2,606,484

21,467,482

2,606,484

Preferred stock, shares authorized (in shares)

5,000,000

Preferred stock authorized (in shares)

18,548,253

400,000

1,200,000

1,625,000

1,650,000

2,000,000

2,700,000

2,042,950

2,700,000

3,030,303

Preferred stock issued (in shares)

16,912,199

107,000

1,107,189

1,069,946

1,583,568

1,633,082

2,000,000

1,934,359

2,013,424

2,433,328

3,030,303

Preferred stock outstanding (in shares)

16,912,199

107,000

1,107,189

1,069,946

1,583,568

1,633,082

2,000,000

1,934,359

2,013,424

2,433,328

3,030,303

Activity of the preferred stock

Balance at the beginning of the period (in shares)

16,912,199

11,227,169

107,000

1,107,189

1,069,946

1,583,568

1,633,082

2,000,000

1,934,359

1,712,960

2,013,424

2,433,328

3,030,303

Balance at the beginning of the period

201,315,000

119,997,000

535,000

12,733,000

7,618,000

18,211,000

18,780,000

23,000,000

22,819,000

18,574,000

22,005,000

20,546,000

26,933,000

48,681,000

Issuance of Preferred Stock (in shares)

5,463,631

2,433,328

3,030,303

Issuance of Preferred Stock

74,563,000

26,767,000

47,796,000

Exercise of warrants (in shares)

221,399

Exercise of warrants

2,802,000

Accretion of redemption premium and issuance costs on Preferred Stock

-2,320,000

-3,953,000

-4,020,000

2,320,000

3,953,000

1,443,000

868,000

1,459,000

226,000

166,000

1,226,000

885,000

Conversion convertible preferred stock into common stock (in shares)

-16,912,199

-107,000

-1,107,189

-1,069,946

-1,583,568

-1,633,082

-2,000,000

-1,934,359

-2,013,424

-2,433,328

-3,030,303

Conversion convertible preferred stock into common stock

203,631,000

-203,635,000

-535,000

-12,733,000

-7,618,000

-18,211,000

-18,780,000

-23,000,000

-22,819,000

-22,873,000

-27,159,000

-49,907,000

Balance at the end of the period (in shares)

16,912,199

107,000

1,107,189

1,069,946

1,583,568

1,633,082

2,000,000

1,934,359

2,013,424

2,433,328

3,030,303

Balance at the end of the period

201,315,000

535,000

12,733,000

7,618,000

18,211,000

18,780,000

23,000,000

22,819,000

22,005,000

26,933,000

48,681,000

Number of voting rights per share of common stock for each holder of preferred stock

Number of shares of common stock issued for each share of preferred stock

0.8

0.85

0.75

0.77

0.75

Percentage of holding of outstanding Series A, Series B and Series C Preferred Stock holders from whom the written request required for redemption at specified price

66.67%

Redemption price (in dollars per share)

$11.50

$7.12

$11.50

$18

Number of days after receipt of the written request for redemption considered for determining redemption date

'60 days

Aggregate redemption value of preferred stock

103,122,000

Number of series of preferred stock contemporaneously subject to redemption considered for following liquidation order of priority

Number of warrants issued (in shares)

6,128

Ratio of the number of warrants issued for each share of preferred stock purchased

0.5

Weighted average assumptions

Exercise price (in dollars per share)

$9.79

Share price (in dollars per share)

$9.79

Expected term

'3 years

Risk-free rate (as a percent)

1.52%

Volatility (as a percent)

85.46%

Change in fair value of warrant liability

($61,000)

$31,000

$2,000

($14,000)

($2,000)

$25,000

($999,000)

$609,000

($42,000)

($367,000)

($1,287,000)

$42,000

$367,000

$1,287,000

Warrants outstanding immediately prior to IPO

6,128

Preferred Stock warrants converted into common stock warrants (in shares)

4,597

Common stock warrants, reverse stock split

1.333

StockBased_Compensation_Detail

Stock-Based Compensation (Details) (USD $)

12 Months Ended

180 Months Ended

0 Months Ended

4 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

1 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Apr. 24, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2013

Jan. 31, 2008

Jul. 31, 2013

Dec. 31, 2013

Stock options

Exercise Price $13.28

Exercise Price $14.75

Exercise Price $15.00

Exercise Price $21.79

Exercise Price $28.81

Exercise Price $27.71

Exercise Price $14.67

Exercise Price $14.68

Exercise Price $13.48

2007 Plan

2013 Plan

Maximum

Stock-based compensation

Percentage of increase in number of shares reserved for issuance under the 2007 Plan equal to fully diluted shares calculated annually

17.00%

Shares of common stock reserved for issuance under the 2013 Plan

6,107,831

4,107,831

6,107,831

Number of shares of Common Stock available for future issuance

676,236

Vesting period

'4 years

Expiration period

'10 years

Number of Options

Balance at the beginning of the period (in shares)

2,564,147

2,026,396

1,823,266

Granted (in shares)

1,967,940

977,807

344,479

310,540

4,800

763,000

17,500

57,500

500

16,000

32,500

765,600

Exercised (in shares)

-81,204

-438,556

-99,896

Forfeited (in shares)

-106,518

-1,500

-41,453

Balance at the end of the period (in shares)

4,344,365

2,564,147

2,026,396

1,823,266

Vested or expected to vest at the end of the period (in shares)

4,344,365

Exercisable at the end of the period (in shares)

2,347,744

Weighted-Average Exercise Price

Balance at the beginning of the period (in dollars per share)

$8.10

$4.81

$4.41

Granted (in dollars per share)

$14.60

$12.51

$6.13

$13.28

$14.75

$15

$21.79

$28.81

$27.71

$14.67

$14.68

$13.48

Exercised (in dollars per share)

$1.93

$2.90

$1.53

Forfeited (in dollars per share)

$12.23

$1.53

$5.43

Balance at the end of the period (in dollars per share)

$11.05

$8.10

$4.81

$4.41

Vested or expected to vest at the end of the period (in dollars per share)

$11.05

Exercisable at the end of the period (in dollars per share)

$8.72

Weighted-Average Remaining Contractual Term

Outstanding at the beginning of the period

'7 years 10 months 28 days

'7 years 6 months 7 days

'6 years 4 months 20 days

'6 years 1 month 2 days

Outstanding at the end of the period

'7 years 10 months 28 days

'7 years 6 months 7 days

'6 years 4 months 20 days

'6 years 1 month 2 days

Vested or expected to vest at the end of the period

'7 years 10 months 28 days

Exercisable at the end of the period

'6 years 7 months 17 days

Additional disclosures

Grant date intrinsic value of awards granted (in dollars per share)

Minimum period for which common stock to be held by option holder prior to selling to the significant holder

'6 months

Stock option award modification

($14,482,000)

Net tax benefits related to the stock-based compensation costs

Compensation expense

8,015,000

13,844,000

6,000

4,733,000

Stock option liability

Balance at the beginning of the period

11,967,000

2,648,000

Change in intrinsic value upon re-measurement

2,553,000

13,844,000

Settlements of option liability awards

-38,000

-4,525,000

Reclassification to stockholders' equity (deficit)

-14,482,000

Balance at the end of the period

11,967,000

2,648,000

Assumptions used to determine fair values for nonemployee options

Dividend yield (as a percent)

0.00%

Contractual life

'5 years 10 months 13 days

Volatility (as a percent)

77.00%

Risk-free interest rate (as a percent)

1.73%

Weighted-average grant-date fair value (in dollars per share)

$9.72

Fair value of shares vested

$9,875,000

$5,554,000

$1,712,000

StockBased_Compensation_Detail1

Stock-Based Compensation (Details 2) (USD $)	9 Months Ended	12 Months Ended
Stock-Based Compensation (Details 2) (USD $)	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock-based compensation	'	'	'	'
Total stock-based compensation	'	$8,015,000	$13,844,000	$6,000
Unrecognized compensation expense of unvested liability awards	1,875,000	1,875,000	'	'
Weighted-average period for recognizing unrecognized compensation expense of unvested liability awards	'	'2 years 3 months 25 days	'	'
Unrecognized compensation expense related to unvested stock options	3,597,000	3,597,000	'	'
Weighted-average period for recognizing unrecognized compensation expense related to unvested stock options	'3 years 7 months 24 days	'	'	'
General and administrative	'	'	'	'
Stock-based compensation	'	'	'	'
Total stock-based compensation	'	4,845,000	7,199,000	3,000
Research and development	'	'	'	'
Stock-based compensation	'	'	'	'
Total stock-based compensation	'	$3,170,000	$6,645,000	$3,000

StockBased_Compensation_Detail2

Stock-Based Compensation (Details 3) (USD $)	12 Months Ended
Stock-Based Compensation (Details 3) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Options Outstanding	'	'	'
Shares	4,344,365	'	'
Weighted Average Remaining Contractual Life	'7 years 10 months 28 days	'	'
Exercisable	'	'	'
Number (in shares)	2,347,744	'	'
Stock options	'	'	'
Exercisable	'	'	'
Intrinsic value of options exercised	$1,076,000	$4,510,000	$459,000
Aggregate intrinsic value of options outstanding	10,212,000	'	'
Aggregate intrinsic value of vested options	$9,742,000	'	'
Exercise Price Range $1.33 - $2.67	'	'	'
Options Outstanding	'	'	'
Shares	154,117	'	'
Weighted Average Remaining Contractual Life	'1 year 4 months 28 days	'	'
Exercisable	'	'	'
Number (in shares)	154,117	'	'
Exercise Price Range $1.33 - $2.67 \| Minimum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$1.33	'	'
Exercise Price Range $1.33 - $2.67 \| Maximum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$2.67	'	'
Exercise Price Range $5.76 - 6.00	'	'	'
Options Outstanding	'	'	'
Shares	801,208	'	'
Weighted Average Remaining Contractual Life	'4 years 11 months 1 day	'	'
Exercisable	'	'	'
Number (in shares)	792,730	'	'
Exercise Price Range $5.76 - 6.00 \| Minimum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$5.76	'	'
Exercise Price Range $5.76 - 6.00 \| Maximum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$6	'	'
Exercise Price Range $6.13 - $7.53	'	'	'
Options Outstanding	'	'	'
Shares	639,888	'	'
Weighted Average Remaining Contractual Life	'6 years 4 months 28 days	'	'
Exercisable	'	'	'
Number (in shares)	553,790	'	'
Exercise Price Range $6.13 - $7.53 \| Minimum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$6.13	'	'
Exercise Price Range $6.13 - $7.53 \| Maximum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$7.53	'	'
Exercise Price Range $13.28 - $13.48	'	'	'
Options Outstanding	'	'	'
Shares	1,870,852	'	'
Weighted Average Remaining Contractual Life	'9 years 11 months 19 days	'	'
Exercisable	'	'	'
Number (in shares)	418,644	'	'
Exercise Price Range $13.28 - $13.48 \| Minimum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$13.28	'	'
Exercise Price Range $13.28 - $13.48 \| Maximum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$13.48	'	'
Exercise Price Range $14.67 - $15.00	'	'	'
Options Outstanding	'	'	'
Shares	805,300	'	'
Weighted Average Remaining Contractual Life	'9 years 7 months 2 days	'	'
Exercisable	'	'	'
Number (in shares)	421,244	'	'
Exercise Price Range $14.67 - $15.00 \| Minimum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$14.67	'	'
Exercise Price Range $14.67 - $15.00 \| Maximum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$15	'	'
Exercise Price Range $21.79 - $28.81	'	'	'
Options Outstanding	'	'	'
Shares	73,000	'	'
Weighted Average Remaining Contractual Life	'9 years 8 months 19 days	'	'
Exercisable	'	'	'
Number (in shares)	7,219	'	'
Exercise Price Range $21.79 - $28.81 \| Minimum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$21.79	'	'
Exercise Price Range $21.79 - $28.81 \| Maximum	'	'	'
Stock-based compensation	'	'	'
Exercise Price (in dollars per share)	$28.81	'	'

Employee_Benefits_Plan_Details

Employee Benefits Plan (Details) (USD $)	12 Months Ended
Employee Benefits Plan (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
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	$0.50	'	'
Employer's match for every dollar of the first specified percentage of payroll that employees invest for period beginning January 1, 2014	0.6	'	'
First specified percentage of payroll that employees invest	6.00%	'	'
Employer's contribution, vesting period	'4 years	'	'
Employer contribution annual vesting percentage	25.00%	'	'
Contributions	$289,000	$159,000	$131,000

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended			0 Months Ended	1 Months Ended	0 Months Ended	1 Months Ended	12 Months Ended		1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Feb. 01, 2012	Nov. 30, 2010	Oct. 02, 2012	Oct. 31, 2009	Dec. 31, 2013	Jan. 31, 2007	Sep. 30, 2012
				Office space of 3,117 square feet area in Pennington, New Jersey	Office space of 3,117 square feet area in Pennington, New Jersey	Additional office space of 2,130 square feet area in Pennington, New Jersey	Office and lab space of 8,100 square feet area in Newtown, Pennsylvania	Office and lab space of 8,100 square feet area in Newtown, Pennsylvania	Office and lab space of 8,100 square feet area in Newtown, Pennsylvania	Additional office space of 1,356 square feet area in Newtown, Pennsylvania
					sqft	sqft	item		sqft	sqft
Operating leases	'	'	'	'	'	'	'	'	'	'
Area of space leased (in square feet)	'	'	'	'	3,117	2,130	'	'	8,100	1,356
Lease term	'	'	'	'	'2 years	'	'	'	'	'1 year
Additional lease term under option	'	'	'	'	'2 years	'	'1 year	'	'	'
Lease rent per month	'	'	'	$5,000	$4,400	$3,100	'	'	'	'
Annual lease rent	'	'	'	'	53,000	38,000	'	'	'	'
Letter of credit provided to landlord	'	'	'	'	125,000	'	'	'	'	'
Increase in lease rent (as a percent)	'	'	'	3.50%	'	'	'	'	'	'
Number of options available for lease extensions	'	'	'	'	'	'	3	'	'	'
Lease rent per month under first and second option exercised	'	'	'	'	'	'	'	11,000	'	'
Sub-lease rent per month	'	'	'	'	'	'	'	'	'	1,600
Annual sub-lease rent	'	'	'	'	'	'	'	'	'	19,000
Future minimum lease payments under these non-cancellable leases	'	'	'	'	'	'	'	'	'	'
2014	245,000	'	'	'	'	'	'	'	'	'
2015	39,000	'	'	'	'	'	'	'	'	'
Total minimum lease payments	284,000	'	'	'	'	'	'	'	'	'
Rent expense	$309,000	$233,000	$186,000	'	'	'	'	'	'	'

Research_Agreements_Details

Research Agreements (Details) (USD $)	1 Months Ended	12 Months Ended			12 Months Ended
	Sep. 30, 2011	Dec. 31, 2013	Dec. 31, 2012	31-May-10	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Jan. 31, 2013	Dec. 31, 2012	31-May-10
	Temple	Temple	Temple	Temple	LLS	LLS	LLS	LLS	LLS	LLS
				Rigosertib	Rigosertib	Rigosertib	Rigosertib	Rigosertib	Rigosertib	Rigosertib
				Maximum	item		Maximum	Maximum	Maximum	Maximum
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	1,875,000	'	'	'	'	1,000,000	'	'	'	'
Obligations to pay in connection with the collaboration agreement	'	'	12,500,000	'	'	'	'	'	'	'
Obligations not yet paid	'	'	1,405,000	'	'	'	'	'	'	'
Potential milestone payments	'	'	'	'	'	'	'	8,000,000	'	10,000,000
Potential royalties payment as multiplier of amount funded	'	'	'	'	3	'	'	'	'	'
Potential milestone and royalty payment obligation	'	'	'	24,000,000	'	'	23,000,000	'	23,000,000	'
Milestone payments received recorded as deferred revenue	'	'	'	'	'	$8,000,000	'	'	'	'

License_and_Collaboration_Agre1

License and Collaboration Agreements (Details) (USD $)

3 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

0 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Sep. 30, 2012

Jul. 31, 2013

Sep. 30, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Sep. 30, 2012

Feb. 01, 2014

Sep. 30, 2012

Jul. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Jul. 31, 2011

Jul. 31, 2012

Baxter

Collaboration arrangement

Series J Preferred Stock

Maximum

Baxter

SymBio

Rigosertib

Collaboration arrangement

item

Baxter

SymBio

Baxter

item

Maximum

Rigosertib IV in higher risk MDS patients

MDS IV indication

Rigosertib IV in pancreatic cancer patients

Rigosertib oral in lower risk MDS patients

Supply agreement

United States and Japan

Maximum

MDS IV indication

Rigosertib oral in lower risk MDS patients

Rigosertib IV in combination with gemcitabine for pancreatic cancer patients

Minimum

United States

Japan

United States

Japan

United States

Japan

License and collaboration agreements

Consideration received for the Preferred Stock

$5,000,000

$50,000,000

Number of initial rigosertib indications

Term of improvement observed

'2 years 4 months 24 days

Upfront payment

50,000,000

7,500,000

Aggregate milestone payments

337,500,000

22,000,000

Potential pre-commercial milestone payments for achievement of the primary endpoint of a Phase 3 clinical trial for indication

50,000,000

Potential pre-commercial milestone payments for joint decision to proceed with the development of rigosertib for certain indications

25,000,000

Potential pre-commercial milestone payments for number of EU Countries where marketing approval is to be filed

Potential pre-commercial milestone payments for drug approval application filed for specified indications

25,000,000

Potential milestone payments for regulatory approvals of specified indications

212,500,000

100,000,000

Additional potential pre-commercial milestone payments related to the timing of regulatory approval of indication

20,000,000

Aggregate potential milestone payments based on annual net sales of rigosertib

250,000,000

30,000,000

Percentage of royalty payments based on net sales of rigosertib

20.00%

Number of employees

50,000

Discount rate (as a percent)

16.00%

BESP of the license

120,000,000

BESP of the research and development services

20,600,000

Up-front payment allocated to license

42,400,000

Up-front payment allocated to research and development services

7,600,000

Allocated up-front payment of license recognized upon execution of agreement

42,400,000

Research and development revenue

197,000

1,260,000

4,176,000

3,100,000

Potential development milestones payments due after enrollment of the first patient in event of decision made to start phase 3 clinical trial of indication

3,000,000

Regulatory milestones payments due upon receipt of marketing approval for indication

5,000,000

3,000,000

5,000,000

3,000,000

Aggregate milestone payments due upon receipt of marketing approval for an additional indication

4,000,000

Binding commitments

Recognized revenues

$1,930,000

$1,116,000

$591,000

$1,116,000

$2,969,000

$42,803,000

$220,000

$198,000

$4,753,000

$46,190,000

$1,487,000

$4,176,000

$45,490,000

$577,000

$503,000

$227,000

$455,000

$227,000

$122,000

$48,000

Preclinical_Collaboration_Deta

Preclinical Collaboration (Details) (GBO, USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
	item	item
Preclinical Collaboration	'	'
Number of new programs to be collaborated and developed	'	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	3	'
GVK BIO	'	'
Preclinical Collaboration	'	'
Initial capital contribution	500,000	'
Ownership interest in the joint venture (as a percent)	10.00%	'
Additional capital contributions	500,000	'
Number of products for which additional capital contributions necessary for IND approval	1	'
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%	'

RelatedParty_Transactions_Deta

Related-Party Transactions (Details) (USD $)	12 Months Ended
Related-Party Transactions (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Mount Sinai	'	'	'
Related-party transactions	'	'	'
Payments to related party	$1,235,000	$1,230,000	$554,000
Amounts due to related party	0	0	'
Supplier business owned by board members	'	'	'
Related-party transactions	'	'	'
Payments to related party	0	157,000	6,000
Amounts due to related party	0	107,000	'
Corporations owned by former board members	'	'	'
Related-party transactions	'	'	'
Payments to related party	804,000	410,000	970,000
Amounts due to related party	50,000	0	'
Member of board of directors	'	'	'
Related-party transactions	'	'	'
Payments to related party	$182,000	$165,000	$158,000

Initial_Public_Offering_Detail

Initial Public Offering (Details) (USD $)	0 Months Ended		12 Months Ended
Initial Public Offering (Details) (USD $)	Jul. 30, 2013	Jul. 17, 2013	Dec. 31, 2013	Sep. 30, 2013	Jul. 31, 2013	Dec. 31, 2012
Initial Public Offering	'	'	'	'	'	'
Preferred stock outstanding (in shares)	0	'	0	0	'	16,912,199
Net proceeds received from the sale, net of underwriting discounts and commissions and other estimated offering expenses	$79,811,000	'	$79,811,000	'	'	'
Reverse stock split of common stock	'	0.75	'	'	'	'
Designated public offering amended threshold gross proceeds, minimum	'	'	'	'	$25,000,000	'

Quarterly_Data_Details

Quarterly Data (Details) (USD $)	3 Months Ended								12 Months Ended
Quarterly Data (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Data (unaudited)	'	'	'	'	'	'	'	'	'	'	'
Revenue	$1,930,000	$1,116,000	$591,000	$1,116,000	$2,969,000	$42,803,000	$220,000	$198,000	$4,753,000	$46,190,000	$1,487,000
Operating expenses:	'	'	'	'	'	'	'	'	'	'	'
General and administrative	4,403,000	5,927,000	3,117,000	3,346,000	2,698,000	8,922,000	1,627,000	2,460,000	16,793,000	15,707,000	6,436,000
Research and development	12,086,000	15,293,000	10,047,000	12,756,000	10,576,000	26,962,000	6,776,000	8,448,000	50,182,000	52,762,000	22,624,000
Total operating expenses	16,489,000	21,220,000	13,164,000	16,102,000	13,274,000	35,884,000	8,403,000	10,908,000	66,975,000	68,469,000	29,060,000
Loss from operations	-14,559,000	-20,104,000	-12,573,000	-14,986,000	-10,305,000	6,919,000	-8,183,000	-10,710,000	-62,222,000	-22,279,000	-27,573,000
Change in fair value of warrant liability	61,000	-31,000	-2,000	14,000	2,000	-25,000	999,000	-609,000	42,000	367,000	1,287,000
Interest expense	1,000	1,000	2,000	'	'	8,357,000	230,000	21,000	4,000	8,608,000	19,000
Other income, net	-126,000	47,000	15,000	127,000	41,000	28,000	-2,000	541,000	63,000	608,000	11,000
Net loss before income taxes	-14,625,000	-20,089,000	-12,562,000	-14,845,000	-10,262,000	-1,435,000	-7,416,000	-10,799,000	-62,121,000	-29,912,000	-26,294,000
Income taxes	3,000	432,000	'	'	'	'	'	'	435,000	'	'
Net loss	-14,628,000	-20,521,000	-12,562,000	-14,845,000	-10,262,000	-1,435,000	-7,416,000	-10,799,000	-62,556,000	-29,912,000	-26,294,000
Net loss attributable to non-controlling interest	13,000	'	'	'	'	'	'	'	13,000	'	'
Net loss attributable to Onconova Therapeutics, Inc.	-14,615,000	-20,521,000	-12,562,000	-14,845,000	-10,262,000	-1,435,000	-7,416,000	-10,799,000	-62,543,000	-29,912,000	-26,294,000
Accretion of redeemable convertible preferred stock	'	-269,000	-1,032,000	-1,019,000	-1,010,000	-785,000	-927,000	-1,231,000	-2,320,000	-3,953,000	-4,020,000
Net loss applicable to common stockholders	($14,615,000)	($20,790,000)	($13,594,000)	($15,864,000)	($11,272,000)	($2,220,000)	($8,343,000)	($12,030,000)	($64,863,000)	($33,865,000)	($30,314,000)
Net loss per share of common stock, basic and diluted (in dollars per share)	($0.68)	($1.34)	($5.21)	($6.08)	($4.89)	($1.02)	($3.84)	($5.53)	($6.12)	($15.35)	($14.18)
Basic and diluted weighted average shares outstanding (in shares)	21,419,208	15,480,416	2,609,495	2,607,406	2,305,315	2,174,392	2,173,549	2,173,553	10,594,227	2,206,888	2,137,403