Document and Entity Information (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	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	Dec. 31, 2013
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			$ 107.3
Entity Common Stock, Shares Outstanding		21,638,029
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY

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 (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 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 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 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 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	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 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.

- Definition

The entire disclosure for the organization, consolidation and basis of presentation of financial statements disclosure, and significant accounting policies of the reporting entity. May be provided in more than one note to the financial statements, as long as users are provided with an understanding of (1) the significant judgments and assumptions made by an enterprise in determining whether it must consolidate a VIE and/or disclose information about its involvement with a VIE, (2) the nature of restrictions on a consolidated VIE's assets reported by an enterprise in its statement of financial position, including the carrying amounts of such assets, (3) the nature of, and changes in, the risks associated with an enterprise's involvement with the VIE, and (4) how an enterprise's involvement with the VIE affects the enterprise's financial position, financial performance, and cash flows. Describes procedure if disclosures are provided in more than one note to the financial statements.

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Property and Equipment

12 Months Ended

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.

- Definition

The entire disclosure for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, accounting policies and methodology, roll forwards, depreciation, depletion and amortization expense, including composite depreciation, accumulated depreciation, depletion and amortization expense, useful lives and method used, income statement disclosures, assets held for sale and public utility disclosures.

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Fair Value Measurements

12 Months Ended

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 December 31, 2013								Fair Value Measurement as of 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.

- Definition

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

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Net Loss Per Share of Common Stock

12 Months Ended

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

- Definition

The entire disclosure for earnings per share.

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Balance Sheet Detail

12 Months Ended

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

Income Taxes

12 Months Ended

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		34.0	%		34.0	%		34.0	%
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	)		0.0			(5.1	)
Change in valuation allowance		(61.2	)		(29.1	)		(51.6	)
Other		(0.2	)		(0.1	)		0.0


Effective income tax rate		(0.6	)%		0.0	%		0.0	%

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

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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 Stockholders' Equity (Deficit)

12 Months Ended

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, 2013		December 31, 2012		December 31, 2013		December 31, 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, 2012		Issuance of Preferred Stock		Exercise of warrants		Accretion of redemption premium and issuance costs on Preferred Stock		Conversion of Preferred Stock into Common Stock			December 31, 2013

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	)	$	—

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).