Madrigal Pharmaceuticals (MDGL) 10-K 12 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Mar. 06, 2015	Jun. 30, 2014
Document and Entity Information
Entity Registrant Name	SYNTA PHARMACEUTICALS CORP
Entity Central Index Key	1157601
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$275,002,606.09
Entity Common Stock, Shares Outstanding		109,120,670
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$46,024	$48,490
Marketable securities	51,666	42,986
Prepaid expenses and other current assets	1,656	765
Total current assets	99,346	92,241
Property and equipment, net	1,024	1,553
Other assets	305	1,409
Total assets	100,675	95,203
Current liabilities:
Accounts payable	3,139	6,589
Accrued contract research costs	12,317	10,407
Other accrued liabilities	6,177	5,718
Current portion of capital lease obligations	42	42
Current portion of term loans	9,214	9,451
Total current liabilities	30,889	32,207
Long-term liabilities:
Capital lease obligations, net of current portion	43	85
Term loans, net of current portion	4,607	13,820
Total long-term liabilities	4,650	13,905
Total liabilities	35,539	46,112
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, par value $0.0001 per share Authorized: 5,000,000 shares at December 31, 2014 and 2013; no shares issued and outstanding at December 31, 2014 and 2013
Common stock, par value $0.0001 per share Authorized: 200,000,000 shares at December 31, 2014 and December 31, 2013; 109,120,670 and 85,232,506 shares issued and outstanding at December 31, 2014 and 2013, respectively	11	9
Additional paid-in-capital	702,694	600,477
Accumulated other comprehensive income	4	17
Accumulated deficit	-637,573	-551,412
Total stockholders' equity	65,136	49,091
Total liabilities and stockholders' equity	$100,675	$95,203

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Condensed Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$0.00	$0.00
Preferred stock, Authorized shares	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$0.00	$0.00
Common stock, Authorized shares	200,000,000	200,000,000
Common stock, shares issued	109,120,670	85,232,506
Common stock, shares outstanding	109,120,670	85,232,506

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Total revenues											$147
Grant revenue									0	0	147
Operating expenses:
Research and development	15,653	16,208	18,761	17,583	19,981	17,623	17,876	16,380	68,205	71,860	49,412
General and administrative	4,241	3,241	2,940	5,324	3,463	4,171	4,187	3,878	15,746	15,699	11,676
Total operating expenses	19,894	19,449	21,701	22,907	23,444	21,794	22,063	20,258	83,951	87,559	61,088
Loss from operations	-19,894	-19,449	-21,701	-22,907	-23,444	-21,794	-22,063	-20,258	-83,951	-87,559	-60,941
Interest expense, net	-458	-517	-585	-650	-718	-721	-724	-470	-2,210	-2,633	-1,849
Net loss	($20,352)	($19,966)	($22,286)	($23,557)	($24,162)	($22,515)	($22,787)	($20,728)	($86,161)	($90,192)	($62,790)
Net loss per common share:
Basic and diluted net loss per common share (in dollars per share)	($0.19)	($0.19)	($0.24)	($0.28)	($0.31)	($0.33)	($0.33)	($0.30)	($0.87)	($1.27)	($1.06)
Basic and diluted weighted average number of common shares outstanding	108,366,504	105,774,949	94,046,278	85,438,127	76,769,199	69,047,161	69,034,823	68,991,371	98,489,470	70,976,705	59,411,476

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Consolidated Statements of Comprehensive Loss
Net loss	($86,161)	($90,192)	($62,790)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	-13	15	-1
Comprehensive loss	($86,174)	($90,177)	($62,791)

Consolidated_Statements_of_Sto

Consolidated Statements of Stockholders' Equity (USD $)	Common stock	Additional paid-in capital	Accumulated other comprehensive income (Loss)	Accumulated deficit	Total
In Thousands, except Share data, unless otherwise specified
Balance at Dec. 31, 2011	$5	$413,196	$3	($398,430)	$14,774
Balance (in shares) at Dec. 31, 2011	49,539,808
Increase (Decrease) in Stockholders' Equity
Issuance of common shares in equity offering, excluding to related parties, net	1	65,106			65,107
Issuance of common shares in equity offering, excluding to related parties, net (in shares)	11,264,102
Issuance of common shares to related parties	1	53,544			53,545
Issuance of common shares to related parties (in shares)	7,762,600
Issuance of restricted common shares (in shares)	45,243
Exercise of stock options		1,141			1,141
Exercise of stock options (in shares)	322,298
Purchase and retirement of common shares from an officer		-32			-32
Purchase and retirement of common shares from an officer (in shares)	-3,969
Compensation expense related to stock options for services		3,322			3,322
Unrealized gain (loss) on marketable securities			-1		-1
Net loss				-62,790	-62,790
Balance at Dec. 31, 2012	7	536,277	2	-461,220	75,066
Balance (in shares) at Dec. 31, 2012	68,930,082
Increase (Decrease) in Stockholders' Equity
Issuance of common shares in equity offering, excluding to related parties, net	1	37,628			37,629
Issuance of common shares in equity offering, excluding to related parties, net (in shares)	10,916,667
Issuance of common shares to related parties	1	19,436			19,437
Issuance of common shares to related parties (in shares)	5,183,333
Issuance of restricted common shares (in shares)	140,000
Forfeitures of restricted common shares (in shares)	-75,000
Exercise of stock options		1,106			1,106
Exercise of stock options (in shares)	137,424
Compensation expense related to stock options for services		6,030			6,030
Unrealized gain (loss) on marketable securities			15		15
Net loss				-90,192	-90,192
Balance at Dec. 31, 2013	9	600,477	17	-551,412	49,091
Balance (in shares) at Dec. 31, 2013	85,232,506				85,232,506
Increase (Decrease) in Stockholders' Equity
Issuance of common shares in equity offering, excluding to related parties, net	2	88,940			88,942
Issuance of common shares in equity offering, excluding to related parties, net (in shares)	21,692,753
Issuance of common shares to related parties		4,992			4,992
Issuance of common shares to related parties (in shares)	1,250,000
Issuance of restricted common shares (in shares)	764,022
Forfeitures of restricted common shares (in shares)	-25,000
Exercise of stock options		854			854
Exercise of stock options (in shares)	206,389
Compensation expense related to stock options for services		7,431			7,431
Unrealized gain (loss) on marketable securities			-13		-13
Net loss				-86,161	-86,161
Balance at Dec. 31, 2014	$11	$702,694	$4	($637,573)	$65,136
Balance (in shares) at Dec. 31, 2014	109,120,670				109,120,670

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net loss	($86,161)	($90,192)	($62,790)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	7,431	6,030	3,322
Depreciation and amortization	673	516	738
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	102	21	-225
Other assets	111	-951	173
Accounts payable	-3,450	928	2,194
Accrued contract research costs	1,910	5,646	1,920
Other accrued liabilities	459	591	533
Net cash used in operating activities	-78,925	-77,411	-54,135
Cash flows from investing activities:
Purchases of marketable securities	-93,845	-114,151	-50,033
Maturities of marketable securities	85,152	90,267	40,595
Purchases of property and equipment	-144	-769	-505
Net cash used in investing activities	-8,837	-24,653	-9,943
Cash flows from financing activities:
Proceeds from issuances of common stock, excluding to related parties, and exercise of common stock options, net of transaction costs	89,796	38,735	66,248
Proceeds from the sale of common stock to related parties	4,992	19,437	53,545
Purchase and retirement of common stock from an officer			-32
Proceeds from term loans		13,500
Payment of term loans	-9,450	-2,617	-4,234
Payment of capital lease obligations	-42	-13	-12
Net cash provided by financing activities	85,296	69,042	115,515
Net increase (decrease) in cash and cash equivalents	-2,466	-33,022	51,437
Cash and cash equivalents at beginning of period	48,490	81,512	30,075
Cash and cash equivalents at end of period	46,024	48,490	81,512
Supplemental disclosure of cash flow information:
Cash paid for interest	1,875	2,512	1,696
Assets acquired under capital lease		$126

Nature_of_Business

Nature of Business	12 Months Ended
	Dec. 31, 2014
Nature of Business
Nature of Business	(1) Nature of Business
	Synta Pharmaceuticals Corp. (the Company) was incorporated in March 2000 and commenced operations in July 2001. The Company is an innovative, agile biopharmaceutical company focused on research, development and commercialization of novel oncology medicines that have the potential to change the lives of cancer patients.
	The Company is subject to risks common to emerging companies in the drug development and pharmaceutical industry including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, dependence on key personnel, uncertainty of market acceptance of products and product reimbursement, product liability, uncertain protection of proprietary technology, potential inability to raise additional financing and compliance with the U.S. Food and Drug Administration and other government regulations.
	The Company has incurred significant operating losses since its inception and, as a result, as of December 31, 2014 had an accumulated deficit of $637.6 million. Operations have been funded principally through the sale of common stock and convertible preferred stock, capital leases, non-refundable payments under the former collaboration agreements with GlaxoSmithKline (GSK) and Hoffman-La Roche (Roche), and proceeds from term loans by General Electric Capital Corporation (GECC) and Oxford Finance Corporation (Oxford) (see Note 9).
	The Company expects its $97.7 million in cash, cash equivalents and marketable securities as of December 31, 2014 will be sufficient to fund operations at least through the end of 2015. This estimate assumes no additional funding from new partnership agreements, equity financings or further sales under the Company's at-the-market-issuance sales agreement (ATM) with MLV & Co. LLC (MLV) (see Note 5). The timing and nature of certain activities contemplated for 2015 will be conducted subject to the availability of sufficient financial resources.
	The Company may require significant additional funds earlier than it currently expects in order to conduct additional clinical trials and continue to fund its operations. There can be no assurances, however, that additional funding will be available on favorable terms, or at all. If adequate funds are not available, the Company may be required to delay, significantly modify or terminate its research and development programs or reduce its planned commercialization efforts.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	(2) Summary of Significant Accounting Policies
	Principles of Consolidation
	The condensed consolidated financial statements include the financial statements of the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.
	Use of Estimates
	The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect certain reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting periods. Significant items subject to such estimates and assumptions include contract research accruals, recoverability of long-lived assets, measurement of stock-based compensation, and the periods of performance under collaborative research and development agreements. The Company bases its estimates on historical experience and various other assumptions that management believes to be reasonable under the circumstances. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
	Cash and Cash Equivalents
	The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase and an investment in a money market fund to be cash equivalents. Changes in the level of cash and cash equivalents may be affected by changes in investment portfolio maturities, as well as actual cash disbursements to fund operations.
	The primary objective of the Company's investment activities is to preserve its capital for the purpose of funding operations and the Company does not enter into investments for trading or speculative purposes. The Company's cash is deposited in a highly rated financial institution in the United States. The Company invests in money market funds and high-grade, short-term commercial paper and corporate bonds, which management believes are subject to minimal credit and market risk. Declines in interest rates, however, would reduce future investment income.
	Marketable Securities
	Marketable securities consist of investments in high-grade corporate obligations, and government and government agency obligations that are classified as available-for-sale. Since these securities are available to fund current operations they are classified as current assets on the consolidated balance sheets.
	The Company adjusts the cost of available-for-sale debt securities for amortization of premiums and accretion of discounts to maturity. The Company includes such amortization and accretion as a component of interest expense, net. Realized gains and losses and declines in value, if any, that the Company judges to be other-than-temporary on available-for-sale securities are reported as a component of interest expense, net. To determine whether an other-than-temporary impairment exists, the Company considers whether it intends to sell the debt security and, if the Company does not intend to sell the debt security, it considers available evidence to assess whether it is more likely than not that it will be required to sell the security before the recovery of its amortized cost basis. During the years ended December 31, 2014, 2013 and 2012, the Company determined it did not have any securities that were other-than-temporarily impaired.
	Marketable securities are stated at fair value, including accrued interest, with their unrealized gains and losses included as a component of accumulated other comprehensive income or loss, which is a separate component of stockholders' equity. The fair value of these securities is based on quoted prices and observable inputs on a recurring basis. Realized gains and losses are determined on the specific identification method. During the years ended December 31, 2014, 2013 and 2012, the Company did not have any realized gains or losses on marketable securities.
	Fair Value of Financial Instruments
	The carrying amounts of the Company's financial instruments, which include cash equivalents, marketable securities and term loan obligations, approximate their fair values. The fair value of the Company's financial instruments reflects the amounts that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value hierarchy has the following three levels:
	Level 1—quoted prices in active markets for identical assets and liabilities.
	Level 2—observable inputs other than Level 1 inputs. Examples of Level 2 inputs include quoted prices in active markets for similar assets or liabilities and quoted prices for identical assets or liabilities in markets that are not active.
	Level 3—unobservable inputs that reflect the Company's own assumptions about the assumptions market participants would use in pricing the asset or liability.
	Financial assets and liabilities are classified in their entirety within the fair value hierarchy based on the lowest level of input that is significant to the fair value measurement. The Company measures the fair value of its marketable securities by taking into consideration valuations obtained from third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker-dealer quotes on the same or similar securities, issuer credit spreads, benchmark securities and other observable inputs. As of December 31, 2014, the Company's financial assets valued based on Level 1 inputs consisted of cash and cash equivalents in a money market fund and its financial assets valued based on Level 2 inputs consisted of high-grade corporate bonds and commercial paper. During the years ended December 31, 2014, 2013 and 2012, the Company did not have any transfers of financials assets between Levels 1 and 2. As of December 31, 2014, the Company did not have any financial liabilities that were recorded at fair value on the balance sheet. The disclosed fair value of the Company's term loan obligations is determined using current applicable rates for similar instruments as of the balance sheet date. The carrying value of the Company's term loan obligations approximates fair value as the Company's interest rate yield is near current market rate yields. The disclosed fair value of the Company's term loan obligations is based on Level 3 inputs.
	Property and Equipment
	Property, equipment and software is carried at cost and depreciated using the straight-line method over the estimated useful lives of the related assets, which range from three to seven years. Leasehold improvements are amortized over the lesser of the lease term or estimated useful life. Repairs and maintenance costs are expensed as incurred.
	Research and Development Costs
	Research and development costs are expensed as incurred. Research and development costs are comprised of costs incurred in performing research and development activities, including internal costs for salaries, bonuses, benefits, facilities, research-related overhead and stock compensation, and external costs for payments to third party contract research organizations, investigative sites and consultants in connection with the Company's preclinical and clinical programs, costs associated with drug formulation and supply of drugs for clinical trials, and other external costs.
	Patents
	Costs to secure and defend patents are expensed as incurred and are classified as general and administrative expense in the Company's consolidated statements of operations. Patent expenses were approximately $1.9 million, $2.9 million, and $1.8 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	Income Taxes
	The Company uses the liability method to account for income taxes. Deferred tax assets and liabilities are determined based on the expected future tax consequences of temporary differences between the Company's consolidated financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. A valuation allowance is provided to reduce the deferred tax assets to the amount that will more likely than not be realized.
	As of December 31, 2014 and 2013, the Company had no items that were considered to be uncertain tax items or accrued interest or penalties related to uncertain tax positions.
	The tax years 2011 through 2014 remain open to examination by the major taxing jurisdictions to which the Company is subject.
	Impairment of Long-Lived Assets
	The Company assesses the potential impairments of its long-lived assets whenever events or changes in circumstances indicate that an asset's carrying value may not be recoverable. If the carrying value exceeds the undiscounted future cash flows estimated to result from the use and eventual disposition of the asset, the Company writes down the asset to its estimated fair value. Management believes that no long-lived assets were impaired as of December 31, 2014 and 2013.
	Revenue Recognition
	Collaboration and License Agreements
	The Company's principal source of revenue to date has been its former collaboration and license agreements, which included upfront license payments, development milestones, reimbursement of research and development costs, potential profit sharing payments, commercial and sales-based milestones and royalties. The accounting for collaboration and license agreements requires subjective analysis and requires management to make estimates and assumptions about whether deliverables within multiple-element arrangements are separable from the other aspects of the contractual arrangement into separate units of accounting and to determine the arrangement consideration to be allocated to each unit of accounting.
	For multiple-element arrangements entered into or materially modified after January 1, 2011, the Company follows the provisions of Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) No. 2009-13—Multiple-deliverable Revenue Arrangements (ASU No. 2009-13). ASU No. 2009-13 amended certain provisions of Accounting Standards Codification (ASC) Topic 605—Revenue Recognition . This standard addresses the determination of the unit(s) of accounting for multiple-element arrangements and how an arrangement's consideration should be allocated to each unit of accounting.
	Pursuant to this standard, each required deliverable is evaluated to determine if it qualifies as a separate unit of accounting. For the Company this determination includes an assessment as to whether the deliverable has "stand-alone value" to the customer separate from the undelivered elements. The arrangement's consideration is then allocated to each separate unit of accounting based on the relative selling price of each deliverable. The estimated selling price of each deliverable is determined using the following hierarchy of values: (i) vendor-specific objective evidence of fair value, (ii) third-party evidence of selling price, or (iii) the Company's best estimate of the selling price (BESP). The BESP reflects the Company's best estimate of what the selling price would be if the deliverable was regularly sold by it on a stand-alone basis. The Company expects, in general, to use BESP for allocating consideration to each deliverable in future collaboration agreements. In general, the consideration allocated to each unit of accounting is then recognized as the related goods or services are delivered limited to the consideration not contingent upon future deliverables. The Company did not recognize any revenue related to collaboration and license agreements during the years ended December 31, 2014, 2013 and 2012.
	The Company accounts for development milestones under collaboration and license agreements pursuant to ASU No. 2010-17 Milestone Method of Revenue Recognition (ASU No. 2010-17). ASU No. 2010-17 codified a method of revenue recognition that has been common practice. Under this method, contingent consideration from research and development activities that is earned upon the achievement of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved. At the inception of each arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive. This evaluation includes an assessment of whether (a) the consideration is commensurate with either (1) the entity's performance to achieve the milestone, or (2) the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the entity's performance to achieve the milestone, (b) the consideration relates solely to past performance and (c) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the respective milestone, the level of effort and investment required and whether the milestone consideration is reasonable relative to all deliverables and payment terms in the arrangement in making this assessment. The Company does not have any ongoing collaboration and license agreements under which milestones may be achieved.
	Royalty revenues are based upon a percentage of net sales. Royalties from the sales of products will be recorded on the accrual basis when results are reliably measurable, collectability is reasonably assured and all other revenue recognition criteria are met. Commercial and sales-based milestones, which are based upon the achievement of certain agreed-upon sales thresholds, will be recognized in the period in which the respective sales threshold is achieved and collectability is reasonably assured. The Company does not have any ongoing collaboration and license agreements under which royalties or commercial and sales-based milestones may be achieved.
	Grant Revenue
	In March 2011, the Company received a grant from the Department of Defense, in the approximate amount of $1 million, for the development of STA-9584 in advanced prostate cancer. The Company conducted work on this study during the grant period from April 2011 through March 2012. Reimbursements were based on actual costs agreed upon in the proposal (salary, fringe benefits, overhead, and direct costs such as materials and subcontractors). During the years ended December 31, 2014, 2013 and 2012, the Company recognized $0, $0 and $147,000, respectively, in grant revenues.
	Stock-Based Compensation
	The Company recognizes stock-based compensation expense based on the grant date fair value of stock options granted to employees, officers and directors. The Company uses the Black-Scholes option pricing model to determine the grant date fair value as management believes it is the most appropriate valuation method for its option grants. The Black-Scholes model requires inputs for risk-free interest rate, dividend yield, volatility and expected lives of the options. Expected volatility is based upon the weighted average historical volatility data of the Company's common stock. The risk-free rate for periods within the expected life of the option is based on the U.S. Treasury yield curve in effect at the time of the grant. The expected lives for options granted represent the period of time that options granted are expected to be outstanding. The Company uses the simplified method for determining the expected lives of options. The Company estimates the forfeiture rate based on historical data. This analysis is re-evaluated at least annually and the forfeiture rate is adjusted as necessary.
	For awards with graded vesting, the Company recognizes compensation costs based on the grant date fair value of awards on a straight-line basis over the requisite service period, which is generally the vesting period.
	Certain of the employee stock options granted by the Company are structured to qualify as incentive stock options (ISOs). Under current tax regulations, the Company does not receive a tax deduction for the issuance, exercise or disposition of ISOs if the employee meets certain holding requirements. If the employee does not meet the holding requirements, a disqualifying disposition occurs, at which time the Company may receive a tax deduction. The Company does not record tax benefits related to ISOs unless and until a disqualifying disposition is reported. In the event of a disqualifying disposition, the entire tax benefit is recorded as a reduction of income tax expense. The Company has not recognized any income tax benefit for its share-based compensation arrangements due to the fact that the Company does not believe it is more likely than not it will realize the related deferred tax assets.
	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. Changes in unrealized gains and losses on marketable securities represent the only difference between the Company's net loss and comprehensive loss.
	Segment Reporting
	Operating segments are determined based on the way management organizes its business for making operating decisions and assessing performance. The Company has a single operating segment, which is the discovery, development and commercialization of drug products.
	Basic and Diluted Loss Per Common Share
	Basic net loss per share is computed using the weighted average number of common shares outstanding during the period, excluding restricted stock that has been issued but is not yet vested. Diluted net loss per common share is computed using the weighted average number of common shares outstanding and the weighted average dilutive potential common shares outstanding using the treasury stock method. However, for the years ended December 31, 2014, 2013 and 2012, diluted net loss per share is the same as basic net loss per share as the inclusion of weighted average shares of unvested restricted common stock and common stock issuable upon the exercise of stock options would be anti-dilutive.
	The following table summarizes outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive for the years ended December 31, 2014, 2013 and 2012:
		Years Ended December 31,
		2014		2013		2012
	Common stock options		8,829,343		6,814,417		5,521,584
	Unvested restricted stock		744,514		45,000		35,122
	Recent Accounting Pronouncements
	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which amends the guidance for accounting for revenue from contracts with customers. This ASU supersedes the revenue recognition requirements in ASC Topic 605, and creates a new Topic 606, Revenue from Contracts with Customers. This guidance is effective for fiscal years beginning after December 15, 2016, with early adoption not permitted. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application. The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its consolidated financial statements.
	In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern. This ASU is intended to define management's responsibility to evaluate whether there is substantial doubt about an organization's ability to continue as a going concern within one year of the date of issuance of the entity's financial statements and to provide related footnote disclosures. This guidance is effective for fiscal years ending after December 15, 2016, with early application permitted. The Company has not yet determined the effect that the adoption of this guidance will have on the disclosures included in its consolidated financial statements.

Cash_Cash_Equivalents_and_Mark

Cash, Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 2014
Cash, Cash Equivalents and Marketable Securities
Cash, Cash Equivalents and Marketable Securities	(3) Cash, Cash Equivalents and Marketable Securities
	A summary of cash, cash equivalents and available-for-sale marketable securities held by the Company as of December 31, 2014 and December 31, 2013 was as follows in thousands (see Note 2):
		December 31, 2014
		Cost		Unrealized		Unrealized			Fair
				gains		losses			value
	Cash and cash equivalents:
	Cash and money market funds (Level 1)	$	45,004	$	—	$	—		$	45,004
	Corporate debt securities due within 3 months of date of purchase (Level 2)		1,020		—		—			1,020
	Total cash and cash equivalents	$	46,024	$	—	$	—		$	46,024
	Marketable securities:
	Corporate debt securities due within 1 year of date of purchase (Level 2)		51,662		12		(8	)		51,666
	Total cash, cash equivalents and marketable securities	$	97,686	$	12	$	(8	)	$	97,690
		December 31, 2013
		Cost		Unrealized		Unrealized			Fair
				gains		losses			value
	Cash and cash equivalents:
	Cash and money market funds (Level 1)	$	40,586	$	—	$	—		$	40,586
	Corporate debt securities due within 3 months of date of purchase (Level 2)		7,904		—		—			7,904
	Total cash and cash equivalents	$	48,490	$	—	$	—		$	48,490
	Marketable securities:
	Corporate debt securities due within 1 year of date of purchase (Level 2)		42,969		18		(1	)		42,986
	Total cash, cash equivalents and marketable securities	$	91,459	$	18	$	(1	)	$	91,476

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2014
Property and Equipment
Property and Equipment	(4) Property and Equipment
	Property and equipment as of December 31, 2014 and December 31, 2013 consisted of the following (in thousands):
		December 31,			December 31,
		2014			2013
	Laboratory equipment	$	12,217		$	12,681
	Leasehold improvements		4,988			4,958
	Computers and software		3,126			3,220
	Furniture and fixtures		1,176			1,170
			21,507			22,029
	Less accumulated depreciation and amortization		(20,483	)		(20,476	)
		$	1,024		$	1,553
	Depreciation and amortization expenses of property and equipment, including equipment purchased under capital leases, were approximately $0.7 million, $0.5 million and $0.7 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	The net book value and accumulated amortization of equipment under capital lease was approximately $84,000 and $42,000 respectively, at December 31, 2014, and $126,000 and $0, respectively, at December 31, 2013.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity
Stockholders' Equity	(5) Stockholders' Equity
	Common Stock
	Each common stockholder is entitled to one vote for each common share of stock held. The common stock will vote together with all other classes and series of stock of the Company as a single class on all actions to be taken by the Company's stockholders. Each share of common stock is entitled to receive dividends, as and when declared by the Company's board of directors.
	The Company has never declared cash dividends on its common stock and does not expect to do so in the foreseeable future.
	Registered Direct Offering
	In April 2014, the Company sold 1,250,000 shares of its common stock at a purchase price of $4.01 per share in a registered direct offering to an affiliate of a director who is its largest stockholder. These shares were sold directly without a placement agent, underwriter, broker or dealer. The net proceeds to the Company were approximately $5.0 million after deducting offering expenses payable by the Company.
	At-The-Market Issuance Sales Agreements
	The Company entered into at-the-market issuance sales agreements (May 2012, May 2014 and July 2014 Sales Agreements) with MLV & Co. LLC (MLV), pursuant to which the Company may issue and sell shares of its common stock from time to time, at the Company's option, through MLV as its sales agent. Sales of common stock through MLV may be made by any method that is deemed an "at-the-market" offering as defined in Rule 415 promulgated under the Securities Act of 1933, as amended, including by means of ordinary brokers' transactions at market prices, in block transactions or as otherwise agreed by the Company and MLV. Subject to the terms and conditions of the Sales Agreements, MLV will use commercially reasonable efforts to sell the common stock based upon the Company's instructions (including any price, time or size limits or other customary parameters or conditions the Company may impose). The Company is not obligated to make any sales of its common stock under the Sales Agreements. Any shares sold will be sold pursuant to an effective shelf registration statement on Form S-3. The Company will pay MLV a commission of up to 3% of the gross proceeds. The May 2012 and May 2014 Sales Agreements were terminated by the Company upon the sale of substantially all stock authorized for sale under each such agreement. The July 2014 Sales Agreement may be terminated by the Company at any time.
	In March and April 2014, the Company sold an aggregate of 6,588,875 shares of common stock pursuant to the May 2012 Sales Agreement for an aggregate of approximately $28.0 million in gross proceeds at an average selling price of $4.25 per share. Net proceeds to the Company were approximately $27.3 million after deducting commissions and other transactions costs.
	From May 2014 through July 2014, the Company sold an aggregate of 9,424,193 shares of common stock pursuant to the May 2014 Sales Agreement for an aggregate of approximately $40.0 million in gross proceeds at an average selling price of $4.24 per share. Net proceeds to the Company were approximately $39.2 million after deducting commissions and other transactions costs.
	In July 2014, the Company reserved up to $50 million under its shelf registration statement for issuance under the July 2014 Sales Agreement. In the third quarter of 2014, the Company sold an aggregate of 5,679,685 shares of common stock pursuant to the July 2014 Sales Agreement for an aggregate of approximately $23.0 million in gross proceeds at an average selling price of $4.05 per share. Net proceeds to the Company were approximately $22.5 million after deducting commissions and other transactions costs. As of December 31, 2014, approximately $27.0 million remained reserved under the Company's shelf registration statement and the applicable prospectus supplement for possible future issuance under the July 2014 Sales Agreement.
	Public Offering
	In November 2013, the Company raised approximately $60.4 million in gross proceeds from the sale of an aggregate 16,100,000 shares of its common stock in a public offering at a public offering price of $3.75 per share, including 14,000,000 shares in the initial offering and 2,100,000 shares upon the full exercise of the underwriters' option to purchase additional shares. Certain of the Company's directors and their affiliates, including its largest stockholder, purchased an aggregate of 5,183,333 shares in this offering. The net offering proceeds to the Company were approximately $57.1 million after deducting underwriters' discounts, fees and commissions, and other offering expenses payable by the Company.
	Registered Direct Offerings
	In December 2012, the Company entered into common stock purchase agreements with investors and certain directors, including its largest stockholder, pursuant to which the Company sold 7,000,000 shares of its common stock in a registered direct offering at a purchase price of $8.60 per share. These shares were sold directly to these investors and directors without a placement agent, underwriter, broker or dealer. The net proceeds to the Company were approximately $59.8 million after deducting estimated offering expenses payable by the Company.
	In July 2012, the Company entered into subscription agreements with certain directors, including its largest stockholder, pursuant to which the Company sold 3,976,702 shares of its common stock in a registered direct offering at a purchase price of $6.49 per share. These shares were sold directly to these directors without a placement agent, underwriter, broker or dealer. The net proceeds to the Company were approximately $25.8 million after deducting estimated offering expenses payable by the Company.
	Public Offering
	In January 2012 and February 2012, the Company raised approximately $35.4 million in gross proceeds from the sale of an aggregate 8,050,000 shares of its common stock in a public offering at $4.40 per share, including 7,000,000 shares in the initial closing in January 2012 and 1,050,000 shares in a second closing in February 2012 upon the full exercise of the over-allotment option granted to the underwriters. One of the Company's directors, who is its largest stockholder, purchased 1,136,363 shares in this offering. The net offering proceeds to the Company were approximately $33.0 million after deducting underwriters' discounts, fees and commissions, and other offering expenses payable by the Company.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2014
Stock-Based Compensation
Stock-Based Compensation	(6) Stock-Based Compensation
	The Company's 2006 Stock Plan provides for the grant of incentive stock options, non-statutory stock options and non-vested restricted stock to employees, officers, directors and consultants of the Company. In January 2015, the number of shares of common stock reserved for issuance under the 2006 Stock Plan was increased from 10,300,000 to 11,600,000 pursuant to an "evergreen" provision, which provides for an annual increase based on the lesser of 1,300,000 shares, 5% of the Company's then outstanding shares of common stock, or such other amount as the board of directors may determine. This increase was approved by the board of directors in December 2014. The administration of the 2006 Stock Plan is under the general supervision of the compensation committee of the board of directors. The exercise price of the stock options is determined by the compensation committee of the board of directors, provided that incentive stock options are granted with an exercise price not less than fair market value of the common stock on the date of grant and expire no later than ten years from the date the option is granted. Options generally vest over four years. As of December 31, 2014, the Company had options outstanding to purchase 8,829,343 shares of its common stock, which includes options outstanding under its 2001 Stock Plan that was terminated in March 2006. As of December 31, 2014, 1,385,022 shares were available for future issuance.
	The following table summarizes stock option activity during the year ended December 31, 2014:
		Shares			Weighted			Weighted			Aggregate
					average			average			intrinsic
					exercise			remaining			value
					price			contractual
								life (years)
	Outstanding at January 1		6,814,417		$	6.9
	Options granted		3,276,427			4.9
	Options exercised		(206,389	)		4.14
	Options cancelled		(1,055,112	)		7.35
	Outstanding at December 31		8,829,343		$	6.17			6.35		$	70,082
	Exercisable at December 31		4,915,662		$	6.67			4.17		$	70,082
	The aggregate intrinsic value of all options outstanding and exercisable represents the total pre-tax amount, net of the exercise price, which would have been received by option holders if all option holders had exercised all options with an exercise price lower than the closing stock price of $2.65 on December 31, 2014, which was the last trading day of the year. The total intrinsic value of options exercised during the years ended December 31, 2014, 2013 and 2012 was approximately $435,000, $385,000 and $904,000, respectively. The total cash received by the Company as a result of stock option exercises during 2014, 2013 and 2012 was $0.9 million, $1.1 million and $1.1 million, respectively. The weighted-average grant date fair values of options granted during the years ended December 31, 2014, 2013 and 2012 were $4.00, $7.28 and $4.10, respectively.
	Non-Vested ("Restricted") Stock Awards With Service Conditions
	The Company's share-based compensation plan provides for awards of restricted shares of common stock to employees, officers, directors and consultants to the Company. Restricted stock awards are subject to forfeiture if employment or service terminates during the prescribed retention period. Restricted shares vest over the service period. The total fair value of restricted stock that vested during the years ended December 31, 2014, 2013 and 2012 was $0.1 million, $0.3 million and $0.6 million, respectively.
	The following table summarizes unvested restricted share activity during the year ended December 31, 2014:
		Shares			Weighted
					average
					grant date
					fair value
	Outstanding at January 1		45,000		$	4.63
	Vested		(39,508	)		4.56
	Granted		764,022			3.67
	Forfeited		(25,000	)		4.34
	Outstanding at December 31		744,514		$	3.65
	Stock-Based Compensation Expense
	For the years ended December 31, 2014, 2013 and 2012, the fair value of each employee stock option award was estimated on the date of grant based on the fair value method using the Black-Scholes option pricing valuation model with the following weighted average assumptions:
		Years ended December 31,
		2014			2013			2012
	Risk-free interest rate		1.88	%		1.20	%		1.11	%
	Expected life in years		6.25 years			6.25 years			6.25 years
	Volatility		104	%		102	%		101	%
	Expected dividend yield		—			—			—
	Stock-based compensation expense during the years ended December 31, 2014, 2013 and 2012 was as follows (in thousands):
		Years ended December 31,
		2014			2013			2012
	Stock-based compensation expense by type of award:
	Employee stock options	$	7,076		$	5,757		$	3,082
	Restricted stock		355			273			240
	Total stock-based compensation expense	$	7,431		$	6,030		$	3,322
	Effect of stock-based compensation expense by line item:
	Research and development	$	4,412		$	3,220		$	2,485
	General and administrative		3,019			2,810			837
	Total stock-based compensation expense included in net loss	$	7,431		$	6,030		$	3,322
	Unrecognized stock-based compensation expense as of December 31, 2014 was as follows (dollars in thousands):
		Unrecognized			Weighted
		stock			average
		compensation			remaining
		expense as of			period
		December 31,			(in years)
		2014
	Employee stock options	$	13,468			2.77
	Restricted stock		2,545			3.39
	Total	$	16,013			2.87

Other_Accrued_Liabilities

Other Accrued Liabilities	12 Months Ended
	Dec. 31, 2014
Other Accrued Liabilities
Other Accrued Liabilities	7) Other Accrued Liabilities
	Other accrued liabilities as of December 31, 2014 and December 31, 2013 consisted of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Compensation and benefits	$	3,852	$	3,137
	Professional fees		1,285		1,585
	Other		1,040		996
		$	6,177	$	5,718

CoDevelopment_and_License_Agre

Co-Development and License Agreements	12 Months Ended
	Dec. 31, 2014
Co-Development and License Agreements
Co-Development and License Agreements	(8) Co-Development and License Agreements
	Co-Development Agreement
	In July 2011, the Company entered into a co-development agreement with a clinical research organization (CRO) for the conduct of certain company-sponsored clinical trials. Under the co-development agreement, this CRO was performing clinical research services under a reduced fee structure in exchange for a share of licensing payments and commercial revenues, if any, resulting from the product under development up to a specified maximum payment, which is defined as a multiple of the fee reduction realized. Research and development expenses were being recognized based on the reduced fee structure and expected payments will be recorded in the future if and when payment is probable. The maximum amount of the service fee discount was realized in the year ended December 31, 2013.
	License Arrangement
	In May 2014, the Company entered into a license arrangement for its CRACM program, including two lead candidates and the associated intellectual property portfolio, with PRCL Research Inc. (PRCL), a company funded by TVM Life Science Venture VII and the Fonds de Solidarité des Travailleurs du Québec, based in Montreal, Canada. PRCL plans to develop one of the two lead candidates licensed from the Company to proof-of-concept. Synta was granted a minority interest in PRCL in exchange for its contribution of know-how and intellectual property and will also hold a seat on PRCL's Board of Directors. Synta will not be required to provide any research funding or capital contributions to PRCL. Synta will be reimbursed by PRCL for any ongoing intellectual property management costs in connection with the contributed intellectual property and may conduct preclinical research activities which would be reimbursed by PRCL. If and when proof-of-concept is reached with either drug candidate, Eli Lilly and Company, which is an investor in TVM, will manage the development program through one of its divisions and will have an option to acquire PRCL or its assets at the then fair value.

Term_Loans

Term Loans	12 Months Ended
	Dec. 31, 2014
Term Loans
Term Loans	(9) Term Loans
	General Electric Capital Corporation
	In March 2013, the Company amended its loan and security agreement entered into in September 2010 with General Electric Capital Corporation (GECC) and another lender (the GECC Term Loan) and obtained $12.9 million in additional loan funding and, as a result, increased the principal balance to $22.5 million at March 31, 2013. This amendment was accounted for as a loan modification. Interest on the borrowings under the GECC Term Loan remains at the annual rate of 9.75%. In January 2014, the Company began making 30 equal monthly payments of principal plus accrued interest on the outstanding balance. During the period from July 2012 through March 2013, the Company made 9 equal monthly payments of principal under the GECC Term Loan. For the periods from April 2013 through December 2013 and prior to July 2012 the Company made interest-only payments.
	The Company has paid various transaction fees and expenses in connection with the GECC Term Loan, which are deferred and are being amortized as interest expense over the remaining term of the GECC Term Loan. In addition, the Company is obligated to pay an exit fee of $788,000 at the time of the final principal payment which is being accreted and expensed as interest over the remaining term of the GECC Term Loan. In the years ended December 31, 2014, 2013 and 2012, the Company recognized GECC Term Loan interest expense of $2.1 million, $2.5 million and $1.7 million, respectively, of which $0.4 million, $0.6 million and $0.3 million, respectively, was in connection with these transaction and exit fees and expenses. The Company may prepay the full amount of the GECC Term Loan, subject to prepayment premiums under certain circumstances. The Company did not issue any warrants in connection with the GECC Term Loan.
	The GECC Term Loan is secured by substantially all of the Company's assets, except its intellectual property. The Company has granted GECC a springing security interest in its intellectual property in the event the Company is not in compliance with certain cash usage covenants, as defined therein. The GECC Term Loan contains restrictive covenants, including the requirement for the Company to receive the prior written consent of GECC to enter into loans, other than up to $4.0 million of equipment financing, restrictions on the declaration or payment of dividends, restrictions on acquisitions, and customary default provisions that include material adverse events, as defined therein. The Company has determined that the risk of subjective acceleration under the material adverse events clause is remote and therefore has classified the outstanding principal in current and long-term liabilities based on the timing of scheduled principal payments.
	Oxford Finance Corporation
	In March 2011, the Company entered into a loan and security agreement with Oxford Finance Corporation (Oxford) and received $2.0 million in loan funding, and in December 2012, the Company entered into a loan modification agreement, as amended, under which the Company could elect to draw down up to an additional $0.6 million in equipment financing until June 30, 2013 that would be payable in 36 equal monthly payments of principal plus accrued interest on the outstanding balance (collectively, the Oxford Term Loan). As of June 30, 2013, the Company had fully utilized the $0.6 million in additional equipment financing. Interest on the borrowings under the Oxford Term Loan accrues at an annual rate of 13.35%. In May 2011, the Company began making 36 equal monthly payments of principal plus accrued interest on the initial $2.0 million outstanding balance that was fully paid in April 2014. The Company continues to make equal monthly payments of principal plus accrued interest on the $0.6 million in additional equipment financing. The Company recognized approximately $59,000, $127,000 and $172,000 in interest expense in the years ended December 31, 2014, 2013 and 2012, respectively, related to the outstanding principal under the Oxford Term Loan. In addition to the interest payable under the Oxford Term Loan, the Company paid approximately $108,000 of administrative and legal fees and expenses in connection with the Oxford Term Loan. These expenses have been deferred and are being expensed over the term of the Oxford Term Loan. The Company did not issue any warrants in connection with the Oxford Term Loan. The Company may prepay the Oxford Term Loan, subject to prepayment premiums under certain circumstances. Oxford has the right to require the Company to prepay the Oxford Term Loan if the Company prepays the full amount of the GECC Term Loan under certain circumstances.
	The Oxford Term Loan is secured by certain laboratory and office equipment, furniture and fixtures. In connection with the Oxford Term Loan, Oxford and GECC entered into a Lien Subordination Agreement, whereby GECC granted Oxford a first priority perfected security interest in the loan collateral. The Oxford Term Loan contains restrictive covenants, including the requirement for the Company to receive the prior written consent of Oxford to enter into acquisitions in which the Company incurs more than $2.0 million of related indebtedness, and customary default provisions that include material adverse events, as defined therein. The Company has determined that the risk of subjective acceleration under the material adverse events clause is remote and therefore has classified the outstanding principal in current and long-term liabilities based on the timing of scheduled principal payments.
	Future principal payments under the GECC and Oxford Term Loans as of December 31, 2014 were approximately as follows (in thousands):
	Years ending December 31,
	2015	$	9,214
	2016		4,607
	Total principal payments		13,821
	Less current portion		(9,214	)
	Long term portion	$	4,607

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Taxes
Income Taxes	(10) Income Taxes
	Differences between the actual tax provision (benefit) and the tax provision (benefit) computed using the United States federal income tax rate is as follows for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		Years ended December 31,
		2014			2013			2012
	Benefit at statutory rate	$	(29,293	)	$	(30,665	)	$	(21,349	)
	State taxes, net of federal benefit		(3,342	)		(3,735	)		(3,220	)
	State net operating loss expiration		—			661			3,167
	Stock-based compensation		1,094			1,118			382
	Tax credits		(1,720	)		(2,462	)		(411	)
	Foreign rate differential		6,243			5,252			—
	Other		100			(47	)		22
	Increase in valuation allowance		26,918			29,878			21,409
	Income tax provision (benefit)	$	—		$	—		$	—
	The effects of temporary differences that give rise to significant portions of deferred tax assets and deferred tax liabilities at December 31, 2014 and 2013 are presented below (in thousands):
		2014			2013
	Deferred tax assets:
	Federal and state net operating loss carryforwards	$	194,091		$	170,557
	Federal and state research and development credits		21,401			19,675
	Depreciation and amortization		2,423			2,412
	Deferred compensation		7,643			6,254
	Other		1,427			1,169
	Deferred tax assets		226,985			200,067
	Less valuation allowance		(226,985	)		(200,067	)
	Net deferred tax assets	$	—		$	—
	The total valuation allowance increased by approximately $26.9 million, $29.9 million and $21.4 million in the years ended December 31, 2014, 2013 and 2012, respectively.
	The Company has established valuation allowances against its deferred tax assets because management believes that, after considering all of the available objective evidence, both historical and prospective, the realization of the deferred tax assets does not meet the "more likely than not" criteria. The Company evaluates the need for a valuation allowance on a quarterly basis.
	For tax years through 2014 the Company performed analyses to determine if there were changes in ownership, as defined by Section 382 of the Internal Revenue Code that would limit its ability to utilize certain net operating loss and tax credit carryforwards. The Company determined that it experienced an ownership change, as defined by Section 382, in connection with its acquisition of Principia Associates, Inc. on September 20, 2002, but did not experience a change in ownership upon the effectiveness of the Company's IPO, or any other equity offerings to date. As a result, the utilization of the Company's federal tax net operating loss carryforwards generated prior to the ownership change is limited. As of December 31, 2014, the Company has net operating loss carryforwards for U.S. federal tax purposes of approximately $529.7 million, after excluding net operating losses that have expired unused as a result of Section 382 limitations, with the remainder expiring in varying amounts through 2034 unless utilized. At December 31, 2014, the Company has state net operating loss carryforwards of approximately $275.4 million, which will expire through 2034 unless utilized. The net operating loss carryforwards include approximately $1.4 million of deductions related to the exercise of common stock options. This amount represents an excess tax benefit and has not been included in the gross deferred tax asset reflected for net operating losses. The utilization of these net operating loss carryforwards may be further limited if the Company experiences future ownership changes as defined in Section 382 of the Internal Revenue Code.
	At December 31, 2014, the Company had approximately $16.7 million and $7.1 million, respectively, in federal and state research and development credits. Unless utilized, the federal credits will expire from 2020 through 2034, state research credits will expire from 2018 through 2029 and state investment tax credits will expire from 2015 through 2017.
	The Company is currently open to examination under the statute of limitations by the Internal Revenue Service and state jurisdictions for the tax years ended 2011 through 2014. Carryforward tax attributes generated in years past may still be adjusted upon future examination if they have or will be used in a future period. The Company is currently not under examination by the Internal Revenue Service or any other jurisdictions for any tax years.
	The Company does not consider any of its tax positions to be uncertain and accordingly there are no tax reserves for the years ended December 31, 2014, 2013 and 2012. The Company will recognize interest expense and penalties related to uncertain tax positions in income tax expense. The Company has not, as yet, conducted a study of its domestic research and development credit carryforwards. This study may result in an increase or decrease to the Company's research and development credit carryforwards; however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company's research and development credits, and if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. As a result, there would be no impact to the consolidated balance sheet, statement of operations and comprehensive loss or cash flows if an adjustment were required.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies
Commitments and Contingencies	(11) Commitments and Contingencies
	Leases
	The Company leases its research and office facilities under three non-cancelable and renewable operating leases with terms expiring in the fourth quarter of 2016. These lease agreements include customary provisions for rent increases, escalations for operating costs and renewals. The Company also leases equipment under various other non-cancellable operating leases. The Company recognizes rent expense on a straight-line basis over the non-cancelable term of the lease.
	Future minimum payments, excluding operating costs and taxes, under the Company's capital and non-cancellable operating leases are approximately as follows (in thousands):
		Operating		Capital
		leases		leases
	Years ending December 31,
	2015	$	2,226	$	44
	2016		1,995		44
	2017		25		—
	Total minimum payments	$	4,246		88
	Less: amount representing interest				(3	)
	Present value of minimum payments				85
	Less current portions of obligations				(42	)
	Long term obligation			$	43
	Rent expense under operating leases was approximately $2.3 million, $2.2 million and $2.2 million, for the years ended December 31, 2014, 2013 and 2012, respectively.
	Guarantees
	As permitted under Delaware law, the Company's Certificate of Incorporation and Bylaws provide that the Company will indemnify certain of its officers and directors for certain claims asserted against them in connection with their service as an officer or director. The maximum potential amount of future payments that the Company could be required to make under these indemnification provisions is unlimited. However, the Company has purchased a directors' and officers' liability insurance policy that reduces its monetary exposure and enables it to recover a portion of any future amounts paid. The Company believes the estimated fair value of these indemnification arrangements is minimal.
	The Company customarily agrees in the ordinary course of its business to indemnification provisions in agreements with clinical trial investigators in its drug development programs, in sponsored research agreements with academic and not-for-profit institutions, in various comparable agreements involving parties performing services for the Company in the ordinary course of business, and in its real estate leases. The Company expects to agree to certain indemnification provisions in drug discovery and development collaboration agreements the Company may enter into. With respect to the Company's clinical trials and sponsored research agreements, these indemnification provisions typically apply to any claim asserted against the investigator or the investigator's institution relating to personal injury or property damage, violations of law or certain breaches of the Company's contractual obligations arising out of the research or clinical testing of the Company's compounds or drug candidates. With respect to lease agreements, the indemnification provisions typically apply to claims asserted against the landlord relating to personal injury or property damage caused by the Company, to violations of law by the Company or to certain breaches of the Company's contractual obligations. The indemnification provisions appearing in collaboration agreements are similar, but in addition provide some limited indemnification for the collaborator in the event of third-party claims alleging infringement of intellectual property rights. In each of the cases above, the term of these indemnification provisions generally survives the termination of the agreement, although the provision has the most relevance during the contract term and for a short period of time thereafter. The maximum potential amount of future payments that the Company could be required to make under these provisions is generally unlimited. The Company purchases insurance policies covering personal injury, property damage and general liability that reduce its exposure for indemnification and would enable it in many cases to recover a portion of any future amounts paid. The Company has never paid any material amounts to defend lawsuits or settle claims related to these indemnification provisions. Accordingly, the Company believes the estimated fair value of these indemnification arrangements is minimal.

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2014
Related Party Transactions
Related Party Transactions	(12) Related Party Transactions
	In April 2014, the Company sold 1,250,000 shares of its common stock at a purchase price of $4.01 per share in a registered direct offering to an affiliate of a director who is its largest stockholder (see Note 5).
	In November 2013, the Company sold an aggregate of 5,183,333 shares of common stock to certain of the Company's directors and their affiliates, including its largest stockholder, at a purchase price of $3.75 per share in a public offering (see Note 5).
	In January 2013, a director exercised an aggregate of 114,250 shares of common stock options that resulted in $1.0 million in proceeds to the Company.
	In December 2012, the Company entered into common stock purchase agreements with certain directors, including its largest stockholder, pursuant to which the Company sold 2,649,535 shares of its common stock in a registered direct offering at a purchase price of $8.60 per share (see Note 5).
	In November 2012, the Company purchased and retired 3,969 shares from an officer upon the vesting of restricted common stock in order to fund the related tax liability.
	In July 2012, the Company entered into subscription agreements with certain directors, including its largest stockholder, pursuant to which the Company sold 3,976,702 shares of its common stock in a registered direct offering at a purchase price of $6.49 per share (see Note 5).
	In January 2012, the Company sold 1,136,363 shares of common stock to a director, who is its largest stockholder, at a purchase price of $4.40 per share in a public offering (see Note 5).

Retirement_Plan

Retirement Plan	12 Months Ended
	Dec. 31, 2014
Retirement Plan
Retirement Plan	(13) Retirement Plan
	In 2003, the Company implemented a 401(k) retirement plan (the Synta 401(k) Plan) in which substantially all of its permanent employees are eligible to participate. Participants may contribute a percentage of their annual compensation to the plan, subject to statutory limitations. The Company may declare discretionary matching contributions to the Synta 401(k) Plan.
	In April 2006, the Company began matching participants' contributions up to 50% of the first 6% of the employee's salary. The match is subject to a three-year equally graded vesting schedule and any forfeitures will be applied to reduce the Company's contributions. Company contributions for the years ended December 31, 2014, 2013 and 2012 were approximately $359,000, $413,000 and $376,000, respectively, subject to forfeitures.

Quarterly_Financial_Data_unaud

Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Data (unaudited)
Quarterly Financial Data (unaudited)	(14) Quarterly Financial Data (unaudited)
	The following tables present a summary of quarterly results of operations for 2014 and 2013:
	[
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2014			2014			2014			2014
		(in thousands, except shares and per share data)
	Revenues:
	Total revenues	$	—		$	—		$	—		$	—
	Operating expenses:
	Research and development		17,583			18,761			16,208			15,653
	General and administrative		5,324			2,940			3,241			4,241
	Total operating expenses		22,907			21,701			19,449			19,894
	Loss from operations		(22,907	)		(21,701	)		(19,449	)		(19,894	)
	Interest expense, net		(650	)		(585	)		(517	)		(458	)
	Net loss	$	(23,557	)	$	(22,286	)	$	(19,966	)	$	(20,352	)
	Basic and diluted net loss per common share	$	(0.28	)	$	(0.24	)	$	(0.19	)	$	(0.19	)
	Basic and diluted weighted average number of common shares outstanding		85,438,127			94,046,278			105,774,949			108,366,504
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2013			2013			2013			2013
		(in thousands, except shares and per share data)
	Revenues:
	Total revenues	$	—		$	—		$	—		$	—
	Operating expenses:
	Research and development		16,380			17,876			17,623			19,981
	General and administrative		3,878			4,187			4,171			3,463
	Total operating expenses		20,258			22,063			21,794			23,444
	Loss from operations		(20,258	)		(22,063	)		(21,794	)		(23,444	)
	Interest expense, net		(470	)		(724	)		(721	)		(718	)
	Net loss	$	(20,728	)	$	(22,787	)	$	(22,515	)	$	(24,162	)
	Basic and diluted net loss per common share	$	(0.30	)	$	(0.33	)	$	(0.33	)	$	(0.31	)
	Basic and diluted weighted average number of common shares outstanding		68,991,371			69,034,823			69,047,161			76,769,199

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies
Principles of Consolidation	Principles of Consolidation
	The condensed consolidated financial statements include the financial statements of the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates
	The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect certain reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting periods. Significant items subject to such estimates and assumptions include contract research accruals, recoverability of long-lived assets, measurement of stock-based compensation, and the periods of performance under collaborative research and development agreements. The Company bases its estimates on historical experience and various other assumptions that management believes to be reasonable under the circumstances. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents
	The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase and an investment in a money market fund to be cash equivalents. Changes in the level of cash and cash equivalents may be affected by changes in investment portfolio maturities, as well as actual cash disbursements to fund operations.
	The primary objective of the Company's investment activities is to preserve its capital for the purpose of funding operations and the Company does not enter into investments for trading or speculative purposes. The Company's cash is deposited in a highly rated financial institution in the United States. The Company invests in money market funds and high-grade, short-term commercial paper and corporate bonds, which management believes are subject to minimal credit and market risk. Declines in interest rates, however, would reduce future investment income.
Marketable Securities	Marketable Securities
	Marketable securities consist of investments in high-grade corporate obligations, and government and government agency obligations that are classified as available-for-sale. Since these securities are available to fund current operations they are classified as current assets on the consolidated balance sheets.
	The Company adjusts the cost of available-for-sale debt securities for amortization of premiums and accretion of discounts to maturity. The Company includes such amortization and accretion as a component of interest expense, net. Realized gains and losses and declines in value, if any, that the Company judges to be other-than-temporary on available-for-sale securities are reported as a component of interest expense, net. To determine whether an other-than-temporary impairment exists, the Company considers whether it intends to sell the debt security and, if the Company does not intend to sell the debt security, it considers available evidence to assess whether it is more likely than not that it will be required to sell the security before the recovery of its amortized cost basis. During the years ended December 31, 2014, 2013 and 2012, the Company determined it did not have any securities that were other-than-temporarily impaired.
	Marketable securities are stated at fair value, including accrued interest, with their unrealized gains and losses included as a component of accumulated other comprehensive income or loss, which is a separate component of stockholders' equity. The fair value of these securities is based on quoted prices and observable inputs on a recurring basis. Realized gains and losses are determined on the specific identification method. During the years ended December 31, 2014, 2013 and 2012, the Company did not have any realized gains or losses on marketable securities.
Fair Value of Financial Instruments	Fair Value of Financial Instruments
	The carrying amounts of the Company's financial instruments, which include cash equivalents, marketable securities and term loan obligations, approximate their fair values. The fair value of the Company's financial instruments reflects the amounts that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value hierarchy has the following three levels:
	Level 1—quoted prices in active markets for identical assets and liabilities.
	Level 2—observable inputs other than Level 1 inputs. Examples of Level 2 inputs include quoted prices in active markets for similar assets or liabilities and quoted prices for identical assets or liabilities in markets that are not active.
	Level 3—unobservable inputs that reflect the Company's own assumptions about the assumptions market participants would use in pricing the asset or liability.
	Financial assets and liabilities are classified in their entirety within the fair value hierarchy based on the lowest level of input that is significant to the fair value measurement. The Company measures the fair value of its marketable securities by taking into consideration valuations obtained from third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker-dealer quotes on the same or similar securities, issuer credit spreads, benchmark securities and other observable inputs. As of December 31, 2014, the Company's financial assets valued based on Level 1 inputs consisted of cash and cash equivalents in a money market fund and its financial assets valued based on Level 2 inputs consisted of high-grade corporate bonds and commercial paper. During the years ended December 31, 2014, 2013 and 2012, the Company did not have any transfers of financials assets between Levels 1 and 2. As of December 31, 2014, the Company did not have any financial liabilities that were recorded at fair value on the balance sheet. The disclosed fair value of the Company's term loan obligations is determined using current applicable rates for similar instruments as of the balance sheet date. The carrying value of the Company's term loan obligations approximates fair value as the Company's interest rate yield is near current market rate yields. The disclosed fair value of the Company's term loan obligations is based on Level 3 inputs.
Property and Equipment	Property and Equipment
	Property, equipment and software is carried at cost and depreciated using the straight-line method over the estimated useful lives of the related assets, which range from three to seven years. Leasehold improvements are amortized over the lesser of the lease term or estimated useful life. Repairs and maintenance costs are expensed as incurred.
Research and Development Costs	Research and Development Costs
	Research and development costs are expensed as incurred. Research and development costs are comprised of costs incurred in performing research and development activities, including internal costs for salaries, bonuses, benefits, facilities, research-related overhead and stock compensation, and external costs for payments to third party contract research organizations, investigative sites and consultants in connection with the Company's preclinical and clinical programs, costs associated with drug formulation and supply of drugs for clinical trials, and other external costs.
Patents	Patents
	Costs to secure and defend patents are expensed as incurred and are classified as general and administrative expense in the Company's consolidated statements of operations. Patent expenses were approximately $1.9 million, $2.9 million, and $1.8 million for the years ended December 31, 2014, 2013 and 2012, respectively.
Income Taxes	Income Taxes
	The Company uses the liability method to account for income taxes. Deferred tax assets and liabilities are determined based on the expected future tax consequences of temporary differences between the Company's consolidated financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. A valuation allowance is provided to reduce the deferred tax assets to the amount that will more likely than not be realized.
	As of December 31, 2014 and 2013, the Company had no items that were considered to be uncertain tax items or accrued interest or penalties related to uncertain tax positions.
	The tax years 2011 through 2014 remain open to examination by the major taxing jurisdictions to which the Company is subject.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets
	The Company assesses the potential impairments of its long-lived assets whenever events or changes in circumstances indicate that an asset's carrying value may not be recoverable. If the carrying value exceeds the undiscounted future cash flows estimated to result from the use and eventual disposition of the asset, the Company writes down the asset to its estimated fair value. Management believes that no long-lived assets were impaired as of December 31, 2014 and 2013.
Revenue Recognition	Revenue Recognition
	Collaboration and License Agreements
	The Company's principal source of revenue to date has been its former collaboration and license agreements, which included upfront license payments, development milestones, reimbursement of research and development costs, potential profit sharing payments, commercial and sales-based milestones and royalties. The accounting for collaboration and license agreements requires subjective analysis and requires management to make estimates and assumptions about whether deliverables within multiple-element arrangements are separable from the other aspects of the contractual arrangement into separate units of accounting and to determine the arrangement consideration to be allocated to each unit of accounting.
	For multiple-element arrangements entered into or materially modified after January 1, 2011, the Company follows the provisions of Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) No. 2009-13—Multiple-deliverable Revenue Arrangements (ASU No. 2009-13). ASU No. 2009-13 amended certain provisions of Accounting Standards Codification (ASC) Topic 605—Revenue Recognition . This standard addresses the determination of the unit(s) of accounting for multiple-element arrangements and how an arrangement's consideration should be allocated to each unit of accounting.
	Pursuant to this standard, each required deliverable is evaluated to determine if it qualifies as a separate unit of accounting. For the Company this determination includes an assessment as to whether the deliverable has "stand-alone value" to the customer separate from the undelivered elements. The arrangement's consideration is then allocated to each separate unit of accounting based on the relative selling price of each deliverable. The estimated selling price of each deliverable is determined using the following hierarchy of values: (i) vendor-specific objective evidence of fair value, (ii) third-party evidence of selling price, or (iii) the Company's best estimate of the selling price (BESP). The BESP reflects the Company's best estimate of what the selling price would be if the deliverable was regularly sold by it on a stand-alone basis. The Company expects, in general, to use BESP for allocating consideration to each deliverable in future collaboration agreements. In general, the consideration allocated to each unit of accounting is then recognized as the related goods or services are delivered limited to the consideration not contingent upon future deliverables. The Company did not recognize any revenue related to collaboration and license agreements during the years ended December 31, 2014, 2013 and 2012.
	The Company accounts for development milestones under collaboration and license agreements pursuant to ASU No. 2010-17 Milestone Method of Revenue Recognition (ASU No. 2010-17). ASU No. 2010-17 codified a method of revenue recognition that has been common practice. Under this method, contingent consideration from research and development activities that is earned upon the achievement of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved. At the inception of each arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive. This evaluation includes an assessment of whether (a) the consideration is commensurate with either (1) the entity's performance to achieve the milestone, or (2) the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the entity's performance to achieve the milestone, (b) the consideration relates solely to past performance and (c) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the respective milestone, the level of effort and investment required and whether the milestone consideration is reasonable relative to all deliverables and payment terms in the arrangement in making this assessment. The Company does not have any ongoing collaboration and license agreements under which milestones may be achieved.
	Royalty revenues are based upon a percentage of net sales. Royalties from the sales of products will be recorded on the accrual basis when results are reliably measurable, collectability is reasonably assured and all other revenue recognition criteria are met. Commercial and sales-based milestones, which are based upon the achievement of certain agreed-upon sales thresholds, will be recognized in the period in which the respective sales threshold is achieved and collectability is reasonably assured. The Company does not have any ongoing collaboration and license agreements under which royalties or commercial and sales-based milestones may be achieved.
	Grant Revenue
	In March 2011, the Company received a grant from the Department of Defense, in the approximate amount of $1 million, for the development of STA-9584 in advanced prostate cancer. The Company conducted work on this study during the grant period from April 2011 through March 2012. Reimbursements were based on actual costs agreed upon in the proposal (salary, fringe benefits, overhead, and direct costs such as materials and subcontractors). During the years ended December 31, 2014, 2013 and 2012, the Company recognized $0, $0 and $147,000, respectively, in grant revenues.
Stock-Based Compensation	Stock-Based Compensation
	The Company recognizes stock-based compensation expense based on the grant date fair value of stock options granted to employees, officers and directors. The Company uses the Black-Scholes option pricing model to determine the grant date fair value as management believes it is the most appropriate valuation method for its option grants. The Black-Scholes model requires inputs for risk-free interest rate, dividend yield, volatility and expected lives of the options. Expected volatility is based upon the weighted average historical volatility data of the Company's common stock. The risk-free rate for periods within the expected life of the option is based on the U.S. Treasury yield curve in effect at the time of the grant. The expected lives for options granted represent the period of time that options granted are expected to be outstanding. The Company uses the simplified method for determining the expected lives of options. The Company estimates the forfeiture rate based on historical data. This analysis is re-evaluated at least annually and the forfeiture rate is adjusted as necessary.
	For awards with graded vesting, the Company recognizes compensation costs based on the grant date fair value of awards on a straight-line basis over the requisite service period, which is generally the vesting period.
	Certain of the employee stock options granted by the Company are structured to qualify as incentive stock options (ISOs). Under current tax regulations, the Company does not receive a tax deduction for the issuance, exercise or disposition of ISOs if the employee meets certain holding requirements. If the employee does not meet the holding requirements, a disqualifying disposition occurs, at which time the Company may receive a tax deduction. The Company does not record tax benefits related to ISOs unless and until a disqualifying disposition is reported. In the event of a disqualifying disposition, the entire tax benefit is recorded as a reduction of income tax expense. The Company has not recognized any income tax benefit for its share-based compensation arrangements due to the fact that the Company does not believe it is more likely than not it will realize the related deferred tax assets.
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. Changes in unrealized gains and losses on marketable securities represent the only difference between the Company's net loss and comprehensive loss.
Segment Reporting	Segment Reporting
	Operating segments are determined based on the way management organizes its business for making operating decisions and assessing performance. The Company has a single operating segment, which is the discovery, development and commercialization of drug products.
Basic and Diluted Loss Per Common Share	Basic and Diluted Loss Per Common Share
	Basic net loss per share is computed using the weighted average number of common shares outstanding during the period, excluding restricted stock that has been issued but is not yet vested. Diluted net loss per common share is computed using the weighted average number of common shares outstanding and the weighted average dilutive potential common shares outstanding using the treasury stock method. However, for the years ended December 31, 2014, 2013 and 2012, diluted net loss per share is the same as basic net loss per share as the inclusion of weighted average shares of unvested restricted common stock and common stock issuable upon the exercise of stock options would be anti-dilutive.
	The following table summarizes outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive for the years ended December 31, 2014, 2013 and 2012:
		Years Ended December 31,
		2014		2013		2012
	Common stock options		8,829,343		6,814,417		5,521,584
	Unvested restricted stock		744,514		45,000		35,122
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which amends the guidance for accounting for revenue from contracts with customers. This ASU supersedes the revenue recognition requirements in ASC Topic 605, and creates a new Topic 606, Revenue from Contracts with Customers. This guidance is effective for fiscal years beginning after December 15, 2016, with early adoption not permitted. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application. The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its consolidated financial statements.
	In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern. This ASU is intended to define management's responsibility to evaluate whether there is substantial doubt about an organization's ability to continue as a going concern within one year of the date of issuance of the entity's financial statements and to provide related footnote disclosures. This guidance is effective for fiscal years ending after December 15, 2016, with early application permitted. The Company has not yet determined the effect that the adoption of this guidance will have on the disclosures included in its consolidated financial statements.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies
Summary of the outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive
		Years Ended December 31,
		2014		2013		2012
	Common stock options		8,829,343		6,814,417		5,521,584
	Unvested restricted stock		744,514		45,000		35,122

Cash_Cash_Equivalents_and_Mark1

Cash, Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2014
Cash, Cash Equivalents and Marketable Securities
Summary of cash, cash equivalents and available-for-sale marketable securities	A summary of cash, cash equivalents and available-for-sale marketable securities held by the Company as of December 31, 2014 and December 31, 2013 was as follows in thousands (see Note 2):
		December 31, 2014
		Cost		Unrealized		Unrealized			Fair
				gains		losses			value
	Cash and cash equivalents:
	Cash and money market funds (Level 1)	$	45,004	$	—	$	—		$	45,004
	Corporate debt securities due within 3 months of date of purchase (Level 2)		1,020		—		—			1,020
	Total cash and cash equivalents	$	46,024	$	—	$	—		$	46,024
	Marketable securities:
	Corporate debt securities due within 1 year of date of purchase (Level 2)		51,662		12		(8	)		51,666
	Total cash, cash equivalents and marketable securities	$	97,686	$	12	$	(8	)	$	97,690
		December 31, 2013
		Cost		Unrealized		Unrealized			Fair
				gains		losses			value
	Cash and cash equivalents:
	Cash and money market funds (Level 1)	$	40,586	$	—	$	—		$	40,586
	Corporate debt securities due within 3 months of date of purchase (Level 2)		7,904		—		—			7,904
	Total cash and cash equivalents	$	48,490	$	—	$	—		$	48,490
	Marketable securities:
	Corporate debt securities due within 1 year of date of purchase (Level 2)		42,969		18		(1	)		42,986
	Total cash, cash equivalents and marketable securities	$	91,459	$	18	$	(1	)	$	91,476

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property and Equipment
Schedule of property and equipment	Property and equipment as of December 31, 2014 and December 31, 2013 consisted of the following (in thousands):
		December 31,			December 31,
		2014			2013
	Laboratory equipment	$	12,217		$	12,681
	Leasehold improvements		4,988			4,958
	Computers and software		3,126			3,220
	Furniture and fixtures		1,176			1,170
			21,507			22,029
	Less accumulated depreciation and amortization		(20,483	)		(20,476	)
		$	1,024		$	1,553

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Stock-Based Compensation
Summary of stock option activity	The following table summarizes stock option activity during the year ended December 31, 2014:
		Shares			Weighted			Weighted			Aggregate
					average			average			intrinsic
					exercise			remaining			value
					price			contractual
								life (years)
	Outstanding at January 1		6,814,417		$	6.9
	Options granted		3,276,427			4.9
	Options exercised		(206,389	)		4.14
	Options cancelled		(1,055,112	)		7.35
	Outstanding at December 31		8,829,343		$	6.17			6.35		$	70,082
	Exercisable at December 31		4,915,662		$	6.67			4.17		$	70,082
Summary of unvested restricted share activity	The following table summarizes unvested restricted share activity during the year ended December 31, 2014:
		Shares			Weighted
					average
					grant date
					fair value
	Outstanding at January 1		45,000		$	4.63
	Vested		(39,508	)		4.56
	Granted		764,022			3.67
	Forfeited		(25,000	)		4.34
	Outstanding at December 31		744,514		$	3.65
Schedule of weighted average assumptions used to estimate fair value of each employee stock option award
		Years ended December 31,
		2014			2013			2012
	Risk-free interest rate		1.88	%		1.20	%		1.11	%
	Expected life in years		6.25 years			6.25 years			6.25 years
	Volatility		104	%		102	%		101	%
	Expected dividend yield		—			—			—
Schedule of stock-based compensation expense	Stock-based compensation expense during the years ended December 31, 2014, 2013 and 2012 was as follows (in thousands):
		Years ended December 31,
		2014			2013			2012
	Stock-based compensation expense by type of award:
	Employee stock options	$	7,076		$	5,757		$	3,082
	Restricted stock		355			273			240
	Total stock-based compensation expense	$	7,431		$	6,030		$	3,322
	Effect of stock-based compensation expense by line item:
	Research and development	$	4,412		$	3,220		$	2,485
	General and administrative		3,019			2,810			837
	Total stock-based compensation expense included in net loss	$	7,431		$	6,030		$	3,322
Schedule of unrecognized stock-based compensation expense	Unrecognized stock-based compensation expense as of December 31, 2014 was as follows (dollars in thousands):
		Unrecognized			Weighted
		stock			average
		compensation			remaining
		expense as of			period
		December 31,			(in years)
		2014
	Employee stock options	$	13,468			2.77
	Restricted stock		2,545			3.39
	Total	$	16,013			2.87

Other_Accrued_Liabilities_Tabl

Other Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2014
Other Accrued Liabilities
Schedule of other accrued liabilities	Other accrued liabilities as of December 31, 2014 and December 31, 2013 consisted of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Compensation and benefits	$	3,852	$	3,137
	Professional fees		1,285		1,585
	Other		1,040		996
		$	6,177	$	5,718

Term_Loans_Tables

Term Loans (Tables)	12 Months Ended
	Dec. 31, 2014
Term Loans
Schedule of future principal payments under the GECC and Oxford Term Loans	Future principal payments under the GECC and Oxford Term Loans as of December 31, 2014 were approximately as follows (in thousands):
	Years ending December 31,
	2015	$	9,214
	2016		4,607
	Total principal payments		13,821
	Less current portion		(9,214	)
	Long term portion	$	4,607

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Taxes
Schedule of differences between the actual tax provision (benefit) and the tax provision (benefit) computed using the United States federal income tax rate	Differences between the actual tax provision (benefit) and the tax provision (benefit) computed using the United States federal income tax rate is as follows for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		Years ended December 31,
		2014			2013			2012
	Benefit at statutory rate	$	(29,293	)	$	(30,665	)	$	(21,349	)
	State taxes, net of federal benefit		(3,342	)		(3,735	)		(3,220	)
	State net operating loss expiration		—			661			3,167
	Stock-based compensation		1,094			1,118			382
	Tax credits		(1,720	)		(2,462	)		(411	)
	Foreign rate differential		6,243			5,252			—
	Other		100			(47	)		22
	Increase in valuation allowance		26,918			29,878			21,409
	Income tax provision (benefit)	$	—		$	—		$	—
Schedule of effects of temporary differences that give rise to significant portions of deferred tax assets and deferred tax liabilities	The effects of temporary differences that give rise to significant portions of deferred tax assets and deferred tax liabilities at December 31, 2014 and 2013 are presented below (in thousands):
		2014			2013
	Deferred tax assets:
	Federal and state net operating loss carryforwards	$	194,091		$	170,557
	Federal and state research and development credits		21,401			19,675
	Depreciation and amortization		2,423			2,412
	Deferred compensation		7,643			6,254
	Other		1,427			1,169
	Deferred tax assets		226,985			200,067
	Less valuation allowance		(226,985	)		(200,067	)
	Net deferred tax assets	$	—		$	—

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies
Schedule of future minimum payments, excluding operating costs and taxes, under the Company's capital and non-cancellable operating leases	Future minimum payments, excluding operating costs and taxes, under the Company's capital and non-cancellable operating leases are approximately as follows (in thousands):
		Operating		Capital
		leases		leases
	Years ending December 31,
	2015	$	2,226	$	44
	2016		1,995		44
	2017		25		—
	Total minimum payments	$	4,246		88
	Less: amount representing interest				(3	)
	Present value of minimum payments				85
	Less current portions of obligations				(42	)
	Long term obligation			$	43

Quarterly_Financial_Data_unaud1

Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Data (unaudited)
Schedule of quarterly results of operations
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2014			2014			2014			2014
		(in thousands, except shares and per share data)
	Revenues:
	Total revenues	$	—		$	—		$	—		$	—
	Operating expenses:
	Research and development		17,583			18,761			16,208			15,653
	General and administrative		5,324			2,940			3,241			4,241
	Total operating expenses		22,907			21,701			19,449			19,894
	Loss from operations		(22,907	)		(21,701	)		(19,449	)		(19,894	)
	Interest expense, net		(650	)		(585	)		(517	)		(458	)
	Net loss	$	(23,557	)	$	(22,286	)	$	(19,966	)	$	(20,352	)
	Basic and diluted net loss per common share	$	(0.28	)	$	(0.24	)	$	(0.19	)	$	(0.19	)
	Basic and diluted weighted average number of common shares outstanding		85,438,127			94,046,278			105,774,949			108,366,504
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2013			2013			2013			2013
		(in thousands, except shares and per share data)
	Revenues:
	Total revenues	$	—		$	—		$	—		$	—
	Operating expenses:
	Research and development		16,380			17,876			17,623			19,981
	General and administrative		3,878			4,187			4,171			3,463
	Total operating expenses		20,258			22,063			21,794			23,444
	Loss from operations		(20,258	)		(22,063	)		(21,794	)		(23,444	)
	Interest expense, net		(470	)		(724	)		(721	)		(718	)
	Net loss	$	(20,728	)	$	(22,787	)	$	(22,515	)	$	(24,162	)
	Basic and diluted net loss per common share	$	(0.30	)	$	(0.33	)	$	(0.33	)	$	(0.31	)
	Basic and diluted weighted average number of common shares outstanding		68,991,371			69,034,823			69,047,161			76,769,199

Nature_of_Business_Details

Nature of Business (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Nature of Business
Accumulated deficit	$637,573,000	$551,412,000
Cash, cash equivalents and marketable securities	$97,700,000

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details) (USD $)	1 Months Ended	12 Months Ended
	Mar. 31, 2011	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Patents
Patent expenses		$1,900,000	$2,900,000	$1,800,000
Income Taxes
Uncertain tax items		0	0
Amount of accrued interest or penalties related to uncertain tax positions		0	0
Impairment of Long-Lived Assets
Impairment of assets		0	0
Grant Revenue
Amount of grant awarded	1,000,000
Grant revenue		$0	$0	$147,000
Minimum
Property and Equipment
Estimated useful lives		3 years
Maximum
Property and Equipment
Estimated useful lives		7 years

Summary_of_Significant_Account4

Summary of Significant Accounting Policies (Details 2)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Common stock options
Anti-dilutive securities
Outstanding securities not included in the computation of diluted net income (loss) per common share as their inclusion would be anti-dilutive (in shares)	8,829,343	6,814,417	5,521,584
Restricted stock
Anti-dilutive securities
Outstanding securities not included in the computation of diluted net income (loss) per common share as their inclusion would be anti-dilutive (in shares)	744,514	45,000	35,122

Cash_Cash_Equivalents_and_Mark2

Cash, Cash Equivalents and Marketable Securities (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Cash, Cash Equivalents and Marketable Securities
Total cash, cash equivalents and marketable securities	97,700
Cash, cash equivalents and marketable securities, unrealized gains	12	18
Cash, cash equivalents and marketable securities, unrealized losses	-8	-1
Cost
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	46,024	48,490
Total cash, cash equivalents and marketable securities	97,686	91,459
Fair value
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	46,024	48,490
Total cash, cash equivalents and marketable securities	97,690	91,476
Corporate debt securities due within 1 year of date of purchase
Cash, Cash Equivalents and Marketable Securities
Marketable securities, Unrealized gains	12	18
Marketable securities, Unrealized losses	-8	-1
Corporate debt securities due within 1 year of date of purchase | Cost
Cash, Cash Equivalents and Marketable Securities
Marketable securities	51,662	42,969
Corporate debt securities due within 1 year of date of purchase | Fair value | Level 2
Cash, Cash Equivalents and Marketable Securities
Marketable securities	51,666	42,986
Cash and money market funds | Cost
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	45,004	40,586
Cash and money market funds | Fair value | Level 1
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	45,004	40,586
Corporate debt securities due within 3 months of date of purchase | Cost
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	1,020	7,904
Corporate debt securities due within 3 months of date of purchase | Fair value | Level 2
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	1,020	7,904
Maximum | Corporate debt securities due within 1 year of date of purchase
Cash, Cash Equivalents and Marketable Securities
Maturity period from date of purchase to classify an investment as marketable securities	1 year	1 year
Maximum | Corporate debt securities due within 3 months of date of purchase
Cash, Cash Equivalents and Marketable Securities
Maturity period from date of purchase to classify an investment as cash and cash equivalents	3 months	3 months

Property_and_Equipment_Details

Property and Equipment (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property and Equipment
Property and equipment, gross	$21,507,000	$22,029,000
Less accumulated depreciation and amortization	-20,483,000	-20,476,000
Property and equipment, net	1,024,000	1,553,000
Depreciation and amortization	673,000	516,000	738,000
Laboratory equipment
Property and Equipment
Property and equipment, gross	12,217,000	12,681,000
Leasehold improvements
Property and Equipment
Property and equipment, gross	4,988,000	4,958,000
Computers and software
Property and Equipment
Property and equipment, gross	3,126,000	3,220,000
Furniture and fixtures
Property and Equipment
Property and equipment, gross	1,176,000	1,170,000
Equipment under capital lease
Property and Equipment
Less accumulated depreciation and amortization	-42,000	0
Property and equipment, net	$84,000	$126,000

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)	12 Months Ended	1 Months Ended	2 Months Ended	1 Months Ended						2 Months Ended	3 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Nov. 30, 2013	Feb. 29, 2012	Jan. 31, 2012	Dec. 31, 2012	Apr. 30, 2014	Jul. 31, 2012	Feb. 29, 2012	Jul. 31, 2014	Apr. 30, 2014	Sep. 30, 2014	Jul. 31, 2014
	Vote
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Number of votes per share that common stockholders are entitled to receive	1
Public Offering
Stockholders' Equity
Number of shares sold by the entity		16,100,000	8,050,000
Selling price per share (in dollars per share)		$3.75	$4.40					4.4
Net proceeds after deducting commissions and other transactions costs		$57.10	$33
Value of shares sold by the entity		60.4	35.4
Public Offering | Largest Shareholder Members Of Board Of Directors And Entities Affiliated With Directors
Stockholders' Equity
Number of shares sold by the entity		5,183,333
Selling price per share (in dollars per share)		$3.75
Public Offering | Largest Shareholder and Member of Board of Directors
Stockholders' Equity
Number of shares sold by the entity			1,136,363	1,136,363
Selling price per share (in dollars per share)				$4.40
Registered Direct Offering
Stockholders' Equity
Number of shares sold by the entity					7,000,000
Selling price per share (in dollars per share)					$8.60
Net proceeds after deducting commissions and other transactions costs					59.8
Registered Direct Offering | Largest Shareholder Members Of Board Of Directors And Entities Affiliated With Directors
Stockholders' Equity
Number of shares sold by the entity						1,250,000
Selling price per share (in dollars per share)						$4.01				$4.01
Net proceeds after deducting commissions and other transactions costs						5
Registered Direct Offering | Directors Including Largest Shareholder
Stockholders' Equity
Number of shares sold by the entity					2,649,535		3,976,702
Selling price per share (in dollars per share)					$8.60		$6.49
Net proceeds after deducting commissions and other transactions costs							25.8
Public Offering-Initial Offering
Stockholders' Equity
Number of shares sold by the entity		14,000,000		7,000,000
Public Offering-Full Exercise
Stockholders' Equity
Number of shares sold by the entity		2,100,000						1,050,000
At-The-Market Issuance Sales Agreement
Stockholders' Equity
Number of shares sold by the entity										6,588,875	5,679,685	9,424,193
Net proceeds after deducting commissions and other transactions costs										27.3	22.5	39.2
Value of shares sold by the entity										28	23	40
Weighted average selling price (in dollars per share)										$4.25	$4.05	$4.24
Maximum aggregate offering price									$50		$27
MLV & Co. LLC | At-The-Market Issuance Sales Agreement | Maximum
Stockholders' Equity
Percentage of gross proceeds payable as commission	3.00%

StockBased_Compensation_Detail

Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2015
Common stock options
Shares
Outstanding at the beginning of the period (in shares)	6,814,417
Options granted (in shares)	3,276,427
Options exercised (in shares)	-206,389
Options cancelled (in shares)	-1,055,112
Outstanding at the end of the period (in shares)	8,829,343	6,814,417
Exercisable at the end of the period (in shares)	4,915,662
Weighted average exercise price
Outstanding at the beginning of the period (in dollars per share)	$6.90
Options granted (in dollars per share)	$4.90
Options exercised (in dollars per share)	$4.14
Options cancelled (in dollars per share)	$7.35
Outstanding at the end of the period (in dollars per share)	$6.17	$6.90
Exercisable at the end of the period (in dollars per share)	$6.67
Weighted average remaining contractual life
Outstanding at the end of the period	6 years 4 months 6 days
Exercisable at the end of the period	4 years 2 months 1 day
Aggregate intrinsic value
Outstanding at the end of the period	$70,082
Exercisable at the end of the period	70,082
Additional disclosures
Closing stock price (in dollars per share)	$2.65
Total intrinsic value of options exercised	435,000	385,000	904,000
Total cash received from stock option exercises	900,000	1,100,000	1,100,000
Weighted-average grant date fair value of options (in dollars per share)	$4	$7.28	$4.10
Weighted average assumptions used to estimate fair value of each employee stock option award
Risk-free interest rate (as a percent)	1.88%	1.20%	1.11%
Expected life in years	6 years 3 months	6 years 3 months	6 years 3 months
Volatility (as a percent)	104.00%	102.00%	101.00%
Restricted stock
Additional disclosures
Total fair value of restricted stock vested during the period	$100,000	$300,000	$600,000
Shares
Outstanding at the beginning of the period (in shares)	45,000
Vested (in shares)	-39,508
Granted (in shares)	764,022
Forfeited (in shares)	-25,000
Outstanding at the end of the period (in shares)	744,514	45,000
Weighted average grant date fair value
Outstanding at the beginning of the period (in dollars per share)	$4.63
Vested (in dollars per share)	$4.56
Granted (in dollars per share)	$3.67
Forfeited (in dollars per share)	$4.34
Outstanding at the end of the period (in dollars per share)	$3.65	$4.63
2006 Stock Plan
Stock-based compensation expense
Shares reserved for issuance	10,300,000
Increase in number of shares reserved for issuance	1,300,000
Percentage of outstanding shares of common stock used to compute annual increase in number of shares reserved for issuance	5.00%
Shares available for future issuance	1,385,022
2006 Stock Plan | Subsequent event
Stock-based compensation expense
Shares reserved for issuance				11,600,000
2006 Stock Plan | Common stock options | Maximum
Stock-based compensation expense
Expiration period	10 years
Vesting period	4 years

StockBased_Compensation_Detail1

Stock-Based Compensation (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-based compensation expense
Stock-based compensation expense	$7,431	$6,030	$3,322
Research and development
Stock-based compensation expense
Stock-based compensation expense	4,412	3,220	2,485
General and administrative
Stock-based compensation expense
Stock-based compensation expense	3,019	2,810	837
Common stock options
Stock-based compensation expense
Stock-based compensation expense	7,076	5,757	3,082
Restricted stock
Stock-based compensation expense
Stock-based compensation expense	$355	$273	$240

StockBased_Compensation_Detail2

Stock-Based Compensation (Details 3) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Unrecognized stock-based compensation expense
Unrecognized stock compensation expense	$16,013
Weighted average remaining period	2 years 10 months 13 days
Common stock options
Unrecognized stock-based compensation expense
Unrecognized stock compensation expense	13,468
Weighted average remaining period	2 years 9 months 7 days
Restricted stock
Unrecognized stock-based compensation expense
Unrecognized stock compensation expense	$2,545
Weighted average remaining period	3 years 4 months 21 days

Other_Accrued_Liabilities_Deta

Other Accrued Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Other Accrued Liabilities
Compensation and benefits	$3,852	$3,137
Professional fees	1,285	1,585
Other	1,040	996
Other accrued liabilities	$6,177	$5,718

CoDevelopment_and_License_Agre1

Co-Development and License Agreements (Details) (License Arrangement)	31-May-14
	item
License Arrangement
Co-Development and License Agreements
Number of lead candidates	2
Number of lead candidates to be developed	1

Term_Loans_Details

Term Loans (Details) (USD $)	12 Months Ended	1 Months Ended		9 Months Ended	12 Months Ended		1 Months Ended			6 Months Ended
	Dec. 31, 2013	Jan. 31, 2014	Mar. 31, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2012	Apr. 30, 2014	31-May-11	Mar. 31, 2011	Jun. 30, 2013
		payment		item				payment
Term Loans
Proceeds from term loans	$13,500,000
Future principal payments under the GECC and Oxford Term Loans
2015					9,214,000
2016					4,607,000
Total principal payments					13,821,000
Less current portion	-9,451,000				-9,214,000
Long term obligation	13,820,000				4,607,000
GECC Term Loan
Term Loans
Proceeds from term loans			12,900,000
Annual interest rate on term loan (as a percent)					9.75%
Number of equal monthly payments of principal plus accrued interest		30		9
Exit fee to be paid					788,000
Interest expense recognized	2,500,000				2,100,000	1,700,000
Transaction and exit fees and expenses recognized in interest expense	600,000				400,000	300,000
Future principal payments under the GECC and Oxford Term Loans
Total principal payments			22,500,000	22,500,000
GECC Term Loan | Maximum
Term Loans
Amount of equipment financing allowed under covenants without any restriction					4,000,000
Oxford Term Loan
Term Loans
Proceeds from term loans									2,000,000
Annual interest rate on term loan (as a percent)					13.35%
Number of equal monthly payments of principal plus accrued interest								36
Interest expense recognized	127,000				59,000	172,000
Number of equal monthly payments of principal plus accrued interest						36
Full payment of the original loan							2,000,000
Principal amount of debt issued										600,000
Administrative, legal fees and expenses paid					108,000
Oxford Term Loan | Maximum
Term Loans
Additional amount that the Company may fully utilized in equipment financing						600,000
Oxford Term Loan | Minimum
Term Loans
Amount of debt assumption from acquisitions requiring prior written consent under covenants					$2,000,000

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Differences between the actual tax provision (benefit) and the tax provision (benefit) computed using the United States federal income tax rate
Benefit at statutory rate	($29,293,000)	($30,665,000)	($21,349,000)
State taxes, net of federal benefit	-3,342,000	-3,735,000	-3,220,000
State net operating loss expiration		661,000	3,167,000
Stock-based compensation	1,094,000	1,118,000	382,000
Tax credits	-1,720,000	-2,462,000	-411,000
Foreign rate differential	6,243,000	5,252,000
Other	100,000	-47,000	22,000
Increase in valuation allowance	26,918,000	29,878,000	21,409,000
Deferred tax assets:
Federal and state net operating loss carryforwards	194,091,000	170,557,000
Federal and state research and development credits	21,401,000	19,675,000
Depreciation and amortization	2,423,000	2,412,000
Deferred compensation	7,643,000	6,254,000
Other	1,427,000	1,169,000
Deferred tax assets	226,985,000	200,067,000
Less valuation allowance	-226,985,000	-200,067,000
Increase (decrease) in valuation allowance	$26,900,000	$29,900,000	$21,400,000

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Income Taxes
Deductions related to the exercise of common stock options included in net operating loss carryforwards	$1.40
Federal
Income Taxes
Net operating loss carryforwards	529.7
State
Income Taxes
Net operating loss carryforwards	$275.40

Income_Taxes_Details_3

Income Taxes (Details 3) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes
Reserves for uncertain tax positions	$0	$0	$0
Liability for uncertain tax positions	0	0
Federal | Research and development credits
Income Taxes
Research and development tax credit carryforwards	16,700,000
State | Research and development credits
Income Taxes
Research and development tax credit carryforwards	$7,100,000

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	lease
Commitments and Contingencies
Number of non-cancelable and renewable operating leases	3
Operating leases
2015	$2,226,000
2016	1,995,000
2017	25,000
Total minimum payments	4,246,000
Rent expense under operating leases	2,300,000	2,200,000	2,200,000
Capital leases
2015	44,000
2016	44,000
Total minimum payments	88,000
Less: amount representing interest	-3,000
Present value of minimum payments	85,000
Less current portions of obligations	-42,000	-42,000
Long term obligation	$43,000	$85,000

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)	1 Months Ended	2 Months Ended	1 Months Ended
In Millions, except Share data, unless otherwise specified	Nov. 30, 2013	Feb. 29, 2012	Dec. 31, 2012	Apr. 30, 2014	Jan. 31, 2013	Jul. 31, 2012	Nov. 30, 2012	Jan. 31, 2012
Public Offering
Related Party Transactions
Shares sold by the entity	16,100,000	8,050,000
Selling price per share (in dollars per share)	$3.75	$4.40
Registered Direct Offering
Related Party Transactions
Shares sold by the entity			7,000,000
Selling price per share (in dollars per share)			$8.60
Largest Shareholder Members Of Board Of Directors And Entities Affiliated With Directors | Public Offering
Related Party Transactions
Shares sold by the entity	5,183,333
Selling price per share (in dollars per share)	$3.75
Largest Shareholder Members Of Board Of Directors And Entities Affiliated With Directors | Registered Direct Offering
Related Party Transactions
Shares sold by the entity				1,250,000
Selling price per share (in dollars per share)				$4.01
Director
Related Party Transactions
Aggregate number of shares of common stock options exercised					114,250
Proceeds resulting from exercise of stock options					$1
Directors Including Largest Shareholder | Registered Direct Offering
Related Party Transactions
Shares sold by the entity			2,649,535			3,976,702
Selling price per share (in dollars per share)			$8.60			$6.49
Officer
Related Party Transactions
Number of shares purchased and retired upon the vesting of restricted common stock in order to fund the related tax liability							3,969
Largest Shareholder and Member of Board of Directors | Public Offering
Related Party Transactions
Shares sold by the entity		1,136,363						1,136,363
Selling price per share (in dollars per share)								$4.40

Retirement_Plan_Details

Retirement Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Matching contribution percentage
Percentage of employee's salary that is subject to Company matching	6.00%
Vesting schedule of employer's matching contribution	3 years
Company contributions	$359,000	$413,000	$376,000
Maximum
Matching contribution percentage
Percentage of participants' contributions matched by Company on the first 6% of the employee's salary	50.00%

Quarterly_Financial_Data_unaud2

Quarterly Financial Data (unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Grant revenue									$0	$0	$147
Total revenues											147
Operating expenses:
Research and development	15,653	16,208	18,761	17,583	19,981	17,623	17,876	16,380	68,205	71,860	49,412
General and administrative	4,241	3,241	2,940	5,324	3,463	4,171	4,187	3,878	15,746	15,699	11,676
Total operating expenses	19,894	19,449	21,701	22,907	23,444	21,794	22,063	20,258	83,951	87,559	61,088
Loss from operations	-19,894	-19,449	-21,701	-22,907	-23,444	-21,794	-22,063	-20,258	-83,951	-87,559	-60,941
Interest expense, net	-458	-517	-585	-650	-718	-721	-724	-470	-2,210	-2,633	-1,849
Net loss	($20,352)	($19,966)	($22,286)	($23,557)	($24,162)	($22,515)	($22,787)	($20,728)	($86,161)	($90,192)	($62,790)
Basic and diluted net loss per common share (in dollars per share)	($0.19)	($0.19)	($0.24)	($0.28)	($0.31)	($0.33)	($0.33)	($0.30)	($0.87)	($1.27)	($1.06)
Basic and diluted weighted average number of common shares outstanding	108,366,504	105,774,949	94,046,278	85,438,127	76,769,199	69,047,161	69,034,823	68,991,371	98,489,470	70,976,705	59,411,476