Molecular Templates (MTEM) 10-Q 1 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	Apr. 25, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Trading Symbol	'THLD	'
Entity Registrant Name	'THRESHOLD PHARMACEUTICALS INC	'
Entity Central Index Key	'0001183765	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	59,346,233

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$6,743	$7,279
Marketable securities, current	65,250	58,390
Collaboration receivable	5,192	18,094
Prepaid expenses and other current assets	1,311	2,246
Total current assets	78,496	86,009
Marketable securities, non-current	14,393	16,364
Property and equipment, net	632	686
Other assets	1,159	1,059
Total assets	94,680	104,118
Current liabilities:	'	'
Accounts payable	4,006	1,689
Accrued clinical and development expenses	5,492	7,444
Accrued liabilities	3,962	3,161
Deferred revenue, current	14,722	14,722
Total current liabilities	28,182	27,016
Warrant liability	21,964	23,421
Deferred revenue, non-current	73,235	76,916
Deferred rent	287	240
Total liabilities	123,668	127,593
Commitments and contingencies (Note 7)	'	'
Stockholders' equity (deficit):	'	'
Preferred stock, $0.001 par value, 2,000,000 shares authorized; no shares issued and outstanding	'	'
Common stock, $0.001 par value, shares authorized: 150,000,000 shares; issued and outstanding: 59,346,025 shares at March 31, 2014 and 59,232,611 shares at December 31, 2013	59	59
Additional paid-in capital	329,727	328,116
Accumulated other comprehensive gain (loss)	13	28
Accumulated deficit	-358,787	-351,678
Total stockholders' equity (deficit)	-28,988	-23,475
Total liabilities and stockholders' equity (deficit)	$94,680	$104,118

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Statement Of Financial Position [Abstract]	'	'
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	'	'
Preferred stock, shares outstanding	'	'
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	59,346,025	59,232,611
Common stock, shares outstanding	59,346,025	59,232,611

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations and Comprehensive Loss (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Income Statement [Abstract]	'	'
Revenue	$3,681	$2,922
Operating expenses:	'	'
Research and development	9,653	6,468
General and administrative	2,634	2,515
Total operating expenses	12,287	8,983
Loss from operations	-8,606	-6,061
Interest income (expense), net	40	36
Other income (expense), net	1,457	-3,116
Loss before provision for income taxes	-7,109	-9,141
Provision for income taxes	'	73
Net loss	-7,109	-9,214
Other comprehensive income (loss):	'	'
Unrealized gain (loss) on available-for sale securities	-15	-5
Comprehensive loss	($7,124)	($9,219)
Net loss per common share:	'	'
Basic	($0.12)	($0.16)
Diluted	($0.14)	($0.16)
Weighted average number of shares used in per common share calculations:	'	'
Basic	59,303	56,486
Diluted	61,300	56,486

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Cash flows from operating activities:	'	'
Net loss	($7,109)	($9,214)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:	'	'
Depreciation and amortization	390	316
Stock-based compensation expense	1,266	1,053
Change in common stock warrant value	-1,457	3,116
Changes in operating assets and liabilities:	'	'
Collaboration receivable	12,902	8,982
Prepaid expenses and other assets	835	5
Accounts payable	2,317	1,446
Accrued clinical and development expenses	-1,952	-126
Accrued liabilities	801	833
Deferred rent	47	-5
Deferred revenue	-3,681	27,078
Net cash provided by operating activities	4,359	33,484
Cash flows from investing activities:	'	'
Acquisition of property and equipment	-24	-14
Acquisition of marketable securities	-22,349	-46,407
Proceeds from sale of marketable securities	3,109	'
Proceeds from maturities of marketable securities	14,024	22,088
Net cash used in investing activities	-5,240	-24,333
Cash flows from financing activities:	'	'
Proceeds from issuance of common stock and warrants, net of offering expenses	345	175
Net cash provided by financing activities	345	175
Net increase (decrease) in cash and cash equivalents	-536	9,326
Cash and cash equivalents, beginning of period	7,279	11,029
Cash and cash equivalents, end of period	$6,743	$20,355

Organization_and_Summary_of_Si

Organization and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Organization and Summary of Significant Accounting Policies	'
	NOTE 1 — ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	The Company
	Threshold Pharmaceuticals, Inc. (the “Company”) is a biotechnology company using its expertise in the tumor microenvironment to discover and develop therapeutic agents that selectively target tumor cells for the treatment of patients living with cancer.
	Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for complete financial statements. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements. In the opinion of management, all adjustments, consisting of normal recurring adjustments necessary for the fair statement of results for the periods presented, have been included. The results of operations of any interim period are not necessarily indicative of the results of operations for the full year or any other interim period.
	The preparation of condensed consolidated financial statements requires management to make estimates and assumptions that affect the recorded amounts reported therein. A change in facts or circumstances surrounding the estimate could result in a change to estimates and impact future operating results.
	The unaudited condensed consolidated financial statements and related disclosures have been prepared with the presumption that users of the interim unaudited condensed consolidated financial statements have read or have access to the audited consolidated financial statements for the preceding fiscal year. The condensed consolidated balance sheet at December 31, 2013 has been derived from the audited financial statements at that date but does not include all the information and footnotes required by accounting principles generally accepted in the United States of America. Accordingly, these unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2013 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 6, 2014.
	The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, and reflect the elimination of intercompany accounts and transactions.
	Revenue Recognition
	The Company recognizes revenue in accordance with ASC 605 “Revenue Recognition”, subtopic ASC 605-25 “Revenue with Multiple Element Arrangements” and subtopic ASC 605-28 “Revenue Recognition-Milestone Method”, which provides accounting guidance for revenue recognition for arrangements with multiple deliverables and guidance on defining the milestone and determining when the use of the milestone method of revenue recognition for research and development transactions is appropriate, respectively.
	The Company’s revenues are related to its collaboration arrangement with Merck KGaA, which was entered in February 2012. The collaboration with Merck KGaA provides for various types of payments to the Company, including non-refundable upfront license, milestone and royalty payments. The Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price is fixed or determinable, and collectability is reasonably assured. The Company also receives reimbursement for Merck KGaA’s 70% share for eligible worldwide development expenses for TH-302. Such reimbursement is reflected as a reduction of operating expenses.
	For multiple-element arrangements, each deliverable within a multiple deliverable revenue arrangement is accounted for as a separate unit of accounting if both of the following criteria are met: (1) the delivered item or items have value to the customer on a standalone basis and (2) for an arrangement that includes a general right of return relative to the delivered item(s), delivery or performance of the undelivered item(s) is considered probable and substantially in the Company’s control. The deliverables under the Merck KGaA agreement have been determined to be a single unit of accounting and as such the revenue relating to this unit of accounting will be recorded as deferred revenue and recognized ratably over the term of its estimated performance period under the agreement, which is the product development period. The Company determines the estimated performance period and it will be periodically reviewed based on the progress of the related product development plan. The effect of a change made to an estimated performance period and therefore revenue recognized ratably would occur on a prospective basis in the period that the change was made.
	Deferred revenue associated with a non-refundable payment received under a collaborative agreement for which the performance obligations are terminated will result in an immediate recognition of any remaining deferred revenue in the period that termination occurred provided that all performance obligations have been satisfied.
	The Company recognizes revenue from milestone payments when: (i) the milestone event is substantive and its achievability has substantive uncertainty at the inception of the agreement, and (ii) the Company does not have ongoing performance obligations related to the achievement of the milestone earned. Milestone payments are considered substantive if all of the following conditions are met: the milestone payment (a) is commensurate with either the Company’s performance subsequent to the inception of the arrangement to achieve the milestone or the enhancement of the value of the delivered item or items as a result of a specific outcome resulting from the Company’s performance subsequent to the inception of the arrangement to achieve the milestone, (b) relates solely to past performance, and (c) is reasonable relative to all of the deliverables and payment terms (including other potential milestone consideration) within the arrangements. See Note 3, “Collaboration Arrangements,” for analysis of milestone events deemed to be substantive or non-substantive.

Net_Loss_Per_Common_Share

Net Loss Per Common Share	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Net Loss Per Common Share	'
	NOTE 2 — NET LOSS PER COMMON SHARE
	Basic net loss per common share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per common share is computed by giving effect to all potential dilutive common shares, including outstanding options and warrants.
	Potential dilutive common shares also include the dilutive effect of the common stock underlying in-the-money stock options and warrants that were calculated based on the average share price for each period using the treasury stock method. Under the treasury stock method, the exercise price of an option or warrant is assumed to be used to repurchase shares in the current period. In addition, the average amount of compensation cost for in-the-money options, if any, for future service that the Company has not yet recognized when the option is exercised, is also assumed to repurchase shares in the current period. A reconciliation of the numerator and denominator used in the calculation is as follows (in thousands, except per share amounts):
		Three Months Ended
		March 31,
		2014			2013
	Numerator:
	Net loss-basic	$	(7,109	)	$	(9,214	)
	Less: noncash income from change in fair value of common stock warrants		1,757			—
	Net loss-diluted	$	(8,866	)	$	(9,214	)
	Denominator:
	Weighted average common shares outstanding		59,303			56,486
	Dilutive effect of warrants		1,997			—
	Weighted-average common shares outstanding and potential dilutive common shares — diluted		61,300			56,486
	Net loss per share
	Basic	$	(0.12	)	$	(0.16	)
	Diluted	$	(0.14	)	$	(0.16	)
	The following outstanding warrants, options and purchase rights under the Company’s 2004 Employee Stock Purchase Plan were excluded from the computation of diluted net loss per share for the periods presented because including them would have had an antidilutive effect (in thousands):
		As of March 31,
		2014			2013
	Shares issuable upon exercise of warrants		4,288			11,573
	Shares issuable upon exercise of stock options		6,656			6,481
	Shares issuable related to the ESPP		31			48

Collaboration_Arrangements

Collaboration Arrangements	3 Months Ended
	Mar. 31, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
Collaboration Arrangements	'
	NOTE 3 — COLLABORATION ARRANGEMENTS
	On February 3, 2012, the Company entered into a global license and co-development agreement with Merck KGaA, Darmstadt, Germany, to co-develop and commercialize TH-302, the Company’s small molecule hypoxia-targeted drug. Under the terms of the agreement, Merck KGaA received co-development rights, exclusive global commercialization rights and provided the Company with an option to co-commercialize TH-302 in the United States. To date the Company received $110 million in upfront and milestone payments, including $12.5 million received during the quarter ended March 31, 2014. The milestones earned to date were not deemed to be substantive milestones because the work related to the achievement of these items was predominately completed prior to the inception of the arrangement. The Company is eligible to earn additional potential milestone payments of up to $100 million in regulatory and development milestones, and $340 million in commercialization milestones.
	In the United States, the Company has primary responsibility for development of TH-302 in the soft tissue sarcoma indication. The Company and Merck KGaA will jointly develop TH-302 in all other cancer indications being pursued. Merck KGaA will pay 70% of worldwide development expenses for TH-302. Subject to FDA approval in the United States, Merck KGaA will initially be responsible for commercialization of TH-302 with the Company receiving a tiered, double-digit royalty on sales. Under the royalty bearing portion of the agreement, Threshold retains the option to co-promote TH-302 in the United States. Additionally, the Company retains the option to co-commercialize TH-302 in the United States, upon the achievement of certain sales and regulatory milestones, allowing the Company to participate in up to 50% of the profits in the United States depending on total sales. Outside of the United States, Merck KGaA will be solely responsible for the commercialization of TH-302 with the Company receiving a tiered, double digit royalty on sales in these territories. The agreement will continue on a country-by-country and product-by-product basis until the later of the last to expire patent covering such product containing TH-302 in such country or ten years following the commercial launch of a product containing TH-302 in such country, unless terminated earlier. Merck KGaA has the right to terminate the agreement on limited notice to the Company, and each party has the right to terminate the agreement following an uncured material breach by the other party.
	The Company’s deliverables under the Merck KGaA agreement, which include delivery of the rights and license for TH-302 and performance of research and development activities, have been determined to be a single unit of accounting. The delivered license does not have standalone value at the inception of the arrangement due to the Company’s proprietary expertise with respect to the licensed compound and related ongoing developmental participation under the global license and co-development agreement, which is required for Merck KGaA to fully realize the value from the delivered license. Therefore, the revenue relating to this unit of accounting will be recorded as deferred revenue and recognized over the estimated performance period under the agreement, which is the product development period. The Company has recorded $110 million of the upfront payment and milestones payments as deferred revenue and is amortizing them ratably over its estimated period of performance, which the Company currently estimates to end on March 31, 2020. As a result, the Company recognized $3.7 million and $2.9 million of revenue during the three months ended March 31, 2014 and 2013, respectively. The Company will periodically review and, if necessary, revise the estimated periods of performance of our collaboration. The Company also earned a $5.9 million and $3.5 million reimbursement for eligible worldwide development expenses for TH-302 from Merck KGaA during the three months ended March 31, 2014 and 2013, respectively. Such earned reimbursement has been reflected as a reduction of operating expenses.
	Of the remaining potential future milestones, $100 million are related to regulatory and development milestones and $340 million are related to commercialization milestones that may be received under the Merck KGaA Agreement. Regulatory milestones include the filing and acceptance of regulatory applications for marketing approval in major markets. Development milestones include primarily the initiation of various phases of clinical trials. Commercialization milestones include the achievement of first commercial sales in a particular market or annual product sales in excess of a pre-specified threshold. At the inception of the collaboration agreement the Company assessed regulatory and development milestones to be substantive where there was substantive scientific and regulatory uncertainty of achievement, the amounts of payments assigned were considered to be commensurate with the enhancement that occurred subsequent to inception of the Merck KGaA agreement, of the value of the delivered rights and license of TH-302 and the Company’s performance is necessary to the achievement of the milestone. Accordingly, the Company will recognize payments related to the achievement of such milestones, if any, when such milestone is achieved. Regulatory and development milestones that do not meet these conditions were considered non-substantive and payments related to the achievement of such milestones, if any, will be recorded as deferred revenue and amortized ratably over the estimated period of performance. Final determination of whether a development or regulatory milestone is substantive will depend upon the Company’s role in achieving the milestone. The specific role and responsibilities related to the regulatory and development activities for certain of these milestones have yet to be determined and may change during the development period. Under the Merck KGaA agreement, Merck KGaA will initially be responsible for commercialization activities and the Company initially may not be involved in the achievement of these commercialization milestones. These commercialization milestones would typically be achieved after the completion of the Company’s regulatory and development activities. If there are no future development obligations, the Company expects to account for the commercialization milestones in the same manner as royalties, with revenue recognized upon achievement of the milestone.

Stockholders_Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2014
Equity [Abstract]	'
Stockholders' Equity	'
	NOTE 4— STOCKHOLDERS’ EQUITY
	Common Stock Warrants
	The Company accounts for its common stock warrants under guidance in ASC 815 that clarifies the determination of whether an instrument (or an embedded feature) is indexed to an entity’s own stock, which would qualify for classification as liabilities. The guidance required the Company’s outstanding warrants to be classified as liabilities and to be fair valued at each reporting period, with the changes in fair value recognized as other income (expense) in the Company’s consolidated statements of operations.
	At both March 31, 2014 and December 31, 2013, the Company had warrants outstanding to purchase 4,287,940 shares of common stock, having an exercise price of $2.05 per share, which warrants were initially issued by us in a private placement in October 2009. The fair value of these warrants on March 31, 2014 and December 31, 2013 was determined using a Black Scholes valuation model with the following level 3 inputs:
		March 31,			December 31,
		2014			2013
	Risk-free interest rate		0.13	%		0.13	%
	Expected life (in years)		0.52			0.76
	Dividend yield		—			—
	Volatility		44	%		49	%
	Stock price	$	4.76		$	4.67
	During the three months March 31, 2014 the change in fair value of $0.3 million related to the October 2009 warrants was recorded as other expense in the Company’s condensed consolidated statement of operations.
	At both March 31, 2014 and December 31, 2013, the Company had also warrants outstanding to purchase 3,993,783 shares of common stock, having an exercise price of $2.46 per share, which warrants were initially issued by us in an underwritten public offering in March 2011. The fair value of these warrants on March 31, 2014 and December 31, 2013 was determined using a Black Scholes valuation model with the following level 3 inputs:
		March 31,			December 31,
		2014			2013
	Risk-free interest rate		0.44	%		0.78	%
	Expected life (in years)		1.96			2.21
	Dividend yield		—			—
	Volatility		55	%		88	%
	Stock price	$	4.76		$	4.67
	During the three months ended March 31, 2014, the change in fair value of $1.8 million related to the March 2011 warrants was recorded as other income in the Company’s consolidated statement of operations.
	The following table sets forth the Company’s financial liabilities, related to warrants issued in the October 2009 and March 2011offerings, subject to fair value measurements as of March 31, 2014 and December 31, 2013:
		Fair Value as of			Basis of Fair Value Measurements
		March 31,
	(in thousands)	2014			Level 1			Level 2		Level 3
	October 2009 warrants	$	11,620		$	—		$	—	$	11,620
	March 2011 warrants		10,344			—			—		10,344
	Total common stock warrants	$	21,964		$	—		$	—	$	21,964
	(in thousands)	Fair Value as of			Basis of Fair Value Measurements
		December 31,
		2013			Level 1			Level 2		Level 3
	October 2009 warrants	$	11,320		$	—		$	—	$	11,320
	March 2011 warrants		12,101			—			—		12,101
	Total common stock warrants	$	23,421		$	—		$	—	$	23,421
	The following table is a reconciliation of the warrant liability measured at fair value using level 3 inputs (in thousands):
		Warrant Liability
	Balance at December 31, 2013	$	23,421
	Change in fair value of common stock warrants during three months ended March 31, 2014		(1,457	)
	Exercise of warrants during three months ended March 31, 2014		—
	Balance at March 31, 2014	$	21,964

Stock_Based_Compensation

Stock Based Compensation	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock Based Compensation	'
	NOTE 5— STOCK BASED COMPENSATION
	The Company recognizes stock-based compensation in accordance with ASC 718, “Compensation—Stock Compensation.” Stock-based compensation expense, which consists of the compensation cost for employee stock options and the Company’s ESPP, and the value of options issued to non-employees for services rendered, was allocated to research and development and general and administrative in the unaudited condensed consolidated statements of operations as follows (in thousands):
		Three Months Ended
		March 31,
		2014			2013
	Research and development	$	671		$	534
	General and administrative		595			519
		$	1,266		$	1,053
	Valuation Assumptions
	The Company estimated the fair value of stock options granted using the Black-Scholes option-pricing formula and a single option award approach. This fair value is being amortized ratably over the requisite service periods of the awards, which is generally the vesting period. The fair value of employee stock options and employee purchase rights under the Company’s ESPP was estimated using the following weighted-average assumptions for the three months ended March 31, 2014 and 2013:
		Three Months Ended
		March 31,
		2014			2013
	Employee Stock Options:
	Risk-free interest rate		1.9	%		1.15	%
	Expected term (in years)		6.04			6.02
	Dividend yield		—			—
	Volatility		96	%		101	%
	Weighted-average fair value of stock options granted	$	3.84		$	4.01
		Three Months Ended
		March 31,
		2014			2013
	Employee Stock Purchase Plan (ESPP):
	Risk-free interest rate		0.18	%		0.2	%
	Expected term (in years)		1.23			1.25
	Dividend yield		—			—
	Volatility		53	%		92	%
	Weighted-average fair value of stock options granted	$	1.79		$	2.44
	To determine the expected term of the Company’s employee stock options granted, the Company utilized the simplified approach as defined by SEC Staff Accounting Bulletin No. 107, “Share-Based Payment” (“SAB 107”). To determine the risk-free interest rate, the Company utilized an average interest rate based on U.S. Treasury instruments with a term consistent with the expected term of the Company’s stock based awards. To determine the expected stock price volatility for the Company’s stock based awards, the Company utilized the historical volatilities of the Company. The fair value of all the Company’s stock based awards assumes no dividends as the Company does not anticipate paying cash dividends on its common stock.
	Employee Stock-based Compensation Expense
	As required by ASC 718, the Company recognized $1.2 million and $1.0 million of stock-based compensation expense related to stock options and purchase rights, under the Company’s stock option plans and ESPP, for the three months ended March 31, 2014 and 2013, respectively. As of March 31, 2014, the total unrecognized compensation cost related to unvested stock-based awards granted to employees under the Company’s stock option plans was approximately $9.8 million before forfeitures. This cost will be recorded as compensation expense on a straight-line basis over the remaining weighted average requisite service period of approximately 2.3 years.
	Non-employee Stock-based Compensation Expense
	The Company accounts for equity instruments issued to non-employees in accordance with ASC 505, “Equity.” The equity instruments consisting of stock options are valued using the Black-Scholes option pricing model. The values attributable to these options are amortized over the service period and the unvested portion of these options is remeasured at each vesting date. In connection with the grant of stock options to non-employees, the Company recorded stock-based compensation of approximately $36,000 and $35,000 for the three months ended March 31, 2014 and 2013, respectively.
	Equity Incentive Plans
	2004 Equity Incentive Plan On January 1, 2014, an additional 1,250,000 shares was authorized for issuance under the 2004 Equity Incentive Plan (“2004 Incentive Plan”), pursuant to the annual automatic increase to the authorized shares under the 2004 Incentive Plan. At March 31, 2014, 1,256,173 shares were authorized and available for issuance under the 2004 Equity Incentive Plan. The 2004 Incentive Plan expired pursuant to its terms on April 7, 2014.
	The following table summarizes stock option activity under the Company’s 2004 Equity Incentive Plan:
	Options	Number of			Weighted-			Weighted-		Aggregate
		Shares			Average			Average		Intrinsic
					Exercise			Remaining		Value
					Price			Contractual
								Term
	Outstanding at December 31, 2013		6,526,506		$	3.66			—		—
	Granted		175,000		$	4.97			—		—
	Exercised		(39,352	)	$	1.4			—		—
	Forfeitures		(5,937	)	$	6.18			—		—
	Outstanding at March 31, 2014		6,656,217		$	3.71			7.43	$	10,708,746
	Vested and expected to vest March 31, 2014		6,617,299		$	3.7			7.42	$	10,701,253
	Exercisable at March 31, 2014		4,077,685		$	2.93			6.78	$	9,204,627
	The total intrinsic value of stock options exercised during the three months ended March 31, 2014 and 2013 were $0.1 million and $0.1 million, respectively, as determined at the date of the option exercise. Cash received from stock option exercises was $55,000 and $33,000 for each of the three months ended March 31, 2014 and 2013, respectively. The Company issues new shares of common stock upon exercise of options. In connection with these exercises, there was no tax benefit realized by the Company due to the Company’s current loss position.
	2004 Employee Stock Purchase Plan On January 1, 2014, an additional 100,000 shares was authorized for issuance under the 2004 Employee Stock Purchase Plan (“2004 Purchase Plan”) pursuant to the annual automatic increase to the authorized shares under the 2004 Purchase Plan. For the three months ended March 31, 2014, plan participants had purchased 74,062 shares at an average purchase price of $3.91. At March 31, 2014, plan participants had $0.1 million withheld to purchase stock on August 14, 2014, which is included in accrued liabilities on the accompanying unaudited condensed consolidated balance sheet. At March 31, 2014, 261,834 shares were authorized and available for issuance under the ESPP.

Fair_Value_Measurements_and_Ma

Fair Value Measurements and Marketable Securities	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements and Marketable Securities	'
	NOTE 6— FAIR VALUE MEASUREMENTS AND MARKETABLE SECURITIES
	The Company accounts for its marketable securities in accordance with ASC 820 “Fair Value Measurements and Disclosures.” ASC 820 defines fair value, establishes a framework for measuring fair value in GAAP, and expands disclosures about fair value measurements. ASC 820 defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. ASC 820 also establishes a fair value hierarchy which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value:
	Level 1 - Quoted prices in active markets for identical assets or liabilities.
	Level 2 - Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
	Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
	The Company utilizes the market approach to measure fair value for its financial assets and liabilities. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. For Level 2 securities that have market prices from multiples sources, a “consensus price” or a weighted average price for each of these securities can be derived from a distribution-curve-based algorithm which includes market prices obtained from a variety of industrial standard data providers (e.g. Bloomberg), security master files from large financial institutions, and other third-party sources. Level 2 securities with short maturities and infrequent secondary market trades are typically priced using mathematical calculations adjusted for observable inputs when available.
	The following table sets forth the Company’s financial assets (cash equivalents and marketable securities) at fair value on a recurring basis as of March 31, 2014 and December 31, 2013:
		Fair Value as of		Basis of Fair Value Measurements
		March 31,
	(in thousands)	2014		Level 1			Level 2			Level 3
	Money market funds	$	5,001	$	5,001		$	—		$	—
	Certificates of deposit		1,464		—			1,464			—
	Corporate debt securities		55,317		—			55,317			—
	U.S. Government securities		18,990		—			18,990			—
	Municipal securities		1,618		—			1,618			—
	Commercial paper		3,996		—			3,996			—
	Total cash equivalents and marketable securities	$	86,386	$	5,001		$	81,385		$	—
		Fair Value as of		Basis of Fair Value Measurements
		December 31,
	(in thousands)	2013		Level 1			Level 2			Level 3
	Money market funds	$	4,285	$	4,285		$	—		$	—
	Certificates of deposit		1,584		—			1,584			—
	Corporate debt securities		49,019		—			49,019			—
	Government securities		21,731		—			21,731			—
	Municipal securities		2,815		—			2,815			—
	Commercial paper		2,599		—			2,599			—
	Total cash equivalents and marketable securities	$	82,033	$	4,285		$	77,748		$	—
	The Company invests in highly-liquid, investment-grade securities. The following is a summary of the Company’s available-for-sale securities at March 31, 2014 and December 31, 2013:
	As of March 31, 2014 (in thousands):	Cost Basis		Unrealized			Unrealized			Fair
				Gain			Loss			Value
	Money market funds	$	5,001	$	—		$	—		$	5,001
	Certificates of deposit		1,464		—			—			1,464
	Corporate debt securities		55,318		15			(16	)		55,317
	U.S. Government securities		18,977		15			(2	)		18,990
	Municipal securities		1,617		1			—			1,618
	Commercial paper		3,996		—			—			3,996
			86,373		31			(18	)		86,386
	Less cash equivalents		6,743		—			—			6,743
	Total marketable securities	$	79,630	$	31		$	(18	)	$	79,643
	As of December 31, 2013 (in thousands):	Cost Basis		Unrealized			Unrealized			Fair
				Gain			Loss			Value
	Money market funds	$	4,285	$	—		$	—		$	4,285
	Certificates of deposit		1,584		—			—			1,584
	Corporate debt securities		49,001		25			(7	)		49,019
	Government securities		21,722		12			(3	)		21,731
	Municipal securities		2,814		1			—			2,815
	Commercial paper		2,599		—			—			2,599
			82,005		38			(10	)		82,033
	Less cash equivalents		7,279		—			—			7,279
	Total marketable securities	$	74,726	$	38		$	(10	)	$	74,754
	There were no realized gains or losses in the three months ended March 31, 2014 and 2013.
	As of March 31, 2014, the weighted average maturity for the Company’s available for sale securities was 6.8 months, with the longest maturity being August 2015.
	The following table provides the breakdown of the marketable securities with unrealized losses at March 31, 2014 (in thousands):
		In loss position for less
		than twelve months
	As of March 31, 2014 (in thousands):	Fair Value		Unrealized Loss
	Government securities	$	6,653	$	(1	)
	Corporate debt securities		20,116		(12	)
	Total marketable securities	$	26,769	$	(13	)
	The Company determined the fair value of the liability associated with its warrants to purchase 8.3 million shares of outstanding common stock using a Black-Scholes Model. See detailed discussion in Note 4 — Stockholders’ Equity.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	NOTE 7— COMMITMENTS AND CONTINGENCIES
	The Company leases certain of its facilities under noncancelable leases, which qualify for operating lease accounting treatment under ASC 840, “Leases,” and, as such, these facilities are not included on its unaudited condensed consolidated balance sheets. The future rental payments required by the Company for all of its facilities under noncancelable operating leases are as follows (in thousands):
	Years Ending December 31,
	2014	$	667
	2015		918
	2016		953
	2017		238
	Thereafter		—
	Total	$	2,776
	Indemnification
	The Company enters into indemnification provisions under its agreements with other companies in the ordinary course of business, including business partners, contractors and parties performing its clinical trials. Pursuant to these arrangements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified parties for losses suffered or incurred by the indemnified party as a result of the Company’s activities. The duration of these indemnification agreements is generally perpetual. The maximum potential amount of future payments the Company could be required to make under these agreements is not determinable. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. As a result, the Company believes the estimated fair value of these agreements is minimal. The Company maintains commercial general liability insurance and products liability insurance to offset certain of its potential liabilities under these indemnification provisions. Accordingly, the Company has not recognized any liabilities relating to these agreements as of March 31, 2014.
	The Company’s bylaws provide that it is required to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers, other than liabilities arising from willful misconduct of a culpable nature, to the fullest extent permissible by applicable law; and to advance their expenses incurred as a result of any proceeding against them as to which they could be indemnified.

Organization_and_Summary_of_Si1

Organization and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for complete financial statements. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements. In the opinion of management, all adjustments, consisting of normal recurring adjustments necessary for the fair statement of results for the periods presented, have been included. The results of operations of any interim period are not necessarily indicative of the results of operations for the full year or any other interim period.
	The preparation of condensed consolidated financial statements requires management to make estimates and assumptions that affect the recorded amounts reported therein. A change in facts or circumstances surrounding the estimate could result in a change to estimates and impact future operating results.
	The unaudited condensed consolidated financial statements and related disclosures have been prepared with the presumption that users of the interim unaudited condensed consolidated financial statements have read or have access to the audited consolidated financial statements for the preceding fiscal year. The condensed consolidated balance sheet at December 31, 2013 has been derived from the audited financial statements at that date but does not include all the information and footnotes required by accounting principles generally accepted in the United States of America. Accordingly, these unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2013 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 6, 2014.
	The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, and reflect the elimination of intercompany accounts and transactions.
Revenue Recognition	'
	Revenue Recognition
	The Company recognizes revenue in accordance with ASC 605 “Revenue Recognition”, subtopic ASC 605-25 “Revenue with Multiple Element Arrangements” and subtopic ASC 605-28 “Revenue Recognition-Milestone Method”, which provides accounting guidance for revenue recognition for arrangements with multiple deliverables and guidance on defining the milestone and determining when the use of the milestone method of revenue recognition for research and development transactions is appropriate, respectively.
	The Company’s revenues are related to its collaboration arrangement with Merck KGaA, which was entered in February 2012. The collaboration with Merck KGaA provides for various types of payments to the Company, including non-refundable upfront license, milestone and royalty payments. The Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price is fixed or determinable, and collectability is reasonably assured. The Company also receives reimbursement for Merck KGaA’s 70% share for eligible worldwide development expenses for TH-302. Such reimbursement is reflected as a reduction of operating expenses.
	For multiple-element arrangements, each deliverable within a multiple deliverable revenue arrangement is accounted for as a separate unit of accounting if both of the following criteria are met: (1) the delivered item or items have value to the customer on a standalone basis and (2) for an arrangement that includes a general right of return relative to the delivered item(s), delivery or performance of the undelivered item(s) is considered probable and substantially in the Company’s control. The deliverables under the Merck KGaA agreement have been determined to be a single unit of accounting and as such the revenue relating to this unit of accounting will be recorded as deferred revenue and recognized ratably over the term of its estimated performance period under the agreement, which is the product development period. The Company determines the estimated performance period and it will be periodically reviewed based on the progress of the related product development plan. The effect of a change made to an estimated performance period and therefore revenue recognized ratably would occur on a prospective basis in the period that the change was made.
	Deferred revenue associated with a non-refundable payment received under a collaborative agreement for which the performance obligations are terminated will result in an immediate recognition of any remaining deferred revenue in the period that termination occurred provided that all performance obligations have been satisfied.
	The Company recognizes revenue from milestone payments when: (i) the milestone event is substantive and its achievability has substantive uncertainty at the inception of the agreement, and (ii) the Company does not have ongoing performance obligations related to the achievement of the milestone earned. Milestone payments are considered substantive if all of the following conditions are met: the milestone payment (a) is commensurate with either the Company’s performance subsequent to the inception of the arrangement to achieve the milestone or the enhancement of the value of the delivered item or items as a result of a specific outcome resulting from the Company’s performance subsequent to the inception of the arrangement to achieve the milestone, (b) relates solely to past performance, and (c) is reasonable relative to all of the deliverables and payment terms (including other potential milestone consideration) within the arrangements. See Note 3, “Collaboration Arrangements,” for analysis of milestone events deemed to be substantive or non-substantive.

Net_Loss_Per_Common_Share_Tabl

Net Loss Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Reconciliation of Numerator and Denominator	'
	A reconciliation of the numerator and denominator used in the calculation is as follows (in thousands, except per share amounts):
		Three Months Ended
		March 31,
		2014			2013
	Numerator:
	Net loss-basic	$	(7,109	)	$	(9,214	)
	Less: noncash income from change in fair value of common stock warrants		1,757			—
	Net loss-diluted	$	(8,866	)	$	(9,214	)
	Denominator:
	Weighted average common shares outstanding		59,303			56,486
	Dilutive effect of warrants		1,997			—
	Weighted-average common shares outstanding and potential dilutive common shares — diluted		61,300			56,486
	Net loss per share
	Basic	$	(0.12	)	$	(0.16	)
	Diluted	$	(0.14	)	$	(0.16	)
Warrants, Options and Purchase Rights Excluded from Computation of Diluted Net Loss Per Share	'
	The following outstanding warrants, options and purchase rights under the Company’s 2004 Employee Stock Purchase Plan were excluded from the computation of diluted net loss per share for the periods presented because including them would have had an antidilutive effect (in thousands):
		As of March 31,
		2014			2013
	Shares issuable upon exercise of warrants		4,288			11,573
	Shares issuable upon exercise of stock options		6,656			6,481
	Shares issuable related to the ESPP		31			48

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2014
Financial Liabilities Subject to Fair Value Measurements	'
	The following table sets forth the Company’s financial liabilities, related to warrants issued in the October 2009 and March 2011offerings, subject to fair value measurements as of March 31, 2014 and December 31, 2013:
		Fair Value as of			Basis of Fair Value Measurements
		March 31,
	(in thousands)	2014			Level 1			Level 2		Level 3
	October 2009 warrants	$	11,620		$	—		$	—	$	11,620
	March 2011 warrants		10,344			—			—		10,344
	Total common stock warrants	$	21,964		$	—		$	—	$	21,964
	(in thousands)	Fair Value as of			Basis of Fair Value Measurements
		December 31,
		2013			Level 1			Level 2		Level 3
	October 2009 warrants	$	11,320		$	—		$	—	$	11,320
	March 2011 warrants		12,101			—			—		12,101
	Total common stock warrants	$	23,421		$	—		$	—	$	23,421
Reconciliation of Warrant Liability Measured at Fair Value	'
	The following table is a reconciliation of the warrant liability measured at fair value using level 3 inputs (in thousands):
		Warrant Liability
	Balance at December 31, 2013	$	23,421
	Change in fair value of common stock warrants during three months ended March 31, 2014		(1,457	)
	Exercise of warrants during three months ended March 31, 2014		—
	Balance at March 31, 2014	$	21,964
October 2009 Offering [Member]	'
Outstanding Warrants Valuation Assumption	'
	The fair value of these warrants on March 31, 2014 and December 31, 2013 was determined using a Black Scholes valuation model with the following level 3 inputs:
		March 31,			December 31,
		2014			2013
	Risk-free interest rate		0.13	%		0.13	%
	Expected life (in years)		0.52			0.76
	Dividend yield		—			—
	Volatility		44	%		49	%
	Stock price	$	4.76		$	4.67
March 2011 Offering [Member]	'
Outstanding Warrants Valuation Assumption	'
	The fair value of these warrants on March 31, 2014 and December 31, 2013 was determined using a Black Scholes valuation model with the following level 3 inputs:
		March 31,			December 31,
		2014			2013
	Risk-free interest rate		0.44	%		0.78	%
	Expected life (in years)		1.96			2.21
	Dividend yield		—			—
	Volatility		55	%		88	%
	Stock price	$	4.76		$	4.67

Stock_Based_Compensation_Table

Stock Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-Based Compensation Expense	'
	Stock-based compensation expense, which consists of the compensation cost for employee stock options and the Company’s ESPP, and the value of options issued to non-employees for services rendered, was allocated to research and development and general and administrative in the unaudited condensed consolidated statements of operations as follows (in thousands):
		Three Months Ended
		March 31,
		2014			2013
	Research and development	$	671		$	534
	General and administrative		595			519
		$	1,266		$	1,053
Weighted-Average Fair Value Valuation Assumptions	'
	The fair value of employee stock options and employee purchase rights under the Company’s ESPP was estimated using the following weighted-average assumptions for the three months ended March 31, 2014 and 2013:
		Three Months Ended
		March 31,
		2014			2013
	Employee Stock Options:
	Risk-free interest rate		1.9	%		1.15	%
	Expected term (in years)		6.04			6.02
	Dividend yield		—			—
	Volatility		96	%		101	%
	Weighted-average fair value of stock options granted	$	3.84		$	4.01
		Three Months Ended
		March 31,
		2014			2013
	Employee Stock Purchase Plan (ESPP):
	Risk-free interest rate		0.18	%		0.2	%
	Expected term (in years)		1.23			1.25
	Dividend yield		—			—
	Volatility		53	%		92	%
	Weighted-average fair value of stock options granted	$	1.79		$	2.44
Stock Option Activity Under Equity Incentive Plan	'
	The following table summarizes stock option activity under the Company’s 2004 Equity Incentive Plan:
	Options	Number of			Weighted-			Weighted-		Aggregate
		Shares			Average			Average		Intrinsic
					Exercise			Remaining		Value
					Price			Contractual
								Term
	Outstanding at December 31, 2013		6,526,506		$	3.66			—		—
	Granted		175,000		$	4.97			—		—
	Exercised		(39,352	)	$	1.4			—		—
	Forfeitures		(5,937	)	$	6.18			—		—
	Outstanding at March 31, 2014		6,656,217		$	3.71			7.43	$	10,708,746
	Vested and expected to vest March 31, 2014		6,617,299		$	3.7			7.42	$	10,701,253
	Exercisable at March 31, 2014		4,077,685		$	2.93			6.78	$	9,204,627

Fair_Value_Measurements_and_Ma1

Fair Value Measurements and Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Financial Assets at Fair Value on Recurring Basis	'
	The following table sets forth the Company’s financial assets (cash equivalents and marketable securities) at fair value on a recurring basis as of March 31, 2014 and December 31, 2013:
		Fair Value as of		Basis of Fair Value Measurements
		March 31,
	(in thousands)	2014		Level 1			Level 2			Level 3
	Money market funds	$	5,001	$	5,001		$	—		$	—
	Certificates of deposit		1,464		—			1,464			—
	Corporate debt securities		55,317		—			55,317			—
	U.S. Government securities		18,990		—			18,990			—
	Municipal securities		1,618		—			1,618			—
	Commercial paper		3,996		—			3,996			—
	Total cash equivalents and marketable securities	$	86,386	$	5,001		$	81,385		$	—
		Fair Value as of		Basis of Fair Value Measurements
		December 31,
	(in thousands)	2013		Level 1			Level 2			Level 3
	Money market funds	$	4,285	$	4,285		$	—		$	—
	Certificates of deposit		1,584		—			1,584			—
	Corporate debt securities		49,019		—			49,019			—
	Government securities		21,731		—			21,731			—
	Municipal securities		2,815		—			2,815			—
	Commercial paper		2,599		—			2,599			—
	Total cash equivalents and marketable securities	$	82,033	$	4,285		$	77,748		$	—
Summary of Company's Available-for-Sale Securities	'
	The Company invests in highly-liquid, investment-grade securities. The following is a summary of the Company’s available-for-sale securities at March 31, 2014 and December 31, 2013:
	As of March 31, 2014 (in thousands):	Cost Basis		Unrealized			Unrealized			Fair
				Gain			Loss			Value
	Money market funds	$	5,001	$	—		$	—		$	5,001
	Certificates of deposit		1,464		—			—			1,464
	Corporate debt securities		55,318		15			(16	)		55,317
	U.S. Government securities		18,977		15			(2	)		18,990
	Municipal securities		1,617		1			—			1,618
	Commercial paper		3,996		—			—			3,996
			86,373		31			(18	)		86,386
	Less cash equivalents		6,743		—			—			6,743
	Total marketable securities	$	79,630	$	31		$	(18	)	$	79,643
	As of December 31, 2013 (in thousands):	Cost Basis		Unrealized			Unrealized			Fair
				Gain			Loss			Value
	Money market funds	$	4,285	$	—		$	—		$	4,285
	Certificates of deposit		1,584		—			—			1,584
	Corporate debt securities		49,001		25			(7	)		49,019
	Government securities		21,722		12			(3	)		21,731
	Municipal securities		2,814		1			—			2,815
	Commercial paper		2,599		—			—			2,599
			82,005		38			(10	)		82,033
	Less cash equivalents		7,279		—			—			7,279
	Total marketable securities	$	74,726	$	38		$	(10	)	$	74,754
Marketable Securities with Unrealized Losses	'
	The following table provides the breakdown of the marketable securities with unrealized losses at March 31, 2014 (in thousands):
		In loss position for less
		than twelve months
	As of March 31, 2014 (in thousands):	Fair Value		Unrealized Loss
	Government securities	$	6,653	$	(1	)
	Corporate debt securities		20,116		(12	)
	Total marketable securities	$	26,769	$	(13	)

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Future Rental Payments under Noncancelable Operating Leases	'
	The future rental payments required by the Company for all of its facilities under noncancelable operating leases are as follows (in thousands):
	Years Ending December 31,
	2014	$	667
	2015		918
	2016		953
	2017		238
	Thereafter		—
	Total	$	2,776

Net_Loss_Per_Common_Share_Reco

Net Loss Per Common Share - Reconciliation of Numerator and Denominator (Detail) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Numerator:	'	'
Net loss	($7,109)	($9,214)
Less: noncash income from change in fair value of common stock warrants	1,757	'
Net loss-diluted	($8,866)	($9,214)
Denominator:	'	'
Weighted average common shares outstanding	59,303	56,486
Dilutive effect of warrants	1,997	'
Weighted-average common shares outstanding and potential dilutive common shares - diluted	61,300	56,486
Net loss per share	'	'
Basic	($0.12)	($0.16)
Diluted	($0.14)	($0.16)

Net_Loss_Per_Common_Share_Warr

Net Loss Per Common Share - Warrants, Options and Purchase Rights Excluded from Computation of Diluted Net Loss Per Share (Detail)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Employee Stock Purchase Plan (ESPP) [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Shares issuable	31	48
Employee Stock Options [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Shares issuable	6,656	6,481
Warrants [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Shares issuable	4,288	11,573

Collaboration_Arrangements_Add

Collaboration Arrangements - Additional Information (Detail) (USD $)	3 Months Ended			26 Months Ended	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
			Merck KGaA [Member]	Merck KGaA [Member]	Merck KGaA [Member]	Merck KGaA [Member]	Merck KGaA [Member]
					United States [Member]	Regulatory and Development Milestones [Member]	Commercialization Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]	'	'	'	'	'	'	'
Upfront and milestone payments received to date	'	'	$12.50	$110	'	'	'
Potential future milestones	'	'	'	'	'	100	340
Merck KGaA's percentage share of worldwide development expenses	'	'	70.00%	'	'	'	'
Portion of profits that Company is eligible to participate, depending upon total sales	'	'	'	'	50.00%	'	'
Revenue recognized by the Company	3.7	2.9	'	'	'	'	'
Company earned a reimbursement for eligible worldwide development expenses	$5.90	$3.50	'	'	'	'	'

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014
In Millions, except Share data, unless otherwise specified		October 2009 Offering [Member]	October 2009 Offering [Member]	October 2009 Offering [Member]	March 2011 Offering [Member]	March 2011 Offering [Member]	March 2011 Offering [Member]
				Warrants [Member]			Warrants [Member]
Class of Warrant or Right [Line Items]	'	'	'	'	'	'	'
Warrants outstanding	8,300,000	4,287,940	4,287,940	'	3,993,783	3,993,783	'
Warrants exercise price	'	2.05	2.05	'	2.46	2.46	'
Change in fair value of common stock warrants	'	'	'	$0.30	'	'	($1.80)

Stockholders_Equity_Outstandin

Stockholders' Equity - Outstanding Warrants Valuation Assumption (Detail) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
October 2009 Offering [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Risk-free interest rate	0.13%	0.13%
Expected life (in years)	'6 months 7 days	'9 months 4 days
Dividend yield	'	'
Volatility	44.00%	49.00%
Stock price	$4.76	$4.67
March 2011 Offering [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Risk-free interest rate	0.44%	0.78%
Expected life (in years)	'1 year 11 months 16 days	'2 years 2 months 16 days
Dividend yield	'	'
Volatility	55.00%	88.00%
Stock price	$4.76	$4.67

Stockholders_Equity_Financial_

Stockholders' Equity - Financial Liabilities Subject to Fair Value Measurements (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
October 2009 Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	$11,620	$11,320
March 2011 Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	10,344	12,101
Total Common Stock Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	21,964	23,421
Basis of Fair Value Measurements, Level 1 [Member] | October 2009 Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	'	'
Basis of Fair Value Measurements, Level 1 [Member] | March 2011 Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	'	'
Basis of Fair Value Measurements, Level 1 [Member] | Total Common Stock Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	'	'
Basis of Fair Value Measurements, Level 2 [Member] | October 2009 Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	'	'
Basis of Fair Value Measurements, Level 2 [Member] | March 2011 Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	'	'
Basis of Fair Value Measurements, Level 2 [Member] | Total Common Stock Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	'	'
Basis of Fair Value Measurements, Level 3 [Member] | October 2009 Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	11,620	11,320
Basis of Fair Value Measurements, Level 3 [Member] | March 2011 Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	10,344	12,101
Basis of Fair Value Measurements, Level 3 [Member] | Total Common Stock Warrants [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Financial liabilities subject to fair value measurements	$21,964	$23,421

Stockholders_Equity_Reconcilia

Stockholders' Equity - Reconciliation of Warrant Liability Measured at Fair Value (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Equity [Abstract]	'	'
Beginning Balance	$23,421	'
Change in fair value of common stock warrants	-1,457	3,116
Exercise of warrants	'	'
Ending Balance	$21,964	'

Stock_Based_Compensation_Stock

Stock Based Compensation - Stock-Based Compensation Expense (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'
Stock-based compensation expense	$1,266	$1,053
Research and Development [Member]	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'
Stock-based compensation expense	671	534
General and Administrative [Member]	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'
Stock-based compensation expense	$595	$519

Stock_Based_Compensation_Weigh

Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Employee Stock Options [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Risk-free interest rate	1.90%	1.15%
Expected life (in years)	'6 years 15 days	'6 years 7 days
Dividend yield	'	'
Volatility	96.00%	101.00%
Weighted-average fair value of stock options granted	$3.84	$4.01
Employee Stock Purchase Plan (ESPP) [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Risk-free interest rate	0.18%	0.20%
Expected life (in years)	'1 year 2 months 23 days	'1 year 3 months
Dividend yield	'	'
Volatility	53.00%	92.00%
Weighted-average fair value of ESPP purchase rights	$1.79	$2.44

Stock_Based_Compensation_Addit

Stock Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Stock-based compensation expense	$1,266,000	$1,053,000
Non-employee stock-based compensation expense	36,000	35,000
Total intrinsic value of stock options exercised	100,000	100,000
Cash received from stock option exercises	55,000	33,000
Amount withheld by plan participants to purchase stock	100,000	'
Employee Stock-Based Compensation Expense [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Stock-based compensation expense	1,200,000	1,000,000
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans	$9,800,000	'
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition	'2 years 3 months 18 days	'
2004 Equity Incentive Plan [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Additional shares authorized for issuance	1,250,000	'
Shares authorized and available for issuance	1,256,173	'
2004 Employee Stock Purchase Plan [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Additional shares authorized for issuance	100,000	'
Shares authorized and available for issuance	261,834	'
Plan participants purchased shares	74,062	'
Average purchase price under 2004 Employee Stock Purchase Plan	$3.91	'

Stock_Based_Compensation_Stock1

Stock Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Number of Shares, Outstanding Beginning Balance	6,526,506
Number of Shares, Granted	175,000
Number of Shares, Exercised	-39,352
Number of Shares, Forfeitures	-5,937
Number of Shares, Outstanding Ending Balance	6,656,217
Number of Shares, Vested and expected to vest	6,617,299
Number of Shares, Exercisable	4,077,685
Weighted-Average Exercise Price, Outstanding at beginning of period	$3.66
Weighted-Average Exercise Price, Granted	$4.97
Weighted-Average Exercise Price, Exercised	$1.40
Weighted-Average Exercise Price, Forfeitures	$6.18
Weighted-Average Exercise Price, Outstanding at end of period	$3.71
Weighted-Average Exercise Price, Vested and expected to vest	$3.70
Weighted-Average Exercise Price, Exercisable	$2.93
Weighted-Average Remaining Contractual Term, Outstanding	'7 years 5 months 5 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	'7 years 5 months 1 day
Weighted-Average Remaining Contractual Term, Exercisable	'6 years 9 months 11 days
Aggregate Intrinsic Value, Outstanding	$10,708,746
Aggregate Intrinsic Value, Vested and expected to vest	10,701,253
Aggregate Intrinsic Value, Exercisable	$9,204,627

Fair_Value_Measurements_and_Ma2

Fair Value Measurements and Marketable Securities - Financial Assets at Fair Value on Recurring Basis (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	$86,386	$82,033
Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	5,001	4,285
Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	1,464	1,584
Corporate Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	55,317	49,019
U. S. Government Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	18,990	21,731
Municipal Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	1,618	2,815
Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	3,996	2,599
Basis of Fair Value Measurements, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	5,001	4,285
Basis of Fair Value Measurements, Level 1 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	5,001	4,285
Basis of Fair Value Measurements, Level 1 [Member] | Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 1 [Member] | Corporate Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 1 [Member] | U. S. Government Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 1 [Member] | Municipal Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 1 [Member] | Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	81,385	77,748
Basis of Fair Value Measurements, Level 2 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 2 [Member] | Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	1,464	1,584
Basis of Fair Value Measurements, Level 2 [Member] | Corporate Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	55,317	49,019
Basis of Fair Value Measurements, Level 2 [Member] | U. S. Government Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	18,990	21,731
Basis of Fair Value Measurements, Level 2 [Member] | Municipal Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	1,618	2,815
Basis of Fair Value Measurements, Level 2 [Member] | Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	3,996	2,599
Basis of Fair Value Measurements, Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 3 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 3 [Member] | Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 3 [Member] | Corporate Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 3 [Member] | U. S. Government Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 3 [Member] | Municipal Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'
Basis of Fair Value Measurements, Level 3 [Member] | Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total cash equivalents and marketable securities	'	'

Fair_Value_Measurements_and_Ma3

Fair Value Measurements and Marketable Securities - Summary of Company's Available-for-Sale Securities (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Cost Basis	$79,630	$74,726
Unrealized Gain	31	38
Unrealized Loss	-18	-10
Fair Value	79,643	74,754
Money Market Funds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cost Basis	5,001	4,285
Unrealized Gain	'	'
Unrealized Loss	'	'
Fair Value	5,001	4,285
Certificates of Deposit [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cost Basis	1,464	1,584
Unrealized Gain	'	'
Unrealized Loss	'	'
Fair Value	1,464	1,584
Corporate Debt Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cost Basis	55,318	49,001
Unrealized Gain	15	25
Unrealized Loss	-16	-7
Fair Value	55,317	49,019
U. S. Government Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cost Basis	18,977	21,722
Unrealized Gain	15	12
Unrealized Loss	-2	-3
Fair Value	18,990	21,731
Municipal Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cost Basis	1,617	2,814
Unrealized Gain	1	1
Unrealized Loss	'	'
Fair Value	1,618	2,815
Commercial Paper [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cost Basis	3,996	2,599
Unrealized Gain	'	'
Unrealized Loss	'	'
Fair Value	3,996	2,599
Marketable Securities Including Cash Equivalents [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cost Basis	86,373	82,005
Unrealized Gain	31	38
Unrealized Loss	-18	-10
Fair Value	86,386	82,033
Less Cash Equivalents [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cost Basis	6,743	7,279
Unrealized Gain	'	'
Unrealized Loss	'	'
Fair Value	$6,743	$7,279

Fair_Value_Measurements_and_Ma4

Fair Value Measurements and Marketable Securities - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Schedule of Available-for-sale Securities [Line Items]	'	'
Realized gain or losses	$0	$0
Weighted average maturity for available for sale securities	'6 years 9 months 18 days	'
Shares of common stock to be purchased with warrants	8,300,000	'
Maximum [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available for sale securities, longest maturity date	'2015-08	'

Fair_Value_Measurements_and_Ma5

Fair Value Measurements and Marketable Securities - Marketable Securities with Unrealized Losses (Detail) (USD $)	Mar. 31, 2014
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'
Marketable securities, in loss position for less than twelve months, Fair Value	$26,769
Marketable securities, in loss position for less than twelve months, Unrealized Loss	-13
U. S. Government Securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Marketable securities, in loss position for less than twelve months, Fair Value	6,653
Marketable securities, in loss position for less than twelve months, Unrealized Loss	-1
Corporate Debt Securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Marketable securities, in loss position for less than twelve months, Fair Value	20,116
Marketable securities, in loss position for less than twelve months, Unrealized Loss	($12)

Commitments_and_Contingencies_1

Commitments and Contingencies - Future Rental Payments under Noncancelable Operating Leases (Detail) (USD $)	Mar. 31, 2014
In Thousands, unless otherwise specified
Leases [Abstract]	'
2014	$667
2015	918
2016	953
2017	238
Thereafter	'
Total	$2,776