Molecular Templates (MTEM) 10-Q 30 Apr 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 24, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	THLD
Entity Registrant Name	THRESHOLD PHARMACEUTICALS INC
Entity Central Index Key	1183765
Current Fiscal Year End Date	-19
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		71,334,362

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$21,063	$8,391
Marketable securities, current	57,822	50,209
Collaboration receivable	1,993	7,248
Prepaid expenses and other current assets	1,226	832
Total current assets	82,104	66,680
Marketable securities, non-current	4,201
Property and equipment, net	503	557
Other assets	1,201	1,159
Total assets	88,009	68,396
Current liabilities:
Accounts payable	1,809	2,074
Accrued clinical and development expenses	8,248	5,998
Accrued liabilities	4,196	3,180
Deferred revenue, current	14,722	14,722
Total current liabilities	28,975	25,974
Warrant liability	20,185	3,961
Deferred revenue, non-current	58,513	62,194
Deferred rent	225	243
Total liabilities	107,898	92,372
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: 71,334,362 shares at March 31, 2015 and 62,898,233 shares at December 31, 2014	71	63
Additional paid-in capital	364,471	349,236
Accumulated other comprehensive gain (loss)	-15	-13
Accumulated deficit	-384,416	-373,262
Total stockholders’ equity (deficit)	-19,889	-23,976
Total liabilities and stockholders’ equity (deficit)	$88,009	$68,396

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
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	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	71,334,362	62,898,233
Common stock, shares outstanding	71,334,362	62,898,233

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, 2015	Mar. 31, 2014
Income Statement [Abstract]
Revenue	$3,681	$3,681
Operating expenses:
Research and development	10,680	9,653
General and administrative	2,616	2,634
Total operating expenses	13,296	12,287
Loss from operations	-9,615	-8,606
Interest income (expense), net	33	40
Other income (expense), net	-1,572	1,457
Net loss	-11,154	-7,109
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	-2	-15
Comprehensive loss	($11,156)	($7,124)
Net loss per common share:
Basic	($0.17)	($0.12)
Diluted	($0.17)	($0.14)
Weighted average number of shares used in per common share calculations:
Basic	66,732	59,303
Diluted	66,732	61,300

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net loss	($11,154)	($7,109)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	239	390
Stock-based compensation expense	1,421	1,266
Change in common stock warrant value	1,532	-1,457
Changes in operating assets and liabilities:
Collaboration receivable	5,255	12,902
Prepaid expenses and other assets	-436	835
Accounts payable	-265	2,317
Accrued clinical and development expenses	2,250	-1,952
Accrued liabilities	1,016	801
Deferred rent	-18	47
Deferred revenue	-3,681	-3,681
Net cash (used in) provided by operating activities	-3,841	4,359
Cash flows from investing activities:
Acquisition of property and equipment	-38	-24
Acquisition of marketable securities	-32,899	-22,349
Proceeds from sale of marketable securities	1,997	3,109
Proceeds from maturities of marketable securities	18,939	14,024
Net cash used in investing activities	-12,001	-5,240
Cash flows from financing activities:
Proceeds from issuance of common stock and warrants, net of offering expenses	28,514	345
Net cash provided by financing activities	28,514	345
Net increase (decrease) in cash and cash equivalents	12,672	-536
Cash and cash equivalents, beginning of period	8,391	7,279
Cash and cash equivalents, end of period	$21,063	$6,743

Organization_and_Summary_of_Si

Organization and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
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, 2014 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, 2014 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 3, 2015.
	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 provide 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 evofosfamide (formerly 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 is 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 is periodically reviewed based on the progress of the related product development plan. The effect of a change made to an estimated performance period, and the related ratably recognized revenue, 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, 2015
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,
		2015			2014
	Numerator:
	Net loss - basic	$	(11,154	)	$	(7,109	)
	Less: noncash income from change in fair		—			1,757
	value of common stock warrants
	Net loss - diluted		(11,154	)		(8,866	)
	Denominator:
	Weighted average common shares outstanding		66,732			59,303
	Dilutive effect of warrants		0			1,997
	Weighted-average common shares outstanding		66,732			61,300
	and dilutive potential common shares —
	diluted
	Net loss per share
	Basic	$	(0.17	)	$	(0.12	)
	Diluted	$	(0.17	)	$	(0.14	)
	The following outstanding warrants, options and purchase rights under the Company’s 2004 Employee Stock Purchase Plan (“2004 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):
		Three Months Ended
		March 31,
		2015			2014
	Shares issuable upon exercise of warrants		12,146			4,288
	Shares issuable upon exercise of stock options		9,993			6,656
	Shares issuable related to the 2004 Purchase Plan		29			31

Collaboration_Arrangements

Collaboration Arrangements	3 Months Ended
	Mar. 31, 2015
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 evofosfamide, the Company’s small molecule hypoxia-targeted drug candidate. 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 evofosfamide in the United States. To date, the Company has received $110 million in upfront and milestone payments. 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 or was not commensurate with Company’s performance subsequent to the inception of the arrangement to achieve the milestone. 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 evofosfamide in the soft tissue sarcoma indication. The Company and Merck KGaA will jointly develop evofosfamide in all other cancer indications being pursued. Merck KGaA will pay 70% of worldwide development expenses for evofosfamide. Subject to FDA approval in the United States, Merck KGaA will initially be responsible for commercialization of evofosfamide 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 evofosfamide in the United States. Additionally, the Company retains the option to co-commercialize evofosfamide 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 evofosfamide 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 evofosfamide in such country or ten years following the commercial launch of a product containing evofosfamide 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 evofosfamide 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 of revenue during the three months ended March 31, 2015 compared to $3.7 million of revenue during the three months ended March 31, 2014. The Company will periodically review and, if necessary, revise the estimated periods of performance of its collaboration. The Company also earned $2.0 million reimbursement for eligible worldwide development expenses for evofosfamide from Merck KGaA during the three months ended March 31, 2015 compared to $5.9 million during the three months ended March 31, 2014. Such earned reimbursement has been reflected as a reduction of research and development 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 evofosfamide 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_Deficit

Stockholders' Equity (Deficit)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Stockholders' Equity (Deficit)	NOTE 4 — STOCKHOLDERS’ EQUITY (DEFICIT)
	Common Stock
	On February 18, 2015, the Company completed an underwritten public offering of 8.3 million shares of its common stock and accompanying warrants to purchase up to 8.3 million shares of common stock. Net proceeds from the sale of common stock and
	accompanying warrants, excluding the proceeds, if any, from the exercise of the warrants issued in the offering, were approximately $28.1 million after deducting the underwriting discount and offering expenses payable by the Company.
	The warrants issued in the February 2015 offering carry an initial exercise price of $10.86 per share and are exercisable commencing with the date six months following the issuance date and continuing through the date that is five years from the issuance date. On the 30th trading day following the earlier of (i) the date two years from the issuance date or (ii) the later to occur of (a) the date on which top-line efficacy data from the Company’s Phase 3 clinical trial of evofosfamide plus doxorubicin versus doxorubicin alone in patients with locally advanced unresectable or metastatic soft tissue sarcoma is publicly announced by the Company or (b) the date on which top-line efficacy data from the Phase 3 MAESTRO clinical trial of evofosfamide in combination with gemcitabine in patients with previously untreated, locally advanced unresectable or metastatic pancreatic adenocarcinoma is publicly announced by the Company, the warrant exercise price will be adjusted to equal the average of the volume-weighted average price of the Company’s common stock for each of the 20 trading days immediately preceding the applicable date, provided that in no event will the exercise price be adjusted above $10.86 or below $3.62. After the date of foregoing adjustment to the warrant exercise price (such date, the “Adjustment Date”), the exercise price of the warrants will then be subject to price-based anti-dilution protection such that to the extent the Company’s issues and sells any shares of common stock, or any securities convertible or exchangeable for shares of common stock (in each case subject to certain exceptions), at a price per share below the warrant exercise price then in effect, the warrant exercise price will be adjusted downward to equal the price at which such securities are issued and sold by the Company (but in no event will the warrant exercise price be reduced below $3.62 per share). The exercise price of the warrants is also subject to adjustment in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting the Company’s common stock. The warrants must be exercised for cash, except that if the Company fails to maintain an effective registration statement covering the exercise of the warrants, the warrants may be exercised on a net, or cashless basis. In addition, subject to the satisfaction of certain conditions set forth in the warrants, at the Company’s option, the Company has the right to force the holders of the warrants to exercise their warrants in full if the volume-weighted average price of the Company’s common stock for any 20 consecutive trading-day period beginning after the 90th day following the Adjustment Date exceeds $18.00 per share.
	Common Stock Warrant Valuation
	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 requires 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 March 31, 2015 and February 18, 2015, the Company had warrants outstanding to purchase 8,300,000 shares of common stock, respectively, having an initial exercise price of $10.86 per share, which warrants were issued by the Company in the February 2015 offering. The fair value of these warrants on March 31, 2015 and February 18, 2015 was determined using a Monte-Carlo simulation model that accounted for the estimated changes to exercise price between the issuance date and the Adjustment Date along with the following key level 3 inputs:
		March 31,			18-Feb-15
		2015
	Risk-free interest rate		1.34	%		1.52	%
	Expected life (in years)		4.89			5
	Dividend yield		—			—
	Volatility		50	%		50	%
	Stock price	$	4.06		$	4.26
	On February 18, 2015, the Company determined the fair value of the February 2015 warrants to be $14.7 million and classified that amount of the net proceeds from the February 2015 offering to warrant liability. During the three months ended March 31, 2015, the change in fair value of $1.2 million of noncash income related to the February 2015 warrants was recorded as other income (expense) in the Company’s consolidated statement of operations.
	At both March 31, 2015 and December 31, 2014, the Company also had warrants outstanding to purchase 3,846,165 shares of common stock, having an exercise price of $2.46 per share, which warrants were initially issued by the Company in an underwritten public offering in March 2011. The fair value of these warrants on March 31, 2015 and December 31, 2014 was determined using a Black Scholes valuation model with the following level 3 inputs:
		March 31,			December 31,
		2015			2014
	Risk-free interest rate		0.26	%		0.67	%
	Expected life (in years)		0.96			1.21
	Dividend yield		—			—
	Volatility		52	%		49	%
	Stock price	$	4.06		$	3.18
	During the three months ended March 31, 2015, the change in fair value of $2.7 million of noncash expense related to the March 2011 warrants was recorded as other income (expense) in the Company’s consolidated statement of operations.
	The following table sets forth the Company’s financial liabilities, related to warrants issued in the February 2015 and March 2011 offerings, subject to fair value measurements as of March 31, 2015 and December 31, 2014:
		Fair Value as of March 31, 2015			Basis of Fair Value Measurements
	(in thousands)				Level 1			Level 2		Level 3
	February 2015 warrants	$	13,493		$	—		$	—	$	13,493
	March 2011 warrants		6,692			—			—		6,692
	Total common stock warrants	$	20,185		$	—		$	—	$	20,185
		Fair Value as of December 31, 2014			Basis of Fair Value Measurements
	(in thousands)				Level 1			Level 2		Level 3
	March 2011 warrants		3,961			—			—		3,961
	Total common stock warrants	$	3,961		$	—		$	—	$	3,961
	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, 2014	$	3,961
	Initial fair value of common stock warrants related to February 2015 offering		14,692
	Change in fair value of common stock warrants during three months ended March 31, 2015		1,532
	Exercise of warrants during three months ended March 31, 2015		—
	Balance at March 31, 2015	$	20,185

Stock_Based_Compensation

Stock Based Compensation	3 Months Ended
	Mar. 31, 2015
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 2004 Purchase Plan, 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 consolidated statements of operations for the three months ended March 31, 2015 and 2014 as follows (in thousands):
		Three Months Ended
		March 31,
		2015				2014
	Amortization of stock-based compensation:
	Research and development	$	817			$	671
	General and administrative		604				595
		$	1,421			$	1,266
	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 2004 Purchase Plan was estimated using the following weighted-average assumptions for the three months ended March 31, 2015 and 2014:
		Three Months Ended
		March 31,
		2015				2014
	Employee Stock Options:
	Risk-free interest rate		1.7	%			1.9	%
	Expected term (in years)		6.02				6.04
	Dividend yield		—				—
	Volatility		83	%			96	%
	Weighted-average fair value of stock options granted	$	3.13			$	3.84
		Three Months Ended
		March 31,
		2015				2014
	Employee Stock Purchase Plan (ESPP):
	Risk-free interest rate		0.38	%			0.18	%
	Expected term (in years)		1.25				1.23
	Dividend yield		—				—
	Volatility		51	%			53	%
	Weighted-average fair value of ESPP purchase rights	$	1.59			$	1.79
	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 $1.4 million and $1.2 million of stock-based compensation expense related to stock options and purchase rights, under the Company’s equity incentive plans and 2004 Purchase Plan, for the three months ended March 31, 2015 and 2014, respectively. As of March 31, 2015, the total unrecognized compensation cost related to unvested stock-based awards granted to employees under the Company’s equity incentive plans was approximately $14.6 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 2.87 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 $24,000 and $36,000 for the three months ended March 31, 2015 and 2014, respectively.
	Equity Incentive Plans
	Equity Incentive Plans At March 31, 2015, 2,537,763 shares were authorized and available for issuance under the 2014 Equity Incentive Plan.
	The following table summarizes stock option activity under the Company’s equity incentive plans:
	Options		Number of				Weighted-		Weighted-		Aggregate
			Shares				Average		Average		Intrinsic
							Exercise		Remaining		Value
							Price		Contractual
									Term
	Outstanding at December 31, 2014			8,168,942			$	3.69		—		—
	Granted			1,911,500			$	4.42		—		—
	Exercised			(61,456	)		$	1.83		—		—
	Forfeitures			(25,770	)		$	5.15		—		—
	Outstanding at March 31, 2015			9,993,216			$	3.83		7.53	$	8,802,913
	Vested and expected to vest March 31, 2015			9,878,829			$	3.83		7.51	$	8,787,468
	Exercisable at March 31, 2015			5,521,561			$	3.33		6.31	$	8,010,861
	The total intrinsic value of stock options exercised during the three months ended March 31, 2015 and 2014 were $0.2 million and $0.1 million, respectively, as determined at the date of the option exercise. Cash received from stock option exercises was $0.1 million and $0.1 million for the three months ended March 31, 2015 and 2014, 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, 2015, an additional 100,000 shares was authorized for issuance under the 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, 2015, plan participants had purchased 74,673 shares at an average purchase price of $3.43 for total cash proceeds of $0.3 million.  At March 31, 2015, 206,231 shares were authorized and available for issuance under the 2004 Purchase Plan.

Fair_Value_Measurements_and_Ma

Fair Value Measurements and Marketable Securities	3 Months Ended
	Mar. 31, 2015
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 accordance with 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, 2015 and December 31, 2014:
		Fair Value as of March 31, 2015		Basis of Fair Value Measurements
	(in thousands)			Level 1			Level 2			Level 3
	Money market funds	$	10,366	$	10,366		$	—		$	—
	Certificates of deposit		1,475		—			1,475			—
	Corporate debt securities		31,935		—			31,935			—
	Government securities		24,021		—			24,021			—
	Commercial paper		14,240		—			14,240			—
	Total cash equivalents and marketable securities	$	82,037	$	10,366		$	71,671		$	—
		Fair Value as of December 31, 2014		Basis of Fair Value Measurements
	(in thousands)			Level 1			Level 2			Level 3
	Money market funds	$	3,369	$	3,369		$	—		$	—
	Certificates of deposit		2,505		—			2,505			—
	Corporate debt securities		28,081		—			28,081			—
	Government securities		19,123		—			19,123			—
	Commercial paper		5,499		—			5,499			—
	Total cash equivalents and marketable securities	$	58,577	$	3,369		$	55,208		$	—
	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, 2015 and December 31, 2014:
	As of March 31, 2015 (in thousands):	Cost Basis		Unrealized			Unrealized			Fair
				Gain			Loss			Value
	Money market funds	$	10,366	$	—		$	—		$	10,366
	Certificates of deposit		1,475		—			—			1,475
	Corporate debt securities		31,950		4			(19	)		31,935
	U.S. Government securities		24,021		2			(2	)		24,021
	Commercial paper		14,240		—			—			14,240
			82,052		6			(21	)		82,037
	Less cash equivalents		20,014		—			—			20,014
	Total marketable securities	$	62,038	$	6		$	(21	)	$	62,023
	As of December 31, 2014 (in thousands):	Cost Basis		Unrealized			Unrealized			Fair
				Gain			Loss			Value
	Money market funds	$	3,369	$	—		$	—		$	3,369
	Certificates of deposit		2,505		—			—			2,505
	Corporate debt securities		28,094		1			(14	)		28,081
	U.S. Government securities		19,123		3			(3	)		19,123
	Commercial paper		5,499		—			—			5,499
			58,590		4			(17	)		58,577
	Less cash equivalents		8,368		—			—			8,368
	Total marketable securities	$	50,222	$	4		$	(17	)	$	50,209
	There were no realized gains or losses in the three months ended March 31, 2015 and 2014.
	As of March 31, 2015, the weighted average maturity for the Company’s available for sale securities was 4.9 months, with the longest maturity being May 2016.
	The following table provides the breakdown of the marketable securities with unrealized losses at March 31, 2015 (in thousands):
		In loss position for less
		than twelve months
	As of March 31, 2015 (in thousands):	Fair		Unrealized
		Value		Loss
	U.S. Government securities	$	12,170	$	(2	)
	Corporate debt securities		22,011		(19	)
	Total marketable securities	$	34,181	$	(21	)
	The Company determined the fair value of the liability associated with its February 2015 and March 2011 warrants to purchase in aggregate 12.1 million shares of outstanding common stock using a Monte Carlo Simulation Model and a Black-Scholes Model, respectively. See detailed discussion in Note 4 — Stockholders’ Equity (Deficit).

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
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,
	2015	$	691
	2016		953
	2017		238
	Thereafter		—
	Total	$	1,882
	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, 2015.
	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, 2015
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, 2014 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, 2014 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 3, 2015.
	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 provide 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 evofosfamide (formerly 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 is 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 is periodically reviewed based on the progress of the related product development plan. The effect of a change made to an estimated performance period, and the related ratably recognized revenue, 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, 2015
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,
		2015			2014
	Numerator:
	Net loss - basic	$	(11,154	)	$	(7,109	)
	Less: noncash income from change in fair		—			1,757
	value of common stock warrants
	Net loss - diluted		(11,154	)		(8,866	)
	Denominator:
	Weighted average common shares outstanding		66,732			59,303
	Dilutive effect of warrants		0			1,997
	Weighted-average common shares outstanding		66,732			61,300
	and dilutive potential common shares —
	diluted
	Net loss per share
	Basic	$	(0.17	)	$	(0.12	)
	Diluted	$	(0.17	)	$	(0.14	)
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 (“2004 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):
		Three Months Ended
		March 31,
		2015			2014
	Shares issuable upon exercise of warrants		12,146			4,288
	Shares issuable upon exercise of stock options		9,993			6,656
	Shares issuable related to the 2004 Purchase Plan		29			31

Stockholders_Equity_Deficit_Ta

Stockholders' Equity (Deficit) (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial Liabilities Subject to Fair Value Measurements	The following table sets forth the Company’s financial liabilities, related to warrants issued in the February 2015 and March 2011 offerings, subject to fair value measurements as of March 31, 2015 and December 31, 2014:
		Fair Value as of March 31, 2015			Basis of Fair Value Measurements
	(in thousands)				Level 1			Level 2		Level 3
	February 2015 warrants	$	13,493		$	—		$	—	$	13,493
	March 2011 warrants		6,692			—			—		6,692
	Total common stock warrants	$	20,185		$	—		$	—	$	20,185
		Fair Value as of December 31, 2014			Basis of Fair Value Measurements
	(in thousands)				Level 1			Level 2		Level 3
	March 2011 warrants		3,961			—			—		3,961
	Total common stock warrants	$	3,961		$	—		$	—	$	3,961
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, 2014	$	3,961
	Initial fair value of common stock warrants related to February 2015 offering		14,692
	Change in fair value of common stock warrants during three months ended March 31, 2015		1,532
	Exercise of warrants during three months ended March 31, 2015		—
	Balance at March 31, 2015	$	20,185
February 2015 Offering
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Outstanding Warrants Valuation Assumption	The fair value of these warrants on March 31, 2015 and February 18, 2015 was determined using a Monte-Carlo simulation model that accounted for the estimated changes to exercise price between the issuance date and the Adjustment Date along with the following key level 3 inputs:
		March 31,			18-Feb-15
		2015
	Risk-free interest rate		1.34	%		1.52	%
	Expected life (in years)		4.89			5
	Dividend yield		—			—
	Volatility		50	%		50	%
	Stock price	$	4.06		$	4.26
March 2011 Offering
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Outstanding Warrants Valuation Assumption	The fair value of these warrants on March 31, 2015 and December 31, 2014 was determined using a Black Scholes valuation model with the following level 3 inputs:
		March 31,			December 31,
		2015			2014
	Risk-free interest rate		0.26	%		0.67	%
	Expected life (in years)		0.96			1.21
	Dividend yield		—			—
	Volatility		52	%		49	%
	Stock price	$	4.06		$	3.18

Stock_Based_Compensation_Table

Stock Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Expense	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 2004 Purchase Plan, 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 consolidated statements of operations for the three months ended March 31, 2015 and 2014 as follows (in thousands):
		Three Months Ended
		March 31,
		2015				2014
	Amortization of stock-based compensation:
	Research and development	$	817			$	671
	General and administrative		604				595
		$	1,421			$	1,266
Weighted-Average Fair Value Valuation Assumptions	The fair value of employee stock options and employee purchase rights under the 2004 Purchase Plan was estimated using the following weighted-average assumptions for the three months ended March 31, 2015 and 2014:
		Three Months Ended
		March 31,
		2015				2014
	Employee Stock Options:
	Risk-free interest rate		1.7	%			1.9	%
	Expected term (in years)		6.02				6.04
	Dividend yield		—				—
	Volatility		83	%			96	%
	Weighted-average fair value of stock options granted	$	3.13			$	3.84
		Three Months Ended
		March 31,
		2015				2014
	Employee Stock Purchase Plan (ESPP):
	Risk-free interest rate		0.38	%			0.18	%
	Expected term (in years)		1.25				1.23
	Dividend yield		—				—
	Volatility		51	%			53	%
	Weighted-average fair value of ESPP purchase rights	$	1.59			$	1.79
Stock Option Activity Under Equity Incentive Plan	The following table summarizes stock option activity under the Company’s equity incentive plans:
	Options		Number of				Weighted-		Weighted-		Aggregate
			Shares				Average		Average		Intrinsic
							Exercise		Remaining		Value
							Price		Contractual
									Term
	Outstanding at December 31, 2014			8,168,942			$	3.69		—		—
	Granted			1,911,500			$	4.42		—		—
	Exercised			(61,456	)		$	1.83		—		—
	Forfeitures			(25,770	)		$	5.15		—		—
	Outstanding at March 31, 2015			9,993,216			$	3.83		7.53	$	8,802,913
	Vested and expected to vest March 31, 2015			9,878,829			$	3.83		7.51	$	8,787,468
	Exercisable at March 31, 2015			5,521,561			$	3.33		6.31	$	8,010,861

Fair_Value_Measurements_and_Ma1

Fair Value Measurements and Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2015
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, 2015 and December 31, 2014:
		Fair Value as of March 31, 2015		Basis of Fair Value Measurements
	(in thousands)			Level 1			Level 2			Level 3
	Money market funds	$	10,366	$	10,366		$	—		$	—
	Certificates of deposit		1,475		—			1,475			—
	Corporate debt securities		31,935		—			31,935			—
	Government securities		24,021		—			24,021			—
	Commercial paper		14,240		—			14,240			—
	Total cash equivalents and marketable securities	$	82,037	$	10,366		$	71,671		$	—
		Fair Value as of December 31, 2014		Basis of Fair Value Measurements
	(in thousands)			Level 1			Level 2			Level 3
	Money market funds	$	3,369	$	3,369		$	—		$	—
	Certificates of deposit		2,505		—			2,505			—
	Corporate debt securities		28,081		—			28,081			—
	Government securities		19,123		—			19,123			—
	Commercial paper		5,499		—			5,499			—
	Total cash equivalents and marketable securities	$	58,577	$	3,369		$	55,208		$	—
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, 2015 and December 31, 2014:
	As of March 31, 2015 (in thousands):	Cost Basis		Unrealized			Unrealized			Fair
				Gain			Loss			Value
	Money market funds	$	10,366	$	—		$	—		$	10,366
	Certificates of deposit		1,475		—			—			1,475
	Corporate debt securities		31,950		4			(19	)		31,935
	U.S. Government securities		24,021		2			(2	)		24,021
	Commercial paper		14,240		—			—			14,240
			82,052		6			(21	)		82,037
	Less cash equivalents		20,014		—			—			20,014
	Total marketable securities	$	62,038	$	6		$	(21	)	$	62,023
	As of December 31, 2014 (in thousands):	Cost Basis		Unrealized			Unrealized			Fair
				Gain			Loss			Value
	Money market funds	$	3,369	$	—		$	—		$	3,369
	Certificates of deposit		2,505		—			—			2,505
	Corporate debt securities		28,094		1			(14	)		28,081
	U.S. Government securities		19,123		3			(3	)		19,123
	Commercial paper		5,499		—			—			5,499
			58,590		4			(17	)		58,577
	Less cash equivalents		8,368		—			—			8,368
	Total marketable securities	$	50,222	$	4		$	(17	)	$	50,209
Marketable Securities with Unrealized Losses	The following table provides the breakdown of the marketable securities with unrealized losses at March 31, 2015 (in thousands):
		In loss position for less
		than twelve months
	As of March 31, 2015 (in thousands):	Fair		Unrealized
		Value		Loss
	U.S. Government securities	$	12,170	$	(2	)
	Corporate debt securities		22,011		(19	)
	Total marketable securities	$	34,181	$	(21	)

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2015
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,
	2015	$	691
	2016		953
	2017		238
	Thereafter		—
	Total	$	1,882

Organization_and_Summary_of_Si2

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) (Merck KGaA)	3 Months Ended
	Mar. 31, 2015
Merck KGaA
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage share of eligible worldwide development expenses	70.00%

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, 2015	Mar. 31, 2014
Numerator:
Net loss - basic	($11,154)	($7,109)
Less: noncash income from change in fair value of common stock warrants		1,757
Net loss - diluted	($11,154)	($8,866)
Denominator:
Weighted average common shares outstanding	66,732	59,303
Dilutive effect of warrants	0	1,997
Weighted-average common shares outstanding and dilutive potential common shares — diluted	66,732	61,300
Net loss per share
Basic	($0.17)	($0.12)
Diluted	($0.17)	($0.14)

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, 2015	Mar. 31, 2014
Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	12,146	4,288
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	9,993	6,656
2004 Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	29	31

Collaboration_Arrangements_Add

Collaboration Arrangements - Additional Information (Detail) (Merck KGaA, USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront and milestone payments received to date	$110
Merck KGaA's percentage share of worldwide development expenses	70.00%
Revenue recognized by the Company	3.7	3.7
Company received a reimbursement for eligible worldwide development expenses	2	5.9
United States
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Portion of profits that Company is eligible to participate, depending upon total sales	50.00%
Regulatory and Development Milestones | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential future milestones	100
Commercialization Milestones | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential future milestones	$340

Stockholders_Equity_Deficit_Ad

Stockholders' Equity (Deficit) - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended
	Feb. 18, 2015	Feb. 28, 2015	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Class Of Warrant Or Right [Line Items]
Common stock sold, shares	8,300,000
Warrants to purchase shares of common stock	8,300,000
Proceeds from issuance of common stock and warrants, net of offering expenses	$28,100,000		$28,514,000	$345,000
Initial exercise price of the warrants		$10.86
Maximum exercise price of warrants after adjustment date		$10.86
Minimum exercise price of warrants after adjustment date		$3.62
Term of warrant		5 years
Company can force exercise of warrant if 20 day VWAP price exceeds		$18
February 2015 Offering
Class Of Warrant Or Right [Line Items]
Warrants outstanding	8,300,000		8,300,000
Warrant exercise price	$10.86		$10.86
February 2015 Offering | Warrants
Class Of Warrant Or Right [Line Items]
Initial fair value of warrants at issuance date classified as warrant liability	14,700,000
Change in fair value of common stock warrants			1,200,000
March 2011 Offering
Class Of Warrant Or Right [Line Items]
Warrants outstanding			3,846,165		3,846,165
Warrant exercise price			$2.46		$2.46
March 2011 Offering | Warrants
Class Of Warrant Or Right [Line Items]
Change in fair value of common stock warrants			$2,700,000

Stockholders_Equity_Deficit_Ou

Stockholders' Equity (Deficit) - Outstanding Warrants Valuation Assumption (Detail) (USD $)	3 Months Ended	12 Months Ended	0 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Feb. 18, 2015
March 2011 Offering
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Risk-free interest rate	0.26%	0.67%
Expected life (in years)	11 months 16 days	1 year 2 months 16 days
Dividend yield	0.00%	0.00%
Volatility	52.00%	49.00%
Stock price	$4.06	$3.18
February 2015 Offering
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Risk-free interest rate	1.34%		1.52%
Expected life (in years)	4 years 10 months 21 days		5 years
Dividend yield	0.00%
Volatility	50.00%		50.00%
Stock price	$4.06		$4.26

Stockholders_Equity_Deficit_Fi

Stockholders' Equity (Deficit) - Financial Liabilities Subject to Fair Value Measurements (Detail) (Warrants, USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	$20,185	$3,961
Basis of Fair Value Measurements, Level 3
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	20,185	3,961
February 2015 Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	13,493
February 2015 Warrants | Basis of Fair Value Measurements, Level 3
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	13,493
March 2011 Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	6,692	3,961
March 2011 Warrants | Basis of Fair Value Measurements, Level 3
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	$6,692	$3,961

Stockholders_Equity_Deficit_Re

Stockholders' Equity (Deficit) - Reconciliation of Warrant Liability Measured at Fair Value (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Equity [Abstract]
Beginning Balance	$3,961
Initial fair value of common stock warrants related to February 2015 offering	14,692
Change in common stock warrant value	1,532	-1,457
Ending Balance	$20,185

Stock_Based_Compensation_Stock

Stock Based Compensation - Stock-Based Compensation Expense (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$1,421	$1,266
Research and Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	817	671
General and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$604	$595

Stock_Based_Compensation_Weigh

Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	1.70%	1.90%
Expected term (in years)	6 years 7 days	6 years 15 days
Volatility	83.00%	96.00%
Weighted-average fair value of stock options granted	$3.13	$3.84
Employee Stock Purchase Plan (ESPP)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.38%	0.18%
Expected term (in years)	1 year 3 months	1 year 2 months 23 days
Volatility	51.00%	53.00%
Weighted-average fair value of ESPP purchase rights	$1.59	$1.79

Stock_Based_Compensation_Addit

Stock Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Jan. 01, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$1,421,000	$1,266,000
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans	14,600,000
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition	2 years 10 months 13 days	2 years 10 months 13 days
Non-employee stock-based compensation expense	24,000	36,000
Total intrinsic value of stock options exercised	200,000	100,000
Cash received from stock option exercises	100,000	100,000
Tax benefit realized upon exercise of option	0	0
2014 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Remaining shares available for issuance	2,537,763
2004 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Remaining shares available for issuance	206,231
Additional shares authorized for issuance			100,000
Plan participants purchased shares	74,673
Average purchase price under 2004 Employee Stock Purchase Plan	$3.43
Cash proceeds	$300,000

Stock_Based_Compensation_Stock1

Stock Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding Beginning Balance	8,168,942
Number of Shares, Granted	1,911,500
Number of Shares, Exercised	-61,456
Number of Shares, Forfeitures	-25,770
Number of Shares, Outstanding Ending Balance	9,993,216
Number of Shares, Vested and expected to vest	9,878,829
Number of Shares, Exercisable	5,521,561
Weighted-Average Exercise Price, Outstanding at beginning of period	$3.69
Weighted-Average Exercise Price, Granted	$4.42
Weighted-Average Exercise Price, Exercised	$1.83
Weighted-Average Exercise Price, Forfeitures	$5.15
Weighted-Average Exercise Price, Outstanding at end of period	$3.83
Weighted-Average Exercise Price, Vested and expected to vest	$3.83
Weighted-Average Exercise Price, Exercisable	$3.33
Weighted-Average Remaining Contractual Term, Outstanding	7 years 6 months 11 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	7 years 6 months 4 days
Weighted-Average Remaining Contractual Term, Exercisable	6 years 3 months 22 days
Aggregate Intrinsic Value, Outstanding	$8,802,913
Aggregate Intrinsic Value, Vested and expected to vest	8,787,468
Aggregate Intrinsic Value, Exercisable	$8,010,861

Fair_Value_Measurements_and_Ma2

Fair Value Measurements and Marketable Securities - Financial Assets at Fair Value on Recurring Basis (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$82,037	$58,577
Basis of Fair Value Measurements, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	10,366	3,369
Basis of Fair Value Measurements, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	71,671	55,208
Basis of Fair Value Measurements, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	10,366	3,369
Money Market Funds | Basis of Fair Value Measurements, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	10,366	3,369
Money Market Funds | Basis of Fair Value Measurements, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Certificates of Deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	1,475	2,505
Certificates of Deposit | Basis of Fair Value Measurements, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	1,475	2,505
Certificates of Deposit | Basis of Fair Value Measurements, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	31,935	28,081
Corporate Debt Securities | Basis of Fair Value Measurements, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	31,935	28,081
Corporate Debt Securities | Basis of Fair Value Measurements, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Government Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	24,021	19,123
Government Securities | Basis of Fair Value Measurements, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	24,021	19,123
Government Securities | Basis of Fair Value Measurements, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	14,240	5,499
Commercial Paper | Basis of Fair Value Measurements, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	14,240	5,499
Commercial Paper | Basis of Fair Value Measurements, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$0	$0

Fair_Value_Measurements_and_Ma3

Fair Value Measurements and Marketable Securities - Summary of Company's Available-for-Sale Securities (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	$62,038	$50,222
Unrealized Gain	6	4
Unrealized Loss	-21	-17
Fair Value	62,023	50,209
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	10,366	3,369
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	10,366	3,369
Certificates of Deposit
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	1,475	2,505
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	1,475	2,505
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	31,950	28,094
Unrealized Gain	4	1
Unrealized Loss	-19	-14
Fair Value	31,935	28,081
U.S. Government Securities
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	24,021	19,123
Unrealized Gain	2	3
Unrealized Loss	-2	-3
Fair Value	24,021	19,123
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	14,240	5,499
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	14,240	5,499
Marketable Securities Including Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	82,052	58,590
Unrealized Gain	6	4
Unrealized Loss	-21	-17
Fair Value	82,037	58,577
Less Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	20,014	8,368
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	$20,014	$8,368

Fair_Value_Measurements_and_Ma4

Fair Value Measurements and Marketable Securities - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Realized gain or losses	$0	$0
Weighted average maturity for available for sale securities		4 months 27 days
February 2015 and March 2011 Offering
Schedule Of Available For Sale Securities [Line Items]
Shares of common stock to be purchased with warrants	12,100,000
Maximum
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, longest maturity date		2016-05

Fair_Value_Measurements_and_Ma5

Fair Value Measurements and Marketable Securities - Marketable Securities with Unrealized Losses (Detail) (USD $)	Mar. 31, 2015
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	$34,181
Marketable securities, in loss position for less than twelve months, Unrealized Loss	-21
U.S. Government Securities
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, in loss position for less than twelve months, Fair Value	12,170
Marketable securities, in loss position for less than twelve months, Unrealized Loss	-2
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, in loss position for less than twelve months, Fair Value	22,011
Marketable securities, in loss position for less than twelve months, Unrealized Loss	($19)

Commitments_and_Contingencies_1

Commitments and Contingencies - Future Rental Payments under Noncancelable Operating Leases (Detail) (USD $)	Mar. 31, 2015
In Thousands, unless otherwise specified
Leases [Abstract]
2015	$691
2016	953
2017	238
Total	$1,882