Molecular Templates (MTEM) 10-Q 1 Aug 16 2016 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2016	Jul. 25, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q2
Trading Symbol	THLD
Entity Registrant Name	THRESHOLD PHARMACEUTICALS INC
Entity Central Index Key	1,183,765
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		71,511,425

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 12,402	$ 9,589
Marketable securities, current	21,189	39,091
Collaboration receivable	921	1,891
Prepaid expenses and other current assets	1,294	2,599
Total current assets	35,806	53,170
Property and equipment, net	208	333
Other assets	166	166
Total assets	36,180	53,669
Current liabilities:
Accounts payable	3,076	725
Accrued clinical and development expenses	2,097	6,834
Accrued liabilities	616	3,269
Total current liabilities	5,789	10,828
Warrant liability	2,490	1,864
Deferred rent	87	131
Total liabilities	8,366	12,823
Commitments and contingencies (Note 7)
Stockholders’ equity:
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: 71,511,425 shares at June 30, 2016 and 71,462,059 shares at December 31, 2015	72	71
Additional paid-in capital	371,893	370,236
Accumulated other comprehensive loss	5	(21)
Accumulated deficit	(344,156)	(329,440)
Total stockholders’ equity	27,814	40,846
Total liabilities and stockholders’ equity	$ 36,180	$ 53,669

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
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	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	71,511,425	71,462,059
Common stock, shares outstanding	71,511,425	71,462,059

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Revenue		$ 3,680		$ 7,361
Operating expenses:
Research and development	$ 4,016	10,141	$ 10,021	20,821
General and administrative	1,892	2,480	4,141	5,096
Total operating expenses	5,908	12,621	14,162	25,917
Loss from operations	(5,908)	(8,941)	(14,162)	(18,556)
Interest income (expense), net	40	39	72	72
Other income (expense), net	(996)	596	(626)	(976)
Net loss	(6,864)	(8,306)	(14,716)	(19,460)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	4	(3)	26	(5)
Comprehensive loss	$ (6,860)	$ (8,309)	$ (14,690)	$ (19,465)
Net loss per share:
Basic	$ (0.10)	$ (0.12)	$ (0.21)	$ (0.28)
Diluted	$ (0.10)	$ (0.12)	$ (0.21)	$ (0.28)
Weighted average number of shares used in net loss per share calculations:
Basic	71,511	71,334	71,500	69,046
Diluted	71,511	72,815	71,500	69,046

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net loss	$ (14,716)	$ (19,460)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	305	503
(Gain) loss on sale of investments, property and equipment	(51)	14
Stock-based compensation expense	1,645	3,316
Change in common stock warrant fair value	626	974
Changes in operating assets and liabilities:
Collaboration receivable	970	3,601
Prepaid expenses and other assets	1,305	(773)
Accounts payable	2,351	(1,439)
Accrued clinical and development expenses	(4,737)	1,722
Accrued liabilities	(2,653)	(729)
Deferred rent	(44)	(74)
Deferred revenue		(7,361)
Net cash used in operating activities	(14,999)	(19,706)
Cash flows from investing activities:
Acquisition of property and equipment		(55)
Purchases of marketable securities	(13,454)	(39,479)
Proceeds from sale of property and equipment	61
Proceeds from sale of marketable securities		1,997
Proceeds from maturities of marketable securities	31,192	30,907
Net cash (used in) provided by investing activities	17,799	(6,630)
Cash flows from financing activities:
Proceeds from issuance of common stock and warrants, net of offering expenses	13	28,514
Net cash provided by financing activities	13	28,514
Net increase (decrease) in cash and cash equivalents	2,813	2,178
Cash and cash equivalents, beginning of period	9,589	8,391
Cash and cash equivalents, end of period	$ 12,402	$ 10,569

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2016
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, 2015 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, 2015 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 10, 2016. 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 in prior periods were related to its former collaboration arrangement with Merck KGaA, which was entered in February 2012. The collaboration with Merck KGaA provided for various types of payments to the Company, including nonrefundable 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 received reimbursement for Merck KGaA’s 70% share for eligible worldwide development expenses for evofosfamide (formerly TH-302). Such reimbursement was reflected as a reduction of operating expenses. In March 2016, the Company and Merck KGaA agreed to terminate the collaboration and all rights evofosfamide were returned to the Company. As a result of the termination of the collaboration the Company is no longer eligible to receive any further milestone payments from Merck KGaA. In addition, the Company is no longer eligible to receive 70% reimbursement of expenses from Merck KGaA related to the further development of evofosfamide other than for costs to wind down the discontinued trials and return the evofosfamide rights back to the Company. 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 were determined to be a single unit of accounting and as such the revenue relating to this unit of accounting was recorded as deferred revenue and recognized ratably over the term of its estimated performance period under the agreement, which was the product development period. The Company determined the estimated performance period and it was 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 developmental 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. As a result of Merck KGaA’s and the Company’s decision to cease further joint development of evofosfamide in December 2015, the Company immediately recognized all of the remaining deferred revenue into revenue during the quarter ended December 31, 2015.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2016
Earnings Per Share [Abstract]
Net Loss Per Share	NOTE 2 — NET LOSS PER 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 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 June 30, Six Months Ended June 30, 2016 2015 2016 2015 Numerator: Net loss $ (6,864 ) $ (8,306 ) $ (14,716 ) $ (19,460 ) Less: noncash income from change in fair value of common stock warrants — (308 ) — — Net loss - diluted (6,864 ) (8,614 ) (14,716 ) (19,460 ) Denominator: Weighted average common shares outstanding - basic 71,511 71,334 71,500 69,046 Dilutive effect of warrants — 1,481 — — Weighted-average common shares outstanding and dilutive potential common shares — diluted 71,511 72,815 71,500 69,046 Net loss per share: Basic $ (0.10 ) $ (0.12 ) $ (0.21 ) $ (0.28 ) Diluted $ (0.10 ) $ (0.12 ) $ (0.21 ) $ (0.28 ) 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 June 30, Six Months Ended June 30, 2016 2015 2016 2015 Shares issuable upon exercise of warrants 8,300 8,300 8,300 12,146 Shares issuable upon exercise of stock options 11,635 10,151 11,635 10,151 Shares issuable related to the 2004 Purchase Plan 42 73 42 73

Collaboration Arrangements

Collaboration Arrangements	6 Months Ended
	Jun. 30, 2016
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, or License Agreement, with Merck KGaA, of Darmstadt, Germany, to co-develop and commercialize evofosfamide, the Company’s small molecule hypoxia-targeted drug. Under the terms of the License 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 The Company’s deliverables under the License Agreement with Merck KGaA, which included delivery of the rights and license for evofosfamide and performance of research and development activities, were determined to be a single unit of accounting. The delivered license did 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 License Agreement, which was required for Merck KGaA to fully realize the value from the delivered license. Therefore, the revenue relating to this unit of accounting was recorded as deferred revenue and recognized over the estimated performance period under the License Agreement, which is the product development period. The Company recorded $110 million of the upfront payment and milestones payments as deferred revenue and was amortizing them ratably over the estimated period of performance, which the Company originally estimated to end on March 31, 2020 for the nine months ended September 30, 2015. Merck KGaA’s decision to cease further joint development of evofosfamide in December 2015 resulted in the immediate recognition of all the remaining deferred revenue into revenue during the quarter ended December 31, 2015. As a result, the Company recognized $0 revenue during the three and six months ended June 30, 2016, and $3.7 million and $7.4 million of revenue during the three and six months ended June 30, 2015, respectively. Further, in March 2016, the Company and Merck KGaA agreed to terminate the License Agreement pursuant to a termination agreement, or the Termination Agreement. Under the terms of the Termination Agreement, all rights under the License Agreement were returned to the Company, as well as all rights to Merck KGaA technology developed under the License Agreement. Under the Termination Agreement Merck KGaA is entitled to tiered royalties on net sales if any, and milestone payments contingent upon the future successful partnering, development and commercialization of evofosfamide. Merck KGaA also paid 70% of worldwide development expenses for evofosfamide under the terms of the License Agreement. With the decision to cease further joint development of evofosfamide and the termination of the License Agreement, the Company is no longer eligible to receive payments from Merck KGaA for expenses related to further development of evofosfamide other than for costs to wind down the discontinued trials and return the evofosfamide rights back to the Company. The Company earned $0.9 million and $1.7 million reimbursement for eligible worldwide expenses for evofosfamide from Merck KGaA during the six and six months ended June 30, 2016, which expenses were solely for trial wind-down efforts, compared to $3.6 million and $5.6 million for eligible worldwide development expenses incurred during the six and six months ended June 30, 2015. Such earned reimbursement has been reflected as a reduction of research and development expenses.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2016
Equity [Abstract]
Stockholders' Equity	NOTE 4 — STOCKHOLDERS’ EQUITY 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 both June 30, 2016 and December 31, 2015 the Company had warrants outstanding to purchase 8.3 million shares of common stock, having an initial exercise price of $10.86 per share, which warrants were issued by the Company in the Company’s February 2015 public offering of common stock and warrants. The exercise price was adjusted to $3.62 on January 21, 2016 pursuant to the terms of warrant. The fair value of these warrants on June 30, 2016 and December 31, 2015 was determined using a Black-Scholes model with the following key level 3 inputs: June 30, 2016 December 31, 2015 Risk-free interest rate 1.01 % 1.76 % Expected life (in years) 3.64 4.14 Dividend yield — — Volatility 116 % 112 % Stock price $ 0.64 $ 0.48 During the three and six months ended June 30, 2016 the change in fair value of $1.0 million and $0.7 million, respectively, of noncash expense related to the February 2015 warrants was recorded as other income (expense) in the Company’s consolidated statement of operations. On March 16, 2016, warrants outstanding, which were initially issued by the Company in an underwritten public offering in March 2011, to purchase 3.8 million shares of common stock expired and noncash income of $38,000 related to the expired warrants was recognized as other income (expense) in the Company’s consolidated statement of operations. At December 31, 2015, the Company had March 2011 warrants outstanding to purchase 3.8 million shares of common stock, having an exercise price of $2.46 per share. The fair value of these warrants on December 31, 2015 was determined using a Black Scholes valuation model with the following key level 3 inputs: December 31, 2015 Risk-free interest rate 0.16 % Expected life (in years) 0.21 Dividend yield — Volatility 179 % Stock price $ 0.48 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 June 30, 2016 and December 31, 2015: Fair Value as of June 30, 2016 Basis of Fair Value Measurements (in thousands) Level 1 Level 2 Level 3 February 2015 warrants $ 2,490 $ — $ — $ 2,490 Fair Value as of December 31, 2015 Basis of Fair Value Measurements (in thousands) Level 1 Level 2 Level 3 March 2011 warrants 38 — — 38 February 2015 warrants 1,826 — — 1,826 Total common stock warrants $ 1,864 $ — $ — $ 1,864 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, 2015 $ 1,864 Change in fair value related to expired March 2016 common stock warrants (38 ) Change in fair value of common stock warrants during six months ended June 30, 2016 664 Exercise of warrants during six months ended June 30, 2016 — Balance at June 30, 2016 $ 2,490

Stock Based Compensation

Stock Based Compensation	6 Months Ended
	Jun. 30, 2016
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 expenses in the unaudited consolidated statements of operations for the three and six months ended June 30, 2016 and 2015 as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Amortization of stock-based compensation: Research and development $ 306 $ 1,174 $ 624 $ 1,991 General and administrative 496 721 1,021 1,325 $ 802 $ 1,895 $ 1,645 $ 3,316 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 and six months ended June 30, 2016 and 2015: Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Employee Stock Options: Risk-free interest rate 1.08 % 1.69 % 1.60 % 1.70 % Expected term (in years) 5.27 5.58 5.97 5.98 Dividend yield — — — — Volatility 109 % 79 % 108 % 83 % Weighted-average fair value of stock options granted $ 0.30 $ 2.65 $ 0.44 $ 3.08 Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Employee Stock Purchase Plan (ESPP): Risk-free interest rate 0.56 % 0.38 % 0.56 % 0.38 % Expected term (in years) 1.24 1.24 1.24 1.24 Dividend yield — — — — Volatility 161 % 51 % 161 % 51 % Weighted-average fair value of ESPP purchase rights $ 0.22 $ 1.59 $ 0.22 $ 1.59 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” Employee Stock-based Compensation Expense As required by ASC 718, the Company recognized $0.8 million and $1.6 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 and six months ended June 30, 2016 and $1.9 million and $3.3 million of stock-based compensation for the three and six months ended June 30, 2015. As of June 30, 2016, the total unrecognized compensation cost related to unvested stock-based awards granted to employees under the Company’s equity incentive plans was approximately $2.4 million before forfeitures. This cost will be recorded as compensation expense on a ratable basis over the remaining weighted average requisite service period of approximately 2.7 years. Equity Incentive Plans Equity Incentive Plans At June 30, 2016, 857,479 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 Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at December 31, 2015 9,032,136 $ 3.77 — — Granted 2,945,000 $ 0.53 — — Exercised — $ — — — Forfeitures (341,939 ) $ 3.07 — — Outstanding at June 30, 2016 11,635,197 $ 2.97 6.32 $ 300,142 Vested and expected to vest June 30, 2016 11,527,107 $ 2.99 6.29 $ 292,477 Exercisable at June 30, 2016 7,444,072 $ 3.61 4.70 $ 16,920 No stock options were exercised during the six months ended June 30, 2016. The total intrinsic value of stock options exercised during six months ended June 30, 2015 was $0.2 million, as determined at the date of the option exercise. Cash received from stock option exercises was $0.1 million for the six months ended June 30, 2015. 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, 2016, 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 six months ended June 30, 2016, plan participants had purchased 49,366 shares at an average purchase price of $0.24 for total cash proceeds of $12,000. At June 30, 2016, 177,471 shares were authorized and available for issuance under the 2004 Purchase Plan.

Marketable Securities and Fair

Marketable Securities and Fair Value	6 Months Ended
	Jun. 30, 2016
Fair Value Disclosures [Abstract]
Marketable Securities and Fair Value	NOTE 6 —MARKETABLE SECURITIES AND FAIR VALUE The Company accounts for its marketable securities in accordance with ASC 820 “Fair Value Measurements and Disclosures.” 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 June 30, 2016 and December 31, 2015: Fair Value as of June 30, 2016 Basis of Fair Value Measurements (in thousands) Level 1 Level 2 Level 3 Money market funds $ 1,857 $ 1,857 $ — $ — Certificates of deposit 100 — 100 — Corporate debt securities 4,067 — 4,067 — Government securities 13,580 — 13,580 — Commercial paper 13,987 — 13,987 — Total cash equivalents and marketable securities $ 33,591 $ 1,857 $ 31,734 $ — Fair Value as of December 31, 2015 Basis of Fair Value Measurements (in thousands) Level 1 Level 2 Level 3 Money market funds $ 5,421 $ 5,421 $ — $ — Certificates of deposit 696 — 696 — Corporate debt securities 12,571 — 12,571 — Government securities 21,769 — 21,769 — Municipal securities 1,908 — 1,908 — Commercial paper 6,145 — 6,145 — Total cash equivalents and marketable securities $ 48,510 $ 5,421 $ 43,089 $ — The Company invests in highly-liquid, investment-grade securities. The following is a summary of the Company’s available-for-sale securities at June 30, 2016 and December 31, 2015: As of June 30, 2016 (in thousands): Cost Basis Unrealized Gain Unrealized Loss Fair Value Money market funds $ 1,857 $ — $ — $ 1,857 Certificates of deposit 100 — — 100 Corporate debt securities 4,068 — (1 ) 4,067 U.S. Government securities 13,574 7 (1 ) 13,580 Commercial paper 13,987 — — 13,987 33,586 7 (2 ) 33,591 Less cash equivalents 12,402 — — 12,402 Total marketable securities $ 21,184 $ 7 $ (2 ) $ 21,189 As of December 31, 2015 (in thousands): Cost Basis Unrealized Gain Unrealized Loss Fair Value Money market funds $ 5,421 $ — $ — $ 5,421 Certificates of deposit 696 — — 696 Corporate debt securities 12,578 1 (8 ) 12,571 Municipal securities 1,908 — — 1,908 U.S. Government securities 21,783 — (14 ) 21,769 Commercial paper 6,145 — — 6,145 48,531 1 (22 ) 48,510 Less cash equivalents 9,419 — — 9,419 Total marketable securities $ 39,112 $ 1 $ (22 ) $ 39,091 There were no realized gains or losses in six months ended June 30, 2016 and 2015, respectively. As of June 30, 2016, the weighted average maturity for the Company’s available for sale securities was 3.2 months, with the longest maturity being June 2017. The Company does not intend to sell the investments that are in an unrealized loss position, and it is unlikely that the Company will be required to sell the investments before recovery of their amortized cost basis, which may be maturity. The following table provides the breakdown of the marketable securities with unrealized losses at June 30, 2016 (in thousands): In loss position for less than twelve months As of June 30, 2016 (in thousands): Fair Value Unrealized Loss Corporate debt securities $ 2,504 $ (1 ) U.S. government securities 3,020 (1 ) Total marketable securities $ 5,524 $ (2 ) The Company determined the fair value of the liability associated with its February 2015 warrants to purchase in aggregate 8.3 million shares of outstanding common stock using a Black-Scholes Model. See detailed discussion in Note 4 —

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2016
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,” Years Ending December 31, 2016 388 2017 260 Thereafter — Total $ 648 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 June 30, 2016. 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.

Accrued Severance Benefits

Accrued Severance Benefits	6 Months Ended
	Jun. 30, 2016
Restructuring And Related Activities [Abstract]
Accrued Severance Benefits	NOTE 8 — ACCRUED SEVERANCE BENEFITS In December 2015, the Company adopted a plan to reduce its operating expenses, following its decision to discontinue joint development of evofosfamide under its former collaboration with Merck KGaA. The plan included a reduction of approximately 40 full-time employees in both research and development and to a lesser extent general and administrative areas of the Company. As a result of the staffing reduction, the Company incurred expenses related to severance benefits of approximately $2.5 million during the quarter ended December 31, 2015, which included approximately $0.2 million of noncash stock compensation expense related to the extension of post-termination exercise period for the outstanding vested stock options for the affected employees. The payout of the accrued expenses related to severance benefits at December 31, 2015 was completed during the first quarter of 2016.

Organization and Summary of S14

Organization and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2016
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, 2015 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, 2015 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 10, 2016. 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 in prior periods were related to its former collaboration arrangement with Merck KGaA, which was entered in February 2012. The collaboration with Merck KGaA provided for various types of payments to the Company, including nonrefundable 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 received reimbursement for Merck KGaA’s 70% share for eligible worldwide development expenses for evofosfamide (formerly TH-302). Such reimbursement was reflected as a reduction of operating expenses. In March 2016, the Company and Merck KGaA agreed to terminate the collaboration and all rights evofosfamide were returned to the Company. As a result of the termination of the collaboration the Company is no longer eligible to receive any further milestone payments from Merck KGaA. In addition, the Company is no longer eligible to receive 70% reimbursement of expenses from Merck KGaA related to the further development of evofosfamide other than for costs to wind down the discontinued trials and return the evofosfamide rights back to the Company. 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 were determined to be a single unit of accounting and as such the revenue relating to this unit of accounting was recorded as deferred revenue and recognized ratably over the term of its estimated performance period under the agreement, which was the product development period. The Company determined the estimated performance period and it was 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 developmental 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. As a result of Merck KGaA’s and the Company’s decision to cease further joint development of evofosfamide in December 2015, the Company immediately recognized all of the remaining deferred revenue into revenue during the quarter ended December 31, 2015.

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2016
Earnings Per Share [Abstract]
Reconciliation of Numerator and Denominator	ERROR: Could not retrieve Word content for note block
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 June 30, Six Months Ended June 30, 2016 2015 2016 2015 Shares issuable upon exercise of warrants 8,300 8,300 8,300 12,146 Shares issuable upon exercise of stock options 11,635 10,151 11,635 10,151 Shares issuable related to the 2004 Purchase Plan 42 73 42 73

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2016
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 June 30, 2016 and December 31, 2015: Fair Value as of June 30, 2016 Basis of Fair Value Measurements (in thousands) Level 1 Level 2 Level 3 February 2015 warrants $ 2,490 $ — $ — $ 2,490 Fair Value as of December 31, 2015 Basis of Fair Value Measurements (in thousands) Level 1 Level 2 Level 3 March 2011 warrants 38 — — 38 February 2015 warrants 1,826 — — 1,826 Total common stock warrants $ 1,864 $ — $ — $ 1,864
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, 2015 $ 1,864 Change in fair value related to expired March 2016 common stock warrants (38 ) Change in fair value of common stock warrants during six months ended June 30, 2016 664 Exercise of warrants during six months ended June 30, 2016 — Balance at June 30, 2016 $ 2,490
February 2015 Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Outstanding Warrants Valuation Assumption	The fair value of these warrants on June 30, 2016 and December 31, 2015 was determined using a Black-Scholes model with the following key level 3 inputs: June 30, 2016 December 31, 2015 Risk-free interest rate 1.01 % 1.76 % Expected life (in years) 3.64 4.14 Dividend yield — — Volatility 116 % 112 % Stock price $ 0.64 $ 0.48
March 2011 Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Outstanding Warrants Valuation Assumption	The fair value of these warrants on December 31, 2015 was determined using a Black Scholes valuation model with the following key level 3 inputs: December 31, 2015 Risk-free interest rate 0.16 % Expected life (in years) 0.21 Dividend yield — Volatility 179 % Stock price $ 0.48

Stock Based Compensation (Table

Stock Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2016
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 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 expenses in the unaudited consolidated statements of operations for the three and six months ended June 30, 2016 and 2015 as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Amortization of stock-based compensation: Research and development $ 306 $ 1,174 $ 624 $ 1,991 General and administrative 496 721 1,021 1,325 $ 802 $ 1,895 $ 1,645 $ 3,316
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 and six months ended June 30, 2016 and 2015: Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Employee Stock Options: Risk-free interest rate 1.08 % 1.69 % 1.60 % 1.70 % Expected term (in years) 5.27 5.58 5.97 5.98 Dividend yield — — — — Volatility 109 % 79 % 108 % 83 % Weighted-average fair value of stock options granted $ 0.30 $ 2.65 $ 0.44 $ 3.08 Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Employee Stock Purchase Plan (ESPP): Risk-free interest rate 0.56 % 0.38 % 0.56 % 0.38 % Expected term (in years) 1.24 1.24 1.24 1.24 Dividend yield — — — — Volatility 161 % 51 % 161 % 51 % Weighted-average fair value of ESPP purchase rights $ 0.22 $ 1.59 $ 0.22 $ 1.59
Stock Option Activity Under Equity Incentive Plan	The following table summarizes stock option activity under the Company’s equity incentive plans: Options Number of Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at December 31, 2015 9,032,136 $ 3.77 — — Granted 2,945,000 $ 0.53 — — Exercised — $ — — — Forfeitures (341,939 ) $ 3.07 — — Outstanding at June 30, 2016 11,635,197 $ 2.97 6.32 $ 300,142 Vested and expected to vest June 30, 2016 11,527,107 $ 2.99 6.29 $ 292,477 Exercisable at June 30, 2016 7,444,072 $ 3.61 4.70 $ 16,920

Marketable Securities and Fai18

Marketable Securities and Fair Value (Tables)	6 Months Ended
	Jun. 30, 2016
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 June 30, 2016 and December 31, 2015: Fair Value as of June 30, 2016 Basis of Fair Value Measurements (in thousands) Level 1 Level 2 Level 3 Money market funds $ 1,857 $ 1,857 $ — $ — Certificates of deposit 100 — 100 — Corporate debt securities 4,067 — 4,067 — Government securities 13,580 — 13,580 — Commercial paper 13,987 — 13,987 — Total cash equivalents and marketable securities $ 33,591 $ 1,857 $ 31,734 $ — Fair Value as of December 31, 2015 Basis of Fair Value Measurements (in thousands) Level 1 Level 2 Level 3 Money market funds $ 5,421 $ 5,421 $ — $ — Certificates of deposit 696 — 696 — Corporate debt securities 12,571 — 12,571 — Government securities 21,769 — 21,769 — Municipal securities 1,908 — 1,908 — Commercial paper 6,145 — 6,145 — Total cash equivalents and marketable securities $ 48,510 $ 5,421 $ 43,089 $ —
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 June 30, 2016 and December 31, 2015: As of June 30, 2016 (in thousands): Cost Basis Unrealized Gain Unrealized Loss Fair Value Money market funds $ 1,857 $ — $ — $ 1,857 Certificates of deposit 100 — — 100 Corporate debt securities 4,068 — (1 ) 4,067 U.S. Government securities 13,574 7 (1 ) 13,580 Commercial paper 13,987 — — 13,987 33,586 7 (2 ) 33,591 Less cash equivalents 12,402 — — 12,402 Total marketable securities $ 21,184 $ 7 $ (2 ) $ 21,189 As of December 31, 2015 (in thousands): Cost Basis Unrealized Gain Unrealized Loss Fair Value Money market funds $ 5,421 $ — $ — $ 5,421 Certificates of deposit 696 — — 696 Corporate debt securities 12,578 1 (8 ) 12,571 Municipal securities 1,908 — — 1,908 U.S. Government securities 21,783 — (14 ) 21,769 Commercial paper 6,145 — — 6,145 48,531 1 (22 ) 48,510 Less cash equivalents 9,419 — — 9,419 Total marketable securities $ 39,112 $ 1 $ (22 ) $ 39,091
Marketable Securities with Unrealized Losses	The following table provides the breakdown of the marketable securities with unrealized losses at June 30, 2016 (in thousands): In loss position for less than twelve months As of June 30, 2016 (in thousands): Fair Value Unrealized Loss Corporate debt securities $ 2,504 $ (1 ) U.S. government securities 3,020 (1 ) Total marketable securities $ 5,524 $ (2 )

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2016
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, 2016 388 2017 260 Thereafter — Total $ 648

Net Loss Per Share - Reconcilia

Net Loss Per Share - Reconciliation of Numerator and Denominator (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net loss	$ (6,864)	$ (8,306)	$ (14,716)	$ (19,460)
Less: noncash income from change in fair value of common stock warrants		(308)
Net loss - diluted	$ (6,864)	$ (8,614)	$ (14,716)	$ (19,460)
Denominator:
Weighted average common shares outstanding - basic	71,511	71,334	71,500	69,046
Dilutive effect of warrants		1,481
Weighted-average common shares outstanding and dilutive potential common shares — diluted	71,511	72,815	71,500	69,046
Net loss per share
Basic	$ (0.10)	$ (0.12)	$ (0.21)	$ (0.28)
Diluted	$ (0.10)	$ (0.12)	$ (0.21)	$ (0.28)

Organization and Summary of S21

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2016
Evofosfamide | Collaborative Arrangement Product Agreement | Merck KGaA
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage share of eligible worldwide development expenses	70.00%

Net Loss Per Share - Warrants,

Net Loss Per Share - Warrants, Options and Purchase Rights Excluded from Computation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	8,300	8,300	8,300	12,146
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	11,635	10,151	11,635	10,151
2004 Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	42	73	42	73

Collaboration Arrangements - Ad

Collaboration Arrangements - Additional Information (Detail) - Merck KGaA - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront and milestone payments received to date			$ 110
Revenue recognized by the Company	$ 0	$ 3.7	0	$ 7.4
Company received a reimbursement for eligible worldwide development expenses	$ 0.9	$ 3.6	$ 1.7	$ 5.6
Collaborative Arrangement Product Agreement | Evofosfamide
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Merck KGaA's percentage share of worldwide development expenses			70.00%

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	Mar. 16, 2016	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
February 2015 Warrants
Class Of Warrant Or Right [Line Items]
Warrants to purchase shares of common stock		8.3	8.3	8.3
Warrant exercise price		$ 3.62	$ 3.62	$ 10.86
February 2015 Warrants | Warrants
Class Of Warrant Or Right [Line Items]
Change in fair value of common stock warrants		$ 1,000,000	$ 700,000
March 2011 Warrants
Class Of Warrant Or Right [Line Items]
Warrants to purchase shares of common stock				3.8
Warrant exercise price				$ 2.46
Number of outstanding warrants that expired	3.8
March 2011 Warrants | Warrants
Class Of Warrant Or Right [Line Items]
Change in fair value of common stock warrants	$ 38,000

Stockholders' Equity - Outstand

Stockholders' Equity - Outstanding Warrants Valuation Assumption (Detail) - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
February 2015 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Risk-free interest rate	1.01%	1.76%
Expected life (in years)	3 years 7 months 21 days	4 years 1 month 21 days
Dividend yield	0.00%	0.00%
Volatility	116.00%	112.00%
Stock price	$ 0.64	$ 0.48
March 2011 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Risk-free interest rate		0.16%
Expected life (in years)		2 months 16 days
Dividend yield		0.00%
Volatility		179.00%
Stock price		$ 0.48

Stockholders' Equity - Financia

Stockholders' Equity - Financial Liabilities Subject to Fair Value Measurements (Detail) - Warrants - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements		$ 1,864
Basis of Fair Value Measurements, Level 3
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements		1,864
February 2015 Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	$ 2,490	1,826
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	$ 2,490	1,826
March 2011 Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements		38
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		$ 38

Stockholders' Equity - Reconcil

Stockholders' Equity - Reconciliation of Warrant Liability Measured at Fair Value (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Change in common stock warrant fair value	$ 626	$ 974
Level 3 Inputs
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,864
Change in common stock warrant fair value	664
Ending Balance	2,490
Level 3 Inputs | Expired March 2016 Warrants
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Change in common stock warrant fair value	$ (38)

Stock Based Compensation - Stoc

Stock Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 802	$ 1,895	$ 1,645	$ 3,316
Research and Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	306	1,174	624	1,991
General and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 496	$ 721	$ 1,021	$ 1,325

Stock Based Compensation - Weig

Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	1.08%	1.69%	1.60%	1.70%
Expected term (in years)	5 years 3 months 7 days	5 years 6 months 29 days	5 years 11 months 19 days	5 years 11 months 23 days
Volatility	109.00%	79.00%	108.00%	83.00%
Weighted-average fair value of stock options granted	$ 0.30	$ 2.65	$ 0.44	$ 3.08
Employee Stock Purchase Plan (ESPP)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.56%	0.38%	0.56%	0.38%
Expected term (in years)	1 year 2 months 27 days	1 year 2 months 27 days	1 year 2 months 27 days	1 year 2 months 27 days
Volatility	161.00%	51.00%	161.00%	51.00%
Weighted-average fair value of ESPP purchase rights	$ 0.22	$ 1.59	$ 0.22	$ 1.59

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Detail) - USD ($)	Jan. 01, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense		$ 802,000	$ 1,895,000	$ 1,645,000	$ 3,316,000
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans		$ 2,400,000		$ 2,400,000
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition				2 years 8 months 12 days
Stock options exercised				0
Total intrinsic value of stock options exercised					200,000
Cash received from stock option exercises					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		857,479		857,479
2004 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Remaining shares available for issuance		177,471		177,471
Additional shares authorized for issuance	100,000
Plan participants purchased shares				49,366
Average purchase price under 2004 Employee Stock Purchase Plan		$ 0.24		$ 0.24
Cash proceeds				$ 12,000

Stock Based Compensation - St31

Stock Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail)	6 Months Ended
	Jun. 30, 2016USD ($)$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding Beginning Balance	9,032,136
Number of Shares, Granted	2,945,000
Number of Shares, Exercised	0
Number of Shares, Forfeitures	(341,939)
Number of Shares, Outstanding Ending Balance	11,635,197
Number of Shares, Vested and expected to vest	11,527,107
Number of Shares, Exercisable	7,444,072
Weighted-Average Exercise Price, Outstanding at beginning of period | $ / shares	$ 3.77
Weighted-Average Exercise Price, Granted | $ / shares	0.53
Weighted-Average Exercise Price, Forfeitures | $ / shares	3.07
Weighted-Average Exercise Price, Outstanding at end of period | $ / shares	2.97
Weighted-Average Exercise Price, Vested and expected to vest | $ / shares	2.99
Weighted-Average Exercise Price, Exercisable | $ / shares	$ 3.61
Weighted-Average Remaining Contractual Term, Outstanding	6 years 3 months 26 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	6 years 3 months 15 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 8 months 12 days
Aggregate Intrinsic Value, Outstanding | $	$ 300,142
Aggregate Intrinsic Value, Vested and expected to vest | $	292,477
Aggregate Intrinsic Value, Exercisable | $	$ 16,920

Marketable Securities and Fai32

Marketable Securities and Fair Value - Financial Assets at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 33,591	$ 48,510
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	1,857	5,421
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	31,734	43,089
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	1,857	5,421
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	1,857	5,421
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	100	696
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	100	696
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	4,067	12,571
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	4,067	12,571
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	13,580	21,769
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	13,580	21,769
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
Municipal Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities		1,908
Municipal 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		1,908
Municipal 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
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	13,987	6,145
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	13,987	6,145
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

Marketable Securities and Fai33

Marketable Securities and Fair Value - Summary of Company's Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	$ 21,184	$ 39,112
Unrealized Gain	7	1
Unrealized Loss	(2)	(22)
Fair Value	21,189	39,091
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	1,857	5,421
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	1,857	5,421
Certificates of Deposit
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	100	696
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	100	696
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	4,068	12,578
Unrealized Gain	0	1
Unrealized Loss	(1)	(8)
Fair Value	4,067	12,571
U.S. Government Securities
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	13,574	21,783
Unrealized Gain	7	0
Unrealized Loss	(1)	(14)
Fair Value	13,580	21,769
Municipal Securities
Schedule Of Available For Sale Securities [Line Items]
Cost Basis		1,908
Unrealized Gain		0
Unrealized Loss		0
Fair Value		1,908
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	13,987	6,145
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	13,987	6,145
Marketable Securities Including Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	33,586	48,531
Unrealized Gain	7	1
Unrealized Loss	(2)	(22)
Fair Value	33,591	48,510
Less Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	12,402	9,419
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	$ 12,402	$ 9,419

Marketable Securities and Fai34

Marketable Securities and Fair Value - Additional Information (Detail) - USD ($) shares in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Realized gain or losses	$ 0	$ 0
Weighted average maturity for available for sale securities	3 months 6 days
February 2015 Warrants
Schedule Of Available For Sale Securities [Line Items]
Warrants to purchase shares of common stock	8.3		8.3
Maximum
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, longest maturity date	2017-06

Marketable Securities and Fai35

Marketable Securities and Fair Value - Marketable Securities with Unrealized Losses (Detail) $ in Thousands	Jun. 30, 2016USD ($)
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, in loss position for less than twelve months, Fair Value	$ 5,524
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	2,504
Marketable securities, in loss position for less than twelve months, Unrealized Loss	(1)
U.S. Government Securities
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, in loss position for less than twelve months, Fair Value	3,020
Marketable securities, in loss position for less than twelve months, Unrealized Loss	$ (1)

Commitments and Contingencies -

Commitments and Contingencies - Future Rental Payments under Noncancelable Operating Leases (Detail) $ in Thousands	Jun. 30, 2016USD ($)
Leases [Abstract]
2,016	$ 388
2,017	260
Total	$ 648

Accrued Severance Benefits - Ad

Accrued Severance Benefits - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended
	Dec. 31, 2015Employee	Dec. 31, 2015USD ($)
Restructuring And Related Activities [Abstract]
Reduction of full-time employees | Employee	40
Expenses related to severance benefits		$ 2.5
Non-cash stock compensation expense		$ 0.2