Viracta Therapeutics (VIRX) 10-K 7 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 01, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	SNSS
Entity Registrant Name	SUNESIS PHARMACEUTICALS INC
Entity Central Index Key	1,061,027
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		67,578,087
Entity Public Float			$ 70,737,319

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 13,696	$ 26,977
Marketable securities		4,773
Prepaids and other current assets	1,504	1,183
Total current assets	15,200	32,933
Property and equipment, net	11	20
Other assets	113	1,381
Total assets	15,324	34,334
Current liabilities:
Accounts payable	1,393	1,697
Accrued clinical expense	500	767
Accrued compensation	943	1,440
Other accrued liabilities	1,091	1,570
Notes payable	7,396	7,204
Total current liabilities	11,323	12,678
Other liabilities	8	112
Total liabilities	11,331	12,790
Commitments and contingencies (Note 9)
Stockholders’ equity:
Convertible preferred stock, $0.0001 par value; 10,000 shares authorized as of December 31, 2018; 18 shares issued and outstanding as of December 31, 2018 and 2017	20,998	20,966
Common stock, $0.0001 par value; 400,000 shares authorized as of December 31, 2018; 37,474 and 34,291 shares issued and outstanding as of December 31, 2018 and 2017, respectively	4	3
Additional paid-in capital	642,460	633,436
Accumulated other comprehensive loss		(7)
Accumulated deficit	(659,469)	(632,854)
Total stockholders’ equity	3,993	21,544
Total liabilities and stockholders’ equity	$ 15,324	$ 34,334

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	18,000	18,000
Preferred stock, shares outstanding	17,697	17,697
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	37,474,000	34,291,000
Common stock, shares outstanding	37,474,000	34,291,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Revenue:
License and other revenue	$ 237	$ 669
Type of Revenue [Extensible List]	snss:LicenseAndOtherRevenueMember	snss:LicenseAndOtherRevenueMember
Operating expenses:
Research and development	$ 14,615	$ 21,540
General and administrative	11,332	13,548
Total operating expenses	25,947	35,088
Loss from operations	(25,710)	(34,419)
Interest expense	(1,154)	(1,396)
Other income, net	249	357
Net loss	(26,615)	(35,458)
Unrealized gain on available-for-sale securities	7	15
Comprehensive loss	(26,608)	(35,443)
Basic and diluted loss per common share:
Net loss:	$ (26,615)	$ (35,458)
Shares used in computing net basic and diluted loss per common share:	35,582	24,516
Net loss per common share:	$ (0.75)	$ (1.45)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2016	$ 21,024	$ 18,808	$ 2	$ 599,632	$ (22)	$ (597,396)
Beginning Balance, shares at Dec. 31, 2016		18,000	20,925,000
Issuance of common stock, preferred stock and warrants in underwritten offering, net of issuance costs	18,510	$ 4,426	$ 1	14,083
Issuance of common stock, preferred stock and warrants in underwritten offering, net of issuance costs, shares		3,000	7,500,000
Issuance of common stock through controlled equity offering facilities, net of issuance costs	14,179			14,179
Issuance of common stock through controlled equity offering facilities, net of issuance costs, shares			5,321,000
Issuance of common stock upon conversion of preferred stock		$ (2,268)		2,268
Issuance of common stock upon conversion of preferred stock, shares		(3,000)	450,000
Issuance of common stock under employee stock purchase plans	$ 217			217
Issuance of common stock under employee stock purchase plans, shares	87,020		87,000
Issuance of common stock pursuant to stock option exercises	$ 24			24
Issuance of common stock pursuant to stock option exercises, shares			8,000
Stock-based compensation expenses	3,033			3,033
Net loss	(35,458)					(35,458)
Unrealized gain on available-for-sale securities	15				15
Ending Balance at Dec. 31, 2017	$ 21,544	$ 20,966	$ 3	633,436	(7)	(632,854)
Ending Balance, shares at Dec. 31, 2017	34,291,000	18,000	34,291,000
Adjustment to issuance cost related to common stock, preferred stock, and warrants issued in prior year	$ 126	$ 32		94
Issuance of common stock through controlled equity offering facilities, net of issuance costs	5,991		$ 1	5,990
Issuance of common stock through controlled equity offering facilities, net of issuance costs, shares			3,009,000
Issuance of common stock from vesting of restricted stock awards	83			83
Issuance of common stock from of restricted stock awards			21,000
Issuance of common stock under employee stock purchase plans	$ 139			139
Issuance of common stock under employee stock purchase plans, shares	104,099		104,000
Issuance of common stock pursuant to stock option exercises	$ 164			164
Issuance of common stock pursuant to stock option exercises, shares	49,000		49,000
Stock-based compensation expenses	$ 2,554			2,554
Net loss	(26,615)					(26,615)
Unrealized gain on available-for-sale securities	7				$ 7
Ending Balance at Dec. 31, 2018	$ 3,993	$ 20,998	$ 4	$ 642,460		$ (659,469)
Ending Balance, shares at Dec. 31, 2018	37,474,000	18,000	37,474,000

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement Of Stockholders Equity [Abstract]
Issuance of common stock in underwritten offering		$ 15,000
Issuance of preferred stock and warrants in underwritten offering		5,000
Issuance of common stock, preferred stock and warrants in underwritten offering, issuance cost		1,500
Issuance of common stock through controlled equity offering facilities	$ 6,068	14,468
Issuance of common stock through controlled equity offering facilities, issuance costs	$ 77	$ 289

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss	$ (26,615)	$ (35,458)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,637	3,033
Depreciation and amortization	9	9
Amortization of debt discount and debt issuance costs	192	269
Changes in operating assets and liabilities:
Prepaids and other assets	1,063	(1,921)
Accounts payable	(304)	(174)
Accrued clinical expense	(267)	(667)
Accrued compensation	(497)	(560)
Other accrued liabilities	(622)	(63)
Deferred revenue		(610)
Net cash used in operating activities	(24,404)	(36,142)
Cash flows from investing activities
Purchases of property and equipment		(26)
Sale and maturities of marketable securities	4,780	29,774
Net cash provided by investing activities	4,780	29,748
Cash flows from financing activities
Principal payments on notes payable and final payment		(7,615)
Proceeds from issuance of convertible preferred stock offering, net		4,633
Proceeds from issuance of common stock, net		13,877
Proceeds from issuance of common stock through controlled equity offering facilities, net	6,040	14,179
Proceeds from exercise of stock options and stock purchase rights	303	241
Net cash provided by financing activities	6,343	25,315
Net increase (decrease) in cash and cash equivalents	(13,281)	18,921
Cash and cash equivalents at beginning of period	26,977	8,056
Cash and cash equivalents at end of period	13,696	26,977
Supplemental disclosure of cash flow information
Interest paid	790	1,066
Supplemental disclosure of non-cash investing and financing activities
Conversion of preferred stock to common stock		$ (2,268)
Issuance of stock from vesting of restricted stock awards	83
Commitment shares issued as cost of equity financing	448
Legal expenses accrued as cost of equity financing, net of adjustments	$ 39

Company Overview

Company Overview	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Company Overview	1. Company Overview Description of Business Sunesis Pharmaceutical, Inc. (“Sunesis” or the “Company”) is a biopharmaceutical company focused on the development of new targeted inhibitors for the treatment of solid and hematologic cancers. The Company’s primary activities since incorporation have been conducting research and development internally and through corporate collaborators, in-licensing and out-licensing pharmaceutical compounds and technology, conducting clinical trials, and raising capital. The Company’s lead program is vecabrutinib, a non-covalent inhibitor of Bruton’s Tyrosine Kinase (“BTK”). In clinical trials, vecabrutinib has shown activity against both wild type and C481S-mutated BTK, the most common mutation associated with resistance to ibrutinib. Vecabrutinib is being studied in a Phase 1b/2 clinical trial to assess safety and activity in patients with advanced B-cell malignancies after two or more prior therapies, including ibrutinib or another covalent BTK inhibitor where approved for the disease. The Phase 1b portion of the study is a dose escalation component that will proceed to define a maximum tolerated dose and/or a recommended Phase 2 dose. Upon identifying the Phase 2 dose, the Phase 2 portion will further explore clinical activity and safety in disease- and mutation-specific cohorts, including patients with and without BTK C481 mutations. The Company is also developing SNS-510, a PDK1 inhibitor licensed from Millennium Pharmaceuticals, Inc., a wholly-owned subsidiary of Takeda Pharmaceutical Company Limited (“Takeda”). The Company acquired from Takeda global commercial rights to several potential first-in class, preclinical inhibitors of the novel target PDK1, including SNS-510. The Company is currently characterizing SNS-510 through preclinical pharmacology studies, manufacturing and formulation activities. The Company is in a collaboration with Takeda for the development of TAK-580 (formerly MLN2480), an oral pan-RAF inhibitor, which is under investigation for pediatric low-grade glioma. The Company is also evaluating strategic alternatives for vosaroxin, a topoisomerase 2 inhibitor for which we conducted a Phase 3 trial in patients with relapsed or refractory acute myeloid leukemia. Liquidity and Going Concern The Company has incurred significant losses and negative cash flows from operations since its inception, and as of December 31, 2018, had cash and cash equivalents totaling $13.7 million and an accumulated deficit of $659.5 million. The Company expects to continue to incur significant losses for the foreseeable future as it continues development of its kinase inhibitor pipeline, including its BTK inhibitor, vecabrutinib. The Company has prioritized development funding on its kinase inhibitor portfolio with a focus on vecabrutinib. The Company has a limited number of products that are still in the early stages of development and will require significant additional investment. The Company’s cash and cash equivalents are not sufficient to support its operations for a period of twelve months from the date these consolidated financial statements are available to be issued. These factors raise substantial doubt about its ability to continue as a going concern. The Company will require additional financing to fund working capital, repay debt and pay its obligations as they come due. Additional financing might include one or more offerings and one or more of a combination of equity securities, debt arrangements or partnership or licensing collaborations. However, there can be no assurance that the Company will be successful in acquiring additional funding at levels sufficient to fund its operations or on terms favorable to the Company. If the Company is unsuccessful in its efforts to raise additional financing in the near term, the Company will be required to significantly reduce or cease operations. The principal payments due under the Loan Agreement (as defined in Note 8) have been classified as a current liability as of December 31, 2018 and 2017 due to the considerations discussed above and the assessment that the material adverse change clause under the Loan Agreement is not within the Company's control. The Company has not been notified of an event of default by the Lenders (as defined in Note 8) as of the date of the filing of this Form 10-K. The accompanying consolidated financial statements have been prepared assuming the Company will continue to operate as a going concern, which contemplates the realization of assets and the settlement of liabilities in the normal course of business. The consolidated financial statements do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts of liabilities that may result from uncertainty related to the Company’s ability to continue as a going concern . Concentrations of Credit Risk In accordance with its investment policy, the Company invests cash that is not currently being used for operational purposes. The policy allows for the purchase of low risk debt securities issued by: (a) the United States and certain European governments and government agencies, and (b) highly rated banks and corporations, denominated in U.S. dollars, Euros, or British pounds, subject to certain concentration limits. The policy limits maturities of securities purchased to no longer than 24 months and the weighted average maturity of the portfolio to 12 months. Management believes these guidelines ensure both the safety and liquidity of any investment portfolio the Company may hold. Financial instruments that potentially subject the Company to concentrations of credit risk generally consist of cash, cash equivalents and marketable securities. The Company is exposed to credit risk in the event of default by the institutions holding its cash, cash equivalents and any marketable securities to the extent of the amounts recorded in the balance sheets.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). Adopted Accounting Pronouncements In January 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities Technical Corrections and Improvements to Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities . In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (“SAB”) No. 118 (SEC Update) Recent Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases Codification Improvements to Topic 842, Leases Leases (Topic 842): Targeted Improvements The Company has elected the package of practical expedients permitted under ASC 842. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease under ASC Topic 842, (b) whether classification of the operating leases would be different in accordance with ASC Topic 842, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs in ASC Topic 842 at lease commencement. In addition, the Company made an accounting policy election to combine the lease and non-lease components and the short-term lease practical expedients allowed under ASC 842. The adoption of ASC 842 will lead to an increase in the assets and liabilities recorded on the balance sheets primarily due to the lease agreement attributable to leased office space. This standard will not have a material impact on the Company’s balance sheets or cash flows from operations. In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Sunesis Europe Limited, a United Kingdom corporation, and Sunesis Pharmaceuticals (Bermuda) Ltd., a Bermuda corporation, as well as a Bermuda limited partnership, Sunesis Pharmaceuticals International LP. All intercompany balances and transactions have been eliminated in consolidation. Segment Reporting Management has determined that the Company operates as a single reportable segment. Significant Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to the valuation of equity and related instruments, revenue recognition, stock-based compensation and clinical trial accounting. Cash Equivalents and Marketable Securities The Company considers all highly liquid securities with original maturities of three months or less from the date of purchase to be cash equivalents, which generally consist of money market funds and corporate debt securities. Marketable securities consist of securities with original maturities of greater than three months, which may include U.S. and European government obligations and corporate debt securities. Management determines the appropriate classification of securities at the time of purchase income equity The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in other income, net in the statements of operations and comprehensive loss. Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale securities, if any, are also recorded to other income, net. The cost of securities sold is based on the specific-identification method. Invoices for certain services provided to the Company are denominated in foreign currencies. To manage the risk of future movements in foreign exchange rates that would affect such amounts, the Company may purchase certain European currencies or highly-rated investments denominated in those currencies, subject to similar criteria as for other investments defined in the Company’s investment policy. There is no guarantee that the related gains and losses will substantially offset each other, and the Company may be subject to significant exchange gains or losses as currencies fluctuate from quarter to quarter. To date, the Company has purchased Euros and Euro-denominated obligations of foreign governments and corporate debt. As of December 31, 2018 and December 31, 2017, the Company held investments denominated in Euros with an aggregate fair value of $0.8 million. Any cash, cash equivalent and short-term investment balances denominated in foreign currencies are recorded at their fair value based on the current exchange rate as of each balance sheet date. The resulting exchange gains or losses and those from amounts payable for services originally denominated in foreign currencies are both recorded in other income, net in the statements of operations and comprehensive loss Fair Value Measurements The Company measures cash equivalents and marketable securities at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP: Level 1 - quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date Level 2 - inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly Level 3 - unobservable inputs The Company’s Level 2 valuations of marketable securities are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets. The carrying amounts of the Company’s financial instruments, including Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the term of the lease. Accounting for Royalty Agreement The payment of $25.0 million by RPI under the Royalty Agreement (see Note 6) is non-refundable, and no revenue participation right payments will be made unless vosaroxin is T , less $3.1 million initially . The fair value of the warrants was recorded to additional paid-in capital. Accounting for Notes Payable The accounting for certain fees and expenses related to the Loan Agreement (see Note 8) is as follows. The facility fee is being accounted for as a debt discount and classified within notes payable on the Company’s balance sheet. The fair value of the warrants issued in connection with the Loan Agreement have been recorded as a debt discount within notes payable and an increase to additional paid-in capital on the Company’s balance sheet. The debt discount is being amortized as interest expense over the term of the loan using the effective interest method. The final payment is being accreted as interest expense over the term of the loans using the effective interest method. The legal fees are being accounted for as deferred debt issuance costs within assets on the Company’s balance sheet and are being amortized as other income, net over the term of the loans using the effective interest method. Revenue Recognition On January 1, 2018, the Company adopted Topic 606, Revenue from Contracts with Customers Revenue Recognition Adoption of the new standard did not result in any change to the Company’s opening retained earnings as of January 1, 2018 as no cumulative impact to the adoption of ASC 606 was noted as a result of the Company’s assessment of the comparative revenue recognized since inception of the contracts under the new revenue standard ASC 606 and historic standard ASC 605. The Company is applying the practical exemption allowed under ASC 606 and does not disclose the value of variable consideration that is a sale-based royalty promised in exchange for a license of intellectual property. The adoption of the new standard resulted in changes to the Company’s accounting policies for revenue recognition as detailed below: The Company’s contracts consist license, milestone and royalty payments primarily generated through agreements with strategic partners for the development and commercialization of the Company’s product candidates. The terms of the agreement typically include non-refundable upfront fees, payments based upon achievement of milestones and royalties on net product sales. The Company has both fixed and variable consideration. Non-refundable upfront fees are considered fixed, while milestone payments are identified as variable consideration. In determining the appropriate amount of revenue to be recognized as it fulfills its performance obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the customer, and the customer can use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Event-based or milestone payments: At the inception of each arrangement that includes event-based or milestone payments, the Company evaluates whether the events or milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated event-based or milestone payments is included in the transaction price. Event-based or milestone payments that are not within the control of the Company are not included in the transaction price until they become probable of being achieved. Royalties: For arrangements that include sales-based royalties and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements. Research and Development Research and development expense consists primarily of: (a) clinical trial costs, which include payments for work performed by contract research organizations (“CROs”), clinical trial sites, labs and other clinical service providers, and for drug packaging, storage and distribution; (b) drug manufacturing costs, which include costs for producing drug substance and drug product, and for stability and other testing; (c) personnel costs for related permanent and temporary employees; (d) other outside services and consulting costs; and (e) payments under license agreements. All research and development costs are expensed as they are incurred. Clinical Trial Accounting The Company records accruals for estimated clinical trial costs, which include payments for work performed by CROs and participating clinical trial sites. These costs are generally a significant component of research and development expense. Costs incurred for setting up clinical trial sites for participation in trials are generally non-refundable, and are expensed as incurred, with any refundable advances related to enrollment of the first patient recorded as prepayments and assessed for recoverability on a quarterly basis. Costs related to patient enrollment are accrued as patients progress through the clinical trial, including amortization of any first-patient prepayments. This amortization generally matches when the related services are rendered, however, these cost estimates may or may not match the actual costs incurred by the CROs or clinical trial sites, and if the Company has incomplete or inaccurate information, the clinical trial accruals may not be accurate. The difference between accrued expenses based on the Company’s estimates and actual expenses have not been significant to date. Warrants for Shares of Common Stock The Company accounts for warrants for shares of common stock as equity instruments in the accompanying balance sheets at their fair value on the date of issuance because such warrants are indexed to the Company’s common stock and no cash settlement is required except for (i) liquidation of the Company, or (ii) a change in control in which the common stockholders also receive cash. Stock-Based Compensation The Company grants options to purchase common stock to its employees, directors and consultants under its stock option plans. Under the Company’s Employee Stock Purchase Plan, eligible employees can also purchase shares of the Company’s common stock at 85% of the lower of the fair market value of the Company’s common stock at the beginning of a 12-month offering period or at the end of one of the two related six-month purchase periods. The Company values these share-based awards using the Black-Scholes option valuation model (the “Black-Scholes model”). The determination of fair value of share-based payment awards on the date of grant using the Black-Scholes model is affected by the Company’s stock price as well as assumptions regarding a number of subjective variables. These variables include, but are not limited to, the expected stock price volatility over the term of the awards and actual and projected employee stock option exercise behaviors. Foreign Currency Transactions that are denominated in a foreign currency are translated into U.S. dollars at the current exchange rate on the transaction date. Any foreign currency-denominated monetary assets and liabilities are subsequently remeasured at current exchange rates as of each balance sheet date, with gains or losses on foreign exchange recognized in other income, net in the statements of operations and comprehensive loss. Income Taxes The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the differences between the tax basis of assets and liabilities and their basis for financial reporting. Deferred tax assets or liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which temporary differences are expected to be recovered or settled. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company’s policy is to recognize interest charges and penalties in other income, net in the statements of operations and comprehensive loss.

Loss per Common Share

Loss per Common Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Loss per Common Share	3. Loss per Common Share Basic loss per common share is calculated by dividing net loss by the weighted-average number of common shares outstanding for the period. Diluted net loss per common share is computed by dividing (a) net loss, less any anti-dilutive amounts recorded during the period, by (b) the weighted-average number of common shares outstanding for the period plus dilutive potential common shares as determined using the treasury stock method for options and warrants to purchase common stock. The following table sets forth the computation of basic and diluted loss per common share for the periods presented (in thousands, except per share amounts): Year Ended December 31, 2018 2017 Numerator: Net loss—basic and diluted $ (26,615 ) $ (35,458 ) Denominator: Weighted-average common shares outstanding—basic and diluted 35,582 24,516 Net loss per common share: Basic and Diluted $ (0.75 ) $ (1.45 ) The following table represents the potential common shares issuable pursuant to outstanding securities as of the related period end dates that were excluded from the computation of diluted loss per common share because their inclusion would have had an anti-dilutive effect (in thousands): As of December 31, 2018 2017 Warrants to purchase shares of common stock 218 5,218 Convertible preferred stock 6,331 6,331 Options to purchase shares of common stock 4,160 3,532 Outstanding securities not included in calculations 10,709 15,081

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Financial Instruments	4. Financial Instruments Financial Assets The following tables summarize the estimated fair value of the Company’s financial assets measured on a recurring basis as of the dates indicated, which were comprised solely of available-for-sale marketable securities with remaining contractual maturities of one year or less (in thousands): Gross Gross Valuation Amortized Unrealized Unrealized Estimated Fair December 31, 2018 Input Level Cost Gains Losses Value Money market funds Level 1 $ 10,845 $ — $ — $ 10,845 Total available-for-sale securities 10,845 — — 10,845 Less amounts classified as cash equivalents (10,845 ) — — (10,845 ) Amounts classified as marketable securities $ — $ — $ — $ — Gross Gross Valuation Amortized Unrealized Unrealized Estimated Fair December 31, 2017 Input Level Cost Gains Losses Value Money market funds Level 1 $ 20,470 $ — $ — $ 20,470 U.S. corporate debt obligations Level 2 3,282 — (5 ) 3,277 U.S. commercial paper Level 2 1,498 — (2 ) 1,496 Total available-for-sale securities 25,250 — (7 ) 25,243 Less amounts classified as cash equivalents (20,470 ) — — (20,470 ) Amounts classified as marketable securities $ 4,780 $ — $ (7 ) $ 4,773 There were no available-for-sale securities in an unrealized gain or loss position as of December 31, 2018. No significant facts or circumstances have arisen to indicate that there has been any deterioration in the creditworthiness of the issuers of these securities. There were no realized gains or losses on the available-for-sale securities in the years ended December 31, 2018 and 2017. There were no sales of available-for-sale debt securities in the years ended December 31, 2018 and 2017.

Other Accrued Liabilities

Other Accrued Liabilities	12 Months Ended
	Dec. 31, 2018
Payables And Accruals [Abstract]
Other Accrued Liabilities	5. Other Accrued Liabilities Other accrued liabilities as of December 31 were as follows (in thousands): 2018 2017 Accrued outside services $ 556 $ 1,096 Accrued professional services 251 471 Accrued interest 284 — Other accruals — 3 Total other accrued liabilities $ 1,091 $ 1,570

Royalty Agreement

Royalty Agreement	12 Months Ended
	Dec. 31, 2018
Revenue Recognition [Abstract]
Royalty Agreement	6. Royalty Agreement In March 2012, the Company entered into a Revenue Participation Agreement (the “Royalty Agreement”), with RPI Finance Trust (“RPI”), an entity related to Royalty Pharma. In September 2012, pursuant to the provisions of the Royalty Agreement, RPI made a $25.0 million cash payment to the Company. The payment, less $3.1 million representing the fair value of the warrants granted under the arrangement, was initially classified as deferred revenue and was fully amortized to revenue as of March 31, 2017. Revenue participation right payments will be made to RPI when and if vosaroxin is commercialized, at a rate of 6.75% of net sales of vosaroxin, on a product-by-product and country-by-country basis world-wide through the later of: (a) the expiration of the last to expire of certain specifically identified patents; (b) 10 years from the date of first commercial sale of such product in such country; or (c) the expiration of all applicable periods of data, market or other regulatory exclusivity in such country with respect to such product.

License Agreements

License Agreements	12 Months Ended
	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
License Agreements	7. License Agreements Biogen Idec The first amended and restated collaboration agreement with Biogen Idec MA, Inc. (the “Biogen 1st ARCA”) amended and restated the collaboration agreement with Biogen (the “Biogen OCA”), to provide for the discovery, development and commercialization of small molecule BTK inhibitors. Under this agreement, the Company no longer has research obligations, but licenses granted to Biogen with respect to the research collaboration under the Biogen OCA (other than the licenses transferred to Takeda under the Takeda Agreement) remain in effect. In June 2012, the Company received an event-based payment and recognized as revenue of $1.5 million from Biogen for the advancement of pre-clinical work in connection with the Biogen 1st ARCA. Under this agreement, the Company is eligible to receive up to an additional $58.5 million in pre-commercialization event-based payments related to the development by Biogen of the first two indications for licensed products against the BTK target. In December 2018, the Company entered into a settlement agreement with Biogen whereas Biogen will no longer be obligated to pay future event-based payments or royalty payments to the Company. In December 2013, the Company entered into a second amended and restated collaboration agreement with Biogen (the “Biogen 2nd ARCA”), to provide the Company with an exclusive worldwide license to develop, manufacture and commercialize vecabrutinib Takeda In March 2011, Takeda Pharmaceuticals, Inc., a wholly-owned subsidiary of Takeda Pharmaceutical Company Limited (“Takeda”) purchased and exclusively licensed Biogen’s rights to a PDK1 inhibitor program and a pan-Raf inhibitor program which were both originally developed through a collaboration agreement between Sunesis and Biogen. In January 2014, the Company entered into an amended and restated license agreement with Takeda (the “Amended Takeda Agreement”), to provide the Company with an exclusive worldwide license to develop and commercialize preclinical inhibitors of PDK1. In connection with the execution of the Amended Takeda Agreement, the Company paid an upfront fee and may be required to make up to $9.2 million in pre-commercialization milestone payments depending on its development of PDK1 inhibitors and tiered royalty payments based on percentages of net sales, if any, beginning in the mid-single-digits and not to exceed the low-teens. With respect to the pan-Raf inhibitor program, the Company may in the future receive up to $57.5 million in pre-commercialization event-based payments related to the development by Takeda of the first two indications for each of the licensed products directed against the Raf target and royalty payments depending on related product sales. Under this program, Takeda is currently supporting a Phase 1b/2 clinical study of an oral investigative drug, TAK-580 (formerly MLN2480), in pediatric low-grade giloma. As of December 31, 2018, all future event-based payments and royalty payments are considered fully constrained variable considerations and therefore, no contract assets have been recorded and no revenue have been recognized.

Notes Payable

Notes Payable	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Notes Payable	8. Notes Payable In 2017, the Company entered into two amendments (the “Amendments”) to its existing loan agreement (the “Loan Agreement”) with Western Alliance Bank and Solar Capital Ltd. (the “Lenders”) and Western Alliance, as Collateral Agent (the “Collateral Agent”). Under terms of the Amendments, the Company will be required to pay interest on the borrowings under the Loan Agreement at a per annum rate equal to 8.54% plus the then effective one-month U.S. LIBOR rate. The average effective interest rates were 10.5% and 9.6% for the years ended December 31, 2018 and 2017, respectively. The Amendments modified the loan repayment terms to be interest-only through January 1, 2019, contingent upon the receipt of at least Twenty-Five Million dollars ($25,000,000) in unrestricted cash proceeds on or prior to September 15, 2018. The Company qualified for the extension and the interest-only period was extended to January 1, 2019. In addition to principal and interest, a final payment equal to $312,500 will be due upon maturity date of April 1, 2020 or such earlier date specified in the Loan Agreement and the Amendments, of which $284,000 has been accrued and recorded in the other accrued liabilities line item in the accompanying consolidated balance sheet as of December 31, 2018. If the Company repays all amounts owed under the Loan Agreement and the Amendments prior to the maturity date, the Company will pay a prepayment fee equal to 0.5% of the amount prepaid. The outstanding principal balance of this loan was $7,500,000 as of December 31, 2018. In conjunction with the Loan Agreement, the Lenders were issued five-year warrants to purchase an Pursuant to the Loan Agreement and the Amendments, the Company is bound during the term of the Loan Agreement and the Amendments by a variety of affirmative covenants, including, without limitation, certain information delivery requirements and notice requirements, and negative covenants, including, without limitation, restrictions on incurring certain additional indebtedness, making certain asset dispositions, entering into certain mergers, acquisitions or other business combination transactions or incurring any non-permitted lien or other encumbrance on the Company’s assets. Upon the occurrence of an event of default under the Loan Agreement and the Amendments (subject to cure periods for certain events of default), all amounts owed by the Company thereunder would begin to bear interest at a rate that is 5.0% higher than the rate that would otherwise be applicable and may be declared immediately due and payable by the Collateral Agent. In the event of default by the Company, the Lenders would be entitled to exercise their remedies thereunder, including the right to accelerate the debt, upon which the Company may be required to repay all amounts then outstanding under the Loan Agreement and the Amendments, which could harm the Company's financial condition. The Company was in compliance with all applicable covenants set forth in the Loan Agreement and the Amendments as of December 31, 2018 and December 31, 2017. The principal payments due under the Loan Agreement and the Amendments have been classified as a current liability at December 31, 2018 and December 31, 2017 due to the considerations discussed in Note 1 and the assessment that the material adverse change clause under the Loan Agreement and the Amendments is not within the Company's control. The Company has not been notified of an event of default by the Lenders as of the date of the filing of this Form 10-K. The Collateral Agent, for the benefit of the Lenders, has a perfected security interest in substantially all of the Company’s property, rights and assets, except for intellectual property, to secure the payment of all amounts owed to the Lenders under the Loan Agreement. Aggregate future minimum payments due under the Loan Facility as of December 31, 2018 Year ending December 31, Total 2019 6,168 2020 2,231 Total minimum payments 8,399 Less amount representing interest (899 ) Total notes payable as of December 31, 2018 7,500 Less unamortized debt discount and issuance costs (104 ) Less current portion of notes payable (7,396 ) Non-current portion of notes payable $ —

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Commitments The Company’s operating lease obligation s solely ing The lease was entered into in January 2014 and was amended several times since 2014. Aggregate non-cancelable future minimum rental payments under operating leases as of December 31, 2018, were as follows (in thousands): Year Ending December 31, Payments 2019 $ 562 2020 $ 578 2021 $ 294 Total rental payments $ 1,434 The Company recognizes rent expense on a straight-line basis. The Company recorded rent expense of $0.5 million and $0.7 Contingencies From time to time, the Company may be involved in legal proceedings, as well as demands, claims and threatened litigation, which arise in the normal course of its business or otherwise. The ultimate outcome of any litigation is uncertain and unfavorable outcomes could have a negative impact on the Company’s results of operations and financial condition. Regardless of outcome, litigation can have an adverse impact on the Company because of the defense costs, diversion of management resources and other factors. The Company is not currently involved in any material legal proceedings.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ Equity Preferred Stock The Company has 10,000,000 shares of authorized preferred stock available for issuance in one or more series. Upon issuance, the Company can determine the rights, preferences, privileges and restrictions thereof. These rights, preferences and privileges could include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of such series, any or all of which may be greater than the rights of common stock. There were 17,697 shares of preferred stock outstanding as of December 31, 2018 2017, respectively. These shares are non-voting Series B, Series C, and Series D Convertible Preferred Stock at a price of $840, $3,850, and $2,000 per share, respectively. Each share of non-voting Series B is convertible into 166 shares of common stock and each share of non-voting Series C Stock and Series D Stock is convertible into 1000 shares of common stock, provided that conversion will be prohibited if, as a result, the holder and its affiliates would own more than 9.98% of the total number of shares of common stock then outstanding • senior to all of the Company’s Common Stock; • senior to any class or series of the Company’s capital stock hereafter created specifically ranking by its terms junior to the Series B, Series C, and Series D Stock; • on parity with any class or series of the Company’s capital stock hereafter created specifically ranking by its terms on parity with the Series B, Series C, and Series D Stock; • junior to any class or series of the Company’s capital stock hereafter created specifically ranking by its terms senior to the Series B, Series C, and Series D Stock; in each case, as to distributions of assets upon the Company’s liquidation, dissolution or winding up whether voluntarily or involuntarily. Common Stock Holders of common stock are entitled to one vote per share on all matters to be voted upon by the stockholders of the Company. Subject to the preferences that may be applicable to any outstanding shares of preferred stock, the holders of common stock are entitled to receive ratably such dividends, if any, as may be declared by the Board of Directors. Under the terms of the Loan Agreement with the Lenders, the Company is precluded from paying cash dividends without the prior written consent of the Lenders. Underwritten Offerings In December 2015, the Company completed underwritten offering of (i) 1,832,698 shares of its common stock, that included the In October 2016, the Company completed underwritten offering of (i) 5,675,825 shares of its common stock at a price of $3.85 per share, and (ii) 1,558 shares of its non-voting Series C Convertible Preferred Stock (“Series C Stock”) at a price of $3,850.00 per share. Gross proceeds from the sale were $27.9 million and net proceeds were $25.9 million. Each share of non-voting Series C Stock is convertible into 1,000 shares of Sunesis common stock, provided that conversion will be prohibited if, as a result, the holder and its affiliates would own more than 9.98% of the total number of shares of Sunesis common stock then outstanding. In October 2017, the Company completed underwritten offerings of (i) 7,500,000 shares of its common stock and accompanying warrants to purchase 3,750,000 shares of its common stock at a price to the public of $2.00 for each share of common stock and warrant to purchase 0.5 shares of common stock, and (ii) 2,500 shares of its non-voting Series D Convertible Preferred Stock (“Series D Stock”) and accompanying warrants to purchase 1,250,000 shares of its common stock at a price to the public of $2,000 for each share of Series D Stock and warrant to purchase 500 shares of common stock. The exercise price of the warrants was $3.00 per whole share of common stock. The warrants expired unexercised on October 28, 2018. Each share of non-voting Series D Stock is convertible into 1,000 shares of its common stock, provided that conversion will be prohibited if, as a result, the holder and its affiliates would own more than 9.98% of the total number of shares of its common stock then outstanding. Gross proceeds from the sale were $20.0 million and net proceeds were $18.5 million. Controlled Equity Offerings In August 2011, the Company entered into a Controlled Equity Offering SM During the years ended December 31, 2018 and 2017, the Company sold 617,967 shares and 5,321,151 2.72 14.2 43.6 Aspire Common Stock Purchase Agreement In June 2018, the Company entered into a Common Stock Purchase Agreement (the “CSPA”) with Aspire Capital Fund, LLC (“Aspire”), pursuant to which the Company could issue and sell shares of its common stock having an aggregate gross sales price of up to $15.5 million. Upon execution of the CSPA, the Company sold to Aspire 228,311 shares of common stock at a price of $2.19 per share, for total proceeds of $0.5 million. In addition, Aspire committed to purchasing up to an additional $15.0 million of common shares, at the Company’s request, from time to time during a 24-month period at prices based on the market price at the time of each sale. Under the CSPA, on any trading day selected by the Company on which the closing price of its common stock is equal to or greater than $0.25 per share, the Company has the right, in its sole discretion, to present Aspire with a purchase notice directing Aspire to purchase up to 200,000 shares of common stock per business day, at a purchase price equal to the lesser of: a) the lowest sale price of common stock on the purchase date; or b) the arithmetic average of the three lowest closing sale prices during the 10 consecutive business days ending on the trading day immediately preceding the purchase date. The Company also has the right to require Aspire to purchase up to an additional 30% of the trading volume of the shares for the next business day at a purchase price (the “VWAP Purchase Price”), equal to the lesser of: (i) the closing sale price of the shares on the purchase date, or (ii) ninety-seven percent (97%) of the next business day’s volume weighted average price (each such purchase, a “VWAP Purchase”). The Company shall have the right, in its sole discretion, to determine a maximum number of shares and set a minimum market price threshold for each VWAP Purchase. The Company can only require a VWAP Purchase if the Company has also submitted a regular purchase on the notice date for the VWAP Purchase. There are no limits on the number of VWAP purchases that the Company may require. There are no trading volume requirements or restrictions under the CSPA, and the Company will control the timing and amount of sales. Aspire has no right to require any sales by the Company, but is obligated to make purchases from the Company as directed by the Company in accordance with the CSPA There are no limitations on use of proceeds, financial or business covenants, restrictions on future fundings, rights of first refusal, participation rights, penalties or liquidated damages in the Purchase Agreement. The CSPA may be terminated by the Company at any time, at its discretion, without any cost to the Company. Aspire has agreed that neither it nor any of its agents, representatives and affiliates shall engage in any direct or indirect short-selling or hedging of common stock during any time prior to the termination of the CSPA. Any proceeds from the Company receives under the CSPA are expected to be used for working capital and general corporate purposes. The Company cannot request Aspire to purchase more than 2,000,000 shares per business day. As consideration for Aspire’s obligation under the CSPA, the Company issued 212,329 shares of common stock to Aspire as a commitment fee. This $0.4 million commitment fee and $0.1 million in other transaction costs were recorded in June 2018 as costs of equity financing, within additional paid-in capital. The Company also entered into a Registration Rights Agreement with Aspire. During the year ended December 31, 2018, the Company issued to Aspire a total of 2,390,640 shares for total net proceeds of $4.6 million. The shares were issued at an average price of $2.20 per share, excluding the 212,329 commitment shares issued. Aspire’s remaining purchase commitment was $10.9 million as of December 31, 2018. Equity Incentive Plans The Company grants options to purchase shares of its common stock primarily to: (i) new employees, of which 25% of the shares subject to such options become exercisable on the first anniversary of the vesting commencement date, and 1/48th of the shares subject to such options become exercisable each month over the remainder of the four-year vesting period, (ii) existing employees with various vesting schedules over three to four years, (iii) new non-employee members of the board of directors, of which 1/24th of the shares subject to such options become exercisable each month following the date of grant over a two-year vesting period, and (iv) continuing non-employee members of the board of directors, of which 1/12th of the shares subject to such options become exercisable each month following the date of grant over a one-year vesting period. On March 15, 2011, the Company’s Board of Directors adopted, and on June 3, 2011, the Company’s stockholders approved, the 2011 Equity Incentive Plan (the “2011 Plan”). The 2011 Plan is intended as the successor to and continuation of the Company’s 1998 Stock Plan, 2001 Stock Plan, 2005 Equity Incentive Award Plan and 2006 Employment Commencement Incentive Plan (collectively, the “Prior Plans”). No additional stock awards will be granted under the Prior Plans. The number of shares of common stock available for issuance under the 2011 Plan automatically increases on January 1st of each year for a period of 10 years commencing on January 1, 2012 by an amount equal to: (i) 4.0% of the Company’s outstanding shares of common stock on December 31st of the preceding calendar year, or (ii) a lesser amount determined by the Board of Directors. On January 1, 2018 and 2017, in accordance with the above, . During the year ended December 31, 2018, options to purchase 1,622,248 755,075 Employee Stock Purchase Plans On March 5, 2011, the Company’s Board of Directors adopted, and on June 3, 2011, the Company’s stockholders approved, the 2011 Employee Stock Purchase Plan (the “2011 ESPP”). The 2011 ESPP permits eligible employees to purchase common stock at a discount through payroll deductions during defined offering periods. Eligible employees can purchase shares of the Company’s common stock at 85% of the lower of the fair market value of the common stock at (i) the beginning of a 12-month offering period, or (ii) at the end of one of the two related 6-month purchase periods. No participant in the 2011 ESPP may be issued or transferred shares of common stock valued at more than $25,000 per calendar year. The number of shares of common stock available for issuance under the 2011 ESPP automatically increases on January 1st of each year for a period of 10 years commencing on January 1, 2012 by an amount equal to: (i) 1.0% of the Company’s outstanding shares of common stock on December 31st of the preceding calendar year, or (ii) a lesser amount determined by the Board of Directors. A total of 104,099 Warrants Warrants to purchase shares of the Company’s common stock outstanding as of December 31, 2018 were as follows (in thousands, except per share amounts): Exercise Price Date Issued Shares Per Share Expiration February 2015 10 $ 13.32 February 2020 March 2016 208 $ 3.25 March 2021 Total warrants outstanding and exercisable 218 Reserved Shares Shares of the Company’s common stock reserved for future issuance as of December 31, 2018 Shares Available Total for Future Outstanding Shares Grant Securities Reserved Warrants — 218 218 Convertible preferred stock — 6,331 6,331 Stock option plans 755 4,160 4,915 Employee stock purchase plan 64 — 64 Total reserved shares of common stock 819 10,709 11,528

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	11. Stock-Based Compensation Overview Employee stock-based compensation expense is calculated based on the grant-date fair value of awards ultimately expected to vest and recognized under the straight-line attribution method, assuming that all stock-based awards will vest. The following table summarizes stock-based compensation expense related to the Company’s stock-based awards for the periods indicated (in thousands): Year ended December 31, 2018 2017 Research and development $ 581 $ 865 General and administrative 903 2,059 Employee stock-based compensation expense 1,484 2,924 Non-employee stock-based compensation expense 1,153 109 Total stock-based compensation expense $ 2,637 $ 3,033 Option Exchange Program On June 9, 2017, we filed a Tender Offer Statement (TO) on Schedule TO relating to an option exchange program for its officers and employees (the Option Exchange) to exchange certain stock options to purchase up to an aggregate of 781,505 shares of its common stock that had been granted to eligible holders, for a lesser number of new stock options with a lower exercise price. Stock options with an exercise price greater than or equal to $8.00, and held by eligible holders in continuous service through the termination of the Option Exchange, were eligible for exchange in the program. An exchange ratio of 1.30 for 1 was applied to options priced from $8.00 to $19.99, and an exchange ratio of 1.75 for 1 was applied to options priced at $20.00 or greater. As of the closing of the Option Exchange on July 10, 2017, 25 eligible holders had tendered an aggregate of 778,928 options for 543,650 new options to purchase shares of its common stock. Each new stock option was granted on July 10, 2017, pursuant to its 2011 Equity Incentive Plan with an exercise price per share of $2.62, which was the closing market price on the grant date of the new options. The exchange of stock options was treated as a modification for accounting purposes and resulted in an incremental expense of $50,957, for the vested options, which was calculated using the Black-Scholes option pricing model. The incremental expense together with the unamortized expense remaining on the unvested options is being amortized over the vesting period of the new options. Fair Value of Awards The Company determines the fair value of stock-based awards on the grant date using the Black-Scholes model, which is impacted by the Company’s stock price, as well as assumptions regarding a number of subjective variables. The following table summarizes the weighted-average assumptions used as inputs to the Black-Scholes model, and resulting weighted-average and total estimated grant date fair values of employee stock options granted during the periods indicated: Year Ended December 31, 2018 2017 Employees Consultants Employees Consultants Assumptions: Expected term (years) 4.3 9.8 4.8 9.7 Expected volatility 126.0 % 117.6 % 112.5 % 121.6 % Risk-free interest rate 2.6 % 2.8 % 2.1 % 2.4 % Expected dividend yield 0.0 % 0.0 % 0.0 % 0.0 % Fair value: Weighted-average estimated grant date fair value per share $ 0.96 $ 1.19 $ 2.68 $ 3.23 Options granted (in thousands) 1,204 418 1,280 287 Total estimated grant date fair value (in thousands) $ 1,161 $ 497 $ 3,434 $ 926 The estimated fair value of stock options that vested in the years ended December 31, 2018 and 2017 was $ 2.0 1.9 Option Plan Activity The following table summarizes stock option activity for the Company’s stock option plans in the periods presented (in thousands, except per share amounts): Weighted Weighted Average Average Number Exercise Remaining Aggregate of Price Per Contractual Intrinsic Shares Share Term (Years) Value Outstanding as of December 31, 2017 3,532 $ 6.18 Options granted 1,622 $ 1.20 Options exercised (49 ) $ 3.34 Options forfeited or expired (945 ) $ 8.91 Outstanding as of December 31, 2018 4,160 $ 3.66 7.55 $ — Vested and expected to vest as of December 31, 2018 4,160 $ 3.66 7.55 $ — Exercisable as of December 31, 2018 2,118 $ 5.44 5.76 $ — The aggregate intrinsic value in the table above represents the total pre-tax intrinsic value (i.e., the difference between the Company’s closing stock price on the last trading day of the period and the exercise price, multiplied by the number of in-the-money options) that would have been received by option holders if they had exercised all their options on December 31, 2018. The intrinsic value of options exercised during each of the years ended December 31, 2018 and 2017 was less than $ 0.1 Total estimated unrecognized stock-based compensation cost related to unvested stock options was $ 2.8 2.8

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes Loss before the provision for income taxes consisted of the following (in thousands): Year Ended December 31, 2018 2017 U.S. operations $ (21,132 ) $ (24,776 ) Foreign operations (5,483 ) (10,682 ) Loss before provision for income taxes $ (26,615 ) $ (35,458 ) No provision for income taxes was recorded in the periods presented due to tax losses incurred in each period. The income tax provision differs from the amount computed by applying the statutory income tax rate of 21% to pre-tax loss as follows (in thousands): Year Ended December 31, 2018 2017 Tax (benefit) at statutory federal rate 21.0 % 34.0 % State tax (benefit), net of federal benefit 4.6 1.2 Foreign tax rate differential (4.3 ) (10.2 ) Permanent differences (0.6 ) (1.0 ) Research and development credits 1.0 0.7 Change in valuation allowance (15.9 ) 127.2 Change in tax rate — (151.6 ) Provision-to-return (0.7 ) — Expired NOLs and research and development credits, and carryfowards (2.2 ) — Non-qualified stock option cancellations (2.9 ) (0.3 ) Effective tax rate — % — % Deferred income taxes reflect the net tax effects of loss and credit carry-forwards and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets for federal and state income taxes are as follows (in thousands): December 31, 2018 2017 Deferred tax assets: Federal and state net operating loss carry-forwards $ 114,254 $ 109,714 Federal and state research credit carry-forwards 14,885 14,520 Capitalized research costs 6,134 6,304 Stock-based compensation 4,002 4,528 Property and equipment 79 83 Accrued liabilities 143 117 Gross deferred tax assets 139,497 135,266 Valuation allowance (139,497 ) (135,266 ) Net deferred tax assets $ — $ — The Company’s unrecognized tax benefits relate to research and development tax credits claimed on the Company’s tax returns. The research and development tax credits have not been utilized, are fully offset by a valuation allowance, and currently have no tax expense impact. A reconciliation of the Company’s beginning and ending amount of unrecognized tax benefits is follows (in thousands): December 31, 2018 2017 Unrecognized tax benefits at beginning of period $ 1,769 $ 1,441 Increases related to current year tax positions 43 57 Increase related to change in tax rate — 271 Unrecognized tax benefits at the end of period $ 1,812 $ 1,769 Realization of the deferred tax assets is dependent upon future taxable income, if any, the amount and timing of which are uncertain. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. The net valuation allowance increased by approximately $4.2 million and decreased by approximately $45.1 million during the years ended December 31, 2018 and 2017, respectively. As of December 31, 2018, the Company had federal net operating loss carry-forwards of $ 448.2 8.7 288.3 .6 Utilization of these net operating loss and tax credits carry-forwards may be subject to a substantial annual limitation due to the ownership change rules under Section 382 of the Internal Revenue Code of 1986, as amended (the “Code”). The limitations are applicable if an “ownership change,” as defined in the Code, is deemed to have occurred or occurs in the future. The annual limitation may result in the expiration of net operating loss and credit carry-forwards before they can be utilized. The Company recognizes the financial statement effect of tax positions when it is more likely than not that the tax positions will be sustained upon examination by the appropriate taxing authorities. As of December 31, 2018 and 2017, the Company had unrecognized tax benefits of $1.8 million. On December 22, 2017, the 2017 Tax Cuts and Jobs Act (the Act") was enacted into law and the new legislation reduces the corporate tax rate to 21 percent, effectively January 1, 2018. Consequently, the Company remeasured the deferred tax assets and recorded a decrease in deferred tax assets and valuation allowance of $53.7 million as of December 31, 2017. The Company believes that the one-time transition tax does not apply because there were no post-1986 earnings and profits (E&P) previously deferred from US income taxes. The Company had reviewed the effects of global intangible low-taxed income (“GILTI”) tax rules and does not expect any significant impact to its deferred tax assets. In accordance with SAB 118, the Company recorded provisional income tax effects from the Act as of December 31, 2017, and amounts were finalized as of December 31, 2018 with no adjustments made to the amounts previously recorded. The Company files U.S. federal and California tax returns. The Company’s wholly owned subsidiaries, Sunesis Europe Limited and Sunesis Pharmaceuticals (Bermuda) Ltd., are currently not required to file tax returns. To date, neither the Company nor any of its subsidiaries have been audited by the Internal Revenue Service, any state income tax authority or tax authority in the related jurisdictions. Due to net operating loss carry-forwards, substantially all of the Company’s tax years remain open to federal tax examination.

Guarantees and Indemnification

Guarantees and Indemnification	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Guarantees and Indemnification	13. Guarantees and Indemnification As permitted under Delaware law and in accordance with the Company’s Bylaws, the Company indemnifies its officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at the Company’s request in such capacity. The indemnification agreements with the Company’s officers and directors terminate upon termination of their employment, but the termination does not affect claims for indemnification relating to events occurring prior to the effective date of termination. The maximum amount of potential future indemnification is unlimited; however, the Company’s officer and director insurance policy reduces the Company’s exposure and may enable the Company to recover a portion of any future amounts paid. The Company believes that the fair value of these indemnification agreements is minimal. In addition, in the ordinary course of business the Company enters into agreements, such as licensing agreements, clinical trial agreements and certain services agreements, containing standard indemnifications provisions. The Company believes that the likelihood of an adverse judgment related to such indemnification provisions is remote. Accordingly, the Company has not recorded any liabilities for any of these agreements as of December 31, 2018.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events In January 2019, the Company completed underwritten public offerings of (i) 23,000,000 shares of its common stock at a price to the public of $0.50 for each share of common stock, and (ii) 17,000 shares of its non-voting Series E Convertible Preferred Stock (“Series E Stock”) at a price to the public of $500 for each share of Series E Stock. Gross proceeds from the sale were $20.0 million and net proceeds were approximately $18.4 million. Each share of non-voting Series E Stock is convertible into 1,000 shares of the Company’s common stock, provided that conversion will be prohibited if, as a result, the holder and its affiliates would own more than 9.98% of the total number of shares of the Company’s common stock then outstanding; provided, however, that a holder may, upon written notice, elect to increase or decrease this percentage (not to exceed the limits under Nasdaq Marketplace Rule 5635(b), to the extent applicable).

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”).
Adopted Accounting Pronouncements	Adopted Accounting Pronouncements In January 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities Technical Corrections and Improvements to Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities . In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (“SAB”) No. 118 (SEC Update) Recent Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases Codification Improvements to Topic 842, Leases Leases (Topic 842): Targeted Improvements The Company has elected the package of practical expedients permitted under ASC 842. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease under ASC Topic 842, (b) whether classification of the operating leases would be different in accordance with ASC Topic 842, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs in ASC Topic 842 at lease commencement. In addition, the Company made an accounting policy election to combine the lease and non-lease components and the short-term lease practical expedients allowed under ASC 842. The adoption of ASC 842 will lead to an increase in the assets and liabilities recorded on the balance sheets primarily due to the lease agreement attributable to leased office space. This standard will not have a material impact on the Company’s balance sheets or cash flows from operations. In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Sunesis Europe Limited, a United Kingdom corporation, and Sunesis Pharmaceuticals (Bermuda) Ltd., a Bermuda corporation, as well as a Bermuda limited partnership, Sunesis Pharmaceuticals International LP. All intercompany balances and transactions have been eliminated in consolidation.
Segment Reporting	Segment Reporting Management has determined that the Company operates as a single reportable segment.
Significant Estimates and Judgments	Significant Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to the valuation of equity and related instruments, revenue recognition, stock-based compensation and clinical trial accounting.
Cash Equivalents and Marketable Securities	Cash Equivalents and Marketable Securities The Company considers all highly liquid securities with original maturities of three months or less from the date of purchase to be cash equivalents, which generally consist of money market funds and corporate debt securities. Marketable securities consist of securities with original maturities of greater than three months, which may include U.S. and European government obligations and corporate debt securities. Management determines the appropriate classification of securities at the time of purchase income equity The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in other income, net in the statements of operations and comprehensive loss. Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale securities, if any, are also recorded to other income, net. The cost of securities sold is based on the specific-identification method. Invoices for certain services provided to the Company are denominated in foreign currencies. To manage the risk of future movements in foreign exchange rates that would affect such amounts, the Company may purchase certain European currencies or highly-rated investments denominated in those currencies, subject to similar criteria as for other investments defined in the Company’s investment policy. There is no guarantee that the related gains and losses will substantially offset each other, and the Company may be subject to significant exchange gains or losses as currencies fluctuate from quarter to quarter. To date, the Company has purchased Euros and Euro-denominated obligations of foreign governments and corporate debt. As of December 31, 2018 and December 31, 2017, the Company held investments denominated in Euros with an aggregate fair value of $0.8 million. Any cash, cash equivalent and short-term investment balances denominated in foreign currencies are recorded at their fair value based on the current exchange rate as of each balance sheet date. The resulting exchange gains or losses and those from amounts payable for services originally denominated in foreign currencies are both recorded in other income, net in the statements of operations and comprehensive loss
Fair Value Measurements	Fair Value Measurements The Company measures cash equivalents and marketable securities at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP: Level 1 - quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date Level 2 - inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly Level 3 - unobservable inputs The Company’s Level 2 valuations of marketable securities are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets. The carrying amounts of the Company’s financial instruments, including
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the term of the lease.
Accounting for Royalty Agreement	Accounting for Royalty Agreement The payment of $25.0 million by RPI under the Royalty Agreement (see Note 6) is non-refundable, and no revenue participation right payments will be made unless vosaroxin is T , less $3.1 million initially . The fair value of the warrants was recorded to additional paid-in capital.
Accounting for Notes Payable	Accounting for Notes Payable The accounting for certain fees and expenses related to the Loan Agreement (see Note 8) is as follows. The facility fee is being accounted for as a debt discount and classified within notes payable on the Company’s balance sheet. The fair value of the warrants issued in connection with the Loan Agreement have been recorded as a debt discount within notes payable and an increase to additional paid-in capital on the Company’s balance sheet. The debt discount is being amortized as interest expense over the term of the loan using the effective interest method. The final payment is being accreted as interest expense over the term of the loans using the effective interest method. The legal fees are being accounted for as deferred debt issuance costs within assets on the Company’s balance sheet and are being amortized as other income, net over the term of the loans using the effective interest method.
Revenue Recognition	Revenue Recognition On January 1, 2018, the Company adopted Topic 606, Revenue from Contracts with Customers Revenue Recognition Adoption of the new standard did not result in any change to the Company’s opening retained earnings as of January 1, 2018 as no cumulative impact to the adoption of ASC 606 was noted as a result of the Company’s assessment of the comparative revenue recognized since inception of the contracts under the new revenue standard ASC 606 and historic standard ASC 605. The Company is applying the practical exemption allowed under ASC 606 and does not disclose the value of variable consideration that is a sale-based royalty promised in exchange for a license of intellectual property. The adoption of the new standard resulted in changes to the Company’s accounting policies for revenue recognition as detailed below: The Company’s contracts consist license, milestone and royalty payments primarily generated through agreements with strategic partners for the development and commercialization of the Company’s product candidates. The terms of the agreement typically include non-refundable upfront fees, payments based upon achievement of milestones and royalties on net product sales. The Company has both fixed and variable consideration. Non-refundable upfront fees are considered fixed, while milestone payments are identified as variable consideration. In determining the appropriate amount of revenue to be recognized as it fulfills its performance obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the customer, and the customer can use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Event-based or milestone payments: At the inception of each arrangement that includes event-based or milestone payments, the Company evaluates whether the events or milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated event-based or milestone payments is included in the transaction price. Event-based or milestone payments that are not within the control of the Company are not included in the transaction price until they become probable of being achieved. Royalties: For arrangements that include sales-based royalties and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements.
Research and Development	Research and Development Research and development expense consists primarily of: (a) clinical trial costs, which include payments for work performed by contract research organizations (“CROs”), clinical trial sites, labs and other clinical service providers, and for drug packaging, storage and distribution; (b) drug manufacturing costs, which include costs for producing drug substance and drug product, and for stability and other testing; (c) personnel costs for related permanent and temporary employees; (d) other outside services and consulting costs; and (e) payments under license agreements. All research and development costs are expensed as they are incurred.
Clinical Trial Accounting	Clinical Trial Accounting The Company records accruals for estimated clinical trial costs, which include payments for work performed by CROs and participating clinical trial sites. These costs are generally a significant component of research and development expense. Costs incurred for setting up clinical trial sites for participation in trials are generally non-refundable, and are expensed as incurred, with any refundable advances related to enrollment of the first patient recorded as prepayments and assessed for recoverability on a quarterly basis. Costs related to patient enrollment are accrued as patients progress through the clinical trial, including amortization of any first-patient prepayments. This amortization generally matches when the related services are rendered, however, these cost estimates may or may not match the actual costs incurred by the CROs or clinical trial sites, and if the Company has incomplete or inaccurate information, the clinical trial accruals may not be accurate. The difference between accrued expenses based on the Company’s estimates and actual expenses have not been significant to date.
Warrants for Shares of Common Stock	Warrants for Shares of Common Stock The Company accounts for warrants for shares of common stock as equity instruments in the accompanying balance sheets at their fair value on the date of issuance because such warrants are indexed to the Company’s common stock and no cash settlement is required except for (i) liquidation of the Company, or (ii) a change in control in which the common stockholders also receive cash.
Stock-Based Compensation	Stock-Based Compensation The Company grants options to purchase common stock to its employees, directors and consultants under its stock option plans. Under the Company’s Employee Stock Purchase Plan, eligible employees can also purchase shares of the Company’s common stock at 85% of the lower of the fair market value of the Company’s common stock at the beginning of a 12-month offering period or at the end of one of the two related six-month purchase periods. The Company values these share-based awards using the Black-Scholes option valuation model (the “Black-Scholes model”). The determination of fair value of share-based payment awards on the date of grant using the Black-Scholes model is affected by the Company’s stock price as well as assumptions regarding a number of subjective variables. These variables include, but are not limited to, the expected stock price volatility over the term of the awards and actual and projected employee stock option exercise behaviors.
Foreign Currency	Foreign Currency Transactions that are denominated in a foreign currency are translated into U.S. dollars at the current exchange rate on the transaction date. Any foreign currency-denominated monetary assets and liabilities are subsequently remeasured at current exchange rates as of each balance sheet date, with gains or losses on foreign exchange recognized in other income, net in the statements of operations and comprehensive loss.
Income Taxes	Income Taxes The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the differences between the tax basis of assets and liabilities and their basis for financial reporting. Deferred tax assets or liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which temporary differences are expected to be recovered or settled. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company’s policy is to recognize interest charges and penalties in other income, net in the statements of operations and comprehensive loss.

Loss per Common Share (Tables)

Loss per Common Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Computation of Basic and Diluted Loss per Common Share	The following table sets forth the computation of basic and diluted loss per common share for the periods presented (in thousands, except per share amounts): Year Ended December 31, 2018 2017 Numerator: Net loss—basic and diluted $ (26,615 ) $ (35,458 ) Denominator: Weighted-average common shares outstanding—basic and diluted 35,582 24,516 Net loss per common share: Basic and Diluted $ (0.75 ) $ (1.45 )
Schedule of Potential Common Shares Issuable Pursuant to Outstanding Securities Excluded from Computation of Diluted Loss per Common Share	The following table represents the potential common shares issuable pursuant to outstanding securities as of the related period end dates that were excluded from the computation of diluted loss per common share because their inclusion would have had an anti-dilutive effect (in thousands): As of December 31, 2018 2017 Warrants to purchase shares of common stock 218 5,218 Convertible preferred stock 6,331 6,331 Options to purchase shares of common stock 4,160 3,532 Outstanding securities not included in calculations 10,709 15,081

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value of Company's Financial Assets Measured on Recurring Basis	The following tables summarize the estimated fair value of the Company’s financial assets measured on a recurring basis as of the dates indicated, which were comprised solely of available-for-sale marketable securities with remaining contractual maturities of one year or less (in thousands): Gross Gross Valuation Amortized Unrealized Unrealized Estimated Fair December 31, 2018 Input Level Cost Gains Losses Value Money market funds Level 1 $ 10,845 $ — $ — $ 10,845 Total available-for-sale securities 10,845 — — 10,845 Less amounts classified as cash equivalents (10,845 ) — — (10,845 ) Amounts classified as marketable securities $ — $ — $ — $ — Gross Gross Valuation Amortized Unrealized Unrealized Estimated Fair December 31, 2017 Input Level Cost Gains Losses Value Money market funds Level 1 $ 20,470 $ — $ — $ 20,470 U.S. corporate debt obligations Level 2 3,282 — (5 ) 3,277 U.S. commercial paper Level 2 1,498 — (2 ) 1,496 Total available-for-sale securities 25,250 — (7 ) 25,243 Less amounts classified as cash equivalents (20,470 ) — — (20,470 ) Amounts classified as marketable securities $ 4,780 $ — $ (7 ) $ 4,773

Other Accrued Liabilities (Tabl

Other Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Payables And Accruals [Abstract]
Summary of Other Accrued Liabilities	Other accrued liabilities as of December 31 were as follows (in thousands): 2018 2017 Accrued outside services $ 556 $ 1,096 Accrued professional services 251 471 Accrued interest 284 — Other accruals — 3 Total other accrued liabilities $ 1,091 $ 1,570

Notes Payable (Tables)

Notes Payable (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Summary of Future Minimum Payments Under Loan Facility	Aggregate future minimum payments due under the Loan Facility as of December 31, 2018 Year ending December 31, Total 2019 6,168 2020 2,231 Total minimum payments 8,399 Less amount representing interest (899 ) Total notes payable as of December 31, 2018 7,500 Less unamortized debt discount and issuance costs (104 ) Less current portion of notes payable (7,396 ) Non-current portion of notes payable $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Aggregate Non-Cancelable Future Minimum Rental Payments under Operating Leases	Aggregate non-cancelable future minimum rental payments under operating leases as of December 31, 2018, were as follows (in thousands): Year Ending December 31, Payments 2019 $ 562 2020 $ 578 2021 $ 294 Total rental payments $ 1,434

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Schedule of Warrants to Purchase Shares of Company's Common Stock	Warrants to purchase shares of the Company’s common stock outstanding as of December 31, 2018 were as follows (in thousands, except per share amounts): Exercise Price Date Issued Shares Per Share Expiration February 2015 10 $ 13.32 February 2020 March 2016 208 $ 3.25 March 2021 Total warrants outstanding and exercisable 218
Shares of Common Stock Reserved for Future Issuance	Shares of the Company’s common stock reserved for future issuance as of December 31, 2018 Shares Available Total for Future Outstanding Shares Grant Securities Reserved Warrants — 218 218 Convertible preferred stock — 6,331 6,331 Stock option plans 755 4,160 4,915 Employee stock purchase plan 64 — 64 Total reserved shares of common stock 819 10,709 11,528

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock-Based Compensation Expense Related to Company's Stock-Based Awards	The following table summarizes stock-based compensation expense related to the Company’s stock-based awards for the periods indicated (in thousands): Year ended December 31, 2018 2017 Research and development $ 581 $ 865 General and administrative 903 2,059 Employee stock-based compensation expense 1,484 2,924 Non-employee stock-based compensation expense 1,153 109 Total stock-based compensation expense $ 2,637 $ 3,033
Summary of Weighted-Average and Total Estimated Grant Date Fair Values of Employee Stock Options Granted	The following table summarizes the weighted-average assumptions used as inputs to the Black-Scholes model, and resulting weighted-average and total estimated grant date fair values of employee stock options granted during the periods indicated: Year Ended December 31, 2018 2017 Employees Consultants Employees Consultants Assumptions: Expected term (years) 4.3 9.8 4.8 9.7 Expected volatility 126.0 % 117.6 % 112.5 % 121.6 % Risk-free interest rate 2.6 % 2.8 % 2.1 % 2.4 % Expected dividend yield 0.0 % 0.0 % 0.0 % 0.0 % Fair value: Weighted-average estimated grant date fair value per share $ 0.96 $ 1.19 $ 2.68 $ 3.23 Options granted (in thousands) 1,204 418 1,280 287 Total estimated grant date fair value (in thousands) $ 1,161 $ 497 $ 3,434 $ 926
Summary of Stock Option Activity for Company's Stock Option Plans	The following table summarizes stock option activity for the Company’s stock option plans in the periods presented (in thousands, except per share amounts): Weighted Weighted Average Average Number Exercise Remaining Aggregate of Price Per Contractual Intrinsic Shares Share Term (Years) Value Outstanding as of December 31, 2017 3,532 $ 6.18 Options granted 1,622 $ 1.20 Options exercised (49 ) $ 3.34 Options forfeited or expired (945 ) $ 8.91 Outstanding as of December 31, 2018 4,160 $ 3.66 7.55 $ — Vested and expected to vest as of December 31, 2018 4,160 $ 3.66 7.55 $ — Exercisable as of December 31, 2018 2,118 $ 5.44 5.76 $ —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Loss before Provision for Income Taxes	Loss before the provision for income taxes consisted of the following (in thousands): Year Ended December 31, 2018 2017 U.S. operations $ (21,132 ) $ (24,776 ) Foreign operations (5,483 ) (10,682 ) Loss before provision for income taxes $ (26,615 ) $ (35,458 )
Income Tax Provision Amount Computed by Applying Statutory Income Tax Rate	The income tax provision differs from the amount computed by applying the statutory income tax rate of 21% to pre-tax loss as follows (in thousands): Year Ended December 31, 2018 2017 Tax (benefit) at statutory federal rate 21.0 % 34.0 % State tax (benefit), net of federal benefit 4.6 1.2 Foreign tax rate differential (4.3 ) (10.2 ) Permanent differences (0.6 ) (1.0 ) Research and development credits 1.0 0.7 Change in valuation allowance (15.9 ) 127.2 Change in tax rate — (151.6 ) Provision-to-return (0.7 ) — Expired NOLs and research and development credits, and carryfowards (2.2 ) — Non-qualified stock option cancellations (2.9 ) (0.3 ) Effective tax rate — % — %
Significant Components of Deferred Tax Assets	Significant components of the Company’s deferred tax assets for federal and state income taxes are as follows (in thousands): December 31, 2018 2017 Deferred tax assets: Federal and state net operating loss carry-forwards $ 114,254 $ 109,714 Federal and state research credit carry-forwards 14,885 14,520 Capitalized research costs 6,134 6,304 Stock-based compensation 4,002 4,528 Property and equipment 79 83 Accrued liabilities 143 117 Gross deferred tax assets 139,497 135,266 Valuation allowance (139,497 ) (135,266 ) Net deferred tax assets $ — $ —
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the Company’s beginning and ending amount of unrecognized tax benefits is follows (in thousands): December 31, 2018 2017 Unrecognized tax benefits at beginning of period $ 1,769 $ 1,441 Increases related to current year tax positions 43 57 Increase related to change in tax rate — 271 Unrecognized tax benefits at the end of period $ 1,812 $ 1,769

Company Overview - Additional I

Company Overview - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Cash and cash equivalents		$ 13,696	$ 26,977		$ 8,056
Accumulated deficit		$ 659,469	$ 632,854
Common stock, shares issued		37,474,000	34,291,000
Preferred stock, shares issued		18,000	18,000
Maturity limits period		24 months
Dollars weighted average maturity limit period		12 months
Underwritten Offering [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common stock, shares issued				7,500,000		5,675,825	1,832,698
Subsequent Event [Member] | Underwritten Offering [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common stock, shares issued	23,000,000
Proceeds from issuance of common and convertible preferred stock, net	$ 18,400
Subsequent Event [Member] | Underwritten Offering [Member] | Series E Convertible Preferred Stock [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Preferred stock, shares issued	17,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2012USD ($)	Dec. 31, 2018USD ($)Segment	Dec. 31, 2017USD ($)
Significant Accounting Policies [Line Items]
Number of reportable segment | Segment		1
Fair value of investments denominated in Euros		$ 0.8	$ 0.8
Common stock offering period		At the beginning of a 12-month offering period or at the end of one of the two related six-month purchase periods.
Employee Stock Purchase Plan [Member]
Significant Accounting Policies [Line Items]
Purchase price of a share as a percentage of fair market value		85.00%
Royalty Agreement [Member]
Significant Accounting Policies [Line Items]
Revenue participation right payments	$ 25	$ 25
Fair value of warrants issued in connection with participation agreement	$ 3.1	$ 3.1
Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of assets		3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of assets		5 years

Loss per Common Share - Computa

Loss per Common Share - Computation of Basic and Diluted Loss per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss	$ (26,615)	$ (35,458)
Denominator:
Weighted-average common shares outstanding—basic and diluted	35,582	24,516
Net loss per common share:
Basic and Diluted	$ (0.75)	$ (1.45)

Loss per Common Share - Schedul

Loss per Common Share - Schedule of Potential Common Shares Issuable Pursuant to Outstanding Securities Excluded from Computation of Diluted Loss per Common Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	10,709	15,081
Warrants to purchase shares of common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	218	5,218
Options to purchase shares of common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	4,160	3,532
Convertible preferred stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	6,331	6,331

Financial Instruments - Fair Va

Financial Instruments - Fair Value of Company's Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost	$ 10,845	$ 25,250
Available-for-sale securities, Gross Unrealized Losses		(7)
Available-for-sale securities, Estimated Fair Value	10,845	25,243
Less amounts classified as cash equivalents, Amortized Cost	(10,845)	(20,470)
Less amounts classified as cash equivalents, Estimated Fair Value	(10,845)	(20,470)
Amounts classified as marketable securities, Amortized Cost		4,780
Amounts classified as marketable securities, Gross Unrealized Losses		(7)
Amounts classified as marketable securities, Estimated Fair Value		4,773
Level 1 [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost	10,845	20,470
Available-for-sale securities, Estimated Fair Value	$ 10,845	20,470
Level 2 [Member] | U.S. corporate debt obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost		3,282
Available-for-sale securities, Gross Unrealized Losses		(5)
Available-for-sale securities, Estimated Fair Value		3,277
Level 2 [Member] | U.S. commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost		1,498
Available-for-sale securities, Gross Unrealized Losses		(2)
Available-for-sale securities, Estimated Fair Value		$ 1,496

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Unrealized gain or loss on available-for-sale securities	$ 0
Sales of available-for-sale securities	0	$ 0
Realized gains or losses on available-for-sale securities	$ 0	$ 0

Other Accrued Liabilities - Sum

Other Accrued Liabilities - Summary of Other Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued outside services	$ 556	$ 1,096
Accrued professional services	251	471
Accrued interest	284
Other accruals		3
Total other accrued liabilities	$ 1,091	$ 1,570

Royalty Agreement - Additional

Royalty Agreement - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2018
Royalty Agreement [Line Items]
Revenue participation right payments, rate		6.75%
Revenue participation right payments, term		10 years from the date of first commercial sale
Maximum term of revenue participation right payments		10 years
Royalty Agreement [Member]
Royalty Agreement [Line Items]
Revenue participation right payments	$ 25	$ 25
Fair value of warrants issued in connection with participation agreement	$ 3.1	$ 3.1

License Agreements - Additional

License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Jun. 30, 2012	Sep. 30, 2017	Dec. 31, 2018	Jan. 31, 2014
Biogen [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Received and recognized milestone revenue	$ 1,500,000
Milestone payment		$ 2,500,000
Biogen [Member] | License Agreement Terms [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential pre-commercialization payments receivable	$ 58,500,000
Takeda License Agreements [Member] | License Agreement Terms [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Received and recognized milestone revenue			$ 0
Potential pre-commercialization payments receivable			57,500,000
Potential pre-commercialization milestone payments payable				$ 9,200,000
Contract assets			$ 0

Notes Payable - Additional Info

Notes Payable - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)$ / sharesYearAmendmentshares
Debt Instrument [Line Items]
Outstanding principal balance of loan	$ 7,500,000
Amended Loan Agreement [Member]
Debt Instrument [Line Items]
Number of loan amendments | Amendment		2
Debt instrument, Effective interest rate description	interest on the borrowings under the Loan Agreement at a per annum rate equal to 8.54% plus the then effective one-month U.S. LIBOR rate.
Average effective interest rates	10.50%	9.60%
Description of monthly interest payment	The Amendments modified the loan repayment terms to be interest-only through January 1, 2019, contingent upon the receipt of at least Twenty-Five Million dollars ($25,000,000) in unrestricted cash proceeds on or prior to September 15, 2018. The Company qualified for the extension and the interest-only period was extended to January 1, 2019.
Debt instrument, minimum threshold amount of unrestricted cash proceeds for interest only payment period		$ 25,000,000
Line of credit facility final payment, additional amount due		$ 312,500
Maturity date		Apr. 1, 2020
Outstanding principal balance of loan	$ 7,500,000
Warrants expiration term		5 years
Number of warrants issued | shares		208,002
Warrants exercise price for shares | $ / shares		$ 3.2454
Estimated fair value of warrants issued		$ 500,000
Loan, Covenant description	Pursuant to the Loan Agreement and the Amendments, the Company is bound during the term of the Loan Agreement and the Amendments by a variety of affirmative covenants, including, without limitation, certain information delivery requirements and notice requirements, and negative covenants, including, without limitation, restrictions on incurring certain additional indebtedness, making certain asset dispositions, entering into certain mergers, acquisitions or other business combination transactions or incurring any non-permitted lien or other encumbrance on the Company’s assets. Upon the occurrence of an event of default under the Loan Agreement and the Amendments (subject to cure periods for certain events of default), all amounts owed by the Company thereunder would begin to bear interest at a rate that is 5.0% higher than the rate that would otherwise be applicable and may be declared immediately due and payable by the Collateral Agent. In the event of default by the Company, the Lenders would be entitled to exercise their remedies thereunder, including the right to accelerate the debt, upon which the Company may be required to repay all amounts then outstanding under the Loan Agreement and the Amendments, which could harm the Company's financial condition. The Company was in compliance with all applicable covenants set forth in the Loan Agreement and the Amendments as of December 31, 2018 and December 31, 2017. The principal payments due under the Loan Agreement and the Amendments have been classified as a current liability at December 31, 2018 and December 31, 2017 due to the considerations discussed in Note 1 and the assessment that the material adverse change clause under the Loan Agreement and the Amendments is not within the Company's control. The Company has not been notified of an event of default by the Lenders as of the date of the filing of this Form 10-K.
Amended Loan Agreement [Member] | Warrants to purchase shares of common stock [Member]
Debt Instrument [Line Items]
Common stock price | $ / shares		$ 3.24
Amended Loan Agreement [Member] | Warrants to purchase shares of common stock [Member] | Exercise Price [Member]
Debt Instrument [Line Items]
Debt instrument, measurement input | $ / shares		3.2454
Amended Loan Agreement [Member] | Warrants to purchase shares of common stock [Member] | Risk-free Interest Rate [Member]
Debt Instrument [Line Items]
Debt instrument, measurement input		0.0121
Amended Loan Agreement [Member] | Warrants to purchase shares of common stock [Member] | Expected Volatility [Member]
Debt Instrument [Line Items]
Debt instrument, measurement input		1.1196
Amended Loan Agreement [Member] | Warrants to purchase shares of common stock [Member] | Measurement Input, Expected Term
Debt Instrument [Line Items]
Debt instrument, measurement input | Year		5
Amended Loan Agreement [Member] | Warrants to purchase shares of common stock [Member] | Dividend Yield [Member]
Debt Instrument [Line Items]
Debt instrument, measurement input		0
Amended Loan Agreement [Member] | Extension of Maturity Date [Member]
Debt Instrument [Line Items]
Percentage of penalty for prepaying loan before maturity		0.50%
Amended Loan Agreement [Member] | Other Accrued Liabilities [Member]
Debt Instrument [Line Items]
Line of credit facility final payment accrued		$ 284,000
Amended Loan Agreement [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		8.54%

Notes Payable - Summary of Futu

Notes Payable - Summary of Future Minimum Payments Under Loan Facility (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total notes payable as of December 31, 2018	$ 7,500
Less current portion of notes payable	(7,396)	$ (7,204)
Notes payable [Member]
Debt Instrument [Line Items]
2,019	6,168
2,020	2,231
Total minimum payments	8,399
Less amount representing interest	(899)
Less unamortized debt discount and issuance costs	$ (104)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Commitments And Contingencies Disclosure [Line Items]
Rent expense	$ 0.5	$ 0.7
Original Operating Lease [Member]
Commitments And Contingencies Disclosure [Line Items]
Operating lease agreement, original date	2014-01
Fifth Amended Operating Lease [Member]
Commitments And Contingencies Disclosure [Line Items]
Operating lease expiration date	Jun. 30, 2021
Operating lease agreement, date of amendment	2017-12
Lease property description	The lease was last amended in December 2017 to extend the expiration date to June 30, 2021, with an option to extend the lease for two additional years.
Operating lease, option to extend, description	Option to extend the lease for two additional years.
Operating lease, renewal term	2 years

Commitments and Contingencies_2

Commitments and Contingencies - Aggregate Non-Cancelable Future Minimum Rental Payments under Operating Leases (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,019	$ 562
2,020	578
2,021	294
Total rental payments	$ 1,434

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information 1 (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Nov. 30, 2017	Oct. 31, 2017	Oct. 31, 2016	Dec. 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Apr. 30, 2013
Stockholders Equity [Line Items]
Preferred stock, shares authorized					10,000,000	10,000,000
Preferred stock, shares outstanding					17,697	17,697
Common stock, voting rights					One vote per share
Shares of common stock issued					37,474,000	34,291,000
Preferred stock, shares issued					18,000	18,000
Proceeds from issuance of common shares, gross			$ 27,900	$ 26,200
Proceeds from issuance of common stock through controlled equity offering facilities, net			$ 25,900	$ 25,200		$ 13,877
Total warrants outstanding, shares					218,000
Common Stock [Member]
Stockholders Equity [Line Items]
Shares of common stock issued					37,474,000	34,291,000	20,925,000
Underwritten Offering [Member]
Stockholders Equity [Line Items]
Price per common share			$ 3.85	$ 5.04
Shares of common stock issued		7,500,000	5,675,825	1,832,698
Proceeds from issuance of common shares, gross		$ 20,000
Proceeds from issuance of common stock through controlled equity offering facilities, net		$ 18,500
Warrants, exercise price per share		$ 3
Underwritten Offering [Member] | Common Stock Warrants [Member]
Stockholders Equity [Line Items]
Price per common share		$ 2
Total warrants outstanding, shares		3,750,000
Number of shares called by each warrant		0.5
Underwritten Offering [Member] | Preferred Stock Warrants [Member]
Stockholders Equity [Line Items]
Price per common share		$ 2,000
Total warrants outstanding, shares		1,250,000
Number of shares called by each warrant		500
Over-Allotment Option [Member]
Stockholders Equity [Line Items]
Shares of common stock issued				239,047
Controlled Equity Offering Facilities [Member]
Stockholders Equity [Line Items]
Proceeds from issuance of common shares, gross					$ 1,400	$ 14,200
Proceeds from issuance of common stock through controlled equity offering facilities, net					$ 1,400	$ 14,200
Common stock sales agreement, date					2011-08
Issuance of common stock, remaining offering value					$ 43,600
Controlled Equity Offering Facilities [Member] | Common Stock [Member]
Stockholders Equity [Line Items]
Price per common share					$ 2.38	$ 2.72
Common stock, shares sold					617,967	5,321,151
Additional Controlled Equity Offerings Facilities [Member]
Stockholders Equity [Line Items]
Issuance of common stock, commission percentage, maximum	3.00%							3.00%
Common stock sales agreement further amended, date					2017-11
Increase in aggregate controlled equity offering agreement as per amendment	$ 45,000
Series B Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Price per common share				$ 840	$ 840
Shares issued upon conversion				166	166
Preferred stock, shares issued				20,200
Series B Convertible Preferred Stock [Member] | Maximum [Member]
Stockholders Equity [Line Items]
Percentage of outstanding common stock				9.98%
Series B, Series C and Series D Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Preferred stock, payment to stock holders in the event of liquidation, dissolution or winding up preference per share					$ 0.0001
Preferred stock, voting rights					Shares of Series B, Series C, and Series D Stock will generally have no voting rights, except as required by law and except that the consent of holders of a majority of the outstanding Series B and Series C Stock will be required to amend the terms of the Series B, Series C, and Series D Stock.
Series B, Series C and Series D Convertible Preferred Stock [Member] | Maximum [Member]
Stockholders Equity [Line Items]
Percentage of outstanding common stock					9.98%
Series C Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Price per common share			$ 3,850		$ 3,850
Shares issued upon conversion			1,000		1,000
Preferred stock, shares issued			1,558
Series C Convertible Preferred Stock [Member] | Maximum [Member]
Stockholders Equity [Line Items]
Percentage of outstanding common stock			9.98%
Series D Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Price per common share					$ 2,000
Shares issued upon conversion					1,000
Series D Convertible Preferred Stock [Member] | Underwritten Offering [Member]
Stockholders Equity [Line Items]
Shares issued upon conversion		1,000
Preferred stock, shares issued		2,500
Series D Convertible Preferred Stock [Member] | Maximum [Member] | Underwritten Offering [Member]
Stockholders Equity [Line Items]
Percentage of outstanding common stock		9.98%

Stockholders' Equity - Additi_2

Stockholders' Equity - Additional Information 2 (Detail) $ / shares in Units, $ in Thousands	Dec. 31, 2018USD ($)$ / shares	Jun. 30, 2018USD ($)ArithmeticaverageDay$ / sharesshares	Oct. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)
Stockholders Equity [Line Items]
Proceeds from issuance of common stock through controlled equity offering facilities, net			$ 25,900	$ 25,200		$ 13,877
CSPA [Member] | Aspire [Member]
Stockholders Equity [Line Items]
Proceeds from issuance of common stock through controlled equity offering facilities, net		$ 500
Common stock purchase agreement period		24 months
Average lowest closing sales price | Arithmeticaverage		3
Consecutive business days | Day		10
Percentage of volume weighted average price		97.00%
Request to purchase shares per business day | shares		2,000,000
Number of shares of common stock issued as commitment fee | shares		212,329
Commitment fee		$ 400
Other transaction costs		100
CSPA [Member] | Aspire [Member] | Registration Rights Agreement [Member]
Stockholders Equity [Line Items]
Common stock, shares sold | shares					2,390,640
Price per common share | $ / shares	$ 2.20				$ 2.20
Proceeds from issuance of common stock through controlled equity offering facilities, net					$ 4,600
Remaining purchase commitment	$ 10,900
CSPA [Member] | Maximum [Member] | Aspire [Member]
Stockholders Equity [Line Items]
Issuance of common stock, offering value		15,500
Commitment to purchase additional common shares		$ 15,000
Percentage of additional trading volume of shares		30.00%
CSPA [Member] | Minimum [Member] | Aspire [Member]
Stockholders Equity [Line Items]
Closing price of common stock | $ / shares		$ 0.25
CSPA [Member] | Common Stock [Member] | Aspire [Member]
Stockholders Equity [Line Items]
Common stock, shares sold | shares		228,311
Price per common share | $ / shares		$ 2.19
CSPA [Member] | Common Stock [Member] | Maximum [Member] | Aspire [Member]
Stockholders Equity [Line Items]
Shares of common stock to purchase per business day | shares		200,000

Stockholders' Equity - Additi_3

Stockholders' Equity - Additional Information 3 (Detail) - shares	Jan. 02, 2018	Jul. 10, 2017	Jan. 02, 2017	Dec. 31, 2018
Stockholders Equity [Line Items]
Options granted, Number of Shares		543,650		1,622,000
Shares Available for Future Grant				819,000
2011 Plan [Member]
Stockholders Equity [Line Items]
Common stock available for issuance automatic increase period				10 years
Common stock available for issuance automatic increase maximum number of shares				4.00%
Shares of common stock available for issuance	1,371,308		836,981
Options granted, Number of Shares				1,622,248
Shares Available for Future Grant				755,075
Stock Option Plans [Member]
Stockholders Equity [Line Items]
Shares Available for Future Grant				755,000
Stock Option Plans [Member] | New Employees [Member]
Stockholders Equity [Line Items]
Option exercisable on first anniversary of vesting commencement date, percent				25.00%
Portion of option exercisable for each month over vesting percent				2.083%
Stock option plans, vesting period				4 years
Vesting rights				New employees, of which 25% of the shares subject to such options become exercisable on the first anniversary of the vesting commencement date, and 1/48th of the shares subject to such options become exercisable each month over the remainder of the four-year vesting period
Stock Option Plans [Member] | Existing Employees [Member]
Stockholders Equity [Line Items]
Vesting rights				Existing employees with various vesting schedules over three to four years
Stock Option Plans [Member] | Existing Employees [Member] | Minimum [Member]
Stockholders Equity [Line Items]
Stock option plans, vesting period				3 years
Stock Option Plans [Member] | Existing Employees [Member] | Maximum [Member]
Stockholders Equity [Line Items]
Stock option plans, vesting period				4 years
Stock Option Plans [Member] | New Non-Employee Board Members [Member]
Stockholders Equity [Line Items]
Portion of option exercisable for each month over vesting percent				4.166%
Stock option plans, vesting period				2 years
Vesting rights				New non-employee members of the board of directors, of which 50% of the shares subject to such options become exercisable on each of the first and second anniversary of the vesting commencement date
Stock Option Plans [Member] | Continuing Non-Employee Board Members [Member]
Stockholders Equity [Line Items]
Portion of option exercisable for each month over vesting percent				8332.00%
Stock option plans, vesting period				1 year
Vesting rights				Continuing non-employee members of the board of directors, of which 1/24th of the shares subject to such options become exercisable each month following the date of grant over a two-year vesting period

Stockholders' Equity - Additi_4

Stockholders' Equity - Additional Information 4 (Detail)	12 Months Ended
	Dec. 31, 2018PurchasePeriodshares	Dec. 31, 2017USD ($)shares
Stockholders Equity [Line Items]
Share of common stock value | $		$ 25,000
Number of shares issued under employee stock purchase plan	104,099	87,020
Shares Available for Future Grant	819,000
Employee Stock Purchase Plan [Member]
Stockholders Equity [Line Items]
Purchase price of a share as a percentage of fair market value	85.00%
Duration of offering period	12 months
Number of purchase periods in each offering period | PurchasePeriod	2
Duration of each purchase period	6 months
Common stock available for issuance automatic increase period	10 years
Common stock available for issuance automatic increase maximum number of shares	1.00%
Shares Available for Future Grant	64,305

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Warrants to Purchase Shares of Company's Common Stock (Detail) shares in Thousands	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Class of Warrant or Right [Line Items]
Total warrants outstanding and exercisable, shares	218
February 2015 [Member]
Class of Warrant or Right [Line Items]
Total warrants outstanding and exercisable, shares	10
Warrants, Exercise Price Per Share | $ / shares	$ 13.32
Warrants Expiration Date	2020-02
March 2016 [Member]
Class of Warrant or Right [Line Items]
Total warrants outstanding and exercisable, shares	208
Warrants, Exercise Price Per Share | $ / shares	$ 3.25
Warrants Expiration Date	2021-03

Stockholders' Equity - Shares o

Stockholders' Equity - Shares of Common Stock Reserved for Future Issuance (Detail)	Dec. 31, 2018shares
Class of Stock [Line Items]
Shares Available for Future Grant	819,000
Outstanding Securities	10,709,000
Total Shares Reserved	11,528,000
Warrants [Member]
Class of Stock [Line Items]
Outstanding Securities	218,000
Total Shares Reserved	218,000
Stock Option Plans [Member]
Class of Stock [Line Items]
Shares Available for Future Grant	755,000
Outstanding Securities	4,160,000
Total Shares Reserved	4,915,000
Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Shares Available for Future Grant	64,305
Total Shares Reserved	64,000
Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Outstanding Securities	6,331,000
Total Shares Reserved	6,331,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expense Related to Company's Stock-Based Awards (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	$ 2,637	$ 3,033
Employee stock-based compensation expense [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	1,484	2,924
Non-employee stock-based compensation expense [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	1,153	109
Research and development [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	581	865
General and administrative [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	$ 903	$ 2,059

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	Jul. 10, 2017	Jun. 09, 2017	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Tender offer announcement date				Jun. 9, 2017
Options to purchase shares of common stock	778,928	781,505
New options granted to purchase shares of common stock	543,650		1,622,000
Exercise price of options	$ 2.62
Incremental expense for vested options				$ 50,957
Estimated fair value of stock options, vested			$ 2,000,000	1,900,000
Payment of cash dividends			$ 0
Dividend yield ratio			0.00%
Tax benefits related to stock option exercised			$ 0
Unrecognized stock-based compensation cost related to unvested stock options			$ 2,800,000
Weighted average term of unrecognized stock-based compensation expense			2 years 9 months 18 days
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of options exercised			$ 100,000	$ 100,000
Options Priced from $8.00-$19.99 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exchange ratio applied to options priced		130.00%
Exercise price of applied option price, minimum		$ 8
Exercise price of applied option price, maximum		$ 19.99
Options Priced for $20.00 or Greater [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exchange ratio applied to options priced		175.00%
Exercise price of applied option price, minimum		$ 20

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Weighted-Average and Total Estimated Grant Date Fair Values of Employee Stock Options Granted (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jul. 10, 2017	Dec. 31, 2018	Dec. 31, 2017
Assumptions:
Expected dividend yield		0.00%
Fair value:
Options granted (in thousands)	543,650	1,622,000
Stock Option Plans [Member] | Employees [Member]
Assumptions:
Expected term (years)		4 years 3 months 18 days	4 years 9 months 18 days
Expected volatility		126.00%	112.50%
Risk-free interest rate		2.60%	2.10%
Expected dividend yield		0.00%	0.00%
Fair value:
Weighted-average estimated grant date fair value per share		$ 0.96	$ 2.68
Options granted (in thousands)		1,204,000	1,280,000
Total estimated grant date fair value (in thousands)		$ 1,161	$ 3,434
Stock Option Plans [Member] | Consultants [Member]
Assumptions:
Expected term (years)		9 years 9 months 18 days	9 years 8 months 12 days
Expected volatility		117.60%	121.60%
Risk-free interest rate		2.80%	2.40%
Expected dividend yield		0.00%	0.00%
Fair value:
Weighted-average estimated grant date fair value per share		$ 1.19	$ 3.23
Options granted (in thousands)		418,000	287,000
Total estimated grant date fair value (in thousands)		$ 497	$ 926

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock Option Activity for Company's Stock Option Plans (Detail) - $ / shares	Jul. 10, 2017	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding, Beginning Balance, Number of Shares		3,532,000
Options granted, Number of Shares	543,650	1,622,000
Options exercised, Number of Shares		(49,000)
Options forfeited or expired, Number of Shares		(945,000)
Outstanding, Ending Balance, Number of Shares		4,160,000
Vested and expected to vest as of December 31, 2018, Number of Shares		4,160,000
Exercisable as of December 31, 2018, Number of Shares		2,118,000
Outstanding, Beginning Balance, Weighted Average Exercise Price Per Share		$ 6.18
Options granted, Weighted Average Exercise Price Per Share		1.20
Options exercised, Weighted Average Exercise Price Per Share		3.34
Options forfeited or expired, Weighted Average Exercise Price Per Share		8.91
Outstanding, Ending Balance, Weighted Average Exercise Price Per Share		3.66
Vested and expected to vest as of December 31, 2018, Weighted Average Exercise Price Per Share		3.66
Exercisable as of December 31, 2018, Weighted Average Exercise Price Per Share		$ 5.44
Outstanding, Weighted Average Remaining Contractual Term (Years)		7 years 6 months 18 days
Vested and expected to vest as of December 31, 2018, Weighted Average Remaining Contractual Term (Years)		7 years 6 months 18 days
Exercisable as of December 31, 2018, Weighted Average Remaining Contractual Term (Years)		5 years 9 months 3 days

Income Taxes - Loss before Prov

Income Taxes - Loss before Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. operations	$ (21,132)	$ (24,776)
Foreign operations	(5,483)	(10,682)
Loss before provision for income taxes	$ (26,615)	$ (35,458)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Income tax provision	$ 0	$ 0
Statutory income tax rate	21.00%	34.00%
Unrecognized tax benefits that would have tax impact	$ 0
Net valuation allowance, increased (decreased)	4,200,000	$ (45,100,000)
Unrecognized tax benefit	1,812,000	1,769,000	$ 1,441,000
Decrease in deferred tax assets and valuation allowance due to enacted tax act		$ 53,700,000
Domestic tax authority [Member]
Income Taxes [Line Items]
Net operating loss carry-forwards	448,200,000
Research and development tax credit carry-forwards	$ 8,700,000
Net operating loss carry-forwards expiration	2,019
State and local jurisdiction [Member]
Income Taxes [Line Items]
Net operating loss carry-forwards	$ 288,300,000
Research and development tax credit carry-forwards	$ 7,600,000
Net operating loss carry-forwards expiration	2,028

Income Taxes - Income Tax Provi

Income Taxes - Income Tax Provision Amount Computed by Applying Statutory Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax (benefit) at statutory federal rate	21.00%	34.00%
State tax (benefit), net of federal benefit	4.60%	1.20%
Foreign tax rate differential	(4.30%)	(10.20%)
Permanent differences	(0.60%)	(1.00%)
Research and development credits	1.00%	0.70%
Change in valuation allowance	(15.90%)	127.20%
Change in tax rate		(151.60%)
Provision-to-return	(0.70%)
Expired NOLs and research and development credits, and carryfowards	(2.20%)
Non-qualified stock option cancellations	(2.90%)	(0.30%)

Income Taxes - Significant Comp

Income Taxes - Significant Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Federal and state net operating loss carry-forwards	$ 114,254	$ 109,714
Federal and state research credit carry-forwards	14,885	14,520
Capitalized research costs	6,134	6,304
Stock-based compensation	4,002	4,528
Property and equipment	79	83
Accrued liabilities	143	117
Gross deferred tax assets	139,497	135,266
Valuation allowance	$ (139,497)	$ (135,266)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Unrecognized tax benefits at beginning of period	$ 1,769	$ 1,441
Increases related to current year tax positions	43	57
Increase related to change in tax rate		271
Unrecognized tax benefits at the end of period	$ 1,812	$ 1,769

Guarantees and Indemnification

Guarantees and Indemnification - Additional Information (Detail)	Dec. 31, 2018USD ($)
Guarantees [Abstract]
Liabilities incurred in indemnification agreements	$ 0

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Shares of common stock issued		37,474,000	34,291,000
Preferred stock, shares issued		18,000	18,000
Underwritten Offering [Member]
Subsequent Event [Line Items]
Shares of common stock issued				7,500,000		5,675,825	1,832,698
Price per common share						$ 3.85	$ 5.04
Common Stock [Member]
Subsequent Event [Line Items]
Shares of common stock issued		37,474,000	34,291,000		20,925,000
Subsequent Event [Member] | Underwritten Offering [Member]
Subsequent Event [Line Items]
Shares of common stock issued	23,000,000
Proceeds from issuance of common and convertible preferred stock, gross	$ 20
Proceeds from issuance of common and convertible preferred stock, net	$ 18.4
Subsequent Event [Member] | Series E Convertible Preferred Stock [Member] | Underwritten Offering [Member]
Subsequent Event [Line Items]
Preferred stock, shares issued	17,000
Shares issued upon conversion	1,000
Subsequent Event [Member] | Series E Convertible Preferred Stock [Member] | Underwritten Offering [Member] | Maximum [Member]
Subsequent Event [Line Items]
Percentage of outstanding common stock	9.98%
Subsequent Event [Member] | Common Stock [Member] | Underwritten Offering [Member]
Subsequent Event [Line Items]
Price per common share	$ 0.50
Subsequent Event [Member] | Preferred Stock [Member] | Series E Convertible Preferred Stock [Member] | Underwritten Offering [Member]
Subsequent Event [Line Items]
Price per common share	$ 500