Viracta Therapeutics (VIRX) 10-Q 8 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 01, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	SNSS
Entity Registrant Name	SUNESIS PHARMACEUTICALS INC
Entity Central Index Key	1,061,027
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		34,371,173

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents		$ 21,365	$ 26,977	[1]
Marketable securities		4,033	4,773	[1]
Prepaids and other current assets		1,480	1,183	[1]
Total current assets		26,878	32,933	[1]
Property and equipment, net		18	20	[1]
Other assets		96	1,381	[1]
Total assets		26,992	34,334	[1]
Current liabilities:
Accounts payable		1,038	1,697	[1]
Accrued clinical expense		570	767	[1]
Accrued compensation		862	1,440	[1]
Other accrued liabilities		1,905	1,570	[1]
Notes payable		7,252	7,204	[1]
Total current liabilities		11,627	12,678	[1]
Other liabilities	[1]		112
Commitments				[1]
Stockholders’ equity:
Convertible preferred stock		20,966	20,966	[1]
Common stock		3	3	[1]
Additional paid-in capital		634,528	633,436	[1]
Accumulated other comprehensive loss		(5)	(7)	[1]
Accumulated deficit		(640,127)	(632,854)	[1]
Total stockholders’ equity		15,365	21,544	[1]
Total liabilities and stockholders’ equity		$ 26,992	$ 34,334	[1]
[1]	The condensed consolidated balance sheet as of December 31, 2017, has been derived from the audited financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
License and other revenue	$ 237	$ 669
Total revenues	237	669
Operating expenses:
Research and development	3,969	6,162
General and administrative	3,359	3,942
Total operating expenses	7,328	10,104
Loss from operations	(7,091)	(9,435)
Interest expense	(281)	(484)
Other income, net	99	85
Net loss	(7,273)	(9,834)
Unrealized gain on available-for-sale securities	2	4
Comprehensive loss	(7,271)	(9,830)
Basic and diluted loss per common share:
Net loss	$ (7,273)	$ (9,834)
Shares used in computing net loss per common share	34,345	21,029
Net loss per common share	$ (0.21)	$ (0.47)

CONDENSED CONSOLIDATED STATEME4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Cash flows from operating activities
Net loss	$ (7,273)		$ (9,834)
Adjustments to reconcile loss to net cash used in operating activities:
Stock-based compensation expense	896		887
Depreciation and amortization	2		2
Amortization of debt discount and debt issuance costs	48		78
Changes in operating assets and liabilities:
Prepaids and other assets	988		(71)
Accounts payable	(659)		776
Accrued clinical expense	(197)		(83)
Accrued compensation	(578)		(945)
Other accrued liabilities	223		143
Deferred revenue			(610)
Net cash used in operating activities	(6,550)		(9,657)
Cash flows from investing activities
Proceeds from maturities of marketable securities	742		10,830
Net cash provided by investing activities	742		10,830
Cash flows from financing activities
Proceeds from issuance of common stock through controlled equity offering facilities, net	32
Proceeds from exercise of warrants, stock options and stock purchase rights	164		2,241
Net cash provided by financing activities	196		2,241
Net increase (decrease) in cash and cash equivalents	(5,612)		3,414
Cash and cash equivalents at beginning of period	26,977	[1]	8,056
Cash and cash equivalents at end of period	$ 21,365		$ 11,470
[1]	The condensed consolidated balance sheet as of December 31, 2017, has been derived from the audited financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

Company Overview

Company Overview	3 Months Ended
	Mar. 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 and commercialization of new therapeutics for the treatment of cancer. 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, formerly known as SNS-062, a non-covalent inhibitor of Bruton’s Tyrosine Kinase (“BTK”). Vecabrutinib is being studied in a Phase 1b/2 clinical trial in B-cell malignancies. In January 2017, the Company announced that its Investigational New Drug (“IND”) application with the U.S. Food and Drug Administration (“FDA”) for vecabrutinib had become effective. In July 2017, the Company announced the dosing of the first patient in a Phase 1b/2 study to assess the safety and activity of vecabrutinib in patients with advanced B-cell malignancies after two or more prior therapies, including ibrutinib or another covalent BTK inhibitor, and including patients with 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”). Sunesis acquired from Takeda global commercial rights to several potential first-in class, preclinical inhibitors of the novel target PDK1, including SNS-510. Sunesis is currently characterizing SNS-510 in preclinical pharmacology and toxicology studies with the goal of filing an IND in 2019. The Company is in a collaboration with Takeda for the development of TAK-580 (formerly MLN2480), an oral pan-RAF inhibitor, for which Takeda is conducting a multi-arm, open-label Phase 1b study in combination with various anticancer agents in adult patients with advanced solid tumor cancers. Liquidity and Going Concern The Company has incurred significant losses and negative cash flows from operations since its inception, and as of March 31, 2018, had cash, cash equivalents and marketable securities totaling $25.4 million and an accumulated deficit of $640.1 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. Following the decision to withdraw the European Marketing Authorization Application (“MAA”) for vosaroxin, 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, cash equivalents and marketable securities are not sufficient to support its operations for a period of twelve months from the date these condensed 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 7) have been classified as a current liability as of March 31, 2018 and December 31, 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 7) as of the date of the filing of this Form 10-Q. The accompanying condensed 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 condensed 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	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The condensed consolidated financial statements include all adjustments (consisting only of normal recurring adjustments) that management believes are necessary for a fair presentation of the periods presented. The balance sheet as of December 31, 2017 was derived from the audited consolidated financial statements as of that date. These interim financial results are not necessarily indicative of results to be expected for the full year or any other period. These unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. Recent Accounting Pronouncements In January 2016, the Financial Accounting Standards Board (“ ASU”) No. 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 February 2016, the FASB issued ASU No. Leases In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments, which will require a reporting entity to use a new forward-looking impairment model for most financial assets that generally will result in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, credit losses will be recognized as allowances rather than as reductions in amortized cost. The standard will be effective for annual periods beginning after December 15, 2019, with early adoption permitted beginning in 2019. Entities will apply the guidance as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company will evaluate the guidance and present the impact in its consolidated financial statements at the time of adoption. In February 2018, the FASB issued ASU No. 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income 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) Revenue Recognition On January 1, 2018, the Company adopted Topic 606 using the modified retrospective method applied to those contracts which were not completed as of January 1, 2018. Results for reporting periods beginning after January 1, 2018 are presented under Topic 606, while prior period amounts are not adjusted and continue to be reported in accordance with the Company’s historic accounting under Topic 605. 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 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 contract revenues consist of license revenue 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. Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, 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. 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 condensed 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, debt instruments, revenue recognition, stock-based compensation and clinical trial accounting. 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 cash, prepayments, accounts payable, accrued liabilities, and notes payable approximated their fair value as of March 31, 2018 and December 31, 2017.

Loss per Common Share

Loss per Common Share	3 Months Ended
	Mar. 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 loss per common share is computed by dividing (a) net loss, less any anti-dilutive amounts recorded during the period for the change in the fair value of warrant liabilities, 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 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): Three months ended March 31, 2018 2017 Warrants to purchase shares of common stock 5,218 218 Convertible preferred stock 6,331 4,270 Options to purchase shares of common stock 3,288 2,655 Restricted stock units — 53 Outstanding securities not included in calculations 14,837 7,196

Financial Instruments

Financial Instruments	3 Months Ended
	Mar. 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 comprised solely of available-for-sale marketable securities with remaining contractual maturities of one year or less (in thousands): March 31, 2018 Input Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Money market funds Level 1 $ 16,106 $ — $ — $ 16,106 U.S. corporate debt obligations Level 2 3,291 — (4 ) 3,287 U.S. commercial paper Level 2 747 — (1 ) 746 Total available-for-sale securities 20,144 — (5 ) 20,139 Less amounts classified as cash equivalents (16,106 ) — — (16,106 ) Amounts classified as marketable securities $ 4,038 $ — $ (5 ) $ 4,033 December 31, 2017 Input Level Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated 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 The following table summarizes the available-for-sale securities that were in an unrealized loss position as of the date indicated, having been in such position for less than 12 months, and none having been deemed to be other-than temporarily impaired (in thousands): March 31, 2018 Gross Unrealized Losses Estimated Fair Value U.S. corporate debt obligations $ (4 ) $ 3,287 U.S. commercial paper (1 ) 746 $ (5 ) $ 4,033 December 31, 2017 Gross Unrealized Losses Estimated Fair Value U.S. corporate debt obligations (5 ) 3,277 U.S. commercial paper (2 ) 1,496 $ (7 ) $ 4,773 No significant facts or circumstances have arisen to indicate that there has been any deterioration in the creditworthiness of the issuers of these securities. As of March 31, 2018, we did not hold any investments with a maturity exceeding 12 months or that have been in a continuous loss position for 12 months or more. The Company does not intend to sell the securities that are in an unrealized loss position and it is more likely than not that the investments will be held until recovery of the amortized cost bases. The Company has determined that the gross unrealized losses on its securities as of March 31, 2018 were temporary in nature. There were no realized gains or losses on the available-for-sale securities during three months ended March 31, 2018 and 2017.

Royalty Agreement

Royalty Agreement	3 Months Ended
	Mar. 31, 2018
Revenue Recognition [Abstract]
Royalty Agreement	5. 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	3 Months Ended
	Mar. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
License Agreements	6. License Agreements Biogen 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 preclinical 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. The Company is also eligible to receive royalty payments depending on related product sales, if any. As of March 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. 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, a BTK inhibitor synthesized under Biogen 1st ARCA, solely for oncology indications. During the third quarter of 2017, the Company made a milestone payment of $2.5 million to Biogen upon the dosing of the first patient in a Phase 1b/2 study to assess the safety and activity of vecabrutinib in patients with advanced B-cell malignancies after two or more prior therapies, including ibrutinib or other covalent BTK inhibitor for those patients with malignancies for which a BTK inhibitor is approved, and including patients with BTK C481 mutations. The payment was recorded in the research and development expenses line item in the consolidated statement of operations. The Company may also be required to make tiered royalty payments based on percentages of net sales of vecabrutinib, if any, in the mid-single-digits. All other of the Company’s rights and obligations contained in the Biogen 1st ARCA remain unchanged, except that potential future royalty payments to the Company were reduced to equal those amounts due to Biogen for potential future sales of 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 conducting Phase 1b/2 clinical studies of an oral investigative drug, TAK-580 (formerly MLN2480). As of March 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	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Notes Payable	7. Notes Payable On March 31, 2016, the Company entered into a loan and security agreement (the “Loan Agreement”) with Western Alliance Bank (“Western Bank”) and Solar Capital Ltd. (“Solar Capital,” and collectively with Western Bank, the “Lenders”) and Western Alliance, as Collateral Agent (the “Collateral Agent”). Pursuant to the terms of the Loan Agreement, the Lenders provided the Company with a loan in the principal amount of $15,000,000, for working capital, to fund its general business requirements and to repay indebtedness of the Company to Oxford Finance LLC, Silicon Valley Bank and Horizon Technology Finance Corporation (collectively, the “Existing Lenders”) pursuant to the Loan and Security Agreement, dated as of October 18, 2011, entered into by and among the Existing Lenders and the Company (the “Oxford Loan Agreement”). On March 31, 2016, the Company used $7.2 million of the loan proceeds to repay the outstanding principal of $6.0 million, a final payment fee of $1.2 million and accrued interest of $45,000 under the Oxford Loan Agreement. The Company paid the Lenders a $0.1 million facility fee and $0.1 million in legal fees. On June 30, 2017, the Company entered into an amendment to the existing Loan Agreement (the “Amended Loan Agreement”). Under terms of the Amended Loan Agreement, 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 Amendment modified the loan repayment terms to be interest-only through July 1, 2018, followed by twenty-two (22) equal monthly payments of principal and interest through the maturity date, contingent upon receipt of at least Fifteen Million Dollars ($15,000,000) in unrestricted cash proceeds received after June 1, 2017 from the issuance by the Company of new equity securities any time after June 1, 2017, but on or prior to December 31, 2017. Thereafter and until the scheduled maturity date of April 1, 2020, in addition to interest accrued during such period, the monthly payments will include an amount equal to the outstanding principal divided by 28 months, unless the interest only period is extended by a further six months, in which case the amortization period will be 22 months. In addition to principal and interest, a final payment equal to $312,500 will be due upon maturity or such earlier date specified in the Loan Agreement, of which $152,000 has been accrued and recorded in the other accrued liabilities line item in the accompanying condensed consolidated balance sheet as of March 31, 2018. If the Company repays all amounts owed under the Loan Agreement prior to the maturity date, the Company will pay a prepayment fee equal to 1.0 % of the amount prepaid if the prepayment occurs after June 30, 2017 but on or prior to March 31, 2018 and 0.5 % of the amount prepaid if the prepayment occurs thereafter. On October 31, 2017, the Company entered into a second amendment to the Amended Loan Agreement (the “Second Amendment”). The Second Amendment modified the loan repayment terms to add two additional extended interest-only periods beyond July 1, 2018. If under the terms of the Amended Loan Agreement, the interest-only period has been extended to July 1, 2018, the Company could further extend the interest-only period to October 1, 2018, contingent upon the receipt of at least Fifteen Million dollars ($15,000,000) in unrestricted net cash proceeds from the issuance by the Company of new equity securities or as a non-refundable upfront payment on a new business development agreement or royalty financing agreement (the “New Capital”), on or after October 24, 2017, but on or prior to December 31, 2017. The Company qualified for the first additional extended interest-only period and extended the interest-only period to October 1, 2018. Subsequently, the Company may further extend the interest-only period to January 1, 2019, contingent upon the receipt of at least Twenty-Five Million dollars ($25,000,000) in New Capital (inclusive of any prior amounts received after October 24, 2017), on or after October 24, 2017, but on or prior to September 15, 2018. In conjunction with the Loan Agreement, the Lenders were issued five-year warrants to purchase an aggregate of up to 208,002 shares of the Company’s common stock at a per share exercise price of $3.2454. The fair value of the warrants issued was estimated to be $0.5 million using a Black-Scholes valuation model with the following assumptions: common stock price at issuance of $3.24; exercise price of $3.2454; risk-free interest rate of 1.21% based upon observed risk-free interest rates; expected volatility of 111.96% based on the Company’s average historical volatility; expected term of five years, which is the contractual life of the warrants; and a dividend yield of 0%. The fair value was 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 Agreement, using the effective interest method . Pursuant to the Loan Agreement and the amendments, the Company is bound by a variety of affirmative covenants during the term of the Loan Agreement, including, without limitation, certain information delivery requirements, notice requirements and obligations to maintain certain insurance. Additionally, the Company is bound by certain negative covenants setting forth actions that are not permitted to be taken during the term of the Amended Loan Agreement without the Lenders’ consent, including, without limitation, 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 Amended Loan Agreement (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. Events of default under the Amended Loan Agreement include, among other things, the following: the occurrence of certain bankruptcy events; the failure to make payments under the Loan Agreement when due; the occurrence of a material impairment on the Collateral Agent’s security interest over the collateral, a material adverse change in the business, operations or condition (financial or otherwise) of the Company or material impairment of the prospect of repayment of the obligations under the Amended Loan Agreement; the occurrence of a default under certain other agreements entered into by the Company; the rendering of certain types of judgments against the Company; the revocation of certain government approvals of the Company; any breach by the Company of any covenant (subject to cure periods for certain covenants) made in the Amended Loan Agreement; and the failure of any representation or warranty made by the Company in connection with the Amended Loan Agreement to be correct in all material respects when made. The Amended Loan Agreement defines certain events of default, including instances of a Material Adverse Change in its operations, which may require prepayment of the outstanding loan. In the event of default by the Company under the Loan Agreement, 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, which could harm the Company's financial condition. The Company was in compliance with all applicable covenants set forth in the Loan Agreement as of March 31, 2018 and December 31, 2017. . 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 Amended Loan Agreement Aggregate future minimum payments due under the Loan Agreement as of March 31, 2018 were as follows (in thousands): Year ending December 31, Total 2018 1,415 2019 5,456 2020 2,015 Total minimum payments 8,886 Less amount representing interest (1,386 ) Total notes payable as of March 31, 2018 7,500 Less unamortized debt discount and issuance costs (248 ) Less carrying amount of notes payable (7,252 ) Non-current portion of notes payable $ —

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Stockholders' Equity	8. Stockholders’ Equity Controlled Equity Offerings During the three months ended March 31, 2018, 9,757 shares of common stock were sold under the Controlled Equity Offering SM

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9. Stock-Based Compensation 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. Forfeitures are recognized as they occur. The following table summarizes stock-based compensation expense related to the Company’s stock-based awards for the periods indicated (in thousands): Three months ended March 31, 2018 2017 Research and development $ 164 $ 252 General and administrative 234 611 Employee stock-based compensation expense 398 863 Non-employee stock-based compensation expense 498 24 Total stock-based compensation expense $ 896 $ 887

Summary of Significant Accoun14

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The condensed consolidated financial statements include all adjustments (consisting only of normal recurring adjustments) that management believes are necessary for a fair presentation of the periods presented. The balance sheet as of December 31, 2017 was derived from the audited consolidated financial statements as of that date. These interim financial results are not necessarily indicative of results to be expected for the full year or any other period. These unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In January 2016, the Financial Accounting Standards Board (“ ASU”) No. 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 February 2016, the FASB issued ASU No. Leases In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments, which will require a reporting entity to use a new forward-looking impairment model for most financial assets that generally will result in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, credit losses will be recognized as allowances rather than as reductions in amortized cost. The standard will be effective for annual periods beginning after December 15, 2019, with early adoption permitted beginning in 2019. Entities will apply the guidance as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company will evaluate the guidance and present the impact in its consolidated financial statements at the time of adoption. In February 2018, the FASB issued ASU No. 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income 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)
Revenue Recognition	Revenue Recognition On January 1, 2018, the Company adopted Topic 606 using the modified retrospective method applied to those contracts which were not completed as of January 1, 2018. Results for reporting periods beginning after January 1, 2018 are presented under Topic 606, while prior period amounts are not adjusted and continue to be reported in accordance with the Company’s historic accounting under Topic 605. 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 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 contract revenues consist of license revenue 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.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, 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.
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 condensed 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, debt instruments, revenue recognition, stock-based compensation and clinical trial accounting.
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 cash, prepayments, accounts payable, accrued liabilities, and notes payable approximated their fair value as of March 31, 2018 and December 31, 2017.

Loss per Common Share (Tables)

Loss per Common Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
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): Three months ended March 31, 2018 2017 Warrants to purchase shares of common stock 5,218 218 Convertible preferred stock 6,331 4,270 Options to purchase shares of common stock 3,288 2,655 Restricted stock units — 53 Outstanding securities not included in calculations 14,837 7,196

Financial Instruments (Tables)

Financial Instruments (Tables)	3 Months Ended
	Mar. 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 comprised solely of available-for-sale marketable securities with remaining contractual maturities of one year or less (in thousands): March 31, 2018 Input Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Money market funds Level 1 $ 16,106 $ — $ — $ 16,106 U.S. corporate debt obligations Level 2 3,291 — (4 ) 3,287 U.S. commercial paper Level 2 747 — (1 ) 746 Total available-for-sale securities 20,144 — (5 ) 20,139 Less amounts classified as cash equivalents (16,106 ) — — (16,106 ) Amounts classified as marketable securities $ 4,038 $ — $ (5 ) $ 4,033 December 31, 2017 Input Level Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated 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
Summary of Available-for-Sale Securities in Unrealized Loss Position	The following table summarizes the available-for-sale securities that were in an unrealized loss position as of the date indicated, having been in such position for less than 12 months, and none having been deemed to be other-than temporarily impaired (in thousands): March 31, 2018 Gross Unrealized Losses Estimated Fair Value U.S. corporate debt obligations $ (4 ) $ 3,287 U.S. commercial paper (1 ) 746 $ (5 ) $ 4,033 December 31, 2017 Gross Unrealized Losses Estimated Fair Value U.S. corporate debt obligations (5 ) 3,277 U.S. commercial paper (2 ) 1,496 $ (7 ) $ 4,773

Notes Payable (Tables)

Notes Payable (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Summary of Future Minimum Payments Under Loan Agreement	Aggregate future minimum payments due under the Loan Agreement as of March 31, 2018 were as follows (in thousands): Year ending December 31, Total 2018 1,415 2019 5,456 2020 2,015 Total minimum payments 8,886 Less amount representing interest (1,386 ) Total notes payable as of March 31, 2018 7,500 Less unamortized debt discount and issuance costs (248 ) Less carrying amount of notes payable (7,252 ) Non-current portion of notes payable $ —

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 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): Three months ended March 31, 2018 2017 Research and development $ 164 $ 252 General and administrative 234 611 Employee stock-based compensation expense 398 863 Non-employee stock-based compensation expense 498 24 Total stock-based compensation expense $ 896 $ 887

Company Overview - Additional I

Company Overview - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	[1]
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash, cash equivalents and marketable securities	$ 25,400
Accumulated deficit	$ 640,127	$ 632,854
Maturity limits period	24 months
Dollars weighted average maturity limit period	12 months
[1]	The condensed consolidated balance sheet as of December 31, 2017, has been derived from the audited financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

Summary of Significant Accoun20

Summary of Significant Accounting Policies - Additional Information (Detail)	Mar. 31, 2018USD ($)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | ASC 606 [Member]
Significant Accounting Policies [Line Items]
Cumulative impact to adoption of new standard	$ 0

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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	14,837	7,196
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	5,218	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	3,288	2,655
Restricted stock units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations		53
Convertible preferred stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities not included in calculations	6,331	4,270

Financial Instruments - Fair Va

Financial Instruments - Fair Value of Company's Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Amortized Cost	$ 20,144	$ 25,250
Available-for-sale securities, Gross Unrealized Losses	(5)	(7)
Available-for-sale securities, Estimated Fair Value	20,139	25,243
Less amounts classified as cash equivalents, Amortized Cost	(16,106)	(20,470)
Less amounts classified as cash equivalents, Estimated Fair Value	(16,106)	(20,470)
Amounts classified as marketable securities, Amortized Cost	4,038	4,780
Amounts classified as marketable securities, Gross Unrealized Losses	(5)	(7)
Amounts classified as marketable securities, Estimated Fair Value	4,033	4,773	[1]
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	16,106	20,470
Available-for-sale securities, Estimated Fair Value	16,106	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	3,291	3,282
Available-for-sale securities, Gross Unrealized Losses	(4)	(5)
Available-for-sale securities, Estimated Fair Value	3,287	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	747	1,498
Available-for-sale securities, Gross Unrealized Losses	(1)	(2)
Available-for-sale securities, Estimated Fair Value	$ 746	$ 1,496
[1]	The condensed consolidated balance sheet as of December 31, 2017, has been derived from the audited financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

Financial Instruments - Summary

Financial Instruments - Summary of Available-for-Sale Securities in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Gross Unrealized Losses	$ (5)	$ (7)
Estimated Fair Value	4,033	4,773
U.S. corporate debt obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Gross Unrealized Losses	(4)	(5)
Estimated Fair Value	3,287	3,277
U.S. commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Gross Unrealized Losses	(1)	(2)
Estimated Fair Value	$ 746	$ 1,496

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Realized gains or losses on available-for-sale securities	$ 0	$ 0

Royalty Agreement - Additional

Royalty Agreement - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Sep. 30, 2012	Mar. 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
Fair value of warrants issued in connection with participation agreement	$ 3.1

License Agreements - Additional

License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended
	Jun. 30, 2012	Mar. 31, 2018	Sep. 30, 2017	Jan. 31, 2014
License Agreement Terms [Member] | Takeda License Agreements [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
Contract assets		0
Potential pre-commercialization milestone payments payable				$ 9,200,000
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]
Received and recognized milestone revenue		0
Potential pre-commercialization payments receivable	$ 58,500,000
Contract assets		$ 0

Notes Payable - Additional Info

Notes Payable - Additional Information (Detail) - USD ($)	Oct. 31, 2017	Jun. 30, 2017	Mar. 31, 2016	Mar. 31, 2018
Loan Agreement [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 15,000,000
Date of Loan and Security Agreement				Oct. 18, 2011
Loan proceeds to repay the outstanding principal			7,200,000
Repayment of outstanding principal			6,000,000
Final payment fee			1,200,000
Accrued interest			45,000
Facility fee			100,000
Legal fees			$ 100,000
Line of credit facility final payment, additional amount due		$ 312,500
Percentage of penalty for prepaying loan after maturity		0.50%
Prepayment penalty expiration date				Jun. 30, 2017
Maturity date				Apr. 1, 2020
Warrants expiration term				5 years
Number of warrants issued				208,002
Warrants exercise price for shares				$ 3.2454
Estimated fair value of warrants issued				$ 500,000
Loan Agreement [Member] | Warrants to purchase shares of common stock [Member]
Debt Instrument [Line Items]
Common stock price				$ 3.24
Exercise price				$ 3.2454
Risk-free interest rates				1.21%
Expected volatility				111.96%
Expected term				5 years
Dividend yield				0.00%
Loan Agreement [Member] | Other Accrued Liabilities [Member]
Debt Instrument [Line Items]
Line of credit facility final payment accrued				$ 152,000
Loan Agreement [Member] | Extension of Maturity Date [Member]
Debt Instrument [Line Items]
Percentage of penalty for prepaying loan before maturity		1.00%
Prepayment penalty expiration date				Mar. 31, 2018
Loan Agreement [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		8.54%
Amended Loan Agreement [Member]
Debt Instrument [Line Items]
Description of monthly interest payment				The Amendment modified the loan repayment terms to be interest-only through July 1, 2018, followed by twenty-two (22) equal monthly payments of principal and interest through the maturity date, contingent upon receipt of at least Fifteen Million Dollars ($15,000,000) in unrestricted cash proceeds received after June 1, 2017 from the issuance by the Company of new equity securities any time after June 1, 2017, but on or prior to December 31, 2017. Thereafter and until the scheduled maturity date of April 1, 2020, in addition to interest accrued during such period, the monthly payments will include an amount equal to the outstanding principal divided by 28 months, unless the interest only period is extended by a further six months, in which case the amortization period will be 22 months.
Debt instrument, minimum threshold amount of unrestricted cash proceeds from issuance of new equity for principal and interest only payment period		$ 15,000,000
Loan, Covenant description				Pursuant to the Loan Agreement and the amendments, the Company is bound by a variety of affirmative covenants during the term of the Loan Agreement, including, without limitation, certain information delivery requirements, notice requirements and obligations to maintain certain insurance. Additionally, the Company is bound by certain negative covenants setting forth actions that are not permitted to be taken during the term of the Amended Loan Agreement without the Lenders’ consent, including, without limitation, 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 Amended Loan Agreement (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. Events of default under the Amended Loan Agreement include, among other things, the following: the occurrence of certain bankruptcy events; the failure to make payments under the Loan Agreement when due; the occurrence of a material impairment on the Collateral Agent’s security interest over the collateral, a material adverse change in the business, operations or condition (financial or otherwise) of the Company or material impairment of the prospect of repayment of the obligations under the Amended Loan Agreement; the occurrence of a default under certain other agreements entered into by the Company; the rendering of certain types of judgments against the Company; the revocation of certain government approvals of the Company; any breach by the Company of any covenant (subject to cure periods for certain covenants) made in the Amended Loan Agreement; and the failure of any representation or warranty made by the Company in connection with the Amended Loan Agreement to be correct in all material respects when made. The Amended Loan Agreement defines certain events of default, including instances of a Material Adverse Change in its operations, which may require prepayment of the outstanding loan. In the event of default by the Company under the Loan Agreement, 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, which could harm the Company's financial condition. The Company was in compliance with all applicable covenants set forth in the Loan Agreement as of March 31, 2018 and December 31, 2017. The principal payments due under the Loan Agreement have been classified as a current liability at December 31, 2017 due to the considerations discussed in Note 1 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 of the date of the filing of this Form 10-Q.
Second Amendment [Member]
Debt Instrument [Line Items]
Description of monthly interest payment				On October 31, 2017, the Company entered into a second amendment to the Amended Loan Agreement (the “Second Amendment”). The Second Amendment modified the loan repayment terms to add two additional extended interest-only periods beyond July 1, 2018. If under the terms of the Amended Loan Agreement, the interest-only period has been extended to July 1, 2018, the Company could further extend the interest-only period to October 1, 2018, contingent upon the receipt of at least Fifteen Million dollars ($15,000,000) in unrestricted net cash proceeds from the issuance by the Company of new equity securities or as a non-refundable upfront payment on a new business development agreement or royalty financing agreement (the “New Capital”), on or after October 24, 2017, but on or prior to December 31, 2017. The Company qualified for the first additional extended interest-only period and extended the interest-only period to October 1, 2018. Subsequently, the Company may further extend the interest-only period to January 1, 2019, contingent upon the receipt of at least Twenty-Five Million dollars ($25,000,000) in New Capital (inclusive of any prior amounts received after October 24, 2017), on or after October 24, 2017, but on or prior to September 15, 2018
Second Amendment Period One [Member]
Debt Instrument [Line Items]
Debt instrument, minimum threshold amount of unrestricted cash proceeds from issuance of new equity for principal and interest only payment period	$ 15,000,000
Second Amendment Period Two [Member]
Debt Instrument [Line Items]
Debt instrument, minimum threshold amount of unrestricted cash proceeds from issuance of new equity for principal and interest only payment period	$ 25,000,000

Notes Payable - Summary of Futu

Notes Payable - Summary of Future Minimum Payments Under Loan Agreement (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	[1]
Debt Instrument [Line Items]
Total notes payable as of March 31, 2018	$ 7,500
Less carrying amount of notes payable	(7,252)	$ (7,204)
Notes payable [Member]
Debt Instrument [Line Items]
2,018	1,415
2,019	5,456
2,020	2,015
Total minimum payments	8,886
Less amount representing interest	(1,386)
Less unamortized debt discount and issuance costs	$ (248)
[1]	The condensed consolidated balance sheet as of December 31, 2017, has been derived from the audited financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - Controlled Equity Offering Facilities [Member] $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)shares
Stockholders Equity [Line Items]
Issuance of common stock, remaining offering value	$ 45
Maximum [Member]
Stockholders Equity [Line Items]
Proceeds from issuance of common stock through controlled equity offering facilities, net	$ 0.1
Common Stock [Member]
Stockholders Equity [Line Items]
Common stock, shares sold | shares	9,757

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expense Related to Company's Stock-Based Awards (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	$ 896	$ 887
Employee stock-based compensation expense [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	398	863
Non-employee stock-based compensation expense [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	498	24
Research and development [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	164	252
General and administrative [Member]
Share-based Compensation, Allocation and Classification in Financial Statements
Total stock-based compensation expense	$ 234	$ 611