Company Overview	3 Months Ended
Mar. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Company Overview	1. Company Overview Description of Business Sunesis Pharmaceuticals, Inc. (the “Company” or “Sunesis”) was incorporated in the state of Delaware on February 10, 1998, and its facilities are located in South San Francisco, California. Sunesis is a biopharmaceutical company focused on the development and commercialization of new oncology therapeutics 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. Our most advanced program is QINPREZO^TM (vosaroxin), our product candidate for the potential treatment of acute myeloid leukemia, or AML. In October 2014, we announced the results of a Phase 3, multi-national, randomized, double-blind, placebo-controlled trial of vosaroxin in combination with cytarabine in patients with relapsed or refractory AML, or the VALOR trial. The VALOR trial did not meet its primary endpoint of demonstrating a statistically significant improvement in overall survival, but based upon the favorable results of other predefined analyses of the data, the Company submitted a letter of intent to the European Medicines Agency, or EMA, in November 2014 describing its intention to file a marketing authorization application, or MAA, for marketing authorization of vosaroxin plus cytarabine for the treatment of relapsed or refractory AML. In June 2015, the Company met separately with our Rapporteur and Co-Rapporteur, who are two appointed members of the EMA’s Committee of Human Medicinal Products. Based upon feedback from these meetings, the Company filed an MAA with the EMA at the end of 2015. In July 2015, the Company met with the U.S. Food and Drug Administration, or FDA, to discuss a potential regulatory filing in the U.S. Based upon the meeting, the FDA recommended that the Company provide additional clinical evidence prior to any regulatory filing in the U.S. As a result, the Company is evaluating regulatory and clinical strategies with the goal of gaining future marketing approval in the U.S. In January 2014, we announced the expansion of our oncology pipeline through separate global licensing agreements for two preclinical kinase inhibitor programs. The first agreement, with Biogen Idec MA, Inc., or Biogen, is for global commercial rights to SNS-062, a selective non-covalently binding oral inhibitor of BTK. We filed a Clinical Trial Authorization, or CTA, application with the EMA in the first quarter of 2016 and enrolled the first patients in a Phase 1A study of SNS-062 in healthy volunteers. The second agreement, with Milennium Pharmaceuticals, Inc., a wholly-owned subsidiary of Takeda Pharmaceutical Company Limited, or Takeda, is for global commercial rights to several potential first-in class, pre-clinical inhibitors of the novel target PDK1. In 2014, we selected two PDK1 inhibitors, SNS-229 and SNS-510, of which we have taken one, SNS-229 into IND-enabling absorption, distribution, metabolism and excretion, or ADME, and safety studies. In addition, we are in a collaboration with Takeda for the development of TAK-580 (formerly MLN2480), an oral pan-RAF inhibitor, for which Takeda recently initiated a multi-arm, open-label Phase 1B study in combination with MLN0128, an oral mTORC 1/2 inhibitor; alisertib, an oral aurora A kinase inhibitor; or paclitaxel, in adult patients with advanced non-hematologic malignancies. Significant Risks and Uncertainties The Company has incurred significant losses and negative cash flows from operations since its inception, and as of March 31, 2016, had cash, cash equivalents and marketable securities totaling $40.0 million and an accumulated deficit of $569.5 million. The Company will need to raise substantial additional capital to pursue a regulatory strategy for the potential commercialization of QINPREZO^TM(vosaroxin), its product candidate for the potential treatment of acute myeloid leukemia, and to continue the development of vosaroxin and the Company’s other programs. The Company expects to finance its future cash needs primarily through equity issuances, debt arrangements, one or more possible licenses, collaborations or other similar arrangements with respect to development and/or commercialization rights to vosaroxin and its other development programs, or a combination of the above. However, the Company does not know whether additional funding will be available on acceptable terms, or at all. If the Company is unable to raise required funding on acceptable terms or at all, it will need to reduce operating expenses, enter into a collaboration or other similar arrangement with respect to development and/or commercialization rights to vosaroxin, outlicense intellectual property rights to vosaroxin or our other development programs, sell unsecured assets, or a combination of the above, or be forced to delay or reduce the scope of its vosaroxin development program, potentially including any regulatory filings related to the VALOR trial, and/or limit or cease its operations. 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.

1. Company Overview

Description of Business

Sunesis Pharmaceuticals, Inc. (the “Company” or “Sunesis”) was incorporated in the state of Delaware on February 10, 1998, and its facilities are located in South San Francisco, California. Sunesis is a biopharmaceutical company focused on the development and commercialization of new oncology therapeutics 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.

Our most advanced program is QINPREZO^TM (vosaroxin), our product candidate for the potential treatment of acute myeloid leukemia, or AML. In October 2014, we announced the results of a Phase 3, multi-national, randomized, double-blind, placebo-controlled trial of vosaroxin in combination with cytarabine in patients with relapsed or refractory AML, or the VALOR trial. The VALOR trial did not meet its primary endpoint of demonstrating a statistically significant improvement in overall survival, but based upon the favorable results of other predefined analyses of the data, the Company submitted a letter of intent to the European Medicines Agency, or EMA, in November 2014 describing its intention to file a marketing authorization application, or MAA, for marketing authorization of vosaroxin plus cytarabine for the treatment of relapsed or refractory AML. In June 2015, the Company met separately with our Rapporteur and Co-Rapporteur, who are two appointed members of the EMA’s Committee of Human Medicinal Products. Based upon feedback from these meetings, the Company filed an MAA with the EMA at the end of 2015. In July 2015, the Company met with the U.S. Food and Drug Administration, or FDA, to discuss a potential regulatory filing in the U.S. Based upon the meeting, the FDA recommended that the Company provide additional clinical evidence prior to any regulatory filing in the U.S. As a result, the Company is evaluating regulatory and clinical strategies with the goal of gaining future marketing approval in the U.S.

In January 2014, we announced the expansion of our oncology pipeline through separate global licensing agreements for two preclinical kinase inhibitor programs. The first agreement, with Biogen Idec MA, Inc., or Biogen, is for global commercial rights to SNS-062, a selective non-covalently binding oral inhibitor of BTK. We filed a Clinical Trial Authorization, or CTA, application with the EMA in the first quarter of 2016 and enrolled the first patients in a Phase 1A study of SNS-062 in healthy volunteers.

The second agreement, with Milennium Pharmaceuticals, Inc., a wholly-owned subsidiary of Takeda Pharmaceutical Company Limited, or Takeda, is for global commercial rights to several potential first-in class, pre-clinical inhibitors of the novel target PDK1. In 2014, we selected two PDK1 inhibitors, SNS-229 and SNS-510, of which we have taken one, SNS-229 into IND-enabling absorption, distribution, metabolism and excretion, or ADME, and safety studies.

In addition, we are in a collaboration with Takeda for the development of TAK-580 (formerly MLN2480), an oral pan-RAF inhibitor, for which Takeda recently initiated a multi-arm, open-label Phase 1B study in combination with MLN0128, an oral mTORC 1/2 inhibitor; alisertib, an oral aurora A kinase inhibitor; or paclitaxel, in adult patients with advanced non-hematologic malignancies.

Significant Risks and Uncertainties

The Company has incurred significant losses and negative cash flows from operations since its inception, and as of March 31, 2016, had cash, cash equivalents and marketable securities totaling $40.0 million and an accumulated deficit of $569.5 million.

The Company will need to raise substantial additional capital to pursue a regulatory strategy for the potential commercialization of QINPREZO^TM(vosaroxin), its product candidate for the potential treatment of acute myeloid leukemia, and to continue the development of vosaroxin and the Company’s other programs. The Company expects to finance its future cash needs primarily through equity issuances, debt arrangements, one or more possible licenses, collaborations or other similar arrangements with respect to development and/or commercialization rights to vosaroxin and its other development programs, or a combination of the above. However, the Company does not know whether additional funding will be available on acceptable terms, or at all. If the Company is unable to raise required funding on acceptable terms or at all, it will need to reduce operating expenses, enter into a collaboration or other similar arrangement with respect to development and/or commercialization rights to vosaroxin, outlicense intellectual property rights to vosaroxin or our other development programs, sell unsecured assets, or a combination of the above, or be forced to delay or reduce the scope of its vosaroxin development program, potentially including any regulatory filings related to the VALOR trial, and/or limit or cease its operations.

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.