Organization and Basis of Presentation	3 Months Ended
Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation Viracta Therapeutics, Inc. (“Viracta,” the “Company,” or the “combined company”), formerly known as Sunesis Pharmaceuticals, Inc., was incorporated in the state of Delaware in February 1998 and is based in San Diego, California. Viracta is a clinical-stage, precision oncology company focused on the treatment and prevention of virus-associated cancers that impact patients worldwide. Viracta’s lead product candidate is an all-oral combination therapy of its proprietary investigational drug, nanatinostat and the antiviral agent valganciclovir (collectively referred to as “Nana-val”). Nana-val is currently being investigated in multiple ongoing clinical trials, including NAVAL-1, a pivotal, global, multicenter, open-label Phase 2 basket trial for the treatment of multiple subtypes of relapsed/refractory (“R/R”) Epstein-Barr virus-positive (“EBV+”) lymphoma, as well as a multinational, open-label Phase 1b/2 trial for the treatment of EBV+ recurrent or metastatic nasopharyngeal carcinoma (“R/M NPC”) and other EBV+ solid tumors. Viracta’s development pipeline also includes vecabrutinib, a clinical-stage non-covalent ITK/BTK inhibitor and VRx-510 (formerly SNS-510), a preclinical-stage PDK-1 inhibitor. Viracta is evaluating future development and collaboration opportunities for vecabrutinib in combination with chimeric antigen receptor (“CAR”) T-cell therapies and VRx-510 in multiple oncology and other indications. Merger Transaction between Private Viracta Therapeutics, Inc. and Sunesis Pharmaceuticals, Inc. and Name Change On November 29, 2020, the Company, then operating as Sunesis Pharmaceuticals, Inc., entered into an agreement and plan of merger and reorganization (the “Merger Agreement”) with privately-held Viracta Therapeutics, Inc. (“Private Viracta”) and Sol Merger Sub, Inc., a wholly-owned subsidiary of the Company (“Merger Sub”). On February 24, 2021, the transactions contemplated by the Merger Agreement were completed, and Merger Sub merged into Private Viracta, with Private Viracta surviving the merger as a wholly owned subsidiary of the Company (the “Merger”). Sunesis changed its name to Viracta Therapeutics, Inc. On February 25, 2021, the combined company’s common stock began trading on The Nasdaq Global Select Market under the ticker symbol “VIRX”. Except as otherwise indicated, references herein to “Viracta,” the “Company,” or the “combined company,” refer to Viracta Therapeutics, Inc. on a post-Merger basis, and the term “Private Viracta” refers to the business of privately-held Viracta Therapeutics, Inc., prior to the completion of the Merger. References to “Sunesis” refer to Sunesis Pharmaceuticals, Inc. prior to completion of the Merger. Liquidity, Risks and Uncertainties As of March 31, 2023, the Company has devoted substantially all of its efforts to product development and has not realized product sales revenues from its planned principal operations. The Company has a limited operating history, and the sales and income potential of the Company’s business and market are unproven. The Company has experienced net losses since its inception and, as of March 31, 2023, had an accumulated deficit of $227.1 million. The Company expects to continue to incur net losses for at least the next several years. A successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company’s cost structure. If the Company is unable to generate revenues adequate to support its cost structure, the Company will need to raise additional capital through the issuance of its common stock, through other equity or debt financings or through collaborations or partnerships with other companies. As of March 31, 2023, the Company had cash, cash equivalents and short-term investments of $80.3 million and working capital of $71.8 million. On November 4, 2021, the Company entered into a loan and security agreement with Silicon Valley Bank, now a division of First-Citizens Bank and Trust Company (“SVB”), and Oxford Finance LLC (“Oxford”), collectively referred to as “Lenders,” for up to $50.0 million, with $5.0 million refinanced at the time of entering into the agreement and $45.0 million available under certain circumstances, as amended August 26, 2022. The second tranche of $20.0 million was drawn by the Company on December 29, 2022 and the third tranche of $25.0 million remains available at the Company's request subject to Lenders' discretion (see Note 5). Based on the Company’s current financial position and business plan, management believes that its existing cash, cash equivalents and short-term investments will be sufficient to fund the Company’s planned operations for at least twelve months from the issuance date of these condensed consolidated financial statements. Viracta uses third party contract labs and facilities for the manufacture and testing of drug substance, drug product, and clinical trial material while providing internal oversight on technical development, quality and regulatory compliance. This outsourcing model allows Viracta to maintain a flexible infrastructure and capital efficiency while focusing its expertise on developing its products. For the three months ended March 31, 2023 and 2022, the Company had one contract lab that provided 10.9% and two contract labs and contract manufacturers that provided 27.4% of total third-party services, respectively. The COVID-19 pandemic caused significant business disruption around the globe and its long-term impact remains uncertain. While the Company has largely resumed normal operations, any resurgence or worsening of the COVID-19 pandemic may cause the Company to reinstitute certain mitigating measures. The Company does not yet know the full extent of potential delays or impacts on its business, its clinical trials, healthcare systems or the global economy as a whole. These effects could have a material impact on the Company’s operations, including the timing and ability of the Company to complete certain clinical trials and other efforts required to advance the development of its product candidates and raise additional capital.

Organization and Basis of Presentation

3 Months Ended

Mar. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

1. Organization and Basis of Presentation

Viracta Therapeutics, Inc. (“Viracta,” the “Company,” or the “combined company”), formerly known as Sunesis Pharmaceuticals, Inc., was incorporated in the state of Delaware in February 1998 and is based in San Diego, California. Viracta is a clinical-stage, precision oncology company focused on the treatment and prevention of virus-associated cancers that impact patients worldwide. Viracta’s lead product candidate is an all-oral combination therapy of its proprietary investigational drug, nanatinostat and the antiviral agent valganciclovir (collectively referred to as “Nana-val”). Nana-val is currently being investigated in multiple ongoing clinical trials, including NAVAL-1, a pivotal, global, multicenter, open-label Phase 2 basket trial for the treatment of multiple subtypes of relapsed/refractory (“R/R”) Epstein-Barr virus-positive (“EBV+”) lymphoma, as well as a multinational, open-label Phase 1b/2 trial for the treatment of EBV+ recurrent or metastatic nasopharyngeal carcinoma (“R/M NPC”) and other EBV+ solid tumors. Viracta’s development pipeline also includes vecabrutinib, a clinical-stage non-covalent ITK/BTK inhibitor and VRx-510 (formerly SNS-510), a preclinical-stage PDK-1 inhibitor. Viracta is evaluating future development and collaboration opportunities for vecabrutinib in combination with chimeric antigen receptor (“CAR”) T-cell therapies and VRx-510 in multiple oncology and other indications.

Merger Transaction between Private Viracta Therapeutics, Inc. and Sunesis Pharmaceuticals, Inc. and Name Change

On November 29, 2020, the Company, then operating as Sunesis Pharmaceuticals, Inc., entered into an agreement and plan of merger and reorganization (the “Merger Agreement”) with privately-held Viracta Therapeutics, Inc. (“Private Viracta”) and Sol Merger Sub, Inc., a wholly-owned subsidiary of the Company (“Merger Sub”). On February 24, 2021, the transactions contemplated by the Merger Agreement were completed, and Merger Sub merged into Private Viracta, with Private Viracta surviving the merger as a wholly owned subsidiary of the Company (the “Merger”). Sunesis changed its name to Viracta Therapeutics, Inc. On February 25, 2021, the combined company’s common stock began trading on The Nasdaq Global Select Market under the ticker symbol “VIRX”.

Except as otherwise indicated, references herein to “Viracta,” the “Company,” or the “combined company,” refer to Viracta Therapeutics, Inc. on a post-Merger basis, and the term “Private Viracta” refers to the business of privately-held Viracta Therapeutics, Inc., prior to the completion of the Merger. References to “Sunesis” refer to Sunesis Pharmaceuticals, Inc. prior to completion of the Merger.

Liquidity, Risks and Uncertainties

As of March 31, 2023, the Company has devoted substantially all of its efforts to product development and has not realized product sales revenues from its planned principal operations. The Company has a limited operating history, and the sales and income potential of the Company’s business and market are unproven. The Company has experienced net losses since its inception and, as of March 31, 2023, had an accumulated deficit of $227.1 million. The Company expects to continue to incur net losses for at least the next several years. A successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company’s cost structure. If the Company is unable to generate revenues adequate to support its cost structure, the Company will need to raise additional capital through the issuance of its common stock, through other equity or debt financings or through collaborations or partnerships with other companies. As of March 31, 2023, the Company had cash, cash equivalents and short-term investments of $80.3 million and working capital of $71.8 million.

On November 4, 2021, the Company entered into a loan and security agreement with Silicon Valley Bank, now a division of First-Citizens Bank and Trust Company (“SVB”), and Oxford Finance LLC (“Oxford”), collectively referred to as “Lenders,” for up to $50.0 million, with $5.0 million refinanced at the time of entering into the agreement and $45.0 million available under certain circumstances, as amended August 26, 2022. The second tranche of $20.0 million was drawn by the Company on December 29, 2022 and the third tranche of $25.0 million remains available at the Company's request subject to Lenders' discretion (see Note 5).

Based on the Company’s current financial position and business plan, management believes that its existing cash, cash equivalents and short-term investments will be sufficient to fund the Company’s planned operations for at least twelve months from the issuance date of these condensed consolidated financial statements.

Viracta uses third party contract labs and facilities for the manufacture and testing of drug substance, drug product, and clinical trial material while providing internal oversight on technical development, quality and regulatory compliance. This outsourcing model allows Viracta to maintain a flexible infrastructure and capital efficiency while focusing its expertise on developing its products. For the three months ended March 31, 2023 and 2022, the Company had one contract lab that provided 10.9% and two contract labs and contract manufacturers that provided 27.4% of total third-party services, respectively.

The COVID-19 pandemic caused significant business disruption around the globe and its long-term impact remains uncertain. While the Company has largely resumed normal operations, any resurgence or worsening of the COVID-19 pandemic may cause the Company to reinstitute certain mitigating measures. The Company does not yet know the full extent of potential delays or impacts on its business, its clinical trials, healthcare systems or the global economy as a whole. These effects could have a material impact on the Company’s operations, including the timing and ability of the Company to complete certain clinical trials and other efforts required to advance the development of its product candidates and raise additional capital.