Sunesis Pharmaceuticals Announces Presentations at the EHA Annual Meeting

Université Claude Bernard de Lyon Study Provides Preclinical Validation of Vecabrutinib Activity Against Ibrutinib-Resistant BTK C481S Mutated Lymphomas

ERIC Study Shows Half of Ibrutinib-Relapse CLL Patients Carry BTK C481S Mutations

SOUTH SAN FRANCISCO, Calif., June 18, 2018 (GLOBE NEWSWIRE) — Sunesis Pharmaceuticals, Inc. (Nasdaq:SNSS) today announced two presentations at the 23rd Congress of the European Hematology Association (EHA) in Stockholm, Sweden. Preclinical data from the laboratory of Professor Gilles Salles at the Université Claude Bernard de Lyon demonstrated the activity of Sunesis’ non-covalent BTK inhibitor vecabrutinib in BTK-dependent lymphomas, including lymphoma cell lines overexpressing mutated BTK C481S. In addition, a Sunesis-supported study led by the European Research Initiative on CLL (ERIC) assessed the real-world prevalence of BTK C481 and PLCg2 mutations in CLL patients relapsing under ibrutinib. Approximately half of the relapsed patients had BTK C481S mutations.

“Vecabrutinib demonstrated the ability to selectively induce apoptosis in BTK-dependent lymphoma cell lines, and to overcome resistance conferred by the BTK C481S mutation,” said Doctor Pierre Sujobert, lead investigator on the vecabrutinib study. “Based on our work, vecabrutinib seems to be a good potential option for patients with B-lymphoid malignancies who develop the C481S mutation and subsequent resistance to ibrutinib.”

“This real-world study confirms that there exists a high frequency of mutations within the Bruton’s tyrosine kinase (BTK) gene at C481, the binding site for ibrutinib, as well as the rarer PLCg2 gene, in CLL patients relapsing under ibrutinib,” said Professor Paolo Ghia, President of ERIC and senior author of the abstract. “These results indicate the outgrowth of several resistant clones and suggest resistance mechanisms that need to be studied further. With around 50% of relapsed patients carrying BTK 481S mutations, there is a strong rationale for the development of a new, innovative treatment to improve outcomes for these patients.”

“We are encouraged by the preclinical data from the laboratory of Professor Salles, which demonstrates vecabrutinib’s activity against ibrutinib-resistant BTK C481S mutated lymphomas,” said Judy Fox, Ph.D., Chief Scientific Officer of Sunesis. “Furthermore, the ERIC effort promoted by Professor Ghia supports earlier reports on the prevalence of BTK C481 mutations in CLL patients who relapse on the covalent BTK inhibitor ibrutinib. With its non-covalent binding mechanism, we believe vecabrutinib represents an important potential new treatment option for patients with CLL and other B-cell hematologic cancers. We remain focused on the execution of the Phase 1b portion of our ongoing trial with vecabrutinib, a dose escalation study evaluating the safety, pharmacokinetics, pharmacodynamics, and antitumor activity over a range of dose levels to determine the maximum tolerated and/or recommended dose, and we are on track to reach that recommended Phase 2 dose this fall.”

The vecabrutinib study, titled, “Preclinical Validation of Vecabrutinib (SNS-062) Efficiency Against BTK-C481S Mutated Lymphomas” was presented in the Aggressive Non-Hodgkin Lymphoma – nonclinical poster session Friday, June 15, by Dr. Camille Libre, a fellow in the laboratory of Dr. Pierre Sujobert at the Université Claude Bernard de Lyon. The ERIC study, titled “Half of Chronic Lymphocytic Leukemia Patients Relapsing Under Ibrutinib Carry BTK and PLCG2 Mutations: A European Research Initiative on CLL (ERIC) Real-World Study,” was presented by Dr. Lydia Scarfo, a senior researcher in the group of Professor Paolo Ghia of the San Raffaele Research Institute in Milan, as an oral presentation in the late-breaker session of the meeting on Sunday, June 17. The vecabrutinib poster is available at www.sunesis.com.

About Sunesis Pharmaceuticals

Sunesis is a biopharmaceutical company developing new therapeutics for the treatment of solid and hematologic cancers. Sunesis has built an experienced cancer drug development organization committed to improving the lives of people with cancer. The Company is focused on advancing its novel kinase-inhibitor pipeline, with an emphasis on establishing proof of concept that its oral non-covalent BTK-inhibitor vecabrutinib is effective in ibrutinib-resistant chronic lymphocytic leukemia. Vecabrutinib is currently being evaluated in a Phase 1b/2 study in adults with chronic lymphocytic leukemia and other B-cell malignancies who have progressed after prior therapies. Beyond the development of vecabrutinib, the Company has two other kinase inhibitor programs, including the Takeda-partnered pan-RAF inhibitor TAK-580, which is in clinical trials for solid tumors, and Sunesis’ proprietary preclinical PDK1 inhibitor SNS-510, which is in preclinical development with an IND submission planned in 2019.  PDK1 is a master kinase that activates other kinases important to cell growth and survival including members of the AKT, PKC, RSK and SGK families.

For additional information on Sunesis, please visit www.sunesis.com.

SUNESIS and the logos are trademarks of Sunesis Pharmaceuticals, Inc.

This press release contains forward-looking statements, including statements related to Sunesis’ cash sufficiency forecast, the continued development of vecabrutinib (SNS-062), including the timing of Phase 1b/2 trial of vecabrutinib and the therapeutic potential of vecabrutinib, further development and potential of its kinase inhibitor pipeline, and planned development of SNS-510. Words such as “believe,” “expect,” “look forward,” “potential,” “will” and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon Sunesis’ current expectations. Forward-looking statements involve risks and uncertainties. Sunesis’ actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, the risk related to the timing or conduct of Sunesis’ clinical trials, including the vecabrutinib Phase 1b/2 trial, the risk that Sunesis’ clinical or preclinical studies for vecabrutinib, SNS-510 or other product candidate may not demonstrate safety or efficacy or lead to regulatory approval, the risk that data to date and trends may not be predictive of future data or results, risks related to the timing or conduct of Sunesis’ clinical trials, that Sunesis’ development activities for vecabrutinib or SNS-510 could be otherwise halted or significantly delayed for various reasons, that Sunesis may not be able to receive regulatory approval of vecabrutinib, or SNS-510 in the U.S. or Europe, and risks related to Sunesis’ ability to raise the capital that it believes to be accessible and is required to fully finance the development and commercialization of vecabrutinib, SNS-510 and other product candidates. These and other risk factors are discussed under “Risk Factors” and elsewhere in Sunesis’ Quarterly Report on Form 10-Q for the quarter ended March 31, 2018 and Sunesis’ other filings with the Securities and Exchange Commission.  Sunesis expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein reflect any change in Sunesis’ expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based.

Investor and Media Inquiries:
Maeve Conneighton
Argot Partners

Willie Quinn
Sunesis Pharmaceuticals Inc.

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