Synta presents ganetespib Phase 1, 2 trial results against solid tumors at ASCO 2011

Synta Pharmaceuticals Corp. (NASDAQ: SNTA) today presented results at the Annual Meeting of the American Society for Clinical Oncology (ASCO) from a Phase 2 single agent clinical trial of ganetespib in gastrointestinal stromal tumors (GIST) and a Phase 1 trial of ganetespib in solid tumors evaluating a twice-weekly administration schedule. Ganetespib is a potent inhibitor of heat shock protein 90 (Hsp90) currently being studied in a broad range of clinical trials with approximately 400 patients treated to date. Ganetespib is structurally unrelated to earlier Hsp90 inhibitors such as 17-AAG.

"Ganetespib results presented this week at ASCO support a strategy of parallel approach to development - both single agent in targeted, biomarker-defined subpopulations, as well as more broadly, in combination with certain other anti-cancer agents," said Safi Bahcall, Ph.D., President and Chief Executive Officer, Synta Pharmaceuticals. "The results reported Saturday demonstrated compelling proof of clinical activity in lung cancer patients with ALK+ tumors. The results reported today show that ganetespib has broad potential, with activity seen in breast cancer, melanoma, as well as GIST. These results support our program of working closely with leading investigators to evaluate the potential of ganetespib in a broad range of tumor types."

Ganetespib has been studied in 15 trials across multiple cancer types. Announcements regarding additional trials and data presentations are expected later this month and the second half of this year.

Phase 2 Results of Ganetespib in GIST

"Few therapeutic options are available to patients with advanced gastrointestinal tumors following treatment with the standard of care tyrosine-kinase inhibitor drugs, imatinib and sunitinib. Ganetespib showed activity in approximately half of GIST patients evaluated with PET imaging in this Phase 2 trial, including a 20% decrease in tumor metabolic activity," said George Demetri, M.D., Principal Investigator of the trial from the Dana-Farber Cancer Institute. "Analysis of tumor biopsies and PET imaging data suggest that optimizing the administration schedule of ganetespib could potentially increase KIT suppression and improve the clinical activity of ganetespib in GIST patients. Ganetespib was well-tolerated in this patient population, with the most common adverse events being Grade 1 and 2 diarrhea which was generally manageable with supportive care."

At the time of the analysis, 23 patients out of 26 patients in the intent to treat (ITT) population were evaluable. Patients enrolled in the ITT population had experienced a median of five prior treatments.

58% of patients (7 of 12 patients evaluated) reported a greater than 20% decrease in Standardized Uptake Value (SUV) as measured by positron emission tomography (PET) imaging. 22% of evaluable patients experienced a clinical benefit at 16 weeks (Partial Response + Complete Response + Stable Disease). There were no objective responses. One patient was non-evaluable.

The most common adverse events reported in more than 5% of patients were blood alkaline phosphatase increase (11.5%), anaemia (7.7%), and diarrhea (7.7%). The most frequent reported adverse events occurring in more than 40% of patients were diarrhea (84.6%), fatigue (53.8%) and nausea (46.2%).