Synta Announces First Patient Treated in the GALAXY Trial™ a Phase 2b/3 Trial for Ganetespib in Advanced 2nd-line Non-small Cell Lung Cancer

Synta Pharmaceuticals Corp. (NASDAQ: SNTA), a biopharmaceutical company focused on discovering, developing, and commercializing small molecule drugs to treat severe medical conditions, today announced that the first patient has been treated in a Phase 2b/3 clinical trial of ganetespib in combination with docetaxel in non-small cell lung cancer (NSCLC).

Ganetespib is a potent inhibitor of heat shock protein 90 (Hsp90) that is structurally unrelated to first-generation, ansamycin-family Hsp90 inhibitors such as 17-AAG or IPI-504, and has shown superior activity to these agents in preclinical studies. Ganetespib is currently being studied in broad range of Phase 2 trials, including NSCLC, with nearly 400 patients treated to date.

"Initiation of the Phase 2b/3 multinational randomized GALAXY trial of docetaxel in combination with ganetespib in NSCLC patients is a major step in exploring the therapeutic potential of Hsp90 inhibitors,” said Vojo Vukovic, M.D., Ph.D., Senior Vice President and Chief Medical Officer, Synta Pharmaceuticals. "The combination of ganetespib and docetaxel has a strong scientific rationale as both drugs have single agent activity in NSCLC, their mechanisms of anticancer activity are complementary, and their toxicities are nonoverlapping. Results from the Phase 1 combination study with docetaxel and the combination cohort from the Phase 2 trial in NSCLC have been encouraging. We look forward to seeing interim results from the Phase 2b portion of the trial early in 2012.”

Results from a Phase 2 single agent NSCLC trial presented in June 2011 at the Annual Meeting of the American Society for Clinical Oncology (ASCO) showed that ganetespib had a 54% disease control rate in the broad population of patients in the trial with advanced relapsed/refractory NSCLC, all of whom had progressive disease upon study entry. In addition, six of eight patients (75%) with ALK rearrangement experienced tumor shrinkage, including four patients (50%) with durable, objective responses. Seven of eight of these patients (88%) received ganetespib for 16 weeks or more. Tumor shrinkage also occurred in 62% of patients whose tumors have a KRAS mutation, a particularly therapeutically challenging population. Ganetespib was well tolerated in this study and did not have the serious hepatic or common ocular toxicities reported with other Hsp90 inhibitors. The favorable safety profile seen in this trial is consistent with results seen in over 15 trials initiated to date with nearly 400 patients treated.

About the Phase 2b/3 GALAXY Trial^TM in NSCLC

The Phase 2b/3 trial will evaluate treatment with ganetespib and docetaxel vs. docetaxel alone, with 1:1 randomization, in patients with Stage IIIB or IV NSCLC who have completed one prior systemic therapy for advanced disease. The first stage, Phase 2b portion, will assess efficacy as measured by progression-free survival in approximately 240 patients. Results from this stage will also be used to inform the choice of patient subpopulation, by histology or biomarker, for the second stage, Phase 3 portion. The second stage will assess efficacy as measured by overall survival, and will enroll between 400 and 600 patients. Interim results from the first-stage portion of the trial are expected in early 2012. More information on the trial can be found at www.clinicaltrials.gov.

About Ganetespib

Ganetespib (formerly STA-9090) is a potent, synthetic, small-molecule inhibitor of heat shock protein 90 (Hsp90). Hsp90 is a molecular chaperone required for the proper folding and activation of many cancer-promoting proteins, and is recognized as a key facilitator of cancer cell growth and survival. In preclinical experiments, ganetespib has shown activity in multiple tumor models both as a single agent and in combination with certain widely used cancer agents. Ganetespib is currently being evaluated in a broad range of cancer clinical trials. In these trials, ganetespib has shown clinical activity in heavily pretreated patients and has been well tolerated to date with no evidence of severe liver or common ocular toxicities seen with other Hsp90 inhibitors. The most common adverse event seen to date has been diarrhea, which has been manageable with standard supportive care. Information on clinical trials with ganetespib can be found at www.clinicaltrials.gov.

About Non-small Cell Lung Cancer

Lung cancer is the leading cause of cancer-related mortality in the United States, with over 225,000 new cases and 157,000 deaths estimated in 2010. The five year survival rate for advanced-staged lung cancer is less than 5%. Approximately 85% of all lung cancers are classified as non-small cell.

About Synta Pharmaceuticals

Synta Pharmaceuticals Corp. is a biopharmaceutical company focused on discovering, developing, and commercializing small molecule drugs to extend and enhance the lives of patients with severe medical conditions, including cancer and chronic inflammatory diseases. Synta has a unique chemical compound library, an integrated discovery engine, and a diverse pipeline of clinical- and preclinical-stage drug candidates with distinct mechanisms of action and novel chemical structures. All Synta drug candidates were invented by Synta scientists using our compound library and discovery capabilities. For more information, please visit www.syntapharma.com.

Safe Harbor Statement

This media release may contain forward-looking statements about Synta Pharmaceuticals Corp. Such forward-looking statements can be identified by the use of forward-looking terminology such as "will", "would", "should", "expects", "anticipates", "intends", "plans", "believes", "may", "estimates", "predicts", "projects", or similar expressions intended to identify forward-looking statements. Such statements, including statements relating to the timing, developments and progress of our ganetespib clinical and preclinical program, reflect our current views with respect to future events and are based on assumptions and subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such forward-looking statements, including those described in "Risk Factors" of our Form 10-K for the year ended December 31, 2010 as filed with the Securities and Exchange Commission. Synta undertakes no obligation to publicly update forward-looking statements, whether because of new information, future events or otherwise, except as required by law.