On March 20, 2014 Synta Pharmaceuticals reported on interim results from the ENCHANT-1 trial, a single-arm multi-center Phase 2 proof-of-concept study designed to evaluate ganetespib, administered as monotherapy for the treatment of metastatic breast cancer (Press release Synta Pharmaceuticals, MAR 20, 2014, View Source [SID:1234500306]). The results were presented in an oral session at the 9th European Breast Cancer Conference (EBCC) in Glasgow, Scotland.
The ENCHANT-1 trial was designed to evaluate ganetespib single agent activity in metastatic breast cancer and identify potential predictive biomarkers. Target enrollment is 35 patients in three cohorts, which include HER2+ breast cancer, triple-negative breast cancer (TNBC), and, recently added and now recruiting, ER/PR-positive patients previously untreated for locally advanced or metastatic disease. The goal of the trial design is to obtain initial evidence of a clinical activity signal with single-agent ganetespib administered for up to 12 weeks. Continuation of ganetespib as a single agent or in combination with paclitaxel after the initial assessment is at investigator discretion.
To date, 10 patients were enrolled into the HER2+ cohort and 38 patients were enrolled into the TNBC cohort. Of the patients evaluable for metabolic response based on having reached the week 3 PET assessment, 6 of 7 achieved a metabolic response in the HER2+ cohort and 18 of 31 achieved a metabolic response in the TNBC cohort. Of the 6 HER2+ and 26 TNBC patients that reached the 6 week assessment and therefore evaluable for objective RECIST response, 4 achieved an objective response (CR+PR) and two achieved stable disease (SD) in the HER2+ cohort, while 2 achieved an objective response, 11 achieved stable disease, and 13 had progressive disease in the TNBC cohort. All objective responses were confirmed by independent radiological review. Of note, one HER2+ patient achieved a complete objective response and has remained on treatment for over 10 months.
Consistent with previously reported results, diarrhea, fatigue, and nausea were the most common adverse events associated with ganetespib treatment, and were mostly Grade 1 or 2 in severity.