The results are being presented today in an oral session at the 9th European Breast Cancer Conference (EBCC) in Glasgow, Scotland at 9:45 AM local time.
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, six of seven achieved a metabolic response in the HER2+ cohort and 18 of 31 achieved a metabolic response in the TNBC cohort.
Of the six HER2+ and 26 TNBC patients that reached the six eek assessment and therefore evaluable for objective RECIST response, four achieved an objective response (CR+PR) and two achieved stable disease (SD) in the HER2+ cohort, while two 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 ten 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.
Synta Clinical Research vice president Dr Iman El-Hariry noted that like the I-SPY 2 breast cancer trial, ENCHANT-1 gives the company the opportunity to rapidly evaluate the clinical activity of ganetespib in an early treatment setting, providing a new paradigm for screening novel agents in the treatment of breast cancer.
"These results continue to provide exciting preliminary evidence of ganetespib’s clinical activity, which we look forward to elucidating further in the ENCHANT-1 and I-SPY 2 trials," Dr El-Hariry added.
Synta recently announced that ganetespib has been selected for study in the I-SPY 2 TRIAL (Investigation of Serial Studies to Predict Your Therapeutic Response with Imaging And moLecular Analysis 2).
I-SPY 2 is a standing Phase II randomized, controlled, multicenter trial for women with newly diagnosed, locally advanced breast cancer (Stage 2 or higher) that is designed to test whether adding investigational drugs to standard chemotherapy is better than standard chemotherapy alone in the neo-adjuvant setting (prior to surgery).
Enrollment in the ganetespib arm of I-SPY 2 is expected to begin in 2014. Ganetespib will initially be available to patients with HER2 negative disease, with the intent to expand its eligibility to all biomarker subtypes after safety testing with trastuzumab is completed.