Synta Pharmaceuticals Corp. (NASDAQ: SNTA) announced today that preliminary results from the ENCHANT-1 clinical trial, which evaluates ganetespib monotherapy in patients with newly diagnosed locally advanced or metastatic HER2 positive or triple-negative breast cancer (TNBC), achieved the prespecified criteria for advancing to the second stage of the trial.
Of the initial five HER2-positive patients enrolled in the study, two achieved objective tumor response and two achieved stable disease (SD) within the three cycles of treatment on study (12 weeks). Of the initial ten TNBC patients enrolled and evaluable for response, two achieved objective tumor response and three achieved SD following treatment with ganetespib monotherapy.
ENCHANT-1 is a ‘window-of-opportunity’ study designed to evaluate the clinical activity of single-agent ganetespib over a 12-week period preceding standard first line treatment. The protocol specifies advancing to the second stage of enrollment in each cohort if there was at least one objective tumor response out of the initial fifteen evaluable patients specified for Stage 1. This criterion was achieved in both cohorts, and therefore both cohorts will continue to enroll patients up to a total of 33 evaluable patients per cohort.
Metabolic response was also assessed in the study, by comparing baseline and week 3 PET scans. Of the five HER2-positive patients, four achieved metabolic responses. Of the 13 TNBC patients with post-baseline PET scans, six achieved metabolic response.
“Ganetespib appears to be what many of us in the Hsp90 field have been seeking for many years: a well tolerated, highly potent Hsp90 inhibitor that is clinically active in tough-to-treat cancers,” said Dr. Neil Spector, Co-Director of Developmental Therapeutics Program, Duke University and an investigator on the trial. “Given the known role of Hsp90 in fueling breast cancer growth and metastasis, and the single-agent activity seen with ganetespib, I believe this compound has potential to be an important new therapy for women with breast cancer.”