Phase II trial of gemcitabine and tanespimycin (17AAG) in metastatic pancreatic cancer: A Mayo Clinic phase II consortium study

Objectives Heat Shock Protein 90 (HSP90) is a molecular chaperone that stabilizes many oncogenic proteins. HSP90 inhibitors may sensitize tumors to cytotoxic agents by causing client protein degradation. Gemcitabine, which has modest activity in pancreas cancer, activates Chk1, a client protein of HSP90. This phase II trial was designed to determine whether 17AAG could enhance the clinical activity of gemcitabine through degradation of Chk1 in patients with stage IV pancreatic cancer. Methods A multicenter, prospective study combining gemcitabine and 17AAG enrolled patients with stage IV pancreatic adenocarcinoma, adequate liver and kidney function, ECOG performance status 0-2, and no prior chemotherapy for metastatic disease. The primary goal was to achieve a 60 % overall survival at 6 months. Sixty-six patients were planned for accrual, with an interim analysis after 25 patients enrolled. Results After a futility analysis to achieve the endpoint, accrual was halted with 21 patients enrolled. No complete or partial responses were seen. Forty percent of patients were alive at 6 months. Median overall survival was 5.4 months. Tolerability was moderate, with 65 % of patients having ≥ grade 3 adverse events (AE), and 15 % having grade 4 events. Conclusions The lack of clinical activity suggests that targeting Chk1 by inhibiting HSP90 is not important in pancreatic cancer sensitivity to gemcitabine alone. Further studies of HSP90 targeted agents with gemcitabine alone are not warranted.