A phase II study of gemcitabine in combination with tanespimycin in advanced epithelial ovarian and primary peritoneal carcinoma

► Gemcitabine and tanespimycin combination therapy was well tolerated but had limited clinical activity. ► Modest downregulation of Chk-1 was observed in clinical samples, but reliable downregulation of HSP90 or client proteins was not observed. ► Based on clinical response and correlative studies, limited response is likely due to inadequate downregulation of HSP90 client proteins at therapeutically achievable concentrations.