A phase Ib trial of IPI-504 (retaspimycin hydrochloride), a novel Hsp90 inhibitor, in combination with docetaxel

3547 Background: IPI-504 is a water-soluble heat shock protein 90 (Hsp90) inhibitor. IPI-504 causes the degradation of a variety of mutated or amplified oncoproteins, including epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2). The combination of IPI-504 and docetaxel demonstrates additive efficacy in murine xenograft models. This Phase 1b trial was undertaken to identify the maximum tolerated dose (MTD) of IPI-504 in combination with docetaxel. Methods: Eligible patients (pts) had advanced solid tumors that were either refractory to available therapies or for which docetaxel alone was an appropriate therapy. Intravenous (IV) 75 mg/m2 docetaxel was given once every three weeks (q 3- weekly). IPI-504 was administered IV q 3-weekly, with 3 pts per cohort and inter-cohort dose escalation. All pts were evaluated for safety, pharmacokinetics (PK), and tumor response. Results: 16 pts have been enrolled at 3 dose levels of IPI-504 (7 at 300 mg/m2, 6 at 450 mg/m2, and 3 a...