A Phase I/II Study of Infusional Vinblastine with the P-Glycoprotein Antagonist Valspodar (PSC 833) in Renal Cell Carcinoma

Purpose: P-glycoprotein (Pgp) inhibitors have been under clinical evaluation for drug resistance reversal for over a decade. Valspodar (PSC 833) inhibits Pgp-mediated efflux but delays drug clearance, requiring reduction of anticancer drug dosage. We designed an infusional schedule for valspodar and vinblastine to mimic infusional vinblastine alone. The study was designed to determine the maximally tolerated dose of vinblastine, while attempting...