Phase I study of the farnesyltransferase inhibitor lonafarnib with weekly paclitaxel in patients with solid tumors

Purpose: To establish the maximum tolerated dose of the farnesyltransferase inhibitor lonafarnib (Sarasar, Schering-Plough Corp., Kenilworth, NJ) in combination with weekly paclitaxel in patients with solid tumors. Tolerability, pharmacokinetics, safety, and dose-limiting toxicity were characterized. Experimental Design: Patients were enrolled form January 2000 to May 2001. Lonafarnib was administered continuously orally twice daily at doses of 100, 125, and 150 mg in combination with paclitaxel at doses of 40, 60, or 80 mg/m² i.v. over 1 h weekly in 28-day cycles in a phase I design. Plasma samples for determinations of lonafarnib and paclitaxel concentrations were collected at selected time points. Results: Twenty-seven patients were enrolled. The maximum tolerated dose (the dose level below where dose-limiting toxicity occurred and the recommended phase II dose) was lonafarnib 125 mg/m² twice daily and paclitaxel 80 mg/m² weekly. Dose-limiting toxicity was neutropenia with or without fever, which occurred in two of three patients treated at the lonafarnib 150 mg twice daily dose level. Diarrhea was a common side effect of lonafarnib but usually was mild to moderate in severity and could be controlled with standard medication without lonafarnib dose adjustment. Other reported adverse events included nausea, vomiting, fatigue, and taste changes. These adverse events were neither more frequent nor more severe than would be expected with paclitaxel alone. There were no apparent pharmacokinetic interactions between weekly paclitaxel and continuous twice-daily lonafarnib. Conclusions: The recommended dose of lonafarnib for phase II trials is 125 mg orally twice daily when combined with weekly paclitaxel 80 mg/m². The dose-limiting toxicity was neutropenia.