A phase I trial of perillyl alcohol in patients with advanced solid tumors

Purpose: Perillyl alcohol is a plant-derived lipid with preclinical antitumor activity. Its proposed mechanism of action involves inhibition of post-translational isoprenylation of small G proteins, including the proto-oncogene p21-ras, thereby blocking signal transduction. This phase I trial was conducted to determine the optimal dose of perillyl alcohol. Methods: The study group comprised 21 adults with advanced solid tumors who were treated with perillyl alcohol, delivered orally, four times daily, without interruption. Doses ranged from 4,800 to 11,200 mg/m² per day. Results: The maximum tolerated dose (MTD) for this schedule was determined to be 8400 mg/m² per day. The dose-limiting toxicities in this trial were nausea and vomiting, encountered in all patients at the highest dose level. No antitumor activity was observed. Pharmacokinetic data suggest dose-dependent increases in C_max of perillic acid, a metabolite of perillyl alcohol, but with high inter- and intrapatient variability. Conclusions: The MTD of perillyl alcohol for this schedule was determined to be 8400 mg/m² per day. This is higher than the MTDs determined in other similar phase I trials. This may have been due to the fact that the gastrointestinal symptoms caused by perillyl alcohol are highly subjective, with high interpatient variability. Phase II trials of perillyl alcohol in hormone-refractory prostate, breast, ovarian and colorectal cancer using doses in the range 4800-6400 mg/m² per day are underway.