Received for publication April 21, 2006.
Revised August 3, 2006.
Accepted for publication August 4, 2006.

Pharmacokinetics, Metabolism, and Routes of Excretion of Intravenous Irofulven in Patients with Advanced Solid Tumors

Abstract

Irofulven is currently in Phase 2 clinical trials against a wide variety of solid tumors and has demonstrated activity in ovarian, prostate, gastro- intestinal and non small cell lung cancer. The objectives of this study were to determine its pharmacokinetics and route of excretion and to characterize its metabolites in human plasma and urine samples after a 30-minute intravenous infusion at a dose of 0.55 mg/kg in patients with advanced solid tumors. Three patients were administered intravenously 100 µCi of [¹⁴C]-irofulven over a 30-minute infusion on Day 1 of Cycle 1. Serial blood and plasma samples were drawn at: 0 (before irofulven infusion), and up to 144 h after the start of infusion. Urine and fecal samples were collected for up to 144 h after the start of infusion. The mean urinary and fecal excretion of radioactivity up to 144 h were 71.2% and 2.9%, respectively, indicating renal excretion was the major route of elimination of [¹⁴C]-irofulven. The Cmax, AUC_0-, and terminal half-life values for total radioactivity were 1130 ng-Eq/mL, 24400 ng-Eq.h/mL, and 116.5 h, respectively, and the corresponding values for irofulven were 82.7 ng/mL, 65.5 ng.h/mL, and 0.3 h, respectively, suggesting that the total radioactivity in human plasma was due to the metabolites. A total of twelve metabolites of irofulven were detected in human urine and plasma by ESI-MS/MS mass spectra. Among these metabolites, the cyclopropane ring-opened metabolite (M₂) of irofulven was found and seven other were proposed as glucuronide and glutathione conjugates.

Key words: anticancer agents, clinical pharmacokinetics, glutathione conjugates, HPLC, human pharmacokinetics, mass spectrometry, pharmacokinetics