Phase I Clinical and Pharmacogenetic Study of Weekly TAS-103 in Patients With Advanced Cancer

PURPOSE: TAS-103 is an inhibitor of both topoiso-merase I and II enzymes with broad antitumor activity. It is metabolized to TAS-103-glucuronide (TAS-103-G) predominantly by uridine diphosphate glucuronosyltransferase isoform 1A1 (UGT1A1). We conducted a phase I study to determine the maximum-tolerated dose (MTD) and dose-limiting toxicity (DLT) of TAS-103 when administered on a weekly schedule to patients with advanced cancer. In addition, we evaluated the influence of UGT1A1 genotype on the pharmacokinetics and toxicity of TAS-103. PATIENTS AND METHODS: Thirty-two patients were treated with escalating doses (50 to 200 mg/m2) of TAS-103, administered intravenously over 1 hour each week for 3 weeks. Pharmacokinetic analysis was performed at the 130-, 160-, and 200-mg/m2 dose levels. UGT1A1 genotypes were determined using reverse-transcription polymerase chain reaction techniques. RESULTS: DLT (grade 3 neutropenia) was observed in 5 of 12 patients at 160 mg/m2 and in 3 of 6 patients at 200 mg/m2. At 160 mg...