[Phase I study of 5'-deoxy-5-fluorouridine (5'-DFUR)].

A phase I study of a new fluorinated pyrimidine compound, 5'-deoxy-5-fluorouridine (5'-DFUR), was performed in 37 patients with various malignant cancers. Starting dose was 600 mg/m2/day (900 mg/body/day) and escalated up to 3900 mg/body/day. The dose given was divided into 3 administrations a day for 5 consecutive days. Subjective symptoms were observed in cases given a dose of over 2,100 mg/body/day. Gastro-intestinal disturbances such as nausea, vomiting and anorexia were the major side effects. In the hematological and urinary examinations, no severe abnormal signs were observed. The maximum tolerated dose was considered to be 2.100 mg/body/day, and the dose-limiting factor was gastro-intestinal disturbance. 5-FU levels were determined in the serum and tumor tissues. 5'-DFUR was well absorbed. The 5-FU level in tumor tissue was very high at 2 to 3 hours post-dose and then rapidly decreased, being 0.05 microgram/g 12 hours after administration. The optimal dosage for a phase II study was suggested to be less than 2,100 mg/body/day.