[A new anticancer drug, 5'-deoxy-5-fluorouridine (5'-DFUR)]

Recently 5'-DFUR (5'-deoxy-5-fluorouridine) was developed as a new anticancer drug in Japan. The compound was active against various murine tumors by oral administration and the toxicity was almost comparable to the other prodrugs of 5-fluorouracil (5-FU). 5'-DFUR is converted to 5-FU in vivo by pyrimidine nucleoside phosphorylase which was found to exist relatively much in tumor tissues compared to normal ones except intestinal tract. In the phase I study, the dose-limiting toxicities were gastro-intestinal (GI) ones such as nausea, vomiting, anorexia etc., and the MTD was 2,100 mg/body/day (oral administration). In the multi-institutional phase II studies, clinical activity of 5'-DFUR was found in head and neck, thyroidal, esophageal, gastric, colo-rectal, gall-bladder and breast cancers at daily doses of 800-1,200 mg/body. The main side effects were consisted of GI-toxicities in which diarrhea appeared most frequently (26.3%). This diarrhea, however, disappeared rapidly by decreasing the dosage or termination of treatment. In the comparative clinical studies of 5'-DFUR with tegafur against advanced breast cancer cases, 5'-DFUR was found superior to tegafur in the clinical responses. From these results, 5'-DFUR was judged as an useful new anticancer drug.