Comparative studies on the metabolism of 2-(tetrahydrofuryl)-5-fluorouracil and 5-fluorouracil.

5=Fluorouracil inhibited DNA synthesis markedly using various DNA precursors such as deoxyuridine, orotic acid, uracil, and uridine except for thymidine. 2-(Tetrahydrofury)-5-fluorouracil (FT-207) did not inhibit DNA synthesis with any of the precursors tested. The metabolisms of 5-fluorouracil and FT-207 in mice and rats were studied. When administered intravenously 5-fluorouracil was rapidly degraded to fluoro-beta-alanine in both mice and rats, while at most 70% of FT-207 was slowly degraded after a prolonged period. The metabolites of FT-207 were found to be 5-fluorouracil and fluoro-beta-alanine in both species of animals. In vitro degradation of FT-207 into 5-fluorouracil was observed mainly in the microsomal fraction in the presence of NADPH. This result suggested that microsomal electron-transport system was concerned with the degradation of FT-207.