Doxifluridine (5'-deoxy-5-fluorouridine) is a second generation nucleoside analog prodrug developed by Roche and used as a cytostatic agent in chemotherapy in several Asian countries including China and South Korea.

[2] 5-FU is normally administered intravenously to prevent its degradation by dihydropyrimidine dehydrogenase in the gut wall.

Doxifluridine was designed to improve oral bioavailability in order to avoid dihydropyrimidine dehydrogenase degradation in the digestive system.

[6][7] Liberation of 5-FU is the active metabolite and leads to inhibition of DNA synthesis and cell death.

High thymidine phosphorylase expression is also found in the human intestinal tract, resulting in dose-limiting toxicity (diarrhea) in some individuals.