5'-Deoxy-5-fluorouridine (doxifluridine) is a prodrug of active antitumor 5-FU [
F0151] and an intermediary metabolite of capecitabine [
C2878] and 5'-deoxy-5-fluorocytidine [
D4342]. The activation of capecitabine follows a pathway with three enzymatic steps and two intermediary metabolites, 5'-deoxy-5-fluorocytidine and doxifluridine, to form 5-FU. Capecitabine and its intermediary metabolites are not cytotoxic by themselves. The final step (doxifluridine to 5-FU) requires thymidine phosphorylase (dThdPase) that is significantly more active in tumor than normal tissue. This tumor-selective delivery of 5-FU ensured greater efficacy and a more favorable safety profile than with other fluoropyrimidines. (The product is for research purpose only.)