The antitumor potency of oral tegafur against adenocarcinoma 755 in mice is markedly enhanced by oral (E)-5-(2-bromovinyl)-2'-deoxyuridine.

A significant inhibition of the growth of adenocarcinoma 755 tumors in BDF1 mice was effected by oral tegafur (FT) in combination with oral (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVdUrd), at doses at which neither drug used alone had antitumor activity. The maximum inhibition of tumor growth (97%) was achieved by using a combination of 50 mg FT/kg with 10 mg BVdUrd/kg but, even at a dose as low as 1 mg BVdUrd/kg, the antitumor potency of FT was enhanced. The effect which BVdUrd has on the antitumor potency of FT is apparently due to inhibitory action by bromovinyluracil, the phosphorolytic product of BVdUrd, on the degradation of 5-fluorouracil, the oxidative product of FT, by dihydrothymine dehydrogenase.