Antitumor activity of two novel low immunosuppressive fluoropyrimidines UK-21 and UK-25

We have previously reported that 2',3',5'-tris-O-[N-(2-n-propyl-n-pentanoyl)glycyl]-5-fluorouridine (UK-21), a derivative of 5-fluorouridine (5-FUR), and 1-(6-[N-(2-n-propyl-n-pentanoyl)-glycyl]amino-n-hexylcarbamoyl)-5- fluorouracil (UK-25), a derivative of 5-fluorouracil (5-FU), exert their antitumor activity in mice bearing Meth A or EL4 tumor, while their immunosuppressive effects are mild. In the present study, we examined the effects of these compounds on Sarcoma-180 (S-180), P388, L1210, and Lewis lung carcinoma (LLC) in mice by p.o. administration and i.p.-administration. UK-21 given p.o. showed an antitumor effect against S-180, but it showed virtually no antitumor effects against P388, L1210 and LLC. UK-21 given i.p., on the other hand, strongly inhibited the growth of Meth A tumor at a far lower dose than that for oral administration. The bioavailability of UK-21 given p.o. was suspected to be poor. UK-25 given p.o., in contrast, showed the antitumor effect on all of the tumors employed. The bioavailability of UK-25 given p.o. seemed to be comparable to those of other drugs. These results suggest that UK-21 has the potential for development as a parenterally applicable anticancer drug, and UK-25 has the potential as an oral one.