Preclinical antitumor efficacy of S-1: a new oral formulation of 5-fluorouracil on human tumor xenografts.
S-1 is a new oral formulation of 5-fluorouracil (5-FU) consisted of 1M tegafur, 0.4M 5-chloro-2,4-dihydroxypyridine that inhibits a degradation of 5-FU, and 1M potassium oxonate that regulates the phosphorylation of 5-FU in the gastrointestinal tract, and has shown excellent antitumor efficacy against various murine tumors in rodents, compared to the oral tegafur-based antitumor drug, UFT (1M tegafur plus 4M uracil), which is used clinically in Japan. To assess the possibility of clinically using S-1, we investigated the antitumor effect of S-1 on various human solid tumor xenografts in athymic rats and mice. In the nude rat system, S-1 was significantly effective against all 12 tumor xenografts tested when its minimum toxic dose (15 mg/kg) was administered for 14 days. Three tumors, stomach (H-81), colon (KM12C) and breast (H-31) markedly regressed in response to treatment with S-1 but not with UFT. The antitumor potency of S-1 was weak against human tumors xenografted into nude mice and likely similar to that of UFT. The reason of the discrepancy in the efficacy of S-1 between rats and mice was found to be that the 5-FU levels in the blood and tumor tissue of rats after oral administration of S-1 persisted much longer than in mice, and this prolonged maintenance of plasma 5-FU levels was significantly related to the potent antitumor activity of S-1. In conclusion, the results of this study suggested that based on its biological and pharmacokinetic characteristics, oral S-1 should be active against various human cancers.
Fukushima
M
M
Cancer Research Laboratory-2, Hanno-City, Saitama 357, Japan.
Satake
H
H
Uchida
J
J
Shimamoto
Y
Y
Kato
T
T
Takechi
T
T
Okabe
H
H
Fujioka
A
A
Nakano
K
K
Ohshimo
H
H
Takeda
S
S
Shirasaka
T
T
D000284:Administration, Oral; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000627:therapeutic use*; D004338:Drug Combinations; D005472:Fluorouracil / Q000097:blood / Q000627:therapeutic use; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000097:blood / Q000188:drug therapy; D010094:Oxonic Acid / Q000627:therapeutic use*; D011725:Pyridines / Q000627:therapeutic use*; D051381:Rats; D011916:Rats, Inbred F344; D011923:Rats, Nude; D013045:Species Specificity; D005641:Tegafur / Q000627:therapeutic use*; D014183:Transplantation, Heterologous; D016896:Treatment Outcome; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000637:transplantation
D000964:Antimetabolites, Antineoplastic; D004338:Drug Combinations; D011725:Pyridines; C079198:S 1 (combination); D005641:Tegafur; D010094:Oxonic Acid; D005472:Fluorouracil