New folate analogs of the 10-deaza-aminopterin series: markedly increased antitumor activity of the 10-ethyl analog compared to the parent compound and methotrexate against some human tumor xenografts in nude mice.

In an extension of our prior studies in murine tumor models, we examined two new folate analogs in the 10-deaza-aminopterin series for antitumor activity against a group of human tumor xenografts in nude mice. In all three xenograft models studied, MX-1 mammary carcinoma, LX-1 lung carcinoma, and CX-1 colon carcinoma, 10-deaza-aminopterin was minimally active, while methotrexate was inactive. In contrast, against the MX-1 and LX-1 tumors, 10-ethyl, 10-deaza-aminopterin at or near the LD10 dose (2-4.5 mg/kg) given once per day X 5 produced frank regressions. Activity of this analog against the CX-1 tumor was less, but retardation of tumor growth was observed with some minor regressions.