Aliphatic α,γ-bis(Amides) of Methotrexate. Influence of Chain Length on In-vitro Activity Against Sensitive and Resistant Tumour Cells

The synthesis of short-chain alkyl bis(amides) (heptyl-, isoheptyl-, octyl-) and nonylamide derivatives as lipophilic derivatives of methotrexate is reported. Direct amine substitution on methotrexate diethyl ester and a carbodiimide-assisted coupling method were used. The compounds were screened for in-vitro inhibitory activity against bovine liver dihydrofolate reductase and growth inhibition of human lymphoblastoid methotrexate-sensitive and resistant CCRF-CEM cells and erythroleukaemic K562 cells. The lipophilic methotrexate derivatives, despite showing lower activity against methotrexate-sensitive tumour cell lines, maintained similar activity to methotrexate, even against a methotrexate-transport resistant cell subline, since they can penetrate tumour cells by a passive route, by-passing the deficient cellular carrier system for the folates. Increasing the lipophilicity of methotrexate is a possible strategy to overcome the clinical resistance to the drug by tumour cells.