Studies on the reversal of the selective antitumour effect of the aziridinyl derivative CB 1954 by 4-amino-5-imidazolecarboxamide

The selective toxicity of CB 1954 (5-aziridinyl-2,4-dinitrobenzamide) for Walker tumour cells, previously shown in the whole animal and in an in vitro/in vivo system, has been confirmed in an in vitro system In each case its actions on the Walker tumour were reversed by 4-amino-5-imidazolecarboxamide, the ribotide of which is a purine precursor, provided it was given before or soon after the CB 1954. Other purines also produced this reversal, while pyrimidines and several other compounds did not. This evidence suggested that CB 1954, in addition to its alkylating properties, had features of a purine antimetabolite. However, anthranilamide was also very effective in protecting against CB 1954, suggesting that reversal could be achieved by compounds structurally related to CB 1954 which competed with it for some receptor site.