The metabolism of the anti-tumour agent 1(1-aziridinyl)- 2,4-dinitrobenzene (CB 1837).

1-(1-Aziridinyl)-2,4-dinitrobenzene (CB 1837) is the parent member of a series of nitrophenyla-ziridines having a highly specific action against the Walker tumour in the rat. CB 1837 was much less cytotoxic in vitro than was predicted on the basis of its antitumour activity in vivo, but its activity was enhanced in the presence of liver 9000-g supernatant and cofactors, which also converted it into a metabolite, 2-amino-1-(1-aziridinyl)-4-nitrobenzene. This metabolite was more active in the in vitro test than was CB 1837.CB 1837 is extensively metabolised in vivo by the rat, and the following urinary metabolites have been identified by mass spectrometry and quantitatively determined after administration of the tritium-labelled drug: 1-(2-chloroethyl)amino-2,4-dinitrobenzene and its 2-hydroxyethylamino analogue; 2,4-dinitroaniline: 2-amino-1-(1 -aziridinyl)-4-nitrobenzene,2-amino-1-(2-chloroethyl)amino-4-nitrobenzene and their respective N(2)-acetyl derivatives; and S-[N-(2,4-dinitrophenyl)-2-aminoethyl] mercapturic acid.