Triazene metabolism. IV. Derivatives of hydroxymethyltriazenes: potential prodrugs for the active metabolites of the anti-tumour triazene, DTIC.

A series of derivatives of the anti-tumour hydroxymethyltriazenes have been investigated for activity in vivo and in vitro. Acetoxymethyltriazenes are active in vivo against the TLX5, P388 and PC6 tumours in mice, and inhibit the growth of TLX5, Np and Li cells in vitro without metabolic activation. The acetoxymethyltriazenes are comparable with the hydroxymethyltriazenes and monomethyltriazenes in their spectrum of activity and thus appear to be prodrugs for these species. On the other hand, a methoxymethyltriazene was found to be active on the TLX5 tumour in vivo, but did not inhibit the growth of Np cells in vitro. This latter observation is consistent with the anticipated chemical stability of the methoxymethyltriazene and the requirement for metabolic O-demethylation to generate an active species. Acetoxymethyltriazenes do not require metabolic intervention and break down chemically in phosphate buffer to the hydroxymethyltriazene, which in turn loses formaldehyde to give the incipient methylating agent, the monomethyltriazene.