Isomer-dependent cytostatic activity of bis(1-aziridinyl)cyclophosphazenes

A number of recently synthesized mono- and bis(1-aziridinyl) derivatives of the inorganic ring systems (NPCl2)3 and (NPCl2)4 was tested for their cytostatic activity in vitro (L1210 and L5178Y cells) and in vivo (intraperitoneal leukemia L1210 in CDF1 mice). Generally, the nongeminal bis(1-aziridinyl) isomers (either trans or cis) appear to be potent tumor growth inhibitors in contrast to their geminally substituted and mono(1-aziridinyl)-substituted analogues. A relationship between the biological activity and the number of alkylating centers (i.e., P atoms carrying one or two aziridinyl groups) is proposed.