Analogues of RSU-1069: radiosensitization and toxicity in vitro and in vivo.

A series of nitroimidazoles containing aziridine and alkyl-substituted aziridine functions has been synthesized. The 2-nitroimidazole compounds examined all show greater radiosensitizing efficiency in vitro than misonidazole. The 4- and 5-nitroimidazole analogues are also more efficient than equivalent compounds which do not contain the alkylating aziridine moiety. All the compounds show increased toxicity towards hypoxic cells relative to aerobic cells, but this toxicity is reduced by alkyl-substitution of the aziridine ring. In vivo toxicity can also be reduced by modification of the aziridine function, but such alterations appear to have less effect upon the high radiosensitizing efficiency of these compounds in vivo. As a consequence of this study, compounds of potentially improved therapeutic utility compared to RSU-1069, the first reported member of this class, have been identified.