The synthesis of N-cyanobenzo[b]carbazoloquinone 4, an isosteric-isoelectronic analogue of prekinamycin, is described. Cytotoxicity studies with K562 human leukemia cells reveal that the cyanamide analogue has a bioactivity profile similar to that of prekinamycin. These results indicate that the diazo functionality may not be an absolute requirement for bioactivity.