Rubidazone vs adriamycin: An evaluation of their differential toxicity in the spleen colony assay system

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Abstract
Rubidazone, the new semisynthetic benzol hydrazone hydrochloride derivative of daunorubicin, proved on an MW basis to be less toxic than adriamycin and similar to daunorubicin in cardiac toxicity studies in the hamster as well as in other in vivo and in vitro test systems. It proved effective against several animal tumors and human acute leukemias. The inhibitory effect of rubidazone was compared to that of adriamycin in P388 leukemia and normal bone marrow colony-forming units (CFU) using the spleen colony assay system in male DBA2 mice. The efficacy ratios (i.e., the ratio of the slopes of the normal bone marrow CFU to leukemic CFU dose-survival curves) in the spleen colony assay system for rubidazone and adriamycin were 7.8 and 7.5, respectively. This near identity of efficacy ratios for rubidazone and adriamycin correlated with the results of median survival time studies in leukemic mice. Their dose-median survival time curves were almost parallel, having nearly identical slopes. Rubidazone''s equal therapeutic index as compared to adriamycin in the spleen colony assay system together with its known decreased toxicity to cardiac muscle cells makes it an extremely promising new anthracycline derivative to study in comparison to adriamycin in human malignancies.