Antitumor activity of idarubicin, a derivative of daunorubicin, against drug sensitive and resistant P388 leukemia.

Idarubicin (IDA) possessed high antitumor activity against mouse P388 leukemia. When P388 leukemia bearing mice were administered an optimal dose of IDA intravenously, 200-250% of T/C and some cured mice were obtained. IDA showed a partial but significant effect against daunorubicin (DNR)-resistant P388 leukemia, whereas DNR, its parent drug, did not. Although IDA failed to show activity against doxorubicin (DX)- and aclarubicin (ACR)-resistant P388 leukemia in this study, IDA might have chemotherapeutic effects in patients in relapse and refractory to other anthracyclines. This assumption is supported by the results on the growth inhibition study in vitro. Among the metabolites, only idarubicinol showed cytotoxicity against P388 leukemia and idarubicinol showed 38% of the activity of IDA, indicating that the active components in animals could be IDA and idarubicinol. The combination of IDA and Ara-C induced some additive effect in P388 leukemia bearing mice as compared to the results with single drug usage.