Toxicity of novel anthracycline derivatives towards normal myeloid bone marrow progenitor cells (CFU-GM) is not increased by verapamil.

Drug-induced myelotoxicity is usually the dose-limiting factor of treatment of malignant tumors with cytostatic drugs. Suppression of in vitro myelopoiesis (CFU-GM) by cytostatics may be a suitable model reflecting the in vivo situation. Thus the inhibitory effects of the anthracyclines doxorubicin, theprubicin, idarubicin and cytorhodin S on CFU-GM were compared. Normal human bone marrow cells were incubated with these drugs for one hour and alternatively, for the whole culture period. For each substance and each incubation time a dose-response curve was established and the D50 determined. As certain calcium antagonists can increase the toxicity of some cytostatic drugs in various tumor models, the effect of the addition of verapamil (2 microM) was also investigated. It could be shown, that the myelotoxicity on CFU-GM of the drugs mentioned above was not increased after short-term or permanent exposure to this calcium antagonist.