Mammary tumour inhibition and subacute toxicity in rats of prednimustine and of its molecular components chlorambucil and prednisolone.

Prednimustine, a chlorambucil ester of pregnisolone, retarded growth of DMBA-induced mammary tumours in rats and reduced the number of tumours. A combination of chlorambucil and prednisolone (C + P) in the same proportion as in prednimustine, had similar effects, 8 and 26 mg per kg of the C + P combination being equipotnet to 16 and 64 mg per kg of prednimustine, respectively. The mortality figures suggested that prednimustine was considerably less toxic than equipotent doses of C + P. This toxicity difference was confirmed in a parallel investigation of the subacute toxicity in rats of prednimustine and C + P. This study showed that the mortality, reduction of lymphocytes and platelets, and bone marrow depression was much lower after pregnimustine than after equimolar amounts of the C + P combination. The results suggest that the low toxicity of prednimustine makes this drug a better cytostatic agent than the C + P combination treatment.