Cytostatic activity of steroid linked nitrosoureas.

First investigations on the therapeutic activity of a new group of steroid-linked N-(2-chloroethyl)-N-nitrosocarbamoyl-L-alanine esters (CNC-L-alanine esters) in a nitrosourea-sensitive rat leukemia (L 5222) characterized by a relatively high content of glucocorticoid binding sites are presented. Despite a considerable range of optimal and toxic doses of the different analogs, the respective therapeutic ratios do not appear to be significantly influenced by the nature of the carrier molecules to which CNC-L-alanine is attached. However several steroid-linked representatives are distinctly more active than CNC-L-alanine. The androsterone-3-ester and the dihydrotestosterone-17-ester, in particular effected high percentages of cures in contrast to CNC-L-alanine.