Prednimustine is chlorambucil ester of prednisolone. Prednimustine is a cytostatic agent. Prednimustine is active against a wide variety of experimental tumors both in vivo and in vitro. In many of these tumor systems, prednimustine exhibits distinct advantages over a mixture of its constituents, chlorambucil and prednisolone. In vitro, a higher cell kill is obtained, and in vivo, at doses that are equally effective, prednimustine is less toxic. It has been used in the treatment of various malignancies, including chronic lymphatic leukaemia and non-Hodgkin's lymphomas. It has also been tested for use in the treatment of breast cancer