Agents having cytotoxic activity, as well as compositions, uses, and methods relating thereto, are described herein. Certain steroid acid-peptide conjugates or moieties have the ability to induce killing or inhibition of proliferation of mammalian cells, in vitro or in vivo upon administration to a subject. The steroid acid-peptide conjugates include bile acids and bile acid analogs and peptides that may include a nuclear localisation signal or a portion thereof. Also described herein is a method for treating cancer, an autoimmune disease, or any other disease or disorder ameliorated by treatment with an antiproliferative drug in a subject in a subject with the cytotoxic agents described herein.