The hydrochloride salt of a modified glutathione analogue with potential antineoplastic activity. Canfosfamide is selectively activated by glutathione S-transferase P1-1 into an alkylating metabolite that forms covalent linkages with nucleophilic centers in tumor cell DNA, which may induce a cellular stress response and cytotoxicity, and decrease tumor proliferation. S-transferase P1-1 is an enzyme that is overexpressed in many human malignancies.