A DNA alkylating agent; active metabolite of dacarbazine (DTIC); active degradation product of temozolomide; cytotoxic to L-cells and decreases thymidine and uridine uptake by 55 and 65%, respectively, at 1 mM; cytotoxic to TLX5 murine lymphoma cells; induces formation of mammary adenofibromas in rats when administered at a cumulative dose of 890 mg per animal over 14 weeks