Inhibitor of O6-methylguanine-DNA methyltransferase (MGMT); (IC50 = 0.009 μM in cell-free extracts from HeLa S3 cells); attenuates MGMT activity in vitro and in vivo. Enhances the antitumor activity of temozolomide (Cat. No. 2706) in both human melanoma and MCF-7 xenografts.