CAY10744 is a topoisomerase II-α poison.1 It inhibits topoisomerase II-α by 78.9% when used at a concentration of 20 μM. CAY10744 is selective for topoisomerase II-α over topoisomerase I providing 100 and 0% inhibition, respectively, at 100 μM. It inhibits proliferation of HCT15 colon, T47D breast, DU145 prostate, and HeLa cervical cancer cells (IC50s = 0.014, 0.00267, 0.072, and 2.46 μM, respectively). CAY10744 induces apoptosis in T47D cells when used at concentrations of 10 and 30 μM. CAY10744 (12 mg/kg per day) reduces tumor growth in an MDA-MB-231 orthotopic mouse model of breast cancer.