An inhibitor of microtubule assembly (IC50 = 2.5 μM); inhibits binding of colchicine to tubulin (Ki = 0.7 μM); inhibits proliferation of MDA-MB-231 and multidrug resistant (MDR) MCF-7 ADRr breast cancer cells (IC50s = 0.6 and 400 nM, respectively) as well MDR CEM-VBL leukemia cells (IC50 = 50 nM)