An inhibitor of tubulin polymerization; covalently binds to Cys239 of the β1, β2, and β4 tubulin isotypes and inhibits polymerization of bovine brain tubulin (IC50 = 2 µM) in cell-free assays; induces cytoskeletal collapse and cell cycle arrest at the G2/M phase in MCF-7 cells at 30, 100, and 300 nM; cytotoxic against a panel of drug-sensitive and -resistant cancer cell lines (IC50s = 11-165 nM); reduces tumor volume in CCRF CEM and CEM/VBL100 mouse xenograft models