An Eg5 inhibitor (Ki = 0.5 nM for microtubule-stimulated ATPase activity); inhibits the growth of various cancer cell lines in vitro (GI50s = 22-82 nM); induces complete tumor regression in a COLO 205 mouse xenograft model and partial regression in MCF-7, SK-MES, H69, and OVCAR-3 mouse xenograft models; reduces tumor volume in a DLBCL mouse xenograft model from 2.5-10 mg/kg