ABT-751 is a tubulin polymerization inhibitor that binds to the colchicine binding site on β-tubulin (Ki = 3.3 μM). It inhibits tubulin polymerization in a concentration-dependent manner and inhibits growth of 26 human tumor cell lines (IC50s = 0.06-0.08 μg/ml). ABT-751 (100 mg/kg, p.o.) induces tumor regression in NB-1382 neuroblastoma, IRS56 rhabdomyosarcoma, and KT-6 Wilms mouse xenograft models. It also induces tumor endothelial cell retraction and reduces tumor perfusion, but not muscle perfusion, in a 9L rat glioma subcutaneous tumor model.