NCIt definition : A synthetic water-soluble analogue of combretastatin A4, derived from the South African
willow bush (Combretum caffrum), with potential vascular-disrupting and antineoplastic
activities. Ombrabulin binds to the colchicine binding site of endothelial cell tubulin,
inhibiting tubulin polymerization and inducing mitotic arrest and apoptosis in endothelial
cells. As apoptotic endothelial cells detach from their substrata, tumor blood vessels
collapse; the acute disruption of tumor blood flow may result in tumor necrosis.;