OXi-4503 is the diphosphate prodrug of the stilbenoid combretastatin A1, originally isolated from the plant Combretum caffrum, with vascular-disrupting and antineoplastic activities. Upon administration, combretastatin A1 diphosphate (CA1P) is dephosphorylated to the active metabolite combretastatin A1 (CA1), which promotes rapid microtubule depolymerization; endothelial cell mitotic arrest and apoptosis, destruction of the tumor vasculature, disruption of tumor blood flow and tumor cell necrosis may ensue.
