Preclinical evaluation of vascular-disrupting agents in Ewing’s sarcoma family of tumours

The effects of the tubulin-binding vascular-disrupting agents (VDAs), combretastatin A4 phosphate (CA4P), OXi4503/CA1P and OXi8007, in subcutaneous mouse models of the Ewing’s sarcoma family of tumours (ESFTs) have been investigated alone and in combination with doxorubicin. Delay in subcutaneous tumour growth was observed following treatment of mice with multiple doses of OXi4503/CA1P but not with CA4P or OXi8007. A single dose of OXi4503/CA1P caused complete shutdown of vasculature by 24 h and extensive haemorrhagic necrosis by 48 h. However, a viable rim of proliferating cells remained, which repopulated the tumour within 10 days following the withdrawal of treatment. Combined treatment with doxorubicin 1 h prior to administration of OXi4503/CA1P enhanced the effects of OXi4503/CA1P causing a synergistic delay in tumour growth (p < 0.001). This study demonstrates that OXi4503/CA1P is a potent VDA in ESFT and in combination with conventional cytotoxic agents represents a promising treatment strategy for this tumour group.