Angiogenesis plays a central role in the progression of solid cancer. TRC105 is an antibody to CD105, an important non-VEGF angiogenic target on proliferating endothelial cells. TRC105 inhibits angiogenesis, tumor growth and metastases in preclinical models. TRC105 has been well tolerated in patients with glioblastoma (GBM) as a single agent. The combination of TRC105 in combination with bevacizumab has demonstrated activity in bevacizumab refractory cancer patients. We hypothesize that TRC105 when administered with bevacizumab will have activity in GBM patients who progress on bevacizumab. By targeting a non-VEGF pathway, TRC105 has the potential to complement VEGF inhibition by bevacizumab, which could represent a major advance in GBM therapy.