 Sorafenib is an oral multikinase inhibitor targeting several receptor tyrosine kinases, including the VEGF receptor VEGFR, implicated in pathologic angiogenesis, tumor growth, and cancer progression. Sorafenib is approved for the treatment of unresectable hepatocellular carcinoma HCC. TRC105 is an antibody to endoglin, an important angiogenic target on proliferating endothelial cells that is distinct from VEGFR. TRC105 inhibits angiogenesis, tumor growth and metastases and complements the activity of bevacizumab and multi-kinase inhibitors that target the VEGFR in preclinical models. Together, the use of TRC105 with sorafenib may result in more effective angiogenesis inhibition and improved clinical efficacy over that seen with sorafenib alone. 