Sorafenib is a multikinase inhibitor that reduces tumor cell proliferation in vitro. Sorafenib inhibits tumor growth of human tumor xenografts in immunocompromised mice by inhibiting tumor angiogenesis. Sorafenib inhibits the activity of intracellular kinases present in the tumor cell (CRAF, BRAF, V600E BRAF, c-KIT, and FLT-3) and the tumor vasculature (CRAF, VEGFR-2, VEGFR-3, and PDGFR-ß). RAF kinases are serine/threonine kinases, while c-KIT, FLT-3, VEGFR-2, VEGFR-3, and PDGFR-ß are receptor tyrosine kinases.