KDR and hepatocellular carcinoma: To date, the most successful clinical inhibitor of RAF activity is sorafenib (Nexavar, BAY 43-9006) [8]–[10], an orally available multi-targeted kinase inhibitor, that blocks the activation of C-RAF, B-RAF (both the wild-type and the activated V600E mutant), c-KIT, FLT-3, RET, vascular endothelial growth factor receptor 2 (VEGFR-2), VEGFR-3, and platelet-derived growth factor receptor β (PDGFR-β) [8]–[10], currently approved for the treatment of metastatic renal cell carcinoma (RCC) and for advanced hepatocellular carcinoma (HCC), and under investigation in other malignancies.