RET and neoplasm: Conversely, regorafenib, a novel oral MKI, blocks several protein kinases involved in the tumor angiogenesis (VEGFR-1, -2, and -3), tumor growth (KIT, RET, RAF-1, and BRAF), and metastasis (PDGFR-β, FGFR1) of cancer cells [5,6,7].