RET and neoplasm: Regorafenib and sorafenib are multikinase inhibitors that block the activity of multiple protein kinases, mainly tumor angiogenesis (VEGFR1-3) and also including RET, FLT3, KIT, PDGFR, FGFR1-2, TIE2, RAF-1, BRAF, BRAFV600E and Abl pathways.