FLT1 and neoplasm: Regorafenib is an oral multikinase inhibitor that targets several protein kinases, including those implied in the regulation of proliferation (KIT, RET, RAF-1, BRAF, and BRAF V600E), angiogenesis [vascular endothelial growth factor receptor-1 (VEGFR1), VEGFR2, VEGFR3, and tie-like receptor tyrosine kinase 3 (TIE3)], and tumor microenvironment [PDGFR and fibroblast growth factor receptor (FGFR)].5