BRAF and metastatic colorectal cancer: Regorafenib is a multi-kinase inhibitor used in metastatic colorectal cancer that blocks a series of protein kinases involved in angiogenesis [(VEGF receptors 1-3 and tyrosine receptor kinase-2 (TIE2)], oncogenesis (KIT, RET, RAF1, BRAF and BRAF V600E) and the tumor microenvironment [platelet-derived growth factor receptor (PDGFR) and fibroblast growth factor receptor (FGFR)] [33].