KIT and neoplasm: Regorafenib, an oral mutikinase inhibitor, can inhibit activity of several protein kinases, including those involved in tumor proliferation (KIT, PDGFR and RET), tumor angiogenesis (VEGFR1-3, TIE2), and tumor microenvironment (PDGFR-B, FGFR) [5, 8, 9].