KIT and neoplasm: As far as tyrosine kinase inhibitors are concerned, the most studied drug in association with immune checkpoint inhibitor monoclonal antibodies is Regorafenib, a potent oral multikinase inhibitor which has a broad spectrum of activity with inhibition of tyrosine kinases involved in tumor angiogenesis mechanisms (e.g. PDGFR, FGFRs 1–2, VEGFRs 1–3, TIE2), proliferation (e.g. RET, RAF, KIT), tumor microenvironment and metastatic processes (VEGFR2–3, PDGFR).