In the search for effective therapies for unresectable gastric cancer, experiments performed on PDXs deriving from 8 patients demonstrated that Regorafenib, a multikinase inhibitor with activity against a range of protein kinases involved in oncogenesis (KIT, RET, and RAF), angiogenesis (VEGFR1–3 and TIE2), and maintenance of the tumour microenvironment (PDGFR and FGFR), was very active in reducing the growth of tumours in mice. This evidence concerns the gene RET and neoplasm.