Regorafenib is a potent oral inhibitor of a wide range of protein kinases, including kinases involved in angiogenesis (VEGFR1, -2, -3, TIE2), tumor oncogenesis (KIT, RET, RAF-1, BRAF, BRAFV600E), tumor metastasis (VEGRF3, PDGFR, FGFR), and tumor immunity (CSF1R). In particular, regorafenib inhibits mutated KIT kinase, a key oncogenic factor in the development of gastrointestinal stromal tumors, and thus blocks tumor cell proliferation. In preclinical studies, regorafenib demonstrated potent antitumor activity against a wide range of tumor models, including colorectal tumor models and gastrointestinal stromal tumors, which is due to its antiangiogenic and antiproliferative properties. In addition, regorafenib showed antimetastatic activity in vivo. The major metabolites found in humans (M-2 and M-5) demonstrated efficacy similar to that of regorafenib in in vitro and in vivo models.