Oritinib mesylate (SH-1028) is a highly selective, orally active, pyrimidine-based irreversible inhibitor of epidermal growth factor receptor (EGFR) with a low IC50 of 18 nM. It is effective against both EGFR-sensitive and resistant (T790M) mutations and suppresses the proliferation of tumor cells harboring EGFR mutations, irrespective of their sensitivity or resistance.