An orally bioavailable, highly selective, second-generation small-molecule inhibitor of the pan-epidermal growth factor receptor (EGFR) family of tyrosine kinases (ErbB family) with potential antineoplastic activity. Dacomitinib specifically and irreversibly binds to and inhibits human EGFR subtypes, resulting in inhibition of proliferation and induction of apoptosis in EGFR-expressing tumor cells. EGFRs play major roles in tumor cell proliferation and tumor vascularization, and are often overexpressed or mutated in various tumor cell types.