An inhibitor of EGFRs (IC50s = 3.2, 5.3, 23.5, 4.2, and 2.2 nM for wild-type EGFR, HER2, HER4, EGFRT790M, and EGFRL858R/T790M, respectively); has greater than 100- to 1,000-fold selectivity for EGFR kinases in vitro over 30 other kinases; inhibits growth of wild-type and mutant EGFR kinase-dependent lung, breast, and gastric cancer cell lines (GI50s = 0.6-5.7 nM); inhibits EGFR phosphorylation and induces apoptosis in vitro; reduces tumor size in an HCC827 non-small cell lung cancer mouse xenograft model,