EGFR-IN-1, an orally active and irreversible selective inhibitor targeting L858R/T790M mutant EGFR, exhibits strong antiproliferative and antitumor activity, particularly against H1975 cells and first line mutant HCC827 cells. This compound potently inhibits Gefitinib-resistant EGFR L858R/T790M mutations with a 100-fold selectivity over the wild-type EGFR.