EGFR-IN-1, an orally active and irreversible selective inhibitor targeting L858RT790M mutant EGFR, exhibits strong antiproliferative and antitumor activity, particularly against H1975 cells and first line mutant HCC827 cells. This compound potently inhibits Gefitinib-resistant EGFRL858RT790M mutations with a 100-fold selectivity over the wild-type EGFR.