Dosimertinib-d 5 (mesylate) is a potent and orally active EGFR inhibitor. Dosimertinib-d 5 (mesylate) decreases the expression of p-EGFR and p-ERK protein levels. Dosimertinib-d 5 (mesylate) shows antiproliferative and anti-tumor activity. Dosimertinib-d 5 (mesylate) has the potential for the research of non-small-cell lung cancer (NSCLC).