Used in targeted cancer therapy, particularly for non-small cell lung cancer (NSCLC) with EGFR mutations. It acts as a third-generation EGFR tyrosine kinase inhibitor, selectively targeting both T790M resistance mutations and activating EGFR mutations while sparing wild-type EGFR. This selectivity reduces side effects and improves efficacy in patients who have developed resistance to earlier EGFR inhibitors. The mesylate salt form enhances solubility and bioavailability, supporting oral dosing in clinical settings.