Tagrisso 80 mg Tablets TAGRISSO contains osimertinib, an irreversible, third-generation Epidermal Growth Factor Receptor (EGFR) tyrosine kinase inhibitor (TKI) that binds covalently to specific mutant forms of EGFR (including T790M, L858R, and exon 19 deletions) at lower concentrations than wild-type EGFR. EGFR mutations drive continuous receptor autophosphorylation and downstream signal transduction (PI3K/AKT, MAPK/ERK pathways), leading to uncontrolled cell proliferation, survival, and oncogenesis. Osimertinib selectively inhibits intracellular phosphorylation of EGFR mutants, suppressing signaling pathways and inducing apoptosis in EGFR-mutant non-small cell lung cancer (NSCLC) cells. TAGRISSO is indicated as first-line treatment for patients with metastatic NSCLC whose tumors have EGFR exon 19 deletions or exon 21 L858R mutations, as adjuvant therapy after tumor resection, and for patients with EGFR T790M mutation-positive NSCLC.