The third generation Epidermal Growth Factor Receptor (EGFR) Tyrosine Kinase Inhibitor (TKI) osimertinib has been initially approved for T790M positive Non-Small Cell Lung Cancer (NSCLC) and more recently for first-line treatment of EGFR-mutant T790M negative NSCLC patients. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.