Osimertinib was the first approved third-generation EGFR TKI for the first-line treatment of patients with metastatic NSCLC whose tumors have EGFR 19Del or L858R mutations and for the treatment of patients with metastatic EGFR T790M mutation-positive NSCLC whose disease has progressed on or after EGFR TKI therapy by the US Food and Drug Administration (FDA) [10–13]. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.