Osimertinib, which targets EGFR exon 19 deletions, exon 21 L858R mutations and T790M mutations, was approved as a third-generation TKI indicated for the first-line treatment of patients with metastatic NSCLC whose tumors were resistant to the first- and second- generation EGFR-TKIs (Wu and Shih, 2018). The gene discussed is EGFR; the disease is non-small cell lung carcinoma.