Osimertinib is a standard therapy for the treatment of advanced non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor gene (<i>EGFR</i>) mutations, but most patients with <i>EGFR</i>-mutant NSCLC develop secondary resistance to osimertinib. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.