Furthermore, epidermal growth factor receptor (EGFR) inhibitor is another major class of small molecule tyrosine kinase inhibitor, given that approximately 15% of lung cancer cases in the U.S. are EGFR-positive, belonging to the NSCLC adenocarcinoma subtype (Roskoski 2023), Particularly, EGFRs have four members: human epidermal growth factor receptor (HER1/EGFR), HER2, HER3, and HER4. The gene discussed is ERBB2; the disease is lung cancer.