Immune checkpoint inhibitors Pembrolizumab, Nivolumab, Atezolizumab, Cemiplimab-rwlc, Ipilimumab for certain PD-L1 positive tumors; hormonal therapy such as Tamoxifen, Fulvestrant, Anastrozole, Letrozole, Exemestane targeting estrogen receptor (ER) in breast cancer; anti-HER2 drugs for HER2 overexpressing breast, colon, rectal, gastric and esophageal tumors are a few examples of targeted therapies in routine clinical use. The gene discussed is ERBB2; the disease is breast cancer.