In breast cancer, targeted therapies such as trastuzumab deruxtecan, immune checkpoint inhibitors, everolimus, CDK4/6i, and PARP inhibitors are frequently implicated, while chemotherapeutics (e.g., bleomycin, platinum agents, methotrexate, taxanes, gemcitabine) are common culprits in broader oncology populations (32, 33). The gene discussed is CDK4; the disease is breast cancer.