Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors are a novel class of targeted anticancer agents with cytostatic activity that have recently been introduced in the clinical practice for the treatment of advanced/metastatic hormone receptor (HR)+ breast cancer, as they have demonstrated pronounced therapeutic effects in the context of manageable (primarily hematological) side effects [1]. The gene discussed is CDK4; the disease is breast carcinoma.