Long-term usage of ribociclib with concomitant drugs, potential drug-drug interaction may develop which can limit the therapeutic value of CDK4/6 inhibitor.<h4>Case</h4>A 62-year-old with history of non-insulin dependent diabetic, dyslipidemia, and essential hypertension was diagnosed with HR-positive, HER-2 negative metastatic breast cancer and treated with fulvestrant plus ribociclib. The gene discussed is ERBB2; the disease is metabolic syndrome.