Inclusion Criteria:

          1. Has the pathologically-confirmed diagnosis of locally recurrent or metastatic,
             hormone-receptor positive, HER2 negative Breast Cancer.

          2. Age: 18 - 75 years old

          3. No prior systemic anti-cancer therapy for advanced HR+ disease.

          4. Eastern Cooperative Oncology Group [ECOG] 0-1

        Exclusion Criteria:

          1. Patients who received prior treatment with any CDK4/6 inhibitor.

          2. Clinically significant cardiovascular and cerebrovascular diseases, including but not
             limited to severe acute myocardial infarction within 6 months before enrollment,
             unstable or severe angina, Congestive heart failure (New York heart association (NYHA)
             class > 2), or ventricular arrhythmia which need medical intervention.