A Study of BPI-16350 in Combination With Fulvestrant in Patients With HR+ and HER2- Locally Advanced, Recurrent or Metastatic Breast Cancer

Inclusion Criteria: * Has the pathologically-confirmed diagnosis of locally advanced, recurrent or metastatic, HR positive, HER2 negative Breast Cancer * One previous line of chemotherapy for advanced/metastatic disease is allowed * Disease Progression following endocrine therapy * Have postmenopausal status * Have 1 of the following, as defined by the Response Evaluation Criteria in Solid Tumors (RECIST) v1.1: measurable disease or nonmeasurable bone-only disease * ECOG: 0\~1 * Adequate organ function Exclusion Criteria: * Previous treatment with cytotoxic drugs within 4 weeks before enrollment * Previous treatment with endocrine or small molecule drug tyrosine kinase inhibitor TKI within 2 weeks before enrollment * Patients who received prior treatment with any CDK4/6 inhibitor, everolimus or fulvestant * HER2 positive * Patients with major surgery within 4 weeks, severe or unstable systemic disease, unstable/symptomatic CNS metastasis, other malignant tumors, ILD, clinical significant cardiac disease, bleeding or embolic disease, active infectious disease, conditions affecting drug swallow and absorption, etc * Pregnancy or lactation * Other conditions considered not appropriate to participate in this trial by the investigators