The study is being conducted to evaluate the safety, PK and efficacy of HRS-6209 in Combination with Fulvestrant, Letrozole, HRS-8080, or HRS-1358 for advanced unresectable or metastatic breast cancer
Females aged 18-75 years (inclusive);
ECOG performance status (PS) score of 0-1;
Patients with histopathologically confirmed metastatic or unresectable locally advanced breast cancer, histopathologically confirmed ER-positive or PR-positive;
Having had bilateral oophorectomy, or aged ≥ 60 years old; or
With symptomatic visceral metastases deemed unfit for endocrine therapy by the investigator;
With active brain metastases, carcinomatous meningitis, spinal cord compression, or a history of primary tumors of the central nervous system;
History of clinically significant cardiovascular disease;
Abnormal ECG findings, which are judged by the investigator to be clinically significantand and need to intervene ;