A Phase 1 Study of HRS8807 Monotherapy and in Combination With SHR6390 in Subjects With ER-Positive, HER2-Negative Metastatic or Locally Advanced Breast Cancer

Inclusion Criteria:

1. Histological diagnosis of metastatic or locally advanced breast cancer; Histologically proven diagnosis of ER-positive, HER2-negative;
2. At least 1 line of endocrine therapy in the metastatic or advanced setting that had progressed or intolerance; ≤ 2 lines of chemotherapy for metastatic or advanced disease;
3. Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 or 1;
4. Expected survival of more than 3 months.

Exclusion Criteria:

1. All patients in monotherapy and or in combination wih phase who are known allergic to HRS8807 or SHR6390 ingredient;
2. Presence of symptomatic metastatic visceral disease ;
3. Patients with known active brain metastases;
4. Clinically serious cardiovascular disease;
5. Abnormal electrocardiographic (ECG) with clinical significancy by investigator judgement;
6. Abnormal thyroid function laboratory results;
7. Active infection or unexplained fever \>38.5℃ during screening period or on the day of the first dose.