A Phase II Study of HLX22 in Combination With Trastuzumab Deruxtecan in HER2-low, Hormone Receptor Positive Locally Advanced or Metastatic Breast Cancer Patients

Inclusion Criteria: 1. Male/female who are at least 18 years of age on the day of signing the informed consent. 2. With histologically confirmed diagnosis of HER2-low, Hormone Receptor Positive Locally Advanced or Metastatic Breast Cancer. 3. HER2-low defined as IHC 2+/ISH- or IHC 1+ (ISH- or untested) as assessed by a central laboratory on metastatic tumor and was never previously HER2-positive，and was documented HR+ disease in the metastatic setting 4. Had measurable disease according to the RECIST v1.1, the target lesion must not be a bone metastatic lesion only. 5. ECOG PS: 0-1. 6. Expected survival ≥ 6 months. 7. Had adequate organ function Exclusion Criteria: 1. Patients with other malignant tumors within 3 years before the randomization 2. Previous treatment with any HER2-target therapy 3. Uncontrolled or significant cardiovascular disease or infection 4. Lung-specific intercurrent clinically significant illnesses 5. Prior documented interstitial lung disease (ILD)/ pneumonitis that required steroids, current ILD/ pneumonitis, or suspected ILD/ pneumonitis 6. Patients with spinal cord compression or clinically active central nervous system metastases