This is an open-label, phase II study evaluating the efficacy and safety of SHR-A1811 alone or in combination with Adebrelimab in Stage II-III HR Positive/HER2 Low Breast Cancer. Subjects will receive the neoadjuvant therapy of SHR-A1811 alone or in combination with Adebrelimab for six cycles, and then undergo surgery within 4 weeks after neoadjuvant therapy. Efficacy will be assessed every 2 cycles.

Inclusion Criteria:

1. Female patients aged ≥ 18 but ≤ 75 years
2. Histologically confirmed to be HR+/HER2-Low invasive breast cancer
3. Treatment-naive patients with stage II-III
4. Eastern Cooperative Oncology Group (ECOG) score is 0 or 1
5. Good level of organ function
6. Subjects must participate voluntarily, sign the informed consent form, have good compliance, and cooperate with follow-up visits

Exclusion Criteria:

1. Previously been treated with any anti-tumor therapy (chemotherapy, radiotherapy, molecular targeted therapy, endocrine therapy, etc.)
2. Received any other anti-tumor therapy at the same time
3. Bilateral breast cancer, inflammatory breast cancer or occult breast cancer
4. Stage IV breast cancer
5. Not confirmed by histopathology
6. With a history of any malignancies in the past 5 years, excluding cured cervical carcinoma in situ and melanoma skin cancer
7. Participated in other drug clinical trials within 4 weeks before enrollment
8. Known allergic history of the drug components of this protocol
9. History of immunodeficiency
10. Clinically significant cardiovascular diseases
11. Known or suspected interstitial lung disease
12. Active hepatitis and liver cirrhosis
13. Known hereditary or acquired bleeding thrombotic tendency
14. History of neurological or psychiatric disorders