Investigators plan to conduct a single-arm clinical study of adebelimab, a novel PD-L1 inhibitor, in the neoadjuvant treatment of early or locally advanced high-risk ER+/HER2- breast cancer, to explore whether the addition of immune checkpoint inhibitors to traditional neoadjuvant chemotherapy can improve the pathologic complete response rate (pCR) of patients, evaluate its therapeutic safety, and further analyze the biomarkers of the efficacy of neoadjuvant immunotherapy for ER+/HER2- breast cancer, so as to support the clinical application of the drug.

Inclusion Criteria:

• pathologically diagnosed as unilateral primary invasive breast cancer with a) cT1c-T2N1-3 or cT3-4N0-3, b) Tumor Grade 3 or Grade 2 with PR- or Ki67 > 20%;
• IHC ER expression ≥1%; IHC HER2 0 or 1+; IHC HER2 2+ and no amplification in FISH test;
• At least one measurable lesion according to RECIST 1.1;
• Available core needle biopsy samples for PD-L1 status testing;
• ECOG 0 or 1 within 10 days prior to initiation of treatment;
• Not currently pregnant or breastfeeding, agree to strict contraception during treatment and at least 6 months after last dose;
• Intact hematologic, liver, renal and heart functions;
• Signed written informed consent.

Exclusion Criteria:

• Bilateral invasive breast cancer or Stage IV breast cancer;
• Severe heart disease;
• Diagnosed as immune deficiency or receiving systemic steroid therapy or any form of immuno-suppressive therapy within 7 days prior to the first dose of treatment;
• Had active autoimmune diseases requiring systemic therapy within the past 2 years;
• Severe systemic infections or other serious medical conditions;
• Other malignant tumors in the past 5 years, except for cured carcinoma in situ of the cervix and skin cancer without melanoma;
• History of HIV infection;
• Active HBV or HCV infection;
• Known allergies or intolerance to the therapeutic drug or its excipients;
• History of application of any immunotherapy targeting PD-1/PD-L1/T cell receptors;
• Judged by the investigator to be unsuitable to participate in this study.