Study of Paclitaxel Polymeric Micelles Combined With HP and Adebelimab Versus Taxane Combined With HP as First-Line Treatment for Advanced HER2-Positive Breast Cancer

1. Age: ≥18 years, no gender restriction; 2. Pathologically confirmed breast cancer: a) Advanced or metastatic breast cancer; b) Locally assessed as HER2-positive (IHC 3+ or IHC 2+ with ISH+); 3. For advanced or metastatic breast cancer, patients should have not previously received chemotherapy or HER2-targeted therapy, or have received only first-line endocrine therapy. Subjects receiving chemotherapy or HER2-targeted therapy as neoadjuvant or adjuvant treatment are eligible if the interval from treatment completion to metastasis diagnosis exceeds 6 months; 4. PD-L1 testing is positive (combined positive score CPS ≥ 1); 5. ECOG score is 0-1; 6. Estimated survival is at least 3 months; 7. There is at least one measurable lesion assessed by computed tomography (CT) and/or magnetic resonance imaging (MRI) (according to RECIST 1.1); 8. Basic normal function of major organs such as the heart, lungs, liver, and kidneys; 9. Sufficient organ and bone marrow function, meeting the following criteria: (1) Complete blood count must meet: a) Hemoglobin (HB) ≥ 90 g/L; b) Absolute neutrophil count (ANC) ≥ 1.5×10⁹/L; c) Platelet count (PLT) ≥ 75×10⁹/L; (2) Biochemical tests must meet: a) Serum total bilirubin (TBIL) ≤ 1.5× upper limit of normal (ULN); b) ALT and AST ≤ 2.5× ULN; if liver metastases are present, ALT and AST ≤ 5× ULN; c) Cr ≤ 1.5× ULN or creatinine clearance (CCr) ≥ 60 mL/min (Cockcroft-Gault formula); 10. Patients voluntarily participate in the study, sign an informed consent form, and demonstrate good compliance. Exclusion Criteria: Subjects were ineligible for this trial if they met any of the following criteria: 1. Known allergy or intolerance to any study agent or excipient; 2. Primary central nervous system malignancy or meningeal metastasis; symptomatic patients with central nervous system metastases; patients with asymptomatic brain metastases or clinically stable conditions requiring no steroid therapy for at least 4 weeks were eligible; 3. History of chemotherapy, targeted therapy, or major surgery within 4 weeks prior to first dose; history of endocrine therapy or local radiotherapy within 2 weeks prior to first dose; 4. Active or previously documented interstitial lung disease (ILD), pneumonia, or suspected ILD that could not be excluded by imaging during screening; pneumonia that could not be excluded by imaging during screening; 5. History of other malignancies within 5 years that could be locally treated and cured (excluding basal cell carcinoma of the skin, superficial or non-invasive bladder cancer, cervical carcinoma in situ, breast ductal carcinoma in situ, papillary thyroid carcinoma, etc.); 6. History of live vaccine vaccination within 28 days prior to treatment; 7. Active autoimmune diseases (including but not limited to myasthenia gravis, myositis, asthma, autoimmune hepatitis, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, antiphospholipid antibody syndrome, Wegener's granulomatosis, Sjögren's syndrome, Guillain-Barré syndrome, multiple sclerosis, vitiligo, psoriasis, etc.); stable-dose hormone replacement therapy for hypothyroidism was excluded; 8. Patients with significant coagulation disorders or other clear evidence of bleeding risk. 9. Patients with the following cardiac conditions within 6 months prior to treatment initiation: acute coronary syndrome, coronary artery bypass grafting, congestive heart failure, aortic dissection, stroke, or other grade 3 or higher cardiovascular events; cardiac dysfunction classified ≥ Class II on the New York Heart Association (NYHA) scale or left ventricular ejection fraction (LVEF) \<50%; myocardial infarction, severe/unstable angina, cerebrovascular accident/stroke, transient ischemic attack, subarachnoid hemorrhage, or severe cardiac rhythm/conductance abnormalities requiring clinical intervention (e.g., ventricular arrhythmias, second-to-third-degree atrioventricular block, congenital long QT syndrome); 10. Patients with active hepatitis B or C virus infection, HIV infection, or active pulmonary tuberculosis; 11. Patients with active infections requiring antimicrobial therapy (e.g., antibiotics, antiviral agents, or antifungal drugs); 12. Patients with a known history of allogeneic organ transplantation or hematopoietic stem cell transplantation; 13. Patients with a history of substance abuse (e.g., psychiatric medications) that cannot be discontinued or those with mental disorders; 14. Pregnant or breastfeeding women; or patients of reproductive age who are unwilling or unable to use effective contraceptive measures.