GB268 Monotherapy or Combination Therapy for Locally Advanced/Metastatic Breast Cancer (Phase Ib/Ⅱ)

Inclusion criteria

• . Age ≥ 18 years, male or female.
• . Histologically confirmed locally advanced unresectable or metastatic breast cancer (Triple-Negative Breast Cancer \[TNBC\] or Hormone Receptor-Positive/Human Epidermal Growth Factor Receptor 2-Negative \[HR+/HER2-\]).
• . At least one measurable lesion per Response Evaluation Criteria in Solid Tumors version 1.1 \[RECIST v1.1\].
• . No prior treatment with any immune checkpoint inhibitor (e.g., anti-Programmed Death-1 \[PD-1\], anti-Programmed Death-Ligand 1 \[PD-L1\], anti-Cytotoxic T-Lymphocyte-Associated Protein 4 \[CTLA-4\]) or Programmed Death-1/Vascular Endothelial Growth Factor \[PD-1/VEGF\] bispecific antibody, except for adjuvant therapy if relapse occurred ≥12 months after discontinuation.
• . Assessed by the investigator as suitable for the assigned combination therapy.
• . Eastern Cooperative Oncology Group \[ECOG\] performance status 0 or 1.
• . Life expectancy ≥ 3 months.
• . Adequate organ function (within 14 days before first dose, without transfusion or Granulocyte Colony-Stimulating Factor \[G-CSF\] support): Hemoglobin ≥ 9 g/dL, Absolute Neutrophil Count \[ANC\] ≥ 1.5×10\^9/L, Platelets ≥ 100×10\^9/L; Aspartate Aminotransferase \[AST\] and Alanine Aminotransferase \[ALT\] ≤ 3×Upper Limit of Normal \[ULN\] (≤5×ULN if liver metastases); Alkaline Phosphatase \[ALP\] ≤ 2.5×ULN (≤5×ULN if bone or liver metastases); Total Bilirubin ≤ 1.5×ULN (≤3×ULN for Gilbert's Syndrome); Serum Creatinine ≤ 1.5×ULN or Creatinine Clearance ≥ 50 mL/min (Cockcroft-Gault formula); Urine protein dipstick ≤ 1+ (if ≥2+, 24-hour urine protein quantification \< 1 g); Coagulation function: International Normalized Ratio \[INR\] or activated Partial Thromboplastin Time \[aPTT\] ≤ 1.5×ULN (for patients not on anticoagulation therapy).