Retlirafusp Alfa Combined With Apatinib and Nab-Paclitaxel as Second-line Treatment for Gastric or Gastroesophageal Junction Cancer

Inclusion Criteria: 1. Able to provide written informed consent prior to any study-specific procedures 2. Age ≥ 18 years 3. ECOG performance status 0 or 1 4. Histologically or cytologically confirmed gastric adenocarcinoma or gastroesophageal junction adenocarcinoma, locally advanced unresectable, locally recurrent, or metastatic 5. Human epidermal growth factor receptor 2 (HER2) negative 6. Failed first-line immunotherapy-containing systemic treatment 7. At least one measurable lesion per RECIST Version 1.1 8. Adequate organ function: 1)Hemoglobin ≥ 90 g/L 2)Absolute neutrophil count ≥ 1.5 × 10⁹/L 3)Platelet count ≥ 80 × 10⁹/L 4)Total bilirubin \< 1.5 × upper limit of normal (ULN) 5)ALT/AST \< 2.5 × ULN; \< 5 × ULN in patients with liver metastasis 6)Serum creatinine ≤ 1.5 × ULN or creatinine clearance \> 60 mL/min 7)Urine protein \< 2+ or 24-hour urine protein \< 1 g 8)Left ventricular ejection fraction (LVEF) ≥ 50% 9)Coagulation function: INR ≤ 1.5 × ULN, APTT ≤ 1.5 × ULN 8.Fertile male and female subjects must agree to use highly effective contraception during the study and for 6 months after the last dose of study treatment; female subjects must have a negative pregnancy test within 7 days before enrollment Exclusion Criteria: 1. Known hypersensitivity to any component of the study drugs 2. Prior treatment with any VEGFR inhibitor (including apatinib, sorafenib, sunitinib) 3. Prior treatment with retlirafusp alf 4. Received any investigational drug within 4 weeks before first dose 5. Received systemic corticosteroid (\> 10 mg prednisone equivalent daily) or other immunosuppressive agents within 2 weeks before first dose, except for allowed topical/inhaled use or physiological replacement 6. Active autoimmune disease or history of autoimmune disease (except controlled hypothyroidism, type 1 diabetes with stable insulin, vitiligo, resolved childhood asthma) 7. Known immunodeficiency (including HIV infection), organ transplantation, or allogeneic hematopoietic stem cell transplantation 8. Uncontrolled cardiac disease: NYHA Class ≥ II heart failure, unstable angina, myocardial infarction within 1 year, clinically significant arrhythmia requiring intervention 9. Severe infection (CTCAE Grade \> 2) within 4 weeks before first dose; active pulmonary infection, interstitial lung disease, non-infectious pneumonitis, pulmonary fibrosis; active tuberculosis 10. Active hepatitis B (HBV DNA ≥ 2000 IU/mL) or active hepatitis C (HCV RNA positive) 11. History of other malignancy within 5 years before enrollment, except adequately treated basal cell carcinoma, squamous cell carcinoma of skin, or carcinoma in situ of cervix 12. Pregnant or lactating women 13. Unwilling or unable to comply with study procedures 14. Any other condition deemed inappropriate by the investigator