A Single-arm, Multicenter Exploratory Clinical Trial of Anlotinib Combined With TQB2450 and the SOX Regimen as First-line Treatment for Advanced Gastric Cancer With Low PD-L1 Expression

Inclusion Criteria: * 1\. Willing and able to provide written informed consent and comply with study procedures. * 2\. Histologically or cytologically confirmed HER2-negative (or HER2 status undetermined) unresectable locally advanced or metastatic gastric/gastroesophageal junction adenocarcinoma (including signet ring cell carcinoma, mucinous adenocarcinoma, and hepatoid adenocarcinoma variants). * 3\. Disease recurrence \>6 months after completion of (neo)adjuvant chemotherapy or radiotherapy. * 4\. At least one measurable or evaluable lesion according to RECIST v1.1 criteria. Measurable lesions must not have received prior local therapy (e.g., radiotherapy); however, lesions within previously irradiated fields may be designated as target lesions if documented progression is demonstrated per RECIST v1.1. * 5\. Age 18 and above. * 6\. ECOG performance status 0-1. * 7\. Life expectancy ≥3 months. * 8\. Organ Function Requirements and Laboratory Test Criteria During Screening (1) Complete Blood Count (CBC) Criteria： Hemoglobin (Hb): ≥ 90 g/L (no blood transfusion within 14 days) Absolute Neutrophil Count (ANC): ≥ 1.5 × 10⁹/L Platelet Count (PLT): ≥ 100 × 10⁹/L (no use of interleukin-11 \[IL-11\] or thrombopoietin \[TPO\] within 14 days) White Blood Cell Count (WBC): ≥ 4.0 × 10⁹/L (no granulocyte colony-stimulating factor \[G-CSF\] administration within 14 days) (2) Biochemical Panel Requirements: Total Bilirubin (TBIL): ≤ 1.5 × ULN (upper limit of normal),Alanine Aminotransfe…