A Study on the Safety and Efficacy of the Combination of Candenizumab, Lenvatinib, and SOX Regimen in the Treatment of HER2 Negative Advanced Gastric or Gastroesophageal Junction Adenocarcinoma Patients

"Phase 1: Conduct a ramp up test on the dosage of lenvatinib according to the traditional 3+3 design; Phase 2: 6 cycles of treatment with candenizumab+lenvatinib+SOX regimen (Q3W); For patients who have not progressed, they will enter the third stage of maintenance treatment.~Phase 3: Maintenance therapy with candenizumab, lenvatinib, and tigio (Q3W)."