This study aims to evaluate the efficacy of disitamab vedotin in combination with sintilimab and SOX as conversion therapy in patients with initially unresectable locally advanced or metastatic gastric cancer exhibiting HER2 IHC 1+/2+ expression. The trial plans to enroll patients with a single initial unresectable factor and HER2 IHC 1+/2+ status. Participants will receive disitamab vedotin combined with sintilimab and SOX for 4 to 6 treatment cycles. Those who achieve successful conversion will undergo surgical resection, while patients with unsuccessful conversion will either continue the original regimen or switch to an alternative treatment at the investigator's discretion.