Combination of QLS31905, QL2107 and Chemotherapy as First-line Therapy in CLDN18.2-positive Unresectable Locally Advanced or Metastatic Gastric or Gastroesophageal Junction (GEJ) Adenocarcinoma

Inclusion Criteria: * Subjects with unresectable locally advanced or metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma confirmed by histopathological or cytological examination; * Subjects with at least one measurable lesion designated as a target lesion, as assessed by the investigator according to RECIST v1.1. Lesions that have received radiotherapy or other local treatments may be considered measurable if they demonstrate imaging PD; * No prior systemic anti-tumor treatment for locally advanced or metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma. Exclusion Criteria: * Subjects with a known history of severe or repeated allergy, intolerance, or contraindication to QLS31905, QL2107, or other large molecule protein preparations, as well as Oxaliplatin Injection or Capecitabine Tablets and any components in their preparations; * Subjects had other second primary malignancies within 5 years prior to the first dose; * Subjects with clinically significant hemorrhage within 3 months before the first dose