M108 Plus CAPOX Versus Placebo Plus CAPOX as First-line Treatment for Claudin (CLDN) 18.2-Positive, HER2-Negative, PD-L1 CPS<5, Locally Advanced Unresectable or Metastatic Gastric or Gastroesophageal Junction (GEJ) Adenocarcinoma.

Gastric/GEJ adenocarcinoma, which is one of the major leading causes of cancer-related deaths worldwide, is a global challenge to human health. However, standard chemotherapy has limited efficacy in advanced gastric cancer, and there is an urgent need to explore and develop new therapeutic targets and combination therapy modalities. The main purpose of this study is to explore the efficacy of M108 monoclonal antibody plus capecitabine and oxaliplatin (CAPOX) versus placebo plus CAPOX as first-line treatment measured by progression free survival (PFS). This study will also evaluate safety, tolerability, pharmacokinetics and the immunogenicity profile of M108 monoclonal antibody, as well as its effects on quality of life.