This clinical trial is focused on studying a type of stomach cancer known as metastatic gastric cancer. The study is exploring a new treatment approach that combines several medications. The main treatment being tested is a gut microbiome intervention with a product called EXL01, which is a live biotherapeutic product. This is being used alongside other medications, including nivolumab, a type of immunotherapy, and a chemotherapy regimen known as FOLFOX. FOLFOX includes the drugs oxaliplatin, fluorouracil sodium, and calcium folinate. The purpose of the study is to assess how well this combination works as a first-line treatment for patients with a specific type of advanced gastric cancer that shows a high level of a protein called PD-L1.

Participants in the study will receive the treatment over a period of up to 24 months. The study will monitor the response of the cancer to the treatment at various points, with a key focus on the response rate at four months. The study will also look at the safety of the treatment and how it affects the gut microbiota, which is the community of microorganisms living in the digestive tract. The trial will include regular check-ups and assessments to track the progress and any side effects experienced by the participants.

This study is part of a larger effort to find more effective treatments for metastatic gastric cancer, particularly for patients whose cancer cells express a high level of PD-L1. By combining different types of therapies, the study aims to improve outcomes for patients with this challenging condition. The trial is being conducted in a structured and monitored environment to ensure the safety and well-being of all participants.