A Dose Optimization/Expansion Study of SAR445877 in Adult Chinese Participants With Advanced Gastric or Gastroesophageal Junction Cancer

This is a Phase 2, open-label, dose optimization/expansion study to assess the preliminary efficacy and safety of SAR445877 as a monotherapy for Chinese participants aged at least 18 years with advanced Gastric Cancer(GC)/Gastroesophageal Junction cancer (GEJ). Participants with advanced GC/GEJ who relapsed to at least 1 prior regimen which may or may not include an anti-PD1/PD-L1-based treatment depending on local standard of care, regardless combined positivity score (CPS) will be randomized in this study. In this study, SAR445877 will be assessed as a monotherapy in approximately 30 participants with advanced unresectable or metastatic GC or Siewert Type 2 and 3 GEJ, and for whom receiving the standard of care (SOC) is not in his or her best interest, or where no SOC is established. Human epidermal growth factor receptor 2 (HER2) positive cases will not be eligible unless they have progressed on a HER2 targeted therapy. Those participants should have received at least 1 prior line of anti-cancer treatment which may or may not include an anti-PD1/PD-L1-based treatment depending on local standard of care. Metastatic microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) cases are not eligible.