Open-label, non-randomized, Phase 1b/2 trial investigating the safety, tolerability, and antitumor activity of S095029 (anti-NKG2A antibody) as a part of combination therapy in participants with locally advanced and unresectable or metastatic MSI-H/dMMR gastroesophageal junction/gastric cancer

A new drug combination is being tested in people with advanced stomach cancer that has spread to other parts of the body. This matters because gastric and gastroesophageal junction cancers that are mismatch repair deficient (MSI-H/dMMR) are aggressive and often stop responding to existing immunotherapies. The experimental drug S095029 blocks a protein called NKG2A on immune cells, which may help the immune system recognise and attack tumours more effectively when combined with the existing immunotherapy pembrolizumab. Current treatment options for these patients are limited, and new combinations are urgently needed. If the combination proves safe and active, it could offer a new treatment pathway for people with these hard-to-treat cancers. The study is a small early-phase trial designed to establish whether the regimen is worth testing in larger studies. It does not aim to change clinical practice immediately, but to generate the safety and efficacy data needed to justify further investigation. The researchers are not claiming a breakthrough—they are systematically checking whether this particular two-drug combination works better than either drug alone in a patient group with few remaining options.