This study is testing a drug called Infigratinib for people with a type of stomach cancer called gastric cancer (GC) or cancer at the junction of the stomach and esophagus (GEJ adenocarcinoma). This is a phase II trial, meaning it checks how well the drug works and its safety. To join, you must be at least 18, have advanced or spreading cancer, and failed at least two previous treatments. You also need to provide a tissue sample for testing and have a life expectancy of at least 3 months.

• The study will require you to visit the hospital or clinic multiple times for testing and treatment.
• You will not be able to join if you have had other cancers or certain treatments recently.
• Participants must not have allergies to the drug or certain health issues that affect digestion.