This study is for adults with advanced **colon**, **rectum**, **stomach**, or **pancreas cancer**. These cancers cannot be removed by surgery or have spread. The study aims to find the highest dose of a new medicine, **BI 765049**, that patients can handle. This medicine may help the immune system fight cancer. Participants will receive the medicine every 3 weeks. They will continue treatment as long as it helps them and they can tolerate it. Participants need to visit the study site regularly, which includes some overnight hospital stays. During visits, doctors will check health and take lab tests. They will also look for any unwanted effects from the medicine. Severe health problems are checked, especially those occurring within a week after the first treatment. **Key Points:** - Participants receive the study drug every 3 weeks with regular hospital visits and some overnight stays. - The study seeks to discover the highest tolerable dose of BI 765049. - The medicine may boost the immune system to fight cancer. **Eligibility:** Adults with specific advanced cancers; must meet certain health criteria. **Exclusion:** Recent major surgery, other cancers in the past 5 years, and some medical conditions.