A Study to Test How Well Different Doses of BI 764532 Are Tolerated by People With a Tumour in the Brain That is Positive for DLL3

This study (1438-0003) is open to adults with a tumour in the brain that is positive for the tumour marker delta-like 3 (DLL3). This study is in people with advanced cancer for whom previous treatment was not successful. The purpose of this study is to find out the highest dose of BI 764532 that people with a brain tumour that is positive for DLL3 can tolerate. BI 764532 is an antibody-like molecule that can attach and link together the cancer cells and T-cells of the immune system (DLL3/CD3 bispecific). This may help the immune system fight cancer. Participants get BI 764532 infusions into a vein when starting treatment. If there is benefit for the participants and if they can tolerate it, the treatment is continued. During this time, participants visit the study site at regular intervals. The total number of visits depends on how they respond to and tolerate the treatment. The first study visits include staying to monitor participants' safety. Doctors record any unwanted effects and regularly check the general health of the participants.