A Study to Test How Well Different Doses of BI 3820768 Are Tolerated by People With Advanced Cancer (Solid Tumours)

This study is open to adults with advanced germ cell tumours, endometrial cancer, or ovarian cancer whose previous treatments were not successful. People can join the study if they have no remaining treatment options or if standard therapy is not suitable. The purpose of this study is to test increasing doses of BI 3820768 to find a dose that people with these types of cancer can tolerate and that may make tumours shrink. BI 3820768 is a type of treatment that may help the immune system fight cancer. This is the first time BI 3820768 is being tested in humans. The study has 2 parts based on the way BI 3820768 is given. Depending on when participants join the study, they will receive BI 3820768 through one of two ways to inject the study medicine. All participants receive the study medicine. The medicine is given as an injection once a week for 2 cycles of 3 weeks each, followed by doses every 3 weeks. Participants are in the study for up to 3 years if they are benefiting from the treatment. During this time, they visit the study site regularly, and some visits will require overnight stays. Doctors will regularly check the size of the tumour and whether it has spread. Researchers want to find the highest dose of BI 3820768 that participants can tolerate by looking at the number of participants with certain severe health problems. The doctors also regularly check participants' health, take blood samples, and note any unwanted effects.