The purpose of this study is to find a suitable dose of BI 764532 that people with advanced cancer can tolerate. Two different doses of BI 764532 are tested in this study. Another purpose is to check whether BI 764532 can make tumours shrink. BI 764532 is an antibody-like molecule (DLL3/CD3 bispecific) that may help the immune system fight cancer. The study has 2 parts. In Part 1, participants are put into 2 groups randomly, which means by chance. Participants have an equal chance of being in either group. One group gets dose 1 of BI 764532 and the other group gets dose 2 of BI 764532. In Part 2, all participants receive the same dose of BI 764532. Part 2 is open to people with a certain kind of tumour called extrapulmonary neuroendocrine carcinoma.
