This study is for adults with small cell lung cancer or other neuroendocrine cancers that show a tumor marker called delta-like 3 (DLL3). These are advanced cancers where other treatments didn't work. The study is testing a new medicine, BI 764532, which might help the immune system fight cancer. BI 764532 is given for the first time to people, so there's no previous data on it. Participants will get BI 764532 weekly or every 3 weeks, for up to 3 years, and will visit the study site about 20 times. These visits help doctors check if the treatment is working and watch for any side effects.

• **Study Length**: Treatment can last up to 3 years with around 20 site visits.
• **Treatment**: BI 764532 is an experimental drug, given weekly or every 3 weeks.
• **Eligibility**: For advanced cancer patients who have no other treatment options.