A Study to Test Different Doses of Obrixtamig in Patients With Small Cell Lung Cancer and Other Neuroendocrine Tumours That Are Positive for DLL3

This study is open to adults with small cell lung cancer and other neuroendocrine cancers that are positive for the tumour marker delta-like 3 (DLL3). The study is in people with advanced cancer for whom previous treatment was not successful or no standard treatment exists. The purpose of this study is to find out the highest dose of obrixtamig and the best treatment schedule that people can tolerate. Obrixtamig is an antibody-like molecule (DLL3/CD3 bispecific) that may help the immune system fight cancer. In this study, obrixtamig is given to people for the first time. Interim clinical data are available for obrixtamig. Participants get obrixtamig either weekly or once every 3 weeks. If there is benefit for the participants and if they can tolerate it, the treatment is given for a maximum of 3 years. During this time, participants visit the study site about 20 times depending on the response to the treatment. Doctors record any unwanted effects and regularly check the general health of the participants.