DAREON®-NEC-1: A Study in People With Advanced Extrapulmonary Neuroendocrine Cancer (epNEC) to Compare Obrixtamig Plus Carboplatin and Etoposide Treatment With Standard Chemotherapy

This study is open to adults with advanced extrapulmonary neuroendocrine cancer. The purpose of this study is to find out if a study medicine called obrixtamig plus standard chemotherapy (carboplatin and etoposide) improves survival when compared to standard chemotherapy (carboplatin and etoposide) alone. Obrixtamig is an antibody-like molecule that may help the immune system fight cancer. Another purpose of the study is to test a medical device being developed to measure levels of the tumour marker delta-like ligand 3 (DLL3). Participants are put into 2 groups randomly, which means by chance. One group (treatment arm) receives obrixtamig and standard chemotherapy followed by obrixtamig alone for up to 3 years. The other group (control arm) receives standard chemotherapy without obrixtamig for about 4 months. All treatments are given as infusions into a vein. During the study, participants in both groups visit the study site regularly. Participants in the treatment arm stay overnight at the study site following the first 2 obrixtamig treatments. The doctors regularly check participants' health and take note of any unwanted effects. At some of the visits, doctors check the size of the tumour(s). The results are compared between the 2 groups to see whether the treatment works.