A Study to Test Obrixtamig in Combination With Pumitamig in People With Advanced Small Cell Lung Cancer (Dareon®-Rosetta35)

This study is open to adults with extensive-stage small cell lung cancer. The purpose of this study is to find out how well people with this type of cancer tolerate taking study medicines called obrixtamig and pumitamig. Another purpose is to check whether the combination study treatment can make tumours shrink. Obrixtamig and pumitamig are being developed to help the immune system fight cancer. Participants are put into 2 groups. One group gets obrixtamig and pumitamig. The other group gets obrixtamig and pumitamig with standard chemotherapy (carboplatin and etoposide). All study treatments are given as infusions into a vein. This study does not have a fixed duration. Participants can receive obrixtamig and pumitamig for up to 2 years if they benefit from treatment and can tolerate it. Participants visit the study site regularly, with some overnight stays required. During this time, doctors regularly check for health problems that could be caused by the study treatment. They also monitor the size of the tumour(s) and take laboratory tests.