Zongertinib & TrastuzumabBeamion BCGC-1: A Study to Find a Suitable Dose of Zongertinib Used Alone and in Combination With Other Treatments to Test Whether it Helps People With Different Types of HER2+ Cancer That Has Spread

This study is open to adults aged 18 years and older with different types of HER2+ cancer that has spread and cannot be removed by surgery. People can take part in this study if their tumours show HER2 aberrations and previous treatment was not successful. The purpose of this study is to find a suitable dose of zongertinib that people with different types of HER2+ cancer that has spread can tolerate best when taken together with trastuzumab deruxtecan (T-DXd), with trastuzumab emtansine (T-DM1), with trastuzumab and capecitabine, with zanidatamab, or with mFOLFOX6 (with or without trastuzumab). Another purpose is to check whether zongertinib alone and in combination with other treatments can make tumours shrink. Zongertinib inhibits HER2. HER2 causes cancer cells to grow.

In this study, participants receive treatment in cycles. Study participants are treated with zongertinib alone or in combination with other treatments. This study has 2 parts. In Part 1, participants in different groups receive increasing doses of zongertinib. In Part 2, participants are put into different groups by chance. Each group receives a different dose of zongertinib. Every participant has an equal chance of being in each group.

During the study, the participants visit the study site regularly. In this study, researchers want to find the highest dose of zongertinib that participants can tolerate when taken together with other treatments. To find this out, researchers look at certain severe health problems that a number of participants have. The doctors regularly check the size of the tumour with imaging methods (CT/MRI) during the study. The doctors also regularly check participants' health and take note of any unwanted effects.