This study is looking at advanced breast cancer and metastatic breast cancer, which are types of breast cancer that have spread beyond the original tumor or to other parts of the body. The study will test two investigational treatments called BNT323 and BNT327, which will be given through an infusion into a vein. These treatments will be tested both alone and in combination with each other. Some patients in the study will receive only BNT323, some will receive only BNT327, and some will receive both treatments together. The study focuses on patients whose breast cancer has a specific status related to a protein called human epidermal growth factor receptor 2 or HER2, which is measured in tumor samples.
The purpose of the study is to find the best dose of BNT323 when used together with BNT327, to check if these treatments are safe, and to see if they help patients with advanced breast cancer. The study is divided into two parts. In the first part, different doses of BNT323 combined with BNT327 will be tested to find the recommended dose for further testing. In the second part, the effectiveness and safety of BNT323 alone, BNT327 alone, and the combination of both treatments will be compared to see how well they work in shrinking or controlling the cancer.
During the study, patients will receive the assigned treatment and will be monitored for any side effects and for how their cancer responds to the treatment. The study will measure things like whether the tumors shrink or disappear, how long any response to treatment lasts, and whether the disease remains stable. Patients will need to have tumors that can be measured and will undergo heart function tests before starting treatment to ensure their heart is working properly. The study will track various safety measures including any unwanted effects from the treatments, whether treatment doses need to be changed or stopped, and overall how well patients tolerate the medications.
France 
Italy 
Spain 