Ph1b/2 Study of the Safety and Efficacy of T-DXd Combinations in Advanced HER2-expressing Gastric Cancer (DESTINY-Gastric03)

To join this study, you need to be at least 18 years old. You must have advanced cancer in your stomach or the connection between your food pipe and stomach (called the GEJ) that can't be removed with surgery, or cancer that has spread to other parts of your body. Your cancer cells must also show the HER2 protein, either at high levels (called HER2-positive) or lower levels (called HER2-low).

Depending on which part of the study you might join, you may have already had some treatment for your cancer, or you might be starting treatment for the first time. The doctors will need to be able to measure your tumour to see if the treatment is working. It's also important that your body is generally well and your organs, like your heart, kidneys, and liver, are working properly. If you can become pregnant, you'll need to agree to use effective birth control during and after the study.

There are also some reasons why you wouldn't be able to join. For example, if you have certain infections like active HIV, Hepatitis B, or C, or if you have a history of a specific lung condition called pneumonitis or other serious lung problems. Uncontrolled infections or certain fluid build-ups around your lungs or heart would also prevent you from joining. The study team will review all your medical information carefully to see if this study is right for you.

If you decide to take part in this study, you will have regular visits to the hospital for checks and treatments. During these visits, doctors and nurses will monitor your health very closely. This will include physical exams, blood tests, and scans (like CT or MRI scans) to see how your body is responding to the treatment and if the cancer is changing. You will be given the study medication (trastuzumab deruxtecan, either alone or with other medicines) as prescribed by the study doctors. The exact number of visits and the duration of your participation will depend on how you respond to the treatment and which part of the study you are in. Researchers will keep checking on your health even after the main treatment ends, which is called follow-up. This is done to understand the long-term effects of the treatment.