This study involves patients with gastric or gastroesophageal junction adenocarcinoma, which is a type of cancer that affects the stomach or the area where the esophagus meets the stomach. The cancer being studied is either locally advanced and cannot be removed by surgery, or it has spread to other parts of the body. The treatment being tested is tislelizumab, which is also known by its code name BGB-A317 and is marketed as Tevimbra. This medication will be given together with chemotherapy, which is a standard cancer treatment that uses drugs to kill cancer cells. The study compares two different ways of giving tislelizumab: one method involves injecting the medication under the skin using a subcutaneous injection, while the other method involves giving it directly into a vein through an intravenous infusion.
The purpose of this study is to find out whether tislelizumab given as an injection under the skin reaches the same levels in the body as when it is given through a vein, and to see if the injection under the skin is as safe and effective as the intravenous method. The study will measure the amount of medication in the blood at different times and compare the results between the two groups. Researchers will also look at how well the treatment works by checking whether tumors shrink or stop growing, how long patients live without their cancer getting worse, and how long the treatment keeps working.
During the study, patients will receive tislelizumab in one of the two ways mentioned, along with chemotherapy, as their first treatment for this type of advanced cancer. The treatment can continue for up to 24 months. Throughout the study, doctors will monitor patients for any side effects and collect information about how the cancer responds to treatment. Patients will need to provide tumor tissue samples for testing, and the study will also check whether the body develops any immune responses against the medication.



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