This clinical trial is focused on studying the effectiveness of two medications, tislelizumab and spartalizumab, in treating patients with advanced or metastatic tumors. These tumors express high levels of a specific protein called PD1, which is a biomarker that can influence how cancer cells grow and respond to treatment. The trial aims to understand how these medications, which are antibodies targeting the PD1 protein, can help in managing different types of cancer.

Participants in the study will receive either tislelizumab or spartalizumab through an intravenous infusion, which means the medication is given directly into a vein. The study will compare the effects of these medications on the tumors over a period of time. Some participants may receive a placebo, which is a substance with no active medication, to help researchers understand the true effects of the treatments. The study will monitor how the tumors respond, whether they shrink, remain stable, or grow, and will also track any side effects experienced by the participants.

The purpose of this study is to assess the overall response rate, which is the proportion of patients whose tumors show a complete or partial response to the treatment. Other aspects being evaluated include the duration of response, time to response, and overall survival of the participants. The study will also look at the clinical benefit rate, which includes patients whose disease remains stable for a certain period. This research is important for developing new treatment options for patients with advanced cancers that express high levels of the PD1 biomarker.