This study investigates the use of immunotherapy in treating patients with rare tumors. The purpose of this study is to evaluate how well the treatment works in patients with advanced rare cancers. Immunotherapy is a type of cancer treatment that helps the immune system fight cancer. In this study, patients will receive a combination of two investigational medications that are designed to boost the immune response against cancer cells.

Participants in this study will undergo certain procedures to monitor their health and the effects of the treatment. These procedures may include regular medical check-ups, blood tests, and imaging studies to assess the response of the tumors to the treatment. The study aims to gather information on the effectiveness and safety of the combination immunotherapy for rare tumors.

• Who can participate: Patients with confirmed rare cancer or cancer of unknown primary, who do not have a match to a molecularly-guided therapy, or have progressed on such therapy, are eligible. There must be histologic evidence of metastatic malignancy with no identifiable primary site.
• Study details: Participants will receive a combination of investigational medications designed to enhance the immune system's ability to fight cancer. A placebo, which is an inactive substance, is not used in this study. Participants will not be paid for their participation.