PRIMARY OBJECTIVE:~I. To evaluate the efficacy, as measured by confirmed overall response rate (ORR) (partial and complete response, PR/CR) per Response Evaluation Criteria in Solid Tumors (RECIST version [v]1.1) based on investigator assessment of the combination niraparib and dostarlimab in patients with recurrent or persistent uterine serous carcinoma (USC).~SECONDARY OBJECTIVES:~I. Estimate the progression-free survival (PFS). II. Estimate clinical benefit rate (CBR), defined as the percentage of patients who have achieved complete response (CR), partial response (PR) or stable disease (SD).~III. Evaluate the safety and tolerability of niraparib and dostarlimab combination.~TRANSLATIONAL OBJECTIVE:~I. Biomarker evaluation to predict response.~OUTLINE:~Patients receive dostarlimab intravenously (IV) and niraparib orally (PO) on study. Patients also undergo magnetic resonance imaging (MRI)/computed tomography (CT) and collection of blood samples throughout the trial.~After completion of study treatment, patients are followed up every 6 months for 2 years and then annually thereafter.
This phase II trial tests how well niraparib and dostarlimab work in treating patients with uterine serous carcinoma that has come back (after a period of improvement) (recurrent) and remains despite treatment (persistent). Niraparib belongs to a class of drugs called PARP inhibitors that prevent cancer cells from growing. Dostarlimab is a monoclonal antibody that may interfere with the ability of tumor cells to grow and spread. Dostarlimab belongs to a class of drugs called PD-1 inhibitors that uses the patient's own immune system to treat cancer (immuno-therapy). Giving niraparib and dostarlimab may work better in treating patients with uterine serous carcinoma.