Study to Estimate Efficacy of Combining Dostarlimab and Niraparib in Relapsed EOC After Treatment With PARPi

Niraparib starting dose of study treatment will be based upon the patient's baseline body weight and baseline platelet count. Patients with a baseline body weight ≥77 kg and baseline platelet count ≥150 x 10\^9/L may start with niraparib 300 mg (3 x 100 mg capsules) daily unless the dose has not already been reduced to 200 mg in a prior treatment line. Patients with a baseline body weight \<77 kg or a baseline platelet count \<150 x 10\^9/L will be administered niraparib 200 mg (2 x 100 mg capsules) daily.

Dostarlimab (TSR-042) is administered 500 mg iv Q3W for the first 12 weeks. For the remainder of the study dostarlimab (TSR-042) is administered 1000 mg iv Q6W.