This is a multicenter, open-label, first-in-human Phase 1 study evaluating the anti-programmed death receptor 1 (anti-PD-1) antibody TSR-042 in patients with advanced solid tumors who have limited available treatment options. The study will be conducted in 2 parts: dose escalation and cohort expansion. The cohort expansion may include various tumor types, including endometrial, Non-Small Cell Lung cancer, and MSI-H solid tumors.