CTLA4 and esophageal squamous cell carcinoma: In the global, phase 3, CheckMate 648 study, nivolumab administered along with ipilimumab (anti-cytotoxic T lymphocyte-associated protein 4 antibody [anti-CTLA4 antibody]) or chemotherapy resulted in significantly longer overall survival (OS) versus chemotherapy alone in advanced ESCC [6].