Ipilimumab is a monoclonal antibody that binds to CTLA-4 and inhibits the interactions with the ligands B7.1 and B7.2, Nivolumab is a monoclonal antibody that targets PD-1. Engagement of PD-1 by its natural ligands, PD-L1 and PD-L2, results in an inhibition of T cell proliferation, survival and cyto-kine secretion. Nivolumab abrogates this interaction between PD-1 and its ligands.