Tremelimumab (formerly ticilimumab, CP-675,206) is a fully human IgG2 monoclonal antibody produced by Pfizer. It binds to the protein CTLA-4, which is expressed on the surface of activated T lymphocytes. Tremelimumab blocks the binding of the antigen-presenting cell ligands B7.1 and B7.2 to CTLA-4, resulting in inhibition of B7-CTLA-4-mediated downregulation of T-cell activation; subsequently, B7.1 or B7.2 may interact with another T-cell surface receptor protein, CD28, resulting in a B7-CD28-mediated T-cell activation unopposed by B7-CTLA-4-mediated inhibition...