Monoclonal antibodies (mAbs) provide a pharmacological platform to block or activate the
function of surface receptors. The immune system has evolved receptor–ligand pairs that
repress or empower the cellular immune response, which, if tampered with, unleash more
potent cellular immunity against tumor antigens. Agonist antibodies directed against CD137
(4-1BB) on the surface of antigen-primed T lymphocytes increase tumor immunity that is
curative against some transplantable murine tumors. A fully human IgG4 anti-CD137 …