Urelumab (BMS-663513 or anti-4-1BB antibody) is a fully human, non‐ligand binding, CD137 agonist immunoglobulin‐γ 4 (IgG4) monoclonal antibody.[1] It was developed utilizing Medarex's UltiMAb(R) technology by Bristol-Myers Squibb for the treatment of cancer and solid tumors.[2] Urelumab promotes anti-tumor immunity, or an immune response against tumor cells, via CD137 activation.[2][3] The application of Urelumab has been limited because it can cause severe liver toxicity.[4][5][6]