» Ibritumomab Tiuxetan is the immunoconjugate resulting from a stable thiourea covalent bond between the monoclonal antibody ibritumomab and the linker-chelator tiuxetan [N-[2-bis(carboxymethyl)amino]-3-(p-isothiocyanatophenyl) propyl]-[N-[2-bis(carboxymethyl)amino]-2-(methyl)ethyl)glycine. This chelate provides a high-affinity, conformationally restricted chelation site for ⁹⁰Y and ¹¹¹In. The approximate molecular weight of Ibritumomab Tiuxetan is 148 kD.