» 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-isothiocyanato phenyl)propyl]-[N-[2-bis(carboxymethyl)amino]⁠-2-(methyl)ethyl)glycine. This chelate provides a high-affinity, conformationally restricted chelation site for Yttrium-90 and Indium-111. The approximate molecular weight of Ibritumomab Tiuxetan is 148 kD.