Definition

A radioimmunoconjugate comprised of rituximab, a recombinant chimeric monoclonal antibody directed against the CD20 antigen, and labeled with iodine I 131 with potential antineoplastic activity. The antibody moiety of iodine I 131 rituximab binds to the CD20 antigen thereby delivering cytotoxic iodine I 131 specifically to cancer cells expressing CD20. The CD20 antigen, a hydrophobic transmembrane protein, is expressed on normal pre-B and mature B lymphocytes.