Radiopharmaceutical preparation of a monoclonal antibody, Lym-1, and its F(ab')₂ fragment for imaging lymphoma with In-111

(S)-4-[2,3 bis[bis(carboxymethylamino)propyl]phenyl isothio-cyanate (CITC) was used to attach In-111 to an intact monoclonal antibody (Lym-1) or its fragment F(ab')₂ to produce two new radiopharmaceuticals. Immunoreactivity of the Lym-1, specific for B cell lymphoma, was not affected by the coupling reaction for 1.0 and 4.3 CITC molecules per whole antibody and 3.0 CITC molecules per F(ab')₂ fragment. Both retained in excess of 90% immunoreactivity even at the level of 25 mCi of In-111 per mg of Lym-1 and 15 mCi per mg F(Ab')₂. The labeling reaction produced yields in excess of 98% eliminating the requirement for routine purification of the final radiopharmaceutical.