Indium-113m labeled monoclonal antibodies for tumor imaging

Terminal radiolabeling of macromolecules by using a bifunctional chelating conjugate is a convenient method for the preparation of radiopharmaceuticals. The high specificity of monoclonal antibodies to its antigens, coupled with a very high specific radioactivity may be a key element in improving the precision of targeting such macromolecules to specific sites, under conditions where minimal interference of foreign protein will occur. Carbodiimide appear to be among the coupling agents used for conjugation of bifunctional chelator to macromolecules, the one which can be coupled under mild reaction; hence it appears they would offer the greatest promise of positive results. Conjugates of monoclonal antibodies coupled to DTPA, obtained by this method can be labeled with /sup 113m/Indium with high specific radioactivity. The present study documents our results, which led to specificity as high as 600 μCi/μg (9000 Ci/mM). The current studies should contribute to the development of techniques of terminal labeling with short-lived radiometals with bifunctional chelating agents