Preparation, biodistribution, and dosimetry of 188Re-labeled MoAb ior ceal and its F(ab′)2 fragments by avidin-biotin strategy

The biotinylated monoclonal antibody (MoAb) ior ceal and its F(ab')(2) fragments were labeled with Re-188 by combination of avidin-biotin strategy. Re-188-MoAb, Re-188-MoAb-biotin, Re-188-F(ab')(2), and Re-188-F(ab')(2)-biotin preparations were produced for these studies with specific activities of 1.30 +/- 0.18 GBq/mg and from instant freeze dried kit formulations using ethane 1-hydroxy-1,1-diphosphonic acid (EHDP) as a weak competing ligand. There mere no significant differences (p > 0.05) between the biodistribution in mice of biotinylated and unbiotinylated Re-188-labeled immunoconjugates. When avidin was injected as a chase after injection of Re-188-MoAb-biotin or Re-188-F(ab')(2)-biotin, the blood radioactivity level decreased approximately 75% (cumulated activity) and the effective dose decreased almost 25% with respect to that of the radioimmunoconjugates in which the chase effect was not used. Our results suggest that Re-188-labeled biotinylated MoAb ior ceal and its F(ab')(2) fragments prepared by this method are stable complexes in vivo. NUCL MED BIOL 261:57-62 1999. (C) 1998 Elsevier Science Inc.