Preparation, biodistribution, and dosimetry of 188Re-Labeled MoAb ior cea1 and its f(ab′) 2 fragments by avidin-biotin strategy

Abstract

The biotinylated monoclonal antibody (MoAb) ior cea1 and its F(ab′) 2 fragments were labeled with Re-188 by combination of avidin-biotin strategy. 188Re-MoAb, 188Re-MoAb-biotin, 188Re-F(ab′) 2, and 188Re-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 were no significant differences ( p > 0.05) between the biodistribution in mice of biotinylated and unbiotinylated 188Re-labeled immunoconjugates. When avidin was injected as a chase after injection of 188Re-MoAb-biotin or 188Re-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 188Re-labeled biotinylated MoAb ior cea1 and its F(ab′) 2 fragments prepared by this method are stable complexes in vivo.