We investigated the effect of stabilized Fab oligomerization by disuccinimidyl suberate on tumor uptake in a pancreatic carcinoma xenograft model in nude mice. Recombinant mouse/human chimeric Fab of the anti-carcinoembryonic antigen (CEA) monoclonal antibody A10, which was previously shown to react specifically with gastrointestinal cancers was used in this study. Fab homo-oligomers (dimers and trimers) chemically linked with ethylene bonds (C-C oligomers) were produced by linkage of chimeric Fab. Oligomers with C-C bonds had similar immunoreactivity against human CEA to parental Fab monomer. In biodistribution studies in animals bearing pancreatic carcinoma xenografts, at 12 and 24 h after infusion, C-C oligomers showed significantly greater uptakes in tumors than Fab or F(ab')2 but lower than IgG. However, oligomers with C-C bonds maintained higher tumor to normal tissue specificity ratios than IgG 24 h post-infusion. In conclusion, tumor uptake was enhanced by Fab oligomerization with C-C bonds, compared to Fab or F(ab')2, perhaps due to the larger molecular size. It was also shown that C-C Fab oligomers could have a potency to deliver high-dose radionuclides with reduced radio-uptakes in normal tissues for the radioimmunotherapy of gastrointestinal carcinomas.

Related Articles