Radiolabelled monoclonal antibodies against alpha-fetoprotein for in vivo localization of human hepatocellular carcinoma by immunotomoscintigraphy

Two high affinity monoclonal antibodies, designated AF01 and AF04, directed against distinct epitopes of human alpha-fetoprotein (AFP) and the Fab fragments of one of them, were labelled with 131I and injected into 18 patients with AFP producing hepatocellular carcinoma (HCC) in order to carry out imaging studies by tomoscintigraphy. Twelve patients were injected with whole antibody, only three of seven patients injected with AF01 and two of five patients injected with AF04 had a positive scan. In contrast, five out of six patients injected with labelled Fab fragments of AF04 had positive imaging. These results confirm that tumour imaging of HCC using 131I labelled monoclonal antibody against AFP is feasible. Moreover, utilization of tomoscintigraphy in place of linear scintigraphy and Fab fragments instead of whole immunoglobulin may improve the sensitivity of radioimmunolocalization. This technique provides useful information on the in vivo distribution of monoclonal antibodies directed against AFP and on the practicability of the eventual therapeutic use of anti-AFP antibodies in HCC.