BIODISTRIBUTION AND TUMOR-LOCALIZATION OF I-131 SWA11 RECOGNIZING THECLUSTER W4 ANTIGEN IN PATIENTS WITH SMALL-CELL LUNG-CANCER

The biodistribution of radiolabelled SWA11, a mouse monoclonal antibod y recognising the cluster w4 group antigen associated with small cell lung cancer (SCLC) was studied in patients with SCLC. Five patients we re injected intravenously with approximately 5 mCi of I-131 conjugated to 1 mg of SWA11. The half-life of the radiolabel in blood was short but there was a prolonged second phase of clearance with a half-life o f about 40 h. Tumour was detected by gamma camera imaging two patients . However, most of the whole body radioactivity was located in the bon e marrow. At least 35% of the radioactivity in blood 18 h after inject ion was bound to circulating granulocytes and this probably accounted for the unusual biodistribution of the radiolabel in man. This study s hows that the biodistribution of radiolabelled SWA11 in man differs fr om human tumour xenograft models and that the antibody in unsuitable f or targeting therapy to SCLC in man.