ASTATINE-211 LABELING OF A MONOCLONAL-ANTIBODY AND ITS FAB FRAGMENT -SYNTHESIS, IMMUNOREACTIVITY

An antigastric cancer monoclonal antibody, 3HII and its Fab fragment, were labelled with a-emitter At-211 using p-(At-211)-astatobenzoic aci d (pAtBA) intermediate, in the yields of more than 30%. The astatinate d antibodies were stable in vitro, and had specific immunoreactivity t o human gastric cancer cell M85. The therapeutic effect of the astatin ated antibodies for subcutaneous xenografts of human gastric cancer we re investigated in nude mice by i.p. injection,once every 5 days for 3 times sucessively, with 1.48X10(4) and 2.22X10(4)Bq/g of At-211-3HII and At-211-3HII Fab per injection, respectively. it was showed that th e volume and weight of xenografts in all tested groups were much small er and lighter than that of control group (PBS) from 12.5 days post fi rst injection. The most evident inhibition was observed in the groups with At-211-3HII Fab, with tumor inhibility of 67.5-69.5% at 15 days a nd 70.7-72.3% at 20 days, respectively.