PREPARATION AND QUALITY-CONTROL OF AT-211-LABELED AND I-125 LABELED MONOCLONAL-ANTIBODIES - BIODISTRIBUTION IN MICE CARRYING HUMAN OSTEOSARCOMA XENOGRAFTS

Two anti-osteosarcoma monoclonal antibodies (TP-3 IgG and TP-1 F(ab')2 ) were labelled with the alpha-particle emitting radionuclide At-211 a nd, for comparison of stability, with I-125 using the N-succinimidyl-3 -(trimethylstannyl)benzoate intermediate. The quality of the final pre parations was measured with immunoreactivity analyses using intact ost eosarcoma cells. Immunoreactivity was well retained with values in the range of 65% to 85% for At-211-labelled and I-125-labelled TP-3 IgG a nd approximately 60% for both At-211-labelled and I-125-labelled TP-1 F(ab)2. Tumour uptake and retention as well as normal tissue distribut ion in mice with osteosarcoma xenografts were measured. The uptake of the two radionuclides in tumour was similar, while there was a slight general increase in normal tissue activity at later points for the At- 211-labelled MoAbs compared to the I-125-labelled MoAbs, probably caus ed by a minor release of free At-211 from the MoAb preparations. The s table retention in tumor tissue demonstrated in this study indicates t hat At-211-labelled MoAbs may have potential in the treatment of tumou rs that allow a rapid uptake.