INACTIVATION OF HUMAN OSTEOSARCOMA CELLS IN-VITRO BY AT-211-TP-3 MONOCLONAL-ANTIBODY - COMPARISON WITH ASTATINE-211-LABELED BOVINE SERUM-ALBUMIN, FREE ASTATINE-211 AND EXTERNAL-BEAM X-RAYS

The potential usefulness of alpha-particle radioimmunotherapy in the treatment of osteosarcoma was studied in vitro by using the monoclonal antibody TP-3 and cells of three human osteosarcoma cell lines (OHS, SAGS and KPDX) differing in antigen expression. Cell survival curves were established after treatment with (a) At-211-TP-3 of different specific activities, (b) At-211-labeled bovine serum albumin (BSA), (c) free At-211 and (d) external-beam X rays. The three osteosarcoma cell lines showed similar survival curves, whether treated with external-beam X rays, At-211-BSA or free At-211. The D-0's were lower for free At-211 than for (211) At-BSA. The survival curves for At-211-TP-3 treatment, on the other hand, differed significantly among the cell lines, suggesting that sensitivity to At-211-TP-3 treatment was governed by cellular properties other than sensitivity to external-beam X rays. The cellular property most important for sensitivity to At-211-TP-3 treatment was the antigen expression. Cell inactivation after At-211-TP-3 treatment increased substantially with increasing specific activity of the At-211-TP-3. At high specific activities, the cytotoxic effect of At-211-TP-3 was significantly higher than that of At-211-BSA. In conclusion, At-211-Tp-3 has the potential to give clinically favorable therapeutic ratios in the treatment of osteosarcoma.