In vitro cytotoxicity of the conjugate adriamycin with anti-sarcoma monoclonal antibody 19-24.

Monoclonal antibody (MoAb) 19-24, which recognizes a cell surface sarcoma-associated antigen p102, was linked via a biotin-avidin-biotin bridge to adriamycin (ADR). The molar ratios of ADR: total protein ranged from 2 to 7.5. Significant differences were not observed between the binding ability of the ADR-MoAb conjugate and of the unconjugated MoAb 19-24 to fresh sarcoma tissue membranes. The ADR-MoAb conjugate also retained the ability to compete with MoAb 19-24 for binding to sarcoma-associated antigen p102. In vitro cytotoxicity studies using human fibrosarcoma cells showed that the ADR-MoAb conjugate maintained 40% of the efficacy of free ADR. However, the conjugate was not cytotoxic to p102 antigen negative rat fibrosarcoma SP-24 cells. These data support the suggestion that MoAb-drug conjugates might be helpful in developing highly specific antisarcoma therapeutic agents.