Preparation and properties of a drug-carrier-antibody conjugate showing selective antibody-directed cytotoxicity in vitro.
The preparation and properties of a drug-carrier-antibody preparation are reported. The antifolate chemotherapeutic agent methotrexate was covalently coupled to human serum albumin as a carrier. The carrier-drug preparation was then chemically linked to a monoclonal antibody, raised originally against a human osteogenic sarcoma cell line, 791T, in a manner permitting retention of antibody-binding activity. The cytotoxic properties of the conjugate were tested in vitro in comparison with carrier-methotrexate and free methotrexate against a panel of tumour cell lines containing both antigenically cross-reactive cell lines and cell lines having low antigenic cross-reactivity with the monoclonal antibody. The cytotoxicity tests demonstrated that coupling of methotrexate to carrier caused a loss of some drug activity but that coupling of the antibody to the carrier-drug preparation permitted full expression of drug cytotoxicity against antibody-reactive cell lines. It was further demonstrated that the conjugate was selective in its action and was preferentially cytotoxic towards antibody-reactive cell types. The cytotoxicity against antibody-reactive cell lines was shown by competitive inhibition by free antibody to be entirely dependent on antibody binding. A clonogenic assay showed that the conjugate was capable of killing greater than 99% of 791T target cells. These results indicate that a drug-carrier antibody conjugate can be synthesized which has all the in vitro properties theoretically necessary for a successful antibody-targeted cytotoxic agent.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000970:Antineoplastic Agents / Q000008:administration & dosage*; D003602:Cytotoxicity, Immunologic; D006801:Humans; D066298:In Vitro Techniques; D008727:Methotrexate / Q000008:administration & dosage; D051379:Mice; D014677:Pharmaceutical Vehicles; D012709:Serum Albumin / Q000008:administration & dosage
D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D014677:Pharmaceutical Vehicles; D012709:Serum Albumin; D008727:Methotrexate