title: Internalizing antibodies are necessary for improved therapeutic efficacy of antibody-targeted liposomal drugs.
abstract: Direct experimental proof has been sought for the hypothesis that liposomal drugs targeted against internalizing epitopes (e.g., CD19) will have higher therapeutic efficacies than those targeted against noninternalizing epitopes (e.g., CD20). Anti-CD19-targeted liposomes were rapidly internalized into human B-lymphoma (Namalwa) cells, whereas those targeted with anti-CD20 were not internalized. Similar in vitro binding and cytotoxicity were observed for anti-CD19-targeted and anti-CD20-targeted liposomal formulations of doxorubicin (DXR). Therapeutic experiments were performed in severe combined immunodeficient mice inoculated i.v. with Namalwa cells. Administration of single i.v. doses of DXR-loaded anti-CD19-targeted liposomes resulted in significantly greater survival times than either DXR-loaded anti-CD20-targeted liposomes or nontargeted liposomes. The therapeutic advantage of targeting internalizing versus noninternalizing epitopes has been directly demonstrated.
authors.affiliation: Department of Pharmacology, University of Alberta, Edmonton, Alberta, T6G 2H7 Canada.
authors.forename: Puja
authors.initials: P
authors.lastname: Sapra
authors.forename: Theresa M
authors.initials: TM
authors.lastname: Allen
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000493:pharmacokinetics*; D000918:Antibody Specificity; D018941:Antigens, CD19 / Q000276:immunology*; D018951:Antigens, CD20 / Q000276:immunology*; D004317:Doxorubicin / Q000276:immunology / Q000493:pharmacokinetics / Q000494:pharmacology; D000939:Epitopes / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006801:Humans; D016130:Immunophenotyping; D000922:Immunotoxins / Q000276:immunology / Q000493:pharmacokinetics* / Q000494:pharmacology; D008081:Liposomes / Q000276:immunology / Q000493:pharmacokinetics* / Q000494:pharmacology; D016393:Lymphoma, B-Cell / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D018613:Microscopy, Confocal; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D018941:Antigens, CD19; D018951:Antigens, CD20; D000939:Epitopes; D000922:Immunotoxins; D008081:Liposomes; D004317:Doxorubicin