Monoclonal Antibody Conjugates of Doxorubicin Prepared with Branched Linkers:  A Novel Method for Increasing the Potency of Doxorubicin Immunoconjugates

• Published in: Bioconjugate chemistry Vol. 10; no. 2; pp. 279 - 288
• Main Authors: King, H. Dalton, Yurgaitis, Derek, Willner, David, Firestone, Raymond A, Yang, Michael B, Lasch, Shirley J, Hellström, Karl Erik, Trail, Pamela A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01-03-1999
• Subjects: Animals; Antibodies, Monoclonal - metabolism; Antibodies, Monoclonal - pharmacokinetics; Cell Survival - drug effects; Doxorubicin - pharmacokinetics; Doxorubicin - toxicity; Humans; Hydrazones; Hydrogen-Ion Concentration; Hydrolysis; Immunoconjugates - chemistry; Immunoconjugates - pharmacokinetics; Immunoconjugates - toxicity; Immunoglobulin G - metabolism; Indicators and Reagents; Kinetics; Lung Neoplasms; Lysosomes - metabolism; Mice; Tumor Cells, Cultured
• ISSN: 1043-1802; 1520-4812
• DOI: 10.1021/bc980100i

Immunoconjugates of monoclonal antibody BR96 and Doxorubicin have been prepared using a novel series of branched hydrazone linkers. Since each linker bound to the mAb carries two DOX molecules, the DOX/mAb molar ratios of these conjugates were approximately 16, twice that of those previously prepared with single-chain hydrazone linkers. The conjugates were stable at a physiological pH of 7, but released DOX rapidly at lysosomal pH 5. The branched series of BR96 conjugates demonstrated antigen-specific cytotoxicity, and were more potent in vitro than the single-chain conjugate on both a DOX (4−14-fold) and mAb (7−23-fold) basis. The results suggest that, by using the branched linker methodology, it is possible to significantly reduce the amount of mAb required to achieve antigen-specific cytotoxic activity. In this paper, the synthesis and in vitro biology of branched chain immunoconjugates are described.