Glycobiology Advance Access originally published online on September 25, 2006
Glycobiology 2007 17(1):36-45; doi:10.1093/glycob/cwl053
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Clearance mechanism of a mannosylated antibody–enzyme fusion protein used in experimental cancer therapy
2 Cancer Research UK Targeting and Imaging Group, Department of Oncology
3 Department of Haematology, Royal Free & University College Medical School, Hampstead Campus, London, NW3 2PF, UK
4 Department of Molecular Biomedical Research, Fundamental and Applied Molecular Biology, Ghent University and Flanders Interuniversity Institute for Biotechnology, Technologiepark 927, B-9052 Ghent-Zwijnaarde, Belgium
1 To whom correspondence should be addressed; e-mail: k.chester{at}ucl.ac.uk
Received on June 22, 2006; revised on August 29, 2006; accepted on September 18, 2006
MFECP1 is a mannosylated antibody–enzyme fusion protein used in antibody-directed enzyme prodrug therapy (ADEPT). The antibody selectively targets tumor cells and the targeted enzyme converts a prodrug into a toxic drug. MFECP1 is obtained from expression in the yeast Pichia pastoris and produced to clinical grade. The P. pastoris-derived mannosylation of the fusion protein aids rapid normal tissue clearance required for successful ADEPT. The work presented provides evidence that MFECP1 is cleared by the endocytic and phagocytic mannose receptor (MR), which is known to bind to mannose-terminating glycans. MR-transfected fibroblast cells internalize MFECP1 as revealed by flow cytometry and confocal microscopy. Immunofluorescence microscopy shows that in vivo clearance in mice occurs predominantly by MR on liver sinusoidal endothelial cells, although MR is also expressed on adjacent Kupffer cells. In the spleen, MFECP1 is taken up by MR-expressing macrophages residing in the red pulp and not by dendritic cells which are found in the marginal zone and white pulp. Clearance can be inhibited in vivo by the MR inhibitor mannan as shown by increased enzyme activities in blood. The work improves understanding of interactions of MFECP1 with normal tissue, shows that glycosylation can be exploited in the design of recombinant anticancer therapeutics and opens the ways for optimizing pharmacokinetics of mannosylated recombinant therapeutics.
Key words: Antibody-directed enzyme prodrug therapy / anti-carcinoembryonic antigen antibody MFE / clearance / mannose receptor / Mannosylated antibody–enzyme fusion protein MFECP1
None declared.