Arzneimittelforschung 2012; 62(S 01): S4-S5
DOI: 10.1055/s-0032-1324900
Symposium der Paul-Martini-Stiftung
Georg Thieme Verlag KG Stuttgart · New York

Glycoengineering of Therapeutic Antibodies

C. Klein
1   Expert Scientist, Roche Glycart AG, Schlieren/Switzerland
› Author Affiliations
Further Information

Publication History

Publication Date:
04 December 2012 (online)

Preview

Antibody dependent cellular cytotoxicity (ADCC) is the process of lysis of (tumor) target cells by immune effector cells. It requires the simultaneous binding of an antibody to a cell surface receptor on the target cell and via the Fc region of the antibody to the FcgRIIIa receptor on immune effector cells such as NK cells or macrophages/monocytes. Binding of the antibody to target and immune effector cells results in the cross-linking of FcgRIIIa with subsequent activation of FcgRIIIa signaling and release of proteins mediating the killing of the target cells such as perforin and of proteases such as granzymes. ADCC has been established as an important mode of action of therapeutic antibodies such as rituximab/MabThera (targeting CD20), cetuximab/Erbitux (targeting EGFR) and trastuzumab/Herceptin (targeting HER2) which are approved for the treatment of various cancers. Translational research on rituximab and cetuximab has established that the response to therapeutic antibodies in patients can be influenced by the FcgRIIIa-158V/F polymorphism. This polymorphism results in the expression of a high affinity FcgRIIIa receptor (158 V) and a low affinity FcgRIIIa receptor (158F) on immune effector cells and impacts the capability of antibodies to mediate ADCC [1], [2], [3], [4], [5], [6], [7]. We have recently developed a so-called GlycoMab technology that enhances the affinity of therapeutic antibodies for both the high and low affinity FcgRIIIa receptors through the introduction of a bisecting N-acetyl-glucosamine residue in the carbohydrate chain of the Fc region of the antibodies. The introduction of this bisecting N-acetyl-glucosamine moiety in the carbohydrate chain results in a steric interference with core fucosylation of the carbohydrate. This process and other approaches resulting in the afucosylation of therapeutic antibodies are known as “antibody glycoengineering”. We and others have demonstrated that glycoengineering and lack of the core fucose residue results in an up to 50-fold enhanced affinity of human IgG1 antibodies for the human FcgRIIIa receptors, and this subsequently results in an up to 100-fold enhanced ADCC induction (potency). Recently, we have demonstrated the structural basis of the enhanced affinity of afucosylated Fc regions for FcgRIIIa by X-ray crystallography. These studies provide a structural explanation for the high affinity and FcgRIIIa specificity of glycoengineering as opposed to other technologies used for Fc-engineering such as the introduction of mutations in the Fc region that also affect binding to other FcgRs [8], [9], [10], [11], [12], [13], [14], [15].