Modulation of IgG1 immunoeffector function by glycoengineering of the GDP‐fucose biosynthesis pathway

Abstract Cross‐linking of the Fcγ receptors expressed on the surface of hematopoietic cells by IgG immune complexes triggers the activation of key immune effector mechanisms, including antibody‐dependent cell mediated cytotoxicity (ADCC). A conserved N‐glycan positioned at the N‐terminal region of the IgG CH2 domain is critical in maintaining the quaternary structure of the molecule for Fcγ receptor engagement. The removal of a single core fucose residue from the N‐glycan results in a considerable increase in affinity for FcγRIIIa leading to an enhanced receptor‐mediated immunoeffector function. The enhanced potency of the molecule translates into a number of distinct advantages in the development of IgG antibodies for cancer therapy. In an effort to significantly increase the potency of an anti‐CD20, IgG1 molecule, we selectively targeted the de novo GDP‐fucose biosynthesis pathway of the host CHO cell line to generate >80% afucosylated IgG1 resulting in enhanced FcγRIIIa binding (13‐fold) and in vitro ADCC cell‐based activity (11‐fold). In addition, this effective glycoengineering strategy also allowed for the utilization of the alternate GDP‐fucose salvage pathway to provide a fast and efficient mechanism to manipulate the N‐glycan fucosylation level to modulate IgG immune effector function.