Fc Sialylation Prolongs Serum Half-Life of Therapeutic Antibodies

The long serum t _1/2 of IgGs is ensured by their interaction with the neonatal Fc receptor (FcRn), which salvages IgG from intracellular degradation. Fc glycosylation is thought not to influence FcRn binding and IgG longevity in vivo. In this article, we demonstrate that hypersialylation of asparagine 297 (N297) enhances IgG serum persistence. This polarized glycosylation is achieved using a novel Fc mutation, a glutamate residue deletion at position 294 (Del) that endows IgGs with an up to 9-fold increase in serum lifespan. The strongest impact was observed when the Del was combined with Fc mutations improving FcRn binding (Del-FcRn⁺). Enzymatic desialylation of a Del-FcRn⁺ mutant or its production in a cell line unable to hypersialylate reduced the in vivo serum t _1/2 of the desialylated mutants to that of native FcRn⁺ mutants. Consequently, our study proves that sialylation of the N297 sugar moiety has a direct impact on human IgG serum persistence.