Identification of human IgG1 variant with enhanced FcRn binding and without increased binding to rheumatoid factor autoantibody

Abstract

Various studies have demonstrated that Fc engineering to enhance neonatal Fc receptor (FcRn) binding is effective for elongating half-life or increasing cellular uptake of IgG. A previous study has shown that a N434H mutation to enhance FcRn binding resulted in increased binding to rheumatoid factor (RF) autoantibody, which is not desirable for therapeutic use in autoimmune disease. In this study, we first showed that all the existing Fc variants with enhanced FcRn binding also show increased RF binding, and then identified specific mutations that could be introduced to those Fc variants to reduce the RF binding. Furthermore, we generated novel Fc variants that do not increase RF binding and show half-lives of 45 d in cynomolgus monkey, which is longer than those of previously reported Fc variants. In addition, we generated novel Fc variants with antigen sweeping activity that do not increase RF binding. We expect that these novel Fc variants will be useful as antibody therapeutics against autoimmune diseases.

Antibody Fc engineering for enhanced neonatal Fc receptor binding and prolonged circulation half-life

“…The DQ variant was comparable to WT, supporting its choice if other antibody engineering efforts affect this property, such as when affinity maturation or engineering multi-specific formats, is envisioned. Importantly, all three lead variants in our study maintain a WT-like or dramatically reduced binding to the RF autoantibody, a key marker for immunogenicity propensity, 12,27 unlike LS and some other engineered variants. Approaches that address increased immunogenicity 12,35 and aggregation propensity have been reported in the literature, but these require more extensive engineering and the incorporation of additional mutations.…”

“…Importantly, all three lead variants in our study maintain a WT-like or dramatically reduced binding to the RF autoantibody, a key marker for immunogenicity propensity, 12,27 unlike LS and some other engineered variants. Approaches that address increased immunogenicity 12,35 and aggregation propensity have been reported in the literature, but these require more extensive engineering and the incorporation of additional mutations. 12 Indeed, the full benefit of the Fc mutations with low immunogenicity propensity can only be recognized once the molecules reach the clinical stage.…”

“…Approaches that address increased immunogenicity 12,35 and aggregation propensity have been reported in the literature, but these require more extensive engineering and the incorporation of additional mutations. 12 Indeed, the full benefit of the Fc mutations with low immunogenicity propensity can only be recognized once the molecules reach the clinical stage.…”

“…Fc engineering to enhance the FcRn binding affinity has been extensively pursued using high-throughput mutagenesis approaches. 3,11,12 The M252Y/S254T/T256E (YTE, Eu Numbering), 4 T307A/E380A/N434A (AAA), 13 Xtend Technology (M428L/N434S, LS) 14 and the NHance platform 15 have consistently shown a 2-to 11-fold enhancement in FcRn binding affinity at pH 6.0. In addition, other variants retained substantial FcRn binding at pH 7.4, 16 which negated any improvement in affinity pH 6.0 and use for serum half-life extension.…”

“…14,21 However, the YTE variant suffers from decreased binding to FcγRIIIa 11 and C1q, reduced thermal stability and increased aggregation propensity, affecting antibody effector function and purification yields, respectively. The LS variant, among others, 12 exhibits enhanced binding to the rheumatoid factor (RF) autoantibody, suggestive of possible immunogenicity concerns in Fc-engineered therapeutic antibodies.…”