Immunoglobulin G Fc engineering for localized therapy: Eliminating neonatal Fc receptor interactions and ensuring purification using protein A

Monoclonal antibodies (mAbs) and bispecific antibodies (bsAbs) have transformed therapeutic strategies for various diseases. However, administering them can lead to unwanted adverse effects and insufficient delivery to local disease sites. Recent research has shown that substitutions in the immunoglobulin G (IgG) Fc region, designed to eliminate binding to the neonatal Fc receptor (FcRn), which accelerates clearance from systemic circulation, may improve the safety of antibody therapies intended for localized use. A major concern with these substitutions is their ability to impair binding to protein A, which is considered the gold standard for large-scale antibody purification. In this study, we investigated multiple amino acid substitutions at residues I253, H310, H435, and Y436-positions known to affect FcRn or protein A interactions-and found that H435F eliminates FcRn binding while maintaining protein A affinity. Importantly, the H435F substitution resulted in accelerated clearance and a shorter serum half-life in human FcRn transgenic mice. Moreover, purification using protein A chromatography proved to be effective without significantly compromising yield. Overall, these findings highlight the potential of the H435F substitution to optimize the pharmacokinetics of antibody therapeutics for localized use, reducing systemic side effects. This study paves the way for the use of antibody-based therapeutics in localized treatments.