Fcγ Receptor Activation by Human Monoclonal Antibody Aggregates

Protein aggregates are a potential risk factor for immunogenicity. The measurement, characterization, and control of protein aggregates in drug products are indispensable for the development of biopharmaceuticals, including therapeutic mAbs. In this study, Fc gamma receptor (Fc gamma R)-expressing reporter cell lines were used to analyze the Fc gamma R-activation properties of mAb aggregates. Comparison of aggregates of mAbs harboring different IgG subclasses revealed that the Fc gamma R-activation profiles of the mAb aggregates were dependent on IgG subclass. In addition, aggregates of Fc-engineered mAb with enhanced FcyR-activation properties exhibited stronger activation of Fc gamma Rs than was observed in the wild-type aggregates, whereas aggregates of Fc-engineered mAb with decreased Fc gamma R-activation properties showed reduced activation. These results suggest that Fc gamma R activation by mAb aggregates depends greatly on the Fc functions of the native (nonaggregated) mAbs. We also showed that aggregates of mAbs smaller than 1 um in size have the potential to directly activate Fc gamma Rs. Unintended immune cell activation can be induced on account of Fc gamma R activation by mAb aggregates and such Fc gamma R activation may contribute to immunogenicity, and therefore, analysis of the Fc gamma R-activation properties of mAb aggregates using Fc gamma R-expressing reporter cell lines is a promising approach for the characterization of mAb aggregates. (C) 2020 The Authors. Published by Elsevier Inc. on behalf of the American Pharmacists Association (R). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).