FcγRIIIa-158V/F polymorphism affects the performance of FcγRIIIa-related bioassay.

ABSTRACT

Bioassays are important for estimating biosimilarity between biological products. Comparability studies including bioassays are needed to demonstrate that a biosimilar product has no meaningful differences that affect safety and efficacy compared with the reference product. Among the most important biological characteristics of therapeutic mAbs are Fc-mediated functions, which induce immune-cell activation which can affect both efficacy and safety. Thus, when developing biosimilar products of therapeutic mAbs, it is necessary to compare the Fc-mediated functions by using various bioassays. Though it is reported that polymorphism of Fcγ receptors (FcγRs) affects Fc-mediated cellular activations of therapeutic mAbs, the impacts of the polymorphism of FcγRs on bioassay performance are still unclear. In this study, we evaluated the impact of FcγRIIIa-158V/F polymorphism on assay performance in distinguishing differences in the biological activities of therapeutic mAbs. The results showed that different bioassay methods produced different assessments of biological activities of mAbs, and that the FcγRIIIa-158V/F polymorphism clearly affected the performance of the FcγRIIIa-binding assay using recombinant proteins and FcγRIIIa-expressing reporter assays. That is, the assays using the FcγRIIIa-158F variant were superior to those using the FcγRIIIa-158V variant in distinguishing the difference in FcγRIIIa-binding and -activation properties. These results indicate that we should evaluate the comparability of biosimilars by considering the impacts of FcγRIIIa-158V/F polymorphism on bioassay performance.