Biosimilar mAb in-process Sample Higher Order Structure Analysis with Protein Conformational Array ELISA

Biologics higher order structure (HOS) plays an important role in the molecule’s biological function and is closely related to its immunogenicity property. A novel technology to study changes in HOS is the Protein Conformational Array (PCA) ELISA which uses a bank of 34 antibodies to measure epitope distribution on the surface of biologics such as mAbs. The objective of this study is to use Protein Conformational Array technology to analyze mAb HOS status during bioprocess development. Under carefully controlled assay conditions, the mAb epitope distribution can be thought of as a ‘fingerprint’ of the biologics being studied and many physiochemical changes would correlate with changes in HOS. MAbs with additional epitope exposure compared to the reference standard or innovator mAb can be considered as conformational impurities. In this study we used the PCA ELISA to follow this epitope ‘fingerprint’ to study the HOS of two biosimilar mAbs under development; a large number of samples from both upstream and downstream of the process were analyzed. In these two particular cases, an increase in epitope exposure was observed from the two biosimilar mAb cell culture samples in the later stage of the upstream process. During the downstream process, the PCA ELISA indicated that almost all of the mAb conformational impurities were removed, producing a biosimilar candidate with high HOS similarity to the reference standard.