Characterization of therapeutic antibody fragmentation using automated capillary western blotting as an orthogonal analytical technique

Fragmentation in protein‐based molecules continues to be a challenge during manufacturing and storage, and requires an appropriate control strategy to ensure purity and integrity of the drug product. Electrophoretic and chromatographic methods are commonly used for monitoring the fragments. However, size‐exclusion chromatography often suffers from low resolution of low molecular weight fragments. Electrophoretic methods like CE‐SDS are not compatible with enriching fragments for additional characterization tests such as MS. These limitations may result in inadequate control strategy for monitoring and characterizing fragments for protein‐based molecules. Capillary western blotting was used in this study as an orthogonal method for characterization of fragments in an IgG1 antibody under reduced conditions. To achieve a comprehensive mapping of various fragments generated by thermal stress, capillary western profiles were generated using recognition antibodies for IgG kappa (κ) light chain, Fc, and Fab regions that enabled unambiguous fragment identification. Additionally, three different enzymatic digestion methods (IdeS, PNGase F, and IgdE) were applied coupled with capillary western blotting for clip identifications. Finally, complementary data collected using traditional chromatographic and electrophoretic methods allowed to establish a comparison of analytical profiles with an added benefit of fragment identification offered by capillary western profiling. In addition to various Fc and Fab‐related low molecular weight fragments, a non‐reducible thio‐ether linked 75 kDa HL fragment was also identified.