Characterization of cetuximab Fc/2 dimers by off-line CZE-MS

Monoclonal antibody (mAb) therapeutics attract the largest concern due to their strong therapeutic potency and specificity. The Fc region of mAbs is common to many new biotherapeutics as biosimilar, antibody drug conjugate or fusion protein. Fc region has consequences for Fc-mediated effector functions that might be desirable for therapeutic applications. As a consequence, there is a continuous need for improvement of analytical methods to enable fast and accurate characterization of biotherapeutics. Capillary zone electrophoresis-Mass spectrometry couplings (CZE-MS) appear really attractive methods for the characterization of biological samples. In this report, we used CZE-MS systems developed in house and native MS infusion to allow precise middle-up characterization of Fc/2 variant of cetuximab. Molecular weights were measured for three Fc/2 charge variants detected in the CZE separation of cetuximab subunits. Two Fc/2 C-terminal lysine variants were identified and separated. As the aim is to understand the presence of three peaks in the CZE separation for two Fc/2 subunits, we developed a strategy using CZE-UV/MALDI-MS and CZE-UV/ESI-MS to evaluate the role of N-glycosylation and C-terminal lysine truncation on the CZE separation. The chemical structure of N-glycosylation expressed on the Fc region of cetuximab does not influence CZE separation while C-terminal lysine is significantly influencing separation. In addition, native MS infusion demonstrated the characterization of Fc/2 dimers at pH 5.7 and 6.8 and the first separation of these dimers using CZE-MS.