Combination of intact, middle-up and bottom-up levels to characterize 7 therapeutic monoclonal antibodies by capillary electrophoresis - Mass spectrometry.

Significant growth of biopharmaceuticals requires powerful analytical methods to better understand their structure by establishing a complete characterization. To this end, a combination of bottom-up, middle-up and intact molecule levels with a capillary electrophoresis-mass spectrometry coupling has been performed to have a comprehensive picture of monoclonal antibodies. In this study, 7 worldwide health authorities approved mAbs have been analyzed to get information about their charge heterogeneity, the identification of post translational modifications (PTMs), their location and relative quantitation. Intact mAbs isoforms have been partially separated in less than 12 min and enabled to have a global illustration of mAbs heterogeneity and high masses PTMs characterization notably major N-glycosylation forms. Particularly, 2X-glycosylated and 1X-glycosylated forms have been partially separated. To deepen characterize PTMs carried by the backbone structure, advanced investigations at a middle-up level have been performed. Limited IdeS proteolysis allowed to study independently Fc/2 and F(ab)'2 fragments. Following the same separation conditions, isoforms of these fragments have been separated and data interpretation allowed to disclose additional PTMs as K-clip, oxidations or deamidations. A second intermediate level has been examined by adding a reduction step to establish a more precise assessment of PTMs and isoforms from the F(ab)'2 fragment. This reduction step released the light chains from the Fd fragment to get only 25 kDa fragments to analyze. CE-ESI-MS coupling allowed to get more information particularly about low masses PTMs. The precise location and relative quantitation of each PTM has been investigated at the peptidic level induced by a tryptic digestion of the studied mAbs. The concordance of the results shows the efficiency of the CE-ESI-MS coupling to characterize mAbs and highlight the need of the multi-level combination to get a comprehensive characterization of biotherapeutics.

Intact monoclonal antibodies separation and analysis by sheathless capillary electrophoresis-mass spectrometry.

Capillary electrophoresis-mass spectrometry coupling is a growing technique in biopharmaceutics characterization. Assessment of monoclonal antibodies is well known at middle-up and bottom-up levels to obtain information about the sequence, post-translational modifications and degradation products. Intact protein analysis is an actual challenge to be closer to the real protein structure. At this level, actual techniques are time consuming or cumbersome processes. In this work, a 20 minutes separation method has been developed to optimize characterization of intact monoclonal antibodies. Thus, separation has been done on a positively charged coated capillary with optimized volatile background electrolyte and sample buffer. Three world-wide health authorities approved monoclonal antibodies have been used to set up a rapid and ease of use method. Intact trastuzumab, rituximab and palivizumab isoforms have been partially separated with this method in less than 20 minutes under denaturing conditions. For each monoclonal antibody, 2X-glycosylated and 1X-glycosylated structures have been identified and separated. Concerning basic and acidic variants, potential aspartic acid isomerization modification and asparagine deamidation have been observed. Accurate mass determination for high-mass molecular species remains a challenge, but the progress in intact monoclonal antibodies separation appears very promising for biopharmaceutics characterization.