Insights from native mass spectrometry and ion mobility-mass spectrometry for antibody and antibody-based product characterization

•Native MS allows rapid intact mAb analysis with limited sample handling.•High resolution native MS is required to distinguish species with similar masses.•IM-MS reveals mAb conformations.•Drug load profiles and average DARs of ADCs can be assessed by native MS and IM-MS.•The formation of bispecific mAbs and mAbs/antigen complexes can be monitored by native MS and IM-MS. Over the past 15 years, monoclonal antibodies (mAbs) have emerged as the most successful class of therapeutics. Their specific structural and functional properties make them highly effective treatments for various diseases. Most therapeutic mAbs are based on chimeric, humanized or human G immunoglobulins (IgGs) selected from three isotypes (1, 2 and 4). IgGs are large and highly complex multimeric glycoproteins. They are constituted of a mixture of isoforms including macro and micro-variants that must be extensively characterized prior to their investigation as a drug candidate in clinical trials. The IgG backbone is also used to design more potent but also more complex biopharmaceuticals such as antibody-drug conjugates, bispecific antibodies, Fc-fusion proteins, and antibody mixtures to name a few. Mass spectrometric approaches in combination with electrophoretic and chromatographic separation methods play a central role in the analytical and structural multi-level (top, middle and bottom) characterization of these compounds. Importantly, techniques allowing the characterization of intact mAbs and related products under non-denaturing conditions are attracting increasing interest. Here, we review the current state of the art in native mass spectrometry and ion mobility methods for the characterization of mAbs and mAb-based products.