Modern analytical ion-exchange chromatography is one of the conventional tools used for assessment of product-related quality attributes in bio-therapeutic monoclonal antibodies (mAbs). Here, we present an approach to resolve, identify, and quantify product-related substances of therapeutic mAb at its intact molecular level by cation exchange (CIEX) HPLC coupled directly to electrospray ionization - quadrupole time of flight mass spectrometry (ESI-QTOF-MS). This method utilizes pH gradient elution mode comprised of ammonium formate buffer components, and a weak cation exchange column as stationary phase. Furthermore, ion-mobility mass spectrometry (IM-MS) provided additional insights on its higher order structure. Also, orthogonal assays such as conventional CIEX-HPLC, high resolution capillary isoelectric focusing, peptide mapping, spectroscopic, and fluorescence methods were used considerably to support the findings. Additionally, an in vitro assay was included to assess the associated impact on Fc mediated function. Overall, the developed method with simultaneous detection of UV peak area percentage at 280 nm and native ESI-MS is found to be a rapid and robust analytical tool for direct assessment of structural and purity attributes, process optimization, product development, and to decipher the relevant role of micro-variants on quality, stability, and clinical outcomes.
Copyright © 2018. Published by Elsevier B.V.