In-Depth Characterization of mAb Charge Variants by On-Line Multidimensional Liquid Chromatography-Mass Spectrometry

In-depth characterization of charge heterogeneity is a pivotal step desired in the therapeutics antibody development. To this end, a novel on-line multidimensional liquid chromatography-mass spectrometry (MDLC-MS) method for charge variant characterization was developed to dig out potential risks on safety and efficacy. This method implemented 96-well plate fractionation and on-column preconcentration by multi-injection, thereby facilitating detection of charged species at low abundance. Eleven charge variants of mAb-A were preliminarily characterized by 2DLC(CEX × RP-C₄)-MS. TRVHS and RVHS signal peptide variants of mAb-A were found in basic peaks of the CEX profile. The results supported process development in a timely manner, and the signal peptide-containing variants with potential immunogenicity were successfully removed by an optimized purification process. The retained seven charge variants of mAb-A were further characterized by 4DLC(CEX × RP-C₄ × Trypsin×RP-C₁₈)-MS. Post-translational modifications including deamidation, cyclization of N-terminal glutamine, C-terminal lysine truncation as well as proline amidation, and methionine oxidation were identified, and their potential risks were evaluated. Biological activity of the seven charge variants was evaluated by 2DLC (CEX × FcγRIIIa). Increased FcγRIIIa receptor binding affinity was observed in the acidic variants. The MDLC-MS detection can be completed in 72 h with 1.25 mg of mAb, demonstrating to be sample-economic, time-effective, and labor-saving. It provided a powerful and timely tool for charge variant characterization and met the aggressive timeline desired for antibody development.