Charge Variants Characterization and Release Assay Development for Co-Formulated Antibodies as a Combination Therapy

MAbs. 2019 Apr;11(3):489-499. doi: 10.1080/19420862.2019.1578137. Epub 2019 Feb 20.


Combination therapy is a fast-growing strategy to maximize therapeutic benefits to patients. Co-formulation of two or more therapeutic proteins has advantages over the administration of multiple medications, including reduced medication errors and convenience for patients. Characterization of co-formulated biologics can be challenging due to the high degree of similarity in the physicochemical properties of co-formulated proteins, especially at different concentrations of individual components. We present the results of a deamidation study of one monoclonal antibody component (mAb-B) in co-formulated combination antibodies (referred to as COMBO) that contain various ratios of mAb-A and mAb-B. A single deamidation site in the complementarity-determining region of mAb-B was identified as a critical quality attribute (CQA) due to its impact on biological activity. A conventional charge-based method of monitoring mAb-B deamidation presented specificity and robustness challenges, especially when mAb-B was a minor component in the COMBO, making it unsuitable for lot release and stability testing. We developed and qualified a new, quality-control-friendly, single quadrupole Dalton mass detector (QDa)-based method to monitor site-specific deamidation. Our approach can be also used as a multi-attribute method for monitoring other quality attributes in COMBO. This analytical paradigm is applicable to the identification of CQAs in combination therapeutic molecules, and to the subsequent development of a highly specific, highly sensitive, and sufficiently robust method for routine monitoring CQAs for lot release test and during stability studies.

Keywords: Immunotherapy; co-formulated combination antibodies charge variant; combination therapy; complementarity-determining regions; critical quality attribute; deamidation; focused peptide mapping; monoclonal antibody; multi-attribute method.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / chemistry*
  • CHO Cells
  • Complementarity Determining Regions / chemistry*
  • Cricetulus
  • Drug Therapy, Combination
  • Humans
  • Immunoglobulin G / chemistry*
  • Quality Control


  • Antibodies, Monoclonal
  • Complementarity Determining Regions
  • Immunoglobulin G