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Publication | LC-MS characterization & purity assessment of a prototype bispecific antibody
Admin Sep 3, 2017 4:34:00 AM
Abstract
Bispecific IgG asymmetric (heterodimeric) antibodies offer enhanced therapeutic efficacy, but present unique challenges for drug development. The proper assembly of heavy and light chains are the cause of many of these challenges. Impurities such as symmetric (homodimeric) antibodies can arise with improper assembly. Because traditional separation-based purity assays are unable to separate or quantify homodimer impurities a new method to assess heterodimer purity of such bispecific antibody products is needed . This paper presents a liquid chromatography-mass spectrometry (LC-MS)-based method for evaluating heterodimeric purity of a prototype asymmetric antibody containing two different heavy chains and two identical light chains. The heterodimer and independently expressed homodimeric standards were characterized by two complementary LC-MS techniques: Intact protein mass measurement of deglycosylated antibody and peptide map analyses. Intact protein mass analysis was used to check molecular integrity and composition. LC-MSE peptide mapping of Lys-C digests was used to verify protein sequences and characterize post-translational modifications, including C-terminal truncation species. Guided by the characterization results, a heterodimer purity assay was demonstrated by intact protein mass analysis of pure deglycosylated heterodimer spiked with each deglycosylated homodimeric standard. The assay was capable of detecting low levels (2%) of spiked homodimers in conjunction with co-eluting half antibodies and multiple mass species present in the homodimer standards and providing relative purity differences between samples. Detection of minor homodimer and half-antibody C-terminal truncation species at levels as low as 0.6% demonstrates the sensitivity of the method. This method is suitable for purity assessment of heterodimer samples during process and purification development of bispecific antibodies, e.g., clone selection.
Keywords
Bispecific antibody; Heterodimeric antibody; LC-MS; Intact protein mass; Peptide map; Deglycosylation; Purity assay; Impurity assessment