title: Separation of oxidized variants of a monoclonal antibody by anion-exchange.
abstract: Monoclonal antibodies are subject to a variety of degradation mechanisms, therefore orthogonal techniques are required to demonstrate product quality. In this study, the three individual antibodies comprising a multi-antibody drug product, XOMA 3AB were evaluated by both cation-exchange (CEX) and anion-exchange chromatography (AEX). In contrast to CEX analysis which showed only a single, broad peak for the force-oxidized antibodies, AEX analysis of Ab-A (pI=7.6) revealed two more basic peaks. Ab-B (pI=6.7) bound but exhibited only a single major peak while Ab-C (pI=8.6) flowed through. Peptide mapping LC/MS analysis of the isolated Ab-A fractions demonstrated that the basic peaks resulted from oxidation in a complementary determining region (CDR). Differential scanning calorimetry (DSC) analysis of the oxidized Ab-A species showed a decrease in the Fab melting point for the oxidized species consistent with unfolding of the molecule. Greater/lesser surface exposure of ionic residues resulting from a conformational change provides a likely explanation for the dramatic shift in retention behavior for the Ab-A oxidized variants. Peptide mapping analysis of the Ab-B antibody showed, in contrast to Ab-A, no detectable CDR oxidation. Hence, the lack of separation of oxidized variants in Ab-B can be explained by the absence of CDR oxidation and the associated changes in secondary/tertiary structure which were observed for oxidized Ab-A. In summary, anion-exchange HPLC shows potential as an orthogonal analytical technique for assessing product quality of monoclonal antibody therapeutics. In the case of the XOMA 3AB drug product, two of the antibodies bound and one, Ab-A, exhibited separation of CDR oxidized variants.
authors.affiliation: XOMA (US) LLC, 2910 Seventh St., Berkeley, CA 94710, USA. teshima@xoma.com
authors.forename: Glen
authors.initials: G
authors.lastname: Teshima
authors.forename: Ming-Xiang
authors.initials: MX
authors.lastname: Li
authors.forename: Rahima
authors.initials: R
authors.lastname: Danishmand
authors.forename: Chidi
authors.initials: C
authors.lastname: Obi
authors.forename: Robert
authors.initials: R
authors.lastname: To
authors.forename: Carol
authors.initials: C
authors.lastname: Huang
authors.forename: Jacob
authors.initials: J
authors.lastname: Kung
authors.forename: Vafa
authors.initials: V
authors.lastname: Lahidji
authors.forename: Joel
authors.initials: J
authors.lastname: Freeberg
authors.forename: Lauren
authors.initials: L
authors.lastname: Thorner
authors.forename: Milan
authors.initials: M
authors.lastname: Tomic
mesh_terms: D000838:Anions; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D019274:Botulinum Toxins, Type A; D002152:Calorimetry, Differential Scanning; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange / Q000379:methods*; D022801:Complementarity Determining Regions / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D010449:Peptide Mapping / Q000379:methods*; D014357:Trypsin
chemical_list: D000838:Anions; D000911:Antibodies, Monoclonal; D022801:Complementarity Determining Regions; D010446:Peptide Fragments; D014357:Trypsin; D019274:Botulinum Toxins, Type A