Heterogeneity of recombinant antibodies: linking structure to function.

Structural heterogeneity of recombinant IgG1 antibodies derives from variations in conserved as well as unique structural features. Common sources of heterogeneity include Fc glycosylation, partial heavy chain C-terminal Lys processing, Fc methionine oxidation, hinge-region cleavage, and the glycation of Lys residues. Aspartate residues that are isomerized to iso-aspartate were detected by cation exchange or hydrophobic interaction chromatography for trastuzumab and omalizumab, respectively. Unpaired cysteines were detected in omalizumab using Ellman's reagent, with the thiol-containing Fab resolved using hydrophobic interaction chromatography after papain digestion. Structural variations that cause chromatographic resolution may indicate the presence of a form with reduced potency.