Identification of multiple sources of charge heterogeneity in a recombinant antibody

Seven forms of a therapeutic recombinant antibody that binds to the her2/ne u gene product were resolved by cation-exchange chromatography. Structural differences were assigned by peptide mapping and HIC after papain digestion . Deamidation of light chain asparagine 30 to aspartate in one or both ligh t chains is responsible for two acidic forms. A low potency form is due to isomerization of heavy chain aspartate 102: the Asp102 succinimide is also present in a basic peak fraction. Forms with both Asn30 deamidation and Asp 102 isomerization modifications were isolated. Deamidation of heavy chain A sn55 to isoaspartate was also detected. Isoelectric focusing in a polyacryl amide gel was used to verify the assignments. All modifications were found in complementarity determining regions. (C) 2001 Elsevier Science B.V. All rights reserved.