Analysis of recombinant monoclonal antibody isoforms by electrospray ionization mass spectrometry as a strategy for streamlining characterization of recombinant monoclonal antibody charge heterogeneity

A therapeutic recombinant monoclonal antibody analyzed by cation-exchange chromatography exhibited a heterogeneous profile composed of approximately 10 isoforms. The peaks were isolated and characterized by electrospray quadrupole time-of-flight mass spectrometry (ESI-q-TOF–MS), N-terminal Edman sequencing, peptide mapping, and other techniques. Acidic (lower pI) peaks were found to represent deamidated and sialyated species. Higher pI peaks were found to contain N- and C-terminal heavy-chain variants. Biological activities of the more abundant isoforms were found to be comparable. An approach streamlining the characterization of antibody charge heterogeneity is proposed.