Structural comparison of two anti-CD20 monoclonal antibody drug products using middle-down mass spectrometry

Liquid chromatography-mass spectrometry (LC-MS) is an information rich analytical tool that can provide fast, robust and sensitive characterization of protein therapeutics for quality assurance and structural comparison. Herein, structural characterization of two anti-CD20 monoclonal antibodies obtained from two different sources was performed using a middle-down LC-MS strategy to determine if they can be analytically differentiated. Through the use of a specific enzymatic digestion method using IdeS with subsequent LC-MS analysis, we show that the anti-CD20 monoclonal antibody that has been approved by the FDA can be partially characterized and differentiated analytically from an Indian sourced product that lacks FDA approval. In comparison to the FDA-approved product, differential modifications to both the N- and C-termini result in increased charge heterogeneity for the Indian product. In addition, significant differences in the intensities of the observed glycoforms between the two antibodies were detected. While this study assesses only one lot of each of a FDA approved drug product and the Indian sourced drug product, the observed differences may represent process specific fingerprints that could be useful for surveillance purposes. Middle-down LC-MS analysis can be used to identify structural heterogeneities between a monoclonal antibody from different sources.