Discovery of a Chemical Modification by Citric Acid in a Recombinant Monoclonal Antibody

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• 作者：Chris Chumsae ; Liqiang Lisa Zhou ; Yang Shen ; Jessica Wohlgemuth ; Emma Fung ; Randall Burton ; Czeslaw Radziejewski ; Zhaohui Sunny Zhou
• 刊名：Analytical Chemistry
• 出版年：2014
• 出版时间：September 16, 2014
• 年：2014
• 卷：86
• 期：18
• 页码：8932-8936
• 全文大小：278K
• ISSN：1520-6882

文摘

Recombinant therapeutic monoclonal antibodies exhibit a high degree of heterogeneity that can arise from various post-translational modifications. The formulation for a protein product is to maintain a specific pH and to minimize further modifications. Generally Recognized as Safe (GRAS), citric acid is commonly used for formulation to maintain a pH at a range between 3 and 6 and is generally considered chemically inert. However, as we reported herein, citric acid covalently modified a recombinant monoclonal antibody (IgG1) in a phosphate/citrate-buffered formulation at pH 5.2 and led to the formation of so-called 鈥渁cidic species鈥?that showed mass increases of 174 and 156 Da, respectively. Peptide mapping revealed that the modification occurred at the N-terminus of the light chain. Three additional antibodies also showed the same modification but displayed different susceptibilities of the N-termini of the light chain, heavy chain, or both. Thus, ostensibly unreactive excipients under certain conditions may increase heterogeneity and acidic species in formulated recombinant monoclonal antibodies. By analogy, other molecules (e.g., succinic acid) with two or more carboxylic acid groups and capable of forming an anhydride may exhibit similar reactivities. Altogether, our findings again reminded us that it is prudent to consider formulations as a potential source for chemical modifications and product heterogeneity.