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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 “acidic species” 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.

The BioPhorum Development Group is an industry-wide consortium enabling networking and sharing of common practices for the development of biopharmaceuticals. Forced degradation studies (FDSs) are often used in biotherapeutic development to assess criticality of quality attributes and in comparability studies to ensure product manufacturing process consistency. To gain an understanding of current industry approaches for FDS, the BioPhorum Development GroupeForced Degradation Point Share group conducted an intercompany collaboration exercise, which included a benchmarking survey and group discussions around FDS of monoclonal antibodies. The results of this industry collaboration provide insights into the practicalities of these characterization studies and how they are being used to support the product lifecycle from innovation to marketed products. The survey requested feedback on the intended purpose, materials, conditions, number and length of time points used, and analytical techniques carried out to give a complete picture of the range of common industry practices. This article discusses the results of this global benchmarking survey across 12 companies and presents these as a guide to a common approach to FDS across the industry which can