Characterization of Excipient Effects on Reversible Self-Association, Backbone Flexibility, and Solution Properties of an IgG1 Monoclonal Antibody at High Concentrations: Part 1

Many challenges limit the formulation of antibodies as high-concentration liquid dosage forms including elevated solution viscosity, decreased physical stability, and in some cases, liquid-liquid phase separation. In this work, an IgG1 monoclonal antibody (mAb-J), which undergoes concentration-dependent reversible self-association (RSA), is characterized in the presence of 4 amino acids (Arg, Lys, Asp, Glu) and NaCl using biophysical techniques and hydrogen exchange-mass spectrometry. The 5 additives disrupt RSA, prevent phase separation, and reduce solution viscosity to varying extents. These excipients also cause decreased turbidity, reduced average hydrodynamic diameter, and increased relative solubility of mAb-J in solution. The RSA disrupting efficacy of the positively charged amino acids is greater than either negatively charged amino acids or NaCI. As measured by hydrogen exchange-mass spectrometry, anionic excipients induced more alterations of mAb-J backbone dynamics at pH 6.0, and weak Fab-Fab interactions likely remained with the addition of either cationic or anionic excipients at high protein concentrations. Along with a companion paper examining a different mAb with a different molecular mechanism of RSA, these results are discussed in the context of various excipient strategies to disrupt protein-protein interactions to formulate mAbs at high protein concentrations with good stability profiles and favorable pharmaceutical properties for subcutaneous administration. (C) 2020 American Pharmacists Association (R). Published by Elsevier Inc. All rights reserved.