Deamidation Can Compromise Antibody Colloidal Stability and Enhance Aggregation in a pH-Dependent Manner

Monoclonal antibodies must be both chemically and physically stable to be developed into safe and effective drugs. Although there has been considerable progress in separately understanding the molecular determinants of antibody chemical and physical stability, it remains poorly understood how defects in one property (e.g., chemical stability) impact the other property (e.g., physical stability). Here, we have investigated the impact of a common chemical modification (deamidation) on the physical stability of two monoclonal antibodies as a function of pH (from pH 3.8 to 7.4). Interestingly, we find that deamidation has significant, antibody-specific impacts on physical stability at low pH values that are common during antibody purification. Deamidation causes increases in self-association and/or aggregation at low pH (3.8), and a key contributor to this behavior appears to be deamidation-dependent increases in antibody hydrophobicity at low pH. Our findings highlight pH-dependent impacts of deamidation on antibody colloidal stability and aggregation, which are important to understand in order to improve the development and production of potent antibody therapeutics with high chemical and physical stabilities.