Identification of monoclonal antibody variants involved in aggregate formation – Part 1: Charge variants

Biopharmaceutical products contain conformational and chemical variants, that are typically well characterized regarding identity and activity. However, little is known about their self-interaction propensity and tendency to unfold, which are critical characteristics for drug stability and safety. This study aimed to separate and compare charge variants of a monoclonal antibody (mAb) and to identify aggregation prone species. We show a semi-preparative cation exchange method, that we developed to separate the individual acidic and basic variants from the naïve mAb. Additionally, we demonstrate, that the yield and purity of the fractionated charge species, extracted by that method, were sufficient for subsequent analysis of aggregate content, conformation stability and self-interaction. Our analysis revealed a differently behaving acidic variant and confirmed its increased aggregation propensity by molecular modeling. During a stability study, the potentially aggregation prone charge variant posed a limited risk to the drug substance (DS). We are the first to look at the stability of single charge variants of biopharmaceuticals, and thus present manufacturers and regulatory authorities with a method to enhance drug safety.