Characterization of Conformational Instability of Monoclonal Antibodies During Chromatographic Purification.

Monoclonal antibodies represent one of the fastest-growing sectors of the biopharmaceutical industry. Their high therapeutic efficacy and reduced incidence of adverse effects compared to conventional therapies have led to an increasing demand for these products. The costliest stages of monoclonal antibody production are the separation and purification processes, which underscores the need for continuous development and optimization of applied methodologies. Active pharmaceutical ingredients must exhibit high purity and preserved biological activity in order to meet stringent regulatory requirements. Macromolecules such as monoclonal antibodies possess complex conformational structures that significantly influence their stability. The application of multi-step chromatographic processes during purification from cell culture harvests may induce structural alterations, including protein unfolding and aggregation, ultimately resulting in decreased product quality and therapeutic effectiveness. Such structural changes may also increase immunogenicity risk and reduce product shelf life, posing additional challenges for downstream processing. In addition, chromatographic media create microenvironments that differ markedly from bulk solution (e.g., high local protein concentration, confined pore spaces and heterogeneous surface chemistry). These effects can promote either self-association driven by colloidal interactions or partial unfolding followed by irreversible aggregation, depending on the unit operation and operating window. Practical mitigation is therefore rarely achieved by a single lever; instead, it requires an integrated view of resin selection, buffer composition (pH, salt type and ionic strength, and stabilizing additives), residence time and temperature, as well as an analytics strategy that combines orthogonal aggregation assays with structural probes. This work discusses the phenomena of unfolding and aggregation of therapeutic proteins, with particular emphasis on monoclonal antibodies occurring during chromatographic purification. Furthermore, key analytical methods, characterization techniques, and mitigation strategies aimed at improving product quality and reducing manufacturing costs are reviewed.