The quality of a purified biopharmaceutical product is judged by its structural and functional characteristics as well as impurity profiles and stability. Product- or process-derived effects on quality attributes can lead to changes in pharmacokinetics and pharmacodynamics of the drug product as well as immunogenicity, often stalling product submission and approval or batch release. Here, the effects of resin ligand density and buffer pH on purity and stability of two mAbs: IgG1 and IgG4, were studied. Monodisperse CEX resin particles with sulfopropyl ligand densities ranging from 0.05 to 0.28 mol/L were manufactured using jetting technology. The purified mAbs were evaluated for changes in their higher order structure including aggregates and isoforms when undergoing binding and elution steps from these resins.<br/>Ligand densities above 0.10 mol/L and pH below 5.0 were a cause of significant peak splitting for the IgG4 molecule, and 60% loss in product recovery. Higher ligand densities provided an increased number of protein-ligand interactions and stronger adsorption. In turn, it led to on-column unfolding and irreversible aggregation detected with a novel fluorescent dye method. Loss of protein structure was confirmed when a stabilizing agent, arginine, was introduced into the process buffers resulting in a significant increase in product recovery. IgG1 was found to be unaffected by the changes in ligand density as it was more thermally and chemically stable than IgG4 resulting in overall higher step yield of &gt;80%.<br/>The effect of ligand density and buffer pH on product recovery and purity were heavily dependent on the general stability of the molecule. Resins with lower ligand densities are recommended for the processes where buffer additives and pH fail to provide desired results.

Ion exchange resin ligand density determines mAb stability and recovery

ACS Fall 2021

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