Routes to improve binding capacities of affinity resins demonstrated for Protein A chromatography

Protein A chromatography is a well-established platform in downstream purification of monoclonal antibodies. Dynamic binding capacities are continuously increasing with almost every newly launched Protein A resin. Nevertheless, binding capacities of affinity chromatography resins cannot compete with binding capacities obtained with modern ion exchange media. Capacities of affinity resins are roughly 50% lower. High binding capacities of ion exchange media are supported by spacer technologies. In this article, we review existing spacer technologies of affinity chromatography resins. A yet known effective approach to increase the dynamic binding capacity of Protein A resins is oligomerization of the particular Protein A motifs. This resembles the tentacle technology used in ion exchange chromatography. Dynamic binding capacities of a hexameric ligand are roughly twice as high compared to capacities obtained with a tetrameric ligand. Further capacity increases up to 130 mg/ml can be realized with the hexamer ligand, if the sodium phosphate buffer concentration is increased from 20 to 100 mM. Equilibrium isotherms revealed a BET shape for the hexamer ligand at monoclonal antibody liquid phase concentrations higher than 9 mg/ml. The apparent multilayer formation may be due to hydrophobic forces. Other quality attributes such as recovery, aggregate content, and overall purity of the captured monoclonal antibody are not affected. (C) 2016 Elsevier B.V. All rights reserved.