Ultrafiltration concentration of monoclonal antibody solutions: Development of an optimized method minimizing aggregation

For the production of highly concentrated monoclonal antibody intermediate solutions in the course of downstream processing, ultra filtration is the industry standard in manufacturing scale. Key challenges are to achieve high end concentrations and to reduce both process time and aggregate formation, particularly for therapeutic proteins, intended for subcutaneous administration. Therefore, in this study the effects of operational parameters on permeate flux and aggregation in the concentrated solutions were investigated. An optimized ultrafiltration concentration method was developed based on systematic screening of cross-flow rate and transmembrane pressure at different protein concentrations in the retentate. In this method flow and pressure values are adjusted depending on the prevailing retentate concentration. The resulting three stage protocol reduces process time and assures a low aggregate burden compared to concentration processes operated at constant flow and pressure conditions. Flow and pressure profiles were set and recorded in lab scale using an automated tangential flow filtration system which has been shown to adequately reflect process conditions at manufacturing scale. The formation of IgG aggregates was monitored by turbidity measurement, SE-HPLC, light obscuration, dynamic light scattering and a microscopic method. These techniques allow characterization of a wide range of aggregate sizes of soluble and insoluble aggregates that can occur during processing. In addition, FT-IR spectroscopy was performed to investigate secondary structure of the aggregates, revealing different quantities of structurally perturbed protein depending on applied flow and pressure conditions. Finally, the concentrated material derived from the optimized method showed improved processability at sterile filtration which is an important manufacturing step prior to storage.