Comparison of different protein concentration techniques within preformulation development.

Highly concentrated antibody solutions are of increasing importance in the pharmaceutical industry. During production highly concentrated solutions are usually prepared by tangential flow filtration (TFF). Since this technique is often not applicable in the early phase of formulation development, where the available amounts of protein are commonly very small, small scale techniques like dialysis or ultrafiltration with stirred cells or centrifugal filters have to be employed. In this study the small scale techniques were compared to tangential flow filtration, with regard to the quality and stability of the concentrated products. The achievable concentration of a protein, when starting from a model antibody solution with 10mg/ml, was also assessed. Concentrations above 100mg/ml could be obtained with all techniques, however with different product qualities. The stability of the highly concentrated solutions (100 mg/ml) was analyzed by turbidity measurements, size exclusion chromatography (SEC), SDS-PAGE and isoelectric focusing (IEF) after storage at 25 and 40°C for 8 weeks. Solutions prepared by dialysis exhibited the smallest degree of instability, whereas those manufactured by centrifugal filtration revealed the best comparability to products obtained by tangential flow filtration with regard to the results of isoelectric focusing, turbidity measurements (UV-vis) and size exclusion chromatography. Stability differences were observed within all analytical methods, primarily after storage and not directly after the concentration process.