Definition and dynamic control of a continuous chromatography process independent of cell culture titer and impurities

Advances in cell culture technology have enabled the production of antibody titers upwards of 30 g/L. These highly productive cell culture systems can potentially lead to productivity bottlenecks in downstream purification due to lower column loadings, especially in the primary capture chromatography step. Alternative chromatography solutions to help remedy this bottleneck include the utilization of continuous processing systems such as periodic counter-current chromatography (PCC). Recent studies have provided methods to optimize and improve the design of PCC for cell culture titers up to about 3 g/L. This paper defines a continuous loading strategy for PCC that is independent of cell culture background and encompasses cell culture titers up to about 31 g/L. Initial experimentation showed a challenge with determining a difference in change in UV280 nm signal (ie. Delta UV) between cell culture feed and monoclonal antibody (mAb) concentration. Further investigation revealed UV280 nm absorbance of the cell culture feedstock without antibody was outside of the linear range of detection for a given cell pathlength. Additional experimentation showed the difference in Delta UV for various cell culture feeds can be either theoretically predicted by Beer's Law given a known absorbance of the media background and impurities or experimentally determined using various UV280 nm cell pathlengths. Based on these results, a 0.35 mm pathlength at UV280 nm was chosen for dynamic control to overcome the background signal. The pore diffusion model showed good agreement with the experimental frontal analysis data, which resulted in definition of a Delta UV setpoint range between 20 and 70% for 3C-PCC experiments. Product quality of the elution pools was acceptable between various cell culture feeds and titers up to about 41 g/L. Results indicated the following Delta UV setpoints to achieve robust dynamic control and maintain 3C-PCC yield: similar to 20-45% for titers greater than 10 g/L depending on UV absorbance of the HCCF and similar to 45-70% for titers of up to 10 g/L independent of UV absorbance of the HCCF. The strategy and results presented in this paper show column loading in a continuous chromatography step can be dynamically controlled independent of the cell culture feedstock and titer, and allow for enhanced process control built into the downstream continuous operations. (C) 2017 Elsevier B.V. All rights reserved.