Precipitation of process-derived impurities prior to capture chromatography in antibody purification offers a simple, robust, and economical method to efficiently remove Chinese hamster ovary (CHO) host cell proteins and DNA. By optimizing the major process parameters—pH, caprylic acid concentration, and mixing time—and understanding their interdependency, one can develop a cost-effective process step. When precipitation is applied directly in CHO cell culture, it combines the clarification and precipitation unit operations. The direct precipitation of contaminants results in seamless transition from upstream to downstream purification processes, particularly in high cell density and high titer cell culture. As a result, demand on the purification process is significantly lowered, and a simple two-step ion exchange process is sufficient to achieve therapeutic purity.
For those reasons, alternative technologies such as precipitation have been explored, particularly to achieve higher throughput for cell culture processes with high titers. Precipitation of the protein of interest has proven successful in food, blood, and enzyme manufacturing. For example, antibodies have been precipitated successfully at large scale by adding polymers of ethylene glycol (PEG)2 or salts3 and pH titration,4 and research-scale precipitation of contaminants by charged polymers,5 cationic detergents, or short-chain fatty acids6,7 has shown promising application at the cell culture clarified bulk (CB) stage.
In this study, we extend the application of precipitation that combines pH control and caprylic acid (a short-chain fatty acid) to remove process-derived impurities directly from CHO cell culture in the production of human monoclonal antibodies (HuMAbs).