Monoclonal antibodies (mAbs) are a very important class of therapeutics. Chinese Hamster Ovary (CHO) cell is widely used for mAb production. However, CHO cells not only release process related impurities such as host cell protein (HCP) and DNA into the mAb product stream, but also create product related impurities such as mAb aggregates. Protein A chromatography is an effective capture and purification step for mAb production. Due to the specific interaction of the mAb with the Protein A ligand, most impurities can flow through the column while mAb can be captured and eluted. However, impurities do interact non-specifically with both the resin and the mAb itself, and could be carried into the elution pool. To reduce the levels of impurities, many researchers have tried to optimize the wash steps in Protein A chromatography. A variety of reagents have been used in wash steps including detergents, organic solvents, salts and excipients. Due to the different physiochemical properties of mAbs, specific reagents work well only with certain mAbs. Time-consuming screening of many wash chemicals and conditions is needed for effective clearance of impurities, mainly process related, such as HCP and DNA, and furthermore, product related impurities such as aggregates are not reduced by wash steps. Our study of Protein A chromatography demonstrates that elution pH is an effective tool to control not only process related impurities but also product related impurities. With the increase of elution pH in a certain range, mAb aggregate levels decreased while step yield was maintained. This trend was found with multiple Protein A resins from multiple suppliers. Increase of elution pH also decreased DNA and HCP levels in certain resins such as MabSelect SuRe™. The impact of increased elution pH on product quality not only was effective for the Protein A elution pool, but the same trends were also maintained after low pH viral inactivation. The results will be demonstrated and the mechanism behind the results will be discussed. The reduction in both product and process related impurities with optimized elution pH provides an additional control point, improving the product quality and overall downstream process robustness.

Impact of elution pH on product and process related impurities in Protein A chromatography

249th National Meeting (2015)

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