Overcoming challenges in mAb polishing: A toolbox approach Monoclonal antibodies (mAbs) are essential in modern biopharmaceuticals, and their growing prevalence demands advanced, scalable purification methods. This article explores the challenges of downstream polishing and highlights the importance of a comprehensive polishing toolkit that includes a variety of chromatography options to optimize the purification process.
Monoclonal antibodies (mAbs) have transformed the biopharmaceutical landscape since the first was licensed for therapeutic use in 1986. In 2023, mAbs accounted for 70% of all drug approvals by the U.S. Food and Drug Administration (FDA), marking their highest share to date.i This growing dominance underscores the critical need for efficient and scalable production methods to meet increasing demand. As mAbs become more prevalent in treating a wide range of diseases, biopharmaceutical manufacturers must optimize both upstream and downstream processes to ensure high yields, consistent quality, and cost-effectiveness. The upstream process focuses on maximizing mAb expression through carefully selected cell lines and culture conditions, while the downstream process is designed to purify and refine the product to meet stringent regulatory standards. Purification involves multiple unit operations, including filtration and chromatography, to remove impurities and ensure product safety, potency, and purity. Continuous advancements in these processes are essential for keeping pace with the growing clinical and commercial applications of mAbs. The downstream purification process for mAbs typically begins with a capture chromatography step, often using Protein A resin to selectively bind antibodies via their Fc regions. This affinity-based capture separates the antibody from impurities, which include host cell proteins (HCPs), host cell DNA, and endotoxin, providing a higher purity starting material for further processing. Following the capture step, additional polishing steps such as ion exchange (IEX), hydrophobic interaction chromatography (HIC), or mixed-mode (MM) chromatography are employed to refine the product, remove residual contaminants, and achieve the required purity for
the final application. The polishing step is also used to remove aggregates of the mAb which can result from the use of high salt concentrations as well as the low pH conditions used for elution from the Protein A column. This article explores the challenges of downstream polishing and highlights the importance of a comprehensive polishing toolkit that includes a variety of chromatography options to optimize the purification process. Examples of the differences between polishing resins and how this can impact purification underscores the necessity of considering multiple approaches to achieve the best outcome.
Challenges in mAb polishing Optimizing the mAb polishing step is essential because no single solution fits all, and the process requires balancing trade-offs between yield, purity, time, and scalability. Variations in impurities from different expression systems, as well as differences in antibody size, charge, isoelectric point (pI), and stability necessitate tailored polishing strategies. Inefficient polishing can result in excessive impurities, antibody loss, prolonged processing times, and product instability, all of which can significantly impact the quality and safety of the final drug product. For example, the presence of too many aggregates can lead to immunogenicity issues while degradation of the antibody can reduce its potency and efficacy. These factors not only affect therapeutic performance but can also lead to regulatory hurdles, increased production costs, and potential batch failures. Therefore, a well-optimized polishing strategy is key to ensuring product consistency, safety, and clinical effectiveness.
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