A typical process to develop a mammalian cell line for recombinant protein manufacturing. DOI:10.3390/ph6050579
Chinese hamster ovary (CHO) cells are the backbone of modern biopharmaceutical manufacturing, especially in the production of monoclonal antibodies (mAbs) and other therapeutic proteins. Derived from the ovary cells of the Chinese hamster (Cricetulus griseus), CHO cells are known for their adaptability to different culture conditions, capability to perform human-like glycosylation, and robust productivity.
Why Are CHO Cells Important for Biologic Production?
CHO cells are favored in biopharmaceutical manufacturing for their ability to produce glycosylated proteins. Unlike bacterial or yeast cells, which lack the machinery for human-compatible post-translational modifications, CHO cells can process proteins in a way that closely mimics human cells. This makes CHO cells highly suitable for producing therapeutic proteins with low immunogenicity—meaning they are less likely to trigger immune reactions when administered to patients.
The popularity of CHO cells is reflected in the fact that around 70% of FDA-approved therapeutic proteins are produced using CHO cells.1 Additionally, these cells can be genetically modified to meet specific manufacturing requirements, making them a versatile and scalable platform for the production of monoclonal antibodies and other biotherapeutics.
The Process of Producing Antibodies in CHO Cells
Producing antibodies in CHO cells involves a series of carefully controlled steps to ensure high yield, purity, and stability of the final product. Here’s an overview of the key stages:
Cell Line Development: The production process begins with the development of a CHO cell line that can stably express the desired antibody. This involves transfecting the cells with genes encoding the antibody and selecting for cells with high productivity.
Optimization of Culture Media and Conditions: To maximize cell density and productivity, the culture media and environment are optimized. CHO cells are typically grown in serum-free media, reducing contamination risks and enabling easier downstream processing.
Fed-Batch Culturing: In fed-batch culture, nutrients are incrementally added to sustain cell growth over an extended period, allowing the cells to produce large quantities of antibodies. This approach is widely used in industrial settings due to its high yield and adaptability to large-scale bioreactors.
Bioreactor Scaling and Process Control: As production scales up, conditions such as pH, temperature, and dissolved oxygen must be carefully monitored. Studies have shown that controlling pH at specific levels can improve antibody yield and quality. For example, in a recent study on the EA5 antibody, maintaining a pH of 7.2 in a 15 L bioreactor led to higher yields and better glycosylation quality, critical factors for therapeutic efficacy.2
Purification and Quality Control: Once the antibodies are harvested, they undergo a series of purification steps, including chromatography, to ensure that impurities are removed. Quality attributes such as glycan structures, aggregation levels, and monomer content are rigorously tested to ensure the final product meets regulatory standards.
Benefits of Using CHO Cells for Antibody Production
Human-like Glycosylation: CHO cells can glycosylate proteins, meaning they add carbohydrate molecules that are essential for the stability and function of therapeutic antibodies. This glycosylation closely resembles that of human cells, reducing the risk of immunogenicity in patients.
High Productivity and Scalability: CHO cells can achieve high cell densities and productivity in large-scale bioreactors, making them cost-effective for producing large quantities of antibodies.
Adaptability to Culture Conditions: CHO cells can be adapted to grow in serum-free and chemically defined media, minimizing contamination risks and simplifying downstream processing.
Regulatory Acceptance: CHO cell-derived biologics have a long track record with regulatory agencies such as the FDA and EMA, giving manufacturers confidence in their regulatory pathway for new products.
Challenges and Future of CHO Cell-Based Antibody Production
While CHO cells are highly effective for antibody production, there are still challenges associated with their use. These include:
Metabolic By-Product Accumulation: In fed-batch cultures, metabolites like lactate can accumulate, leading to toxic conditions that may reduce cell viability and productivity. To counteract this, advanced process control strategies and optimized media formulations are continually being developed.
Maintaining Consistent Product Quality: Consistency in antibody glycosylation and other critical quality attributes (CQAs) is essential. Variations in glycan structures can influence the antibody’s activity, half-life, and immune interactions, making robust control of culture conditions crucial.
Addressing Regulatory Requirements for New Antibody Formats: As the industry advances, there is increasing interest in complex antibody formats, such as bispecific antibodies and antibody-drug conjugates. These novel formats present additional regulatory and manufacturing challenges, as they often require even more stringent control over glycosylation patterns and stability.
Despite these challenges, ongoing research and process innovations are pushing the boundaries of what can be achieved with CHO cells. Genetic engineering approaches, such as CRISPR, are being used to create CHO variants with improved traits, such as faster growth rates or enhanced protein folding capabilities.3 Furthermore, the use of automation and data analytics in bioreactor monitoring promises to improve process efficiency and product consistency, allowing manufacturers to meet the increasing demand for high-quality therapeutic antibodies.
References:
Li, W., Fan, Z., Lin, Y., & Wang, T. (2021). Serum-Free Medium for Recombinant Protein Expression in Chinese Hamster Ovary Cells. Frontiers in Bioengineering and Biotechnology, 9, 646363. https://doi.org/10.3389/fbioe.2021.646363
Liang, K., Luo, H., & Li, Q. (2024). Optimization of the Process of Chinese Hamster Ovary (CHO) Cell Fed-Batch Culture to Stabilize Monoclonal Antibody Production and Overall Quality: Effect of pH Control Strategies. Fermentation, 10(7), 352. https://doi.org/10.3390/fermentation10070352
Glinšek, K., Bozovičar, K., & Bratkovič, T. (2023). CRISPR Technologies in Chinese Hamster Ovary Cell Line Engineering. International Journal of Molecular Sciences, 24(9), 8144. https://doi.org/10.3390/ijms24098144
