The commercial production of safe and effective biotherapeutic agents relies on the supply of large-scale mammalian cell cultures with the right nutrients at the right time. But for some critical amino acids, this is a challenge. Innovations in media ingredient chemistry overcome the issues and enable the delivery of soluble, stable, and usable amino acid derivatives for consistent and high-performance processes.
Mammalian cell cultures are indispensable in many areas of the life sciences and have enabled countless advances in biomedical research, such as the discovery and development of small-molecule drugs and the development and production of biologics, like antibodies and other proteins, viral vector vaccines, and cell therapies.
The culturing of mammalian cells outside of their native environment requires a growth medium, which is designed to support all of the specialized cell functions and supplies the essential nutrients to keep the cells alive and proliferating.
For example, carbohydrates provide an energy source, amino acids serve as the basic building blocks for protein synthesis, buffers and pH indicators ensure an ideal pH level, salts help maintain the correct osmotic pressure in the cells, and assorted vitamins, growth factors, hormones, and trace elements also play critical roles.
“In recent years, media formulations used for manufacturing clinical drugs have evolved from complex, animal-derived compositions to well-defined, animal origin-free, chemical compositions,” explained Christian Kessler, Global Director of Amino Acids and Peptides at the German specialty chemicals company Evonik.
“This trend increases the overall safety, consistency, and performance of the media and also overcomes the ethical challenges associated with using animal components in cell culture.”
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Consistency is key for cell culture intensification
The use of biologics is rapidly increasing and opening new possibilities for the treatment or prevention of diseases with an unmet medical need.
“It is not possible to solve all medical conditions using chemically derived, small molecule drugs,” said Kessler. “Biologics offer an elegant, alternative approach to treating critical diseases, such as cancer.”
Many of these biological therapies can only be produced with the help of mammalian cell cultures. However, the rapid growth in this area is increasing the need for greater production capacity. Hence, it is important to intensify and optimize large-scale culture processes so that they generate as much of the therapeutic material as possible.
Technologies for growing suspension cultures in large bioreactors are well established, but some new approaches, such as cell therapy, can only be realized with adherent cells, which are more difficult to scale up. Regardless of the format, successful culture intensification requires the consistent delivery of high-quality nutrients at the right time. This ensures that these fine-tuned processes work as intended and produce high yields of safe and effective biologics.
Fluctuations or variations in the nutrient supply can reduce yields or even ruin entire batches, and result in a significant financial impact. Consistency is therefore extremely critical for the generation of highly optimized biologics like monoclonal antibodies and for newer therapies such as CAR-T cells, which are highly complex and even more sensitive to fluctuations.
The need for soluble, stable, and usable amino acids
Ensuring optimal feeding of bench-scale mammalian cell cultures is typically straightforward, but once cultures are scaled up to many thousands of liters for high cell density, commercial production, the limitations become more apparent.
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“Amino acids can be problematic at the production scale,” explained Martin Schilling, Global Director of Cell Culture Ingredients at Evonik. “They are necessary for protein synthesis and other cellular functions, and they must be supplied in liquid form. Unfortunately, some amino acids are not as soluble as we need them to be, some are not as stable, and some react with other components in the culture media.”
L-glutamine, for instance, has considerably low chemical stability in solution and tends to degrade easily. This can lead to elevated levels of metabolites that negatively impact cell culture performance, product quality, and long-term stability in liquid media.
L-tyrosine exhibits poor solubility in water and culture media and cannot be prepared at the necessary pH-neutral concentrations. Raising the pH values increases its solubility but results in a caustic solution that adds safety concerns and risks dosage variations.
L-cysteine is highly reactive and readily dimerizes into L-cystine, which will often precipitate at neutral pH.
Dipeptide formulations for enhanced media processes
Evonik is helping to overcome these bioprocessing challenges and is optimizing cell culture performance with its cQrex® portfolio, an innovative range of media ingredients and amino acid dipeptide formulations.
Dipeptides consist of two identical or different amino acids joined together. They offer an alternative for supplying amino acids to production cultures, where they are taken up by cells and then broken down again into their individual amino acids.
“We have chemically coupled the key problematic amino acids with carrier amino acids to create dipeptides that overcome the chemical limitations commonly associated with the free amino acid forms,” said Schilling.
The cQrex® dipeptides from Evonik are specially designed for high-density cell culture applications. The portfolio includes different dipeptide alternatives to meet specific cell line and process requirements.
Their high stability, solubility, and bioavailability eliminate the need for high pH levels, simplifying the biologics production process and reducing production risks. The dipeptides are efficiently used by a variety of mammalian cells and actually increase productivity over alternative solutions.
“A lot of science goes into the design of these molecules,” Schilling continued. “The selection and sequence of amino acids strongly affect solubility, stability, and bioavailability of the final peptide.”
Evonik has a long history of supplying free amino acids to the cell culture space. With the cQrex® portfolio, the company has effectively combined its expertise in amino acids, GMP purification, and chemical synthesis to create an innovative solution that meets specific biochemical and biological requirements.
Kessler explained Evonik’s motivation, “We have been mostly known in the chemical realm, but helping our pharmaceutical partners develop better solutions for the well-being of patients and society fulfills our common purpose, which is to lead beyond chemistry, to improve life, today and tomorrow.”
Want to know more? Discover Evonik’s complete range of cQrex® cell culture ingredients!
Header image via Shutterstock.com. Article images via Evonik.
