The biopharmaceutical industry relies heavily on optimized media formulation to maximize cell growth and productivity while ensuring cost-efficiency. However, significant challenges persist due to certain amino acids, including L-glutamine, L-tyrosine, and L-cysteine, which have limited stability and solubility in cell culture media. These issues often impede the intensification of bioprocesses.

To address these challenges, Evonik has developed cQrex^® peptides, a range of chemically defined, non-animal-derived peptides. These innovative compounds are soluble and stable forms of amino acids which simplify bioprocesses and enhance cell culture performance across a variety of applications. Evonik recently published a white paper, “Boosting cell culture performance with cQrex® peptides in biopharma applications”, which explores the mechanisms, benefits, and practical applications of cQrex^® peptides in mesenchymal stem cells (MSCs) and Chinese hamster ovary (CHO) cells, two critical systems in modern biomanufacturing. 

The Challenges of Amino Acid Limitations

Amino acids are indispensable for cell culture media, serving as building blocks for proteins and supporting metabolic pathways. However, three key amino acids—glutamine, tyrosine, and cysteine—pose specific challenges:

• L-Glutamine: A primary energy source for cells, but prone to rapid degradation into ammonia and pyroglutamate, which are toxic to cells.
• L-Tyrosine: Hardly soluble at neutral pH, requiring extreme pH adjustments to dissolve adequately, which complicates media preparation.
• L-Cysteine: Prone to oxidation, forming reactive oxygen species (ROS) that damage cellular and media components. Its oxidized form L-cystine requires extreme pH to solubilize.

Traditional mitigation techniques, such as preparing solutions shortly before use and adding feed media at alkaline pH, introduce complexity and increase risk for the process and operators, resulting in an inefficient and cost-intensive bioprocess.

How cQrex^® Peptides Address These Challenges

cQrex^® peptides overcome these amino acid limitations by coupling the target amino acids with stable carriers, forming peptides that are highly soluble, chemically stable, and safe for use in neutral pH environments. The peptides serve as reservoirs of amino acids, making them available to cells and allowing for higher concentrations of nutrients in media. This helps to improve cell growth and productivity.

Key properties include:

1. Chemical Stability: cQrex^® peptides remain stable in culture media, preventing degradation and oxidation.
2. High Solubility: Unlike the free amino acids, these peptides dissolve easily in pH-neutral media.
3. Non-animal-derived ingredients: cQrex^® peptides are manufactured synthetically, without the use of animal-derived materials.

Mechanisms of Peptide Uptake and Metabolism

Peptides act as dynamic nutrient sources in cell culture. Cellular transporters facilitate the uptake of peptides and intracellular enzymes cleave them , releasing the amino acids they contain.

Studies reveal that peptide metabolism is influenced by different factors such as its sequence and concentration. The regularly expanding cQrex^® portfolio offers diverse solutions for tailored optimization based on specific bioprocessing goals, such as maximizing cell growth or enhancing protein production.

cQrex^® Peptides in Cell Culture

1. Glutamine Peptides (cQrex^® AQ and cQrex^® GQ)

L-Glutamine is a vital energy source for rapidly dividing mammalian cells, but its instability poses challenges in cell culture. Evonik offers a solution with two glutamine peptides: cQrex^® AQ (L-Alanyl-L-glutamine) and cQrex^® GQ (Glycyl-L-glutamine). These peptides are chemically stable, preventing glutamine degradation and ammonia accumulation, while simplifying media preparation.

In a case study, their different uptake kinetics were highlighted:

• cQrex^® AQ: Rapidly consumed by CHO cells, promoting faster cell growth.
• cQrex^® GQ: Slower uptake, leading to higher monoclonal antibody titer.

2. Tyrosine Peptides (cQrex^® AY and cQrex^® GY)

L-Tyrosine is essential for cell metabolism and growth in cell culture, but its poor solubility at neutral pH complicates its use in concentrated media. Evonik addresses this issue with tyrosine peptides: cQrex^® AY (L-Alanyl-L-tyrosine) and cQrex^® GY (Glycyl-L-tyrosine). These highly soluble peptides enable safe and efficient inclusion in pH-neutral media. This eliminates the need for separate feeds at extreme pH, simplifying bioprocesses and reducing risks.

A case study using CHO-K1 GS cells demonstrated that supplementing commercial basal media with cQrex^® GY significantly improved productivity. Benefits included:

• Higher cell viability
• Extended production time
• Increased cell-specific productivity
• Substantial antibody titer increase (+20%).

3. Cystine Peptides (cQrex^® AC and cQrex^® KC)

L-Cysteine is a key amino acid in mammalian cells, supporting protein synthesis, glutathione production, and intracellular redox balance. However, its high reactivity in media poses challenges: it leads to the formation of reactive oxygen species (ROS) and undergoes oxidation to hardly soluble L-cystine. Evonik offers innovative solutions with cystine peptides, cQrex^® AC (N,N’-di-L-Alanyl-L-cystine) and cQrex^® KC (N,N’-di-L-Lysyl-L-cystine dihydrochloride). These derivatives are highly soluble at neutral pH and enable concentrated feed, basal, or perfusion media. A recent case study on MSCs and CHO cells demonstrated their advantages:

• Reduced oxidative stress: Unlike L-cysteine, high concentrations of cQrex^® AC and cQrex^® KC did not decrease cell viability.
• Enhanced cell proliferation: The peptides supported stronger cell growth without the adverse effects linked to high L-cysteine concentration.

Advantages of cQrex^® Peptides

The cQrex^® peptides can be either formulated in a media as replacements of challenging amino acids, or simply supplemented to existing media that are commercially available. The inclusion of cQrex^® peptides into biopharmaceutical workflows offers multiple benefits:

1. Intensified Bioprocess: Enables high concentration of nutrients in basal, feed and perfusion media without adjusting the pH, thanks to the high stability and solubility of the peptides.
2. Streamlined Bioprocess: Eliminates the need for extreme pH feeds, reducing complexity and risks.
3. Enhanced Productivity: Supports increased cell viability, extended production times, and higher protein titer, resulting in reduced production cost.

Conclusion

Evonik’s cQrex^® peptides represent a transformative advancement in cell culture media optimization. By addressing the solubility and stability challenges of amino acids like glutamine, tyrosine, and cystine, these peptides enable biopharmaceutical manufacturers to optimize bioprocesses, offering a robust solution to achieve higher yields and reduce bioprocessing cost. Their proven benefits in CHO and MSC cultures make them indispensable tools for next-generation biomanufacturing. The versatility and performance of cQrex^® peptides position them as key enablers of innovation and efficiency in the biopharmaceutical industry.

For the full white paper and data, please see Boosting cell culture performance with cQrex^® peptides in biopharma applications