Growth Media Considerations
Raw material consumables for cell and gene therapies, excluding equipment, fall into two main categories; growth support for living systems (cell culture), and vectors for alteration of cellular material or disease states. The highly bespoke nature of cell and gene therapies and the need to scale-up manufacturing mean that long-term reliable raw material sourcing is crucial. The pandemic has made regional redundancy in the supply chain more important than ever to mitigate events such as lockdowns. The vast permutations of the cell and gene therapy design space fuel the strong demand for raw material supplies by the industry.
Contract Development and Manufacturing Organizations (CDMOs) play an increasingly important role in cell and gene therapy production. Key research services supplier Charles River Laboratories (CRL) will expand its manufacturing business, pursuing a “technology agnostic” strategy that emphasizes innovation and flexibility. In 2021 CRL bought Cognate BioServices and its subsidiary Cobra Biologics adding cell and gene therapy manufacturing and capacity. Vigene Biosciences, a gene therapy-focused CDMO, was also acquired.
Cell growth media must be given as big a consideration as the cells themselves in manufacturing. Chemically defined media is a must to meet the FDA’s stringent CGMP criteria of comparability and quality control for lot release. In addition, viral vector production is particularly vulnerable to adventitious agents as the vector could mask other impurities. The use of defined media without any animal products can eliminate this concern.
The pandemic heightened scrutiny of cell culture component supplies as companies sought to circumvent supply chain weaknesses and upgrade outdated processes to reflect the very latest process knowledge in the field. (1)
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Ideal manufacturing processes cannot accept undefined media as inputs. If only undefined extracts such as serum are known to support the growth of certain therapeutic cell types, further research into that cell type’s basic growth requirements is needed. A batch of growth media that contains a variable fetal serum component, for example, could compromise the quality of a whole product batch.
The advantages of serum-free media include: • Less batch-to-batch variability. • Increased definition of cellular components in assays. • Straightforward purification and downstream processing. • Easier to interpret cellular function assays. • Cellular mediators are more detectable. • Better growth/ productivity. • Controls are clearer
There are several types of defined media commercially available including serum-free, protein-free, chemically defined media, and animal origin-free products. Common growth medias have been specifically optimized to support cells regularly used to produce viral vectors for gene therapies, such as Chinese Hamster Ovary (CHO), Human Embryonic Kidney (HEK) 293, Per.C6, several non-human mammalian cell lines, and insect cell lines. Bacterial, yeast, and algal systems may also be used for plasmid extraction.
Optimizing the supply chain, using the available resources most effectively, is key to mitigating unforeseen circumstances such as COVID-19. Media performance should be optimized using the fewest possible components to reduce the supply chain dependencies. Such a strategy reduces costs and secures the supply chain, ensuring that products can be manufactured continuously long after eventual market approval regardless of circumstances, such as COVID-19 and geopolitical unrest that limit supply chains.
The cell therapy developer must determine if each component of their product production media is sustainable for the predicted commercial lifetime.
Supply chain sustainability is key to long-term success, given increasingly restricted global resources. The cell therapy developer must determine if each component of their product production media is sustainable for the predicted commercial lifetime. A compromise in manufacturing efficiency or product specifications may be required to ensure supply chain continuity in exceptional circumstances.
There have been several challenges in upstream cell therapy production with the supply chain. In upstream manufacturing, host cell lines require raw materials such as growth media and bioreactors along with storage systems such as liquid nitrogen tanks. These component systems and tools have been effected by supply chain issues.
Transfection efficiencies can be improved with advanced transfection reagents and the development of stable producer cell lines, in addition to viral vectors. Some of the most commonly used viral vectors are Adenovirus (AdV), Adeno-Associated (AAV), and Lentiviral (LV). Plasmids and advanced transfection reagents have come to the forefront as alternatives to viral vectors, however, the pandemic has been a boon to viral vector manufacturing. Industrial-scale bioreactors are essential for CGTs. Bioreactors and integrated equipment are part of the upstream processing and cell expansion and microfluidics-based process improvement platforms are becoming increasingly important. The pandemic has triggered several emerging opportunities for upstream processes.
There have also been downstream cell therapy bioprocess bottlenecks and developments including the downstream processing of viral vectors. Because the cells themselves are the product, cell therapy downstream processing requires specialized equipment and continues to be an area of active innovation. Supply chain disruptions are a risk due to the limited hardware solutions available (2). The The pandemic has also led to process improvements that allowed COVID-19 mRNA vaccines such as those by Moderna and Pfizer to be produced.
References
1. “Global Serum-Free Media Market 2021 Research Study with Trends and Opportunities to 2027 Impact of COVID-19.” MarketWatch, MarketWatch, 14 March 2022.
2. Pigeau, G.M., Csaszar, E., Dulgar-Tulloch, A. Commercial Scale Manufacturing of Allogeneic Cell Therapy, Front. Med., 22 August 2018.
