Cryopreservation is the process of using ultra-low temperatures to preserve living cells and tissues for a prolonged time period.
In a typical immunotherapy commercial manufacturing workflow, cells may be selectively isolated from peripheral blood or tumour tissues, genetically engineered, activated and expanded to relevant doses, harvested, packaged and cryopreserved, before transporting the final cellular product to the site of clinical administration. At the clinical site, the cryopreserved cells are eventually thawed and infused into patients awaiting treatment.
Importance of cryopreservation:
Cryopreservation has become an integral part of the manufacturing process of many cellular therapies as it sometimes precedes cell culture (by preserving the starting cellular material before beginning large-scale manufacturing) and generally follows cell expansion. The flexibility that comes with storing the cells at multiple points in time during manufacturing helps to design and build a customized workflow.
A notable benefit of cryopreservation is that it can be incorporated in both types of transplant manufacturing workflows as follows: a patient-specific therapy, like an autologous therapy; and/or an “off-shelf” allogeneic therapy. This enables patients with variable medical conditions to access cells for treatment.
In case of immune cell-based cancer therapies, the success of a therapy relies upon infusion of highly-viable cells post-thaw that effectively recognize and destroy the target tumour cells. High-quality cells can be produced when following best practices during manufacturing, such as by selecting Good Manufacturing Practices (GMP) grade or compatible cryoprotective agents (CPA), and control rate freezing equipment with appropriate cooling profiles for immune cells. This ensures product consistency and maintains cell efficacy.
In addition, cryopreservation of cellular therapies helps to:
- Quarantine donor cells and final products to allow extended microbiological testing;
- Coordinate and transport the final product according to the patient’s treatment plan; and,
- Extend the shelf-life of the final product prior to patient administration.
Challenges in cryopreservation:
A major challenge in cryopreservation is ensuring cell survival during freezing and while thawing cells prior to infusion. Suboptimal cryopreservation can lead not only to batch-to-batch variability in cell viability and recovery, but also lowers potency. Optimizing the cryopreservation process is critical for avoiding osmotic shock and membrane damage, which may cause cell death post-freezing.
Standard cooling profiles may not be universally applicable to preserve cells of various tissue and donor source, as they may have differing biological responses to cryopreservation. Improper use of freezing parameters can lead to artificial selection of subpopulations with genetic characteristics divergent from the original parent population of interest. Hence, new freezing protocols may have to be designed and developed specifically for each cell product, rather than using legacy protocols adapted from academic or historical workflows.
Lastly, regulatory requirements will drive the documentation needs, storage and thawing conditions and selection of reagents, as the final manufactured product must be robust and reproducible.
Designing cryopreservation processes to effectively overcome these challenges is paramount to ensure cell quality and potency. Please read our next post that focuses on top considerations to design a cryopreservation process.
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