Building a Robust Cold Chain for CGTs

Pharmaceutical Commerce, Pharmaceutical Commerce - October 2022, Volume 17, Issue 5

Strategies to boost the reproducibility and traceability of cell and gene therapies for more effective clinical studies and commercialization

Cell and gene therapies (CGTs) require complex manufacturing and distribution processes that are often difficult to scale.1 Unlike conventional pharmaceuticals such as small molecules and biologics, many advanced therapies are made to order and have an extremely limited shelf life. This is especially true for ex vivo therapies: living cells are collected from donors, transported to manufacturing sites, manipulated, and delivered to the patient. The separation in distance and time between each step in the process demands that cells be cryogenically frozen to maintain their viability and function.2 A temperature below the glass transition of water (Tg), about -135°C, is recommended, as it halts metabolic activity and inhibits degradation.3 Warming above this threshold, even briefly, can damage cells and threaten the efficacy of treatment.4

A robust and coordinated cold chain is, therefore, necessary to ensure that cell and gene therapies are delivered on time with high quality. This article discusses the challenges of building a cold chain for CGTs and proposes strategies to improve their reproducibility and traceability for better clinical studies and more successful commercialization.

Reproducibility protects CGT quality

Cells are at risk of damage once separated from the body. Routine handling in and out of storage or during transport can expose CGT materials to temperatures above Tg, threatening their viability and downstream efficacy. Given the large temperature differential between storage and working conditions, even short exposures to ambient temperature can lead to rapid warming for cryopreserved materials.

With a boiling point of -196°C, liquid nitrogen (LN2) is the gold standard for cryogenic storage. Samples can be safely stored in either the liquid or vapor phase of LN2. When retrieving samples from an LN2 freezer, both target and non-target (innocent) materials can experience warming.5 Cells moved from -180°C to ambient temperature will reach Tg in about 90 seconds, providing a short window of time for the removal of the target materials and safe return of the innocents. Transient warming events, especially if frequent, can significantly damage cells.6

A strong quality management system with safeguards and risk mitigation protocols is necessary to ensure that CGTs are stored safely and securely during their time outside the human body. Facilities for LN2-based cryogenic storage should follow best practices recommended by leading authorities in the industry, such as the International Society of Biological and Environmental Repositories (ISBER).7,8 For companies lacking the necessary infrastructure or expertise, storing CGT materials and clinical samples offsite with external partners is a viable alternative.

Implementing automation in the cold chain can bring major benefits to reproducibility. Pulling racks by hand to locate the target box or cassette exposes the entire rack to ambient conditions, increasing the risk of damage to innocent materials. Unlike a human, robotics can find and select samples at very low temperatures within the freezer, creating a much more controlled environment for retrieval.9 Manual workflows expose materials to temperature fluctuations that are larger, longer, and more variable than automated systems. Speed and technique can vary considerably between users and even over repeat performances of the same individual. Handling errors further increase the risk to CGT quality, such as pulling the wrong cryobag, misplacing materials, improperly securing freezer doors, and dropping racks. In contrast, a robot is highly consistent when removing and adding materials to/from the storage unit, outmatching a human in terms of reproducibility.

Traceability through the cold chain

Manufacturing and delivering ex vivo therapies is significantly more complicated than traditional pharmaceuticals. Advanced therapies not only require nascent, expensive technologies to produce but also significantly increase the burden for tracking critical materials through the cold chain. Take autologous therapies like CAR-T for example. The patient is both the donor and recipient of cells, positioning them upstream as well as downstream of manufacturing. End-to-end tracking of the product—from collection of raw materials to manipulation at the manufacturing site to administration at the clinical site—is critical for patient safety and therapeutic efficacy. Both chain of identity (linking the product back to the original donor) and chain of custody (handling information, storage conditions, and description/date/location of actions performed, etc.) must be thoroughly documented to avoid errors and provide an audit trail in compliance with regulatory standards.

Since building the necessary infrastructure for transportation logistics may be too complex or costly, many CGT companies choose to partner with third parties to ensure proper tracking and delivery of materials. CGT-specialized vendors have developed the core competencies to mitigate risk and deliver efficiencies to the supply chain.10

At manufacturing sites, automated storage can streamline many of the tedious and complicated aspects of tracking critical materials. Automated LN2 freezers have built-in software that provides real-time visibility, comprehensive event tracking, and integration with a laboratory information management system (LIMS). The processes of sample addition and removal are more controlled and simplified, especially when the system can automatically scan and register barcode-labeled materials. All transactions are automatically logged, promoting better compliance and traceability. Audit trails and cold-chain-of-custody records are substantially easier to generate and, importantly, are more accurate and thorough than those created by hand. Automated systems can also be implemented with 21 CFR Part 11 compliance in mind to better support clinical trials and commercial operations.

Advanced therapies have the promise to treat previously intractable diseases, yet their fragile and bespoke nature pose major challenges to clinical scale-up and commercial scale-out. It behooves CGT companies to maximize reproducibility and traceability in the cold chain to adequately protect the value of critical materials from collection to product administration. Incorporating automation and working with expert partners can mitigate risk in CGT manufacturing and distribution.


1. Cell and gene therapies: Delivering scientific innovation requires operating model innovation. Deloitte Insights (2020).

2. Meneghel, J., Kilbride, P. & Morris, G. J. “Cryopreservation as a Key Element in the Successful Delivery of Cell-Based Therapies—A Review.” Frontiers in Medicine. Vol. 7 (2020).

3. Hubel, A., Spindler, R. & Skubitz, A. P. N. “Storage of Human Biospecimens: Selection of the Optimal Storage Temperature.” Biopreservation and Biobanking. Vol. 12 165–175 (2014).

4. Angel, S. et al. “Toward Optimal Cryopreservation and Storage for Achievement of High Cell Recovery and Maintenance of Cell Viability and T Cell Functionality.” Biopreservation and Biobanking. Vol. 14 539–547 (2016).

5. Sample Warming During Innocent Exposures From an LN2 Freezer: Comparing Temperature, Time & Workflow Using Manual vs. Automated Systems. Azenta Life Sciences White Paper (2015).

6. Angel, S. et al. Op. Cit.

7. ISBER Best Practices: Recommendations for Repositories. 4th ed. International Society for Biological and Environmental Repositories (2018).

8. ISBER Best Practices Addendum 1: Liquid Nitrogen-Based Cryogenic Storage of Specimens. International Society for Biological and Environmental Repositories (2019).

9. Sample Warming During Innocent Exposures From an LN2 Freezer. Op. Cit.

10. Cell and gene therapies: Deloitte Insights. Op. Cit.

About the Author

Sarah Eckenrode, PhD, is Vice President, Sample & Repository Solutions, Azenta Life Sciences.