Speed Showdown

6th October 2024

Symcel’s calScreener+™ vs. alternative microbial methods for rapid sterility testing in ATMP quality control

Navigating the landscape of rapid sterility testing presents a challenge, particularly when it comes to advanced therapy medicinal products (ATMPs) like CAR-T cell therapies. These types of treatments are especially tricky because of their often short shelf-life and are more prone to contamination due to the very nature of being made from living cells, which doesn’t allow for a final sterilization step (21 CFR Part 610 – General Biological Products Standards).

Compendial sterility testing, to make sure products were sterile and safe, would take 14 days, which is too slow. This led to the development and implementation of rapid microbial methods that can deliver results in about 7 -10 days for the final release. But even with this improvement, these times are still too long and fail to meet the demand for rapid testing solutions.

The industry is in urgent need of methods that can clear products in less than three days. This sets a new bar for cGMP compliance, making sure patients are safe and get their treatments on time – creating a critical need for faster and more reliable alternatives (Gebo and Lau, 2020).

Biocalorimetry championed by Symcel’s calScreener+™

Biocalorimetry, also known as Isothermal Microcalorimetry (IMC), is a growth-based method that provides a direct and continuous measurement of released heat, a measure of the metabolic rate of living cells.

This is a game-changer for detecting living microorganisms, especially in rapid microbial sterility testing for product release and in-process testing. The calScreener+™ detects even the smallest amounts of metabolic heat from living microorganisms. With this high sensitivity, it objectively detects contaminations originating from a single cell (LOD 1) even in small-volume samples. This makes it a reliable tool that meets the standards for the release of short shelf-life products as outlined in USP <1071>. (USP〈1071〉, 2024)

Biocalorimetry with the calScreener+™ stands out because it measures continuously and in real-time, catching any contaminant as it hits the detection threshold of replicating cells, in most cases before the total test window closes. Matched with the rapid detection of pathogenic organisms, this capability can make it possible to implement intermediate release or conditional release within just one day. It also supports early intervention and contamination source mitigation and helps to reduce vein-to-vein time for patients awaiting cell and gene therapy (C&GT) treatments. Additionally, an automated readout reduces manual labor, bias and simplifies the process of the release test.

Another significant benefit is the non-disruptive nature of isothermal microcalorimetry. In the event of contamination, direct downstream investigation for species identification, etc. can be started immediately. This makes the calScreener+™ particularly promising for ensuring product safety and timely delivery in cases like cell & gene therapy with short shelf lives and expensive individualized material.

Confronting Complexity: a sterility testing solution for ATMP challenges
Traditional sterility testing methods often face challenges with ATMPs due to their complex product matrices. Due to high cell densities, these products are inertly turbid or contain components that potentially inhibit microbial growth. Several alternative methods rely on filtration of the cell therapy product, where the high cell densities hinder filtration and require a prior lysis step of the cellular components. These factors can compromise the speed, accuracy, and reliability of the result and introduce additional costs. That is why a streamlined and optimized test procedure is important.

When it comes to cell and gene therapies, some testing methods face yet another hurdle – they require more of the product’s volume than what’s required for the small testing volumes of ATMPs. This calls for additional steps to concentrate the sample (Gebo and Lau, 2020), which prolongs the testing process and adds layers of complexity, increasing the chance of errors. This is why there is an urgent need for a more adaptable and efficient solution that’s up to the task of handling the unique characteristics of ATMPs.

IMC is recognized as one of the candidate technologies for rapid microbial sterility testing under USP General Chapters (Bonnevay et al., 2017). The calScreener+™, based on IMC, is tailor-made for getting ATMPs out fast and safely, boasting:

  • Rapid real-time results in less than 3 days
  • Sensitive detection with an LOD of 1
  • Direct testing on complex products
  • Non-destructive, facilitating recovery of contaminants for further analysis
  • Low-volume sample sufficiency without the fuss of filtration
  • Detects only viable microorganisms
  • Automated readout, objective result
  • Speed up product release with the calScreener+™: the fastest growth-based assay with direct inoculation

The calScreener+™ can solve all the needs of today’s sterility testing for cell and gene therapies. It tackles challenges that traditional and alternative methods often struggle with, including the detection of environmental isolates such as molds  (England et al., 2019). We demonstrated timely detection of different species of fungi Cladosporium cladosporioides (37 h), Penecillium. venetum (39 h), Penecillium chrysogenum (49 h), Aspergillus brasiliensis (44 h).

The method excels at not only detecting fungi but also accurately and fast detects pathogenic bacteria including slow-growing species like Cutibacterium acnes. It has shown effectiveness, detecting bacteria such as Staphylococcus aureus in as little as 9.5 hours, Clostridium sporogenes in 17 hours, and Cutibacterium acnes in 59 hours, all within remarkable timeframes and using the media and temperature conditions recommended by official compendia. (https://symcel.com/applications/rapid-sterility-testing)

To ensure our testing method works well across different types of samples, we’ve tested a range of cell therapy and antibody products, even those containing cryoprotectants. We introduced a small number of contaminants (less than 5 CFU per test) from six USP <71> recommended microbial strains, along with C. acnes. Among the cell lines tested was the T-cell line Jurkat. In this test, C. acnes was detected within 72 hours. The detection times for other microbes, such as S. aureus and C. sporogenes, were just as quick as they were in samples without any cell material (see above). We noted that when used at sufficient dilution, the presence of the product didn’t have a major impact on the detection time.

The calScreener+™ enables the fastest sterility test for live cell products available to date, ensuring final results in under three days. Its straightforward approach to sample measurement, in compliance with USP <71> recommended media formulations and temperature ranges, eliminates the need for additional probes, reagents, or sample manipulation, maintaining test accuracy and simplicity.

With the calScreener’s™ direct metabolic readout, contaminants are objectively detected. Through continuous data readings, it keeps track of the data all the time, so if it detects something, you can intervene immediately. For most organisms this is usually within 12 hours but no more than three days. Its suitability for small volumes, and various product matrices, and detection of a wide range of microorganisms, add to its adaptability, ensuring that ATMPs meet high sterility standards and are thus safe.

We’ve come a long way and onward we go
The calScreener+™ is making waves in the world of sterility testing for ATMPs. With isothermal calorimetry, a technology that detects live microorganisms with unprecedented speed and sensitivity, we are changing the game. With this innovation, we are tackling the tough parts of testing cell-based therapies. We are talking about achieving intermediate release within just one day, and final product release in less than three days – that is cutting the industry standards by over a half. Its ability to test directly on the product and follow the USP <71> guidelines for media and temperatures sets it up to be the go-to for making sure treatments are safe and high quality, all while staying ahead in the rapidly evolving field of cell-based therapies.

We’re not stopping there; we’re committed to making the calScreener+™ even better, focusing on faster and more accurate results that are easier to get. With optimized detection algorithms, we’re fine-tuning the analysis so that it’s quicker and more precise in pointing out any contamination. Our goal is to enable a detection within two days by 2025, which would be 70% faster than what’s usually done.

Let’s work together
Here at Symcel, we are experts in biocalorimetry to detect microorganisms. But we’re not content to just lead the way — we want to team up, face new challenges, and revolutionize microbial detection together. If you are looking to make your testing more efficient, let’s have a conversation.

References
21 CFR Part 610 — General Biological Products Standards [WWW Document], n.d. URL https://www.ecfr.gov/current/title-21/part-610 (accessed 3.28.24).

Bonnevay, T., Breton, R., Denoya, C., Cundell, A.M., Duguid, J., Jenkins, M., Julian, F.M., Kenney, J., McDaniel, A., Miller, M., Moulin, G., Newton, D., Hussong, D., Patel, K., Richter, S., Roesti, D., Tidswell, E., Zhang, Y., Zigler, S., Tirumalai, R.S., 2017. The development of compendial rapid sterility tests. Pharmacopeial Forum 43.

England, M.R., Stock, F., Gebo, J.E.T., Frank, K.M., Lau, A.F., 2019. Comprehensive Evaluation of Compendial USP<71>, BacT/Alert Dual-T, and Bactec FX for Detection of Product Sterility Testing Contaminants. Journal of Clinical Microbiology 57, e01548-18. https://doi.org/10.1128/JCM.01548-18

Gebo, J.E.T., Lau, A.F., 2020. Sterility Testing for Cellular Therapies: What Is the Role of the Clinical Microbiology Laboratory? J Clin Microbiol 58, e01492-19. https://doi.org/10.1128/JCM.01492-19

General Chapter, 〈1071〉 Rapid Microbial Tests for Release of Sterile Short-Life Products: A Risk-Based Approach., 2024. https://doi.org/10.31003/USPNF_M12457_02_01

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