Testing short-life cell and gene therapeutics for microbiological contamination is a challenge because they usually need to be administered before the result of a compendial sterility test becomes available. This is why manufacturers are implementing alternative rapid methods that take only a fraction of the time. Estelle Alvergnas and Lamin Jallow, two experts on rapid microbial technologies, discuss how flexible rapid testing can serve the different needs of ATMP manufacturers.
Which rapid detection technologies are available for microbial QC?
Estelle Alvergnas: USP <1071> gives an overview of several rapid technologies deemed suitable for release testing of sterile short-life products, including ATP bioluminescence, nucleic acid amplification, respiration, and solid phase cytometry. For some of these technologies, dedicated chapters have been drafted, for example, USP <73>for ATP bioluminescence-based methods. The gold standard for compendial sterility testing of filterable samples involves membrane filtration, so rapid methods that are also filtration-based and thus also report results in CFUs are easier to compare and validate.
Lamin Jallow: All rapid methods significantly reduce the time-to-result—to exactly how long depends mostly on the spectrum of organisms you need to cover (see my earlier article). Most contaminants grow fast, so rapid methods will usually detect these within a day, or even faster. But then there are slow-growing organisms that can take three, four, or five days to detect. That’s a lot shorter than the 14 days a compendial sterility test will take, though probably still longer than you would like for your short-life therapeutic.
Are there ways to reconcile product safety and the efficiency and speed of your process?
Lamin Jallow: Testing for levels of contamination along the entire manufacturing process can increase your confidence in the safety of your processed cell or gene product. If, for example, you test your raw materials, media, and intermediates for their bioburden, and the results are within the alert limits you have set, you will reduce the probability of getting a disappointing sterility test result at the very end. A USP <61>bioburden test gives a quantitative result which, unlike a yes/no sterility test, can indicate by how much you are off the mark as your process progresses toward completion. Should your rapid bioburden test results indicate that levels are too high, you can take corrective action before moving on. If they are routinely within your limits, there may even be justification to validate your rapid sterility test for results a day or two earlier.
Estelle Alvergnas: This is why we designed a solution for both rapid sterility and rapid bioburden testing, the Milliflex® Rapid System 2.0. It is based on membrane filtration, bioluminescence detection of emerging microcolonies’ ATP, and image analysis using dedicated software. Two of the three required small-footprint instruments can be used for both rapid tests. Of course, sampling and membrane filtration set-ups may differ, as these tasks must be performed in a Grade A environment for the sterility test. However, the application of reagents and colony detection are done the same way, on the same instruments, with the detection tower’s software capable of microcolony detection as well as enumeration in CFUs. The instruments do not need to be moved from one place to another when switching between the two rapid tests.
How do you validate a system for both rapid sterility and rapid bioburden testing?
Estelle Alvergnas: In principle, they are separate tasks. However, with the Milliflex® Rapid System 2.0 there is a huge overlap. Much of the validation work can be used for both rapid methods because of common technology, instruments, and consumables, and this is reflected in the validation studies we have published for the two applications. Two of my colleagues focused on the validation of rapid sterility testing in an earlier article. For bioburden, some extra validation needs to be done because it’s a quantitative assay. It is worth noting that bioburden testing is gaining regulatory attention for ATMPs, as the FDA’s January 2024 industry guidance on CAR T-cell products suggests. Using the same platform for both rapid sterility and rapid bioburden testing involves significantly less validation and implementation work, staff training, and investment into instrumentation than if you go for two different systems, or for a rapid sterility solution that won’t support rapid bioburden testing should you need this capability at a later date.
Lamin Jallow: A system validated for both rapid sterility and rapid bioburden testing gives manufacturers of ATMPs the flexibility to better adapt to the specific requirements determined in their risk-based approach, which takes into account the nature and stability of their product, the time to grow relevant microbial strains, the health status of the patient and other factors. Rapid bioburden testing increases the flexibility further if based on membrane filtration as any sample volume from 100 µL in added diluent to several hundred milliliters or more can be used, depending on the test sensitivity you want.
Find out more about the 21 CFR Part 11 compliant Milliflex® Rapid System 2.0 for rapid sterility and bioburden testing & get in touch with our microbial QC testing experts. www.SigmaAldrich.com/milliflex-rapid
Author Details
Lamin Jallow - Microbiology Technology Specialist, MilliporeSigma; Burlington ; MA; USA, An affiliate of Merck, KGaA Darmstadt, Germany; Estelle Alvergnas - Global Product Manager, Pyrogens testing and Rapid technologies, Millipore SAS, Molsheim, France, An affiliate of Merck, KGaA Darmstadt, Germany.
Publication Details
This article appeared in American Pharmaceutical Review:Vol. 27, No. 3April 2024Pages: 32-33
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