Accuracy in extractables and leachables (E&L) testing is a necessity—it directly impacts the reliability of results and, consequently, the safety of end users. Appropriate standards, reference materials, and techniques provide a framework for consistency and comparability in testing methodologies, but there is room for improvement in all of these areas. With the help of Sven Hackbusch, Senior Applications Scientist at Thermo Fisher Scientific, and Chongming Liu, Supervisor of E&L at SGS, we delve into the intricacies of E&L testing, the critical importance of accuracy, and the role that standards, reference materials, and techniques play in elevating the effectiveness of analytical outcomes.
The current state of E&L testing
E&L testing ensures that drug products are not contaminated by harmful substances that may be transferred from containers, closures, or manufacturing equipment, but the accuracy of this testing has been a subject of concern.
"One of the limitations in E&L testing is the need to accurately quantify unknown compounds against an analytical evaluation threshold (AET)," advises Hackbusch. "This is challenging because of the inherent variations in analyte response from the different detection techniques, especially for non-volatile and semi-volatile organic extractable compounds, which are typically measured based on their UV or MS response."
Hackbusch goes on to explain that the standard approach to this challenge is to use an uncertainty factor, but this decreases accuracy. He adds that detection techniques with lower variation in analyte responses, such as charged aerosol detection (CAD), are one potential way to overcome this challenge and lead to higher accuracy.
"Additionally, the accuracy of the compound identification for any detected extractables or leachables above the AET will have an impact on the determination of toxicological risk, as incorrect identifications could either result in the underestimation of risk, posing a hazard to patient safety, or overestimation of risk, resulting in onerous follow-up studies."
Liu echoes concerns about the arduousness of identifying unknown compounds and adds that there is a need for expanded data-sharing in this area. Liu also notes the challenge of trying to understand exactly what regulatory bodies are looking for and describes how leachable studies tend to be evaluated on a case-by-case basis. "In Formula 1, there are clear regulations for building a car, but in leachable studies, the rules are not always clear, so labs provide different results."
Improved standards for E&L testing
As Hackbusch explains, having specific E&L standards allows labs to evaluate their testing methods against known values, ensuring they are fit for the purpose of screening and quantitating E&L compounds.
He adds that the availability of a wider range of E&L standards would enable testing labs to build in-house libraries of mass spectral fragmentation data and relative response factor values. This would provide higher confidence in compound identification and estimated quantitation, boosting the accuracy of E&L testing.
Liu agrees with Hackbusch's view that there is a need for more standardization as well as access to a comprehensive database. He also notes that United States Pharmacopeia (USP) is trying to establish a mixture standard that includes 20–30 compounds in each testing method, and he hopes that these will become available in the near future.
Enhanced references and techniques
A laboratory standard is a specimen or substance used for calibration or validation, ensuring measurement accuracy, while laboratory reference materials serve as benchmarks for assessing the quality and reliability of analytical procedures and results. The use of representative reference materials is critical in identifying and quantifying leachables accurately. "Reference materials for E&L testing allow for the evaluation of a lab's testing methods in terms of the accuracy of compound identification and quantitation," explains Hackbusch. He notes that they also serve as benchmarking material, similar to reference materials used in other areas of analytical testing and untargeted analyses, such as metabolomics and proteomics.
Moreover, advanced analytical techniques, including mass spectrometry, nuclear magnetic resonance (NMR), and chromatography, can provide unparalleled insights into the composition of leachables. These techniques enable the identification and quantification of trace-level substances, further enhancing the precision of E&L testing. "Mass spectrometry, hyphenated to either liquid or gas chromatography, is an essential part of E&L testing, especially in the case of high sensitivity requirements associated with low AET testing materials," advises Hackbusch. "At sub-ppm levels, orthogonal detection techniques (UV, CAD) have an insufficient response to provide the necessary sensitivity and specificity."
Liu concurs with the emphasis on hyphenated techniques centered around mass spectrometry. "High-resolution mass spectrometry provides clear identification of molecular composition, and in particular, tandem mass spectrometry can provide very detailed structural information." He notes that this can be particularly useful during the screening process.
A collaborative approach to E&L testing
From a regulatory and industry standpoint, it's vital to foster collaboration among regulators, industry stakeholders, and analytical experts to advance E&L testing accuracy. "It is essential to have an exchange of information between all involved parties to discuss industry best practices, as it is ultimately in everyone's interest to increase E&L testing accuracy for patient safety," says Hackbusch. "The development of enhanced standards or techniques without combined input and buy-in from regulatory bodies, industry, and CRO partners may not yield the necessary advances."
As Liu notes, regulations are evolving every few years, and it can be difficult to keep up with guidelines that have been extended from 10 pages to 100 pages. He would like to see more dialogue and cooperation between regulatory agencies and testing laboratories. "We need some practical resolutions to improve cost and time efficiency while achieving the core goal of lowering uncertainty." He also highlights training involving relevant stakeholders as a crucial component of future success.
Enhancing the accuracy of E&L testing is not just a technical endeavor; it's a moral and regulatory imperative. The safety and well-being of patients depend on the precision of these tests. With updated standards, representative reference materials, and advanced analytical techniques, the pharmaceutical industry can ensure the integrity of its products and, most importantly, safeguard the health of those it serves.
This article is featured in our May 2024 publication, Pharmaceutical Purity and Precision. Find out what’s happening in the world of pharmaceutical impurity analysis and learn about the latest topics and techniques.
