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Toxikon on in-vitro toxicological evaluation of materials and the potential of using AMES assay

Ahead of his presentation at Extractables & Leachables USA 2017, we spoke with Peter Cornelius, R&D Scientist at the Toxikon about in-vivo (USP <88>) and in-vitro (USP <87>) biocompatibility testing of materials, their research into identifying the right testing conditions, performing AMES testing as an alternative and more.

Your presentation looks at ‘In-Vitro toxicological evaluation of materials and the potential of using AMES assay’, can you briefly explain what this means and what your presentation will cover?

A USP Workshop, held in June 2016, addressed the potential upcoming changes and revisions in the in-vivo (USP <88>) and in-vitro (USP <87>) biocompatibility testing of materials to be used in pharmaceutical and medical applications. During this workshop, it was observed that the current status of these biocompatibility screening tests, as they are currently described in the USP, were not really fully covering the needs of the pharmaceutical and medical industry anymore in addressing the basic safety qualification issues of materials of construction (MoC). One of the potential alternative tests that were suggested during that workshop was to perform an AMES test on these MoC. However, it was also mentioned that USP needed to be careful not to replace non-adequate tests by another one.

It is clear that, although the standard has interesting features, the current ISO 10993-3 standard for AMES testing on medical devices may not be really “fit for purpose” to support the safety qualification of materials. Our research is trying to identify the right testing conditions (extraction conditions, ratio’s, selection of solvents that are AMES compatible and allow to perform an exhaustive extraction, concentration factors, positive controls, etc…) for such an AMES test to guarantee that a new “modified AMES test” could really contribute to the safety qualification – from a mutagenicity perspective – of materials in both pharmaceutical and medical applications. This new test should also allow making the correlation between the result of an AMES test and the evaluation of an extraction profile, obtained via a rigorously performed controlled extraction study.

What are the benefits of using this method and what can it hope to achieve?

The problem that the pharmaceutical and medical industries are facing at this moment, when performing exaggerated or exhaustive extraction studies on MoC’s is that it potentially generates a long list of extractable compounds, of which, in some cases the identity – and by consequence, their toxicity – is not always known.

If the research that we are conducting would ever come to an AMES test that is a practical and adequate test that would be “fit for purpose”, it could address some of these concerns and may be incorporated in the overall safety qualification of materials. It ultimately could lead to a better and more targeted analytical safety qualification, this through subsequent extractables or leachable studies.

Where do you foresee extractable and leachable testing headed in the future?

I think that the testing of extractable and leachable testing is still, for the most part, based upon an analytical chemistry approach. If we want to look into the future, we need to look at the latest developments in analytical instrumentation to find clues for the future. In this respect, I think the E/L labs will generally adopt accurate mass analytical technology. One of the main challenges in E/L testing is identification of compounds, as only a unique identification of a compound allows performing an in-depth safety assessment.   

What are you most looking forward to at the E&L US 2017 conference?

When I went through the programme, there are so many extremely interesting subjects that it is very hard to choose one out of the total programme. However, if I would need to select one, it would be the one of Carsten Worsoe about the interaction of leachables with pharmaceutical drug products. Interactions of leachables with biopharmaceuticals is a new area of research, because it is growing concern for both regulators and the pharmaceutical industry. While the current safety qualifications for single use systems (eg BPOG, USP) and primary packaging for biopharmaceuticals still take the traditional route of safety qualification via PDE or threshold (SCT, AET) calculations, the concern of Immunogenicity is not yet sufficiently brought into the equation. The recent FDA Guidance document (2014) on “Immunogenicity Assessment for Therapeutic Protein Products”, however, explicitly addresses the concerns of leachables – with respect to potential immunogenicity concerns - in both primary packaging systems (eg pre-filled syringes) and single use systems for bioproduction.

It is particularly interesting for me, because, apart from the AMES development, my department also is conducting research in this area. Similar to the AMES test to assess the mutagenic potential of extracts or leachables, we are developing an in-vitro assay to assess the immunogenic potential. This assay will be based on the maturation of human dendritic cells and T-cell activation which is a parameter of an early immune response in patients.

Peter will be presenting as part of the 'Biocompatibility and safety evaluation' session at Extractables & Leachables USA 2017 this May.

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