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Continuing our education in the comet assay

Earlier this month, the European Environmental Mutagen Society (EEMS) held its annual meeting in Lancaster, UK.  This year, the meeting was hosted by UKEMS (United Kingdom Environmental Mutagen Society) and preceding the event, there was a Continuing Education Program, which specialised on the comet assay. The session focussed on the regulation of the comet assay within the GeneTox test battery.

Experts from all over Europe gathered to share their findings and opinions on the recent developments and future of the comet assay. It is expected that the OECD guideline for the comet assay will be published in the autumn of this year.   This is good news, as this guideline has been long-awaited and the revised ICH S2 “guideline for genotoxicity testing and data interpretation for medicines intended for human use” recommends the comet assay as a second genotoxicity endpoint.

One of the largest concerns about including the comet assay in the test battery is the potential for inter-laboratory variation within the results.  Discussions suggested that ‘proper experimental performance’ is crucial to creating control comet data which fall in the required ‘low, reproducible range’.   The session also covered the correct interpretation of comet data, which should include an assessment of other supportive information.  Analysing comet assay data may trigger further experimentation in order to reach final genotoxicity-related conclusions.

Specific case studies were presented which included the combination and integration of the comet assay into repeat dose toxicity studies.  The data presented demonstrated that the comet assay can be combined with a variety of genotoxicity endpoints. In addition, results from the EFPIA (European Federation of Pharmaceutical Industries and Associations) preclinical development committee, who had asked a group of comet assay experts to collect, analyse and interpret comet data, were presented.  Then, the discussions moved onto the subject of what is acceptable in regulatory terms.  It was concluded that regulatory bodies have been accepting comet data (based on the ICH guidelines) and although there are no universal acceptance criteria, it seem the regulators will look at the comet data on a case-by-case basis.