Selection of Chemicals for the Development and Evaluation of In Vitro Methods for Skin Sensitisation Testing

Advances in the understanding of the biological mechanisms underlying skin sensitisation, and the need to comply with recent regulatory requirements, have favoured the development of alternative approaches, some of which may provide promising screening or partial replacement methods. However, efforts are still required to identify more-robust predictive endpoints, and to further optimise existing methods to be integrated into a testing strategy, with a view to achieving the full replacement of the current animal tests. The European Centre for the Validation of Alternative Methods (ECVAM) and the European Cosmetics Association (Colipa) have been collaborating with the aim of identifying a core set of reference chemicals for test method development and/or optimisation. The use of a common set of reference chemicals in the method development phase, would facilitate an early assessment of the performance of a method with respect to existing tests, and of its possible contribution to a testing strategy. By applying pre-defined criteria, existing databases were mined, and a list of 16 chemicals, including 12 positive controls, of which four require metabolic activation to act as sensitisers, and four negative controls, was collated. The chemicals and the criteria used for their selection are presented.