Relevance and reliability of the PREDISAFE assay in the COLIPA eye irritation validation program (phase 1)

The 6th Amendment of the European Directive on Cosmetics induces a potential ban on animal testing for cosmetic ingredients and finished products. In this new context, COLIPA (The European Cosmetic Toiletry and Perfumery Association) has initiated an international multicentric study with the main goal of validating available alternatives to in vitro methods for assessing the eye irritation potential of cosmetic raw materials and formulations. In order to test undiluted and hydrophobic ingredients and formulations, a cytotoxicity test named PREDISAFE was incorporated into our internal battery of in vitro tests for 3 years. This cell culture test based on the neutral red release procedure was prevalidated with several cosmetic formulations and used systematically by comparison with internal benchmarks. In this article, the defined prediction model and the protocol used in the COLIPA eye irritation program are described, and furthermore the PREDISAFE assay results obtained during Phase I of the above mentioned study are presented and discussed in detail. The statistical analysis proves clearly a great interest in the PREDISAFE test for the prediction of eye irritation potential of cosmetic formulations. Its strong compatibility for a wide category of finished products associated with its ease of use offer relevant advantages for a routine use in the ocular irritancy screening in the cosmetics industry. This paper also explains the reasons for false negative and false positive in vitro tests results and describes possible technical modifications to avoid these wrong predictions. At the end, some recommendations for the Phase II of the COLIPA study are considered with the main objective to prove that a multivariable analysis could be useful to find the best battery of in vitro assays for acceptance by the regulators for the replacement of the Draize eye irritation test.