FOLLOW-UP VALIDATION OF THE EPIDERM SKIN IRRITATION TEST (SIT): RESULTS OF A MULTI-CENTRE STUDY OF TWENTY REFERENCE TEST SUBSTANCES.

This multi-center validation study performed by scientists at BfR (ZEBET), BASF SE, the Institute for In Vitro Sciences, Inc., the Centre for Alternative and Complementary Methods to Animal Testing (zet–LSL) and MatTek Corp. demonstrated that the modified Skin Irritation Test (SIT) based on MatTek’s EpiDerm in vitro human skin tissue equivalent can be used to as stand alone assay for the prediction of skin irritating and non-irritating test substances. In April 2007, ECVAM endorsed 2 alternative test methods (EPISKIN and EpiDerm Skin Irritation Tests (SIT)) as replacements of the in vivo rabbit skin irritation test. While the EPISKIN SIT was recognized as a stand alone method, the EpiDerm SIT was endorsed for use in a tiered testing strategy, where irritating results are accepted and non-irritating results may require further testing by another method (e.g. QSAR) (1). Based on results published by Faller et al. (2,3), and analysis of results of the ECVAM validation study (4), there was evidence that the differences in the barrier properties between the 2 models were responsible for the lower sensitivity of EpiDerm SIT when using an identical protocol as used for EPISKIN. Therefore, modifications of the exposure conditions were introduced to EpiDerm SIT protocol: a) exposure time was increased from 15 min to 60 min; b) the temperature during the exposure was increased to 37°C. With these modifications, when testing chemicals from the pre-validation and validation studies, a significant increase in sensitivity (84%) was obtained, while maintaining an acceptable specificity of the method. In autumn 2007, an international multi-centre validation study was performed to evaluate reproducibility of the Modified EpiDerm method. Overall, sensitivity of 80% and specificity of 77.5 % were obtained, which is comparable to results for the EPISKIN SIT for the same set of chemicals (sensitivity of 70%, specificity 80%). In 2008 ESAC concluded that the performance of this assay met the criteria outlined to be considered to have sufficient accuracy and reliability for prediction of R38 skin irritating and non-skin irritating test substances (5). The test performance under the GHS was regarded also sufficient by an OECD Expert Group. Modified EpiDerm SIT is now implemented into the draft EU method B46 and draft OECD guideline as stand alone assay for prediction of skin irritating and non-skin irritating test substances.

Barrier properties, ECVAM, ESAC, EpiDerm, Full Replacement, In vivo rabbit skin irritation test, Irritancy, Irritation, Multi-center Validation study, R38, Skin irritancy, Skin irritation, Skin irritation test (SIT)

1-Bromo-4-chlorobutane, 1-Bromohexane, 1-Decanol, 4-Methyl-thio-benzaldehyde, A-Terpineol, Allyl heptanoate, Allyl phenoxy-acetate, Butyl methacrylate, Cyclamen aldehyde, Di-n-propyl disulphide, Di-propylene glycol, Diethyl phthalate, Heptanal, Heptyl butyrate, Hexyl salicylate, Isopropanol, Methyl stearate, Naphthalene acetic acid, Terpinyl acetate, Tri-isobutyl phosphate