The use of human keratinocytes in the EU/COLIPA international in vitro phototoxicity test validation study and the ECVAM/COLIPA study on UV filter chemicals

The EU/COLIPA in vitro phototoxicity study involved the testing of 30 chemi cals in Phase II, and the ECVAM/COLIPA study on UV filter chemicals involve d the testing of 20 chemicals, for which in vivo human and/or animal data w ere available. Primary human keratinocytes, from four separate male donors, were not found to be sensitive to the 5J/cm(2) WA produced by the SOL500 l amp when assayed by using the neutral red uptake endpoint, as employed with the 3T3 cells used in these international interlaboratory validation studi es. The primary human keratinocytes tested in one laboratory alongside the 3T3 fibroblasts gave consistent indications of phototoxicity with all the p hototoxicants tested in the Phase II and UV filter studies. The one excepti on was bithionol, which was predicted to be non-phototoxic in both studies. None of the non-phototoxic chemicals resulted in a positive reaction with the Photo-irritation Factor (PIF) version of the prediction model. However, when the Mean Photo Effect (MPE) prediction model version was applied (wit h a cut-off point of 0.1), one sunscreen agent, octyl salicylate, was deeme d to have phototoxic potential. The entire set of negative rated chemicals included in Phase II and in the UV filter study were also rated as non-phot otoxic by the MPE prediction model.