In vitro methods for phototoxicity and photocarcinogenicity testing of drugs

In vitro methods for phototoxicity and photocarcinogenicity testing of drug s Phototoxicity is an acknowledged property of some UV and/or visible light a bsorbing substances some of which are used as pharmaceuticals or in cosmeti c preparations. In recent years attention has been called upon the fact tha t toxic intermediates that are generated upon photoactivation of a substanc e cart also lead to DNA damage. Such damage may lean to mutated/initiated s kin cells which in turn can contribute to an elevated skin cancer risk. The method of choice choice to test for. photo-related skin carcinogenesis is a 1-year study in genetically hairless mice in which the formation of skirt papilloma and their latency time are assessed. Here, in vitro test approac hes to test for photogenotoxicity can be used in a tiered assessment approa ch asking the use of in vitro genotoxicity tests for prediction of rodent/h uman carcinogenicity. In the past few years some effort has been put into t he evaluation for such systems, in particular standard test protocols have been generated for the in vitro photo-micronucleus test and the in vitro ph oto-comet assay with Chinese hamster V79 cells. The data that have been pro duced so far show promising results regarding the implementation of these s ystems in a tiered approach for photocarcinogenicity assessment of UV- and/ or visible light absorbing substances but the systems will have to be valid ated in further collaborative studies.