The implementation of in silico, in chemico, and in vitro methods addressing key events in the skin sensitization Adverse Outcome Pathway (AOP) has led to the development of a non-animal testing strategy to assess skin sensitization.
AOP-based testing for skin sensitization is now specifically requested for REACH, EPA, and EU Cosmetic Directive submissions. With current non-animal methods, it is very challenging to assign a potency (i.e., LP/GHS sub-categories 1A and 1B) to a chemical that is classified as a skin sensitizer. In the case of REACH, animal testing is often still required to get a potency prediction in case of a positive classification in non-animal tests.
In cooperation with BASF and Givaudan, scientists at our Den Bosch site introduced and validated the kinetic Direct Peptide Reactivity Assay (kinetic DPRA). The kinetic DPRA is a modification of the DPRA (OECD TG 442C) and uses kinetic rates of peptide cysteine depletion to determine, and distinguish between, two levels of skin sensitization potency (i.e., to discriminate between CLP/GHS sub-categories 1A and 1B).
For this purpose, several concentrations of a test item are incubated with the cysteine peptide at six incubation times (10-1,440 min) and the remaining non-depleted cysteine peptide is determined at each time point using a fluorescence readout. Kinetic rates measured with this assay have a strong quantitative correlation to sensitizing potency and can therefore be used in defined approaches with a quantitative data integration procedure for skin sensitization potency assessment.
Now available to our clients, the kinetic DPRA is a powerful tool to distinguish between two levels of skin sensitization potency (i.e., CLP/GHS sub-categories 1A and 1B).