2.4. In Chemico Skin Sensitization: Direct Peptide Reactivity Assay (DPRA) (OECD 442C)

The direct peptide reactivity assay (DPRA) is an in chemico method which quantified the remaining concentration of cysteine- or lysine-containing peptide after 24 h incubation with the test chemical at 25 °C. Relative peptide concentration was measured by HPLC (Waters, Milford, MA, USA) with gradient elution and UV detection (220 nm). Cysteine and lysine peptide percent depletion values were calculated for a prediction model (Table 1). This model allowed to classify the test chemical to one of four reactivity classes used to support the discrimination between sensitisers and non-sensitisers. The study is carried out according to the OECD guideline 442C (2015).

Cysteine 1:10/lysine 1:50 prediction model