DPRA.
OECD TG 442C: Direct Peptide Reactivity Assay
The Direct Peptide Reactivity Assay (DPRA) assay is an in chemical method used to assess skin sensitization hazard of chemicals.
The assay evaluates a substance’s ability to react with synthetic model peptides, providing a binary classification that identifies test substances as either skin sensitizers or non‑sensitizers.
Targeting Key Event 1 of the skin sensitization AOP
DPRA is included in OECD Test Guideline 442C and addresses Key Event 1 (KE1) of the Adverse Outcome Pathway (AOP) for skin sensitization: Covalent binding to skin proteins.
Best suited for neat, straightforward organic chemicals
Available data* show that DPRA performs best for neat, soluble organic chemicals with direct protein reactivity, and may also be applicable to mixtures of known composition. Substances requiring metabolic activation (pro‑haptens) or containing metals fall outside the assay’s applicability domain.
*Reference: OECD TG 442C, Appendix I
A first-line KE1 assay supporting DASS under OECD TG 497
In regulatory context requiring multiple assays addressing different key events, DPRA serves as a first‑line KE1 method that efficientily complements GARDskin (OECD TG 442E), supporting Defined Approaches for Skin Sensitization (DASS) under OECD TG 497:
- 2o3 Defined Approach: Combination of DPRA and GARD®skin for hazard identification.
- Integrated testing strategy (ITS): Combination of DPRA, GARD®skin, and in silico methods to support hazard identification and GHS/CLP potency sub-categorization 1A or 1B.
