Replacing Animals for Skin Sensitization Testing Gains Momentum as OECD Publishes Test Guidelines for Non-Animal Based Methods
GAITHERSBURG, MD - Determination of skin sensitization potential is a critical toxicological endpoint in the safety assessment of new chemicals. Although the Guinea Pig Maximization Test (GPMT) and in vivo Local Lymph Node assay (LLNA) have traditionally been used to assess skin sensitization, recent activity has focused on the development of novel non-animal assays for the endpoint. As a culmination of these efforts, the Organization for Economic Cooperation and Development (OECD) published the following test guidelines for non-animal skin sensitization testing on 5 February 2015: ARE-Nrf2 Luciferase Test Method (also referred to as the KeratinoSensTM Assay) (OECD TG 442D) and Direct Peptide Reactivity Assay (DPRA) (OECD TG 442C). The Institute for In Vitro Sciences (IIVS), a participating laboratory in the validation studies for the KeratinoSensTM assay, is pleased to offer each of these non-animal assays for detecting skin sensitizers.
The KeratinoSensTM assay is a cell-based reporter gene assay which identifies skin sensitizers by measuring the induction of luciferase under the control of the antioxidant response element (ARE) derived from the human AKR1C2 gene. In the proposed Adverse Outcome Pathway (AOP) leading to skin sensitization, this method addresses the second key event, gene expression in keratinocytes associated with the antioxidant/electrophile response element (ARE)-dependent pathway. The IIVS laboratory participated in the validation studies led by Givaudan to assess the KeratinoSensTM assay which demonstrated that the assay was transferable, reproducible, and predictive as compared to the historical animal data. Following extensive review of the data by EURL ECVAM, the assay was endorsed by ECVAM, and the OECD followed with a test guideline. Based on our experiences with the assay, IIVS has developed a GLP protocol for broader use, and since 2011 has offered the assay as a commercial service.
The DPRA is an in chemico assay that identifies dermal sensitizers based on their reactivity with synthetic peptides containing either lysine or cysteine. The assay models the first key event, protein reactivity, in the skin sensitization AOP. Through collaboration with the method developers at Procter & Gamble, IIVS scientists received training, successfully transferred the technology in-house, and are offering the assay as a commercial service. IIVS is currently exploring the use of the DPRA method in combination with the KeratinoSensTM assay to improve predictions.
Given the complex cascade of events leading to skin sensitization, it is generally thought that an integrated testing approach combining multiple assays and in silico predictive tools will be needed to fully replace the animal based methods. There is a significant effort underway to ascertain how the non-animal assays may be combined to both qualitatively and quantitatively assess skin sensitization most effectively. IIVS toxicologist Dr. Kimberly Norman served as a member of the OECD Expert Panel on skin sensitization, and IIVS offers both OECD approved methods for non-animal skin sensitization testing, as part of our GLP-compliant laboratory testing services. Please contact us for information on these skin sensitization assays and how they may be used as part of an integrated testing strategy within your existing testing program.