Determining a point of departure for skin sensitization potency and quantitative risk assessment of fragrance ingredients using the GARDskin dose-response assay
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Abstract
Potency and quantitative risk assessment are essential for determining safe concentrations for the formulation of potential skin sensitizers into consumer products. Several new approach methodologies (NAMs) for skin sensitization hazard assessment have been developed, validated, and adopted in OECD test guidelines. However, work is ongoing to develop NAMs for predicting skin sensitization potency on a quantitative scale for use as a point of departure (POD) in next-generation risk assessment (NGRA). GARDskin Dose-Response (DR) is an adaptation of the validated GARDskin assay (OECD TG 442E), and the readout of the assay is a quantitative potency prediction similar to the No Expected Sensitization Induction Level (NESIL) value (µg/cm2). The goal of this study was to evaluate the performance of the GARDskin DR assay for potency prediction of fragrance ingredients. One hundred (100) fragrance ingredients from a reference database covering varied structural reactivity domains and potency were tested in GARDskin DR. Materials tested had varied protein-binding reactivity alerts, including Schiff base, Michael addition, SN2, and acylation. Potency categories were predicted with a total accuracy of 37% and an approximate accuracy (exact match or off by 1 category) of 81%. Combining predicted weak and very weak categories increased total accuracy to 53% and approximate accuracy to 98%. The mean prediction error for the NESIL and local lymph node assay (LLNA) EC3 was 3.15- and 3.36-fold, respectively. Based on the results of this study, GARDskin DR is a promising predictor of skin sensitization potency with an applicability domain covering a wide range of fragrance ingredient reaction mechanisms, increasing the confidence in using the assay to conduct NGRA, ultimately reducing the need for animal testing.
Plain language summary
This study focused on testing a new in vitro method, GARDskin Dose-Response (DR), to predict the quantitative potency of fragrance ingredients in causing skin sensitization. This potency is important for setting safe levels of chemicals in consumer products. The GARDskin DR assay, based on an existing skin sensitization test (OECD TG 442E), provides a quantitative measure of potency similar to the No Expected Sensitization Induction Level (NESIL). One hundred (100) fragrance ingredients with different chemical structures and reactivity patterns were tested. The assay accurately distinguished between sensitizers and non-sensitizers for 81% of the materials, and also correctly predicted their approximate potency categories. The results show that GARDskin DR is a promising tool for predicting quantitative potency for skin sensitization risk, helping to reduce animal testing and support safer product development.
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