Characterization of dermal sensitization potential for industrial or agricultural chemicals with EpiSensA

Abstract

The regulatory community is transitioning to the use of nonanimal methods for dermal sensitization assessments; however, some in vitro assays have limitations in their domain of applicability depending on the properties of chemicals being tested. This study explored the utility of epidermal sensitization assay (EpiSensA) to evaluate the sensitization potential of complex and/or “difficult to test” chemicals. Assay performance was evaluated by testing a set of 20 test chemicals including 10 methacrylate esters, 5 silicone‐based compounds, 3 crop protection formulations, and 2 surfactant mixtures; each had prior in vivo data plus some in silico and in vitro data. Using the weight of evidence (WoE) assessments by REACH Lead Registrants, 14 of these chemicals were sensitizers and, six were nonsensitizers based on in vivo studies (local lymph node assay [LLNA] and/or guinea pig studies). The EpiSensA correctly predicted 16/20 materials with three test materials as false positive and one silane as false negative. This silane, classified as weak sensitizer via LLNA, also gave a “false negative” result in the KeratinoSens™ assay. Overall, consistent with prior evaluations, the EpiSensA demonstrated an accuracy level of 80% relative to available in vivo WoE assessments. In addition, potency classification based on the concentration showing positive marker gene expression of EpiSensA was performed. The EpiSensA correctly predicted the potency for all seven sensitizing methacrylates classified as weak potency via LLNA (EC3 ≥ 10%). In summary, EpiSensA could identify dermal sensitization potential of these test substances and mixtures, and continues to show promise as an in vitro alternative method for dermal sensitization.

Reconstructed human epidermis‐based testing strategy of skin sensitization potential and potency classification using epidermal sensitization assay and in silico data

“…The EpiSensA successfully assesses the sensitizing potential of complex mixtures such as silicone-based compounds, surfactant mixtures, and crop-protection formulations (Mizumachi et al, 2021) by the RTS when compared with the LLNA. However, this LLNA result was reported to be probably a false positive, as confirmed by the human repeat insult patch test and human maximization test results (Natsch et al, 2023;Urbisch et al, 2015).…”

“…The EpiSensA successfully assesses the sensitizing potential of complex mixtures such as silicone‐based compounds, surfactant mixtures, and crop‐protection formulations (Mizumachi et al, 2021). It allows the direct topical application of materials on the RhE, mimicking the condition of animal testing such as the LLNA.…”

Adjuvants in fungicide formulations can be skin sensitizers and cause different types of cell stress responses

“…In this study, we have investigated 3 fungicides, 3 adjuvants, and 3 associated fungicide formulations for their skin sensitizing properties in a DC cell-based model. Studies using in vitro methods for skin sensitization assessment in the context of agricultural chemicals have been published [38] , [39] , [40] , [41] , however, to our knowledge none with the chemicals investigated here or with focus on the mechanisms of potential cocktail effects. For some of the chemicals and PPPs, animal and/or human data indicating their skin sensitizing capacity/potency is available ( Table 1 ).…”