Recommended DNT Reference Chemical Test Set For In Vitro Assay Development*

New approach methodologies (NAMs) for developmental neurotoxicology are being developed and used to provide information on chemical hazard and risk for humans while limiting the use of animals. Recently OECD published an initial guidance document for use of the Developmental Neurotoxicity In Vitro Battery (DNT IVB), composed of in vitro assays that assess critical neurodevelopmental processes. To evaluate assay performance and develop new assays for inclusion in the DNT IVB, positive and negative control compounds with known actions neurodevelopmental processes are required. In contrast, to evaluate the ability of the battery of in vitro DNT assays to predict developmental neurotoxicity in vivo in mammals (and particularly in humans), a different set of positive and negative controls are required. These are DNT Reference Chemicals - chemicals with evidence for in vivo developmental neurotoxicity identified in studies of humans or experimental animals (positives), as well as chemicals with evidence that they do not result in developmental neurotoxicity in vivo (negatives). The OECD guidance proposed a draft list of approximately 100 chemicals for use as DNT Reference Chemicals. The importance of this common set of chemicals was to provide a basis for beginning the evaluation of the current DNT-IVB performance vs. the available in vivo DNT studies and determine the added value of possible new assays developed for inclusion in the DNT IVB. The purpose of the current report is to update Appendix A of OCED 337 (OECD, 2023) and provide a Recommended DNT Reference Chemical Test Set for use in in vitro DNT assay development and evaluation.