On occasion of the DNT5 meeting in Konstanz, Germany (April 2024), participants brainstormed on future challenges concerning a regulatory implementation of the developmental neurotoxicity (DNT) in vitro test battery (DNT-IVB). The five discussion topics below outline some of the key issues, opportunities, and research directions for the next several years: (1) How to contextualize DNT hazard with information on potential maternal toxicity or other toxicity domains (non-DNT)? Several approaches on how to use cytotoxicity data from new approach methodologies (NAMs) were discussed. (2) What opportunities exist for an immediate or near-future application of the DNT-IVB, e.g., as a prioritization step or add-on to other information? Initial examples are already emerging; the data can be used even if the battery is not converted to a defined approach. (3) How to establish data interpretation procedures for multi-dimensional endpoints that reduce dimensionality and are suitable for classification? A decision framework is required on how to use the DNT-IVB in a regulatory context. Machine learning may provide novel classification models. (4) How can a battery of molecular initiating events (MIEs) be smartly linked to the DNT-IVB? At what tier of an overall strategy would MIEs be evaluated, and how would one optimally balance cost vs information yield. (5) What is the way forward to scientific validation of DNT NAMs and the DNT-IVB? A large set of animal data would be required for conventional approaches, while mechanistic information may establish relevance in other ways.
Keywords: DNT in vitro test battery (DNT-IVB); adverse outcome pathways (AOP); cytotoxicity, screening; key neurodevelopmental processes (KNDP); new approach methodologies (NAMs); next generation risk assessement (NGRA); physiologically-based kinetic modelling (PBK.
A meeting on developmental neurotoxicity (DNT) testing was held in Konstanz, Germany in April 2024 (DNT5 meeting). A major topic of discussion was the DNT in vitro test battery (DNT-IVB) and how this set of cell-based animal-free test methods may be used in a regulatory context. Opportunities for future developments were addressed in discussion groups: How specific DNT readouts can be combined with more general toxicity data; opportunities for applying the DNT-IVB as soon as possible; and what decision framework will be needed on how to use the DNT-IVB for regulatory purposes. Moreover, the use of signaling assays (evaluating the interaction of test compounds with receptors, enzymes and transporters) in combination with the DNT-IVB was discussed. Finally, ideas and concepts to achieve scientific validation of the DNT-IVB were collected.