WP 9 aims to advance the mechanistic understanding and prediction of developmental neurotoxicity (DNT) induced by prenatal exposure to environmental, pharmaceutical, and other compounds.

It focuses on two major adverse outcomes of concern: cognitive function defects—including impairments in learning and memory—and structural malformations such as neural tube closure defects. To address these outcomes, WP 9 integrates experimental and computational approaches grounded in the Adverse Outcome Pathway (AOP) framework. The experimental arm of the WP 9 is dedicated to the development and characterization, and scientific validation of human-relevant in vitro test systems using primary and induced pluripotent stem cell (iPSC)-derived neural progenitor cells. These assays are designed to model key neurodevelopmental processes such as proliferation and differentiation, which are known to be vulnerable during prenatal exposure to toxicants. Particular emphasis is placed on transcriptomic and functional characterization of these models, as well as mapping the biological pathways involved in neurodevelopmental disorders to ensure human neurodevelopmental relevance.

Parallel to the in vitro work, WP 9 is developing a physiology-based computational model of neural tube closure, which is being iteratively refined and validated using experimental data. The integration of these systems aims to improve the predictive power of DNT assessments and support the development of next-generation risk assessment strategies. Ultimately, WP 9 contributes to the overarching ONTOX vision by establishing robust New Approach Methodologies (NAMs) that are mechanistically informed, human-relevant, and aligned with regulatory needs.