Integration of new approach methods in a structure based read-across for DART effects
Résumé
Read-across is one of the most often applied alternative tools for hazard assessment, in particular for complex endpoints such as toxicity after repeated exposure or developmental and reproductive toxicity. We have applied this approach to a series of six aliphatic carboxylic acids that have developmental toxicity data, some being positive, some negative. For one of these compounds, 2-Methylhexanoic acid (MHA), we have specifically blinded this toxicity data, and we have applied new approach methodologies (NAM) to substantiate the read across of the other compounds (as source compounds) to MHA, and to explore whether these NAM correctly predict the in vivo developmental toxicity of MHA. Thus, we have tested MHA and the five analogues in a battery of in vitro tests with clear relevance to DART, i.e. the Zebrafish Embryo Test (ZET), mouse Embryonic Stem cell Test (mEST), iPSC-based neurodevelopmental model (UKN1), and a series of CALUX Reporter assays, and combined this with toxicokinetic models to calculate effective cellular concentrations and associated in vivo exposure doses. We also included two positive, and one negative control compound in this test. As the histone deacetylase enzyme is postulated to be the molecular initiating target leading to neural tube defects with these compounds, we have also investigated the potential of these six analogues to inhibit this enzyme in ZET, mEST, and UKN1 models. The NAM quite well predicted the in vivo developmental outcome of these six aliphatic carboxylic acids. This presentation will discuss the combining of results from multiple NAMs for predicting the teratogenic properties and potency of this series of structurally related chemicals and how this information can be used to establish a framework of testing for regulatory applications. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 681002.