In Vitro to In Vivo Extrapolation
A workflow for conducting in vitro to in vivo extrapolation (IVIVE) analyses is available in the Integrated Chemical Environment (ICE). A poster presented at the 2019 SOT Annual Meeting (Chang et al.) provided an overview of how to run IVIVE analyses in ICE. The IVIVE workflow in ICE version 2.0, released in May 2019, provides more complex models based on the EPA’s httk package to improve prediction accuracy.
A key issue with high-throughput in vitro testing methods is how to accurately relate concentrations of substances that induce in vitro responses to in vivo exposure levels that could result in human or animal adverse effects. This relationship is established through IVIVE, the focus of a NICEATM webinar series and following workshop during 2015 and 2016.
Scientists interested in the use of IVIVE for substance screening and risk decision-making met at the 2016 workshop to develop best practices and identify areas for further research. The workshop, co-organized by NICEATM and EPA, was summarized in a 2018 publication in the journal Toxicology In Vitro (Bell et al. 2018).
NICEATM's computational toxicologists developed methods for conducting IVIVE analyses, described in a publication in the journal Applied In Vitro Toxicology (Chang et al. 2014). Subsequent work focused on understanding the impact of various parameters, such as using free plasma concentration as a surrogate for total plasma concentration, and comparing multiple modeling approaches. This work is described in a publication in Environmental Health Perspectives (Casey et al. 2018).
Application of these IVIVE approaches to predict the potential of substances to cause developmental toxicity and to interact with the endocrine system was described in a poster presented at the 2017 SOT Annual Meeting (Chang et al.). Current work on developmental toxicity is evaluating the impact of pharmacokinetics and different modeling approaches on predicting relevant external exposure. Preliminary results using data from a specific in vitro stem cell-based assay as input for IVIVE suggest that these approaches could quantitatively predict in vivo developmental toxicity potential of valproate analogues. A poster describing this work (Chang et al.) will be presented at the 2020 SOT annual meeting.