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ICCVAM Biennial Report 2018-2019

Biennial Progress Report 2018-2019 Interagency Coordinating Committee on the Validation of Alternative Methods

Expanded Decision Tree Software for Toxicity Classification

FDA is developing the Expanded Decision Tree software, which will be a free tool to classify compounds into six classes of relative toxic potential.

During the last seven decades, scientific advancements have led to an exponential increase in the number and types of chemicals to which humans are known to be exposed, leading to an ever-increasing need to screen and prioritize these substances according to their relative toxicity. The Cramer et al. (1978) Decision Tree is a screening and prioritization tool that sorts chemicals into three classes of relative toxicity. FDA updated and expanded the Cramer et al. Decision Tree to reflect the current state of the science and to make the decision tree applicable to a broader scope of substances, including those present in food, food contact materials, cosmetics, and dietary supplements. Additionally, FDA increased the number of classes of relative toxicity to six (non-toxic, low, medium, high, very high, and extreme toxicity) and quantified the toxic potential of each class by calculating a threshold of toxicological concern level for each class. By screening and prioritizing substances, the Expanded Decision Tree software will help focus resources on the safety assessments of substances with greater potential for public health risk and help reduce the use of animals for safety testing. An update on the development of the Expanded Decision Tree was presented at the September 2019 FDA workshop, “Implementing FDA’s Predictive Toxicology Roadmap: An Update of FDA Activities,” which highlighted activities to support and implement its Predictive Toxicology Roadmap.