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ICCVAM Biennial Report 2020-2021

Biennial Progress Report 2020-2021 Interagency Coordinating Committee on the Validation of Alternative Methods

The Tox21 Compound Library: Collaborative Chemistry Advancing Toxicology

Since 2009, the Tox21 project has screened about 8,500 chemicals in more than 70 high-throughput assays, generating upward of 100 million data points, with all data publicly available. Underpinning this public effort is the largest compound library ever constructed specifically for improving understanding of the chemical basis of toxicity across research and regulatory domains. The different programmatic objectives of the Tox21 partners led to three distinct, overlapping compound libraries that, when combined, not only covered a diversity of chemical structures, use categories, and properties but also incorporated many types of compound replicates. A 2021 publication (Richard et al. 2021) describes the history of development of the Tox21 "10K" chemical library and data workflows implemented to ensure quality chemical annotations and allow for various reproducibility assessments. The paper presents cheminformatics profiles that demonstrate how the three partner libraries complement one another to expand the reach of each individual library, as reflected in coverage of regulatory lists, predicted toxicity endpoints, and physicochemical properties.