News Details

QSAR Toolbox extension broadens possibilities for animal-free chemicals assessment

The new add-on helps users to predict chemical properties, including endocrine activity, while avoiding testing on animals.

The OPERA extension contains models for predicting properties that are important for assessing chemical hazards. The extension can be used to screen chemical databases to identify substances that may cause endocrine disruption. It also helps users to estimate acute oral toxicity and other regulatory relevant properties.

Developed by the US National Institute of Environmental Health Sciences (NIEHS), OPERA can predict properties related to the absorption, distribution and metabolism of substances that can strengthen read-across justifications and facilitate the regulatory use of in vitro test results.

The extension can be downloaded for free from the QSAR Toolbox Repository.


The OECD QSAR Toolbox supports animal-free chemical hazard assessment by making data available and offering predictive tools for data gaps. It is co-developed by ECHA and the Organisation for Economic Co-operation and Development (OECD) and has almost 30 000 users worldwide, including regulatory authorities.

Users can add extensions from the QSAR Toolbox Repository to expand its functionalities. The repository now offers more than 10 free extensions developed by authorities and private companies.

OPERA (Open (Quantitative) Structure-activity/property Relationship App) is an ongoing collaboration between NIEHS and the United States Environmental Protection Agency (US EPA). It provides robust models for predicting chemical properties that can be used for regulatory purposes.