The Open (Quantitative) Structure-activity/property Relationship App is now available as an extension to the OECD QSAR Toolbox. The Toolbox was co-developed by OECD and the European Chemicals Agency to support animal-free chemical hazard assessment. QSAR Toolbox is available at The OPERA extension is available at

OPERA is a free and open-source/open-data suite of quantitative structure-activity relationship (QSAR) models that provides predictions for physicochemical properties, environmental fate parameters, ADME, and toxicity endpoints. OPERA is an ongoing collaboration between NICEATM and EPA and is being constantly being maintained and updated with additional models, data, and features. For more information about OPERA visit