The Open (Quantitative) Structure-activity/property Relationship App (OPERA) is a free and open-source/open-data suite of QSAR models providing predictions for toxicity endpoints and physicochemical, environmental fate, and ADME properties. OPERA was created in alignment with rigorous OECD standards to provide a regulatory-oriented alternative to experimental measurements. All OPERA models were built on curated data and QSAR-ready chemical structures standardized using an open-source workflow implemented in the application. Models are explained in the 2018 publication by Mansouri et. al in the Journal of Cheminformatics, titled "OPERA models for predicting physicochemical properties and environmental fate endpoints."
OPERA is accessible via a downloadable application or command line.