The AOP Framework
Cobble Straße

In regulatory toxicology, an Adverse Outcome Pathway (AOP) is a conceptual construct that portrays existing knowledge concerning the linkage between a direct molecular initiating event and an adverse outcome at a biological level of organisation relevant to risk assessment.

The AOP Framework originates from regulatory toxicology, but molecular initiating events can be triggered by much more than chemicals.

In the CIAO project, we consider the SARS-CoV-2 virus as the stressor.

The AOP Framework is managed by the Organisation for Economic Co-operation and Development (OECD), but the CIAO project is an independent undertaking, making use of the OECD standards.

Useful resources:


(*) The course was designed and developed by etioLogic, LLC for the Human Toxicology Project Consortium and is now hosted on the "Animal-Free Safety Assessment (AFSA) Collaboration" website ( and is freely available to any and every one. The course can be downloaded as zip files or run directly online by clicking on the link above.