Adverse Outcome Pathways

Adverse outcome pathways (AOPs) were first proposed by the Organisation of Economic Co-operation and Development (OECD), with the goal of reducing the need for animal testing.^[1] AOPs describe how an exposure to a stimulus can produce a series of changes resulting in a disease or adverse outcome (AO).

In an AOP, a stimulus, such as a chemical exposure, can result in an initial change or molecular initiating event (MIE). The pathway consists of a series of key events (KE) that are adverse changes to cells, tissues and organs. For the purposes of an AOP, any change must be both critical and measurable to become a KE. Any change that leads to a measurable increase in a KE, is likely to lead to progress to the next KE and in turn potentially disease.