Currently, the main methodologies for RA of chemicals/materials mostly rely on in vivo (animal) testing. The limited in vivo toxicity data, coupled with the recent paradigm shift in toxicity testing towards the development and use of pathway-based testing strategies rather than traditional animal-based methods, triggered interest in the development of New Approach Methodologies (NAMs), based on in chemico, in vitro, in silico and alternative species test methods. This reinforces the implementation of the 3R's (Replacement, Reduction and Refinement of animals) concept . Although NAMs are not envisioned as a direct replacement for in vivo testing, it offers an opportunity for a fit-for-purpose testing strategy in the context of an Integrated Approach to Testing and Assessment (IATA) framework to inform decision-making bodies. It is envisioned that the NAMs should strategically be accompanied by the Adverse Outcome Pathway (AOP) concept , which has been formalized by the OECD in 2012 as the basis for organizing data and developing an IATA .