Adverse Outcome Pathway (AOP) Coaching Program—how it functions and contributes to a more harmonized approach to AOP development and construction of AOP networks with regulatory utility

The adverse outcome pathway (AOP) framework contributes to understanding how specific and measurable biological perturbations cause adverse effects on human and environmental health. Recognizing the value of AOPs to support regulatory decisions around the world, the Organisation for Economic Co-operation and Development (OECD) launched the AOP Programme in 2012, which sought to promote and guide the development of AOPs to ensure their suitability for the downstream applications in the context of regulatory safety assessment. The OECD published the initial guidance on AOP development and assessment in 2013, which has been expanded as practices have evolved and matured. Adverse outcome pathway development requires adherence to specific principles and considerations for identifying and describing key events (KEs) and representing and assessing the weight of evidence for the key event relationships. Ultimately, the structured and consistent application of the principles helps build confidence in the applicability of the knowledge represented in the AOP for decision-making in the regulatory context. To assist new AOP developers, in 2019, the OECD introduced a coaching program. This program primarily aims to pair novices with experienced AOP developers (i.e., coaches). International partnerships in the coaching program contribute to harmonizing and promoting AOP development according to OECD guidance. Coaches have also helped to identify and initiate "gardening" efforts that remove redundant/synonymous KEs in the AOP-Wiki, allowing for improved AOP network creation, promoting the reuse of extensively reviewed KEs, and ensuring the development of high-quality AOPs. The AOP Coaching Program represents the latest international activity to ensure that AOPs are developed in a consistent manner that is designed to enhance their use for supporting public health decisions around the world.