Development of the fish invitrome for animal-free environmental risk assessment of chemicals.

Given the need to reduce animal testing for environmental risk assessment, we aim to develop a fish invitrome, an alternative fish modular framework capable of predicting chemical toxicity in fish without the use of animals. The central module of the framework is the validated RTgill-W1 cell line assay that predicts fish acute toxicity of chemicals (Organisation for Economic Co-operation and Development test guideline 249). Expanding towards prediction of chronic toxicity, the fish invitrome includes two other well-advanced modules for chemical bioaccumulation/biotransformation and inhibition of fish growth. This framework is expected to continuously evolve with the development of modules that predict, for instance, neurotoxicity and reproductive toxicity. We envisage the fish invitrome framework becoming part of the broader academic field of new approach methodologies (NAMs), where it will remain flexible and open to integration of new developments from research groups around the world. To accelerate the development and uptake of this framework, we strive for transdisciplinarity, integrating both natural and social sciences, along with broader stakeholder interactions. A stepwise socio-technical approach was chosen, where mainstreaming the fish invitrome involves progressive adoption across various ecotoxicological contexts. The framework will be codesigned with stakeholders from academia, industry, and regulatory bodies. Rather than aiming for immediate regulatory acceptance, this approach aims to build trust and familiarity with fish cell line-based testing among stakeholders. By doing so, it encourages broader use of the framework in practical applications while gradually overcoming institutional, cultural, and technical barriers. Additionally, establishing a clear roadmap for mainstreaming the fish invitrome will help identify and address challenges to its uptake, ensuring a smoother transition to nonorganismal testing methodologies.