The Decision Tree approach as a strategy for the global phase out of animal testing for acute and local toxicity for chemicals: recommendations from an expert workshop

Abstract

The Animal-Free Safety Assessment (AFSA) Collaboration invited a select group of international experts, representing regulatory bodies, industry, method developers, and academia, to a workshop to develop a regulatory strategy implementing non-animal approaches to assess acute toxicity endpoints. The workshop, held in Loch Lomond, Scotland, from 28 April to 1 May, 2025, aimed to develop a decision tree (DT) approach that could support the implementation of non-animal methods and the phased-out use of animal testing for systemic acute and local toxicity. This DT approach provides a transparent decision-making workflow that assists users in applying appropriate opportunities for waiving testing, non-animal testing methods (NAMs), and other adaptations consistently across chemical regulations. DTs also serve to increase awareness of the application of non-animal approaches and ensure compliance with the last resort requirement for animal studies. This workshop aimed to review the suitability of the proposed framework, formulate overarching recommendations for its implementation and provide specific feedback and timelines to finalise endpoint-specific DTs for acute oral toxicity, eye irritation and corrosion, skin irritation and corrosion, and skin sensitisation. This report summarises the overarching discussions and findings tackled during the meeting. The individual endpoint-specific DTs will be described in follow-up scientific publications.

Keywords: Acute toxicity endpoints; Last Resort Decision Tree; Non-animal methods; Regulatory workflow.