Bio: Mark Blee joined the Toxicology Team as a Programme Manager in 2024 at the UK National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs), where he works on Toxicology projects, particularly focusing on acute studies. Mark previously worked at a large global Contract Research Organization for over 30 years, mainly as a Study Director for Toxicology and DART studies and, for the past 15 years, as the UK Director of Toxicology. He has a B.Sc. in Pharmacology from the University of Liverpool and is a member of the British Toxicology Society, the Royal Society of Biology and the Society of Toxicology. 

Abstract: Acute toxicity studies are conducted in animals for classification and labelling purposes, and human health risk assessment and management. Traditionally, these tests rely on determination of an LD50 or LC50 (lethal dose/concentration to 50% of animals) during short erm exposure and comparison of the acute lethality between substances. They are the only standardised toxicity tests where death is the intended endpoint. This presentation will describe collaborative efforts and data-sharing activities led by the NC3Rs that refine, reduce or avoid animal testing for acute toxicity testing purposes across sectors. Activities include data-sharing initiative which led to the removal of the requirement for acute toxicity testing of pharmaceuticals from ICH M3, eliminating the need to conduct these studies in the registration of new animals. In other sectors, where these tests remain a regulatory requirement (e.g. for classification and labelling purposes), efforts have focused on providing scientific evidence to support the refinement of mammalian acute toxicity tests for (agro) chemical testing (via oral and inhalation routes), replacing death with evident toxicity as an endpoint.