New approach methods (NAMs) for multiple non-animal based test methods Helena Kandarova, Institute of Experimental Pharmacology & Toxicology, Centre of Experimental Medicine SAS, Slovak Academy of Sciences, Bratislava, Slovakia; Institute of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Bratislava, Slovakia © 2024 Elsevier Inc. All rights reserved. Introduction 741 Definitions—Alternatives and NAMs 742 NAMs in regulatory toxicity testing 742 Implementation challenges 743 International collaborations and initiatives in NAMs development 743 NAMs and disruptive technologies 743 Conclusion 745 References 745 Further reading 746 Abstract This chapter aims to present the concept of New Approach Methodologies (NAMs) as modern tools in the toxicology of the 21st century. NAMs can be defined as any technology, methodology, approach, or combination thereof that can provide information on hazard and risk assessment of chemicals and mixtures without the use of animals. This process includes in silico, in chemico, in vitro, and ex vivo approaches. The chapter describes the use of NAMs for regulatory testing purposes as well as their use in basic research. It gives several examples of interdisciplinary approaches that can be used in modern toxicology to derive information of interest without the use of experiments in animals and discusses challenges in the broader implementation of NAMs. Keywords Adverse outcome pathway (AOP); Alternatives to animal testing; Human cells and tissues; In vitro and in silico toxicology; Integrated approaches to testing and assessment (IATA); Integrated testing strategies; New approach methods (NAMs); Regulatory testing; Validation Key points • The advantages of using NAMs toward traditional animal-based approaches • Regulatory use of NAMs • Challenges in implementation of NAMs • Advanced interdisciplinary technologies as basic components of NAMs. Introduction Risk and safety assessment of chemicals, consumer products, as well as the development and efficacy of new drugs and biologicals, has relied for many decades almost exclusively on the data generated in experimental animals. Animal use in fundamental science has also increased, especially with the development of advanced in transgenic models. The scientific and animal welfare community has repeatedly questioned the approach of acquiring predictions from rodent models or any other animal species for human safety purposes. The poor predictivity of animal models (especially for human diseases) due to the differences in physiology, metabolism and chemical susceptibilities and questionable reproducibility of animal studies has led to several projects and international policies requesting phasing out animal testing. Thanks to technological progress over the past decades, toxicology as science has become an interdisciplinary field, especially regarding its ability to model complex physiological and pathological processes in simpler systems and identify Modes of action (MoA) that lead to adverse events. This knowledge enabled the development of “Alternatives to animal testing” and the imple- mentation of testing strategies, now commonly called “New Approach Methodologies” or NAMs. Encyclopedia of Toxicology 4th Edition https://doi.org/10.1016/B978-0-12-824315-2.01036-8 741