The Evolution and Application of Animal-Free Models in Drug Discovery and Disease Mechanism Research

Abstract Animal models have been key for disease mechanism research for years, but ethical concerns partly fuelled by the realisation that not all diseases can be recapitulated in animal systems have led to regulatory changes that are driving a shift towards animal-free alternatives. As regulations continue to evolve, the transition to animal-free models is becoming increasingly crucial for laboratories aiming to comply with new standards without compromising on scientific progress. The past decade has seen a boost in the development of animal-free three-dimensional models including explants, co-cultures, spheroids, organoids, and organ-on-chip systems, creating a varied landscape that has significantly transformed disease research. These models incorporate advancements in stem cell technology, bioengineering, and microfluidics to provide more physiologically relevant systems that bridge the gap between traditional two-dimensional cell culture and in-vivo studies. Whilst traditional two-dimensional cultures offer a cost-effective method with replicable results, they fail to accurately represent the natural structure of tissues and cell–cell interactions. By contrast, animal-free culture systems provide a more appropriate representation of human physiology and tissue architecture with relevance to in-vivo conditions. Therefore, these models enable more translatable research outcomes and have the potential to provide data for the reduction of the high failure rates currently marring clinical trials. This review explores the evolution, advantages, and applications of animal-free models in advancing human disease research and refining preclinical studies with an emphasis on cancer research.