The era of animal testing in scientific research is showing signs of waning, with governments and institutions worldwide increasingly focused on alternative methodologies. While a complete cessation isn’t imminent, a significant shift is underway, driven by both ethical concerns and the rapid advancement of technologies that offer potentially more accurate and humane research pathways.
Last November, the UK government unveiled a plan to phase out animal testing in specific areas, beginning with eliminating tests for skin irritation this year and aiming to significantly reduce studies involving dogs by 2030. The overarching goal, as stated in government policy, is to reach “a world where the use of animals in science is eliminated in all but exceptional circumstances.” This move mirrors similar initiatives gaining traction internationally.
In April of last year, the US Food and Drug Administration (FDA) announced intentions to make animal studies the “exception rather than the norm” in drug safety and toxicity testing within the next three to five years. Simultaneously, the US National Institutes of Health (NIH) revealed an initiative to reduce animal use in its funded research. The European Commission is also preparing to publish a roadmap to end animal testing in chemical safety assessments this year.
These changes aren’t simply driven by ethical considerations, though those are paramount. A key catalyst is the development of what are being called ‘new approach methodologies’ (NAMs). These include sophisticated tools like organs-on-chips – microdevices that simulate the function of human organs – 3D tissue cultures known as organoids, and increasingly, computational models powered by artificial intelligence.
The growth in publications utilizing solely NAMs is striking. Analysis by Animal Free Research UK shows a surge from around 25,000 biomedical publications employing these methods in 2006 to over 100,000 in 2022. China is also making substantial investments in this field, launching a $382 million infrastructure project in 2024 dedicated to developing and refining NAMs.
Proponents of NAMs argue they can often better mimic human biology and more accurately predict the safety and efficacy of new drugs than traditional animal models. Organs-on-chips and organoids are frequently created using human cells, and computational models are designed using human data. Donald Ingber, a bioengineer at the Wyss Institute for Biologically Inspired Engineering in Boston, and a co-founder of Emulate, a biotechnology company specializing in organs-on-chips, describes the shift as “long overdue.”
However, the transition isn’t without its challenges. Some biological systems are inherently complex and difficult to replicate outside of a living organism. Many of these alternative methods are still undergoing validation – the process of demonstrating their accuracy and reproducibility to meet the rigorous standards of regulatory bodies.
Despite these hurdles, the overall trend indicates a decline in animal testing. Data from the United Kingdom reveals a decrease in scientific procedures performed on animals from 4.14 million in 2015 to 2.64 million in 2024. Similar reductions have been observed in the European Union and Norway, with a 5% drop in animal use between 2018, and 2022. While precise figures for the United States are difficult to ascertain due to reporting exemptions for certain species like rats, mice, and fish, the momentum towards reduction is clear.
The majority of animal experiments in the UK – approximately 76% – are conducted for basic and applied research, aimed at understanding organisms, modeling diseases, and developing new therapies. Around 22% fall under regulatory procedures, primarily focused on assessing the toxicity and safety of new medicines and chemicals. Mice and rats account for a significant portion of the animals used, representing 67% of all procedures.
A key issue driving the search for alternatives is the limited predictive power of animal models when it comes to human responses. A substantial 86% of investigational drugs that show promise in animal testing ultimately fail during clinical trials. This disconnect is particularly evident in conditions like sepsis, where over 100 therapies that appeared effective in rodent models have proven ineffective in human patients due to fundamental differences in immune systems and the complexity of the disease.
Researchers are increasingly turning to NAMs to address these limitations. Joseph Wu, a cardiologist and researcher at Stanford University, is pioneering a “clinical trials in a dish” approach, generating induced pluripotent stem cells (iPSCs) from patients and using them to grow cells or organoids for drug screening. A 2020 study demonstrated the potential of this method in identifying a drug that improved cardiovascular function in family members with a specific genetic mutation.
Emulate’s Liver-Chip, a device designed to assess liver toxicity, has also shown promising results. A 2022 study indicated its ability to accurately identify liver-damaging compounds with 87% accuracy, even detecting substances previously deemed safe based on animal models. The FDA has accepted Liver-Chip into its Innovative Science and Technology Approaches for New Drugs (ISTAND) pilot program, potentially paving the way for its use in drug approval applications.
While these advancements are encouraging, researchers emphasize that NAMs aren’t a complete replacement for animal testing. Edward Kelly, a toxicologist at the University of Washington, notes that some models, like his team’s kidney chip, are reductionist and focus on specific cell types, requiring continued animal studies for a comprehensive understanding. Similarly, organoids, while promising, still represent simplified versions of complex organs.
Despite these caveats, the momentum behind alternatives to animal testing is undeniable. The pharmaceutical industry is responding, with companies like Roche investing in human model systems and exploring opportunities to incorporate NAMs data into regulatory submissions. While animal data remains a requirement for most new drug applications, Roche has already secured waivers to use NAMs data for a dozen submissions to regulatory authorities. The future of scientific research appears to be moving towards a more humane and potentially more effective paradigm, one that prioritizes innovation and minimizes reliance on animal models.
