The global push to reduce animal testing in drug development

Governments and regulatory bodies across the UK, US, EU and Canada are taking steps to reduce reliance on animal testing, while advances in human-relevant science continue to expand the range of available non-animal test methods. The question now is how quickly those scientific advances can be translated into regulatory practice.

The UK has published a strategy to replace animal testing, while agencies in the US, including the Food and Drug Administration (FDA), National Institutes of Health (NIH) and Environmental Protection Agency (EPA), have announced measures designed to accelerate the adoption of non-animal methods.

Despite increasing regulatory interest in non-animal methods, animal testing remains deeply embedded within drug development and regulatory safety assessment. Human-relevant approaches are already used during drug discovery, but their use across later stages of development and regulatory testing remains more limited.

To understand what these developments could mean for drug development and regulatory testing, we spoke with Laura Alvarez, Deputy Director of Science & Regulatory Affairs at Cruelty Free International.

Earlier in her career as a veterinary microbiologist, Alvarez developed and validated a cell-based method designed to replace an animal-based assay used to test disinfectants against H1N1 and other clinically important viruses. The experience, she says, demonstrated both what is required to develop non-animal approaches and the challenges involved in translating scientific progress into wider adoption.

She believes the current level of international activity is unlike anything seen before.

“We are at a genuinely important moment globally,” she says. “When you step back and look at these developments collectively, it represents a level of international momentum that we have not seen before.”

Why the pressure for change is growing

For decades, animal testing has been a standard requirement in preclinical drug development, helping researchers evaluate the safety of drug candidates before they progress into human studies. However, questions have been raised about how accurately animal models predict human responses.

According to Alvarez, the scientific limitations of animal testing are becoming more widely recognised across both academia and industry.

“The scientific case has become increasingly difficult to ignore,” she explains. “There is growing recognition that animal models are poor predictors of human outcomes and that more human-relevant approaches offer a genuine opportunity to do better.”

There is growing recognition that animal models are poor predictors of human outcomes and that more human-relevant approaches offer a genuine opportunity to do better.

Advances in technologies such as cell-based models, organs-on-chips, three-dimensional human tissue systems and computational approaches are providing researchers with new ways to assess drug candidates during early development. Their role often becomes more restricted once programmes move into formal preclinical development and regulatory safety assessment.

“The challenge is what happens as candidates progress further,” Alvarez says. “Once a compound moves from early discovery into formal preclinical development and regulatory safety assessment, the system largely reverts to animal testing because that is what regulations have historically required and expected.”

From policy announcements to practical change

Much of the recent attention has focused on the growing number of policy initiatives being announced across major markets.

The UK’s recently published strategy to replace animal testing has been widely welcomed by organisations advocating for greater adoption of non-animal methods. Alvarez describes the strategy as a significant development, particularly given concerns that the UK risked becoming disconnected from international efforts following Brexit.

The strategy includes time-bound commitments and plans for a UK-based centre dedicated to validating new test methods, helping support the development and regulatory acceptance of non-animal methods.

However, Alvarez stresses that policy announcements alone are not enough.

“Turning policy commitments into lasting change requires more than a strategy document,” she says. “Without transparent public accountability and clear mechanisms for tracking progress, there is a real risk that momentum stalls or is lost over time.”

Turning policy commitments into lasting change requires more than a strategy document.

The same challenge applies globally. While individual agencies are announcing roadmaps and commitments, the extent to which those plans ultimately translate into changes in day-to-day practice remains uncertain.

The US gathers momentum

Recent regulatory activity in the United States has attracted particular attention.

Alongside the FDA’s roadmap, other US agencies have also announced initiatives aimed at reducing reliance on animal testing. The NIH has launched programmes focused on accelerating the development and adoption of human-relevant research methods, while the EPA has reinstated its commitment to end mammalian toxicity testing by 2035.

Legislative developments have also helped focus attention on the issue. Alvarez points to the Replace Animal Tests Act, introduced in late 2025, which would make it unlawful for covered federal agencies to require animal test data where a scientifically satisfactory non-animal alternative is available. She believes that kind of cross-agency requirement could help drive more consistent change than individual agency initiatives alone.

“The current political focus in the US on reducing government spending and improving efficiency has created additional alignment with the case for change, since animal tests are slow, expensive and frequently fail to deliver reliable results,” she says.

However, Alvarez notes that the US still lacks a comprehensive national framework.

“What we have is a collection of individual agency commitments and roadmaps, each developed somewhat independently, rather than a unified national plan with shared goals, timelines and accountability mechanisms.”

Implications for drug discovery

For drug developers, the implications extend beyond animal welfare. Modern non-animal approaches are already being used to inform key decisions during drug discovery, helping researchers select candidates, identify safety signals and prioritise programmes for further development. If regulators provide greater clarity on how these approaches can be used during formal preclinical development, their role could expand significantly.

“The regulatory developments we are seeing now have the potential to make the biggest practical difference,” Alvarez explains. “If agencies provide clearer guidance on when and how non-animal approaches can satisfy regulatory requirements, companies will have much greater confidence in relying on them throughout the full development process.”

This could allow companies to use the same approaches across a greater portion of the development process, reducing the need to switch between different testing methods as programmes progress.

“The prize is significant,” Alvarez says. “This is not just better for animals. It is better science and it is better for patients who need safer and more effective medicines faster.”

Barriers to wider adoption

While interest in non-animal methods is growing, several scientific, regulatory and practical challenges continue to limit their wider adoption.

Regulatory inertia continues to be one of the most significant challenges. Many testing requirements are embedded within legislation, international guidelines and long-established regulatory practices. Updating those systems requires coordination between regulators, industry and policymakers across multiple jurisdictions.

Global harmonisation presents another obstacle. Pharmaceutical companies operating internationally must satisfy regulatory requirements in every market where their products will be sold. If a non-animal approach is accepted in one region but not another, companies may still be required to perform animal studies.

There is a lack of trust, a reluctance to change and not enough training or familiarity with these approaches.

Questions are also being raised about some longstanding testing requirements. Alvarez highlights the routine requirement under ICH M3 guidance to test new medicines in two animal species, typically a rodent and a non-rodent such as a dog or primate. Growing evidence suggests that the second species does not always provide additional scientific value, prompting discussions about whether greater regulatory flexibility could be introduced.

To explore the issue further, Cruelty Free International recently co-hosted a workshop with the Johns Hopkins Bloomberg School of Public Health Toxicology Policy Programme, bringing together regulators, industry representatives and scientific experts to examine the evidence and discuss potential alternatives.

Building confidence in newer approaches is also an ongoing challenge.

“There is a lack of trust, a reluctance to change and not enough training or familiarity with these approaches,” Alvarez says.

“Animal tests are still treated as the gold standard against which new methods are validated. In practice, this means a new method is judged not on whether it predicts human outcomes well, but on whether it agrees with an animal test that was itself never formally validated.”

What happens next

Alvarez believes a pathway towards substantially reducing animal testing is realistic but cautions that progress is likely to be gradual.

Alvarez points to Cruelty Free International’s Replacement Animal Tests (RAT) List as one example of where progress could be made more quickly. The initiative highlights animal tests that continue to be used despite the availability of scientifically satisfactory non-animal alternatives.

The immediate priority, Alvarez says, should be ending tests that already have scientifically satisfactory alternatives, while continuing to invest in areas where replacement remains more challenging.

Ultimately, she believes the greatest obstacle is no longer the science itself, but the systems responsible for evaluating and adopting new approaches.

“The science is ready to move faster than the regulatory and cultural systems that govern it. Closing that gap is the challenge this moment demands,” Alvarez concludes.