Review revisits the 5% animal-to-human translation problem
Bottom line
A new review in Animals examines how the biomedical community has responded to a widely cited 2024 finding that only 5% of therapies tested in animals ultimately gain regulatory approval for human use. The paper, by Cédric Sueur, looks at how later articles interpreted that figure and argues that the field is coalescing around a more mixed view: some researchers defend animal models as still necessary in parts of biomedical science, while others see the low translation rate as a strong case for expanding non-animal methods. The 5% figure comes from a 2024 umbrella review in PLOS Biology, which found that about half of animal-tested interventions reached any human trial, but only 5% reached regulatory approval, with average timelines of five years to first human study, seven years to randomized trials, and 10 years to approval. (journals.plos.org)
Why it matters: For veterinary professionals, this is less about human drug development politics and more about where research norms are heading. Regulators and funders are already moving toward new approach methodologies, or NAMs, including organoids, organ-on-chip systems, computational models, and other human-relevant platforms. FDA announced a plan in April 2025 to phase out some animal testing requirements for monoclonal antibodies and other drugs, then issued draft guidance in 2026 on validating alternatives in drug development, while NIH has also encouraged investigators to consider NAMs in grant planning. That shift could influence comparative research, laboratory animal use, ethics review, and how veterinarians engage with welfare questions in biomedical science. (fda.gov)
What to watch: Expect more debate over where animal models remain scientifically justified, and more regulatory detail on when NAMs can replace them in practice. (fda.gov)
A review article in Animals is revisiting one of the most uncomfortable numbers in biomedical research: only 5% of therapies tested in animals go on to receive regulatory approval for human use. According to the paper by Cédric Sueur, that finding has become a focal point for a broader argument over whether animal models are still fit for purpose in modern translational science, and whether non-animal methods should move from supplemental tools to default options in more parts of the pipeline. (journals.plos.org)
The 5% benchmark comes from a June 2024 umbrella review in PLOS Biology led by researchers at the University of Zurich’s Center for Reproducible Science. That study evaluated systematic reviews across multiple disease areas and found that roughly 50% of therapies tested in animals progressed to some form of human trial, 40% reached randomized controlled trials, and just 5% achieved regulatory approval. It also estimated average lag times of five years from animal study to first human study, seven years to randomized trials, and 10 years to approval. University of Zurich researchers said at the time that the work offered unusually robust figures for a debate that had long relied on scattered estimates. (journals.plos.org)
That finding landed in a research environment already wrestling with reproducibility, publication bias, and pressure to improve clinical relevance. The original PLOS Biology paper did not argue for abandoning animal research outright; its authors said the results pointed to the need for more robust and generalizable study design in both animal and human research. But the low approval rate gave new weight to critics who argue that species differences, selective reporting, and weak preclinical design can limit how well animal findings predict human outcomes. Broader commentary in the field has also emphasized that null and negative findings remain underreported, which can distort the evidence base that later translational decisions rely on. (journals.plos.org)
The policy backdrop has shifted quickly since then. In April 2025, FDA announced plans to reduce, refine, or potentially replace some animal testing requirements for monoclonal antibodies and other drugs with NAMs such as AI-based toxicity models, organoids, and organ-on-chip platforms. In 2026, the agency followed with draft guidance on alternatives to animal testing in drug development and reported “Year 1” progress on a roadmap that includes qualification pathways, validation frameworks, and more explicit timelines for phasing out animal testing where equivalent or better alternatives exist. NIH, meanwhile, has signaled growing support for NAMs in funding and study planning, and NIEHS continues to describe non-animal approaches as capable, in some cases, of matching or outperforming standard animal models. (fda.gov)
Industry and expert reaction remains mixed rather than uniform. Supporters of reform point to the 5% figure as evidence that human-centered models deserve faster uptake, especially in areas where animal predictivity has been weak. NC3Rs, for example, has argued that human-relevant in vitro preclinical models can both reduce animal use and improve translation. Others caution against overinterpreting the number. Coverage from UZH and follow-on discussion noted that drug development is difficult in general, and some commentators have argued that a low final approval rate does not mean animal studies lack value in every domain, particularly where they contribute safety, mechanism, or feasibility data even if a therapy never reaches market. (nc3rs.org.uk)
Why it matters: For veterinary professionals, this debate sits at the intersection of welfare, ethics, and research quality. Veterinarians involved in laboratory animal medicine, IACUC work, translational research, or academic oversight are likely to see increasing pressure to justify animal use with stronger evidence that a model is relevant, rigorous, and not replaceable by a validated alternative. As NAMs gain regulatory credibility, the practical question shifts from whether alternatives exist in principle to where they are mature enough to change protocol design, funding expectations, and review standards. That has implications not only for animal welfare, but also for how veterinary expertise is used in shaping humane, scientifically defensible research programs. (niehs.nih.gov)
There’s also a broader professional signal here. The move toward non-animal methods is no longer confined to advocacy circles or early-stage innovation programs. It is now showing up in FDA guidance, NIH funding language, and international discussions about validation and implementation. For clinicians and researchers in veterinary medicine, that means the conversation is becoming operational: which questions still require animal models, which can be answered better with human- or tissue-based systems, and how should oversight committees weigh those options in real time. (fda.gov)
What to watch: The next key developments will be whether Sueur’s review gains traction as a framing paper in the welfare-and-ethics debate, how FDA finalizes its 2026 draft guidances, and whether funders and journals begin to expect more explicit justification for animal use when validated non-animal methods are available. (fda.gov)