Animal testing is supported by a broad coalition of government agencies, scientific institutions, pharmaceutical companies, and medical organizations. Their core argument is consistent: testing on animals has been essential for developing safe drugs, vaccines, and medical treatments, and no single alternative method can yet replicate the complexity of a living biological system. That said, even most supporters are actively working to reduce their reliance on animal models as newer technologies mature.
Government Regulatory Agencies
The most powerful supporters of animal testing are the agencies that have historically required it by law. The U.S. Food and Drug Administration (FDA) has long mandated animal toxicity studies before any new drug can be tested in humans. For antibody-based therapies alone, this meant months of repeated dosing in animals to assess safety. The European Medicines Agency (EMA) maintains similar requirements for drugs sold in Europe, publishing detailed guidelines on which animal tests are expected at each stage of drug development.
This regulatory support is shifting, though. In late 2022, Congress passed the FDA Modernization Act 2.0, which removed the blanket requirement to use animal studies for certain drug applications and authorized alternatives like cell-based lab tests and computer models. In 2025, the FDA went further, announcing a plan to phase out animal testing for monoclonal antibody therapies (a large and growing class of drugs used for cancer, autoimmune diseases, and more). Companies that submit strong safety data from non-animal methods may now receive streamlined review as the need for certain animal studies is eliminated. The agency is also launching a pilot program allowing select drug developers to use a primarily non-animal testing strategy. So while government agencies remain the institutional backbone of animal testing, they are actively building off-ramps.
The National Institutes of Health
The NIH, which funds more biomedical research than any other organization in the world, is one of the most prominent advocates for animal research. Its position rests on a straightforward claim: many of the medical advances that improve human lives were developed through carefully planned studies in animals. Laboratory animals share enough biological and physiological similarities with humans that researchers can study disease processes, test new treatments, and gather evidence of risks before moving to human trials.
The NIH also points to the controlled conditions that animal studies provide. In a lab setting, scientists can isolate variables in ways that are impossible in human populations, where diet, genetics, environment, and behavior all introduce noise. Every NIH-funded project involving live vertebrate animals must justify why the work is scientifically important, hypothesis-driven, and relevant to public health. This isn’t blanket endorsement of any study involving animals. It’s a framework that treats animal research as a tool requiring rigorous justification each time it’s used.
The Pharmaceutical Industry
Drug companies are among the largest users of animal testing and have long defended the practice as a necessary step in bringing safe medicines to market. The Pharmaceutical Research and Manufacturers of America (PhRMA), the industry’s main trade group, describes animal model studies as a standard phase of drug development, used after initial lab work to determine whether a potential medicine can influence a disease target in a living system before it reaches human volunteers.
The industry’s support is partly pragmatic. Drug development takes over a decade on average and costs billions of dollars. A failed drug that reaches human trials is catastrophically expensive. Animal testing serves as a filter, catching some dangerous compounds before they ever reach people. At the same time, pharmaceutical companies are investing heavily in alternatives, not out of altruism alone, but because animal models frequently fail to predict human outcomes. Drugs that work in mice often fail in people. Faster, cheaper, and more human-relevant testing methods are a competitive advantage, which is why many companies are early adopters of the cell-based and AI-driven tools the FDA is now encouraging.
Medical and Veterinary Organizations
Most major medical associations support the continued, regulated use of animals in research. Their argument draws on history: the majority of Nobel Prizes in Physiology or Medicine have been awarded to researchers who relied on animal models. Since the prize was first given, there have been 112 awards and 224 laureates, and animal experiments underpinned most of their discoveries, from insulin for diabetes to vaccines for polio.
The American Veterinary Medical Association (AVMA) adds a less commonly discussed angle. Many diseases that affect animals are identical to those in people, including osteoarthritis, diabetes, and many cancers. Research on animals doesn’t just benefit humans. Animals themselves are beneficiaries of therapeutic advances that flow in both directions between veterinary and human medicine. Veterinary research on diseases that jump between species (zoonoses) protects both wildlife and people, a point that gained visibility during the COVID-19 pandemic.
The “Three Rs” Framework
Supporters of animal testing rarely argue for it without conditions. The dominant ethical framework in the scientific community is known as the Three Rs, first proposed in 1959 by two British researchers. It defines three principles: Replacement, meaning using non-animal methods whenever possible; Reduction, meaning using fewer animals to achieve the same quality of data; and Refinement, meaning minimizing pain and distress for animals that are still used.
The Three Rs are now embedded in law and institutional policy across the U.S., Europe, and most countries with significant research sectors. Institutional animal care committees review every proposed study. This framework is what separates most modern supporters of animal testing from unconditional advocates. Their position is closer to “animal testing is still necessary in some cases, and we should be working to make those cases fewer and less harmful” than it is to a full-throated endorsement.
Where Support Is Weakening
Even among traditional supporters, the ground is moving. The FDA’s 2025 announcement to phase out animal testing for certain drug categories would have been unthinkable a decade ago. The agency now encourages companies to submit data from AI-based toxicity models, lab-grown human tissue (organoids), and cell-based assays alongside or instead of animal data. Real-world safety data from countries where a drug has already been tested in humans can also substitute for some animal work.
This isn’t a sudden shift in values. It reflects a growing recognition that animal models have significant scientific limitations. A drug’s behavior in a mouse or monkey does not reliably predict what it will do in a human body. As alternative technologies become more accurate and more validated, the practical justification for animal testing narrows. The organizations that support animal testing today are, in many cases, the same ones funding and regulating the technologies designed to replace it.