Press release

Published: 05 August 2026

A scientific study conducted by an international research team and led by the German organisation Doctors Against Animal Experiments (DAAE) has examined the success rate of drug development. The findings show that despite the increasing use of animal experiments, drug development has not become more successful at producing safe and effective medicines for humans over the past half-century. During the 2000s and 2010s, approximately 91% of drug candidates on average failed in human clinical trials despite having successfully passed preclinical animal testing. In around 77% of these failures, biological factors – such as insufficient efficacy or inadequate safety – were decisive. These are precisely the factors that animal experiments are intended to predict. Both figures highlight the systematic shortcomings of animal experiments and the urgent need for human-relevant, non-animal methods.

The development of new drugs involves multiple stages. Before a drug candidate can be tested in humans for the first time, it must undergo extensive preclinical investigations. These include animal experiments, which are intended to provide information on the drug candidate’s efficacy, safety and pharmacological properties. Only after their successful completion, drug candidates proceed to clinical trials in human volunteers and patients.

Nevertheless, the vast majority of drug candidates fail in the subsequent clinical trials. DAAE has long criticised the limited translatability of results obtained from animal studies to humans.

An international team of 13 researchers from six countries, led by DAAE, investigated the failure rates and causes of failure in clinical drug development from the 1960s to 2017. One of the authors is Dr Wolfgang Boomgaarden, recipient of the 2021 Herbert Stiller Research Prize for his work on computer-based, non-animal methods for drug development.

The analysis shows that, from the 1980s onwards, drug failure rates increased in every subsequent decade. During the 2000s and 2010s, an average of 91% of drug candidates failed in human clinical trials after successfully passing preclinical testing.

Approximately 77% of unsuccessful drug candidates failed because of biological factors, including insufficient efficacy, unexpected adverse effects or inadequate safety. These are characteristics that are assessed particularly in late-stage preclinical animal studies before a drug candidate is tested in humans.

“For decades, researchers have claimed that animal experiments are a necessary and reliable basis for developing new medicines. However, our systematic analysis shows that the situation has not improved – it has actually become worse,” says Dr Dilyana Filipova, Scientific Officer at DAAE and one of the study’s two lead authors.

“Our analysis makes clear that animal experiments frequently fail to identify the risks that are decisive for use in humans. A drug candidate may appear safe and effective in animals, yet prove ineffective in humans or cause serious adverse effects,” Filipova explains.

The study findings demonstrate that drug development urgently needs to be reformed. Instead of relying on inefficient animal experiments, greater use should be made of non-animal methods that more accurately reproduce human disease mechanisms and drug responses, thereby enabling more reliable predictions. Growing interest among regulatory authorities and pharmaceutical companies, as well as roadmaps published by the US Food and Drug Administration, the UK Government and the European Commission, show that international awareness of the shortcomings of the animal-testing system is increasing. Human-relevant and scientifically meaningful methods must therefore also become the central foundation of modern, human-focused pharmaceutical research – and replace animal experiments.

“We need a paradigm shift: away from animal experiments which is constrained by the biological differences between animals and humans, and towards precise methods based on human cells, tissues and disease processes,” Filipova urges. “The available data show that this transition must happen not at some point in the future, but now – in the interests of patients, scientific quality and animals.”

Doctors Against Animal Experiments calls for the consistent promotion of the development and regulatory approval of human-relevant, non-animal methods, and for these methods to become the central basis of disease research and drug development.

References

Filipova D. et al. Need for NAMs: A systematic evidence synthesis revealing over half a century of drug development failure. NAM Journal. 2026; 2:100119. Read the study