Animal Testing in Biomedical Research and New Approach Methodologies (NAMs)

Introduction

A significant shift is underway in how regulatory agencies approach drug development and safety testing. Organizations such as the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA)—often considered the EU equivalent of the FDA—are increasingly supporting the validation and adoption of New Approach Methodologies (NAMs). These methodologies encompass a broad range of techniques or approaches that can be used as alternatives to animal testing or as complementary approaches, including in vitro systems, computational models, and advanced analytical techniques. This transition reflects growing scientific consensus that animal models do not always accurately predict human responses to new therapies, can be more expensive, time-consuming, and present ethical concerns. This article examines the current landscape of animal use in research and what the rise of NAMs means for the future of drug development.

Animal Testing Stats: How Many Animals Are Used In Research?

Despite increasing interest in alternatives to animal research, animal models remains widely used across drug development and the life sciences. Estimates suggest that millions of animals are used in scientific research, safety testing, and education globally each year, although precise global animal testing figures remain difficult to establish due to differences in reporting standards.

In regions with robust regulatory frameworks like Europe, reported use has declined in recent years, reflecting regulatory pressure and the gradual adoption of alternative testing strategies. The most recent EU and Norway data (2023) documented a total of 8.08 million animals used for scientific purposes — a 4.7% decline from 2022 and a 10.1% decrease since 2018. In Great Britain, 2.64 million scientific procedures involving living animals were carried out in 2024, the lowest figure recorded since 2001. In the United States, while official figures for 2024 reported just under 0.8 million animals, these reporting requirements exclude mice, rats, fish, and birds — species that collectively account for the majority of research subjects.

Understanding how many animals are used for testing each year is important for tracking progress, but it also underscores a broader challenge: while usage may be decreasing, reliance on animal-based systems has not yet been fully replaced.

Which Animals Are Used In Testing?

Mice are the most commonly used species for animal testing, which account for 44.6% of all EU animal studies, followed by fish (34.7%), rats (7.2%), birds (5.4%), and rabbits (4.4%). Across Great Britain and the United States, animal testing follows a similar distribution, with mice, rats, fish, birds, and rats representing the majority of subjects.

These species have been adopted as standard research models for practical and biological reasons: they are relatively affordable to house, reproduce quickly, and share sufficient genetic and physiological similarity to humans to serve as proxies for early-stage safety assessment.

Why Animal Models Remain In Use

The continued reliance on animal models in drug development is not without justification. Before a new drug can enter human clinical trials, regulatory agencies require evidence of safety and efficacy to protect healthy volunteers and patients. Living organisms are highly complex that are governed by dynamic and highly integrated biological processes that cannot yet be fully replicated by any existing in vitro or computational method.

Animal studies provide toxicologists with a means to observe whole-body responses to new compounds, capturing unexpected off-target effects, systemic organ interactions, and pharmacokinetic behaviours that cell cultures and computer models are not yet capable of predicting reliability.

Limitations of Animal Models

Despite their continued use, animal models carry well-documented limitations. Species differences in genetics, physiology, and ADME properties (absorption, distribution, metabolism, and excretion) mean that results from laboratory animals do not always translate reliably to humans. Where in vitro ADME assays and in human cell systems can offer more direct insights into how a drug will behave in the human body, traditional animal models can only approximate these processes. This translational gap is a key contributor to the failure of new drug candidates in clinical trials.

New Approach Methodologies: Potential Solutions To Animal Testing

New Approach Methodologies (NAMs) represent a broad and rapidly advancing set of tools designed to Replace, Reduce or Refine the use of animals in scientific research (the 3Rs principles). NAMs include a wide range of alternative testing methods, such as:

Legislative changes and updated guidance increasingly encourage or require the use of non-animal methods where scientifically appropriate, accelerating their integration into standard workflows. The US FDA Modernization Act 2.0 removed the longstanding statutory requirement for using animals for experiments prior to human drug trials. In 2025, the FDA announced plans to phase out animal testing requirements for monoclonal antibodies. Similarly, the EMA is supporting the validation of non-animal methodologies for regulatory decision-making. The EU Directive 2010/63/EU legally mandates that non-animal methods must be used wherever scientifically satisfactory alternatives exist.

A Persistent Challenge: Antibody Generation

One of the persistent challenges in the transition away from animal models is the production of high-quality polyclonal antibodies. Animals (mainly rabbits) continue to be favoured in certain situations because alternative in vitro methods like phage display often yield antibodies that lack the functional diversity and performance of traditional animal-derived polyclonals.

“Alternative methods are always considered before animals are used for the generation of monoclonal antibodies. The phage display method is often used and tested, but sometimes synthetic monoclonal antibodies are found to be slightly different from animal antibodies.”

-Summary report on statistical information on the use of animals for scientific purposes in the Member States of the European Union and Norway in 2023

Addressing this gap requires strategies that can preserve the functional advantages of polyclonal antibodies while eliminating the need for continued animal use. One emerging approach is the sequencing and recombinant expression of monoclonal and polyclonal antibodies.

Polyclonal Antibody Sequencing

Rapid Novor’s REpAb^® service offers a unique approach for switching animal-derived polyclonal antibodies for recombinantly manufactured monoclonal antibodies: polyclonal antibody sequencing. This sequencing platform employs tandem mass spectrometry and advanced proprietary algorithms to sequence the dominant monoclonal antibodies within a potent polyclonal antibody. These sequences can then be expressed into defined, recombinant monoclonal or recombinant polyclonal antibodies that faithfully reproduce the performance of the original animal-derived product, offering a defined, reproducible, and manufacturable alternative that does not require ongoing animal use.

For more information on our REpAb services, please contact our scientists