"No more lab animals?” - FDA to phase out animal testing requirement

For decades, animal models have played a crucial role in biomedical research and drug development. From understanding disease mechanisms to evaluating drug safety, studies involving animal work have helped to lay the groundwork for many of the medical advances we benefit from today. However, as scientific innovation continues to evolve, so does our ability to explore safer, more precise, and humane alternatives. 

The FDA’s April 2025 Announcement

In a milestone move on April 10 2025¹, the U.S Food and Drug Administration (FDA) announced a transformative step, signalling a departure from its long-standing reliance on animal research. With the goal of reducing, and in some cases replacing, the need for animal-based studies, the FDA plans to integrate New Approach Methodologies (NAMs), such as use of in silico models, into its drug evaluation process. The FDA intends for animal work to become the exception, as opposed to the standard, within the next three to five years. 

This development, however, isn’t entirely new. The groundwork was laid with the FDA Modernisation Act 2.0, passed in late 2022², which first authorised the use of non-animal methods in Investigational New Drug (IND) applications. Notably, the pace of progress has been brisk; within just a couple of years, regulatory change has taken hold in an area that typically evolves slowly. Technologies like organ-on-a-chip, which have been around since the early 2010s, are now finally gaining traction in official guidance. The FDA’s latest announcement signals a more concrete step toward implementation. As part of their broader strategy, the FDA has released a ‘roadmap’ outlining plans to incorporate NAMs, including artificial intelligence (AI)-based computational modelling, advanced in vitro assays, and organ-on-a-chip systems to enhance drug safety while reducing reliance on animal testing. 

The FDA is also placing greater emphasis on incorporating real-world human data into the drug evaluation process, such as from electronic health records, clinical registries, and patient-reported outcomes. By leveraging data from pre-existing human studies, the agency aims to not only reduce reliance on animal models, but also identify rare side effects and gain deeper insight into long-term drug impacts, especially in populations that may be underrepresented in clinical trials. These groups often include older adults, women, ethnic minorities, and patients with multiple chronic conditions, who are frequently excluded or under-enrolled in early-phase clinical research due to strict inclusion criteria, lack of access to information, or logistical barriers^3-5. 

Pilot Programme for Monoclonal Antibody Therapies

To start, the FDA will concentrate its efforts on monoclonal antibody (mAb) therapies and biologics, where animal testing has long been a central component of evaluation. In an effort to reduce animal use in these research areas, a variety of NAMs will be employed instead. This will immediately take place for IND applications. These alternative strategies will be supported by real world human data to make determinations of efficacy. If successful, this pilot programme could serve as a blueprint for how alternative methods can be integrated into the regulatory framework, accelerating the shift away from routine animal work. 

New Approach Methodologies (NAMs): What’s Replacing Animal Research?

The spotlight is now on NAMs – a diverse and evolving set of tools designed to assess drug safety, efficacy and toxicity with greater precision and ethical responsibility. In some cases, these alternatives have demonstrated comparable, and sometimes enhanced, relevance to human biology. 

In Silico Modelling

One major area of growth is in silico modelling, which uses computational tools to simulate how a compound behaves in the human body. Such models can predict pharmacokinetics, toxicity, and drug interactions early in the drug development pipeline, helping to prioritise candidate drugs for further testing. With the integration of machine learning and AI, in silico platforms are becoming increasingly accurate in forecasting biological responses based on chemical structure and known datasets⁶. 

Organ-on-a-chip

Another promising technology is the organ-on-a-chip system. These micro-engineered devices replicate the structure and function of human organs on a miniature scale, using human cells to mimic key aspects of tissue physiology. For example, lung-on-a-chip models can be used to study respiratory toxicity in a highly specific, controlled environment – something that is difficult to achieve in traditional animal models⁷. 

Organoids

Organoids – three-dimensional cell cultures grown from human stem cells - offer a different, yet complementary, approach. These miniature organ-like structures are used to model complex interactions within tissues, providing a more holistic picture of how a drug might affect human biology. Organoids are particularly useful in studying disease mechanisms and screening potential treatments in a human-relevant context⁸. 

In Vitro Assays

In vitro assays use cultured human cells to assess cellular responses to compounds of interest. When combined with high-content imaging (HCI) and omics-based approaches, such as transcriptomics or proteomics, these assays can provide detailed insight into mechanisms of action and toxicology pathways. 

Integrated Testing Strategies 

Integrated testing strategies combine several NAMs to create robust, multi-faceted safety evaluations. By combining results across different models (computational, cellular, and organoid-based), researchers are able to build a more complete picture of a drug’s profile without relying on animal data. 

While NAMs still face regulatory and standardisation challenges, their potential to revolutionise pharmacology is clear. As these technologies continue to improve, they promise not only to reduce animal use, but also to enhance the precision, speed and human relevance of drug development. 

Challenges And Considerations: Why Animal Research Still Matters

While the move towards NAMs represents an exciting shift in drug development, it is important to recognise that animal research continues to play a vital role in pharmacology. 

Animal models provide an integrated view of how drugs interact in a complete living system, capturing the complexity of whole-body physiology. This includes processes such as the immune response, hormonal regulation, and multi-organ interactions – functions that even the most advanced in vitro and computational models cannot fully replicate at their current stage. As such, animal models help researchers understand not just whether a compound is toxic or effective in isolation, but its wider behaviour in the system of a living organism. For instance, toxicology studies or assessments on long-term safety profiles often require sustained observation over a period of time, which is difficult to model on current NAMs. 

Moreover, not all NAMs are fully validated or standardised as of yet. While progress is being made, many of these tools are still in the early adoption or development phases. Until robust and universally accepted frameworks are in place, animal studies will continue to serve as an important safeguard. 

Eliminating animal research would require a significant shift, not just in technology, but in regulatory framework, scientific training, and institutional culture. Regulators and researchers continue to refine and reduce animal work, but replacing it completely remains a long-term goal rather than an immediate reality. For now, the goal is not to discard animal work in its entirety, but rather use them more judiciously in combination with alternative methods, as we work towards safer and more efficient drug development. 

 
References: 
¹ U.S. Food and Drug Administration. FDA announces plan to phase out animal testing requirement for monoclonal antibodies and other drugs [Internet]. Silver Spring (MD): FDA; 2025 Apr 10 Available at: https://www.fda.gov/news-events/press-announcements/fda-announces-plan-phase-out-animal-testing-requirement-monoclonal-antibodies-and-other-drugs. 
² CONGRESS, U. S. 2022. S. 5002: FDA Modernization Act 2.0. 117th Cong., 2nd Sess., introduced 29 September. Available at: https://www.congress.gov/bill/117th-congress/senate-bill/5002. 
³ Duggal M, Sacks L, Vasisht KP. Eligibility criteria and clinical trials: An FDA perspective. Contemp Clin Trials. 2021 Oct;109:106515. doi:10.1016/j.cct2021.106515. 
⁴ Oh SS, Galanter J, Thakur N, Pino-Yanes M, Barcelo NE, White MJ, et al. Diversity in clinical and biomedical research: a promise yet to be fulfilled. PLoS Med. 2015 Dec;12(12):e1001918.
⁵ Wolfe LA, Collins T, Smith P, Nguyen A, Patel R. Advancing the inclusion of underrepresented women in clinical trials and biomedical research. Clin Transl Sci. 2022;15(3):499-509. 
⁶ Terstappen GC, Reggiani A. In silico research in drug discovery. Trends Pharmacol Sci. 2001 Jan;22(1):23-6. doi: 10.1016/s0165-6147(00)01584-4. PMID: 11165668.
⁷ Yan J, Li Z, Guo J, Liu S, Guo J. Organ-on-a-chip: A new tool for in vitro research. Biosens Bioelectron. 2022 Nov 15;216:114626. doi: 10.1016/j.bios.2022.114626. Epub 2022 Aug 10. PMID: 35969963. 
⁸ Corrò C, Novellasdemunt L, Li VSW. A brief history of organoids. Am J Physiol Cell Physiol. 2020 Jul 1;319(1):C151-C165. doi: 10.1152/ajpcell.00120.2020. Epub 2020 May 27. PMID: 32459504; PMCID: PMC7468890.

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