MHRA announces new regulatory action to support the phase‑out of animal testing

25 Mars 2026

The UK's Medicines and Healthcare products Regulatory Agency (MHRA), responsible for ensuring that medicines and healthcare products available in the UK are safe and effective, has announced new regulatory guidance in support of the government policy to phase out animal testing.

This guidance applies to the MHRA’s approach to its review of Clinical Trial Authorisation applications and of Marketing Authorisation applications for medicinal products.

The MHRA starts by acknowledging advancements in drug development methods that do not rely on the use of animals. The MHRA indicates that a transitional period can be expected in which applications based on animal studies and those relying solely on non‑animal methods may coexist, with both potentially deemed acceptable, suggesting regulatory flexibility on a case-by-case basis.

Importantly, MHRA does not expect non-animal methods to directly replace specific animal studies that are currently expected in guidance, such as repeat dose general toxicity studies in two animal species and reproductive toxicity study in pregnant animals. Instead, it will judge whether the full evidence package — whether or not it includes animal data — is sufficient to support safe and scientifically justified use of the product.

Developers are encouraged to submit data derived from non-animal in vitro methods, explaining how this data is relevant to humans and robust. Interestingly, the MHRA does not require developers to demonstrate the human relevance of animal data, probably because current international guidelines simply assume that relevance by default. As a result, animal studies are accepted without evidentiary justification, producing an asymmetry that slows the shift toward human-relevant science.

Crucially, for products where regulators have strong prior knowledge of the mechanisms of action, pharmacological target, and the effects in humans from earlier trials, the MHRA considers it may be acceptable to permit UK clinical trials without animal studies. This includes generic products, biosimilar products, but also new chemical entities or new biologicals.

For instance, when considering applications for novel systemically administered small molecules, the MHRA supports the use of scientifically robust non-animal approaches as longs as they  provide sufficient assurance of safety in relation to the proposed clinical population and context of use. For vaccines and certain other biological medicinal products, the MHRA may consider the use of data generated with a highly similar product, provided that similarity is adequately justified and relevant to the question being addressed

For some monoclonal antibodies and similar modalities, animal studies may provide limited or no meaningful information for human risk assessment. For instance, an antibody may bind to a human-specific target, or may have different downstream effects in humans due to inter-species differences in physiology and disease mechanisms. In such situations, the MHRA may consider applications that do not include animal studies, and that are grounded in human-relevant mechanistic studies, prior human experience, and robust analytical and functional characterisation. 

For certain advanced therapy medicinal products, such as gene-based therapies, cell-based therapies, and bioengineered tissues, that often rely on human-specific mechanisms, animal models may not be scientifically relevant or predictive of human safety. In these cases, applicants are expected to present a human-relevant non-clinical evidence package that addresses key safety considerations using alternative approaches, including in vitro studies.

For companies developing medicines without any animal studies, MHRA is creating a new early‑review mechanism. By 2026, companies will be able to submit Module 4 nonclinical data to MHRA before submitting the full Marketing Authorisation Application (MAA). In this manner, MHRA will allow to companies to get regulatory feedback on their non-animal-only package early, reducing regulatory uncertainty and helping them understand whether their data package is likely to be acceptable before submitting a full MAA.

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