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NC3Rs | 20 Years: Pioneering Better Science
Office-led project

Reducing the use of recovery animals

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  • Reduction


Rodents, dogs and non-human primates are included as 'recovery animals' in many toxicology studies to determine whether animals can recover from any adverse effects caused by the compound being tested. Working with the MHRA, and 32 other organisations (including companies and regulators), we have examined whether recovery animals are required on all studies and all dose groups and how reducing this use might impact on internal and regulatory decision making.  

Our analysis has shown that there is variation in industry practice, for example, with the number of recovery animals used per compound to support first-in-human clinical trials ranging from 0 to over 100. The most common rationale for the inclusion of recovery animals is ‘default’ company practice or perceived regulatory expectation. By sharing data on 259 studies for 137 compounds (including 53 biologicals and 78 small molecules) we have identified that the use of recovery animals could be reduced by up to 66%, saving thousands of animals globally each year.  Based on this we have developed recommendations that move away from a default approach to the inclusion of recovery animals and instead encourage science-based case-by-case consideration. This work has been published in Regulatory Toxciology and Pharmacology [1].

Figure: Variation in the number of recovery animals included per compound in regulatory toxicology studies to support first-in-human trials

Bar graph showing the number of recovery animals used per compound on x-axis and the number of compounds studies on the y-axis. The most popular option was the use of between 26-50 recovery animals per compound, however this varied between 0 and 101+ animals.

Related content


  1. Sewell F et al. (2014) Recommendations from a global cross-company data sharing initiative on the incorporation of recovery phase animals in safety assessment studies to support first-in-human clinical trials. Regulatory Toxicology and Pharmacology 70: 413-429. doi:10.1016/j.yrtph.2014.07.018
  2. Sewell F et al. (2018). Trends towards a reduction in the use of recovery animals for First-in-Human (FIH) studies from 2013 to 2017. Poster presented at ACT, November 2018.
  3. Sewell F et al. (2018). Use of recovery animals for human safety assessment across the pharmaceutical development package. Toxicology Letters 295 (S1): S223-4.  Poster presented at EuroTox, September 2018.
  4. Poster presented at the NC3Rs Toxicology Showcase, September 2016: Global cross-company data-sharing on the use of recovery animals for human safety assessment.