Safety of Botulinum Toxin Still Tested on Thousands of Mice Each Year
PhD candidate calls on EU member states for greater transparency and attention to this issue
Thousands of mice are tested on each year to ensure that botulinum toxin can be safely injected into humans. This is still done, despite non-animal methods existing for over a decade for these safety tests. This issue was raised in a scientific article in 2019 but was reported to be still occurring in the Europe Union and the United Kingdom by Justine Watkins, a PhD candidate at the Faculty of Veterinary Medicine at Utrecht University, supervised by Professor Merel Ritskes-Hoitinga and fellow shared first author, research assistant Jordi Middelkoop and his supervisor Professor Daniela Salvatori. On November 12th, Watkins will make a plea at a European Union Member State meeting for greater transparency and increased regulatory attention to this topic to facilitate the phasing out of the mouse test.
Botulinum toxin blocks nerve signals to the muscles, which softens facial wrinkles for a few months, but can also help with, for example, spastic muscle twitches. This product can therefore be used for medical and aesthetic applications; however, it's shown that aesthetic concerns are the main economic driver for this product. Due to its highly potent effects on nerves and muscles, it is considered one of the most lethal substances on earth.
Effective alternatives
European regulations require that every batch of a biological substance, like botulinum toxin, used in products for human use be tested for safety and potency, as errors can occur in the production processes. Such errors can be harmful to people receiving the substance. Botulinum toxin batch testing is still performed on mice, even though over the last thirteen years companies have developed replacement methods for their specific products. One of the most promising alternatives is the so called “cell-based assay” which is a test in a petri-dish based that uses human cells to determine the safety and potency of botulinum toxin products.
Animal testing for cosmetics is banned in the European Union, but since botulinum toxin is injected independent of its use, whether aesthetical or medical, it is always classified as a pharmaceutical, meaning different rules apply.
Public Data
Justine Watkins and her co-authors studied numerous articles, product market authorisations, and public data on animal testing to reach her findings. She reviewed over thirty public Non-Technical Summaries of animal testing projects and discovered that especially the United Kingdom, Ireland, and Germany have conducted animal tests for botulinum toxin in the past ten years. The number of mice used for batch potency testing has mostly decreased since 2019 but is still estimated at over 100,000 per year. Though it appears that Germany has recently stopped the practice.
Reasons cited by applicants for (granted) animal testing permits included:
• As a precaution, in case the non-animal method failed
• For export of botulinum toxin to countries that still require animal testing
• To compare data from the new non-animal assay to the data from the animal test
• Because the company has yet to develop a specific non-animal assay for their product
• Because the company’s specific non-animal assay has not (yet) received all necessary approvals
Severe Suffering
For each batch of botulinum toxin, approximately 100 mice are injected with varying doses of the toxin. The mice are observed for 3 to 4 days. During this period, they become ill, which may result in breathing difficulties, paralysis, or even death. The test is therefore classified under the highest category of welfare impact, known as “severe discomfort”.
Obstacles in Transition to Animal-Free Safety Testing
The study also shows how difficult the transition to animal-free safety testing is. Even when non-animal methods exist, it can take years before the corresponding animal tests are discontinued. Watkins and her colleagues believes the solution lies in speeding up the phase-out of animal testing where alternatives are available. More specifically, Watkins suggests U.K. and EU regulators ensure aesthetic uses of botulinum toxin are tested without mice. Furthermore, she suggests market authorisations of new botulinum toxin products be conditional on the company developing a suitable assay within a specific timeframe, to incentivize the faster development of alternatives. In general, she believes that regulators should prioritize botulinum toxin for immediate phase out given the advancements in the field (especially by industry), the severity of the test, and the ethical concerns about using a severe animal test for a product that is popularized for its aesthetic/cosmetic applications. The study shows us that more research is needed into how to accelerate the transition to animal-free safety testing. It also makes clear that the involvement of many parties is needed: industry, regulators, academic institutions, and non-governmental organisations.
Finally, Watkins noted how hard it was to obtain reliable information about animal testing. She said: “It was incredibly difficult just to determine how many mice are used for botulinum toxin testing. That shows us that a lot still needs to be done in terms of transparency about animal testing — especially regarding animals that experience severe distress.”
The article, with co-authors from John Hopkins University, European Coalition to End Animal Experiments and Doctors Against Animal Experiments, was published as part of the SAFE Consortium in collaboration with Ombion Centre for Animal-freee biomedical translation. See also: Accelerating the transition to animal-free NGRA: A transformative governance approach.