XCellR8 has been awarded Innovate UK funding to continue development of its animal-free replacements for acute oral toxicity testing. We’re so excited to be starting a ground-breaking research project this month, and we hope it will make a significant impact on the replacement of animal testing.

Outdated acute toxicity tests aren’t relevant enough to humans

LLNA tests involve suffering for miceMore than 80,000 animals are currently used every year in acute toxicity testing in the EU alone1, using the outdated “LD50” type methods even though they’ve been widely discredited. Chemicals are assessed for short term toxic effects by force feeding high doses until scientists find the dose that is lethal to 50% of the animals. Not only is this ethically unacceptable, it’s poor science too, with very little relevance to humans.

The LD50 concentration is of extremely limited value when it comes to interpreting the consequences for day-to-day life, when humans are exposed to much lower concentrations in a range of application scenarios. For example, our exposure to an ingredient in a personal care product could vary enormously depending on whether it’s a rinse-off or leave-on product. When it comes to make up, extent of use can play a big part, for example, how many times a day lipstick is re-applied. When it comes to household cleaning products, some users may wear a mask or gloves and use the product more regularly than others.

Latest developments in Next Generation Risk Assessment (NGRA) are moving away from the tick-box exercise of simply performing traditional animal tests and are looking at multi-faceted approaches combining the latest in vitro science with computer-based modelling (in silico). One of the challenges with this endpoint has always been a lack of human data for benchmarking, with only small numbers of anecdotal cases of accidental exposure, which often don’t record the level of detail needed to inform future risk assessment.

It’s time for a scientifically and ethically advanced solution

At XCellR8, we’re determined to play our part in finding a scientifically and ethically advanced solution that’s highly predictive of human acute oral toxicity and relevant to our real-life exposure to chemicals.

Scientist in the labBased on ECHA’s statements about the role in vitro cytotoxicity tests can play in reducing the numbers of animal tests through a weight of evidence approach, we have already developed AcutoX – a human cell-based test correlating an in vitro equivalent of the LD50 value with GHS class for acute oral toxicity. AcutoX is in use by leading cosmetic ingredient suppliers to help build a weight of evidence for REACH submissions without the use of animals.

The Challenge

Now, we’re delighted to have been awarded funding through Innovate UK to build on this work. We’ll be adapting the human fibroblasts used in the test to fully defined culture conditions, to ensure maximum reproducibility as well as the ethical benefits of our animal product free approach. Then we’ll introduce a second cytotoxicity endpoint and incorporate metabolism, to create a more comprehensive picture of how chemicals impact cell health with and without metabolic conversion. ECVAM have highlighted the critical need to include metabolic capability into in vitro cytotoxicity assays, and we’ll be applying our expertise in animal product free systems to achieve this without using any animal derived components.

Once we’ve optimised the test, we’ll be screening a reference set of up to 75 chemicals. We’ll choose the reference set in collaboration with our industry partners and aim to create a robust prediction model with relevance across a range of industry sectors.

Combining this work with exciting developments in in silico modelling for acute toxicity, such as the recent publication from Kamel Mansouri and colleagues2, we’re starting to feel much more optimistic that the end of the LD50 type tests could finally be in sight, giving way to 21st Century human-relevant science.

We welcome comments and questions about this work and please let us know if you’d like to receive updates on the progress of the project.

1 2019 report on the statistics on the use of animals for scientific purposes in the member states of the European Union 2015-2017.

2 Mansouri, K et al (2021). CATMoS: Collaborative acute toxicity modelling suite. Environmental Health Perspectives 129 (4): 047013-1 – 18.

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