Question and Answer with…

Question and Answer with…

Dr Carol Treasure

Founder and Managing Director of
Non-Animal Testing Lab, XCellR8

How did you get involved in the world of non-animal testing?

It started with a childhood interest in biology, nurtured by long walks in the countryside with my Dad. Then, I went to Sheffield to do my degree in Physiology & Pharmacology which is where I first witnessed animal testing and resolved that there had to be a better way, not just ethically but scientifically too.

A PhD at FRAME (Fund for the Replacement of Animals in Medical Experiments) followed, and I’ve since spent my career helping organisations adopt non-animal technologies.

Why are you such a strong advocate of non-animal tests?

Strict validation processes now mean that a non-animal test must satisfy a high number of criteria to gain regulatory acceptance, which proves to regulators around the globe that they are reliable and robust when compared to historical animal tests, most of which were never validated. This gives us a much higher level of scientific confidence in the new in vitro approaches than in the traditional animal models. The ethical aspect of this shift is self-evident, and the sooner animal testing can be eradicated, the better.

Can the non-animal tests provided by XCellR8 help companies with REACH compliance?

Yes! Key human health endpoints using regulatory methods include skin corrosion, skin and eye irritation and skin sensitisation. In the cosmetics sector, most ingredients fall under Annex VII of REACH (1-10 tonnes imported into the EU each year). Non-animal tests are available for all of the human health tests required under Annex VII, with the exception of acute toxicity. For other chemical industry sectors importing greater quantities, additional tests are required and in some cases there are currently no regulatory in vitro methods available.

Which tests do you receive most questions about and why?

Definitely skin sensitisation testing. This is a more complex pathway in the body compared with things like irritation and corrosion, and so a combination of 3 in vitro tests are required to model the process accurately. All 3 tests now have regulatory approval and are OECD Test Guidelines, but this fact is often overlooked when people are considering their testing strategy.

In a nutshell, can you explain the 3 regulatory in vitro tests for skin sensitisation?

The complex pathway of skin sensitisation was only recently mapped out in detail, using a system known as an Adverse Outcome Pathway (AOP). The 3 tests measure human responses to a chemical at 3 points in AOP – these are described as key events. The first key event is contact between the chemical and skin proteins. Protein binding increases the likelihood of the chemical being a skin sensitiser. This is measured by the Direct Peptide Reactivity Assay (DPRA). Key events 2 and 3 are measured using human cell culture based tests that assess the activation of skin epidermal cells (keratinocytes) and immune cells (dendritic cells) – these are the KeratinoSens and h-CLAT methods respectively. For REACH compliance, these in vitro methods must now be used and current guidance recommends a “2 out of 3” approach, whereby 2 positive results would result in classification of a chemical as a skin sensitiser.

Which non-animal tests aren’t yet available for REACH?

A current drawback of the 3 in vitro skin sensitisation tests is that they are not validated for potency ie. how strong is the sensitising potential? In some cases, regulators are asking for an animal test as a follow-up, usually the Local Lymph Node Assay. Efforts are underway to ensure that in vitro methods for potency assessment are available ASAP, and new methods – such as the human genomic screen GARD – are already being validated for potency prediction. Other human endpoints for which there are currently no in vitro tests available include reproductive toxicity, repeat-dose and acute toxicity.

How do companies address the gaps when non-animal tests aren’t available?

In some cases, non-regulatory methods can be used as part of a weight-of-evidence approach. Annex XI of REACH allows for methods that have reached an appropriate stage of pre-validation to be used. They may be combined with read-across data to argue against the need for animal testing. XCellR8 has developed a non-regulatory screen for acute toxicity, which some companies are already using for this purpose. The European Chemicals Agency (ECHA) states that animal testing for REACH compliance should only be used as a last resort, but confusingly it is still requiring it in quite a few scenarios. At XCellR8, we want to provide the best possible prediction of human health, and so we work with companies to look at non-animal strategies that enable them to challenge the status quo.

What do you think the future holds – will animal testing in the chemical industry ever be completely eradicated?

These are very exciting times in test development and I truly believe that a major shift has occurred over the past decade. A huge number of industry scientists and regulators now recognise animal testing as an archaic approach that will one day be as extinct as the dinosaurs, and we’re doing all we can to help accelerate that process!

To find out more about testing services offered by XCellR8, visit