How PXB-Mouse? helps in 3Rs

Russell and Burch's “The Principles of Humane Experimental Technique” was first published in 1959. They introduced and defined the terms Replacement, Reduction, and Refinement, known as 3Rs, for minimizing the potential for animal pain and distress in biomedical research. In this summary we explain how using PXB-Mouse? (mouse model with a highly humanized liver) helps in advancing the 3Rs.

"Happy animals make good science" (Trevor Poole, 1997)

Replacement

In many types of biomedical and toxicological research, animals are used because ethical considerations preclude conducting the experiments on humans. At this point complete replacement of animals in preclinical research is not achievable. In the meantime, animal experiments are irrelevant and misleading when animals do not provide understanding of human response to xenobiotics. So, utilizing a relevant animal model capable of predicting human specific outcome, is, in fact, the relative Replacement.

As mentioned above, utilizing relevant animal models capable of predicting human-specific outcome can be considered as relative Replacement. The toxicity evaluation of drug candidates and chemicals in primates and humans would be unethical, while predicting toxicity with in silico methods can be oversimplified and sometimes irrelevant. Moreover, controversy surrounding issues of informed consent highlight additional ethical constrains on obtaining human tissue for research.

PXB-Mouse? has up to 95% of stable human hepatocyte engraftment. It allows relevant human-specific responses of human hepatocytes to be studied in a true in vivo setting. Thus, utilizing PXB-Mouse? for liver-related studies of xenobiotics replaces less relevant testing in rats, dogs, rabbits and other small species, as well as in monkeys and other primates.

A recent study in drug metabolism and pharmacokinetics (DMPK) shows that PXB-Mouse? is more predictive in DMPK than species such as rats and monkeys. Clearance values of known drugs were predicted at 83.3% with PXB mice, 70% with monkeys and 46.7% with rats within a three-fold range of actual values among 30 compounds. With regard to human volume of distribution at steady state (Vdss), PXB-Mouse? predicted Vdss with high accuracy for 29 of the 30 drugs*.

PXB-Mouse? use in drug and chemicals development is aligned with the Relative Replacement in 3Rs approach

Reduction

Reduction in the number of animals used in experiments while preserving animal welfare is a major objective of the 3Rs. This can be achieved in different ways. One of them is data sharing – publishing results, generated with the use of animals to avoid duplication of experiments. PhoenixBio encourages its customers to publish their research results and has an internal research group, which shares experimental results through publications in peer-reviewed journals.

There are multiple production facilities for PXB mice and PhoenixBio has achieved high efficiency in generating significant number of PXB-grade mice every month. PhoenixBio selects PXB-mice with similar parameters (such as body weight, replacement index, age, etc.). This allows lower variability in experiments and reduced statistical errors, despite the use of smaller number of mice per group than regular toxicity and drug metabolism studies.

New methodologies were reported recently in a study with PXB-Mouse? - repeated-dosing and cassette dosing. Applying these methods to the DMPK studies with PXB-Mouse? allowed evaluation of 30 known drugs with three live animals*.

As well, three live PXB mice were used in the identification of human-specific metabolic pathways prior to a human radio-labeled mass-balance study**.

PXB-Mouse? is proven in achieving research objectives using noticeably less animals per study in comparison to regular toxicity and DMPK studies

Refinement

Russel and Burch’s Refinement aim to decrease “inhumane procedures applied to those animals which still have to be used [in experiments]”. It is implemented through best practices in housing, husbandry and care, experimental procedures, pain management and humane endpoints. Standards for laboratory practice are defined in countries’ guidelines, and PhoenixBio Group of companies follow the proposed standards. Improvement of experimental procedures is a continuous process and evolves as resources improve.

PhoenixBio project management team work directly with clients to make sure that:

• PXB-Mouse? is sufficiently relevant to the scientific question clients are evaluating
• Experimental design is optimal, and the study targets scientific objectives set by client
• Experienced and trained staff will conduct the study and use reliable equipment throughout the process
• Animals have very tight parameters, which allows for fewer animals in each experiment without compromising scientific output or statistical significance of obtained results
• Animal ethics committees and research teams systematically make sure to prevent, detect, reduce and eliminate pain

Good animal welfare at every PhoenixBio Group location is consistent with good science

*Miyamoto M. et al, Xenobiotica 2017; 47(12): 1052

**Igawa Y. et al, Xenobiotica 2014; 44(2): 154