The first problem arises with the study design of animal experiments as they are often “poorly designed, conducted and analysed” according to Michael Bracken, Professor of Epidemiology, referring to the difficult task to summarize literature based on animal studies. 

This leads to the next issue caused by the difference of metabolism rate of the commonly used mice for preclinical testing and humans. Even though mice are seen as practical test animals as they have the same organs as humans, they are approximately 3000 times smaller in size but have a seven times higher metabolic rate, leading to major differences regarding the pharmacokinetics of drugs.

Just last year researchers tried to summarize the translational success from animals to humans by comparing the preclinical outcome to the success rate of the first phases of clinical trials of 121 studies. Together a 0–100% translational success rate was reported, with some studies showing no translational success at all, while others reached a high translational success, stressing the need for a more suitable model to predict the outcome for humans.

We should re-think the settings of preclinical studies, not just to ensure the safety of volunteers for clinical trials, but also to improve animal welfare by reducing their value in this process.