These consider some of the issues relating to the use of animals in biomedical research:
Evolutionary biologists (e.g. Perlman 2016) note that while animal research might be useful for understanding processes that arose early in evolution (i.e. processes that humans share with other species) it is less useful for understanding the chronic diseases suffered by modern humans because these chronic diseases are a result of human lifestyles and the unique way in which human life has evolved. Although human and non-human animals may have many genetic, biochemical and physiological similarities, when it comes to complex and evolved living systems even minor differences can result in significant differences in biological processes and outcomes.
Phase 1 trials (where drugs are first tested in human volunteers) have shown that even the smallest biological differences between humans and animals can lead to disaster when first applying animal data to humans. TGN1412 was tested in non-human primates (NHPs) because of their close relationship to humans but soon after being given a dose 500 times smaller than that found safe in animal studies, all six human volunteers began to experience a chain of events which rapidly led to severe inflammation and multiple organ failure (Attarwala 2010). Intractable differences between species mean that animals cannot reliably predict how the human body will respond to a disease or a drug.
Many believe that NHPs, because of their close relation to human primates, must have relevance for human medicine. However the ability of NHPs to predict human adverse drug reactions is poor and some drugs that were safe for NHPs have gone on to injure or kill humans. For example the arthritis drug Vioxx, which killed approximately 55,000 people in the US alone, was found to be safe in monkeys. NHPs are also used for brain research, yet the most dramatic differences between humans and other primates are found in the brain. Perhaps this helps explain why, of over one thousand drugs for stroke that have been developed and tested in primates and other animals (O’Collins et al 2006), all but one have failed and even harmed patients in clinical trials (e.g. Tirilazad International Steering Committee 2001). And even the benefits of the one ‘successful’ drug are controversial (Sandercock and Ricci 2017).