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Scientific Unreliability of Primate Research

Although it is true that the development of new treatments almost always involves animals, the key question is whether, scientifically, their use is necessary or beneficial. There are many reasons why animals are used in experiments, the conservatism of regulators being one of them. This is illustrated by the insistence of European regulators on continuing with acute toxicity experiments on animals when even the pharmaceutical industry agrees they are all but redundant (1). Toxicological research accounts for almost 70% of the procedures carried out on primates within the EU. Despite the general physical similarity between nonhuman primates and humans, however, this does not mean that the effect of a chemical will be the same in both species.

Whilst there is little scientific evidence that animal experiments, including those on primates, are predictive of human effects (2), there are countless examples of where they have not been. Examples include significant differences in metabolism of drugs (3,4) as well as serious side effects (5,6,7). A key international regulatory forum, the International Conference on Harmonisation, acknowledged that in terms of the way in which a drug is handled by the body, monkeys can differ from humans as much as any other species (8). The Food and Drug Administration in the US stated in a press release in January 2006, that “nine out of 10 experimental drugs fail in clinical studies because we cannot accurately predict how they will behave in people based on laboratory and animal studies” (9). The failure to find a vaccine for HIV/AIDS is an example of this. Not one of the 80 or more candidate vaccine tested successfully on primates has worked in human patients (10)


1. Robinson S, Delongeas JL, Donald E, Dreher D, Festag M, Kervyn S et al.  European pharmaceutical company initiative challenging the regulatory requirement for acute toxicity studies in pharmaceutical drug development. Regulatory Toxicology and Pharmacology 2008;50:345–52.

2. Pound P, Ebrahim S, Sandercock P, Bracken MB, Roberts I (2004). Where is the evidence that animal research benefits humans? BMJ 328:514-7.

3. Sludden J et al (1998). Liver dihydropyrimidine dehydrogenase activity in human, cynomolgus monkey, rhesus monkey, dog, rat and mouse. Pharmacol. 56:276-280.

4. Kling J (1996). In vitro models for in vivo drug profiles. Nature Biotech.14:1655-1656.

5. Morton DM, Toxicology. Letters, 1998, 102-103:545-550.

6. Gad SC (1990). Model selection in toxicology: principles and practice. J. Am. Coll. Toxicol. 291-302.10.

7. Duff, G.W. (2006) Expert Group on Phase One Clinical Trials: Independent report to the Secretary of State for Health. 7 December 2006. The Stationery Office; London UK. P.65.

8. ICH Harmonised Tripartite Guidelines: Detection of toxicity to reproduction for medicinal products (1993)

9. Mike Leavitt, Food and Drug Administration, Press Release. Jan 12th 2006.

10. Bailey, J. (2008) An assessment of the role of chimpanzees in AIDS vaccine research