An Associated Press article reported: Malaysia minister: God made animals for testing. The minister was commenting on plans by an Indian company, Vivo BioTech Ltd, to start an animal testing facility in Malaysia. Even though it appears the minister has no scientific training, his statements accurately reflect the position of many scientists I have spoken with.
"God created animals for the benefits of human beings. That's why he created rats and monkeys ... We cannot test on human beings," he told The Associated Press. "This is the way it has to be. God created monkeys, and some have to be tested."
What is left unaddressed here, and in many such statements from scientists with a vested interest in the outcome is whether animal testing works in the first place; whether it predicts human response. Many scientists admit it does not.
The executive director for cancer research at Merck Research Laboratory 1997: "The fundamental problem in drug discovery for cancer is that the model systems are not predictive at all." (Gura 1997) Meijers, Swaen and Bloemen compared epidemiological evidence of cancer risk to tests performed on animals. They concluded that animal tests for carcinogenicity: “have limited predictive value for the human situation.” (Meijers, Swaen and Bloemen 1997)
Chabner and Roberts:
Fewer than 10% of new drugs entering clinical trials in the period from 1970 to 1990 achieved FDA approval for marketing, and animal models seemed unreliable in predicting clinical success . . . (Chabner and Roberts 2005) (Emphasis added.)
January 12, 2006, then U.S. Secretary of Health and Human Services Mike Leavitt: "Currently, nine out of ten experimental drugs fail in clinical studies because we cannot accurately predict how they will behave in people based on laboratory and animal studies." (FDA 2006)
Spedding et al writing in Nature Reviews Drug Discovery 2005:
Animal models often cannot be transposed to Phase I and Phase II clinical testing, and Phase I/II clinical testing is often not transposable to Phase III trials and the general population. (Spedding, Jay, Costa e Silva and Perret 2005)
In the April 1, 2010 issue of The Scientist:
Mouse models that use transplants of human cancer have not had a great track record of predicting human responses to treatment in the clinic. It’s been estimated that cancer drugs that enter clinical testing have a 95 percent rate of failing to make it to market, in comparison to the 89 percent failure rate for all therapies . . . Indeed, “we had loads of models that were not predictive, that were [in fact] seriously misleading,” says NCI’s Marks, also head of the Mouse Models of Human Cancers Consortium . . . (Emphasis added.)
In a survey of the toxicological profiles of 50 compounds in rodent and non-rodent species, sensitive criteria of toxicity were found to be the simple characteristics, such as clinical observation of the living animal, growth and organ weight analysis, liver and kidney function tests and histological examination of selected tissues. There was poor correlation of target organ toxicity across the species . . . It is more relevant to ask how often the same target systems can be identified for the rodent and non-rodent species. The best correlations were never greater than 20%, even when considering hepatotoxicity . . . It must be accepted that simple extrapolation across species is unrealistic. (Heywood 1981) (Emphasis added.)
The present paper deals with 45 major new drugs that have been considered by the Committee on Safety of Medicines during the past eight or nine months . . . It can be said with certainty that correlations between animal toxicity and adverse side effects in man do exist and that they are considerably more frequent than discrepancies. As a very approximate estimate, for any individual drug, up to 25% of the toxic effects observed in animal studies might be expected to occur as adverse reactions in man. (Fletcher 1978) (Emphasis added.)
Dr. Ralph Heywood, former director of Huntington Research Center (UK) 1989 said: “… the best guess for the correlation of adverse reactions in man and animal toxicity data is somewhere between 5 and 25%.” [(Heywood 1990) p57-67] (Emphasis added.)
In a comparative drug study, scientists examined the results from six drugs in animals and humans. They found the groups shared 22 side effects (true positives). The animals incorrectly identified 48 side effects that did not in fact occur in humans (false positives).
The animals incorrectly missed 20 side effects that did occur in humans (false negatives).
The above translates to a sensitivity of 52% and a positive predictive value of 31% [(Lumley 1990) p73]. (The values are actually less, but I will leave that for another time.) This is one piece of empirical evidence that proves animals cannot predict human response. If people who claim to be scientists disagree with me and insist that animal models are predictive, this is the kind of study that needs to be presented. Not anecdotes or a series of anecdotes.
(See Animal Models in Light of Evolutionfor an in depth examination of the above in addition to the evolutionary biology and complex systems analysis supporting my position).
Animal models cannot predict human response to drugs and disease. Empirical evidence, evolutionary biology, and a study of complex systems all confirm and explain this. There is no law against consulting a Ouija board or tossing a coin before deciding whether to develop a new drug. There are laws mandating animal testing. Unfortunately all three methods give about the same results. That’s not my opinion, that’s what the science supports.
(If all this science talk is a little too much for you but you are nonetheless interested in the subject, please try reading FAQs About the Use of Animals in Science: A handbook for the scientifically perplexed.)
Chabner, B. A., and T. G. Roberts, Jr. 2005. Timeline: Chemotherapy and the war on cancer. Nat Rev Cancer 5 (1):65-72.
FDA. 2010. FDA Issues Advice to Make Earliest Stages Of Clinical Drug Development More Efficient. FDA, June 18, 2009 2006 [cited March 7 2010]. Available from http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/2006/ucm108576.htm.
Fletcher, A. P. 1978. Drug safety tests and subsequent clinical experience. J R Soc Med 71 (9):693-6.
Gura, T. 1997. Cancer Models: Systems for identifying new drugs are often faulty. Science 278 (5340):1041-2.
Heywood, R. 1990. Clinical Toxicity--Could it have been predicted? Post-marketing experience. In Animal Toxicity Studies: Their Relevance for Man, edited by CE Lumley and S. Walker. Lancaster: Quay.
Heywood, R. 1981. Target organ toxicity. Toxicol Lett 8 (6):349-58.
Lumley, C. 1990. Clinical toxicity: could it have been predicted? Premarketing experience. In Animal Toxicity Studies: Their Relevance for Man, edited by C. Lumley and S. Walker: Quay.
Meijers, J. M., G. M. Swaen, and L. J. Bloemen. 1997. The predictive value of animal data in human cancer risk assessment. Regul Toxicol Pharmacol 25 (2):94-102.
Spedding, M., T. Jay, J. Costa e Silva, and L. Perret. 2005. A pathophysiological paradigm for the therapy of psychiatric disease. Nat Rev Drug Discov 4 (6):467-76.