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It Worked in Monkeys Therefore . . .

A press release titled Experimental treatment protects monkeys from lethal Ebola virus post-exposure and could be used to protect humans, apparently from Thomas W. Geisbert of Boston University School of Medicine concerning his article in Lancet, states:

Use of tiny particles of genetic material to interfere in the replication process of the lethal Zaire Ebola virus (ZEBOV) has protected monkeys exposed to the virus from death from haemorrhagic fever. This proof-of-concept study shows that such protection should also be possible in humans, and further studies in monkeys to analyse dosing and toxicology will be required before the treatment is licensed for human use . . . Professor Geisbert adds: "We are excited to publish the first demonstration of complete postexposure protection against a lethal human infectious disease in non-human primates using siRNAs. We believe this work justifies the immediate development of this treatment as an agent to treat EBOV-infected patients either in outbreaks or accidental laboratory exposures." (Emphasis added.)

Before I begin let me emphatically state that I sincerely hope this vaccine does work in humans thus preventing much suffering and death. My issue with this release is once again the prediction question.

Geisbert equates proof of concept with proof that the pertubation under study, namely the vaccine, will work in humans. While this is standard for the animal-based research literature, it is also wrong. Proof of concept in this context means nothing more than “we had an idea and it turned out that the idea was viable in species X.” After showing that the vaccine was effective in one particular nonhuman primate the researchers then have a hypothesis about human reaction and that is all.

Shanks and I state in Animal Models in Light of Evolution:

This chapter addresses the use of the word predict as applied to animal models. It is our position that there has been insufficient attention to the meaning of prediction in the context of biomedical inquiry. Predictions are statements about expected future observations, but in science they are not, as they are in ordinary usage, merely lucky guesses. Scientific predictions are derived from hypotheses. Crudely speaking, a hypothesis is something that explains past and present observations and enables the investigator to form (under suitable conditions) expectations—predictions—about the course of future events. These predictions about the course of future events must be testable—they must be sensitive to the fruits of evidential inquiry (which may, in the biological sciences, involve carefully-controlled experiments, field observations, or some combination of both).

In the case of predictive animal modeling, what we are typically interested in is prediction of human outcomes. The animal model systems are stimulated (perhaps by some toxicological insult of interest) and animal data is gathered. This data derived from the animal model, in and of itself, settles nothing about the actual course of human phenomena. The animal data enables the investigator to form hypotheses—expectations—about what he or she thinks is likely to happen when humans are similarly stimulated (with all the due allowances for differences in dose and so on). At this point all the investigator has is a hypothesis about human responses. The business of science is the very business of the testing of hypotheses. In the present case this requires careful studies of humans so that the human data can be compared with the expectations rooted in animal model data, thereby confirming or falsifying the animal-based hypotheses (it is also possible that the evidence gathered does not settle the issue one way or another, and hence that there is a need for more detailed studies). We again point out—to forestall a species of fatuous criticism—that not all tests and studies involving animals are done with prediction in mind. Nevertheless, those tests promoted as being predictive must be judged by how well they actually predict human response. It also makes sense to ask whether a particular method has a track record of predictive success, and if so, how this was determined. (p251-2)

The animal-based research community relentlessly berates those opposed to animal-based research by equating the advocacy of abandoning animal testing with human experimentation. Test the drug on “your dog or your child” is a frequently heard refrain. This is a false dichotomy. Animal testing for efficacy and safety is simply not predictive for humans. If the animal-based research community is concerned about humans, they should not be so flippant in suggesting drugs proceed to clinical trials on the basis of animal testing.

Human-based research and testing can be ethically performed (and is everyday). But the notion that “it worked in animals therefore it should work in humans” is a straightforward example of a researcher admitting he believes that animal testing is predictive and such faith has been repeatedly tested and proven wrong. As I have said many times before, the myth that animals can predict human response to drugs and disease is constantly purported by those with a vested interest in animal models. This is but one example.

(See Animal Models in Light of Evolutionfor more on why animal models cannot predict human response to drugs and disease.)


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