Empirical evidence regarding the predictive value of animal models comes in the form of research amenable to quantification via table table11 and examples of multiple failures over many years in the same subject. Examples of the latter would include the search for a vaccine against HIV and neuroprotective drugs. Approximately 100 vaccines have been shown effective against an HIV-like virus in animal models, however, none have prevented HIV in humans 67, 68. Even if an HIV vaccine came from animal-based research tomorrow, the animal model per se would not be predictive for humans as the PPV would be somewhere in the 0.01 area. Likewise, up to one-thousand drugs have been shown effective for neuroprotection in animal models but none have been effective for humans 23-25, 29, 38, 61, 69-71. The predictive value is again minimal even if a successful drug is currently in development. The animal model has failed as a modality for predicting neuroprotection. Along the same lines, of twenty two drugs tested on animals and shown to be therapeutic in spinal cord injury, none were effective in humans 72. As we are attempting to prove that animal models are not predictive such examples are important. Relatively few failures can disqualify a practice from being of predictive value while proving the opposite requires a large number of successes.
The success of the animal model in basic research can also be questioned based on the fact that, according to one report, only 0.004% of basic research papers in leading journals led to a new class of drugs 41, 73 and the fact that the success rate for target identification is similarly dismal 74-78. For example, in part because the targets derived from animal models are not predictive for humans, the percentage of new drugs in development, after initial evaluation, that ultimately make it to market is somewhere in the area of 0.0002% 79, 80. We acknowledge that the goals of basic research differ from the goals of applied research where predictive values are most often evaluated. However, because of funding challenges, research that would have historically been considered basic is now being promoted as applied and hence should be judged accordingly 41.
Well that kinda sucks, but is in line with how I’ve been feeling lately. I see an interesting study title, get excited, and then saddened to see that it was done in mice.
