Newly developed drugs that display high levels of efficacy in scientific mouse models often fail when brought to human clinical trials, according to a report from NPR.
These failures are simultaneously disappointing and pricey as they increase the cost of new drug development.
Here are four things to know.
1. The use of animals in scientific research began more than 100 years ago, though at the onset of this practice the animals were not seen as surrogates for humans. Researchers using rats in experiments simply wanted to know more about rats, said Todd Preuss, PhD, an anthropologist at the Yerkes National Primate Research Center at Emory University in Atlanta, according to NPR.
2. Eventually rodents became viewed as prototypical mammals and not specialized animals. Sellers of rats and mice pitched scientists on the idea rodents could be used to learn more about humans.
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"It wasn't strictly a financial interest," Dr. Preuss told NPR. "[The sellers] really believed that you could do almost anything [with rodents]. You could learn about any feature of human organization, you could cure almost any disease by studying these animals."
3. Rodents and humans have been on separate evolutionary paths for millions of years, according to the report. The development of distinct genetic differences is the reason some treatments that prove effective in mice do not translate into effective human treatments. Still, the momentum to continue using mice as human proxies in the laboratory setting is significant.
"Once these communities exist, then you have an infrastructure of knowledge: how to raise the animals, how to keep them healthy," Dr. Preuss told NPR. "You have companies that spring up to provide you with specialized equipment to study these animals. So there's a whole institution that develops."
4. Some experts argue mouse models would be more successful if the experiments were set up like human trials. Currently, the populations of mice used in studies are tightly controlled. Dr. Joseph Garner, associate professor of comparative medicine at Stanford (Calif.) University, told NPR he and his colleagues once attempted to run identical experiments in six different mouse facilities, which produced inconsistent results. Dr. Garner said experiments should no longer be conducted this way.
"We try to control everything we can possibly think of, and as a result we learn absolutely nothing," said Dr. Garner in reference to animal studies. "Maybe we need to stop thinking of animals as these little furry test tubes that can be or even should be controlled. And maybe instead we should think of them as patients."
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