Of Mice and Men: A Cancer Drug Combats Alzheimer’s in Rodents, but Will It Work in Humans?

It can take years to progress from a mouse study to an effective treatment for people

Less than two weeks after a New York Times article reported that two mouse studies had “immediate” implications for people with Alzheimer’s, a Case Western University press release announced that researchers in its school of medicine “have made a dramatic breakthrough in their efforts to find a cure” for the disease. Here again, the study was in mice … but that didn’t stop numerous media outlets from flooding the airwaves and Web with the press release, which implied that the results could have implications, soon, for the treatment of Alzheimer’s in humans.
Those who bothered to contact the researchers fared better in their coverage. CBS News wrote: “One caveat to the study — mice aren’t people. Despite how promising the findings may seem, the researchers tempered expectations.” Study author Gary Landreth, a neuroscientist, told CNN: “I want to say as loudly and clearly as possible that this was a study in mice, not in humans. … We’ve fixed Alzheimer’s in mice lots of times, so we need to move forward expeditiously but cautiously.” The Washington Post acknowledged that  the “findings were dramatic, but their relevance to people with Alzheimer’s disease is unknown.”
Moving from mice to humans is no simple matter. Potential drugs normally have to be proven safe in a larger animal model — in Alzheimer’s that may include rabbits, dogs and/or non-human primates (e.g., monkeys). It takes many steps to get to that point, after which the compound being tested then has to be proven safe in humans. These safety studies are done at varying doses, and the compound also may need to be given various ways — by pill, injection, IV drip, etc. Given all these steps, it can take years before efficacy — whether the compound actually works — can be tested and assessed. In a disease as complex as Alzheimer’s, proving efficacy is extraordinarily difficult. How long does the study have to run before it can show that a compound halts or reverses disease progression? Add to that the fact that no drug works in everyone, nor at every stage of the disease, so populations who are most likely to benefit need to be identified. And what about side effects? If they significantly interfere with a person’s quality of life, as current Alzheimer’s drugs often do, the people who are testing the drug must weigh benefits versus risks. All this takes time, money and most of all, patience.
On the positive side: Because bexarotene — the drug tested by Case Western researchers — has already undergone safety tests that led to Food and Drug Administration approval for a type of cancer (cutaneous T-cell lymphoma), it could be easier/faster to get it into clinical trials for Alzheimer’s than it would be for a new, untested therapeutic. The drug would, however, still have to undergo significant testing re: efficacy, tolerability, dosing and so forth.
Particularly worrying about the skewed nature of much of the media coverage of the Case Western research is that people are clamoring for the drug and, according to Landreth, some have started taking it. This is potentially dangerous because it is untested in humans for anything other than the specific cancer it was approved for. Media would do well to provide some context for the progress that is taking place against Alzheimer’s and other degenerative diseases. Many discoveries stemming from today’s research may well lead to treatments, and perhaps cures, down the road. But that road is long and paved with challenges — and to imply otherwise promotes false hopes and, in the near term at least, disappointment.

Marilynn Larkin
By Marilynn Larkin
Marilynn Larkin is an award-winning health and medical journalist and editor. Her work has appeared in national consumer magazines and medical/scientific  publications. She is a former contributing editor to The Lancet and the author of five health books for consumers.

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