May 23, 2013 at 5:31 PM ET
It sounded too good to be true and unfortunately it was. Three research studies out Thursday severely diminish the hope that a cancer drug already on the market could be an Alzheimer’s treatment.
In February 2012 scientists at Case Western University Medical Center reported that a drug approved to treat skin cancer cured a mouse of a form of Alzheimer’s. They reported the drug eliminated the plaque that is the hallmark of Alzheimer’s from the brains of the mice and that the mice seemed to recover from their memory and other cognitive problems.
The study, published in the journal Science, got doctors and patients alike excited.
If this were true it would have been a gigantic step. Since the drug, Targretin, was already approved as a cancer treatment, doctors knew its safety profile and were free to prescribe it “off label” to treat any condition, including Alzheimer’s.
Researchers quickly set up trials of the drug in people with Alzheimer’s. But some patients’ families did not want to wait for the human experiments. They asked their doctors for prescriptions and in many cases, according to anecdotal reports, they got them.
But in this week’s edition of Science, three other teams of highly respected Alzheimer’s experts report they could not repeat the mouse results.
"It was hot stuff. It was the new miracle drug for Alzheimer's,’ said Sangram Sisodia, a professor of neuroscience at the University of Chicago.
Sisodia said he and fellow Alzheimer's colleagues, who included Dr. Rudolph Tanzi of Massachusetts General Hospital in Boston and Dr. David Holtzman of Washington University School of Medicine, wanted to see if they could replicate the stunning results in their own labs. Scientists don’t usually accept results as valid until they’ve been repeated several times.
It’s one of the main reasons researchers publish their findings – so that others can try them out and validate them.
The three labs failed to see any effects on Alzheimer's plaques in three strains of mice that were treated with Targretin.
"There is absolutely no reduction in amyloid levels in the brains of mice treated with this compound," Sisodia wrote in a technical comment in the journal Science. Teams at the University of Florida and researchers at the University of Leuven in Belgium published similar findings in the same journal.
"I was a fan of the original study," said Dr. Samuel Gandy, associate director of the Mount Sinai Alzheimer's Disease Research Center in New York, who was not involved in any of the studies.
"It was very dramatic. It cut plaque loads by three-quarters over less than a week. No one had ever seen anything like it before."
Gandy has had several patients asking for the treatment, but he said the drug can damage the liver and requires very careful monitoring.
"I have universally declined and advised others to decline,” he told Reuters.
(Reuters contributed to this story)