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Scientists Can't Replicate Surprising Finding on Alzheimer's Treatment

Skin cancer drug had no effect on brain plaques in mice, three separate research teams report

THURSDAY, May 23 (HealthDay News) -- Although a study in 2012 suggested a cancer drug could reverse the thinking and memory problems associated with Alzheimer's disease, three groups of researchers now say they have been unable to duplicate those findings.

The teams said their research could have serious implications for patient safety since the drug involved in the study, bexarotene (Targretin), has serious side effects, such as major blood-lipid abnormalities, pancreatitis, headaches, fatigue, weight gain, depression, nausea, vomiting, constipation and rash.

"Anecdotally, we have all heard that physicians are treating their Alzheimer's patients with bexarotene, a cancer drug with severe side effects," said study co-author Robert Vassar, a professor of cell and molecular biology at Northwestern University Feinberg School of Medicine, in Chicago. "This practice should be ended immediately, given the failure of three independent research groups to replicate the plaque-lowering effects of bexarotene."

The U.S. Food and Drug Administration approved bexarotene in 1999 to treat refractory cutaneous T-cell lymphoma. Once approved, however, the drug also was available by prescription for "off-label" uses.

The 2012 study suggested that bexarotene was able to rapidly reverse the build-up of beta amyloid plaques in the brains of mice. The authors of the initial study concluded that treatment with the drug might reverse the cognitive and memory problems associated with the development of Alzheimer's.

Sangram Sisodia, a professor of neurosciences at the University of Chicago and a study co-author of the latest research, admitted being skeptical about the initial findings.

"We were surprised and excited -- even stunned -- when we first saw these results presented at a small conference," Sisodia said in a University of Chicago Medical Center news release. "The mechanism of action made some sense, but the assertion that they could reduce the areas of plaque by 50 percent within three days and by 75 percent in two weeks seemed too good to be true."

In attempting to duplicate the findings, the research teams found that they were indeed too good to be true.

"We all went back to our labs and tried to confirm these promising findings," Sisodia said. "We repeated the initial experiments -- a standard process in science. Combined results are really important in this field. None of us found anything like what they described in the 2012 paper."

Researchers at the University of Chicago, Northwestern University, Massachusetts General Hospital, Washington University in St Louis and the University of Tubingen in Germany reported in the May 24 issue of the journal Science that they did not find any reduction in beta amyloid plaques during or after treatment with bexarotene in three different strains of mice.

Bexarotene has never been tested on people as a treatment for Alzheimer's disease. Currently, there is no cure or effective treatment for the progressive condition, which affects an estimated 5.3 million Americans.

More information

The U.S. National Institutes of Health provides more information on Alzheimer's disease.


SOURCE: University of Chicago Medical Center, news release, May 23, 2013.

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