A drug hailed as a pioneering method of treating Alzheimer’s has been discredited by scientists, after experts were unable to replicate its results this week.
Bexarotene, sold under the name Targretin, had caused ripples of excitement across the medical profession, following high profile research that suggested it could be used to treat the symptoms of Alzheimer’s.
The 2012 research, produced by Gary Landreth and colleagues at Case Western Reserve University in Cleveland and published in Science journal, reported that the drug appeared to reduce the brain plaque build-ups linked to the disease when administered to mice.
Once the results of the study were made public, patients began requesting the drug and some doctors reportedly began prescribing it.
However, a team of experts have now written in the same journal that they have been unable to re-create the results found in the original survey, plunging its validity into doubt.
Sangram Sisodia, professor of neuroscience at the University of Chicago, decided to investigate claims made that the drug could reduce the areas of plaque by 50 per cent within three days, and by 75 per cent in two weeks.
In his replica study published on Thursday, he said: “In view of the significant implications of these landmark findings for the development of novel AD therapeutics, we performed a small pilot study […] using 8-month-old male APP/PS1 mice that were treated orally with a commercial source of bexarotene for seven days.”
Crucially, he said: “We failed to observe any differences in hippocampal or cortical amyloid plaque area or plaque counts between vehicle and bexarotene-treated animals.”
Bexarotene was approved by the FDA in 1999 as a treatment for skin cancer, but has never before been tested as a treatment for humans with Alzheimer’s. Because it has been approved by the FDA it can be prescribed by physicians for use ‘off label.’
However, some scientists argued that whilst the effects on brain plaque had not been replicated, the cognitive improvements had.
Writing in Science, Professor Koldamova said: “We believe these findings make a solid case for continued exploration of bexarotene as a therapeutic treatment for Alzheimer's disease.”
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