Close up image of a caretaker helping older woman walk

A “breakthrough” Alzheimer’s drug now looks much less promising after follow-up experiments failed to reproduce successful results, scientists recently announced. Non-standard use of the drug should be halted, they say.

The drug bexarotene was able to rapidly reduce buildup of Alzheimer’s-related beta amyloid plaques in the brains of mice, reversing symptoms of the disease by 75% within two weeks, according to a 2012 report in the journal Science.

“We were surprised and excited, even stunned, when we first saw these results presented at a small conference,” said Sangram Sisodia, Ph.D., a professor of neuroscience at the University of Chicago. Sisodia was part of a multi-institution research team that repeated the initial experiments — with disappointing results.

Three different types of mice were tested, and the drug did not reduce amyloid plaques in any of them, the researchers announced.

The reasons for the failures are unclear, but the scientists said any off-label use of bexarotene to treat Alzheimer’s should stop, to protect patient safety. Bexarotene is FDA-approved to treat a type of skin cancer.

The results of the follow-up experiments were announced in the May 24 issue of the journal Science.