Mice treated with the drug, known as bexarotene, became rapidly smarter and the plaque in their brains that was causing their Alzheimer’s started to disappear within hours, said the research in the journal Science.

“We were shocked and amazed,” lead author Gary Landreth of the Department of Neurosciences at Case Western Reserve University School of Medicine in Ohio told AFP.

“Things like this had never, ever been seen before,” he said.

The drug works by boosting levels of a protein, Apolipoprotein E (ApoE), that helps clear amyloid plaque buildup in the brain, a key hallmark of Alzheimer’s disease.