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A cancer drug given to mice eliminates brain-damaging proteins, leading to improved cognition within days, but will it work in humans?

A nearly 13-year-old skin cancer drug rapidly alleviates molecular signs of Alzheimer's disease and improves brain function, according to the results of a new mouse study being hailed as extremely promising. Early-stage human clinical trials could begin within months.

In the study, published online February 9 by Science, researchers from Case Western Reserve University in Cleveland and colleagues used mice genetically engineered to exhibit some of the symptoms of Alzheimer's. Most notably, the mice produced amyloid beta peptides—toxic protein fragments that gum up neurons and lead to cell death—and showed signs of forgetfulness.

The Case Western team, led by Gary Landreth, decided to try the drug bexarotene (Targretin), approved in 1999 for cutaneous T cell lymphomas. The team chose this drug because of its long experience working with proteins in the nucleus of brain cells that can induce biochemical processes that affect amyloid beta.

Landreth and his colleagues fed bexarotene to the demented mice, and with just a single dose it lowered the most toxic form of the amyloid beta peptide by 25 percent within six hours, an effect that lasted for up to three days. Mice that were cognitively impaired by the amyloid buildup resumed normal behaviors after 72 hours: They began to crinkle toilet paper placed nearby to make nests, a skill lost as amyloid increased in their brains.

"We have successfully reversed all of the known pathological features and behavioral deficits found in mouse models of Alzheimer's disease," Landreth says. "Never before has anyone observed clearance of amyloid plaques with such speed in mouse models."