NEW ORLEANS--An antibiotic once used to treat traveler's diarrhea and other infections might battle Alzheimer's disease, researchers announced here 7 November at the Society for Neuroscience's annual meeting. The compound dissolves Alzheimer's-like deposits in rat brains, probably by pulling at heavy metals. A trial to test whether the drug helps people with Alzheimer's is under way.
Alzheimer's disease disables about 4 million people in the United States--a number expected to jump to 14 million by 2050. In patients' brains, hallmark protein deposits called plaques appear to kill neurons or somehow scramble their signals. Many researchers have focused on finding ways to prevent the buildup of the plaques' main ingredient, a protein called amyloid. But there may be another target: copper and zinc atoms that stud the surface of the plaques. In test tube experiments, compounds that bind to these heavy metals dissolve the plaques.
One such compound is an old antibiotic called clioquinol, which was withdrawn from the market several years ago because it caused acute B-12 vitamin deficiency in some people. To test whether clioquinol could clear up amyloid plaques in the brain, a team led by neurologist Ashley Bush of Massachusetts General Hospital in Boston first fed the drug to young rats genetically engineered to develop Alzheimer's-like deposits. The drug appeared to prevent some plaques from forming: The animals developed fewer plaques overall; some 30% had no detectable plaques at the age when untreated rats' brains are riddled with them. In a second study, the drug appeared to clear up plaques in older rats. Those given the drug for 9 weeks had 50% less amyloid deposited in their brains than untreated animals. The drug is undergoing a clinical trial in people with early or middle-stage Alzheimer's disease. Bush expects the results in about a year.
The rat studies are "very impressive," says Alzheimer's researcher David Morgan of the University of South Florida in Tampa. Clearing amyloid plaques is difficult, he says, and the researchers "showed a dramatic reduction in a very short time." But he cautions that although the drug was used safely in people for many years--and the B-12 deficiency could be addressed by vitamin supplements--the long-term use needed to treat Alzheimer's may produce side effects.