"This was one of the early anti-amyloid approaches," Schneider said. "It was a definitive trial showing definitely that there was nothing here. But it doesn't mean that anti-amyloid strategies will fail, just that this drug isn't effective."
A number of other therapies that target amyloid are now in human trials, Schneider said. They include monoclonal antibodies that bind to the protein and drugs that inhibit the production of the amyloid fragments that are believed to be toxic to the brain.
Those trials are still recruiting participants, and results are not expected for a few years, Schneider said. Even if the results are negative, the anti-amyloid strategy can live on, although with a different approach, in which the drugs are given earlier in life, he said.
Alzheimer's drugs are being tried on people in the early stages of the disease, Schneider said. "But they are pathologically already well along," he said. Starting therapy earlier might give some benefit, he noted, which would make a marker such as low leptin levels a useful indicator for preventive therapy.
Latest news and basic facts about Alzheimer's disease are available from the Alzheimer's Association.
SOURCES: Sudha Seshadri, M.D., associate professor, neurology, Boston University School of Medicine; Lon S. Schneider, M.D., professor, psychiatry, neurology and gerontology, University of Southern California, Los Angeles; Dec. 16, 2009, Journal of the American Medical Association