* FDA encourages testing drugs before dementia strikes
* One prevention study to focus on family in Colombia
* U.S. aims to find effective treatment by 2025
CHICAGO, Feb 7 (Reuters) - Proposed U.S. guidelines may make it easier for drug companies to test Alzheimer's treatments in people at an earlier stage, when scientists think they may have the best shot at working.
The draft guidance document, issued on Thursday by the U.S. Food and Drug Administration, reflects changes in scientists' understanding of Alzheimer's. They now believe the disease begins at least a decade before symptoms appear.
"The scientific community and the FDA believe that it is critical to identify and study patients with very early Alzheimer's disease before there is too much irreversible injury to the brain," said Dr. Russell Katz, director of the Division of Neurology Products in the FDA's Center for Drug Evaluation and Research.
Current Alzheimer's drugs treat symptoms, but none has been proven to interrupt the steady destructive course of Alzheimer's that robs sufferers of their memories and independence.
"I think this will be hugely useful to the pharmaceutical industry," said Dr. Paul Aisen of the University of Southern California San Diego and director of the Alzheimer's Disease Cooperative Study, a joint effort between the university and the National Institute on Aging focused on identifying the earliest signs of Alzheimer's.
Aisen said the draft document will help companies design clinical trials to test drugs in people before dementia strikes, such as prodromal disease, a precursor to Alzheimer's in which mild cognitive changes have occurred and there is some biomarker evidence, such as a brain scan, that suggests the changes are related to Alzheimer's disease.
The need for new treatments is great and growing. A study on Wednesday suggested that the number of Americans with Alzheimer's disease would triple to 13.8 million by 2050.
Drug companies have been working for years to develop so-called disease-modifying drugs, but so far, with little success.
Last summer, a promising drug called bapineuzumab being developed by Johnson & Johnson, Pfizer and Elan, failed to show a benefit in large trials of patients with mild to moderate Alzheimer's.
And a drug by Eli Lilly and Co known as solanezumab also failed to meet the main goals of two large trials in this same population. But the drug did appear to show a slight benefit in mild patients when results of both studies were pooled.
Researchers now plan to study Lilly's drug in patients with earlier-stage disease, including a trial known as the "A4" prevention study, which will study 1,000 volunteers aged 70 to 85 with pre-symptomatic disease, who have not yet developed significant memory problems.
The trial will be managed by the Alzheimer's Disease Cooperative Study under Aisen's direction.
Several other so-called prevention studies are testing drugs in people who are genetically predisposed to develop Alzheimer's at an early age. In one study, members of a large family in Colombia will test a drug from Roche Holding AG's Genentech unit known as crenezumab.
Maria Carrillo of the Alzheimer's Association, which has worked with the National Institute on Aging to develop new guidelines for identifying Alzheimer's at an earlier stage, said the proposed changes "open the door wider for those of us working on and thinking about prevention trials."
The FDA said the move is part of the government's efforts to respond to Alzheimer's as part of the National Alzheimer's Plan signed by President Obama last year. The plan aims to find an effective way to prevent or treat Alzheimer's by 2025.
The draft document can be found at: