UPDATE 1-Medivation Alzheimer's drug helps - if used early

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By Julie Steenhuysen

CHICAGO, July 30 (Reuters) - A drug for Alzheimer's disease made by Medivation Inc (MDVN.O) kept symptoms at bay for 18 months, U.S. researchers said on Wednesday, but people who got the drug after first taking a placebo fared less well, suggesting early treatment is best.

The latest results, being presented at the Alzheimer's Association's international meeting in Chicago, found Dimebon was safe and continued to benefit people who took it for a year and a half.

"The most important thing from my point of view is there were no new safety issues that emerged with longer exposure of the patients," said Dr. Jeffrey Cummings of UCLA, who helped with the study.

The results from the 183-patient study conducted in Russia found people continued to improve, with benefits seen in cognition, memory, activities of daily living and behavior.

The study also found that people who were treated with a placebo for a year and then took Dimebon stabilized across five measures of thinking ability, but were unable to catch up to the group who had taken it for the full 18 months.

"People initially treated with the placebo and then crossed over to Dimebon did not show the same level of benefit as those people who took Dimebon for the full 18 months," Cummings said in a statement.

"This emphasizes the benefit of earlier treatment and suggests the possibility that Dimebon may slow the progress of Alzheimer's," he said.