The drug, called solanezumab, was the subject of two studies on Alzheimer's patients. Each study's results were insufficient to significantly slow the disease, but combining the two studies' results showed 34 percent less mental decline in mild Alzheimer's patients compared to a placebo treatment over 18 months.
The results are not expected to be strong enough to win approval for the drug for the time being. Doctors say though that the results indicate researchers are making progress on the right track toward treating Alzheimer's by clearing sticky deposits that clog patients' brains.
The results of the two studies were released at a Boston neurology conference Monday.
The drug is being developed by Eli Lilly and Company.
The Associated Press contributed to this report.