The drug, AZD05030, proved disappointing in treating solid tumours but appears to block damage triggered during the formation of amyloid-beta plaques, a hallmark of Alzheimer's disease.
The new study, funded by an innovative National Institutes of Health (NIH) programme to test failed drugs on different diseases, has led to the launch of human trials to test the efficacy of AZD05030 in Alzheimer's patients.
"With this treatment, cells under bombardment by beta amyloid plaques show restored synaptic connections and reduced inflammation, and the animal's memory, which was lost during the course of the disease, comes back," said Stephen M Strittmatter, the Vincent Coates Professor of Neurology at Yale University School of Medicine and senior author of the study.
The drug, developed by Astra Zeneca, blocks one of those molecular steps, activation of the enzyme FYN, which leads to the loss of synaptic connections between brain cells.
Several other steps in the disease process have the potential to be targets for new drugs, Strittmatter said.
The study is published in the journal Annals of Neurology.