The drug is called solanezumab. The analysis of data from two large studies were presented Monday at a medical meeting in Boston. But this closely watched drug did not significantly protect against loss of physical functions.
Scientists say the latest data lend further credence to the theory that Alzheimer's must be attacked early in the disease for drugs to have a clinically meaningful impact.
The drug works by blocking a protein called beta amyloid that forms plaque deposits on the brain.