One drug, called a BACE inhibitor, has been in development for more than 10 years. In very early tests, it dramatically reduced levels of beta amyloid, a sticky protein that forms plaques in the brains of Alzheimer's patients.
The second drug is thought to reduce damaging inflammation. Patients with mild mental impairment who took the drug for over a year saw significant improvements in some measures of memory and thinking.
The results of the studies, both sponsored by companies hoping to market the medications, are scheduled to be presented Sunday at the Alzheimer's Association International Conference, in Boston.
Normally, those reports would be cause for optimism in a disease that affects 5 million people and currently has no effective treatments.