Investigational medications for treatment of patients with Alzheimer disease

Development of effective treatments for patients with Alzheimer disease has been challenging. Currently approved treatments include acetylcholinesterase inhibitors and the N-methyl-D-aspartate receptor antagonist memantine hydrochloride. To investigate treatments in development for patients with Alzheimer disease, the author conducted a review of the literature. New approaches for treatment or prevention focus on several general areas, including cholinergic receptor agonists, drugs to decrease β-amyloid and tau levels, antiinflammatory agents, drugs to increase nitric oxide and cyclic guanosine monophosphate levels, and substances to reduce cell death or promote cellular regeneration. The author focuses on medications currently in clinical trials. Cholinergic agents include orthostatic and allosteric muscarinic M1 agonists and nicotinic receptor agonists. Investigational agents that target β-amyloid include vaccines, antibodies, and inhibitors of β-amyloid production. Anti-inflammatory agents, including nonsteroidal anti-inflammatory drugs, the natural product curcumin, and the tumor necrosis factor α inhibitor etanercept, have also been studied. Some drugs currently approved for other uses may also show promise for treatment of patients with Alzheimer disease. Results of clinical trials with many of these investigational drugs have been disappointing, perhaps because of their use with patients in advanced stages of Alzheimer disease. Effective treatment may need to begin earlier-before neurodegeneration becomes severe enough for symptoms to appear.