Personalized medicine for effective Alzheimer disease treatment.

Treatments for Alzheimer disease—even treatments thatminimallymodify the disease—have remained stubbornly elusive. Although hypotheses concerning a diseasemechanism have resulted in target-engaging drugs that have been tested in large clinical trials, the results of all trials to date have been negative. Most of the rethinking prompted by these clinical trial failures has driven researchers to reexamine their hypotheses concerning the disease mechanism and to initiate trials earlier in the course of the disease.1 However, another reason for the apparent failure of large clinical trials to identify effective treatments may be the erroneous assumption that Alzheimer disease is a single clinical entity. A complete risk profile of a patient with Alzheimer disease reveals vast variation in risk markers that may serve to guide treatment. Associating diseases that require different treatment