BACE-1 (beta amyloid converting enzyme, or beta-secretase), a member of the aspartic proteinase family, is an important target for development of a drug therapy for Alzheimer's disease. It is hypothesized that inhibition of BACE-1 will prevent the formation of amyloid plaques, which are protein fragments that accumulate in the brains of Alzheimer's disease patients. If so, a BACE-1 inhibitor may prove effective in preventing and treating Alzheimer's disease.