Theb-amyloid peptide (Ab) is a major component of toxic amyloid plaques found in the brains of patients with Alzheimer’s liberated by sequential cleavage of amyloid precursor protein (APP) level of Abdepends directly on the hydrolytic activity , b-secretase is an excel-lent target for drug approach based on RNA-cleaving ribozymes was developed to control expression ofb-secretase.