beta-Secretase as a therapeutic target for Alzheimer's disease.

beta-Secretase (memapsin 2, BACE1) is an attractive target for the development of inhibitor drugs to treat Alzheimer's disease (AD). Not only does this protease function at the first step in the pathway leading to the production of amyloid-beta (Abeta), its gene deletion produces only mild phenotypes. In addition, beta-secretase is an aspartic protease whose mechanism and inhibition are well known. The development of beta-secretase inhibitors, actively pursued over the last seven years, has been slow, due to the difficulty in combining the required properties in a single inhibitor molecule. Steady progress in this field, however, has brought about inhibitors that contain many targeted characteristics. In this review, we describe the strategy of structure-based inhibitor evolution in the development of beta-secretase inhibitor drug. The current status of the field offers grounds for some optimism, in that beta-secretase inhibitors have been shown to reduce brain Abeta and to rescue the cognitive decline in transgenic AD mice, and an orally available beta-secretase inhibitor drug candidate is in clinical trial. With this knowledge base, it seems reasonable to expect that more drug candidates will be tested in human, and then successful disease-modifying drugs may ultimately emerge from this target.