Present and Future Therapies for Alzheimer’s Disease

Abstract

Alzheimer's disease (AD) is an incurable, progressive neurodegenerative disorder and the most common type of dementia. Although four kinds of drugs are currently available for AD, these are symptomatic treatments and do not halt disease progression. Therefore, there is an urgent need for development of curative drugs for AD. Amyloid plaques are the main disease hallmark observed in AD brains. As amyloid-β (Aβ) is a major constituent of amyloid plaques, Aβ has been supposed to be pathogenic for AD (amyloid hypothesis). Thus, current, mainstream AD drug development is based around this hypothesis. In particular, both active and passive immunotherapies are aggressively employed. However, most clinical trials based on this hypothesis, including immunotherapies, failed to improve cognitive impairment in AD. Therefore, it is likely that AD onset is caused by factors besides Aβ. We have previously demonstrated that the intracellular domain of amyloid precursor protein (AICD) induces dynamic changes in gene expression and neuron-specific apoptosis, probably related to AD pathogenesis. Therefore, AICD may be a favorable target for AD therapies. In this chapter, current trials for AD therapies, especially immunotherapies targeting Aβ, are summarized. In addition, therapies targeting tau, another possible pathogenic molecule, are also described. Furthermore, we discuss the possibility of AICD as a novel therapeutic target for AD.