[Toward Preclinical Trials for Alzheimer's Disease].

A variety of disease-modifying therapies for Alzheimer's disease (AD) have been developed and advanced to late-phase clinical trials in AD dementia patients, but thus far, no single drug has proven its efficacy in a large phase III trial. In 2011, the National Institute on Aging-Alzheimer's Association (NIA-AA) criteria redefined the concept of AD to encompass the earlier amyloid-related pathophysiological changes of the preclinical stage and mild cognitive impairment (MCI). Clinical trials for AD are now moving toward these earlier stages of the disease, targeting MCI due to AD and preclinical AD. Intervention in the earlier stages of the amyloid cascade is believed to have a better chance at changing the natural course of AD and preventing or at least delaying the conversion to dementia. Although conducting a large and prolonged costly clinical trial in the preclinical stage is challenging, the first step in overcoming this challenge has been taken with enthusiasm and commitment.