EU./U.S. CTAD Task Force on Alzheimer's Trial Populations.

Successful therapeutic trials require well-targeted populations to demonstrate the effectiveness of a drug candidate. Most trials in the field of Alzheimer's disease (AD) have been conducted in patients with mild to moderate dementia. However, the advent of amyloid PET imaging has demonstrated that a significant proportion of individuals enrolled in such studies do not have evidence of brain amyloidosis and may in fact not have Alzheimer's disease. Further, dementia represents an advanced stage of neurodegeneration, perhaps too late for significant benefits of disease-modifying interventions. The successful development of effective disease-slowing therapies requires a study population selected in accordance with the mechanism of the specific intervention. An international task force of investigators from academia, industry, non-profit foundations, and regulatory agencies met in San Diego, California, USA, on November 13, 2013, to address issues related to screening and identification of clinical trial participants, and the ramifications of decisions made in this regard for drug development in AD and other dementias.