Prevention trials in Alzheimer's disease: an EU-US task force report.

Despite enormous financial and scientific efforts, still no approved disease-modifying therapies exist for Alzheimer's disease (AD). During the last decade all Phase III clinical trials on disease modifiers in AD have failed. The dementia stage of AD being probably too late in order to allow for successful disease modification has been identified as a possible culprit that could explain the failure of so many clinical trials. In parallel, a major development in the diagnostic research field of AD was achieved by the recent proposal of new diagnostic criteria for AD, which also specifically incorporate the use of biomarkers as defining criteria for preclinical stages of AD, thus extending the traditional definition of disease to very early stages that may be a more feasible target for various disease modifying therapeutic interventions. This ongoing paradigm shift in AD definition and diagnosis represents a fundamental basis for redefinition of interventional trials in AD, allowing to specifically focus on preventative measures during very early pathophysiologically confirmed stages of disease. This consensus paper reflects the outcome from a European Union and North American Task Force meeting comprised of experts from academia, industry, private foundations, and regulatory agencies that was convened in Toulouse, France on November 5, 2010 and that focused on prevention trials in AD. This position paper thoroughly analyzes prerequisites for successful preventative trials in AD and concludes with concrete recommendations on biomarkers, statistical tools and other variables important for improved study designs suitable for preventative as well as for early therapeutic interventional trials in AD.