Study design considerations: conducting global clinical trials in early Alzheimer's disease.

An increasing number of Alzheimer's disease (AD) clinical trials are being conducted in countries in which such trials have infrequently, if ever, been conducted. The infrastructure for conducting trials in many of these regions is not well developed, leading to particular challenges in collection of biomarkers, which are becoming increasingly important in trials in early AD. Linguistic and cultural differences make scale translation, adaptation, validation and implementation across countries and regions difficult. In addition, multiple translations and versions of scales and differences in their administration increase variability and thus decrease the chance of detecting a signal. These issues are magnified in trials in early AD, where detecting subtle neuropsychological deficits is even more challenging. Two additional significant factors for global AD research include: 1) Differing regulatory authority requirements resulting in the need for repeat studies to satisfy diverse regulatory requirements in different parts of the world; and 2) reimbursement and access may be limited due to different data requirements for country specific economic evaluations. While standardization of biochemical assays and neuroimaging protocols have recently been undertaken, there remains a pressing need for standardization of clinical measures (including translation, linguistic and cultural validation and administration). In addition, a global consensus on regulatory requirements for approval of drugs for the treatment of early AD and identification of universally accepted variables from a cost-effectiveness or value perspective would have significant impact on advancing drug development in early AD.