New approaches to clinical trials in vascular dementia: memantine in small vessel disease

Abstract

Although criteria for the diagnosis of vascular dementia (VaD) are established, the diagnostic concept is still controversial and there is no regulatory guidance for clinical drug development. Clinical trials in VaD present a number of pitfalls and challenges and, so far, no compound has received regulatory approval for this indication. The methodological issues of clinical VaD trials are discussed using the development of memantine for this indication as an example. In a pooled analysis of two placebo-controlled trials with the NMDA-antagonist memantine in VaD, the cognitive benefit by memantine treatment was more pronounced for patients with 'small vessel disease' than for those with other neuroradiological findings at baseline. In a subgroup of patients with 'large vessel disease' or macrolesions, there was less cognitive decline among the placebo patients. It may therefore be helpful to use predefined diagnostic subcategories in clinical studies in this indication. The findings further suggest that stroke or multiple infarctions may not be the primary reason for cognitive decline in VaD patients.