Despite extensive research for over two decades, the medical science is yet to assign the exact aetiology and mode of progression of Alzheimer's disease (AD). The modern era of AD drug development began with the proposal of the cholinergic hypothesis of memory impairment. Since then, despite the proposal and phase trials of many therapeutic options, only few drugs have shown some efficacy and safety. The reasons behind this have been many including the ineffectiveness of tested drugs and inadequacy of clinical development methods.