A Multicenter, Randomized, Double-blind, Placebo-controlled, Parallel-group, Bayesian Adaptive Randomization Design, Dose Response Study of the Efficacy of E2006 in Adults and Elderly Subjects With Chronic Insomnia

The study will have 2 phases, Prerandomization and Randomization. The Prerandomization Phase will last up to 21 days and will consist of a Screening Period (Days -21 to -2) and a Baseline Period (Day -1). Following the Baseline Period, all eligible subjects will be randomized, in a double-blind manner, to receive E2006 or placebo for 15 nights during the Treatment Period (Days 1 to 15), then all subjects will receive placebo, in a single-blind manner, for 2 nights (Days 16 to 17) during the Rebound Insomnia Assessment Period (Days 16 to 18). Subjects will not receive any treatment during the Follow-up Period (Days 19 to 29). All subjects will come to the clinic for screening procedures. During the Screening Period, subjects will complete the Sleep Diary each day. Polysomnographic sleep will be measured during the Screening Period on 2 consecutive nights between Day -9 and Day -3. These 8-hour polysomnograms (PSGs) will start at the median habitual bedtime calculated from responses on the Sleep Diary completed 7 days immediately prior to the first PSG night. Subjects may leave the clinic between the screening/baseline PSG nights.