Efficacy and Safety of Tasimelteon Compared With Placebo in Totally Blind Subjects With Non-24-Hour Sleep-Wake Disorder

Non-24-Hour Sleep-Wake Disorder (N24HSWD) occurs when individuals, primarily those without light perception, are unable to synchronize their endogenous circadian pacemaker to the 24-hour light-dark cycle, and the timing of their circadian rhythm instead reflects the intrinsic period of their endogenous circadian pacemaker. As a result, the circadian rhythm of sleep-wake propensity in these individuals moves gradually later and later each day if there circadian period is \> 24 hours and earlier and earlier if \< 24 hours. These individuals will be able to sleep well at night when their sleep-wake propensity rhythm is approximately aligned with the 24-hour light-dark and social cycle. However, after a short time, the endogenous sleep-wake propensity rhythm and the 24-hour light-dark cycle will move out of synchrony with each other, and they may have difficulty falling asleep until well into the night. In addition to problems sleeping at the desired time, the subjects experience daytime sleepiness and daytime napping. This will be a multicenter, randomized, double-masked, placebo-controlled, parallel study. The study has two phases: the pre-randomization phase followed by either the randomization phase or the open-label extension (OLE). The pre-randomization phase comprises a screening visit where subject's initial eligibility will be evaluated, a circadian period (τ) estimation segment, and a variable-length in-phase transition segment in which subjects will wait to start treatment until their circadian phase is aligned with their target bedtime. Subjects that meet all entry criteria for the study will enter the randomization phase. During the randomization phase, subjects will be asked to take either 20 mg tasimelteon or placebo approximately 1 hour prior to their target bedtime for 26 weeks in a double-masked fashion. Subjects who have a τ greater than 24.0 and meet all entry criteria but that are ineligible for the randomization phase due to their τ estimate may be given the opportunity to participate in the OLE phase. During the OLE phase, subjects will take open-label 20mg tasimelteon for 26 weeks.