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Purpose To assess the efficacy of tasimelteon to improve sleep in Smith–Magenis syndrome (SMS). Methods A 9-week, double-blind, randomized, two-period crossover study was conducted at four US clinical centers. Genetically confirmed patients with SMS, aged 3 to 39, with sleep complaints participated in the study. Patients were assigned to treatment with tasimelteon or placebo in a 4-week crossover study with a 1-week washout between treatments. Eligible patients participated in an open-label study and were followed for >3 months. Results Improvement of sleep quality (DDSQ50) and total sleep time (DDTST50) on the worst 50% of nights were primary endpoints. Secondary measures included actigraphy and behavioral parameters. Over three years, 52 patients were screened, and 25 patients completed the randomized portion of the study. DDSQ50 significantly improved over placebo (0.4, p = 0.0139), and DDTST50 also improved (18.5 minutes, p = 0.0556). Average sleep quality (0.3, p = 0.0155) and actigraphy-based total sleep time (21.1 minutes, p = 0.0134) improved significantly, consistent with the primary outcomes. Patients treated for ≥90 days in the open-label study showed persistent efficacy. Adverse events were similar between placebo and tasimelteon. Conclusion Tasimelteon safely and effectively improved sleep in SMS.

Introduction Smith-Magenis Syndrome (SMS) is a rare (1/15,000 - 25,000 births) neurodevelopmental disorder resulting from an interstitial deletion of chromosome 17p11.2, or from a point mutation in the RAI1 gene. Severe sleep disorder is almost universal in patients with SMS and poses a significant challenge to patients and their families. Tasimelteon improved sleep symptoms in a randomized, double-blind, two-period, crossover study; and here we show that this effect persists for up to four years in an open-label extension. To our knowledge, this is the largest interventional study of SMS patients to date. Methods Following the 4-week crossover study, all eligible participants had the option to enroll in an open-label extension. 31/39 (79.4%) of all individuals who participated in the efficacy study have continued on tasimelteon treatment. Participants in the open-label extension provided daily diary sleep quality (DDSQ), and daily diary total sleep time (DDTST) measures via parental post sleep questionnaire and characterized behavior using the Aberrant Behavior Checklist (ABC). Results In the open-label extension, tasimelteon continued to show improvement in the primary endpoints of 50% worst sleep quality (mean = 0.7, SD = 0.94) and 50% worst total nighttime sleep duration (mean = 53.3, SD = 59.01) when compared to baseline. Tasimelteon also improved overall sleep quality (mean=0.7, SD=0.83) and overall total nighttime sleep duration (mean = 51.9, SD=53.03). ABC scores also improved with tasimelteon (mean= -16.3, SD = 15.82). Conclusion Tasimelteon continues to demonstrate persistence in efficacy (longest approximately 4 years) with similar magnitudes observed in the 4-week crossover study for sleep quality and total sleep time. Interestingly, daytime behavior also demonstrates long-term improvement in patients with SMS treated with tasimelteon. These results further confirm tasimelteon as a novel therapy for the treatment of sleep disorders in patients with SMS and may provide benefit for behavioral symptoms. Support This work was supported by Vanda Pharmaceuticals Inc.

An impairment in next day driving performance has been reported for almost every drug currently United States Food and Drug Administration (FDA) approved for improvement of sleep in chronic and transient insomnia. Tasimelteon, a melatonin receptor agonist, demonstrated significant improvements in night-time sleep, daytime naps, and sleep timing in non-24-hr sleep-wake disorder (Non-24) by entraining these patients to a 24-hr day as measured by melatonin and cortisol rhythms. Given this new mechanism of action of entraining the biological clock, we conducted a study to evaluate the potential effect tasimelteon may have on the ability to operate a motor vehicle. The study was conducted in 48 healthy adult subjects using a randomised, double-blind, placebo and active (zopiclone 7.5 mg) controlled study with a 3-period cross-over design. Driving performance was assessed by measuring standard deviation of lateral position (SDLP) using the validated Cognitive Research Corporation Driving Simulator-MiniSim. The difference in least square mean SDLP for tasimelteon was 1.22 cm reflecting a non-significant increase in SDLP change from placebo (p = .1119). In contrast, treatment with the active control, zopiclone 7.5 mg, was associated with a meaningful and significant increase in SDLP, change from placebo for zopiclone was 4.14 cm (p < .0001). The lack of clinically meaningful and statistically significant finding with tasimelteon was further supported by the symmetry analysis, which showed the distribution of within-subject differences between tasimelteon and placebo was symmetric about zero. At the FDA-approved 20 mg dose to treat Non-24, tasimelteon did not impair next-day driving performance compared to placebo in adult healthy volunteers.