Tasimelteon safely and effectively improves sleep in Smith–Magenis syndrome: a double-blind randomized trial followed by an open-label extension

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.