The Food and Drug Administration (FDA) has granted Priority Review to tasimelteon (Hetlioz®; Vanda) for the treatment of Smith-Magenis Syndrome (SMS), a rare developmental disorder characterized by disruptive sleep patterns, among other physical, mental and behavioral problems. 

Tasimelteon is a melatonin receptor agonist at melatonin MT1 and MT2 receptors. These receptors are thought to be involved in the control of circadian rhythms. The regulatory submission includes a supplemental New Drug Application (sNDA) for tasimelteon capsules and an NDA for the liquid formulation of tasimelteon. 

The applications are supported by positive results from a double-masked, 4-week, pivotal phase 2/3 clinical trial that compared the effects of tasimelteon to placebo in 25 patients with SMS. Patients were evaluated using a parental post sleep questionnaire (PSQ) for daily diary sleep quality (DDSQ) and for daily diary total nighttime sleep duration (DDTST).

Results showed that tasimelteon met the co-primary end points achieving significant improvement in the 50% worst sleep quality (DDSQ; P =.0139) and 50% worst total nighttime sleep duration (DDTST; P =.0556) compared with placebo. Additionally, tasimelteon was associated with a statistically significant improvement in overall sleep quality (P =.0155) and overall total nighttime sleep duration (P =.0134).

Patients in the tasimelteon treatment arm also had an improvement in sleep duration of 46.6 minutes for the best half of the baseline nights compared with placebo (50% best DDTST; P =.0052), along with improvements in aberrant behaviors. 

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A Prescription Drug User Fee Act (PDUFA) target date of December 1, 2020 has been set for these applications.

Hetlioz is currently approved for the treatment of non-24-hour sleep-wake disorder (Non-24).

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