Phase 3 Trial Update of Suvorexant for Insomnia

Merck announced new data for suvorexant, an investigational medicine in development for the treatment of insomnia. The new data are from a continuously-dosed, placebo-controlled, 12-month study designed to assess the safety of suvorexant, while also evaluating its longer term efficacy. New results are from a two-month discontinuation phase that followed the 12-month study.

In a long-term, double-blind, Phase 3 trial, 781 patients with primary insomnia were randomized to receive a consistent dose of suvorexant (40mg/night in patients 18–64 years of age or 30mg/night in patients ≥65 years) (n=521) or placebo (n=258) over a 12-month treatment period. Patients who completed the entire 12-month study (n=484) continued into a two-month, randomized, placebo-controlled, parallel-group discontinuation phase to evaluate both the effects of stopping suvorexant and switching to placebo (n=166), as well as the efficacy of continued suvorexant treatment at months 13 and 14 (n=156). Patients who took placebo during the initial 12-month study continued to take placebo (n=162).

During the first month of the 12-month study, patients who took suvorexant reported that they fell asleep significantly faster, stayed asleep significantly longer and spent significantly less time awake during the night compared to patients who received placebo (P<0.001).

During the two-month discontinuation phase (months 13 and 14), patients who stopped taking suvorexant (after 12 months) and switched to placebo (for months 13 and 14) reported worsening of their ability to fall asleep and stay asleep compared to patients who continued taking suvorexant. This return of sleeping difficulties was similar to levels reported by patients who received placebo for the full 14 months. Specifically, at the end of the two-month discontinuation phase (end of month 14), patients who switched from suvorexant to placebo reported that it took them 14.9 minutes longer to fall asleep and that they slept 21.6 minutes less compared to patients who continued taking suvorexant (P<0.0001 for both measures).  Additionally, compared to patients who continued on placebo, those who switched from suvorexant (after 12 months) to placebo (for months 13 and 14) had no clinically meaningful evidence of withdrawal or rebound insomnia when they stopped taking suvorexant.

Suvorexant targets and blocks orexins, chemical messengers that originate from the hypothalamus that maintain wakefulness. By blocking the actions of orexins, suvorexant helps to facilitate sleep. If approved, suvorexant would be the first medicine approved in a new class of medicines, called orexin receptor antagonists, for use in patients with difficulty falling or staying asleep.  

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