Effects of suvorexant on the Insomnia Severity Index in patients with insomnia: analysis of pooled phase 3 data

Suvorexant is an orexin receptor antagonist that is approved in the US, Japan and Australia for the treatment of insomnia. Using outcomes from the Insomnia Severity Index (ISI) in the core registration studies, we explored suvorexant effects on sleep problems and their impact on daytime function. Data were pooled from two similar Phase 3, randomized, double-blind, placebo-controlled, parallel-group, three-month trials in elderly (≥65 years) and non-elderly (18–64 years old) insomnia patients. Age-adjusted (non-elderly/elderly) dose-regimes of 40/30 mg and 20/15 mg were evaluated. The ISI, a 7-item self-rated questionnaire with each item rated on 0–4 scale (higher score corresponds to increasing severity), was administered to patients as an exploratory assessment in both studies at baseline and one and three months after randomization. The analysis included 1824 patients. Suvorexant improved change-from-baseline ISI total scores to a greater extent than placebo (Month three: 20/15 mg = −6.2, 40/30 mg = −6.7, placebo = −4.9, p-values for both active arms vs. placebo <0.001) and resulted in a greater proportion of responders than placebo using a variety of definitions (eg, ≥6-point improvement from baseline at Month three: 20/15 mg = 55.5%, 40/30 mg = 54.9%, placebo = 42.2%, p-values for both active arms vs. placebo <0.001). Additionally, the “impact of insomnia” component, which assesses the impact of insomnia on daytime function/quality-of-life, was improved to a greater extent by suvorexant than placebo. Suvorexant 20/15 mg and 40/30 mg improved sleep to a greater extent than placebo as assessed by the ISI in patients with insomnia. Improvement in sleep onset/maintenance as well as a reduction of the impact of sleep problems on daytime function contributed to the overall improvement observed in ISI total score. NCT01097616, NCT01097629.