SEATTLE, WA—The orexin receptor antagonist suvorexant improves sleep in patients with insomnia, analysis of pooled results of two Phase 3 clinical trials presented at SLEEP 2015 have found.

Previously, Phase 3 results have shown that suvorexant improves sleep maintenance and onset. In this analysis, W. Joseph Herring, MD, PhD, from Merck & Co in Kenilworth, NJ, and colleagues used the Insomnia Severity Index (ISI) to assess the agent’s effects on sleep problems and their impact on daytime function.

Data from two similar randomized, double-blind, placebo-controlled, parallel-group three-month trials in patients with insomnia >65 years of age and in those 18–64 years of age were pooled. The investigators evaluated age-adjusted dose-regimens of suvorexant 40mg/30mg for the older group and 20mg/15mg for the younger group. Fewer patients were assigned to the 20mg/15mg group than the 40mg/30mg group or placebo. The seven-item ISI patient questionnaire was administered as an exploratory assessment at Months 1 and 3, Dr. Herring reported.

A total of 1,824 patients were included in the analysis. Suvorexant improved change from baseline in total score at Months 1 and 3; at Month 3, the total score was -6.2 in the 20mg/15mg group and -6.7 in the 40mg/30mg group, compared with -4.9 in the placebo group (P<0.001 for both groups).

The percentage of responders, defined as ≥6-point improvement from baseline, was also greater at both time points. At Month 3, 55.5% of patients in the 20mg/15mg group and 54.9% in the 40mg/30mg group had responded, compared with 42.2% in the placebo group (P<0.001 for both groups).

“Scores for individual items of the ISI showed numerical improvement for both suvorexant dose regimens versus placebo at both time points,” Dr. Herring reported. For the 40mg/30mg group, P<0.01 for all items, and for the 20mg/15mg group, P<0.01 at greater than one time point for all items except for “sleep problem interferes with daily functioning.”

The “impact of insomnia” component, the last three items, which assesses the impact of insomnia on daytime function and quality-of-life, was improved by both dose regimens vs. placebo at Months 1 and 3 (P<0.01 for both groups).

“Improvement in sleep onset/maintenance as well as a reduction of the impact of sleep problems on daytime function contribute to the overall improvement observed in ISI total score,” he stated. “Given that the maximum approved dose is 20mg, the 20mg/15mg data are the most clinically relevant.”