Suvorexant, in a new class of medicines, proved to be significantly better than placebo, meeting all but one of the goals in one of the two Phase III trials with about 1,000 patients in each.

Based on the data from these and other trials, Merck said it expects to file for approval of the drug later this year.

Unlike sleep drugs that are typically taken as needed, suvorexant is designed to be taken nightly over long periods of time. A new type of medicine, suvorexant works by blocking chemical messengers called orexins that help to keep you awake. Blocking orexins, which originate from the hypothalamus in the brain, helps facilitate sleep.

"The potential for a new and different option would be welcomed by patients with insomnia who cannot sleep through the night," Andrew Krystal, professor of psychiatry and behavioral sciences at Duke University Medical Center, said in a statement.

Darryle Schoepp, head of neuroscience and ophthalmology for Merck, said suvorexant appears to be well suited for patients who are not getting a full night sleep from existing drugs, including the long-acting version of Sanofi's Ambien.

"Ambien CR only keeps you asleep five to six hours," he said in an interview. "We've shown our drug keeps you asleep the last third of the night as well."

Patients in the three-month studies were suffering from insomnia not caused by another medical condition. One study tested the drug at 40 milligrams in patients 18-64 years of age and 30 mg in those 65 and older. The second study tested suvorexant at 20 mg in the younger group and 15 mg in patients 65 and older.

The data was being presented on Wednesday at the Annual Meeting of the Associated Professional Sleep Societies in Boston.

In the high dose trial, at three months suvorexant reduced the time it took to fall asleep by 25.7 minutes and helped patients sleep 60.3 minutes longer than prior to starting on the medicine. That compared with a time to sleep reduction of 17.3 minutes and 40.6 minutes more sleep on placebo.

Suvorexant patients entered into continuous sleep 36 minutes faster compared with 26.6 minutes faster in the placebo group, and spent less time awake during the night -- 47.9 minutes less versus 25 minutes less for placebo compared with prior to beginning the study.

In the low dose trial, suvorexant proved to be significantly better than placebo on all measures save for difference in time to fall into continuous sleep at three months, which did not achieve statistical significance.

In that study, the Merck drug reduced the time it took to fall asleep by 33.7 minutes versus 20.5 minutes in the placebo group. It helped them to sleep an average of 62.8 minutes longer, while a placebo led to 37.7 minutes more sleep.

Low dose suvorexant patients spent 54.2 fewer minutes awake during the night than before they started taking the drug, compared with 24.8 minutes for the placebo group.

In addition to the three-month data, suvorexant was superior to a placebo after the first night and after one month of treatment, Merck said.

The most common side effects from the Merck drug was headache and sleepiness. No serious drug related side effects were reported, Merck said.

Discontinuation rates due to side effects were small and similar between the drug and placebo groups. There were also no statistically significant next day residual effects compared with placebo as measured by an assessment of memory, attention, visual scanning and motor speed, Merck said.

(Reporting By Bill Berkrot and Ransdell Pierson; Editing by Tim Dobbyn)

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