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Suvorexant for insomnia hits most goals of pivotal trials

(Reuters) – Suvorexant, an experimental dual orexin receptor antagonist being developed by Merck & Co for primary insomnia, significantly reduced the time it took patients to fall asleep and helped them stay asleep longer, according to data from a pair of phase III studies released today.

Suvorexant, in a new class of medicines, proved to be significantly better than placebo, meeting all but one of the goals in one trial.

The studies each involved about 1,000 patients. Based on the data from these and other trials, Merck said it expects to file for approval of the drug later this year.

Suvorexant has a novel mechanism of action. The drug targets orexin neuropeptides that play an integral part in the wake-sleep cycle. Blocking orexins, which originate from the hypothalamus, helps facilitate sleep.

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

Dr. 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 zolpidem (Ambien, Sanofi).

“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 mg 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 were presented Wednesday at SLEEP 2012, the 26th 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 — 48 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 suvorexant reduced the time it took to fall asleep by 33.7 minutes vs 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, investigators reported.

The most common side effects of the drug were headache and sleepiness. No serious drug related side effects were reported.

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, the investigators said.