Executive Summary

Merck's investigational dual orexin receptor antagonist (DORA) was significantly better than placebo at improving overall sleep at one night and at the end of week four in patients with primary insomnia in a Phase IIb study, the company reported at the annual Meeting of the Associated Professional Sleep Societies in San Antonio June 9. Orexin antagonists are thought to block the stimulation of the brain's arousal system in the hypothalamus. In the dose-ranging study, 243 patients were randomized to one of four doses of MK-4305 and 249 to placebo. The co-primary endpoint was improvement in sleep efficiency on night one and at the end of four weeks. Secondary endpoints were improvement in wake after sleep onset and latency to persistent sleep, compared to placebo. Phase III trials examining MK-4305 in elderly and non-elderly insomnia populations are ongoing, and Merck is targeting 2012 for a filing