Clinical results from a Phase IIb study showed that MK-4305, Merck‘s investigational dual orexin receptor antagonist, was significantly more effective than placebo (p <0.005) in improving overall sleep efficiency at night one and at the end of week four in patients with primary insomnia. MK-4305 was generally well tolerated in the study. The data were presented for the first time at the SLEEP 2010 24th Annual Meeting of the Associated Professional Sleep Societies.

Orexins are neuropeptides that are released by specialized neurons in the hypothalamus region of the brain and are believed to be an important regulator of the brain’s sleep-wake process. "Since the discovery and characterization of orexin over the past decade as an important component of the sleep-wake system, Merck has been actively committed to discovering and developing potential interventions for sleep disorders that target the orexin receptors,” said David Michelson, MD, vice president of Neuroscience Clinical Research, Merck. “We are encouraged by these phase II results showing positive effects of MK-4305 in patients with primary insomnia.”

Phase III trials studying the efficacy and safety of MK-4305 in elderly and nonelderly insomnia patients are ongoing. Merck anticipates filing regulatory applications for MK-4305 in 2012. “Phase III research will provide further insight into the safety and efficacy profile of MK-4305, which, if approved, would provide a new class of insomnia treatments.”