MK-4305 is an investigational dual orexin receptor antagonist compound that is thought to inhibit the actions of the neuropeptides orexin A and orexin B, which bind with the OX1R and OX2R receptors.

These neuropeptides are produced by neurons, located within the hypothalamus region of the brain, and play a key part in regulation of the brain's sleep–wake process. Orexin antagonists are thought to block the stimulation of the brain's arousal system.

The data were presented for the first time at the SLEEP 2010 24th Annual Meeting of the Associated Professional Sleep Societies. Phase III trials studying the efficacy and safety of MK-4305 in insomnia patients are ongoing, and Merck anticipates filing regulatory applications for MK-4305 in 2012.

‘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, M.D., 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 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.’

Insomnia is a sleep disorder that affects approximately 10 per cent of the general population. People with insomnia can have one or more sleeping problems, including difficulty falling asleep, difficulty staying asleep and difficulty returning to sleep.