Therapeutic potential of targeting the orexin (hypocretin) system in sleep disorders.

Sleep is emerging as a key health topic in modern society. The prevalence of and focus on sleep-wake disorders is increasing, which has led to a large interest from the pharmaceutical industry to develop new treatments targeting sleep biology (that is, drugs that have the potential to mimic normal sleep-wake physiology). The orexin (also known as hypocretin) system is one of the key targets and regulators of sleep and wakefulness. In this Review, we will discuss the mechanisms by which loss of orexin signalling is involved in narcolepsy type 1 and whether loss and/or disruption of orexin signalling might have a role in other sleep disorders such as narcolepsy type 2, idiopathic hypersomnia and obstructive sleep apnoea. We will also describe current and emerging therapies for sleep disorders involving orexin, such as orexin receptor antagonists for insomnia and orexin receptor agonists for narcolepsy.