Several drugs acting on the orexin system are under development, either orexin agonists for the treatment of conditions such as narcolepsy, or orexin antagonists for insomnia. No non-peptide agonists are yet available, although synthetic Orexin-A polypeptide has been made available as a nasal spray and tested on monkeys. Several non-peptide antagonists are in development however; SB-649,868 byGlaxoSmithKline for sleep disorders is a non-selective orexin receptor antagonist. Another dual orexin antagonist, almorexant(ACT-078573) by Actelion, was abandoned because of side effects. A third entry is Merck'ssuvorexant (Belsomra), which has recently been approved for use. A new antagonist compound, ACT-462206, was recently studied in humans.
Most ligands acting on the orexin system so far are polypeptides modified from the endogenous agonists Orexin-A and Orexin-B, however there are some subtype-selective non-peptide antagonists available for research purposes.
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