Tasimelteon is a drug which is under development for the treatment of insomnia

Insomnia

Insomnia is most often defined by an individual's report of sleeping difficulties. While the term is sometimes used in sleep literature to describe a disorder demonstrated by polysomnographic evidence of disturbed sleep, insomnia is often defined as a positive response to either of two questions:...

 and other sleep disorders. It is a selective agonist for the melatonin receptor

Melatonin receptor

A melatonin receptor is a G protein-coupled receptor which binds melatonin.Three types of melatonin receptor have been cloned. The MT1 and MT2 receptor subtypes are present in humans and other mammals, while an additional melatonin receptor subtype MT3 has been identified in amphibia and...

s MT₁ and MT₂ in the suprachiasmatic nucleus

Suprachiasmatic nucleus

The suprachiasmatic nucleus or nuclei, abbreviated SCN, is a tiny region on the brain's midline, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms...

 of the brain, similar to older drugs such as ramelteon

Ramelteon

Ramelteon, marketed as Rozerem by Takeda Pharmaceuticals North America, is the first in a new class of sleep agents that selectively binds to the MT1 and MT2 receptors in the suprachiasmatic nucleus , instead of binding to GABA A receptors, such as with drugs like zolpidem, eszopiclone, and...

. It has been through Phase III trials successfully and was shown to improve both onset and maintenance of sleep, with few side effects.