Tasimelteon (trade name Hetlioz) is a drug approved by the FDA solely for the treatment of non-24-hour sleep–wake disorder (often designated as N24HSWD) in totally blind adults. It is a selective agonist for the melatonin receptors MT1 and MT2 in the suprachiasmatic nucleus of the brain, similar to other members of the melatonin receptor agonist class of which ramelteon (2005) and agomelatine (2009) were the first approved.