 Tasimelteon completed the phase III clinical trial in the United States for primary insomnia in 2010.The Food and Drug Administration (FDA) granted tasimelteon orphan drug designation status for blind individuals without light perception with non-24-hour sleep–wake disorder in January the same year, and final FDA approval for the same purpose was achieved in January 2014 under the trade name Hetlioz®.In humans there are two subtypes of melatonin receptors targeted by melatonin agonists, MT1 and MT2.