Vanda Pharmaceuticals requested FDA approval of its melatonin receptor agonist, tasimelteon (Hetlioz), as an orphan drug to treat non-24-hour sleep–wake disorder (non-24). To qualify as an orphan drug, a medication must target a rare medical condition.

Non-24 is a circadian rhythm disorder that occurs almost exclusively in patients who are completely blind without light perception. The FDA’s initial approval letter correctly stated that Hetlioz was indicated for this population, and the agency also issued a press release stating the same.
 
When the FDA approved Hetlioz, however, it did not specify in the product indication that the drug was solely for use in blind patients. According to consumer watchdog Public Citizen, at least 26 FDA review documents signed by 42 agency officials prior to Hetlioz 's approval explicitly stated that Vanda Pharmaceuticals was seeking approval for use in totally blind patients.

The FDA’s blunder opened the door for the drug's use in a wide range of sleep disorders in patients who are not blind. Pharmacy benefit managers and insurance companies cannot limit the use of this drug to blind patients, as these requests will be overturned. Overturned denials lead to poor member satisfaction and a lower Star rating from the US Centers for Medicare & Medicaid Services, which can result in the loss of a Medicare contract.
 
After discovering its error, the FDA did not ask Vanda to change Hetlioz's indication. Instead, the agency issued a second approval letter acknowledging an error in the drug's original “indications for use” section.

In a petition, Public Citizen has requested that the FDA correct the labeling by adding “in blind patients without light perception” to the indication. The Hetlioz prescribing information is still incorrect as of the publishing of this article.