Vanda Pharmaceuticals has escalated its regulatory dispute with the FDA to the highest level, formally requesting Commissioner Martin Makary to review the agency's controversial approval of two generic versions of its sleep disorder drug Hetlioz (tasimelteon). The appeal comes just days after the company secured a significant federal court victory against the FDA in a separate matter.
Challenging Generic Drug Standards
In 2023, Vanda filed citizen petitions challenging the FDA's approval of generic versions of Hetlioz manufactured by MSN Pharmaceuticals and Teva Pharmaceuticals. The company argued that both approvals were "improperly approved in light of significant flaws in the studies and data presented."
According to Vanda's petition, MSN Pharma "only tested its drug in 44 Indian males" and "did not test the drug in any women nor in a population representative of the racial and ethnic makeup of the United States." The company also claimed that Teva had failed to satisfy the bioequivalence requirement for generic drugs.
CDER Director's Controversial Decision
In July 2025, outgoing CDER director Jacqueline Corrigan-Curay issued a decision upholding the FDA's original approvals of these generic versions. Vanda characterized this decision as "seemingly agreeing that generic drug manufacturers need only conduct small studies that include only Indian male subjects to establish bioequivalence for use in the general US population."
The company expressed particular concern about data inconsistencies in one generic version, noting that Corrigan-Curay "accepted that significant inexplicable data inconsistencies measuring a drug's exposure levels in the blood could be justified by the supposedly different 'psychological state' of participants at different times." More alarmingly, Vanda reported that "one of the generic versions showed exposure levels more than double those Vanda has obtained for Hetlioz."
Recent Court Victory Strengthens Position
Vanda's appeal to Commissioner Makary comes on the heels of a federal court ruling in the company's favor regarding Hetlioz's jet lag disorder indication. On Monday, a federal court found that Vanda had "clearly offered meaningful evidence of tasimelteon's efficacy in improving sleep disturbance," ruling against the FDA's previous denial of the expanded indication.
The court victory stemmed from Vanda's 2022 lawsuit alleging that the FDA violated the Food, Drug, and Cosmetic Act by failing to grant a hearing within 60 days of the company's request. The court has now passed the matter back to the FDA, which Vanda expects will either issue an approval for Hetlioz in jet lag disorder or grant the requested hearing.
Systemic Concerns About Generic Drug Oversight
Vanda's challenge reflects broader concerns about FDA oversight of generic drug approvals. The company referenced Katherine Eban's 2019 book "Bottle of Lies: The Inside Story of the Generic Drug Boom," which exposed serious flaws in generic drug regulation. Vanda argued that this "unacceptable culture of bias toward approving generic drugs regardless of whether they meet the requisite legal and evidentiary standards" continues to endanger "the well-being of American citizens."
Call for Leadership Change
In its appeal to Commissioner Makary, Vanda emphasized the need for regulatory reform, stating: "It is time that the rule of law return to the FDA under Dr. Makary's leadership. Agency personnel must abide by the law and Commissioner priorities."
The company expressed frustration with the FDA's bureaucratic processes, noting that "FDA bureaucrats have suggested that the Office of the Commissioner (not the Commissioner) will take two months to decide whether the Office of the Commissioner will review the merits of this decision."
About Hetlioz
Hetlioz (tasimelteon) is a melatonin receptor agonist designed for oral administration that was first approved in 2014 for sleep-wake disorder. The FDA has previously granted approvals for several generic drugs containing tasimelteon, including MSN Pharmaceuticals' version in May 2020 and Teva Pharmaceuticals' version in September 2021. In both cases, the FDA informed the companies that their products use patent-protected technologies and would need to delay market entry until patent protections expire.
