Vanda Pharmaceuticals (NASDAQ:VNDA) saw its shares drop about 12% on Thursday after announcing that the U.S. Food and Drug Administration has declined to approve its application to use HETLIOZ for the treatment of jet lag disorder.
The FDA’s Center for Drug Evaluation and Research said the supplemental New Drug Application (sNDA) for HETLIOZ (tasimelteon) cannot be approved in its current form. Although regulators acknowledged that Vanda’s controlled clinical trials showed positive efficacy signals, they concluded that the evidence did not meet the threshold for demonstrating effectiveness in treating jet lag disorder.
According to the agency, the phase-advance study designs used by Vanda—based on 5-hour and 8-hour shifts in bedtime—do not adequately replicate real-world jet travel. The FDA noted that actual long-haul travel also involves factors such as lower oxygen pressure, physical confinement, noise exposure and changes in lighting conditions.
Vanda pushed back against that assessment, arguing that phase-advance models are “widely accepted in circadian rhythm research as valid and reliable surrogates for simulating the core circadian misalignment underlying eastward jet lag.” The company said it continues to believe that the data it submitted satisfies the requirement for substantial evidence of effectiveness.
The rejection follows a re-review process agreed with the FDA in October 2025 under a collaborative framework. That review was triggered after an August 2025 decision by the U.S. Court of Appeals for the D.C. Circuit, which overturned an earlier FDA refusal and described Vanda’s evidence as “specific, reasoned, and rooted in evidence.”
HETLIOZ is already approved in the United States for the treatment of Non-24-Hour Sleep-Wake Disorder, as well as nighttime sleep disturbances associated with Smith-Magenis Syndrome.