FDA Rejects sNDA of Tasimelteon for Treating Insomnia


FDA issued a Complete Response Letter to Vanda Pharmaceuticals stating tasimelteon for treating insomnia cannot be approved in its current form due to identified deficiencies.

FDA Rejects sNDA of Tasimelteon for Treating Insomnia

Vanda Pharmaceuticals Inc. announced on March 4, 2024, the US Food and Drug Administration (FDA) rejected the supplemental New Drug Application (sNDA) for tasimelteon (HETLIOZ®) in the treatment of insomnia.1

In July 2023, the FDA assigned a Prescription Drug User Fee Act target date of March 4, 2024, to make their decision on tasimelteon for insomnia, characterized by difficulties with sleep initiation. A month prior on February 4, 2024, the FDA identified deficiencies regarding labeling and post-marketing requirements. As a result of these deficiencies, the FDA issued a Complete Response Letter (CRL) stating the submission of tasimelteon could not be approved in its current form.

The FDA already approved tasimeleton on January 31, 2014, for non-24-hour sleep-wake disorder in blind individuals.2 Tasimeleton is also already approved for the treatment of nighttime sleep disturbances in Smith-Magenis Syndrome.3

Aiming to evaluate the effectiveness of tasimelteon for treating insomnia, Vanda Pharmaceuticals completed extensive research. For instance, investigators conducted a phase 3, multi-center, placebo-controlled, 4-week trial evaluating 322 patients with primary insomnia.4 Patients were randomized to receive either 20 mg or 50 mg of tasimelteon or placebo over 4 weeks.

Investigators sought to assess the immediate and short-term effectiveness of tasimelteon on improving sleep onset as measured by Latency to Persistent Sleep through polysomnography.5 The study found patients taking 20 mg and 50 mg of tasimeleton fell asleep 22.9 minutes (P < .001) and 25.9 minutes (P < .001) faster, respectively.

Additionally, investigators conducted 2 transient insomnia studies induced by phase advance of the sleep-wake cycle, with 5-hour and 8-hour phase advance.4 The studies demonstrated tasimelteon significantly improved sleep parameters the first night.

“We are excited that the results of this Phase III chronic insomnia study demonstrate the clinical utility of tasimelteon and the ability of the compound to treat sleep disorders over a period of four weeks,” said Paolo Baroldi, MD, PhD, Vanda’s Chief Medical Officer, in a press release for the phase 3 data.5 “The mechanism of action of tasimelteon as a circadian regulator gives Vanda the opportunity to explore its use for the treatment of circadian rhythm sleep disorders as well as chronic primary insomnia.”


  1. Vanda Pharmaceuticals Announces FDA Update for Supplemental NDA for HETLIOZ® in the Treatment of Insomnia. Vanda Pharmaceuticals. March 6, 2024. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://vandapharmaceuticalsinc.gcs-web.com/node/15816/pdf. Accessed March 6, 2024.
  2. FDA Approves Hetlioz. Drugs.com. January 2014. https://www.drugs.com/newdrugs/fda-approves-hetlioz-first-non-24-hour-sleep-wake-disorder-blind-individuals-4005.html. Accessed March 6, 2024.
  3. FDA Approves Hetlioz (Tasimelteon) For the Treatment of Nighttime Sleep Disturbances In Smith-Magenis Syndrome. Drugs.com. December 2020. https://www.drugs.com/newdrugs/fda-approves-hetlioz-tasimelteon-nighttime-sleep-disturbances-smith-magenis-syndrome-5398.html. Accessed March 6, 2024.
  4. Vanda Pharmaceuticals Announces FDA Update for Supplemental NDA for HETLIOZ® in the Treatment of Insomnia. Vanda Pharmaceuticals. February 5, 2024. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://vandapharmaceuticalsinc.gcs-web.com/node/15716/pdf. Accessed March 6, 2024.
  5. Phase III Data Show Vanda Pharmaceuticals&#039; Tasimelteon (VEC-162) Significantly Improves Sleep in Patients with Chronic Insomnia. Vanda Pharmaceuticals. https://vandapharmaceuticalsinc.gcs-web.com/news-releases/news-release-details/phase-iii-data-show-vanda-pharmaceuticals-tasimelteon-vec-162. Accessed March 6, 2024.
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