Merck announced that the FDA has issued a Complete Response Letter regarding the New Drug Application (NDA) for suvorexant, an investigational orexin receptor antagonist for the treatment of insomnia. Suvorexant targets and blocks orexins, chemical messengers that help to keep an individual awake. Temporarily blocking the actions of orexins, helps facilitate sleep.

In the Complete Response Letter, the FDA advised Merck that:

  • Efficacy of suvorexant has been established at doses of 10–40mg in elderly and non-elderly adult patients
  • 10mg should be the starting dose for most patients, and must be available before suvorexant can be approved
  • 15mg and 20mg doses would be appropriate in patients in whom the 10mg dose is well-tolerated but not effective
  • Patients taking concomitant moderate CYP3A4 inhibitors, a 5mg dose would be necessary
  • Safety data does not support the approval of suvorexant 30mg and 40mg

In response to the letter, Merck has determined that it will need to conduct more manufacturing studies to advance the 10mg dosage form. If approved, suvorexant will be part of a new class of medications for patients with insomnia.

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