A Long Term Safety Study of Suvorexant in Participants With Primary Insomnia (MK-4305-009 AM3)

A Phase III, Multicenter, Randomized, Double-Blind, Placebo-Controlled, Parallel-Group, Long Term Safety Study of MK-4305 in Patients With Primary Insomnia

This study will establish the safety and tolerability of suvorexant (MK-4305) when administered for up to 14 months. Participants will be randomized to receive suvorexant or placebo for a 12-month double-blind (DB) Treatment Phase. Participants who complete the 12-month DB Treatment Phase will enter a 2-month DB Randomized Discontinuation Phase. At the time of initial randomization, participants assigned to receive suvorexant during the initial 12-month Treatment Phase will be simultaneously randomized, in a 1:1 ratio, to receive either suvorexant or placebo during the 2-month Randomized Discontinuation Phase. Participants randomized to receive placebo in the initial 12-month Treatment Phase will continue to receive placebo during the 2-month Randomized Discontinuation Phase.

The first 3 nights of the Randomized Discontinuation Phase are referred to as the Run-Out Phase, and will assess rebound and withdrawal.

Inclusion Criteria:

• Diagnosis of primary insomnia
• Participant is able to read, understand, and complete questionnaires and diaries
• If female, participant and partner both agree to use acceptable contraception. If male partner does not use an effective form of contraception, female participant must use 2 acceptable forms of contraception
• If ≥65 years of age, score of ≥25 on the Mini Mental State Examination (MMSE)

Exclusion Criteria:

• If female, participant is pregnant
• Participant expects to donate eggs or sperm during the study
• Recent and/or active history of a confounding neurological disorder
• History of clinically unstable cardiovascular disorder within the last 6 months
• Lifetime history of bipolar disorder
• Psychiatric condition that requires treatment with a medication prohibited by the study, or any other psychiatric condition that would interfere with the participant's ability to participate in the study
• History of substance abuse/dependence
• History of cancer ≤5 years prior to study participation except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer
• Evidence of suicidality (based on a score of 2 on the Quick Inventory of Depressive Symptomatology Self-Report 16-Item ([QIDS-SR16] suicide item #12)
• Participant has travelled across >3 time zones or >3 hour time difference in the last 2 weeks
• History of permanent night shift work or rotating day/night shift work in the past 2 weeks
• Body Mass Index (BMI) >40 kg/m^2