Safety and Efficacy Study of Suvorexant in Participants With Primary Insomnia - Study A (MK-4305-028)

A Phase III, Multicenter, Randomized, Double-Blind, Placebo-Controlled, Parallel Group Study to Evaluate the Safety and Efficacy of MK-4305 in Patients With Primary Insomnia - Study A

This is a multicenter study to test the hypothesis that suvorexant (MK-4305) is superior to placebo in improving insomnia as measured by change from baseline in: subjective total sleep time and time to sleep onset, wake time after persistent sleep onset, and latency to onset of persistent sleep. Participants who complete the initial 3-month Treatment (TRT) Phase may participate in an optional 3-month Extension (EXT) Phase.

Inclusion Criteria:

• Must be ≥18 yrs old on the day of signing informed consent
• Diagnosed with Primary Insomnia
• Good physical and mental health
• Participant ≥65 yrs old score at least 25 on the Mini Mental State Examination
• A female participant who is of reproductive potential has a negative serum pregnancy test and agrees to use contraception
• Reports difficulty with initiating and maintaining sleep during the 4 weeks prior to Visit 1 (accordingly to specific protocol criteria)
• Reports spending 6.5 to 9 hours nightly in bed on at least 3 out of 7 nights prior to Visit 1
• Regular bedtime is between 9 pm-1 am
• Willing to refrain from napping while in study
• Able to read, understand and complete questionnaires and all diaries
• Willing to limit alcohol, caffeine, and nicotine consumption while in the study
• For a portion of participants: Must be willing to stay overnight in a sleep laboratory and must be willing to stay in bed for at least 8 hours each night while at the sleep laboratory

Exclusion Criteria:

• Female participant is pregnant and/or breastfeeding at Prestudy visit, or expecting to conceive while in study
• History or diagnosis of another sleep disorder
• Difficulty sleeping due to a medical condition
• History of a neurological disorder
• History of bipolar disorder, psychotic disorder, or posttraumatic stress disorder, or current psychiatric disorder that requires a prohibited medication
• Ongoing depression
• History of substance abuse or dependence
• History or current evidence of a clinically significant cardiovascular disorder or clinically significant electrocardiogram (ECG) at Prestudy Visit
• Taking certain prohibited medications
• Consumption of the equivalent of >15 cigarettes a day
• History of malignancy ≤5 years prior to signing informed consent, except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer
• Participant is considered morbidly obese
• Previously randomized in another investigational study of suvorexant