A Study of Seltorexant in Participants With Probable Alzheimer's Disease

Inclusion Criteria:

• Participant has received a diagnosis of probable Alzheimer Disease (AD) (Diagnosticand Statistical Manual of Mental Disorders-5 [DSM-5]) with the followingcharacteristics at screening: Clinical Dementia Rating (CDR) global score greaterthan or equal to (>=) 1; Mini-Mental State Examination (MMSE) total score of 10 to 24 (inclusive)

• Participant meets the criteria of a syndrome diagnosis of agitation based onInternational Psychogeriatric Association (IPA) consensus clinical and researchdefinition of agitation in cognitive disorders for at least 2 weeks before screening

• Participant meets the criteria of Neuropsychiatric Inventory (NPI-12)Agitation/Aggression (A/A) domain score >= 4 with frequency score >= 2 at screeningand baseline with no more than 35 percent (%) of improvement in NPI-12 A/A domainscore from the screening to baseline assessments

• Female participants must be postmenopausal before study entry (amenorrhea for atleast 12 months)

• Body Mass Index (BMI) within the range 18-40 kilograms per square meter (kg/m^2) (inclusive)

Exclusion Criteria:

• Participant fulfils diagnostic criteria for non-Alzheimer's Dementia: example,Frontotemporal Dementia (FTD), Diffuse Lewy Body Dementia (DLBD), and post-strokedementia, based on clinical history. (Participants may be included with mixedAD/vascular dementia)

• Participant has a clinically significant acute illness within 7 days prior to studyintervention administration

• Participants with a history of delirium within 30 days prior to or during screening

• Participant with a cause of agitation that is not secondary to dementia (such aspain) or significant history of aggression prior to dementia based on investigatorjudgment

• Participants who are not stable on concomitant medications or take prohibitedmedications