An Active-Controlled Early Phase Study of MK-8189 in Adults With Schizophrenia (MK-8189-005)

Inclusion Criteria:

- 18 to 50 years of age at Screening

- Male

- Female not of reproductive potential (e.g., postmenopausal or has had a hysterectomy),
or agrees to practice abstinence or use acceptable contraception

- Meets the diagnostic criteria for schizophrenia according to the DSM-5 criteria, or
has a past diagnosis of schizophrenia with the onset of the first episode being >=1
year prior to study entry, and has illness duration of <=20 years

- Is confirmed to be experiencing an acute episode of schizophrenia

- Minimum PANSS score >= 80 at Screening

- Has a score of >=4 in 3 or more of the following items (delusions, conceptual
disorganization, hallucinatory behavior, grandiosity, suspiciousness/persecution) in
the positive subscale of the PANSS at Screening

- Has a CGI-S score >= 4 at Screening

- Is able to taper off psychotropic medications without significant destabilization or
increased suicidality

- Has responded positively to an antipsychotic medication other than clozapine in a
prior psychotic episode

- Has an identified responsible external contact person who has regular contact (no less
than once per week) with the participant

Exclusion Criteria:

- Is currently under involuntary commitment because he/she is considered a danger to
himself/herself or others

- Is unwilling to remain hospitalized for the duration of trial treatment

- Is currently participating in or has participated in an interventional clinical
research study <=6 months prior to Screening, or has participated in more than one
interventional clinical trial research study within 12 months prior to Screening

- Is unwilling to allow audio/video taping of the Mini International Neuropsychiatric
Interview for Schizophrenia and Psychotic Disorders (MINI) and/or PANSS interview at
Screening and Baseline

- Is currently being treated with and benefiting from medications with a moderate or
strong inhibiting or inducing effect on Cytochrome P450 (CYP) 3A and/or CYP2C9 and/or
sensitive substrates of CYP2B6

- Has a history of malignancy <= 5 years except for adequately treated basal cell or
squamous cell skin cancer or in situ cervical cancer

- Has a body mass index <18.5 or >40 kg/m˄2

- Has a history of treatment-resistant schizophrenia

- Has a prolactin laboratory value of >= 5 times the upper limit of normal at Screening

- Has a known history or clinical evidence of clinically significant hepatic,
cardiovascular, or renal disease, or of untreated narrow-angle glaucoma- Has ever been
diagnosed with epilepsy or had any seizure disorder beyond one childhood febrile
seizure

- Has known serological evidence of human immunodeficiency virus (HIV) antibody

- Has a history of neuroleptic malignant syndrome

- Has a current diagnosis other than schizophrenia, or a comorbid diagnosis primarily
responsible for current symptoms and functional impairment

- Has a known history of borderline personality disorder, antisocial personality
disorder, or bipolar disorder

- Has a known history of traumatic brain injury, or Alzheimer's disease or another form
of dementia

- Currently meets DSM-5 criteria for substance abuse or alcohol use disorder

- Is at imminent risk of self-harm or harm to others