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