Efficacy and Safety of MK-8189 in Participants With an Acute Episode of Schizophrenia (MK-8189-008)

Inclusion Criteria:

The main inclusion criteria include, but are not limited to the following:

• Meet the diagnostic criteria for schizophrenia according to the DSM-5

• Have an illness duration for schizophrenia of at least 1 year

• Be confirmed to be experiencing an acute episode of schizophrenia as evidenced byALL of the following: (a) onset of the current acute episode is ≤6 weeks beforescreening (b) current symptoms represent a marked and substantial worsening comparedwith the participant's usual symptomatic state prior to the current acute episode,and are associated with diminished functional ability (c) in need of increasedpsychiatric attention to treat worsening acute episode symptoms

• Have a CGI-S score of ≥4 (moderately ill) at screening and baseline

• Have an identified responsible person referred to as the "external contact person"who has agreed to provide information about the participant's location if neededduring outpatient portion of the study. The site personnel must consider thisidentified responsible person a reliable contact person, and the contact person musthave regular contact with the participant (defined at screening as direct contact nofewer than 3 times per week), and with the expectation that this frequency ofcontact would continue (either in person or via other contact method), throughoutduration of the study, including the follow-up period)

Exclusion Criteria:

The main exclusion criteria include, but are not limited to the following:

• Has a primary current diagnosis other than schizophrenia or a comorbid diagnosisthat is primarily responsible for the current symptoms and functional impairment

• Meets criteria for moderate to severe substance use disorder within past 6 monthsprior to screening (excluding those related to caffeine or nicotine)

• Has a known history of the following: (a) borderline personality disorder,anti-social personality disorder, or bipolar disorder (b) traumatic brain injurycausing ongoing cognitive difficulties, Alzheimer's Disease, or another form ofdementia, or any chronic organic disease of the central nervous system (c)intellectual disability of a severity that would impact ability to participate inthe study

• Has a current diagnosis of a psychotic disorder other than schizophrenia or abehavioral disturbance thought to be due to substance abuse

• Is or was under involuntary commitment for the acute episode, because theparticipant is considered a danger to themselves or others

• Has a history of treatment resistance exhibited by any of the following: (a) no orminimal response to at least 2 periods of treatment lasting 6 weeks or longer, withantipsychotic agents at the maximally tolerated dose. Participants who haveresponded to antipsychotics only when paired with clozapine are consideredtreatment-resistant (b) history of electroconvulsive therapy (ECT) treatment fortreatment-resistant schizophrenia within the past 6 months (c) past or current useof clozapine as single or adjunctive therapy for schizophrenia within the past 3months

• Is currently participating in or has participated in another clinical study andreceived an experimental or investigational drug agent within 3 months prior toscreening visit of this current study and has participated in no more than 2 studiesin the past 2 years