A Study of MK-5720 in Participants With Schizophrenia (MK-5720-001)

A Single Ascending Dose Study to Evaluate the Safety, Tolerability, and Pharmacokinetics of the Long-Acting Injectable of MK-5720 in Participants With Schizophrenia

The purpose of this study is to evaluate the safety, tolerability, and pharmacokinetics (PK) of single ascending intramuscular doses of MK-5720, and the safety and tolerability of multiple once-daily oral doses of MK-8189, in participants with schizophrenia. The primary study hypothesis is that the administration of MK-5720 is safe and well tolerated.

In Period 1, participants receive once-daily MK-8189 for 7 days, followed by a 72-hour washout. In Period 2, participants receive a single dose of MK-5720.

Inclusion Criteria:

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

• Meets diagnostic criteria for schizophrenia or schizoaffective disorder according to the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) criteria with the onset of the first episode being no less than 2 years prior to screening and monotherapy with antipsychotics for treatment should be indicated
• Has a history of receiving and tolerating antipsychotics medication within the usual dose range employed for schizophrenia
• Can discontinue the use of all antipsychotic medication at least 5 days or 3 half-lives (which ever in longer) prior to the start of the treatment period and during the study

Exclusion Criteria:

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

• Is at imminent risk of self-harm, based on clinical interview and responses on the Columbia-Suicide Severity Rating Scale (C-SSRS), or of harm to others in the opinion of the investigator
• Has history of mental retardation, borderline personality disorder, or organic brain syndrome
• Has a history of neuroleptic malignant syndrome or moderate to severe tardive dyskinesia
• Has a substance-induced psychotic disorder or behavioral disturbance thought to be due to substance abuse
• Has a history of seizure disorder beyond childhood or is receiving treatment with any anticonvulsant to prevent seizures
• Has a family history of sudden death
• Has claustrophobia to a degree that prevents tolerance of magnetic resonance imaging (MRI) scanning procedure
• Has a metallic implant of any sort that prevents MRI examination, or any other contraindication to MRI examination
• Presents any concern by the investigator regarding safe participation in the study or for any other reason the investigator considers the participant inappropriate for participation in the study
• History of significant multiple and/or severe allergies or has had an anaphylactic reaction or significant intolerability to prescription or nonprescription drugs or food
• Positive test(s) for hepatitis B surface antigen (HBsAg), hepatitis C antibodies or human immunodeficiency virus (HIV)
• Has received or is currently receiving treatment with clozapine for any length of time
• Has received any live vaccines within 30 days prior to the first dose of study intervention or is scheduled to receive any live vaccine through 60 days following study intervention