MK-8189 Multiple Dose Study in Healthy Volunteers and Schizophrenia Participants (MK-8189-003)

This 3-part dose titration study will assess MK-8189 safety, tolerability, pharmacokinetics (PK), and central nervous system activity. Part 1 (Panels A and B) will assess MK-8189 administered as monotherapy in participants with schizophrenia. Part 2 (Panel C) will assess MK-8189 administered as add-on to atypical antipsychotic treatment in participants with schizophrenia. Part 3 (Panel D) will assess monotherapy with MK-8189 in healthy participants, including those of Japanese descent. The primary hypothesis is that there is at least one dose of MK-8189 that is generally safe and well-tolerated which will have the desired PK parameters in participants with schizophrenia.