The main objective of the study is to evaluate NBI-1117568 compared with placebo in delaying relapse of symptoms of schizophrenia in adults who have a stable response after open-label treatment with NBI-1117568.

Key Inclusion Criteria:

• Participant has a primary diagnosis of schizophrenia established by a comprehensive psychiatric evaluation based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) criteria.
• Participant had the initial diagnosis of schizophrenia ≥1 year before screening.
• Participant has had a positive response to ≥1 antipsychotic therapy (other than clozapine) at a therapeutic dose.

Key Exclusion Criteria:

• Participant has an unstable or poorly controlled medical condition or chronic disease (including history of neurological [including dementing illness, myasthenia gravis], hepatic, renal, cardiovascular, gastrointestinal, pulmonary, autoimmune, or endocrine disease that may affect study participation or results) or malignancy within 30 days before Day 1.
• Participant has any laboratory abnormalities suggestive of clinically significant, poorly managed, or unmanaged undiagnosed disease.
• Participant has a history of clozapine treatment for treatment-resistant psychosis.
• Participant has a history of a stay in a psychiatric inpatient facility for ≥30 consecutive days (other than for purely social reasons or due to participation in a different clinical trial) during the 90 days before screening.
• Participant has initiated or increased intensity of nonpharmacological psychosocial therapeutic treatment within 3 weeks before screening or is expected to change throughout the length of the study.

Note: Other protocol-defined Inclusion and Exclusion criteria may apply.

The initial Open-label Stabilization Period is open-label and non-randomized.