Study ATS3020 was closed due to business reasons. Neurocrine Biosciences will continue to conduct study ATS3019 (NCT05110157). There were no unexpected safety findings for this compound that motivated the decision.

This primary objective for this study is to evaluate the effect of adjunctive valbenazine versus placebo on symptoms of schizophrenia in participants who have inadequate response to antipsychotic treatment.

Key Inclusion Criteria:

• Medically confirmed diagnosis of schizophrenia
• Participant is receiving a stable regimen of background antipsychotic medication
• Plasma levels for at least 1 of the participant's antipsychotic medications must be detectable by an available assay
• Participant is an outpatient with stable symptomatology
• Participant must have an adult informant (for example, a family member, relative, partner, social worker, caseworker, residential facility staff, or nurse)

Key Exclusion Criteria:

• Has a history of treatment resistant schizophrenia
• Have a clinically significant unstable medical condition in the judgement of the investigator or any laboratory value outside the normal range that is considered by the investigator to be clinically significant at the screening visit
• Prior (within 6 months of Screening) or concomitant use of any vesicular monoamine transporter 2 (VMAT2) inhibitor (that is, valbenazine, reserpine, tetrabenazine, deutetrabenazine); or a history of intolerance to VMAT2 inhibitors