A Study to Evaluate 3 Dose Levels of Luvadaxistat of Adults With Negative Symptoms of Schizophrenia

The drug being tested in this study is called luvadaxistat. Luvadaxistat is being tested to treat negative symptoms in participants who have schizophrenia.

Participants will be randomly assigned (by chance, like flipping a coin) to one of the four treatment groups in the double-blind period-which will remain undisclosed to the participant and study doctor during the study (unless there is an urgent medical need):

• Luvadaxistat 50 mg once daily
• Luvadaxistat 125 mg once daily
• Luvadaxistat 500 mg once daily
• Placebo once daily

Inclusion criteria

• Has a current diagnosis of schizophrenia as defined by the Mini International Neuropsychiatric Interview (MINI) 7.0.2 for Psychotic Disorders for the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) and the general psychiatric evaluation.
• Initial diagnosis must be greater than or equal to (>=1) year from screening.
• Is receiving primary background antipsychotic therapy (other than clozapine) at a total daily dose between 2 and 6 mg of risperidone equivalents. Concomitant treatment with a sub-therapeutic dose of a second antipsychotic may be permitted with sponsor or designee approval if used to treat specific symptoms, such as insomnia or anxiety (for example, quetiapine 25-50 mg or its equivalent as needed for anxiety), but not if it is used for refractory positive psychosis symptoms.
• Is treated with a stable regimen of psychotropic medications with no clinically meaningful change (no increase in dose, less than or equal to [<=] 25 percent [%] decrease in dose for tolerability) in the prescribed dose for 2 months before the screening visit and no dose adjustment is anticipated throughout study participation up to the Day 84/early termination visit.
• Has a BNSS total score (12-item, excluding number 4) >=28; stable Single-blind Placebo Run-in and baseline BNSS total (12-item, excluding number 4) scores (<= 20% change from the screening score).
• Has no more than moderate-severe (<=5) rating on PANSS positive symptom items P1, P3, P4, P5, P6, or unusual thought content (G9), with a maximum of 2 of these items rated '5'; no more than moderate (<=4) rating on conceptual disorganization (P2).
• There is evidence that the participant has stable symptomatology >=3 months prior to the screening visit (example, no hospitalizations for schizophrenia, no emergency room admission due to symptoms of schizophrenia, no increase in level of psychiatric care due to worsening of symptoms of schizophrenia).
• Have an adult informant who will be able to provide input for completing study rating scales, including the PANSS and SCoRS (for example, a family member, social worker, caseworker, residential facility staff, or nurse who spends >=4 hours/week with the participant) and is considered reliable by the investigator. The informant must be able and willing to provide written informed consent and to participate in at least 1 in-person interview, then be able to provide continuing input by attending each clinical assessment visit or via participating in a telephone interview for other study visits that include the PANSS or SCoRS endpoints.

Exclusion criteria

• Has a lifetime diagnosis of schizoaffective disorder; a lifetime diagnosis of bipolar disorder; or a lifetime diagnosis of obsessive compulsive disorder based on the MINI combined with the general psychiatric evaluation.
• Has a recent (within the last 6 months) occurrence of panic disorder, depressive episode, or other comorbid psychiatric conditions currently requiring clinical attention based on the MINI for DSM-5 and the general psychiatric evaluation.
• Has a diagnosis of substance use disorder (with the exception of nicotine dependence) within the preceding 6 months based on the MINI for DSM-5 and the general psychiatric evaluation.
• Is participating in a formal structured nonpharmacological psychosocial therapeutic treatment program (cognitive remediation, cognitive-behavioral therapy, intensive symptom/vocational rehabilitation) for a duration of less than (<) 3 months before randomization. In addition, initiation of such nonpharmacological treatment programs is not permitted during study participation through the Day 84 visit.
• The participant exhibits more than a minimal level of antipsychotic-induced parkinsonism symptoms, as documented by a score on the modified Simpson Angus Scale (SAS) (excluding item number 10, Akathisia) greater than (>) 6.
• Has evidence of depression as measured by a Calgary Depression Scale Score (CDSS) > 9.
• Is considered by the investigator to be at imminent risk of suicide or injury to self, others, or property, or the participant has attempted suicide within the past year prior to screening. Participants who have positive answers on item number 4 or 5 on the Columbia-Suicide Severity Rating Scale (C-SSRS) (based on the past year) prior to randomization are excluded.
• Has a history of brain trauma associated with loss of consciousness for >15 minutes.
• Diagnosis of schizophrenia occurred prior to 12 years of age.
• Has received electroconvulsive therapy within 6 months (180 days) before Screening.
• Has a history of developmental intellectual disability or mental retardation.
• Antipsychotic plasma levels for the participant's primary background antipsychotic are below the minimum acceptable concentration criteria per the Antipsychotic Reference document at the screening or placebo run-in visits. This criterion is not applicable to participants on a primary background antipsychotic for which a clinical assay is unavailable.
• Is treatment resistant. Treatment resistance is defined as prior nonresponse of positive symptoms of schizophrenia to 2 courses of treatment with antipsychotics of different chemical classes for at least 4 weeks, each at doses considered to be effective.
• Does not have a stable residence or is homeless.