The purpose of this study is to evaluate the potential efficacy of oral F17464 in comparison to placebo over 6 weeks in patients with acute exacerbation of schizophrenia. Study design: double-blind, randomized, placebo-controlled, parallel-groups, fixed-dose design, multicentre study.

Inclusion Criteria:

Demographic and other characteristics

• Male or female, 18-64 years of age inclusive
• primary diagnosis of schizophrenia undergoing an acute exacerbation with prominent "active phase" symptoms, as described by the Diagnostic and Statistical Manual of Mental Disorders, 4th edition - Text Revision (DSM IV-TR) using the MINI 6.0 (Mini-International Neuropsychiatric Interview) for schizophrenia and psychotic disorders related to DSM IV-TR
• Well-documented diagnosis of schizophrenia for a minimum of 1 year before the screening visit
• Since the diagnosis of schizophrenia, the average number of hospitalisations should be no higher than 2 per year (the minimum duration of hospitalization should be more than 4 days)
• During the year before Visit 1, maximum 3 acute psychotic episodes that required hospitalization or change of antipsychotic medication or other therapeutic intervention
• Adequate clinical response to well-conducted treatment courses during previous acute episodes. A well conducted treatment course is defined as an antipsychotic treatment with the usual doses for at least 4 weeks

Current acute episode

• Structured Clinical Interview for the Positive And Negative Syndrome Scale (SCI-PANSS) with a PANSS total score ≥ 70 to < 120 (at Visit 1 and 2)
• Rating of at least 4 (moderate) on at least 2 of the following 4 PANSS positive symptoms: delusions, hallucinatory behaviour, conceptual disorganization, suspiciousness/persecution
• Clinical Global Impression of Severity (CGI-S) score ≥ 4 (moderate or severe)
• Antipsychotic initiated for this acute episode and/or ongoing chronic antipsychotic treatment, with a maximum of 2 antipsychotics in total needed to be changed (due to inefficacy or safety reasons)
• Hospitalization and/ or treatment for the current psychotic episode for less than 2 weeks prior to Visit 1
• No significant improvement of PANSS total score between enrolment (Visit 1) and inclusion (Visit 2) corresponding to a score improvement < 20% on positive symptoms subscale

Exclusion Criteria:

Related to the pathology

• Patients in their first acute episode of psychosis

• Current schizophrenic episode with predominant negative symptoms

• Patient " known to be refractory " defined as lack of significant improvement (no significant relief of symptoms, and no period of good function) despite adequate courses with at least 3 different antipsychotics medication cycles of an adequate duration (at least 4 weeks) and at adequate dosage during the previous 5 years;

• Schizoaffective disorder, schizophreniform disorder and other psychotic disorders;

• Bipolar I and II disorder

• Pervasive developmental disorder, mental retardation, delirium, dementia, memory impairment and other cognitive disorders that would compromise a reliable assessment according to the investigator's opinion

• Known or suspected borderline or antisocial personality disorder or other DSM IV axis II disorder of sufficient severity to interfere with participation in this study

• History of tardive dyskinesia or chronic extra-pyramidal symptoms (EPS), serotonin syndrome or neuroleptic malignant syndrome

• Major depressive disorder which requires a pharmacological treatment

• At imminent risk of injuring him/herself or others or causing significant damage to property, as judged by the investigator

• Suicidal risk based on the Columbia-Suicide Severity Rating Scale (C-SSRS)

  • Any suicidal behavior in the past year
  • Suicidal ideation of type 4 or 5 in the past month

Related to treatments

• Structured psychotherapy (e.g. cognitive behavioural therapy) started within 6 weeks before visit 1
• Electroconvulsive therapy within 3 months before Visit 1
• Previous lack of response to electroconvulsive therapy
• Treatment ongoing with a depot neuroleptic (even if less than 1 cycle in duration before Visit 1)
• Patient having previous treatment course with clozapine within the 4 months prior to Visit 1
• Requirement of concomitant treatment with any of the prohibited medications
• History of intolerance or hypersensitivity to other drugs of the same chemical class as F17464 or to rescue medications or any history of severe drug allergy or hypersensitivity