['schizophrenia']
['f17464', 'placebo']

        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
      