Inclusion Criteria:

• Male or female
• 18 to 65 years of age, inclusive
• meet criteria for chronic (diagnosis established > 1 year ago) schizophrenia with adequate psychotic symptoms as demonstrated by a PANSS total score > 60
• current diagnosis of schizophrenia (disorganized type, 295.10; catatonic type, 295.20; paranoid type, 295.30; undifferentiated type, 295.90) or schizoaffective disorder (295.7) in accordance with DSM-IV
• Agree to be fully hospitalized until at least Day 14 of the study
• Females must be of non-childbearing potential: surgically sterilized (i.e. tubal ligation), have had a hysterectomy prior to the screening phase, or be post-menopausal. Females who have been post-menopausal for more than 12 months but less than 24 months must have a FSH > 40 mU/mL.

Exclusion Criteria:

• Pregnant or lactating women
• administration of clozapine within 60 days prior to Baseline
• DSM-IV diagnosis of schizophreniform disorder (295.40) or schizophrenia residual sub-type (295.60), or other primary psychiatric diagnoses, such as bipolar disorder or major depressive disorder
• Severity of psychosis rated severe or higher (CGI-S 6 or 7)
• Known suicidal risk (modified ISST score>7)
• Requiring disallowed concomitant psychotropic medication following enrolment into the study
• Current evidence of clinically significant or unstable illness
• Clinically significant abnormal laboratory data (e.g. creatinine, AST or ALT greater than 3 x the upper limit of normal, TSH>10 IU) at screening, or any abnormal laboratory values that could interfere with the assessment of safety (e.g. blood cell count, etc.).