Clozapine/Paliperidone Versus Clozapine/Placebo in Resistant Schizophrenia

This is a 12 weeks, blind study (the patient, investigator, and sponsor do not know the study drug and dosage being taken by the patient) of the safety and tolerability of flexible-dose (3 to 12mg per day), extended-release (ER) paliperidone in combination with clozapine with a diagnosis of schizophrenia. Patients who have completed study or who discontinued from that study because of lack of efficacy but completed a minimum of 21 days of the study may enter this study. This study consists of a 21-day screening and washout phase (to discontinue and "wash out" any medication not allowed in the study), and a double blind treatment phase of 12 weeks, during which all patients will take oral paliperidone ER every day and clozapine versus clozapine alone, and a post-treatment phase consisting of a follow-up visit completed 1 week after a patient has received the final dose of paliperidone ER. The study, including the screening and posttreatment phase, will last approximately 30 weeks. Screening and washout may be conducted while a patient is an outpatient. Safety will be assessed by laboratory measurements (chemistry, liver function tests, hematology, hormone, lipid assessments, prolactin \[blinded\], urinalysis, and urine drug screens; body weight, height, and waist circumference measurements; ECGs and the ESRS (extrapyramidal syndrome rating scale). These instruments will be used to assess extrapyramidal symptoms (EPS) and dyskinesias. Adverse events will be monitored including psychiatric adverse events of interest (worsening of psychosis, hyperprolactinemia, weight gain) that may be associated with paliperidone ER in this population. The primary aim of this study is to evaluate the long-term (12 weeks) safety and tolerability of clozapine/paliperidone ER in resistant schizophrenia. As exploratory secondary aims, the study will assess the effect of clozapine/paliperidone ER on the long-term symptoms of schizophrenia as measured by the changes in the Positive and Negative Syndrome Scale for Schizophrenia (PANSS) scores, the global improvement in severity of illness as measured by the Clinical Global Impression(CGI) scale. Patients begin the study at 6.0 mg/day of oral paliperidone ER. If a higher dosage is needed, the dosage will be increased (in increments of 3 mg/day not more frequently than once every 5 days) to 12 mg/day. If the 6.0 mg/day dosage is not well tolerated, the dosage may be decreased (not more frequently than once every 5 days) to 3.0 mg/day. Patients will be dosed for up to 6 months.