A Study of the Safety, Tolerability and Pharmacokientics of RO5545965 in Patients With Schizophrenia on Risperidone

Oral daily administration from Days 1-12

Oral daily administration from Days 1-12

13 day run-in phase until 4 mg daily dose level is reached. 4 mg daily oral dose until Day 17 of study, for a total of 30 days. Dose may be increased up to 6 mg at the investigator's discretion. After study treatment, risperidone dosage may be decreased, increased or omitted at the investigator's discretion during a wash-out phase while patients return to their chronic antipsychotic treatment. Patient response during wash-out will be monitored in-house for 48 hours after the last dose of RO5545965 or placebo is administered. This in-house observation may be extended as needed by the investigator.