Phase III, Multi-center, Randomized, 12-week, Double-blind, Parallel-group, Placebo-controlled Study to Evaluate the Efficacy and Safety of RO4917838 in Patients With Sub-optimally Controlled Symptoms of Schizophrenia Treated With Antipsychotics Followed by a 40-week Double-blind, Parallel-group, Placebo-controlled Treatment Period.

This randomized, multi-center, double-blind, parallel-group, placebo-controlled study will evaluate the efficacy and safety of RO4917838 in patients with sub-optimally controlled symptoms of schizophrenia. Patients, on stable treatment with antipsychotics, will be randomized to receive daily oral doses of RO4917838 or matching placebo for 52 weeks, followed by an optional treatment extension for up to 3 years.