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

Inclusion Criteria:

- Males or females aged >/= 18 years and
- Clinically stable, mild or moderate schizophrenia

- On stable antipsychotic treatment for the last 6 months

- Generally healthy in the investigator's opinion, based on assessment of medical
history, physical examination, vital signs, electrocardiogram (ECG), and the results
of the hematology, clinical chemistry, urinalysis, serology, and other laboratory
tests

- Willingness to be hospitalized for approximately 3 weeks

- BMI > 18.5 kg/m2 and < 38 kg/m2

- Use of highly effective contraception as defined by the study protocol. Men must also
not donate sperm until at least 30 days after the last dose, and women cannot be
pregnant or breastfeeding

Exclusion Criteria:

- Treatment with antiparkinson medication including anticholinergic drugs

- Treatment with depot antipsychotic medication within the last three months prior to
screening

- Participation in a clinical trial with an investigational drug or device < 3 months
prior to screening

- Smokes more than 20 cigarettes per day

- Current drug abuse (excluding nicotine) or drug abuse within 3 months prior to the
screening visit

- Any donation of blood or significant blood loss within three months prior to first
administration of the study drug

- Use of prohibited medications (including vitamins or herbal remedies) taken within 14
days or within 5 times the elimination half-life of the medication (whichever is
longer) before the first study drug administration