Evaluation of Tolcapone as a Cognitive Enhancer in Schizophrenia

• Tolcapone (Drug): Tolcapone (Film-coated tablet) 200 mg orally every 8 hours for 7 days

Primary outcomes

• Efficacy: Change from baseline in cognitive test scores at day 8 [Day 8]: Performance in the cognitive tests scores: Dot Pattern Expectancy Task and cognitive tests (including subtests of the MATRICS* battery) (*MATRICS=Measurement and Treatment Research to Improve Cognition in Schizophrenia cognitive battery established by the National Institute of Mental Health) .
• Efficacy: Change from baseline in the brain blood-oxygen-level-dependent (BOLD) response at day 8 [Day 8]: Elicited brain activation during functional magnetic resonance neuroimaging (relative degree of activation of different brain regions) measured by BOLD signal.

Secondary outcomes

• Efficacy: change from baseline in psychotic symptoms intensity measured by the PANSS scores at day 8 [Day 8]: Change in psychotic symptoms intensity measured by the PANSS symptom scores
• Efficacy: negative symptoms intensity: change from baseline in the 16-item Negative Symptom Assessment (NSA-16) scale scores at day 8 [Day 8]: Change in negative symptoms intensity measured by the NSA-16 scale
• Efficacy: change from baseline in the intensity of psychotic symptoms measured by the Brief Psychiatric Rating Scale (BPRS) scores at day 8 [Day 8]: Clinical outcome measured by the change in the scores on the BPRS
• Efficacy: change from baseline in the clinical global impression measured by the Clinical Global Impression (CGI) scale scores at day 8 [Day 8]: Clinical outcome measured by the change in the scores on the CGI scale
• Efficacy: change from baseline in the global assessment of functioning measured by the Global Assessment of Functioning (GAF) scale scores at day 8 [Day 8]: Clinical outcome measured by the change in the scores on the GAF scale
• Efficacy: change from baseline in the anxiety symptoms measured by the Hamilton Anxiety Rating Scale (HAM-A) scale scores at day 8 [Day 8]: Clinical outcome measured by the change in the scores on the HAM-A scale
• Efficacy: change from baseline in the depressive symptoms measured by the Hamilton Depression Rating Scale (HAM-D) scale scores at day 8 [Day 8]: Clinical outcome measured by the change in the scores on the HAM-D scale
• Efficacy: change from baseline in the Clinician-Rated Dimensions of Psychosis Symptom Severity (CRDPSS) scale scores at day 8 [Day 8]: Clinical outcome measured by the change in the scores on the CRDPSS scale
• Change from baseline in plasmatic homocysteine (umol/L) [Day 8]: Clinical outcome measured by the change in homocystinemia (umol/L)

Other outcomes

• Patient Reported Outcome: change from baseline in the Profile of Mood States (POMS) scores at day 8 [Day 8]: Patient Reported Outcome measured by the change in the POMS scores
• Patient Reported Outcome: change from baseline in the mood state Visual Analogue Scale (VAS) scores at day 8 [Day 8]: Patient Reported Outcome measured by the change in the mood state VAS scores

Sex: All, ages: 18 Years to 65 Years

Inclusion Criteria:

* Ability to give informed consent and express the wish to fulfill all the requirements of the protocol during the study period.
* The patient must be capable of fulfillment of all the requirements of the clinical trial, at the investigator's discretion.
* Patients diagnosed with schizophrenia according to the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). Only chronic patients will be recruited, and they must be clinically compensated in order to consent to participate. The determination of clinical compensation will be conducted according with these criteria: i) outpatients, with absence of hospitalization due to acute psychiatric decompensation in the previous year, and ii) maintained GAF score equal or higher than 60 during the previous month. The recruitment process will include a clinical interview to verify the diagnosis.
* Caucasic ethnicity
* Negative pregnancy test for women of childbearing age.

Exclusion Criteria:

* Severe infections or diseases or hepatic failure (or increased liver enzymes), renal failure or bone marrow failure that advise against participation in the study at the investigator's discretion
* Positive pregnancy test, or breastfeeding women.
* Carriers of pacemaker or any kind of metallic prosthesis incompatible with magnetic resonance imaging.
* History of hypersensitivity to Tasmar® (tolcapone) or to any of its components
* Active (in the last 12 months) substance abuse, or other disease that causes psychiatric symptoms
* Cardiovascular disease and electrocardiogram alterations
* Patients receiving treatment with monoamine oxidase inhibitors during the study or up to 15 days prior to the beginning of the study.
* Patients receiving treatment with a catechol-O-methyltransferase (COMT) inhibitor
* Participation in another clinical trial in the previous 30 days.
* Other circumstances which involve Tasmar® (tolcapone) contraindications: history of Neuroleptic Malignant Syndrome and/or non-traumatic rhabdomyolysis or hyperthermia. Severe dyskinesia. Phaeochromocytoma. Hereditary galactose intolerance. Lapp lactase deficiency or glucose or galactose malabsorption.

• Patricio Molero, MD, PhD, Principal investigator, Clinica Universidad de Navarra