Pilot Study to Evaluate Pimavanserin for the Treatment of Motor and Behavioral Symptoms of Tourette Syndrome

Background: Pimavanserin is a serotonin 2A receptor inverse agonist and antagonist used for the treatment of hallucinations and delusions in Parkinson's disease psychosis. Numerous studies support a modulatory role of serotonin in Tourette syndrome (TS). Objectives: To determine whether or not pimavanserin affects TS symptoms. Methods: In this open-label study of TS adult patients, pimavanserin was titrated to 34 mg/day over 1 week and continued for an additional 7 weeks followed by a 2-week washout. Tic severity, the primary outcome measure, was assessed by the Yale Global Tic Severity Scale Total Tic Severity score (YGTSS-TTS). Secondary outcome measures included changes in the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), the Tourette Syndrome Clinical Global Impression of Change (TS-CGIC), the Tourette Syndrome-Patient Global Impression of Impact (TS-PGII), and the Gilles de la Tourette Syndrome – Quality of Life scale (GTS-QOL). Results: We enrolled 12 patients, but 2 dropped out after week 2 due to non-serious side effects. In the 10 patients, mean (standard deviation (SD)) age 34 (12.9) who completed the study the mean (SD) baseline YGTSS-TTS was 34 (9.3). This decreased by 3.6 (4.9) points at week 8, a 12% reduction in tic severity (P = 0.03). This improvement is small and may not be clinically important. Significant improvement was noted in the TS-CGIC, TS-PGII and GTS-QO. No serious adverse events were reported. Conclusions: The results of this study suggest that pimavanserin is safe and associated with improvement in motor and non-motor TS symptoms. These findings warrant further study by a larger, placebo-controlled, trial.