A Study to Investigate a New Treatment in Patients With Parkinson's Disease

Administration of IPT803 three times a day for 12 weeks as add-on therapy to patient regular PD medication(s) or as a new therapy for drug naïve patients.

Blood sample of 3 milliliters for genotyping assessment (according to patient consent).

Personality, Health and Disease questionnaires completion during the study (Visits 1, 2, 3 and 4)

BOLD fMRI performed in a sub-group of patients, depending of randomization (exploratory)

Regular PD treatment stopped 12 or 24 hours prior to Visits 2, 3 and 4 depending on the drug form (extended vs standard release). Motor assessments using UPDRS Part III are performed when patients are OFF regular PD treatment. Regular PD treatment is taken on site during the visit after the motor assessments are performed.

Regular PD treatment is not modified before the visits. The motor assessments using UPDRS Part III are performed while the patient is on regular PD treatment.