Randomized Safety Study of CVT-301 Compared to an Observational Control Group

Inclusion Criteria: * Has signed and dated an Internal Review Board/Independent Ethics Committee (IRB/IEC)-approved informed consent form before any protocol-specific screening procedures are performed. * Women of child-bearing potential must use protocol-defined contraceptive measures and must have a negative serum human chorionic gonadotropin (hCG) test at screening. These patients must be willing to remain on their current form of contraception for the duration of the study. * Patients who have idiopathic PD (i.e., not induced by drugs or other diseases) as defined by fulfilling Steps 1 and 2 of the United Kingdom (UK) Brain Bank criteria, diagnosed after the age of 30 years. * Patients who are classified as Stage 1 to 3 (in the ON state) on the modified Hoehn and Yahr scale for staging of PD severity. * Patients who have experienced motor fluctuations for a minimum of 2 hours of average daily OFF time per waking day (excluding early morning OFF time) by self-report and confirmed by the PD Diary (on 3 consecutive days) during the screening period. Exclusion Criteria: * Patients who have dyskinesia of a severity that would significantly interfere with their ability to participate or perform study procedures. * Pregnant or lactating females or females wishing to become pregnant. * Patients who have any known contraindication to the use of levodopa (LD), including a history of malignant melanoma or a history of narrow-angle glaucoma. * Patients who have had previous surgery for PD (including but not limited to deep brain stimulation \[DBS\] or cell transplantation). * Patients with a history of psychotic symptoms requiring treatment, or suicide ideation or attempt within the prior 12 months.