2 Year Study to Evaluate the Effects of GPI 1485 on [123I]b-CIT/SPECTScanning and Clinical Efficacy in Patients With PD

This study was designed to assess whether GPI 1485 has the ability to delay or stop disease progression and improve symptoms in patients with Parkinson's disease (PD) that is already being treated with a dopamine agonist therapy. Whether the drug is working will be assessed by evaluating clinical endpoints such as UPDRS scores and by evaluating images, obtained by SPECT scan, of brain activity. Participants in the study will be given either placebo or GPI 1485 treatment. The duration of the study is 2-years and patients are required to complete 12 safety visits and 3 SPECT scans. SPECT scans will be taken before, after 1-year, and after 2-years of treatment with GPI 1485. In completing the SPECT scan, patients will be injected with a radioactive investigational drug b-CIT and pictures taken using a Single Photon Emission Computed Tomography (SPECT) camera.