Study of KW-6002 (Istradefylline) in Parkinson's Disease in Patients With Motor Response Complications on Levodopa

This is a Phase III open-label study, in which patients with Parkinson's disease (PD) who have completed a qualifying istradefylline study will be treated with istradefylline for a period of up to one additional year. Starting dosage of istradefylline will be 40 mg/d and maintenance dosage will be at the discretion of the Investigator. The available doses for istradefylline are 20 and 40 mg/d. Open-label istradefylline treatment will be initiated after a patient has satisfied all criteria for participation. Patients will undergo screening and baseline evaluations during which they will be assessed for eligibility. Screening procedures will vary slightly depending upon the allocation of patients to one of the following two groups: Group A: Patients who have completed double-blind treatment studies 6002-US-0 13, 6002- US-Ol S or 6002-EU-007 immediately prior to entering this open-label trial and may have had an interruption of study drug of 14 days or less. The screening visit for these patients will correspond to the final visit of the previous istradefylline study. Group B: Patients who have previously completed double-blind treatment studies 6002-US- 013, 6002-US-O 18 or 6002-EU-007 or discontinued from open-label study 6002-US-007 and have had an interruption of study drug greater than 14 days. Screening for these patients will occur at the Week -2 and Day -1 Visits. Visits should occur in the ON state and procedures should be conducted in the order specified, whenever possible. Safety outcomes will be assessed by physical examination (including neurological examination), clinical laboratory tests and 12-lead electrocardiogram (ECG) at screening and at selected subsequent scheduled visits. Vital signs, including weight, concomitant medications, and adverse events will be monitored regularly throughout the trial. Changes in anti-parkinsonian medications will be permitted at the Investigator's discretion.