A Study of Istradefylline (KW-6002) for the Treatment of Parkinson's Disease in Patients Taking Levodopa

A 12-week, Double Blind, Placebo-controlled, Randomized, Parallel Group, Multicenter, Fixed Dose Study to Evaluate the Efficacy and Safety of a 20 mg/d Oral Dose of KW-6002 (Istradefylline) as Treatment for Parkinson's Disease in Patients With Motor Response Complications on Levodopa/Carbidopa Therapy.

To establish the efficacy of a 20 mg/day dose of istradefylline for reducing the percentage of OFF time in patients with advanced Parkinson's disease (PD) treated with levodopa.

To establish the efficacy of a 20 mg/d dose of istradefylline for reducing the percentage of OFF time in patients with advanced Parkinson's disease (PD) treated with levodopa. Patients who meet entry criteria will be randomized in a 1 to 1 ratio to either istradefylline or matching placebo. Patients will be treated for 12 weeks and will have interim visits and end of treatment visit to assess the efficacy and safety of istradefylline as compared to placebo.

Inclusion Criteria:

1. UK Parkinson's Disease Society (UKPDS) brain bank criteria (Step 1 and 2) for PD.
2. PD stages 2-4 in the OFF state for Modified Hoehn and Yahr Scale.
3. On levodopa/carbidopa for at least one year, stable dose in past 4 weeks.
4. Currently take at least three doses of levodopa/carbidopa per day.
5. Predictable end of dose wearing off.
6. Able to satisfactorily complete Hauser version of a Parkinson's diary.
7. Have an average of 180 minutes of OFF time on two 24 hour diaries.
8. Be at least 30 years of age.

Exclusion Criteria:

1. Neurosurgical treatment for PD.
2. History of psychosis.
3. Diagnosis of atypical parkinsonism, secondary parkinsonism variant or Parkinson's plus syndromes.
4. Diagnosis of cancer within 5 years.
5. Mini-mental status examination score of 25 or less.
6. History of seizures or neurologic malignant_syndrome.
7. Clinical depression.