Long Term Study of Istradefylline in Subjects With Moderate to Severe Parkinson's Disease

Inclusion Criteria:

1. Written informed consent;

2. Subjects who completed Study No. 6002-014 inclusive of the 30-day follow-up period;

3. Currently taking levodopa combination (carbidopa/levodopa or benserazide/levodopa)
therapy plus at least one adjunctive PD medication;

4. Women of child-bearing potential (WOCBP) must use a reliable method of contraception
and have a negative serum pregnancy test at Screening;

Exclusion Criteria:

1. Subjects with less than 70% treatment compliance throughout their enrollment on Study
No 6002-014 and or with major protocol deviations in Study No. 6002-014 (subjects who
failed to meet any of the inclusion criteria, subjects who met any of the exclusion
criteria or subjects who met the criteria for subject withdrawal but who were not
withdrawn);

2. Subjects on apomorphine and/or dopamine receptor antagonists or direct
gastrointestinal levodopa infusion;

3. Subject who have had neurosurgical operation for PD;

4. Subjects taking A2a antagonist, potent CYP3A4 inhibitors, potent CYP34A inducers;

5. Subjects who have had a diagnosis of cancer or evidence of continued malignancy within
the past three years (with the exception of adequately treated basal cell or squamous
cell skin cancer, in situ cervical cancer, or in situ prostate cancer with normal
prostate-specific antigens post resection).