KW-6002 to Treat Parkinson's Disease

This study will evaluate the effects of an experimental drug called KW-6002 on Parkinson's disease symptoms and on dyskinesias (involuntary movements) that develop as a result of long-term treatment with levodopa. This drug blocks the action of the neurotransmitter adenosine, thought to be involved in producing Parkinson's symptoms. Patients with relatively advanced (Stage II to IV) Parkinson's disease between 30 and 80 years of age may be eligible for this 7-week study. Participants will have a complete medical history and physical examination, including blood tests and an electrocardiogram, and possibly brain magnetic resonance imaging (MRI), CT scan, and chest X-ray. Patients enrolled in the study will, if possible, stop taking all antiparkinsonian medications except levodopa (Sinemet) for one month before the study begins and throughout its duration. For the first 1 to 3 days, patients will be admitted to the NIH Clinical center to undergo a levodopa "dose-finding" procedure. For this study, patients will stop taking Sinemet and instead will have levodopa infused through a vein for up to 8 hours/day. During the infusions, the drug dose will be increased slowly until either 1) parkinsonian symptoms improve, 2) unacceptable side effects occur, or 3) the maximum study dose is reached. Symptoms will be monitored frequently to find two infusion rates: 1) one that is less than what is needed to relieve symptoms, and 2) one that relieves symptoms but may produce dyskinesias. This procedure will be repeated at the end of weeks 2, 4 and 6 of the study. When the patient's optimal dose is determined treatment will begin. Patients will take tablets or capsules containing KW-6002 or placebo (a look-alike pill with no active ingredient) once a day for 2 weeks, in addition to their regular Sinemet. All participants will receive placebo at least 2 weeks during the study; some patients will receive only placebo throughout the entire 7 weeks. At the end of weeks 1, 3 and 5, pa