Acute Effects of Preladenant (SCH 420814) on Dyskinesia and Parkinsonism in Levodopa Treated Participants (P05550)

Acute Effects of SCH 420814 on Dyskinesia and Parkinsonism in Levodopa Treated Patients

This is a randomized, placebo-controlled, 3-period crossover, balanced, single-site, third party-blind study of preladenant (SCH 420814) in participants with Parkinson disease (PD) to be conducted in conformance with Good Clinical Practices. This trial will investigate the effects of single doses of preladenant and placebo on the dyskinesia and antiparkinsonian actions of a levodopa infusion. The study will examine 10 mg ("low dose") or 100 mg ("high dose") study drug, given as single, oral administrations in conjunction with intravenous (IV) levodopa infusion and oral carbidopa.

Inclusion Criteria:

• Participant must have a diagnosis of idiopathic PD based on history, exam and any relevant laboratory tests
• Participants must have been treated with levodopa for one or more years
• Participants must have motor fluctuations that can be measured as a 10% change in tapping speed between "on" and "off" and concurrent motor Unified PD Rating Scale (UPDRS) must also show a 20% improvement when "on"
• Participants must have dyskinesia when "on" measured as at least 2 in one or more body parts on scale using 0 (absent) to 4 (severe) for four limbs, trunk, neck and face (total 7 body parts and 28 points)
• Participant must be free of any clinically significant disease that would interfere with the study evaluations
• Female participants must be postmenopausal and/or surgically sterilized and have a negative serum pregnancy test at the screening visit and a negative urine or serum pregnancy test upon each admission to the study center
• Premenopausal, unsterilized female participants have to agree to use a medically accepted method of contraception
• Male participants must agree to use a medically accepted method of contraception as or abstain from sexual intercourse during the trial and for 2 months after stopping the medication.

Exclusion Criteria:

• Female participants who are pregnant, intend to become pregnant (within 3 months of ending the study), or are lactating
• Participants with dementia (mini-mental state examination [MMSE] <23), hallucinations, confusion, major psychiatric disorders, and unstable medical conditions
• Participants with any stable surgical or medical condition which might significantly alter the absorption, distribution, metabolism or excretion of any drug
• Participants with a positive screen for drugs of abuse
• Participants who are positive for hepatitis B surface antigen, hepatitis C antibodies or human immunodeficiency virus (HIV)
• Participants who are currently participating in another medical interventional clinical study or have participated in a medical interventional clinical study within 30 days and who have previously received this compound.