A Placebo- and Active-Controlled Study of Preladenant in Early Parkinson's Disease (P05664 AM5)

Inclusion Criteria:

• Has a diagnosis of idiopathic PD for < 5 years
• If receiving amantadine and/or anticholinergics must have been on a stable regimen of treatment for at least the 5 weeks immediately before Screening. (Note: Subjects who are not taking any medications for PD are permitted to enroll in this trial.)
• Must have a UPDRS Part 3 score of ≥10, a Hoehn and Yahr Stage ≥3, be ≥30 to ≤85 years of age, and have results of Screening clinical laboratory tests drawn within 3 weeks prior to Randomization, clinically acceptable to the investigator, and not within the parameters specified for exclusion
• If sexually active or plan to be sexually active, must agree to use a highly effective method of birth control while the subject is in the study and for 2 weeks after the last dose of study drug. A male subject must also not donate sperm during the trial and within 2 weeks after the last dose of study drug

Exclusion Criteria:

• Must not have a form of drug induced or atypical Parkinsonism, cognitive impairment (ie, Montreal Cognitive Assessment [MoCA] score <22), bipolar disorder, untreated major depressive disorder, schizophrenia, or other psychotic disorder; history of exposure to a known neurotoxin, or any neurological features not consistent with the diagnosis of PD as assessed by the investigator
• Must not have had surgery for PD
• Must not have a history of repeated strokes with stepwise progression of Parkinsonism or head injuries, or a stroke within 6 months of Screening; poorly controlled diabetes; abnormal renal function; or a severe or ongoing unstable medical condition
• Must not have failed to show a therapeutic response if a diagnostic levodopa (L dopa) challenge had been done with a large test dose (>500 mg) of L dopa (if malabsorption excluded), or failed to respond to an adequate previous treatment with dopaminergic therapy.
• Must not have been treated with L dopa or dopamine agonists for 30 days or more. A participant who has been treated with L-dopa or dopamine agonists for <30 days will be allowed to enter the study. These participants must stop taking dopaminergic medication 30 days prior to Randomization.
• Must not be at imminent risk of self-harm or harm to others
• Must not have elevated blood pressure (BP) (systolic BP ≥150 mm Hg or diastolic BP ≥95 mm Hg) that cannot be adequately controlled with antihypertensive medication, as demonstrated by 2 BP measurements meeting acceptable BP criterion at consecutive scheduled or unscheduled visits between Screening and Randomization (a 5-6 week period), one of which must be the Randomization visit.
• Must not have had any clinically significant cardiovascular event or procedure for 6 months prior to Randomization, including, but not limited to, myocardial infarction, angioplasty, unstable angina, or heart failure; and a subject must not have heart failure staged New York Heart Association Class III or IV
• Must not have an alanine aminotransferase (ALT) or aspartate amino transferase (AST) > 3 x the upper limit of normal (ULN) or total bilirubin (T BIL) > 1.5 x ULN
• Must not have active serologically-confirmed hepatic dysfunction (defined as viral infection [Hepatitis B, C, or E; Epstein-Barr virus (EBV)]; cytomegalovirus [CMV] or a history of diagnosis of drug- or alcohol-induced hepatic toxicity or frank hepatitis, or a history of diagnosis of drug- or alcohol-induced hepatic toxicity or frank hepatitis
• Must not have a history within the past 5 years of a primary or recurrent malignant disease with the exception of adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, or in situ prostate cancer with a normal prostate-specific antigen (PSA) post resection
• Must not have received certain prespecified medications or ingested high tyramine-containing aged cheeses (eg, Stilton) for a prespecified time window before the trial, during the trial, and for 2 weeks after the trial.
• Must not have an average daily consumption of more than three 4 ounce glasses (118 mL) of wine or the equivalent.
• Must not have a severe or ongoing unstable medical condition (eg, any form of clinically significant cardiac disease, symptomatic orthostatic hypotension, seizures, or alcohol/drug dependence).
• Must not have allergy/sensitivity to investigational product(s) or its/their excipients.
• Must not be breast-feeding, considering breast-feeding, pregnant or intending to become pregnant.
• Must not have used preladenant ever, or any investigational drugs within 90 days immediately before Screening.