The "on" state is defined as the period of time during which a patient's symptoms of PD improve or disappear following treatment with L-dopa or dopamine agonists. The "off" state is defined as the period of time characterized by the return of symptoms (i..e. tremor, slowness, and rigidity) following treatment with L-dopa or dopamine agonists. Study participants reported their symptoms at half-hour intervals as "off", "on", or "asleep" on their daily diary for 3 days before randomization (baseline) and for the 3 days immediately before their Week 12 visit. The mean change from baseline in "off" time was based on a constrained longitudinal data analysis (cLDA) with treatment, time, and treatment-by-time interaction as fixed effects and subject as random effect.

The number of participants with Systolic Blood Pressure (SBP) ≥180 mmHg and 20 mmHg increase was reported. Participants lie supine at rest for 5 minutes, then have a single BP measurement taken (ie, 1 reading). Participants then stand for 3 minutes at rest, followed by a single BP measurement (1 reading) in the standing position.

The number of participants with Diastolic Blood Pressure (DBP) ≥105 mmHg and 15 mmHg increase was reported. Participants lie supine at rest for 5 minutes, then have a single BP measurement taken (ie, 1 reading). Participants then stand for 3 minutes at rest, followed by a single BP measurement (1 reading) in the standing position.

The percentage of participants with suicidality using the Columbia - Suicide Severity Rating Scale (C-SSRS) was reported. The C-SSR was used in this study only for the purpose of safety monitoring by measuring the incidence of different types of suicidality categories during treatment. The assessment was done by the nature of the responses, not by a numbered scale. Participants who reported at least one occurrence of suicidal behavior or suicidal ideation were counted as having experienced suicidality. Suicidal behavior included suicide attempt, aborted attempt, interrupted attempt, or preparatory behavior. Suicidal ideation included a wish to die or active suicidal thought with or without method, intent or plan.

The ESS is a self-administered questionnaire providing a measure of a person's general level of daytime sleepiness, or their average sleep propensity in daily life. The scale consists of 8 situations in which the participant rates their tendency to become sleepy on a scale of 0=no chance of dozing to 3=high chance of dozing. The overall score is the sum of the scores for the 8 situations for a minimum of 0 and a maximum of 24 with a higher score indicating greater sleepiness. The mean change from baseline in total EES was based on a cLDA with treatment, time, and treatment-by-time interaction as fixed effects and subject as random effect.

The "on" state is defined as the period of time during which a patient's symptoms of PD improve or disappear following treatment with L-dopa or dopamine agonists. The "off" state is defined as the period of time characterized by the return of symptoms (i..e. tremor, slowness, and rigidity) following treatment with L-dopa or dopamine agonists. Study participants reported their symptoms at half-hour intervals as "off", "on", or "asleep" on their daily diary for 3 days before randomization (baseline) and for the 3 days immediately before their Week-12 visit. The mean change from baseline in "off" time was based on a constrained longitudinal data analysis with treatment, time, and treatment-by-time interaction as fixed effects and subject as random effect.

The number of participants with Systolic Blood Pressure \>=180 mm Hg was reported.

The number of participants with Diastolic Blood Pressure \>=105 mm Hg was reported.

The number of participants with alanine aminotransferase \>=3 times the upper limit of normal and a \>=10% increase was reported.

The number of participants with aspartate aminotransferase \>=3 times the upper limit of normal and a \>=10% increase was reported.

The ESS is a self-administered questionnaire providing a measure of a person's general level of daytime sleepiness, or their average sleep propensity in daily life. The scale consists of 8 situations in which the participant rates their tendency to become sleepy on a scale of 0=no chance of dozing to 3=high chance of dozing. The overall score is the sum of the scores for the 8 situations for a minimum of 0 and a maximum of 24.

An adverse event is defined as any unfavorable and unintended sign including an abnormal laboratory finding, symptom or disease associated with the use of a medical treatment or procedure, regardless of whether it is considered related to the medical treatment or procedure. A serious adverse event is an adverse event that that results in death, life threatening adverse event, permanent or significant disability / unfitness for work, hospital treatment (i.e., admission to hospital) or prolongation of a patient's length of stay, or congenital deformity or birth defect.

"Off" time refers to periods of inadequate control of Parkinson disease symptoms (worsening or presence of symptoms). For baseline and the 12 weeks treatment period, hours spent in the "off" state during awake time were recorded in half-hour time intervals using a daily diary at least 3 full days before scheduled visits. For baseline, the 24-hour average over 3 consecutive days was derived for Week -1. For endpoint, the 24-hour average was derived for the last available 3 consecutive days with postbaseline data available during the treatment period. Change from baseline in least squares (LS) means and pooled standard deviation (SD) were obtained from an analysis of covariance (ANCOVA) model with effect for treatment and baseline covariate. A negative change from baseline signifies less time spent in the "off" state.

Blood samples were taken at the following timepoints: pre-dose, 0.25, 0.50, 0.75, 1, 2, 4, 6, 12, 16, 24, 30, 36 and 48 hours postdose in order to determine the AUC0-∞ of preladenant

Blood samples were taken at the following timepoints: pre-dose, 0.25, 0.50, 0.75, 1, 2, 4, 6, 12, 16, 24, 30, 36 and 48 hours postdose in order to determine the AUC0-∞ of preladenant

Blood samples were taken at the following timepoints: pre-dose, 0.25, 0.50, 0.75, 1, 2, 4, 6, 12, 16, 24, 30, 36 and 48 hours postdose in order to determine the AUC0-∞ of preladenant