2 mg BID capsules

5 mg BID capsules

10 mg BID capsules

BID capsules

Participants must receive L-dopa as part of their usual ongoing treatment for Parkinson's Disease. L-dopa is often administered concomitantly with a dopa decarboxylase inhibitor (e.g., carbidopa).

Participants may also receive other drugs as part of their usual ongoing treatment for Parkinson's Disease, such as dopamine agonists (e.g., pramipexole) and/or the catechol-O-methyl transferase (COMT) inhibitor entacapone.

"On" time refers to periods of adequate control of Parkinson disease symptoms (symptoms better or absent). Hours spent in the "on" 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. A positive (+) change from baseline signifies more time spent in the "on" state.

"On" time refers to periods of adequate control of Parkinson disease symptoms (better/absent). Dyskinesias refers to maintenance therapy (e.g., L-dopa) side effects of chorea, dystonia, or in combination. Hours spent in the "on" state with no dyskinesias 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained from an ANCOVA model with effect for treatment & baseline covariate. A (+) change from baseline signifies more time spent in the "on" state (no dyskinesias).

"On" time refers to periods of adequate control of Parkinson disease symptoms (better/absent). Troublesome dyskinesias refers to maintenance therapy side effects of chorea, dystonia, or in combination that impair function. Hours spent in the "on" state with troublesome dyskinesias 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained using ANCOVA with treatment effect & baseline covariate. A (+) change from baseline signifies more time spent in the "on" state (troublesome dyskinesias).

"On" time refers to periods of adequate control of Parkinson disease symptoms (better/absent). Troublesome dyskinesias refers to maint. therapy side effects of chorea, dystonia, or in combination that impair function. Hours spent in the "on" state without troubles. dyskinesias 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained using ANCOVA with treatment effect & baseline covariate. A (+) change from baseline signifies more time spent in the "on" state (without troubles. dyskinesias).

Dyskinesias refers to maintenance therapy side effects of chorea, dystonia, or in combination (that occur in the ON time). Hours spent with dyskinesias (troublesome and not troublesome) 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained using ANCOVA with treatment effect & baseline covariate. A negative change from baseline signifies less time spent with dyskinesia.

Hours spent in the sleep state were recorded using a daily diary at least 3 full days before scheduled visit. 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained using ANCOVA with treatment effect & baseline covariate. A positive change from baseline means more time asleep and a negative change means less time asleep.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 2) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 2 would be reported as BL >2 to WK2 1-2. BL = baseline. WK = week.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 4) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 4 would be reported as BL >2 to WK4 1-2. BL = baseline. WK = week.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 6) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 6 would be reported as BL >2 to WK6 1-2. BL = baseline. WK = week.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 8) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 8 would be reported as BL >2 to WK8 1-2. BL = baseline. WK = week.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 10) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 10 would be reported as BL >2 to WK10 1-2. BL = baseline. WK = week.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 12) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 12 would be reported as BL >2 to WK12 1-2. BL = baseline. WK = week.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. Part 1 assesses mentation (4 items scored from 0 [best] to 4 [worst]; total range 0-16). Assessments were obtained at baseline (predose Day 1) and 2 hours postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. Part 2 assesses daily living (13 items scored from 0 [best] to 4 [worst]; total range 0-52). Assessments were obtained at baseline (predose Day 1) and 2 hours postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. The Part 3 subscale assesses motor function across 14 categories for 27 items. Scores for each item range from 0 (best) to 4 (worst) with a total range of 0-108. Assessments were obtained at baseline (predose Day 1) and 1 hour postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. The Part 3 subscale assesses motor function across 14 categories for 27 items. Scores for each item range from 0 (best) to 4 (worst) with a total range of 0-108. Assessments were obtained at baseline (predose Day 1) and 2 hours postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled standard deviation were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. The Part 4 subscale assesses complications of therapy over the past week for a total of eleven question items. The first three questions and question 8 are rated from 0 (best) to 4 (worst), and the remaining seven questions are simple no (0) / yes (1) questions. The total subscale score ranges from 0 to 23. Assessments were obtained at baseline (predose Day 1) and 2 hours postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

Participants received preladenant 5 mg BID during the 12-week treatment period.

Participants received preladenant 10 mg BID during the 12-week treatment period.

Participants received preladenant matching placebo BID during the 12-week treatment period.

Total of all reporting groups

"Off" time refers to periods of inadequate control of Parkinson disease symptoms (worsening or presence of symptoms). 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 treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with treatment effect and baseline covariate. A negative change from baseline signifies less time spent in the "off" state.

The Efficacy Population consisting of all treated participants who had post-baseline data (awake time per day in the "off" state) for the assessment week was used for analysis.

"On" time refers to periods of adequate control of Parkinson disease symptoms (symptoms better or absent). Hours spent in the "on" 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. A positive (+) change from baseline signifies more time spent in the "on" state.

The Efficacy Population consisting of all treated participants who had post-baseline data (awake time per day in the "on" state) for the assessment week was used for analysis.

"On" time refers to periods of adequate control of Parkinson disease symptoms (better/absent). Dyskinesias refers to maintenance therapy (e.g., L-dopa) side effects of chorea, dystonia, or in combination. Hours spent in the "on" state with no dyskinesias 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained from an ANCOVA model with effect for treatment & baseline covariate. A (+) change from baseline signifies more time spent in the "on" state (no dyskinesias).

The Efficacy Population consisting of all treated participants who had post-baseline data (awake time per day in the "on" state with no dyskinesias) for the assessment week was used for analysis.

"On" time refers to periods of adequate control of Parkinson disease symptoms (better/absent). Troublesome dyskinesias refers to maintenance therapy side effects of chorea, dystonia, or in combination that impair function. Hours spent in the "on" state with troublesome dyskinesias 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained using ANCOVA with treatment effect & baseline covariate. A (+) change from baseline signifies more time spent in the "on" state (troublesome dyskinesias).

The Efficacy Population consisting of all treated participants who had post-baseline data (awake time per day in the "on" state with troublesome dyskinesias) for the assessment week was used for analysis.

"On" time refers to periods of adequate control of Parkinson disease symptoms (better/absent). Troublesome dyskinesias refers to maint. therapy side effects of chorea, dystonia, or in combination that impair function. Hours spent in the "on" state without troubles. dyskinesias 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained using ANCOVA with treatment effect & baseline covariate. A (+) change from baseline signifies more time spent in the "on" state (without troubles. dyskinesias).

The Efficacy Population consisting of all treated participants who had post-baseline data (awake time per day in the "on" state without troublesome dyskinesias) for the assessment week was used for analysis.

Dyskinesias refers to maintenance therapy side effects of chorea, dystonia, or in combination (that occur in the ON time). Hours spent with dyskinesias (troublesome and not troublesome) 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained using ANCOVA with treatment effect & baseline covariate. A negative change from baseline signifies less time spent with dyskinesia.

The Efficacy Population consisting of all treated participants who had post-baseline data (awake time per day in the "on" state with troublesome and not troblesome dyskinesias) for the assessment week was used for analysis.

Hours spent in the sleep state were recorded using a daily diary at least 3 full days before scheduled visit. 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. For treatment period visits, the 24-hour average was derived for the final 3 consecutive days with data available for the particular visit. Change from baseline in LS means & pooled SD were obtained using ANCOVA with treatment effect & baseline covariate. A positive change from baseline means more time asleep and a negative change means less time asleep.

The Efficacy Population consisting of all treated participants who had post-baseline data (total sleep time) for the assessment week was used for analysis.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 2) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 2 would be reported as BL >2 to WK2 1-2. BL = baseline. WK = week.

The Efficacy Population consisting of all treated participants who had post-baseline data (sleep attacks) for the assessment week was used for analysis.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 4) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 4 would be reported as BL >2 to WK4 1-2. BL = baseline. WK = week.

The Efficacy Population consisting of all treated participants who had post-baseline data (sleep attacks) for the assessment week was used for analysis.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 6) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 6 would be reported as BL >2 to WK6 1-2. BL = baseline. WK = week.

The Efficacy Population consisting of all treated participants who had post-baseline data (sleep attacks) for the assessment week was used for analysis.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 8) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 8 would be reported as BL >2 to WK8 1-2. BL = baseline. WK = week.

The Efficacy Population consisting of all treated participants who had post-baseline data (sleep attacks) for the assessment week was used for analysis.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 10) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 10 would be reported as BL >2 to WK10 1-2. BL = baseline. WK = week.

The Efficacy Population consisting of all treated participants who had post-baseline data (sleep attacks) for the assessment week was used for analysis.

Sleep attacks are uncontrollable episodes of sleep that occur during the daytime lasting a few seconds to several minutes. A questionnaire to determine sleep attacks over the prior 2 week period was administered at baseline and at 2-week intervals during the treatment period. Frequency of sleep attacks over the two-week treatment period intervals were tabulated in relation to the baseline assessment. Results are presented as participants showing the respective change in frequency of sleep attacks at baseline to the week of assessment (Week 12) (as reported by the participant). For example, someone who had >2 sleep attacks at BL who had a decrease of 1-2 by Week 12 would be reported as BL >2 to WK12 1-2. BL = baseline. WK = week.

The Efficacy Population consisting of all treated participants who had post-baseline data (sleep attacks) for the assessment week was used for analysis.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. Part 1 assesses mentation (4 items scored from 0 [best] to 4 [worst]; total range 0-16). Assessments were obtained at baseline (predose Day 1) and 2 hours postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

The Efficacy Population consisting of all treated participants who had post-baseline data (UPDRS Part 1) for the assessment week was used for analysis.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. Part 2 assesses daily living (13 items scored from 0 [best] to 4 [worst]; total range 0-52). Assessments were obtained at baseline (predose Day 1) and 2 hours postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

The Efficacy Population consisting of all treated participants who had post-baseline data (UPDRS Part 2) for the assessment week was used for analysis.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. The Part 3 subscale assesses motor function across 14 categories for 27 items. Scores for each item range from 0 (best) to 4 (worst) with a total range of 0-108. Assessments were obtained at baseline (predose Day 1) and 1 hour postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

The Efficacy Population consisting of all treated participants who had post-baseline data (UPDRS Part 3) for the assessment week was used for analysis.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. The Part 3 subscale assesses motor function across 14 categories for 27 items. Scores for each item range from 0 (best) to 4 (worst) with a total range of 0-108. Assessments were obtained at baseline (predose Day 1) and 2 hours postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled standard deviation were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

The Efficacy Population consisting of all treated participants who had post-baseline data (UPDRS Part 3) for the assessment week was used for analysis.

The UPDRS is a frequently used multi-item 4-part questionnaire designed to assess various aspects of Parkinson's disease severity. A total of 42 items are assessed divided across Parts 1 to 4. The Part 4 subscale assesses complications of therapy over the past week for a total of eleven question items. The first three questions and question 8 are rated from 0 (best) to 4 (worst), and the remaining seven questions are simple no (0) / yes (1) questions. The total subscale score ranges from 0 to 23. Assessments were obtained at baseline (predose Day 1) and 2 hours postdose at Weeks 2, 4, 6, 8, 10, and 12. For endpoint, the last postbaseline visit while on study medication was used. Change from baseline in LS means and pooled SD were obtained from an ANCOVA model with effect for treatment and baseline covariate. Negative change from baseline indicates a decrease in severity.

The Efficacy Population consisting of all treated participants who had post-baseline date (UPDRS Part 4) for the assessment week was used for analysis.

Participants received preladenant 2 mg BID during the 12-week treatment period.

Participants received preladenant 5 mg BID during the 12-week treatment period.

Participants received preladenant 10 mg BID during the 12-week treatment period.

Participants received preladenant matching placebo BID during the 12-week treatment period.