Flexible-Dose, Adjunctive Therapy Trial in Adults With Parkinson's Disease With Motor Fluctuations (TEMPO-3)

Key Inclusion Criteria

• Male and female participants aged 40 to 80 years, inclusive, at the time of signing the informed consent form (ICF).
• Sexually active men or women of childbearing potential must agree to use acceptable (at minimum) or highly effective birth control, or remain abstinent during the trial and for 4 weeks after the last dose of trial treatment.
• Participants who are capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the ICF and in this protocol.
• Participants with a diagnosis of PD that is consistent with the UK Parkinson's Disease Society Brain Bank diagnostic criteria, with bradykinesia and motor asymmetry.
• Participants with modified Hoehn and Yahr stage 2, 2.5, or 3 in the "on" state.
• Participants with a good response to levodopa (L- Dopa) in the judgment of the investigator.
• Participants who return a completed self-reported home diary for motor function status (Hauser diary) during the screening period (after diary training and concordance testing has occurred), with recordings for 2 consecutive days (ie, 2 consecutive 24-hour periods) showing at least 2 and half hours of "off" time on each of the 2 days.
• Participants who are on a stable dose of L-Dopa for at least 4 weeks prior to screening and are taking a minimum total daily dose of 400 milligram (mg) divided in at least 4 doses per day of standard carbidopa/levodopa or divided in at least 3 doses per day of extended-release carbidopa/levodopa capsules. The carbidopa/levodopa dose and frequency must be maintained for the duration of the trial.
• Prior and concurrent use of catechol-O-methyltransferase (COMT) inhibitors, monoamine oxidaseB (MAO-B) inhibitors, amantadine, istradefylline or anticholinergic drugs are permitted if the use was initiated greater than (>) 90 days before the baseline visit and the dosage will remain stable for the duration of the trial (ie, no change in the COMT,MAO-B inhibitor, amantadine, istradefylline or anticholinergic dose is permitted during the trial).

Key Exclusion Criteria

• Participants with a history or clinical features consistent with essential tremor, atypical or secondary parkinsonian syndrome (including, but not limited to, progressive supranuclear palsy, multiple system atrophy, cortico-basal degeneration, or drug-induced or post stroke parkinsonism).
• Participants with a history of nonresponse or insufficient response to L-Dopa at therapeutic dosages.
• Participants with a history or current diagnosis of a clinically significant impulse control disorder(Disruptive, Impulse Control, and Conduct Disorder per DSM-5).
• Participants with the presence of or history of brain tumor, hospitalization for severe head trauma, epilepsy (as defined by the International League Against Epilepsy), or seizures.
• Participants with a history of psychosis or hallucinations within the previous 12 months.
• Participants who answer "yes" on the Columbia-Suicide Severity Rating Scale (C-SSRS) Suicidal Ideation Item 4 or Item 5 (Active Suicidal Ideation with Some Intent to Act, Without Specific Plan, or Active Suicidal Ideation with Specific Plan and Intent)and whose most recent episode meeting the criteria for C-SSRS Item 4 or Item 5 occurred within the last6 months, OR Participants who answer "yes" on any of the 5 C-SSRS Suicidal Behavior Items (actual attempt, interrupted attempt, aborted attempt, preparatory acts, or behavior) and whose most recent episode meeting the criteria for any of these 5C-SSRS Suicidal Behavior Items occurred within the last 2 years, OR Participants who, in the opinion of the investigator, present a serious risk of suicide.
• Participants with substance abuse or dependence disorder, including alcohol, benzodiazepines, and opioids, but excluding nicotine, within the past 6months (180 days).
• Participants with dementia or cognitive impairment that, in the judgement of the investigator, would exclude the participant from