Fixed-Dose Trial in Early Parkinson's Disease (PD)

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 the protocol
• Participants with a diagnosis of PD that is consistent with the UK Parkinson's Disease Society Brain Bank diagnostic criteria
• Participants with modified Hoehn and Yahr stage 1, 1.5, or 2
• Participants with disease duration (from time of diagnosis) of less than ( =2 and Part III score >=10 at the Screening Visit and at the Baseline Visit
• Participants with early PD who, in the opinion of the investigator, require pharmacologic intervention for disease management
• Participants who are treatment naïve or have a history of prior incidental treatment with dopaminergic agents (including Levodopa [L-Dopa] and dopamine receptor agonist medications) for 90 days before the Baseline Visit and the dosage will remain stable for the duration of the trial (i.e, no change in the MAO-B inhibitor dose is permitted during the trial)
• Participants who are willing and able to refrain from any PD medications that are not permitted by the protocol (including dopaminergic agents) throughout participation in 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 supra nuclear 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 last 6 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 5 C-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 6 months (180 days)
• Participants with dementia or cognitive impairment that, in the judgement of the investigator, would exclude the participant from understanding the ICF or participating in the trial
• Participants with any condition that could possibly affect drug absorption, including bowel resections, bariatric weight loss surgery, or gastrectomy (this does not include gastric banding).
• Participants who have a positive result for human immunodeficiency virus (HIV) antibodies, hepatitis B surface antigen (HbsAg), or hepatitis C virus (HCV) antibodies at screening.
• Participants with a history of myocardial infarction with residual atrial, nodal, or v