Flexible-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 signingthe 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 trialand for 4 weeks after the last dose of trial treatment.

• Participants who are capable of giving signed informed consent, which includescompliance with the requirements and restrictions listed in the ICF and in theprotocol.

• Participants with a diagnosis of PD that is consistent with the UK Parkinson'sDisease 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 (<) 3 yearsand disease progression in the 3 years before signing the ICF.

• Participants with an MDS-UPDRS Part II score >=2 and Part III score >=10 at theScreening Visit and at the Baseline Visit.

• Participants with early PD who, in the opinion of the investigator, requirepharmacologic intervention for disease management.

• Participants who are treatment naive or have a history of prior incidental treatmentwith dopaminergic agents (including L-Dopa and dopamine receptor agonistmedications) for <3 months in total but not within 2 months of the Baseline Visit.Prior and concurrent use of MAO-B inhibitors is permitted if use was initiated >90days before the Baseline Visit and the dosage will remain stable for the duration ofthe trial (ie, 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 arenot permitted by the protocol (including dopaminergic agents) throughoutparticipation 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-basaldegeneration, or drug-induced or post stroke parkinsonism).

• Participants with a history of nonresponse or insufficient response to L-Dopa attherapeutic dosages.

• Participants with a history or current diagnosis of a clinically significant impulsecontrol disorder (Disruptive, Impulse Control, and Conduct Disorder per DSM-5).

• Participants with the presence of or history of brain tumor, hospitalization forsevere head trauma, epilepsy (as defined by the International League AgainstEpilepsy), or seizures.

• Participants with a history of psychosis or hallucinations within the previous 12months.

• Participants who answer "yes" on the C-SSRS Suicidal Ideation Item 4 or Item 5 (Active Suicidal Ideation with Some Intent to Act, Without Specific Plan, or ActiveSuicidal Ideation with Specific Plan and Intent) and whose most recent episodemeeting 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, orbehavior) and whose most recent episode meeting the criteria for any of these 5C-SSRS Suicidal Behavior Items occurred within the last 2 years, OR Participantswho, 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 (180days).

• Participants with dementia or cognitive impairment that, in the judgement of theinvestigator, would exclude the participant from understanding the ICF orparticipating in the trial.

• Participants with any condition that could possibly affect drug absorption,including bowel resections, bariatric weight loss surgery, or gastrectomy (this doesnot 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, orventricular arrhythmias that are not controlled with medical and/or surgicalintervention; second- or third-degree atrioventricular block; sick sinus syndrome;severe or unstable angina; or congestive heart failure within the last 12 months. Arecent (less than or equal to [<=] 12 months) history of myocardial infarction withsecondary arrhythmias is exclusionary regardless of the therapeutic control.

• Participants with a history of neuroleptic malignant syndrome.

• Participants who are currently receiving moderate or strong CYP3A4 inducers orCYP3A4 inhibitors (except for topical administration).

• Participants with a positive urine drug screen for illicit drugs are excluded andmay not be retested or rescreened. Participants with a positive urine drug screenresulting from use of marijuana (any Tetrahydrocannabinol [THC]-containing product),prescription, or over-the-counter medications or products that, in theinvestigator's documented opinion, do not signal a clinical condition that wouldimpact the safety of the participant or interpretation of the trial results maycontinue evaluation for the trial following consultation and approval by the medicalmonitor.

• Participants with a Montreal Cognitive Assessment (MoCA) score <26.

• Participants with clinically significant orthostatic hypotension (eg, syncope).

• Participants with a 12-lead ECG demonstrating a QTcF interval >450 msec.

• Participants with moderate or severe renal impairment (creatinine clearance asestimated by Cockcroft-Gault formula <30 mL/min or on dialysis).

• Participants with any of the following abnormalities in clinical laboratory tests atthe Screening Visit, as assessed by the central laboratory and confirmed by a singlerepeat measurement, if deemed necessary:

• Aspartate Aminotransferase (AST) or Alanine Aminotransferase (ALT) >=3 × UpperLimit Normal (ULN).

• Total bilirubin >=1.5 × ULN. Participants with a history of Gilbert's syndromemay be eligible provided they have a value <ULN for direct bilirubin.

• Participants with other abnormal laboratory test results, vital sign results, or ECGfindings unless, in the judgment of the investigator, the findings are not medicallysignificant and would not impact the safety of the participants or theinterpretation of the trial results.