Inclusion Criteria:  Participant must be 18 to 55 years of age inclusive or 35 to 75 years for part C, at the time of signing the informed consent Participants who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and cardiac monitoring Study participant has a blood pressure (BP) and heart rate (HR) before the first dose, as determined by triplicate BP/HR measurements in a supine position, of mean systolic BP ranging between 90 and 130 millimeters of mercury (mmHg), mean diastolic BP ranging between 50 and 80 mmHg, and mean HR between 45 and 90 beats per minute (bpm) Participant has a body weight of at least 45 kg and body mass index (BMI) within the range 18 to 30 kg/m^2 (inclusive) Participants are male or female: A male participant must agree to use contraception as detailed in the protocol during the treatment period and for at least 7 days after the last dose of study treatment and refrain from donating sperm during this period A female participant is eligible to participate if she is not pregnant, not breastfeeding, and at least 1 of the following conditions applies:  Not a woman of childbearing potential (WOCBP) as defined in the protocol OR A WOCBP who agrees to follow the contraceptive guidance in the protocol during the Treatment Period and for at least 90 days after the last dose of study treatment  Part C only:  Patient must have a documented history of idiopathic Parkinson's disease confirmed by a neurologist, and with no other atypical or secondary parkinsonism (eg, multiple-system atrophy, progressive supranuclear palsy, or evidence of drug-induced parkinsonism) Participants with Hoehn and Yahr Stages of 1 to 3 inclusive, (Hoehn and Yahr, 1967) at Screening when in the ON state Participants on stable dosage of all anti-Parkinsonian therapy for at least 30 days prior to first investigational medicinal product (IMP) administration (with the exception that MAO-B inhibitors that must be maintained at a stable level for at least 8 weeks prior), and it is anticipated that no changes will be needed during the course of the study Participant has a BP and HR at Screening, as determined by triplicate BP/HR measurements in a supine position, of mean systolic BP ranging between 90 and 140 mmHg, mean diastolic BP ranging between 50 and 90 mmHg, and a mean HR between 50 and 90 bpm  Exclusion Criteria:  Participant has history or presence of cerebro/cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrinological, hematological, psychiatric or neurological disorders capable of significantly altering the absorption, metabolism, or elimination of drugs; constituting a risk when taking the study intervention; or interfering with the interpretation of data Participant has a high risk for cardiovascular accident based on family history or on laboratory test Participants with hypertension requiring medical treatment within 6 months before the Screening, or with clinically significant orthostatic hypotension Participant has a known hypersensitivity to any components of the study medication or comparative drugs (and/or an investigational device) as stated in this protocol Participant has a history of unexplained syncope or a family history of sudden death due to long QT syndrome Participant has active neoplastic disease or history within the past 5 years of screening visit except for basal cell or squamous epithelial carcinomas of the skin that have been treated with SOC. Study participant has a history of a major organ transplant or hematopoietic stem cell/marrow transplant Participant has past or intended use of over-the-counter or prescription medication including herbal medications within 2 weeks or 5 half-lives prior to dosing Participant has used hepatic enzyme-inducing drugs within 2 months prior to dosing Participant has alanine transaminase (ALT), aspartate aminotransferase (AST), or alkaline phosphatase (ALP) >1.0x upper limit of normal (ULN) Participant has current or chronic history of liver disease or known hepatic or biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones) Participant has a current history of alcohol or drug use disorder within the last Y Statistical Manual of Mental Disorders Version 5 (DSM-5), within the last year Participant has any clinically relevant electrocardiogram (ECG) finding at the Screening Visit or at Baseline Participant has the presence of hepatitis B surface antigen (HBsAg) at Screening or within 3 months prior to dosing Participant has a positive hepatitis C antibody test result at Screening or within 3 months prior to starting study intervention Participant has a positive human immunodeficiency virus (HIV) antibody test Participant has clinical signs and symptoms consistent with COVID-19 or had a positive Sars-Cov-2 test result within the last 4 weeks prior to dosing Active treatment or a history of glaucoma  Part C only:  Participant with implantable intracranial stimulator or history of intracranial surgery Participant with documented diagnosis of dementia or a Montreal Cognitive Assessment (MoCA) score <26 at screening Participant with history of psychotic symptoms (including significant hallucinations) requiring treatment with an antipsychotic medication within the 12 months prior to Admission