Patient description: A 57-year old farmer was diagnosed with Parkinson's disease a year ago. He experiences slowness of movement and tremors. His past medical history is significant for hypertension and hypercholesterolemia. He lives with his wife. They have three children. He used to be active with planting and taking care of their farm animals before his diagnosis. The patient complains of shaking and slow movement. He had difficulty entering through a door, as he was frozen and needed guidance to step in. His handwriting is getting smaller. He is on Levodopa and Trihexyphenidyl. He stated his medications help with shaking and slow movement. But he still has difficulty initiating movements, stiffness and slowness in general. He is an alert and cooperative man who doesn't have any signs of dementia. He doesn't smoke or use any illicit drugs.

Clinical trial eligibility criteria: eligible ages (years): 40.0-80.0,  Parkinson's Disease Idiopathic PD with bradykinesia plus one of the other cardinal signs of PD (resting tremor, rigidity) being present, without any other known or suspected cause of PD untreated or treated with MAO-B inhibitor Body weight range between: >/=45 kg/ 99 pounds (lbs) and less than or equal to (</=) 110 kg/242 lbs Body mass index (BMI) of 18 to 34 kilograms per meter-squared (kg/m^2) A diagnosis of PD for 2 years or less at screening Hoehn and Yahr Stage I or II A screening brain DaT-SPECT consistent with PD (central reading) Clinical status does not require dopaminergic PD medication and is not expected to require dopaminergic treatment within 52 weeks from baseline If presently being treated for PD, a stable dose of MAO-B inhibitor (rasagiline or selegiline) for at least 90 days prior to baseline and not expected to change within 52 weeks For women of childbearing potential: use of highly effective contraceptive methods (that result in a failure rate of <1 percent [%] per year) during the treatment period and for at least 30 days (or longer if required by local regulations) after the last dose of study drug For men with female partners of childbearing potential or pregnant female partners, must use a condom during the treatment period and for at least 30 days (or longer if required by local regulations) after the last dose of study drug to avoid exposing the embryo. Men must refrain from donating sperm during this same period. The female partners should use a contraception method with a failure rate of <1% per year during the treatment period and for at least 30 days (or longer if required by local regulations) after the last dose of study drug  Medical history indicating a Parkinson syndrome other than idiopathic PD, including but not limited to, progressive supranuclear gaze palsy, multiple system atrophy, drug-induced parkinsonism, essential tremor, primary dystonia Known carriers of certain familial PD genes (as specified in study protocol) History of PD related freezing episodes or falls A diagnosis of a significant CNS disease other than Parkinson's disease; history of repeated head injury; history of epilepsy or seizure disorder other than febrile seizures as a child Mini Mental State Examination (MMSE) </=25 Reside in a nursing home or assisted care facility History of or screening brain magnetic resonance imaging (MRI) scan indicative of clinically significant abnormality Concomitant disease or condition that could interfere with, or treatment of which might interfere with, the conduct of the study, or that would, in the opinion of the Investigator, pose an unacceptable risk to the participant in this study or interfere with the participant's ability to comply with study procedures or abide by study restrictions, or with the ability to interpret safety data Any significant cardiovascular condition Any significant laboratory abnormality