University of Kansas Medical Center

1. Participants voluntarily agree to participate in this study and sign an Institutional Review Board (IRB)-approved informed consent form (ICF) prior to performing any of the screening procedures. Parkinson's Disease Related Criteria: 2. Diagnosis of Parkinson's disease (PD) with motor symptom improvement from levodopa, if applicable. 3. Less than 5 years from the initial PD diagnosis, at the time of ICF. 4. Early-stage PD, with mild symptoms based on standard clinical staging in OFF state. 5. Participants who are on immediate-release levodopa-carbidopa/benserazide. Other Health Related Criteria 6. No active cancer, unless in remission for ≥10 years without ongoing treatment, except fully removed basal cell carcinoma. 7. Free of significant health issues that might interfere with study participation. Other Criteria/Social Circumstances 8. Negative screening for illegal drugs (excluding cannabis), with willingness to abstain during the study and avoid cannabis or alcohol effects during visits.

Parkinsons's Disease Related Criteria 1. History of sudden, unexpected PD medication OFF episodes. 2. Severe motor complications or disabling symptoms that may impact study involvement. Other Health Related Criteria 3. Any condition or health concern deemed a safety risk or likely to interfere with study results. 4. Severe psychiatric disorders, including psychosis or substance addiction. 5. Allergies or sensitivities to specific study-related treatments or substances. 6. Any prior history of a severe infusion reaction. Other Criteria/Social Circumstances 7. Pregnancy, breastfeeding, or plans for pregnancy or ova donation during or shortly after the study. 8. Recent use of investigational drugs or therapeutic antibodies.