⁃ Part A Single Ascending Dose (SAD) and B Multiple Ascending Dose (MAD)

• Have a body mass index within the range of 18 to 34 kilogram/square meter (kg/m²) (inclusive).

• For Japanese participants: To qualify as a participant of first-generation Japanese origin, the participant, the participant's biological parents, and all of the participant's biological grandparents must be of exclusive Japanese descent and born in Japan.

• Have venous access sufficient to allow for blood sampling or administration of study intervention for IV administration, or both.

⁃ Part A (SAD) Only

• Participant must be 30 to 85 years of age (inclusive), at the time of signing the informed consent

• Are overtly healthy

• For Chinese participants: To qualify as Chinese for this study, all 4 of the participant's biological grandparents must be exclusive Chinese descent and born in China.

⁃ Part B (MAD) Only

• Participant must be 40 to 85 years of age (inclusive), at the time of signing the informed consent

• Diagnosis of Parkinson's disease per United Kingdom (UK) Parkinson's Disease Society Brain Bank Clinical Diagnostic Criteria.

• If presently untreated for Parkinson's disease, clinical status is not expected to require changes in symptomatic treatment within 52 weeks from baseline.

• If presently being treated for Parkinson's disease, receiving a stable dose of symptomatic dopaminergic therapy, including monoamine oxidase-B inhibitor, levodopa/carbidopa or dopamine agonist for at least 90 days prior to baseline and not expected to change within 52 weeks.

• Have a Montreal Cognitive Assessment (MoCA) score of greater than or equal to (≥) 24.