LY-3962681

The purpose of this study is to evaluate the safety, tolerability, and PK/PD of LY3962681 in healthy volunteers and patients with Parkinson's disease.
The study will be comprised of two parts, the Single Ascending Dose (SAD) study and the Multiple Ascending Doses (MAD) study. During the SAD portion of the study, healthy volunteers will receive a single dose of LY3962681 or placebo (no active drug) given into the spinal fluid. During the MAD portion of the study, patients with Parkinson's disease will receive two doses of either LY3962681 or placebo administered into the spinal fluid.
* The treatment period in the SAD study will be 1 day. The treatment period in the MAD study will be 2 days, 12 to 24 weeks apart.
* The follow-up period in the SAD study will be up to 52 weeks. The follow-up period in the MAD study will be up to 52 weeks post Dose 2.