The main purpose of this study is to test the safety and efficacy (how well it works) of an experimental intervention called VY-AADC02 on the severity of PD. VY-AADC02 involves placing a gene in the brain that programs brain cells to produce an enzyme (protein) called AADC (aromatic amino acid decarboxylase) in patients with Parkinson's Disease.The study group to which you are assigned will be chosen by chance (like flipping a coin); this is known as randomization. Subjects who take part in this study will be randomized 2:1 to receive either treatment with the study product or a sham surgical procedure. It is necessary to evaluate the benefit of a new, experimental treatment by having a similar group for comparison (sham). PD studies in the past have used a sham surgery for this reason. Other than the surgical team, neither you nor the rest of the study team will know if you received the active treatment or sham until the study has ended.

You may be eligible for this study if you meet the following criteria:

• Conditions: Medical Research
• Age: 99 years or below
• Gender: All