The objective of this Phase 1b investigation is to evaluate the safety and potential clinical effect of AAV2-GDNF delivered to the putamen in subjects with either a recent or a long-standing diagnosis of PD.

Key Inclusion Criteria:

• Male and female adults 35-75 years of age (inclusive)

• Diagnosed with Parkinson's disease

• Modified Hoehn and Yahr stage I-III OFF medication

• Time since receiving a clinical diagnosis of PD and disease severity consistent with one of the following:

  1. EITHER: Less than 5 years since clinical diagnosis of PD and mild to moderate UPDRS III OFF score
  2. OR: At least 4 years since clinical diagnosis of PD and moderate to severe UPDRS III OFF score

• Responsiveness to levodopa

Key Exclusion Criteria:

• Atypical parkinsonism
• Severe dyskinesia
• Presence of dementia, psychosis, substance abuse or qualify as "severe depression"
• Prior brain surgery (i.e. deep brain stimulator or DBS implantation) or other brain imaging abnormalities
• Receiving an investigational drug
• History of cancer or poorly controlled medical conditions that would increase surgical risk
• Inability to tolerate laying flat in an MRI or allergy to gadolinium