The objective of this randomized, surgically controlled, double-blinded, Phase 2 study is to evaluate the safety and efficacy of AAV2-GDNF delivered to the putamen in subjects with moderate Parkinson's Disease.

Inclusion Criteria:

Age

1. Male and female adults 45-75 years of age inclusive, at the time of signing of informed consent Type of Subject and Disease Characteristics

2. Diagnosed with Parkinson's disease in the past 4-10 years (inclusive) as defined by the following:

   1. Presence of bradykinesia PLUS any of the following:

      • Rigidity
      • Rest tremor
      • Postural instability

   2. Presence of motor fluctuations as measured by the PD Motor Diary

   3. Stable anti-parkinsonian medication regimen for >/= 4 weeks prior to screening

   4. Must demonstrate responsiveness to levodopa therapy

Exclusion Criteria:

• Known history or current evidence of medical, genetic, or neurological conditions that may provide an alternative to idiopathic PD diagnosis
• Presence or history of significant vascular and/or cardiovascular disease
• Presence of significant cognitive impairment, poorly controlled depression/anxiety
• Presence or history of psychosis or impulse control disorder
• History of malignancy other than treated cutaneous squamous or basal cell carcinomas
• Presence of clinically relevant conditions that could compromise surgical suitability and/or subject safety
• Contraindication to magnetic resonance imaging and/or use gadolinium-based contrast agents
• Prior history of brain surgery including, but no limited: DBS, pallidotomy focused ultrasound thalamotomy, or other experimental neurosurgical procedure
• Chronic immunosuppressive therapy