A Study of AAV2-GDNF in Adults With Moderate Parkinson's Disease (REGENERATE-PD)

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