Clinical Study to Test the Safety of CDNF by Brain Infusion in Patients With Parkinson's Disease

Inclusion Criteria: 1. Idiopathic Parkinson's disease based on UK brain bank criteria 2. Duration of PD motor symptoms 5-15 years (inclusive) 3. Age 35-75 years (inclusive) 4. Presence of motor fluctuations. 5. At least 5 daily doses of levodopa 6. Ability to reliably distinguish motor states and accurately complete fluctuation diaries 7. UPDRS motor score (part III) in a practically defined OFF-state between 25-50 (inclusive) 8. Hoehn and Yahr ≤ stage III in the OFF-state 9. Responsiveness to levodopa 10. No change in anti-parkinsonian medication for 6 weeks before screening 11. Provision of Informed Consent Exclusion Criteria: 1. Diagnosed with atypical parkinsonism or any known secondary parkinsonian syndrome. 2. Signs or symptoms suggestive of atypical parkinsonian syndrome. 3. Drug-resistant rest tremor. 4. Prior neurosurgical treatment for PD, including lesioning or deep brain stimulation 5. Significant neurological disorder other than PD including clinically significant head trauma, cerebrovascular disease, epilepsia, CSF shunt or other implanted CNS device 6. Presence of significant depression as defined as a BDI score ≥ 20 7. Current psychosis requiring therapy. 8. Presence of clinically significant impulse control disorder ((QUIP-RS) score \> 20), or, presence of dopamine dysregulation syndrome. 9. MoCA score \< 24. 10. Use within 3 months of planned catheter insertion of concomitant medications known to affect PD symptoms other than prescribed PD therapy. 11. Any medical condition, which might impair outcome measure assessments or safety measures including ability to undergo MRI or DAT-PET. 12. Hypersensitivity or allergy to gadolinium or to any of excipients of macrocyclic GBCA used for the surgical planning MRI. 13. Screening and/or planning MRI demonstrating any abnormality, which would suggest an alternative cause for patient's parkinsonism or preclude neurosurgery. 14. Any medical condition that would put the patient at undue risk from surgical treatment or chronic implants including but not limited to bleeding disorders, chronic infections, or immunosuppressive illness 15. History within the last 5 years of cancer with the exception of basal cell carcinoma of the skin 16. History of drug or alcohol abuse within 2 years of screening 17. Use of any investigational drug or device within 90 days of screening 18. Active breastfeeding