Study on Tolerability of Repeat i.c.v. Administration of sNN0031 Infusion Solution in Patients With PD

Main Inclusion Criteria: 1. Disease duration ≥ 5 years (diagnosis based on medical history and neurological examination). 2. Male or female, age 30 - 75 years inclusive. 3. Motor fluctuations, with OFF-time \>1.5 hours during the day 4. A Hoehn and Yahr stage of 2 to 4 during OFF phase 5. Score \>22 on the UPDRS part III during ON phase 6. Patients should be L-dopa responsive and demonstrate at least a 30% decrease in the UPDRS part III score after administration of L-dopa (L-dopa challenge test) 7. Optimised and stable anti-Parkinson treatment for at least 3 months before screening Main Exclusion Criteria: 1. The patient has any indication of forms of parkinsonism other than idiopathic Parkinson's disease 2. The patient is in a late stage of Parkinson's disease, and is experiencing severe, disabling peak-dose or biphasic dyskinesia and/or unpredictable or widely swinging fluctuations in their symptoms 3. Patients who are on treatment with Duodopa or Apomorphine pump at the time of screening 4. The patient has an implanted shunt for the drainage of CSF or an implanted Central Nervous System (CNS) catheter, or have received neurosurgical intervention related to PD (e.g. deep brain stimulation, thalamotomy etc.) or is scheduled to do so during the trial period 5. Concurrent diagnoses of dementia with a score of 24 or lower on Mini-Mental State Examination (MMSE). 6. The patient is depressed, as indicated by a Hamilton Depression Rating Scale (GRID-HAMD, 17-item scale) score \> 17 7. Patients who are at high risk of suicide as judged by the rating of the Columbia Symptoms Suicide Rating Scale (C-SSRS) 8. Patients with a history of increased intracranial pressure 9. Ophthalmologic examination (funduscopy and visual acuity by Early Treatment of Diabetic Retinopathy Study (EDTRS) and perimetry) with clinically significant findings that imply safety concerns for this study 10. The patient has a current clinically significant gastrointestinal, renal, hepatic, endocrine, pulmonary or cardiovascular disease 11. The patient has heart problems or a significant ECG abnormality 12. Uncontrolled hypertension. 13. The patient has in the past experienced psychotic symptoms (e.g. schizophrenia or psychotic depression) 14. The patient has a mental or physical condition which would preclude performing study assessments 15. Alcohol or substance dependence within the prior 12 months, or abuse within 3 months, with the exceptions of nicotine 16. MRI examination with findings of tumours or potential sources of pathological bleedings, or any abnormality that may put the patient at risk 17. History of structural brain disease including tumours and hyperplasia 18. Ongoing or suspected primary or recurrent malignant disease (currently active or in remission for less than one year) 19. Any disorder that precludes a surgical procedure, alters wound healing or renders chronic i.c.v. delivery or device implants medically unsuitable 20. The patient has a history or a current diagnosis of HIV, Hepatitis B or C. 21. Increased susceptibility to infections 22. Women who are pregnant or breast feeding or unwilling to use adequate contraception during the trial (only women of child bearing potential)