Efficacy and Safety of BIA 9-1067 in Idiopathic Parkinson's Disease Patients.

Inclusion Criteria: 1. Able to comprehend and willing to sign an informed consent form. 2. Male and female subjects between 30 and 83 years old, inclusive. 3. Diagnosed with idiopathic PD according to the UK Parkinson's Disease Society Brain Bank Clinical Diagnostic Criteria for at least 3 years. 4. Disease severity Stages I-III (modified Hoehn \&Yahr staging) at ON. 5. Treated with L-DOPA/DDCI for at least 1 year with clear clinical improvement. 6. Treated with 3 to 8 daily doses of L-DOPA/DDCI, which can include a slow-release formulation. 7. On a stable regimen of L-DOPA/DDCI and other anti-PD drugs for at least 4 weeks before screening. 8. Signs of "wearing-off" phenomenon (end-of-dose deterioration) for a minimum of 4 weeks before screening with average total daily OFF time while awake of at least 1.5 hours, excluding the early morning pre-first dose OFF, despite optimal anti-PD therapy (based on the investigator's judgment. Exclusion Criteria: 1. Non-idiopathic PD (atypical parkinsonism, secondary \[acquired or symptomatic\] parkinsonism, Parkinson-plus syndrome). 2. Dyskinesia disability score \>3 in the Unified Parkinson's Disease Rating Scale UPDRS) Sub-section IV A, item 33. 3. Severe and/or unpredictable OFF periods. 4. Treatment with prohibited medication: entacapone, tolcapone, neuroleptics, venlafaxine, MAO inhibitors (except selegiline up to 10 mg/day in oral formulation or 1.25 mg/day in buccal absorption formulation or rasagiline up to 1mg/day), or antiemetics with antidopaminergic action (except domperidone) within the month before screening. 5. Treatment with apomorphine within the month before screening or likely to be needed at any time during the study. 6. Dosage change of concomitant anti-PD medication within 4 weeks of screening. 7. Previous or planned (during the entire study duration, including the OL period)deep brain stimulation. 8. Previous stereotactic surgery (e.g. pallidotomy, thalamotomy) for PD or with planned stereotactic surgery during the study period. 9. Any investigational medicinal product within the 3 months (or within 5 half-lives, whichever is longer) before screening. 10. Any medical condition that might place the subject at increased risk or interfere with assessments.