The study was terminated on 31 May, 2011, due to strategic considerations.

This is a multicenter, randomized, double blind, pramipexole-controlled parallel group study of pardoprunox as adjunctive treatment to levodopa.

Approximately 44 patients are to be randomized in a 3:1 ratio to two possible treatment groups, pardoprunox and pramipexole, respectively. The first part of the study will be blinded and consists of a minimum 1-week screening period, a 4-week switch and stabilization period and an 8-week maintenance period. The second part of the study will be open label pardoprunox treatment with a dose adjustment period of 4 weeks followed by long term maintenance treatment.

Inclusion Criteria

• Patients who have signed informed consent
• Diagnosis of idiopathic Parkinson's Disease
• Stable treatment with L-dopa and dopamine agonist for at least 28 days prior to randomization
• Presence of a recognizable ON and OFF state (motor fluctuations)
• Minimum hours of OFF-time per day of 1.5 hours (during waking hours including early morning akinesia) as recorded per baseline diaries
• Minimum hours of ON time with troublesome dyskinesia of 2 hours (during waking hours) as recorded per baseline diaries
• Prevalent expression of severely disabling dyskinesias during the waking day, i.e. dyskinesias are present at least 25% of the waking hours (UPDRS Part 4 item 32 >= 2) in combination with a degree of disability which is moderate or higher (UPDRS Part 4 item 33 >=2)

Exclusion Criteria

• Diagnosis is unclear or a suspicion of other parkinsonian syndromes
• Patients who have undergone surgery for the treatment of PD