Inclusion Criteria:  Patients with Parkinson's Disease on a stable regimen of antiparkinson's medications, including a levodopa preparation administered not less than 3 times daily. Meet protocol-specified criteria for moderate to severe dyskinesia symptoms based on UDysRS and Movement Disorder Society - Unified Parkinson's Disease Rating Scale (MDS-UPDRS) assessments. Meet protocol specified criteria for ON time with troublesome dyskinesia based on a standard PD home diary.  Exclusion Criteria:  Prior surgical treatment for Parkinson's Disease (e.g., deep brain stimulation). Other neurological disease (including psychiatric disease and/or cognitive impairment) that, in the opinion of the investigator, would affect the patient's ability to complete study assessments. Other significant medical condition that may affect the safety of the patient or preclude adequate participation in the study. Pregnant or breast-feeding. Female patients who are of child-bearing potential must be using adequate contraceptive methods (e.g. oral contraceptive, double-barrier method, intra-uterine device, intra-muscular hormonal contraceptive), and have a negative pregnancy test at Screening.  Other protocol-defined inclusion and exclusion criteria may apply