A Study in Parkinson's Disease in Patients With Moderate to Severe Dyskinesia

Inclusion Criteria: * Is able to read, understand, and provide written, dated informed consent prior to Screening Visit. * Is male or female, between 18 and 80 years of age at Screening Visit. * Is diagnosed with idiopathic PD that meets UK Parkinson's Disease Society (UKPDS) Brain Bank Clinical Diagnostic Criteria and requires treatment with and shows responsiveness to levodopa. * Has experienced dyskinesia over a period of at least 3 months prior to Screening Visit * Has stable peak-effect dyskinesia * Has more than one hour of "ON" time with troublesome dyskinesia during daily waking hours on a 24-hour PD subject diary * Is on a stable levodopa dosing regimen requiring at least 3 dose administrations but no more than 6 dose administrations per day Exclusion Criteria: * Has undergone surgery for the treatment of PD * Has a current diagnosis of Substance Use (including alcohol) Disorder (Abuse or Dependence, as defined by Diagnostic and Statistical Manual, Fifth Edition \[DSM 5\]), * Has psychiatric diagnosis of acute psychotic disorder or other psychiatric diagnoses * Has a significant risk for suicidal behaviour in the opinion of the investigator during the course of their participation in the study * Has current seizure disorders (other than febrile seizures in childhood) requiring treatment with anticonvulsants. * Has known serious ongoing symptomatic cerebral disease or cerebrovascular disease or any acute brain trauma requiring treatment with anti-convulsant therapy within 5 years prior Visit 2, Week 0 (Baseline Visit). * Has a history of exclusively diphasic, OFF state, myoclonic, dystonic, or akathetic dyskinesia without peak-dose dyskinesia. Other criteria related to other medical conditions to be referred to the protocol.