A Study of KW-6356 in Patients With Parkinson's Disease on Treatment With Levodopa-containing Preparations

Inclusion Criteria: * Subject fulfills the UK Parkinson's Disease Society brain bank clinical diagnostic criteria. * Parkinson's disease patients in Stages 2 to 4 on the Modified Hoehn and Yahr Scale. (mH\&Y, Evaluation at ON state for patients who experience Wearing-off phenomenon) * MDS-UPDRS partIII score of \>= 15. (Evaluation at ON state) * Subject who are responsive to levodopa/DCI (carbidopa or benserazide) combination therapy and who have been on the therapy for 6 months or longer without interruption at enrollment. * Subject who have not started any new antiparkinsonian drugs and have been on a stable regimen of antiparkinsonian drugs in the 3 months before enrollment. Exclusion Criteria: * Use of any CYP3A4/5-related drugs within 2 weeks prior to enrollment. * Use of any of the following drugs within 3 months (or 6 month in case of depot preparations) prior to enrollment; Antipsychotics, tiapride, metoclopramide, amoxapine, reserpine, tetrabenazine, methyldopa, papaverine, Levodopa/carbidopa intestinal gel and apomorphine hydrochloride injection * Treatment by transcranial magnetic stimulation (TMS) within 6 months prior to enrollment. * Neurosurgical operation for Parkinson's disease. (stereotactic surgery, deep brain stimulation or gamma knife) * Subject who have received administration of adenosine A2A receptor antagonist. * Either of the following criteria consecutively at screening and enrollment; Resting Pulse \> 100 bpm Resting systolic blood pressure \> 140 mmHg, or diastolic blood pressure \> 90 mmHg * Significant dementia or a Mini-Mental State Examination (MMSE) score of =\< 23. * Subject has a history or evidence of suicidal ideation (severity of 4 or 5) or any suicidal behavior based on an assessment with the Columbia-Suicide Severity Rating Scale (C-SSRS) at baseline. * Anyone otherwise considered unsuitable for the study by the investigator or subinvestigator including those who are unable to communicate or to cooperate with the investigator or subinvestigator.