The purpose of this study in healthy adult males is to investigate safety and pharmacokinetics of single and multiple oral doses of KDT-3594.

The purpose of this study in patients with Parkinson's disease is to investigate safety and pharmacokinetics of single and multiple oral doses of KDT-3594. The exploratory efficacy of KDT-3594 will also be investigated.

Inclusion Criteria:

• Healthy volunteer part

  • Healthy Japanese males aged 20 to 35 years, inclusive

• Patient part

  • Patients who are diagnosed with Parkinson's disease according to UK Parkinson's Disease society brain bank clinical diagnostic criteria
  • Patients with Parkinson's disease in Stages 1 to 3 on the Modified Hoehn and Yahr Scale
  • Male patients with Parkinson's disease aged 20 to 74 years inclusive, post-menopausal female patients with Parkinson's disease aged 50 to 74 years inclusive

Exclusion Criteria:

• Healthy volunteer part

  • Subjects with any abnormal findings in physical examination vital signs, 12-lead ECG, clinical laboratory tests, ophthalmic examinations and electroencephalography

• Patient part

  • Patients who are suspected any parkinsonism except for idiopathic Parkinson's disease

• Healthy volunteer part and patient part

  • Subjects who do not agree to avoid dangerous works such as driving, mechanical operation and high-place work until completion of the follow-up examination

Healthy volunteer part -Multiple dose: Participant, Healthy volunteer part -Single dose and Patient part: No Masking