The purpose of this study is to investigate the pharmacodynamic effect of single doses of MT-8554 in healthy subjects.

Inclusion Criteria:

• Healthy and free from clinically significant illness or disease
• Male Caucasian subjects aged 18 to 55
• A body weight of ≥60 kg

Exclusion Criteria:

• Participation in more than three clinical studies involving administration of an Investigational Medicinal Product (IMP) in the previous year, or any study within 12 weeks.
• Clinically significant endocrine, thyroid, hepatic, respiratory, gastro-intestinal, renal, cardiovascular disease, or history of any significant psychiatric/psychotic illness disorder.
• Clinically relevant abnormal medical history, physical findings or laboratory values