The purpose of this study is to investigate the safety, tolerability and pharmacokinetics of MT-8554 in healthy Caucasian subjects.

Inclusion Criteria:

• Healthy and free from clinically significant illness or disease
• Male or female subjects aged 18 to 55 years or elderly male subjects aged ≥65
• A body weight of ≥60 kg male and ≥50 kg female

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