To assess the safety and tolerability of ascending single oral doses of SAM-531, an investigational drug, in healthy Japanese male subjects. Secondary: To obtain preliminary pharmacokinetic (PK) and pharmacodynamic (PD) profiles of SAM-531 in healthy Japanese male subjects.

Inclusion criteria:

• Men aged 20 to 45 years (inclusive) at the time of getting informed consent.
• Body mass index (BMI) in the range of 17.6 to 26.4 kg/m2 and body weight ≥50 kg (BMI = [weight (kg)]/[height (m)2).
• Healthy as determined by the investigator on the basis of medical history, physical examination, clinical laboratory test results, vital signs, and digital 12-lead electrocardiogram (ECG). Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and creatinine levels must be within the upper limit of normal for eligibility.

Exclusion criteria

• Any significant cardiovascular, hepatic, renal, respiratory, gastrointestinal, endocrine, immunologic, dermatologic, hematologic, neurologic, or psychiatric disease.
• Any clinically important deviation from normal limits in physical examination, vital signs, digital 12-lead ECGs, or clinical laboratory test results.
• Consumption of any caffeine-containing products (e.g., coffee, tea, chocolate, or soda) or alcoholic beverages is prohibited from 48 hours and consumption of grapefruit or a grapefruit-containing product is prohibited from 72 hours before study day 1.](streamdown:incomplete-link)