To assess the safety and tolerability of ascending multiple oral doses of SAM-531, an investigational drug, in healthy young adult and elderly subjects.To assess the pharmacokinetics (PK) and pharmacodynamics (PD) profiles of multiple oral doses of SAM-531 in healthy young adult and elderly subjects.

Inclusion criteria :

• Men or women of nonchildbearing potential aged 18 to 45 years
• Elderly men or women aged 65 years and above as of study day 1.
• Body mass index in the range of 18 to 30 kg/m2 and body weight ≥50 kg. Body weight for elderly subjects must be ≥45 kg.

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.
• Tobacco use or the consumption of any caffeine-containing products (e.g., coffee, tea, chocolate, or soda) or alcoholic beverages within 48 hours before study day 1, or grapefruit or grapefruit-containing products 72 hours before study day 1, and until the end of the inpatient confinement period.
• Elderly men or women aged 65 years and above as of study day 1.
• Body mass index in the range of 18 to 30 kg/m2 and body weight ≥50 kg. Body weight for elderly subjects must be ≥45 kg.