This study is to assess the safety, tolerability, plasma concentration and pharmacodynamics of ASP7991 after multiple oral administrations to non-elderly subjects.

In each step (lowest dose, middle dose, highest dose), subjects are randomly assigned in a double blinded manner to receive either ASP7991 (n=9) or Placebo (n=3) and are administered repeatedly. Once daily, the subjects are administered ASP7991 or placebo orally 30 minutes after breakfast with 150 mL water for 7 days. After the each step the sponsor evaluates the safety in the blinded manner for deciding an escalation to the step.

Inclusion Criteria:

• Healthy, as judged by the investigator/sub investigator based on the results of physical examination obtained before study drug administration
• Body weight: ≥50.0 kg, <80.0 kg
• BMI: ≥17.6, <26.4
• Serum corrected calcium concentration: ≥9.0mg/dL, <10.4 mg/dL

Exclusion Criteria:

• Received any investigational drugs in other clinical or post-marketing studies within 120 days before screening
• Donated 400 mL of whole blood within 90 days, 200 mL of whole blood within 30 days, or blood components within 14 days before screening
• Received medication (including marketed drug) within 7 days before hospitalization, vitamin preparation including vitamin D and supplement including calcium or is scheduled to receive medication
• A deviation from normal criteria range of 12-lead ECG (QT evaluation)
• A deviation from the normal range in clinical laboratory tests
• Highly sensitive cardiac troponin T (at screening): ≥0.014 ng/mL
• History of drug allergies
• Upper gastrointestinal disease (e.g. nausea, vomiting, stomachache) within 7 days before admission
• Concurrent or previous hepatic disease (e.g., viral hepatitis, drug-induced liver injury)
• Concurrent or previous endocrine disorders (e.g., hyperthyroidism, aberration in growth hormone)