This study is to assess the safety, tolerability, plasma concentration and pharmacodynamics of ASP7991 after single oral administration to healthy volunteers. In part-1, ASP7991 is administered in a dose escalation design. In part-2, plasma concentration changes of ASP7991 in fasted and fed conditions are compared.

This study consists of two parts. In Part 1, the study will begin as a single rising dose escalation design under randomized double-blind and fasting conditions. In each dose group, volunteers will be randomized to receive an oral administration of either active drug (ASP7991) or placebo. The dose escalation will be determined after blinded safety assessment.

Part 2 is a study to evaluate the effect of food intake. ASP7991 will be administered to volunteers under 2 conditions, fasting and fed, on 2-way crossover method.

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)