A Safety, Tolerability, Pharmacokinetic and Pharmacodynamic Study of ACE-031 (ActRIIB-IgG1)in Healthy Postmenopausal Volunteers

Key Inclusion Criteria: 1. Subject is a postmenopausal woman, 45-75 years old (inclusive) 2. Subject has a body mass index (BMI) of \> 18.5 to \< 30 3. Subject must give written informed consent Key Exclusion Criteria: 1. Subject has a history of malignancy. However, a subject with a history of excised or treated basal cell carcinoma, cervical carcinoma in-situ, or less than or equal to 2 squamous cell carcinomas is eligible to participate in this study. 2. Subject has a history of clinically significant (as determined by the Investigator) cardiac, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, renal, and/or other major disease. 3. Subjects with chronic stable diseases including migraines, hypertension, hyperthyroid disorder, hypothyroid disorder, gastroesophageal reflux disease, or mild depression/anxiety will be excluded unless the investigator does not have safety or compliance concerns at study entry. 4. Subject has a history of opportunistic infection (e.g. invasive candidiasis or pneumocystis pneumonia). 5. Subject has had a serious local infection (e.g., cellulitis, abscess) or systemic infection (e.g., septicemia) within the 3 months prior to screening. 6. Subject has a history of severe allergic or anaphylactic reactions. 7. Subject had surgery within the previous 3 months (other than minor cosmetic surgery or minor dental procedures). 8. Subject had a fever (body temperature \> 38°C) or symptomatic viral or bacterial infection within 2 weeks prior to dosing. 9. Subject has a positive Tuberculin skin test (Mantoux) 10. Subject has a history of hepatitis B surface antigen (HBsAg), hepatitis C antibody (HCV), or human immunodeficiency virus (HIV). 11. Subject has a recent or clinically significant history of drug or alcohol abuse, or tests positive in a urine screen for alcohol or drugs of abuse. 12. Subject consumed any alcohol within 48 hours prior to dosing. 13. Subject has donated or lost ≥ 499 mL of whole blood within 56 days prior to study drug administration. 14. Subject has taken any hormone replacement therapy within 3 months prior to study enrollment, or plans to begin hormone replacement therapy at any time during the study.