The purpose of this study is to establish safe dose levels of ACE-031 in healthy postmenopausal women following multiple dose administration. This study will also evaluate if ACE-031 has an effect on muscle.

Inclusion Criteria:

• Postmenopausal
• Body mass index (BMI) of ≥ 18.5 to < 32.

Exclusion Criteria:

• History of malignancy, except excised or treated basal cell carcinoma, cervical carcinoma in-situ, or ≤ 2 squamous cell carcinomas
• History of clinically significant cardiac, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, renal, and/or other major disease.
• History of opportunistic infection (e.g. invasive candidiasis or pneumocystis pneumonia) within 6 months prior to screening or serious local infection (e.g., cellulitis, abscess) or systemic infection (e.g., septicemia) within 3 months prior to screening.
• Surgery within 3 months prior to Day 1 (other than minor cosmetic or dental procedures).
• Fever or symptomatic viral or bacterial infection within 7 days prior to Day 1.
• Donation or significant loss of blood within 2 months prior to Day 1.
• Hormone replacement therapy within 3 months prior to Day 1.
• Treatment with erythropoiesis stimulating agents (Epogen, Procrit, Aranesp, etc) within 2 months prior to Day 1.
• Systemic glucocorticoid therapy within 6 months prior to Day 1.
• Treatment with another investigational drug or approved therapy for investigational use within 1 month prior to Day 1.
• Previous treatment with ACE-031.