The primary objective of this study is to determine the effect of treatment with AGA2118 versus placebo at Month 12 on lumbar spine bone mineral density (BMD) in postmenopausal women with low bone mass.

This Phase 2 dose-finding study will evaluate the safety, tolerability, and efficacy of AGA2118 at a range of dosing regimens in postmenopausal women with low BMD at the lumbar spine, total hip, or femoral neck and no prior history of fragility fractures.

This study includes a 12 month blinded treatment phase where participants will be randomized 1:1:1:1:1:1:1 to receive double-blind dosing regimens of AGA2118 or placebo. At Month 12, participants who have completed the double-blind portion of the study will continue on to a 12 month open-label period where they will be re-randomized based on their prior dosing regimen to either continue their current dosing regimen, receive a new dosing regimen, or discontinue treatment and be actively surveilled throughout Months 12 to 24.

Inclusion Criteria:

• Healthy, ambulatory, postmenopausal women age ≥ 55 to ≤ 80.
• BMD T-score of ≤ -2.5 to > -3.5 at the lumbar spine, total hip, or femoral neck.

Exclusion Criteria:

• History of vertebral fracture, or fragility fracture of the wrist, humerus, proximal femur, or pelvis.
• Vitamin D deficiency.
• Known intolerance to calcium or vitamin D supplements.
• Untreated hyper- or hypothyroidism.
• Current hyper- or hypoparathyroidism.
• Elevated transaminases.
• Significantly impaired renal function.
• Current hypo- or hypercalcemia.
• Positive for HIV, hepatitis C virus, or hepatitis B surface antigen.
• Malignancy within the last 5 years.
• Diagnosis of a familial cancer syndrome or known genetic mutation that increases risk of cancer.
• Myocardial infarction or stroke within the past 12 months.
• Use of agents affecting bone metabolism.