The purpose of this study is to determine whether BA058 (abaloparatide), a parathyroid hormone-related peptide, is effective in preventing fractures in postmenopausal women with severe osteoporosis who are at risk of fractures.

This is a randomized, double-blind, placebo-controlled, comparative Phase 3, multicenter international study to evaluate the efficacy and safety of BA058 (abaloparatide) 80 µg in the prevention of fracture in otherwise healthy ambulatory postmenopausal women with severe osteoporosis.

Inclusion Criteria:

• Healthy ambulatory postmenopausal (≥ 5 years) women from 50 to 85 years of age (inclusive) with a diagnosis of osteoporosis
• The women are to have a bone mineral density (BMD) T score ≤ -2.5 and > -5.0 at the lumbar spine or hip (femoral neck) by dual energy x-ray absorptiometry (DXA) and radiological evidence of 2 or more mild or one or more moderate lumbar or thoracic vertebral fractures, or history of low trauma forearm, humerus, sacral, pelvic, hip, femoral, or tibial fracture within the past 5 years. Postmenopausal women older than 65 who meet the above fracture criteria but have a T score ≤ -2.0 and > -5.0 may be enrolled. Women older than 65 who do not meet the fracture criteria may also be enrolled if their T score is ≤ -3.0 and > -5.0
• Normal physical exam, vital signs, electrocardiogram (ECG) and medical history
• Laboratory tests within the normal range including serum calcium, PTH(1-84), serum phosphorus and alkaline phosphatase

Exclusion Criteria:

• History of more than 4 mild or moderate spine fractures or any severe fracture
• Abnormality of the spine or hip that would prohibit assessment of bone mineral density (BMD)
• Unexplained elevation of serum alkaline phosphatase, history of bone disorders (such as Paget's disease) or a diagnosis of cancer within the last 5 years (with the exception of basal cell or squamous cancer of the skin)
• History of thyroid, parathyroid, or adrenal disorders, or malabsorptive syndromes or any chronic or recurrent diseases or disturbances that would interfere with the interpretation of study data or compromise the safety of the patient
• Prior treatment with parathyroid hormone (PTH) or parathyroid hormone-related peptid (PTHrP)
• Prior treatment with bisphosphonates, fluoride, or strontium within the past five years or treatment with androgens, anabolic steroids, corticosteroids or selective estrogen receptor modulators within the past 12 months (except hormone replacement therapy)
• Prior treatment with an investigational drug within the past 12 months
• History of nephrolithiasis or urolithiasis within the past five years, or history of osteosarcoma at any time