The purpose of this study is to evaluate the efficacy and safety of ONO-5334 in postmenopausal women with osteopenia or osteoporosis.

Inclusion Criteria:

1. Osteoporosis defined as a value DXA BMD 2.5 SD or more below the young adult mean (T-score, ≤-2.5) at the lumbar spine (L1 to L4) or total hip, OR

• Osteoporosis defined as a value of DXA BMD more than 1 SD below the young adult mean, but less than 2.5 SD below this value (T-score <-1 and >2.5) at the lumbar spine (L1 to L4) or total hip.

Exclusion Criteria:

1. Patients with a value of DXA BMD more that 3.5 SD below the young adult mean, (T-score <-3.5) at the lumbar spine (L1 to L4) or total hip.

2. Osteoporosis patients (T-score ≤-2.5) who have any vertebral fragility fracture between T4 and L4 inclusive.

3. Osteopenia patients (T-score <-1 and >-2.5) who have no vertebral fragility fractures between T4 and L4 inclusive, OR

   • Osteopenia patients (T-score <-1 and >-2.5) who have two or more vertebral fragility fractures between T4 and L4 inclusive.

4. Patients who have abnormalities of the lumbar spine or femoral neck or internal organs around them precluding the assessment of BMD.

5. Patients who have secondary causes of osteoporosis or other disorders of bone and mineral metabolism.

6. Other exclusion criteria as specified in the study protocol.