24-Month Open-Label Teriparatide Once-Weekly Efficacy Research Trial Examining Bone Mineral Density in Subjects with Primary Osteoporosis and High Fracture Risk

Introduction: To clarify the additional efficacy and safety benefits of 24 months' treatment with the once-weekly formulation of teriparatide, which is currently used for 72 weeks. Methods: This was a multicenter, open-label, single-arm study conducted in Japan. Subjects who were 65 years or older with prevalent vertebral fractures received once-weekly subcutaneous injection of 56.5 mu g teriparatide for 24 months. The main outcome measure was percentage change from baseline in lumbar (L2-L4) BMD measured by dual-energy X-ray absorptiometry. Results: A total of 189 subjects received at least one dose of the once-weekly formulation of teriparatide. Lumbar, femoral neck, and total hip BMD increased significantly compared with baseline at Weeks 24, 48, 72, and 104. In addition, significant increases in lumbar (+1.5%) and femoral neck (+0.8%) BMD were noted at Week 104 compared with Week 72. Significant increases from baseline in BMD for radius 1/10 were noted at Weeks 24 and 104. No substantial increases were noted in the cumulative incidences of new vertebral fracture and other types of fracture after Week 72. The safety profile seen in the first 72 weeks remained unchanged until 104 weeks. Conclusion: The once-weekly formulation of teriparatide is effective and safe for the treatment of osteoporosis over 24 months. The limitation of this study is that this was an open-label, single-arm study.