Introduction: Bisphosphonates are the standard treatment for glucocorticoid-induced osteoporosis (GIOP) with teriparatide being another option. While daily teriparatide has been shown to be effective in increasing bone mineral density (BMD), the efficacy of once-weekly teriparatide (56.5 µg) has not yet been evaluated. The TOWER-GO study, a 72-week, multicenter, open-label, randomized controlled trial, was conducted in patients with GIOP to compare the effects of once-weekly teriparatide and once-weekly alendronate 35 mg on BMD.
Materials and methods: Patients (N = 180) with GIOP for whom drug treatment was indicated according to the 2004 guidelines in Japan were randomized to receive once-weekly teriparatide (n = 89) or once-weekly alendronate (n = 91). The primary endpoint was the non-inferiority of percentage change in lumbar spine BMD at final follow-up. The secondary endpoints were the percentage change in BMD from baseline, incidence of bone fractures, and changes in bone turnover markers.
Results: While the non-inferiority of teriparatide to alendronate was not confirmed, BMD increased significantly from baseline with teriparatide and alendronate by 5.09% and 4.04%, respectively (both p < 0.05), at 72 weeks. The incidence of vertebral and non-vertebral fractures was similar in both groups. Bone formation markers increased in the teriparatide group and decreased in the alendronate group.
Conclusions: The non-inferiority of once-weekly teriparatide versus once-weekly alendronate in BMD change at 72 weeks was not shown, but the increase in bone formation markers over time and the increase of BMD in GIOP patients treated with once-weekly teriparatide were confirmed.
Keywords: Bone mineral density; Glucocorticoid-induced osteoporosis; Once-weekly administration; Teriparatide.