Once-weekly teriparatide reduces the risk of vertebral fracture in patients with various fracture risks: subgroup analysis of the Teriparatide Once-Weekly Efficacy Research (TOWER) trial

Once-weekly teriparatide (human parathyroid hormone [1–34]) (56.5 μg for 72 weeks) injections provided a vertebral fracture risk reduction in Japanese osteoporotic patients evaluated in the Teriparatide Once-Weekly Efficacy Research (TOWER) trial. Using data from the TOWER trial, a subgroup analysis was performed to study the efficacy of once-weekly teriparatide for a variety of baseline clinical risk factors in placebo (n = 281) and teriparatide (n = 261) groups. Significant fracture risk reductions were observed in the subgroups of individuals aged <75 years [relative risk (RR) 0.06, p = 0.007] and ≥75 years (RR 0.32, p = 0.015). A significant risk reduction was observed among patients with prevalent vertebral fracture in the subgroup with 1 (RR 0.08, p = 0.015) or ≥2 (RR 0.29, p = 0.009) prevalent vertebral fractures, and in those with grade 3 deformity (RR 0.26, p = 0.003). Significant risk reduction was observed in the subgroup with lumbar bone mineral density (BMD) < −2.5 SD (RR 0.25, p = 0.035). In the teriparatide group, no incident fracture was observed in the subgroups with a prevalent vertebral fracture number of 0, with grade 0–2 vertebral deformity, or with lumbar BMD ≥2.5 SD. Significant risk reduction was observed in all of the bone turnover marker and estimated glomerular filtration rate subgroups. In conclusion, once-weekly 56.5 μg teriparatide injection reduced the vertebral fracture risk in patients with varying degrees of fracture risk, age, vertebral fracture number and grade, bone turnover level, and renal function.