Randomized Teriparatide [Human Parathyroid Hormone (PTH) 1–34] Once-Weekly Efficacy Research (TOWER) Trial for Examining the Reduction in New Vertebral Fractures in Subjects with Primary Osteoporosis and High Fracture Risk

Weekly teriparatide injection at a dose of 56.5 μg has been shown to increase bone mineral density.A phase 3 study was conducted to determine the efficacy of once-weekly teriparatide injection for reducing the incidence of vertebral fractures in patients with osteoporosis.In this randomized, multicenter, double-blind, placebo-controlled trial conducted in Japan, the incidence of morphological vertebral fractures by radiographs was assessed.Subjects were 578 Japanese patients between the ages of 65 and 95 yr who had prevalent vertebral fracture.Subjects were randomly assigned to receive once-weekly s.c. injections of teriparatide (56.5 μg) or placebo for 72 wk.The primary endpoint was the incidence of new vertebral fracture.Once-weekly injections of teriparatide reduced the risk of new vertebral fracture with a cumulative incidence of 3.1% in the teriparatide group, compared with 14.5% in the placebo group (P < 0.01), and a relative risk of 0.20 (95% confidence interval, 0.09 to 0.45). At 72 wk, teriparatide administration increased bone mineral density by 6.4, 3.0, and 2.3% at the lumbar spine, the total hip, and the femoral neck, respectively, compared with the placebo (P < 0.01). Adverse events (AE) and the dropout rates by AE were more frequently experienced in the teriparatide group, but AE were generally mild and tolerable.Weekly s.c. administration of teriparatide at a dose of 56.5 μg may provide another option of anabolic treatments in patients with osteoporosis at higher fracture risk.