Amgen and UCB have unveiled Phase III results backing romosozumab’s efficacy in boosting bone mineral density in certain postmenopausal women with osteoporosis. 

Data from the STRUCTURE study show that the investigational monoclonal antibody induced a statistically significant increase in hip bone mineral density (BMD) and strength compared with teriparatide (Lilly’s Forteo) in postmenopausal women with osteoporosis transitioning from bisphosphonate treatment. 

The percent change from baseline in BMD at the total hip through month 12 was significantly greater with romosozumab compared with teriparatide: 2.6 percent versus –0.6 percent, respectively, for a mean difference between the two groups of 3.2 percent. 

"These findings are especially important because they show romosozumab provided significant improvements in hip bone strength in a population that remained at high risk of fracture despite bisphosphonate therapy," said Bente Langdahl, professor at the department of endocrinology and internal medicine at the Aarhus University Hospital in Denmark and STRUCTURE investigator. 

"Across the primary and secondary endpoints, patients transitioning from oral bisphosphonates to romosozumab showed consistent and significant gains in bone mass and estimated strength over teriparatide. At the hip, patients transitioning to teriparatide showed either no gains or significant decreases in these parameters,” he said.

On the safety side, the overall incidence of adverse events was generally balanced between the two study arms, with with 75.2 percent in the romosozumab arm versus 69.2 percent for teriparatide. Serious adverse events occurred in 7.8 percent and 10.7 percent of patients, respectively. 

Romosozumab is an investigational bone-forming monoclonal antibody designed to inhibit the protein sclerostin. It has a dual effect on bone, increasing bone formation and decreasing bone resorption. 

Last month, the groups posted positive top-line data from the Phase III BRIDGE trial, which demonstrated a statistically significant increase in BMD at the lumbar spine in male osteoporosis patients treated with the drug compared with placebo after 12 months.