Romosozumab is a monoclonal antibody that binds to and inhibits sclerostin, increases bone formation, and decreases bone resorption. In postmenopausal women with osteoporosis who were at high risk for fracture, romosozumab treatment for 12 months followed by alendronate resulted in a significantly lower risk of fracture than alendronate alone.

NEJM

Also see:

New osteoporosis medication on the horizon (romosozumab)

Osteoporosis guidelines, an ACP update 2017

N  E  J  M

Randomized

October 2017

BACKGROUND

Romosozumab is a monoclonal antibody that binds to and inhibits sclerostin, increases bone formation, and decreases bone resorption.

METHODS

We enrolled 4093 postmenopausal women with osteoporosis and a fragility fracture and randomly assigned them in a 1:1 ratio to receive monthly 210 mg subcutaneous romosozumab or weekly 70 mg oral alendronate in a blinded fashion for 12 months, followed by open-label alendronate in both groups.

Primary end points were the cumulative incidence of new vertebral fracture at 24 months and the cumulative incidence of clinical fracture (nonvertebral and symptomatic vertebral fracture) at the time of the primary analysis (after clinical fractures had been confirmed in ≥330 patients).

Secondary end points included the incidences of nonvertebral and hip fracture at the time of the primary analysis.

Serious cardiovascular adverse events, osteonecrosis of the jaw, and atypical femoral fractures were adjudicated.

RESULTS

Over a period of 24 months, a 48% lower risk of new vertebral fractures was observed in the romosozumab-to-alendronate group (6.2%, 127/2046 patients) than in the alendronate-to-alendronate group (11.9%, 243/ 2047 patients) (P<0.001).

Clinical fractures occurred in 198 of 2046 patients (9.7%) in the romosozumab-to-alendronate group versus 266 of 2047 patients (13.0%) in the alendronate-to-alendronate group, representing a 27% lower risk with romosozumab (P<0.001).

The risk of nonvertebral fractures was lower by 19% in the romosozumab-to-alendronate group than in the alendronate-to-alendronate group (178/2046 patients, 8.7% vs. 217/2047 patients, 10.6%; P=0.04), and the risk of hip fracture was lower by 38% (41/2046 patients, 2.0% vs. 66/2047 patients 3.2%; P=0.02).

Overall adverse events and serious adverse events were balanced between the two groups. During year 1, positively adjudicated serious cardiovascular adverse events were observed more often with romosozumab than with alendronate (50/2040 patients, 2.5% vs. 38/2014 patients, 1.9%).

During the open-label alendronate period, adjudicated events of osteonecrosis of the jaw (1 event each in the romosozumab-to-alendronate and alendronate-to-alendronate groups) and atypical femoral fracture (2 events and 4 events, respectively) were observed.

CONCLUSIONS

In postmenopausal women with osteoporosis who were at high risk for fracture, romosozumab treatment for 12 months followed by alendronate resulted in a significantly lower risk of fracture than alendronate alone.