Romosozumab Boosted Bone Strength in Postmenopausal Women

SEATTLE — Romosozumab, an experimental bone-forming agent that inhibits sclerostin, may increase bone strength at the spine and hip in postmenopausal women after 12 months of treatment, according to new data.

The findings, which were presented at the American Society for Bone and Mineral Research (ASBMR) 2015 Annual Meeting, confirm and extend existing data as well as support further evaluation of romosozumab in an ongoing phase 3 clinical program, according to investigators.

“This new treatment may provide physicians with a new anabolic that can rapidly increase bone strength at the hip and spine,” said lead study author Tony Keaveny, PhD, who is a professor of mechanical engineering and bioengineering at the University of California, Berkeley, and the Chief Scientific Officer at O.N. Diagnostics in Berkeley.

Romosozumab is an anti-sclerostin monoclonal antibody that has been shown to both increase bone formation and decrease resorption. A previously published phase 2 study showed that 12 months of romosozumab increased bone mineral density (BMD) in postmenopausal women with low bone mass.1

A subset of these women then underwent spine and hip quantitative computed tomography (QCT) imaging that confirmed the BMD gains. According to the investigators, romosozumab produced better results than teriparatide. They found that integral volumetric BMD gains were 17.7% for the romosozumab arm compared with only 12.9% for teriparatide at the spine. The findings at the hip were even greater, with an improvement of 4.1% for romosozumab compared with 1.2% for teriparatide.

In the current analysis, patients were randomly assigned to receive blinded subcutaneous romosozumab 210 mg monthly (n=24) or placebo (n=27) or open-label teriparatide 20 mcg daily (n=28).

The investigators performed QCT scans at the L1 and L2 lumbar vertebrae and proximal femur at baseline and at 1 year, and applied the FDA-approved Virtuost (O.N. Diagnostics) software to the QCT scans to perform a virtual stress test of the hip and spine, allowing for an estimated change in strength.

Results indicated that romosozumab increased bone strength from baseline by 27.3% at month 12 in the spine. That was significantly greater than for teriparatide (18.5%) and placebo (–3.9 %). 

At the hip, in the romosozumab group, bone strength increased by 3.6% from baseline compared with no change in the teriparatide arm or the placebo arm. The investigators noted the strengthening effect was due to contributions from both the cortical and trabecular compartments.

“This is early evidence that the substantial BMD changes reported for this treatment by McClung in the New England Journal of Medicine are indeed associated with substantial changes in the strength of the bone, the increases coming from positive effects on the both the trabecular and cortical bone. The clinical implications are that this treatment, if confirmed in follow-up studies, may provide patients with rapid and large increases in bone strength at both the hip and spine,” Dr Keaveny told Endocrinology Advisor.

References

1. McClung MR, Grauer A, Boonen S, et al. Romosozumab in Postmenopausal Women with Low Bone Mineral Density. N Engl J Med. 2014; 370:412-420.
2. Keaveny T. Abstract 1143: Romosozumab Improves Strength at the Lumbar Spine and Hip in Postmenopausal Women With Low Bone Mass Compared With Teriparatide. Presented at: American Society for Bone and Mineral Research (ASBMR) 2015 Annual Meeting; Oct. 9-12, 2015; Seattle.