Antibody Found That Targets Osteoporosis

Good news for postmenopausal women came from a report given by Michael R. McClung, M.D., at the annual meeting of the American Society for Bone and Mineral Research. McClung and colleagues have found an antibody that targets the Wnt signaling pathway and its osteocyte-regulating molecule sclerostin, which increases bone formation while decreasing bone resorption, according to Nancy Walsh, staff writer for MedPage Today.

Walsh reports that one year of treatment with the antibody romosozumab (formerly AMG 785) led to an 11.3% absolute increase in bone mineral density (BMD) in postmenopausal women with low BMD (body mass index). That compared with BMD increases of only 7% with teriparatide (Forteo), 4% with alendronate (Fosamax), and no change with a placebo. “The discovery of sclerostin as an osteocyte-mediated stimulator of osteoblast function and bone formation opened the door for considering the inhibition of this protein and regulator as a target for osteoporosis treatment, ” McClung said.

To further explore the therapeutic potential of this antibody, the researchers conducted a Phase II study that enrolled 419 women whose lumbar spine, total hip, or femoral neck T-scores were between −2 and −3.5. The mean age of the participating women was 67. Researchers randomized participants to receive romosozumab in dosages of 70 mg, 140 mg, or 210 mg each month, 140 or 210 mg every three months, or a placebo.

The total hip increase in BMD with romosozumab was 4.1% at 12 months, which was approximately double that seen with alendronate and teriparatide. The researchers also saw changes in biomarkers of bone metabolism, McClung noted. The pattern seen with romosozumab, McClung said, was increases for serum P1NP, favoring bone formation, and decreases in serum CTX, suggesting a slowing of bone resorption after one week of treatment.

Adverse events were similar in the treatment groups. The most common was back or extremity pain. Serious adverse events occurred in 9.8% of the romosozumab groups and in 14% of the placebo group. The only treatment-related adverse events that occurred in the romosozumab groups were injection site reactions, but these were mild and did not lead to a discontinuation of treatment, said McClung.