SAN FRANCISCO – Denosumab was superior to zoledronic acid (ZA) in building bone at the lumber spine, total hip, and femoral neck in postmenopausal women with osteoporosis previously treated with oral bisphosphonate therapy in a randomized phase III trial. This study is one more piece of level I evidence to support the effectiveness of transitioning to denosumab in such patients.
“In postmenopausal women with osteoporosis on prior oral bisphosphonates for 2 or more years, transitioning to denosumab resulted in significantly greater increases in bone mineral density [BMD], compared with zoledronic acid at all measured skeletal sites,” said lead author Dr. Paul D. Miller of the Colorado Center for Bone Research, Lakewood, Colo.
Alice Goodman/Frontline Medical News
Dr. Paul D. Miller
Speaking at the annual meeting of the American College of Rheumatology, Dr. Miller said: “This study completes a suite of trials that show transitioning from oral bisphosphonates to denosumab provides greater increases in bone mineral density and reduction in bone turnover markers, compared to maintaining therapy with another bisphosphonate.”
“Adherence rates to oral bisphosphonates are low,” he continued. “Patients who are intolerant to or fail other bisphosphonates may cycle from one bisphosphonate to another, but clinical benefits are not shown. Previous trials have shown that denosumab increased bone mineral density in women previously treated with oral bisphosphonates, whereas zoledronic acid did not, in women previously treated with alendronate.”
A prospective, double-blind, double-dummy, randomized trial was mounted to compare denosumab given subcutaneously at 60 mg every 6 months (n = 321) vs. ZA 5 mg once a year (n = 322) in postmenopausal women with osteoporosis who were intolerant to or who failed oral bisphosphonate therapy after at least 2 years of treatment.
Baseline characteristics were similar between both treatment arms. Median age was 69 years. About 38% had previous osteoporotic fracture. Bone mineral density T scores were similar between groups. Prior oral bisphosphonate exposure was a median of 6.4 years. Bone turnover marker levels were similar between the two arms.
For the primary endpoint, at 12 months, denosumab achieved a greater increase in BMD at all sites, compared with ZA: a 2.1% difference was observed at the lumbar spine and a 1.4% difference at the total hip.
Changes in bone turnover markers over time were more favorable with denosumab, he continued. Serum C-terminal cross-linking telopeptide (CTX) level was maintained in the denosumab arm and increased with ZA over 12 months. A similar pattern was observed with procollagen type 1 N-terminal propeptide (P1NP).
Adverse events were comparable between both groups. Serious adverse events were reported in 7.8% in the denosumab arm versus 9.1% in the ZA arm, but this difference was not statistically significant. Slightly more hypersensitivity adverse events were reported in the denosumab group: 3.8% versus 1.9% for ZA. The number of osteoporotic-related fractures was doubled in the ZA arm: 7 for denosumab vs. 15 for ZA.
Dr. Miller told listeners that this is the fourth study to show that denosumab is effective in osteoporotic patients previously on oral bisphosphonates, including prior risedronate, ibandronate, and alendronate.