Denosumab Rivals Fosamax for Treating Osteoporosis

The human monoclonal antibody denosumab is about as safe and effective as Fosamax (alendronate), according to a new study. When injected subcutaneously every three or six months, denosumab increased bone mineral density about as effectively and safely as weekly administration of Fosamax (a leading oral bisphosphonate).

The study by Michael R McClung, MD, of the Oregon Osteoporosis Center, and colleagues was reported by MedPage Today on February 23, 2006.

Clinical Trial

The researchers conducted an open-label, multi-center trial that included 412 post-menopausal women with low bone-mineral density. Study participants were randomized to receive denosumab every three months (6-30 mg), denosumab every six months (14-210 mg) or Fosamax once a week (70 mg - the standard dose), or placebo.

Denosumab binds to and inhibits a receptor activator necessary for the activation and survival of bone-resorbing osteoclast cells.

At 12 months, examinations revealed that, among women taking denosumab (all doses), bone-mineral density at the lumbar spine had increased by 3-6.7%, compared with a 0.8% decrease for women in the placebo group, according to the researchers. Women receiving Fosamax had a 4.6% increase in bone-mineral density at the lumbar spine.

Moreover, women in both the denosumab and Fosamax groups showed comparable increases in bone-mineral density of the total hip and distal third of the radius, compared with women taking placebo. Finally, C-telopeptide (a marker of bone turnover) levels decreased on average of 88% in the denosumab groups, but only 6% in the placebo group.

Among the various doses of denosumab, optimal doses appeared to be 30 mg for the three-month injections and 60 mg for the six-month injections. Higher doses of denosumab were no more effective, and lower doses were not as effective.

Adverse event profiles among the denosumab groups, the placebo group and the Fosamax group were also similar.

"These results support the continued investigation of denosumab for use in the treatment and prevention of osteoporosis and other diseases associated with bone loss," the authors wrote.

In an accompanying editorial, Michael P Whyte, MD, of the Shriners Hospital for Children in St Louis, noted that "long-acting doses of denosumab should enhance our pharmaceutical arsenal for the treatment of osteoporosis by improving convenience and compliance for some patients."

Fosamax and other bisphosphonates are increasingly being converted from daily to weekly to monthly oral formulations, wrote Dr White, which will increase convenience and, presumably, patient compliance. Also, a newer bisphosphonate - zoledronic acid (brand name Zometa) - is undergoing tests in an intravenous formulation administered annually, he noted.

Amgen, who developed denosumab, supported the study.

Sources: Investigational Long-Term Osteoporosis Drug Shows Merit, MedPage Today, February 23, 2006. Denosumab in postmenopausal women with low bone mineral density. McClung MR et al, New England Journal of Medicine, volume 354(8), pages 821-831, 2006. The long and short of bone therapy. Whyte MP, New England Journal of Medicine, volume 354(8), pages 860-863, 2006.

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