SAN FRANCISCO – Switching to denosumab boosted bone mineral density more than did switching to ibandronate or risedronate in high-risk osteoporosis patients who were not adherent to oral bisphosphonate therapy, an assessment of data from 1,576 patients in two studies found.
The open-label studies included postmenopausal women who previously had been prescribed oral bisphosphonate therapy for osteoporosis but had either stopped the drug or were insufficiently adherent to therapy, by a score of less than six on the Osteoporosis-Specific Morisky Medication Adherence Scale.
Dr. Christopher Recknor
One study randomized patients to denosumab (Prolia) 60 mg subcutaneously every 6 months or ibandronate (Boniva) 150 mg orally every month.
The other study randomized patients to the same denosumab regimen or risedronate (Actonel) 150 mg orally per month, taken as a 75-mg tablet on each of two consecutive days.
BMD measurements on 1,576 women in the studies showed significantly greater increases at 12 months at the hip, femoral neck, and spine in patients receiving denosumab, compared with either of the oral bisphosphonates, Dr. Christopher Recknor and his associates reported at the annual meeting of the Endocrine Society.
Bone density in patients on denosumab increased at the hip by about 2.3% in one study and 2% in the other, increased at the femoral neck by roughly 1.7% in one study and 1.5% in the other, and increased at the spine by 4% in one study and 3.5% in the other. In comparison, BMDs in patients on ibandronate increased by roughly 1.1% at the hip, 0.7% at the femoral neck, and 2% at the spine. BMDs in patients on risedronate increased by about 0.4% at the hip and 1% at the spine but decreased by 0.1% at the femoral neck.
The changes in bone density did not differ significantly between the 33% of patients who had had a prior fragility fracture and patients with no history of fragility fracture, with one exception: The gains in femoral neck BMD from denosumab compared with ibandronate were significantly larger in patients with a prior fracture, compared with those with no prior fracture, reported Dr. Recknor, medical director of the United Osteoporosis Centers, Gainesville, Ga.
In patients with a prior fragility fracture, femoral neck BMD increased by about 2.2% on denosumab and by 0.1% on ibandronate, compared with gains in patients with no prior fracture of 1.5% on denosumab and 1% on ibandronate.
The study defined fragility fractures as those not involving the skull, facial bones, fingers, and toes and not associated with severe trauma or pathological fractures.
In the lower-risk patients without a prior fracture, "that is where Boniva does not seem to work very well" in comparison with switching to another oral bisphosphonate, Dr. Recknor said in an interview. For high-risk patients with a prior fracture, however, "I’m even more convinced that if I’ve got somebody who’s at high risk and they’re noncompliant" with bisphosphonate therapy, "giving Prolia would be the way to go."
Even if the bisphosphonate regimen is switched to monthly dosing to try to improve adherence, "the bone density increases are just not going to be that great," he said.
BMDs at baseline did not differ significantly between treatment groups or between patients with or without a prior fragility fracture.
Infections, though not serious ones, were reported in 24% of patients on denosumab in each study and in 19% of patients on ibandronate and 21% of patients on risedronate. There were no cases of atypical femoral fracture, delayed fracture healing, or osteonecrosis of the jaw.
The study was funded by Amgen, which markets denosumab, and by GlaxoSmithKline. Dr. Recknor disclosed ties with Amgen, Novartis Pharmaceuticals, Ion Med Systems, Eli Lilly, Merck, and UCB. Some coinvestigators were employees of Amgen and others reported financial ties with these companies and/or Warner Chilcott, which markets risedronate; Roche Pharmaceuticals, which markets ibandronate through Genentech; Tarsa, Wyeth, Takeda, Nycomed, Servier, and Pfizer.
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