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Monthly Bisphosphonate Holds Its Own at 2 Years


 

VIENNA — Oral ibandronate at 150 mg once monthly showed continued impressive therapeutic efficacy in women with postmenopausal osteoporosis at the 2-year mark in the Monthly Oral Ibandronate in Ladies (MOBILE) trial, Pierre D. Delmas, M.D., said at the annual European congress of rheumatology.

Ibandronate (Boniva) was approved by the Food and Drug Administration this spring as the first once-monthly oral bisphosphonate, in part because of the persuasive 1-year results of MOBILE.

The new 2-year data provide reassurance that over the longer term this therapy continues to be a highly effective and well-tolerated alternative to daily or weekly bisphosphonates, said Dr. Delmas, professor of medicine and rheumatology at Claude Bernard University, Lyon, France.

MOBILE is a randomized, double-blind, phase III, Roche- and GlaxoSmithKline-sponsored clinical trial involving 1,609 women with postmenopausal osteoporosis who were placed on oral ibandronate at 2.5 mg/day, 100 mg once per month, 150 mg once per month, or 50 mg on each of two consecutive days per month.

The daily-therapy arm served as the comparator group in this trial because 2.5 mg/day was the first FDA-approved ibandronate regimen, and it was previously shown to reduce vertebral fracture risk by 62% compared with placebo in a 3-year trial. Dr. Delmas focused on the once-monthly 150-mg group because this dosage showed the greatest efficacy and is already approved in the United States.

MOBILE wasn't designed or powered to evaluate fracture risk. Instead, it was a bridging trial that relied upon the surrogate end points of change in bone mineral density (BMD) and bone resorption markers in an effort to establish that monthly therapy was noninferior to the 2.5 mg/day regimen.

In fact, the 150-mg once-monthly regimen proved to be superior to daily therapy in terms of improvement in BMD at various sites at 2 years. (See chart.)

The mean decrease in the bone resorption marker serum C-terminal cross-linking telopeptide of type I collagen (sCTX) was 67.7% in the 150-mg once-monthly group and 61.5% with daily therapy.

Tolerability and the incidence of side effects in all of the once-monthly study arms at 2 years were similar to rates with daily therapy, as was also true after 1 year, Dr. Delmas said during the meeting, which was sponsored by the European League Against Rheumatism.

MOBILE coinvestigator Jean-Yves Reginster, M.D., said it's a reasonable hypothesis that once-monthly bisphosphonate therapy will result in better therapeutic adherence than weekly or daily therapy, as 1-year adherence to bisphosphonate therapy has previously been shown to be nearly twice as great with weekly versus daily treatment.

This hypothesis is supported by data from a large new European patient survey indicating that four-fifths of women with postmenopausal osteoporosis would be interested in dosing regimens that are less frequent than weekly, and three-quarters of physicians believe that such regimens would have a strong favorable effect upon adherence.

“We're now facing a new challenge in the management of osteoporosis: It's that bisphosphonate compliance and persistence with daily or weekly regimens remain largely suboptimal. More than one-half of patients don't even take their drug for 12 months,” commented Dr. Reginster, who is a professor of epidemiology, public health, and health economics at the University of Liège, Belgium.

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