Odanacatib Increases Bone Mineral Density in Postmenopausal Women After 2 Years: Presented at ASBMR

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Title: Odanacatib Increases Bone Mineral Density in Postmenopausal Women After 2 Years: Presented at ASBMR
URL: http://www.pslgroup.com/dg/22CDE2.htm
Doctor's Guide
September 19, 2008

By Louise Gagnon

MONTREAL -- September 19, 2008 -- Data from a phase 2 study suggest that therapy with a new class of drugs is effective in managing postmenopausal women with low bone mineral density (BMD).

Presented here at an oral session at the American Society for Bone and Mineral Research (ASBMR) 30th Annual Meeting, the randomised, double-blind study compared the safety and efficacy of odanacatib to placebo in 399 women with low BMD.

Odanacatib works by inhibiting cathepsin K enzyme, which is believed to play a role in osteoclastic bone resorption, explained lead investigator Michael McClung, MD, Oregon Osteoporosis Center, Portland, Oregon.

"The process of bone resorption is a complex one," he noted in an oral presentation on September 16.

Postmenopausal women with BMD scores of -2.0 or less at the lumbar spine, femoral neck, trochanter, or total hip and scores of -3.5 or more at all sites were randomised to receive odanacatib at 1 of 4 doses (3, 10, 25, or 50 mg) or placebo on a weekly basis. Patients also were provided with vitamin D and calcium if they failed to acquire at least 1,000 mg of calcium daily through diet.

The first phase of the study demonstrated that the drug has a convenient dosing schedule, said Dr. McClung, as well as demonstrating a dose-dependent increase in lumbar spine BMD. A total of 320 women from the initial phase of the trial opted to continue to the second phase of the study, and 280 completed 2 years of treatment.

The trend of dose-dependent increases in BMD continued into the second year, with increases observed at several sites, including the lumbar spine, total hip, and femoral neck.

Specifically, the 24-month data showed that the maximal 50-mg dose of odanacatib resulted in an increase of 5.5% in the lumbar spine BMD and 3.2% in the total hip BMD. By comparison, BMD at these same sites did not increase in patients on placebo.

Odanacatib also outperformed placebo in markers of bone turnover. Urinary N-telopeptide decreased by 52% in patients on odanacatib 50 mg whereas it decreased by 5% in placebo patients, and bone-specific alkaline phosphatase decreased by 13% in odanacatib patients and increased by 3% in those on placebo.

Previous studies with other selective inhibitors of cathepsin K enzyme have observed that adverse events such as skin problems and respiratory infections are more pronounced in patients taking such therapy, according to Dr. McClung.

He noted there was no significant difference in the incidence of these adverse events between odanacatib and placebo in this investigation. Of note, rash was reported in 4.8% of patients receiving odanacatib 50 mg and in 7.9% of patients receiving placebo.

"Overall, the drug was very well tolerated," he said.

The drug is currently being evaluated in a phase 3 trial, noted Dr. McClung.

Funding for this study was provided by Merck Research Laboratories.

[Presentation title: A Randomized, Double-Blind, Placebo-Controlled Study of Odanacatib (MK-822) in the Treatment of Postmenopausal Women With Low Bone Mineral Density: 24-Month Results. Abstract 1291]

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