SAN DIEGO – Teriparatide has received a boost in status as a preferentially effective treatment for glucocorticoid-induced osteoporosis in the form of a second, confirmatory, randomized double-blind trial demonstrating the anabolic agent achieves substantially greater increases in bone mineral density compared to a bisphosphonate.

One of these studies also included fracture rates as a preplanned secondary endpoint; the trial demonstrated a significant reduction in vertebral fractures with teriparatide (Forteo) as compared to alendronate (Fosamax).

These positive study findings are bolstered by a biologically plausible mechanism of benefit, Dr. Kenneth G. Saag observed at the annual meeting of the American Society for Bone and Mineral Research.

"Based upon the pathogenesis of glucocorticoid-induced osteoporosis [(GIOP)], we think that an anabolic agent makes some sense. It may be beneficial to stimulate osteoblasts to promote new bone formation," said Dr. Saag, professor of medicine and epidemiology at the University of Alabama at Birmingham.

Steroids are known to have apoptosis-mediated deleterious effects on both osteocytes and osteoblasts that lead to decline in bone function and an abrupt increase in fracture risk independent of bone mineral density (BMD). Osteoclasts are also unfavorably impacted due to crosstalk and the indirect effects of sex steroids, insulin-like growth factor, and a modest effect of secondary hyperparathyroidism mediated through altered calcium absorption. In addition, higher-dose steroids have adverse effects upon muscle that can independently lead to a higher fracture rate, the rheumatologist explained.

The FDA has approved alendronate, zoledronic acid (Reclast), and risedronate (Actonel) for treatment GIOP. More recently, raloxifene (Evista) has joined the ranks of agents shown to increase BMD in patients on long-term steroids; this came in the form of a double-blind, placebo-controlled, 12-month study (Ann. Rheum. Dis. 2011;70:778-84).

Subcutaneous daily teriparatide for up to 2 years also has the approval of the Food and Drug Administration for use in adults at high fracture risk because they are on sustained systemic steroid therapy.

There is no definitive study demonstrating that any of these agents actually prevents fractures in patients with GIOP. Nor is it likely such a study will be undertaken. Such trials require large numbers of patients and lengthy follow-up, and pharmaceutical companies have little incentive to mount such a costly project given that the medications are already approved for use in patients on steroids, Dr. Saag noted.

However, data from a study in which Dr. Saag was lead investigator showed that teriparatide-treated patients had significantly fewer vertebral fractures than those assigned to alendronate. The study was a 36-month randomized, double-blind, clinical trial that assessed fracture rates as a preplanned secondary endpoint. The radiographic and clinical vertebral fracture rates in 169 alendronate-treated patients were 7.7% and 2.4%, respectively, compared to 1.7% and 0% in 173 teriparatide-treated patients (P = .007 and .037). No significant difference in nonvertebral fractures was found between the two treatment arms.

The primary study endpoint was the change in BMD from baseline. Here again teriparatide proved significantly more effective than the bisphosphonate, with a mean 11% increase at the lumbar spine, compared to 5.3% with alendronate. Teriparatide-treated patients also had a 5.2% increase in BMD at the total hip and a 6.3% boost at the femoral neck, compared to 2.7% and 3.4%, respectively, with alendronate (Arthritis Rheum. 2009;60:3346-55).

09/30/11  

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EXPERT ANALYSIS FROM THE ANNUAL MEETING OF THE AMERICAN SOCIETY FOR BONE AND MINERAL RESEARCH

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