SAN FRANCISCO, California—Yearly infusions of 5 milligrams of zoledronic acid reduced fractures and increased bone mineral density (BMD) when administered with and without concomitant osteoporosis therapy, according to additional data from the HORIZON-PFT trial  presented at The Endocrine Society’s 90th Annual Meeting in San Francisco.¹

“Zoledronic acid significantly increased BMD and yielded similar reductions in vertebral and nonvertebral fracture risk whether given alone or with concomitant nonbisphosphonate antiresorptive therapy,” concluded researchers led by D. M. Reid, MD, from the department of medicine and therapeutics at the University of Aberdeen in the UK. “The use of zoledronic acid can yield significant antifracture benefits even in patients on existing osteoporosis therapies.”

Study patients were treated with zoledronic acid or placebo and calcium plus vitamin D alone (stratum I) or concomitant non-bisphosphonate antiresorptive therapy including hormone therapy or selective estrogen receptor modulators calcitonin or tibolone with zoledronic acid (stratum II).

In stratum I, 3.3% of zoledronic-acid-treated patients sustained a morphometric vertebral fracture over 3 years compared with 10.9% of placebo-treated patients. This corresponds to a 70% relative risk reduction, the study showed. In stratum II, 3.9% of zoledronic-treated patients experienced a morphometric vertebral fracture compared with 8.8% of placebo-treated patients. This corresponds to a relative risk reduction of 56%.

Reductions in hip fractures risk were similar between the two groups, 41% and 42% respectively, the study showed. In addition, risk reductions were similar between the groups for nonvertebral fractures. The risk reduction for clinical vertebral fractures was 83% for stratum I and 66% for stratum II. There were no significant treatment-by-stratum interactions observed for any of the fracture endpoints.

BMD increases seen

Zoledronic acid significantly increased BMD in the hip, femoral neck, and lumbar spine by 4.8 % to 6.7% relative to placebo over 36 months indicated. The researchers found that BMD increases were seen across both strata, however, there were smaller increases favoring zoledronic acid in stratum I patients at the lumbar spine, femoral neck, and total hip.

Treatment with zoledronic acid had a favorable safety profile and was generally well tolerated, with adverse events rates similar in both arms.

Translating research into practice

"There is a lot of interest in the use of these drugs and the marketplace is very competitive right now,” said Henry Anhalt, DO, a pediatric endocrinologist in Hackensack, NJ and a member of the advocacy and public outreach core committee of the Endocrine Society. “As long as we continue to see morbidity and mortality related to osteoporosis, the greater the pressure will be to fine tune and improve our armamentarium of drugs including the bisphosphonates.”

Although there have been some safety setbacks with this class in regard to risk of jaw osteonecrosis, “as a general rule, the marketplace will continue to be competitive around the bisphosphonates,” he told MSKreport.com.

Reference

1. Reid DM Delmas PD, Skag A. Zoledronic acid reduces fractures and increases BMD with and without concomitant osteoporosis therapy. Presented at: ENDO 2008; June 15-18, 2008; San Francisco, Calif. Abstract P1-512.