SAN DIEGO — An injectable drug being studied for the treatment of postmenopausal osteoporosis known as abaloparatide-SC may help reduce the rate of new spinal fractures by a statistically significant 86%.
In addition, this agent may also produce statistically significant reductions in the fracture rate at other parts of the body, according to new results from a phase3 clinical trial presented at the ENDO 2015.
Abaloparatide-SC is a new manmade form of human parathyroid hormone-related protein, a naturally occurring bone-building hormone, according to its manufacturer, Radius Health, which funded this study.
The Waltham, Massachusetts drug maker is studying the medication in various forms, including a transdermal patch, in addition to the subcutaneous (SC) injection studied in the ACTIVE trial.
The international ACTIVE trial studied whether abaloparatide-SC could reduce fractures in postmenopausal women with severe osteoporosis who are at high risk for fracture.
The investigators compared rates of new fractures in 690 women who received a daily injection of abaloparatide 80 mcg and 711 women who received placebo injections. Both groups were blinded to their respective treatments, while a third group of 717 women knowingly received a daily injection of teriparatide 20 mcg. All patients also received calcium and vitamin D supplements.
“Abaloparatide, as compared to teriparatide, significantly increased BMD (bone mineral density) at the total hip and femoral neck at all time points and significantly increased BMD at the spine at 6 and 12 months. This earlier gain in BMD is likely to be the basis for the reduction in both vertebral and non-vertebral fractures seen in the ACTIVE phase 3 study,” said lead investigator Paul Miller, MD, medical director of the Colorado Center for Bone Research in Lakewood, Colorado.
“Abaloparatide shows a significant early reduction in the risk of 43% new non-vertebral and 45% clinical fractures based on the Kaplan-Meier curves.”
He said if abaloparatide-SC is approved, it may offer patients the potential to reduce their risk for fracture and increase bone density at all sites, even the most difficult to treat, such as the hip and wrist.
The study showed that over 18 months of treatment, the abaloparatide-SC-treated group had the greatest reduction in the rate of new vertebral fractures as shown on x-rays.
Compared with the placebo group’s new vertebral fracture rate of 4.2%, women who were treated with abaloparatide-SC had a new vertebral fracture rate of about 0.58% — representing an 86% reduction in the rate of broken bones at the spine, according to Dr. Miller.
He also said this reduction seen in the abaloparatide-SC treated group could be the largest reduction ever demonstrated in the vertebral fracture rate for any potential therapeutic drug being researched for the treatment of postmenopausal osteoporosis.
For nonvertebral fractures, which included the hip, wrist and femoral neck, Dr. Miller said the abaloparatide-SC treatment had a statistically significant 43% fracture-rate reduction compared with placebo. The rate of vertebral and nonvertebral fractures combined fell by 45% in the abaloparatide-treated group compared with placebo.
In addition, the time to the first nonvertebral fracture was significantly delayed for women receiving abaloparatide-SC than for those who received placebo.