VIENNA — Strontium ranelate reduced the risk of new vertebral fractures by 41% over 3 years in a very-high-risk population of osteoporotic women with at least two prevalent vertebral fractures at baseline, Sergio Ortolani, M.D., reported at the annual European congress of rheumatology.
That's roughly as robust a relative risk reduction as seen in much lower-risk postmenopausal osteoporotic women with no previous vertebral fractures, noted Dr. Ortolani of the Center for Metabolic Bone Disease, Milan.
“It appears we have a new first-line treatment for postmenopausal osteoporosis,” he declared.
Dr. Ortolani presented a prespecified subgroup analysis drawn from two large phase-III multinational placebo-controlled randomized trials of strontium ranelate for the reduction of fracture risk in osteoporotic postmenopausal women. The Spinal Osteoporosis Therapeutic Intervention (SOTI) involved 1,649 women randomized to 2 g/day of oral strontium ranelate or placebo, while the Treatment of Peripheral Osteoporosis Study (TROPOS) included 5,091 women. Both Servier Laboratories-sponsored trials will run for 5 years, although the 3-year primary outcome data have been published.
Among 2,605 combined study participants without prior vertebral fractures at baseline, the 3-year incidence of new vertebral fractures was 14.4% with placebo and 7.5% with strontium ranelate, for a 48% relative risk reduction. Among the 734 participants with two or more prevalent vertebral fractures at enrollment, the absolute 3-year new vertebral fracture rates were far higher—42.7% in the placebo group, compared with 28.5% in those taking strontium ranelate—but the relative risk reduction conferred by strontium ranelate remained highly robust at 41%.
Strontium ranelate has a unique mode of action. It simultaneously increases bone formation and reduces bone resorption. The antiresorptive effect is less potent than with bisphosphonates; however, in combination with the simultaneous bone-forming effect, strontium ranelate becomes a highly effective antiosteoporosis medication, Dr. Ortolani said at the meeting sponsored by the European League Against Rheumatism.
The drug's chief adverse effect is diarrhea, which was limited to the first few months of therapy in the clinical trials. When the data from TROPOS and SOTI were pooled, there was a small but statistically significant increase in deep venous thrombosis in strontium ranelate-treated patients, but no increase in strokes or cardiovascular events. “The absolute incidence of DVT is much less than with raloxifene or estrogen replacement therapy,” Dr. Ortolani added.
Strontium ranelate is approved in several European countries and soon will be marketed throughout Europe. The Food and Drug Administration has requested that Servier conduct a U.S. clinical trial before filing for marketing approval in the United States, Dr. Ortolani said.