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IOF World Congress Abstracts Strontium ranelate may stimulate formation of new bone Strontium ranelate, a promising new osteoporosis therapeutic, represents the first osteoporosis treatment agent to stimulate the formation of new bone as well as preventing loss of existing bone, according to researchers presenting at the IOF World Congress on Osteoporosis in Lisbon. Unlike existing osteoporosis therapies, which are designed to limit the loss of existing bone (so-called antiresorptive agents), strontium ranelate appears to also promote the formation of new bone (known as anabolic effect) and thus is doubly effective in increasing bone strength and density. The results of four major randomized, double-blind, placebo-controlled long-term studies were presented during a Servier-sponsored satellite symposium held in conjunction with the IOF World Congress on Osteoporosis, during the satellite symposium. STRATOS (STRontium Administration for Treatment of Osteoporosis) and PREVOS (PREVention of Osteoporosis Study) were two-year studies carried out to assess the minimum active doses of strontium ranelate required for the treatment and prevention of bone loss in postmenopausal women. STRATOS enrolled 353 postmenopausal women with at least one previous vertebral fracture and lumbar bone mineral density (BMD) T-score < -2.4 who were randomized for treatment over two years with placebo or strontium ranelate. All patients also received daily supplements of calcium and vitamin D. In the PREVOS trial, 160 healthy early postmenopausal women were randomized for treatment with placebo or strontium ranelate (0.125, 0.5 or 1 g/day) for one year, in addition to daily calcium supplements. Following final analysis of STRATOS and PREVOS, investigators Dr. Pierre J. Meunier, Department of Rheumatology and Bone Diseases, Edouard Herriot Hospital, Lyon, France and Dr. Jean-Yves Reginster, Bone and Cartilage Metabolism Unit, University of Liege, Belgium, reported that the dose of 2 g/day strontium ranelate provided the best efficacy-safety ratio for the curative treatment of postmenopausal osteoporosis, while a dose of 1 g/day was optimum for the prevention of bone loss in early postmenopausal women. "Treatment with strontium ranelate is well tolerated," says Meunier. "It is a very promising treatment of postmenopausal osteoporosis." The same investigators also announced preliminary results from the ongoing five-year TROPOS (TReatment Of Peripheral Osteoporosis) and SOTI (Spinal Osteoporosis Therapeutic Intervention) trials. These two multinational, prospective, randomized, double-blind, placebo-controlled studies are evaluating the therapeutic efficacy of strontium ranelate at a dose of 2 g/day in the treatment of severe osteoporosis in postmenopausal women. SOTI is assessing the drug's ability to reduce new vertebral fractures in women with low BMD and a history of at least one vertebral fracture, and TROPOS is assessing its effects on reducing the incidence of peripheral fractures. The results of this study show a 41% reduction in relative risk of experiencing a first new vertebral fracture. These results have also been confirmed when combining both diagnostic methods for incident vertebral fracture. This drug is a new orally effective and safe treatment of vertebral osteoporosis with a unique mechanism of action. The first part of this ongoing phase III program is expected to end in late 2002. The human skeleton is a highly specialized and dynamic organ that is continuously regenerated through the processes of modeling and remodeling. Two specialized classes of cells are implicated in the process of bone remodeling. Osteoclasts, or bone-eroding cells, invade the bone's surface and create small cavities that are subsequently filled in by osteoblasts, or bone-forming cells. During childhood and adolescence, new bone is formed more quickly than old bone is resorbed, causing bones to become larger, heavier and denser (the process of modeling). This pace normally continues until the mid-20s, when peak bone mass is typically obtained. When the skeleton has reached maturity, regeneration continues with new bone replacing old (the process of remodeling), such that the entire adult skeleton is renewed approximately every ten years. After age 30, however, the pace of bone resorption begins to overtake that of new bone formation, with the result that in women and men over age 50, approximately 1-3% of bone mass is lost each year. Osteoporosis develops when bone resorption leads to extremely low bone mass and skeletal fragility, increasing the patient's susceptibility to fractures, especially of the hip, spine and wrist. Existing treatments for osteoporosis, including estrogens, bisphosphonates and calcitonin, act by decreasing bone resorption and thus preventing further bone loss. Most, however, are incapable of promoting the formation of new bones. Anabolic agents are a newer type of osteoporosis therapeutic designed to restore the balance between bone-forming osteoblasts and bone-eroding osteoclasts, now believed to lie at the root of osteoporosis. While this represents a highly attractive theoretical approach, to date few true anabolic agents are available.
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