Anti-resorptive therapies for osteoporosis

The treatment of osteoporosis is largely based around the use of agents that inhibit bone resorption by osteoclasts. The main classes of anti-resorptives currently in use are calcium, bisphosphonates, estrogen, selective estrogen receptor modulators (SERMs) and calcitonin. Novel agents in development are: inhibitors of the osteoclast enzyme, cathepsin K; and a monoclonal antibody against receptor activator of NFkappaB-ligand (RANKL), a factor made by osteoblasts which stimulates osteoclast development. Potent anti-resorptive agents decrease numbers of vertebral fractures by about 50%, and non-vertebral fractures by only 25%. Whether the newer agents can improve on this remains to be seen, though it is possible that anabolic agents which increase bone mass more substantially will be needed to achieve greater reductions in all fracture numbers.