[New anti-osteoporotic drugs under development].

Cathepsin K is a cysteine protease indispensable for collagen degradation and bone resorption by osteoclasts. Cathepsin K inhibitors suppress bone resorption while keeping osteoclasts alive, which is believed to maintain osteoblast-stimulating activity of osteoclasts. Sclerostin is an osteocyte-derived soluble factor that inhibits the Wnt canonical pathway. Neutralizing antibody against sclerostin strongly but transiently stimulates bone formation. This review will discuss unique actions on bone metabolism and clinical efficacy of these two anti-osteoporotic drugs under development.