Inhibitors of sclerostin: emerging concepts.

PURPOSE OF REVIEW: Recent data suggest that inhibitors of sclerostin, an osteocyte-produced Wnt signaling pathway antagonist, can stimulate bone formation. This review provides rationale and summarizes recent evidence supporting this novel approach to skeletal anabolism. RECENT FINDINGS: Data from numerous preclinical models in rodents and monkeys consistently demonstrate that antisclerostin monoclonal antibody (Scl-Ab) treatment leads to improvements in bone mass and strength, as well as enhanced fracture repair. Delivery of Scl-Ab therapy either subcutaneously or intravenously in phase 1 and 2 human clinical trials demonstrates short-term anabolic responses in excess of those seen with teriparatide, the only currently available anabolic skeletal agent. Gains have been primarily at central (spine and hips) versus peripheral (wrist) sites. Strikingly, Scl-Ab treatment appears to both stimulate bone formation and inhibit bone resorption in humans. If proven, Scl-Ab would be the first pharmacologic agent with such dual properties. Data on fractures are not yet available. SUMMARY: Scl-Ab therapy represents a novel pharmacologic approach to skeletal anabolism. Although many questions remain before Scl-Ab treatment can be introduced into clinical practice, phase 3 human clinical trials are currently underway and could provide the necessary data to bring this exciting class of skeletal anabolic agents to patient care.