title: Skeletal and extraskeletal actions of denosumab.
abstract: Osteoclasts and osteoblasts define skeletal mass, structure and strength through their respective actions in resorbing and forming bone. This remodeling process is orchestrated by the actions of hormones and growth factors, which regulate a cytokine system comprising the receptor activator of nuclear factor κB ligand (RANKL), its receptor RANK and the soluble decoy receptor osteoprotegerin (OPG). Bone resorption depends on RANKL, which determines osteoclast formation, activity and survival. Importantly, cells of the osteoblastic lineage mainly provide RANKL and therefore, are central in the regulation of osteoclast functions. Catabolic effects of RANKL are inhibited by OPG, a TNF receptor family member that binds RANKL, thereby preventing the activation of its receptor RANK, which is expressed by osteoclast precursors. Because this cytokine network is pivotal for the regulation of bone mass in health and diseases, including osteoporosis, rheumatoid arthritis and malignant bone conditions, it has been successfully used for the generation of a targeted therapy to block osteoclast actions. The clinical approval of denosumab, a fully monoclonal antibody against RANKL, provides a novel option to treat bone diseases with a potent, targeted and reversible inhibitor of bone resorption. Although RANKL is also expressed by endothelial cells, T lymphocytes, synovial fibroblasts and various tumor cells, no meaningful clinical extraskeletal effects have been reported after administration of denosumab. This article summarizes the molecular and cellular basis of the RANKL/RANK/OPG system and presents preclinical and clinical studies on the skeletal actions of denosumab.
authors.affiliation: Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine III, Technical University Medical Center, Fetscherstr. 74, 01307, Dresden, Germany. kathrin.sinningen@uniklinikum-dresden.de
authors.forename: Kathrin
authors.initials: K
authors.lastname: Sinningen
authors.forename: Elena
authors.initials: E
authors.lastname: Tsourdi
authors.forename: Martina
authors.initials: M
authors.lastname: Rauner
authors.forename: Tilman D
authors.initials: TD
authors.lastname: Rachner
authors.forename: Christine
authors.initials: C
authors.lastname: Hamann
authors.forename: Lorenz C
authors.initials: LC
authors.lastname: Hofbauer
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology* / Q000627:therapeutic use; D001842:Bone and Bones / Q000187:drug effects* / Q000502:physiology; D000069448:Denosumab; D006801:Humans; D007249:Inflammation / Q000188:drug therapy; D009369:Neoplasms / Q000188:drug therapy; D010024:Osteoporosis / Q000188:drug therapy; D053245:RANK Ligand / Q000037:antagonists & inhibitors*; D061205:Vascular Calcification / Q000188:drug therapy
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D053245:RANK Ligand; D000069448:Denosumab