Structure-Based Discovery of Receptor Activator of Nuclear Factor-κB Ligand (RANKL)-Induced Osteoclastogenesis Inhibitors

Abstract

Receptor activator of nuclear factor-κB ligand (RANKL) has been actively pursued as a therapeutic target for osteoporosis, given that RANKL is the master mediator of bone resorption as it promotes osteoclast differentiation, activity and survival. We employed a structure-based virtual screening approach comprising two stages of experimental evaluation and identified 11 commercially available compounds that displayed dose-dependent inhibition of osteoclastogenesis. Their inhibitory effects were quantified through TRAP activity at the low micromolar range (IC50 < 5 μΜ), but more importantly, 3 compounds displayed very low toxicity (LC50 > 100 μΜ). We also assessed the potential of an N-(1-aryl-1H-indol-5-yl)aryl-sulfonamide scaffold that was based on the structure of a hit compound, through synthesis of 30 derivatives. Their evaluation revealed 4 additional hits that inhibited osteoclastogenesis at low micromolar concentrations; however, cellular toxicity concerns preclude their further development. Taken together with the structure–activity relationships provided by the hit compounds, our study revealed potent inhibitors of RANKL-induced osteoclastogenesis of high therapeutic index, which bear diverse scaffolds that can be employed in hit-to-lead optimization for the development of therapeutics against osteolytic diseases.

Molecular and Cellular Mechanisms of Osteoporosis

“…s Selectively inhibit the enzyme farnesyl pyrophosphate synthase in osteoclasts, leading to their apoptosis [131] Gastrointestinal adverse effects [132] Atypical fractures [133] Not recommended for patients with low creatinine clearance [134] rs Inhibits the binding of RANKL to its receptor, inhibits osteoclastogenesis [135,136] Duration of denosumab administration increases the rate of bone resorption after treatment cessation [137] Binds the PTH receptor (PTH1R), activates protein kinase A, enhances the formation of osteoblasts [138,139] Decreases bone mineral density after withdrawal [140] Slow down the binding of sclerostin to LRP5/6, reduce blocking of the osteogenic Wnt pathway, increases the number of osteoblasts [141] Increase the risk of cardiovascular events [142]…”

“…Selectively inhibit the enzyme farnesyl pyrophosphate synthase in osteoclasts, leading to their apoptosis [131] Gastrointestinal adverse effects [132] Atypical fractures [133] Not recommended for patients with low creatinine clearance [134] RANKL inhibitors Inhibits the binding of RANKL to its receptor, inhibits osteoclastogenesis [135,136] Duration of denosumab administration increases the rate of bone resorption after treatment cessation [137] PTH analogues Binds the PTH receptor (PTH1R), activates protein kinase A, enhances the formation of osteoblasts [138,139] Decreases bone mineral density after withdrawal [140] Antisclerostin antibodies Slow down the binding of sclerostin to LRP5/6, reduce blocking of the osteogenic Wnt pathway, increases the number of osteoblasts [141] Increase the risk of cardiovascular events [142] Hormone therapy Binds to estrogen receptors [143] Used for postmenopausal osteoporosis [143] Calcitonin Inhibit osteoclast activity [144] Used for postmenopausal osteoporosis, low efficiency [144,145] Targeting STING Activation of STING/IFN-β [146] It is a potential target Targeting semaphorins Modulate plexin receptors, enhanced bone formation, and reduced bone resorption [147] It is a potential target…”

“…The main preparation of the group of RANKL inhibitors approved and widely used for the treatment of postmenopausal osteoporosis is denosumab, a monoclonal antibody that binds to RANKL and prevents its binding to the RANK receptor [135]. Since RANKL is a major mediator of bone resorption that initiates a signaling cascade essential for differentiation, activation, and survival of osteoclasts.…”