RANKL inhibition halts lesion progression and promotes bone remineralization in mice with fibrous dysplasia

Fibrous dysplasia (FD) is a rare bone disease caused by GNAS mutation in skeletal stem cells, typically originating from and worsening in childhood. Till now, no cure for FD exists despite the well-recognized etiology. Studies have demonstrated that osteoclastogenesis hyperactivity is caused by elevated RANKL expression, making RANKL inhibition a potential therapy. Although a human monoclonal anti-RANKL antibody, denosumab, has been used in FD patients, the effects and mechanisms of RANKL inhibition for FD treatment require assessment. Denosumab is expensive and can only be injected. Therefore, formulating an oral-administered, cost-effective medicine is encouraged. In the current study, we evaluated the effects of a small-molecule RANKL inhibitor, A52676293, on a transgenic FD mouse model. A52676293 effectively suppressed osteoclastogenesis and halted FD progression. The pre-existing bone defects were primarily replaced by newly formed mineralized bone after two weeks of A52676293 administration. The potent RANKL inhibitory effect and easier route of delivery make A52676293 a promising target therapy of FD. Results from our study suggested that RANKL inhibition is effective in halting FD progression and promoting bone remineralization, which could benefit the patients with early onset of FD.

Automated summary

Fibrous dysplasia (FD) is a rare bone disease caused by GNAS mutation, and there is currently no cure available. Inhibition of RANKL expression has been identified as a potential therapy for FD. This study evaluated the effects of a small-molecule RANKL inhibitor (A52676293) on a transgenic FD mouse model, and found that it effectively suppressed osteoclastogenesis and halted FD progression. The results suggest that RANKL inhibition could be an effective treatment for FD.