Denosumab failure associated with escape from suppression of bone resorption

Molecular Signaling Pathways and MicroRNAs in Bone Remodeling: A Narrative Review

Bone remodeling is an intricate process executed throughout one's whole life via the cross-talk of several cellular events, progenitor cells and signaling pathways. It is an imperative mechanism for regaining bone loss, recovering damaged tissue and repairing fractures. To achieve this, molecular signaling pathways play a central role in regulating pathological and causal mechanisms in different diseases. Similarly, microRNAs (miRNAs) have shown promising results in disease management by mediating mRNA targeted gene expression and post-transcriptional gene function. However, the role and relevance of these miRNAs in signaling processes, which regulate the delicate balance between bone formation and bone resorption, are unclear. This review aims to summarize current knowledge of bone remodeling from two perspectives: firstly, we outline the modus operandi of five major molecular signaling pathways, i.e.,the receptor activator of nuclear factor kappa-B (RANK)-osteoprotegrin (OPG) and RANK ligand (RANK-OPG-RANKL), macrophage colony-stimulating factor (M-CSF), Wnt/β-catenin, Jagged/Notch and bone morphogenetic protein (BMP) pathways in regards to bone cell formation and function; and secondly, the miRNAs that participate in these pathways are introduced. Probing the miRNA-mediated regulation of these pathways may help in preparing the foundation for developing targeted strategies in bone remodeling, repair and regeneration.

Risk factors for poor response to denosumab treatment in Japanese postmenopausal women with osteoporosis

INTRODUCTION

Denosumab has been reported to increase bone mineral density (BMD) and suppress fractures, but poor responders are not uncommon. This study aimed to identify risk factors for poor response to denosumab treatment. This is the first study to explore risk factors for poor response to denosumab.

MATERIALS AND METHODS

This retrospective observational study investigated 227 Japanese postmenopausal women who received denosumab with monitoring of BMD by dual-energy X-ray absorptiometry at 6-month intervals. Risk factors were identified using Cox's proportional hazard modeling. Poor responders were defined as not exceeding the least significant change of BMD from baseline for 3 years.

RESULTS

Mean relative change from baseline for 3 years in lumbar spine (LS)-BMD, femoral neck (FN)-BMD, and total hip (TH)-BMD were 12.6%, 6.8%, and 6.1%, respectively. Numbers of poor responders were 10 in LS-BMD, 47 in FN-BMD, 38 in TH-BMD. Risk factors for poor response were concomitant glucocorticoid use for LS-BMD, low body mass index or initiation at higher BMD for FN-BMD, and pretreatment with bisphosphonates or initiation at higher BMD for TH-BMD.

CONCLUSION

Risk factors for insufficient denosumab effect differed between BMD measurement sites. These results should be taken into consideration when selecting denosumab in clinical practice.

When and how to stop denosumab therapy in a patient with osteoporosis

Denosumab is a human monoclonal antibody that competitively inhibits the receptor activator of nuclear factor kappa B ligand which regulates osteoclast activity. It is an effective treatment for osteoporosis with a reduced cumulative rate of vertebral fractures, hip and nonvertebral fractures as well as an increase in bone mineral density. The benefits have been shown to be maintained when treatment is continued up to and likely after 10 years of therapy, but the effects are lost rapidly if treatment is discontinued abruptly. There are rare medical indications for discontinuation of treatment. Discontinuation of denosumab is often driven by concern about complications such as osteonecrosis of the jaw, atypical femoral fractures and hypocalcaemia, which remain rare events. Further studies are required to confirm safety and efficacy beyond 10 years of treatment, but it is likely that patients will have ongoing benefits from therapy beyond this. We aim to present a personal perspective of why and how denosumab should be discontinued in patients with osteoporosis.