Do RANKL inhibitors (denosumab) affect inflammation and immunity?

Synthesis and Antiosteoporotic Characterization of Diselenyl Maleimides: Discovery of a Potent Agent for the Treatment of Osteoporosis by Targeting RANKL

To discover new osteoclast-targeting antiosteoporosis agents, we identified forty-six diselenyl maleimides, which were efficiently prepared using a novel, simple, and metal-free method at room temperature in a short reaction time. Among them, 3k showed the most marked inhibition of osteoclast differentiation with an IC50 value of 0.36 ± 0.03 μM. Moreover, 3k significantly suppressed RANKL-induced osteoclast formation, bone resorption, and osteoclast-specific genes expression in vitro. Mechanistic studies revealed that 3k remarkably blocked the RANKL-induced mitogen-activated protein kinase (MAPK) and NF-κB signaling pathways. In ovariectomized mice, intragastric administration of 3k significantly alleviated bone loss, exhibiting an effect similar to that of alendronate. Surface plasmon resonance assay and microscale thermophoresis assay results suggested that RANKL might be a potential molecular target for 3k. Collectively, the findings presented above provided a novel candidate for further development of bone antiresorptive drugs that target RANKL.

Synergistic effect between denosumab and immune checkpoint inhibitors (ICI)? A retrospective study of 268 patients with ICI and bone metastases

Background

Bone metastasis is a significant concern in advanced solid tumors, contributing to diminished patient survival and quality of life due to skeletal-related events (SREs). Denosumab (DMAB), a monoclonal antibody targeting the receptor activator of nuclear factor kappa-B ligand (RANKL), is used to prevent SREs in such cases. The RANK/RANKL axis, crucial in immunological processes, has garnered attention, especially with the expanding use of immune checkpoint inhibitors (ICI) in modern oncology.

Objective

Our study aims to explore the potential synergistic antitumor effects of combining immunotherapy with denosumab, as suggested by anecdotal evidence, small cohort studies, and preclinical research.

Methods

We conducted a retrospective analysis using the IMMUCARE database, encompassing patients receiving ICI treatment since 2014 and diagnosed with bone metastases. We examined overall survival (OS), progression-free survival (PFS) and switch of treatment line based on denosumab usage. Patients were stratified into groups: without denosumab, ICI followed by denosumab, and denosumab followed by ICI. Survival curves and multivariate Cox regression analyses were performed.

Results

Among the 268 patients with bone metastases, 154 received treatment with ICI alone, while 114 received ICI in combination with denosumab at some point during their oncological history. No significant differences were observed in overall survival (OS) or progression-free survival (PFS) between patients receiving ICI monotherapy and those receiving ICI with denosumab (p = 0.29 and p = 0.79, respectively). However, upon analyzing patients who received denosumab following ICI initiation (17 patients), a notable difference emerged. The group receiving ICI followed by denosumab exhibited a significant advantage compared to those without denosumab (154 patients) or those receiving denosumab before ICI initiation (72 patients) (p = 0.022).

Conclusion

This retrospective investigation supports the notion of potential benefits associated with sequential administration of ICI and denosumab, although statistical significance was not achieved. Future studies, including prospective trials or updated retrospective analyses, focusing on cancers treated with first-line immunotherapy, could provide further insights into this therapeutic approach.

The use of denosumab in osteoporosis - an update on efficacy and drug safety

INTRODUCTION

Denosumab (Prolia) is a fully human monoclonal antibody against the receptor activator of the nuclear factor kappaB ligand. It is a potent antiresorptive agent that reduces osteoclastogenesis.

AREAS COVERED

Denosumab has been shown to improve bone mineral density and reduce the incidence of new fractures in postmenopausal women and men. It is also used in the treatment of glucocorticoid-induced osteoporosis, as well as for the prevention of bone loss and reduction of fracture risk in men receiving androgen deprivation therapy for non-metastatic prostate cancer and women receiving adjuvant aromatase inhibitor therapy for breast cancer. Initial safety concerns included infections, cancer, skin reactions, cardiovascular disease, hypocalcemia, osteonecrosis of the jaw, and atypical femur fractures; however, further study and experience provide reassurance on these issues. Anecdotal reports have raised concerns about an increased risk of multiple vertebral fractures following discontinuation of denosumab.

EXPERT OPINION

Although bisphosphonates are often selected as initial therapy for osteoporosis, denosumab may be an appropriate initial therapy in patients at high risk for fracture, including older patients who have difficulty with the dosing requirements of oral bisphosphonates, as well as patients who are intolerant of, unresponsive to, or have contraindications to other therapies. Additional data is needed to address questions regarding treatment duration and discontinuation.

Sophoraflavanone G Inhibits RANKL-Induced Osteoclastogenesis via MAPK/NF-κB Signaling Pathway

Osteoporosis is a common chronic bone metabolism disorder characterized by decreased bone mass and reduced bone density in the bone tissue. Osteoporosis can lead to increased fragility of the skeleton, making it prone to brittle fractures. Osteoclasts are macrophage-like cells derived from hematopoietic stem cells, and their excessive activity in bone resorption leads to lower bone formation than absorption during bone remodeling, which is one of the important factors inducing osteoporosis. Therefore, how to inhibit osteoclast formation and reducing bone loss is an important direction for treating osteoporosis. Sophoraflavanone G, derived from Sophora flavescens Alt and Rhizoma Drynariae, is a flavonoid compound with various biological activities. However, there have been few studies on osteoporosis and osteoclasts so far. Therefore, we hypothesize that genistein G can inhibit osteoclast differentiation, alleviate bone loss phenomenon, and conduct in vitro and in vivo experiments for research and verification purposes.

Cancer risk in patients treated with denosumab compared with alendronate: A population-based cohort study

BACKGROUND

Antiresorptive treatment is currently used in millions of patients with osteoporosis and cancer worldwide. Early studies of denosumab suggested a small signal in ovarian cancer incidence and emerging data suggest that denosumab stimulates germ cell proliferation in the gonads. This study aims to determine the association between the use of denosumab and the risk of reproductive cancers compared with the use of alendronate.

RESEARCH DESIGN AND METHODS

Using a cohort study design, we used the Danish nationwide registries to identify a population of subjects ≥50 years of age during 2010-2017 who started denosumab after being on alendronate treatment for at least six months. The cohort was matched 1:2 with patients who had been treated with alendronate alone for at least six months. The risk of reproductive cancers and the risk difference between groups were estimated using the Longitudinal Targeted Maximum Likelihood Estimation (L-TMLE) method.

RESULTS

We identified 6054 Danish individuals who underwent treatment with denosumab. These individuals were matched with 12,108 receiving alendronate. The absolute risk of reproductive cancer was 1.05 % (95 % CI 0.75-1.34) after three years for denosumab users and was not different 0.03 % (-0.34-0.39) than for alendronate users. In supplemental analyses, there was no increased risk of non-reproductive cancers associated with the use of denosumab (risk difference of 0.54 % (-0.41-1.19). Analysis comparing denosumab users with the general population gave similar results.

CONCLUSION

There was no difference in the risk of cancer following treatment with denosumab compared to treatment with alendronate assessed after a short follow-up of 3 years.

Clinical Impact on Dental Implant Survival in Patients Taking Antiresorptive Medications: A Systematic Review and Meta-Analysis

Dental implants are a predictable option to replace missing teeth. Patients on antiresorptive medications used to treat disorders associated with bone resorption may need dental implants to replace missing teeth. The data on implant failure in patients on antiresorptive medication requiring dental implants, is conflicting and limited. This systematic review aims to investigate if antiresorptive medications have any clinical impact on dental implant survival. Electronic databases were searched until May 2020. The focus question (PICOS): Participants: humans, Interventions: implant placement surgery in patients on antiresorptive medication, Comparisons: patients on antiresorptive medication vs control (patients not on antiresorptive medication), Outcomes: implant survival, and Study design: clinical studies. The protocol of this systematic review was registered in PROSPERO (CRD42020209083). Fourteen nonrandomized studies were selected for data extraction and risk of bias assessment using the ROBINS-1 tool. Only studies with a control were included for the meta-analysis, 8 articles were included in the meta-analysis using implant-level data, and 5 articles were included in the meta-analysis using patient-level data. There was no statistical significance between the 2 groups at the patient level based on 265 patients. However, there was a statistically significant difference at the implant level based on 2697 implants. Therefore, antiresorptive medications, mainly bisphosphonates (BPs), may significantly contribute to implant failure. Antiresorptive medications, especially BPs may reduce implant survival and impair the osseointegration of dental implants. Failed implants in patients on BPs may not lead to osteonecrosis and may be replaced with success.

Biologic Antiresorptive: Denosumab

Background

Osteoporosis is an age-related common bone disorder characterized by low bone mineral density and increased fragility fracture risk. Various Antiresorptive medications are being used to target osteoclast mediated bone resorption to prevent bone loss and reduce fracture risk.

About Denosumab

Denosumab is a novel biological antiresorptive drug that belongs to the class of monoclonal antibodies. It binds to and inhibits the cytokine receptor activator of nuclear factor kappa-B ligand (RANKL), which is requisite for osteoclast differentiation, function and survival.

Effectiveness

Denosumab has been shown to be a potent and effective therapy for osteoporosis, with clinical trial data demonstrating significant improvement in bone mineral density (BMD) and reductions in fracture risk at various skeletal sites for more than 10 years of treatment.

Safety Profile

Denosumab has a favourable benefit/risk profile, with low rates of complications such as infection, atypical femoral fracture and osteonecrosis of the jawbone.

Challenges

However, denosumab treatment requires continuous administration, as discontinuation leads to rapid bone mineral loss and increased risk of multiple vertebral fractures due to rebound of bone turnover. Therefore, modification to another anti-osteoporosis drug therapy after denosumab discontinuation is required to maintain bone health.

Conclusion

Denosumab is a promising biological antiresorptive therapy for osteoporosis that offers high efficacy and safety, but also poses challenges for long-term management.

RANKL/RANK is required for cytokine-induced beta cell death; osteoprotegerin, a RANKL inhibitor, reverses rodent type 1 diabetes

Treatment for type 1 diabetes (T1D) requires stimulation of functional β cell regeneration and survival under stress. Previously, we showed that inhibition of the RANKL/RANK [receptor activator of nuclear factor kappa Β (NF-κB) ligand] pathway, by osteoprotegerin and the anti-osteoporotic drug denosumab, induces rodent and human β cell proliferation. We demonstrate that the RANK pathway mediates cytokine-induced rodent and human β cell death through RANK-TRAF6 interaction and induction of NF-κB activation. Osteoprotegerin and denosumab protected β cells against this cytotoxicity. In human immune cells, osteoprotegerin and denosumab reduce proinflammatory cytokines in activated T-cells by inhibiting RANKL-induced activation of monocytes. In vivo, osteoprotegerin reversed recent-onset T1D in nonobese diabetic/Ltj mice, reduced insulitis, improved glucose homeostasis, and increased plasma insulin, β cell proliferation, and mass in these mice. Serum from T1D subjects induced human β cell death and dysfunction, but not α cell death. Osteoprotegerin and denosumab reduced T1D serum-induced β cell cytotoxicity and dysfunction. Inhibiting RANKL/RANK could have therapeutic potential.

Phase I, Randomized, Placebo-Controlled, Dose-Escalation Study of GB223, a Fully-Humanized Monoclonal Antibody to RANKL, in Healthy Chinese Adults

BACKGROUND

GB223 is a novel, fully-humanized monoclonal antibody against the receptor activator of nuclear factor-kappa B ligand (RANKL). In this phase I study, the safety, tolerability, pharmacokinetics, pharmacodynamics, and immunogenicity of GB223 were investigated.

PATIENTS AND METHODS

This was a randomized, double-blinded, placebo-controlled, single-dose escalation study conducted in 44 healthy Chinese adults. Participants were randomly assigned to receive a single subcutaneous injection dose of 7, 21, 63, 119, or 140 mg of GB223 (n = 34) or placebo (n = 10) and were followed up for 140-252 days.

RESULTS

The results of noncompartmental analysis showed that GB223 was slowly absorbed after dosing, with a time to reach maximum concentration (Tmax) ranging from 5 to 11 days. Serum GB223 concentrations decreased slowly, with a long half-life ranging from 7.91 to 19.60 days. A two-compartment Michaelis-Menten model was found to best describe the pharmacokinetics of GB223, and the absorption rate of GB223 differed between males (0.0146 h-1) and females (0.0081 h-1). Serum C-terminal telopeptide of type I collagen decreased significantly postdose, and the inhibition lasted 42-168 days. No deaths or drug-related serious adverse events occurred. The most frequent adverse events were blood parathyroid hormone increased (94.1%), blood phosphorus decreased (67.6%) and blood calcium decreased (58.8%). In the GB223 group, 44.1% (15/34) of subjects were antidrug antibody positive after dosing.

CONCLUSION

In this study, we demonstrated for the first time that a single subcutaneous injection of GB223, from 7 to 140 mg, is safe and well tolerated in healthy Chinese subjects. GB223 has a nonlinear pharmacokinetic profile, and sex was a potential covariate that may affect the absorption rate of GB223.

CLINICAL TRIAL REGISTRATION

NCT04178044 and ChiCTR1800020338.

Current therapies and future prospective for locally aggressive mesenchymal tumors

Locally aggressive mesenchymal tumors comprise a heterogeneous group of soft tissue and bone tumors with intermediate histology, incompletely understood biology, and highly variable natural history. Despite having a limited to absent ability to metastasize and excellent survival prognosis, locally aggressive mesenchymal tumors can be symptomatic, require prolonged and repeat treatments including surgery and chemotherapy, and can severely impact patients' quality of life. The management of locally aggressive tumors has evolved over the years with a focus on minimizing morbid treatments. Extensive oncologic surgeries and radiation are pillars of care for high grade sarcomas, however, play a more limited role in management of locally aggressive mesenchymal tumors, due to propensity for local recurrence despite resection, and the risk of transformation to a higher-grade entity following radiation. Patients should ideally be evaluated in specialized sarcoma centers that can coordinate complex multimodal decision-making, taking into consideration the individual patient's clinical presentation and history, as well as any available prognostic factors into customizing therapy. In this review, we aim to discuss the biology, clinical management, and future treatment frontiers for three representative locally aggressive mesenchymal tumors: desmoid-type fibromatosis (DF), tenosynovial giant cell tumor (TSGCT) and giant cell tumor of bone (GCTB). These entities challenge clinicians with their unpredictable behavior and responses to treatment, and still lack a well-defined standard of care despite recent progress with newly approved or promising experimental drugs.

Influence of antiresorptive/antiangiogenic therapy on the extension of experimentally induced peri-implantitis lesions

OBJECTIVES

To investigate the extension of experimentally induced peri-implantitis lesions under various antiresorptive and antiangiogenic medications.

MATERIAL AND METHODS

Fourty-eight albino rats had randomly received the following medications (dual application, n = 8 each): (1) amino-bisphosphonate (zoledronate) (Zo), (2) RANKL inhibitor (denosumab) (De), (3) antiangiogenic (bevacizumab) (Be), (4) Zo+Be, (5) De+Be, or (6) no medication (Co). Ligature- and lipopolysaccharide-induced peri-implantitis lesions were established at 2 maxillary implants over a period of 16 weeks. Histological (e.g., apical extension and surface area of the inflammatory cell infiltrate-aICT, ICT; defect length; defect width; CD68 positive cells) and bone micromorphometric (μCT) outcomes were assessed. The animal was defined as a statistical unit.

RESULTS

A total of n = 38 animals (Zo = 6, De = 6, Be = 8, Zo + Be = 6, De + Be = 5, Co = 7) were analyzed. ICT's were commonly marked by a positive CD68 antigen reactivity. Comparable median aICT (lowest-Zo: 0.53 mm; highest-Be: 1.22 mm), ICT (lowest-De + Be: 0.00 mm2; highest-Co: 0.49 mm2), defect length (lowest-Zo: 0.90 mm; highest-Co: 1.93 mm) and defect width (lowest-De+Be: 1.27 mm; highest-Be: 1.80 mm) values were noted in all test and control groups. Within an inner (diameter: 0.8 mm) cylindric volume of interest, the bone microstructure did not significantly differ between groups.

CONCLUSIONS

The present analysis did not reveal any marked effects of various antiresorptive/ antiangiogenic medications on the extension of experimentally induced peri-implantitis lesions.

CLINICAL RELEVANCE

The extension of peri-implantitis lesions may not be facilitated by the antiresorptive and antiangiogenic medications investigated.

Efficacy and safety of COVID-19 vaccines for patients with spinal tumors receiving denosumab treatment: An initial real-clinical experience study

Background

Even if COVID-19 vaccine has gradually been adopted in the world, information of side effects and crosstalk in patients with spinal tumors is absent due to the exclusion from clinical research. In this research, we aimed to investigate the efficacy and safety for the patients with spinal tumors treated by denosumab.

Methods

In this retrospective research, 400 patients under treatment of denosumab against spinal tumors in real-clinical experience were grouped into two cohorts according to the treatment of COVID-19 vaccine. And linked hospital data, serum samples and unsolicited related adverse events had been collected from January 22nd 2021 to June 1st 2021 respectively.

Results

233 patients of all participants who received regular treatment of denosumab were vaccinated by mRNA or inactivated vaccine. Patients of metastatic disease and primary osseous spinal tumor showed similar distribution in both two groups. Over the study period, within 176 patients tested the status of serologic response of vaccine, 88(81.48%) and 41(87.23%) individuals injected one or two inactivated vaccines had effective antibody against SARS-CoV-2 infections. As 21 patients (85.71%) treated by mRNA vaccine did. Considering of the safety of vaccine, most common systemic adverse events were nausea or vomiting (45 events vs 23events). Interestingly, fewer participants in the vaccine group were statistically recorded in local adverse events than in the placebo group (16 events vs 33 events).

Conclusions

Our initial real-clinical experience suggests that COVID-19 vaccines are likely safe and effective in in patients with spinal tumors receiving denosumab treatment.

Malignant Transformation of Giant Cell Tumour of Bone: A Review of Literature and the Experience of a Referral Centre

Giant cell tumour of bone (GCTB) is a benign, locally aggressive primary bone neoplasm that represents 5% of all bone tumours. The principal treatment approach is surgery. Although generally GCTB is considered only a locally aggressive disease, it can metastasise, and lung metastases occur in 1–9% of patients. To date, only the use of denosumab has been approved as medical treatment for GCTB. Even more rarely, GCTB undergoes sarcomatous transformation into a malignant tumour (4% of all GCTB), but history of this malignant transformation is unclear and unpredictable. Considering the rarity of the event, the data in the literature are few. In this review, we summarise published data of GCTB malignant transformation and we analyse three cases of malignant transformation of GCTB, evaluating histopathology, genetics, and radiological aspects. Despite the rarity of this event, we conclude that a strict follow up is recommended to detect early malignant transformation.

Identification of a binding site on soluble RANKL that can be targeted to inhibit soluble RANK-RANKL interactions and treat osteoporosis

One of the major challenges for discovering protein-protein interaction inhibitors is identifying selective and druggable binding sites at the protein surface. Here, we report an approach to identify a small molecular binding site to selectively inhibit the interaction of soluble RANKL and RANK for designing anti-osteoporosis drugs without undesirable immunosuppressive effects. Through molecular dynamic simulations, we discovered a binding site that allows a small molecule to selectively interrupt soluble RANKL-RANK interaction and without interfering with the membrane RANKL-RANK interaction. We describe a highly potent inhibitor, S3-15, and demonstrate its specificity to inhibit the soluble RANKL-RANK interaction with in vitro and in vivo studies. S3-15 exhibits anti-osteoporotic effects without causing immunosuppression. Through in silico and in vitro experiments we further confirm the binding model of S3-15 and soluble RANKL. This work might inspire structure-based drug discovery for targeting protein-protein interactions.

Mini Review Therapeutic Strategies Targeting for Biofilm and Bone Infections

Bone infection results in a complex inflammatory response and bone destruction. A broad spectrum of bacterial species has been involved for jaw osteomyelitis, hematogenous osteomyelitis, vertebral osteomyelitis or diabetes mellitus, such as Staphylococcus aureus (S. aureus), coagulase-negative Staphylococcus species, and aerobic gram-negative bacilli. S. aureus is the major pathogenic bacterium for osteomyelitis, which results in a complex inflammatory response and bone destruction. Although various antibiotics have been applied for bone infection, the emergence of drug resistance and biofilm formation significantly decrease the effectiveness of those agents. In combination with gram-positive aerobes, gram-negative aerobes and anaerobes functionally equivalent pathogroups interact synergistically, developing as pathogenic biofilms and causing recurrent infections. The adhesion of biofilms to bone promotes bone destruction and protects bacteria from antimicrobial agent stress and host immune system infiltration. Moreover, bone is characterized by low permeability and reduced blood flow, further hindering the therapeutic effect for bone infections. To minimize systemic toxicity and enhance antibacterial effectiveness, therapeutic strategies targeting on biofilm and bone infection can serve as a promising modality. Herein, we focus on biofilm and bone infection eradication with targeting therapeutic strategies. We summarize recent targeting moieties on biofilm and bone infection with peptide-, nucleic acid-, bacteriophage-, CaP- and turnover homeostasis-based strategies. The antibacterial and antibiofilm mechanisms of those therapeutic strategies include increasing antibacterial agents’ accumulation by bone specific affinity, specific recognition of phage-bacteria, inhibition biofilm formation in transcription level. As chronic inflammation induced by infection can trigger osteoclast activation and inhibit osteoblast functioning, we additionally expand the potential applications of turnover homeostasis-based therapeutic strategies on biofilm or infection related immunity homeostasis for host-bacteria. Based on this review, we expect to provide useful insights of targeting therapeutic efficacy for biofilm and bone infection eradication.

Secondary Malignancy in Giant Cell Tumor: A Single-Center Study

Giant cell tumor of bone (GCTB) undergoes a sarcomatous transformation. Secondary malignancy in giant cell tumor (MGCT) is associated with radiotherapy and has a dismal prognosis. We reviewed medical records to investigate the clinicopathological characteristics and prognosis of MGCT patients. The enrollment criterion was high-grade spindle-cell sarcoma, which developed at the site of prior GCTB treatment. Twelve patients were analyzed: six females and six males. The median age was 42.5 years. Benign recurrence occurred in five GCTB patients not treated with radiotherapy. No pulmonary implants were observed. The median latency to the malignant transformation was 63 months. Nine patients were AJCC stage IIB, and three were stage IVA. The median follow-up period after malignant transformation was 62.5 months. Five patients developed local recurrence, and six had distant metastasis. Five-year overall recurrence and metastasis-free survival rates were 61.9%, 66.7%, and 58.3%, respectively. Initial metastasis was a predictive factor for overall survival. Benign local recurrence of GCTB was also a negative factor for metastasis-free survival of MGCT patients. Differences in overall survival according to benign recurrence also showed a tendency toward significance. In our series, secondary MGCT did not occur after radiotherapy. The prognosis was better than previous findings. Benign recurrence of GCTB could reflect the prognosis of MGCT.

Epigenetic quantification of immunosenescent CD8+ TEMRA cells in human blood

Age‐related changes in human T‐cell populations are important contributors to immunosenescence. In particular, terminally differentiated CD8⁺ effector memory CD45RA⁺ TEMRA cells and their subsets have characteristics of cellular senescence, accumulate in older individuals, and are increased in age‐related chronic inflammatory diseases. In a detailed T‐cell profiling among individuals over 65 years of age, we found a high interindividual variation among CD8⁺ TEMRA populations. CD8⁺ TEMRA proportions correlated positively with cytomegalovirus (CMV) antibody levels, however, not with the chronological age. In the analysis of over 90 inflammation proteins, we identified plasma TRANCE/RANKL levels to associate with several differentiated T‐cell populations, including CD8⁺ TEMRA and its CD28⁻ subsets. Given the strong potential of CD8⁺ TEMRA cells as a biomarker for immunosenescence, we used deep‐amplicon bisulfite sequencing to match their frequencies in flow cytometry with CpG site methylation levels and developed a computational model to predict CD8⁺ TEMRA cell proportions from whole blood genomic DNA. Our findings confirm the association of CD8⁺ TEMRA and its subsets with CMV infection and provide a novel tool for their high throughput epigenetic quantification as a biomarker of immunosenescence.

Adverse events associated with bone-directed therapies in patients with cancer

Bone metastatic disease may lead to serious adverse events in patients with cancer. Bone-directed therapies, including bisphosphonates such as pamidronate and zoledronic acid and the human monoclonal antibody denosumab, are currently approved for the prevention of bone-related adverse events. However, despite the benefits of these drugs, they may cause side effects that are mostly associated with dosages and treatment durations. These side effects range from more frequent, mostly mild, and generally self-limited side effects-such as fever, myalgias, arthralgias, and electrolyte imbalances-to less frequent and more severe side effects such as medication-related osteonecrosis of the jaw and atypical femoral fractures. The purpose of this review is to familiarize clinicians with the literature regarding adverse events associated with bone-directed therapies in patients with cancer. It is important to be aware of these possible adverse events and to educate patients about the predisposing factors associated with side effects from bone-directed therapies and the preventive measures necessary to decrease the risk of occurrence.

Indigenous microbiota protects development of medication-related osteonecrosis induced by periapical disease in mice

Bacterial infection is a common finding in patients, who develop medication-related osteonecrosis of the jaw (MRONJ) by the long-term and/or high-dose use of anti-resorptive agents such as bisphosphonate (BPs). However, pathological role of bacteria in MRONJ development at the early stage remains controversial. Here, we demonstrated that commensal microbiota protects against MRONJ development in the pulp-exposed periapical periodontitis mouse model. C57/BL6 female mice were treated with intragastric broad-spectrum antibiotics for 1 week. Zoledronic acid (ZOL) through intravenous injection and antibiotics in drinking water were administered for throughout the experiment. Pulp was exposed on the left maxillary first molar, then the mice were left for 5 weeks after which bilateral maxillary first molar was extracted and mice were left for additional 3 weeks to heal. All mice were harvested, and cecum, maxilla, and femurs were collected. ONJ development was assessed using μCT and histologic analyses. When antibiotic was treated in mice, these mice had no weight changes, but developed significantly enlarged ceca compared to the control group (CTL mice). Periapical bone resorption prior to the tooth extraction was similarly prevented when treated with antibiotics, which was confirmed by decreased osteoclasts and inflammation. ZOL treatment with pulp exposure significantly increased bone necrosis as determined by empty lacunae and necrotic bone amount. Furthermore, antibiotics treatment could further exacerbate bone necrosis, with increased osteoclast number. Our findings suggest that the commensal microbiome may play protective role, rather than pathological role, in the early stages of MRONJ development.

Roles of the RANKL-RANK Axis in Immunity-Implications for Pathogenesis and Treatment of Bone Metastasis

A substantial amount patients with cancer will develop bone metastases, with 70% of metastatic prostate and breast cancer patients harboring bone metastasis. Despite advancements in systemic therapies for advanced cancer, survival remains poor for those with bone metastases. The interaction between bone cells and the immune system contributes to a better understanding of the role that the immune system plays in the bone metastasis of cancer. The immune and bone systems share various molecules, including transcription factors, signaling molecules, and membrane receptors, which can stimulate the differentiation and activation of bone-resorbing osteoclasts. The process of cancer metastasis to bone, which deregulates bone turnover and results in bone loss and skeletal-related events (SREs), is also controlled by primary cancer-related factors that modulate the intratumoral microenvironment as well as cellular immune process. The nuclear factor kappa B ligand (RANKL) and the receptor activator of nuclear factor kappa B (RANK) are key regulators of osteoclast development, bone metabolism, lymph node development, and T-cell/dendritic cell communication. RANKL is an osteoclastogenic cytokine that links the bone and the immune system. In this review, we highlight the role of RANKL and RANK in the immune microenvironment and bone metastases and review data on the role of the regulatory mechanism of immunity in bone metastases, which could be verified through clinical efficacy of RANKL inhibitors for cancer patients with bone metastases. With the discovery of the specific role of RANK signaling in osteoclastogenesis, the humanized monoclonal antibody against RANKL, such as denosumab, was available to prevent bone loss, SREs, and bone metastases, providing a unique opportunity to target RANKL/RANK as a future strategy to prevent bone metastases.

Denosumab in the Treatment of Osteoporosis: 10 Years Later: A Narrative Review

The fully human monoclonal antibody denosumab was approved for treatment of osteoporosis in 2010 on the basis of its potent antiresorptive activity, which produces clinically meaningful increases in bone mineral density (BMD) and reduces fracture risk at key skeletal sites. At that time, questions remained regarding the long-term safety and efficacy of this receptor activator of nuclear factor kappa-B ligand (RANKL) inhibitor; and with clinical experience, new questions have arisen regarding its optimal use. Here, we examine these questions through the lens of data from the FREEDOM trial program and other studies to determine where denosumab fits in the osteoporosis treatment landscape. Clinical consensus and evidentiary support have grown for denosumab as a highly effective anti-osteoporosis therapy for patients at high risk of fracture. In the 10-year FREEDOM Extension study, denosumab treatment produced progressive incremental increases in BMD, sustained low rates of vertebral fracture, and further reduction in nonvertebral fracture risk without increased risk of infection, cancer, or immunogenicity. There was no evidence that suppression of bone turnover or mineralization was excessive, and rates of osteonecrosis of the jaw (ONJ) and atypical femoral fracture (AFF) were very low. It is now recognized, however, that transitioning to another anti-osteoporosis therapy after denosumab discontinuation is essential to mitigate a transient rebound of bone turnover causing rapid BMD loss and increased risk of multiple vertebral fractures (MVFs). Taken together, the available data show that denosumab has a favorable benefit/risk profile and is a versatile agent for preventing osteoporotic fractures in the short and long term.

Regulation of TNF-Induced Osteoclast Differentiation

Increased osteoclast (OC) differentiation and activity is the critical event that results in bone loss and joint destruction in common pathological bone conditions, such as osteoporosis and rheumatoid arthritis (RA). RANKL and its decoy receptor, osteoprotegerin (OPG), control OC differentiation and activity. However, there is a specific concern of a rebound effect of denosumab discontinuation in treating osteoporosis. TNFα can induce OC differentiation that is independent of the RANKL/RANK system. In this review, we discuss the factors that negatively and positively regulate TNFα induction of OC formation, and the mechanisms involved to inform the design of new anti-resorptive agents for the treatment of bone conditions with enhanced OC formation. Similar to, and being independent of, RANKL, TNFα recruits TNF receptor-associated factors (TRAFs) to sequentially activate transcriptional factors NF-κB p50 and p52, followed by c-Fos, and then NFATc1 to induce OC differentiation. However, induction of OC formation by TNFα alone is very limited, since it also induces many inhibitory proteins, such as TRAF3, p100, IRF8, and RBP-j. TNFα induction of OC differentiation is, however, versatile, and Interleukin-1 or TGFβ1 can enhance TNFα-induced OC formation through a mechanism which is independent of RANKL, TRAF6, and/or NF-κB. However, TNFα polarized macrophages also produce anabolic factors, including insulin such as 6 peptide and Jagged1, to slow down bone loss in the pathological conditions. Thus, the development of novel approaches targeting TNFα signaling should focus on its downstream molecules that do not affect its anabolic effect.

The Roadmap of RANKL/RANK Pathway in Cancer

The receptor activator of the nuclear factor-κB ligand (RANKL)/RANK signaling pathway was identified in the late 1990s and is the key mediator of bone remodeling. Targeting RANKL with the antibody denosumab is part of the standard of care for bone loss diseases, including bone metastases (BM). Over the last decade, evidence has implicated RANKL/RANK pathway in hormone and HER2-driven breast carcinogenesis and in the acquisition of molecular and phenotypic traits associated with breast cancer (BCa) aggressiveness and poor prognosis. This marked a new era in the research of the therapeutic use of RANKL inhibition in BCa. RANKL/RANK pathway is also an important immune mediator, with anti-RANKL therapy recently linked to improved response to immunotherapy in melanoma, non-small cell lung cancer (NSCLC), and renal cell carcinoma (RCC). This review summarizes and discusses the pre-clinical and clinical evidence of the relevance of the RANKL/RANK pathway in cancer biology and therapeutics, focusing on bone metastatic disease, BCa onset and progression, and immune modulation.

Denosumab in chronic kidney disease: a narrative review of treatment efficacy and safety

People with chronic kidney disease (CKD) are at high risk of bone fractures. In this review, we summarize the complexity of fracture prevention in CKD, describe the usefulness of a medication called denosumab, and review its safety in this population. Our article will help doctors manage brittle bones in CKD and encourage researchers to conduct more studies to improve bone health in CKD.

PURPOSE

Patients with CKD are at increased risk of fragility fractures and associated consequences. We discuss the complexity of fracture prevention in CKD, summarize the efficacy and safety of denosumab, and provide an approach to denosumab-induced hypocalcemia.

METHODS

Using predefined terms, we searched PubMed, MEDLINE, and Google Scholar for studies on fracture prevention in CKD and the efficacy and safety of denosumab. We included observational studies, randomized controlled trials (RCTs), meta-analyses, evidence-based reviews, and clinical practice guidelines.

RESULTS

The diagnosis of osteoporosis and prevention of related fragility fractures is complex in CKD, particularly in those with advanced and end-staged kidney disease (ESKD). Prior to initiating denosumab, it is important to assess for and optimize CKD-mineral and bone disorders (CKD-MBD). In observational studies and small RCTs, denosumab has been shown to improve bone mineral density and reduce bone turnover in CKD, but there have been no studies focused upon its fracture efficacy. Denosumab-induced hypocalcemia has also been reported, which disproportionately impacts those with ESKD. Risk factors for hypocalcemia with denosumab use in CKD include lower baseline serum calcium and 25 hydroxyvitamin D and both low and high bone turnover. Choosing the "right patient" for denosumab, supplementing with calcium and vitamin D, adjusting calcium dialysate, and close clinical monitoring are essential if considering this drug.

CONCLUSION

With optimization of CKD-MBD, calcium and vitamin D supplementation, and close monitoring, denosumab can be considered in CKD. There are however opportunities to better understand its fracture efficacy and safety in an RCT setting.

Pharyngeal spreading of peri-implant infections under antiresorptive/antiangiogenic therapy

Objectives

To assess the influence of antiresorptive/antiangiogenic therapy on the spreading of peri-implant infections in the pharyngeal region.

Material and methods

This analysis was based on tissue biopsies obtained from a total of twenty-five albino rats having either received (1) amino-bisphosphonate (Zoledronate) (Zo) (n=4), (2) RANKL inhibitor (Denosumab) (De) (n=4), (3) antiangiogenic medication (Bevacizumab) (Be) (n=4), (4) Zo+Be (n=3), (5) De+Be (n=5), or (6) no medication (Co) (n=5). Drug administration was repeated at 12 weeks. Chronic-type peri-implant infections were induced at titanium implants located in the upper jaws. The surface area (%) of infiltrated connective tissue (ICT) and CD68-positive cells was assessed within the lateral pharyngeal/retropharyngeal connective tissue zone.

Results

Mean (±SD) and median ICT% values and CD68 counts were markedly highest in the De+Be (11.10±6.04; 11.81; 95% CI − 3.89; 26.11) and De (5.70±5.06; 6.19; 95% CI − 2.34; 13.75) groups, reaching statistical significance for De CD68 counts over the Co (0.18±0.25; 0.18; 95% CI −2.14; 2.51) group. In both De+Be and De groups, the ICTs were occasionally associated with an ulceration of the epithelial compartment.

Conclusions

Induced peri-implant infections were not associated with any inflammatory lesions in pharyngeal tissues. While these findings were similar under Zo and Be medication, De and De+Be had a marked effect on ICT and CD68 values. The clinical relevance of these adverse findings needs further investigation.

Molecular Targeted Therapy for the Bone Loss Secondary to Pyogenic Spondylodiscitis Using Medications for Osteoporosis: A Literature Review

Pyogenic spondylodiscitis can cause severe osteolytic and destructive lesions in the spine. Elderly or immunocompromised individuals are particularly susceptible to infectious diseases; specifically, infections in the spine can impair the ability of the spine to support the trunk, causing patients to be bedridden, which can also severely affect the physical condition of patients. Although treatments for osteoporosis have been well studied, treatments for bone loss secondary to infection remain to be elucidated because they have pathological manifestations that are similar to but distinct from those of osteoporosis. Recently, we encountered a patient with severely osteolytic pyogenic spondylodiscitis who was treated with romosozumab and exhibited enhanced bone formation. Romosozumab stimulated canonical Wnt/β-catenin signaling, causing robust bone formation and the inhibition of bone resorption, which exceeded the bone loss secondary to infection. Bone loss due to infections involves the suppression of osteoblastogenesis by osteoblast apoptosis, which is induced by the nuclear factor-κB and mitogen-activated protein kinase pathways, and osteoclastogenesis with the receptor activator of the nuclear factor-κB ligand-receptor combination and subsequent activation of the nuclear factor of activated T cells cytoplasmic 1 and c-Fos. In this study, we review and discuss the molecular mechanisms of bone loss secondary to infection and analyze the efficacy of the medications for osteoporosis, focusing on romosozumab, teriparatide, denosumab, and bisphosphonates, in treating this pathological condition.

Denosumab is not associated with risk of malignancy: systematic review and meta-analysis of randomized controlled trials

The immunomodulatory effects of denosumab have raised concerns for risk of malignancy. This meta-analysis of 25 randomized controlled trials (21,523 patients) shows similar risk of malignancy between denosumab (60 mg every 6 months, up to 48 months) and any comparator. Post-marketing surveillance may detect rare or late-occurring drug effects. Possible increased risk of malignancy in patients treated with denosumab has been concerned due to inhibition of the immune modulator receptor activator of nuclear factor κ-Β ligand (RANKL). We aimed to assess the risk of malignancy associated with denosumab treatment. PubMed and Cochrane Central Register of Controlled Trials were searched up to May 27, 2019 to include all randomized controlled trials of denosumab (60 mg every 6 months) versus any comparator. Trials using higher drug doses for prevention of skeletal-related events were excluded. Data were independently extracted by two reviewers and analyzed using a fixed-effect model to pool risk ratios (RRs) with 95% confidence intervals (CI). Twenty-five trials (21,523 patients) were included. The risk of malignancy was similar between denosumab and other comparators (absolute risk difference 0%, RR 1.08 [95% CI, 0.93-1.24], I² = 0%). Sensitivity analysis based on adequate allocation concealment showed similar results. The risk of malignancy did not differ between groups in any of the subgroup analyses, including stratification by race, individual comparators, indications for treatment, and longer drug exposure (≥ 24 months, 9 studies). The risk ratio of malignancy-related death was similar between groups. Early concerns about a potential increased risk of malignancy resulting from an immunomodulatory effect of denosumab are not supported by evidence from this meta-analysis of 25 RCTs with drug exposure of up to 48 months. Since RCTs with longer observation for safety outcomes are not expected, post-marketing surveillance will be the main means for detection of rare or late-occurring events.

Bone loss in patients with inflammatory bowel disease: cause, detection and treatment

PURPOSE OF REVIEW

Inflammatory bowel disease (IBD) is associated with bone loss leading to osteoporosis and increased fracture risk. Bone loss is the result of changes in the balanced process of bone remodeling. Immune cells and cytokines play an important role in the process of bone remodeling and it is therefore not surprising that cytokines as observed in IBD are involved in bone pathology. This review discusses the role of cytokines in IBD-associated bone loss, including the consequences for treatment.

RECENT FINDINGS

Many studies have been conducted that showed the effect of a single cytokine on bone cells in vitro, including interleukin (IL)-1β, IL-6, IL-8, IL-12/IL-23, IL-17, IL-18, IL-32 and interferon-γ. Recently new members of the IL-1 family (IL-1F) have been related to IBD but the consequences for bone health remain uncertain.

SUMMARY

Overall, patients have to deal with a cocktail of cytokines, present in their serum. The combination of cytokines can affect bone cells differently compared to the effects of a single cytokine. This implicates that treatment, focused on reducing the inflammation could work best for bone health as well. Vitamin D might also play a role in this.

Multicentric carpotarsal osteolysis syndrome (MCTO) with generalized high bone turnover and high serum RANKL: Response to denosumab

MCTO is a rare disorder, caused by mutations in the MafB gene, a negative regulator of receptor activator of nuclear factor-кB ligand (RANKL). Manifestations include carpal and tarsal osteolysis and renal failure. Pathophysiology is poorly understood, and no effective treatment is available.

In this case report we describe a patient with MCTO (MafB, mutation c.206C>T, p.Ser69Leu), diagnosed at the age of 5 years. At 7 years, skeletal survey showed diffuse osteopenia. BMD was mildly reduced, and bone turnover markers increased. He was treated with denosumab, a human monoclonal RANKL inhibitor for two years. Each injection was followed by a marked reduction in C-telopeptide (CTX). Following denosumab his BMD and bone symptoms improved and the osteolysis stabilized. At the age of 13 years, osteoporosis was diagnosed using high resolution peripheral quantitative computed tomography (HRpQCT) and serum RANKL was found to be markedly increased.

This initial experience suggests that the associated osteoporosis may be ameliorated by denosumab, although further study will be needed to understand the appropriate dose, frequency, and the extent of efficacy. Monitoring of CTX and bone specific alkaline phosphatase will be especially useful in this regard. Further study in other MCTO patients is also needed to determine whether high bone turnover is specific to this mutation or more common than previously appreciated. We propose a model in which osteolysis in this condition is strongly associated with the systemic osteoporosis.

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MCTO (MafB gene mutation (c.206C>T,p.Ser69Leu) is associated with osteoporosis and very high levels of serum RANKL.

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Denosumab appears to ameliorate the osteoporosis. Further study is needed regarding the dose and frequency of injections.

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Examination of the frequency of osteoporosis and association with osteolysis is needed in MCTO

Inhibition of the RANKL with denosumab has no effect on circulating markers of atherosclerosis in women with postmenopausal osteoporosis: a pilot study

PURPOSE

We evaluated the early effect of denosumab on circulating markers of atherosclerosis in women with postmenopausal osteoporosis.

METHODS

Denosumab (60 mg) was administered subcutaneously every 6 months (m) in 27 women (mean age 75 ± 5 years) with postmenopausal osteoporosis and high cardiovascular risk for a total of 24 m. Zoledronic acid was administered in 6 age-matched women as a single intravenous dose. Serum levels of vascular cell adhesion protein 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1), E and P selectin, CD-40 ligand (CD40L), interleukin-6 (IL-6), matrix metalloproteinase (MMP) 1 and 9, monocyte chemoattractant protein-1 (MCP-1), fibrinogen (FBG), and high sensitivity C-reactive protein (hs-CRP) were measured at baseline, 15 days (d), 2, 6 and 12 m after dosing. In the denosumab group, observation was extended to 24 m as secondary endpoint.

RESULTS

Serum ICAM-1 levels showed significant increase in the zoledronic acid group (+18 ± 0.1%; p < 0.01) at 12 m. In the denosumab group, we observed a significant increase in serum CD40L (+2 ± 0.8%; p < 0.001), MMP-1 (+11 ± 0.4%, p < 0.02), and MMP-9 (+39.4 ± 0.8%, p < 0.01) at 24 m. There was a significant increase in serum FBG and hs-CRP in both groups at 12 m (denosumab:+2.2 ± 0.2% and +50.3 ± 1.6%; zoledronic acid: +9.4 ± 0.1 and +81.8 ± 0.8%; p < 0.01). No significant between-group differences were found.

CONCLUSIONS

24-m treatment with denosumab has no effect on the circulating markers of atherosclerosis in women with postmenopausal osteoporosis. Fluctuation of serum ICAM-1, CD40L, MMPs, FBG and hs-CRP can be ascribed to perturbation of immunological mechanisms stimulated by denosumab and zoledronic acid.

The safety profile of denosumab in oncology beyond the safety of denosumab as an anti-osteoporotic agent: still more to learn

INTRODUCTION

Initially endorsed as an antiosteoporotic agent, denosumab ‒ human monoclonal antibody inhibiting the receptor activator of nuclear factor kappa-B ligand (RANKL)‒ has currently shown an anticancer potential, rationalizing its exploitation in oncology. A prerequisite for leveraging denosumab in oncology is a favorable safety profile.

AREAS COVERED

The present review provides an overview of the adverse events of denosumab in oncology, with a focus on hypocalcemia, medication-related osteonecrosis of the jaw, atypical femoral fracture(s), post-denosumab vertebral fractures, increased risk of infections, and excess of second primary cancer. Representative studies addressing the safety and efficacy of denosumab compared to bisphosphonates in oncology are summarized. Critical gaps in the literature concerning the safety of denosumab in oncology are highlighted as opposed to plenty of available safety data on denosumab as an antiosteoporotic agent.

EXPERT OPINION

Despite the generally acceptable safety profile of denosumab in oncology, many issues remain unresolved. Further research is mandatory to counteract current challenges, namely: (i) validation of risk factors for adverse events; (ii) elucidation of the pathophysiology of the adverse events in search of actionable molecular pathways; (iii) illumination of the association of denosumab with increased risk of infections and/or second primary cancer; (iv) establishment of optimal diagnostic, and therapeutic protocols.

RANK/RANKL/OPG Signaling in the Brain: A Systematic Review of the Literature

Together with its dominant immunological and bone remodeling involvement, RRO axis, comprising of receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) signaling, is as well-implicated in CNS functioning and corresponding pathologies. The CNS aspects of RANKL/RANK/OPG (RRO) axis were systematically reviewed. With search 10 databases, and 7 additional resources from first article publication to July 2019, resulted in total 2,222 hits, from which 33 relevant articles were selected. The elements of RRO axis in CNS include cells involved in neuroinflammation, predominantly in microglia, but as well in resident macrophages and inflammatory cells migrating across the blood-brain barrier. The expression in neurons and oligodendrocytes is mainly confined to processes of differentiation and cell death. RRO axis tunes the neuroinflammatory response, depending on the molecular, cellular and pathological context. RANK/RANKL signaling is neuroprotective in TLR-mediated inflammation, while OPG seems detrimental in stroke, but beneficial in multiple sclerosis. The levels of RRO axis elements can serve as biomarkers in the blood and cerebrospinal fluid. They act as neuroprotectant after brain damage even being implicated in body weight- and thermo-regulation. As derivatives of RRO axis already exist as therapeutic agents in bone remodeling, it would be intriquing to see if these or new RRO-based pharmaceuticals would appear effective in CNS therapies.

Pathogenesis and multidisciplinary management of medication-related osteonecrosis of the jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a serious side effect of bone-modifying agents and inhibits angiogenesis agents. Although the pathogenesis of MRONJ is not entirely clear, multiple factors may be involved in specific microenvironments. The TGF-β1 signalling pathway may have a key role in the development of MRONJ. According to the clinical stage, multiple variables should be considered when selecting the most appropriate treatment. Therefore, the prevention and management of treatment of MRONJ should be conducted in patient-centred multidisciplinary team collaborative networks with oncologists, dentists and dental specialists. This would comprise a closed responsibility treatment loop with all benefits directed to the patient. Thus, in the present review, we aimed to summarise the pathogenesis, risk factors, imaging features, clinical staging, therapeutic methods, prevention and treatment strategies associated with MRONJ, which may provide a reference that can inform preventive strategies and improve the quality of life for patients in the future.

The Role of the RANKL/RANK Axis in the Prevention and Treatment of Breast Cancer with Immune Checkpoint Inhibitors and Anti-RANKL

The receptor activator of nuclear factor-κB (RANK) and the RANK ligand (RANKL) were reported in the regulation of osteoclast differentiation/activation and bone homeostasis. Additionally, the RANKL/RANK axis is a significant mediator of progesterone-driven mammary epithelial cell proliferation, potentially contributing to breast cancer initiation and progression. Moreover, several studies supported the synergistic effect of RANK and epidermal growth factor receptor (EGFR) and described RANK's involvement in epidermal growth factor receptor 2 (ERBB2)-positive carcinogenesis. Consequently, anti-RANKL treatment has been proposed as a new approach to preventing and treating breast cancer and metastases. Recently, RANKL/RANK signaling pathway inhibition has been shown to modulate the immune environment and enhance the efficacy of anti-CTLA-4 and anti-PD-1 monoclonal antibodies against solid tumors. Clinical and experimental trials have emerged evaluating RANKL inhibition as an enhancer of the immune response, rendering resistant tumors responsive to immune therapies. Trials evaluating the combinatorial effect of immune checkpoint inhibitors and anti-RANKL treatment in double-positive (RANK+/ERBB2+) patients are encouraging.

Denosumab in Giant Cell Tumor of Bone: Current Status and Pitfalls

Denosumab is a monoclonal antibody against RANK ligand for treatment of giant cell tumor of bone (GCTB). Clinical trials and case series have demonstrated that denosumab is relevant to beneficial tumor response and surgical down-staging in patients of GCTB. However, these trials or case series have limitations with a short follow-up. Recent increasing studies revealed that denosumab probably increased the local recurrence risk in patients treated with curettage. This may be caused by the thicken bone margin of tumor that trapped tumor cells from curettage. The direct bone formation by tumor cells in the margin after denosumab treatment also contributed to the local recurrence. in vitro studies showed denosumab resulted in a cytostatic instead of a true cytotoxic response on neoplastic stromal cells. More importantly, denosumab-treated GCTB exhibited morphologic overlap with malignancy, and a growing number of patients of malignant transformation of GCTB during denosumab treatment have been reported. The optimal duration, long term safety, maintenance dose, and optimum indications remain to be elucidated. With these concerns in mind, this review warns that the denosumab therapy of GCTB should be applied with caution.

Gene Expression Profile and Acute Gene Expression Response to Sclerostin Inhibition in Osteogenesis Imperfecta Bone

Sclerostin antibody (SclAb) therapy has been suggested as a novel therapeutic approach toward addressing the fragility phenotypic of osteogenesis imperfecta (OI). Observations of cellular and transcriptional responses to SclAb in OI have been limited to mouse models of the disorder, leaving a paucity of data on the human OI osteoblastic cellular response to the treatment. Here, we explore factors associated with response to SclAb therapy in vitro and in a novel xenograft model using OI bone tissue derived from pediatric patients. Bone isolates (approximately 2 mm3) from OI patients (OI type III, type III/IV, and type IV, n = 7; non-OI control, n = 5) were collected to media, randomly assigned to an untreated (UN), low-dose SclAb (TRL, 2.5 μg/mL), or high-dose SclAb (TRH, 25 μg/mL) group, and maintained in vitro at 37°C. Treatment occurred on days 2 and 4 and was removed on day 5 for TaqMan qPCR analysis of genes related to the Wnt pathway. A subset of bone was implanted s.c. into an athymic mouse, representing our xenograft model, and treated (25 mg/kg s.c. 2×/week for 2/4 weeks). Implanted OI bone was evaluated using μCT and histomorphometry. Expression of Wnt/Wnt-related targets varied among untreated OI bone isolates. When treated with SclAb, OI bone showed an upregulation in osteoblast and osteoblast progenitor markers, which was heterogeneous across tissue. Interestingly, the greatest magnitude of response generally corresponded to samples with low untreated expression of progenitor markers. Conversely, samples with high untreated expression of these markers showed a lower response to treatment. in vivo implanted OI bone showed a bone-forming response to SclAb via μCT, which was corroborated by histomorphometry. SclAb induced downstream Wnt targets WISP1 and TWIST1, and elicited a compensatory response in Wnt inhibitors SOST and DKK1 in OI bone with the greatest magnitude from OI cortical bone. Understanding patients' genetic, cellular, and morphological bone phenotypes may play an important role in predicting treatment response. This information may aid in clinical decision-making for pharmacological interventions designed to address fragility in OI. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Pros and Cons of Denosumab Treatment for Osteoporosis and Implication for RANKL Aptamer Therapy

Osteoporosis is age-related deterioration in bone mass and micro-architecture. Denosumab is a novel human monoclonal antibody for osteoporosis. It is a receptor activator of nuclear factor-κB ligand (RANKL) inhibitor, which binds to and inhibits osteoblast-produced RANKL, in turn reduces the binding between RANKL and osteoclast receptor RANK, therefore decreases osteoclast-mediated bone resorption and turnover. However, adverse events have also been reported after denosumab treatment, including skin eczema, flatulence, cellulitis and osteonecrosis of the jaw (ONJ). Extensive researches on the mechanism of adverse reactions caused by denosumab have been conducted and may provide new insights into developing new RANKL inhibitors that achieve better specificity and safety. Aptamers are single-stranded oligonucleotides that can bind to target molecules with high specificity and affinity. They are screened from large single-stranded synthetic oligonucleotides and enriched by a technology named SELEX (systematic evolution of ligands by exponential enrichment). With extra advantages such as high stability, low immunogenicity and easy production over antibodies, aptamers are hypothesized to be promising candidates for therapeutic drugs targeting RANKL to counteract osteoporosis. In this review, we focus on the pros and cons of denosumab treatment in osteoporosis and the implication for novel aptamer treatment.

[Current status and perspectives in the development of therapeutic agents targeting post-ischemic inflammation in the acute stage of stroke]

We have developed a partial peptide of RANKL (receptor activator of NF-κB ligand) that suppresses TLR (toll-like receptor)-related inflammation via RANKL/RANK (receptor activator of nuclear factor-κB) signals in the acute phase of ischemic stroke. This peptide has been found to be a therapeutic agent for ischemic stroke that can be used in combination with tPA in a mouse model. Based on the findings, we are working on translational research to aim for clinical application of this peptide through collaboration with pharmacy companies. However, the problem is that the need for development of medication in the acute stage of ischemic stroke is currently low in pharmaceutical companies due to the failure of many investigational drugs in the past. To overcome the problem, we are examining the effects of this peptide in other diseases included in the company's priority areas and explaining the environmental changes in the clinical trials due to the development of endovascular treatment in the acute stage of ischemic stroke.

Role of Bone Targeting Agents in the Prevention of Bone Metastases from Breast Cancer

Breast cancer (BC) is the most common malignancy in women worldwide and leads, in more than 70% of patients with advanced disease, to skeleton colonization and formation of bone metastases (BM). This condition implies a severe disability and deterioration of the quality of life, with consequent additional social costs. In recent decades, several studies explored the role of agents acting within the bone microenvironment to counteract BM development, and several bone-targeting agents (BTAs) have been introduced in the clinical practice to manage bone lesions and reduce the risk of skeletal complications. However, long-term exposure to these agents is not free from potential toxicities and needs careful monitoring. In this context, the potential capability to prevent BM onset in selected BC patients, through the early administration of BTAs, has been explored by several researchers, with the belief that “prevention is better than cure” and that, ultimately, metastatic BC is an incurable condition. Here, we revised the mechanisms of BM development in BC as well as the strategies for selecting high-risk patients suitable for early BTA treatment.

Perspective on skeletal health in inflammatory bowel disease

Osteopenia and osteoporosis are common features in inflammatory bowel disease (IBD), comprising both Crohn's disease and ulcerative colitis. Moreover, Crohn's disease is associated with increased fracture risk. The etiology of bone loss in IBD is multifactorial. It includes insufficient intake or absorption of calcium, vitamin D, and potassium; smoking; a low peak bone mass; a low body mass index; and decreased physical activity. In several studies, it has been shown that elevated concentrations of systemic and local pro-inflammatory cytokines, including tumor necrosis factor alpha (TNF-α), interferon-γ (IFNγ), interleukin (IL)-1β, IL-4, IL-5, IL-6, IL-13, and IL-17, present in IBD patients are potentially detrimental for bone metabolism and may be responsible for bone loss and increased fracture risk. This perspective aims to review the current literature on the role of inflammatory factors in the pathophysiology of skeletal problems in IBD and to suggest potential treatment to improve bone health, based on a combination of evidence and clinical and pathophysiological reasoning.

Predictive Value of Osteoprotegerin and Neutrophil Gelatinase-associated Lipocalin on Multiple Organ Failure in Multiple Trauma

BACKGROUND/AIM

Multiple organ dysfunction syndrome (MODS) is the leading cause of late posttraumatic mortality. This study analyzed the prognostic values of osteoprotegerin (OPG) and neutrophil gelatinase-associated lipocalin (NGAL/lipocalin 2) compared to interleukin-6 (IL-6) in multiply injured patients.

PATIENTS AND METHODS

A retrospective observational cohort study on multiply injured patients with an injury severity score (ISS) of ≥16 was performed. OPG, NGAL and IL-6 blood concentrations were measured. Statistical analysis comprised receiver-operating-characteristic (ROC) analysis with the corresponding area under the curve (AUC).

RESULTS

Thirty-nine patients with a mean ISS of 34±11 were included. Fourteen patients (36%) developed MODS and 8 patients (21%) died. Plasma levels of NGAL, OPG, and IL-6 were significantly elevated in the MODS+ group. Each biomarker positively correlated with MODS score and diagnosis of MODS.

CONCLUSION

NGAL and OPG might be indicative of MODS and could have the potential to be biomarkers in the early detection of patients at risk of posttraumatic MODS.

Role of dendritic cell-mediated immune response in oral homeostasis: A new mechanism of osteonecrosis of the jaw

Dendritic cells are an important link between innate and adaptive immune response. The role of dendritic cells in bone homeostasis, however, is not understood. Osteoporosis medications that inhibit osteoclasts have been associated with osteonecrosis, a condition limited to the jawbone, thus called medication-related osteonecrosis of the jaw. We propose that disruption of the local immune response renders the oral microenvironment conducive to osteonecrosis. We tested whether zoledronate (Zol) treatment impaired dendritic cell (DC) functions and increased bacterial load in alveolar bone in vivo and whether DC inhibition alone predisposed the animals to osteonecrosis. We also analyzed the role of Zol in impairment of differentiation and function of migratory and tissue-resident DCs, promoting disruption of T-cell activation in vitro. Results demonstrated a Zol induced impairment in DC functions and an increased bacterial load in the oral cavity. DC-deficient mice were predisposed to osteonecrosis following dental extraction. Zol treatment of DCs in vitro caused an impairment in immune functions including differentiation, maturation, migration, antigen presentation, and T-cell activation. We conclude that the mechanism of Zol-induced osteonecrosis of the jaw involves disruption of DC immune functions required to clear bacterial infection and activate T cell effector response.

Treatment Effects of Bisphosphonates and Denosumab on Survival and Refracture from Real-World Data of Hip-Fractured Patients

We examined differences in patients' survival after hip fracture (HF) and risk for subsequent HF among patients treated with oral and intravenous bisphosphonates (oBPs, iBPs), denosumab (DMAB), and patients without therapy. We used data from all patients in Austria aged ≥ 50 who sustained a HF between 2012 and 2017 and were followed for a subsequent HF and all-cause mortality until 2017. Antiosteoporotic treatment-naïve patients, who were incident users of BPs and DMAB, were eligible for propensity score matching 1:1 to obtain comparable user groups. We applied competing risk approach and calculated cumulative incidence functions and subdistribution-hazards for refracture. Cox regression models were applied for mortality risk. A total of 54,145 hip-fractured patients were observed (1919 oBPs; 1870 iBPs; 555 DMAB users; and 42,795 untreated patients were included in the matched sets) and followed up for a median (interquartile range) of 22.6 months (26.2). Patients treated with antiresorptive medications had significantly longer survival time than patients without treatment. Receiving treatment significantly decreased a hazard of dying only for women by 17% for iBPs (HR 0.83, 95% CI 0.71-0.98, p = 0.023). For DMAB and oBPs, the results were not statistically significant. Higher risk of a subsequent HF was observed in women on DMAB (SHR 1.77, 95% CI 1.08-2.91) and on iBP (SHR 1.81, 95% CI 1.35-2.41), and in men on oBPs (SHR 2.89, 95% CI 1.58-5.30). Patients who were treated with antiresorptive medications after HF had longer survival than patients without treatment, highlighting the importance of initiation of antiresorptive treatment after HF.

Development of a novel RANKL-based peptide, microglial healing peptide1-AcN (MHP1-AcN), for treatment of ischemic stroke

Although the regulation of post-ischemic inflammation is an important strategy to treat ischemic stroke, all clinical trials have failed to show its efficacy. To solve the problem, we previously developed a novel partial peptide of RANKL, microglial healing peptide 1 (MHP1), which could reduce ischemic injury by inhibiting Toll-like receptor (TLR) induced inflammation. However, optimization of the peptide was necessary to increase the stability and efficacies for clinical use. According to information gathered through HPLC/MS in serum, we have newly designed a series of modified MHP1 peptides and have found that N-terminal acetylation and C-terminal amidation in MHP1 (MHP1-AcN), can strengthen its anti-inflammatory effects and increase its stability with anti-osteoclastogenic effects. Anti-TLR activity was reported to be reduced in MHP1 when incubated at 37 °C for 24 hrs, but MHP1-AcN could keep the activity under the same condition. The therapeutic effect of MHP1-AcN was observed in transient ischemic stroke model at lower dose than MHP1. Importantly, MHP1-AcN did not affect thrombolytic effects of tissue plasminogen activator (tPA) and inhibited tPA-induced hemorrhagic transformation. These findings indicated that MHP1-AcN was stable and effective anti-TLR signal peptide and could be a promising agent for treating stroke patients receiving tPA and endovascular therapy.

The triptolide-induced apoptosis of osteoclast precursor by degradation of cIAP2 and treatment of rheumatoid arthritis of TNF-transgenic mice

This study aims to discuss the effect of triptolide (TPL) on rheumatoid arthritis (RA) and the mechanism related to osteoclast precursor (OCP) and osteoclast (OC). TNF-transgenic RA mice were treated with different doses of TPL by gavage. After the administration was finished, the curative effects were evaluated and compared, and the OCP apoptosis rates, the OC number, and the OC differentiation ability in vitro were detected. Finally, splenocytes of wild-type mice were cultured in vitro and induced to differentiate into OCP, and the cell apoptosis rate, cIAP2, and apoptotic effectors expression level were detected after cIAP2 overexpression and TPL administration. After TPL administration, the RA symptoms in the TPL groups were all better, the apoptosis rate of OCP was higher, and the amount of OC in vitro were lower than that in the control group (all P < 0.05), and all of the changes in the high-dose group were more obvious than the low-dose group. In splenocytes cells cultured in vitro, cIAP2 overexpression could decrease the apoptosis rate of OCPs and increase the OC number, and TPL treatment could down-regulate the cIAP2 and promote OCP apoptosis and OC reduction. In conclusion, TPL could induce OCP apoptosis and inhibit OC formation to effectively treat RA by mediating cIAP2 degradation.

Osteogenesis imperfecta and therapeutics

Osteogenesis imperfecta, or brittle bone disease, is a congenital disease that primarily causes low bone mass and bone fractures but it can negatively affect other organs. It is usually inherited in an autosomal dominant fashion, although rarer recessive and X-chromosome-linked forms of the disease have been identified. In addition to type I collagen, mutations in a number of other genes, often involved in type I collagen synthesis or in the differentiation and function of osteoblasts, have been identified in the last several years. Seldom, the study of a rare disease has delivered such a wealth of new information that have helped our understanding of multiple processes involved in collagen synthesis and bone formation. In this short review I will describe the clinical features and the molecular genetics of the disease, but then focus on how OI dysregulates all aspects of extracellular matrix biology. I will conclude with a discussion about OI therapeutics.

Therapeutic Effects of Systemic Administration of the Novel RANKL-Modified Peptide, MHP1, for Ischemic Stroke in Mice

Microglial healing peptide 1, "MHP1", is a newly developed synthetic peptide composed of the DE and a part of the EF loop of the receptor activator of nuclear factor-кB (NFκB) ligand (RANKL). Our previous report demonstrated that MHP1 significantly inhibits Toll-like receptor (TLR) 2- and 4-induced inflammation in microglia/macrophages through RANK signaling without osteoclast activation. However, its inhibitory effects on ischemic stroke when administered intravenously have not been clarified. First, we examined whether MHP1 could penetrate the brain parenchyma. Intravenous injection of FITC-conjugated MHP1 demonstrated that MHP1 could cross the blood-brain-barrier in peri-infarct regions, but not in intact regions. Because MHP1 in the parenchyma was reduced at 60 minutes after injection, we speculated that continuous injection was necessary to achieve the therapeutic effects. To check the possible deactivation of MHP1 by continuous injection, the anti-inflammatory effects were checked in MG6 cells after incubation in 37°C for 24 hours. Although the inhibitory effects for IL6 and TNFα were reduced compared to nonincubated MHP1, its anti-inflammatory efficacy remained, indicating that continuous administration with pump was possible. The single and successive continuous administration of MHP1 starting from 4 or 6 hours after cerebral ischemia successfully reduced infarct volume and prevented the exacerbation of neurological deficits with reduced activation of microglia/macrophages and inflammatory cytokines. Different from recombinant RANKL, MHP1 did not activate osteoclasts in the paralytic arm. Although further modification of MHP1 is necessary for stabilization, the MHP1 could be a novel agent for the treatment ischemic stroke.

Removal of Pre-Existing Periodontal Inflammatory Condition before Tooth Extraction Ameliorates Medication-Related Osteonecrosis of the Jaw-Like Lesion in Mice

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but detrimental intraoral lesion that predominantly occurs in patients with long-term use of antiresorptive agents, such as bisphosphonate and denosumab, a human anti-receptor activator of NF-κB ligand (RANKL) monoclonal antibody (Ab). Surgical intervention, such as tooth extraction, is a known risk factor for MRONJ, which is often performed to eliminate preexiting pathologic inflammatory conditions, such as periodontal diseases. Nonetheless, it remains unknown whether pre-existing periodontal disease condition exacerbates, or removal of such condition ameliorates, MRONJ development after tooth extraction. In this study, we combined the ligature-induced periodontitis and the tooth extraction mouse models under the administration of zoledronic acid (ZOL) or anti-RANKL Ab, and provide experimental evidence that a pre-existing pathologic inflammatory condition exacerbates MRONJ development after tooth extraction in mice. Under ZOL administration, tooth extraction alone induced ONJ lesions; however, extraction of a ligature-placed tooth further exacerbated ONJ development. When the ligature was removed and the inflammatory condition was deescalated, ONJ development was ameliorated. Anti-RANKL Ab administration resulted in similar outcomes. Interestingly, unlike ZOL-administered mice, anti-RANKL Ab-administered mice exhibited complete absence of osteoclasts, suggesting that physical presence of osteoclasts is not directly involved in ONJ development. Collectively, our study demonstrated that periodontal disease is a functionally linked risk factor that predisposes ONJ development after tooth extraction in the presence of bisphosphonate and denosumab.

Up-regulated expression of CD147 gene in malignant bone tumor and the possible induction mechanism during osteoclast formation

It is increasingly evident that the microenvironment of bone can influence cancer phenotype in many ways that favor growth in bone. CD147, a transmembrane protein of the immunoglobulin (Ig) superfamily, was identified independently in different species and has many designations across different species. However, expression levels of CD147 mRNA in bone cancer have not been described. In this study, we have used real-time fluorescence quantification (RT-PCR) to demonstrate CD147 expression in malignant bone cancer and benign bone tumor tissues. The results suggested that the expression of CD147 gene was significantly up-regulated in malignant bone cancer. Moreover, we found that over-expressed RANKL progressively enhanced osteoclast formation up to 48 h, which suggested that RANKL could promote the formation of osteoclast, indicating that both CD147 and RANKL play important roles in the formation of osteoclasts. Furthermore, the expressions of four osteoclast specific expression genes, including TRACP, MMP-2, MMP-9 and c-Src, were analyzed using RT-PCR. The results indicated that four osteoclast-specific expression genes were detectable in all osteoclast with different treatments. However, the highest expression level of these four osteoclast-specific expression genes appears in the CD147+ RANKL group and the lowest expression level of these four osteoclast-specific expression genes appears with si-RANKL treatment. Characterization of the role of CD147 in the development of tumors should lead to a better understanding of the changes occurring at the molecular level during the development and progression of primary human bone cancer.