Infections in postmenopausal women with osteoporosis treated with denosumab or placebo: coincidence or causal association?

Novel therapies for osteoporosis

Since the identification of osteoporosis as a major health issue in aging populations and the subsequent development of the first treatment modalities for its management, considerable progress has been made in our understanding of the mechanisms controlling bone turnover and disease pathophysiology, thus enabling the pinpointing of new targets for intervention. This progress, along with advances in biotechnology, has rendered possible the development of ever more sophisticated treatments employing novel mechanisms of action. Denosumab, a monoclonal antibody against RANKL, approved for the treatment of postmenopausal and male osteoporosis, significantly and continuously increases bone mineral density (BMD) and maintains a low risk of vertebral, non-vertebral, and hip fractures for up to 8 years. Currently available combinations of estrogens with selective estrogen receptor modulators moderately increase BMD without causing the extra-skeletal adverse effects of each compound alone. The cathepsin K inhibitor odanacatib has recently been shown to decrease vertebral, non-vertebral, and hip fracture rates and is nearing approval. Romosozumab, an anti-sclerosin antibody, and abaloparatide, a PTH-related peptide analog, are at present in advanced stages of clinical evaluation, so far demonstrating efficaciousness together with a favorable safety profile. Several other agents are currently in earlier clinical and preclinical phases of development, including dickkopf-1 antagonists, activin A antagonists, β-arrestin analogs, calcilytics, and Src tyrosine kinase inhibitors.

Risk of hospitalized infection among rheumatoid arthritis patients concurrently treated with a biologic agent and denosumab

OBJECTIVE

Denosumab is a biologic agent used to treat osteoporosis. Its safety profile given concurrently with biologic drugs for rheumatoid arthritis (RA) has not been well studied. We evaluated hospitalized infections among patients treated with biologic agents for RA who initiated denosumab or zoledronic acid (ZA), a parenteral bisphosphonate without known associations with infection. We hypothesized that the rate of hospitalized infection with denosumab would be noninferior to ZA.

METHODS

We identified RA patients enrolled in Medicare in 2006-2012 treated with biologic agents who initiated denosumab or ZA. Cox proportional hazards models compared the risk for hospitalized infection, comparing denosumab users to ZA users and adjusting for potentially confounding factors. A noninferiority margin was specified a priori to demonstrate that denosumab had no greater infection risk than ZA if the upper bound of the 95% confidence interval (95% CI) of the hazard ratio (HR) was <1.5.

RESULTS

Eligible RA patients receiving biologic agents initiated denosumab (n = 1,354) or ZA (n = 4,460). Characteristics of the denosumab users were as follows: mean ± SD age 73.0 ± 8.9, 98.2% women, with a majority receiving infliximab (35.7%) or abatacept (18.6%). Denosumab users had a higher prevalence of prior infections (11.5% hospitalized and 48.3% outpatient) and infection-related risk factors. The crude rate of hospitalized infections for denosumab (14.9/100 person-years [95% CI 12.2-18.1]) was comparable to that for ZA (13.9/100 person-years [95% CI 12.5-15.4]). After adjustment, the HR of hospitalized infection for denosumab users was noninferior to that for ZA users (HR 0.89 [95% CI 0.69-1.15]).

CONCLUSION

The rate of hospitalized infection among RA patients receiving denosumab concurrently with biologic agents for RA was not increased compared to those receiving zoledronate.

Switching of oral bisphosphonates to denosumab in chronic glucocorticoid users: a 12-month randomized controlled trial

OBJECTIVES

To evaluate the effect of switching from oral bisphosphonates to denosumab on bone mineral density (BMD) in long-term glucocorticoid users.

METHODS

Adult patients who were receiving long-term prednisolone (≥2.5 mg/day for ≥1 year) and oral bisphosphonates (≥2 years) were recruited. Participants were randomized to either continue oral bisphosphonates or switch to denosumab (60 mg subcutaneously every 6 months) for 12 months. Serial BMD (lumbar spine, hip) and bone turnover markers (serum osteocalcin, P1NP, β-CTX) were measured.

RESULTS

42 women were recruited (age 54.7±12.9 years; 21 shifted to denosumab and 21 continued on bisphosphonates). The duration of prednisolone therapy was 101±66.3 months and the daily dose was 4.4±2.1 mg. Baseline demographic data, osteoporosis risk factors, and BMD at various sites were similar between the two groups of patients. At month 12, BMD of the spine and hip increased by +3.4±0.9% (p=0.002) and +1.4±0.6% (p=0.03), respectively, in the denosumab group; whereas the corresponding change was +1.5±0.4% (p=0.001) and +0.80±0.5% (p=0.12) in the bisphosphonate group. The spinal BMD at month 12 was significantly higher in the denosumab than bisphosphonate group after adjustment for baseline BMD and β-CTX values, and other confounding factors (p=0.01). Bone turnover markers (β-CTX and P1NP) were more strongly suppressed by denosumab than the bisphosphonates. Minor infections were more common in denosumab-treated patients while other adverse events occurred at similar frequencies between the two groups.

CONCLUSIONS

In patients receiving long-term glucocorticoids, switching from oral bisphosphonates to denosumab resulted in greater gain of the spinal BMD and suppression of bone turnover markers after 12 months of therapy. The results have to be confirmed by a larger clinical trial with fracture as endpoint.

New antiresorptive therapies for postmenopausal osteoporosis

Osteoporosis is a systemic skeletal disease whose risk increases with age and it is common among postmenopausal women. Currently, almost all pharmacological agents for osteoporosis target the bone resorption component of bone remodeling activity. Current antiresorptive agents are effective, but the effectiveness of some agents is limited by real or perceived intolerance, longterm adverse events (AEs), coexisting comorbidities, and inadequate long-term adherence. New antiresorptive therapies that may expand options for the prevention and treatment of osteoporosis include denosumab, combination of conjugated estrogen/bazedoxifene and cathepsin K inhibitors. However, the long-term efficacy and AEs of these antiresorptive therapies need to be confirmed in studies with a longer follow-up period.

Denosumab: a review of its use in postmenopausal women with osteoporosis

Subcutaneous denosumab (Prolia(®) [USA, Europe]; Pralia(®) [Japan]) once every 6 months is indicated in several countries for the treatment of postmenopausal women with osteoporosis at increased or high risk for fractures (featured indication). In some countries, it is also indicated for use in postmenopausal women who have failed or are intolerant to other osteoporosis treatments. In several international, phase III trials (≤3 years' duration) involving more than 12,000 women with postmenopausal osteoporosis or low bone mineral density (BMD), including Asian studies, denosumab was an effective and generally well tolerated treatment. Relative to placebo, denosumab treatment significantly reduced the risk of vertebral, nonvertebral and hip fractures and increased BMD at all skeletal sites evaluated, including the lumbar spine and total hip. Furthermore, the benefits of denosumab treatment were generally evident after the first dose and were maintained during up to 8 years of treatment in an ongoing extension study. The tolerability profile of denosumab during this extension phase was consistent with that observed during the initial 3-year FREEDOM trial. At 12 months, denosumab treatment increased BMD at the total hip, lumbar spine and/or femoral neck and reduced markers of bone turnover to a significantly greater extent than oral bisphosphonates in women who were essentially bisphosphonate-naive and in those who had switched from alendronate to denosumab treatment. Further clinical experience, including an ongoing postmarketing safety study, will more fully define the long-term safety of denosumab. In the meantime, denosumab is an important option for the treatment of women with postmenopausal osteoporosis at increased or high-risk of fractures, including in women at increased risk of fracture who are unable to take other osteoporosis treatments.

Denosumab for the treatment of osteoporosis

INTRODUCTION

Low trauma fractures due to osteoporosis are a major health concern worldwide. Despite the availability of many therapeutic compounds to reduce fracture risk, osteoporosis remains undertreated and the burden of osteoporotic fractures remains high. Denosumab is a novel agent that acts to reduce bone turnover, improve bone mineral density, and reduce fracture risk, offering a favorable efficacy and safety profile.

AREAS COVERED

This review covers the pharmacology and major clinical trials with extension/post-marketing follow-up, including trials for all FDA-approved indications of denosumab to date.

EXPERT OPINION

Denosumab is an efficacious and safe osteoporosis treatment option, with current data from up to 8 years of continued use showing continued improvement in bone density with sustained fracture risk reduction. Safety profiles overall are similar to placebo, with no new safety concerns in extension trials, though a theoretical increased risk of infection exists with RANKL inhibition. Future considerations include safety of prolonged treatment beyond 8 years, and efficacy/fracture risk after discontinuation or with non-adherence, given the characteristic pharmacodynamic profile of denosumab.

Bone targeted therapies for the prevention of skeletal morbidity in men with prostate cancer

Men with prostate cancer suffer substantially from bone-related complications. Androgen deprivation therapy itself is a cause of loss of bone mineral density and is associated with an increased incidence of osteoporotic fractures. In advanced disease, bone is by far the most common site of metastasis. Complications of bone metastases prominently include pain and the potential for skeletal events such as spinal cord compression and pathologic fractures. Elevated osteoclast activity is an important aspect of the pathophysiology of both treatment-related osteoporosis and skeletal complications due to metastases. The osteoclast is therefore a therapeutic target. Denosumab is a fully human monoclonal antibody to receptor activator of nuclear factor-κ-B ligand that was designed to potently inhibit osteoclast activity and is the central focus of this review. Bisphosphonates, radiopharmaceuticals and systemically-active hormonal agents such as abiraterone acetate and enzalutamide have each been shown to improve skeletal morbidity in specific clinical situations. Denosumab is the only agent that has been shown to prevent osteoporotic fractures in men receiving androgen deprivation therapy and at elevated risk for fracture. It has also demonstrated superiority to the potent bisphosphonate zoledronic acid for the prevention of skeletal-related events in men with castration-resistant prostate cancer metastatic to bone. Efficacy and toxicity data will be discussed.

Utility of the trabecular bone score (TBS) in secondary osteoporosis

Altered bone micro-architecture is an important factor in accounting for fragility fractures. Until recently, it has not been possible to gain information about skeletal microstructure in a way that is clinically feasible. Bone biopsy is essentially a research tool. High-resolution peripheral Quantitative Computed Tomography, while non-invasive, is available only sparsely throughout the world. The trabecular bone score (TBS) is an imaging technology adapted directly from the Dual Energy X-Ray Absorptiometry (DXA) image of the lumbar spine. Thus, it is potentially readily and widely available. In recent years, a large number of studies have demonstrated that TBS is significantly associated with direct measurements of bone micro-architecture, predicts current and future fragility fractures in primary osteoporosis, and may be a useful adjunct to BMD for fracture detection and prediction. In this review, we summarize its potential utility in secondary causes of osteoporosis. In some situations, like glucocorticoid-induced osteoporosis and in diabetes mellitus, the TBS appears to out-perform DXA. It also has apparent value in numerous other disorders associated with diminished bone health, including primary hyperparathyroidism, androgen-deficiency, hormone-receptor positive breast cancer treatment, chronic kidney disease, hemochromatosis, and autoimmune disorders like rheumatoid arthritis. Further research is both needed and warranted to more clearly establish the role of TBS in these and other disorders that adversely affect bone.

Management of postmenopausal osteoporosis

A hallmark of menopause, which follows the decline in the ovarian production of estrogen, is the aggressive and persistent loss of bone mineral and structural elements leading to loss of bone strength and increased fracture risk. This review focuses on newer methods of diagnosing osteoporosis and assessing fracture risk, as well as on novel management strategies for prevention and treatment. Fracture-risk prediction has been significantly enhanced by the development of methods such as the trabecular bone score, which helps assess bone microarchitecture and adds value to standard bone densitometry, and the Fracture Risk Assessment Tool (FRAX) algorithm techniques. The treatment of osteoporosis, which has the goals of fracture prevention and risk reduction, is moving beyond traditional monotherapies with antiresorptives and anabolic agents into new combination regimens.

Understanding and communicating the benefits and risks of denosumab, raloxifene, and teriparatide for the treatment of osteoporosis

The number needed to treat is a valuable metric to determine the benefit of therapy, but it must be viewed against the respective number needed to harm. Denosumab and teriparatide (TPTD) have proven antifracture efficacy at vertebral and nonvertebral sites, whereas raloxifene has proven antifracture efficacy at the spine only. Denosumab use has been associated with a small, yet statistically significant, increased incidence of eczema and serious cellulitis. Raloxifene use has been associated with statistically significant increases in the risk of venous thromboembolism and possibly deadly stroke, although not an increase in total strokes. No significant, nontransient adverse events have been reported with TPTD use. When used for the treatment of postmenopausal osteoporosis, denosumab, raloxifene, and TPTD all generally have favorable risk-to-benefit profiles, but therapy-specific contraindications necessitate thoughtful consideration of all available clinical information and individualization of treatment decisions.

Spanish Menopause Society position statement: Use of denosumab in postmenopausal women

Denosumab is a new drug developed for the treatment of osteoporosis. Moreover, increasing evidences link denosumab with benefits in cancer, an area of interest for those in charge of the postmenopausal health. Denosumab has shown efficacy in the control of bone loss associated with hypogonadic states created by chemotherapy in breast and other cancers. Moreover, some studies reveal efficacy in reducing the progression of metastases. A panel of experts from the Spanish Menopause Society has met to develop usage recommendations based on the best available evidence.

Osteoporosis, fractures, and diabetes

It is well established that osteoporosis and diabetes are prevalent diseases with significant associated morbidity and mortality. Patients with diabetes mellitus have an increased risk of bone fractures. In type 1 diabetes, the risk is increased by ∼6 times and is due to low bone mass. Despite increased bone mineral density (BMD), in patients with type 2 diabetes the risk is increased (which is about twice the risk in the general population) due to the inferior quality of bone. Bone fragility in type 2 diabetes, which is not reflected by bone mineral density, depends on bone quality deterioration rather than bone mass reduction. Thus, surrogate markers and examination methods are needed to replace the insensitivity of BMD in assessing fracture risks of T2DM patients. One of these methods can be trabecular bone score. The aim of the paper is to present the present state of scientific knowledge about the osteoporosis risk in diabetic patient. The review also discusses the possibility of problematic using the study conclusions in real clinical practice.

The inhibition of RANK-ligand in the management of postmenopausal osteoporosis and related fractures: the role of denosumab

There is great interest in new treatments of osteoporosis owing to general ageing of population and increased risk for fragility fractures in the elderly. Current therapies show a good efficacy in improving bone quality and bone density, but, in spite of a certain reduction in fracture rate, according to each treatment, the problem of osteoporotic fractures is yet far from to be solved. Moreover, some treatments may produce different side effects. Denosumab (Dmab), a receptor activator of nuclear factor kappa-B ligand (RANKL)-inhibitor, is an agent recently introduced in clinical practice for treatment of osteoporosis of postmenopausal women. Dmab has improved bone mineral density and prevented new vertebral and non-vertebral fractures with a similar efficacy in comparison with alendronate. Many clinical studies showed Dmab produces also significant improvement versus placebo in bone quality as indicated by decreasing markers of bone turnover. Patients using Dmab reported less risk of AFF (Atypical Femoral Fractures) and ONJ (Osteonecrosis of the Jaw) with an increased number of cellulitis. Here, we review articles using Dmab for female post-menopausal osteoporosis.

Denosumab: A comprehensive review

The clinical sequelae from bone metastases, termed skeletal-related events (SREs), are among the most frequent and debilitating complications in patients with advanced cancer. Bone metastases are characterized by pathologically increased osteoclast activity, and accumulating evidence indicates that tumor cells interact within the bone to stimulate the receptor activator of nuclear factor kB (RANK)-RANK ligand (RANKL) pathway. RANKL is an essential mediator of osteoclast formation, function, and survival. Because of the central role of RANKL in cancer-induced bone destruction, the inhibition of RANKL has the potential to result in the reduction of pathologic bone resorption. Denosumab is a fully human monoclonal antibody specific for RANKL that inhibits the formation, activation, and survival of osteoclasts. This in turn decreases bone resorption and reduces cancer-induced bone destruction. In this review, we give an overview of the drug Denosumab with its history, mechanism of action, clinical trial data, adverse effects, and future challenges.

Denosumab in osteoporosis

INTRODUCTION

Denosumab is a fully human monoclonal antibody against the receptor activator of nuclear factor kappa-B ligand. It is an antiresorptive agent that reduces osteoclastogenesis.

AREAS COVERED

This drug evaluation reviews denosumab for use in osteoporosis. Denosumab has been shown to improve bone mineral density (BMD) and to reduce the incidence of new vertebral, hip and nonvertebral fractures in postmenopausal women. It prevents bone loss and reduces vertebral fracture risk in men with nonmetastatic prostate cancer who are receiving androgen deprivation therapy. It has also been shown to improve BMD in men with osteoporosis unrelated to androgen deprivation therapy. Safety concerns include infections, cancer, skin reactions, cardiovascular disease, hypocalcemia, osteonecrosis of the jaw and atypical femur fractures.

EXPERT OPINION

Although bisphosphonates are typically preferred as initial therapy for osteoporosis, denosumab could be used as initial therapy in select patients at high risk for fracture, including older patients who have difficulty with the dosing requirements of oral bisphosphonates, patients who are intolerant of or unresponsive to other therapies, and in those with impaired renal function. Additional data is needed to address issues regarding treatment duration and discontinuation, as well as to provide more information regarding denosumab's efficacy and safety.

A new antiresorptive approach to the treatment of fragility fractures: long-term efficacy and safety of denosumab

An imbalance of the remodeling process for bone resorption leads to a loss of tissue with consequent microarchitectural damage, evident in conditions such as osteoporosis and related fragility fractures. Currently, pharmacological therapies are able to prevent or slow down bone resorption by inhibiting osteoclast activity. An innovative and targeted anti-resorptive approach is represented by the inhibition of RANK ligand (RANK-L), essential for the proliferation and activity of osteoclastic cells. The human monoclonal antibody against RANK-L (denosumab) has been approved for the treatment of osteoporosis. In clinical trials of patients with osteoporosis, inhibition of RANK-L has reduced bone loss and damage to the microarchitecture and was associated with an increase in mass and resistance at different skeletal sites, with most significant effects than those demonstrated by any other antiresorptive drugs. In addition, after 3 years of treatment, it showed a reduction in vertebral and non-vertebral fracture risk. Denosumab treatment also has not revealed any alteration in the physiological processes of fracture repair, showing no increase in the onset of complications 3 years after the fracture. The data show that denosumab offers an effective alternative therapeutic approach for the treatment of severe osteoporosis, with positive effects on BMD and reduction of fragility fractures risk. So, promising results in terms of therapeutic efficacy and reliability make desirable the wide clinical use of denosumab for the treatment of osteoporotic fractures in the near future.

Challenges and approaches for the development of safer immunomodulatory biologics

Immunomodulatory biologics are a class of biotechnology-derived therapeutic products that are designed to engage immune-relevant targets and are indicated in the treatment and management of a range of diseases, including immune-mediated inflammatory diseases and malignancies.

Despite their high specificity and therapeutic advantages, immmunomodulatory biologics have been associated with adverse reactions such as serious infections, malignancies and cytokine release syndrome, which arise owing to the on-target or exaggerated pharmacological effects of these drugs. Immunogenicity resulting in the generation of antidrug antibodies is another unwanted effect that leads to loss of efficacy and — rarely — hypersensitivity reactions.

For some adverse reactions, mitigating and preventive strategies are in place, such as stratifying patients on the basis of responsiveness to therapy and the risk of developing adverse reactions. These strategies depend on the availability of robust biomarkers for therapeutic efficacy and the risk of adverse reactions: for example, seropositivity for John Cunningham virus is a risk factor for progressive multifocal leukoencephalopathy. The development of effective biomarkers will greatly aid these strategies.

The development and design of safer immunomodulatory biologics is reliant on a detailed understanding of the nature of the disease, target biology, the interaction of the target with the immunomodulatory biologic and the inherent properties of the biologic that elicit unwanted effects.

The availability of in vitro and in vivo models that can be used to predict adverse reactions associated with immunomodulatory biologics is central to the development of safer immunomodulatory biologics. Some progress has been made in developing in vitro and in silico tests for predicting cytokine release syndrome and immunogenicity, but there is still a lack of models for effectively predicting infections and malignancies.

Two pathways can be followed in designing and developing safer immunomodulatory biologics. The first pathway involves generating a biologic that engages an alternative target or mechanism to produce the desired pharmacodynamic effect without the associated adverse reaction, and is followed when the adverse reaction cannot be dissociated from the target biology. The second pathway involves redesigning the biologic to 'engineer out' components within the biologic structure that trigger adverse effects or to alter the nature of the target–biologic interactions.

Owing to their specificity, immunomodulatory biologics generally have better safety profiles than small-molecule drugs. However, adverse effects such as an increased risk of infections or cytokine release syndrome are of concern. Here, Park and colleagues discuss the current strategies used to predict and mitigate these adverse effects and consider how they can be used to inform the development of safer immunomodulatory biologics.

Immunomodulatory biologics, which render their therapeutic effects by modulating or harnessing immune responses, have proven their therapeutic utility in several complex conditions including cancer and autoimmune diseases. However, unwanted adverse reactions — including serious infections, malignancy, cytokine release syndrome, anaphylaxis and hypersensitivity as well as immunogenicity — pose a challenge to the development of new (and safer) immunomodulatory biologics. In this article, we assess the safety issues associated with immunomodulatory biologics and discuss the current approaches for predicting and mitigating adverse reactions associated with their use. We also outline how these approaches can inform the development of safer immunomodulatory biologics.

Safety concerns with the long-term management of osteoporosis

INTRODUCTION

Postmenopausal osteoporosis is a chronic disease that exerts a significant burden on both individuals and the community. Hence, there is a requirement for long-term treatment to be associated with a positive benefit-risk balance.

AREAS COVERED

In this descriptive review, the long-term safety of calcitonin, selective estrogen receptor modulators (SERMs), bisphosphonates, denosumab and strontium ranelate was reviewed based on randomized controlled trials of 3 years or longer supplemented by extension study data and data from large, observational studies.

EXPERT OPINION

Rare adverse events become apparent with all currently available treatments for osteoporosis with long-term therapy. Due to the rarity of these adverse events and to the worldwide burden of osteoporosis, the benefit-risk balance remains in favor of the beneficial effects of treatment on an outcome rather than the probability of an adverse effect. No single antiosteoporosis agent is appropriate for all patients. Treatment decisions should be made on an individual basis, taking into account the relative benefits and risks in different patient populations.

Denosumab in breast cancer treatment

The bone is the most common site to which breast cancer metastasises. Recently, denosumab, a fully human monoclonal antibody that binds to receptor activator of nuclear factor kappa-B ligand (RANKL) has been developed as a new targeted bone therapy. In a large randomized phase III study with a head-to-head comparison of denosumab to zoledronic acid in patients with bone metastases of breast cancer, denosumab significantly delayed the time to first skeletal related event. In the adjuvant setting denosumab significantly increased bone mineral density compared to placebo in a phase III study in patients treated with aromatase inhibitors. Preclinical data suggest an effect of denosumab on tumour growth and even on carcinogenesis. This review describes the current indications for denosumab in the various settings of breast cancer treatment, with special attention for efficacy, short and long term toxicity and other relevant issues for clinical practice. Furthermore possible and necessary future research questions are proposed.

New and emerging therapies for bone metastases in genitourinary cancers

CONTEXT

Bone metastases are a common feature of advanced genitourinary malignancies and a prominent cause of morbidity and mortality.

OBJECTIVE

The objective of this review is to discuss the incidence, pathophysiology, and management of bone metastases in the most prevalent genitourinary malignancies.

EVIDENCE ACQUISITION

We reviewed the relevant medical literature, with a particular emphasis on prospective randomized controlled trials. Much of the relevant clinical trial data focus on prostate cancer (PCa). We provide a nonsystematic review and our perspective on the available data.

EVIDENCE SYNTHESIS

Clinical manifestations can include pain, hypercalcemia, pathologic fractures, and spinal cord compression. Optimal systemic therapy for skeletal metastases often features a combination of disease-specific therapy and bone-targeted therapy. Some agents, such as the radiopharmaceutical radium-223, blur the line between those categories. Osteoclast inhibition is a validated strategy in the management of selected patients with bone metastases. Zoledronic acid, a bisphosphonate, is approved for the prevention of skeletal events caused by solid tumors metastatic to bone. Denosumab is a fully human monoclonal antibody that inactivates receptor activator of nuclear factor-κB ligand and is approved for the same indication. Beta-emitting radiopharmaceuticals can be effective for the palliation of pain caused by bone metastases, but their use is often limited by marrow suppression. The alpha-emitting radiopharmaceutical radium-223 has recently been shown to improve overall survival and prevent skeletal events in select men with castration-resistant PCa metastatic to bone. Multiple ongoing clinical trials are designed to examine the potential for therapeutic inhibition of additional targets such as Src and hepatocyte growth factor (MET).

CONCLUSIONS

Bone metastases cause considerable morbidity and mortality among patients with genitourinary malignancies. Optimal management requires consideration of bone-targeted therapy as well as disease-specific therapy. Further research is needed to optimize the use of existing agents and to define the therapeutic potential of novel targets.

Denosumab, a RANK ligand inhibitor, for the management of bone loss in cancer patients

Bone loss is a common side effect of cancer treatments, especially antihormonal treatments used in the treatment of breast and prostate cancer. Denosumab is a monoclonal antibody given subcutaneously that inhibits osteoclast activity by targeting the RANK ligand. It is effective in settings ranging from preventing skeletal-related complications in cancer patients with metastatic disease to increasing bone mineral density in patients with osteoporosis. In cancer patients with early stage disease, denosumab can attenuate bone loss from antihormonal treatments, and in prostate cancer, may reduce disease progression. Here, we will discuss the important role denosumab may play in the management of bone loss in patients with cancer.

Skeletal and extraskeletal actions of denosumab

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.

The development of denosumab for the treatment of diseases of bone loss and cancer-induced bone destruction

Denosumab is a fully human monoclonal antibody against RANK ligand (RANKL), an essential cytokine for the formation, function, and survival of osteoclasts. The role of excessive RANKL as a contributor to conditions characterized by bone loss or bone destruction has been well studied. With its novel mechanism of action, denosumab offers a significant advance in the treatment of postmenopausal osteoporosis; bone loss associated with hormone ablation therapy in women with breast cancer and men with prostate cancer; and the prevention of skeletal-related events in patients with bone metastases from solid tumors by offering clinical benefit to these patients in need.

Therapeutic options for low bone mineral density in HIV-infected subjects

With the advent of effective antiretroviral therapy (ART), the recognition and management of long-term complications of HIV infection and ART are increasingly important for HIV physicians. Low bone mineral density (BMD) is more common in those with HIV infection and this review will outline therapeutic options for the management of low bone mineral density relevant to HIV-infected populations.

Role of RANK ligand and denosumab, a targeted RANK ligand inhibitor, in bone health and osteoporosis: a review of preclinical and clinical data

BACKGROUND

Postmenopausal osteoporosis results from bone loss and decreased bone strength mediated by an increased rate of bone remodeling secondary to reduced estrogen levels. Remodeling cycles are initiated by osteoclasts, the formation, function, and survival of which depend on RANK ligand (RANKL). RANKL inhibition therefore represents a novel strategy for reducing remodeling and its effects on fracture risk.

OBJECTIVES

The goal of this study was to review the preclinical and clinical evidence supporting the value of RANKL inhibition in conditions of bone loss and to provide the rationale for the use of the fully human antibody denosumab, a RANKL inhibitor, in such conditions.

METHODS

We searched PubMed from January 2005 to May 2011 using the following terms: RANK Ligand, RANKL, denosumab, and NOT cancer, metastatic bone, or rheumatoid in the title.

RESULTS

The search method retrieved 111 articles. Preclinical evidence from several bone disease models suggests that RANKL inhibition leads to increased bone volume, density, and strength. Denosumab prevents RANKL from binding to its receptor, decreasing osteoclast activity and thereby reducing bone resorption and increasing cortical and trabecular bone mass and strength. It has consistently been reported to reduce bone turnover, increase bone density, and reduce the risk of fracture in clinical studies of postmenopausal women. Phase III head-to-head trials comparing denosumab with the bisphosphonate alendronate reported that denosumab was associated with significantly greater increases in bone density. Eczema as an adverse event and cellulitis as a serious adverse event were more common with denosumab than with placebo.

CONCLUSIONS

Preclinical studies defined the role of RANKL in bone remodeling and provided evidence for the therapeutic potential of RANKL inhibition in conditions of bone loss. Clinical studies evaluating RANKL inhibition with denosumab in postmenopausal women have reported significant reductions in vertebral, nonvertebral, and hip fractures, providing evidence compatible with the use of denosumab in postmenopausal women with osteoporosis.

Long-term treatment of osteoporosis: safety and efficacy appraisal of denosumab

Denosumab is a fully human monoclonal antibody to the receptor activator of nuclear factor-κB ligand (RANKL), a member of the tumor necrosis factor receptor superfamily essential for osteoclastogenesis. Denosumab treatment is associated with a rapid, sustained, and reversible reduction in bone turnover markers, a continuous marked increase in bone mineral density at all sites, and a marked decrease in the risk of vertebral, hip, and nonvertebral fractures in women with postmenopausal osteoporosis. Therefore, it could be considered as an effective alternative to previous bisphosphonate treatment as well as first-line treatment of severe osteoporosis. Cost-effectiveness studies support this suggestion. In addition, denosumab seems to be the safest treatment option in patients with impaired renal function. Denosumab is characterized by reversibility of its effect after treatment discontinuation, in contrast with bisphosphonates. Large-scale clinical trials, including the extension of FREEDOM trial for up to 5 years, are reassuring for its safety. However, given its brief post-market period, vigilance regarding adverse events related to putative RANKL inhibition in tissues other than bone, as well as those related to bone turnover oversuppression, is advised.

Antiresorptive therapies in oncology and their effects on cancer progression

Bone health is an emerging concern in the early breast cancer setting. Current adjuvant therapies, especially hormonal therapies in premenopausal patients (e.g. goserelin) and aromatase inhibitors in postmenopausal patients, have been associated with substantial decreases in bone mineral density that may place patients at risk for fractures. Bisphosphonates--and the recently approved anti-RANKL antibody, denosumab--have both demonstrated activity for the treatment of postmenopausal osteoporosis and cancer treatment-induced bone loss (CTIBL) in breast cancer patients, although neither has received widespread approval specifically for CTIBL. However, some bisphosphonates, especially the nitrogen-containing bisphosphonate zoledronic acid, have also demonstrated clinically meaningful anticancer effects in patients receiving adjuvant hormonal therapy for breast cancer and in other oncology settings. The effects of denosumab on cancer disease outcomes in the adjuvant setting remain to be established. This discrepancy has created a dilemma in terms of how to evaluate the complete benefit:risk profile of bone-health management options in the adjuvant breast cancer setting. This review summarises the current data on the course of cancer in clinical trials of the antiresorptive agents and provides important insight into the relative anticancer potential of the various therapies.

Safety and tolerability of denosumab for the treatment of postmenopausal osteoporosis

Denosumab is a fully human monoclonal antibody to receptor activator of nuclear factor kappa-B ligand (RANKL), a cytokine member of the tumor necrosis factor family that is the principal regulator of osteoclastic bone resorption. Postmenopausal osteoporosis (PMO) is a systemic skeletal disease associated with high levels of RANKL, resulting in a high rate of bone remodeling and an imbalance of bone resorption over bone formation. By inhibiting RANKL in women with PMO, denosumab reduces the rate of bone remodeling, thereby increasing bone mineral density, improving bone strength, and reducing the risk of fractures. In clinical trials of women with osteoporosis and low bone mineral density, denosumab has been well tolerated, with overall rates of adverse events and serious adverse events in women treated with denosumab similar to those receiving placebo. In the largest clinical trial of denosumab for the treatment of women with PMO, there was a significantly greater incidence of cellulitis reported as a serious adverse event, with no difference in the overall incidence of cellulitis, and a significantly lower incidence of the serious adverse event of concussions with denosumab compared with placebo. The evidence supports a favorable balance of benefits versus risks of denosumab for the treatment of PMO. Assessments of the long-term safety of denosumab are ongoing. Denosumab 60 mg subcutaneously every 6 months is an approved treatment for women with PMO who are at high risk for fracture.