Denosumab for prevention of fractures in postmenopausal women with osteoporosis

[Diagnosis and treatment of osteoporosis in persons aged more than 75 years]

Osteoporosis is a progressive skeletal disease characterized by a decrease in bone strength and an increase in the number of fractures. This disease is considered by the World Health Organization to be the second most important health problem in the world after cardiovascular disease. The prevalence of osteoporosis is increasing due to population aging. With age, the loss of bone mass in the spine and hip, which starts at menopause in women and around the age of 60 years in men, continues. Old age is when most fragility fractures occur and the incidence of these fractures is increasing exponentially in persons aged more than 75 years. Several treatments with demonstrated effectiveness in decreasing fracture risk and increasing bone mineral density are currently available for osteoporosis. Nevertheless, the scientific evidence on the safety and efficacy of these treatments is much more scarce in older people than in young populations. There are few reports on the efficacy of these treatments in non-vertebral--specifically hip--fractures in the elderly. Consequently, the present review aims to analyze the scientific evidence on the diagnosis and treatment of osteoporosis, and particularly the evidence on the antifracture efficacy of distinct antiresorptive agents and anabolic drugs in people older than 75 years.

Denosumab--an emerging treatment for postmenopausal osteoporosis

IMPORTANCE OF THE FIELD

Osteoporosis is a common skeletal disease that is associated with an imbalance in bone remodeling. Denosumab is an investigational fully human monoclonal antibody to receptor activator of NF-kappaB ligand (RANKL), a cytokine member of the TNF family that is the principal mediator of osteoclastic bone resorption.

AREAS COVERED IN THIS REVIEW

The efficacy and safety of denosumab in the management of postmenopausal osteoporosis is evaluated by reviewing the published literature and presentations at scientific meetings through 2009.

WHAT THE READER WILL GAIN

This review focuses on the data on fracture risk reduction and safety endpoints of denosumab in the treatment of postmenopausal osteoporosis.

TAKE HOME MESSAGE

In postmenopausal women with osteoporosis, denosumab (60 mg by subcutaneous injection every 6 months) increased bone mineral density, reduced bone turnover markers, and reduced the risk of vertebral, hip and non-vertebral fractures. Denosumab was well tolerated with a safety profile generally similar to placebo. It is a promising emerging drug for the prevention and treatment of postmenopausal osteoporosis.

Bone fractures after menopause

BACKGROUND

Every year 30% of individuals above age 65 fall, and falls are the principal cause of bone fractures. To reduce fracture incidence requires both prevention of falls and maintenance of bone strength.

METHODS

PubMed searches were performed, for studies of the epidemiology of fractures, bone physiology, endocrine effects, osteoporosis measurement, genetics, prevention and effectiveness. Topic summaries were presented to the Workshop Group and omissions or disagreements were resolved by discussion.

RESULTS

Ageing reduces bone strength in post-menopausal women because estrogen deficiency causes accelerated bone resorption. Bone mineral density (BMD) decreased more than 2.5 standard deviation below the mean of healthy young adults defines osteoporosis, a condition associated with an increased risk of fractures. Risk factors such as age and previous fracture are combined with BMD for a more accurate prediction of fracture risk. The most widely used assessment tool is FRAX™ which combines clinical risk factors and femoral neck BMD. General preventive measures include physical exercise to reduce the risk of falling and vitamin D to facilitate calcium absorption. Pharmacological interventions consist mainly in the administration of inhibitors of bone resorption. Randomized controlled trials show treatment improves BMD, and may reduce the relative fracture risk by about 50% for vertebral, 20-25% for non-vertebral and up to 40% for hip fractures although the absolute risk reductions are much lower.

CONCLUSIONS

Although diagnosis of osteoporosis is an important step, the threshold for treatment to prevent fractures depends on additional clinical risk factors. None of the presently available treatment options provide complete fracture prevention.

New treatment targets in osteoporosis

Postmenopausal osteoporosis is characterized by bone remodeling alterations with an imbalance between excessive bone resorption and inadequate bone formation. At present, osteoporosis treatment rests on bone resorption inhibitors and, more specifically, on bisphosphonates. However, the introduction of anabolic agents such as parathyroid hormone that stimulate bone formation has expanded the range of treatment options. New treatment targets have been identified via improved knowledge on bone pathophysiology, bone remodeling, bone cells and intracellular signaling pathways. RANKL inhibition by anti-RANKL antibodies is undergoing considerable development as a treatment for osteoporosis. Also under development are anti-catabolic drugs that target the molecular mechanisms involved in bone resorption, including cathepsin K inhibitors and integrin alpha(v)beta(3) antagonists. The identification of new pathways involved in bone formation is directing clinical research efforts toward the development of anabolic agents. The signaling pathways involved in bone formation, most notably the Wnt-pathway, hold considerable promise as treatment targets in conditions characterized by insufficient bone formation. Current focuses of interest include antibodies against naturally occurring Wnt-pathway antagonists (e.g., sclerostin and Dkk1) and modulators of parathyroid hormone production (calcilytic agents). Thus, active research is ongoing to improve the treatment of osteoporosis, a disease whose high prevalence and considerable functional and socioeconomic impact will raise formidable challenges in the near future.

[Molecular basis of bone metastasis formation and its targeted therapy]

Formation of bone metastasis is a hallmark of the progression of several solid cancers, providing example for the organ specificity of the process. Bone metastasis may result in both venous and arterial dissemination. Though the molecular basis of the lytic and plastic bone metastasis formation is different, in reality these organ metastases represent a mixture of the two processes. The basis of bone metastasis formation is the activation of osteoclasts and the resulting bone resorption, initiating a vicious circle by activating the initiator cancer cell. The discovery of osteoclast-bone matrix interaction inhibitor bisphosphonates revolutionized the therapy of bone metastasis. Clarifying the molecular pathways involved in bone metastasis formation identified osteoclast differentiation as another feasible target. This process is under control of the TNF receptor family member RANK and its ligand RANKL. The feasibility of using this system to control bone resorption or cancer-induced skeletal events was proven clinically in trials using an anti-RANKL antibody. The clinical success of anti-RANKL antibody therapy provide further evidence that only precise identification of molecular pathways operational in cancers can lead to discovery of more effective (targeted) therapies.

Effect of osteoporosis treatment on mortality: a meta-analysis

CONTEXT

Fragility fractures cause significant morbidity and mortality. Effective osteoporosis treatment can reduce fracture incidence, but it is not known whether it reduces mortality.

OBJECTIVE

The aim of the study was to determine whether effective osteoporosis treatment reduces mortality.

DATA SOURCES

We searched Medline and the Cochrane Central Register of Trials prior to September 2008, as well as 2000-2008 American Society for Bone and Mineral Research conference abstracts.

STUDY SELECTION

Eligible studies were randomized placebo-controlled trials of approved doses of medications with proven efficacy in preventing both vertebral and nonvertebral fractures, in which the study duration was longer than 12 months and there were more than 10 deaths. Trials of estrogen and selective estrogen receptor modulators were specifically excluded.

DATA EXTRACTION

Data were extracted from the text of the retrieved articles, published meta-analyses, or the Food and Drug Administration web site.

DATA SYNTHESIS

Eight eligible studies of four agents (risedronate, strontium ranelate, zoledronic acid, and denosumab) were included in the primary analysis. During two alendronate studies, the treatment dose changed, and those studies were only included in secondary analyses. In the primary analysis, treatment was associated with an 11% reduction in mortality (relative risk, 0.89; 95% confidence interval, 0.80-0.99; P = 0.036). In the secondary analysis, the results were similar (relative risk, 0.90; 95% confidence interval, 0.81-1.0; P = 0.044). Mortality reduction was not related to age or incidence of hip or nonvertebral fracture, but was greatest in trials conducted in populations with higher mortality rates.

CONCLUSIONS

Treatments for osteoporosis with established vertebral and nonvertebral fracture efficacy reduce mortality in older, frailer individuals with osteoporosis who are at high risk of fracture.

The role of microbial biofilms in osteonecrosis of the jaw associated with bisphosphonate therapy

Microbial biofilms have been observed and described in bone specimens of patients with bisphosphonate (BP)-associated osteonecrosis of the jaw (BONJ) and investigators are more recently suggesting that this condition essentially represents an osteomyelitis of the jaw clinically, with greater susceptibility in some patients on BP therapy. This article explains the role of microbial biofilms in BONJ and also discusses associated factors in the disease pathogenesis, which include BP effects on bone remodeling, anti-angiogenesis, matrix necrosis, microcracks, soft tissue toxicity, and inflammation and wound healing. Recent findings suggest a key role for microbial biofilms in the pathogenesis of BONJ; this has important therapeutic implications because biofilm organisms represent a clinical target for prevention and treatment efforts aimed at reducing the significant morbidity and costs associated with this condition.

Glucocorticoid-induced osteoporosis: management update

Osteoporosis due to glucocorticoid-induced osteoporosis (GIOP) for inflammatory disorders continues to be a common problem. Well-distributed guidelines have provided evidence-based recommendations for management, yet many patients have little attention paid to their increased fracture risk. The purpose of this article is to discuss how new treatments for GIOP may improve overall management. Intravenous zoledronic acid (ZA), an antiresorptive agent, and teriparatide (TPT), which stimulates osteoblasts, have received US Food and Drug Administration (FDA) approval for treating GIOP. ZA is appealing because one 15-min infusion covers the patient for a year and potentially will increase the proportion of GIOP patients who are treated. TPT makes physiologic sense because GIOP is mostly due to decreased osteoblast function, and TPT stimulates osteoblasts. Although there is only one small published study in humans with GIOP, denosumab is a potentially useful antiresorptive agent, if it is approved by the FDA. The efficacy and safety of these medications in GIOP are discussed.

Strategies for treatment to prevent fragility fractures in postmenopausal women

The objective of treatment of osteoporosis is to decrease the risk of fractures in patients at high risk for a first or subsequent fracture. The efficacy of treatment will depend on the efficiency and level of implementation of clinical case finding to select patients at risk, the results of additional investigations, the efficacy, tolerance and safety of medical intervention and the adherence to treatment during follow-up. Each of these steps is critical in treatment in daily practice. Failure to consider one or another step can result in suboptimal fracture prevention or overtreatment. The aim of case finding is to identify patients for treatment, who have disease characteristics of patients in whom fracture prevention has been demonstrated in randomised controlled trials (RCTs). These include patients with a low-trauma hip or vertebral fracture, with a low bone mineral density (BMD) or with a high risk of fracture based on the presence of clinical risk factors (CRFs) for osteoporosis and fractures such as included in the FRAX case-finding algorithm, with or without BMD. Case finding starts clinically, with systematic or opportunistic doctor- and/or patient-driven evaluation for the presence of CRFs, but its implementation is low. Further investigations aim to assess the risk of fracture(s) and to have baseline measurements for the subsequent monitoring of treatment, to exclude diseases that mimic osteoporosis, to identify the cause of osteoporosis and contributory factors and to select the most appropriate treatment. Medical intervention consists of providing information about osteoporosis to the patient, lifestyle advice, optimalisation of calcium intake and vitamin D status, fall prevention to reduce fall risk, correction of reversible contributors to secondary osteoporosis and a wide array of drugs for prevention of a first or subsequent vertebral, hip and non-vertebral, non-hip fracture. Drug treatment is based on manipulation of bone remodelling by inhibiting bone resorption (bisphosphonates, selective oestrogen-receptor modulator (SERMs), calcitonin), stimulating bone formation (parathyroid hormone) or mixed effects (strontium ranelate). Follow-up allows to check tolerance and safety, to optimise adherence and to decide about adequacy of response, duration and switching of therapy.

Molecular biology of bone remodeling: implications for new therapeutic targets for osteoporosis

Osteoporosis is a major public health problem for adults over age 55 years costing billions of euros/dollars. Over the last 20 years anti-resorptive drugs were the treatment of choice for osteoporosis and most were derived from the bisphosphonate molecule. In the last 7 years remarkable advances in molecular biology and genetics have led to a detailed understanding of the bone remodeling cycle and as a result new therapeutic targets for treatment emerged. These new compounds have different modes of action depending on their role in the bone remodeling cycle. A major discovery was the important role of RANKL (receptor activator of nuclear factor kappa B ligand) secreted by osteoblasts and responsible for stimulating osteoclastic bone resorption. This led to development of a potent monoclonal antibody that blocks its action. This drug should be available soon as a new treatment for osteoporosis. Other molecular targets in resorption have been identified and several specific antagonists are potential treatments. However, a significant limiting factor for a new anti-resorptive drug is the cost of bringing it to the market because of the huge costs of a fracture trial. Although anti-resorptive agents have been the backbone of osteoporosis treatment they do not rebuild bone architecture and development of anabolic agents is needed. These are likely to evolve from an understanding of the LRP/Wnt signaling pathway. Already an antibody against sclerostin has shown promise in animal studies, and not to forget parathyroid hormone which was the first clinically useful anabolic treatment for osteoporosis.

Bone mineral density and prediction of non-osteoporotic disease

It is widely recognized that bone mineral density (BMD) is one of the best predictors of osteoporotic fractures. Sex hormone status clearly affects bone either directly or indirectly and a longer estrogen exposure appears to be a major determinant of postmenopausal BMD. Accordingly, several studies have led to the hypothesis that BMD might represent a marker of the accumulated lifetime exposure of estrogen and therefore be used as a predictor factor of the risk of other postmenopausal conditions such as breast cancer or cardiovascular diseases (CVD). With regard to the risk of breast cancer, there is evidence that different surrogate markers of lifetime exposure to estrogen are associated with an increased risk for breast cancer. Most of these markers are the opposite of those for the risk of fracture. Furthermore, several studies have also reported that women with higher BMD have an increased risk of breast cancer compared to women with lower BMD. On the other hand, postmenopausal women with osteoporosis are at increased risk for acute cardiovascular events and mortality independently of age and cardiovascular risk factors. BMD has been shown to inversely correlate with surrogate markers of CVD including aortic calcifications and atherosclerosis. The underlying mechanisms of such a relationship are not fully understood. Several plausible molecular links are serum lipids, pro-inflammatory cytokines or the RANK/RANK ligand/osteoprotegerin system. Interestingly, all of these factors are modulated by estrogens. It could thus be hypothesized that the intensity of postmenopausal estrogen deficiency could be also the common pathogenic factor between atherosclerosis and osteoporosis.

Central control of fever and female body temperature by RANKL/RANK

Receptor-activator of NF-kappaB ligand (TNFSF11, also known as RANKL, OPGL, TRANCE and ODF) and its tumour necrosis factor (TNF)-family receptor RANK are essential regulators of bone remodelling, lymph node organogenesis and formation of a lactating mammary gland. RANKL and RANK are also expressed in the central nervous system. However, the functional relevance of RANKL/RANK in the brain was entirely unknown. Here we report that RANKL and RANK have an essential role in the brain. In both mice and rats, central RANKL injections trigger severe fever. Using tissue-specific Nestin-Cre and GFAP-Cre rank(floxed) deleter mice, the function of RANK in the fever response was genetically mapped to astrocytes. Importantly, Nestin-Cre and GFAP-Cre rank(floxed) deleter mice are resistant to lipopolysaccharide-induced fever as well as fever in response to the key inflammatory cytokines IL-1beta and TNFalpha. Mechanistically, RANKL activates brain regions involved in thermoregulation and induces fever via the COX2-PGE(2)/EP3R pathway. Moreover, female Nestin-Cre and GFAP-Cre rank(floxed) mice exhibit increased basal body temperatures, suggesting that RANKL and RANK control thermoregulation during normal female physiology. We also show that two children with RANK mutations exhibit impaired fever during pneumonia. These data identify an entirely novel and unexpected function for the key osteoclast differentiation factors RANKL/RANK in female thermoregulation and the central fever response in inflammation.

Emerging therapeutic targets in breast cancer bone metastasis

In the past decade, our understanding of the molecular mechanisms that underlie breast cancer pathology and progression has dramatically improved. Using this knowledge, we have identified additional targets and developed novel therapeutic interventions in breast cancer. Together, these translational research efforts are helping to usher us into an age of personalized cancer therapy. Metastasis to bone is a common and devastating consequence of breast cancer. Bisphosphonates, which represent the current gold standard in bone metastasis therapies, are being improved with newer and more efficacious generations of these compounds being developed. Breast cancer growth in the bone requires activation of various signaling pathways in both cancer cells and stromal cells, including those that are stimulated by TGF-β and RANKL, and mediated through the Src tyrosine kinase. Bone cells and cancer cells alike express promising targets for therapeutic intervention, including Cathepsin K, CXCR4 and GPNMB. In this article we discuss the molecular mechanisms behind these pro-metastatic molecules and review the most recent findings in the clinical development of their associated targeted therapies.

2009 Santa Fe Bone symposium

Osteoporosis is a common skeletal disease with serious clinical consequences because of fractures. Despite the availability of clinical tools to diagnose osteoporosis and assess fracture risk, and drugs proven to reduce fracture risk, it remains a disease that is underdiagnosed and undertreated. When treatment is started, it is commonly not taken correctly or long enough to be effective. Recent advances in understanding of the regulators and mediators of bone remodeling have led to new therapeutic targets and the development of drugs that may offer advantages over current agents in reducing the burden of osteoporotic fractures. Many genetic factors that play a role in the pathogenesis of osteoporosis and metabolic bone disease have now been identified. At the 2009 Santa Fe Bone Symposium, held in Santa Fe, New Mexico, USA, the links between advances in genetics, basic bone science, recent clinical trials, and new and emerging therapeutic agents were presented and explored. Socioeconomic challenges and opportunities in the care of osteoporosis were discussed. This is a collection of medical essays based on key presentations at the 2009 Santa Fe Bone Symposium.

Genetics of osteoporosis: accelerating pace in gene identification and validation

Osteoporosis is characterized by low bone mineral density and structural deterioration of bone tissue, leading to an increased risk of fractures. It is the most common metabolic bone disorder worldwide, affecting one in three women and one in eight men over the age of 50. In the past 15 years, a large number of genes have been reported as being associated with osteoporosis. However, only in the past 4 years we have witnessed an accelerated pace in identifying and validating osteoporosis susceptibility loci. This increase in pace is mostly due to large-scale association studies, meta-analyses, and genome-wide association studies of both single nucleotide polymorphisms and copy number variations. A comprehensive review of these developments revealed that, to date, at least 15 genes (VDR, ESR1, ESR2, LRP5, LRP4, SOST, GRP177, OPG, RANK, RANKL, COLIA1, SPP1, ITGA1, SP7, and SOX6) can be reasonably assigned as confirmed osteoporosis susceptibility genes, whereas, another >30 genes are promising candidate genes. Notably, confirmed and promising genes are clustered in three biological pathways, the estrogen endocrine pathway, the Wnt/beta-catenin signaling pathway, and the RANKL/RANK/OPG pathway. New biological pathways will certainly emerge when more osteoporosis genes are identified and validated. These genetic findings may provide new routes toward improved therapeutic and preventive interventions of this complex disease.

Good clinical endpoints with denosumab in osteoporosis and cancer

BACKGROUND

Bone loss associated with low oestrogen levels in postmenopausal women, and with androgen deprivation therapy in men with hormone-sensitive prostate cancer, result in an increased incidence of fractures. Denosumab has been shown to increase bone mineral density in these two conditions.

OBJECTIVES/METHODS

The objective of this evaluation is to review the clinical trials that have studied clinical endpoints in these conditions.

RESULTS

FREEDOM (Fracture Reduction Evaluation of Denosumab in Osteoporosis Every 6 Months) was an International Phase III clinical trial that measured the clinical endpoints with denosumab in postmenopausal women with osteoporosis. At 36 months, new vertebral fractures had occurred in 7.2% of subjects in the placebo group and this was lowered to 2.3% of subjects treated with denosumab. HALT (Denosumab Hormone Ablation Bone Loss Trial) studied the clinical endpoints in men with non-metastatic prostate cancer receiving androgen-deprivation therapy. The incidence of vertebral fractures was significantly lower in the denosumab group (1.5%) than in the placebo group (3.9%). The incidence of adverse effects with denosumab in both clinical trials was low.

CONCLUSIONS

Denosumab reduces the incidence of fractures in postmenopausal women with osteoporosis and in men with non-metastatic prostate cancer receiving androgen-deprivation therapy. Denosumab is well tolerated.

Assessing fracture risk and effects of osteoporosis drugs: bone mineral density and beyond

Although there have been numerous advances in the assessment of bone strength and fracture risk, the majority of these techniques can only be performed in research laboratories, making them largely unavailable to practicing clinicians. Prospective epidemiologic studies have identified risk factors that can be assessed within the clinic and combined with bone mineral density to allow clinicians to better identify untreated individuals at heightened risk for fracture and to make informed treatment decisions based on 10-year absolute fracture risk. This article discusses the assessment of fracture risk in clinical practice, reviews currently and soon-available bone measurement tools, and details the impacts of osteoporosis therapies on fracture risk.

Progress in osteoporosis and fracture prevention: focus on postmenopausal women

In the past decade, we have witnessed a revolution in osteoporosis diagnosis and therapeutics. This includes enhanced understanding of basic bone biology, recognizing the severe consequences of fractures in terms of morbidity and short-term re-fracture and mortality risk and case finding based on clinical risks, bone mineral density, new imaging approaches, and contributors to secondary osteoporosis. Medical interventions that reduce fracture risk include sufficient calcium and vitamin D together with a wide spectrum of drug therapies (with antiresorptive, anabolic, or mixed effects). Emerging therapeutic options that target molecules of bone metabolism indicate that the next decade should offer even greater promise for further improving our diagnostic and treatment approaches.