Pharmacologic profile of zoledronic acid: A highly potent inhibitor of bone resorption

Bioactive coatings with anti-osteoclast therapeutic agents for bone implants: Enhanced compliance and prolonged implant life

The use of therapeutic agents that inhibit bone resorption is crucial to prolong implant life, delay revision surgery, and reduce the burden on the healthcare system. These therapeutic agents include bisphosphonates, various nucleic acids, statins, proteins, and protein complexes. Their use in systemic treatment has several drawbacks, such as side effects and insufficient efficacy in terms of concentration, which can be eliminated by local treatment. This review focuses on the incorporation of osteoclast inhibitors (antiresorptive agents) into bioactive coatings for bone implants. The ability of bioactive coatings as systems for local delivery of antiresorptive agents to achieve optimal loading of the bioactive coating and its release is described in detail. Various parameters such as the suitable concentrations, release times, and the effects of the antiresorptive agents on nearby cells or bone tissue are discussed. However, further research is needed to support the optimization of the implant, as this will enable subsequent personalized design of the coating in terms of the design and selection of the coating material, the choice of an antiresorptive agent and its amount in the coating. In addition, therapeutic agents that have not yet been incorporated into bioactive coatings but appear promising are also mentioned. From this work, it can be concluded that therapeutic agents contribute to the biocompatibility of the bioactive coating by enhancing its beneficial properties.

Bisphosphonate drugs have actions in the lung and inhibit the mevalonate pathway in alveolar macrophages

Bisphosphonates drugs target the skeleton and are used globally for the treatment of common bone disorders. Nitrogen-containing bisphosphonates act by inhibiting the mevalonate pathway in bone-resorbing osteoclasts but, surprisingly, also appear to reduce the risk of death from pneumonia. We overturn the long-held belief that these drugs act only in the skeleton and show that a fluorescently labelled bisphosphonate is internalised by alveolar macrophages and large peritoneal macrophages in vivo. Furthermore, a single dose of a nitrogen-containing bisphosphonate (zoledronic acid) in mice was sufficient to inhibit the mevalonate pathway in tissue-resident macrophages, causing the build-up of a mevalonate metabolite and preventing protein prenylation. Importantly, one dose of bisphosphonate enhanced the immune response to bacterial endotoxin in the lung and increased the level of cytokines and chemokines in bronchoalveolar fluid. These studies suggest that bisphosphonates, as well as preventing bone loss, may boost immune responses to infection in the lung and provide a mechanistic basis to fully examine the potential of bisphosphonates to help combat respiratory infections that cause pneumonia.

Bisphosphonate-Based Conjugates and Derivatives as Potential Therapeutic Agents in Osteoporosis, Bone Cancer and Metastatic Bone Cancer

Metastatic bone cancer occurs in every type of cancer but is prevalent in lung, breast, and prostate cancers. These metastases can cause extensive morbidity, including a range of skeletal-related events, often painful and linked with substantial hospital resource usage. The treatment used is a combination of chemotherapy and surgery. However, anticancer drugs are still limited due to severe side effects, drug resistance, poor blood supply, and non-specific drug uptake, necessitating high toxic doses. Bisphosphonates are the main class of drugs utilized to inhibit metastatic bone cancer. It is also used for the treatment of osteoporosis and other bone diseases. However, bisphosphonate also suffers from serious side effects. Thus, there is a serious need to develop bisphosphonate conjugates with promising therapeutic outcomes for treating metastatic bone cancer and osteoporosis. This review article focuses on the biological outcomes of designed bisphosphonate-based conjugates for the treatment of metastatic bone cancer and osteoporosis.

Radiopharmaceuticals for Bone Metastases

As a single organ distributed diffusely throughout the body, bones represent both a unique challenge and unique opportunity for the treatment of symptomatic metastatic disease. While the multifocality of bone metastases often prevents effective complete treatment with focal radiotherapy, the similar pathophysiology of these diffuse sites of disease opens the door to targeted systemic therapy. The relatively rapid dose fall-off from beta- or alpha-emitting particles, if correctly and reliably targeted to osseous metastases, might reduce tumor burden and enhance pain control or improve survival. Radioisotopes have thus been studied keenly with the first generation of primarily beta-emitting radioisotopes, strontium-89 and samarium-153, which reached early FDA approval based on successful endpoints of pain control. More recently, an alpha-emitting therapy, radium-223, has demonstrated a successful endpoint of improved overall survival in patients with a burden of symptomatic, metastatic castrate-resistant prostate cancer (mCRPC) confined to the bones. With this discovery, an additional survival-improving tool beyond systemic and hormonal agents was added to the treatment arsenal for mCRPC for suitable candidates. With an improved understanding of the optimization of hormonal and systemic therapies in the context of mCRPC, there is lingering uncertainty regarding the safety and efficacy of combinatorial use of alpha and beta-emitting therapies with the current generation of systemic agents. In this narrative review, we will highlight the current understanding of the relative utility and clinical paradigms involving alpha- and beta-emitting radioisotopes. We discuss fundamental mechanisms for antineoplastic activity, initial clinical trials validating their use, the use of concurrent antiresorptive therapies to provide bone protection, and ongoing clinical trials targeted at best utilization of these agents in the broader context of mCRPC treatment.

Molecular mechanisms of action of bisphosphonates and new insights into their effects outside the skeleton

Bisphosphonates (BP) are a class of calcium-binding drug used to prevent bone resorption in skeletal disorders such as osteoporosis and metastatic bone disease. They act by selectively targeting bone-resorbing osteoclasts and can be grouped into two classes depending on their intracellular mechanisms of action. Simple BPs cause osteoclast apoptosis after cytoplasmic conversion into toxic ATP analogues. In contrast, nitrogen-containing BPs potently inhibit FPP synthase, an enzyme of the mevalonate (cholesterol biosynthesis) pathway. This results in production of a toxic metabolite (ApppI) and the loss of long-chain isoprenoid lipids required for protein prenylation, a process necessary for the function of small GTPase proteins essential for the survival and activity of osteoclasts. In this review we provide a state-of-the-art overview of these mechanisms of action and a historical perspective of how they were discovered. Finally, we challenge the long-held dogma that BPs act only in the skeleton and highlight recent studies that reveal insights into hitherto unknown effects on tumour-associated and tissue-resident macrophages.

Zoledronic Acid Attenuates Early Bone Loss at Forearm in Patients with Acute Spinal Cord Injury

STUDY DESIGN

Randomized controlled trial.

OBJECTIVES

To study the magnitude of bone loss at forearm in persons with acute spinal cord injury (SCI) & the effect of early administration of Zoledronic acid on its' prevention.

SETTINGS

Sawai Man Singh Medical College, Jaipur, India.

METHODS

Sixty patients with acute SCI were randomized either to receive standard medical and nursing care or Zoledronic acid infusion in combination with standard medical and nursing care. Areal bone mineral density (aBMD) was measured at the forearm (radius + ulna) once patients were medically stable using Dual Energy X-Ray Absorptiometry (DXA) at baseline and at 3, 6 and 12 months.

RESULTS

Significant differences in aBMD was found between the control & Zoledronic acid group at 1/3 forearm (- 0.064; 95% CI - 0.092 to - 0.036, p = 0.001), mid forearm (- 0.059; 95% CI - 0.084 to - 0.034, p = 0.001), UD forearm (- 0.048; 95% CI - 0.097 to 0.001, p = 0.016) and total forearm (- 0.048; 95% CI - 0.088 to - 0.008, p = 0.021) at 1 year in the paraplegic patients with SCI. Similar significant difference was also observed at 1/3 forearm (- 0.046; 95% CI - 0.073 to - 0.019, p = 0.002), mid forearm (- 0.063; 95% CI - 0.088 to - 0.037, p < 0.0001), UD forearm (- 0.084; 95% CI - 0.101 to - 0.067, p < 0.0001) and total forearm (- 0.115; 95% CI - 0.132 to - 0.097, p < 0.0001) respectively at 1 year in the quadriplegic patients with SCI. Significant differences in aBMD between the groups at 6 months post infusion was also observed at these sites in quadriplegic patients. [1/3 forearm - 0.022; 95% CI - 0.039 to - 0.005; p = 0.015, Mid forearm - 0.023; 95% CI - 0.042 to - 0.004; p = 0.019, UD forearm - 0.041; 95% CI - 0.055 to - 0.027; p < 0.0001 and Total forearm - 0.049; 95%CI - 0.062 to - 0.036; p < 0.0001]. Bone loss was reduced in the Zoledronic acid treated group compared to the standard treatment group in both paraplegic and quadriplegic patients.

CONCLUSION

Single dose of 5mg intravenous Zoledronic acid is an effective treatment in preventing bone loss at the forearm for 12 months following acute spinal cord injury.

Phosphate functionalization and enzymatic calcium mineralization synergistically enhance oligo[poly(ethylene glycol) fumarate] hydrogel osteoconductivity for bone tissue engineering

A current approach in bone tissue engineering is the implantation of polymeric scaffolds that promote osteoblast attachment and growth as well as biomineralization. One promising polymer is oligo[poly(ethylene glycol) fumarate] (OPF), a polyethylene glycol-based material that is biocompatible, injectable, and biodegradable, but in its native form does not support robust bone cell attachment or growth. To address this issue, this study evaluated the osteoconductivity of bis[02-(methacryloyloxy)ethyl] phosphate (BP) functionalized OPF hydrogels (OPF-BP) using MC3T3-E1 pre-osteoblast cells, both before and after enzymatic mineralization with a calcium solution. The inclusion of negatively charged functional groups allowed for the tailored uptake and release of calcium, while also altering the mechanical properties and surface topography of the hydrogel surface. In cell culture, OPF-BP hydrogels with 20 and 30% (w/w) BP optimized osteoblast attachment, proliferation, and differentiation after a 21-day in vitro period. In addition, the OPF-BP30 treatment, when mineralized with calcium, exhibited a 128% increase in osteocalcin expression when compared with the non-mineralized treatment. These findings suggest that phosphate functionalization and enzymatic calcium mineralization can act synergistically to enhance the osteoconductivity of OPF hydrogels, making this processed material an attractive candidate for bone tissue engineering applications.

Acquired resistance to pamidronate treated effectively with zoledronate in juvenile Paget's disease

Juvenile Paget's disease (JPD) is a rare autosomal recessive osteopathy. There is still a question about the most effective treatment modality in long-term prognosis. A 9-month-old boy who suffered from bone pain and deformities with a very high alkaline phosphatase level was diagnosed as JPD by radiographic findings. Genetic analysis showed a homozygous large deletion in TNFRSF11B gene encoding osteoprotegerin. Clinical improvement was observed with intravenous pamidronate therapy. However, the effect of drug reduced in time so the annual dose per kilogram body weight was increased after 2 years. Despite this increment, bone fractures developed and bone pain recurred with high-ALP levels, which suggested resistance to pamidronate. Switching to zoledronate resulted a significant improvement in bone findings radiographically and ALP level. Severe hypocalcemia requiring intravenous calcium treatment complicated the first dose of zoledronate, but not recurred thereafter. Intravenous pamidronate therapy is effective in reducing bone pain, improving bone deformities and motor development in infantile onset JPD. However, this effect can be transient. Switching to another bisphosphonate like zoledronate may provide long-term clinical and biochemical improvement as an alternative treatment in case of resistance to pamidronate therapy.

Effect of bisphosphonates on root resorption after tooth replantation - a systematic review

BACKGROUND/AIM

Replantation of avulsed teeth may lead to root resorption. Bisphosphonates (BPs), a class of drugs of used to treat resorptive diseases of the bone such as osteoporosis and Paget's disease, have been observed to exert an antiresorptive effect on periodontal bone as well. The antiresorptive properties of BPs could prove them useful in preventing root resorption of replanted avulsed teeth. The aim of this systematic review was to analyze and summarize the currently available literature concerning the use of BPs in preventing root resorption of avulsed teeth.

MATERIALS AND METHODS

PubMed/MEDLINE, Google Scholar, ISI Web of Knowledge, and Embase databases were searched using keywords 'bisphosphonate', 'replantation', and 'tooth'. Quality assessment of each study was carried out. In addition, general characteristics and outcomes of each study were summarized.

RESULTS

After exclusion of 116 irrelevant articles, 10 animal studies were included in this review. The majority of the studies suggest that surface application of zoledronate or alendronate reduces root resorption of replanted teeth in animal models. Surface treatment with etidronate had no significant effect on root resorption, and intracanal etidronate accelerated resorption.

CONCLUSION

Surface application of zoledronate and alendronate reduces root resorption of replanted teeth in animal models. However, the efficacy of intracanal usage of BPs is still debatable.

Effect of antiresorptive and anabolic bone therapy on development of osteoarthritis in a posttraumatic rat model of OA

Introduction

Osteoarthritis (OA) is a leading cause of disability, but despite the high unmet clinical need and extensive research seeking dependable therapeutic interventions, no proven disease-modifying treatment for OA is currently available. Due to the close interaction and interplay between the articular cartilage and the subchondral bone plate, it has been hypothesized that antiresorptive drugs can also reduce cartilage degradation, inhibit excessive turnover of the subchondral bone plate, prevent osteophyte formation, and/or that bone anabolic drugs might also stimulate cartilage synthesis by chondrocytes and preserve cartilage integrity. The benefit of intensive zoledronate (Zol) and parathyroid hormone (PTH) therapy for bone and cartilage metabolism was evaluated in a rat model of OA.

Methods

Medial meniscectomy (MM) was used to induce OA in male Lewis rats. Therapy with Zol and human PTH was initiated immediately after surgery. A dynamic weight-bearing (DWB) system was deployed to evaluate the weight-bearing capacity of the front and hind legs. At the end of the 10-week study, the rats were euthanized and the cartilage pathology was evaluated by contrast (Hexabrix)-enhanced μCT imaging and traditional histology. Bone tissue was evaluated at the tibial metaphysis and epiphysis, including the subchondral bone. Histological techniques and dynamic histomorphometry were used to evaluate cartilage morphology and bone mineralization.

Results

The results of this study highlight the complex changes in bone metabolism in different bone compartments influenced by local factors, including inflammation, pain and mechanical loads. Surgery caused severe and extensive deterioration of the articular cartilage at the medial tibial plateau, as evidenced by contrast-enhanced μCT and histology. The study results showed the negative impact of MM surgery on the weight-bearing capacity of the operated limb, which was not corrected by treatment. Although both Zol and PTH improved subchondral bone mass and Zol reduced serum CTX-II level, both treatments failed to prevent or correct cartilage deterioration, osteophyte formation and mechanical incapacity.

Conclusions

The various methods utilized in this study showed that aggressive treatment with Zol and PTH did not have the capacity to prevent or correct the deterioration of the hyaline cartilage, thickening of the subchondral bone plate, osteophyte formation or the mechanical incapacity of the osteoarthritic knee.

A highly sensitive prenylation assay reveals in vivo effects of bisphosphonate drug on the Rab prenylome of macrophages outside the skeleton

Bisphosphonate drugs such as zoledronic acid (ZOL), used for the treatment of common bone disorders, target the skeleton and inhibit bone resorption by preventing the prenylation of small GTPases in bone-destroying osteoclasts. Increasing evidence indicates that bisphosphonates also have pleiotropic effects outside the skeleton, most likely via cells of the monocyte/macrophage lineage exposed to nanomolar circulating drug concentrations. However, no effects of such low concentrations of ZOL have been reported using existing approaches. We have optimized a highly sensitive in vitro prenylation assay utilizing recombinant geranylgeranyltransferases to enable the detection of subtle effects of ZOL on the prenylation of Rab- and Rho-family GTPases. Using this assay, we found for the first time that concentrations of ZOL as low as 10nM caused inhibition of Rab prenylation in J774 macrophages following prolonged cell culture. By combining the assay with quantitative mass spectrometry we identified an accumulation of 18 different unprenylated Rab proteins in J774 cells after nanomolar ZOL treatment, with a >7-fold increase in the unprenylated form of Rab proteins associated with the endophagosome pathway (Rab1, Rab5, Rab6, Rab7, Rab11, Rab14 and Rab21). Finally, we also detected a clear effect of subcutaneous ZOL administration in vivo on the prenylation of Rab1A, Rab5B, Rab7A and Rab14 in mouse peritoneal macrophages, confirming that systemic treatment with bisphosphonate drug can inhibit prenylation in myeloid cells in vivo outside the skeleton. These observations begin a new era in defining the precise pharmacological actions of bisphosphonate drugs on the prenylation of small GTPases in vivo.

Gorham's Disease With Chest Wall Involvement: A Case Report and a Review of the Literature

Introduction:

Gorham's disease is a rare disorder characterized by osteolysis and abnormal vascular growth within bones. Diagnosis of Gorham's disease is often delayed and for accurate and early diagnosis high clinical suspicion is crucial. No specific treatment is available. Management options include surgery, radiation therapy and medical therapy. We aimed to present the first case of Gorham’s disease with chest wall involvement in Iran. By review of the literature we discussed important issues of this rare disease including clinical findings, diagnosis and treatment options.

Case Presentation:

We present a 48-year-old man with a history of dyspnea following a blunt chest trauma who was admitted to our clinic several times due to reaccumulation of pleural fluid and chylothorax. Gorham's disease was finally established according to clinical manifestations and radiological findings including massive osteolysis in his left ribs and also histological examination.

Discussion:

According to review of the literature and considering all treatment modalities the patients was successfully treated with a combination of radiotherapy, pamidronate and thalidomide. We suggest that this disease should be considered among differential diagnoses of patients with chest pain, pleural effusion and/or chylothorax with an unknown reason and more importantly history of chest trauma. In suspected cases, it is essential to examine biopsy specimens of the bone adjacent to the inflammated tissues in order to confirm diagnosis.

Remission over 3 years in patients with Paget disease of bone treated with a single intravenous infusion of 5 mg zoledronic acid

Using data from the Belgian Paget's Disease Registry of 142 patients treated with a 5 mg intravenous infusion of zoledronic acid, we examined disease remission over 3 years in 98 patients with Paget disease of bone (PDB) seen in routine practice. Median age was 76 years, most patients (60.2 %) were male, and all were Caucasian. Median time since PDB diagnosis was 11.5 years, few patients (5.1 %) had a family history of PDB, and 32.6 % had received prior bisphosphonate and/or other treatments. The most common pagetic locations were pelvis, spine, femur, tibia, and skull. The most common symptoms included pain, impaired mobility, bone deformities, and joint disease: 36.7 % of patients had comorbid osteoarthritis and 16.3 % comorbid osteoporosis. Response rates were 93.3 % at 1 year, 89.5 % at 2 years, and 91.6 % at 3 years, statistically similar to an extension study of the original zoledronic acid trials. Twenty-one patients experienced a relapse over the 3-year period at a median of 20.7 months posttreatment; of these, 13 regained remission by the end of the observation period. Relapse was not associated with osteoarthritis, osteoporosis, or other comorbidities. Safety data were similar to those reported elsewhere. In summary, in this somewhat frailer sample of patients with PDB, effectiveness and safety data were similar to those observed in the original trial populations. These findings, which are the first on the use of zoledronic acid for PDB in routine clinical practice, underscore the therapeutic benefits and relative safety of zoledronic acid in the management of PDB in "real-world" clinical settings.

Bisphosphonate-based strategies for bone tissue engineering and orthopedic implants

Bisphosphonates (BPs) are a group of well-established drugs that are applied in the development of metabolic bone disorder-related therapies. There is increasing interest also in the application of BPs in the context of bone tissue engineering, which is the topic of this review, in which an extensive overview of published studies on the development and applications of BPs-based strategies for bone regeneration is provided with special focus on the rationale for the use of different BPs in three-dimensional (3D) bone tissue scaffolds. The different alternatives that are investigated to address the delivery and sustained release of these therapeutic drugs in the nearby tissues are comprehensively discussed, and the most significant published approaches on bisphosphonate-conjugated drugs in multifunctional 3D scaffolds as well as the role of BPs within coatings for the improved fixation of orthopedic implants are presented and critically evaluated. Finally, the authors' views regarding the remaining challenges in the fields and directions for future research efforts are highlighted.

Zoledronate and pamidronate depress neutrophil functions and survival in mice

BACKGROUND AND PURPOSE

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) has been identified as a severe complication of patients previously treated with i.v. bisphosphonates. It has been noted that necrotic bone from BRONJ sites display signs of bacterial infection suggesting that an immune defect may play a role in the pathophysiology of BRONJ. Here, we have examined the effect of two potent bisphosphonates, zoledronate and pamidronate, on neutrophil function, differentiation and survival.

EXPERIMENTAL APPROACH

The effect of bisphosphonates on chemotaxis, NADPH oxidase activity and neutrophil survival were assessed in vitro using bone marrow-derived primary neutrophils or in vitro differentiated haematopoetic progenitors from mice. The same parameters and the number of circulating neutrophils were quantified in neutrophils isolated from mice treated in vivo with zoledronate. In vivo recruitment of neutrophils was assessed by sodium periodate-induced peritonitis.

KEY RESULTS

Zoledronate and pamidronate inhibited in vitro neutrophil chemotaxis and NADPH oxidase activity in a dose-dependent manner. In vivo recruitment of neutrophils was also suppressed. Zoledronate did not affect in vitro differentiation of neutrophils but shortened their life span in a granulocyte-colony stimulating factor-dependent manner. fMLP-induced activation of RhoA activity was decreased by zoledronate treatment.

CONCLUSIONS AND IMPLICATIONS

Our results show that bisphosphonate exposure leads to impaired neutrophil chemotaxis, neutrophil NADPH oxidase activity and reduced circulating neutrophil counts. This work suggests that bisphosphonates have the potential to depress the innate immune system for a prolonged time, possibly contributing to the pathogenesis of BRONJ.

Extraskeletal benefits and risks of calcium, vitamin D and anti-osteoporosis medications

Drugs used for the prevention and the treatment of osteoporosis exert various favourable and unfavourable extra-skeletal effects whose importance is increasingly recognized notably for treatment selection.

INTRODUCTION

The therapeutic armamentarium for the prevention and the treatment of osteoporosis is increasingly large, and possible extra-skeletal effects of available drugs could influence the choice of a particular compound.

METHODS

The present document is the result of a national consensus, based on a systematic and critical review of the literature.

RESULTS

Observational research has suggested an inverse relationship between calcium intake and cardiovascular diseases, notably through an effect on blood pressure, but recent data suggest a possible deleterious effect of calcium supplements on cardiovascular risk. Many diverse studies have implicated vitamin D in the pathogenesis of clinically important non-skeletal functions or diseases, especially muscle function, cardiovascular disease, autoimmune diseases and common cancers. The possible effects of oral or intravenous bisphosphonates are well-known. They have been associated with an increased risk of oesophageal cancer or atrial fibrillation, but large-scale studies have not found any association with bisphosphonate use. Selective oestrogen receptor modulators have demonstrated favourable or unfavourable extra-skeletal effects that vary between compounds. Strontium ranelate has a limited number of non-skeletal effects. A reported increase in the risk of venous thromboembolism is not found in observational studies, and very rare cases of cutaneous hypersensitivity reactions have been reported. Denosumab has been introduced recently, and its extra-skeletal effects still have to be assessed.

CONCLUSION

Several non-skeletal effects of bone drugs are well demonstrated and influence treatment choices.

Skeletal remodeling following clinically relevant radiation-induced bone damage treated with zoledronic acid

Our aim was to determine if zoledronic acid (ZA) changes (45)Ca pharmacokinetics and bone microstructure in irradiated, ovary-intact (I) and irradiated, ovariectomized mice (OVX), two groups with different patterns of skeletal damage. The hind limbs of I and OVX BALB/c mice received a single 16-Gy radiation dose, simulating pre- and postmenopausal female cancer patients undergoing radiation treatment. All I and OVX mice were radiolabeled with 15 μCi (45)Ca. Mice were treated with or without a 0.5 mg/kg injection of ZA. The time course of bone mineral remodeling was evaluated using a fecal (45)Ca assay, measured by liquid scintillation. A group of nonirradiated, intact mice were used for the longitudinal evaluation of (45)Ca biodistribution. Distal femur bone histomorphometric parameters were measured using microCT at 50 days post-ZA intervention. Most (45)Ca was incorporated into the skeleton and eliminated from the soft tissues within 3-5 days postirradiation, attaining a steady state of excretion at 25-30 days. ZA intervention in both groups resulted in a rapid decrease in fecal (45)Ca excretion. There was a significant difference in (45)Ca excretion in the OVX ± ZA (P = 0.005) group but not in the I ± ZA (P = 0.655) group. The rate of excretion of fecal (45)Ca was slower in the OVX + ZA compared to the I + ZA group (P = 0.064). (45)Ca assay is useful to monitor the time course of bone mineral remodeling after an antiresorptive intervention in irradiated mice, providing a basis to investigate bone effects of cancer therapy protocols. For equivalent doses of ZA, recovery may depend on the nature and degree of skeletal damage.

Transplantable delivery systems for in situ controlled release of bisphosphonate in orthopedic therapy

IMPORTANCE OF THE FIELD

Bisphosphonates (BPs), structurally similar to pyrophosphates and functionally superior in restraining osteoclast-induced bone resorption, have been widely used as clinical drugs in the treatment of osteoporosis, bone voids and associated inflammation. However, owing to their high aqueous solubility and the consequently high rate of loss during oral administration, the loading and targeting of BPs pose major challenges in practice. Alternative delivery routes such as nasal, subcutaneous/intramuscular injection have contributed little to improving the bioavailiability and efficacy of BPs. To improve and optimize the delivery efficiency and efficacy of BPs, numerous strategies have been developed and adopted. Studies on controlled release of BPs provide important information on the fabrication of BP delivery systems for in situ treatment. As BPs play an important therapeutic role in osteoporosis and similar diseases, it has become essential and vital to survey various reported fabrication methodologies of these systems and the consequential orthopedic treatments so as to keep abreast with advances in their clinical use.

AREAS COVERED IN THIS REVIEW

Transplantable delivery systems for controlled release of BP are reviewed from literature published since 2000. The fabrication pathways and the release of BPs from various material systems are discussed in case studies. Recent progress in CaP models based on the strong and specific chelation between BPs and calcium phosphate crystals is highlighted.

WHAT THE READER WILL GAIN

This review offers an outline of the advances in BP controlled release and delivery systems for orthopedic therapy.

TAKE HOME MESSAGE

Understanding the cutting-edge BP controlled release and delivery systems for in situ treatment is key to the successful design of a more promising and perfect delivery system for orthopedic therapy. Moreover, developing such delivery systems incorporating the numerous advantages of BPs and controlled release environment requires substantially more flexible models to control better the fate of BP drugs.

In vivo effects of zoledronic acid on oral mucosal epithelial cells

OBJECTIVE

Osteonecrosis of the jaw is a serious complication of bisphosphonate treatment for which the pathophysiology is unknown. The purpose of this study was to investigate whether in vivo zoledronic acid (ZA) induces alterations in cell proliferation, apoptosis, and matrix metalloproteinases (MMPs) expression in oral mucosal epithelial cells.

METHODS

One-year-old dogs were either untreated (control group) or given high doses of intravenous ZA (ZA group) for 3 months. The doses of ZA were equivalent to those given to cancer patients, yet were administered two times more frequently (every 2 weeks). Mucosal tissues were assessed immunohistochemically for cell proliferation (proliferating cell nuclear antigen, PCNA), matrix metalloproteinase (MMP) expression, and apoptosis (caspase 3 and TUNEL).

RESULTS

There were no significant differences between the groups with respect to PCNA, MMP-2, MMP-14, and TUNEL positive cells. However, the expression of MMP-9 was significantly higher in the control group than in the ZA group (P < 0.05), whereas the expression of caspase 3 was significantly lower in the control group than in the ZA group (P < 0.05).

CONCLUSION

  These results suggest that high doses of ZA resulted in higher levels of apoptosis and lower levels of MMP-9 in the oral epithelial cells supporting the idea of bisphosphonate treatment affects the oral mucosa.

The role of zoledronic acid in the management of osteoporosis

Bisphosphonates are the current standard of care for treatment of osteoporosis. However, oral bisphosphonates are associated with complicated dosing regimens because of poor absorption and have the potential for upper gastrointestinal (GI) tract irritation, resulting in poor adherence and persistence. Zoledronic acid (ZOL) 5 mg, a once-yearly intravenous bisphosphonate, is approved for treatment and prevention of postmenopausal osteoporosis, increasing bone mass in men with osteoporosis, and treatment and prevention of glucocorticoid-induced osteoporosis. Because it is administered as an infusion, ZOL ensures adherence and persistence over the entire 12-month dosing interval and bypasses the GI absorption/irritation problems associated with oral bisphosphonates. The objective of this study was to review the safety and efficacy of 5 mg ZOL and its potential for improving patient compliance. Published reports dating back to 2001 were reviewed, with emphasis on osteoporosis treatment. In the HORIZON-Pivotal Fracture Trial, annual infusions of 5 mg ZOL produced significant reductions in risk of morphometric vertebral fractures (70%) and hip fractures (41%) vs placebo over 3 years in postmenopausal women with osteoporosis. In the HORIZON-Recurrent Fracture Trial, an annual infusion of 5 mg ZOL after repair of a recent low-trauma hip fracture was associated with significant reductions in risk for new clinical fractures (35%) vs placebo. In men with osteoporosis, an annual treatment of ZOL over 2 years increased lumbar spine bone mineral density (BMD) by 6% compared with baseline. In patients starting or continuing treatment with chronic glucocorticoids, ZOL resulted in significantly greater increases in lumbar spine BMD over 1 year than an oral bisphosphonate. In postmenopausal women with osteopenia, a single infusion of ZOL over a 2-year period produced significantly greater gains in lumbar spine and hip BMD than placebo. ZOL is generally safe and well tolerated. Five milligrams of ZOL has the potential to improve compliance with osteoporosis therapy and, consequently, to reduce fracture risk in clinical practice.

Intravenous zoledronic acid: what are the indications for male osteoporosis?

Osteoporosis and fractures are under-recognized and undertreated, both in men and women worldwide. Male osteoporosis is not the epidemic problem that female osteoporosis is; however, the National Osteoporosis Foundation estimates that over 14 million American men have osteoporosis or low bone mass, and approximately 25% to 30% of all hip fractures occur in male individuals who incur greater morbidity and mortality than their female counterparts. Until recently, alendronate, risedronate, and teriparatide were the only pharmacologic agents approved by the US Food and Drug Administration for treating male osteoporosis. In December 2008, zoledronic acid was approved for "treatment to increase bone mass in men with osteoporosis." In 2009, zoledronic acid was also approved for "treatment and prevention of glucocorticoid-induced osteoporosis in patients (both men and women) expected to be on glucocorticoids for at least 12 months."

Superparamagnetic nanovector with anti-cancer properties: gamma Fe2O3@Zoledronate

We elaborate a magnetic nanovector to vectorize Zoledronate, an anti-cancer interest molecule of the hydroxmethylenebisphosphonate's family. In fact, Zoledronate is a powerful adjuvant in the treatment of bone diseases such as osteoporosis and Paget's disease. But, recent studies have shown that in addition to anti-osteoclastic properties, it presents antitumour properties notably in the case of breast and prostate cancer. However, these properties cannot be exploited due to their very high affinity to divalent cations and their preferentially accumulation in bone. To overcome this problem, one strategy is the vectorization trough maghemite nanocrystal functionalization. The specific surface coating permits to consider gamma Fe(2)O(3)@Zoledronate as a drug delivery vehicle for therapeutic activity. The anchoring to the nanoparticle's surface allowed to increase their hydrophobicity and also to change the therapeutic target, increasing the Zoledronate intestinal absorption instead of their accumulation in bone. We show that Zoledronate link the nanoparticle surface through phosphonate groups. The biological in vitro tests performed on breast cancer cell line, MDA-MB 231, showed that gamma Fe(2)O(3)@Zoledronate have antiproliferative activity. In addition, the gamma Fe(2)O(3) core could be used as MRI contrast agent for a good therapeutic evaluation.

Mechanisms of action of bisphosphonates: similarities and differences and their potential influence on clinical efficacy

Bisphosphonates (BPs) are well established as the leading drugs for the treatment of osteoporosis. There is new knowledge about how they work. The differences that exist among individual BPs in terms of mineral binding and biochemical actions may explain differences in their clinical behavior and effectiveness.

INTRODUCTION

The classical pharmacological effects of bisphosphonates (BPs) appear to be the result of two key properties: their affinity for bone mineral and their inhibitory effects on osteoclasts.

DISCUSSION

There is new information about both properties. Mineral binding affinities differ among the clinically used BPs and may influence their differential distribution within bone, their biological potency, and their duration of action. The antiresorptive effects of the nitrogen-containing BPs (including alendronate, risedronate, ibandronate, and zoledronate) appear to result from their inhibition of the enzyme farnesyl pyrophosphate synthase (FPPS) in osteoclasts. FPPS is a key enzyme in the mevalonate pathway, which generates isoprenoid lipids utilized for the post-translational modification of small GTP-binding proteins that are essential for osteoclast function. Effects on other cellular targets, such as osteocytes, may also be important. BPs share several common properties as a drug class. However, as with other families of drugs, there are obvious chemical, biochemical, and pharmacological differences among the individual BPs. Each BP has a unique profile that may help to explain potential clinical differences among them, in terms of their speed and duration of action, and effects on fracture reduction.

A review of Paget's disease of bone with a focus on the efficacy and safety of zoledronic acid 5 mg

BACKGROUND

Paget's disease of bone, the second most common metabolic bone disease in the United States, is characterized by localized areas of excessive bone resorption coupled with accelerated bone formation, resulting in new bone that is less structurally organized and is weaker than normal bone. Complications of Paget's disease can include bone pain, osteoarthritis, skeletal deformity, hearing loss, and fractures. The objective of this review is to provide a comprehensive overview of current standards of treatment in Paget's disease.

SCOPE

A review of literature from 1974 to 2007 was performed on topics such as epidemiology, etiology, treatment of Paget's disease of bone, and bisphosphonates.

FINDINGS

Paget's disease affects an estimated 2-7% of persons of age 55 years or older in North America and western Europe. Antiresorptive treatment with bisphosphonates is the standard treatment, but there may be limitations to oral therapy. Intravenous pamidronate is efficacious and has long been available, but its use is hindered by an impractical recommended dosing regimen of 30 mg IV over 4 h for three consecutive days. In two identical, double-blind, 6-month trials, 96% of patients treated with a one-time intravenous treatment of zoledronic acid 5 mg achieved therapeutic response, compared with 74% treated with 60 days of daily oral treatment with risedronate 30 mg (p < 0.001). One limitation of this review is that historical data are not reviewed in the same level of detail as newer treatments, because recent advances in pharmacotherapy of Paget's disease have reduced the clinical utility of the older drugs.

CONCLUSION

The etiology of Paget's disease is unclear, but some evidence suggests genetic and viral components. Bisphosphonates restore normal bone turnover and relieve bone pain, but oral formulations may be limited by complicated dosing regimens and poor gastrointestinal absorption. The bisphosphonate, zoledronic acid is administered as a single intravenous infusion and offers antiresorptive efficacy and longer-lasting remission.

New and emerging treatments for osteoporosis

PURPOSE OF REVIEW

This review will focus on three new treatments for postmenopausal osteoporosis which have either been recently released (intravenous ibandronate), or have completed (zoledronic acid) or are currently in (denosumab) phase III trials.

RECENT FINDINGS

A number of agents have demonstrated fracture risk reduction in randomized clinical trials, however, successful treatment of osteoporosis in the individual patient remains a challenge. Adherence to, and persistence with, all current osteoporosis medications are poor, being approximately 50% at 1 year for weekly bisphosphonates. Poor adherence to therapy makes it unlikely that the significant fracture reduction seen in clinical trials will be realized in clinical practice.

SUMMARY

New therapies will not only have to demonstrate safety and efficacy, but also provide some advantage to patient persistence through either less frequent dosing schedules or elimination of gastrointestinal disturbances, the most common adverse effects encountered with bisphosphonates. This review will focus on three such agents that have either been recently released (intravenous ibandronate), or have completed (zoledronic acid) or are currently in (denosumab) phase III trials.

Dental endosseous implants in patients on bisphosphonate therapy

About a decade ago, bisphosphonates were introduced as an alternative to hormone replacement therapies for osteoporosis and to treat osteolytic tumors. More recently, it has became evident that the bisphosphonates used intravenously such as pamidronate (Aredia; Novartis Pharmaceuticals Corp., East Hanover, NJ) and zoledronate (Zometa; Novartis Pharmaceuticals Corp.), in particular, could lead to painful refractory bone exposure (sometimes termed osteochemonecrosis or osteonecrosis) in the jaws. Patients with osteonecrosis of the jaws usually present after dental treatment with oral signs and symptoms of painful, exposed, and necrotic bone, primarily of the mandible and, to a lesser extent, the maxilla. Although the precipitating event that produces this complication may be spontaneous, there is little doubt that oral surgery and endosseous implants can be responsible. Exodontia is the main precipitant. The present postulated mechanism of osteonecrosis of the jaws is that prolonged use of bisphosphonates may suppress bone turnover to the point that the repair function of physiologic microdamage of bone is abolished. Such a mechanism could presumably interfere with the healing process after implant placement. Although, to our knowledge, there is no evidence that bone disorders are a contraindication to implants, there is evidence that bisphosphonate therapy is a contraindication. Where possible, extractions should be avoided, and it is best to avoid all elective oral surgery in patients on bisphosphonates, including endosseous implant placement, or the treatment should be performed well before commencing bisphosphonates. If surgery is essential on a patient taking bisphosphonate therapy, the patient must be counseled about the risks.

[Therapy of Paget's disease]

Paget's disease of bone, an often undiagnosed metabolic bone disease, can lead to dramatic skeletal changes with enlargement and bowing of the affected bones. The etiology of this localized bone disease has not yet been determined. Genetic factors and viral infections may be involved. Recently, the treatment options for Paget's disease have been greatly improved due to the development of potent bisphosphonates. These agents inhibit osteoclastic bone resorption and allow the suppression of the excessive bone turnover in Paget's disease. This leads to a stabilization of affected bones and to symptomatic improvements. Treatment should be initiated early after diagnosis to limit the extent of damage. The article gives an overview of recent perspectives on epidemiology, diagnosis, and treatment of the disease according to the new German guidelines for the diagnosis and therapy of Paget's disease.

Zoledronic Acid

The third-generation, nitrogen-containing bisphosphonate zoledronic acid (Aclasta) is approved in the EU for the treatment of Paget's disease of bone. Results of well designed trials show that a single intravenous dose of zoledronic acid 5 mg is effective and well tolerated in the treatment of Paget's disease of bone. A single intravenous dose of zoledronic acid was associated with a significantly higher therapeutic response rate and a more rapid reduction in bone turnover than that achieved with 60 days of oral risedronic acid. Moreover, biochemical remission was sustained after 24 months of follow-up in zoledronic acid recipients. Preliminary results suggest that zoledronic acid is a cost-effective option in Paget's disease of bone. Thus, zoledronic acid is an important first-line treatment for Paget's disease of bone.

Long-term control of bone turnover in Paget's disease with zoledronic acid and risedronate

A single 5-mg infusion of zoledronic acid restores biochemical markers of bone turnover into the reference range in the majority of patients with Paget's disease and maintains biochemical remission for at least 2 years. This effect is largely independent of pretreatment disease activity and prior bisphosphonate therapy.

INTRODUCTION

Zoledronic acid (ZOL) is a potent bisphosphonate that produces a rapid and complete control of the increased bone turnover of Paget's disease. Long-term control of disease activity is an important aim of treatment in the hope that this will reduce the risk of complications such as deformity, fracture, and degenerative joint disease.

MATERIALS AND METHODS

This study compares the ability of ZOL 5 mg given as a 15-minute intravenous infusion with risedronate (RIS) 30 mg daily by mouth for 60 days to maintain long-term control of bone turnover. No bisphosphonate was given during the extension study. All patients (n = 296) who achieved a therapeutic response, defined as normalization or a >75% reduction in the total alkaline phosphatase (total ALP) excess above the midpoint of the reference range, were eligible for inclusion.

RESULTS

ZOL maintained the mean level of total ALP at the middle of the reference range, whereas those treated with risedronate showed a linear increase in total ALP from the 6-month post-treatment time-point. Both treatments resulted in a linear relationship between the 6-month nadir and 24-month total ALP. The relationship for RIS was shifted upward, showing that for a given level of post-treatment biochemical activity, bone turnover increased with time. This was in contrast to the ZOL-treated patients where total ALP generally remained unchanged over this 18-month extension period. A similar pattern of response was seen with the other bone turnover markers.

CONCLUSIONS

ZOL maintains bone turnover within the reference range over 24 months from the initiation of treatment. A reduction in the incidence and severity of long-term complications may require persistent normalization of bone turnover over many years, and this now seems a realistic possibility with ZOL.

Molecular mechanisms of action of bisphosphonates: current status

PURPOSE

Bisphosphonates are currently the most important class of antiresorptive agents used in the treatment of metabolic bone diseases, including tumor-associated osteolysis and hypercalcemia. These compounds have high affinity for calcium ions and therefore target bone mineral, where they are internalized by bone-resorbing osteoclasts and inhibit osteoclast function.

EXPERIMENTAL DESIGN

This article reviews the pharmacology of bisphosphonates and the relationship between chemical structure and antiresorptive potency. We also describe new insights into their intracellular molecular mechanisms of action, methods for assessing the effects of bisphosphonates on protein prenylation, and their potential as direct antitumor agents.

RESULTS

Nitrogen-containing bisphosphonates act intracellularly by inhibiting farnesyl diphosphate synthase, an enzyme of the mevalonate pathway, thereby preventing prenylation of small GTPase signaling proteins required for normal cellular function. Inhibition of farnesyl diphosphate synthase also seems to account for their antitumor effects observed in vitro and for the activation of gamma,delta T cells, a feature of the acute-phase response to bisphosphonate treatment in humans. Bisphosphonates that lack a nitrogen in the chemical structure do not inhibit protein prenylation and have a different mode of action that seems to involve primarily the formation of cytotoxic metabolites in osteoclasts.

CONCLUSIONS

Bisphosphonates are highly effective inhibitors of bone resorption that selectively affect osteoclasts in vivo but could also have direct effects on other cell types, such as tumor cells. After >30 years of clinical use, their molecular mechanisms of action on osteoclasts are finally becoming clear but their exact antitumor properties remain to be clarified.

Myeloma bone disease and treatment options

Multiple myeloma (MM) is a B-cell malignancy characterized by enhanced bone loss commonly associated with a diffuse osteopenia, focal lytic lesions, pathologic fractures, hypercalcemia, and bony pain. Bone destruction in MM results from asynchronous bone turnover wherein increased osteoclastic bone resorption is not accompanied by a comparable increase in bone formation. Recent characterization of osteoclast-activating factors (OAFs), receptor activator of nuclear factor-kappaB (RANK) ligand (RANKL)-osteoprotegerin-RANK system, and inhibitors of Wnt signaling have provided a better understanding of myeloma bone disease in molecular level. The development of minimally invasive surgical procedures such as kyphoplasty and vertebroplasty allows myeloma patients with vertebral compression fractures to have immediate improvement in quality of life and shorter hospital stays. Monthly intravenous infusion of either pamidronate or zoledronic acid have reduced the skeletal complications among MM patients and are now a mainstay of myeloma therapy. Orally administered bisphosphonates, in contrast, have shown little ability to slow the development of skeletal complications in these patients. Although pre-clinical studies suggest nitrogen-containing bisphosphonates have potent anti-tumor effects, clinical trials will be necessary, probably at higher doses given more slowly, to establish their possible anti-tumor effects clinically. As our understanding of the pathophysiology of myeloma bone disease continues to increase, new target therapies will continue to emerge offering new and more advanced options for the management of myeloma bone disease.

Mechanisms of Disease: preclinical reports of antineoplastic synergistic action of bisphosphonates

For patients with malignant bone disease, bisphosphonate therapy is the standard treatment. Preclinical and preliminary clinical data suggest that bisphosphonates have direct or indirect antitumor effects: they affect growth-factor release, cancer-cell adhesion, invasion and viability, angiogenesis, and apoptosis of cancer cells. These effects might be enhanced through co-administration with chemotherapy agents, biological agents, or both. We survey the biochemical pathways and molecular targets of bisphosphonates, and discuss the molecular mechanisms of these antitumor effects, as well as the documented antineoplastic preclinical effects of bisphosphonates used in combination with cytotoxic and biological drugs. Moreover, the positive interactions between bisphosphonates and farnesyltransferase inhibitors, KIT receptor tyrosine kinase inhibitors (e.g. imatinib mesylate) and cyclo-oxygenase-2 inhibitors are discussed in relation to their potential synergistic and additive effects. We briefly discuss identification of new molecular targets of bisphosphonates from genomic and proteomic analysis, and highlight the cellular consequences of drug-related enzyme inhibition.

The use of zoledronic acid for Paget's disease of bone

Paget's disease of bone is a common skeletal disorder of the elderly that often results in significant morbidity and disability. Although there are a number of oral bisphosphonates currently available for treatment, normalization of biochemical markers of bone turnover with these agents is rarely accomplished due to difficulty with administration, adherence, and possibly resistance to individual bisphosphonates. This paper will focus on zoledronic acid, a potent and easily administered intravenous bisphosphonate that appears to result in a higher percentage of patients with normalization of markers of bone turnover and results in improvements in quality of life in patients with Paget's disease of bone.

Pharmacological therapy of Paget's and other metabolic bone diseases

Paget's disease is a relatively common high-turnover metabolic bone disease that can serve as a model for osteoporosis and other metabolic bone diseases in investigation of therapeutic strategies to normalize bone turnover. Aims of treatment include rapid normalization of bone formation and resorption to prevent loss of mechanical integrity. Treatment will also reduce pain, while long-term maintenance of normal turnover may prevent long-term complications. Newer bisphosphonates have high antiresorptive potency and increased retention in bone, permitting a strategy of intermittent intravenous (IV) administration in achieving and maintaining normal bone turnover. In pivotal zoledronic acid Paget's disease trials, patients received a single 15-min IV infusion of zoledronic acid 5 mg (ZOL 5 mg) or risedronate 30 mg/day orally for 2 months. Treatment with ZOL 5 mg was associated with significant improvement in serum alkaline phosphatase, normalization in both the short and long term, and significant prolongation of biochemical therapeutic response in long-term follow-up. No changes in serum creatinine levels were observed with either treatment, and no clinically significant renal abnormalities were reported. Intermittent IV administration of potent bisphosphonates constitutes an intriguing strategy for treatment of Paget's disease and other metabolic bone diseases.