Bisphosphonates: a review of their pharmacokinetic properties

Osteonecrosis of the jaw and bisphosphonates: a comparison with white phosphorus, radium, and osteopetrosis

INTRODUCTION

Recent reports of bisphosphonate-associated jaw osteonecrosis are reminiscent of earlier incidents in which a comparable syndrome was caused by occupational exposure to white phosphorus or radium. Osteonecrosis of the jaw is also caused by an inherited disease: osteopetrosis. This review analyzes the biomedical and social aspects of these four situations associated with jaw osteonecrosis.

RESULTS

Clinical evidence is contradictory but suggests aminobisphosphonates cause rare cases of jaw necrosis. In addition to jaw problems, generalized skeletal defects characterize osteopetrosis and exposure to phosphorus or radium and there is evidence of decreased bone resorption in these conditions and with bisphosphonate therapy.

CONCLUSION

Bisphosphonate-induced jaw necrosis appears to be an on-target toxicity as the same mechanism, inhibition bone resorption, probably underlies both the therapeutic and adverse effects. Since bisphosphonates are retained for long periods by bone the theoretical potential for skeletal toxicity is increased by using higher doses of potent aminobisphosphonates administered less frequently.

Renal disease in patients with cancer

Kidney disease is very common in patients with cancer. Nephrologists are vital members of the multidisciplinary care team for these patients. Given the high prevalence of comorbidities in patients treated for active malignancy, it is not surprising that these individuals frequently develop renal diseases that are common among other hospitalized patients, such as those arising from sepsis, hypotension or use of nephrotoxic agents (e.g. radiocontrast or antimicrobial agents). The role of the nephrologist in these cases differs little with respect to the presence or absence of cancer. On the other hand, there are several renal syndromes that are unique to patients with cancer, being caused either by the cancer itself or by its treatment. These syndromes are reviewed here. In addition, patients who are receiving chemotherapy often require dialysis for either acute or chronic kidney disease. Unfortunately, there is very little information on the clearance characteristics of most chemotherapeutic agents. In cancer patients with renal disease, both the timing of administration and the dose-adjustment of chemotherapy must rely on clinical experience and close clinical observation.

Alendronate treatment promotes bone formation with a less anisotropic microstructure during intramembranous ossification in rats

There are safety concerns regarding administration of bisphosphonates to children. Little is known about the effects of bisphosphonates on bone matrix organization during bone modeling. The present study examined the effects of alendronate (ALN) on bone matrices formed by intramembranous ossification in the appendicular growing skeleton. ALN was administered to 1-week-old Sprague-Dawley rats at a dose of 0, 35, or 350 microg/kg/week for 4 or 8 weeks. The position of femoral diaphysis formed exclusively by intramembranous ossification was identified, and cross sections of cortical bone at this position were analyzed. Bone mineral density (BMD) and geometric parameters were evaluated using peripheral quantitative computed tomography. The preferential orientation degree of biological apatite (BAp) crystals in the bone longitudinal direction, which shows the degree of bone matrix anisotropy, was evaluated using microbeam X-ray diffraction analysis. We analyzed bone histomorphometrical parameters and performed bone nanomechanical tests to examine the material properties of newly developing cortical bone. The preferential orientation degree of BAp crystals significantly decreased in 35 microg/kg/week ALN-treated groups compared with vehicle-treated groups, although there were no significant differences in BMD between the two groups. The periosteal mineral apposition rate significantly increased in the 35 microg/kg/week ALN-treated group. We found a high negative correlation between bone matrix anisotropy and the regional periosteal mineral apposition rate (r = -0.862, P < 0.001). Nanomechanical tests revealed that 35 microg/kg/week ALN administration caused deterioration of the material properties of the bone microstructure. These new findings suggest that alendronate affects bone matrix organization and promotes bone formation with a less anisotropic microstructure during intramembranous ossification.

The role of bisphosphonates in the management of patients that have cancer

Bisphosphonates are pharmacologic agents widely used in people for managing pathologic bone resorptive conditions. Based on their physicochemical properties, bisphosphonates concentrate within areas of active bone remodeling and induce osteoclast apoptosis. Appropriate use of bisphosphonates for treating companion animals requires a thorough understanding of how bisphosphonates exert their biologic effects. This review article highlights general properties of bisphosphonates, including their pharmacology, mechanisms of action, adverse side effects, anticancer mechanisms, surrogate markers for assessing response, and potential clinical utility for treating dogs and cats diagnosed with malignant skeletal tumors.

Renal safety of intravenous bisphosphonates in the treatment of osteoporosis

Oral bisphosphonates are the mainstay of treatment for osteoporosis but cannot be used in some patients due to gastrointestinal contraindications, gastrointestinal intolerance, malabsorption or the inability to comply with dosing requirements. In such patients, intravenous bisphosphonates are a useful alternative. This review summarises the renal safety issues associated with the use of intravenous bisphosphonates for osteoporosis. Intravenous bisphosphonates are generally well tolerated, which may be a reflection of their selective activity in bone and metabolic stability. Adverse effects on renal function are primarily related to infusion rate and dose. Due to lack of data, no conclusions can be made regarding bisphosphonate safety in patients with intrinsic renal disease or an estimated glomerular filtration rate of < 30 ml/min.

Ligand-modified aminobisphosphonate for linking proteins to hydroxyapatite and bone surface

An increase in bone resorption is one of the main symptoms of osteoporosis, a disease that affects more and more individuals every day. Bisphosphonates are known to inhibit bone resorption and thus are being used as a treatment for osteoporosis. Aminobisphosphonates present a functionality that can be easily used for conjugation to other molecules, such as peptides, proteins, and ligands for protein recognition. In this study, an aminobisphosphonate conjugated with biotin was used as a model linker for protein attachment to bone. With this system, the interaction of biotinylated aminobisphosphonate with hydroxyapatite, a major mineral component of bone, was investigated. Quantification of the binding of aminobisphosphonate to hydroxyapatite was performed using a fluorescently labeled antibody for biotin. Additionally, the interaction of the biotinylated aminobisphosphonate with multiple treatments of cortical bone from the midshaft of a cow femur was studied. It was demonstrated that modified aminobisphosphonate reagents can bind hydroxyapatite and bone at high levels, while the biotin functionality is free to be recognized by the fluorescently labeled antibiotin antibody, suggesting that modified aminobisphosphonates could be used to link other peptides or proteins to the bone surface.

[Bisphosphonate therapy for children and adolescents with primary and secondary osteoporotic diseases]

Bisphosphonates have a set place in the treatment of osteoporosis in adults. For the last 10 years they have also been used in pediatrics. Due to inhibition in differentiation and reduction in osteoclasts, both pamidronate and alendronate, the most commonly used preparations, cause an increase in bone density. Most experience comes from the i.v. treatment of forms with severe courses of osteogenesis imperfecta (OI). There is an increase in bone substance, a decrease in rate of fractures and a reduction in pain with higher mobility of those effected. In addition to the use of drugs, intramedullary nailing and physiotherapy are important therapeutic standards. Bisphosphonates are also used for other diseases involving bone remodeling, such as juvenile idiopathic osteoporosis or familial hyperphosphatemia. Acute side effects usually occur with the first infusion, involve "flu-like" symptoms and are self limiting. The question of long-term side effects cannot be answered with the currently available data.

Modeling and spectroscopic studies of bisphosphonate-bone interactions. The Raman, NMR and crystallographic investigations of Ca-HEDP complexes

Raman spectroscopy was used to study the interactions of bovine bone, hydroxyapatite (HA, as a model of bone) and calcium hydrogen phosphate (CaHPO4) with 1-hydroxyethylidene-1,1-diphosphonic acid, CH(3)C(OH)(PO(3)H(2))2 (HEDP, the oldest known member in the class of bisphosphonates (BPs) that is commonly used as (i) a reference compound for BP activity, a scale of a BP's potency, and (ii) a pain palliative agent). Raman spectra with diminished background fluorescence were obtained using a visible laser line of 514.5 nm. The Raman spectra of the products from the reaction of HEDP with bone, HA and CaHPO4 could be considered virtually identical. This strongly suggests that CaHPO4 forms first from the reaction of bone or HA with HEDP (which also acts as a strong acid), upon which free Ca2+ ions become available for complexation reactions with HEDP. Two complexes were observed using Raman spectroscopy for each of the interactions of HEDP studied here. This shows that HA can be substituted for bone in studies concerned with the interaction of bone with chemical compounds. Also, Raman spectroscopy can be utilized to distinguish between different complexes formed at the solid/solution interface. One of the two complexes has been further characterized using Nuclear Magnetic Resonance (NMR) spectroscopy, as well as single crystal and powder X-ray diffraction (XRD). This complex has been found to be calcium dihydrogen ethane-1-hydroxy-1,1-diphosphonate dihydrate (Ca(CH(3)C(OH)(PO(3)H)(2)).2H2O). Molecular modeling of this calcium complex using Gaussian03 software confirmed the assignments of the Raman vibrational bands.

Pathophysiology, risk factors and management of bisphosphonate-associated osteonecrosis of the jaw: Is there a diverse relationship of amino- and non-aminobisphosphonates?

Reports of osteonecrosis of the jaw (ONJ) in patients receiving long-term bisphosphonate therapy have appeared in the literature since 2003. This condition involves avascular necrotic bone in the area of maxilla or mandibula and there may be a secondary infection. Most cases of ONJ have been reported in cancer patients receiving the intravenous aminobisphosphonates zoledronic acid and pamidronate monthly or q 3 week; of note these are also the two most commonly used agents of this class. Risk factors for ONJ include a history of trauma, dental surgery or dental infection and intravenous bisphosphonate administration; in addition, the extent and duration of exposure to bisphosphonates also seem to correlate with the risk. Although a direct causal relationship with bisphosphonates cannot be assumed, these agents may possibly contribute to the development of ONJ by suppression of bone remodeling in the jaw which leads to increased rates of bone mineralisation and accumulation of microfractures. Clodronate, a non-aminobisphosphonate, appears to have a different mechanism of suppressing bone remodeling compared with aminobisphosphonates, and this may explain why few cases of ONJ have been reported with clodronate despite extensive use over the past 20 years; however, the potential of clodronate to reduce the risk of ONJ while providing equivalent clinical benefit to the aminobisphosphonates needs to be substantiated in controlled clinical trials. Use of bisphosphonate therapy should be carefully planned in patients with metastatic bone disease who have risk factors for ONJ, and appropriate preventive measures taken to avoid the development of this condition.

Novel biomineral-binding cyclodextrins for controlled drug delivery in the oral cavity

A biomineral-binding alendronate-beta-cyclodextrin conjugate (ALN-beta-CD, Fig. 1) was developed as a novel drug delivery system. "Click" chemistry was used in conjugation of alendronate (ALN) to beta-cyclodextrin (beta-CD). The delivery system shows very strong binding to hydroxyapatite (HA, main component of tooth enamel). Its ability in forming molecular inclusion complex with dexamethsone (Dex, model drug) was investigated independently with phase solubility experiments, isothermal titration calorimetry (ITC), Job plot and (1)H NMR. The stoichiometry of ALN-beta-CD/Dex molecular complex was determined as 1:1, and the binding constant of the complex obtained from ITC study is 3.8 x 10(3) M(-1), which is similar to the binding constant of beta-CD/Dex. In vitro data indicate that the ALN-beta-CD/Dex complex bound to HA could gradually release Dex upon repeated extraction with phosphate buffer saline (PBS). This novel drug delivery system may have great potential in improving treatment of diseases in the oral cavity.

Large scale expansion of gamma 9 delta 2 T lymphocytes: Innacell gamma delta cell therapy product

gamma9delta2 T lymphocytes are non-conventional lymphocytes presenting a direct cytotoxic effect against a broad range of tumour targets. These cells also secrete inflammatory cytokines that can boost the other components of the immune system. In contrast to conventional CD8(+) T cells, the cytotoxic effect of gamma9delta2 T lymphocytes does not depend on the expression of major histocompatibility complex molecules by target tumour cells. INNACELL gammadeltatrade mark is a cell therapy product obtained by ex vivo amplification of mononuclear cells. The stimulation is achieved by a specific synthetic agonist of gamma9delta2 T lymphocytes, bromohydrin pyrophosphate (BrHPP). After a single stimulation with BrHPP, gamma9delta2 T lymphocytes are expanded for 2 weeks in a closed system in culture medium with interleukin-2 (IL-2). On day 15, cells are washed and harvested in 4% human serum albumin. In this manufacturing process, the total cell population is expanded by approximately 10-fold and gamma9delta2 T lymphocytes undergo a specific 1000-fold expansion, corresponding to a gamma9delta2 T lymphocyte enrichment of more than 70% at the end of the culture. This manufacturing process is much simpler than most current cellular therapy approaches using conventional CD8(+) T-cell lines or clones: there is no final or initial separation, no purification step and no use of feeder cells; the specific T-cell receptor-mediated signal provided by BrHPP is sufficient to trigger the IL-2-dependent expansion of the gamma9delta2 subset, which then becomes predominant in the cell culture in large amounts.

Bisphosphonate action: Revelations and deceptions from in vitro studies

Bisphosphonates (BPs) are a class of drugs used in the treatment of osteoporosis and diseases of high bone turnover, as well as for control of skeletal related events secondary to malignant disease. The key to BP specificity is their capacity to bind rapidly and with high affinity to bone surfaces. The cellular targets of BPs at the bone surface have been a source of controversy. In addition to osteoclasts, it has been frequently proposed that BPs may affect a variety of cell types including osteoclast precursors, osteoblasts and bone-lining cells, immunogenic cells, and tumour cells. However, there is an emerging body of literature from in vitro studies indicating that BPs are only released and taken up from bone surfaces by resorbing osteoclasts. In this scenario, the only significant exposure of non-resorbing cells to BP would occur during the initial period after dosing, prior to drug clearance from the soft tissues. Auspiciously, several groups have reported on revised culture systems that better reflect the pharmacology of BP dosing.

Surface-bound bisphosphonates enhance screw fixation in rats--increasing effect up to 8 weeks after insertion

BACKGROUND

A bisphosphonate coating improves screw fixation 2 weeks after implantation in cancellous bone. This study on rats examined further development of fixation over time for screws inserted in cancellous and cortical bone.

METHODS

SS screws were coated with a multiple layer of fibrinogen. Half of the screws were coated further with bisphosphonates, which were linked to the fibrinogen. The screws were inserted in cancellous and cortical bone in rats. The rats were killed after 5 h, 4 days, 1, 2, 4, 8, and 24 weeks, and fixation was evaluated by pullout test.

RESULTS

There was a gradual increase in pull-out force over time in both cancellous and cortical bone. The bisphosphonate coating improved fixation. Moreover, the difference between the bisphosphonate and control groups increased with time. The pull-out force was almost twice that of the controls for screws inserted in cancellous bone at 8 weeks. Energy uptake was increased more than 3-fold.

DISCUSSION

The energy uptake and pull-out force of a screw depends on the bone engaged with the threads. Thus, the presence of bisphosphonates increased the amount or quality of this bone by affecting the resorption/formation in a positive way. The increased effect of the bisphosphonates with time thus suggests that bisphosphonate is retained within the remodeling bone, with a positive effect on its gradual adaptation to the implant.

The Interaction of Cationic Polymers and Their Bisphosphonate Derivatives with Hydroxyapatite

Conjugating proteins with bisphosphonates (BPs), a class of molecules with exceptional affinity to hydroxyapatite (HA), is a feasible means to impart bone affinity to protein-based therapeutic agents. To increase the targeting effectiveness while minimizing protein modification, a polymeric linker containing multiple copies of BPs could be constructed for protein conjugation and targeting to bone. Towards this goal, poly(L-lysine) (PLL) and poly(ethylenimine) (PEI) were utilized as the polymeric backbones to incorporate a BP, namely 2-(3-mercaptopropylsulfanyl)-ethyl-1,1-bisphosphonic acid (thiolBP), by using N-hydroxysuccinimidyl polyethylene glycol maleimide and succinimidyl-4-(N-maleimidomethyl)-cyclohexane-1-carboxylate, respectively. In vitro and in vivo mineral affinity of the polymer-BP conjugates were determined in comparison with the unmodified polymers. The in vitro results indicated strong binding of the cationic polymers to HA in their unmodified form. BP conjugation did not enhance the inherent mineral affinity of the polymers; in contrast, certain modifications negatively affected the polymers' binding to the HA. In vivo results from a subcutaneous implant model in rats also showed no significant difference in mineral affinity of the BP modified and unmodified PEI. We conclude that thiolBP conjugation to the cationic polymers PLL and PEI was not beneficial for increasing the mineral affinity of the polymeric molecules. The strong interaction between the cationic polymers and HA may make the polymers suitable for imparting mineral affinity to bone-acting therapeutics.

Alendronate treatment in women with normal to severely impaired renal function: an analysis of the fracture intervention trial

To determine if alendronate had differential effects on BMD and fracture by renal function, we performed a secondary data analysis of women participating in the FIT. Alendronate increased BMD and decreased fractures to a similar degree among women with and without reduced renal function. There was no increase in adverse events among women with impaired renal function treated with alendronate. Alendronate is safe and effective among this group of women with reduced renal function.

INTRODUCTION

Alendronate is cleared by the kidney and may have sustained effects on bone in subjects with impaired renal function. We hypothesized that, with decreasing renal function, alendronate treatment would result in greater increases in BMD and greater decreases in fractures and that the frequency of adverse events would be increased.

MATERIALS AND METHODS

We studied women participating in the Fracture Intervention Trial (FIT), a randomized controlled trial of alendronate or placebo (n = 6458). We estimated baseline creatinine clearance (eGFR) using the Cockcroft Gault Formula.

RESULTS

Five hundred eighty-one (9.9%) participants had a severely reduced eGFR (<45 ml/minute). Alendronate increased BMD regardless of eGFR, but women with reduced eGFR had a 5.6% (95% CI: 4.8-6.5) increase in total hip BMD compared with 4.8% (95% CI: 4.6-5.0) among women with normal to moderate renal dysfunction (interaction: p = 0.04). Compared with placebo, alendronate increased spine BMD by 6.6 +/- 5.8%, but there was no significant interaction for the increase in spine BMD (interaction: p = 0.75). Treatment with alendronate reduced the risk of clinical fractures to a similar degree in those with (OR: 0.78; 95% CI: 0.51-1.21) and without reduced renal function (OR: 0.80; 95% CI; 0.70-0.93; p for interaction = 0.89). Treatment with alendronate reduced the risk of spine fractures to a similar degree in those with (OR: 0.72; 95% CI: 0.31-1.7) and without reduced renal function (OR: 0.50; 95% CI: 0.32-0.76; p for interaction = 0.44). There were no differences in adverse events by renal function.

CONCLUSIONS

Alendronate is safe and effective at increasing BMD and decreasing fractures among this group of women with reduced renal function.

Development and Validation of a Physiology-based Model for the Prediction of Oral Absorption in Monkeys

PURPOSE

The development and validation of a physiology-based absorption model for orally administered drugs in monkeys is described.

MATERIALS AND METHODS

Physiological parameters affecting intestinal transit and absorption of an orally administered drug in monkeys have been collected from the literature and implemented in a physiological model for passive absorption previously developed for rats and humans. Predicted fractions of dose absorbed have been compared to experimentally observed values for a set of N = 37 chemically diverse drugs. A sensitivity analysis was performed to assess the influence of various physiological model parameters on the predicted fraction dose absorbed.

RESULTS

A Pearson's correlation coefficient of 0.94 (95% confidence interval: [0.88, 0.97]; p < 0.0001) between the predicted and observed fraction dose absorbed in monkeys was obtained for compounds undergoing non-solubility limited passive absorption (N = 29). The sensitivity analysis revealed that the predictions of fractions dose absorbed in monkeys are very sensitive with respect to inter-individual variations of the small intestinal transit time.

CONCLUSIONS

The model is well suited to predict the fraction dose absorbed of passively absorbed compounds after oral administration and to assess the influence of inter-individual physiological variability on oral absorption in monkeys.

Bisphosphonate treatment: An orthodontic concern calling for a proactive approach

The purpose of this article is to raise awareness among orthodontists of the effects of bisphosphonates, a commonly prescribed type of drug that can inhibit tooth movement and increase serious osteonecrosis risks in the alveolar bones of the maxilla and the mandible. Common medical uses of bisphosphonates, applicable pharmacology, pharmacokinetics, reports of impaired bone healing and induced osteonecrosis, and a drug effect accumulation theory are reviewed. Potential orthodontic issues and proposed orthodontic recommendations for intravenous and oral bisphosphonate treatments are discussed. Bisphosphonate medication screening, patient counseling, informed consent, and, perhaps, changes in treatment planning might be considered.

Tolerability of different dosing regimens of bisphosphonates for the treatment of osteoporosis and malignant bone disease

Bisphosphonates are the primary pharmacological agents used for the management of osteoporosis and hypercalcaemia of malignant bone disease. The efficacy of these agents in these two conditions has been demonstrated in many well designed trials published over the past 2 decades. The variety of bisphosphonates currently available to us provides a wide range of tolerability and dosing profiles thus necessitating a thorough comparison of the most recent oral and intravenous bisphosphonates to differentiate the clinical context in which they should be used. Despite the fact that bisphosphonates are generally well accepted, their tolerability is dependent on complications which encompass gastrointestinal (GI) and renal toxicity. Other adverse events include osteonecrosis of the jaw, arthralgias, flu-like symptoms and uveitis. Studies have shown that various dosing regimens are able to modulate these rates of toxicity. To maximise tolerability, the direction of future therapy will likely fall into a pattern of decreasing the frequency of administration of bisphosphonates, whether it is oral or intravenous formulations, thus improving patient adherence. To review the literature on different dosing regimens of various bisphosphonates and their associated tolerability, we searched MEDLINE for articles from 1975 to 2006. Oral bisphosphonates, in particular alendronate and risedronate, have been systematically evaluated with regards to GI toxicity. Overall tolerability with these oral formulations has found GI toxicity to be the primary adverse event of interest. Both alendronate and risedronate have been found to have similar rates of GI toxicity when compared with placebo. Mounting evidence has developed validating the use of intravenous ibandronate and zoledronic acid for the purpose of treating hypercalcaemia secondary to malignancy. Unique to all other bisphosphonates, ibandronate also has an oral form which has a similar GI-toxicity profile to placebo. In addition, no significant differences in renal toxicity have been observed between those receiving intravenous ibandronate compared with placebo. Because of its potency and mode of administration, zoledronic acid has been widely accepted for the treatment of hypercalcaemia secondary to malignancy. However, a decrease in renal function, albeit rare, remains a significant complication of zoledronic acid; therefore, regular renal monitoring is recommended.

Therapy insight: the risks and benefits of bisphosphonates for the treatment of tumor-induced bone disease

Bisphosphonates are a valuable class of drugs with potent anti-resorptive actions that make them ideal for skeletal protection in osteoporosis, cancer bone metastasis, multiple myeloma, and Paget's disease of bone. It has become apparent, however, that these drugs also have the potential to cause a number of adverse effects. While these do not limit bisphosphonate use, the incidence of these adverse events can be minimized if appropriate care is taken with their administration, and by maintaining appropriate surveillance and patient care. We review the range of adverse reactions to bisphosphonate therapy with a particular emphasis on the recently identified association between long-term bisphosphonate treatment and osteonecrosis of the jaw. This is a potentially serious side effect seen mostly in patients with multiple myeloma or breast cancer bone metastases who receive intravenous bisphosphonate treatment. While the etiology is uncertain, a strong association with dental pathology and interventions highlights the need for close attention to dental health in this patient group.

Application of a semi-automated 96-well format solid-phase extraction, column-switching, fluorescence detection protocol for the determination of alendronate in human urine samples obtained from a bioequivalence study

In the current study, a semi-automated, 96-well format, solid-phase extraction (SPE), analytical column-switching method for alendronate determination in human urine is developed, validated and applied to a bioequivalence study. The current protocol was a substantial improvement of an existing classical method. A robotic liquid handling system was employed to simplify and reduce the time of sample preparation procedure. Automated SPE was carried out using a 96-well cartridge plate and a vacuum control system. Urine samples were determined by applying a column-switching protocol with fluorescence detection. Analysis time, due to the column-switching procedure, was about half of the conventional LC approach (11.5 min instead of 21 min). The method application required the determination of alendronate in urine samples obtained from 96 healthy volunteers as part of a bioequivalence study of two 70 mg alendronate sodium tablets. All major pharmacokinetic parameters of the bioequivalence study were estimated and reported.

Optimising antiresorptive therapies in postmenopausal women: why do we need to give due consideration to the degree of suppression?

Accelerated bone turnover with bone resorption exceeding bone formation is a major mechanism underlying postmenopausal bone loss and hence the development of osteoporosis. Accordingly, inhibition of bone resorption is a rational approach for the prevention of osteoporosis. In this context, the most logical option, hormone replacement therapy, reverses the rate of bone turnover to premenopausal levels, whereas the magnitude of inhibition by amino-bisphosphonates and the recently introduced anti-receptor activator of NFkappaB ligand (RANKL) antibody often exceeds this. As bone turnover has crucial implications for the continuous renewal of bone tissue, the over-suppression of bone turnover has potential consequences for bone quality and strength. Long-term treatment with potent bisphosphonates has recently been associated with osteonecrosis of the jaw and dose-dependent increases in micro-crack accumulation in animals. Although these observations are the subject of ongoing discussions, it is timely to discuss whether the over-suppression of bone turnover below premenopausal levels is really our ultimate goal when defining the success criteria for antiresorptive agents. In this review, the implications of high and excessively low bone turnover of endogenous origin for bone quality, fracture risk and integrity of the jaw are discussed. In addition, animal and clinical research revealing initial findings regarding the potential adverse effects of drug-induced suppression of bone remodeling are summarised. The inhibition of bone resorption, which is either transient between doses (e.g. with calcitonin) or does not exceed premenopausal levels (with hormone replacement therapy or selective estrogen receptor modulators), is preferable because it not only provides similar antifracture efficacy but can also assist in the maintenance of the dynamic repair of micro-cracks/micro-fractures.

Nanosuspensions of alendronate with gallium or gadolinium attenuate neointimal hyperplasia in rats

Monocytes/macrophages play a pivotal role in the formation of neointinal hyperplasia following vascular injury. Transient depletion of circulating monocytes by particulate delivery systems containing bisphosphonates, such as alendronate, results in restenosis inhibition. We hypothesized that a self-suspendable nanoparticulate dosage form, with a minimum amount of expients, could be formulated by complexing the negatively charged alendronate with gallium or gadolinium. We further hypothesized that a synergistic biological effect could be obtained by nanosuspensions of alendronate with these counter ions. Nanosuspensions (150-250 nm) of alendronate-gallium and alendronate-gadolinium were successfully formulated with no additives except for the active agents and HCl for pH adjustment. Both nanosuspensions exhibited macrophage cell line growth inhibition in a dose-response relationship in comparison to the various agents in solution and in liposomes. A synergistic effect of the nanosuspensions was observed in the inhibition of raw264 macrophages, and in reducing IL-1beta and TNF-alpha secretion in cell culture. Single IV administration at the time of injury, of alendronate-gallium or alendronate-gadolinium nanosuspensions resulted in inhibition of neointimal hyperplasia and stenosis in the rat model of vascular injury. The results correlated with the significant reduction of circulating monocytes. The nanosuspensions possess the advantages of no additives for minimal provocation of side effects, and the potential of immunomodulating inflammatory disorders.

Importance of calcium co-medication in bisphosphonate therapy of osteoporosis: an approach to improving correct intake and drug adherence

BACKGROUND AND OBJECTIVE

In all of the large, pivotal, multicentre trials of bisphosphonate therapy, patients have received added calcium in amounts ranging from 500 to 1000 mg/day above individual dietary intake. Accordingly, calcium supplements or calcium/vitamin D combinations are currently recommended as co-medication with anti-resorptive therapy in all recently published guidelines on the treatment of osteoporosis. However, the consistent use or effectiveness of calcium may be impaired by several factors in the individual patient, including low prescription rate or lack of advice to purchase calcium, reduced adherence because of the complexity of the regimen, and incorrect intake (e.g. taking calcium with bisphosphonates at the same time). Patients with osteoporosis who adhere to drug therapy experience a significantly lower fracture rate. Therefore, there is a need to improve correct intake of bisphosphonates together with calcium supplementation, which may enhance adherence. The dosage regimen could be simplified by providing the two compounds in an integrated pack. Such a pack, containing one tablet of risedronic acid and six calcium carbonate tablets (Actonel), Procter & Gamble Pharmaceuticals, Weiterstadt, Germany), has been developed to facilitate correct intake. In this study, the impact of this fixed-combination pack on patient understanding of dosing instructions and on preference was tested by comparing the fixed combination with separate risedronic acid and calcium packages.

PATIENTS AND METHODS

A new blister strip was developed containing one tablet of risedronic acid 35mg and six tablets of calcium carbonate 1250mg (500mg elemental calcium), representing 1 week of therapy; the control was the same medications in separate packaging. The study was conducted in a cohort of 164 postmenopausal women (mean age 69 years). Half of the participants were bisphosphonate users (n = 83). The combined understanding of five instructions - risedronic acid intake in the morning, only with water, without food, without other medication, and separate from calcium - was tested in a crossover design. Participants were also asked to state their preference for the combination packaging versus separate packs.

RESULTS

Understanding of the five instructions for the separate packaging was 70%. The combination pack significantly improved understanding of these instructions to 80% (p < 0.05). Eighty-three percent of participants preferred the combination pack over separate packs (p < 0.05). The most frequently given reasons for preferring the combination pack were prefer one pack over two packs, easy/convenient to use/practical/handy, easy to understand/less confusion, and easier to remember/less likely to forget.

CONCLUSIONS

The availability of a fixed-combination pack of risedronic acid 35 mg/week and calcium tablets can increase the likelihood that postmenopausal osteoporotic patients will receive both a bisphosphonate and calcium, which in turn is likely to enhance the correct intake of combination therapy.

Bisphosphonate-associated osteonecrosis of the jaws: a therapeutic dilemma

OBJECTIVE

To describe our experience in prevention and treatment of mandibular and maxillary osteonecrosis, an emerging complication of long-term intravenous administration of bisphosphonates.

STUDY DESIGN

Between February 2004 and February 2006, 10 patients who had received zoledronic acid intravenously because of multiple bone myelomas or bone metastases were treated for mandibular and maxillary osteonecrosis in the Departments of Otorhinolaryngology and Maxillofacial Surgery of our institution.

RESULTS

All of the patients underwent surgical sequestrectomies. More extensive surgery was necessary in 3 cases. There were no major complications, and the majority of the patients are alive with no signs of infection or bone exposure.

CONCLUSIONS

Our experience confirms that bisphosphonate therapy contributes to the pathogenesis of mandibular and maxillary osteonecrosis. Surgery seems to be necessary in the majority of the patients, although the most adequate procedure is far from being standardized and prevention seems to play a pivotal role.

Retention, distribution, and effects of intraosseously administered ibandronate in the infarcted femoral head

The local distribution, retention, and effects of intraosseous administration of ibandronate in the infarcted femoral heads were studied. Intraosseous administration effectively delivered and distributed ibandronate in the infarcted femoral heads and decreased the femoral head deformity in a large animal model of Legg-Calve-Perthes disease.

INTRODUCTION

Bisphosphonate therapy has gained significant attention for the treatment of ischemic osteonecrosis of the femoral head (IOFH) because of its ability to inhibit osteoclastic bone resorption, which has been shown to contribute to the pathogenesis of femoral head deformity. Because IOFH is a localized condition, there is a need to explore the therapeutic potential of local, intraosseous administration of bisphosphonate to prevent the femoral head deformity. The purpose of this study was to investigate the distribution, retention, and effects of intraosseous administration of ibandronate in the infarcted head.

MATERIALS AND METHODS

IOFH was surgically induced in the right femoral head of 27 piglets. One week later, a second operation was performed to inject (14)C-labeled or unlabeled ibandronate directly into the infarcted head. (14)C-ibandronate injected heads were assessed after 48 h, 3 weeks, or 7 weeks later to determine the distribution and retention of the drug using autoradiography and liquid scintillation analysis. Femoral heads injected with unlabeled ibandronate were assessed at 7 weeks to determine the degree of deformity using radiography and histomorphometry.

RESULTS

Autoradiography showed that (14)C-Ibandronate was widely distributed in three of the four heads examined at 48 h after the injection. Liquid scintillation analysis showed that most of the drug was retained in the injected head, and almost negligible amount of radioactivity was present in the bone and organs elsewhere at 48 h. At 3 and 7 weeks, 50% and 30% of the (14)C-drug were found to be retained in the infarcted heads, respectively. Radiographic and histomorphometric assessments showed significantly better preservation of the infarcted heads treated with intraosseous administration of ibandronate compared with saline (p < 0.001).

CONCLUSIONS

This study provides for the first time the evidence that local intraosseous administration is an effective route to deliver and distribute ibandronate in the infarcted femoral head to preserve the femoral head structure after ischemic osteonecrosis. In a localized ischemic condition such as IOFH, local administration of bisphosphonate may be preferable to oral or systemic administration because it minimizes the distribution of the drug to the rest of the skeleton and bypasses the need for having a restored blood flow to the infarcted head for the delivery of the drug.

Bisphosphonate complexation and calcium doping in silica xerogels as a combined strategy for local and controlled release of active platinum antitumor compounds

The production of bone substitute biomimetic materials which could also act as antitumoral drug release agents is of enormous interest. We report in this paper the synthesis and characterization of a novel platinum dinuclear complex containing a geminal bisphosphonate and its embodiment into xerogels prepared by the sol-gel method. Our goal was to obtain a hybrid inorganic matrix that could release a platinum species active against bone tumors or metastases, upon local implant. Two silica xerogels were considered: one was composed of pure silica, while the other contained also some calcium as potential release-modulating agent thanks to its high affinity for bisphophonates. The platinum-complex loading capacity of the inorganic matrices, the release kinetics in buffer simulating physiological conditions, and the stability upon storage were investigated as a function of Pt-complex concentration and calcium addition. We found that the presence of calcium in the composites deeply influences not only the stability of the formulations but also the nature of the platinum complex liberated in solution.

The circadian rhythm of biochemical markers of bone resorption is normally synchronized in breast cancer patients with bone lytic metastases independently of tumor load

BACKGROUND

Bone metastases are devastating events resulting in disruption of local bone remodeling processes. Physiological bone turnover has a circadian rhythm. No data are available on the circadian pattern of bone turnover markers in patients with bone metastases.

METHODS

Twenty post-menopausal women with breast cancer (BC) at first disease relapse and at least one bone metastasis were consecutively recruited. Twenty healthy women served as controls. Patients were free from concomitant chemotherapy/endocrine therapy. Throughout a 24-h period, urine samples were collected at 4-h intervals, and blood samples were collected at 4-h intervals between 08:00 and 24:00, and at 2-h intervals between 24:00 and 08:00. Serum osteocalcin (OC), total and bone-alkaline phosphatase (tALP and bALP, respectively) and C-terminal telopeptide of type I collagen (CTX), and urinary NTX and free deoxypyridinoline (fDPD) were measured together with serum parathyroid hormone (PTH) and serum and urinary calcium and phosphorus. Temporal variations of measured analytes were assessed by ANOVA and the COSINOR model.

RESULTS

At 08:00, patients had higher levels of bone resorption indices (NTX, CTX and fDPD) than controls (p<0.0001). tALP and bALP, but not OC, were higher in patients than controls (p<0.001). PTH, serum and urinary calcium and urinary phosphorus did not differ between groups; serum phosphorus was higher in controls (p<0.0001). A circadian rhythm was evident for CTX and fDPD values in both patients and controls. A circadian rhythm in NTX, OC, phosphorus and PTH was apparent in controls only. However, it was detected also in patients when percent changes from MESOR were considered. Serum phosphorus showed a circadian rhythm, while no rhythm was detected for tALP, bALP, serum and urinary calcium. The rhythmicities in cancer patients were normally synchronized, and rhythmic parameters were independent of tumor load in the skeleton, age and menopausal status.

CONCLUSIONS

This is the first study to yield information on the maintenance of the temporal program of bone turnover in bone metastatic cancer patients. Whether administration of bisphosphonates in the nighttime leads to a different outcome with respect to the current administration in the morning is a matter of future research.

Oncologic Emergencies

It has been estimated that genitourinary malignancies will account for 25% of new cancer diagnoses in the United States in 2005 (Jemal et al. 2005). While the incidence of many of these malignancies has increased over the past two decades, the mortality rates appear to be decreasing. Early cancer detection combined with improvements in surgical and nonsurgical oncologic therapy account for these trends. Although not common, newly diagnosed cancer patients occasionally present in an emergent, life-threatening manner that warrants immediate medical or surgical intervention. As the prevalence of genitourinary malignancies continues to expand, additional patients can be expected to develop disease or treatment-related complications. This chapter will serve to review the diagnosis and management of oncologic emergencies as they pertain to the urologist.

RANKL inhibition: a novel strategy to decrease femoral head deformity after ischemic osteonecrosis

A novel therapeutic strategy to decrease the development of femoral head deformity after ischemic osteonecrosis was studied in a large animal model of total head infarction. RANKL inhibition through exogenous osteoprotegerin administration significantly decreased pathologic bone resorption and deformity during repair of the infarcted head.

INTRODUCTION

Legg-Calvé-Perthes disease (LCPD) is a juvenile form of osteonecrosis of the femoral head that can produce permanent femoral head deformity (FHD) and premature osteoarthritis. The development of FHD in LCPD is closely associated with the repair process, characterized by a predominance of bone resorption in its early stage that produces a fragmented appearance and collapse of the femoral head. We present here a novel strategy to preserve the femoral head structure after ischemic osteonecrosis based on inhibition of interaction between RANK and RANKL using exogenous administration of osteoprotegerin (OPG-Fc) in a large animal model of ischemic osteonecrosis.

MATERIALS AND METHODS

Ischemic osteonecrosis was surgically induced in 18 male piglets by placing a ligature tightly around the right femoral neck to disrupt the blood flow to the right femoral head. Two weeks after the induction of total head infarction, OPG-Fc or saline was administered subcutaneously to nine animals per group for 6 weeks. The contralateral, normal (left) femoral heads from the animals treated with saline served as normal, nondisease controls. All animals were killed at 8 weeks when severe FHD has been previously shown to occur because of the repair process dominated by osteoclastic bone resorption. Radiographic, histomorphometric, and immunohistochemical assessments were performed.

RESULTS

Radiographic assessment showed significantly better preservation of the femoral head structure in the OPG-Fc group compared with the saline group. Epiphyseal quotient (the ratio of epiphyseal height to diameter) was significantly higher in the OPG-Fc group (0.41 +/- 0.09) compared with the saline group (0.24 +/- 0.08, p < 0.001). Histomorphometric assessment revealed a significant reduction in the number of osteoclasts present in the OPG-Fc group (5.9 +/- 5.3mm(-2)) compared with the saline group (39.6 +/- 13.8 mm(-2), p < 0.001). Trabecular bone volume, number, and separation were significantly better preserved in the OPG-Fc group compared with the saline group (p < 0.001). No significant difference in femoral length was observed between the OPG-Fc and saline groups. Immunostaining revealed the presence of OPG-Fc only within the blood vessels, with no apparent staining of bone matrix or trabecular bone surfaces.

CONCLUSIONS

To our knowledge, this is the first study to show that RANKL inhibition decreases bone resorption and FHD after ischemic osteonecrosis. Because RANKL inhibitors do not bind to bone, their effects on resorption are reversible as the drug is cleared from circulation. The reversible nature of RANKL inhibitors is very appealing for treating pediatric bone diseases such as LCPD, where the resorptive stage of the disease lasts for 1-2 years.

Open Issues in Anorexia Nervosa: Prevention and Therapy of Bone Loss

Anorexia nervosa and diet-induced amenorrhea have an important impact not only on gynecological health but also on bone mass, especially if the disease is not promptly recognized and treated. This is particularly important because these conditions usually arise in adolescence, when peak bone mass is normally achieved. In this article we discuss the therapeutic issues related to bone loss associated with eating disorders.

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.

Novel Therapeutic Agents for Bone Resorption. Part 1. Synthesis and Protonation Thermodynamics of Poly(amido-amine)s Containing Bis-phosphonate Residues

Two poly(amido-amine)s (oligoPAM and oligoNER) containing bis-phosphonate residues were obtained by a Michael-type polyaddition of pamidronate and neridronate to 1,4-bis(acryloyl)piperazine. The SEC (size-exclusion chromatography) and the MALDI-TOF (matrix assisted laser desorption ionization) analyses were consistent with the presence of oligomeric species (2-3 kDa) and with a narrow polydispersity index. The thermodynamic results (log Ks, -DeltaH(o) , and DeltaS(o) obtained at 25 degrees C in 0.15 M NaCl) of both the oligomers and the corresponding low molecular weight precursors were in line with a cluster structure formed during the protonation of the basic nitrogen in the pamidronate. The solubility of the oligoNER with a longer aliphatic chain was improved at high pHs, allowing the evaluation of their solution properties. Preliminary biological results show that both the oligomers do not negatively affect the in vitro viability, proliferation, and cellular activity of either normal animal or human osteoblasts.

'Magic bullets' for bone diseases: progress in rational design of bone-seeking medicinal agents

An ideal therapeutic agent for bone diseases should act solely on bone tissue with no pharmacological activity at other anatomical sites. Current therapeutic agents, however, do not usually display a preferential affinity to bones and non-specifically distribute throughout the body after administration. Attempts to design bone-specific agents have relied on engineering a desired therapeutic agent with bone-seeking molecules so that the latter delivers the therapeutic agents specifically to bones. In this critical review, we summarize the latest attempts to engineer bone-seeking therapeutic agents based on formulating therapeutic agents with bisphosphonates, a class of compounds with high affinity to biological apatite. We first provide a relevant summary of the structure of bone mineral and bisphosphonates, highlighting the mode of interaction between these two entities. The use of bisphosphonates in the diagnosis of bone diseases is then presented, since this application helps us to understand the bone-carrier properties of bisphosphonates under physiological conditions. A summary of recent attempts to formulate bisphosphonates with traditional therapeutic agents to restrict their activities to bone tissues is then provided, with special emphasis on the structure-function relationships of the engineered compounds. Finally, attempts to use bisphosphonates to deliver macromolecular therapeutics (i.e., proteins) are summarized, based on recent data from the authors' lab. The collective research into bone-seeking medicinal agents is progressively laying the foundation for next-generation 'magic bullets' that display desirable activities at the disease sites with no undesirable activity on other organ systems. (164 references.).

How much calcium is in your drinking water? A survey of calcium concentrations in bottled and tap water and their significance for medical treatment and drug administration

INTRODUCTION

Different forms of water vary in calcium content. High divalent ion (i.e., Ca(2+), Mg(2+), etc.) concentration is deleterious to the absorption and efficacy of the bisphosphonate group of drugs in osteoporosis treatment. Water with high calcium concentration may also present an alternate pathway of calcium administration. In either case, knowing the actual concentration is critical.

HYPOTHESIS

The current paper is a surveillance study. We hypothesize that there is considerable variation in the calcium concentrations in the various water sources: tap water from US and Canadian cities of different regions and purified, spring, and mineral bottled waters. In addition, we hypothesize that the water filter removes a significant amount of minerals including calcium from the water.

METHODOLOGY

Calcium concentrations in various city tap waters, as well as an assorted number of bottled waters, were determined through the direct inspection of scientific data. The effect of filtering was also determined by mineral analysis of mineral water directly before and after filtration.

RESULT

The calcium concentration of water varies from 1 to 135 mg/L across the USA and Canada. Most spring waters were found to have a relatively low calcium concentration, with an average of 21.8 mg/L. Purified waters contain a negligible calcium concentration. Mineral waters, on the other hand, were generally found to contain higher calcium concentrations, an average of 208 mg/L of calcium. Filtration was found to remove a considerable amount of calcium from the water, removing 89% on average.

CONCLUSION

Calcium concentration in water varied substantially from different sources in the USA and Canada. Bottled waters presented with concentrations of calcium covering a very large range. Certain tap and bottled waters present with concentrations of calcium sufficient to exhibit a deleterious effect on bisphosphonate treatment. Alternatively, certain waters may be used as a source of calcium that may provide over 40% of the recommended daily intake for calcium.

Prevalence of bisphosphonate associated osteonecrosis of the jaw within the field of osteonecrosis

OBJECTIVES

Prevalence of bisphosphonate-associated osteonecrosis of the jaws within the catchment area of a university hospital maxillofacial unit and to review the outcome of treatment.

METHODS

In a retrospective study, all patients with osteonecrosis, osteomyelitis and osteoradionecrosis treated in the period from January 2000 to March 2005 in the department for Maxillo Facial Surgery at the University of Mainz, Germany were analysed.

RESULTS

Forty percent of the patients are grouped to odontogenic or surgically induced osteomyelitis. The second largest group (28%) were patients with osteoradionecrosis (ORN). Ten percent of all patients developed an osteonecrosis after treatment with bisphosphonates (BOJ). Eight percent showed osteomyelitis or sequester due to a trauma while 14% of all patients had osteomyelitis of unknown origin. All BOJ patients took bisphosphonates because of metastatic diseases of the bone (plasmocytoma, mamma carcinoma and prostate cancer) for up to 5 years. All had been administered a nitrogen-containing bisphosphonate (either pamidronat or zoledronat). Thirteen out of the 17 patients with BOJ and 14 of the 45 with ORN reported a possible trigger like previous tooth extraction, pressure denture sore or periodontal diseases.

CONCLUSION

These findings support the association of bisphosphonate therapy and osteonecrosis of the jaw. The importance of this new disease is characterised by the growing number of patients. The role of dental trigger factors and the poor surgical outcome both seem to justify a prophylactic dental care concept in high-risk patients.

Alendronate-loaded nanoparticles deplete monocytes and attenuate restenosis

Systemic transient depletion of monocytes and macrophages by liposome-encapsulated bisphosphonates (BPs), reduces neointimal formation in experimental restenosis. The aim of this study was to examine the antirestenotic effect of a polymeric nanoparticulate formulation containing the BP alendronate (ALN). The BP was successfully formulated in polylactide-co-glycolide (PLGA) nanoparticles (NP). ALN NP with negative charge, size of 223+/-64 nm, and high entrapment efficiency (55.1%) have been formulated. ALN NP exhibited a significant cytotoxic effect, in a dose-response relationship, on macrophage-like RAW264 cells in cell culture. Subcutaneously (SC) administrated ALN NP (1.5 mg/kg on days -1 and +6) resulted in a significant attenuation of neointima to media ratio (N/M) by 52.7% and stenosis by 39.7% 28 days after balloon injury in the hypercholesterolemic rabbit model. Moreover, a good correlation was found between macrophage abundance in the injured arteries and the extent of stenosis. ALN NP treatment resulted in the reduction of both interleukin-1beta and matrix metalloproteinases (2 and 9). It is concluded that a particulated dosage form of polymeric NP loaded with ALN reduce neointimal formation in vivo by systemic transient depletion of monocytes.

What is new in the treatment of steroid-induced osteoporosis?

Glucocorticoid-induced osteoporosis (GIOP) is a serious complication resulting from long-term steroid treatment. In addition to several nonpharmacologic therapies recommended by the American College of Rheumatology, various pharmacologic therapies, such as calcium, vitamin D, hormone-replacement therapy, calcitonin, and bisphosphonates, can be used to prevent and/or treat GIOP. Bisphosphonates, which are potent inhibitors of bone resorption, are considered the most effective and first-line agents for increasing bone mineral density and decreasing the risk of fracture. Human parathyroid hormone has emerged as a promising agent for the treatment of severe GIOP when used alone or in combination with a bisphosphonate.

Synthesis and Study of Alendronate Derivatives as Potential Prodrugs of Alendronate Sodium for the Treatment of Low Bone Density and Osteoporosis

Alendronate derivatives were evaluated as potential prodrugs for the osteoporosis drug alendronate sodium in an attempt to enhance the systemic exposure after oral administration. An investigation of the chemical behavior of alendronate derivatives led to development of practical synthetic strategies and prediction of each structural class's prodrug potential. Pharmacokinetic studies of N-myristoylalendronic acid revealed that 25% have been converted in vivo after i.v. administration in rat, providing an important proof-of-concept for this strategy.

Antiallodynic effect of etidronate, a bisphosphonate, in rats with adjuvant-induced arthritis: involvement of ATP-sensitive K+ channels

Bisphosphonates, pyrophosphate analogues, known as inhibitors of bone resorption, appear to cause analgesia in certain clinical painful situations. To detect clinically relevant analgesic property of etidronate, a non-aminobisphosphonate, we examined and characterized its antiallodynic effect in the rat with adjuvant-induced arthritis, in comparison with alendronate, an aminobisphosphonate, as determined by the von Frey test. Repeated systemic administration of etidronate at 10-40 mg/kg/day suppressed the adjuvant-induced mechanical allodynia in rat hindpaw, an effect reaching a plateau in approximately 10 days. Systemic or intraplantar (i.pl.) administration of ATP-sensitive K+ (K+ ATP) channel inhibitors, glibenclamide and/or tolbutamide, completely reversed the antiallodynic effect of etidronate within 1h in the arthritic rats, without affecting the nociceptive scores in naïve or arthritic animals that had not received etidronate. Alendronate, administered repeatedly, also revealed similar glibenclamide-reversible antiallodynic effect. In contrast, the antiallodynic effect of repeated systemic indomethacin was resistant to i.pl. glibenclamide in the arthritic rats. Repeated administration of etidronate or alendronate only slightly attenuated the adjuvant-evoked hindpaw edema. Among K+ ATP channel subunits, mRNAs for Kir6.1, SUR1, SUR2A and SUR2B were abundant in rat dorsal root ganglia, while Kir6.2 mRNA was poor. Our data demonstrate that repeated etidronate as well as alendronate exhibits antiallodynic activity in arthritic rats, which might be clinically relevant, and suggest involvement of K+ ATP channels in the underlying mechanisms.

A new dimethyl ester bisphosphonate inhibits angiogenesis and growth of human epidermoid carcinoma xenograft in nude mice

Bisphosphonates are extensively used in the treatment of patients with metastasis-induced osteolysis. The major drawback in the efficacy of all bisphosphonates lies in their high hydrophilic nature, which results in poor membrane permeability and low availability for soft tissues. A reasonable approach to overcome these problems consists in masking one or more ionizable groups of bisphosphonates, notably by esterification of the hydroxyl functions. We have previously shown that the novel non-nitrogen-containing bisphosphonate BP7033 inhibited angiogenesis and growth of primary tumors in nude mice. The present study focuses on the dimethyl-esterified analog of this compound (Me-BP7033). In-vitro, Me-BP7033 inhibited proliferation of human carcinoma A431 cells as well as their invasive activity based on a transwell invasion assay. in-vivo, administration of Me-BP7033 (0.3 mg/kg) twice a week for 5 weeks inhibited the tumor growth of A431 cells xenografted in nude mice by 65%. Immunostaining of endothelial cells (ECs) in tumor sections revealed that Me-BP7033 inhibited the intratumor ECs density by 60%. The in-vivo anti-angiogenic properties of Me-BP7033 were also demonstrated in an in-vivo angiogenesis assay showing that Me-BP7033 reduced the vascular endothelial growth factor-stimulated infiltration of ECs in a Matrigel plug by 70%. In summary, we demonstrated for the first time that a diesterified bisphosphonate exhibited in vivo both anti-tumoral and anti-angiogenic activities with no apparent sign of toxic effects. These new diesterified compounds, which could display enhanced bioavailability and pharmacokinetics, thus represent interesting candidates for therapeutic applications such as cancer treatment.