Treatment of Paget's disease with (3-amino-1-hydroxypropylidene)-1, 1-bisphosphonate (A.P.D.)

Drug treatment strategies for Paget's disease: relieving pain and preventing progression

INTRODUCTION

Paget's disease of bone (PDB) is a focal bone disorder caused by a marked dysregulation of osteoblasts and osteoclasts in basic multicellular units, leading to abnormal and disorganized deposition of collagen fibers (the so-called "woven bone"). Therefore, pagetic bones are increased in size, and at increased risk for bone pain, deformities, fractures, osteoarthritis, and, more rarely, neoplastic degeneration.

AREAS COVERED

In this review we revise the available information concerning the pharmacological treatment of PDB.

EXPERT OPINION

PDB progresses slowly within the affected skeletal sites and, if untreated, often leads to bone overgrowth, with bone pain, deformity and a likely increased risk of complications. Thus, the primary goal of treatment is the restoration of a normal bone turnover, in order to relieve bone pain or other symptoms and possibly prevent the complications. PDB long remained a poorly treatable disorder until the discovery of antiresorptive agents such as calcitonin first and bisphosphonates (BPs) later. With the recent development of potent intravenous BPs like zoledronate, allowing a better control of disease activity over the long term with a single infusion, has contributed to a marked improvement of the clinical management of this invalidating disorder.

Updates on Paget's Disease of Bone

Paget's disease of the bone is a prevalent bone disease characterized by disorganized bone remodeling; however, it is comparatively uncommon in East Asian countries, including China, Japan, and Korea. The exact cause still remains unknown. In genetically susceptible individuals, environmental triggers such as paramyxoviral infections are likely to cause the disease. Increased osteoclast activity results in increased bone resorption, which attracts osteoblasts and generates new bone matrix. Fast bone resorption and formation lead to the development of disorganized bone tissue. Increasing serum alkaline phosphatase or unique radiographic lesions may serve as the diagnostic indicators. Common symptoms include bone pain, bowing of the long bones, an enlarged skull, and hearing loss. The diagnosis is frequently confirmed by radiographic and nuclear scintigraphy of the bone. Further, bisphosphonates such as zoledronic acid and pamidronate are effective for its treatment. Moreover, biochemical monitoring is superior to the symptoms as a recurrence indicator. This article discusses the updates of Paget's disease of bone with a clinical case.

Bisphosphonates in the management of Paget's disease

The first clinical use of bisphosphonates was in Paget's disease of bone (PDB) when disodium etidronate was found to be effective at suppressing metabolic activity of the disease. Subsequently, PDB became a testing ground for many bisphosphonates using changes in alkaline phosphatase (ALP) as the primary outcome measure in clinical trials. Bisphosphonates are now considered to be the treatment of choice for PDB since they are highly effective at suppressing the elevations in bone turnover that are characteristic of the disease. Short term studies have shown that treatment with alendronate and risedronate can promote formation of lamellar bone in affected sites and improve x-ray appearances in some patients. Bisphosphonates have also been shown to improve bone pain in PDB and within the bisphosphonates, zoledronic acid (ZA) is most likely to give a favourable pain response. Many patients with PDB do not have pain however, even when there is increased metabolic activity and more research is needed to find out why this is the case. The effects of bisphosphonates on complications of PDB such as deformity, pathological fractures and deafness have not been adequately studied since most clinical trials have been short term and have not collected information on these important outcomes. The PRISM and PRISM-EZ studies investigated the long-term effects of bisphosphonates in patients with established PDB using a treat-to-target approach and showed that intensive bisphosphonate therapy aimed at normalising ALP was no more effective than symptom directed treatment with bisphosphonates at preventing complications of PDB. The Zoledronate in the Prevention of Paget's Disease (ZiPP) trial, which is currently in progress, seeks to determine whether early intervention with this potent bisphosphonate might be effective in preventing disease progression. Should the ZiPP study yield positive results, genetic testing coupled to prophylactic bisphosphonate therapy might represent a new indication for these highly effective inhibitors of bone resorption in future years.

The Influence of Local Pamidronate Application on Alveolar Dimensional Preservation after Tooth Extraction-An Animal Experimental Study

The aim of this randomized, controlled animal exploratory trial was to investigate the influence of local application of aminobisphosphonate pamidronate during the socket preservation procedure. Mandibular premolars were extracted in five Göttingen minipigs. Two animals underwent socket preservation using BEGO OSS (n = 8 sockets) and three animals using BEGO OSS + Pamifos (15 mg) (n = 12 sockets). After jaw impression, cast models (baseline, eight weeks postoperative) were digitized using an inLab X5 scanner (Dentsply Sirona) and the generated STL data were superimposed and analyzed with GOM Inspect 2018 (GOM, Braunschweig). After 16 weeks, the lower jaws were prepared and examined using standard histological methods. In the test group (BEGO OSS + pamidronate), buccooral dimensional loss was significantly lower, both vestibulary (−0.80 ± 0.57 mm vs. −1.92 ± 0.63 mm; p = 0.00298) and lingually (−1.36 ± 0.58 mm vs. −2.56 ± 0.65 mm; p = 0.00104) compared with the control group (BEGO OSS). The test group showed a significant difference between vestibular and lingual dimensional loss (p = 0.04036). Histology showed cortical and cancellous bone in the alveolar sockets without signs of local inflammation. Adjuvant application of pamidronate during socket preservation reduces alveolar dimensional loss significantly. Further investigations with regard to dose–response relationships, volume effects, side effects, and a verification of the suitability in combination with other bone substitute materials (BSMs) are necessary.

Pamidronate: A model compound of the pharmacology of nitrogen-containing bisphosphonates; A Leiden historical perspective

Pamidronate [3-amino-1-hydroxypropylidene-1,1-bisphosphonate (APD)] was the first nitrogen-containing bisphosphonate (N-BP) investigated in clinical studies. In contrast to other clinically used bisphosphonates, pamidronate was discovered and its properties were initially studied in an Academic Institution. On the occasion of the 50th Anniversary of the first publications on the biological effects of bisphosphonates, I review in this article the contribution of Leiden investigators to the development of pamidronate that led to the recognition of the significance of the Nitrogen atom in the side chain of bisphosphonates for their action on bone resorption and to the formulation of principles for the use of N-BPs in the management of patients with different skeletal disorders.

Management of Paget's disease of bone

Paget's disease is a progressive focal bone condition which can result in pain, low quality of life, deformity and other complications. Disease progression can be halted with potent bisphosphonates, resulting in improvement in both quality of life and pain, and normalisation of scintigraphy, plain radiographs and bone histology. Zoledronate has transformed the treatment of Paget's disease, producing sustained remissions in almost all patients. Thus, it is now possible to normalise bone cell activity and prevent disease progression at low cost, with one or two intravenous injections of zoledronate, greatly reducing follow-up costs. Patients with Paget's disease who are symptomatic or at risk of complications should have the opportunity to reap these therapeutic benefits. Potent bisphosphonates are highly effective in halting disease progression in Paget's disease, but guidelines disagree about treatment indications. The efficacy, safety and low cost of zoledronate recommend its use in any patient who is symptomatic or judged to be at risk of complications from Paget's disease.

Bisphosphonates-much more than only drugs for bone diseases

α,α-Bisphosphonates (BPs) are well established in the treatment of bone diseases such as osteoporosis and Paget's disease. Their successful application originates from their high affinity to hydroxyapatite. While the initially appreciated features of BPs are already beneficial to many patients, recent developments have further expanded their pleiotropic applications. This review describes the background of the interactions of BPs with bone cells that form the basis of the classical treatment. A better understanding of the mechanism behind their interactions allows for the parallel application of BPs against bone cancer and metastases followed by palliative pain relief. Targeted therapy with bone-seeking BPs coupled with a diagnostic agent in one particle resulted in theranostics which is also described here. For example, in such a system, BP moieties are bound to contrast agents used in magnetic resonance imaging or radionuclides used in positron emission tomography. In addition, another example of the pleiotropic function of BPs which involves targeting the imaging agents to bone tissues accompanied by pain reduction is presented in this work.

Role of Pamidronate Disodium in the Treatment of Metastatic Bone Disease

Aims and Background

Bone metastases are a common feature of advanced neoplastic disease and are considered to be among the most frequent causes of pain and complications in oncologic patients. The main objective of the treatment of such patients is to control their symptoms and improve their quality of life. Pamidronate disodium is a second-generation bisphosphonate capable of inhibiting bone resorption (particularly osteoclast activity) without affecting bone reminerali-zation. After a brief introduction concerning the pathophysiology of bone metastases and neoplastic bone pain, we herein present data on the clinical pharmacology and toxicity of bisphosphonates in general, and pamidronate in particular. We conclude by reviewing the literature on the use of pamidronate in phase II and III trials involving patients with metastatic bone disease.

Methods

The paper is based on a review of articles published between 1984 and 1997 selected from the Cancerline and Medline databases.

Results

In the considered phase II and III studies involving patients with bone metastases (breast cancer and multiple myeloma in particular), pamidronate proved to be efficacious in reducing the incidence of pain and skeletal complications, decreasing the excretion of metabolic markers of bone resorption and improving the quality of life. Intravenous infusions of 60-90 mg over a period of 2 hr every 3-4 weeks did not cause any significant toxic effects and was easily managed.

Conclusions

Pamidronate is a bisphosphonate that is efficacious in the treatment of symptomatic bone metastases and can be considered an important therapeutic option in association with systemic treatments, radiotherapy and normal supportive care, especially in patients with breast cancer and multiple myeloma. Further randomized studies are necessary to confirm the positive preliminary results in other neoplasms, analyze the cost/benefit ratio of the treatment, and verify the possibility that, in addition to being used for palliative purposes, pamidronate may also prevent or delay the appearance of bone metastases.

Long-Term Effects of Intravenous Ibandronate in Paget's Disease of Bone

We have previously demonstrated that intravenous ibandronate produces high initial response rates in Paget's disease, but the durability of this effect is unknown. It might be expected to be short lived because ibandronate has a low affinity for bone. Here we report long-term follow-up (up to 14 years) of patients from that trial. Twenty-five patients with active Paget's disease [baseline serum total alkaline phosphatase (ALP) ~3 times the upper limit of normal] received either 6 or 12 mg intravenous ibandronate at baseline. There were prompt reductions in ALP following treatment, with normalization in 88%. ALP remained in the normal range in most patients for 20-30 months, but some subjects then showed gradual increases. Three years after ibandronate, before any patients had received additional treatment, ALP was normal in 61%. Six patients maintained normal ALP beyond 6 years without further intervention. Responses to 6 and 12 mg were similar. These results indicate that long-term remissions in Paget's disease can be achieved with bolus delivery of a potent bisphosphonate, even if the drug has a low affinity for bone. Therefore, bisphosphonate retention in bone might not be the only factor determining duration of remission. Intravenous bisphosphonates are likely to produce high drug concentrations within pagetic lesions which might result in cytotoxicity to the pagetic cells, leading to long durations of remission. These findings strengthen the evidence that potent bisphosphonates delivered in a single intravenous dose are a very efficient way to manage this condition.

Treatment of Paget's disease of bone

Paget's disease of bone is the paradigm of bone focal distortion with accelerated bone turnover. Over the years, a number of different drugs have been used to control its activity but, since biphosphonates were introduced for the treatment of the disease, they have become the preferred treatment. This review will update the therapeutic indications, available drugs and therapeutic response monitoring.

Circulating γδ T cells and the risk of acute-phase response after zoledronic acid administration

The use of intravenous nitrogen-containing bisphosphonates (N-BPs) is associated with the appearance of an acute phase response (APR) in a proportion of the patients for reasons that are poorly understood. The APR was attributed to the indirect activation of γδ T cells with the release of interferon-γ and tumor necrosis factor (TNF). Forty patients with postmenopausal or senile osteoporosis (age range = 53-91 years) never previously treated with intravenous (i.v.) bisphosphonate, received a single 5-mg zoledronic acid (ZOL) iv infusion over 15 minutes. White blood cells were counted and analyzed with an automated hematology analyzer (ADVIA 2120i Siemens, New York, USA) and by flow cytometer (BD FACSCanto, Becton Dickinson). The occurrence of APR was defined by the occurrence of fever (>37 °C) during the next 2 days. Forty-two percent of patients (17 of 40) receiving the infusion of ZOL experienced an APR. Compared with the others they were younger (69 ± 7 years versus 74 ± 8 years; p = 0.06), and both the proportion and absolute number of γδ T cells were significant higher (p = 0.02 and p = 0.013, respectively). Nonsignificant differences were found between the two groups for white blood cells and for the other circulating lymphocyte subpopulations. Age was inversely correlated with circulating γδ T cells (p = 0.003) but the difference between the two groups in circulating γδ T cells persisted for age-adjusted values and vice versa. In conclusion, the results of this study indicate that the number of circulating γδ T cells, together with age, are important determinant of the occurrence of APR after intravenous infusion of ZOL and possibly of any other N-BPs.

Preventive effects of zoledronic acid on bone metastasis in mice injected with human breast cancer cells

Bisphosphonates are used routinely to reduce bone-related events in breast cancer patients with bone metastasis. We evaluated the effects of zoledronic acid, a third generation, nitrogen-containing bisphosphonate, to prevent bone metastasis in breast cancer. Zoledronic acid or vehicle alone was administered to nude mice either simultaneously or after intracardiac injection of human breast cancer MDA-MB-231 cells. Nude mice treated with zoledronic acid at early time points showed a lower incidence of bone metastases than did vehicle-treated nude mice, but these differences were not statistically significant. Only 37.5% of mice treated with zoledronic acid at the time of tumor cell inoculation developed bone metastases compared to over 51.8% of mice receiving vehicle alone (P = 0.304). Cell count of apoptosis confirmed by immunohistochemical staining in metastatic bone tissue significantly increased in the zoledronic acid-treated groups compared to non-treated group (1,018.3 vs 282.0; P = 0.046). However, metastatic tumor cells, which invade soft tissue around the bone, did not show extensive apoptosis; there were no differences between the zoledronic acid-treated and control groups. These results suggest that zoledronic acid increases apoptosis of metastatic breast tumor cells in the bone and could therefore reduce metastatic tumor burden. These results support the use of zoledronic acid to reduce the incidence of bone metastasis in breast cancer.

Bisphosphonates in the treatment of osteoporosis: a review of their contribution and controversies

The bisphosphonates have revolutionized the therapy of osteoporosis, particularly the prevention of vertebral and hip fractures. The development of tools for defining absolute fracture risk facilitates their targeting to appropriate, at-risk individuals. Prescribers need to be aware of their common side effects (gastrointestinal intolerance with oral dosing and flu-like illness following intravenous use). Whether these agents carry a real risk of other problems such as osteonecrosis of the jaw and subtrochanteric fractures remains uncertain at the present time. If the association of these problems with bisphosphonates is real, it is important that the major therapeutic benefits that can accrue from bisphosphonates' appropriate targeted use are not lost as a result of the anxiety concerning these extremely rare adverse events.

Safety of bisphosphonates

Bisphosphonates are one of the most well studied groups of medications and they are bone specific. This tissue specificity is a rare property for a drug introduced into clinical practice as long as 40 years ago. Over the years, the therapeutic boundaries of bisphosphonates were explored and their safety profile has withstood the challenges of the harsh clinical reality and widespread use. Certainly, the esophageal or gastric irritation caused by the oral preparations is an established adverse effect, the risk of which can be reduced by the recommended routine of taking the medication. From the other reported associations with adverse events, osteonecrosis of the jaw (ONJ) and subtrochanteric fractures have attracted most of the attention mainly because their pathophysiology remains unclear. However, overall, only a very small proportion of patients treated with bisphosphonates, especially with the oral formulations, experience adverse events and the overall benefits have consistently outweighed their potential risks. Furthermore, bisphosphonates improve the quality of life in patients with metastatic bone cancer and delay the development of adverse skeletal effects.

Bisphosphonates: the first 40 years

The first full publications on the biological effects of the diphosphonates, later renamed bisphosphonates, appeared in 1969, so it is timely after 40years to review the history of their development and their impact on clinical medicine. This special issue of BONE contains a series of review articles covering the basic science and clinical aspects of these drugs, written by some of many scientists who have participated in the advances made in this field. The discovery and development of the bisphosphonates (BPs) as a major class of drugs for the treatment of bone diseases has been a fascinating story, and is a paradigm of a successful journey from 'bench to bedside'. Bisphosphonates are chemically stable analogues of inorganic pyrophosphate (PPi), and it was studies on the role of PPi as the body's natural 'water softener' in the control of soft tissue and skeletal mineralisation that led to the need to find inhibitors of calcification that would resist hydrolysis by alkaline phosphatase. The observation that PPi and BPs could not only retard the growth but also the dissolution of hydroxyapatite crystals prompted studies on their ability to inhibit bone resorption. Although PPi was unable to do this, BPs turned out to be remarkably effective inhibitors of bone resorption, both in vitro and in vivo experimental systems, and eventually in humans. As ever more potent BPs were synthesised and studied, it became apparent that physico-chemical effects were insufficient to explain their biological effects, and that cellular actions must be involved. Despite many attempts, it was not until the 1990s that their biochemical actions were elucidated. It is now clear that bisphosphonates inhibit bone resorption by being selectively taken up and adsorbed to mineral surfaces in bone, where they interfere with the action of the bone-resorbing osteoclasts. Bisphosphonates are internalised by osteoclasts and interfere with specific biochemical processes. Bisphosphonates can be classified into at least two groups with different molecular modes of action. The simpler non-nitrogen containing bisphosphonates (such as etidronate and clodronate) can be metabolically incorporated into non-hydrolysable analogues of ATP, which interfere with ATP-dependent intracellular pathways. The more potent, nitrogen-containing bisphosphonates (including pamidronate, alendronate, risedronate, ibandronate and zoledronate) are not metabolised in this way but inhibit key enzymes of the mevalonate/cholesterol biosynthetic pathway. The major enzyme target for bisphosphonates is farnesyl pyrophosphate synthase (FPPS), and the crystal structure elucidated for this enzyme reveals how BPs bind to and inhibit at the active site via their critical N atoms. Inhibition of FPPS prevents the biosynthesis of isoprenoid compounds (notably farnesol and geranylgeraniol) that are required for the post-translational prenylation of small GTP-binding proteins (which are also GTPases) such as rab, rho and rac, which are essential for intracellular signalling events within osteoclasts. The accumulation of the upstream metabolite, isopentenyl pyrophosphate (IPP), as a result of inhibition of FPPS may be responsible for immunomodulatory effects on gamma delta (γδ) T cells, and can also lead to production of another ATP metabolite called ApppI, which has intracellular actions. Effects on other cellular targets, such as osteocytes, may also be important. Over the years many hundreds of BPs have been made, and more than a dozen have been studied in man. As reviewed elsewhere in this issue, bisphosphonates are established as the treatments of choice for various diseases of excessive bone resorption, including Paget's disease of bone, the skeletal complications of malignancy, and osteoporosis. Several of the leading BPs have achieved 'block-buster' status with annual sales in excess of a billion dollars. As a class, BPs share properties in common. However, as with other classes of drugs, there are obvious chemical, biochemical, and pharmacological differences among the various BPs. Each BP has a unique profile in terms of mineral binding and cellular effects that may help to explain potential clinical differences among the BPs. Even though many of the well-established BPs have come or are coming to the end of their patent life, their use as cheaper generic drugs is likely to continue for many years to come. Furthermore in many areas, e.g. in cancer therapy, the way they are used is not yet optimised. New 'designer' BPs continue to be made, and there are several interesting potential applications in other areas of medicine, with unmet medical needs still to be fulfilled. The adventure that began in Davos more than 40 years ago is not yet over.

Bisphosphonates in Paget's disease

Paget's disease is the best example of a common high turnover bone disease. A review of the early use of bisphosphonates in the treatment of this condition shows that many of the fundamental therapeutic issues were identified using drugs which by today's standards were far from ideal. Over the succeeding decades there has been a steady increase in potency culminating in the introduction of intravenous zoledronic acid which is capable of inducing long term remissions which were unthinkable when bisphosphonates were first introduced.

Characterization of and risk factors for the acute-phase response after zoledronic acid

CONTEXT

Intravenous aminobisphosphonates often cause an acute-phase response (APR), but the precise components of this, its frequency, and the risk factors for its development have not been systematically studied.

OBJECTIVE

The objective of the study was to characterize the APR and determine its frequency and the risk factors for its development.

DESIGN

The study was an analysis of adverse events from a large randomized trial.

SETTING

This was a multicenter international trial.

PATIENTS

Patients included 7765 postmenopausal women with osteoporosis.

INTERVENTION

Zoledronic acid 5 mg annually or placebo was the intervention.

MAIN OUTCOME MEASURE

Adverse events occurring within 3 d of zoledronic acid infusion were measured.

RESULTS

More than 30 adverse events were significantly more common in the zoledronic acid group and were regarded collectively as constituting an APR. These were clustered into five groups: fever; musculoskeletal (pain and joint swelling); gastrointestinal (abdominal pain, vomiting, diarrhea); eye inflammation; and general (including fatigue, nasopharyngitis, edema). A total of 42.4% of the zoledronic acid group had an APR after the first infusion, compared with 11.7% of the placebo group. All APR components had their peak onset within 1 d, the median duration of the APR was 3 d, and severity was rated as mild or moderate in 90%. Stepwise regression showed that APR was more common in non-Japanese Asians, younger subjects, and nonsteroidal antiinflammatory drug users and was less common in smokers, patients with diabetes, previous users of oral bisphosphonates, and Latin Americans (P < 0.05 for all).

CONCLUSION

This analysis identifies new components of the APR and provides the first assessment of risk factors for it. Despite its frequency, APR rarely resulted in treatment discontinuation in this study.

Long-term treatment with bisphosphonates and their safety in postmenopausal osteoporosis

Bisphosphonates are the leading drugs for the treatment of osteoporosis. In randomized controlled trials (RCTs), alendronate, risedronate, and zoledronate have shown to reduce the risk of vertebral, nonvertebral, and hip fractures, whereas RCTs with ibandronate show antifracture efficacy at vertebral sites. Bisphosphonates are generally well tolerated and safe. Nevertheless, adverse events have been noted, and it is important to consider the strength of the evidence for causal relationships. Effects on the gastrointestinal tract and kidney function are well recognized, as are transient acute-phase reactions. Atrial fibrillation was first identified as a potential adverse event in a zoledronate trial, but subsequent trials and analyses failed to substantiate an association with bisphosphonates. Case reports have suggested a relationship between oral bisphosphonates and esophageal cancer, but this has not been demonstrated in epidemiologic studies. A possible association between bisphosphonate use and osteonecrosis of the jaw (ONJ) has also been suggested. However, the risk of ONJ in patients with osteoporosis appears to be very low, with no evidence from prospective RCTs of a causal association. There are reports of occasional occurrence of subtrochanteric or diaphyseal fractures in osteoporotic patients, but an association with bisphosphonate therapy is not substantiated by epidemiologic studies or prospective RCTs.

Current options for the treatment of Paget's disease of the bone

Paget’s disease of bone (PDB) is a chronic bone remodelling disorder characterized by increased osteoclast-mediated bone resorption, with subsequent compensatory increases in new bone formation, resulting in a disorganized mosaic of woven and lamellar bone at affected skeletal sites. This disease is most often asymptomatic but can be associated with bone pain or deformity, fractures, secondary arthritis, neurological complications, deafness, contributing to substantial morbidity and reduced quality of life. Neoplastic degeneration of pagetic bone is a relatively rare event, occurring with an incidence of less than 1%, but has a grave prognosis. Specific therapy for PDB is aimed at decreasing the abnormal bone turnover and bisphosphonates are currently considered the treatment of choice. These treatments are associated with a reduction in plasma alkaline phosphatase (ALP) activity and an improvement in radiological and scintigraphic appearance and with a reduction in bone pain and bone deformity, Recently, the availability of newer, more potent nitrogen-containing bisphosphonates has improved treatment outcomes, allowing a more effective and convenient management of this debilitating disorder.

Management of patients with Paget's disease: a consensus document of the Belgian Bone Club

Paget's disease of bone (PDB) is a potentially crippling condition. Pain, fracture, spinal stenosis, nerve entrapment, vascular steal syndrome, secondary osteoarthritis, bone deformity, dental problems, deafness, excessive bleeding during orthopaedic surgery, rare sarcomatous degeneration, and hypercalcaemia constitute complications that may impair the quality of life. The therapeutic approach varies from symptomatic (analgesics, anti-inflammatory drugs) to more specific drugs such as increasingly potent bisphosphonates. Studies such as the PRISM study should in the future help to determine the superiority or not of aggressive treatment over symptomatic treatment in the prevention of complications. Various oral and/or intravenous (i.v.) bisphosphonates have been tested and are currently on the market. The most recently available nitrogen-containing bisphosphonate, i.v. zoledronic acid, is the most potent therapy available for the treatment of PDB. Its therapeutic efficacy, its long-term effect on biologic activity and its good tolerance currently supports its use as a first-line therapeutic option in patients suffering from PDB.

[Treatment of Paget's disease of bone: importance of the zoledronic acid]

Paget's disease is a localised monostotic or polyostotic bone disease of unknown origin. It may be caused by a slow viral infection and/or genetic factors. It is characterised by increased bone remodelling and an initially excessive osteoclastic bone resorption, followed by a secondary increase in osteoblastic activity, leading to replacement of the normal bone by a disorganized, enlarged, and weakened osseous structure prone to deformities and fractures. The disease may be diagnosed by radiography, scintigraphy and biochemical tests. The primary aim of treatment is to reduce pain and risk of developing long-term complications. Potent antiresorptive drugs are now available, which control the increased bone remodelling and have led to a dramatic improvement in treatment. Zoledronic acid, a new generation of bisphosphonates, has the advantage of great potency and long duration of remission and a short infusion time.

Paget's disease of bone

Paget's disease of bone is a focal disorder of bone remodeling accompanied initially by an increase in bone resorption, followed by a disorganized and excessive formation of bone, leading to pain, fractures and deformities. It exhibits a marked geographical variation in its prevalence. In Brazil it predominantly affects persons of European descent. The majority of the reported cases of the disease in Brazil are from Recife, owing to its peculiar mixed European colonization over approximately four centuries. The etiology is complex and involves both genetic and environmental factors. The disease is often asymptomatic and diagnosis is usually based on biochemical markers of bone turnover, radionuclide bone scan and radiological examination. Bisphosphonates, in particular zoledronic acid, are regarded as the treatment of choice for Paget's disease of bone.

Bisphosphonates: new indications and methods of administration

In the course of 2002, several new studies were published confirming the efficacy of bisphosphonate drugs in fracture prevention in patients with osteoporosis. Further evidence was provided of their long duration of action, making intermittent administration possible. The potent bisphosphonate zoledronate can be given at intervals of as long as 1 year and produces changes in bone density and in markers of bone turnover comparable with those seen with conventional daily oral dosing with alendronate or risedronate. If such regimens are proven to prevent fractures, their convenience is likely to result in their widespread adoption and potentially an increase in compliance with these medications. Further evidence has been presented documenting the value of bisphosphonates in preventing the skeletal complications of malignancy, and possibly in reducing mortality in patients with breast cancer. The role of bisphosphonates in osteogenesis imperfecta was further confirmed, and novel roles in ankylosing spondylitis, myelofibrosis, and hypertrophic pulmonary osteoarthropathy were suggested.

Calcitonin in the treatment of transient osteoporosis of the hip

BACKGROUND

Transient osteoporosis of the hip (TOH) is a rare clinical disorder of unknown etiology characterized by hip pain and functional disability that resolve spontaneously in 6-24 months.

OBJECTIVES

To report 2 patients with TOH during pregnancy who had rapid resolution of their illness with the use of calcitonin. To review the literature on TOH with special emphasis on its treatment.

METHODS

A MEDLINE search of studies published from 1966 to 2002 was performed to review treatment options for TOH and their effect on the natural history of the disease.

RESULTS

Our 2 patients developed hip pain during pregnancy with classical changes of TOH on MRI. Both patients received calcitonin, 1 during pregnancy and 1 postpartum with resolution of their symptoms within 6 to 9 weeks. Previous reports in the literature of treatment of TOH showed that antiresorptive agents (bisphosphonates and calcitonin) had shortened the duration of the illness compared with the natural history of the disease.

CONCLUSIONS

TOH is an under-recognized entity associated with pain and disability. The use of antiresorptive agents may be of help in reducing the duration of the disease.

RELEVANCE

To increase the recognition of TOH and to consider therapeutic interventions to shorten the duration of the disease.

Inhibition of matrix metalloproteinase-14 in osteosarcoma cells by clodronate

BACKGROUND

Bisphosphonates reduce the bone metastasis formation and angiogenesis but the exact molecular mechanisms involved are unclear. Progelatinase A (proMMP-2; 78 KDa) is activated up during the tumor spread and metastasis by a cell surface-associated matrix metalloproteinase (membrane-type matrix metalloproteinase [MT1-MMP] or MMP-14).

MATERIAL AND METHODS

We evaluated the effects of a bisphosphonate (clodronate) on MT1-MMP mRNA expression and protein production, catalytic activity and proteolytic activation of proMMP-2 by cultured human MG-63 osteosarcoma cells.

RESULTS

Clodronate, at therapeutically attainable noncytotoxic concentrations, dose-dependently inhibited phorbol myristic acetate (PMA)-induced proteolytic activation of proMMP-2 by human MG-63 osteosarcoma cells. Clodronate also downregulated the PMA-induced expression of MT1-MMP mRNA and protein production in human MG-63 osteosarcoma cells, as evidenced by Northern analysis and fluorescent immunohistochemistry. Furthermore, clodronate inhibited directly and dose-dependently MT1-MMP activity, and the MT1-MMP inhibition by clodronate was reduced in the presence of an increased (5 mM) Ca(2+) concentrations when compared to physiological (1 mM) Ca(2+) concentrations.

CONCLUSION

We conclude that (1) the extracellular/cell-associated mechanism of bisphosphonate involves inhibition of MT1-MMP catalytic activity eventually by chelation, and that (2) intracellular mechanism involves downregulation of induced MT1-MMP mRNA and protein expression. The inhibition and downregulation of MT1-MMP by clodronate can be related to their ability to reduce MG-63 osteosarcoma cell invasion and spread. These findings may, at least in part, explain at molecular level the antitumor and antibone resorption activities of clodronate observed in clinical studies.

Intravenous pamidronate in the treatment of transient osteoporosis of the hip

The aim of this study was to evaluate the efficacy of intravenous pamidronate in patients with transient osteoporosis of the hip (TOH). Thirteen men and three women (mean age 38.3 years, range 30-49) were recruited. The diagnosis was made by means of radiographs, bone scintigraphy, and magnetic resonance imaging (MRI). Pamidronate (45 mg) was intravenously administered three times, once every third day. The outcome measures included a clinical assessment using a pain visual analog scale (VAS; range 0-100), and the WOMAC functional impairment score (FUI; range 0-100). The bone mineral density (BMD) of the total hip and femoral neck was measured using dual-energy X-ray absorptiometry (DXA). Clinical assessments were made before treatment (T(0)) and 1 month later (T(1)), and the densitometric measurements at T(0), and then after 2 (T(2)) and 4 months (T(4)). A further MRI scan was made 3 months after treatment. In comparison to the unaffected side, there was a significant decrease at T(0) in the BMD of both the total hip (median 16.6%, range 8.5%-29.1%, p < 0.00001) and femoral neck (median 22.5%, range 12.0%-34.2%, p < 0.00001). By T(1), both VAS and FUI had decreased significantly (p < 0.00001). By T(2), the total hip and femoral neck BMD had increased by 10.9% (range 2.7%-23.6%, p < 0.00001) and 12.3% (range 7.8%-26.9%, p < 0.00001), respectively, and all patients were asymptomatic. By T(3), the MRI findings had normalized in all patients and, at T(4), there was a further increase in BMD. None of the patients experienced symptom relapse during the follow-up of 39.5 +/- 17.7 months. These results suggest that a short course of pamidronate is effective in treating TOH, and leads to a prompt and long-lasting recovery.

Daily oral pamidronate in women and men with osteoporosis: a 3-year randomized placebo-controlled clinical trial with a 2-year open extension

The efficacy and safety of oral pamidronate was examined in a double-blind, placebo-controlled trial in women and men with established osteoporosis. Seventy-eight postmenopausal women and 23 men with at least one prevalent vertebral fracture were randomized separately to 150 mg/day of pamidronate or placebo for 3 years followed by 150 mg/day of pamidronate for an additional 2 years. In addition, all patients received 400 U/day of cholecalciferol and 500 mg/day of elemental calcium. Pamidronate increased significantly bone mineral density of the lumbar spine (LS-BMD) and of the femoral neck (FN-BMD). The total increase in BMD of the spine after 5 years of treatment was 14.3%. Lateral spine radiographs were obtained at baseline and after 3 years of treatment. Fractures of previously normal vertebrae occurred in 15 of 45 patients treated with placebo (33.3%) and in 5 of 46 patients treated with pamidronate (11%). The relative risk was 0.33 (95% CI, 0.14-0.77). Treatment was well tolerated and there was no difference in gastrointestinal toxicity between pamidronate and placebo-treated patients. One hundred fifty milligrams daily of pamidronate is an effective and safe treatment of women and men with established osteoporosis.

Modern Therapy for Paget??s Disease of Bone

There has been a dramatic change in the therapeutic approach to patients with Paget's disease of bone over the last 40 years. In the 1960s, only symptomatic therapy could be given, with control of pain the main objective. Analgesics and nonsteroidal anti-inflammatory drugs were the most commonly used agents. From 1968 onwards, antiosteoclastic agents became available, including calcitonin, plicamycin (mithramycin) and etidronate (etidronic acid), a first-generation bisphosphonate. Limitations with these agents, including potentially deleterious effects on bone mineralization with etidronate (etidronic acid), has cleared the way for increasingly potent second- and third-generation bisphosphonates, including clodronate (clodronic acid), pamidronate (pamidronic acid), alendronate (alendronic acid) and risedronate (risedronic acid). Even more potent bisphosphonates will become available in the near future. With the newer bisphosphonates, there is some hope for long-term remission (if not definitive healing) of pagetic lesions, as well as prevention of long-term complications in both symptomatic and asymptomatic patients. Thus, indications for therapy have been extended to include younger patients to prevent bone deformity of the limbs and skull, leading to secondary osteoarthritis, facial deformities and potentially to sarcoma transformation; as well as to elderly patients to prevent bone fragility, leading to fracture, and pagetic vascular steal syndromes. The increased potency and longer duration of action of newer bisphosphonates more than compensates for their marginally increased cost compared with older bisphosphonates.

Effect of pamidronate in preventing local bone loss after total hip arthroplasty: a randomized, double-blind, controlled trial

Acute periprosthetic bone loss occurs after total hip arthroplasty. Bone loss undermines the support of the implant and may contribute to prosthetic failure. At present, there is no established prophylaxis for this process. We studied the effect of a single-dose infusion of 90 mg of pamidronate on early periprosthetic bone mineral density (BMD), biochemical markers of bone turnover, radiological, and clinical outcome in a 26-week, prospective, randomized, double-blinded study of 47 men and women undergoing total hip arthroplasty. Pamidronate therapy led to a significant reduction in bone loss compared with placebo for both the proximal femur and the pelvis (repeated measures analysis of variance [ANOVA]); p = 0.001 and p = 0.01, respectively). Pamidronate therapy was associated with suppression of all biochemical markers of bone turnover compared with placebo (repeated measures ANOVA; p < 0.05 for all comparisons), with the exception of urinary free deoxypyridinoline. Pamidronate did not interfere with the clinical improvement in symptoms after total hip arthroplasty, or radiological outcome, and was not associated with an increase in adverse events. This study provides clinical data on the efficacy and safety of bisphosphonates for the prevention of bone loss after total hip arthroplasty and supports the establishment of larger-scale clinical trials to determine the long-term clinical efficacy of this intervention using implant failure as the primary endpoint.

Alendronate blocks metalloproteinase secretion and bone collagen I release by PC-3 ML cells in SCID mice

We have previously shown that alendronate, a potent bisphosphonate compound, can prevent human PC-3 ML tumor cell metastasis to the bone (Stearns and Stearns, 1996, Oncol Res, 8, 69-75). In this paper, tumor cells were injected into the bone medullary cavity of SCID mice femurs both in vivo and following isolation in vitro. ELISAs showed that the amount of collagen I released in the bone marrow (i.e. in in vitro experiments) and the blood plasma (i.e. in in vivo experiments) was a function of the time of incubation or the number of cells injected in the femurs. ELISAs also showed that the levels of matrix metalloproteinase (MMP-2 and MMP-9) secreted in the bone medullary cavity of the femurs directly correlated with the extent of collagen 1 release. In vitro experiments carried out with 'live' and 'devitalized bone' yielded similar results suggesting that the tumor cells (not the osteoclasts) were primarily responsible for the bone solubilization observed. Alendronate pretreatment of the SCID mice (0.1 mg/kg biweekly for 3 weeks) (or the tumor cells) blocked both MMP production by the tumor cells (and the osteoclasts) and collagen I release, providing direct evidence that alendronate might be utilized to prevent bone destruction by metastatic tumor cells. Zymography indicated that MMP-2 activation might be responsible for bone solubilization. In addition, the data suggest that the plasma levels of collagen I might be a marker of bone metastasis and osteolysis.

Risedronate, a highly effective oral agent in the treatment of patients with severe Paget's disease

Thirteen patients with severe Paget's disease of bone [mean serum alkaline phosphatase (SAP) level 17 times the upper limit of normal] were treated with 30 mg oral risedronate daily for 8 weeks. Patients were followed for 16 weeks without treatment. The change from baseline SAP was the primary end point. Those patients whose SAP levels did not reach the normal range were retreated with 30 mg for another 8 weeks. There was a mean percent decrease in SAP of 77% after the first course of risedronate treatment and 87% after the second course of treatment. All patients who completed the study had a decrease in SAP of at least 77% from the baseline. The urinary hydroxyproline/creatinine level was decreased by 64% and 79%, respectively, during the first and second treatment courses. There were transient asymptomatic decreases in serum calcium and phosphorus levels. The urinary calcium/creatinine ratio also decreased in these patients. Serum intact PTH and 1,25-dihydroxyvitamin D levels increased transiently during risedronate treatment. Oral risedronate was well tolerated by the patients. Only one patient discontinued treatment because of an adverse event (diarrhea) thought to be related to risedronate therapy.

Alendronate blocks TGF-beta1 stimulated collagen 1 degradation by human prostate PC-3 ML cells

We have previously shown that alendronate can prevent human PC-3 ML tumor cell metastasis to the bone (Wang and Stearns, 1991, Differentiation, 48, 115-25). In this paper, ELISAs and Western blots showed that TGF-beta1 stimulated the secretion of a 72 kDa matrix metalloproteinase 2 (MMP-2) to enhance the solubilization of radiolabeled collagen 1 by metastatic human prostate PC-3 ML cells. A potent bisphosphonate compound, alendronate, inhibited MMP-2 secretion to block solubilization of collagen 1. Alendronate failed to inhibit MMP-2 activity directly, but instead appeared to block cellular secretion of MMP-2. Alendronate failed to inhibit secretion of tissue inhibitor of metalloproteinase-2 (TIMP-2; the inhibitor of MMP-2) and the decrease in collagen 1 solubilization observed may occur, in part, from changes in the molar stoichiometry of TIMP-2 to MMP-2. We conclude that alendronate may be a potent inhibitor of bone resorption based on its ability to block MMP-2 secretion by tumor cells.

Modification of serum apolipoprotein A-I, apolipoprotein B and lipoprotein(a) levels after bisphosphonates-induced acute phase response

Lipoprotein(a) (Lp(a)) is a low density lipoprotein-like particle displaying strong atherothrombotic properties. Although the concentration of Lp(a) in plasma is under strong genetic regulation, there are emerging evidences that several other factors, such as hormonal disorders, acute phase, liver and renal failure may affect its metabolism. The aim of the present study was to investigate whether bisphosphonates, an effectual drug in the treatment of malignant hypercalcemia and Paget's disease of bone, known to induce a concomitant acute phase, may have a significant influence on Lp(a) concentrations. Nine subjects (four men and five women), with plasma Lp(a) concentrations in the range between 6.4 and 17.7 mg/dl, were subjected to a single intravenous infusion of bisphosphonates (7.5 mg of aminohydroxybutylidene and 5.0 mg of aminohydroxylidene), previously dissolved in 250 ml of saline. Lp(a), apo A-I, apo B, C reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were measured at the baseline and after days one, two, four and seven. CRP, ESR and Lp(a) started to increase after two days from the treatment, reaching statistical significance after day two, four and seven, respectively. Apo B and apo A-I decreased significantly after days one and two, respectively. Although patterns and relative amounts of the increase of CRP were substantially different among the subjects studied, the increase of Lp(a) was more homogeneous; the peak of Lp(a) concentrations was reached only seven days after treatment in the group as a whole, in agreement with previous observations. In univariate regression analysis, significant correlations were found only between apo A-I and ESR, and apo A-I and Lp(a). The present study suggest that Lp(a) behaves as an acute phase protein. Besides, we observed a slight but significant decrease of apo A-I and apo B after administration of bisphosphonates.

Pamidronate content and turnover in sternum, vertebral body, and iliac bones of dogs

Therapeutic efficacy of bisphosphonates depends on how much drug is present in bone. Therefore, it is important to measure the amount of bone bisphosphonate in toxicological and pharmacological studies. We analyzed pamidronate content of bone samples from two previously published long-term dose studies. In the first study, mature beagle dogs were given oral pamidronate at doses of 0, 2.5, 12.5 and 25 mg/kg per day for 1 year. The dogs in the second study received the same dosages for 1 year followed by 1 year without drug. In both studies, the amount of pamidronate measured was dependent upon dose in bone samples of ilium, sternum, and vertebral body. After 1 year of treatment, vertebral bone had more pamidronate than sternum or iliac bone on a permilligram basis. After 2 years, there was significantly less pamidronate in the vertebral body, sternum, and ilium than there had been at 1 year. The fall in pamidronate content was largest in vertebral body and least in the ilium. The higher uptake of pamidronate by the vertebral body during the 1 year study, and its greater loss of pamidronate after a year without drug treatment, would reflect the higher turnover of trabecular bone in the vertebral body vs. cortical bone in the ilium. The percent difference in bone pamidronate content between the 1 and 2 year dogs varied with dose. The largest percent loss occurred in the intermediate-dose group. These data suggest that, after 1 year without the drug, bone turnover rates in dogs treated with the highest dose of pamidronate were lower than at the intermediate dose. Thus, the time required for bone turnover rates to return to pretreatment levels is probably dose-dependent.

Paget's disease of bone: clinical, pathogenetic and therapeutic aspects

Paget's disease of bone is a focal disorder of bone remodelling due to abnormally increased osteoclast-mediated bone resorption. It rarely presents before the age of 35 years and its prevalence increases with age affecting 2-5% of the population above 50 years, making Paget's disease the most common skeletal disorder after osteoporosis. Its aetiology is not known but available evidence favours an infection of genetically predisposed individuals with a paramyxovirus. Affected bones change in shape, size and direction causing considerable morbidity but the majority of patients are asymptomatic. In Paget's disease increased bone resorption is tightly linked to increased bone formation which are reflected in the proportional increases in biochemical indices of bone turnover. Because the primary abnormality lies in the osteoclasts, inhibitors of bone resorption are used for its therapy and bisphosphonates are currently the treatment of choice. These decrease bone turnover effectively and their effect lasts after stopping treatment. With available bisphosphonates clinical and biochemical, long-lasting, remissions can be obtained in the majority of patients. Symptomatic disease and preparation for orthopaedic surgery are no longer the only indication for treatment, but asymptomatic patients with localizations at sites likely to induce complications should be considered candidates for bisphosphonate therapy.

Development of a monoclonal antibody to urinary degradation products from the C-terminal telopeptide alpha 1 chain of type I collagen. Application in an enzyme immunoassay and comparison to CrossLaps ELISA

A monoclonal antibody MAbA7 was raised against a synthetic peptide having a sequence (EKAHDGGR) specific for a part of the C-telopeptide alpha 1 chain of type I collagen. MAbA7 was labelled with horseradish peroxide and used in a competitive one-step enzyme-linked immunosorbent assay (ELISA) for measurement of urinary type I collagen degradation products. The assay was technically evaluated and preliminary clinical data are presented. The measuring range was 200-7000 micrograms l-1 with a detection limit of 25 micrograms l-1. Within-run and total CVs were 5.5 and 8.0%, respectively. Analytical recovery averaged 96.6% +/- 5.3 (mean +/- 1SD). Values obtained in the ELISA were highly correlated (r = 0.93) to values obtained by a commercially available assay (CrossLaps ELISA) known to measure urinary degradation products derived from the C-telopeptide of type I collagen reflecting the rate of bone resorption. Investigation of the urinary fragments responsible for the immunological response in the two assays revealed, however, that they are not identical. Values obtained in urine samples from postmenopausal women (n = 108) and patients with Paget's disease (n = 6) increased 43% (p < 0.01) and 28-fold (p < 0.001), respectively, when compared to a premenopausal level (n = 50). A decrease in the urinary concentrations of 67% (p < 0.01) was seen after 6 months in urine samples from postmenopausal women (n = 13) receiving hormone replacement therapy (HRT) compared to a group receiving placebo (n = 9). Likewise, the urinary concentrations decreased 88% (p < 0.001) in early postmenopausal women receiving bisphosphonate therapy (n = 11) for a period of 9 months compared to a group receiving placebo (n = 12). These results suggest that the monoclonal antibody and the new assay may be useful for further investigations of the physiological and clinical importance of type I collagen degradation.

Stimulation of neonatal mouse calvarial bone resorption by the glucocorticoids hydrocortisone and dexamethasone

In vitro stimulation of bone resorption was observed with the glucocorticoids hydrocortisone and dexamethasone. Dosage-dependent release of 45Ca from neonatal mouse calvarial bones was found for both steroids, with half-maximal responses for hydrocortisone and dexamethasone of 0.3 and 0.08 microM, respectively. Significant release of stable calcium (Ca2+), inorganic phosphate (Pi), and the lysosomal enzyme beta-N-acetylglucosaminidase was noted following treatment of mouse calvariae with either 1 microM hydrocortisone or 1 microM dexamethasone. Additionally, both 1 microM hydrocortisone and 1 microM dexamethasone elicited release of 3H from calvarial bones prelabeled with [3H]proline. The stimulation of bone resorption by the glucocorticoids, as assessed by 45Ca release, was sustained over 120 h of culture. Inhibition of 45Ca release from calvariae treated with either 1 microM hydrocortisone or 0.1 microM dexamethasone was observed with 0.01-30 nM salmon calcitonin (sCT), 0.1 mM acetazolamide, and 0.1 mM of the bisphosphonate AHPrBP. Inhibition of glucocorticoid-induced bone resorption by sCT occurred without "escape from calcitonin-induced inhibition." The 45Ca release stimulated by 1 microM hydrocortisone and 0.1 microM dexamethasone was also inhibited by 10 microM progesterone in a competitive manner and by 1 microM of the antiglucocorticoid RU38486, both of which are modulators of glucocorticoid binding. Prostaglandin E2 (PGE2) formation by 10 nM parathyroid hormone (PTH) in neonatal mouse calvarial bones was inhibited by both 1 microM hydrocortisone and 1 microM dexamethasone, but neither compound altered basal PGE2 formation. Exposure of calvarial bones to the mitotic inhibitors hydroxyurea and mitomycin C inhibited 45Ca release stimulated by 1 microM hydrocortisone and 1 microM dexamethasone. In contrast, addition of 1 ng/ml of recombinant murine granulocyte macrophage colony stimulating factor (rmGM-CSF) had no effect on 45Ca release elicited by the glucocorticoids. These results suggest that hydrocortisone and dexamethasone stimulate osteoclastic resorption in neonatal mouse calvariae by a receptor-mediated mechanism that is dependent on cellular replication.

Clinical, biochemical, hematologic, and radiographic responses in Paget's disease following intravenous pamidronate disodium: a 2-year study

An intravenous dosage schedule using pamidronate disodium, based on biochemical severity, was used to treat 71 patients with Paget's disease who had no previous bisphosphonate treatment. Disease severity was stratified by fasting hydroxyproline excretion (HypE): Group (Gp) I (mild disease; HypE < 5.0 mumol/LGF) received a total dose of 120 mg; Gp II (moderate; HypE 5.00-9.99) received 180 mg; and Gp III (severe; HypE > or = 10) received 240 mg. Within each group patients were randomly allocated to receive daily 30 mg or 60 mg infusions. Observations for 2 years included pain scores, indices of bone turnover, and radiology of lytic lesions. There was no difference in biochemical responses, or in the percentage of patients with early fever, between the 30 mg and 60 mg daily subgroups; for convenience, 60 mg infusions are recommended. Neutrophils and total white cell counts were both significantly below baseline 4 days after the first infusion; lymphocytes were significantly reduced by day 2; and all three measures had returned to within the reference range by day 6. Remission was assessed at 6 months, when both plasma alkaline phosphatase (ALP) and HypE had reached stable nadirs. Increasing severity was associated with increasing resistance to suppression of HypE at 6 months to within the reference range: Gp I, 87%; Gp II, 44%; and Gp III, 0% (p < 0.0001 by chi-square test). Biochemical relapse at 2 years (defined as ALP 50% above the 6 month level) was also dependent on initial disease severity (Gp I, 6%; GpII, 39%; Gp III, 62%; p < 0.0005 by chi-square test). There was no association between time to relapse and either initial dose or log dose. Radiologic lytic lesions (in 22 patients) were all in remission at 3 months; however, relapse rates at 2 years appeared to be severity-dependent: Gp I, 13%; Gp II, 43%; and Gp III, 57% (n.s. by chi-square test). Remission rates based on a fall to < 50% of pretreatment of either HypE or ALP were more in accord with lytic lesion remission rates than were rates based on HypE falling to within the reference range. Pamidronate produced a significant reduction from baseline in Pagetic bone, Pagetic joint, and unrelated musculoskeletal pain in the first 6 months (p < 0.0001). From 0 months to 2 years the maintenance of improvement in bone pain (p < 0.005) and joint pain (p < 0.05) was significantly better than in unrelated pain. Pamidronate is a safe, welltolerated, and effective treatment for Paget's disease. In spite of larger dosage in severe disease, increasing severity was associated with resistance to normalization of biochemistry and a higher incidence of biochemical and radiological relapse at 2 years. Our current dosage recommendation would be for two 60 mg infusions for mild disease (Gp I); and four 60 mg infusions for moderate disease (Gp II). Severe disease (Gp III) remains a challenge; regardless of dosage, the majority of patients will be in relapse 2 years after a single course of treatment.

Biochemical and radiologic improvement in Paget's disease of bone treated with alendronate: a randomized, placebo-controlled trial

PURPOSE

The potent bisphosphonates offer great promise in the management of Paget's disease of bone, but are currently available only as parenteral preparations in most countries. There is a need for a well-tolerated, oral therapy. Furthermore, none of the currently available therapies have been rigorously demonstrated to heal the lytic bone lesions characteristic of this condition. Alendronate is a potent new oral aminobisphosphonate that has shown promising effects on Paget's disease in preliminary studies.

METHODS

We report a double-blind, randomized comparison of oral alendronate 40 mg/day and placebo over 6 months in 55 patients with Paget's disease. Efficacy was determined from measurements of biochemical indices of bone turnover (serum alkaline phosphatase and urine N-telopeptide) and blinded radiologic assessment of lytic bone lesions.

RESULTS

N-telopeptide excretion declined by 86% and serum alkaline phosphatase by 73% in patients receiving alendronate, but remained stable in patients receiving placebo (P < 0.001 between groups for both indices). Responses were similar whether or not patients had previously received bisphosphonate treatment. Alendronate treatment normalized alkaline phosphatase in 48% of patients. Forty-eight percent of alendronate-treated patients showed radiologic improvement in osteolysis whereas in the placebo group only 4% improved (P = 0.02 for between-groups comparison). No patient in either group showed worsening of osteolysis. Bone histomorphometry indicated that alendronate tended to normalize turnover indices. There was no evidence of abnormal mineralization in bone biopsies taken from 12 alendronate-treated subjects. The treatment was well tolerated.

CONCLUSION

Oral alendronate appears to be a safe and effective therapy for Paget's disease and results in healing of lytic bone lesions.

Recovery from pamidronate (APD): a two-year study in the dog

The goal of this study was to find out if bone can recover after long-term administration of bisphosphonate. Disodium pamidronate (APD) was given orally by gavage to mature beagle dogs at doses of 0, 2.5, 12.5, and 25 mg/kg/day for 1 year (0.1% concentration) and the animals were allowed to recover for another year. At sacrifice, the os ilium was used to determine bone mineralization profile and, subsequently, each density fraction was analyzed chemically. The ribs were used to determine the lattice parameters and the size of the apatite crystals of bone. The sternum was used to determine selected morphometric parameters using image analysis of specimen X-ray films and, subsequently, to determine bone mechanical properties using a 3-point bending technique. We found that the 12.5 and 25 mg/kg/day doses exhibit a significant shift towards greater mineralization versus control, whereas the lower dose (2.5 mg/kg/day) was indistinguishable from the controls. The lattice parameters and crystal size of bone apatite remained unchanged. The image analysis shows a dose-related increase in trabecular volume and thickness. The connectivity increased with dose but the anisotropy of bone remained unchanged. Both the elastic modulus and the maximum stress of bone remain unaffected by APD. We conclude that when dogs are treated with APD for 1 year, their bones can reestablish their physical-chemical characteristics (mineralization profile, chemistry, and crystal size/strain) after 1 year of recovery, provided that the treatment dose is 2.5 mg/kg/day. In addition, the mechanical properties of the bone remained unaffected and the gains in trabecular volume and thickness are maintained.

The effect of alendronate on renal tubular reabsorption of phosphate

We report the effects of alendronate on phosphate homeostasis in two patients. In a woman with postmenopausal osteoporosis, the infusion of alendronate (7.5 mg intravenously daily for 4 consecutive days) was not associated with secondary hyperparathyroidism despite a reduction in serum calcium. This was associated with a rise in serum phosphate and TmP/GFR. This response contrasted with those observed in 14 other patients with osteoporosis, in whom PTH rose significantly following the infusion of alendronate in association with a significant fall in serum phosphate and TmP/GFR. The second patient, a woman with Paget's disease, was treated with intravenous alendronate (10 mg daily for 5 consecutive days) on two occasions for relapse of disease activity. On the first occasion there was a 150% rise in serum PTH associated with a fall in serum phosphate and TmP/GFR. On the second occasion, when the rise in serum PTH was less marked, there was a rise in serum phosphate and TmP/GFR. We conclude that alendronate may increase renal tubular reabsorption of phosphate, but that this effect is usually offset by secondary hyperparathyroidism.